8,212 research outputs found
Data for: Kinetic Clumped Isotope Fractionation in the DIC-H2O-CO2 System: Patterns, Controls, and Implications
No full textTable S1. Theoretically estimated kinetic clumped isotope and carbon isotope fractionation factors for CO2 hydration and hydroxylation and their reverse reactions over 0-375oC.Table S2. Theoretically estimated kinetic isotope fractionation factors associated with each CO2 hydration and hydroxylation isotoplogue reaction and their reverse reactions over 0-375oC.Table S3. Theoretically estimated isotopic composition of HCO3- kinetic endmembers, relative to the expected equilibrium isotope composition, in an isotopically equilibrated DIC-H2O-CO2 system over 0-375oC
Data for: Triple Oxygen Isotope Fractionation in the DIC-H2O-CO2 system: A Numerical Framework and Its Implications
No full textTheoretically estimated equilibrium and kinetic triple oxygen isotope fractionation factors in the DIC-H2O-CO2 system over 0-375oC
Data for: Patterns and Controls of Disequilibrium Isotope Effects in Speleothems: Insights from An Isotope-Enabled Diffusion-Reaction Model and Implications for Quantitative Thermometry
No full textTable S1. Kinetic isotope fractionation factors associated with CO2 hydration, CO2 hydroxylation, and their reverse reactions at 15oC (the default model temperature).Table S2. Equilibrium isotopologue fractionation between carbonate solid (calcite) and HCO3- at 15oC (the default model temperature)
Applicability of Phase-Function Normalization Techniques for Radiation Transfer Computation
No full textThe applicability of recently-developed four phase-function (PF) normalization techniques for modeling radiation transfer in strongly anisotropic scattering media is intensively examined using the discrete-ordinate method. The three simple techniques via normalization of only the forward- and/or backward-scattering directions were shown to reduce normalization complexity whilst retaining diffuse radiation computation accuracy for Henyey-Greenstein (HG) PFs. For Legendre PFs, however, such simple techniques are found to result in unphysical negative PF value at one or few correction direction in some cases. Additionally, negative PF values can occur for these simple techniques for ballistic radiation transfer for both HG and Legendre PF types. If negative-intensity correction is applied, however, radiative heat transfer calculation can still converge regardless of the appearance of negative PF values. The relatively complex Hunter and Guo 2012 technique, in which normalization is realized through a correction matrix covering all discrete directions, is shown to be applicable for diffuse and ballistic radiation for both PF types.Peer reviewed
Clumped isotope composition of travertine from hyperalkaline springs in Oman
No full textCarbonate formation at hyperalkaline springs is typical of serpentinization in peridotite massifs worldwide. These travertines have long been known to exhibit large variations in their carbon and oxygen isotope compositions, extending from apparent equilibrium values to highly depleted values. However, the exact causes of these variations are not well constrained. We analyzed a suite of well-characterized fresh carbonate precipitates and travertines associated with hyperalkaline springs in the peridotite section of the Samail ophiolite, Sultanate of Oman, and found their clumped isotope compositions vary systematically with formation environments. Based on these findings, we identified four main processes controlling the stable isotope compositions of these carbonates. These include hydroxylation of CO2, partial isotope equilibration of dissolved inorganic carbon, mixing between isotopically distinct carbonate end-members, and post-depositional recrystallization. Most notably, in fresh crystalline films on the surface of hyperalkaline springs and in some fresh carbonate precipitates from the bottom of hyperalkaline pools, we observed large enrichments in Δ47 (up to ~0.2‰ above expected equilibrium values) which accompany depletions in δ18O and δ13C, yielding about 0.01‰ increase in Δ47 and 1.1‰ decrease in δ13C for every 1‰ decrease in δ18O, relative to expected equilibrium values. This disequilibrium trend, also reflected in preserved travertines ranging in age from modern to ~40,000 years old, is interpreted to arise mainly from the isotope effects associated with the hydrox- ylation of CO2 in high-pH fluids and agrees with our first-order theoretical estimation. In addition, in some fresh carbonate precipitates from the bottom of hyperalkaline pools and in subsamples of one preserved travertine terrace, we observed additional enrichments in D47 at intermediate δ13C and d18O, consistent with mixing between isotopically distinct carbonate end- members. Our results suggest that carbonate clumped isotope analysis can be a valuable tool for identifying and distinguishing processes not readily apparent from the carbonate bulk stable isotope compositions alone, e.g., kinetic effects or mixing of different carbonate end-members, which can significantly alter both the apparent formation temperatures and apparent radiocarbon ages. The isotope trends observed in these travertine samples could be applied more broadly to identify extinct hyperalkaline springs in terrestrial and extraterrestrial environments, to better constrain the formation conditions and post-depositional alteration of hyperalkaline spring carbonates, and to extract potential paleoclimate information.</span
Flow and heat transfer inside a new diversion-type gas heating device
No full textThe present paper characterizes ethylene glycol flow and heat transfer inside a new diversion-type gas heating device. A 2-D natural convection heat transfer model was built and solved by the finite volume method with unstructured body-fitted grids. The numerical model was first validated through temperature comparison with experimental measurements in a conventional device structure. Then analyses and comparisons of the flow fields and temperature distributions with use of different guide plate structures were carried out. The numerical results show that using the guide plate structures can form better organized flow patterns that augment heat transfer. The heat required for heating up the gas passing through the heating device can be reduced by 3% via installing two guide plates.Peer reviewed
Reborn Translated: Xiaolu Guo as a World Author
No full textThis paper introduces the concept of “world author,” taking as its exemplar the Chinese British writer and filmmaker Xiaolu Guo. It investigates how Guo utilizes her bilingualism to construct and negotiate her creative agency, especially when dealing with the political and commercial forces imposed on diasporic authors. Through engaging with Rebecca Walkowitz’s idea of world literature as being “born translated,” I point out that the translational should not be limited to the thematic and representational arrangements internal to a given text. Instead, translation as movements between linguistic systems and media forms can generate multipleversions of a text, to the point that such translational multiplicity fundamentally challenges its supposed singularity. This argument is demonstrated with Guo’s self-translation of the stories of Fenfang and her filmic adaptation of the novel UFO in Her Eyes. Through these examples of what I call “translational rebirths,” I demonstrate the importance of paratextual details and intertextual connections between clusters of an author’s creative output for the interpretation and appreciation of l’oeuvre d’un auteur instead of une oeuvre d’art. This case study also shows the need for the academic debates on world literature to go beyond the singularity of texts and evaluative criteria of worldliness based on this assumption, so that the discipline can realize its full potential in accommodating multilingual transnational authors like Guo
Ocean acidification affects coral growth by reducing skeletal density
No full textOcean acidification (OA) is considered an important threat to coral reef ecosystems, because it reduces the availability of carbonate ions that reef-building corals need to produce their skeletons. However, while theory predicts that coral calcification rates decline as carbonate ion concentrations decrease, this prediction is not consistently borne out in laboratory manipulation experiments or in studies of corals inhabiting naturally low-pH reefs today. The skeletal growth of corals consists of two distinct processes: extension (upward growth) and densification (lateral thickening). Here, we show that skeletal density is directly sensitive to changes in seawater carbonate ion concentration and thus, to OA, whereas extension is not. We present a numerical model of Porites skeletal growth that links skeletal density with the external seawater environment via its influence on the chemistry of coral calcifying fluid. We validate the model using existing coral skeletal datasets from six Porites species collected across five reef sites and use this framework to project the impact of 21st century OA on Porites skeletal density across the global tropics. Our model predicts that OA alone will drive up to 20.3 ± 5.4% decline in the skeletal density of reef-building Porites corals
3-D simulation of gases transport under condition of inert gas injection into goaf
No full textTo prevent coal spontaneous combustion in mines, it is paramount to understand O2 gas distribution under condition of inert gas injection into goaf. In this study, the goaf was modeled as a 3-D porous medium based on stress distribution. The variation of O2 distribution influenced by CO2 or N2 injection was simulated based on the multi-component gases transport and the Navier-Stokes equations using Fluent. The numerical results without inert gas injection were compared with field measurements to validate the simulation model. Simulations with inert gas injection show that CO2 gas mainly accumulates at the goaf floor level; however, a notable portion of N2 gas moves upward. The evolution of the spontaneous combustion risky zone with continuous inert gas injection can be classified into three phases: slow inerting phase, rapid accelerating inerting phase, and stable inerting phase. The asphyxia zone with CO2 injection is about 1.25~2.4 times larger than that with N2 injection. The efficacy of preventing and putting out mine fires is strongly related with the inert gas injecting position. Ideal injections are located in the oxidation zone or the transitional zone between oxidation zone and heat dissipation zone.Peer reviewed
Seawater temperature and buffering capacity modulate coral calcifying pH
No full text© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Guo, W. Seawater temperature and buffering capacity modulate coral calcifying pH. Scientific Reports, 9(1), (2019):1189, doi:10.1038/s41598-018-36817-y.Scleractinian corals promote the precipitation of their carbonate skeleton by elevating the pH and dissolved inorganic carbon (DIC) concentration of their calcifying fluid above that of seawater. The fact corals actively regulate their calcifying fluid chemistry implies the potential for acclimation to ocean acidification. However, the extent to which corals can adjust their regulation mechanism in the face of decreasing ocean pH has not been rigorously tested. Here I present a numerical model simulating pH and DIC up-regulation by corals, and use it to determine the relative importance of physiological regulation versus seawater conditions in controlling coral calcifying fluid chemistry. I show that external seawater temperature and buffering capacity exert the first-order control on the extent of pH elevation in the calcifying fluid and explain most of the observed inter- and intra-species variability. Conversely, physiological regulation, represented by the interplay between enzymatic proton pumping, carbon influx and the exchange of calcifying fluid with external seawater, contributes to some variability but remain relatively constant as seawater conditions change. The model quantitatively reproduces variations of calcifying fluid pH in natural Porites colonies, and predicts an average 0.16 unit decrease in Porites calcifying fluid pH, i.e., ~43% increase in H+ concentration, by the end of this century as a combined result of projected ocean warming and acidification, highlighting the susceptibility of coral calcification to future changes in ocean conditions. In addition, my findings support the development of coral-based seawater pH proxies, but suggest the influences of physicochemical and biological factors other than seawater pH must be considered.This work was supported by the U.S. National Science Foundation Award ANT-1246387 and by the Woods Hole Oceanographic Institution through the Ocean Life Institute, Investment in Science Fund and an Early Career Award
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