TY - JOUR. T1 - pH Dependence of and Kinetic Solvent Isotope Effects on the Methanolysis and Hydrolysis of β-Lactams Catalyzed by Class C β-Lactamase. AU - Page, Michael I.. AU - Vilanova, Bartolomé. AU - Layland, Nicola J.. PY - 1995/12. Y1 - 1995/12. N2 - The methanolysis of benzylpenicillin is catalyzed by Enterobacter cloacae P99 class C β-lactamase and the pH dependence of kcat indicates that the catalytic groups involved of pKa ca. 5 and 10 are the same as those for hydrolysis. The kinetic solvent isotope effect (KSIE) is 1.42 for both the hydrolysis and methanolysis of benzylpenicillin. However, there is an inverse KSIE on of 0.83 ± 0.05 for the hydrolysis of benzylpenicillin and cephaloridine. There is also an abnormally high shift in the low pKa on going from H2O to D2O of 0.85 ± 0.15 from the pH dependence of both kcat and kcat/Km for both methanolysis and hydrolysis. The D2O shift on the high pKa of ca. 10 is the normal value of ca. 0.4. These results are consistent with a ...
A method for the detection of six trace heavy metal elements Cr,Ni,Cu,As,Cd,Pb and four lead isotopes in PM2.5by HNO3- H2O2digestion and ICP-MS was established.By the correction of internal elements,the effects of matrix and physics,and fluctuation of instrument were overcome effectively.Under the optimum instrumental operation parameters,the correlation coefficients of working curves of six elements and lead isotopes were over 0.9997.The detection limits of five trace elements and four lead isotopes were 0.01 ~ 0.07μg/L and 0.014 ~ 0.07μg/L,respectively.The mean values of national standard reference material GBW(E) 080212 and NIST981 were in good agreement with certified standard values.It was found that the relative standard deviation(RSD) of lead isotope was stable when the concentration of lead was more than 10 μg/L.Using this method,the detection system of PM2.5has a good stability with RSDs of six trace elements less than 4.8%,and with RSD of lead isotopes less than 0.5%.It shows that the
A general method for computing kinetic isotope effects is described. The method uses the quantum-instanton approxn. and is based on the thermodn. integration with respect to the mass of the isotopes and on the path-integral Monte- A general method for computing kinetic isotope effects is described. The method uses the quantum-instanton approximation and is based on the thermodynamic integration with respect to the mass of the isotopes and on the path- integral Monte-Carlo evaluation of relevant thermodynamic quantities. The central ingredients of the method are the Monte-Carlo estimators for the logarithmic derivatives of the partition function and the delta-delta correlation function. Several alternative estimators for these quantities are described here and their merits are compared on the benchmark hydrogen-exchange reaction, H+H_2-|H_2+H on the Truhlar-Kuppermann potential energy surface. Finally, a qualitative discussion of issues arising in many- dimensional systems is provided. Vanicek, Jiri;
Lead isotopes are studied to determine possible sources of lead in aqueous environments and mixing of different waters, and to elucidate groundwater flow paths. The method has been applied in numerous and various cases, for example in anthropogenic contamination studies, such as gasoline-contamination (Landmeyer et al. 2003) and in traffic-related pollution (Walraven et al. 2014), in mineral exploration (De Caritat et al. 2005), in studying an impact of local contamination in continental-scale and in mapping natural geochemical background (Reimann et al. 2012), in determining impact of historical mining in the environment (Camizuli et al. 2014), and in studying water-rock interaction (Négrel et al. 2010). The history of environmental lead isotope studies is described, for example, by Dickin (2005).. Lead has four stable isotopes (natural abundance in brackets); 204Pb (1.4%), 206Pb (24.1%), 207Pb (22.1%), and 208Pb (52.4%). The last three of them are radiogenic, and are produced from the ...
Analytical methods were developed for precise isotope effect studies of the solvolysis of alkyl halides in CD3OH-CH3OH mixtures, determining the isotope effect for product formation by competition. The products of solvolysis can be isolated from the relatively large volume of solvent, without isotope fractionation, using gas chromatography and special collectors cooled with liquid nitrogen. These products can then be analyzed for the ratio of CD3 to CH3 groups present by high-precision mass spectrometric measurements. Precise isotope effect data have not as yet been collected. (Author)(*ORGANIC SOLVENTS
TY - JOUR. T1 - Metabolism of fructose in B-cells. T2 - A 13C NMR spectroscopy based stable isotope tracer study. AU - Ijare, Omkar B.. AU - Baskin, David S.. AU - Sharpe, Martyn A.. AU - Pichumani, Kumar. N1 - Funding Information: This study was supported by the Donna and Kenneth R. Peak Foundation, The Kenneth R. Peak Brain and Pituitary Tumor Treatment Center at Houston Methodist Hospital, The Houston Methodist Foundation, The Taub Foundation, The Pauline Sterne Wolff Foundation, The Veralan Foundation, and The John S. Dunn Foundation. We would like to thank Sophie Lopez for maintaining the cell lines and growing cells for this study. Funding Information: This study was supported by the Donna and Kenneth R. Peak Foundation , The Kenneth R. Peak Brain and Pituitary Tumor Treatment Center at Houston Methodist Hospital , The Houston Methodist Foundation , The Taub Foundation , The Pauline Sterne Wolff Foundation , The Veralan Foundation , and The John S. Dunn Foundation . We would like to thank ...
My PhD thesis involved determining kinetic isotope effects (KIE) for aromatic electrophilic substitution reactions in an effort to learn more about the nature
What do experimentally measured kinetic isotope effects (KIEs) tell us about H-abstraction reactions with multispin-state reactivity options? Using DFT calculations with tunneling corrections for experimentally studied H-abstraction reactions of porphyrin-Compound II species (Chem.-Eur. J. 2014, 20, 14437; Angew. Chem., Int. Ed. 2008, 47, 7321) with cyclohexane, dihydroanthracene (DHA), and xanthene (Xan), we show here that KIE is a selective probe that identifies the experimentally reactive spi
The abundance of different isotopes in a system are usually reported as isotope ratio R or more commonly in the delta notation relative to the isotope ratio of reference material (see Chapter 2) where HA is the amount of heavy isotope in the system, LA the amount of the light isotopes, and Rstd the isotope ratio of the reference material. Since variations of isotope ratios are often small, the 5-values are usually expressed on a per mill scale by multiplication with 1000. For example a value of.... ...
[116 Pages Report] Check for Discount on Europe Stable Isotopes Market by Manufacturers, Countries, Type and Application, Forecast to 2022 report by Global Info Research. This report studies the Stable Isotopes market, stable isotopes included...
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Protein stable isotope probing (protein-SIP) has strong potential for revealing key metabolizing taxa in complex microbial communities. While most protein-SIP work to date has been performed under controlled laboratory conditions to allow extensive isotope labeling of the target organism, a key application will be in situ studies of microbial communities under conditions that result in small degrees of partial labeling. One hurdle restricting large scale in situ protein-SIP studies is the lack of algorithms and software for automated data processing of the massive data sets resulting from such studies. In response, we developed Stable Isotope Probing Protein Extraction Resources software (SIPPER) and applied it for large scale extraction and visualization of data from short term (3 h) protein-SIP experiments performed in situ on Yellowstone phototrophic bacterial mats. Several metrics incorporated into the software allow it to support exhaustive analysis of the complex composite isotopic ...
Trends in Ecology and Evolution 16:153-162. , L. Aragua´s-Aragua´s, and R. Gonfiantini. 1993. Isotopic patterns in modern global precipitation. Geophysical Monograph 78:1-36. Ruddiman, W. F. 2004. Earths Climate: Past and Future. H. Freeman Publishers, New York. Rundel, P. , J. R. Ehleringer, and K. A. ). 1989. Stable Isotopes in Ecological Research. Ecological Studies, Vol. 68, Springer-Verlag, Heidelberg. 525 p. , J. Radke, and G. Gleixner. 2006. dD values of individual n-alkanes from terrestrial plants along a climatic gradient- Implications for the sedimentary biomarker record. 1997. Environmental Isotopes in Hydrogeology. CRC Press, Boca Raton. Coplen, T. , J. A. Hopple, J. K. Bo¨hlke, H. S. Peiser, S. E. Rieder, H. R. Krouse, K. J. R. Rosman, T. Ding, R. D. , K. M. Re´ve´sz, A. Lamberty, P. Taylor, et al. 2002. Compilation of minimum and maximum isotope ratios of selected elements in naturally occurring terrestrial materials and reagents. USGS Water-Resources Investigations Report ...
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Isotopes can be thought of as different flavours of a particular element (such as oxygen or carbon), that are distinguished by the number of neutrons in their nucleus (and hence their atomic mass). Carbon for instance most commonly has a mass of 12 (written as 12C), but there are also a small fraction of carbon atoms with mass 13 and 14 (13C and 14C), similarly oxygen is normally 16O, but with small amounts of 17O and 18O. All of the isotopes of an element behave in similar way chemically. However, because the mass of each isotope is slightly different there are certain physical processes that will discriminate (or fractionate) between them. For instance, during evaporation of water, it is slightly easier for the lighter isotopes to escape from the liquid, and so water vapour generally has less 18O than the liquid water from which it came. Because of these physical effects, looking at the ratio of one isotope to another can often be very useful in tracing where these atoms came from.. ...
Isotopes may be referred to in the medical literature alone or as a component of a radiopharmaceutical administered for therapeutic or diagnostic purposes. The nomenclature for the isotopes incorporated in radiopharmaceuticals follows the international nonproprietary name (INN) drug nomenclature and therefore differs from that of isotopes that occur as elements alone. | An isotope referred to as an element rather than as part of the name of a chemical compound may be described at first mention by providing the name of the element spelled out followed by the isotope number in the same typeface and type size (no hyphen, subscript,
Isotopes may be referred to in the medical literature alone or as a component of a radiopharmaceutical administered for therapeutic or diagnostic purposes. The nomenclature for the isotopes incorporated in radiopharmaceuticals follows the international nonproprietary name (INN) drug nomenclature and therefore differs from that of isotopes that occur as elements alone. | An isotope referred to as an element rather than as part of the name of a chemical compound may be described at first mention by providing the name of the element spelled out followed by the isotope number in the same typeface and type size (no hyphen, subscript,
Free amino acids. Stable isotopes for metabolic studies. CortecNet is a Stable Isotopes-driven company. We produce over than 2000 innovative labeled compounds with stable isotopes (13C, 15N, D).
Cambridge Isotope Laboratories offers a complete listing of Stable Isotope Labeled Deuterated Solvents for Dissolution DNP for all your research needs. View pricing, availability and product specifications.
Medical Isotopes, Inc. a premier manufacturer of stable isotope chemicals labeled with: Deuterium, C13, N15, O18 and metal isotopes. We specialize in custom synthesis with isotopes and non-labeled compounds.
Medical Isotopes, Inc. a premier manufacturer of stable isotope chemicals labeled with: Deuterium, C13, N15, O18 and metal isotopes. We specialize in custom synthesis with isotopes and non-labeled compounds.
Helium-4 (also written 4He) is an isotope of helium. It is the most common isotope of helium in the universe. Out of all the helium on the Earth, 99.99986% are helium-4. The nucleus (the center) of a helium-4 atom is also known as the alpha particle. Helium-4 is made of 2 protons (the part of an atomic nucleus with a positive charge), 2 neutrons (the part of an atomic nucleus with a negative charge) and 2 electrons (the part of an atom that goes around the nucleus with a negative charge).. Many helium-4 on Earth is produced from alpha decay of heavy elements. In the Sun and the whole universe, most helium-4 is made during the Big Bang, the event that created the universe. This Big Bang helium-4 is known as the primordial helium. Helium-4 is also made in nuclear fusion at the center of stars. Primordial helium is not much on Earth, because most of it had escaped from the Earth when it was created and the temperatures were very high. Helium-4 on Earth was made through radioactive decay (when ...
So, how do you trap a helium-8 isotope? The answer is far from simple, but Argonne physicist Peter Mueller has found a solution. Using the GANIL cyclotron facility in northern France, helium-4, 6, and occasionally helium-8 isotopes can be generated. This is one of the only cyclotrons is the world with enough energy to generate the helium-8 isotope. It is all very well creating the particle, but to separate helium-8 from its other helium isotope siblings requires a clever and highly accurate laser prison for the heavier helium isotope to fall in to, whilst allowing the other, lighter, isotopes to fly straight through.. Acting as the bars of prison gates, six lasers are accurately aligned at such spacing that only isotopes with the dimensions of helium-8 are trapped. When aligned, helium-8 will fall between them, and should the isotope try to escape, repulsion forces keep the isotope still. Once enough time is allowed to pass (about one helium-8 atom is generated every two minutes) the team ...
The appeal of helium-3 fusion stems from the nature of its reaction products. Helium-4 is non-radioactive and the lone high-energy proton produced is easily contained using electric and magnetic fields. In contrast, most other proposed fusion processes for power generation lead to the production of energetic neutrons, bombardment with which renders reactor components radioactive. Most of the energy from the conventional fusion reaction is given off in this form, which is difficult to harness for energy; whereas the proton can be contained and leads to high temperatures which might be liberated for energy generation. Helium-3 is used in cryogenics to achieve temperatures as low as a few thousandths of a kelvin; it was discovered by the Australian nuclear physicist Mark Oliphant while based at Cambridge Universitys Cavendish Laboratory. An important property of helium-3, which distinguishes it from the more common helium-4, is that its nucleus is a fermion since it contains an odd number of ...
Polarean Imaging Ltd. is manufacturer and service provider for noble gas polarizer devices and ancillary instruments with special focus on pulmonary imaging using hyperpolarized gas MRI. Current product offerings of Polarean Imaging Ltd. include xenon-129 and helium-3 polarizers, polarization measurement stations and upgrade kits for existing polarizers
Chris Knowles of Oregon State University and I got into some SERIOUS chemistry last week. Lets see how it applies to the wood industry now.. Chris, you gave us a chemistry lesson last week. How do we USE this stable isotope analysis in the real world?. Among other uses, stable isotope analysis has a relatively long history of use for dating materials. Carbon dating provides an estimation of generally ±50 years for samples less than about 10,000 years old. However, the older the material, the less accurate the estimation will be. This estimate is based on a number of assumptions that may or may not be accurate. The bottom line is that this type of analysis will not identify the exact age of any material. It will only provide an estimate.. More recently, scientists have been exploring the potential to use the natural variability in stable isotopes by region to determine geographic origin of natural materials, including wood products. While the chemical analysis has a long history of use in other ...
This article presents an overview of the history of Caribbean archaeological carbon and nitrogen stable isotope studies, a history that is paradoxically notable both for the precociousness of its first appearance and the subsequent dearth of large and meaningful studies. It provides a synopsis of the methodological underpinnings of paleodietary reconstruction by stable isotope analysis and discusses some of the unique challenges encountered in the use of this technique in Caribbean contexts. After reviewing some of the more meaningful studies of Caribbean archaeological materials, the article concludes with some thoughts on future prospects for the use of C and N stable isotope analysis for paleodietary reconstruction in archaeological research in the Caribbean Basin.
TY - GEN. T1 - Stable isotope analysis of breath using the optogalvanic effect. AU - Murnick, Daniel E.. AU - Colgan, M. J.. AU - Lie, H. P.. AU - Stoneback, D.. PY - 1996/1/1. Y1 - 1996/1/1. N2 - A new technique based on the optogalvanic effect has been developed for the measurement of stable isotope ratios in the carbon dioxide of exhaled breath. Data obtained before and after ingestion of harmless stable isotope labeled compounds, metabolized to carbon dioxide, can be used for sensitive noninvasive diagnostics of various disease conditions. The technique uses the specificity of laser resonance spectroscopy and achieves sensitivity and accuracy typical of sophisticated isotope ratio mass spectrometers. Using fixed frequency carbon dioxide lasers, 13C/ 12C ratios can be determined with a precision of 2 ppm with 100 second averaging times. Multiple samples can be analyzed simultaneously providing real time continuous calibration. In a first application, analysis of 13C/ 12C ratios in exhaled ...
HHe3 magnetic resonance provides a new technique for imaging the distribution of inhaled air in the lungs. The technique is suitable for following responses to treatment of asthma and changes after methacholine or exercise challenge.
PubMed Central Canada (PMC Canada) provides free access to a stable and permanent online digital archive of full-text, peer-reviewed health and life sciences research publications. It builds on PubMed Central (PMC), the U.S. National Institutes of Health (NIH) free digital archive of biomedical and life sciences journal literature and is a member of the broader PMC International (PMCI) network of e-repositories.
TY - JOUR. T1 - Deuterium and carbon-13 kinetic isotope effects for the reaction of OH with CH4. AU - Melissas, Vasilios S.. AU - Truhlar, Donald G.. PY - 1993/1/1. Y1 - 1993/1/1. N2 - Interpolated variational transition state theory calculations with centrifugal-dominant, small-curvature tunneling coefficients have been carried out for the case of the deuterium kinetic isotope effect (KIE) in the reaction OH + 12CD4 → HDO+12CD3 and for the 13C KIE for the reaction OH + 13CH4 → H2O + 13CH3. The interpolated variationally optimized generalized transition states predict notably different nontunneling KIEs than the conventional ones, and factorization analyses of the KIEs are presented to illustrate the origin of the differences. The zero-point energies at the variational transition states differ from those at the saddle point by up to 0.19 kcal/mol for the OH + 12CD4 reaction and by up to 0.34 kcal/mol for the OH + 12CH4 reaction. The incorporation of multidimensional tunneling effects partly ...
Helium-3 occurs as a primordial nuclide, escaping from the Earths crust into the atmosphere and into outer space over millions of years. Helium-3 is also thought to be a natural nucleogenic and cosmogenic nuclide, one produced when lithium is bombarded by natural neutrons. Those are released by spontaneous fission and by nuclear reactions with cosmic rays. Some of the helium-3 found in the terrestrial atmosphere is also a relic of atmospheric and underwater nuclear weapons testing, conducted by the three big nuclear powers before 1963. Most of this comes from the decay of tritium (hydrogen-3), which decays into helium-3 with a half life of about 12.3 years. Furthermore, some nuclear reactors (landbound or shipbound) periodically release some helium-3 and tritium into the atmosphere, especially whenever something goes wrong. The nuclear reactor disaster at Chernobyl released a huge amount of radioactive tritium into the atmosphere, and smaller problems cause smaller releases. Furthermore, ...
name=full demo , conventional atomic weight= , standard atomic weight=238.02891(3) , standard atomic weight ref=,ref,Reference for A,sub,r,/sub,,/ref, , isotopes table footnote=* = [[excited state]]{{sfn,Chisté,2006}} , isotopes = {{Infobox element isotopes/isotopes stable , link=Fluorine-19 , mn=19 , sym=F , na=100% , n=10 }} {{Infobox element isotopes/isotopes decay , mn=251 , sym=Cf , na=trace , hl=898 y , dm=α , de=6.172 , link1=curium-247 , pn=247 , ps=Cm }} {{Infobox element isotopes/isotopes decay2 , mn=252 , sym=Cf , na=trace , hl=2.645 y , dm1=α (96.91%) , de1=6.217 , link1=curium-248 , pn1=248 , ps1=Cm , dm2=SF (3.09%) , de2=- , pn2= , ps2=- }} {{Infobox element isotopes/isotopes decay3 , mn=26 , sym=Al , na=[[trace radioisotope,trace]] , hl=7.17×105 y , dm1=[[Positron emission,β,sup,+,/sup,]] , de1=1.17 , link1=magnesium-26 , pn1=26 , ps1=Mg , dm2=[[electron capture,ε]] , de2=- , link2=magnesium-26 , pn2=26 , ps2=Mg , dm3=[[Gamma radiation,γ]] , de3=1.8086 , pn3= , ps3=- }} ...
name=full demo , conventional atomic weight= , standard atomic weight=238.02891(3) , standard atomic weight ref=,ref,Reference for A,sub,r,/sub,,/ref, , isotopes table footnote=* = [[excited state]]{{sfn,Chisté,2006}} , isotopes = {{Infobox element isotopes/isotopes stable , link=Fluorine-19 , mn=19 , sym=F , na=100% , n=10 }} {{Infobox element isotopes/isotopes decay , mn=251 , sym=Cf , na=trace , hl=898 y , dm=α , de=6.172 , link1=curium-247 , pn=247 , ps=Cm }} {{Infobox element isotopes/isotopes decay2 , mn=252 , sym=Cf , na=trace , hl=2.645 y , dm1=α (96.91%) , de1=6.217 , link1=curium-248 , pn1=248 , ps1=Cm , dm2=SF (3.09%) , de2=- , pn2= , ps2=- }} {{Infobox element isotopes/isotopes decay3 , mn=26 , sym=Al , na=[[trace radioisotope,trace]] , hl=7.17×105 y , dm1=[[Positron emission,β,sup,+,/sup,]] , de1=1.17 , link1=magnesium-26 , pn1=26 , ps1=Mg , dm2=[[electron capture,ε]] , de2=- , link2=magnesium-26 , pn2=26 , ps2=Mg , dm3=[[Gamma radiation,γ]] , de3=1.8086 , pn3= , ps3=- }} ...
Results from Hammett correlation studies and primary kinetic isotope effects for the CuCl-TEMPO catalysed aerobic benzyl alcohol oxidations are inconsistent with an oxoammonium based mechanism. We postulate a copper-mediated dehydrogenation mechanism, in which TEMPO regenerates the active Cu(ii)-species. Thi
Most of the other cards that use power counters have been discussed in @tiggys review below; however there are a few notable additions to the power counter suite that allow for interesting new interactions with Helium-3.. Estelle Moon will probably have no lack of power counters on her already, especially in a asset-heavy deck. Two extra power counters on her counts towards two more cards and 4 extra when you cash her in.. Free Lunch will probably not be seeing play in your Weyland deck, unless youre playing some kind of porous successful-run based murder play. But it is also a card that is likely to see power counters, unlike Data Raven and its cousins. Two extra power counters on it counts towards the Runner losing 1, 2, or 3 at any point, maybe even at a critical juncture. (jank: right before a psi game?). Chief Slee has been mentioned already, as two power counters go a long way towards making those critical five. Two extra power counters on her counts towards... death???? (its ...
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Horse Racing Forum - Helium- Mark Casse runnner - Gerh said... s for long shots,Rombauer impressed me over the weekend.Good ride by Geroux I have a feeling he is better for the belmont. Was looking at timeform stuff and his last furlong isnt fast enough to win I dont think? He can take his time in the BEL and run em down because he has the lungs to do so. Of course so do many others, I have a feeling that is going to be the most exciting race of the TC series this year. This is why I hope O Besos gets in. I think he ran the fastest adj. last furlong of any horse besides Known Agenda so far.....
Horse Racing Forum - Helium- Mark Casse runnner - Wintertrian said: My job this week is to rewatch the Southwest and Rebel Stakes carefully Thats Your back in the saddle Sneaky longshot play and toss ! :)
Greater and lesser scaup are often found together, but the larger size of the greater scaup is very obvious. Male greater scaup also have a larger, more round, green-tinted head than male lesser scaup. Male greater scaup have a glossy black head tinted green. The neck, breast and upper mantle are glossy black, and the flanks and belly are white, sometimes with gray vermiculations on the lower flanks. The back is whitish with fine black vermiculations, and the tail and upper- and under-tail coverts are black. The wing has a broad white speculum spanning nearly the entire length of the primaries and secondaries. The bill is a light blue-gray with a black nail, the legs and feet are gray and the iris is yellow. Female greater scaup are brown with white oval patches around their bills. The females bill is similar to that of the male, but slightly duller, and the legs and feet are gray. ...
Free Online Library: Lead Isotopes as a Supplementary Tool in the Routine Evaluation of Household Lead Hazards. by Environmental Health Perspectives; Health, general Environmental issues
Iwai, Yasunori; Kubo, Hitoshi*; Sato, Katsumi; Oshima, Yusuke*; Noguchi, Hiroshi*; Taniuchi, Junichi*. Hydrophobic platinum catalysts have been developed especially for combustion of hydrogen isotopes released in a nuclear facility. A new type of hydrophobic hydrogen combustion catalyst commercially named TKK-KNOITS catalyst is hardly susceptible to water mist and water vapor in the atmosphere and water produced by hydrogen combustion. It is capable of maintaining the activity even at relatively low temperatures. The TKK-KNOITS catalyst is superior to other previous hydrophobic catalysts in applicability to wide range of hydrogen concentration from very thin to dense. The catalyst which carrier is composed of inorganic oxide has thermal stability up to 873 K.. ...
Fingerprint Dive into the research topics of Investigation of hydrogen isotopes interaction with lithium CPS under reactor irradiation. Together they form a unique fingerprint. ...
On the previous Isotope page, you learned a bit about what isotopes are, how they are obtained, and how the isotopes of certain elements are measured. Here, well elaborate on how to read carbon and oxygen isotope data and how the values are often interpreted by paleoclimatologists. Reading Isotope Data Measurements of carbon and oxygen…
ISOFLEX supplies stable and radioactive isotopes. We lead in pricing, enrichment, processing, and customer service. ISOFLEX is your premier isotope supplier.
ISOFLEX supplies stable and radioactive isotopes. We lead in pricing, enrichment, processing, and customer service. ISOFLEX is your premier isotope supplier.
Natural calcium is a mixture of five stable isotopes (40Ca, 42Ca, 43Ca, 44Ca, and 46Ca) and one isotope with a half-life so long that it can be considered stable for all practical purposes (48Ca, with a half-life of about 4.3 × 1019 years). Calcium is the first (lightest) element to have six naturally occurring isotopes.[12] By far the most common isotope of calcium in nature is 40Ca, which makes up 96.941% of all natural calcium. It is produced in the silicon-burning process from fusion of alpha particles and is the heaviest stable nuclide with equal proton and neutron numbers; its occurrence is also supplemented slowly by the decay of primordial 40K. Adding another alpha particle would lead to unstable 44Ti, which quickly decays via two successive electron captures to stable 44Ca; this makes up 2.806% of all natural calcium and is the second-most common isotope. The other four natural isotopes, 42Ca, 43Ca, 46Ca, and 48Ca, are significantly rarer, each comprising less than 1% of all natural ...
These elements have several common characteristics: 1)They have low atomic mass; 2)The relative mass difference between the isotopes is large; 3)They form bonds with a high degree of covalent character; 4)They exist in more than one oxidation state, form a wide variety of compounds; 5)The abundance of the rare isotope is sufficiently high (at least tenths of a percent) to facilitate analysis. Terrestrial Abundance of Stable Isotopes: ElementIsotopeAbundance % Hydrogen 1 H H0.015 Carbon 12 C C1.11 Nitrogen 14 N N0.37 Oxygen 16 O O O0.204 Sulfur 32 S S S S0.014
|p|The only circumpolar diving duck, the Greater Scaup breeds across the tundra regions in North America and Europe. They congregate by the hundreds and thousands along the Pacific and Atlantic coasts during winter. Here, black-and-white males and chocolatey-brown females bob along on the waves. They look remarkably similar to the Lesser Scaup, with only slight differences in head shape: the Greater Scaup has a rounded head, the Lesser Scaup a peaked head. These underwater divers eat aquatic invertebrates and plants at the bottom of lakes and bays. |/p|
Isotopic distribution is a function of physical and biological processes. In general, equilibrium-controlled reactions occur at high temperatures among solid phases, whereas low-temperature reactions, especially those mediated by organisms, are kinetically controlled. The solar and stellar abundance of isotopes is poorly known. Knowledge of extra-terrestrial distributions of the isotopes of light elements presently comes from lunar and meteorite measurements. On Earth, the elements associated with biological synthesis which have been studied most intensively, are hydrogen, carbon, nitrogen, oxygen and sulphur. In general, reduced products of metabolism are enriched in light isotopes. Thus, 1H and 12C are enriched in hydrogen gas and methane, when produced by fermentation or CO2 reduction. Nitrogen gas is enriched in 14N when produced by denitrification, and H2S is highly enriched in 32S when it results from sulphate reduction. A pattern of biological enrichment factors has been recognized on ...
Amino acid stable isotope tracer methodologies are increasingly used in metabolic research for the measurement of muscle protein synthesis (MPS); yet a number of factors restrict their implementation, such as, i.v infusions, multiple cannulae, tissue samples and significant tracer, and pharmacy costs. The orally administered stable isotope tracer deuterium oxide (D2O) has the potential to provide a less invasive, restrictive and more cost‐effective alternative to these traditional amino acid (AA) tracer techniques. In the present study, we performed an internal comparison between L‐[ring‐13C6] phenylalanine and D2O within the same individuals in order to determine whether D2O could provide a robust, simpler, and less burdensome approach, for use in difficult to study clinical populations where repeated invasive sampling and i.v tracer administration may not be desirable. Measures of MPS yielded indistinguishable technique differences with respect to anabolic stimulus (20 g EAA feed), with ...
Principal Investigator:SAKURAI Yoichi, Project Period (FY):1996 - 1998, Research Category:Grant-in-Aid for Scientific Research (B), Section:一般, Research Field:Digestive surgery
Stable isotope ratios of hydrogen and oxygen are widely used in hydrology, biology, chemistry, environmental sciences, food and drug authentication,
Focuses on measurements and calculations of isotope effects in chemical reactions and photodissociation. Covers a variety of processes, ranging from the very simple (atom-diatom reactions) to the complex (multiligand coordination compounds) and includes both neutral and ionic species. Examines a variety of applications, including those to astrophysical, planetary, and atmospheric science. Both light- and heavy-atom isotope effects are covered.
In this study we obtain analytically the transition temperature T(c) which is similar to the one due to Allen and Dynes, and the isotope effect. Using the Eliashberg theory that includes both the electron-electron and electron-phonon interactions in superconductors, we calculate the transition temperature T(c) and the coefficient alpha of the isotope effect for a group of superconductors under study. ...
Cambridge Isotope Laboratories offers a complete listing of Stable Isotope Labeled Deuterium Bromide for all your research needs. View pricing, availability and product specifications.
Quantification of stable isotope tracers after metabolic labeling provides a snapshot of the dynamic state of living cells and tissue. A form of imaging mass spectrometry quantifies isotope ratios with a lateral resolution <50 nm, using a methodology that we refer to as multi-isotope imaging mass spectrometry (MIMS). Despite lateral resolution exceeding diffraction-limited light microscopy, lack of contrast has largely limited use of MIMS to large or specialized subcellular structures, such as the nucleus and stereocilia. In this study, we repurpose the engineered peroxidase APEX2 as the first genetically encoded marker for MIMS. Coupling APEX2 labeling of lysosomes and metabolic labeling of protein, we identify that individual lysosomes exhibit substantial heterogeneity in protein age, which is lost in iPSC-derived neurons lacking the lysosomal protein progranulin. This study expands the practical use of MIMS for cell biology by enabling measurements of metabolic function from stable isotope ...
UK – Meat procurement experts are calling in three years’ worth of data to assemble a Scotch beef authenticity test involving isotope analysis.
Fatty Acids. Stable isotopes for Metabolomics. CortecNet is a Stable Isotopes-driven company. We produce over than 2000 innovative labeled compounds with stable isotopes (13C, 15N, D).
TY - JOUR. T1 - Isotope effects in solution thermodynamics. T2 - Excess properties in solutions of isotopomers. AU - Jancsó, G.. AU - Rebelo, Luis P N. AU - Van Hook, W. Alexander. PY - 1993/12. Y1 - 1993/12. UR - http://www.scopus.com/inward/record.url?scp=0001431007&partnerID=8YFLogxK. UR - http://www.scopus.com/inward/citedby.url?scp=0001431007&partnerID=8YFLogxK. M3 - Article. AN - SCOPUS:0001431007. VL - 93. SP - 2645. EP - 2666. JO - Chemical Reviews. JF - Chemical Reviews. SN - 0009-2665. IS - 8. ER - ...
The abnormally large collectivity of neutron-rich magnesium isotopes in the island of inversion has not been well understood. It has been commented that the unexpectedly large deformations observed in the magnesium isotopes are attributed to the neutron f7/2 intruder orbits involved remarkably even in the ground states, which points to nuclear force directly. Recently, a new isospin-dependent Nilsson potential was suggested to improve the calculations of the ground states of magnesium isotopes. With the improved Nilsson potential, in the present work we investigate the collectivity of excited states by using the projected shell model. To avoid the collapse of the BCS pairing, which occurs in weak pairing, we improved pairing calculations by using the Lipkin-Nogami approach. The collectivity and the erosion of the N = 20 shell in neutron-rich magnesium isotopes are discussed by calculating spectra and electric quadrupole transitions. The gyromagnetic factors are calculated and compared with ...
Isotopes In 1932 James Chadwick, a British scientist, discovered the neutron. His discovery explains how isotopes are formed. Isotopes have the same number of protons, but different numbers of neutrons. We can also say that the atomic number is the same, but the mass numbers are different. Isotopes are the same element because their atomic…
The CURIEMENTOR 4 isotope calibrator is a highly sophisticated instrument for activity measurements in nuclear medicine including PET. It includes and exceeds the features of the CURIEMENTOR 3 isotope calibrator. The user has direct access to 30 different isotope calibrations. When measuring isotopes with rapid decay, the displayed measuring values are updated each half second, which provides continuous display. 18F activities of up to 92 GBq for PET applications can be measured. Up to 140 measuring results including administrative data can be stored internally. The features with respect to the chamber design, check device, RS232 interface and printer option are identical with the CURIEMENTOR 3 features. ...