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32 results for “isotope effect”
Processed model output of the climate simulation in the study: The effects of diachronous surface uplift of the European Alps on regional climate and the isotopic composition of precipitation (δ18Op) [Boateng et al.]
<p><strong>The geodynamic evolution of the Alps suggests that the Alps did not rise monotonically due to the different post-collisional processes such as slab break-off. However, understanding such subsurface dynamics would require adequate knowledge about its surface uplift history. Stable isotope paleoaltimetry methods are widely used to infer past surface elevation using geologic archives. However, its accurate interpretation relies on attributing the extracted isotopic signal from proxies to surface uplift despite other influences such as climate. To resolve this issue, topographic sensitivity experiments across the Alps are used to investigate the impacts of the diachronous surface uplift on regional climate and δ18Op. The Atmospheric General Circulation Model ECHAM5 with water isotope tracking capabilities (ECHAM5-wiso) is used to simulate the climate with varied topographic scenarios. We present the processed (long-term means) model output of the relevant climate variables (i.e δ18Op, near-surface temperature, precipitation amount, near-surface meridional and zonal winds, mean sea level pressure, and elevation) in response to the changes in topography. The file names are representative of the topographic scenarios used for the simulations. For example, the file “W2E1.nc” is the model output produced by a topographic scenario in which the topography across the west-central Alps was set to 200% of its modern height, and the Eastern Alps were kept at 100%. The “CTL.nc” file contains model output from the control simulation that uses present-day topography. The datasets for instance can be used to select far-field sampling points for the δ-δ paleoaltimetry method that are not significantly affected by the topographic changes.</strong></p>
Reproducibility in science: calculated kinetic isotope effects for cyclopropyl carbonyl radical.
<p>Calculated kinetic isotope effects, without tunnelling corrections, for the ring opening of cyclopropylcarbinyl radical using a variety of different Hamiltonians and basis sets.</p>
Raw plot data for: Accelerating equilibrium isotope effect calculations. II. Stochastic implementation of direct estimators
<p>Data for publication: K. Karandashev, J. Vanicek, Accelerating equilibrium isotope effect calculations. II. Stochastic implementation of direct estimators, J. Chem. Phys. <strong>151</strong>, 134116 (2019) <a href="https://doi.org/10.1063/1.5124995">https://doi.org/10.1063/1.5124995</a></p> <p>This data set contains the raw numerical data for reproducing Figures 1-8 in the publication.</p>
Observation of an isotope effect in state-selective mutual neutralization of lithium with hydrogen
<p>The data files found here contain the data as obtained and displayed in : "Observation of an isotope effect in state-selective mutual neutralization of lithium with hydrogen" published in Physical Review A (2023). Each file contains an explanatory header. Header lines start with #.</p> <p> </p>
Data from: Stable isotopes reveal the effect of trawl fisheries on the diet of commercially exploited species
Bottom trawling can change food availability for benthivorous demersal species by (i) changing benthic prey composition through physical seabed impacts and (ii) by removing overall benthic consumer biomass increasing the net availability of benthic prey for remaining individuals. Thus trawling may both negatively and positively influence the quantity and quality of food available. Using δ13C and δ15N we investigated potential diet changes of three commercially exploited species across trawling gradients in the Kattegat (plaice, dab and Norway lobster (Nephrops)) and the Irish Sea (Nephrops). In the Kattegat, trawling affected primarily the biomass of benthic consumers, lowering competition. Nephrops showed significant positive relationships for δ13C and a domed relationship for δ15N with trawling. In the Irish Sea, intense trawling had a negative effect on benthic prey. δ13C and δ15N thus showed the inverse relationships to those observed in the Kattegat. Plaice from the Kattegat, showed a significant relationship with trawling intensity for δ13C, but not for δ15N. No relationship was found for dab. Changes of δ13C and δ15N correlated with changes in condition of species. The results show that the removal of demersal competitors and benthos by trawling can change the diets of commercial species, ultimately affecting their body condition.
Size-Dependent Dynamics of the Internal Carbon Pool Drive Isotopic Vital Effects in Calcifying Phytoplankton
<p>Isotopic offsets in biogenic calcite from equilibrium values can provide unique insights into the physiology and mechanisms of carbon regulation in calcifying phytoplankton. This study examines the impact of varying CO2 (controlled via pH) on five coccolithophore species chosen for varied cell sizes, physiology, and calcification. The study investigates isotopic offsets in coccolith calcite and organic matter, in relation to carbon demand and supply (<i>µ</i>/CO2). Species-specific CO2/pH optima for growth (<i>µ</i>opt) were derived from variations in growth rates with varying CO2 concentrations. Growth rates for all species declined with rising CO2 (decreasing pH) due to H+-driven inhibition. <i>C. braarudii </i>and<i> C. leptoporus</i> exhibited high <i>µ</i>opt values (suggesting high carbon-demand) and limited growth under low CO2 (high pH) suggesting carbon limitation. Under low CO2 supply, when growth rates were CO2-limited, both species exhibited coincident isotopic depletion in calcite and organic matter as a consequence of CO2 diffusion into the cell that experienced no equilibration as a result of a highly depleted internal carbon pool. In these two species, isotopic values in calcite remained unaffected by growth rates and CO2 concentration (<i>µ</i>/CO2) when CO2 was sufficient for optimal growth. <i>G. huxleyi </i>and<i> G. oceanica </i>displayed optima for growth (<i>µ</i>opt) at low CO2 concentrations and showed no growth limitation under low CO2 (indicating low carbon-demand). Both species experienced depleted (negative) vital effects caused by an excess of CO2 diffusion into the small internal carbon pool of the cell when diffusive carbon supply outpaced low demand (low <i>µ</i>/CO2). Enriched (positive) vital effects were observed under low carbon supply and high demand, likely due to diffusive loss of CO2 from the cell's intracellular carbon pool due to a lower intracellular pH. <i>C. carterae</i> exhibited an intermediate <i>µ</i>opt and isotopically equilibrated intracellular carbon pool such that δ13C values in calcite and organic matter suggested a shared carbon pool. This study illustrates that pH-CO2 driven vital effects and fractionation into organic matter indicate the residence time for carbon in the intracellular carbon pool, and the size of this pool is proportional to cell size. <i>C. leptoporus </i>and<i> C. carterae</i> can elevate intracellular pH to minimise CO2 leakage, whereas vital effects in <i>G. huxleyi</i> and <i>G. oceanica </i>are caused by diffusive CO2 due to the small size of their internal carbon pool.</p>
Dataset: Testing for effects of growth rate on isotope trophic discrimination factors and evaluating the performance of Bayesian stable isotope mixing models experimentally: a moment of truth?
<p><span>Discerning assimilated diets of wild animals using stable isotopes is well established where potential dietary items in food webs are isotopically distinct. With the advent of mixing models, and Bayesian extensions of such models (Bayesian Stable Isotope Mixing Models, BSIMMs), statistical techniques available for these efforts have been rapidly increasing. The accuracy with which BSIMMs quantify diet, however, depends on several factors including uncertainty in tissue discrimination factors (TDFs; <em>Δ</em>) and identification of appropriate error structures. Whereas performance of BSIMMs has mostly been evaluated with simulations, here we test the efficacy of BSIMMs by raising domestic broiler chicks (<em>Gallus gallus domesticus</em>) on four isotopically distinct diets under controlled environmental conditions, ideal for evaluating factors that affect TDFs and testing how BSIMMs allocate individual birds to diets that vary in isotopic similarity. For both liver and feather tissues,<em> δ</em><sup>13</sup>C and <em>δ </em><sup>15</sup>N values differed among dietary groups. <em>Δ</em><sup>13</sup>C of liver, but not feather, was negatively related to the rate at which individuals gained body mass. For <em>Δ</em><sup>15</sup>N, we identified effects of dietary group, sex, and tissue type, as well as an interaction between sex and tissue type</span><span><span>, </span></span><span><span>with f</span></span><span>emales having higher liver <em>Δ</em><sup>15</sup>N relative to males. For both tissues, BSIMMs allocated most chicks to correct dietary groups, especially for models using combined TDFs rather than diet specific TDFs, and those applying a multiplicative error structure. These findings provide new information on how biological processes affect TDFs and confirm that adequately accounting for variability in consumer isotopes is necessary to optimize performance of BSIMMs. Moreover, they demonstrate experimentally that these types of models reliably characterize consumed diets when appropriately parameterized.<span> </span></span></p>
Dataset for ""A dynamic isotope effect in the nucleophilic substitution reaction F- + CD3I"
<p>Dataset for ""A dynamic isotope effect in the nucleophilic substitution reaction F- + CD3I"</p>
Data reported in: Effects of ozone isotopologue formation on the clumped-isotope composition of atmospheric O2
<p>Tropospheric <sup>18</sup>O<sup>18</sup>O is an emerging proxy for past tropospheric ozone and free-tropospheric temperatures. The basis of these applications is the idea that isotope-exchange reactions in the atmosphere drive <sup>18</sup>O<sup>18</sup>O abundances toward isotopic equilibrium. However, previous work used an offline box-model framework to explain the <sup>18</sup>O<sup>18</sup>O budget, approximating the interplay of atmospheric chemistry and transport. This approach, while convenient, has poorly characterized uncertainties. To investigate these uncertainties, and to broaden the applicability of the <sup>18</sup>O<sup>18</sup>O proxy, we developed a scheme to simulate atmospheric <sup>18</sup>O<sup>18</sup>O abundances (quantified as ∆<sub>36</sub> values) online within the GEOS-Chem chemical transport model. These results are compared to both new and previously published atmospheric observations from the surface to 33 km. Simulations using a simplified O<sub>2</sub> isotopic equilibration scheme within GEOS-Chem show quantitative agreement with measurements only in the middle stratosphere; modeled ∆<sub>36</sub> values are too high elsewhere. Investigations using a comprehensive model of the O-O<sub>2</sub>-O<sub>3</sub> isotopic photochemical system and proof-of-principle experiments suggest that the simple equilibration scheme omits an important pressure dependence to ∆<sub>36</sub> values: the anomalously efficient titration of <sup>18</sup>O<sup>18</sup>O to form ozone. Incorporating these effects into the online ∆<sub>36</sub> calculation scheme in GEOS-Chem yields quantitative agreement for all available observations. While this previously unidentified bias affects the atmospheric budget of <sup>18</sup>O<sup>18</sup>O in O<sub>2</sub>, the modeled change in the mean tropospheric ∆<sub>36</sub> value since 1850 C.E. is only slightly altered; it is still quantitatively consistent with the ice-core ∆<sub>36</sub> record, implying that the tropospheric ozone burden increased less than ~40% over the twentieth century.</p>
Data from: Arithmetic normalization models for the effects of lipid on carbon stable isotope values in silver carp (Hypophthalmichthys molitrix) tissue
Open the record for dataset details and reuse information.
Data reported in: Effects of ozone isotopologue formation on the clumped-isotope composition of atmospheric O2
Open the record for dataset details and reuse information.
Data from: Stable isotopes reveal the effect of trawl fisheries on the diet of commercially exploited species
Open the record for dataset details and reuse information.
Bayesian stable isotope mixing models effectively characterize the diet of an Arctic raptor
<p>1. Bayesian stable isotope mixing models (BSIMMs) for δ13C and δ15N can be a useful tool to reconstruct diets, characterize trophic relationships, and assess spatiotemporal variation in food webs. However, use of this approach typically requires a priori knowledge on the level of enrichment occurring between the diet and tissue of the consumer being sampled (i.e., a trophic discrimination factor or TDF).</p> <p>2. TDFs derived from captive feeding studies are highly variable, and it is challenging to select the appropriate TDF for diet estimation in wild populations. We introduce a novel method for estimating TDFs in a wild population: a proportionally balanced equation that uses high-precision diet estimates from nest cameras installed on a subset of nests in lieu of a controlled feeding study (TDFCAM).</p> <p>3. We tested the ability of BSIMMs to characterize diet in a free-living population of gyrfalcon (Falco rusticolus) nestlings by comparing model output to high-precision nest camera diet estimates. We analyzed the performance of models formulated with a TDFCAM against other relevant TDFs and assessed model sensitivity to an informative prior. We applied the most parsimonious model inputs to a larger sample to analyze broad-scale temporal dietary trends.</p> <p>4. BSIMMs fitted with a TDFCAM and uninformative prior had the best agreement with nest camera data, outperforming TDFs derived from captive feeding studies. BSIMMs produced with a TDFCAM produced reliable diet estimates at the nest level and accurately identified significant temporal shifts in gyrfalcon diet within and between years.</p> <p>5. Our method of TDF estimation produced more accurate estimates of TDFs in a wild population than traditional approaches, consequently improving BSIMM diet estimates. We demonstrate how BSIMMs can complement a high-precision diet study by expanding its spatiotemporal scope of inference and recommend this integrative methodology as a powerful tool for future trophic studies. </p>
Evaluating Bayesian stable isotope mixing models of wild animal diet and the effects of trophic discrimination factors and informative priors
<blockquote> <p>1. Ecologists quantify animal diets using direct and indirect methods, including analysis of faeces, pellets, prey items and gut contents. For stable isotope analyses of diet, Bayesian stable isotope mixing models (BSIMMs) are increasingly used to infer the relative importance of food sources to consumers. Although a powerful approach, it has been hard to test BSIMM performance for wild animals because precise, direct dietary data are difficult to collect.<br> 2. We evaluated the performance of BSIMMs in quantifying animal diets when using δ13C and δ15N stable isotope ratios from the feathers and red blood cells of common buzzard Buteo buteo chicks. We analysed mixing model outcomes with various trophic discrimination factors (TDFs), with and without informative priors, and compared these to direct observations of prey provisioned to chicks by adults at nests, using remote cameras. <br> 3. Although BSIMMs with different TDFs varied markedly in their performance, the statistical package SIDER generated TDFs for both feathers and blood that resulted in model outputs that accorded well with direct observations of prey provisioning. Using feather TDFs derived from captive peregrines Falco peregrinus resulted in estimates of diet composition that were also similar to provisioned prey, though blood TDFs from the same study performed poorly. The inclusion of informative priors, based on conventional analysis of pellet and prey remains, markedly reduced model performance.<br> 4. BSIMMs can provide accurate assessments of diet in wild animals. TDF estimates from the SIDER package performed well. The inclusion of informative priors from conventional methods in Bayesian mixing models can transfer biases into model outcomes, leading to erroneous results.</p> </blockquote>
Data for Kinetic isotope effects during reduction of Fe(III) to Fe(II): Large normal and inverse isotope effects for abiotic reduction and smaller fractionations by phytoplankton in culture
<p>Supplemental data for the manuscript "Kinetic isotope effects during reduction of Fe(III) to Fe(II): Large normal and inverse isotope effects for abiotic reduction and smaller fractionations by phytoplankton in culture."</p>
Data from the paper: D. Malko and A. Kucernak, "Kinetic isotope effect in the oxygen reduction reaction (ORR) over Fe-N/C catalysts under acidic and alkaline conditions", Electrochemistry Communications,2017, https://doi.org/10.1016/j.elecom.2017.09.004
<p>Data used to generate the figures in the paper: D. Malko and A. Kucernak, "Kinetic isotope effect in the oxygen reduction reaction (ORR) over Fe-N/C catalysts under acidic and alkaline conditions", Electrochemistry Communications,2017, https://doi.org/10.1016/j.elecom.2017.09.004</p> <p> </p>
Visual, thermal, chemical, and stable isotope effects of near-infrared laser cutting on freezer ice
<p>This dataset includes visible-light and thermal imaging video of tap water ice being cut with millisecond-range pulses of 1070 nm laser light, as well as stable isotope and chemical (commonly-used ion species) composition data of ice samples frozen from Fiji bottled water and South Pole 1980 meltwater.</p> <p>This is a copy of the dataset published to USAP-DC, which requires that visitors arrange a download by email. The only changes are that the subdirectories have each been zipped—as Zenodo does not, at time of writing, support directories—and the .docx version of the README file has been omitted.</p>
Data from: The effects of spatial scale and isoscape on consumer isotopic niche width
1. The mean and variance of ecological variables are dependent on sampling attributes such as the coverage of environmental heterogeneity (sampling extent) and spatial scale. Trophic niche width is often approximated by bulk tissue stable isotopes of C and N, i.e. the population isotopic niche. However, recent studies suggest that environmental heterogeneity (experienced by individuals) may be more important in defining the isotopic niche width than trophic variability. We hypothesised that isotopic niche width will increase monotonically with spatial scale, largely produced by environmental variation, e.g. nutrient source. 2. To refine this hypothesis, by describing the shapes of isotope scaling curves, we explored a previously published dataset describing three Chilean intertidal species representing different feeding guilds (grazing snails, suspension feeding mussel). We tested these hypotheses on a new, larger dataset describing three functionally-analogous intertidal species from Northern Ireland. We generated isotopic variance-area curves from a spatially-explicit bootstrap and investigated the scale-dependency of environment-isotope relationships, including wave exposure and sub-habitat heterogeneity. 3. Spatial scale explained 50% of the variance in population isotopic niche widths (bivariate C-N ellipse area) by simple, non-linear relationships. Finer scales (< 1 to 10 km lag) accounted for most variance. Scale dependence was strong for ẟ15N variance, of which > 40% was explained by modelling linear coefficients. A ẟ15N baseline gradient, or isoscape, dominated ẟ15N variance scaling patterns, from sheltered, terrestrially-influenced embayments to exposed, pelagic-dominated coastline. Consumer ẟ13C variance had a weaker scale-dependence, plateauing at mesoscales (> 20 km lag). 4. We show that isotopic niche width is strongly dependent on sampling spatial extent, which controls the environmental heterogeneity experienced by individual consumers. Environmental heterogeneity must be accounted for before isotopic niche width can be considered to accurately represent trophic niche width. Studies conducted at different spatial scales are likely to identify different environment-isotope relationships. 5. We recommend that spatial scale should be incorporated into sampling designs explicitly, easiest by maintaining a consistent lag distance or area within which populations are sampled. Identified isoscapes can be de-trended, where necessary.
Modulation of effective precipitation by temperature in East Asia during Marine Isotope Stage 5
<p>Magnetic susceptibility and microcodium Mg/Ca, Sr/Ca, and <sup>87</sup>Sr/<sup>86</sup>Sr records from the Huanxian section, northern Chinese Loess Plateau.</p>
The Effect of Genetic Variation in TMPRSS6 Gene (SNP rs855791) on Oral Iron Absorption: an Iron Stable Isotope Study
ClinicalTrials.gov study NCT03317873. IPD Sharing: Not stated. Countries: 1. Publications: 1.
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
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The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
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