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palaeogeographic variation in the permian-Triassic boundary microbialites:A discussion of microbial and ocean process esafter the end-permian mass extinction

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Journal of palaeogeography 2017年第2期6卷 97-107页

作者： stephen Kershaw Department of Life Sciences Brunel University Kingston Lane Uxbridge UB8 3PH UK

Shallow marine carbonate sediments that formed after the end-permian mass extinction are rich in a thin(maximum ca.15 m) deposit of *** communities that constructed the microbialites have geographic variability of composition,broadly divisible into two groups:1) eastern Tethys sites are calcimicrobe-dominated(appearing as thrombolites in the field),with rare occurrence of sedimentconstructed microbialites and uncommon cements either within microbial structure or as inorganic precipitates,2) other Tethys sites are sediment-dominated structures forming stromatolites and thrombolites,composed of micrites and cements,with some inorganic *** other Tethys locations include western and central Tethys sites but their palaeogeographic positions depend on the accuracy of continental reconstructions,of which there are several *** contrast to geographic variation of microbialites,the conodont Hindeodus parvus,which appeared after the extinction and defines the base of the Triassic,is widespread,indicating easy lateral migration throughout *** animals were active nekton,although being small animals were presumably at least partly carried by water currents,implying active Tethyan surface water circulation after the extinction ***-extinction ammonoid taxa,presumed active swimmers,show poor evidence of a wide distribution in the Griesbachian beds immediately after the extinction,but are more cosmopolitan higher up,in the Dienerian strata in *** shelly fossils also have poorly defined distributions after the extinction,but ostracods show some wider distribution suggesting migration was possible after the *** there is a contrast between the geographic differences of microbialites and some shelly *** the cause of geographic variation of post-extinction microbialites is problematic and may include one or more of the following possibilities:1) because calcifying microbial organisms th

关键词： Stromatolite Thrombolite Microbialite permian-Triassic boundary Conodonts Tethys Mass extinction

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Altitude-dependent distribution of 137Cs in the environment:a case study of Aragats massif, Armenia

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Acta Geochimica 2020年第1期39卷 127-138页

作者： Konstantin pyuskyulyan stephen p.LaMont Vovik Atoyan Olga Belyaeva Nona Movsisyan Armen Saghatelyan Armenian Nuclear power plant MetsamorArmenia Nuclear and Radiochemistry Los Alamos National LaboratoryLos AlamosUSA Radioecology Department Center for Ecological-Noosphere StudiesNAS RA.YerevanArmenia

This paper considers the distribution of technogenic 137Cs and naturally occurring radionuclides:238 U,232 Th and40 R concentrations in soils and 137Cs in atmospheric dry depositions by altitudinal belts of the Aragats mountain massif,Republic of *** soil samples were collected at altitudes from 1000 to 3200 *** the determination of geochemical variability,two soil sampling campaigns were *** dry depositions were sampled from five stations at1100-3200 m collected onto organic fiber filters between June and December 2016.137Cs activity was measured using a high-purity Germanium detector coupled to a multichannel analyzer(Canberra).Results indicated that specific activity of 137Cs in soils at 1000 m is495-528 Bq m^-2,andat3200 mis10,500-11,470 Bq m^-*** correlation observed for 137Cs versus naturally occurring radionuclides,which varies in distribution by *** activities of 137Cs in dry atmospheric depositions varies from 1.06 at 846 m to2.37 Bq m^-2 per quarter at 3200 m and increases as the altitude *** of 137Cs in soil and dry atmospheric deposition correlated significantly,and 137Cs activity in soils and atmospheric dry depositions decrease as the absolute altitude *** 50-year effective dose from exposure to 137Cs fallout varies with altitude from 0.007 to 1.42 m Sv.

关键词： 137Cs Distribution by altitude Naturally occurring radionuclides Topsoil Dry atmospheric depositions Gamma radiation Mountain regions

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Structural development of vegetation on rehabilitated North Stradbroke Island:Above/belowground feedback may facilitate alternative ecological outcomes

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Ecological processes 2013年第1期2卷 195-211页

作者： patrick Audet Amanda Gravina Vanessa Glenn phill McKenna Helen Vickers Melina Gillespie David mulligan Centre for Mined Land Rehabilitation Sustainable Minerals Institute The University of QueenslandBrisbane(St.Lucia)QLD 4072Australia

Introduction:This study depicts broad-scale revegetation patterns following sand mining on North Stradbroke Island,south-eastern Queensland,***:Based on an ecological timeline spanning 4–20 years post-rehabilitation,the structure of these ecosystems(n=146)was assessed by distinguishing between periods of‘older’(pre-1995)and‘younger’(post-1995)rehabilitation ***:The general rehabilitation outlook appeared promising,whereby an adequate forest composition and suitable levels of native biodiversity(consisting of mixed-eucalypt communities)were achieved across the majority of rehabilitated sites over a relatively short ***,older sites(n=36)appeared to deviate relative to natural analogues as indicated by their lack of under-storey heath and simplified canopy composition now characterised by mono-dominant black sheoak(Allocasuarina littoralis)reaching up to 60%of the total tree *** changes coincided with lower soil fertility parameters(e.g.,total carbon,total nitrogen,and nutrient holding capacity)leading us to believe that altered growth conditions associated with the initial mining disturbance could have facilitated an opportunistic colonisation by this *** established,it is suspected that the black sheoak’s above/belowground ecological behaviour(i.e.,relating to its leaf-litter allelopathy and potential for soil-nitrogen fixation)further exacerbated its mono-dominant distribution by inhibiting the development of other native ***:Although rehabilitation techniques on-site have undergone refinements to improve site management,our findings support that putative changes in edaphic conditions in combination with the competitive characteristics of some plant species can facilitate conditions leading to alternative ecological outcomes among rehabilitated *** on these outcomes,future studies would benefit from in depth spatio-temporal analyses to verify these mechanisms at finer investigative sc

关键词： Eucalypts Mono-dominance Forest regeneration Ecological restoration Mineral sands Mining

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Facile In Situ Fabrication of Nanostructured Graphene–CuO Hybrid with Hydrogen Sulfide Removal Capacity

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Nano-Micro Letters 2016年第4期8卷 312-319页

作者： Sunil p.Lonkar Vishnu V.pillai Samuel stephen Ahmed Abdala Vikas Mittal Department of Chemical Engineering The Petroleum Institute

A simple and scalable synthetic approach for one-step synthesis of graphene–Cu O(TRGC) nanocomposite by an in situ thermo-annealing method has been *** graphene oxide(GO) and copper hydroxide as a precursors reagent,the reduction of GO and the uniform deposition of in situ formed Cu O nanoparticles on graphene was simultaneously *** method employed no solvents,toxic-reducing agents,or organic *** resulting nanostructured hybrid exhibited improved H2 S sorption capacity of 1.5 mmol H2S/g-sorbent(3 g S/100 g-sorbent).Due to its highly dispersed sub-20 nm Cu O nanoparticles and large specific surface area,TRGC nanocomposite exhibits tremendous potential for energy and environment applications.

关键词： CuO/graphene Adsorption Breakthrough capacity Hydrogen sulfide Thermal stability In situ synthesis

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Combining Aluminum Heat Treat with Hot Isostatic pressing: A Comparison of Structure, properties, and processing Routes for a Cast AI-Si-Mg Alloy

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材料热处理学报 2004年第5期25卷 546-551页

作者： stephen J. Mashl Body cote HIp Inc. Andover Massachusetts USA

Bodycote researchers have successfully demonstrated that a T6 heat treatment can be integrated with Densal?, a proprietary, aluminum specific, hot isostatic pressing (HIp) process. In this combined operation, at least a portion of the solution heat treatment is conducted at elevated pressure. During development, two issues, adiabatic cooling during depressurization and a possible variation in the kinetics of homogenization resulting from conducting the solution heat treat at elevated pressure were perceived as factors which could alter the heat treat response from that seen in conventional processing. This paper reviews the results of experiments performed to Al-Si-Mg (A356.0) castings subjected to both combined and conventional processing routes. Results indicate that the combined HIp and heat treat process is an efficient means of achieving a microstructure characteristic of a conventionally T6 processed material while eliminating porosity within the casting. Further, the fatigue life of an A356.0 casting processed using the combined cycle can be improved by more than an order of magnitude over the as-cast and T6 treated component.

关键词： Al-Si-Mg合金热处理热等静压缩 HIp 机械性质疲劳寿命

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RADIATION BOUNDARY CONDITIONS FOR MAXWELL'S EQUATIONS:A REVIEW OF ACCURATE TIME-DOMAIN FORMULATIONS

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Journal of Computational Mathematics 2007年第3期25卷 305-336页

作者： Thomas Hagstrom stephen Lau Department of Mathematics and Statistics University of New MexicoAlbuquerqueNM 87131USA Division of Applied Mathematics Brown University182 George StreetProvidenceRI 02912USA

We review time-domain formulations of radiation boundary conditions for Maxwell＇s equations, focusing on methods which can deliver arbitrary accuracy at acceptable compu-tational cost. Examples include fast evaluations of nonlocal conditions on symmetric and general boundaries, methods based on identifying and evaluating equivalent sources, and local approximations such as the perfectly matched layer and sequences of local boundary conditions. Complexity estimates are derived to assess work and storage requirements as a function of wavelength and simulation time.

关键词： Maxwell's equations Radiation boundary conditions Fast algorithms Kirchoffformulas perfectly matched layers.

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Mineral sulphide-lime reactions and effect of CaO/C mole ratio during carbothermic reduction of complex mineral sulphides

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International Journal of Minerals,Metallurgy and Materials 2014年第1期21卷 1-11页

作者： Yotamu stephen Rainford Hara Institute for Materials Research(IMR) School of ProcessEnvironmental and Materials Engineering(SPEME)University of Leeds

Mineral sulphide （MS）-lime （CaO） ion exchange reactions （MS ＋ CaO = MO ＋ CaS） and the effect of CaO/C mole ratio during carbothermic reduction （MS ＋ CaO ＋ C = M ＋ CaS ＋ CO（g）） were investigated for complex froth flotation mineral sulphide concentrates. phases in the partially and fully reacted samples were characterised by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The primary phases during mineral sulphide-lime ion exchange reactions are Fe304, CaSO4 Cu2S, and CaS. A complex liquid phase of Ca2CuFeO3S forms during mineral sulphide-lime exchange reactions above 1173 K. The formation mechanisms of Ca2CuFeO3S liquid phase are determined by characterising the partially reacted samples. The reduction rate and extent of mineral sulphides in the presence of CaO and C increase with the increase in CaO/C ratio. The metallic phases are surrounded by the CaS rich phase at CaO/C 〉 1, but the metallic phases and CaS are found as separate phases at CaO/C 〈 1. Experimental results show that the stoichiometric ratio of carbon should be slightly higher than that of CaO. The reactions between CaO and gangue minerals （SiO2 and A1203） are only observed at CaO/C 〉 1 and the reacted samples are excessively sintered.

关键词： sulphide minerals ion exchange carbothermic reduction lime

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Cellular signaling in sinecatechins-treated external genital and perianal warts: unraveling the mechanism of action of a botanical therapy

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Virologica Sinica 2015年第3期30卷 214-217页

作者： Harrison p Nguyen Hung Q Doan peter Rady stephen K Tyring Department of Dermatology Baylor College of Medicine Department of Dermatology University of Texas Houston Health Science Center Center for Clinical Studies

Dear Editor,Derived from green tea leaves,sinecatechins(Veregen)ointment,15%is a topical therapy that is FDA-approved to treat human papillomavirus(HpV)-induced external genital and perianal warts(EGW)in immunocompetent patients aged 18 years and *** two phase 3 trials enrolling over 1,000 participants with EGW,a 16-week treatment regimen with sinecatechins ointment resulted in higher rates of complete clearance of all warts—both

关键词： genital papillomavirus clearance older regimen approved signaling transcriptase salient biopsy

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MOLECULAR AND SUpRAMOLECULAR ORDERING IN CONFINED ENVIRONMENTS

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Chinese Journal of polymer Science 2000年第4期18卷 287-300页

作者： stephen Z.D.Cheng Bret H.Calhoun Roderic p.Quirk Benjamin S.Hsiao Maurice Morton Institute and Department of polymer Science The University of Akron Akron Ohio 44325-3909 USAMaurice Morton Institute and Department of Polymer Science The University of Akron Akron Ohio 44325-3909 USAMaurice Morton Institute and Department of Polymer Science The University of Akron Akron Ohio 44325-3909 USADepartment of ChemistryThe State University of New York at Stony Brook Stony Brook New York 11794-3400 USA

Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (pEO-b-pS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (D_(CF)) diblock copolymer, the competition between crystalli-zation of the pEO blocks and vitrification of the pS blocks is momtored by time-resolved simultaneous small angle X-rayscattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques. In the case of T_cpS-rich), the crystallization of thepEO blocks is observed to be confined within the bicontinuous D_(CF) phase due to the rapid vitrification of the pS-rich *** crystallization rate, crystal melting behavior, and crystallinity results further confirm the competition betweencrystallization and vitrification at different temperatures. In an ordered lamellar pEO-b-pS diblock copolymer, the crystalli-zation of the pEO blocks is completely confined within the ordered lamellae due to rapid vitrification of the pS layers asobserved by time-resolved SAXS and WAXD experiments. From the combined two-dimensional SAXS and WAXDmeasurements, the crystal orientation within the confined lamellar geometry is found parallel to the lamellar surface normalwhen it is isothermally crystallized at 35℃. In an ordered cylindrical pEO-b-pS sample, the crystallization of the pEO blocksis also observed to be confined within the ordered cylinders because of rapid vitrification of the pS matrix. The crystalorientation within the confined cylinders is found perpendicular to the cylinder axis as it is crystallized at 35℃.

关键词： poly(ethylene oxide)-b-polystyrene diblock copolymer Molecular ordering, Supramolecular ordering, Confined environment

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A new hadron spectroscopy

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Frontiers of physics 2015年第2期10卷 1-34页

作者： stephen Lars Olsen Center for Underground physics Institute of Basic Science Daejeon 305-811 Korea

QCD-motivated models for hadrons predict an assortment of ＂exotic＂ hadrons that have structures that are more complex than the quark-antiquark mesons and three-quark baryons of the original quark-parton model. These include pentaquark baryons： the six-quark H-dibaryon~ and tetraquark, hybrid and glueball mesons. Despite extensive experimental searches, no unambiguous candidates for any of these exotic configurations have been identified. On the other hand, a number of meson states, one that seems to be a proton-antiproton bound state, and others that contain either charmed- anticharmed quark pairs or bottom-antibottom quark pairs, have been recently discovered that neither fit into the quark-antiquark meson picture nor match the expected properties of the QCD- inspired exotics. Here I briefly review results from a recent search for the H-dibaryon, and discuss some properties of the newly discovered states -the proton-antiproton state and the so-called XYZ mesons- and compare them with expectations for conventional quark-antiquark mesons and the predicted QCD-exotic states.

关键词： quarks charmonium pentaquarks di-baryons baryonium tetraquarks

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