82 research outputs found
Calcite Dissolution-Reprecipitation Reactions Are a Key Control on the Sr/Ca, Mg/Ca and δ88/86Sr Compositions of Himalayan River Waters
No full textSilicate weathering on the continents is thought to play a critical part in regulating global climate on geological time scales but determination of the magnitude of silicate weathering fluxes is frustrated by the complexity of the weathering processes. Here we present analyses of stable Sr-isotopic compositions (delta Sr-88/86) in a suite of river waters and bedloads from the Himalayas in Nepal to establish the lithological controls on delta Sr-88/86 values and the secondary processes that impact carbonate weathering. A control on delta Sr-88/86 values is lithology with the rivers in carbonate-dominated catchments marginally lower (similar to 0.07 parts per thousand) than in silicate-dominated catchments. However, as for Sr-87/Sr-86 ratios, delta Sr-88/86 values of carbonates are altered by silicate-carbonate mineral exchange during metamorphism. The major potential secondary control on delta Sr-88/86 values in Himalayan catchments is precipitation of secondary calcite responsible for the marked elevation of Sr/Ca and Mg/Ca ratios in the waters. We re-evaluate the mechanisms for secondary calcite formation and conclude that a balanced solution and re-precipitation process, driven by the relative instability of the primary Mg-rich calcite, provides a better explanation for the elevated Sr/Ca ratios than simple precipitation from a highly over saturated solution. This solution-re-precipitation process is akin to that invoked to explain diagenesis of deep-sea sediments. The mechanism of secondary calcite formation impacts the distinction of cation inputs from carbonate and silicate minerals. The correlation between delta Sr-88/86 water-calcite fractionations, Sr/Ca partition coefficients and precipitation rates allows the calcite re-precipitation rates to be inferred from the covariation of water delta Sr-88/86 values and Sr/Ca ratios. These rates are very low (<10(-8) mol m(-2) s(-1)) but are consistent with those inferred from field estimates of the amount of calcite re-precipitated, the surface area of carbonate exposed to weathering and the calcite weathering flux. The low precipitation rates are also consistent with previously reported Delta Ca-44/40 isotope fractionations of similar to-0.2 parts per thousand. The calcite reprecipitation rates are comparable to silicate weathering rates previously inferred from Li-isotopic compositions which is consistent with calcite re-precipitation taking place very close to equilibrium following the initial rapid saturation of the fluids by calcite
Saskatchewan wheat pool: A profile of one Canadian grain cooperative
No full textPhotographs not included in Web versio
Geochemistry of Geologic CO2 Sequestration/ Donald J. DePaolo, David R. Cole, Alexandra Navrotsky, Ian C. Bourg.
No full textIn English.Volume 77 of Reviews in Mineralogy and Geochemistry focuses on important aspects of the geochemistry of geological CO2 sequestration. It is in large part an outgrowth of research conducted by members of the U.S. Department of Energy funded Energy Frontier Research Center (EFRC) known as the Center for Nanoscale Control of Geologic CO2 (NCGC). Eight out of the 15 chapters have been led by team members from the NCGC representing six of the eight partner institutions making up this center - Lawrence Berkeley National Laboratory (lead institution, D. DePaolo - PI), Oak Ridge National Laboratory, The Ohio State University, the University of California Davis, Pacific Northwest National Laboratory, and Washington University, St. Louis.DePaolo, Donald J. / Cole, David R. -- Bickle, Mike / Kampman, Niko / Wigley, Max -- Radha, A. V. / Navrotsky, A. -- Bodnar, Robert J. / Steele-Maclnnis, Matthew / Capobianco, Ryan M. / Rimstidt, J. Donald / Dilmore, Robert / Goodman, Angela / Guthrie, George -- Kaszuba, John / Yardley, Bruce / Andreani, Muriel -- De Yoreo, James J. / Waychunas, Glenn A. / Jun, Young-Shin / Fernandez-Martinez, Alejandro -- Power, Ian M. / Harrison, Anna L. / Dipple, Gregory M. / Wilson, Siobhan A. / Kelemen, Peter B. / Hitch, Michael / Southam, Gordon -- Chialvo, Ariel A. / Vlcek, Lukas / Cole, David R. -- Kharaka, Yousif K. / Cole, David R. / Thordsen, James J. / Gans, Kathleen D. / Thomas, R. Burt -- Crawshaw, John P. / Boek, Edo S. -- Fitts, Jeffrey P. / Peters, Catherine A. -- Tokunaga, Tetsu K. / Wan, Jiamin -- Carey, J. William Frontmatter -- Reviews -- Preface -- TABLE OF CONTENTS -- 1. Geochemistry of Geologic Carbon Sequestration: An Overview / 2. Natural Analogues / 3. Thermodynamics of Carbonates / 4. PVTX Properties of H2 0-C02-"salt" at PTX Conditions Applicable to Carbon Sequestration in Saline Formations / 5. Experimental Perspectives of Mineral Dissolution and Precipitation due to Carbon Dioxide-Water-Rock Interactions / 6. Molecular Simulation of C02- and C03-Brine-Mineral Systems -- 7. In situ Investigations of Carbonate Nucleation on Mineral and Organic Surfaces / 8. Pore Scale Processes Associated with Subsurface C02 Injection and Sequestration -- 9. Carbon Mineralization: From Natural Analogues to Engineered Systems / 10. Acid Gases in C02-rich Subsurface Geologic Environments / 11. Geochemical Monitoring for Potential Environmental Impacts of Geologic Sequestration of C02 / 12. Multi-scale Imaging and Simulation of Structure, Flow and Reactive Transport for C02 Storage and EOR in Carbonate Reservoirs / 13. Caprock Fracture Dissolution and C02 Leakage / 14. Capillary Pressure and Mineral Wettability Influences on Reservoir C02 Capacity / 15. Geochemistry of Wellbore Integrity in C02 Sequestration: Portland Cement-Steel-Brine-C02 Interactions /1 online resource (553 p.)
Improving Future Climate Prediction using Palaeoclimate Data (an outcome of The Leverhulme Climate Symposium 2008 - Earth's Climate: Past, Present and Future)
No full textThis White Paper represents an outcome of "The Leverhulme Climate Symposium 2008 - Earth's Climate: Past, Present and Future", convened by H. Elderfield, M. Bickle, G. Allen and E. Shuckburgh, and held at the University of Cambridge and the Royal Society, London, 10th - 13th March 2008.Information on the Symposium is available at http://www.leverhulmeclimatesymposium.org/. Knowledge of past climate change can be used to improve our understanding of future climate change, but the full benefits of this archive have yet to be realised. The Symposium focused on determining what lessons from the past can be used to inform the future. This document builds on that objective and discusses how improved future climate prediction may be achieved using palaeoclimate data.The symposium and this report have been made possible by generous funding from The Leverhulme Trust.<br/
Microstratigraphic Traces within Houses, Animal Pens and Settlements
No full textIn this chapter, the authors review how integrated microstratigraphic, phytolith and chemical analyses can contribute to our understanding of continuity and change in ecological and social practices during the transition to agriculture, in Zagros, with selective comparative reference to central Anatolia. They examine how micro-contextual analysis of plant materials preserved in large thin-sections and phytolith analyses are contributing to a fuller understanding of the ecology and use of both wild and domesticated plants than is possible from study of charred plants alone. They consider how integrated analyses of animal dung are informing on the earliest stages of animal management, including penning, foddering and use of dung for fuel. Lastly they briefly review the microstratigraphic evidence for how the transition to agriculture was shaped by and impacted on particular activities, roles and relations within households and communities by study of continuity and change in the nature, timing and organisation of these
The discovery of SycO reveals a new function for type three secretion effector chaperones
No full textThe Type Three Secretion (T3S) system is a device used by many Gram-negative pathogens that allows bacteria to deliver effector proteins straight into the eukaryotic cell cytosol. These effectors interfere with various signaling pathways to subvert the host cell functions. The secretion machinery of the T3S system consist of a basal body spanning the bacterial inner and outer membrane followed by a stiff hollow needle outside the bacterium. The fully assembled secretion apparatus constitute a continuous hollow conduit that connects the bacteria to the eukaryotic target cell. After cell contact, virulence proteins -called effectors- are injected directly into the cytosol of the host cell via the T3S apparatus. Several effectors of the T3S system require the assistance of specific cytosolic chaperones to be efficiently exported. There are three classes of T3S chaperones. Effector proteins are assisted by Class I chaperones. Although Class I chaperones are well characterized, their main function is still a matter of controversy. In this thesis, we demonstrate that orf155 encodes a specific chaperone for the effector YopO that we called SycO. We showed that SycO enhances YopO secretion in vitro and is required for translocation of YopO into infected cells. By pulldown assay we demonstrated that residues 20 to 77 of YopO are required and sufficient for SycO binding. Using crosslinking experiments and size exclusion chromatography analysis, we determined the stoichiometry of purified SycO and YopO-SycO complexes. SycO alone forms dimers in solution and the YopO-SycO complex has a 1:2 stoichiometry. These results suggested that SycO is a typical chaperone of the Class I. YopO is a serine/theronine kinase that interacts with Rho and Rac and disrupts the cytoskeleton of the target cells. YopO has been shown to localize at the cell plasma-membrane. By transfection of YopO-EGFP hybrid proteins into HEK293T cells, we demonstrated that the chaperone-binding domain (CBD) coincides with the membrane localization domain of YopO. Nevertheless, the CBD was not needed for the kinase activity of YopO. By ultracentrifugation, we also showed that the CBD causes YopO aggregation in the bacteria, when SycO does not cover it. Further, we show that the CBD of YopE and YopT also caused aggregation in the bacteria in the absence of SycE and SycT respectively. YopE, YopT and T3S effectors in other systems also act at the membrane of the eukaryotic host cell. We propose a new hypothesis concerning the role of T3S chaperones. The sub-cellular localization domain of effectors is aggregation-prone and creates the need for a chaperone inside bacteria. We propose that masking such aggregation-prone localization domains may be a general function for type III effector chaperones
¿Unirealizabilidad?: una crítica a un modelo reduccionista reduccionista [Unirealizability? a critique of a reductionist model]
No full textIn the frame of the materialist movement “New Wave Reductionism”, in the last decade, the idea of “Ruthless Reductionism” presented by the philosopher John Bickle in his book “Philosophy and Neuroscience: a ruthlessly reductive account” (2003) had a major impact producing a wave of researches interlinking philosophy and neuroscience, which contents vary between protocols and experimental designs, causality, mechanisms and multiple realizations. This paper is intended to present John Bickle‟s model (1998, 2003, 2006) within this movement. Furthermore, it includes a review of two authors: Jaquelline Sullivan (2008, 2008) and Ken Aizawa (2007, 2008), with the purpose of examining the mentioned model and raising the main critiques that have been pointed to it. Some of these critiques refer to the nature of the investigation, setting protocol differences in the study of the same phenomenon in different labs.
Further developments, make reference to the construct used in the experiments in order to support the results obtained by Bickle: Long Term Social Recognition Memory – LTSRM – together with some warnings about social recognition cues that are not the same among
different organisms, as well as the components that build the main intra neural pathway of the LTSRM – AMPc – PKA – CREB among species. It‟s intended to point out how these aspects, when considering some experimental bias and mistakes in the reading of the LTSRM experiment, discredit the author‟s idea about the Unity Realization of Ruthlessly Reductionism.status: Publishe
Application of RNAi to Genomic Drug Target Validation in Schistosomes.
No full textConcerns over the possibility of resistance developing to praziquantel (PZQ), has stimulated efforts to develop new drugs for schistosomiasis. In addition to the development of improved whole organism screens, the success of RNA interference (RNAi) in schistosomes offers great promise for the identification of potential drug targets to initiate drug discovery. In this study we set out to contribute to RNAi based validation of putative drug targets. Initially a list of 24 target candidates was compiled based on the identification of putative essential genes in schistosomes orthologous of C. elegans essential genes. Knockdown of Calmodulin (Smp_026560.2) (Sm-Calm), that topped this list, produced a phenotype characterised by waves of contraction in adult worms but no phenotype in schistosomula. Knockdown of the atypical Protein Kinase C (Smp_096310) (Sm-aPKC) resulted in loss of viability in both schistosomula and adults and led us to focus our attention on other kinase genes that were identified in the above list and through whole organism screening of known kinase inhibitor sets followed by chemogenomic evaluation. RNAi knockdown of these kinase genes failed to affect adult worm viability but, like Sm-aPKC, knockdown of Polo-like kinase 1, Sm-PLK1 (Smp_009600) and p38-MAPK, Sm-MAPK p38 (Smp_133020) resulted in an increased mortality of schistosomula after 2-3 weeks, an effect more marked in the presence of human red blood cells (hRBC). For Sm-PLK-1 the same effects were seen with the specific inhibitor, BI2536, which also affected viable egg production in adult worms. For Sm-PLK-1 and Sm-aPKC the in vitro effects were reflected in lower recoveries in vivo. We conclude that the use of RNAi combined with culture with hRBC is a reliable method for evaluating genes important for larval development. However, in view of the slow manifestation of the effects of Sm-aPKC knockdown in adults and the lack of effects of Sm-PLK-1 and Sm-MAPK p38 on adult viability, these kinases may not represent suitable drug targets
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