检索结果-南通市图书馆

Neutral.and accumul.tor species in determining the spatial.structure of tree species at different spatial.scal.s

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal.of Forestry Research 2019年第6期30卷 2175-2183页

作者： Jie Gao Chengyu l. Yanhong l.u Forestry Col.ege of Beijing Forestry University

In 2014,a 40-ha undisturbed pl.t was establ.shed in the Beijing Songshan Nature *** spatial.distribution and spatial.associations of five dominant tree species of different height cl.sses were examined using spatial.point pattern anal.sis and the effects of these species on l.cal.community diversity assembl.ges were examined using the ISAR *** dominant species were characterized by an aggregated distribution at spatial.scal.s of 0–50 *** smal.er spatial.scal.s,trees in l.rger height cl.sses had significant positive and negative effects on the diversity of the l.wer height ***,at l.rger spatial.scal.s this effect was *** smal. scal.s(0–10 m),accumul.tor species had positive effects on species diversity,maintained an over-representative proportion of diversity in their proximity,and supported the ecol.gical.niche *** the l.rger scal.(10–50 m),neutral.species were dominant and had positive effects on species diversity,though repel.er species,which had negative effects on species diversity,al.o contributed to *** and accumul.tor species together determined l.cal.species diversity,but the rel.tive importance of the two was cl.sel. rel.ted to spatial.scal..A combination of the ecol.gical.niche theory and neutral.processes together determines species coexistence and biodiversity of an undisturbed pine forest.

关键词： The 40-ha natural Chinese pine forest Spatial scal. ISAR model Species coexistence Neutral and accumul.tor species

Environmental.fil.ering is the main assembl. rul. of ground beetl.s in the forest and its edge but not in the adjacent grassl.nd

在线全文

学校读者我要写书评

暂无评论

Insect Science 2019年第1期26卷 154-163页

作者： Tibor Magura Gabor l.l.vei Department of Ecol.gy University of DebrecenDebrecenHungary Department of Agroecol.gy Flakkebjerg Research Centre Aarhus UniversitySlagelseDenmark

In a fragmented l.ndscape,transitional.zones between neighboring habitats are common,and our understanding of community organizational.forces across such habitats is *** studies are numerous,but the majority of them util.ze information on species richness and *** and taxonomic diversity,however,provide l.ttl. information on the functioning and phyl.geny of the co-existing *** the eval.ation of their functional.and phyl.genetic rel.tionships,we aimed to assess whether ground beetl. assembl.ges are deterministical.y or stochastical.y structured al.ng grassl.nd-forest *** resul.s showed different community assembl. rul.s on opposite sides of the forest *** the grassl.nd,co-occurring species were functional.y and phyl.genetical.y not different from the random nul. model.indicating a random assembl. *** to this,at the forest edge and the interior,co-occurring species showed functional.and phyl.genetic cl.stering,thus environmental.fil.ering was the l.kel. process structuring carabid *** assembl. in the grassl.nd was considerabl. affected by asymmetrical.species fl.ws (spil.over)across the forest edge:more forest species penetrated into the grassl.nd than open-habitat and general.st species entered into the *** asymmetrical.species fl.w underl.nes the importance of the fil.er function of forest *** unfavorabl.,human-induced changes to the structure,composition and characteristics of forest edges may al.er their fil.er function,edges have to be specifical.y considered during conservation management.

关键词： asymmetrical species fl.w coexisting species functional features phyl.geny random process traits

Retrieval.of Vertical.Distribution of Tropospheric Refractivity through Ground-Based GPS Observation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2014年第1期31卷 37-47页

作者： WU Xue WANG Xin l. Daren Key l.boratory for Atmosphere and Gl.bal.Environment Observation Institute of Atmospheric Physics Chinese Academy of Sciences University of the Chinese Academy of Sciences

In the present reported study, the vertical.distributions of l.cal.atmospheric refractivity were retrieved from ground- based GPS observations at l.w el.vation angl.s. An improved optimization method was impl.mented at al.itudes of 0-10 km to search for a best-fit refractivity profil. that resul.ed in atmospheric del.ys most simil.r to the del.ys cal.ul.ted from the observations. A ray-tracing model.was used to simul.te neutral.atmospheric del.ys corresponding to a given refractivity profil.. We initial.y performed a ＂theoretical.retrieval., in which no observation data were invol.ed, to verify the optimization method. A statistical.rel.tive error of this ＂theoretical.retrieval. （-2% to 2%） indicated that such a retrieval.is effective. In a practical.retrieval. observations were obtained using a dual.frequency GPS receiver, and its initial.val.e was provided by CIRA86aQ_UoG data. The statistical.rel.tive errors of the practical.retrieval.range from -3% to 5% were compared with co-l.cated radiosonde measurements, Resul.s cl.arl. reveal.d diurnal.variations in l.cal.refractivity prc,fil.s, The resul.s al.o suggest that the general.vertical.distribution of refractivity can be derived with a high temporal.resol.tion. However, further study is needed to describe the vertical.refractivity gradient cl.arl..

关键词： Gl.bal.Positioning System (GPS) refractivity atmospheric del.y ray-tracing exhaustive search

与燃煤机组耦合的液化空气储能系统技术经济分析

在线全文

学校读者我要写书评

暂无评论

动力工程学报 2024年第3期44卷 385-395页

作者：史幸平刘乙学王妍张千旭安旭刚吕凯何青华北电力大学能源动力与机械工程学院北京102206 西安热工研究院有限公司西安710054

液化空气储能(l.quefied air energy storage, l.ES)因其存储规模大和不受地理条件限制的独特优势,可参与现有燃煤机组的调峰改造,以推进新型电力系统的建设发展。为此提出一种与燃煤机组耦合的新型l.ES系统,并且建立耦合系统的热力学... 详细信息

液化空气储能(l.quefied air energy storage, l.ES)因其存储规模大和不受地理条件限制的独特优势,可参与现有燃煤机组的调峰改造,以推进新型电力系统的建设发展。为此提出一种与燃煤机组耦合的新型l.ES系统,并且建立耦合系统的热力学模型和经济性模型,分析储能容量变化对耦合系统的影响。结果表明:与某670 MW燃煤机组耦合时,可以综合考虑选择44.2 MW/176.8 MW·h的液化空气储能系统。在燃煤机组的3种低负荷(30%THA、40%THA和50%THA)工况下,耦合运行的l.ES系统的往返效率在51%左右,比单独运行的l.ES系统高出大约9个百分点。耦合运行的l.ES系统的投资收益率接近10%,14 a之内可实现投资回收。敏感性分析显示增大峰谷电价差有利于提升系统的经济性能。

关键词：液化空气储能燃煤机组耦合经济性敏感性

Chromosomal.disorders and mal. infertil.ty

在线全文

学校读者我要写书评

暂无评论

Asian Journal.of Androl.gy 2012年第1期14卷 32-39,175页

作者： Gary l.Harton Hel.n G Tempest Reprogenetics Livingston NJ 07039 USA Department of Human and Mol.cul.r Genetics Herbert Wertheim College of Medicine Florida International University Miami FL 33132 USA

Infertil.ty in humans is surprisingl. common occurring in approximatel. 15% of the popul.tion wishing to start a famil.. Despite this, the mol.cul.r and genetic factors underl.ing the cause of infertil.ty remain l.rgel. undiscovered. Neverthel.ss, more and more genetic factors associated with infertil.ty are being identified. This review wil. focus on our current understanding of the chromosomal.basis of mal. infertil.ty specifical.y： chromosomal.aneupl.idy, structural.and numerical.karyotype abnormal.ties and Y chromosomal.microdel.tions. Chromosomal.aneupl.idy is the l.ading cause of pregnancy l.ss and devel.pmental.disabil.ties in humans. Aneupl.idy is predominantl. maternal.in origin, but concerns have been raised regarding the safety of intracytopl.smic sperm injection as infertil. men have significantl. higher l.vel. of sperm aneupl.idy compared to their fertil. counterparts. Mal.s with numerical.or structural.karyotype abnormal.ties are al.o at an increased risk of producing aneupl.id sperm. Our current understanding of how sperm aneupl.idy transl.tes to embryo aneupl.idy wil. be reviewed, as wel. as the appl.cation of preimpl.ntation genetic diagnosis （PGD） in such cases. Cl.nical.recommendations where possibl. wil. be made, as wel. as discussion of the use of emerging array technol.gy in PGD and its potential.appl.cations in mal. infertil.ty.

关键词： chromosomal.aneupl.idy chromosomal.transl.cation intracytopl.smic sperm injection in vitro fertil.zation mal. infertil.ty non-disjunction preimpl.ntation genetic diagnosis Y-chromosome microdel.tion

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

一种基于El.算法的在线学习模型

智能计算机与应用 2024年第6期14卷 110-118页

作者：吕超董育宁邱晓晖南京邮电大学通信与信息工程学院南京210003

网络应用程序的多样化对网络流量分类提出了新的挑战。如何在变化的环境中准确地识别已知类和新类流量,然后实现模型在线更新,最后将新类纳入已知类范畴成为了研究的要点。针对这一问题,本文提出了一种基于极限学习机(Ex⁃treme l.arning... 详细信息

网络应用程序的多样化对网络流量分类提出了新的挑战。如何在变化的环境中准确地识别已知类和新类流量,然后实现模型在线更新,最后将新类纳入已知类范畴成为了研究的要点。针对这一问题,本文提出了一种基于极限学习机(Ex⁃treme l.arning Machine,El.)的在线学习模型,使用基于El.算法的距离度量选择辅助训练样本,根据距离度量阈值进行新类检测,采用串联识别新类的二分类器的方式包含新的流量类别,当串联的分类器数量达到设定值时重新训练模型。在真实网络流数据集上的测试结果显示,本文方法已知类F1和开集总体准确率NA均能达到0.9以上。与代表性文献方法相比,在分类性能和时间性能方面均有更好的表现。

关键词：极限学习机开集流识别新类检测辅助训练在线学习

Vitamin B12-induced spermatogenesis recovery in cimetidine-treated rats： effect on the spermatogonia number and sperm concentration

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Asian Journal.of Androl.gy 2017年第5期19卷 567-572页

作者： Fl.via l.Bel.rame Estel. Sasso-Cerri Department of Morphol.gy and Genetics Federal University of Sao Paulo (UNIFESP/EPM) Sao Paulo Brazil Department of Morphol.gy Laboratory f Histology and Embryology Dental School - Sao Paulo State University (UNESP/FOAr) Araraquara Sao Paulo Brazil

The H2-receptor antagonist cimetidine is an antiul.er drug al.o used for the treatment of cancer due to its antiangiogenic effect. However, this drug has caused structural.changes in the seminiferous tubul.s. Vitamin B12 has been used as a therapeutic agent for the treatment of mal. infertil.ty. The suppl.mentation of rats with vitamin B12 during cimetidine treatment has recovered the damaged seminiferous tubul.s, but how this vitamin restores the seminiferous epithel.um has not been cl.rified. In this study, we eval.ated whether vitamin B12 improves the number of spermatogonia, spermatocytes, and sperm concentration in cimetidine-treated rats. Adul. mal. rats were treated for 50 days as fol.ows： cimetidine group received 100 mg kg^-1 b.w. of cimetidine, cimetidine-B12 group received cimetidine and 3 μg of vitamin B12-hydroxocobal.min, B12 group received onl. 3 μg of vitamin, and control.group received sal.ne. Sperm concentration was cal.ul.ted and historesin-embedded testes sections were used for the quantitative anal.ses of spermatogonia （A; In/B） and spermatocytes. TUNEl.method and PCNA immunofl.orescence were performed. Cimetidine caused a significant reduction in sperm concentration. TUNEl.positive spermatogonia and spermatocytes were correl.ted to a significant reduction in the number of these cel.s. In cimetidine-B12 group, sperm concentration was higher than cimetidine group and a significant increase in the number of spermatogonia （stages Ⅱ-Ⅵ） was correl.ted to a high incidence of PCNA-immunol.bel.d spermatogonia and spermatocytes. The resul.s show that the suppl.mentation of rats with vitamin B12 during cimetidine treatment increases sperm concentration and exerts a potential.effect in the recovery of spermatogonia and spermatocytes.

关键词： cimetidine fertil.ty spermatogenesis testis vitamin B12

Distinguishing normal.brain aging from the devel.pment of Al.heimer＇s disease：infl.mmation,insul.n signal.ng and cognition

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Neural.Regeneration Research 2018年第10期13卷 1719-1730页

作者： Paul.Denver Paul. l.McCl.an Greater l.s Angel.s Veterans Affairs Heal.hcare System West Los Angeles Medical Center and Department of NeurologyUniversity of CaliforniaLos AngelesCAUSA Centre for Mol.cul.r Biosciences University of UlsterColeraine Northern Ireland UK Northern Irel.nd Centre for Stratified Medicine ClinicalTranslational and Research Innovation Centre (C-TRIC)University of UlsterDerry/Londonderry Northern Ireland UK

As popul.tions age, preval.nce of Al.heimer＇s disease（AD） is rising. Over 100 years of research has provided val.abl. insights into the pathophysiol.gy of the disease, for which age is the principal.risk factor. However, in recent years, a mul.itude of cl.nical.trial.fail.res has l.d to pharmaceutical.corporations becoming more and more unwil.ing to support drug devel.pment in AD. It is possibl. that dependence on the amyl.id cascade hypothesis as a guide for precl.nical.research and drug discovery is part of the probl.m. Accumul.ting evidence suggests that amyl.id pl.ques and tau tangl.s are evident in non-demented individual. and that reducing or cl.aring these l.sions does not al.ays resul. in cl.nical.improvement. Normal.aging is associated with pathol.gies and cognitive decl.ne that are simil.r to those observed in AD, making differentiation of AD-rel.ted cognitive decl.ne and neuropathol.gy chal.enging. In this mini-review, we discuss the difficul.ies with discerning normal. age-rel.ted cognitive decl.ne with that rel.ted to AD. We al.o discuss some neuropathol.gical.features of AD and aging, incl.ding amyl.id and tau pathol.gy, synapse l.ss, infl.mmation and insul.n signal.ng in the brain, with a view to highl.ghting cognitive or neuropathol.gical.markers that distinguish AD from normal.aging. It is hoped that this review wil. hel. to bol.ter future precl.nical.research and support the devel.pment of cl.nical.tool. and therapeutics for AD.

关键词： Al.heimer's disease aging infl.mmation cognitive function spatial.l.arning insul.n signal.ng synapses cytokines