The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Bin Jiang - One of the best experts on this subject based on the ideXlab platform.
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relative efficacy of vibrational vs translational excitation in promoting atom diatom reactivity rigorous examination of polanyi s rules and proposition of sudden vector projection svp model
Journal of Chemical Physics, 2013Co-Authors: Bin JiangAbstract:To provide a systematic and rigorous re-examination of the well-known Polanyi's rules, excitation functions of several A + BC(v = 0, 1) reactions are determined using the Chebyshev real wave packet method on accurate potential energy surfaces. Reactions with early (F + H2 and F + HCl), late (Cl + H2), and central (H/D/Mu + H2, where Mu is a short-lived Light Isotope of H) barriers are represented. Although Polanyi's rules are in general consistent with the quantum dynamical results, their predictions are strictly valid only in certain energy ranges divided by a cross-over point. In particular, vibrational excitation of the diatomic reactant typically enhances reactivity more effectively than translational excitation at high energies, while reverse is true at low energies. This feature persists irrespective of the barrier location. A sudden vector projection model is proposed as an alternative to Polanyi's rules. It is found to give similar, but more quantitative, predictions about mode selectivity in thes...
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relative efficacy of vibrational vs translational excitation in promoting atom diatom reactivity rigorous examination of polanyi s rules and proposition of sudden vector projection svp model
Journal of Chemical Physics, 2013Co-Authors: Bin Jiang, Hua GuoAbstract:To provide a systematic and rigorous re-examination of the well-known Polanyi's rules, excitation functions of several A + BC(v = 0, 1) reactions are determined using the Chebyshev real wave packet method on accurate potential energy surfaces. Reactions with early (F + H2 and F + HCl), late (Cl + H2), and central (H/D/Mu + H2, where Mu is a short-lived Light Isotope of H) barriers are represented. Although Polanyi's rules are in general consistent with the quantum dynamical results, their predictions are strictly valid only in certain energy ranges divided by a cross-over point. In particular, vibrational excitation of the diatomic reactant typically enhances reactivity more effectively than translational excitation at high energies, while reverse is true at low energies. This feature persists irrespective of the barrier location. A sudden vector projection model is proposed as an alternative to Polanyi's rules. It is found to give similar, but more quantitative, predictions about mode selectivity in these reactions, and has the advantage to be extendible to reactions involving polyatomic molecules.
John T. Stults - One of the best experts on this subject based on the ideXlab platform.
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Selective Detection of Membrane Proteins Without Antibodies A MASS SPECTROMETRIC VERSION OF THE WESTERN BLOT*
2015Co-Authors: James C. Marsters, John T. StultsAbstract:A method has been developed, called the mass western experiment in analogy to the Western blot, to detect the presence of specific proteins in complex mixtures without the need for antibodies. Proteins are identified with high sensitivity and selectivity, and their abundances are com-pared between samples. Membrane protein extracts were labeled with custom Isotope-coded affinity tag reagents and digested, and the labeled peptides were analyzed by liquid chromatography-tandem mass spectrometry. Ions corresponding to anticipated tryptic peptides from the proteins of interest were continuously subjected to colli-sion-induced dissociation in an ion trap mass spectrom-eter; heavy and Light Isotope-coded affinity tag-labeled peptides were simultaneously trapped and fragmented accomplishing identification and quantitation in a singl
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Selective Detection of Membrane Proteins Without Antibodies A Mass Spectrometric Version of the Western Blot
Molecular & cellular proteomics : MCP, 2002Co-Authors: David Arnott, James C. Marsters, Adrianne Kishiyama, Elizabeth Luis, Sarah G. Ludlum, John T. StultsAbstract:A method has been developed, called the mass western experiment in analogy to the Western blot, to detect the presence of specific proteins in complex mixtures without the need for antibodies. Proteins are identified with high sensitivity and selectivity, and their abundances are compared between samples. Membrane protein extracts were labeled with custom Isotope-coded affinity tag reagents and digested, and the labeled peptides were analyzed by liquid chromatography-tandem mass spectrometry. Ions corresponding to anticipated tryptic peptides from the proteins of interest were continuously subjected to collision-induced dissociation in an ion trap mass spectrometer; heavy and Light Isotope-coded affinity tag-labeled peptides were simultaneously trapped and fragmented accomplishing identification and quantitation in a single mass spectrum. This application of ion trap selective reaction monitoring maximizes sensitivity, enabling analysis of peptides that would otherwise go undetected. The cell surface proteins prostate stem cell antigen (PSCA) and ErbB2 were detected in prostate and breast tumor cell lines in which they are expressed in known abundances spanning orders of magnitude.
Julia A. Lee-thorp - One of the best experts on this subject based on the ideXlab platform.
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Middle Palaeolithic Diets
The Oxford Handbook of the Archaeology of Diet, 2016Co-Authors: Eugène Morin, John D. Speth, Julia A. Lee-thorpAbstract:This chapter examines the evidence for diet amongst Middle Palaeolithic foragers in Europe and south-west Asia from c. 300,000 to 40,000 years ago, concentrating on faunal and isotopic approaches. Published faunal evidence shows that Middle Palaeolithic hominins in both regions hunted a relatively narrow range of medium- to large-sized ungulates, with occasional exploitation of megaherbivores more evident in open sites than in caves and rockshelters. Broader diets have been documented in southern Europe, although regular consumption of fast, small-sized taxa emerged only later during the Upper Palaeolithic. Stable Light Isotope data, often interpreted as indicating that European Neanderthals were top-level predators preferring either megaherbivores, or bovids and horses, only partly accords with the faunal evidence. Taphonomic considerations suggest that energy procurement, especially as fat, and the effects of transport constraints have so far not been sufficiently considered when assessing the dietary composition of Middle Palaeolithic hominins.
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Opportunities and constraints for reconstructing palaeoenvironments from stable Light Isotope ratios in fossils
Geological Quarterly, 2010Co-Authors: Julia A. Lee-thorp, Matt SponheimerAbstract:Stable Light Isotope ratios (13 C/12 Cand 18 O/16 O) in fossil teeth provide key archives for understanding ecology of past faunal communities and the evolution of environments during the Plio-Pleistocene. Given the inevitable processes of diagenesis during fossilisation, the integrity of isotopic information and the degree of detailed information that can be extracted, remain important issues in all fossil studies. The most appropriate tests are those intrinsic to isotopic abundances in ecosystems. They are easier to develop for 13 C/12 C in savanna environments where large 13 C/12 C differences exist between C4 tropical grasses and C3 trees and shrubs. Validating 18 O/16 O ratios in fossil carbonate or phosphate is more difficult, but patterned variability, mainly tracking water-related behaviour, within modern faunal communities has been replicated in several fossil assemblages. The identification of seasonal variation in 13 C/12 C and 18 O/16 O along the growth axis of a tooth crown, also applicable in areas composed solely of C3 plants, fills a dual role as a test and for providing data on seasonal amplitude. The results of studies from low- and mid-latitude African sites suggest that isotopic variation in rainfall on short timescales and ecological differences amongst animals, dominate over smaller differences in 18 O/16 O composition due to temperature.
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Palaeoecology of late Early Miocene fauna in the Namib based on 13C/12C and 18O/16O ratios of tooth enamel and ratite eggshell carbonate
Palaeogeography Palaeoclimatology Palaeoecology, 2009Co-Authors: Loïc Ségalen, Julia A. Lee-thorpAbstract:Abstract We explored the stable Light Isotope ecology of a sample of extinct Namibian mammals from the early Miocene, a period when conditions are believed to have been relatively warm and moist. Where possible we compared Isotope values of mammalian tooth enamel (Rhinocerotidae, Suidae, Climacoceratidae, Pliohyracidae, Gomphotheriidae and Deinotheriidae) with those of eggshells of a co-existing Aepyornithoid (19–20 Ma). In general, the isotopic values of tooth enamel in all mammalian fauna, including likely mixed feeders/grazers, are consistent with C 3 diets as expected for this period, and the ratite eggshells are consistently enriched in both 13 C and 18 O compared to the mammals. High eggshell carbon and oxygen Isotope values at the sites of Grillental and Elisabethfeld suggest that ratite birds occupied a dry niche that possibly included CAM plants, while results for Langental suggest moister, cooler conditions. Arrisdrift (ca. 17–17.5 Ma) mammalian tooth enamel values overlap those of the 19–20 Ma sites. The dataset for Arrisdrift reveals distinctive patterning between species. In particular the two suid species differ significantly in δ 18 O and δ 13 C, suggesting distinct ecological niches consistent with predictions from their dental morphology. On the other hand, two distinct data populations for one species of Prohyrax may suggest different environmental conditions during the period in which the site formed.
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ON IsotopeS AND OLD BONES
Archaeometry, 2008Co-Authors: Julia A. Lee-thorpAbstract:This review charts the developments and progress made in the application of stable Light Isotope tools to palaeodietary adaptations from the 1970s onwards. It begins with an outline of the main principles governing the distribution of stable Light Isotopes in foodwebs and the quality control issues specific to the calcified tissues used in these analyses, and then proceeds to describe the historical landmark studies that have marked major progress, either in their archaeological applications or in enhancing our understanding of the tools. They include the adoption of maize agriculture, marine-focused diets amongst coastal hunter–gatherers, trophic level amongst Glacial-period modern humans and Neanderthals, and the use of savannah resources by early hominins in Africa. Particular attention is given to the progress made in addressing the challenges that have arisen out of these studies, including issues related to the routing of dietary nutrients. I conclude with some firm, and some more speculative, pointers about where the field may be heading in the next decade or so.
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The palaeoecology of the non-mammalian cynodonts Diademodon and Cynognathus from the Karoo Basin of South Africa, using stable Light Isotope analysis
Palaeogeography Palaeoclimatology Palaeoecology, 2005Co-Authors: Jennifer Botha, Julia A. Lee-thorp, Anusuya ChinsamyAbstract:Abstract The palaeoecology of the coeval Middle Triassic non-mammalian cynodonts, Diademodon and Cynognathus (Therapsida) remains poorly understood although their gross morphology has been studied intensively. Significant differences in their growth patterns suggest inherent biological differences, despite having inhabited similar environments. In this study, the palaeoecology of Cynognathus and Diademodon specimens were examined using intra-tooth stable carbon and oxygen Isotope analyses of enamel carbonate. The resulting stable Isotope patterns of Cynognathus and Diademodon were compared with that of Crocodylus niloticus and published mammalian tooth enamel data. Predictably, the non-mammalian cynodont δ 13 C values fall within the expected range for C 3 plant diets. Both δ 18 O and δ 13 C values of Diademodon are markedly more depleted than those of Cynognathus , suggesting that the former fed in shadier, damper areas, was nocturnal and/or depended more directly on environmental water. The seasonal amplitude reflected in the Cynognathus teeth is relatively low. However, high amplitude, directional δ 18 O intra-tooth variations in the Diademodon teeth are comparable to, or higher than, those observed for extant mammalian and C. niloticus teeth from semi-arid, seasonal regions. This suggests that marked seasonality prevailed in the Karoo Basin during the Middle Triassic, and that Diademodon was sensitive to these variations. These isotopic differences between Diademodon and Cynognathus indicate differing responses to climatic fluctuations and reveal new insights into the palaeoecology of non-mammalian cynodonts.
Koichiro Watanabe - One of the best experts on this subject based on the ideXlab platform.
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k ar analyses of the post caldera lavas of bratan volcano in bali island indonesia ar Isotope mass fractionation to Light Isotope enrichment
Journal of Volcanology and Geothermal Research, 2013Co-Authors: Sunyoung Ryu, Hiroshi Kitagawa, Eizo Nakamura, Tetsumaru Itaya, Koichiro WatanabeAbstract:Abstract The post-caldera lavas of Bratan volcano in Bali Island, Indonesia were collected for whole rock chemical analyses and K–Ar analyses. Major and trace element chemistry shows that the lavas are basalts to andesites and typical of subduction-related tectonic setting. The 38 Ar/ 36 Ar ratios are 0.1851 ± 3–0.1875 ± 2 and the 40 Ar/ 36 Ar, 294.3 ± 0.3–301.6 ± 0.1, which strongly suggest that the mass fractionation to Light Isotope enrichment took place. The effect of the groundwater on magma is common on the basis of systematic mass fractionation of the atmospheric Ar enriched in Lighter Isotopes. This case was under the mass fractionation law analyzed numerically, giving the mass fractionation correction ages (14 ± 15, 31 ± 6, 55 ± 22, 66 ± 23, 94 ± 32 and 125 ± 51 ka) consistent with the volcano stratigraphy though the magma composition that changed frequently in time.
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K–Ar analyses of the post-caldera lavas of Bratan volcano in Bali Island, Indonesia — Ar Isotope mass fractionation to Light Isotope enrichment
Journal of Volcanology and Geothermal Research, 2013Co-Authors: Sunyoung Ryu, Hiroshi Kitagawa, Eizo Nakamura, Tetsumaru Itaya, Koichiro WatanabeAbstract:Abstract The post-caldera lavas of Bratan volcano in Bali Island, Indonesia were collected for whole rock chemical analyses and K–Ar analyses. Major and trace element chemistry shows that the lavas are basalts to andesites and typical of subduction-related tectonic setting. The 38 Ar/ 36 Ar ratios are 0.1851 ± 3–0.1875 ± 2 and the 40 Ar/ 36 Ar, 294.3 ± 0.3–301.6 ± 0.1, which strongly suggest that the mass fractionation to Light Isotope enrichment took place. The effect of the groundwater on magma is common on the basis of systematic mass fractionation of the atmospheric Ar enriched in Lighter Isotopes. This case was under the mass fractionation law analyzed numerically, giving the mass fractionation correction ages (14 ± 15, 31 ± 6, 55 ± 22, 66 ± 23, 94 ± 32 and 125 ± 51 ka) consistent with the volcano stratigraphy though the magma composition that changed frequently in time.
Hua Guo - One of the best experts on this subject based on the ideXlab platform.
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relative efficacy of vibrational vs translational excitation in promoting atom diatom reactivity rigorous examination of polanyi s rules and proposition of sudden vector projection svp model
Journal of Chemical Physics, 2013Co-Authors: Bin Jiang, Hua GuoAbstract:To provide a systematic and rigorous re-examination of the well-known Polanyi's rules, excitation functions of several A + BC(v = 0, 1) reactions are determined using the Chebyshev real wave packet method on accurate potential energy surfaces. Reactions with early (F + H2 and F + HCl), late (Cl + H2), and central (H/D/Mu + H2, where Mu is a short-lived Light Isotope of H) barriers are represented. Although Polanyi's rules are in general consistent with the quantum dynamical results, their predictions are strictly valid only in certain energy ranges divided by a cross-over point. In particular, vibrational excitation of the diatomic reactant typically enhances reactivity more effectively than translational excitation at high energies, while reverse is true at low energies. This feature persists irrespective of the barrier location. A sudden vector projection model is proposed as an alternative to Polanyi's rules. It is found to give similar, but more quantitative, predictions about mode selectivity in these reactions, and has the advantage to be extendible to reactions involving polyatomic molecules.