检索结果-南通市图书馆

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

GRACE:轨道上的毫米和微米级测量

控制工程（北京） 2004年第3期 32-37页

作者： W.Betiger Y.bar-seber s.Desai

GRACE卫星已于2002年3月17发射入轨。CRACE任务的实验目的旨在改进地球重力场模型的精度。CRACE任务由两颗几乎完全一样的孪生卫星来执行,两颗GRACE卫星运行在约500km高度的同一个准极轨道平面内,相距约200km。每颗卫星携带四种仪器:一... 详细信息

GRACE卫星已于2002年3月17发射入轨。CRACE任务的实验目的旨在改进地球重力场模型的精度。CRACE任务由两颗几乎完全一样的孪生卫星来执行,两颗GRACE卫星运行在约500km高度的同一个准极轨道平面内,相距约200km。每颗卫星携带四种仪器:一台GPs接收机,一个K/Ka波段微波测距系统,一台星像机(这三种仪器均与一个公用处理器组装为一体),一个精密加速度计。GPs接收机能够跟踪最多14颗GPs卫星,可获得的双频数据精度与精密测地型地面接收机相当。K/Ka波段微波测距系统能实现μm级的测距精度(有一个常值偏差)。加速度计的测量精度高达1mm/s^2。而星跟踪器的姿态测量精度为10″。GPs数据经处理后可用于:(1)复原地球的长波引力场;(2)消除星上振荡器长期漂移引起的误差;(3)使2个GRACE卫星的K/Ka波段测量的定时精度校准到优于0.1ns。加速度计的标度因子和偏值参数是综合利用GPs数据和加速度计误差模型确定的。本文着重介绍利用GPs实现的这些定时和标定功能,而不讨论地球重力场的恢复问题。当然,GPs的定时功能与精确定轨(POD)密切相关。三轴的定轨精度均优于2cm。本文发表了GRACE的验证结果,包括GPs残差,轨道重叠,K/Ka波段测距以及卫星激光测距(sLR)的结果。为确定轨道参数和时钟参数,所有GPs数据的处理都是利用一个数据驱动的自动化系统完成的,该处理系统是专门为装备GPs接收机的卫星星座设计的。

关键词： GPs数据 GPs接收机地球重力场模型卫星激光测距 sLR GPs卫星轨道 Ka波段地面接收测距系统

维普期刊数据库

Hydrogen absorption properties of amorphous(Ni0.6Nb0.4-yTay)100-xZrx membranes

在线全文

学校读者我要写书评

暂无评论

Progress in Natural science:materials International 2017年第1期27卷 126-131页

作者： O.Palumbo F.Trequattrini N.Pal m.Hulyalkar s.sarker D.Chandra T.Flanagan m.Dolan A.Paolone CNR-IsC U.O.S. La Sapienza Department of Physics Sapienza University of Rome Department of Chemical and materials Engineering University of Nevada Department of Chemistry University of Vermont CsIRO QCAT Energy 1 Technology CourtPullenvale

Ni based amorphous materials have great potential as hydrogen purification membranes. In the present work the melt spun(Ni0.6Nb0.4-yTay)100-xZrxwith y=0, 0.1 and x=20, 30 was studied. The result of X-ray diffraction spectra of the ribbons showed an amorphous nature of the alloys. Heating these ribbons below T mosphere（1-10 bar）, the amorphous structure was retained. The crystallization process was characterized by differential thermal analysis and the activation energy of such process was obtained. The hydrogen absorption properties of the samples in their amorphous state were studied by the volumetric method,and the results showed that the addition of Ta did not significantly influence the absorption properties, a clear change of the hydrogen solubility was observed with the variation of the Zr content. The values of the hydrogenation enthalpy changed from37 k J/mol for x=30 to9k J/mol for x=20. The analysis of the volumetric data provides the indications about the hydrogen occupation sites during hydrogenation, suggesting that at the beginning of the absorption process the deepest energy levels are occupied, while only shallower energy levels are available at higher hydrogen content, with the available interstitial sites forming a continuum of energy levels.

关键词： Amorphous Ni based alloy ribbons High temperature X-ray diffraction DTA Activation energy Crystallization temperature Hydrogen solubility

Tailoring nanocomposite membranes of cellulose acetate/silica nanoparticles for desalination

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 materiomics 2022年第6期8卷 1122-1130页

作者： Amira s.mohammed Ali moataz m.soliman sherif H.Kandil shaker Ebrahim marwa Khalil materials science Department Institute of Graduate Studies and Research(IGSR)Alexandria University163 Horrya AvenueEl-ShatbyP.O.Box 83221526AlexandriaEgypt Nanotechnology and Composite materials Department Advanced Technology and New Materials Research InstituteCity of Scientific Research and Technological Applications(SRTA-City)P.O.Box 21934New Borg El Arab CityAlexandriaEgypt

Herein, the fabrication of cellulose acetate (CA) silica-based nanocomposite membranes via the dry-wetphase inversion procedure for water desalination was investigated. The modified and unmodified silicananoparticles (msNPs and sNPs) were prepared by the sol-gel technique. The effect of the sNPs andmsNPs was investigated on the CA membrane's properties and their performance for water *** CA nanocomposite membranes were characterized to study their structure, hydrophilicity, andmorphology. The fabricated nanocomposite membranes showed hydrophilic surface properties. Theperformance of reverse osmosis (RO) membranes was measured using a crossflow RO unit at 10 bar(1 bar = 0.1 mPa). The membrane with 10 mg of sNPs enhanced permeate water flux compared to thepristine CA membrane by 1.6 L/(m2·h). The effect of msNPs on the nanocomposites' performance waslower than their counterpart in the case of adding sNPs. The membrane with 30 mg of msNPs showedthe highest permeate water flux among other nanocomposite membranes with a value oAQsf 35.7 L/(m2·h)at 24 bar.

关键词： silica nanoparticles Amino-modified silica Cellulose acetate Nanocomposite membrane Water desalination Reverse osmosis

Role of nestin in glioma invasion

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Translational medicine 2015年第3期4卷 78-87页

作者： Alex Lin Luigi marchionni Jeffrey sosnowski David Berman Charles G Eberhart Eli E bar Department of Pathology Johns Hopkins University School of Medicine Department of Oncology Johns Hopkins University School of Medicine Department of Orthopedic surgery Johns Hopkins University School of Medicine Department of Ophthalmology Johns Hopkins University School of Medicine Department of Neurological surgery School of Medicine Case Western Reserve University Case Comprehensive Cancer Center Case Western Reserve University School of Medicine

AIm: To determine the role for the intermediate filament protein nestin in glioma invasion. mETHODs: We examined the expression and function of nestin in gliomas(Grades Ⅱ-Ⅳ as defined by the World Health Organization). We determined nestin expression using Immunohistochemical methods. To elucidate nestin's biological function(s), we reduced m RNA levels by 61% and 87% in two glioblastomaderived neurosphere lines using short hairpin RNAs and determined the effect of reduced nestin expression on glioma cell proliferation and invasion using mTs and matrigel migration assays, respectively. We also utilized quantitative real time polymerase chain reaction assaysto determine the effect of reduced nestin expression on the expression of other markers associated with glioma stem cells and their differentiated progenies. REsULTs: We found a significant correlation between nestin immunoreactivity and astrocytoma tumor grade, with 36% of grade Ⅱ, 75% of grade Ⅲ, and 100% of grade Ⅳtumors expressing significant levels of the protein when assessed using immunohistochemistry. Reduction in nestin expression had no effect on cell growth in culture, but did retard the capacity of one line to migrate in-vitro on matrigel. Interestingly, in the line whose migration was not affected, m RNA levels of a second intermediate filament, synemin(also knowns as desmuslin), were elevated following introduction of sh RNA targeting nestin. As synemin was not induced in the line which required nestin for migration, it is a possibility that synemin may compensate for the loss of nestin in this process. CONCLUsION: Nestin expression is prominent in high-grade astrocytomas. Nestin is not required for cell growth but it may, however, be required for cell motility.

关键词： Nestin stem cells migration Glioma Neurosphere

Hematotesticular barrier is altered from early stages of liver cirrhosis:Effect of insulin-like growth factor 1

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Gastroenterology 2004年第17期10卷 2529-2534页

作者： Inma Castilla-Cortázar Nieves Diez maría García-Fernández Juan Enrique Puche Fernando Diez-Caballero Jorge Quiroga matías Díaz-sánchez Alberto Castilla Amelia Díaz Casares Isabel Varela-Nieto Jesǘs Prieto salvador González-barón Department of Human Physiology University of NavarraPamplonaNavarraSpain Department of Human physiologySchool of MedicineUniversity of MlagaMalagaSpain Department of Human Physiology University of NavarraPamplonaNavarraSpain Department of Human Physiology School of MedicineUniversity of MálagaMalagaSpain Instituto de Investigaciones Biomédicas "Alberto sols" Consejo Superior de Investigaciones CientificasUniversidad Autónoma de Madrid (CSIC-UAM)MadridSpain Supported by the Spanish Program I+DSAF 99/0072 and SAF 2001/1672 Department of Internal medicine Hospital SierrallanaTollelavega and School of MedicineUniversity of the Basque Country-Vitoria-GasteizSpain Instituto de Investigaciones Biomedicas"Alberto sols"Consejo superior de Investigaciones Cientificas Universidad Autonoma de madrid(CsIC-UAm) MadridSpain Department of Internal medicine Liver Unit University of Navarra PamplonaNavarraSpain

AIm:The pathogenesis of hypogonadism in liver cirrhosis is not well *** results from our laboratory showed that IGF-1 deficiency might play a pathogenetic role in hypogonadism of *** administration of IGF-1 for a short period of time reverted the testicular atrophy associated with advanced experimental cirrhosis. The aim of this study was to establish the historical progression of the described alterations in the testes, explore testicular morphology,histopathology,cellular proliferation,integrity of testicular barrier and hypophyso- gonadal axis in rats with no ascitic cirrhosis. mETHODs:male Wistar rats with histologically-proven cirrhosis induced with carbon tetrachloride(CCI_4)for 11 wk, were allocated into two groups(n=12,each)to receive recombinant IGF-1(2 μg/100 gd,sc)for two weeks or *** rats receiving vehicle were used as control group(n=12). REsULTs:Compared to controls,rats with compensated cirrhosis showed a normal testicular size and weight and very few histopathological testicular abnormalities. However,these animals showed a significant diminution of cellular proliferation and a reduction of testicular transferrin *** addition,pituitary-gonadal axis was altered,with significant higher levels of FsH(Pscontrols)and increased levels of LH in untreated cirrhotic ***,IGF-1 treatment normalized testicular transferrin expression and cellular proliferation and reduced serum levels of LH(P=ns vs controls,and Ps untreated cirrhotic group). CONCLUsION:The testicular barrier is altered from an early stage of cirrhosis,shown by a reduction of transferrin expression in sertoli cells,a diminished cellular proliferation and an altered gonadal *** treatment with IGF-1 could be also useful in this initial stage of testicular disorder associated with compensated cirrhosis.

关键词： Animals Atrophy Carbon Tetrachloride Estrogens Follicle stimulating Hormone Hypogonadism Insulin-Like Growth Factor I Liver Cirrhosis Luteinizing Hormone male Pituitary Gland Rats Rats, Wistar Research support, Non-U.s. Gov't sertoli Cells Testis Testosterone Transferrin

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

顺序控制滑动凸轮转换气门升程

汽车与新动力 2020年第6期3卷 54-57页

作者： [德]H.NEUKIRCHNER [德]m.WEIDAUER [德]s.bar [德]J.sCHIRmER 范明强(译) 不详

滑动凸轮技术的特点在于其机械可靠性和循环实时工作原理,不过这种系统由于缺乏转换所必需的边界条件或由于成本原因而无法应用。蒂森克虏伯公司采用顺序滑动凸轮(PssC)系统成功解决了滑动凸轮技术与简单控制之间的目标冲突。

关键词：滑动凸轮技术顺序控制执行器计算优化

维普期刊数据库

Additive friction stir deposition of AZ31B magnesium alloy

在线全文

学校读者我要写书评

暂无评论

Journal of magnesium and Alloys 2022年第9期10卷 2404-2420页

作者： sameehan s.Joshi shreyash m.Patil sangram mazumder shashank sharma Daniel A.Riley shelden Dowden Rajarshi Banerjee Narendra B.Dahotre Department of materials science and Engineering University of North Texas3940 N Elm StDentonTX 76207USA Center for Agile and Adaptive Additive manufacturing University of North Texas3940 N Elm StDentonTX 76207USA

The current work explored additive friction stir deposition of AZ31B magnesium alloy with the aid of mELD?***31B magnesium bar stock was fed through a hollow friction stir tool rotating at constant velocity of 400 rpm and translating at linear velocity varied from 4.2 to 6.3 mm/s.A single wall consisting of five layers with each layer of 140×40×1 mm^(3)dimensions was deposited under each processing ***,phase,and crystallographic texture evolutions as a function of additive friction stir deposition parameters were studied with the aid of scanning electron microscopy including electron back scatter diffraction and X-ray *** feed material and additively produced samples consisted of theα-mg *** additively produced samples exhibited a refined grain structure compared to the feed *** feed material appeared to have a weak basal texture,while the additively produced samples experienced a strengthening of this basal *** additively produced samples showed a marginally higher hardness compared to the feed *** current work provided a pathway for solid state additive manufacturing of mg suitable for structural applications such as automotive components and consumable biomedical implants.

关键词： Additive friction stir deposition magnesium alloys Additive manufacturing Thermomechanical processing materials processing solid state additive manufacturing

维普期刊数据库

Breakup of the Neoarchean supercontinent Kenorland:Evidence from zircon and baddeleyite U-Pb ages of LIP-related mafic dykes in the Coorg Block,southern India

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2024年第4期15卷 97-114页

作者： Cheng-Xue Yang m.santosh Jarred Lloyd stijn Glorie Y.Anilkumar K.s.Anoop Pin Gao sung-Won Kim school of Earth sciences and Resources China University of Geosciences BeijingBeijing 100083PR China Institute of Earth sciences China University of Geosciences BeijingBeijing 100083PR China Department of Earth sciences University of AdelaideAdelaide SAAustralia Department of Geology University of KeralaKariavattomTrivandrumIndia Geology Division Korea Institute of Geoscience and Mineral ResourcesDaejeon 34132Republic of Korea

The Coorg Block in southern Peninsular India is one of the oldest crustal blocks on Earth that preserves the evidence for continental crust formation during the Paleo-mesoarchean through subductionrelated arc magmatism,followed by granulite facies metamorphism in the *** this study,we report for the first time,the'bar codes'of a major Paleoproterozoic Large Igneous Province in the Coorg Block through the finding of mafic dyke *** gabbroic dykes from the Coorg Block,dom-inantly composed of plagioclase-pyroxene assemblage,show a restricted range in siO_(2)values of 50.04-51.27 wt.%,and exhibit a sub-alkaline tholeiitic *** rocks show relatively flat LREE and constant HREE patterns and lack obvious Eu *** element modeling suggests that the dyke swarm was fed from a melt that originated at a shallow mantle level in the spinel stability *** grains are rare in the gabbro samples and those separated from two samples yielded 207Pb/206Pb weighted mean dates of 2214±12 ma and 2221±7 *** grains show magmatic features with depleted LREE and enriched HREE and positive Ce and negative Eu *** grains were dated from five gabbro samples which yielded 207Pb/206Pb weighted mean ages ranging between 2217±7 ma and 2228±10 *** combined data show a clear age peak at ca.2.2 *** mafic dykes in the Coorg Block show geochemical similarities with ca.2.2 Ga mafic dyke swarms in different regions of the Dharwar and other cratons in Peninsular India and elsewhere on the *** data also support the inference that the global mafic magmatism at ca.2.2 Ga was linked with intracontinental rifting of the Archean cratons through mantle upwelling or plume *** correlate the mafic dyke swarms in the Coorg Block with attempted rifting of the Neoarchean supercontinent Kenorland.

关键词： mafic dyke swarm Paleoproterozoic Large Igneous Province Geochronology Continental rifting Neoarchean supercontinent

mICROENDOsCOPIC sPECTRAL ImAGING As A TOOL FOR smALL DUCTUAL DIAGNOsTICs:PRELImINARY EXPERIENCE

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Innovative Optical Health sciences 2012年第3期5卷 64-70页

作者： A.DOUPLIK W.L.LEONG A.m.EAssON s.DONE B.C.WILsON A.sHAHmOON Z.ZALEVsKY Department of Physics Ryerson University 350 Victoria StreetToronto M5B 2K3Canada school of Advanced Optical Technologies(sAOT)Friedrich-Alexander Erlangen-Nuremberg University ErlangenGermany Ontario Cancer Institute University Health Network TorontoCanada Xillix Ltd TorontoCanada medical Photonics Engineering Group(mPEG)Chair of Photonics Technologies Friedrich-Alexander Erlangen-Nuremberg University ErlangenGermany Department of surgical Oncology Princess margaret Hospital University Health Network TorontoCanada Department of medical Biophysics University of Toronto TorontoCanada Faculty of Engineering bar-Ilan University Ramat GanIsrael

A technical feasibility of autofluorescence ductoscopy in breast milk ducts as blood vessels phantoms has been assessed as *** tumor can be clearly identified through the milk *** also present the operation principle as well as the preliminary experimental results of a new type of microsize multicorefiber that enables imaging through blood vessel *** of a manipulated microwire through a drilled phantom is presented.

关键词： Cancer margin delineation endoscopy microendoscopy autofluorescence imaging surgical guidance multicorefibers