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, ...
TY - JOUR. T1 - Diffusion-controlled reactions among spherical traps. T2 - Effect of polydispersity in trap size. AU - Miller, C. A.. AU - Torquato, S.. PY - 1989. Y1 - 1989. N2 - We consider determining the steady-state trapping rate k associated with diffusion-controlled reactions among static, spherical traps with a polydispersity in trap size. Both discrete and continuous size distributions are examined. Theoretical methods, such as rigorous bounds and survival-probability theory, as well as computer-simulation techniques, are employed to address this problem. It is found that the trapping rate for the polydisperse system generally increases or decreases (relative to the monodisperse case) depending upon whether the relative interfacial surface area increases or decreases.. AB - We consider determining the steady-state trapping rate k associated with diffusion-controlled reactions among static, spherical traps with a polydispersity in trap size. Both discrete and continuous size ...
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 ...
This paper is devoted to develop a new matrix scheme for solving two-dimensional time-dependent diffusion equations with Dirichlet boundary conditions. We first transform these equations into equivalent integro partial differential equations (PDEs). Such these integro-PDEs contain both of the initial and boundary conditions and can be solved numerically in a more appropriate manner. Subsequently, all the existing known and unknown functions in the latter equations are approximated by Bernoulli polynomials and operational matrices of differentiation and integration together with the completeness of these polynomials can be used to reduce the integro-PDEs into the associated algebraic generalized Sylvester equations. For solving these algebraic equations, an efficient Krylov subspace iterative method (i.e., BICGSTAB) is implemented. Two numerical examples are given to demonstrate the efficiency, accuracy, and versatility of the proposed method ...
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.
Abstract: Diffusion on a quenched heterogeneous environment in the presence of bias is considered analytically. The first-passage-time statistics can be applied to obtain the drift and the diffusion coefficient in periodic quenched environments. We show several transition points at which sample-to-sample fluctuations of the drift or the diffusion coefficient remain large even when the system size becomes large, i.e., non-self-averaging. Moreover, we find that the disorder average of the diffusion coefficient diverges or becomes zero when the corresponding annealed model generates superdiffusion or subdiffusion, respectively. This result implies that anomalous diffusion in an annealed model is traced by anomaly of the diffusion coefficients in the corresponding quenched model ...
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.
the diffusion of the hydrodynamic velocity field Photon diffusion Plasma diffusion Random walk, model for diffusion Reverse ... it's called a normal diffusion (or Fickian diffusion); Otherwise, it's called an anomalous diffusion (or non-Fickian diffusion ... Knudsen diffusion of gas in long pores with frequent wall collisions Lévy flight Molecular diffusion, diffusion of molecules ... self-diffusion). In this case, the elementary mean free path theory of diffusion gives for the diffusion coefficient D = 1 3 ℓ ...
... is the hypothesis that a sound change is an abrupt change that spreads gradually across the words in a ... Lexical diffusion represents a change in the phonemes in a word (substitution, metathesis, elision, epenthesis). It is abrupt ... Paul Kiparsky argues that under a proper definition of analogy as optimization, lexical diffusion is a non-proportional type of ... Wang accounted for such irregularities by positing a form of lexical diffusion: we hold that words change their pronunciations ...
The main difference between rotational diffusion and translational diffusion is that rotational diffusion has a periodicity of ... Diffusion equation Perrin friction factors Rotational correlation time False diffusion Conggang Li, Yaqiang Wang, and Gary J. ... If two eigenvalues of the diffusion tensor are equal, the particle diffuses as a spheroid with two unique diffusion rates and ... However at long times, t » t0 , the behaviour of rotational diffusion is different to translational diffusion: P ( θ , t ∣ θ 0 ...
... also refers to when water is forced from a region of lower concentration to high. It can occur in osmosis. v ... Reverse diffusion refers to a situation where the transport of particles (atoms or molecules) in a medium occurs towards ... t e (Articles lacking sources from December 2009, All articles lacking sources, Diffusion, All stub articles, Physics stubs). ... regions of higher concentration gradients, opposite to that observed during diffusion. This phenomenon occurs during phase ...
... has been used to study many structural problems in the past, ranging from domain sizes in polymers and disorder ... Spin diffusion is a process by which magnetization can be exchanged spontaneously between spins. The process is driven by ... Spin diffusion describes a situation wherein the individual nuclear spins undergo continuous exchange of energy. This permits ... EPS2:Spin-Diffusion v t e (Articles with short description, Short description matches Wikidata, Wikipedia articles needing ...
Official website Diffusion Facebook Diffusion MySpace v t e (Use dmy dates from April 2022, Articles lacking sources from March ... Diffusion Pictures is a distributor of feature films in the United Kingdom. Formed in late 2006, its first two releases, Funny ... Diffusion then released Reprise by Norwegian director, Joachim Trier and Lars von Trier's film, The Boss of It All. The ...
While diffusion hardening is performed mainly on steel parts and carbon is mainly the element used for diffusion, diffusion ... Diffusion hardening is a process used in manufacturing that increases the hardness of steels. In diffusion hardening, diffusion ... Besides metals and diffusion elements used, diffusion hardening processes differ in the temperature required for diffusion, the ... All these things must come into consideration when choosing a diffusion hardening process. case-hardening "Diffusion Treatment ...
... can be in the same or opposite direction of a drift current. The diffusion current and drift current together ... Diffusion current Density is a current in a semiconductor caused by the diffusion of charge carriers (electrons and/or electron ... In a region where n and p vary with distance, a diffusion current is superimposed on that due to conductivity. This diffusion ... This current is called the diffusion current. The drift current and the diffusion current make up the total current in the ...
"Bohm diffusion". Physics portal Classical diffusion Hsu diffusion Plasma diffusion Bohm, D. (1949) The characteristics of ... Bohm diffusion is characterized by a diffusion coefficient equal to D B o h m = 1 16 k B T e B {\displaystyle D_{\rm {Bohm}}={\ ... Bohm diffusion is always greater than classical diffusion. In the common low collisionality regime, classical diffusion scales ... The diffusion of plasma across a magnetic field was conjectured to follow the Bohm diffusion scaling as indicated from the ...
A diffusion line (also known as a bridge line) is a secondary line of merchandise created by a high-end fashion house or ... Diffusion products may be on sale alongside designers' signature line but they can also be made available at concession outlets ... The use of a diffusion line is a part of the strategy of massification where luxury brands attempt to reach a broader market in ... Diffusion lines serve several purposes for designers. They can substantially increase sales volumes as their products become ...
The Diffusion Inhibitor is the first known attempt to build a working fusion power device. It was designed and built at the ... To disguise the actual purpose from NACA leadership, they called it the "Diffusion Inhibitor". Lewis agreed to provide $5,000 ( ...
The motion of magnetic fields is described by the magnetic diffusion equation and is due primarily to induction and diffusion ... Magnetic diffusion refers to the motion of magnetic fields, typically in the presence of a conducting solid or fluid such as a ... Also, different diffusion time equations can be derived for nonlinear saturable materials such as steel. Holt, E. H.; Haskell, ... The magnetic diffusion equation is ∂ B → ∂ t = ∇ × [ v → × B → ] + 1 μ 0 σ ∇ 2 B → {\displaystyle {\frac {\partial {\vec {B ...
Unlike typical diffusion, anomalous diffusion is described by a power law, ⟨ r 2 ( τ ) ⟩ = K α τ α {\displaystyle \langle r^{2 ... Anomalous diffusion is a diffusion process with a non-linear relationship between the mean squared displacement (MSD), ⟨ r 2 ( ... Fractional diffusion equations were introduced in order to characterize anomalous diffusion phenomena. Recently, anomalous ... It has been found that equations describing normal diffusion are not capable of characterizing some complex diffusion processes ...
Physics portal Bohm diffusion Classical diffusion Hsu diffusion Hsu, Jang-Yu; Wu, Kaibang; Kumar Agarwal, Sujeet; Ryu, Chang-Mo ... Plasma diffusion across a magnetic field is an important topic in magnetic confinement of fusion plasma. It especially concerns ... Hsu diffusion predicts 1/B3/2 scaling, which is presumably the best confinement scenario in magnetized plasma. ... v t e (Articles with short description, Short description matches Wikidata, Diffusion, Plasma physics, All stub articles, ...
... (ambipolar: relating to or consisting of both electrons and positive ions moving in opposite directions) is ... In astrophysics, "ambipolar diffusion" refers specifically to the decoupling of neutral particles from plasma, for example in ... In plasma physics, ambipolar diffusion is closely related to the concept of quasineutrality. In most plasmas, the forces acting ... "Definition of AMBIPOLAR". Kizilyalli, M.; Corish, J.; Metselaar, R. (1999). "Definitions of terms for diffusion in the solid ...
Diffusion, in architectural acoustics, is the spreading of sound energy evenly in a given environment. A perfectly diffusive ... Diffusors can aid sound diffusion, but this is not why they are used in many cases; they are more often used to remove ... The new goal was to find a new surface geometry that would combine the excellent diffusion characteristics of MLS designs with ... "The effects of 2d diffusers on sound diffusion". PF. (in Dari) T. J. Cox and P. D'Antonio, Acoustic Absorbers and Diffusors - ...
Contrary to its name, a diffusion flame involves both diffusion and convection processes. The name diffusion flame was first ... A nearly-turbulent diffusion flame A candle in a microgravity environment. This is a rare example of a diffusion flame which ... Diffusion flames tend to have a less-localized flame front than premixed flames.[citation needed] The contexts for diffusion ... The burning rate is however still limited by the rate of diffusion. Diffusion flames tend to burn slower and to produce more ...
... is typically used in video games, when multiple agents must path towards a single target agent. For ... Collaborative Diffusion is a type of pathfinding algorithm which uses the concept of antiobjects, objects within a computer ... Collaborative Diffusion is favored for its efficiency over other pathfinding algorithms, such as A*, when handling multiple ... "Collaborative Diffusion: Programming Antiobjects" (PDF). AgentSheets Inc & University of Colorado. Retrieved 25 July 2015. v t ...
Fickian diffusion theory and further advancements in research on atmospheric diffusion can be applied to model the effects that ... Diffusion flame Fick's laws of diffusion Planar laser-induced fluorescence Particle image velocimetry False diffusion Hideto ... and molecular diffusion results in the following differential equation considering only the turbulent diffusion approximation ... Turbulent diffusion is the transport of mass, heat, or momentum within a system due to random and chaotic time dependent ...
... , as opposed to trans-cultural diffusion, is a demographic term referring to a migratory model, developed by ... That is referred to as the Neolithic demic diffusion model. Craniometric and archaeological studies have also arrived at the ... Y genetic data support the Neolithic demic diffusion model. Proc. Natl. Acad. Sci. 99(17): 11008-11013. C. Loring Brace, Noriko ... Estimating the Impact of Prehistoric Admixture on the Genome of Europeans, Dupanloup et al., 2004 Origin, Diffusion, and ...
... (sometimes referred to simply as 'diffusion') is a performance practice in the field of acousmatic music. ... It is up to the diffusion engineer to perform the piece in such a way that the musical content is adequately interpreted as ... In many cases, the sound diffusion is performed by the composer themselves, whose task it is to integrate and interpret the ... Modern diffusion practice also tries to articulate musical material by playing different passages through different sounding ...
This numerical effect takes the form of an extra high diffusion rate. When numerical diffusion applies to the components of the ... Numerical diffusion is a difficulty with computer simulations of continua (such as fluids) wherein the simulated medium ... A simple way to avoid the difficulty is to add diffusion that smooths out the shock or current sheet. Higher order numerical ... As an example of numerical diffusion, consider an Eulerian simulation using an explicit time-advance of a drop of green dye ...
... most commonly refers to the diffusion, or spread of momentum between particles (atoms or molecules) of ... Understanding the exact nature of diffusion is a key aspect towards understanding momentum diffusion due to pressure. A fluid ... "momentum diffusion" can also refer to the diffusion of the probability for a single particle to have a particular momentum. In ... Momentum diffusion can be attributed to either external pressure or shear stress or both. When pressure is applied on an ...
The problem of diffusion in the atmosphere is often reduced to that of solving the original gradient based diffusion equation ... Eddy diffusion, eddy dispersion, or turbulent diffusion is a process by which substances are mixed in the atmosphere, the ocean ... Statistical diffusion theory originated with G. I. Taylor's (1921) paper titled "Diffusion by continuous movements" and later ... The concept of turbulence or turbulent flow causes eddy diffusion to occur. The theory of eddy diffusion was first developed by ...
... where the charge transport was via the diffusion mechanism. See Fick's laws of diffusion. To implement this notion ... Diffusion Capacitance is the capacitance that happens due to transport of charge carriers between two terminals of a device, ... The change in the amount of transiting charge divided by the change in the voltage causing it is the diffusion capacitance. The ... the corresponding diffusion capacitance: C d i f f {\displaystyle C_{diff}} . is C d i f f = d Q d V = d I ( V ) d V τ F {\ ...
By running the diffusion with an edge seeking diffusion coefficient for a certain number of iterations, the image can be ... This diffusion process is a linear and space-invariant transformation of the original image. Anisotropic diffusion is a ... Anisotropic diffusion can be used to remove noise from digital images without blurring edges. With a constant diffusion ... Anisotropic diffusion is normally implemented by means of an approximation of the generalized diffusion equation: each new ...
... uses a variant of diffusion model (DM), called latent diffusion model (LDM). Introduced in 2015, diffusion ... Stable Diffusion is a latent diffusion model, a variety of deep generative neural network developed by the CompVis group at LMU ... "hakurei/waifu-diffusion · Hugging Face". Retrieved 2022-10-31. Mercurio, Anthony (2022-10-31), Waifu Diffusion ... Wikimedia Commons has media related to Stable Diffusion. Stable Diffusion Demo (CS1 Japanese-language sources (ja), Articles ...
... is very popular in Algeria and is also well known in many other countries including Morocco, Tunisia and France ... Gnawa Diffusion started their career in 1993 with the release of the album Légitime différence. Members of the band: Amazigh ... Gnawa Diffusion is an Algerian Gnawa music band based in Grenoble, France. The group's lead singer, Amazigh (literally meaning ...
In general, surface diffusion occurs much faster than grain boundary diffusion, and grain boundary diffusion occurs much faster ... Atomic diffusion is a diffusion process whereby the random thermally-activated movement of atoms in a solid results in the net ... In substitutional lattice diffusion (self-diffusion for example), the atom can only move by substituting place with another ... Atomic diffusion in polycrystalline materials is therefore often modeled using an effective diffusion coefficient, which is a ...
Brownian motion Diffusion Molecular diffusion S. J. Chalk (1997). A. D. McNaught, A. Wilkinson (ed.). "IUPAC Compendium of ... According to IUPAC definition, self-diffusion coefficient is the diffusion coefficient D i ∗ {\displaystyle D_{i}^{*}} of ... It is linked to the diffusion coefficient D i {\displaystyle D_{i}} by the equation: D i ∗ = D i ∂ ln ⁡ c i ∂ ln ⁡ a i . {\ ... v t e (Diffusion, All stub articles, Physics stubs). ... term is commonly assumed to be equal to the tracer diffusion ...
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 [4 MB (154 pages)]. Contract No. 200-2004-03805. Task Order No. 1. ...
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 ...
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... 0-9. A. B. C. D. E. F. G. H. I. J. K. L. M. N. O. P. Q. R. S. T. U. V. W. ...
... V. Leino*, N. Brambilla, P. Petreczky, A. Vairo on behalf of the ... Using a multilevel algorithm and tree-level improvement, we study the behavior of the diffusion coefficient as a function of ... We report progress towards computing the heavy quark momentum diffusion coefficient from the correlator of two chromoelectric ...
A diffusion index measures the cumulative number of stocks that are advancing over time. It can be used to see how many ... Diffusion Index Formula  Diffusion Index (DI) = ( Advances − Declines ) + PDIV where: Advances = Number of stocks moving ... What Is a Diffusion Index? Used in technical analysis, a diffusion index measures the number of stocks that have advanced in ... Diffusion Index vs. Tick Index A diffusion index measures how many stocks are advancing within an index, typically on a daily ...
Gaseous diffusion. A uranium enrichment process used to prepare uranium for use in fabricating fuel for nuclear reactors by ... The only gaseous diffusion plant in operation in the United States is in Paducah, KY. A similar plant near Piketon, OH, was ...
Ces 25 textes couvrent l ensemble de l uvre, de 1929 1954. Voici Cingria : esprit critique exceptionnellement aff t , r veur ternellement enfantin, anti-conformiste, po te, vagabond v locip dique, provocateur, loufoque, styliste incomparable. De la litt rature comme un appel d air ...
Gel diffusion and electrophoretic techniques in the serology of malaria / by Judith A. Deans  ... An Adaptation of the gel diffusion technique for identifying the source of mosquito bloodmeals / by R. T. Collins ... [‎et al ...
NIST Diffusion Workshop Series Expand or Collapse. * 2011 Diffusion Workshop Presentations * 2010 NIST Diffusion Workshop ... 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 ... Ni/René-88 and René-88/IN718 Diffusion couple data reported in J. Phase Equilibria & Diffusion 25 (2004) 6-15. ...
Diffusion. - Diffusion-rate component of continuous-time stochastic differential equations (SDEs). value stored from diffusion- ... diffusion. function to create diffusion. objects of the form. G. (. t. ,. X. t. ). =. D. (. t. ,. X. t. α. (. t. ). ). V. (. t ... Diffusion: diffusion rate function G(t,X(t)) Simulation: simulation method/function simByEuler Sigma: 0.16 Return: 0.03 ... diffusion. objects in the most general form to emphasize the functional (t, Xt) interface. However, you can specify the ...
Increase and Diffusion were placed in the tower in January 1977, and they hatched three young owlets that spring. However, when ... The pair were named "Increase" and "Diffusion" in a nod to the language in James Smithsons bequest to the U.S. to found the ... Institution, which was to be "an establishment for the increase and diffusion of knowledge." ...
Nokia sites use cookies to improve and personalize your experience and to display advertisements. The sites may also include cookies from third parties. By using this site, you consent to the use of cookies. Learn more ...
DISK-DIFFUSION TEST PROCEDURE. *Warm, to room temperature, the appropriate number of GC agar plates for each strain to be ... Examine the disk diffusion plates from the back, viewed against a black background and illuminated with reflected light. With a ... In the disk-diffusion susceptibility test, disks containing known amounts of an antimicrobial agent are placed on the surface ... However, when performed correctly, the disk-diffusion and Etest susceptibility tests can be used to identify isolates of N. ...
Network Visualization / diffusion, network, simulation Kevin Simler uses interactive simulations to explain how things - ideas ...
Atmospheric Turbulence & Diffusion Division. Research into climate variability, boundary layer observations, and chemical ...
Diffusion of medical technologies. Examines the effects of new technologies introduced into the NHS in front of existing ... Health Care Technology Diffusion. Health Care Technology Diffusion in the NHS and Workforce Impact. ... It builds upon, and extends, existing research that focuses on the diffusion of medical technologies. The objective of this ...
Diffusion is a PR agency in London, New York and LA ... Welcome to Diffusion: A PR agency in London, New York and LA,/ ...
Reaction-diffusion in NEURON. Extending NEURON to handle reaction-diffusion problems.. Moderators: hines, wwlytton, ramcdougal ... Reaction-diffusion is included with NEURON 7.3 Last post by ted « Thu Apr 11, 2013 10:41 am. ... Node.d (Diffusion) for Node3D objects Last post by RBJ « Sat Nov 30, 2019 9:29 am. ... diffusion intracellular-,extracellular-,intracellular Last post by bremen « Sun Mar 03, 2019 8:17 am. ...
Lannan Foundation is a family foundation dedicated to cultural freedom, diversity, and creativity in support of exceptional contemporary artists, writers,…
... The Diffusion Studio is a sonically isolated, floating-construction room for advanced sound diffusion design and ... The core of the diffusion system is the RME Micstasy and RME M-32 DA providing 8 Mic inputs and 32 analogue outputs, Mac Pro 12 ...
... Chest. 1990 Oct;98(4):816-20. doi: 10.1378/ ... Diffusion impairment occurred as the sole abnormality in 31 percent of the patients and in combination with a restrictive ... Recognition of diffusion impairment as a common finding in patients with severe chronic congestive heart failure who are ... Diffusion impairment either alone or combined with restrictive and/or obstructive ventilatory defects occurred in 67 percent of ...
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... and exploiting heterogeneous technology diffusion from immigrant communities in the United States for identification. The ... "Migration, Knowledge Diffusion and the Comparative Advantage of Nations," PSE-Ecole déconomie de Paris (Postprint) halshs- ... "Migration, Knowledge Diffusion and the Comparative Advantage of Nations," CESifo Working Paper Series 5769, CESifo. * Bahar, ... "Migration, Knowledge Diffusion and the Comparative Advantage of Nations," Economic Journal, Royal Economic Society, vol. 128( ...
Now, Stable Diffusion offers the same capability but, critically, its open [...] ... Now, Stable Diffusion offers the same capability but, critically, its open source. Anyone with access to a powerful graphics ... Stable Diffusion now includes an AI-based safety classifier; however, given its open-source nature, people can disable the ...
Ive been using diffusion filters on my lenses for many years, but recently LEE Filters, the brand that makes the one that I ... If you like the soft, dreamy look of a diffusion filter, Josh Zaring has come up with a great idea of how to make your own. ... Its one of those ideas that make you think "why didnt I think of that?" He made his DIY diffusion filter from the stuff that ...
We then stipulate diffusion as the mechanism for mass transport. Please do let us know which apsepct of this section troubles ... I am reading your paper, "A theory of coupled diffusion and large deformation in polymeric gels", which I like very much. I am ... If you have a diffusion equation for. the internal order parameter, I have never seen any work (I might be ignorant here). ... re: coupled stress and diffusion in gels. Permalink Submitted by John E. Dolbow on Tue, 2007-09-18 09:37. ...
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This necessitates modification of the conventional laboratory diffusion experiments so that the diffusion of ions through the ... However, the influence of the applied electric field on diffusion characteristics of the intact rock mass has not been studied ... With this in view, diffusion tests were conducted on the samples of chalk and sandstone by applying electric fields of ... Efforts were also made to study the influence of the applied electric field on diffusion characteristics of these rocks. ...
Apparatus Diffusion Engineering Experiment Mass Permeability Science Spectrometer Safe for Work?. Yes. Download. SVG (Vector) ... Diffusion and Permeability Measurement Apparatus- Mass Spectrometer. by sunblaed - uploaded on August 23, 2011, 4:23 am ... An experimental apparatus to measure the diffusion or permeability of a compound through a membrane using a mass spectrometer. ...
  • We report progress towards computing the heavy quark momentum diffusion coefficient from the correlator of two chromoelectric fields attached to a Polyakov loop in pure SU(3) gauge theory. (
  • The relaxation parameters of the maltenes protons/deuterons were measured using the inversion recovery (T 1 ) and the Carr-Purcell-Meiboom-Gill (T 2 ) pulse sequence, while the stimulated echo pulse sequence was used to determine the self-diffusion coefficient. (
  • The question is where in the code/galdeffile can I find option to change the parameter D_z - diffusion coefficient in SDZ (slow diffusion region)? (
  • By employing Fick's second law, the diffusion behavior was investigated and the diffusion coefficient was obtained. (
  • Wong pointed out that non-specific low back pain patients who responded with greater than 30% relief to spinal manipulation therapy compared with non-responders demonstrated a higher apparent diffusion coefficient for diffusion of water into the disc. (
  • The Markov model exhibits some instability with grid length aspect when turbulence is incorporated by way of the turbulent diffusion coefficient, and advection is present. (
  • Levkovitch, A, Nachmani, E & Wolf, L 2022, ' Zero-Shot Voice Conditioning for Denoising Diffusion TTS Models ', Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH , vol. 2022-September, pp. 2983-2987. (
  • Stable Diffusion is a deep learning, text-to-image model released in 2022. (
  • 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. (
  • The only gaseous diffusion plant in operation in the United States is in Paducah, KY. (
  • Now, Stable Diffusion offers the same capability but, critically, it's open source. (
  • This is the fine-tuned Stable Diffusion model trained on high resolution 3D artworks. (
  • This model can be used just like any other Stable Diffusion model. (
  • For more information, please have a look at the Stable Diffusion . (
  • Stable Diffusion is a latent diffusion model, a variety of deep generative neural network developed by the CompVis group at LMU Munich.The model has been released by a collaboration of Stability AI, CompVis LMU, and Runway with support from EleutherAI and LAION. (
  • Stable Diffusion is an open-source machine learning model that can generate images from text, modify images based on text, or fill in details on low-resolution or low-detail images. (
  • The dynamic team of Robin Rombach (Stability AI) and Patrick Esser (Runway ML) from the CompVis Group at LMU Munich headed by Prof. Dr. Björn Ommer, led the original Stable Diffusion V1 release. (
  • You can read more about the original Stable Diffusion V1 release in our earlier blog post. (
  • Stable Diffusion 2.0 delivers a number of big improvements and features versus the original V1 release, so let's dive in and take a look at them. (
  • The Stable Diffusion 2.0 release includes robust text-to-image models trained using a brand new text encoder (OpenCLIP), developed by LAION with support from Stability AI, which greatly improves the quality of the generated images compared to earlier V1 releases. (
  • Stable Diffusion 2.0 also includes an Upscaler Diffusion model that enhances the resolution of images by a factor of 4. (
  • Combined with our text-to-image models, Stable Diffusion 2.0 can now generate images with resolutions of 2048×2048-or even higher. (
  • The underlying dataset for Stable Diffusion was the 2b English language label subset of LAION 5b, a general crawl of the internet created by the German charity LAION. (
  • To establish the most efficient method for extracting diffusion data (diffusion coefficients, fluxes, marker location) from multicomponent diffusion couple experiments. (
  • This dataset contains data to obtain the NMR relaxation parameters T 1 and T 2 , as well as the self-diffusion coefficients of different small molecules (maltenes) in a solvent in the absence and presence of a high asphaltene concentration. (
  • Also it is used to calculate the ion-ion recmbination coefficients and the rate of dispersion in the gas due to the ion mutual repulsion.Finally, diffusion and mobility data give information to understand the electrical discharges in gases. (
  • however, at 3 months the imaging showed increased L5S1 diffusion coefficients . (
  • The increased 'apparent diffusion coefficients' is promising yet when we look at other articles about diffusion of water into the disc. (
  • IMSEAR at SEARO: Effect of salbutamol on pulmonary diffusion functions in asymptomatic smokers. (
  • Mahajan SK, Mahajan KK, Singh K, Mishra N. Effect of salbutamol on pulmonary diffusion functions in asymptomatic smokers. (
  • Studies of manual therapy and traction effects on the intervertebral disc in back pain patients documented that there is an effect on the physiology (the structure and function) of the disc mainly via water diffusion and molecular transport . (
  • In this paper, we particularly investigate the reliability issue for diffusion‐based molecular communication. (
  • The results indicate that ATV algorithm works well in general case in improving reliability performance for diffusion‐based molecular communication. (
  • Reference strains listed in this brochure are quality control (QC) strains for the agar-dilution, disk diffusion, and Etest susceptibility procedures used to determine the antimicrobial susceptibilities of isolates of Neisseria gonorrhoeae . (
  • However, when performed correctly, the disk-diffusion and Etest susceptibility tests can be used to identify isolates of N. gonorrhoeae that exhibit decreased susceptibility, intermediate resistance, and resistance to antimicrobial agents. (
  • In the disk-diffusion susceptibility test, disks containing known amounts of an antimicrobial agent are placed on the surface of an agar plate containing a nonselective medium that has been inoculated with a suspension of a strain of N. gonorrhoeae to give a confluent lawn of growth. (
  • ABSTRACT We evaluated the utility of 2 methods for detection of methicillin-resistant Staphylococcus aureus (MRSA) directly from signal-positive blood culture bottles: loop-mediated isothermal amplification (LAMP) assay, and direct cefoxitin disk diffusion (DCDD) test using a 30 μg cefoxitin disk. (
  • Gonococcal Antimicrobial Surveil ance Programme has antimicrobials representing four different classes, namely operated in the Western Pacific and South-East Asian penicil in (PEN), ciprofloxacin (CIP), tetracycline (TCY), regions since 1992, but surveil ance of gonococcal anti- ceftriaxone (CRO) and cefixime (CFX), by disc diffusion microbial resistance (AMR) remains limited in the Asia- and gradient diffusion (Etest, BioMerieux). (
  • This paper surveys the existing literature on diffusion of environmentally beneficial technology. (
  • We explore the role of business services in knowledge accumulation and growth and the determinants of knowledge diffusion including the role of distance. (
  • A decreasing diffusion index shows there are fewer stocks moving higher, which indicates buying pressure is weakening and/or selling pressure is increasing on the stock index. (
  • In this work we study reaction-diffusion processes of topological signals coupled through the Dirac operator. (
  • This necessitates modification of the conventional laboratory diffusion experiments so that the diffusion of ions through the intact rock mass is accelerated. (
  • In case of using GEM detector as gaseous chambers, there are some assumptions to reach an analytical solution for the ions' diffusion in the gas. (
  • In his book, Diffusion of Innovations published in 1962, Everett Rogers, a sociology professor, provides a full framework for diffusion of innovation based on over 500 studies into the phenomenon in many different disciplines. (
  • Innovations in health and medicine : diffusion and resistance in the twentieth century / edited by Jennifer Stanton. (
  • To agree on a common diffusion mobility database assessment procedure. (
  • Importance of Ion Diffusion Study= Ion diffusion and mobility data in a gas theoretically and experimentally are important. (
  • In 1962, Everett Rogers proposed a 5-stage model to outline the diffusion of innovation process. (
  • We present a novel way of conditioning a pretrained denoising diffusion speech model to produce speech in the voice of a novel person unseen during training. (
  • A Markov chain model previously applied to the simulation of advection and diffusion process of gaseous contaminants is extended to three-dimensional transport of particulates in indoor environments. (
  • Comparisons with turbulent eddy diffusion models indicate that the Markov model exhibits numerical diffusion in the first seconds after release, but over time accurately predicts mean lateral dispersion. (
  • To develop standard problems and web site for inter-laboratory comparison of diffusion simulation methods and data extraction techniques. (
  • The terms diffusion, diffuse ligh t, or subsurface scattering all describe the effect of light that has been absorbed or scattered internally. (
  • The mechanism for the diffusion impairment is unclear but could be due to chronic passive congestion with pulmonary fibrosis and/or recurrent pulmonary emboli. (
  • The empirical analysis has three comparative advantages: including emerging and advanced economies, isolating panel variation regarding the link between productivity and exports, and exploiting heterogeneous technology diffusion from immigrant communities in the United States for identification. (
  • Heterogeneous Technology Diffusion and Ricardian Trade Patterns ," Harvard Business School Working Papers 14-039, Harvard Business School. (
  • Heterogeneous Technology Diffusion and Ricardian Trade Patterns ," The World Bank Economic Review , World Bank Group, vol. 32(1), pages 163-182. (
  • Heterogeneous technology diffusion and Ricardian trade patterns ," Policy Research Working Paper Series 8027, The World Bank. (
  • Heterogeneous Technology Diffusion and Ricardian Trade Patterns ," CESifo Working Paper Series 6216, CESifo. (
  • Heterogeneous Technology Diffusion and Ricardian Trade Patterns ," NBER Working Papers 19657, National Bureau of Economic Research, Inc. (
  • This is diffusion and so it's really just the spreading of particles or molecules from high concentration to low concentration areas, right? (
  • When we learn about diffusion , we often hear about the movement of particles from an area of high concentration to an area of low concentration, as if the particles themselves are somehow motivated to move in this direction. (
  • Return to the AX-65 Diffusion Pump here . (
  • Alternatively diffusion curves can be seen as minimizing the integral (over the entire image) of the squared gradient magnitude, with color constraints at certain points. (
  • Additional diffusion gradient pre-pulses can be applied with three diffusion directions and up to 16 b-values. (
  • To improve communication between experts in multicomponent diffusion measurement, analysis and simulation. (
  • Method of measurement: Diffusion tensor imaging and fiber tractography. (
  • Technology Diffusion, Services, and Endogenous Growth in Europe. (
  • Economic growth in Europe is enhanced to the extent that: trade in services increases, technology accumulation and diffusion increase, regulation becomes both less intensive and more uniform across countries, and human capital accumulation increases in all countries. (
  • Corey Allan, Adam B. Jaffe and Isabelle Sin (2014), "Diffusion of Green Technology: A Survey", International Review of Environmental and Resource Economics: Vol. 7: No. 1, pp 1-33. (
  • With respect to policy instruments, there is some evidence that the flexibility of market-based instruments can have a beneficial impact on technology diffusion, but there are also numerous cases in which regulations have forced the adoption of new technologies. (
  • The diffusion of innovation incorporates a 5-part process for adoption which includes knowledge, persuasion, decision making, implementation and finally confirmation. (
  • The diffusion of innovation is the process by which new products are adopted (or not) by their intended audiences. (
  • Rogers' draws on Ryan and Gross's work to deliver a 5 stage process for the diffusion of innovation. (
  • Diffusion started working with GoPro at the beginning of April, following an RFP process that took place in March. (
  • An in-situ refractive index method is applied to study the diffusion process of sucrose in hydrogels. (
  • Performing the characterization of plates after diffusion welding using this method allows a useful assessment of the material state as a function of the diffusion bonding process. (
  • The heat exchanger assembly procedure currently proposed involves high temperature and high pressure diffusion welding of stainless steel plates. (
  • Single-shot EPI diffusion imaging (DWI) can be used for non-invasive assessment of tissue structure and to demonstrate pathology based on fluid motion states at the cellular level. (
  • A diffusion index also refers to how many Business Cycle Indicators (BCI) are moving together. (
  • A diffusion index refers to the common tendency within a group of numbers or statistics. (
  • In the stock market, a diffusion index refers to whether more stocks are declining or falling within an index like the S&P 500 . (
  • Diffusion refers to the pattern of adoption of a new product. (
  • An in situ diffusion parameter is defined and calculated for a hypothetical unfractured lump of coal in the Pittsburgh and Pocahontas No. 3 Coalbeds. (
  • Diffusion of innovation explains how target audiences react to new products, whether the new products are adopted or rejected. (
  • These dimensions respectively draw upon three theories: diffusion of innovation theory, resource dependence theory, and institutional theory. (
  • Does anybody out there have any experience of using Fluent for multiphase models where diffusion of the phases may be important. (
  • They built on their prior work of the lab with Latent Diffusion Models and got critical support from LAION and Eleuther AI. (
  • To establish a general approach to data handling and diffusion modeling in ordered phases. (
  • This solidified previous research into the adoption of seeds in agricultural communities and provided a strong basis for diffusion research in the future. (
  • Diffusion will also generate press for initiatives that go beyond product, including GoPro's global creator initiatives and its GoPro Awards program. (
  • Diffusion, especially FACILITATED DIFFUSION , is a major mechanism of BIOLOGICAL TRANSPORT . (
  • The study of reaction-diffusion systems on networks is of paramount relevance for the understanding of nonlinear processes in systems where the topology is intrinsically discrete, such as the brain. (
  • Efforts were also made to study the influence of the applied electric field on diffusion characteristics of these rocks. (
  • A gas diffusion study measures how much oxygen and other gases transfer from your lungs to your blood. (
  • The theoretical and experimental study of alpha RF discharges presented in this paper has resulted in the formulation of a set of similarity and scaling laws for diffusion-cooled alpha RF discharge-excited CW waveguide CO 2 lasers. (
  • En parallèle, une identification microbiologique normalisée et un test de sensibilité à l'oxacilline par PCR visant l'amplification du gène MecA ont été réalisés. (
  • Until now reaction-diffusion systems have been studied only when species are defined on the nodes of a network. (
  • Diffusion index" is a general term that may be used in other areas of statistics or finance to assess how many components of a group are moving higher or lower. (
  • S. Cerrai, Stochastic reaction-diffusion systems with multiplicative noise and non-Lipschitz reaction term , Probab. (
  • I've been using diffusion filters on my lenses for many years, but recently LEE Filters, the brand that makes the one that I use, ceased production of them. (
  • The convection-diffusion eigenvalue problems have important physical background, such as convection-diffusion in fluid mechanics and environmental problems. (
  • This is a delicious example of diffusion , or the movement of matter from a region of high concentration (the cookie pan in the kitchen) to a region of low concentration (the corner bedroom). (
  • The Diffusion Studio is a sonically isolated, floating-construction room for advanced sound diffusion design and experimentation. (
  • In this report the importance of diffusion in controlling the emission of methane in mines is examined. (
  • It builds upon, and extends, existing research that focuses on the diffusion of medical technologies. (
  • Rogers' text, to this day, provides the formal understanding on which modern research into the diffusion of innovation is based. (
  • Their original contributions cover the key issues and questions around policy transfer, diffusion and circulation research. (
  • Offering a pluralist perspective and focusing on critical areas of research including policy transfer, diffusion, circulation and mobilities, this Handbook overcomes epistemological and methodological cleavages in the field. (
  • Generally, if the diffusion index is rising with a stock index, that helps confirm that the uptrend within the stock index is strong, as an increasing number of stocks are moving higher. (
  • Diffusion difficult to implement efficiently (fast solvers on grids generally use multigrid methods or kernels of spatially varying size). (