检索结果-南通市图书馆

A planet in transition:The onset of plate tectonics on Earth between 3 and 2 Ga?

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2018年第1期9卷 51-60页

作者： kent C.Condie Department of Earth and Environmental science New Mexico Tech

Many geological and geochemical changes are recorded on Earth between 3 and 2 *** the more important of these are the following:(1)increasing proportion of basalts with"arc-like"mantle sources;(2)an increasing abundance of basalts derived from enriched(EM)and depleted(DM)mantle sources;(3)onset of a Great Thermal Divergence in the mantle;(4)a decrease in degree of melting of the mantle;(5)beginning of large lateral plate motions;(6)appearance of eclogite inclusions in diamonds;(7)appearance and rapid increase in frequency of collisional orogens;(8)rapid increase in the production rate of continental crust as recorded by zircon age peaks;(9)appearance of ophiolites in the geologic record,and(10)appearance of global LIP(large igneous province)events some of which correlate with global zircon age *** of these changes may be tied directly or indirectly to cooling of Earth's mantle and corresponding changes in convective style and the strength of the lithosphere,and they may record the gradual onset and propagation of plate tectonics around the *** further understand the changes that occurred between 3 and 2 Ga,it is necessary to compare rocks,rock associations,tectonics and geochemistry during and between zircon age *** of peak and inter-peak basalts and TTGs needs to be evaluated in terms of geodynamic models that predict the existence of an episodic thermal regime between stagnant-lid and plate tectonic regimes in early planetary evolution.

关键词： Plate tectonics Zircon age peaks Mantle evolution stagnant lid Continental crust LIP events

An assessment of coal pillar system stability criteria based on a mechanistic evaluation of the interaction between coal pillars and the overburden

在线全文

学校读者我要写书评

暂无评论

International Journal of Mining science and Technology 2017年第1期27卷 9-15页

作者： Reed Guy Mctyer kent Frith Russell Mine Advice Pry Ltd NewcastleNSW 2322Australia

Coal pillar design has historically assigned a factor of safety(Fo s) or stability factor(sF) according to their estimated strength and the assumed overburden load acting on them. Acceptable Fo s values have been assigned based on past mining experience or a statistical link between Fo s and probability of failure(Po F). Pillar width-to-height(w/h) ratio has long been established as having a material influence on both pillar strength and its potential failure mode. However, there has been significant disagreement on using both factor of safety(Fo s) and w/h as part of pillar system stability criterion, as compared to using Fo s in isolation. This paper will argue that there are valid technical reasons to bring w/h ratio into system stability criteria(other than its influence on pillar strength), as it is related to the post-failure stiffness of the pillar, as measured in situ, and its interaction with overburden stiffness. When overburden stiffness is also brought into pillar system stability considerations, two issues emerge. The first is the width-todepth(W/D) ratio of the panel and whether it is sub-critical or super-critical from a surface subsidence perspective. The second relates to a re-evaluation of pillar Fo s based on whether the pillar is in an elastic or non-elastic(i.e., post-yield) state in its as-designed condition, as this is relevant to maintaining overburden stiffness at the highest possible level. The significance of the model is the potential to maximise both reserve recovery and mining efficiencies without any discernible increase in geotechnical risk, particularly in thick seams and higher depth of cover mining situations. At a time when mining economics are, at best, marginal, removing potentially unnecessary design conservatism is of interest to all mine operators and is an important topic for discussion amongst the geotechnical community.

关键词： Coa] pillars stability Overburden Post-failure behaviour stability criteria

RHEOLOGICAL CHARACTERIsTICs,POWER CONsUMPTION,MAss AND HEAT,TRANsFER DURING XANTHAN GUM FERMENTATION

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 1994年第4期2卷 15-27页

作者：赵学明胡宗定 A.W.Nienow C.A.kent s.Chatwin Centre for Biochemical Engineering The University of BirminghamB15 2TTUK

Xanthan gum fermentation is probably the most complex fermentation process in terms ofrheological property variations and associated mixing,power consumption,mass and heat *** order to obtain these data,fermentations of Xanthomonas campestris were carried outon pilot scale bioreactor with different D/T ratios and different feeding strategies(batch andfed-batch).It was discovered that the rheology of xanthan fermentation broth is of paramountimportance to the above *** aerated power consumption and power number are both afunction of aeration rate during the initial stage of the fermentation when the viscosity is low andthe Reynolds number *** when the becames viscous and Reynolds unmber≤10~3,thegas velocity does not show any effect on the power *** oxygen mass transfer coefficientsand the overall heat transfer coefficients are both dependent on the impeller speed,the apparentviscosity of the broth and the D/T *** data taken from practical

关键词： xanthan fermentation rheology power consumption mass transfer heat transfer

On the Bifurcations and Multiple Endemic states of a single strain HIV Model Dedicated to Professor Toshikazu sunada on the Occasion of his 60th Birthday

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae sinica 2014年第4期30卷 913-930页

作者： Lindley kent M.FAINA Lorna s.ALMOCERA Polly W.sY College of Arts and sciences University of the Philippines Visayas Natural sciences and Mathematics Division University of the Philippines VisayasCebu College Institute of Mathematics University of the Philippines

The dynamics of a single strain HIV model is studied. The basic reproduction number R0 used as a bifurcation parameter shows that the system undergoes transcritical and saddle-node bifurcations. The usual threshold unit value of R0 does not completely determine the eradication of the disease in an HIV infected person. In particular, a sub-threshold value Rc is established which determines the system＇s number of endemic states： multiple if Rc 〈 Ro 〈 1, only one if Rc=Ro = 1, and none if R0 〈 Rc 〈 1.

关键词： single strain HIV model multiple endemic states transcritical bifurcation s^idle-node bifurcation hysteresis

Artificial-intelligence-assisted mass fabrication of nanocantilevers from randomly positioned single carbon nanotubes

在线全文

学校读者我要写书评

暂无评论

Microsystems & Nanoengineering 2023年第2期9卷 333-343页

作者： Yukihiro tadokoro Keita Funayama Keisuke Kawano Atsushi Mura Jun Hrotani Yutaka Ohno Hiroya Tanaka Toyota Central R&D Labs. Inc.NagakuteAichiJapan Toyota Research Institute of North America Ann ArborMIUSA Nagoya University NagoyaAichiJapan

Nanoscale cantilevers(nanocantilevers)made from carbon nanotubes(CNTs)provide tremendous benefits in sensing and electromagnetic *** nanoscale structure is generally fabricated using chemical vapor deposition and/or dielectrophoresis,which contain manual,time-consuming processes such as the placing of additional electrodes and careful observation of single-grown ***,we demonstrate a simple and Artificial Intelligence(Al)-assisted method for the effcient fabrication of a massive CNT-based *** used randomly positioned single CNTs on the *** trained deep neural network recognizes the CNTs,measures their positions,and determines the edge of the CNT on which an electrode should be clamped to form a *** experiments demonstrate that the recognition and measurement processes are automatically completed in 2 s,whereas comparable manual processing requires 12 *** the small measurement error by the trained network(within 200 nm for 90%of the recognized CNTs),more than 34 nanocantilevers were successfully fabricated in one *** high accuracy contributes to the development of a massive field emitter using the CNT-based nanocantilever,in which the output current is obtained with a low applied *** further showed the benefit of fabricating massive CNT-nanocantilever-based field emitters for neuromorphic *** activation function,which is a key function in a neural network,was physically realized using an individual CNT-based field *** introduced neural network with the CNT-based field emitters recognized handwritten images *** believe that our method can accelerate the research and development of CNT-based nanocantilevers for realizing promising future applications.

关键词： cantilever carbon network

Growth factor delivery using extracellular matrix-mimicking substrates for musculoskeletal tissue engineering and repair

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

Bioactive Materials 2021年第7期6卷 1945-1956页

作者： Robert C.H.Gresham Chelsea s.Bahney J.kent Leach UC Davis Department of Biomedical EngineeringDavisCAUSA steadman Phillippon Research Institute VailCOUSA UCsF Orthopaedic Trauma Institute San FranciscoCAUSA UC Davis Health Department of Orthopaedic SurgeryDavisCAUSA

Therapeutic approaches for musculoskeletal tissue regeneration commonly employ growth factors(GFs)to influence neighboring cells and promote migration,proliferation,or *** promising results in preclinical models,the use of inductive biomacromolecules has achieved limited success in translation to the *** field has yet to sufficiently overcome substantial hurdles such as poor spatiotemporal control and supraphysiological dosages,which commonly result in detrimental side *** presentation and retention of biomacromolecules is regulated by the extracellular matrix(ECM),which acts as a reservoir for GFs via electrostatic *** in the manipulation of extracellular proteins,decellularized tissues,and synthetic ECM-mimetic applications across a range of biomaterials have increased the ability to direct the presentation of *** application of biomaterial technologies utilizing ECM mimetics increases tissue regeneration without the reliance on supraphysiological doses of inductive *** review describes recent strategies to manage GF presentation using ECM-mimetic substrates for the regeneration of bone,cartilage,and muscle.

关键词： Growth factor Extracellular matrix spatiotemporal control Tissue engineering Affinity

Greenhouse gases fluxes and soil thermal properties in a pasture in central Missouri

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

Journal of Environmental sciences 2010年第7期22卷 1029-1039页

作者： Nsalambi Vakanda Nkongolo shane Johnson kent schmidt Frieda Eivazi Department of Agriculture and Environmental sciences College of Agriculture and Natural Science Lincoln University Harvard Forest Faculty of Arts and Sciences Harvard University

Fluctuations of greenhouse gases emissions and soil properties occur at short spatial and temporal scales, however, results are often reported for larger scales studies. We monitored CO2, CH4, and N2O fluxes and soil temperature （T）, thermal conductivity （K）, resistivity （R） and thermal diffusivity （D） from 2004 to 2006 in a pasture. soil air samples for determination of CO2, CH4 and N2O concentrations were collected from static and vented chambers and analyzed within two hours of collection with a gas chromatograph. T, K, R and D were measured in-situ using a KD2 probe. soil samples were also taken for measurements of soil chemical and physical properties. The pasture acted as a sink in 2004, a source in 2005 and again a sink of CH4 in 2006. CO2 and CH4 were highest, but N2O as well as T, K and D were lowest in 2004. Only K was correlated with C02 in 2004 while T correlated with both N2O （r = 0.76, p = 0.0001） and CO2 （r = 0.88, p = 0.0001） in 2005. In 2006, all gases fluxes were significantly correlated with T, K and R when the data for the entire year were considered. However, an in-depth examination of the data revealed the existence of month-to-month shifts, lack of correlation and differing spatial structures. These results stress the need for further studies on the relationship between soil properties and gases fluxes. K and R offer a promise as potential controlling factors for greenhouse gases fluxes in this pasture.

关键词： greenhouse gases soil thermal properties fluxes

Inhibition of GABAA-ρreceptors induces retina regeneration in zebrafish

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2021年第2期16卷 367-374页

作者： Matthew R.kent Nergis Kara James G.Patton Department of Biological sciences Vanderbilt UniversityNashvilleTNUSA

A potential treatment for retinal diseases is to induce an endogenous Müller glia(MG)-derived regenerative response to replace damaged *** contrast to mammalian MG,zebrafish MG are capable of mediating spontaneous *** seek to define the mechanisms that enable retina regeneration in zebrafish in order to identify therapeutic targets to induce mammalian retina *** previously used pharmacological and genetic methods to inhibit gamma aminobutyric acid A(GABAA)receptors in undamaged zebrafish retinas and showed that such inhibition could induce initiation of retina regeneration,as measured by the dedifferentiation of MG and the appearance of MG-derived proliferating progenitor ***,we show that inhibition of a pharmacologically distinct subset of GABAA receptors(GABAA-ρ)can also induce retina *** inhibition of both GABA receptor subtypes led to enhanced retina *** expression analyses indicate that inhibition of GABAA-ρreceptors induces a canonical retinal regenerative *** results support a model in which decreased levels of GABA,such as would occur after retinal cell death or damage,induce dedifferentiation of MG and the generation of proliferating progenitor cells during zebrafish retina *** experiments were approved by the Vanderbilt's Institutional Animal Care and Use Committee(Protocol M1800200)on January 29,2019.

关键词： gamma aminobutyric acid morpholino Müller glia neurotransmitter regeneration retina stem cells zebrafish

Dilution sampling and analysis of particulate matter in biomass-derived syngas

在线全文

学校读者我要写书评

暂无评论

Frontiers of Environmental science & Engineering 2011年第3期5卷 320-330页

作者： Xiaoliang WANG Curtis ROBBINs s.kent HOEKMAN Judith C.CHOW John G.WATsON Dennis sCHUETZLE Division of Atmospheric sciences Desert Research Institute(DRI)RenoNV 89512USA Renewable Energy Institute International(REII)McClellanCA 95652USA

Thermochemical biomass gasification,followedby conversion of the produced syngas to fuels andelectrical power,is a promising energy *** of particulate matter(PM)and othercontaminants in the syngas is important to minimizedamage and ensure efficient operation of the engines itpowers and the fuels created from it.A dilution samplingsystem is demonstrated to quantify PM in syngas generatedfrom two gasification plants utilizing different biomassfeedstocks:a BioMax®15 Biopower system that uses rawand torrefied woodchips as feedstocks,and an integratedbiorefinery(IBR)that uses rice hulls and woodchips ***_(2.5)mass concentrations in syngas from theIBR downstream of the purification system were 12.8-13.7μg·m^(-3),which were significantly lower than themaximum level for catalyst protection(500μg·m^(-3))andwere 2-3 orders of magnitude lower than those inBioMax®15 syngas(2247-4835μg·m^(-3)).Ultrafine particlenumber concentration and PM_(2.5)chemical constituentswere also much lower in the IBR syngas than in theBioMax®*** dilution sampling system enabledreliable measurements over a wide range of concentrations:the use of high sensitivity instruments allowed measurementat very low concentrations(~1μg·m^(-3)),while theflexibility of dilution minimized sampling problems thatare commonly encountered due to high levels of tars in rawsyngas(~1 g·m^(-3)).

关键词： dilution source sampling syngas characterization biomass gasification ultrafine particles