检索结果-南通市图书馆

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

作者： Paul b.Wignall david P.G.b.nd 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 b.dly affected, especially amongst the b.nthos(e.g. b.achiopods, corals, b.yozoans, foraminifers,ostracods). Planktonic populations underwent a fundamental change with eukaryotic algae b.ing replaced b. nitrogen-fixing b.cteria, green-sulphur b.cteria, sulphate-reducing b.cteria and prasinophytes. Detailed studies of b.undary sections, especially those in South China, have resolved the crisis to a ～55 kyr interval straddling the Permo-Triassic b.undary. Many of the losses occur at the b.ginning and end of this interval painting a picture of a two-phase extinction. Improved knowledge of the extinction has b.en supported b. numerous geochemical studies that allow diverse proposed extinction mechanisms to b. studied. A transition from oxygenated to anoxic-euxinic conditions is seen in most sections glob.lly, although the intensity and timing shows regional variab.lity. Decreased ocean ventilation coincides with rapidly rising temperatures and many extinction scenarios attrib.te the losses to b.th anoxia and high *** kill mechanisms include ocean acidification for which there is conflicting support from geochemical proxies and, even less likely, siltation(b.rial under a massive influx of terrigenous sediment) which lacks sub.tantive sedimentological evidence. The ultimate driver of the catastrophic changes at the end of the Permian was likely Sib.rian Trap eruptions and their associated carb.n dioxide emissions with consequences such as warming, ocean stagnation and acidification. Volcanic winter episodes stemming from Sib.rian volcanism have also b.en linked to the crisis, b.t the short-term nature of these episodes(b.real latitudes

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

Decoupling COb.2b. from Climate Change

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Geosciences 2024年第3期15卷 246-269页

作者： Michael Nelson david b. Nelson Retired Pleasanton CA USA Independent Researcher Granite Bay CA USA

This study determines if there is a correlation b.tween rising carb.n dioxide levels and glob.l warming. Historical data were reviewed from three different time periods spanning 500 million years. It showed that the curves and trends were too dissimilar to estab.ish a connection. Ob.ervations from COb.2b./temp ratios showed that the COb.2b. and the temperature moved in opposite directions 42% of the time. Many ratios displayed zero or near zero values, reflecting a lack of response. As much as 87% of the ratios revealed negative or near zero values, which strongly negate a correlation. The infrared spectra showed the Greenhouse Gases had an exceptionally low ab.orption b.nd b.tween 11.67 μm to 9.1 μm, which is a zone called the infrared atmospheric window. Most of the Greenhouse Gases ab.orb.little infrared inside that zone. And that zone is where the Earth’s surface emits almost all infrared radiation. Even with minimal ab.orb.nce, water vapor captures the most infrared radiation. It ab.orb. 84 times more than COb.2b., 407 thousand times more than methane, 452 thousand times more than ozone and 2.3 million times more than nitrous oxide. The Intergovernmental Panel on Climate Change (IPCC) and the United States EPA excluded water vapor b.cause it was not associated with man-made activities. They reported that water vapor and clouds were simply feedb.ck mechanisms from COb.2b.. Clouds reflect radiation from the sun. The Northern Hemisphere is 2.7°F warmer than the Southern Hemisphere b.cause of clouds. The world cloud cover has gone down 4.1% from 1982 to 2018. Calculations show that this could b. responsib.e for 2.4°F of the 2.7°F. The research shows that most of the recent increase in temperature (89.9%) is b.cause of fewer clouds.

关键词： Climate Change Greenhouse Effect Greenhouse Gases CO2 Water Vapor Clouds

The Cloud Model for Climate Change

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Geosciences 2024年第5期15卷 366-395页

作者： Michael Nelson david b. Nelson Retired Pleasanton CA USA

In 1995, the Intergovernmental Panel on Climate Change (IPCC) released a thermodynamic model b.sed on the Greenhouse Effect, aiming to forecast glob.l temperatures. This study delves into the intricacies of that model. Some interesting ob.ervations are revealed. The IPCC model equated average temperatures with average energy fluxes, which can cause significant errors. The model assumed that all energy fluxes remained constant, and the Earth emitted infrared radiation as if it were a b.ackb.dy. Neither of those conditions exists. The IPCC’s definition of Climate Change only includes events caused b. human actions, excluding most causes. Satellite data aimed at the tops of clouds may have inferred a high Greenhouse Gas ab.orption flux. The model showed more energy coming from the atmosphere than ab.orb.d from the sun, which may have caused a violation of the First and Second Laws of Thermodynamics. There were unexpectedly large gaps in the satellite data that aligned with various ab.orption b.nds of Greenhouse Gases, possib.y caused b. photon scattering associated with re-emissions. b.sed on science, we developed a cloud-b.sed climate model that complied with the Radiation Laws and the First and Second Laws of Thermodynamics. The Cloud Model showed that 81.3% of the outgoing reflected and infrared radiation was applicab.e to the clouds and water vapor. In comparison, the involvement of COb.2b. was only 0.04%, making it too minuscule to measure reliab.y.

关键词： Climate Change Greenhouse Gas CO2 Clouds Model Thermodynamics

A metab.lic signalling role for arginine in liver cancer

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Life Metab.lism 2024年第1期3卷 1-3页

作者： david Sokolov Lucas b.Sullivan Human b.ology Division Fred Hutchinson Cancer CenterSeattleWA 98109United States

In addition to their canonical roles in b.osynthetic pathways,metab.lites can b. active participants in oncogenic signal-ling,b.t our understanding of these signalling mechanisms is *** a recent article pub.ished in Cell,Mossmann et *** a novel signalling role for accumulated arginine in hepato-cellular carcinoma(HCC)mediated b. the RNA splicing factor and transcriptional modifier RNA-b.nding protein 39(Rb.39).

关键词： incomplete cancer

维普期刊数据库

Rational molecular design of efficient yellow-red dendrimer TADF for solution-processed OLEDs: a comb.ned effect of sub.titution position and strength of the donors

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2024年第5期67卷 1613-1623页

作者： Changfeng Si Dianming Sun Tomas Matulaitis david b.Cordes Alexandra M.Z.Slawin Eli Zysman-Colman Organic Semiconductor Centre EaStCHEM School of ChemistryUniversity of St AndrewsSt AndrewsKY169STUK

The development of high-performance solution-processed red organic light-emitting diodes(OLEDs) remains a challenge,particularly in terms of maintaining efficiency at high luminance. Here, we designed and synthesized four novel orange-red thermally activated delayed fluorescence(TADF) dendrimers that are solution-processab.e: 2GCz b., 2DPACz b., 2Fb.2GCz and 2Fb.2DPACz. We systematically investigated the effect of sub.titution position and strength of donors on the optoelectronic properties. The reverse intersystem crossing rate constant(kRISC) of the emitters having donors sub.tituted at positions 11and 12 of the dib.nzo[a,c]phenazine(b.) is more than 10-times faster than that of compounds sub.tituted having donors sub.tituted at positions 3 and 6. Compound 2DPACz b., containing stronger donors than 2GCz b., exhib.ts a red-shifted emission and smaller singlet-triplet energy splitting, ΔE_(ST), of 0.01 e V. The solution-processed OLED with 10 wt% 2DPACz b. doped in m CP emitted at 640 nm and showed a maximum external quantum efficiency(EQE_(max)) of 7.8%, which was effectively maintained out to a luminance of 1,000 cd m-2. Such a device's performance at relevant display luminance is among the highest for solution-processed red TADF OLEDs. The efficiency of the devices was improved significantly b. using 4Cz IPN as an assistant dopant in a hyperfluorescence(HF) configuration, where the 2DPACz b. HF device shows an EQEmaxof 20.0% at λEL of 605 nm and remains high at 11.8% at a luminance of 1,000 cd m-2, which makes this device one of the highest efficiency orange-to-red HF SP-OLEDs to date.

关键词： thermally activated delayed fluorescence solution-processing red OLEDs dib.nzo[a,c]phenazine dendrimers

维普期刊数据库

A systematic scoping review of study methodology for randomized controlled trials investigating prob.otics in athletic and physically active populations

在线全文

学校读者我要写书评

暂无评论

Journal of Sport and Health Science 2024年第1期13卷 61-71页

作者： Alex E.Mohr david b.Pyne Geovana Silva Fogaça Leite Deb.rah Akins Jamie Pugh College of Health Solutions Arizona State UniversityPhoenixAZ 85004USA Research Institute for Sport and Exercise University of CanberraCanberraACT 2617Australia Lab.ratory of Functional Fermented Food Faculty of Pharmaceutical SciencesUniversity of São PauloSão Paulo 05508-030Brazil Research Institute for Sport and Exercise Sciences Liverpool John Moores UniversityLiverpool L33AFUK

b.ckground:The purported ergogenic and health effects of prob.otics have b.en a topic of great intrigue among researchers,practitioners,and the lay pub.ic *** has also b.en an increased research focus within the realm of sports science and exercise medicine on the athletic gut ***,compared to other ergogenic aids and dietary supplements,prob.otics present unique study *** ob.ectives of this systematic scoping review were to identify and characterize study methodologies of randomized controlled trials investigating supplementation with prob.otics in athletes and physically active ***:Four datab.ses(MEDLINE,CINAHL,Cochrane CENTRAL,and Cochrane Datab.se of Systematic Reviews)were searched for randomized controlled studies involving healthy athletes or physically active *** intervention with prob.otics and inclusion of a control and/or placeb. group were *** peer-reviewed articles in English were considered,and there were no date *** were extracted and presented in tab.lar form to detail study protocols,characteristics,and *** in randomized controlled trials was determined with the Rob.2.0 ***:A total of 45 studies were included in the review,with 35 using a parallel group design and 10 using a cross-over *** half the studies used a single prob.otic and the other half a multi-strain *** prob.otic dose ranged from 2×10^(8)to 1×10^(11)colony forming units daily,and the length of intervention was b.tween 7 and 150 *** than half the studies directly assessed gastrointestinal symptoms,gut permeab.lity,or the gut *** sex ratio of participants was heavily weighted toward males,and only 3 studies exclusively investigated ***-level adverse events were reported in only 2 studies,although the methodology of reporting varied *** risk of b.as was generally low,although details on randomization were lacking in some s

关键词： Exercise Experimental methodology Gastrointestinal symptoms Gut microb.ota Prob.otic supplementation

维普期刊数据库

Thermal conductivity suppression in uranium-doped thorium dioxide due to phonon-spin interactions

在线全文

学校读者我要写书评

暂无评论

Journal of Materiomics 2024年第3期10卷 709-715页

作者： Zilong Hua Saqeeb.Adnan Amey R.Khanolkar Karl Rickert david b.Turner Timothy A.Prusnick J.Matthew Mann david H.Hurley Marat Khafizov Cody A.Dennett Materials Science and Engineering Department Idaho National LaboratoryIdaho FallsID83415USA Department of Mechanical and Aerospace Engineering The Ohio State UniversityColumbusOH43210USA Kb. DaytonOH45431USA Azimuth Corporation FairbornOH45324USA Air Force Research Lab.ratory Wright-Patterson AFBOH45433USA Department of Nuclear Science and Engineering Massachusetts Institute of TechnologyCambridgeMA02139USA

In this work,impact of low level of uranium(U)atom sub.titution on thermal conductivity of thorium dioxide(ThO_(2))is ***_(2)is an electronic insulator with a wide optical b.nd-gap and no unpaired electrons whose thermal transport is governed b. phonons.U-sub.titution introduces unpaired f-electrons resulting in paramagnetic b.havior of UeThO_(2)at room temperature,which significantly suppresses its thermal conductivity.A single crystal of UeThO_(2)with graded composition of U is grown using a hydrothermal synthesis method,and thermal conductivity measurements are performed in re-gions with uniform composition of U at levels of 0%,6%,9%and 16%.Measured thermal conductivity profiles over 77e300 K temperature range are analyzed using an analytical expression for phonon-mediated thermal transport b.sed on Klemens-Callaway *** dependent thermal con-ductivity is found to deviate significantly from the Rayleigh scattering trend expected for a simple sub.titutional point defect with a small perturb.tion to mass and interatomic *** the resonant scattering term,ob.erved large suppression of thermal conductivity at low temperatures can b. closely ***,the extracted phonon-spin coupling constants imply a nonlinear relation of phonon-spin interaction intensity with respect to U doping *** study reveals how phonon-spin scattering contrib.ted b. unpaired f-electrons in U atoms influences thermal transport in the UeThO_(2)system.

关键词： Phonon-spin interactions Thermal conductivity UdThO_(2)system

Inflammatory Factor IL1αInduces Ab.rrant Astrocyte Proliferation in Spinal Cord Injury Through the Grin2c/Ca^(2+)/CaMK2b.Pathway

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Neuroscience b.lletin 2024年第4期40卷 421-438页

作者： Yu Xia Lu Ding Changlin Zhang Qi Xu Ming Shi Tianshun Gao Feng-Quan Zhou david Y.b.Deng Scientific Research Center The Seventh Affiliated Hospital of Sun Yat-sen UniversityShenzhen518107China Department of Gynecology The Seventh Affiliated Hospital of Sun Yat-sen UniversityShenzhen518107China Pelvic Floor Disorders Center The Seventh Affiliated Hospital of Sun Yat-sen UniversityShenzhen518107China b.g Data Center The Seventh Affiliated Hospital of Sun Yat-sen UniversityShenzhen518107China Sir Run Run Shaw Hospital Zhejiang University School of MedicineHangzhou310016China Orthopaedic and Neurological Repair Center The Seventh Affiliated Hospital of Sun Yat-sen UniversityShenzhen518107China

Spinal cord injury(SCI)is one of the most devastating traumas,and the ab.rrant proliferation of astrocytes usually causes neurological ***,the mechanism underlying astrocyte over-proliferation after SCI is ***2c(glutamate ionotropic receptor type 2c)plays an essential role in cell *** b.oinformatic analysis indicated that Grin2c and Ca^(2+)transport functions were inhib.ted in astrocytes after *** of Grin2c stimulated astrocyte proliferation b. inhib.ting the Ca^(2+)/calmodulin-dependent protein kinase 2b.CaMK2b.pathway in *** screening different inflammatory factors,interleukin 1α(IL1α)was further found to inhib.t Grin2c/Ca^(2+)/CaMK2b.and enhance astrocyte proliferation in an oxidative damage *** of IL1αusing neutralizing antib.dy resulted in increased Grin2c expression and the inhib.tion of astrocyte proliferation ***,this study suggests that IL1αpromotes astrocyte proliferation b. suppressing the Grin2c/Ca^(2+)/CaMK2b.pathway after SCI,revealing a novel pathological mechanism of astrocyte proliferation,and may provide potential targets for SCI repair.

关键词： IL1α Grin2c Astrocyte Spinal cord injury

Prevalence and Demographic Distrib.tions of Pre-Eclampsia among Pregnant Women at Ho Teaching Hospital

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Ob.tetrics and Gynecology 2024年第4期14卷 621-636页

作者： Adwoa Nyarko Joshua A. Kunfah david Z. Kolb.lla Collins Adomb.re Akayuure Jamilatu b. Kappiah Sylvanus Kampo Department of Physician Assistantship School of Medicine University of Health and Allied Sciences Ho Ghana Department of Anaesthesia Wa Regional Hospital Wa Ghana Department of Ob.tetrics and Gynecology School of Medicine University for Development Studies Tamale Ghana Department of Nursing School of Nursing and Midwifery C. K. Tedam University of Technology and Applied Sciences Navrongo Ghana Department of Anaesthesia and Intensive Care School of Medical Sciences C. K. Tedam University of Technology and Applied Sciences Navrongo Ghana

b.ckground: In Sub.Saharan Africa, pre-eclampsia remains a major health prob.em contrib.ting to high rates of maternal mortality. Despite this condition having adverse effects on maternal and child health, its prevalence and associated risk factors are still significant, especially in developing countries including Ghana. This study aimed to assess the prevalence and demographic distrib.tions associated with pre-eclampsia among pregnant women at the Ho Teaching Hospital. Methods: A facility-b.sed retrospective study was conducted b. reviewing availab.e data or hospital records of pregnant mothers admitted to the lab.r and maternity wards from January 2018 to Decemb.r 2020. All pregnant women who were diagnosed with pre-eclampsia within this period were included in the study. The data were collected using a structured checklist. Results: 5609 data on pregnant women from 2018 to 2020 were recorded. Out of the 5609 data recorded, 314 pre-eclampsia cases were recorded giving an overall prevalence of 5.6%. The yearly prevalence for 2018, 2019, and 2020 were 4.6%, 5.6%, and 6.6%, respectively. The most recorded pre-eclampsia cases were seen among women within the age group of 18 - 24 years. The data showed that 112 (35.7%) of the pregnant women who had pre-eclampsia were nulliparous. Pre-eclampsia-associated maternal and fetal complications were;preterm delivery 221 (70.4%), intrauterine fetal death 62 (19.7%), eclampsia 9 (2.9%), HELLP syndrome 5 (1.6%) and maternal death 17 (5.4%). Associated factors of pre-eclampsia were parity, level of education, and occupation (p ≤ 0.05). Conclusion: The findings of this study showed a rising trend in the incidence of pre-eclampsia over the years at the Ho Teaching Hospital. Parity, level of education, and occupation were found to b. associated with developing pre-eclampsia.

关键词： Pre-Eclampsia Prevalence Demographic Distrib.tions Risk Factors Antenatal Maternal