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The great catastrophe: causes of the permo-Triassic marine mass extinction

National Science Review 2024年第1期11卷 37-50页

作者： paul B.Wignall David p.G.Bond School of Earth & Environment University of Leeds School of Environmental Sciences University of Hull

The marine losses during the permo-Triassic mass extinction were the worst ever experienced. All groups were badly affected, especially amongst the benthos(e.g. brachiopods, corals, bryozoans, foraminifers,ostracods). planktonic populations underwent a fundamental change with eukaryotic algae being replaced by nitrogen-fixing bacteria, green-sulphur bacteria, sulphate-reducing bacteria and prasinophytes. Detailed studies of boundary sections, especially those in South China, have resolved the crisis to a ～55 kyr interval straddling the permo-Triassic boundary. Many of the losses occur at the beginning and end of this interval painting a picture of a two-phase extinction. Improved knowledge of the extinction has been supported by numerous geochemical studies that allow diverse proposed extinction mechanisms to be studied. A transition from oxygenated to anoxic-euxinic conditions is seen in most sections globally, although the intensity and timing shows regional variability. Decreased ocean ventilation coincides with rapidly rising temperatures and many extinction scenarios attribute the losses to both anoxia and high *** kill mechanisms include ocean acidification for which there is conflicting support from geochemical proxies and, even less likely, siltation(burial under a massive influx of terrigenous sediment) which lacks substantive sedimentological evidence. The ultimate driver of the catastrophic changes at the end of the permian was likely Siberian Trap eruptions and their associated carbon dioxide emissions with consequences such as warming, ocean stagnation and acidification. Volcanic winter episodes stemming from Siberian volcanism have also been linked to the crisis, but the short-term nature of these episodes(overwhelming evidence for rapid warming during the crisis makes this an unlikely cause. Finally, whilst the extinction is well studied in equatorial latitudes, a different history is found in northern Boreal latitudes

关键词： ocean anoxia ocean acidification siltation productivity collapse volcanic winter

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Colorectal resections for malignancy: A pilot study comparing conventional vs freehand robot-assisted laparoscopic colectomy

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World Journal of Clinical Cases 2024年第3期12卷 488-494页

作者： Shamir o Cawich Joseph Martin plummer Sahle Griffith Vijay Naraynsingh Department of Surgery University of the West IndiesSt AugustineTrinidad and Tobago Department of General Surgery and Consultant General and Colorectal Surgeon Department of SurgeryUniversity of the West IndiesKingstonKIN7Jamaica Department of Surgery Queen Elizabeth HospitalBridgetownBarbados Department of Surgery Port of Spain General HospitalPort of SpainTrinidad and Tobago

BACKGRoUND Laparoscopic colectomy is widely accepted as a safe operation for colorectal cancer,but we have experienced resistance to the introduction of the FreeHandffrobotic camera holder to augment laparoscopic colorectal *** To compare the initial results between conventional and FreeHandffrobot-assisted laparoscopic colectomy in Trinidad and *** This was a prospective study of outcomes from all laparoscopic colectomies per-formed for colorectal carcinoma from November 29,2021 to May 30,*** following data were recorded:operating time,conversions,estimated blood loss,hospitalization,morbidity,surgical resection margins and number of nodes *** data were entered into an excel database and the data were analyzed using SpSS ver *** There were 23 patients undergoing colectomies for malignant disease:8(35%)FreeHandff-assisted and 15(65%)conventional laparoscopic *** were no *** time was significantly lower in patients under-going robot-assisted laparoscopic colectomy(95.13±9.22 vs 105.67±11.48 min;p=0.045).otherwise,there was no difference in estimated blood loss,nodal harvest,hospitalization,morbidity or *** The FreeHandffrobot for colectomies is safe,provides some advantages over conventional laparoscopy and does not compromise oncologic standards in the resource-poor Caribbean setting.

关键词： Laparoscopic Colectomy Robot Surgery Minimally invasive

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Newly Launched Satellite Seeks to Keep Methane Emitters Honest

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Engineering 2024年第10期41卷 1-3页

作者： Sean o’Neill Senior Technology Writer

on 4 March 2024,a new methane-observing satellite,MethaneSAT,was launched atop a SpaceX Falcon 9 rocket and successfully placed in orbit[1].Developed by the New York City,NY,USA-headquartered Environmental Defense Fund(EDF)in partnership with the New Zealand Space Agency and funded by multiple philanthropic donors including the Bezos Earth Fund,the spacecraft promises to greatly improve scientists’ability to pinpoint and monitor methane emissions,particularly those related to the oil and gas industry.

关键词： funded Methane methane

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Constraining the variable generalized Chaplygin gas model in matter creation cosmology

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Communications in Theoretical physics 2024年第10期76卷 121-136页

作者： Yogesh Bhardwaj C p Singh Department of Applied Mathematics Delhi Technological University

We explore the variable generalized Chaplygin gas（VGCG） model in the theory of matter creation cosmology within the framework of a spatially homogeneous and isotropic flat Friedmann—Lemai tre—Robertson—Walker space-time. Matter creation cosmology is based on reinterpretation of the energy–momentum tensor in Einstein's field equations. This creation corresponds to an irreversible energy flow from the gravitational field to the created matter constituents. The variable Chaplygin gas（VCG） is also studied as a particular solution. We use the Markov chain Monte Carlo method to constrain the free parameters of three models, namely,Lambda-Cold-Dark matter（ΛCDM）, VGCG and VCG models with and without matter creation from the latest observational data from baryon acoustic oscillations, cosmic chronometer, type Ia supernovae（pantheon） including gamma-ray bursts, quasars and the local measurement of H0from R21 data. Two different combinations of dataset provide a fairly tight constraint on the parameters of the ΛCDM, VGCG and VCG models. The present values of various cosmological parameters are obtained, which are very close to the ΛCDM model. Furthermore, we perform stability analysis, Bayesian evidence analysis and information criteria analysis for these models through studying the sound speed, Bayes factor, and Akaike information criteria（AIC） and Bayesian information criteria（BIC） selection criteria. The values of sound speed for VGCG and VCG models shows that both the models are stable. According to AIC, it is observed that VGCG and VCG models with matter creation are supported considerably less by current observations,while BIC shows that these models are not favoured by observational data.

关键词： Chaplygin gas model cosmological model dark energy matter creation

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The effects of relative density of metal foams on the stresses and deformation of beam under bending

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Acta Mechanica Sinica 2007年第4期23卷 409-414页

作者： Aiyu Zhu Tianyou Fan Department of Mathematics,School of Science,Beijing Institute of Technology,p.o.box.327,Beijing 100081,China Department of physics,School of Science,Beijing Institute of Technology,p.o.box.327,Beijing 100081,China Department of Mathematics School of Science Beijing Institute of Technology P. O. Box 327 Beijing 100081 China Department of physics School of Science Beijing Institute of Technology P. O. Box 327 Beijing 100081 China

The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive law （TG model） taken as the analysis basis. Several examples for individual foams are discussed, showing the importance of compressibility of the cellular materials. one of the objects of this study is to generalize Hill＇s solution for incompressible plasticity to the case of compressible plasticity, and a kinematics parameter is brought into the analysis so that the velocity field can be determined.

关键词： Metal foams - Relative density Compressible plasticity Constitutive law - TG model

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Exact solutions for magnetohydrodynamic nanofluids flow and heat transfer over a permeable axisymmetric radially stretching/shrinking sheet

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Chinese physics B 2024年第2期33卷 108-114页

作者： U.S.Mahabaleshwar G.p.Vanitha L.M.pérez Emad H.Aly I.pop Department of Studies in Mathematics Davangere UniversityShivagangothriDavangereIndia Departamento de F´ısica FACIUniversidad de Tarapac´aCasilla 7DAricaChile Department of Mathematics Faculty of EducationAin Shams UniversityRoxyCairoEgypt Department of Mathematics Babes-Bolyai University400084 Cluj-NapocaRomania

We report on the magnetohydrodynamic impact on the axisymmetric flow of Al_(2)o_(3)/Cu nanoparticles suspended in H_(2)o past a stretched/shrinked *** the use of partial differential equations and the corresponding thermophysical characteristics of nanoparticles,the physical flow process is *** resultant nonlinear system of partial differential equations is converted into a system of ordinary differential equations using the suitable similarity *** transformed differential equations are solved *** of the magnetic parameter,solid volume fraction and stretching/shrinking parameter on momentum and temperature distribution have been analyzed and interpreted *** skin friction and Nusselt number were also *** addition,existence of dual solution was deduced for the shrinking sheet and unique solution for the stretching ***,Al_(2)o_(3)/H_(2)o nanofluid flow has better thermal conductivity on comparing with Cu/H_(2)o ***,it was found that the first solutions of the stream are stable and physically realizable,whereas those of the second ones are unstable.

关键词： magnetohydrodynamic nanofluid stretching/shrinking sheet axisymmetric flow analytical solution suction/injection

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Study on the Effects of End-bend Cantilevered Stator in a 2-stage Axial Compressor

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Journal of Thermal Science 2009年第2期18卷 119-125页

作者： Songtao WANG Xin DU Zhongqi WANG Harbin Institute of Technology, p.o. box 458, Harbin 150001, China Harbin Institute of Technology P.O. BOX 458 Harbin 150001 China

Leading edge recambering is applied to the cantilevered stator vanes in a 2-stage compressor in this paper. Differentcurving effects are produced when the end-bend stator vanes are stacked in different ways. Stacking on theleading edge induces a positive curving effect near the *** it is stacked on the centre of gravity, a negativecurving effect takes place. The numerical investigation shows that the flow field is redistributed when theend-bend stators with leading edge stacking are applied. The variations in the stage matching for the mainstreamand near the hub have an impact on the performance of the 2-stage compressor. The isentropic efficiency and thetotal pressure ratio of the compressor are increased near the design condition. The compressor total pressure ratiois decreased near choke and near stall. The maximum flow rate is reduced and the stall margin is decreased.

关键词： axial compressor end-bend blade stacking stage matching

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Influence of railway wheel tread damage on wheel-rail impact loads and the durability of wheelsets

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Railway Engineering Science 2024年第1期32卷 20-35页

作者： Michele Maglio Tore Vernersson Jens C.o.Nielsen Anders Ekberg Elena Kabo CHARMEC Department of Mechanical and Maritime SciencesChalmers University of TechnologySE‑41296 GothenburgSweden

Dynamic wheel-rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle *** on laser scanning,the measured three-dimensional damage geometry is employed in simulations of dynamic vehicle-track interaction to calibrate and verify a simulation *** relation between the magnitude of the impact load and various operational parameters,such as vehicle speed,lateral position of wheel-rail contact,track stiffness and position of impact within a sleeper bay,is *** calibrated model is later employed in simulations featuring other forms of tread damage;their effects on impact load and subsequent fatigue impact on bearings,wheel webs and subsurface initiated rolling contact fatigue of the wheel tread are *** results quantify the effects of wheel tread defects and are valuable in a shift towards condition-based maintenance of running gear,and for general assessment of the severity of different types of railway wheel tread damage.

关键词： Wheel tread damage Rolling contact fatigue cluster Field measurements Dynamic vehicle-track interaction Wheel-rail impact load Wheelset durability

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A Class of parallel Implicit Runge-Kutta Formulas

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Journal of Systems Engineering and Electronics 1993年第4期4卷 53-63页

作者： Fei JinggaoBeijing Institute of Computer Application and Simulation Technology p.o. box 3929, Beijing 100854, China Beijing Institute of Computer Application and Simulation Technology p.o. box 3929 Beijing 100854 China

A class of parallel implicit Runge-Kutta formulas is constructed for multiprocessor system. A family of parallel implicit two-stage fourth order Runge-Kutta formulas is given. For these formulas, the convergence is proved and the stability analysis is given. The numerical examples demonstrate that these formulas can solve an extensive class of initial value problems for the ordinary differential equations.

关键词： Multiprocessor system parallel algorithm ordinary differential equation Implicit Runge-Kutta formula.

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Dielectronic Recombination Rate Coefficients for Nickel-like Ytterbium

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Chinese Journal of Lasers 1996年第3期B5卷 242-247页

作者： ZHAo Libol LI Shichang(Institute of physics, Academic Sinica, p. o. box 603, Beijing 100080,Institute of Applied physics and Computational Mathematics, p. o. box 8009, Beijing, China) Inst of physics Academia Sinica Beijing China

Ｄｉｅｌｅｃｔｒｏｎｉｃ　Ｒｅｃｏｍｂｉｎａｔｉｏｎ　Ｒａｔｅ　Ｃｏｅｆｆｉｃｉｅｎｔｓ　ｆｏｒ　Ｎｉｃｋｅｌ－ｌｉｋｅ　ＹｔｔｅｒｂｉｕｍＤｉｅｌｅｃｔｒｏｎｉｃＲｅｃｏｍｂｉｎａｔｉｏｎＲａｔｅＣｏｅｆｆｉｃｉｅ... 详细信息

Ｄｉｅｌｅｃｔｒｏｎｉｃ　Ｒｅｃｏｍｂｉｎａｔｉｏｎ　Ｒａｔｅ　Ｃｏｅｆｆｉｃｉｅｎｔｓ　ｆｏｒ　Ｎｉｃｋｅｌ－ｌｉｋｅ　ＹｔｔｅｒｂｉｕｍＤｉｅｌｅｃｔｒｏｎｉｃＲｅｃｏｍｂｉｎａｔｉｏｎＲａｔｅＣｏｅｆｆｉｃｉｅｎｔｓｆｏｒＮｉｃｋｅｌ－ｌｉｋｅ...

关键词： dielectronic recombination autoionizing state Auger rate

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