TY - JOUR. T1 - Positional isotope exchange analysis of the Mycobacterium smegmatis cysteine ligase (MshC). AU - Williams, La Kenya. AU - Fan, Fan. AU - Blanchard, John S.. AU - Raushel, Frank M.. PY - 2008/4/22. Y1 - 2008/4/22. N2 - MshC catalyzes the ATP-dependent condensation of GlcN-Ins and cysteine to form Cys-GlcN-Ins, which is an intermediate in the biosynthetic pathway of mycothiol, i.e., 1-D-myo-inosityl-2-(N-acetyl-L-cysteinyl)amido-2-deoxy-α- D-glucopyranoside (MSH or AcCys-GlcN-Ins). MSH is produced by Mycobacterium tuberculosis, members of the Actinomycetes family, to maintain an intracellular reducing environment and protect against oxidative and antibiotic induced stress. The biosynthesis of MSH is essential for cell growth, and therefore, the MSH biosynthetic enzymes present potential targets for inhibitor design. The formation of kinetically competent adenylated intermediates was suggested by the observation of positional isotope exchange (PIX) reaction using [βγ-18O6]-ATP in ...
PANGAEA - Publishing Network for Geoscientific and Environmental Data. (Appendix E) Stable carbon and oxygen isotope composition of Globigerinoides sacculifera of ODP Hole 121-758B. Occurrence Dataset https://doi.org/10.1594/pangaea.759093 accessed via GBIF.org on 2017-12-15 ...
Single garnet crystals from a large, multicyclic hydrothermal system in Far East Russia are strongly growth zoned. Microscale ion microprobe analysis reveals consistent intracrystalline patterns in oxygen isotope composition and boron and iron contents, reflecting evolution of the hydrothermal system from magmatic- to meteoric-dominated conditions, and repetitive influx of magmatic fluids. Large intracrystalline variations in oxygen isotope composition (,12‰ δ18O) delimit temporal evolution of magmatic and meteoric fluid input within different portions of the hydrothermal system, and suggest that fluid-flow regimes differed between central and distal portions of the system. These results provide compelling evidence that microanalytical data can be extrapolated from intracrystalline scales to study macroscale processes in complex, large-scale fluid-rock systems. ...
Topographic development of the southern Washington Cascade Range and its influence on regional climate on the leeward side of the range for the past 15.6 m.y. are evaluated, using oxygen isotope ratios (δ18O) of ancient meteoric water recorded in authigenic smectites. The δ18O values of authigenic smectites from paleosols and altered tuffs on the east side of the range exhibit a temporal and continuous decrease of ∼3‰-4‰ from 15.6 Ma to the present. Taking into account a regional temperature change in eastern Washington since the middle Miocene, the calculated δ18O values of regional meteoric water show a negative shift of ∼3.5‰-4.5‰ over the same interval. Such a decrease is similar to the change in the δ18O values of modern precipitation from the coastal side to a region downwind of the Washington Cascades. This negative shift of the calculated δ18O values on the east side of the range is best explained by the development of a rain shadow due to the tectonic rock uplift of the ...
A recurrent interpretation of ancient climate based on the oxygen isotopic composition of marine carbonates and cherts suggests that Earths climate was substantially warmer in the distant past and remained so until as recently as 400 Myr ago. This interpretation is difficult to reconcile with the long-term glacial record, with evidence for modest weathering rates during most of Earths history, with biomarker and fossil evidence for eukaryotes and even vertebrates at times of anomalously low δ18O values, and with the predicted faintness of the young Sun. We argue here, following earlier suggestions, that the low δ18O values in ancient rocks are a consequence of the low δ18O of ancient seawater. A modest increase in ocean depth with time, together with progressive increases in pelagic sedimentation on midocean ridge flanks since about 550 Ma, could account for the variation in seawater isotopic composition. The required change in ocean depth, coupled with thinning of the oceanic crust, is a ...
Abstract The paper presents the principle of a method to measure infiltration rates in sewer systems based on the use of oxygen isotopes and its application in Lyon (France). Investigations in the urban area of Lyon benefit from the isotopic differences between underground waters originating from the two rivers Rhône and Saône and from their associated alluvial aquifers. The oxygen isotopic composition of the Rhône water is roughly 3 ‰ lighter than that of the Saône river, due to the large differences in the mean altitude and topographic situation of their catchments. Large amounts of water are pumped from the Rhône aquifer for drinking water supply. As a consequence, this difference in the oxygen isotopic composition between wastewater and local groundwater can be used to evaluate infiltration in sewers in some parts of the city. The results obtained in a case study allow to evaluate the reliability and the uncertainties of this method. ...
This dissertation investigates hydrological variability within tropical Asia over the past several few centuries as reflected in the stable oxygen isotope composition of atmospheric moisture. The stable isotopes of water in the climate system are unique tracers of moisture transport and tropical rainfall variability. The isotopic signal of atmospheric moisture within the tropics is transferred to cellulose of tropical trees during photosynthesis. Thus, the isotopic composition of tree cellulose can provide an archive of past hydrologic variability through isotopic reconstructions of the cellulose extracted from annual rings of long lived trees. The tropical atmospheric variability reflected in tropical trees can include variations in the Indian Monsoon and changes in moisture availability over Asia in response to the El Niño-Southern Oscillation (ENSO). Here an attempt has been made to better understand how the atmospheric dynamics associated within these climate phenomena influence the ...
This dissertation investigates hydrological variability within tropical Asia over the past several few centuries as reflected in the stable oxygen isotope composition of atmospheric moisture. The stable isotopes of water in the climate system are unique tracers of moisture transport and tropical rainfall variability. The isotopic signal of atmospheric moisture within the tropics is transferred to cellulose of tropical trees during photosynthesis. Thus, the isotopic composition of tree cellulose can provide an archive of past hydrologic variability through isotopic reconstructions of the cellulose extracted from annual rings of long lived trees. The tropical atmospheric variability reflected in tropical trees can include variations in the Indian Monsoon and changes in moisture availability over Asia in response to the El Niño-Southern Oscillation (ENSO). Here an attempt has been made to better understand how the atmospheric dynamics associated within these climate phenomena influence the ...
Oxygen isotope composition of main-group pallasites and mesosiderites. Data for main-group pallasites and mesosiderites from Greenwood et al. (2006). Solid lines through data points show the mean Δ17O value for each group. Grey-shaded boxes depict the 2σ error on the mesosiderite and main-group pallasite population Δ17O and δ18O mean values. Open squares are individual mesosiderite analyses, open circles individual pallasite analyses. The dashed line labelled (1) is the eucrite fractionation line of Greenwood et al. (2005); the dashed line labelled (2) shows the range of HED values obtained by Weichert et al. (2004). Δ17O is linearized using the format of Miller (2002): Δ17O = 1000 ln (1+ (δ17O/1000)) - λ1000 ln (1+ ( δ18O/1000)) where λ = 0.5247. TFL = Terrestrial Fractionation Line ...
Oxygen isotope composition of Martian meteorites. Data for Martian meteorites from Franchi et al. (1999) and compiled from laser fluorination analyses in the Meteoritical Bulletin. MFL: Martian fractionation line of Franchi et al. (1999), TFL: terrestrial fractionation line.Δ17O calculated as: Δ17O = δ17O - 0.52δ18O ...
The Antarctic Glaciological Data Center (AGDC) at NSIDC is pleased to announce the release of a new data set, the WAIS Divide WDC06A Oxygen Isotope Record. This data set contains complete low resolution (0.25 to 100 cm) oxygen isotope data from the WAIS Divide Ice Core WDC06A, 0 to 3404.7 m depth. Also included is the WDC2014 timescale.. ...
We measured the δ18O of cellulose (δ18Ocel) extracted from fossil wood collected at 9 sites in the northern and southern hemispheres as a potential source of information about precipitation δ18O (δ18Oppt) in the past and paleotemperatures. The samples had been buried in fluvial sediments for periods of time ranging from ca. 45 million to 250 years. At the oldest localities (high latitude, Eocene- through Pliocene-age sites in Canada and Russia), mean annual temperature (MAT) estimates derived from the modern relationship between MAT and δ18Ocel are 6-16°C lower than the MAT estimates derived from other biological proxies. Estimates of Pleistocene and Holocene mean annual temperatures are close to the modern values at those sites. These results are consistent with other recent findings that the MAT/δ18Oppt relationship across North America was not constant throughout the Cenozoic. Paleo-δ18Oppt estimates derived from fossil cellulose and the modern North American relationship between ...
Margaret Barbour holds a BSc in Biology and Earth Sciences and an MSc in Biology from the University of Waikato, New Zealand, and a PhD in Plant Science from the Australian National University. During her PhD she developed new understanding, and mechanistic models, of variability in the oxygen isotope composition of plant tissue. Her work was the first to theoretically describe and demonstrate the record of leaf evaporative environment present in the oxygen isotope composition of plant material. This work has subsequently been applied to reconstruct past climates from tree ring stable isotopes, as an indicator of plant regulation of water loss, and as a selection tool for yield in grain crops. Margaret was employed by Landcare Research in New Zealand from 2001 to 2009, where she led a Foundation-funded objective investigating the exchange of carbon dioxide in terrestrial systems at site scales, and the sensitivities and uncertainties of these processes to variation in climate, environmental and ...
Deep-water pockmarks are frequently accompanied by the occurrence of massive gas hydrates in shallow sediments. A decline in pore-water Cl− concentration and rise in δ18O value provide compelling evidence for the gas hydrate dissociation. Mega-pockmarks are widely scattered in the southwestern Xisha Uplift, northern South China Sea (SCS). Pore water collected from a gravity-core inside of a mega-pockmark exhibits a downward Cl− concentration decrease concomitant with an increase in δ18O value at the interval of 5.7-6.7 mbsf. Concentrations of Cl−, Na+, and K+ mainly cluster along the seawater freshening line without distinct Na+ enrichment and K+ depletion. Thus, we infer that the pore water anomalies of Cl− concentrations and δ18O values are attributed to gas hydrate dissociation instead of clay mineral dehydration. Moreover, the lower δ18O values of sulfate in the target core (C14) than those in the reference core (C9) may be associated with the equilibrium oxygen fractionation during
Granger, J., M. G. Prokopenko, D. M. Sigman, C. W. Mordy, Z. M. Morse, L. V. Morales, R. N. Sambrotto, and B. Plessen (2011), Coupled nitrification-denitrification in sediment of the eastern Bering Sea shelf leads to (15)N enrichment of fixed N in shelf waters, J. Geophys. Res., 116, C11006, doi:10.1029/2010JC006751 ...
This thesis work is aimed at examining the oxygen atom mixing between common iron(III) oxides and Fe(II)aq solution during the sorption process. First, O labeled iron(III) minerals were used in batch sorption reactors to study the exchange of oxygen atom within the Fe(II)aq - iron(III) oxide system. Results showed a much lesser extent of oxygen mixing than reported Fe mixing from previous studies, even when dissolved Fe(II) is present. The oxygen mixing extents are 3.95 % more for goethite and 9.66 % more for ferrihydrite than their respective controls within 14 days. A consecutive atom exchange kinetic study indicated that O exchange is not inhibited by surface Fe sorptive site saturation, and that after 40d sorption experiment, the maximum O exchange is 54.96 % across reactors with different initial solid loadings and Fe(II)aq levels. The second part of this work examined the influence of aqueous Fe(II) on the sorption of selenium oxyanions (selenite and selenate) in Fe(II)aq - iron(III) systems. It
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…
Langer, G. , Ziveri, P. , Geisen, M. and Thoms, S. (2008): Oxygen isotope fractionation during calcification in Calcidiscus leptoporus: The influence of carbonate chemistry , European Geosciences Union, General Assembly 2008, 13 18 April, Vienna, Austria ...
Abstract. Stable oxygen isotope composition of atmospheric precipitation (δ18Op) was scrutinized from 39 stations distributed over Switzerland and its border zone. Monthly amount-weighted δ18Op values averaged over the 1995-2000 period showed the expected strong linear altitude dependence (−0.15 to −0.22‰ per 100 m) only during the summer season (May-September). Steeper gradients (~ −0.56 to −0.60‰ per 100 m) were observed for winter months over a low elevation belt, while hardly any altitudinal difference was seen for high elevation stations. This dichotomous pattern could be explained by the characteristically shallower vertical atmospheric mixing height during winter season and provides empirical evidence for recently simulated effects of stratified atmospheric flow on orographic precipitation isotopic ratios. This helps explain "anomalous" deflected altitudinal water isotope profiles reported from many other high relief regions. Grids and isotope distribution maps of the ...
In the next two lectures we will examine past climates (paleoclimates) and the forces. We have already discussed the importance of isotopes for rock dating. The ratio of these two oxygen isotopes has changed over the ages and these. Other factors which work in conjunction with the Earths orbital changes include.
Carbon mineralogy, phosphorus and oxygen isotope records from the Late Pleistocene at ODP Hole 1198 A (Leg 194 Marion Plateau, Australia ...
Fertilizers Res. 45, 91-100. , 1961. Precipitation of silver phosphate from homogeneous solution. Anal. Chem. 33, 873-887. , 1982. UV-sensitive complex phosphorus: association with dissolved humic material and iron in a bog lake. Limnol. Oceonogr. 27, 564-569. , 2012. Variation in the photochemical lability of dissolved organic matter in a large boreal watershed. Aquatic Sci. 74, 751-768. , 1996. Inter- and intra-tooth variation in the oxygen isotope composition of mammalian tooth enamel: some implications for paleoclimatological and paleobiological research. Orig. Life Evol. Biosphere 29, 555-561. , 2005. Phosphine in soils, sludges, biogases and atmospheric implications-a review. Ecolog. Eng. 24, 457-463. , 2011a. Phosphate oxygen isotopes: insights into sedimentary phosphorus cycling from the Benguela upwelling system. Geochim. Cosmochim. Acta 75, 3741-3756. , 2011b. Marine sediment pore-water profiles of phosphate delta O-18 using a refined micro-extraction. Limnol. Oceanogr. Met. 9, ...
In order to investigate mid-Cretaceous terrestrial climates of low paleolatitudes, Moroccan, Tunisian and Brazilian vertebrate apatites have been analyzed for their oxygen and carbon isotope compositions of phosphates (delta O-18(p)) and carbonates (delta O-18(c), delta C-18(c)). At each site, coexisting theropod dinosaurs, titanosaurid sauropods, pterosaurs, crocodilians, turtles and fish have distinct delta O-18(p) and delta C-18(c) values reflecting their ecologies, diets and foraging environments. Oxygen isotope compositions of surface waters (delta O-18(w)) estimated from turtle and crocodile delta O-18(p) values range from -5.0 +/- 1.0 parts per thousand to -2.4 +/- 1.0 parts per thousand, which do not differ from mean annual rainwater values occurring today under inter-tropical sub-arid to arid climates. High water temperatures ranging from 21 +/- 6 degrees C to 34 +/- 2 degrees C deduced from fish delta O-18(p) values are in agreement with those published for mid-Cretaceous low ...
Abstract: Few long and well-dated summer precipitation reconstructions that extend beyond the longest records of instrumental measurements exist in Europe. Further understanding of the past trends in summer precipitation and the mechanisms driving that variability are necessary to improve the predictions of climate models. Tree rings are unique in their ability to provide high-resolution, absolutely dated climate signals for the study of palaeoclimatology. The physiological processes controlling oxygen isotope composition (δ18O) in wood are reasonably well understood highlighting its potential as a climate proxy in a variety of environments. Significant correlation between wood δ18O and precipitation has been demonstrated worldwide reflecting both direct rainout processes and indirectly evaporative enrichment. We present an annually resolved reconstruction of precipitation based upon oxygen isotope variations in tree ring cellulose covering the most recent ˜400 years for England. The ...
The site-specific quantitation of N- and O-glycosylation is vital to understanding the function(s) of different glycans expressed at a given site of a protein under physiological and disease conditions. Most commonly used precursor ion intensity based quantification method is less accurate and other labeled methods are expensive and require enrichment of glycopeptides. Here, we used glycopeptide product (y and Y0) ions and (18)O-labeling of C-terminal carboxyl group as a strategy to obtain quantitative information about fold-change and relative abundance of most of the glycoforms attached to the glycopeptides. As a proof of concept, the accuracy and robustness of this targeted, relative quantification LC-MS method was demonstrated using Rituximab. Furthermore, the N-glycopeptide quantification results were compared with a biosimilar of Rituximab and validated with quantitative data obtained from 2-AB-UHPLC-FL method. We further demonstrated the intensity fold-change and relative abundance of 46 ...
The Akiri vein copper mineralization was investigated for its carbon and oxygen isotopic composition to determine the characteristics of the mineralizing fluid. Carbon and oxygen isotope analyses of Akiri siderite range between δ13C values (-1.05 to -1.71‰) and δ13O values (-14.94 to -15.18) respectively. δ13C isotopic composition is comparable to values expected for Cretaceous marine carbonates. The 18O depletion in the vein siderite indicates dominant meteoric water sources involved for carbonates precipitation. This significant depletion between the δ18O compositions of Akiri siderite compared with carbonates from other parts of the basin probably indicate differential formational temperature or fluid composition ...
Biologic rhythms give insight into normal physiology and disease. They can be used as biomarkers for neuronal degenerations. We present a diverse data set to show that hair and teeth contain an extended record of biologic rhythms, and that analysis of these tissues could yield signals of neurodegenerations. We examined hair from mummified humans from South America, extinct mammals and modern animals and people, both healthy and diseased, and teeth of hominins. We also monitored heart-rate variability, a measure of a biologic rhythm, in some living subjects and analyzed it using power spectra. The samples were examined to determine variations in stable isotope ratios along the length of the hair and across growth-lines of the enamel in teeth. We found recurring circa-annual periods of slow and fast rhythms in hydrogen isotope ratios in hair and carbon and oxygen isotope ratios in teeth. The power spectra contained slow and fast frequency power, matching, in terms of normalized frequency, the ...
Ikaite crystals incorporate ocean bottom water into their structure as they form. During cooling periods, when ice sheets are expanding, ocean bottom water accumulates heavy oxygen isotopes (oxygen 18). When glaciers melt, fresh water, enriched in light oxygen isotopes (oxygen 16), mixes with the bottom water. The scientists analyzed the ratio of the oxygen isotopes in the hydration water and in the calcium carbonate. They compared the results with climate conditions established in Northern Europe across a 2,000-year time frame. They found a direct correlation between the rise and fall of oxygen 18 in the crystals and the documented warming and cooling periods. ...
This thesis investigates how variations in the oxygen isotopic composition of lake waters in northern Fennoscandia are recorded in lake sediment archives, especially diatoms, and how these variations can be used to infer past changes in climate and atmospheric circulation. Results from analyses of the oxygen isotopic composition of lake water samples (δ18Olakew) collected between 2001 and 2006 show that δ18O of northern Fennoscandian lakes is mainly controlled by the isotopic composition of the precipitation (δ18Op). Changes in local δ18Op depend on variations in ambient air temperature and changes in atmospheric circulation that lead to changes in moisture source, vapour transport efficiency, or winter to summer precipitation distribution. This study demonstrates that the amount of isotopic variation in lake water δ18O is determined by a combination of the original δ18Olakew, the amount and timing of the snowmelt, the amount of seasonally specific precipitation and groundwater, any ...
ABSTRACT: In 2007 a ceremonial complex representing the Globular Amphora Culture was discovered in Kowal (the Kuyavia region, Poland). Radiocarbon dating demonstrated that the human remains associated with the complex are of similar antiquity, i.e. 4.105 ± 0.035 conv. and 3.990 ± 0.050 conv. Kyrs. After calibration, this suggests a period between 2850 and 2570 BC (68.2% likelihood), or more specifically, 2870 to 2500 BC (95.4% likelihood). Morphological data indicate that the skeleton belonged to a male who died at 27-35 years of age. The unusual morphology of his hard palate suggests this individual may have had a speech disorder. Stable oxygen isotope values of the individuals teeth are above the locally established oxygen isotope range of precipitation, but due to sample limitations we cannot conclusively say whether the individual is of non-local origin. Stable carbon and nitrogen isotope ratios were analyzed to reconstruct the diet of the studied individual, and show a terrestrial-based ...
You know that water is made of hydrogen and oxygen atoms arranged in molecules of H2O, but you may not be aware that there are different types of oxygen atoms. Different atoms of the same element are called isotopes. All oxygen atoms have 16 protons and 16 electrons, but some oxygen atoms have 16, 17, or 18 neutrons in the nucleus. The most abundant isotopes of oxygen in seawater are oxygen sixteen (16O) and oxygen eighteen (18O). Water molecules with 16O atoms evaporate more easily than water molecules with 18O atoms, so the relative numbers of 16O and 18O atoms that remain in the water change as evaporation occurs. Water from which 16O atoms have preferentially evaporated has a higher ratio of 18O to 16O atoms than water that has experienced less evaporation. As salinity also increases as evaporation occurs, we can generalize the relationship to state that water with an increased 18O to 16O ratio is saltier than water with a lower 18O to 16O ratio.. ! Click the red dot in the Caribbean to see ...
Ehleringer, J.R., Bowen, G.J., Chesson, L.A., West, A.G., Podlesak, D.W. & Cerling, T.E. (2008) Hydrogen and oxygen isotope ratios in human hair are related to geography. Proceedings of the National Academy of Sciences of the United States of America, 105, 2788-2793 ...
Munich, Germany (SPX) Oct 05, 2012 - Oxygen isotopes in tree rings are an excellent archive of precipitation dynamics in the tropical Amazon region. The precise determination of the ratios of stable oxygen isotopes (18O/16O) proves to
Ng, J., B. Williams, D.M Thomson, and J. Halfar. "Developing a forward model of encrusting coralline algae." Geochimica et Cosmochimica Acta, 194, 2016, 279-290.. Abstract: An increased number of climate proxy records and more refined interpretation of proxy data are crucial to improve projections of future climate at high latitudes, where internal feedbacks amplify warming and established high-resolution climate archives are especially sparse. Encrusting coralline algae are being developed as a mid- to high-latitude marine climate archive. These long-lived algae form a solid high-Mg calcite skeleton with annual growth bands similar to those of trees and tropical corals. The oxygen isotope ratio of the algal skeleton (d18Oalg) records local environmental and climatic factors, notably sea surface temperature and seawater d18O. Here we assess the d18Oalg-climate relationship in diverse environments across the algal habitat range utilizing two species of coralline algae from the genus ...
Teeth provide remarkable evidence about the early years of an individuals life. The region where a person grew up can be traced in the tooth enamel laid down in their first 14 years because strontium and oxygen isotope ratios in the teeth reflect the food a person ate and the water they drank. When rocks form, they contain minute traces of radioactive rubidium 87, which decays to strontium 87. Over millions of years, the ratio of strontium 87 to the stable isotope strontium 86 changes, so, in very young rocks, the ratio will be smaller than in very old rocks.. These rocks weather and become the soils where animals are grazed and crops grown. Some of the strontium in the soil gets into the meat and cereals produced from it and then into the teeth of the people who eat them. The strontium ratio in a persons teeth thus mirrors the strontium ratio of the geology of the area in which they spent their childhood. For example, someone who grew up in southern England would have a much lower ratio than ...
The isotope mass-balance approach was used to estimate ground-water inflow to 81 lakes in the central highlands and coastal lowlands of central Florida. The study area is characterized by a subtropical climate and numerous lakes in a mantled karst terrain. Ground-water inflow was computed using both steady-state and transient formulations of the isotope mass-balance equation. More detailed data were collected from two study lakes, including climatic, hydrologic, and isotopic (hydrogen and oxygen isotope ratio) data. For one of these lakes (Lake Starr), ground-water inflow was independently computed from a water-budget study. Climatic and isotopic data collected from the two lakes were similar even though they were in different physiographic settings about 60 miles apart. Isotopic data from all of the study lakes plotted on an evaporation trend line, which had a very similar slope to the theoretical slope computed for Lake Starr. These similarities suggest that data collected from the detailed ...
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Knowledge and management of aquatic ecosystems (formerly Bulletin Français de la Pèche et de la Pisciculture), an international journal on freshwater ecosystem
Whole-plant 13C discrimination, Δ13Cp, showed a strong correlation with instantaneous measurements of ci/ca (Fig. 7), suggesting that in general Δ13Cp was a faithful recorder of ci/ca, as predicted by Equation 6. The mean value for d that we estimated for the full data set was 3.1‰, reasonably similar to a value of 4.0‰, recently estimated for Ficus insipida (Cernusak et al., 2007b). The Δ13Cp was also a reasonably good predictor of variation in TEc, Dg·TEc, and vg·TEc (Table VI). We previously observed that the relationship between Δ13Cp and TEc broke down at the species level, appearing to reflect species-specific offsets in the relationship between the two parameters (Cernusak et al., 2007a). Whereas there was some evidence of similar behavior in this study, as can be seen in Figure 8, the species-level relationship between Δ13Cp and Dg·TEc was generally much stronger in this study. For example, in a least-squares linear regression between Δ13Cp and Dg·TEc using species means, ...
palindrom (#27 on the WUWT article)- Im doing my graduate work in the area of oxygen isotope paleothermometry (which I do think has a lot of advantage over dendroclimatology), so Ill just say a few general things, but I dont plan on reading the WUWT article in enough depth to disentangle it piece by piece (note for people who reply that Id rather continue this in the April Open Thread since it is OT and this thread is still young).. First, I do think that there is a lot of work to be done in the interpretation of oxygen/hydrogen isotope values obtained at a site, and theres still plenty of disagreement in the paleo-community on how to best connect the isotopic signal in a record with climate. However, there are also many well understood thermodynamic, physical principles at play. There are also a number of paleoclimatic recorders of oxygen isotopes, including lake/ocean records, speleothems (in caves), corals, ice cores, etc. The factors and caveats that impact all of these different ...
This work projects photoluminescence (PL) as an alternative technique to estimate the order of resistivity of zinc oxide (ZnO) thin films. ZnO thin films, deposited using chemical spray pyrolysis (CSP) by varying the deposition parameters like solvent, spray rate, pH of precursor, and so forth, have been used for this study. Variation in the deposition conditions has tremendous impact on the luminescence properties as well as resistivity. Two emissions could be recorded for all samples-the near band edge emission (NBE) at 380 nm and the deep level emission (DLE) at ∼500 nm which are competing in nature. It is observed that the ratio of intensities of DLE to NBE (DLE/NBE) can be reduced by controlling oxygen incorporation in the sample. - measurements indicate that restricting oxygen incorporation reduces resistivity considerably. Variation of DLE/NBE and resistivity for samples prepared under different deposition conditions is similar in nature. DLE/NBE was always less than resistivity by an ...
around 950 to 1250 C.E. While this time period is known as being a "dry period," the Pitt researchers have discovered an unexpected complexity to the patterns of drought. ...
Sophia Hopps 20 senior thesis research explored Sodic-Calcic alteration of the White Rock Pluton. Her thesis advisor was Jim Rougvie. Metasomatism is a process that involves a change in the chemical composition. Sodic-Calcic alteration, or metasomatism, is a type of hydrothermal alteration in which sodium and calcium are added to a rock at the expense of other elements. This type of alteration is widespread in contact metamorphic aureoles and is commonly associated with iron oxide-copper-gold (IOCG) deposits. The altering fluids can mobilize and deposit these valuable elements. The composition of geothermal fluids vary with their setting, which can directly impact the capacity for metal transport and deposition. Understanding the fluid involved in sodic-calcic alteration is crucial to understanding element mobility and deposition in metasomatism processes. Whiterock Pluton, located at the southwestern side of the Elk Mountain Range in Aspen, Colorado, has locally been affected by sodic-calcic ...
For the African nation of Niger, the effect of seasonal atmospheric variability on the weather is poorly understood. Because most residents rely on local agriculture, improving the predictability of seasonal weather and precipitation ...
With advancements in the analytical technologies and methodologies in proteomics, there is great interest in biomarker discovery in biofluids such as serum and plasma. Current hypotheses suggest that
Article Abstract MATERIALS AND METHODS RESULTS DISCUSSION GRANTS DISCLOSURES AUTHOR CONTRIBUTIONS ACKNOWLEDGMENTS REFERENCES Figures & Data Info PDF Alert me when this article is cited Alert me if a correction is posted Email Print Citation Tools Request Permissions Share View Full Page PDF Reddit logo RedditCiteULike logo CiteULikeMendeley logo MendeleyStumbleUpon logo StumbleUpon More in this TOC Section A sandwich ELISA for measurement of the primary glucagon-like peptide-1 metabolite Quantifying rates of glucose production in vivo following an intraperitoneal tracer bolus Dynamics of glucagon secretion in mice and rats revealed using a validated sandwich ELISA for small sample volumes Show more Innovative Methodology Related Articles Cited By... Calls for Papers Most Cited Most Read Role of Gut Microbiota and Gut-Brain and Gut-Liver Axes in Physiological Regulation of Inflammation, Energy Balance, and Metabolism. Deadline for Submission: September 30, 2017 Role of Fetal Programming and ...
Losartan is a 4-chloro-5-hydroxymethylimidazole derivative that is a potent and highly selective angiotensin II receptor antagonist. Losartan is metabolized in vivo in rats, monkeys, and humans to a carboxylic acid derivative E3174 that is pharmacologically more active than the parent compound. We have investigated the mechanism of this biotransformation in human liver preparations. The oxidation of both losartan and the putative aldehyde intermediate E3179 was catalyzed by the microsomal fraction, required both NADPH and molecular oxygen, and was inhibited by SKF 525-A, implicating cytochrome P450 (CYP). When incubations with each substrate were performed under an atmosphere of 18O2, the extent of 18O incorporation into the carboxylic acid product was consistent with a mechanism for losartan oxidation involving an aldehyde intermediate. To substantiate the involvement of CYP in these reactions, incubations with losartan and the aldehyde E3179 were performed in the presence of isoform-selective ...
Gem deposits offer particularly interesting challenges to the geologist: because they are relatively rare, unusual circumstances are necessary for their formation. Stable isotope geochemistry is one of the tools with which we can investigate these exceptional geological conditions. Apart from the intrinsic scientific interest of understanding formation mechanisms and conditions, such research can also elucidate genetic models to guide exploration and exploitation strategies, and identify diverse contributions to placer deposits. As an aid in constraining provenance, stable isotope ratios may have application in fingerprinting conflict minerals and materials.. The stable isotope (18O/16O; D/H) composition of silicate and oxide minerals is usually a function of the temperature, isotopic characteristics and chemistry of the parental fluid from which they precipitated. The oxygen isotope fractionation factor between the fluid and the mineral depends on the environment of chemical bonding in a ...
Changes in the stable isotope composition of copper in blood serum as a result of biological processes in the liver were quantified as coupled equilibrium fractionation processes. The model used calculated reduced partition function ratios corresponding to interactions involving individual proteins using Density Functional Theory. This quantified the effect that each process had on the redistribution of copper isotopes in the liver. It was not possible to calculate the reduced partition function of CTR1 as a high resolution crystal structure of its copper binding domains are unavailable at the time of writing, and an optimization process was used to estimate the reduced partition function of CTR1 and constrain the possible isotopic fractionation associated with interactions involving CTR1 independent of direct DFT calculations and assumptions of its structure ...
In this activity, students will use oxygen isotope values of two species of modern coral to reconstruct ambient water temperature over a four-year period. They use Microsoft Excel, or similar application, to create a spreadsheet of temperature values calculated from the isotope values of the corals by means of an algebraic equation. Students then use correlation and regression techniques to determine whether isotope records can be considered to be good proxies for records of past temperatures.. ...