The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially FACILITATED DIFFUSION, is a major mechanism of BIOLOGICAL TRANSPORT.
A diagnostic technique that incorporates the measurement of molecular diffusion (such as water or metabolites) for tissue assessment by MRI. The degree of molecular movement can be measured by changes of apparent diffusion coefficient (ADC) with time, as reflected by tissue microstructure. Diffusion MRI has been used to study BRAIN ISCHEMIA and tumor response to treatment.
The use of diffusion ANISOTROPY data from diffusion magnetic resonance imaging results to construct images based on the direction of the faster diffusing molecules.
The passive movement of molecules exceeding the rate expected by simple diffusion. No energy is expended in the process. It is achieved by the introduction of passively diffusing molecules to an enviroment or path that is more favorable to the movement of those molecules. Examples of facilitated diffusion are passive transport of hydrophilic substances across a lipid membrane through hydrophilic pores that traverse the membrane, and the sliding of a DNA BINDING PROTEIN along a strand of DNA.
A physical property showing different values in relation to the direction in or along which the measurement is made. The physical property may be with regard to thermal or electric conductivity or light refraction. In crystallography, it describes crystals whose index of refraction varies with the direction of the incident light. It is also called acolotropy and colotropy. The opposite of anisotropy is isotropy wherein the same values characterize the object when measured along axes in all directions.
A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves.
The broad dissemination of new ideas, procedures, techniques, materials, and devices and the degree to which these are accepted and used.
A method used to study the lateral movement of MEMBRANE PROTEINS and LIPIDS. A small area of a cell membrane is bleached by laser light and the amount of time necessary for unbleached fluorescent marker-tagged proteins to diffuse back into the bleached site is a measurement of the cell membrane's fluidity. The diffusion coefficient of a protein or lipid in the membrane can be calculated from the data. (From Segen, Current Med Talk, 1995).
A method where a culturing surface inoculated with microbe is exposed to small disks containing known amounts of a chemical agent resulting in a zone of inhibition (usually in millimeters) of growth of the microbe corresponding to the susceptibility of the strain to the agent.
Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.
Methods developed to aid in the interpretation of ultrasound, radiographic images, etc., for diagnosis of disease.
A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.
The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.
Improvement of the quality of a picture by various techniques, including computer processing, digital filtering, echocardiographic techniques, light and ultrastructural MICROSCOPY, fluorescence spectrometry and microscopy, scintigraphy, and in vitro image processing at the molecular level.
Broad plate of dense myelinated fibers that reciprocally interconnect regions of the cortex in all lobes with corresponding regions of the opposite hemisphere. The corpus callosum is located deep in the longitudinal fissure.
Devices used in a technique by which cells or tissues are grown in vitro or, by implantation, in vivo within chambers permeable to diffusion of solutes across the chamber walls. The chambers are used for studies of drug effects, osmotic responses, cytogenic and immunologic phenomena, metabolism, etc., and include tissue cages.
Computer-based representation of physical systems and phenomena such as chemical processes.
A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.
Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.
The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
The rate dynamics in chemical or physical systems.
Light-induced change in a chromophore, resulting in the loss of its absorption of light of a particular wave length. The photon energy causes a conformational change in the photoreceptor proteins affecting PHOTOTRANSDUCTION. This occurs naturally in the retina (ADAPTATION, OCULAR) on long exposure to bright light. Photobleaching presents problems when occurring in PHOTODYNAMIC THERAPY, and in FLUORESCENCE MICROSCOPY. On the other hand, this phenomenon is exploited in the technique, FLUORESCENCE RECOVERY AFTER PHOTOBLEACHING, allowing measurement of the movements of proteins and LIPIDS in the CELL MEMBRANE.
The study of PHYSICAL PHENOMENA and PHYSICAL PROCESSES as applied to living things.
Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses).
Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.
The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.
The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.
The resistance that a gaseous or liquid system offers to flow when it is subjected to shear stress. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
WHITE MATTER pathway, flanked by nuclear masses, consisting of both afferent and efferent fibers projecting between the WHITE MATTER and the BRAINSTEM. It consists of three distinct parts: an anterior limb, posterior limb, and genu.
The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.
The physical characteristics and processes of biological systems.
Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.
Property of membranes and other structures to permit passage of light, heat, gases, liquids, metabolites, and mineral ions.
Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)
Agents that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.
Elements of limited time intervals, contributing to particular results or situations.
The motion of phospholipid molecules within the lipid bilayer, dependent on the classes of phospholipids present, their fatty acid composition and degree of unsaturation of the acyl chains, the cholesterol concentration, and temperature.
Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).
A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.
Measurement of the intensity and quality of fluorescence.
The movement of molecules from one location to another as effected by temperature changes.
Substances that reduce the growth or reproduction of BACTERIA.
The amount of a gas taken up, by the pulmonary capillary blood from the alveolar gas, per minute per unit of average pressure of the gradient of the gas across the BLOOD-AIR BARRIER.
Fibers that arise from cells within the cerebral cortex, pass through the medullary pyramid, and descend in the spinal cord. Many authorities say the pyramidal tracts include both the corticospinal and corticobulbar tracts.
Helium. A noble gas with the atomic symbol He, atomic number 2, and atomic weight 4.003. It is a colorless, odorless, tasteless gas that is not combustible and does not support combustion. It was first detected in the sun and is now obtained from natural gas. Medically it is used as a diluent for other gases, being especially useful with oxygen in the treatment of certain cases of respiratory obstruction, and as a vehicle for general anesthetics. (Dorland, 27th ed)
Technique involving the diffusion of antigen or antibody through a semisolid medium, usually agar or agarose gel, with the result being a precipitin reaction.
Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.
Neural tracts connecting one part of the nervous system with another.
A complex sulfated polymer of galactose units, extracted from Gelidium cartilagineum, Gracilaria confervoides, and related red algae. It is used as a gel in the preparation of solid culture media for microorganisms, as a bulk laxative, in making emulsions, and as a supporting medium for immunodiffusion and immunoelectrophoresis.
The homogeneous mixtures formed by the mixing of a solid, liquid, or gaseous substance (solute) with a liquid (the solvent), from which the dissolved substances can be recovered by physical processes. (From Grant & Hackh's Chemical Dictionary, 5th ed)
Artificially produced membranes, such as semipermeable membranes used in artificial kidney dialysis (RENAL DIALYSIS), monomolecular and bimolecular membranes used as models to simulate biological CELL MEMBRANES. These membranes are also used in the process of GUIDED TISSUE REGENERATION.
A group of glucose polymers made by certain bacteria. Dextrans are used therapeutically as plasma volume expanders and anticoagulants. They are also commonly used in biological experimentation and in industry for a wide variety of purposes.
Layers of lipid molecules which are two molecules thick. Bilayer systems are frequently studied as models of biological membranes.
The process of generating three-dimensional images by electronic, photographic, or other methods. For example, three-dimensional images can be generated by assembling multiple tomographic images with the aid of a computer, while photographic 3-D images (HOLOGRAPHY) can be made by exposing film to the interference pattern created when two laser light sources shine on an object.
In statistics, a technique for numerically approximating the solution of a mathematical problem by studying the distribution of some random variable, often generated by a computer. The name alludes to the randomness characteristic of the games of chance played at the gambling casinos in Monte Carlo. (From Random House Unabridged Dictionary, 2d ed, 1993)
Uptake of substances through the SKIN.
The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.
Physical motion, i.e., a change in position of a body or subject as a result of an external force. It is distinguished from MOVEMENT, a process resulting from biological activity.
Colloids with a solid continuous phase and liquid as the dispersed phase; gels may be unstable when, due to temperature or other cause, the solid phase liquefies; the resulting colloid is called a sol.
Microscopy of specimens stained with fluorescent dye (usually fluorescein isothiocyanate) or of naturally fluorescent materials, which emit light when exposed to ultraviolet or blue light. Immunofluorescence microscopy utilizes antibodies that are labeled with fluorescent dye.
Any visible result of a procedure which is caused by the procedure itself and not by the entity being analyzed. Common examples include histological structures introduced by tissue processing, radiographic images of structures that are not naturally present in living tissue, and products of chemical reactions that occur during analysis.
The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.
Fluids composed mainly of water found within the body.
Interstitial space between cells, occupied by INTERSTITIAL FLUID as well as amorphous and fibrous substances. For organisms with a CELL WALL, the extracellular space includes everything outside of the CELL MEMBRANE including the PERIPLASM and the cell wall.
A phthalic indicator dye that appears yellow-green in normal tear film and bright green in a more alkaline medium such as the aqueous humor.
An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.
Transmission of energy or mass by a medium involving movement of the medium itself. The circulatory movement that occurs in a fluid at a nonuniform temperature owing to the variation of its density and the action of gravity. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed; Webster, 10th ed)
A family of spiro(isobenzofuran-1(3H),9'-(9H)xanthen)-3-one derivatives. These are used as dyes, as indicators for various metals, and as fluorescent labels in immunoassays.
The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
Lipids, predominantly phospholipids, cholesterol and small amounts of glycolipids found in membranes including cellular and intracellular membranes. These lipids may be arranged in bilayers in the membranes with integral proteins between the layers and peripheral proteins attached to the outside. Membrane lipids are required for active transport, several enzymatic activities and membrane formation.
Statistical formulations or analyses which, when applied to data and found to fit the data, are then used to verify the assumptions and parameters used in the analysis. Examples of statistical models are the linear model, binomial model, polynomial model, two-parameter model, etc.
Any of various diseases affecting the white matter of the central nervous system.
Heavily myelinated fiber bundle of the TELENCEPHALON projecting from the hippocampal formation to the HYPOTHALAMUS. Some authorities consider the fornix part of the LIMBIC SYSTEM. The fimbria starts as a flattened band of axons arising from the subiculum and HIPPOCAMPUS, which then thickens to form the fornix.
A synthetic phospholipid used in liposomes and lipid bilayers for the study of biological membranes.
The property of emitting radiation while being irradiated. The radiation emitted is usually of longer wavelength than that incident or absorbed, e.g., a substance can be irradiated with invisible radiation and emit visible light. X-ray fluorescence is used in diagnosis.
A relatively common sequela of blunt head injury, characterized by a global disruption of axons throughout the brain. Associated clinical features may include NEUROBEHAVIORAL MANIFESTATIONS; PERSISTENT VEGETATIVE STATE; DEMENTIA; and other disorders.
The characteristic three-dimensional shape of a molecule.
Derivatives of phosphatidic acids in which the phosphoric acid is bound in ester linkage to a choline moiety. Complete hydrolysis yields 1 mole of glycerol, phosphoric acid and choline and 2 moles of fatty acids.
Condition of having pores or open spaces. This often refers to bones, bone implants, or bone cements, but can refer to the porous state of any solid substance.
A light microscopic technique in which only a small spot is illuminated and observed at a time. An image is constructed through point-by-point scanning of the field in this manner. Light sources may be conventional or laser, and fluorescence or transmitted observations are possible.
Fluorescent probe capable of being conjugated to tissue and proteins. It is used as a label in fluorescent antibody staining procedures as well as protein- and amino acid-binding techniques.
Relating to the size of solids.
The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.
Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.
A chemical system that functions to control the levels of specific ions in solution. When the level of hydrogen ion in solution is controlled the system is called a pH buffer.
Increased intracellular or extracellular fluid in brain tissue. Cytotoxic brain edema (swelling due to increased intracellular fluid) is indicative of a disturbance in cell metabolism, and is commonly associated with hypoxic or ischemic injuries (see HYPOXIA, BRAIN). An increase in extracellular fluid may be caused by increased brain capillary permeability (vasogenic edema), an osmotic gradient, local blockages in interstitial fluid pathways, or by obstruction of CSF flow (e.g., obstructive HYDROCEPHALUS). (From Childs Nerv Syst 1992 Sep; 8(6):301-6)
A comprehensive map of the physical interconnections of an organism's neural networks. This modular organization of neuronal architecture is believed to underlie disease mechanisms and the biological development of the CENTRAL NERVOUS SYSTEM.
Artificial, single or multilaminar vesicles (made from lecithins or other lipids) that are used for the delivery of a variety of biological molecules or molecular complexes to cells, for example, drug delivery and gene transfer. They are also used to study membranes and membrane proteins.
Characteristics or attributes of the outer boundaries of objects, including molecules.
A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.
Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.
Neoplasms of the intracranial components of the central nervous system, including the cerebral hemispheres, basal ganglia, hypothalamus, thalamus, brain stem, and cerebellum. Brain neoplasms are subdivided into primary (originating from brain tissue) and secondary (i.e., metastatic) forms. Primary neoplasms are subdivided into benign and malignant forms. In general, brain tumors may also be classified by age of onset, histologic type, or presenting location in the brain.
Stable elementary particles having the smallest known positive charge, found in the nuclei of all elements. The proton mass is less than that of a neutron. A proton is the nucleus of the light hydrogen atom, i.e., the hydrogen ion.
Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.
The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)
Thin layers of tissue which cover parts of the body, separate adjacent cavities, or connect adjacent structures.
A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)
Devices or objects in various imaging techniques used to visualize or enhance visualization by simulating conditions encountered in the procedure. Phantoms are used very often in procedures employing or measuring x-irradiation or radioactive material to evaluate performance. Phantoms often have properties similar to human tissue. Water demonstrates absorbing properties similar to normal tissue, hence water-filled phantoms are used to map radiation levels. Phantoms are used also as teaching aids to simulate real conditions with x-ray or ultrasonic machines. (From Iturralde, Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990)

A processive single-headed motor: kinesin superfamily protein KIF1A. (1/5959)

A single kinesin molecule can move "processively" along a microtubule for more than 1 micrometer before detaching from it. The prevailing explanation for this processive movement is the "walking model," which envisions that each of two motor domains (heads) of the kinesin molecule binds coordinately to the microtubule. This implies that each kinesin molecule must have two heads to "walk" and that a single-headed kinesin could not move processively. Here, a motor-domain construct of KIF1A, a single-headed kinesin superfamily protein, was shown to move processively along the microtubule for more than 1 micrometer. The movement along the microtubules was stochastic and fitted a biased Brownian-movement model.  (+info)

Transport of solutes through cartilage: permeability to large molecules. (2/5959)

A review of the transport of solutes through articular cartilage is given, with special reference to the effect of variations in matrix composition. Some physiological implications of our findings are discussed. Also, results of an experimental study of the permeability of articular cartilage to large globular proteins are presented. Because of the very low partition coefficients of large solutes between cartilage and an external solution new experimental techniques had to be devised, particularly for the study of diffusion. The partition coefficients of solutes were found to decrease very steeply with increase in size, up to serum albumin. There was, however, no further decrease for IGG. The diffusion coefficient of serum albumin in cartilage was relatively high (one quarter of the value in aqueous solution). These two facts taken together suggest that there may be a very small fraction of relatively large pores in cartilage through which the transport of large molecules is taking place. The permeability of cartilage to large molecules is extremely sensitive to variations in the glycosaminoglycan content: for a threefold increase in the latter there is a hundredfold decrease in the partition coefficient. For cartilage of fixed charge density around 0-19 m-equiv/g, there is no penetration at all of globular proteins of size equal to or larger than serum albumin.  (+info)

Increased lipophilicity and subsequent cell partitioning decrease passive transcellular diffusion of novel, highly lipophilic antioxidants. (3/5959)

Oxidative stress is considered a cause or propagator of acute and chronic disorders of the central nervous system. Novel 2, 4-diamino-pyrrolo[2,3-d]pyrimidines are potent inhibitors of iron-dependent lipid peroxidation, are cytoprotective in cell culture models of oxidative injury, and are neuroprotective in brain injury and ischemia models. The selection of lead candidates from this series required that they reach target cells deep within brain tissue in efficacious amounts after oral dosing. A homologous series of 26 highly lipophilic pyrrolopyrimidines was examined using cultured cell monolayers to understand the structure-permeability relationship and to use this information to predict brain penetration and residence time. Pyrrolopyrimidines were shown to be a more permeable structural class of membrane-interactive antioxidants where transepithelial permeability was inversely related to lipophilicity or to cell partitioning. Pyrrole substitutions influence cell partitioning where bulky hydrophobic groups increased partitioning and decreased permeability and smaller hydrophobic groups and more hydrophilic groups, especially those capable of weak hydrogen bonding, decreased partitioning, and increased permeability. Transmonolayer diffusion for these membrane-interactive antioxidants was limited mostly by desorption from the receiver-side membrane into the buffer. Thus, in this case, these in vitro cell monolayer models do not adequately mimic the in vivo situation by underestimating in vivo bioavailability of highly lipophilic compounds unless acceptors, such as serum proteins, are added to the receiving buffer.  (+info)

Novel, highly lipophilic antioxidants readily diffuse across the blood-brain barrier and access intracellular sites. (4/5959)

In an accompanying article, an in vitro assay for permeability predicts that membrane-protective, antioxidant 2,4-diamino-pyrrolo[2, 3-d]pyrimidines should have improved blood-brain barrier (BBB) permeation over previously described lipophilic antioxidants. Using a first-pass extraction method and brain/plasma quantification, we show here that two of the pyrrolopyrimidines, one of which is markedly less permeable, readily partition into rat brain. The efficiency of extraction was dependent on serum protein binding, and in situ efflux confirms the in vitro data showing that PNU-87663 is retained in brain longer than PNU-89843. By exploiting inherent fluorescence properties of PNU-87663, its distribution within brain and within cells in culture was demonstrated using confocal scanning laser microscopy. PNU-87663 rapidly partitioned into the cell membrane and equilibrates with cytoplasmic compartments via passive diffusion. Although partitioning of PNU-87663 favors intracytoplasmic lipid storage droplets, the compound was readily exchangeable as shown by efflux of compound from cells to buffer when protein was present. The results demonstrated that pyrrolopyrimidines were well suited for quickly accessing target cells within the central nervous system as well as in other target tissues.  (+info)

Free energy landscapes of encounter complexes in protein-protein association. (5/5959)

We report the computer generation of a high-density map of the thermodynamic properties of the diffusion-accessible encounter conformations of four receptor-ligand protein pairs, and use it to study the electrostatic and desolvation components of the free energy of association. Encounter complex conformations are generated by sampling the translational/rotational space of the ligand around the receptor, both at 5-A and zero surface-to-surface separations. We find that partial desolvation is always an important effect, and it becomes dominant for complexes in which one of the reactants is neutral or weakly charged. The interaction provides a slowly varying attractive force over a small but significant region of the molecular surface. In complexes with no strong charge complementarity this region surrounds the binding site, and the orientation of the ligand in the encounter conformation with the lowest desolvation free energy is similar to the one observed in the fully formed complex. Complexes with strong opposite charges exhibit two types of behavior. In the first group, represented by barnase/barstar, electrostatics exerts strong orientational steering toward the binding site, and desolvation provides some added adhesion within the local region of low electrostatic energy. In the second group, represented by the complex of kallikrein and pancreatic trypsin inhibitor, the overall stability results from the rather nonspecific electrostatic attraction, whereas the affinity toward the binding region is determined by desolvation interactions.  (+info)

pH-dependent conformational change of gastric mucin leads to sol-gel transition. (6/5959)

We present dynamic light scattering (DLS) and hydrophobic dye-binding data in an effort to elucidate a molecular mechanism for the ability of gastric mucin to form a gel at low pH, which is crucial to the barrier function of gastric mucus. DLS measurements of dilute mucin solutions were not indicative of intermolecular association, yet there was a steady fall in the measured diffusion coefficient with decreasing pH, suggesting an apparent increase in size. Taken together with the observed rise in depolarized scattering ratio with decreasing pH, these results suggest that gastric mucin undergoes a conformational change from a random coil at pH >/= 4 to an anisotropic, extended conformation at pH < 4. The increased binding of mucin to hydrophobic fluorescent with decreasing pH indicates that the change to an extended conformation is accompanied by exposure of hydrophobic binding sites. In concentrated mucin solutions, the structure factor S(q, t) derived from DLS measurements changed from a stretched exponential decay at pH 7 to a power-law decay at pH 2, which is characteristic of a sol-gel transition. We propose that the conformational change facilitates cross-links among mucin macromolecules through hydrophobic interactions at low pH, which in turn leads to a sol-gel transition when the mucin solution is sufficiently concentrated.  (+info)

Structural dynamics of ligand diffusion in the protein matrix: A study on a new myoglobin mutant Y(B10) Q(E7) R(E10). (7/5959)

A triple mutant of sperm whale myoglobin (Mb) [Leu(B10) --> Tyr, His(E7) --> Gln, and Thr(E10) --> Arg, called Mb-YQR], investigated by stopped-flow, laser photolysis, crystallography, and molecular dynamics (MD) simulations, proved to be quite unusual. Rebinding of photodissociated NO, O2, and CO from within the protein (in a "geminate" mode) allows us to reach general conclusions about dynamics and cavities in proteins. The 3D structure of oxy Mb-YQR shows that bound O2 makes two H-bonds with Tyr(B10)29 and Gln(E7)64; on deoxygenation, these two residues move toward the space occupied by O2. The bimolecular rate constant for NO binding is the same as for wild-type, but those for CO and O2 binding are reduced 10-fold. While there is no geminate recombination with O2 and CO, geminate rebinding of NO displays an unusually large and very slow component, which is pretty much abolished in the presence of xenon. These results and MD simulations suggest that the ligand migrates in the protein matrix to a major "secondary site," located beneath Tyr(B10)29 and accessible via the motion of Ile(G8)107; this site is different from the "primary site" identified by others who investigated the photolyzed state of wild-type Mb by crystallography. Our hypothesis may rationalize the O2 binding properties of Mb-YQR, and more generally to propose a mechanism of control of ligand binding and dissociation in hemeproteins based on the dynamics of side chains that may (or may not) allow access to and direct temporary sequestration of the dissociated ligand in a docking site within the protein. This interpretation suggests that very fast (picosecond) fluctuations of amino acid side chains may play a crucial role in controlling O2 delivery to tissue at a rate compatible with physiology.  (+info)

The forward rate of binding of surface-tethered reactants: effect of relative motion between two surfaces. (8/5959)

The reaction of molecules confined to two dimensions is of interest in cell adhesion, specifically for the reaction between cell surface receptors and substrate-bound ligand. We have developed a model to describe the overall rate of reaction of species that are bound to surfaces under relative motion, such that the Peclet number is order one or greater. The encounter rate between reactive species is calculated from solution of the two-dimensional convection-diffusion equation. The probability that each encounter will lead to binding depends on the intrinsic rate of reaction and the encounter duration. The encounter duration is obtained from the theory of first passage times. We find that the binding rate increases with relative velocity between the two surfaces, then reaches a plateau. This plateau indicates that the increase in the encounter rate is counterbalanced by the decrease in the encounter duration as the relative velocity increases. The binding rate is fully described by two dimensionless parameters, the Peclet number and the Damkohler number. We use this model to explain data from the cell adhesion literature by incorporating these rate laws into "adhesive dynamics" simulations to model the binding of a cell to a surface under flow. Leukocytes are known to display a "shear threshold effect" when binding selectin-coated surfaces under shear flow, defined as an increase in bind rate with shear; this effect, as calculated here, is due to an increase in collisions between receptor and ligand with increasing shear. The model can be used to explain other published data on the effect of wall shear rate on the binding of cells to surfaces, specifically the mild decrease in binding within a fixed area with increasing shear rate.  (+info)

0028]In one embodiment of the invention, the binder resin is carbonized to be electrically conductive. In another variation of that embodiment, the binder resin is not carbonized thereby acting simply as a solid filler In either of these variations, the binder resin may be present in a first amount such that the gas diffusion layer has a ratio of water vapor free diffusion coefficient to water vapor effective diffusion coefficient greater than 1.5. In another variation, the ratio of the water vapor free diffusion coefficient to the effective diffusion coefficient may be less than or equal to 20. In yet another variation, the ratio of the water vapor free diffusion coefficient to the effective diffusion coefficient is from 3 to 15. In still another variation, the ratio of the water vapor free diffusion coefficient to the effective diffusion coefficient is from 10 to 12. In this context, the water vapor free diffusion coefficient is the diffusion coefficient of the water vapor in the gas mixture ...
GATICA, Y.A.; SALINAS, C. H. and ANANIAS, R.A.. Modeling conventional one-dimensional drying of radiata pine based on the effective diffusion coefficient. Lat. Am. appl. res. [online]. 2011, vol.41, n.2, pp. 183-189. ISSN 0327-0793.. We modeled conventional one-dimensional drying of radiata pine (Pinus radiata) wood using the concept of effective diffusion. The experimentally determined effective diffusion coefficients for the radial and tangential directions were related exponentially to the moisture content. These coefficients were characterized by two parameters that were determined through optimization within the context of an inverse problem. One-dimensional drying experiments were carried out under constant drying 44/36 (°C/°C) in order to determine transitory spatial distributions of moisture and drying curves, which were used then to determine the model parameters and validate the model. The mathematical model consisted of a partial, non-linear, differential equation of the second ...
A new method for determining the gas effective diffusion coefficient in brine-saturated porous rocks was developed on the basis of the radial diffusion model. T...
[email protected] Abstract - We modeled conventional one-dimensional drying of radiata pine (Pinus radiata) wood using the concept of effective diffusion. The experimentally determined effective diffusion coefficients for the radial and tangential directions were related exponentially to the moisture content. These coefficients were characterized by two parameters that were determined through optimization within the context of an inverse problem. One-dimensional drying experiments were carried out under constant drying 44/36 (°C/°C) in order to determine transitory spatial distributions of moisture and drying curves, which were used then to determine the model parameters and validate the model. The mathematical model consisted of a partial, non-linear, differential equation of the second order and was characterized by coefficients that varied exponentially with moisture content; this later was integrated numerically through the finite volume method. Simulations of the transitory distribution ...
In this article, we discuss the theoretical background for diffusion weighted imaging and diffusion tensor imaging. Molecular diffusion is a random process involving thermal Brownian motion. In biological tissues, the underlying microstructures restrict the diffusion of water molecules, making diffusion directionally dependent. Water diffusion in tissue is mathematically characterized by the diffusion tensor, the elements of which contain information about the magnitude and direction of diffusion and is a function of the coordinate system. Thus, it is possible to generate contrast in tissue based primarily on diffusion effects. Expressing diffusion in terms of the measured diffusion coefficient (eigenvalue) in any one direction can lead to errors. Nowhere is this more evident than in white matter, due to the preferential orientation of myelin fibers. The directional dependency is removed by diagonalization of the diffusion tensor, which then yields a set of three eigenvalues and eigenvectors, ...
Premier atelier de lERC « Reaction-Diffusion Equations, Propagations and Modelling » Journées détude organisées par Henri Berestycki et Jean-Michel Roquejoffre EHESS, 24-25 septembre 2013 Séquence 1: Hiroshi Matano (University of Tokyo) Spreading speed for some two-component reaction-diffusion system In this talk I will discuss the spreading properties of solutions of a prey-predator type reaction-diffusion system. This system belongs to the class of reaction-diffusion systems for which the comparison principle does not hold. For such class of systems, little has been know about the spreading properties of the solutions. Here, by a spreading property, we mean the way the solution propagates when starting from compactly supported initial data. We show that propagation of both the prey and the predator occur with a definite spreading speed. Furthermore, quite intriguingly, the spreading speed of the prey and that of the predator are different in some
Author(s): Digiacomo, Luca; Digman, Michelle A; Gratton, Enrico; Caracciolo, Giulio | Abstract: Fluorescence microscopy and spectroscopy techniques are commonly used to investigate complex and interacting biological systems (e.g. proteins and nanoparticles in living cells), since these techniques can explore intracellular dynamics with high time resolution at the nanoscale. Here we extended one of the Image Correlation Spectroscopy (ICS) methods, i.e. the image Mean Square Displacement, in order to study 2-dimensional diffusive and flow motion in confined systems, whose driving speed is uniformly distributed in a variable angular range. Although these conditions are not deeply investigated in the current literature, they can be commonly found in the intracellular trafficking of nanocarriers, which diffuse in the cytoplasm and/or may move along the cytoskeleton in different directions. The proposed approach could reveal the underlying systems symmetry using methods derived from fluorescence correlation
Brownian diffusion is the motion of one or more solute molecules in a sea of very many, much smaller solvent molecules. Its importance today owes mainly to cellular chemistry, since Brownian diffusion is one of the ways in which key reactant molecules move about inside a living cell. This book focuses on the four simplest models of Brownian diffusion: the classical Fickian model, the Einstein model, the discrete-stochastic (cell-jumping) model, and the Langevin model.
VV B337 Title: Relationships between several particle-based stochastic reaction-diffusion models. Abstract: Particle-based stochastic reaction-diffusion models have recently been used to study a number of problems in cell biology. These methods are of interest when both noise in the chemical reaction process and the explicit motion of molecules are important. Several different mathematical models have been used, some spatially-continuous and others lattice-based. In the former molecules usually move by Brownian Motion, and may react when approaching each other. For the latter molecules undergo continuous time random-walks, and usually react with fixed probabilities per unit time when located at the same lattice site. As motivation, we will begin with a brief discussion of the types of biological problems we are studying and how we have used stochastic reaction-diffusion models to gain insight into these systems. We will then introduce several of the stochastic reaction-diffusion models, ...
The present invention relates to systems and methods for minimizing or eliminating diffusion effects. Diffused regions of a segmented flow of multiple, miscible fluid species may be vented off to a waste channel, and non-diffused regions of fluid may be preferentially pulled off the channel that contains the segmented flow. Multiple fluid samples that are not contaminated via diffusion may be collected for analysis and measurement in a single channel. The systems and methods for minimizing or eliminating diffusion effects may be used to minimize or eliminate diffusion effects in a microfluidic system for monitoring the amplification of DNA molecules and the dissociation behavior of the DNA molecules.
TY - BOOK. T1 - Recent progress on reaction-diffusion systems and viscosity solutions. AU - Du, Yihong. AU - Ishii, Hitoshi. AU - Lin, Wei Yueh. PY - 2009/1/1. Y1 - 2009/1/1. N2 - This book consists of survey and research articles expanding on the theme of the International Conference on Reaction-Diffusion Systems and Viscosity Solutions, held at Providence University, Taiwan, during January 3-6, 2007. It is a carefully selected collection of articles representing the recent progress of some important areas of nonlinear partial differential equations. The book is aimed for researchers and postgraduate students who want to learn about or follow some of the current research topics in nonlinear partial differential equations. The contributors consist of international experts and some participants of the conference, including Nils Ackermann (Mexico), Chao-Nien Chen (Taiwan), Yihong Du (Australia), Alberto Farina (France), Hitoshi Ishii (Japan), N Ishimura (Japan), Shigeaki Koike (Japan), Chu-Pin ...
The role of di-boron diffusion in evolution of B diffusion profiles has been investigated. We find that boron pair (B[sub s]â€B[sub i]) diffusion can become as important as boron-interstitial pair (B[sub s]â€Si[sub i]) diffusion when both boron concentration and annealing temperature are very high, leading to concentration-dependent B diffusion. Our simulated B diffusion profiles with dramatic shouldering are in excellent agreement with experimental ones reported by Schroer et al. [Appl. Phys. Lett. 74, 3996 (1999)] for high-temperature (≈1200 °C) postimplantion annealing of ultralow-energy (≈500 eV) implanted high-concentration (>10[sup 19] cm[sup -3]) boron in silicon. © 2003 American Institute of Physics ...
TY - JOUR. T1 - Stability of stationary solutions for a scalar non-local reaction-diffusion equation. AU - Frettas, Pedro. PY - 1995/11. Y1 - 1995/11. N2 - The stability of stationary solutions of the non-local reaction-diffusion equation with homogeneous Neumann boundary conditions is studied. Depending on a, bounds on the dimension of the unstable manifold of a stationary solution are given. In particular, it is shown that only constant or monotone stationary solutions may be stable. For the specific case of a cubic like f, the existence of a Hopf bifurcation is proven. Finally, some related equations are discussed. © 1995 Oxford University Press.. AB - The stability of stationary solutions of the non-local reaction-diffusion equation with homogeneous Neumann boundary conditions is studied. Depending on a, bounds on the dimension of the unstable manifold of a stationary solution are given. In particular, it is shown that only constant or monotone stationary solutions may be stable. For the ...
TY - JOUR. T1 - Protein diffusion and long-term adsorption states at charged solid surfaces. AU - Kubiak-Ossowska, Karina. AU - Mulheran, Paul A. PY - 2012/11/6. Y1 - 2012/11/6. N2 - The diffusion pathways of lysozyme adsorbed to a model charged ionic surface are studied using fully atomistic steered molecular dynamics simulation. The simulations start from existing protein adsorption trajectories, where it has been found that one particular residue, Arg128 at the N,C-terminal face, plays a crucial role in anchoring the lysozyme to the surface [ Langmuir 2010 , 26 , 15954 - 15965 ]. We first investigate the desorption pathway for the protein by pulling the Arg128 side chain away from the surface in the normal direction, and its subsequent readsorption, before studying diffusion pathways by pulling the Arg128 side chain parallel to the surface. We find that the orientation of this side chain plays a decisive role in the diffusion process. Initially, it is oriented normal to the surface, aligning ...
PAHs are the reactive toxic chemical compounds which are present as environmental pollutants. These reactive compounds not only diffuse through the membranes of the cell but also partition into the membranes. They react with the DNA of the cell giving rise to toxicity and may cause cancer. To understand the cellular behavior of these foreign compounds, a mathematical model including the reaction-diffusion system and partitioning phenomenon has been developed. In order to reduce the complex structure of the cytoplasm due to the presence of many thin membranes, and to make the model less computationally expensive and numerically treatable, homogenization techniques have been used. The resulting complex system of PDEs generated from the model is implemented in Comsol Multiphysics. The numerical results obtained from the model show a nice agreement with the in vitro cell experimental results. Then the model was reduced to a system of ODEs, a compartment model (CM). The quantitative analysis of the ...
H. Lekkerkerker (Debye Research Institute, The Netherlands). You described the use of optical tweezers to drag a colloidal particle through a nematic liquid and measure from the velocity the viscosity. Would the measurement of the mean square displacement of a particle fixed in a trap be viable and perhaps allow a more detailed analysis?. H. Gleeson. A measurement of the mean square displacement of the particle would be expected to show anisotropy in the viscosity. However, additional complications might arise from the optical anisotropy of the medium in determining the mean square displacement of the particle in the trap by interferometry of the scattered light. Furthermore, this method provides only a passive measurement of the dynamics within the system. Our measurement evaluates the effective viscosity under flow conditions and is comparable to the theory of Stark & Ventzki (2001) and Stark et al. (2003).. V. Götz (Department of Chemistry, University of York, UK). Is the direction of ...
Spatially fractional order diffusion equations are generalizations of classical diffusion equations which are increasingly used in modeling practical super diffusive problems in fluid flow, finance and others areas of application. This paper presents the analytical solutions of the space fractional diffusion equations by Adomians decomposition method (ADM). By using initial conditions, the explicit solutions of the equations have been presented in the closed form. Two examples, the first one is one-dimensional and the second one is two-dimensional fractional diffusion equation, are presented to show the application of the present techniques. The present method performs extremely well in terms of efficiency and simplicity.
The sheet-like endoplasmic reticulum (ER) of eukaryotic cells has been found to be riddled with spiral dislocations, known as Terasaki ramps, in the vicinity of which the doubled bilayer membranes which make up ER sheets can be approximately modeled by helicoids. Here we analyze diffusion on a surface with locally helicoidal topological dislocations, and use the results to argue that the Terasaki ramps facilitate a highly efficient transport of water-soluble molecules within the lumen of the endoplasmic reticulum.. ...
A coated substrate and a method of forming a diffusion barrier coating system between a substrate and a MCrAl coating, including a diffusion barrier coating deposited onto at least a portion of a substrate surface, wherein the diffusion barrier coating comprises a nitride, oxide or carbide of one or more transition metals and/or metalloids and a MCrAl coating, wherein M includes a transition metal or a metalloid, deposited on at least a portion of the diffusion barrier coating, wherein the diffusion barrier coating restricts the inward diffusion of aluminum of the MCrAl coating into the substrate.
Covering both basic and advanced thermodynamic and phase principles, as well as providing stability diagrams relevant for diffusion studies, Thermodynamics, Diffusion and the Kirkendall Effect in Solids maximizes reader insights into Ficks laws of diffusion, atomic mechanisms, interdiffusion, intrinsic diffusion, tracer diffusion and the Kirkendall effect. Recent advances in the area of interdiffusion will be introduced, while the many practical examples and large number of illustrations given will serve to aid researches working in this area in learning the practical evaluation of various diffusion parameters from experimental results. With a unique approach to the two main focal points in solid state transformations, energetics (thermodynamics) and kinetics (interdiffusion) are extensively studied and their combined use in practise is discussed. Recent developments in the area of Kirkendall effect, grain boundary diffusion and multicomponent diffusion are also covered extensively. This book ...
We study systems of two nonlinear reaction-diffusion partial differential equations undergoing diffusion driven instability. Such systems may have spatially inhomogeneous stationary solutions called Turing patterns. These solutions are typically non-unique and it is not clear how many of them exists. Since there are no analytical results available, we look for the number of distinct stationary solutions numerically. As a typical example, we investigate the reaction-diffusion system designed to model coat patterns in leopard and jaguar ...
The purpose of this report is to investigate possible enhancement of diffusion rates in ceramic oxides through imposed stress or the presence of grain boundaries. Diffusion rates of impurity cations such as Ni(2+), Co(2+), Zn(2+), or Ca(2+) have been investigated in single crystal MgO subjected to imposed stress and also in bicrystal and polycrystalline MgO. The solute oxides are supplied as either an initial thin surface film, or through continuous deposition from the vapor phase. Diffusion coefficients are determined from concentration profiles obtained with the aid of electron microbeam probe spectroscopy. Diffusion rates of Ni(2+) in directions normal to the tension and compression surfaces of single crystal MgO subjected to fourpoint loading are not, within experimental error, enhanced above normal lattice diffusion rates for loads up to 5000 psi. Diffusion couples have now been sucessfully prepared from MgO subjected to higher compressive loads of up to 15,000 psi and are currently undergoing
I have another question related to the longitudinal diffusion. I would like to monitor the ion concentration change incurred by longitudinal diffusion of specific ion to and from the specific section. If I only had longitudinal diffusion mechanism in this section, I would simply compute this change by taking the difference between ion concentrations at two edges of the section. But, I have some transmembrane ion exchange mechanisms (such as channels, pumps, etc.) in this section as well....How can I see how much ion concentration change is specifically due to the diffusion of ion from one of this sections neighboring sections? Is there any built-in variable that I can access to view the diffusional current ...
Using Embedded-atom-method (EAM) potential, we have performed in detail molecular dynamics studies on a Fe adatom adsorption and diffusion dynamics on three low miller index surfaces, Fe (110), Fe (001), and Fe (111). Our results present that adatom adsorption energies and diffusion barriers on these surfaces have similar monotonic trend: adsorption energies, Ea(110) Ea(001) Ea(111), diffusion barriers, Ed(110) Ed(001) Ed(111). On the Fe (110) surface, adatom simple jump is the main diffusion mechanism with relatively low energy barrier; nevertheless, adatoms exchange with surface atoms play a dominant role in surface diffusion on the Fe (001).
A diffusion barrier layer comprising TiNxBy is disclosed for protection of gate oxide layers in integrated transistors. The diffusion barrier layer can be fabricated by first forming a TiN layer and then incorporating boron into the TiN layer. The diffusion barrier layer can also be fabricated by forming a TiNxBy layer using a TDMAT process including boron. The diffusion barrier layer can also be fabricated by forming a TiNxBy layer using a CVD process. The diffusion barrier layer is of particular utility in conjunction with tungsten or tungsten silicide conductive layers formed by CVD.
TY - JOUR. T1 - Diffusion Coefficient Measurement of Cu in Liquid Sn by Long Capillary Method. AU - Uchida, Y.. AU - Masaki, T.. PY - 2010/9/22. Y1 - 2010/9/22. M3 - Article. JO - 8th Japan-China-Korea Workshop on Microgravity Sciences. JF - 8th Japan-China-Korea Workshop on Microgravity Sciences. ER - ...
TY - JOUR. T1 - Nitric oxide uptake by erythrocytes is primarily limited by extracellular diffusion not membrane resistance. AU - Liu, Xiaoping. AU - Samouilov, Alexandre. AU - Lancaster, Jack R.. AU - Zweier, Jay L.. PY - 2002/7/19. Y1 - 2002/7/19. N2 - The process of NO transfer into erythrocytes (RBCs) is of critical biological importance because it regulates the bioavailability and diffusional distance of endothelial-derived NO. It has been reported that the rate of NO reaction with oxyhemoglobin (Hb) within RBCs is nearly three orders of magnitude slower than that by equal amounts of free oxyhemoglobin. Consistent with early studies on oxygen uptake by RBCs, the process of extracellular diffusion was reported to explain this much lower NO uptake by RBC encapsulated Hb (Liu, X., Miller, M. J., Joshi, M. S., Sadowska-Krowicka, H., Clark, D. A., and Lancaster, J. R., Jr. (1998) J. Biol. Chem. 273, 18709-18713). However, it was subsequently proposed that the RBC membrane provides the main ...
Diffusion in lipid membranes is an essential component of many cellular process and fluorescence a method of choice to study membrane dynamics. The goal of this work was to directly compare two common fluorescence methods, line-scanning fluorescence correlation spectroscopy and single-particle tracking, to observe the diffusion of a fluorescent lipophilic dye, DiD, in a complex five-component mitochondria-like solid-supported lipid bilayer. We measured diffusion coefficients of \(D_{\text{FCS}} \sim\) 3 \(μ\text{m}^2\cdot\text{s}^{-1}\) and \(D_{\text{SPT}} \sim\) 2 \( μ\text{m}^2\cdot\text{s}^{-1}\), respectively. These comparable, yet statistically different values are used to highlight the main message of the paper, namely that the two considered methods give access to distinctly different dynamic ranges: \(D \gtrsim\) 1 \(μ\text{m}^2\cdot\text{s}^{-1}\) for FCS and \(D \lesssim\) 5 \(μ\text{m}^2\cdot\text{s}^{-1}\) for SPT (with standard imaging conditions). In the context of membrane diffusion,
Confocal or multi-photon laser scanning microscopes are convenient tools to perform FRAP diffusion measurements. Despite its popularity, accurate FRAP remains often challenging since current methods are either limited to relatively large bleach regions or can be complicated for non-specialists. In order to bring reliable quantitative FRAP measurements to the broad community of laser scanning microscopy users, here we have revised FRAP theory and present a new pixel based FRAP method relying on the photo bleaching of rectangular regions of any size and aspect ratio. The method allows for fast and straightforward quantitative diffusion measurements due to a closed-form expression for the recovery process utilizing all available spatial and temporal data. After a detailed validation, its versatility is demonstrated by diffusion studies in heterogeneous biopolymer mixtures.. ©2010 Optical Society of America. Full Article , PDF Article ...
Molecular diffusion, often called simply diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of the particles. Diffusion explains the net flux of molecules from a region of higher concentration to one of lower concentration, but it is important to note that diffusion also occurs when there is no concentration gradient. The result of diffusion is a gradual mixing of material. In a phase with uniform temperature, absent external net forces acting on the particles, the diffusion process will eventually result in complete mixing.. Diffusive equilibrium is reached when the concentrations of the diffusing substance in the two compartments becomes equal.. Consider two systems; S1 and S2 at the same temperature and capable of exchanging particles. If there is a change in the potential energy of a system; for example μ1>μ2 (μ is Chemical potential) an ...
Abstract The VAPEX analytical model is extended to cover situations when diffusion coefficients are dependent on concentration due to the extreme viscosity reduction with solvent dissolution into bitumen. The new analytical model covers such situati
Managing an invasive species is particularly challenging as little is generally known about the species biological characteristics in its new habitat. In practice, removal of individuals often starts before the species is studied to provide the information that will later improve control. Therefore, the locations and the amount of control have to be determined in the face of great uncertainty about the species characteristics and with a limited amount of resources. We propose framing spatial control as a linear programming optimization problem. This formulation, paired with a discrete reaction-diffusion model, permits calculation of an optimal control strategy that minimizes the remaining number of invaders for a fixed cost or that minimizes the control cost for containment or protecting specific areas from invasion. We propose computing the optimal strategy for a range of possible model parameters, representing current uncertainty on the possible invasion scenarios. Then, a best strategy can be
The purpose of our study was to determine the incidence, causes, and reversibility of leukoencephalopathies demonstrating confluent areas of restricted diffusion on magnetic resonant imaging (DWI+LE). We hypothesized DWI+LE would have a low incidence, and be primarily caused by toxic exposures. We performed a logic sentence based search of the Yale-New Haven MRI database to select for reports indicating restricted diffusion within the cerebral white matter. We examined patients neuroimaging studies and medical record. We identified a total of 35 cases of DWI+LE, which resulted in an overall incidence of 0.2% over the five-year period queried. The medical conditions associated with DWI+LE were as follows: toxic exposure (7), hypoxia with concurrent trauma (7), hypoxia with concurrent toxic exposure (4), hypoxia with concurrent metabolic derangements (4), seizure with concurrent metabolic derangements (2), metabolic derangements (2), antiepileptic therapy (2), hypoxia (1), trauma (1), and unknown (5). The
The diffusive arrival of transcription factors at the promoter sites on DNA sets a lower bound on how accurately a cell can regulate its protein levels. Using results from the literature on diffusion-influenced reactions, we derive an analytical expression for the lower bound on the precision of transcriptional regulation. In our theory, transcription factors can perform multiple rounds of one-dimensional (1D) diffusion along the DNA and 3D diffusion in the cytoplasm before binding to the promoter. Comparing our expression for the lower bound on the precision against results from Greens function reaction dynamics simulations shows that the theory is highly accurate under biologically relevant conditions. Our results demonstrate that, to an excellent approximation, the promoter switches between the transcription-factor bound and unbound state in a Markovian fashion. This remains true even in the presence of sliding, i.e., with 1D diffusion along the DNA. This has two important implications: (1)
In a previous study [21], a class of efficient semi-implicit schemes was developed for stiff reaction-diffusion systems. This method which treats linear diffusion terms exactly and nonlinear reaction terms implicitly has excellent stability properties, and its second-order version, with a name IIF2, is linearly unconditionally stable. In this paper, we present another linearly unconditionally stable method that approximates both diffusions and reactions implicitly using a second order Crank-Nicholson scheme. The nonlinear system resulted from the implicit approximation at each time step is solved using a multi-grid method. We compare this method (CN-MG) with IIF2 for their accuracy and efficiency. Numerical simulations demonstrate that both methods are accurate and robust with convergence using even very large size of time steps. IIF2 is found to be more accurate for systems with large diffusion while CN-MG is more efficient when the number of spatial grid points is large.
In this paper we investigate additional regularity properties for global and trajectory attractors of all globally defined weak solutions of semi-linear parabolic differential reaction-diffusion equations with discontinuous nonlinearities, when initial data uτ ∈ L2(Ω). The main contributions in this paper are: (i) sufficient conditions for the existence of a Lyapunov function for all weak solutions of autonomous differential reaction-diffusion equations with discontinuous and multivalued interaction functions; (ii) convergence results for all weak solutions in the strongest topologies; (iii) new structure and regularity properties for global and trajectory attractors. The obtained results allow investigating the long-time behavior of state functions for the following problems: (a) a model of combustion in porous media; (b) a model of conduction of electrical impulses in nerve axons; (c) a climate energy balance model; (d) a parabolic feedback control problem. ...
Aquatic vegetation has major influence on the local water environment, affecting flow velocities and solute mixing. Extensive research has been conducted on the flow characteristics of vegetated areas, but little is known about solute transport. In this study, Laboratory experiments were carried out to investigate how solute transport is affected by emergent and submerged rigid vegetation. Vegetation greatly reduces the mean velocity, especially within the vegetated region. Near the bottom, the solute concentration is greater in the dense vegetation than in the sparse vegetation. The vertical distribution of the solute concentration decreases rapidly with the relative water depth. Generally, the longitudinal and lateral diffusion coefficients are less affected by denser vegetation, but both coefficients are strongly influenced by the relative water depth (submerged vegetation height). A modified function to estimate the longitudinal diffusion coefficients is proposed under both emergent and submerged
Nutrition All living organisms requires energy. They take in nutrition to produce energy, to grow and repair.. Below is an illustration which shows simple diffusion. Simple diffusion is when molecules travel from a place which has a lot of molecules to a place that either lacks or has low amounts of molecules. They do this by travelling down through the membrane until both places have, more or less equal amounts of molecules. Molecules that travel through the simple diffusion method must be nonpolar and they must be small in size. Below is an illustration which shows facilitated diffusion. Facilitated diffusion is different to simple diffusion because the molecules can not travel directly through the membrane. In order to go from a place which has lots of molecules to a place which lacks or doesnt have many molecule, it needs to use a channel. This channel is named a protein channel and it provides the molecules a way of getting through to the membrane.. Below is an illustration that shows ...
We study the existence and stability of spike clusters for biological reaction-diffusion systems with two small diffusion constants. In particular we consider a consumer chain model and the Gierer-Meinhardt system with a precursor gradient. In a spike cluster the spikes converge to the same limiting point. We will present results on the asymptotic behaviour of the spikes including their shapes, positions, and amplitudes. We will also compute the asymptotic behaviour of the eigenvalues. Such systems and their solutions play an important role in biological modelling to account for the bridging of lengthscales, e.g. between genetic, nuclear, intra cellular, cellular and tissue levels, or for the hierarchy of biological processes, e.g. first a large scale structure appears and then it induces patterns on a smaller scale. This is joint work with Juncheng Wei ...
DAB = liquid phase diffusion coefficient (diffusion coefficient of solution A in solution B). MB = molecular weight of solution B. Φ = correlation factor of solution B. T = absolute temperature. μ = viscosity of solution B. VA = molar volume of solution A. Diffusion can be defined as the mixing of two or more substances or the net motion of a substance from a high concentration to a low concentration region.. The diffusion coefficient can be defined as the ratio of the proportion of the substance represented by the diffusion through the unit concentration gradient per unit area per unit time.. ...
In this article we present a system of coupled bulk-surface reaction-diffusion equations on exponentially evolving volumes. Detailed linear stability analysis of the homogeneous steady state is carried out. It turns out that due to the nature of the coupling (linear Robin-type boundary conditions) the characterisation of the dispersion relation in the absence and presence of spatial variation (i.e. diffusion), can be decomposed as a product of the dispersion relation of the bulk and surface models thereby allowing detailed analytical tractability. As a result we state and prove the conditions for diffusion-driven instability for systems of coupled bulk-surface reaction-diffusion equations. Furthermore, we plot explicit evolving parameter spaces for the case of an exponential growth. By selecting parameter values from the parameter spaces, we exhibit pattern formation in the bulk and on the surface in complete agreement with theoretical predictions.. ...
7.7. NUMERICAL METHODS FOR UNSTEADY-STATE MOLECULAR DIFFUSION 7.7A. Introduction Unsteady-state diffusion often occurs in inorganic, organic, and biological solid materials. If the boundary conditions are constant with time ... - Selection from Transport Processes and Separation Process Principles (Includes Unit Operations) Fourth Edition [Book]
Surova Y, Nilsson M, Lampinen B, Lätt J, Hall S, Widner H, van Westen D, Hansson O. Alteration of putaminal fractional anisotropy in Parkinsons disease: a longitudinal diffusion kurtosis imaging study. Neuroradiology. 2018;60 (3) :247-254.
Kilner J, Shen Z, Skinner SJ, 2018, Electrical conductivity and oxygen diffusion behaviour of the (La0.8Sr0.2)0.95CrxFe1-xO3-δ (x=0.3, 0.5 and 0.7) A-site deficient perovskites, Physical Chemistry Chemical Physics, Vol: 20, Pages: 18279-18290, ISSN: 1463-9076 Lanthanum strontium chromite ferrite ((La0.8Sr0.2)0.95CrxFe1−xO3−δ, LSCrF) pellets with 5% A-site deficiency were fabricated and the electrical conductivity and oxygen diffusion behaviour with different Cr substitution levels (x = 0.3, 0.5 and 0.7) were investigated. As the Cr content increased, the electrical conductivity increased and then a maximum value was achieved at x = 0.7. In the oxygen diffusion studies, all the measured materials present good surface exchange rates (,9 × 10−8 cm s−1 at 900 °C) while the bulk diffusivity of the investigated materials decreased as the Cr substitution level increased: at 900 °C the oxygen diffusion coefficients of the LSCrF materials (x = 0.3, 0.5 and 0.7) are 1.1 × 10−10 cm2 s−1, ...
Diffusion Processes. Basic idea:. In its simplest form, diffusion is the transport of a material or chemical by molecular motion. If molecules of a chemical are present in an apparently motionless fluid, they will exhibit microscopic erratic motions due to being randomly struck by other molecules in the fluid. Individual particles or molecules will follow paths sometimes known as random walks.. In such processes, a chemical initially concentrated in one area will disperse. That is, there will be a net transport of that chemical from regions of high concentration to regions of low concentration.. An analogous form of diffusion is called conduction. In this case, heat is the chemical that is transported by molecular motion. As in chemical diffusion, heat migrates from regions of high heat to regions of low heat. The mathematics describing both conduction and diffusion are the same.. What this lab is about:. In this laboratory, students will explore two-dimensional diffusion phenomena by ...
Long-term potentiation (LTP) of excitatory synaptic transmission has long been considered a cellular correlate for learning and memory. Early LTP (eLTP, ,1 hour) had initially been explained either by presynaptic increases in glutamate release or by direct modification of post-synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) function. Compelling models have more recently proposed that synaptic potentiation can occur by the recruitment of additional post-synaptic AMPARs, sourced either from an intracellular reserve pool by exocytosis or from nearby extra synaptic receptors pre-existing on the neuronal surface. However, the exact mechanism through which synapses can rapidly recruit new AMPARs during eLTP is still unknown. In particular, direct evidence for a pivotal role of AMPAR surface diffusion as a trafficking mechanism in synaptic plasticity is still lacking. Using AMPAR immobilization approaches, we show that interfering with AMPAR surface diffusion ...
We find a continuum of extinction rates of solutions of the Cauchy problem for the fast diffusion equation $u_\tau=\nabla\cdot(u^{m-1}\,\nabla u)$ with $m=m_*:=(n-4)/(n-2)$, here $n|2$ is the space-dimension. The extinction rates depend explicitly on the spatial decay rates of initial data and contain a logarithmic term.
Surface Diffusion of Large Molecules: A Computational Study Kutay B. Sezginel and Christopher E. Wilmer Department of Chemical and Petroleum Engineering, University of Pittsburgh, 3700 Oâ Hara Street, Pittsburgh, Pennsylvania 15261, United States. Controlling molecular motion on surfaces is one of the first steps towards bottom-up construction of nanoscale machines. This process is commonly utilized in cells to transport molecular cargo: enzyme molecules are moved along protein filament tracks converting chemical energy into mechanical work. Careful design of the molecular structure and selection of the appropriate surface can enable precise manipulation of the molecular diffusion. Several strategies have been shown to greatly influence diffusion such as molecular functionalization and adjusting the orientation of the molecule with respect to the substrate lattice. Although these strategies are useful, to achieve a nanoscale understanding and control over the dynamics of molecular motion on ...
Diffusion behaviors of co-sputtered metals during thermal treatments were investigated, where these co-sputtered metals can be used as bonding materials for 3D Interconnects. In this paper, we report the diffusion behaviors and discuss the diffusion mechanisms of co-sputtered metals before and after annealing. Atom and vacancy volume, vacancy formation energy, and activation energy are proposed to explain the diffusion direction and diffusion rate among different co-sputtered metals. Based on the excellent bonding performance of this method, Cu/metal co-sputtering bonding is considered as a potential candidate for advanced bonding technology ...
Dexamethasone and dexamethasone 21-phosphate were loaded into NDGA-polymerized collagen fibers and release rate studies were performed to calculate their diffusion coefficients. Dexamethasone loaded fibers were placed in a PBS solution for specified time intervals (1, 3, 6, 7, 12, 24, 30, and 48 hours) after which the eluant was removed and analyzed by capillary zone electrophoresis (CZE). CZE is a tool that can be utilized for quantitative analysis of chemical compounds. This data was incorporated into mathematical models to determine the diffusion coefficient. The diffusion coefficient (D) for dexamethasone in NDGA-polymerized collagen fibers is D = 1.86 x 10⠻¹⠴ m²/s. Similarly, dexamethasone 21-phosphate loaded fibers were placed into a PBS solution and analyzed using CZE at these specified intervals (15, 30, 45, 60, and 75 minutes). Applying this data to the mathematical model provided a diffusion coefficient for dexamethasone 21-phosphate in NDGA-polymerized collagen fibers of D = 2
CS1 maint: discouraged parameter (link) Attarashany, Rida (Autumn 2001). "Yugoslavia: turning a corner?" (PDF). Diffusion. ...
He continued towards a PhD also at Wisconsin, 1965, with his thesis entitled, "Multicomponent Diffusion in Macromolecules," ... Cussler, E.L., Multicomponent Diffusion, Elsevier Publishing Company, Amsterdam, 1976. "Ed Cussler". National ... CS1 maint: discouraged parameter (link) Cussler, E. L. (2009-01-15). Diffusion. ISBN 978-0521871211. "AIChE Institute Award". ... "Diffusion" (Cambridge, 2009, 3rd Edition). He has served as Director, Vice President and President of the American Institute of ...
The tale type enjoys "almost universal ... diffusion". Audio readings/dramatizations include: Dick Bentley played Ali Baba in a ...
"Diffusion". Diffusion: Cardiff International Festival of Photography. Ffotogallery. Retrieved 10 October 2015. Heywood, Nicola ... Ffotogallery organises Diffusion: Cardiff International Festival of Photography. The biannual festival was held in 2013, ... "Diffusion Photography Festival". BBC Radio Wales. Retrieved 2019-04-12. "exhibitions archive". Ffotogallery. Retrieved 24 April ... Sritharan, Brennavan (8 October 2015). "Looking for America - Diffusion: Cardiff International Festival of Photography returns ...
Anwar, Zakarya (June 2009). "An evaluation of a post-colonial critique of Tolkien". Diffusion. 2 (1): 1-9. Kocher 1974, pp. 73- ...
... while acting as a diffusion barrier to block the diffusion of the metal into the silicon. In this context, TiN is classified as ... doi:10.1016/0925-8388(94)01315-9. Lengauer, Walter (1992). "Properties of bulk δ-TiN1-x prepared by nitrogen diffusion into ... "Wear coatings for industrial products". Diffusion Alloys. Archived from the original on 2013-05-19. Retrieved 2013-06-14. " ...
Diffusion Dimedia. p. 122. ISBN 978-2894480502. Explains that Bishop François de Laval in the 17th century posed the question ...
... dictated by the convection/diffusion (the relative importance between convection and diffusion depends on the Reynolds number) ... ISBN 0-19-507626-5. Liñán, A. (2001). "Diffusion-controlled combustion". In Aref, H.; Phillips, J. W. (eds.). Mechanics for a ... Activation energy asymptotics Liñán's equation Liñán's diffusion flame theory Burke, S. P.; Schumann, T. E. W. (1928). " ... "Diffusion flames". Industrial & Engineering Chemistry. 20 (10): 998-1004. doi:10.1021/ie50226a005. Williams, F. A. (2018). ...
"Diffusion Books". SPCK Publishing. Retrieved 13 March 2019. "What We Do , Improving Literacy". Diffusion Books. Retrieved 13 ... By the end of 2018, the SPCK had sent Diffusion books to 70% of prisons in the UK. In 2018 alone, it sent out over 6,500 books ... At the end of each chapter, the Diffusion books contain questions which can be discussed in a reading group, thereby developing ... In these ways, the Diffusion prison fiction programme not only develops hard skills, such as literacy, but also soft skills ...
Cogeco Diffusion. FM93. Retrieved November 18, 2012. Duration: 21:23. La séquence évoquant l'embarras manifeste de Bastian ... Diffusion. Cogeco. Retrieved November 20, 2012. Duration: 21:23 min. Bergeron, Mélanie (November 18, 2012). "Des vedettes ...
CS1 maint: discouraged parameter (link) "Francophonie Diffusion • Radio stations comments • ALIZÉE". Francophonie Diffusion. ... "Francophonie Diffusion • French International Music Download Charts". Retrieved 2012-11-09. CS1 maint: ...
His monographs Diffusion in Zeolites and Other Microporous Solids (Wiley, 1992, together with D. M. Ruthven) and Diffusion in ... The mechanism of two-range diffusion he applied became a widely used model for NMR diffusion measurements in complex systems, ... see Books "Diffusion Fundamentals Conferences". "Diffusion Fundamentals". "Literaturpreis der chemischen Industrie 2019 für das ... His scientific career was determined by his work on the use of NMR spectroscopy to measure molecular diffusion in nanoporous ...
According to Francophonie Diffusion, "Être une femme" and "Cesse la pluie" were the second and the fifth most-played French ... "Le Palmarès International des Musiques Francophones - Année 2005". Francophonie Diffusion. Archived from the original on 8 May ... Document archive (1997), La diffusion en radio 1997, Syndicat National de l'Édition Phonographique "Discographie Anggun". ... According to Francophonie Diffusion, "Nos vies parallèles" was the third-most played French song worldwide during March 2016. ...
Burton, Steve (2011). "Isobaric Counter Diffusion How to avoid a Isobaric Counter Diffusion hit". Retrieved ... and diffusion is faster when the temperature is higher as the average energy of the molecules is greater. Diffusion is also ... Diffusion is the movement of molecules or ions in a medium when there is no gross mass flow of the medium, and can occur in ... Diffusion is driven by the kinetic energy of the diffusing molecules - it is faster in gases and slower in solids when compared ...
"The Yearly Airplay Charts: 2009". Francophonie Diffusion. Archived from the original on 21 September 2013. Retrieved 14 January ...
According to Francophonie Diffusion, it was the most-played French single worldwide during 2007. This is the fifth studio album ... AllMusic Review "The Yearly Airplay Charts: 2007". Francophonie Diffusion. Archived from the original on 2016-03-04. Retrieved ...
La Diffusion, GAGNON, Claude-L. 1971. «La diffusion». Vie des Arts, no 63, p. 52-53. "Stuart Ash - Canada Modern". Canada ...
Thermal diffusion. Mixing of hot and cold gases. The most usually used (also the most efficient) method is cooling by thermal ... diffusion. Most abundantly used working fluid is n-butanol; during last years water is also encountered in this use. ...
The final structure established nine general directions: Artistic Heritage, Archives and Museums; Cultural Diffusion; Books and ...
Diffusion-weighted images (DWI): DWI uses the diffusion of water molecules to generate contrast in MR images. Proton density ( ... Basser PJ (2010). "Invention and Development of Diffusion Tensor MRI (DT-MRI or DTI) at the NIH". Diffusion MRI. Oxford ... Le Bihan D, Breton E (1987). "Method to Measure the Molecular Diffusion and/or Perfusion Parameters of Live Tissue". US Patent ... Filler A (October 2009). "Magnetic resonance neurography and diffusion tensor imaging: origins, history, and clinical impact of ...
According to Francophonie Diffusion, "Alors on danse" was the most-played Francophone single worldwide of 2010. As of July 2014 ... CS1 maint: discouraged parameter (link) "The Yearly Airplay Charts: 2010". Francophonie Diffusion. Archived from the original ...
"Francophonie diffusion - Christina Goh". Francophonie Diffusion. France. 2010. Archived from the original on 4 March 2016. Goh ... "Francophonie Diffusion-Radio comments". Francophonie Diffusion. Paris. 2009. Archived from the original on 3 March 2016. ...
Francophonie Diffusion. Retrieved 2013-01-14. CS1 maint: discouraged parameter (link) 2006 certifications in France ...
"Episode 14: Cheryl Mitchell". Diffusion Network. 2018-10-02. Retrieved 2020-07-28. "Shuttered Dairy Company Launches Vegan Milk ...
Where the two diffusion fronts meet, if any of the antibodies recognize any of the antigens, they will bind to the antigens and ... Ouchterlony, O. (1962). "Diffusion-in-gel methods for immunological analysis. II". Progress in Allergy. 6: 30-154. doi:10.1159/ ... Ouchterlony, O. (1958). "Diffusion-in-gel methods for immunological analysis". Progress in Allergy. 5: 1-78. PMID 13578996. ... "Diffusion Patterns". Immunodiffusion principles and application. Archived from the original on 2019-12-11. Retrieved 2017-05-19 ...
"Diffusion (EP)". Apple Music. 13 February 2017. Retrieved 9 September 2020. "Pandora Charts Archive". Retrieved 4 April 2015. " ...
The Fink effect, also known as "diffusion anoxia", "diffusion hypoxia", or the "second gas effect", is a factor that influences ... ISBN 978-0-443-06785-3. Bernard R. Fink (1955). "Diffusion Anoxia". Anesthesiology. 16 (4): 511-519. doi:10.1097/00000542- ...
Diffusion Processes • State Space Models C33 Panel Data Models • Spatio-temporal Models C34 Truncated and Censored Models • ... Diffusion Processes O34 Intellectual Property and Intellectual Capital O35 Social Innovation O38 Government Policy O39 Other O4 ... Diffusion Processes C23 Panel Data Models • Spatio-temporal Models C24 Truncated and Censored Models • Switching Regression ...
"Rasbora sarawakensis" (in French). Aquaterra-Diffusion. Retrieved 11 October 2017. CS1 maint: discouraged parameter (link) " ...
Basser, Peter J. (2010). "Invention and Development of Diffusion Tensor MRI (DT-MRI or DTI) at the NIH". Diffusion MRI. pp. 730 ... In the 1960s, the results of work on relaxation, diffusion, and chemical exchange of water in cells and tissues of various ... Le Bihan, D; Breton E. (1987). "Method to Measure the Molecular Diffusion and/or Perfusion Parameters of Live Tissue". US ... Filler A (October 2009). "Magnetic resonance neurography and diffusion tensor imaging: origins, history, and clinical impact of ...
Lexical diffusion, Trans-cultural diffusion).. Diffusion in physics. In molecular diffusion, the moving entities are small ... Momentum diffusion, ex. the diffusion of the hydrodynamic velocity field. *Osmosis is the diffusion of water through a cell ... Electronic diffusion, resulting in an electric current called the diffusion current.. *Facilitated diffusion, present in some ... The concept of diffusion emerged from physical sciences. The paradigmatic examples were heat diffusion, molecular diffusion and ...
Eddy diffusion, eddy dispersion, multipath, or turbulent diffusion is any diffusion process by which substances are mixed in ... In this approach, the diffusion rate at each pressure level is parameterized by a quantity known as the eddy diffusion ... Retrieved from "" ...
Error diffusion with several gray levels[edit]. Error Diffusion may also be used to produce output images with more than two ... Two-dimensional error diffusion[edit]. One dimensional error diffusion tends to have severe image artifacts that show up as ... Floyd and Steinberg described a system for performing error diffusion on digital images based on a simple kernel: 1. 16. [. −. ... One-dimensional error diffusion[edit]. The simplest form of the algorithm scans the image one row at a time and one pixel at a ...
Diffusions of Innovation theory. The theory categorises innovat... ... Diffusion of Innovation Theory : The Adoption Curve - Duration: 3:34. Rare 99,970 views ... Diffusion of Innovation Theory: The S Curve - Duration: 3:36. Rare 54,785 views ... Understanding the adoption lifecycle of innovation can be characterised using Everett Rogers Diffusions of Innovation theory. ...
The Diffusion of Tangrams. Every now and then a puzzle or game sweeps a population. We had Rubiks Cube in the early Eighties, ... during a time of slower information diffusion. A puzzle from China around 1,000 years ago that requires arranging seven pieces ...
Solution: Well let r1 represent the rate of diffusion of methane and r2 represent the rate of diffusion of carbon dioxide. ... Diffusion is the rate at which a gas travels across a room. Both of these phenomena are illustrated by the following figure. ... Other important behaviors of gases explained by the Kinetic Molecular Theory are effusion and diffusion. Effusion is the rate ... b) Diffusion is the rate at which a gas travels across the room. ... Chemistry: Effusion and Diffusion. Effusion and Diffusion. ...
This book is an introduction to the multidisciplinary field of anomalous diffusion in complex systems, with emphasis on the ... This book is an introduction to the multidisciplinary field of anomalous diffusion in complex systems, with emphasis on the ...
Diffusion Information Center (Hrsg) (1967ff) Diffusion Data. Cleveland: Diffusion Information CenterGoogle Scholar ... Mehrer H (2007) Diffusion in Solids: Fundamentals, Methods, Materials, Diffusion-Controlled Processes, SpringerGoogle Scholar ... Shewmon P (1989) Diffusion in Solids. 2nd ed. Warrendale: The Minerals, Metals & Materials SocietyGoogle Scholar ... Heumann Th, Mehrer H (Mitarb) (1992) Diffusion in Metallen. Berlin: Springer-VerlagCrossRefGoogle Scholar ...
Diffusion is important in many life processes. It occurs, for example, across the alveolar membrane of the ... Diffusion is not confined to gases; it can take place with matter in any state. For example, salt diffuses (dissolves) into ... Diffusion of a solute across a membrane is called dialysis, especially when some solutes pass and others are retained. ... Diffusion often masks gravitational effects. For example, if a relatively dense gas (such as CO2, carbon dioxide) is introduced ...
... Simulation of the brownian diffusion of particles deviation and a graph of the radial density ... You just viewed Particle Diffusion . Please take a moment to rate this material. ...
Public Comments on Paducah Gaseous Diffusion Plant Documents. How to Submit Comments. Comments on Paducah Gaseous Diffusion ... Advisory Board and NIOSH Discussions on Paducah Gaseous Diffusion Plant. The Paducah Gaseous Diffusion Plant discussion papers ... Paducah Gaseous Diffusion Plant, and Portsmouth Gaseous Diffusion Plant Time/Location:. 1:00 p.m. Eastern Standard Time (EST). ... Draft: Paducah Gaseous Diffusion Plant Site Profile Review pdf icon[4 MB (154 pages)]. Contract No. 200-2004-03805. Task Order ...
Gaseous Diffusion Plants - Employees who worked at least 250 days before February 1, 1992, at a gaseous diffusion plant in ... NIOSH/ORAU: Portsmouth Gaseous Diffusion Plant and Oak Ridge Gaseous Diffusion Plant (K-25) pdf icon[102 KB (4 pages)]. ... Advisory Board and NIOSH Comments and Discussion Papers on Portsmouth Gaseous Diffusion Plant. The Portsmouth Gaseous Diffusion ... Paducah Gaseous Diffusion Plant, and Portsmouth Gaseous Diffusion Plant Time/Location:. 1:00 p.m. Eastern Standard Time (EST). ...
NIST Diffusion Workshop Series Expand or Collapse. * 2011 Diffusion Workshop Presentations * 2010 NIST Diffusion Workshop ... NIST Diffusion Workshop Group. The 2017 Diffusion Workshop was held September 11-12, 2017 at NIST. The presentations are now ... Upcoming Diffusion Conferences. * 14th International Conference on Diffusion in Solids and Liquids - DSL2018, June 25-29, 2018 ... To provide a forum to solve common diffusion software execution problems.. *To agree on a common diffusion mobility database ...
... Diego A. Comin, Mikhail Dmitriev, Esteban Rossi-Hansberg. NBER Working Paper No. 18534. ... w11928 Five Facts You Need to Know About Technology Diffusion. Desmet and Rossi-Hansberg. w18546 On the Spatial Economic Impact ... We study empirically technology diffusion across countries and over time. We find significant evidence that technology diffuses ... Overall, we document the significant role that geography plays in determining technology diffusion across countries. ...
This class practical shows that diffusion takes place in liquids. Students place colourless crystals of lead nitrate and ... Diffusion in liquids. Class practical. This class practical shows that diffusion. takes place in liquids. . Students place ... Practical chemistryExperiment & investigationParticles & matterCharacteristics of the states of matterDiffusionSaltsIonic ... This class practical shows that diffusion takes place in liquids. Students place colourless crystals of lead nitrate and ...
Analytical Techniques Types of Diffusion Guest Lecturers Literature Additional Literature Related Links What is diffusion? ... ... Diffusion medium-based classification:. 1) Volume diffusion: Diffusion within a system, where the diffusion medium can be ... Types of Diffusion When the word diffusion is mentioned without further explanation, diffusion describes the volume diffusion ... Example: diffusion of Mg and Fe2+ in a garnet crystal. 2) Grain-boundary diffusion: Diffusion along interfaces, such as ...
Diffusion Diffusion refers to the process by which molecules intermingle as a result of their kinetic energy of random motion. ... Their average diffusion rate is expected to depend upon that average velocity, which gives a relative diffusion rate ... Rate of Diffusion Since the average kinetic energy of different types of molecules (different masses) which are at thermal ... The tendency toward diffusion is very strong even at room temperature because of the high molecular velocities associated with ...
... basic results in international technology diffusion; (ii) the importance of specific channels of diffusion, in particular trade ... I first review the major concepts, and how international technology diffusion relates to other factors affecting economic ... I discuss the concept and empirical importance of international technology diffusion from the point of view of recent work on ... "International technology diffusion through imports and its impact on economic growth," European Economy Group Working Papers 12 ...
See an archive of all cut/diffusion lines stories published on the New York Media network, which includes NYMag, The Cut, ... Were sorry, but we didnt find any results for "Cut/diffusion Lines ". Please try again or browse Nymags main page.. ...
Lung diffusion testing measures how well the lungs exchange gases. This is an important part of lung testing, because the major ... Lung diffusion testing measures how well the lungs exchange gases. This is an important part of lung testing, because the major ...
... diffusion, and other kinetic properties of phases. It features critical phase diagram evaluations on scientifically and ... The Journal of Phase Equilibria and Diffusion (JPED) focuses on the crystallographic, chemical, ... The Journal of Phase Equilibria and Diffusion (JPED) is focused on the crystallographic, chemical, diffusion, and other kinetic ... The Journal of Phase Equilibria and Diffusion (JPED) focuses on the crystallographic, chemical, diffusion, and other kinetic ...
... During his doctoral studies in Oxford and subsequently, John Murphy and his colleagues ( ... Enhanced oxygen diffusion in highly-doped p-type Czochralski silicon, J.D. Murphy, P.R. Wilshaw, B.C. Pygall, S. Senkader, R.J ... The effect of impurity-induced lattice strain and Fermi level position on low temperature oxygen diffusion in silicon, Z. Zeng ... gave evidence for enhanced oxygen diffusion. The dependence of the behaviour on oxygen concentration strongly suggests that the ...
We implement this test in a unique dataset compiled by us that covers the diffusion of 20 technologies for 23 countries over ... relevant institutional variables that affect the costs of erecting barriers has a significantly larger effect on the diffusion ... This paper explores whether lobbies slow down technology diffusion. To answer this question, we exploit the differential effect ... "Divergent diffusion: Understanding the interaction between institutions, firms, networks and knowledge in the international ...
However, it has been the common practice to report diffusion coefficients calculated on the basis of concentration gradients as ... it is clearly established that the driving force for molecular diffusion in liquids, such as occurs in the well-known diaphragm ... WHETHER an equilibrium concept is applied to a consideration for diffusion in liquids or whether the methods of irreversible ... Activity-based Diffusion Coefficients for Liquid Solutions. *F. A. L. DULLIEN1. & ...
Diffusion kurtosis imaging (DKI) increases sensitivity to microstructural changes by extending the diffusion signal expression ... that includes three diffusion directions at a low b-value to determine the mean diffusivity and 9 specific diffusion directions ... One of the editors picks for the month of July is a paper entitled "Gibbs Ringing in Diffusion MRI". Recently, we talked with ... Jussi Toivonen recently published a paper on diffusion imaging of prostate, and we invited him and senior author Ivan Jambor to ...
Self-Diffusion of Water. AIMD simulations using the CP2K package (30) were conducted for three systems: pure water, 3 M NaCl, ... 2012) Self-diffusion and viscosity in electrolyte solutions. J Phys Chem B 116(39):12007-12013. ... Anomalous water diffusion in salt solutions. Yun Ding, Ali A. Hassanali, and Michele Parrinello ... 5, Bottom). This trend is consistent with what we observe for the self-diffusion of water discussed earlier. On the other hand ...
... William R. Kerr. NBER Working Paper No. 19657. Issued in ... and exploiting heterogeneous technology diffusion from immigrant communities in the United States for identification. The ...
Scientific American is the essential guide to the most awe-inspiring advances in science and technology, explaining how they change our understanding of the world and shape our lives.
Solar Energy Evolution and Diffusion Studies. The Solar Energy Evolution and Diffusion Studies (SEEDS) are a series of industry ... Develop new datasets and modeling approaches to analyze solar diffusion. *Validate alternative marketing techniques and ...
Diffusion definition is - the state of being spread out or transmitted especially by contact : the action of diffusing. How to ... Other Words from diffusion Synonyms More Example Sentences Learn More about diffusion ... Examples of diffusion in a Sentence. the authors tendency toward diffusion makes the novel a tedious read ... Comments on diffusion. What made you want to look up diffusion? Please tell us where you read or heard it (including the quote ...
  • In this approach, the diffusion rate at each pressure level is parameterized by a quantity known as the eddy diffusion coefficient , K [4] (also sometimes called eddy diffusivity , with units of m 2 s −1 ). (
  • D is a diffusion coefficient, which we usually assume to be a constant. (
  • The diffusion coefficient is chosen to vary spatially in such a way as to encourage intraregion smoothing in preference to interregion smoothing. (
  • So, I have to calculate diffusion coefficient three times (x,y,z) and finally add-up together to get in 3D? (
  • diffusion coefficient in each spatial dimension. (
  • diffusion coefficient for each lipid component in 3D. (
  • A procedure for identification of optimal Apparent Diffusion Coefficient (ADC) thresholds for automatic delineation of prostatic lesions with restricted diffusion at differing risk for cancer was developed. (
  • In a real laboratory, such experiment would take place at very high temperatures, for the process to take place in a reasonable amount of time (note that the diffusion coefficient varies exponentially with the inverse of the temperature). (
  • where x is the maximum diffusion distance, D is the diffusion coefficient, and t is elapsed time. (
  • The 'diffusion coefficient' of the system is proportional to the slope, and can be easily calculated using the above equation. (
  • The diffusion of water molecules in a tissue is not the same in all direction (anisotropic diffusion) due to tissue heterogeneity. (
  • Based on the axonal orientation, anisotropic diffusion can produce completely new image contrast, which is very useful in visualizing important brain structures. (
  • We show how the phenomenon of anisotropic diffusion of water (or metabolites) in anisotropic tissues, measured noninvasively by these NMR methods, is exploited to determine fiber tract orientation and mean particle displacements. (
  • As diffusion is truly a three-dimensional process, molecular mobility in tissues may be anisotropic, as in brain white matter. (
  • Recent studies have shown that diffusion is anisotropic in brain white matter (i.e., dependent on the fiber tract's orientation in space), offering new insights into myelin disorders. (
  • We study empirically technology diffusion across countries and over time. (
  • Overall, we document the significant role that geography plays in determining technology diffusion across countries. (
  • I discuss the concept and empirical importance of international technology diffusion from the point of view of recent work on endogenous technological change. (
  • I first review the major concepts, and how international technology diffusion relates to other factors affecting economic growth in open economies. (
  • International Technology Diffusion ," NBER Working Papers 8573, National Bureau of Economic Research, Inc. (
  • International Technology Diffusion ," CEPR Discussion Papers 3133, C.E.P.R. Discussion Papers. (
  • This paper explores whether lobbies slow down technology diffusion. (
  • Lobbies and Technology Diffusion ," NBER Working Papers 11022, National Bureau of Economic Research, Inc. (
  • Lobbies and Technology Diffusion ," The Review of Economics and Statistics , MIT Press, vol. 91(2), pages 229-244, May. (
  • Atomic diffusion , in solids. (
  • Shewmon P (1989) Diffusion in Solids. (
  • Diffusion may take place in solids, that is, in regions occupied by matter which continues to exhibit the properties of the solid state. (
  • This model describes how diffusion occurs between two adjacent solids. (
  • Diffusion can take place in gases, liquids, or solids. (
  • In solids, particularly, diffusion occurs due to thermally-activated random motion of atoms - unless the material is at absolute zero temperature (zero Kelvin), individual atoms keep vibrating and eventually move within the material. (
  • There are many mechanisms for diffusion in solids. (
  • Jill Kiedaisch, Popular Mechanics , "An Advance in Bioengineering Could Pave the Way for Tomorrow's Superplants," 12 Mar. 2019 One of the earliest and most primitive enrichment techniques used in this endeavor was gaseous diffusion . (
  • Other important behaviors of gases explained by the Kinetic Molecular Theory are effusion and diffusion. (
  • The transport of gases across membranes depends upon diffusion and the solubility of the gases involved. (
  • Lung diffusion testing measures how well the lungs exchange gases. (
  • One end of the capsule contains a gas-permeable membrane that allows for fast diffusion of gut gases. (
  • Diffusion of gases may be shown to exist by taking glass jars containing vapours of hydrochloric acid and ammonia , and placing them in communication with the heavier gas downmost. (
  • From the considerations of the preceding section, the effects of inertia of the diffusing gases may be neglected, and at any instant of the process either of the gases is to be treated as kept in equilibrium by its partial pressure and the resistance to diffusion produced by the other gas . (
  • Because the microscopic processes responsible for atmospheric mixing are too complex to model in detail, atmospheric modelers generally treat atmospheric mixing as a macroscopic "eddy" diffusion process. (
  • Diffusion is important in many life processes. (
  • In geology the study of diffusion is used to understand magmatic and metamorphic processes, mass transport, fluid/rock interactions, thermal and physico-chemical history of rocks and crystal growth, mineral zonation, atom ordering, exsolution features and isotopic characteristics. (
  • Many of these transport processes proceed by diffusion through membranes which are selectively permeable, allowing small molecules to pass but blocking larger ones. (
  • Diffusion focuses on unconventional photographic processes and photo related artwork. (
  • Diffusion is an independent annual that highlights and celebrates unconventional photographic processes and photo related artwork. (
  • Diffusion strives to spotlight artists pushing the boundaries of traditional photographic processes as well as introducing new and innovative voices through articles, interviews, and image galleries. (
  • Diffusion processes have been used to model many real-world phenomena, including rumor spreading on the Internet, epidemics in human beings, emotional contagion through social networks, and even gene regulatory processes. (
  • Adoption is similar to diffusion except that it deals with the psychological processes an individual goes through, rather than an aggregate market process. (
  • Sections include a systematic introduction to malware diffusion processes in computer and communications networks, an analysis of the latest state-of-the-art malware diffusion modeling frameworks, such as queuing-based techniques, calculus of variations based techniques, and game theory based techniques, also demonstrating how the methodologies can be used for modeling in more general applications and practical scenarios. (
  • BioTensor is a program that processes and visualizes diffusion tensor images. (
  • In molecular diffusion , the moving entities are small molecules which are self propelled by thermal energy and do not require a concentration gradient to spread out through random motion. (
  • Diffusion is this thermal motion of all (liquid and gas) molecules at temperatures above absolute zero . (
  • While Brownian motion of large molecules is observable under a microscope, small-molecule diffusion can only be probed in carefully controlled experimental conditions. (
  • Because of the random nature of the motion of molecules, the rate of diffusion of molecules out of any region in a substance is proportional to the concentration of molecules in that region, and the rate of diffusion into the region is proportional to the concentration of molecules in the surrounding regions. (
  • A common example is the initial phase of explosive volcanic eruptions, in which diffusion controls bubble growth by allowing gas molecules to migrate into bubbles. (
  • Diffusion refers to the process by which molecules intermingle as a result of their kinetic energy of random motion. (
  • Osmosis is a selective diffusion process driven by the internal energy of the solvent molecules. (
  • The term 'diffusion' denotes random thermal motion of water molecules. (
  • Another limitation is that, since DTI is based on the diffusion of water molecules, it is not possible to differentiate axon directionalities through this technique. (
  • The success of diffusion magnetic resonance imaging (MRI) is deeply rooted in the powerful concept that during their random, diffusion-driven displacements molecules probe tissue structure at a microscopic scale well beyond the usual image resolution. (
  • Diffusion weighted imaging uses the diffusion of water molecules to probe the directional micro-structure of living tissue. (
  • A single diffusion weighted image generally measures diffusivity of water molecules along a particular direction. (
  • Play media Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) from a region of higher concentration to a region of lower concentration. (
  • The time dependence of the statistical distribution in space is given by the diffusion equation . (
  • 1) Fick's first law (steady-state diffusion equation) describes the relationship between diffusive flux and concentration gradient. (
  • This study proposes a semi-Lagrangian scheme for numerical simulation of advection-diffusion equation. (
  • inproceedings{HIC2018:Semi_Lagrangian_Scheme_for_Advection_Diffusion, author = {Ersin Bahar and Gurhan Gurarslan}, title = {A Semi-Lagrangian Scheme for Advection-Diffusion Equation}, booktitle = {HIC 2018. (
  • Delay reaction-diffusion equation for infection dynamics. (
  • This anisotropy (directional dominance of water diffusion within a region) is used in DTI to determine the nerve cell organization in the brain. (
  • Two main parameters that are calculated from the tensor to define the nerve cell orientation are fractional anisotropy (FA) and mean diffusivity (MD). FA defines the degree of diffusion directionality, and MD provides the information on the average diffusivity of water. (
  • Since diffusion anisotropy is significantly related to the axon myelination status, measurement of this parameter using DTI can also provide substantial insight into neuropathological conditions related to demyelination, such multiple sclerosis. (
  • DTI provides a thorough anatomical overview of the white matter in terms of diffusion anisotropy and fiber orientation. (
  • With diffusion tensor imaging (DTI), diffusion anisotropy effects can be fully extracted, characterized, and exploited, providing even more exquisite details on tissue microstructure. (
  • We'll let r 1 represent the rate of diffusion of methane and r 2 represent the rate of diffusion of carbon dioxide. (
  • The rate of diffusion is dependent on three aspects: the temperature, the mass of the particles and the thickness of the liquid or gas. (
  • The rate of diffusion is the speed that the new idea spreads from one consumer to the next. (
  • There are currently no open/active petitions from Paducah Gaseous Diffusion Plant. (
  • The Paducah Gaseous Diffusion Plant was one of the classes that Congress included when The Act was signed. (
  • To date, there are no open/active SEC petitions from Portsmouth Gaseous Diffusion Plant. (
  • And let's put that Gaseous Diffusion Plant in. (
  • In each diffusion reaction the flux of matter equals the conductivity multiplied by a driving force, with the conductivity being the mobility of the diffusing species (diffusivity) and the driving force being the presence of a concentration gradient as a function of distance in a direction (where a constant concentration gradient depicts a linear variation of concentration in one direction). (
  • Brian and Sune's group had previously described a fast protocol, referred to as the 1-3-9 scheme, that includes three diffusion directions at a low b-value to determine the mean diffusivity and 9 specific diffusion directions at a higher b-value to calculate mean kurtosis [Hansen et al. (
  • A large set of DWIs along carefully chosen gradient directions permits estimation of a diffusion tensor that models the relationship between direction and diffusivity. (
  • This class practical shows that diffusion takes place in liquids. (
  • WHETHER an equilibrium concept is applied to a consideration for diffusion in liquids or whether the methods of irreversible thermodynamics 1,2 are used, it is clearly established that the driving force for molecular diffusion in liquids, such as occurs in the well-known diaphragm cell, is the gradient of the chemical potential. (
  • diffusion, in chemistry, the spontaneous migration of substances from regions where their concentration is high to regions where their concentration is low. (
  • Diffusion has been of interest in a diversity of fields since then, such as physics, metallurgy and chemistry. (
  • Diffusion is one of the most important phenomena in fields such as biology, chemistry, geology, chemistry, engineering and physics. (
  • Diffusion describes the spread of particles through random motion from regions of higher concentration to regions of lower concentration. (
  • Diffusion describes mass transport, which happens in the absence of bulk flow and is due to thermally activated random motion of particles. (
  • In diffusion reactions particles migrate from places of higher concentration to those of lower concentration. (
  • The tendency toward diffusion is very strong even at room temperature because of the high molecular velocities associated with the thermal energy of the particles. (
  • Diffusion is caused when heat in a gas or water environment creates energy that is absorbed by particles, making them move. (
  • There are two ways to introduce the notion of diffusion: either a phenomenological approach starting with Fick's laws of diffusion and their mathematical consequences, or a physical and atomistic one, by considering the random walk of the diffusing particles. (
  • The Journal of Phase Equilibria and Diffusion (JPED) focuses on the crystallographic, chemical, diffusion, and other kinetic properties of phases. (
  • Diffusion rate is a function of only temperature, and is not affected by concentration. (
  • This demo is repeated in cold water and hot water to study the effect of temperature on the process of diffusion. (
  • Since an increase in temperature represents an increase in the average molecular speed, diffusion occurs faster at higher temperatures. (
  • e.g., gold will diffuse into lead, although at room temperature this diffusion is very slow. (
  • Simplified diffusion SE for biology students (doesn't have mass or temperature foci). (
  • How does temperature affect diffusion? (
  • The extent to which the diffusion can happen depends on the temperature and the number of vacancies in the crystal. (
  • Future applications include diffusion-localized spectroscopy and temperature imaging. (
  • Osmosis is the diffusion of water through a cell membrane. (
  • Diffusion may take place through a semipermeable membrane, which allows some, but not all, substances to pass. (
  • Diffusion of a solute across a membrane is called dialysis , especially when some solutes pass and others are retained. (
  • In 1855 the German physician and physiologist Adolf Eugen Fick (1829-1901) introduced Fick's law of diffusion, describing diffusion of a gas across a fluid membrane, and thus the relationship between diffusion flux of a component and its concentration gradient. (
  • Calculations elucidate how the lateral diffusion of macromolecules within a liquid membrane depends on the properties of the solvent layer surrounding it. (
  • Calculations have shown that the diffusion coefficients of inclusions moving within the membrane generally increase when the thickness of the solvent on either side of the membrane increases, but this earlier work was limited either to numerical calculations or to certain limiting cases. (
  • The authors performed total internal reflection fluorescence microscopy (TIRFM) and found that although some fluorescently labeled BCRs were highly mobile within the plasma membrane, most showed slow, restricted diffusion in naive, unstimulated primary B cells. (
  • Thus, the authors propose that the cytoskeleton restricts the diffusion of the BCR, and thereby its ability to initiate signal transduction events, and that tonic signaling is mediated by the mobile fraction of BCR in the plasma membrane. (
  • Diffusion tensor imaging (DTI) is a newly developed magnetic resonance imaging (MRI) technique that analyzes the anatomy of nerve cells and a complex neuronal network of the brain. (
  • This paper describes a new NMR imaging modality--MR diffusion tensor imaging. (
  • In this work, the feasibility of this approach for diffusion-tensor imaging of inner field-of-views in the human brain and cervical spinal cord at in-plane resolution of up to 0.5x0.5 mm2 is demonstrated. (
  • An important application of diffusion tensor imaging is determining the connective structure of central nervous tissue, made possible by the directionally constrained diffusion of water within or between the myelinated axon sheaths of white matter. (
  • This study reports the quantitative difference of n-butane diffusion and breakthrough under three experimental conditions. (
  • An experimental study has been conducted at small kerosene droplet behavior near well-defined butane diffusion flame for the critical need on high efficient and cleaner energy technology. (
  • This book is an introduction to the multidisciplinary field of anomalous diffusion in complex systems, with emphasis on the scaling approach as opposed to techniques based on the quantitative analysis of underlying transport equations. (
  • Otherwise, it's called an anomalous diffusion (or non-Fickian diffusion). (
  • Ni/René-88 and René-88/IN718 Diffusion couple data reported in J. Phase Equilibria & Diffusion 25 (2004) 6-15. (
  • In a less quantitative way, the concept of diffusion is invoked in the social sciences to describe the spread of ideas ( Diffusion of innovations , Lexical diffusion , Trans-cultural diffusion ). (
  • The diffusion of medical innovations-which also often originated in Europe-contributed to population explosions in the rest of the world. (
  • Diffusion of innovations between countries also occurs through foreign direct investment. (
  • In this installment, we continue Ms. Shure's analysis with "Part 2: Diffusion of Innovations," an anthropological study of how new ideas become accepted in societies and, based on that, a look at possible ways the truth about what really happened on 9/11 can become accepted. (
  • This description of how change occurs in societies is called "Diffusion of Innovations. (
  • The diffusion theory , also known as the diffusion of innovations theory, is a theory concerning the spread of innovation, ideas, and technology through a culture or cultures. (
  • Diffusion theory is also concerned with the rate at which innovations spread. (
  • To establish the most efficient method for extracting diffusion data (diffusion coefficients, fluxes, marker location) from multicomponent diffusion couple experiments. (
  • However, it has been the common practice to report diffusion coefficients calculated on the basis of concentration gradients as the driving force rather than the gradients of the chemical potential. (
  • Now, in Physical Review E , Kazuhiko Seki at the AIST in Tsukuba, Japan, and his colleagues have presented largely analytical results for diffusion coefficients that can take into account solvent layers of arbitrary thickness. (
  • introduce an analytical expression relating diffusion coefficients to these screening lengths. (
  • The 2017 Diffusion Workshop was held September 11-12, 2017 at NIST. (
  • Relocation diffusion occurs when people migrate from one place to another, thereby transferring an idea or innovation to a new location. (
  • Lastly, hierarchical diffusion occurs when an idea or innovation leapfrogs from one individual, group or location to another without affecting the spaces in between. (
  • Set of functions to perform nonlinear diffusion on images. (
  • This toolbox has functions to perform nonlinear diffusion on images. (
  • Nonlinear Diffusion Toolbox (, MATLAB Central File Exchange. (
  • but there is a tiny question, the function name of 3d nonlinear diffusion should be nldif3, not nldif, this maybe a typo. (
  • Eddy diffusion , eddy dispersion , multipath , or turbulent diffusion is any diffusion process by which substances are mixed in the atmosphere or in any fluid system due to eddy motion . (
  • In diffusion-weighted MRI, eddy current effects notoriously result in geometrical image distortions. (
  • Understanding the adoption lifecycle of innovation can be characterised using Everett Rogers' Diffusions of Innovation theory. (
  • A short video that gives an introductory explanation to Diffusion of Innovation theory. (
  • By identifying and leveraging unique source signatures, this project advances the state of the art of diffusion source localization by addressing the following three challenges: (1) On the theory side, this project establishes the fundamental limits of source localization for realistic networks. (
  • Malware Diffusion Models for Wireless Complex Networks: Theory and Applications provides a timely update on malicious software (malware), a serious concern for all types of network users, from laymen to experienced administrators. (
  • Many of you are familiar with Rogers' diffusion of innovation theory , even if you didn't know its formal name. (
  • What is the Diffusion Theory? (
  • Diffusion theory states that there are many qualities in different people that cause them to accept or not to accept an innovation. (
  • According to diffusion theory, there are five stages to the process of adopting an innovation. (
  • These qualities of the innovation are of the utmost importance to diffusion theory. (
  • It seems to me that the way in which we define innovation would affect the workability of the diffusion theory. (
  • The paradigmatic examples were heat diffusion , molecular diffusion and Brownian motion . (
  • Under normal conditions, molecular diffusion is relevant only on length scales between nanometer and millimeter. (
  • As the proliferation of portable devices, namely smartphones and tablets, and their increased capabilities, has propelled the intensity of malware spreading and increased its consequences in social life and the global economy, this book provides the theoretical aspect of malware dissemination, also presenting modeling approaches that describe the behavior and dynamics of malware diffusion in various types of wireless complex networks. (
  • You just viewed Diffusion of Innovation Educational... . (
  • Spatial diffusion is the process by which an idea or innovation is transmitted between individuals and groups across space. (
  • Expansion diffusion, on the other hand, is the spread of an idea or innovation through a fixed, non-migrating population. (
  • Contagious diffusion refers to the dissemination of an idea or innovation from one individual to neighbors or other adjacent individuals. (
  • Diffusion is defined as the process by which an innovation is adopted and gains acceptance by members of a certain community. (
  • Diffusion is not an element overtly described in a typical ID model (Andrews and Goodson, 1991), but the adoption of an innovation does have an implied place in the ID process. (
  • In their most recent MRM paper, they complement their simultaneous multi-slice (SMS) acquisition with an additional 3D RF-encoding for each 3mm slice (or thin slab), in order to push the resolution of diffusion imaging to 600 µm isotropic in the brain. (
  • Diffusion kurtosis imaging (DKI) increases sensitivity to microstructural changes by extending the diffusion signal expression to account for non-Gaussian effects, but it typically requires time-consuming acquisitions with high diffusion weighting. (
  • MR diffusion tensor spectroscopy and imaging. (
  • Diffusion-weighted imaging employs large gradient lobes which are known to cause vibration of the patient table. (
  • It can read diffusion weighted images (DWIs), perform correction for a common class of distortions in echo-planar imaging (EPI registration), estimate tensors from DWIs, and visualize the diffusion tensor field. (
  • With ultrafast acquisition schemes, diffusion imaging has also been used outside the CNS, for instance, in the eye and kidney. (
  • Lexical diffusion is the hypothesis that a sound change is an abrupt change that spreads gradually across the words in a language to which it is applicable. (
  • Wang accounted for such irregularities by positing a form of lexical diffusion: we hold that words change their pronunciations by discrete, perceptible increments (i.e. phonetically abrupt), but severally at a time (i.e. lexically gradual) rather than always in a homogeneous block. (
  • They present a revised model that distinguishes between the initial "actuation" of a sound change by language contact or internal factors, and its "implementation" by lexical diffusion. (
  • Lexical diffusion represents a change in the phonemes in a word (substitution, metathesis, elision, epenthesis). (
  • In other words, DTI uses the diffusion of water as a probe to determine the anatomy of a brain network, which basically provides information on static anatomy that is not influenced by brain functions. (
  • William Meyers, WSJ , "'Eye to I: Self-Portraits From 1900 to Today' Review: How Artists See Themselves," 19 Nov. 2018 Michael Kors Holdings acquired Jimmy Choo last year, setting itself apart from other fashion conglomerates that tend to grow in scale and revenue strictly via licenses, diffusion lines, and the acquisition of more mass-market labels. (
  • Beth Mole, Ars Technica , "With ingestible pill, you can track fart development in real time on your phone," 9 Jan. 2018 Furthermore, Kors' success is based upon his licensing and diffusion brands, like Michael Michael Kors, as well as his fragrance, timepieces, and accessories partnerships. (
  • The analysis of water diffusion is performed by applying magnetic field gradients to generate an image that is sensitized to diffusion in a particular direction. (
  • We further show data supporting the assumption that S/V can not be determined properly by just shaping the gradients, e.g. using a train of short gradients, if the slow diffusion condition is not fulfilled as has been proposed previously. (
  • In particular, for two-dimensional systems where only the interaction between species is delayed, the interdependence of stability against delay and against diffusion (Turing instability) can be clearly exhibited. (
  • Degenerate Hopf instability in oscillatory reaction-diffusion equations. (
  • Instability of multi-spot patterns in shadow systems of reaction-diffusion equations. (
  • Instability of planar traveling waves in bistable reaction-diffusion systems. (
  • Characterization of turing diffusion-driven instability on evolving domains. (
  • Diffusion is a microscopic process, which can lead to macroscopic effects. (
  • In addition, the spatial distribution of complex brain network can also be investigated by measuring the microscopic length scale of water diffusion. (
  • Schematic illustrates common diffusion mechanisms and pathways, such as vacancies and interstitial atoms, and intragrain and grain-boundary diffusion. (
  • a conductive layer above at least a portion of the polysilicon layer, wherein the conductive layer has at least some fluorine atoms or ions therein, and wherein the titanium boronitride barrier layer inhibits diffusion of the fluorine atoms or ions from the conductive layer into the gate oxide layer. (
  • a conductive layer formed over at least a portion of the diffusion barrier layer, wherein the conductive layer has at least some fluorine atoms or ions therein, and wherein the diffusion barrier layer inhibits diffusion of the fluorine atoms or ions from the conductive layer into the polysilicon layer. (
  • Interestingly, before becoming a famous for the Relativity Laws, Albert Einstein wrote extensively about diffusion, and was one of the first to connect diffusion to the Brownian motion of atoms. (
  • One of the possible net effects of diffusion is that atoms move from regions of high concentration of one element to regions with low concentration, until the concentration is equal throughout the sample. (
  • The purpose of this work is to compare the numerical calculation results of the hydrogen diffusion with the experimental results. (
  • We examine how messages detailing risks are transmitted from one person to another in experimental diffusion chains and how people influence each other as they propagate this information. (
  • Here, we study the social dynamics of risk perception by analyzing how messages detailing the benefits and harms of a controversial antibacterial agent undergo change when passed from one person to the next in 10-subject experimental diffusion chains. (
  • Heumann Th, Mehrer H (Mitarb) (1992) Diffusion in Metallen. (
  • These example sentences are selected automatically from various online news sources to reflect current usage of the word 'diffusion. (
  • Bentley RA, Garnett P, O'Brien MJ, Brock WA (2012) Word Diffusion and Climate Science. (
  • The word diffusion derives from the Latin word, diffundere, which means "to spread out. (
  • Albert Einstein (1879-1955) continued working on the relationship between random atomic movement and the process of diffusion. (
  • The concept of diffusion is tied to that of mass transfer driven by a concentration gradient, but diffusion can still occur when there is no concentration gradient (but there will be no net flux ). (
  • In addition, there are various other conditions that are needed for solid diffusion to occur. (
  • An example of a process where both bulk motion and diffusion occur is human breathing. (
  • diffusion dominates only in perfect thermal equilibrium. (
  • Diffusion" is the gradual movement/dispersion of concentration within a body, due to a concentration gradient, with no net movement of matter. (
  • Oxygen then moves by diffusion, down the concentration gradient, into the blood. (
  • Unlike many other halftoning methods, error diffusion is classified as an area operation, because what the algorithm does at one location influences what happens at other locations. (
  • The simplest algorithm is exactly like one dimensional error diffusion, except half the error is added to the next pixel, and half of the error is added to the pixel on the next line below. (
  • In this paper, we present a method which combines the trust diffusion (DiffTrust) algorithm and the probabilistic matrix factorization (PMF). (
  • 2) On the algorithm side, this project develops a suite of effective and scalable diffusion source detection algorithms whose theoretical properties are well-understood. (
  • Diffusion research, in its simplest form, investigates how theàse major factors, and a multitude of other factors, interact to facilitate or impede the adoption of a specific product or practice among members of a particular adopter group. (
  • This explains why the diffusion of heat was explained mathematically before the diffusion of mass. (
  • Existing research on social networks almost exclusively focuses on deriving realistic but mathematically trackable network models and diffusion models. (
  • In this study, we addressed this issue by combining SAP-EPI with the novel non-linear tensor estimation scheme that estimates the diffusion tensors from the complex k-space data directly. (
  • There are two types of diffusion reactions, steady-state and nonsteady-state. (
  • For reaction-diffusion equations with delay, the joint effects of diffusion and delay are studied. (