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Double Fertilization in Arabidopsis thaliana Involves a Polyspermy Block on the Egg but Not the Central Cell

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Molecular Plant 2008年第4期1卷 611-619页

作者： Rod j. Scott Susan j. Armstrong james Doughty Melissa Spielman Department of Biology and Biochemistry University of Bath Claverton Down Bath BA2 7AY United Kingdom School of Biosciences The University of Birmingham Edgbaston Birmingham B15 2TT United Kingdom

In animal reproduction, thousands of sperm may compete to fertilize a single egg, but polyspermy blocks prevent multiple fertilization that would otherwise lead to death of the embryo. In flowering plants, successful seed development requires that only two sperm are delivered to the embryo sac, where each must fertilize a female gamete （egg or central cell） to produce the embryo and endosperm. Therefore, polyspermy must be avoided, not only to prevent abnormalities in offspring, but to ensure double fertilization. It is not understood how each sperm fertilizes only one female gamete, nor has the existence of polyspermy barriers been directly tested in vivo. Here, we sought evidence for poly- spermy blocks in angiosperms using the polyspermic tetraspore （tes） mutant of Arabidopsis, which allows in-vivo challenge of egg and central cell with multiple male gametes. We show that tes mutant pollen tubes can transmit more than one sperm pair to an embryo sac, and that sperm from more than one pair can participate in fertilization. We detected endosperms but not embryos with ploidies that could only result from multiple fertilization. Our results therefore demonstrate an in-vivo polyspermy block on the egg, but not the central cell of a flowering plant.

关键词： Double Fertilization Arabidopsis thaliana Involves Polyspermy Block Central Cell

HEALTHCARE: A COMPLEX SERVICE SYSTEM

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journal of Systems Science and Systems Engineering 2009年第3期18卷 257-282页

作者： james M. TIEN Pascal j. GOLDSCHMIDT-CLERMONT Dean College of Engineering University of Miami Coral GablesFlorida USA Dean Miller School of Medicine University of Miami Coral GablesFlorida USA

Healthcare is indeed a complex service system, one requiring the technobiology approach of systems engineering to underpin its development as an integrated and adaptive system. In general, healthcare services are carried out with knowledge-intensive agents or components which work together as providers and consumers to create or co-produce value. Indeed, the engineering design of a healthcare system must recognize the fact that it is actually a complex integration of human-centered activities that is increasingly dependent on information technology and knowledge. Like any service system, healthcare can be considered to be a combination or recombination of three essential components - people （characterized by behaviors, values, knowledge, etc.）, processes （characterized by collaboration, customization, etc.） and products （characterized by software, hardware, infrastructures, etc.）. Thus, a healthcare system is an integrated and adaptive set of people, processes and products. It is, in essence, a system of systems which objectives are to enhance its efficiency （leading to greater interdependency） and effectiveness （leading to improved health）. Integration occurs over the physical, temporal, organizational and functional dimensions, while adaptation occurs over the monitoring, feedback, cybernetic and learning dimensions. In sum, such service systems as healthcare are indeed complex, especially due to the uncertainties associated with the human-centered aspects of these systems. Moreover, the system complexities can only be dealt with methods that enhance system integration and adaptation.

关键词： Services healthcare system integration system adaptation system complexity system of systems customization co-production decision informatics real-time decision making

Comparative study of well soaking timing(pre *** flowback)for water blockage removal from matrix-fracture interface

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Petroleum 2020年第3期6卷 286-292页

作者： Nur Wijaya james j.Sheng Bob L.Herd Department of Petroleum Engineering Texas Tech UniversityTexasUSA

Water blockage after hydraulic fracturing is one of the major challenges in shale oil recovery which affects the optimal production from the *** water blockage represents a higher water saturation near the matrixfracture interface,which decreases the hydrocarbon relative *** removal of water blockage in the field is typically carried out by soaking the well(i.e.,shut-in)after hydraulic fracturing operation is *** soaking period allows water redistribution,which decreases the water saturation near the matrix-fracture ***,previous field reports show that there is not a strong consensus on whether shut-in is beneficial in terms of production rate or ultimate oil *** to the large number of parameters involved in hydraulic fracturing and tight formations,it is challenging to select which parameter plays the dominant role in determining the shut-in ***,literature on field case studies does not frequently report the parameters which are of researchers’*** other words,the challenge of evaluating shut-in performance not only lies on the complexity of parameters and effects involved within the reservoir,but also the limited number of field case studies which report a comprehensive list of fracturing and reservoir *** paper aims to investigate the effect of well soaking timing on shut-in *** idea to investigate the shut-in timing effect is motivated by the fact that in the field,shut-in can take place either immediately after hydraulic fracturing but before the first flowback(i.e.,pre-flowback)or sometime after the first flowback(i.e.,post-flowback).The timing of shut-in is believed to influence the production performance,because it dictates how much water is allowed to imbibe from the fractures to the matrix before the extended production.A numerical model is built and validated by a successful history match with numerous data from core-flood *** previous s

关键词： Water blockage Formation damage Flowback Shut-in Desiccation

Flu channel drug resistance:a tale of two sites

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Protein & Cell 2010年第3期1卷 246-258页

作者： Rafal M.Pielak james j.Chou Department of Biological Chemistry and Molecular Pharmacology Harvard Medical SchoolBostonMA 02115USA Program in Biological and Biomedical Sciences Harvard Medical SchoolBostonMA 02115USA

The M2 proteins of influenza A and B virus,AM2 and BM2,respectively,are transmembrane proteins that oligomerize in the viral membrane to form proton-selective *** conductance of the M2 proteins is required for viral replication;it is believed to equilibrate pH across the viral membrane during cell entry and across the trans-Golgi membrane of infected cells during viral *** addition to the role of M2 in proton conductance,recent mutagenesis and structural studies suggest that the cytoplasmic domains of the M2 proteins also play a role in recruiting the matrix proteins to the cell surface during virus *** viral ion channels of minimalist architecture,the membrane-embedded channel domain of M2 has been a model system for investigating the mechanism of proton ***,as a proven drug target for the treatment of influenza A infection,M2 has been the subject of intense research for developing new anti-flu ***2 is the target of two anti-influenza A drugs,amantadine and rimantadine,both belonging to the adamantane class of ***,resistance of influenza A to adamantane is now widespread due to mutations in the channel domain of *** review summarizes the structure and function of both AM2 and BM2 channels,the mechanism of drug inhibition and drug resistance of AM2,as well as the development of new M2 inhibitors as potential anti-flu drugs.

关键词： M2 BM2 influenza proton channel amantadine rimantadine

Heme oxygenase system in hepatic ischemia-reperfusion injury

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World journal of Gastroenterology 2010年第48期16卷 6068-6078页

作者： james A Richards Stephen j Wigmore Luke R Devey Centre for Inflammation Research The University of EdinburghThe Queen's Medical Research Institute

Hepatic ischemia-reperfusion injury (IRI) limits access to transplantation. Heme oxygenase-1 (HO-1) is a powerful antioxidant enzyme which degrades free heme into biliverdin,free iron and carbon monoxide. HO-1 and its metabolites have the ability to modulate a wide variety of inflammatory disorders including hepatic IRI. Mechanisms of this protective effect include reduction of oxygen free radicals,alteration of macrophage and T cell phenotype. Further work is required to understand the physiological importance of the many actions of HO-1 identified experimentally,and to harness the protective effect of HO-1 for therapeutic potential.

关键词： Ischemia-reperfusion injury Heme oxygenase Transplantation Ischemic pre-conditioning

Cortico-centric effects of general anesthetics on cerebrocortical evoked potentials

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Neuroscience Bulletin 2015年第6期31卷 697-704页

作者： Logan j.Voss james W.Sleigh Anaesthesia Department Waikato District Health Board University of Auckland Waikato Clinical School

Despite their ubiquitous use for rendering patients unconscious for surgery, our understanding of how general anesthetics cause hypnosis remains rudimentary at best. Recent years have seen increased interest in ＂top-down＂ cortico-centric theories of anesthetic action. The aim of this study was to explore this by investigating direct cortical effects of anesthetics on cerebrocortical evoked potentials in isolated mouse brain slices. Evoked potentials were elicited in cortical layer IV by electrical stimulation of the underlying white matter. The effects of three anesthetics （ketamine, etomidate, and isoflurane） on the amplitude, latency, and slope of short-latency evoked potentials were quantified. The N2/P3/N4 potentials - which represent the early cortical response - were enhanced by etomidate （increased P3-N4 slope, P 〈0.01）, maintained by ketamine, and reduced by isoflurane （lower N2/P3 amplitude, P 〈0.01）. These effects closely resemble those seen in vivo for the same drugs and point to a cortical mechanism independent of effects on subcortical structures such as the thalamus.

关键词： anesthesia evoked potentials corticalslice thalamus

The song remains the same： juvenile Richardson＇s ground squirrels do not respond differentially to mother＇s or colony member＇s alarm calls

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Current Zoology 2012年第5期58卷 773-780页

作者： james F. HARE Kurtis j. WARKENTIN Department of Biological Sciences University of Manitoba Winnipeg MB Canada R3T 2N2 Department of Zoology Brandon University Brandon MB R7A 6A9

Alarm calls are emitted by Richardson＇s ground squirrels Urocitellus richardsonii in response to avian and terrestrial predators. Conspecifics detecting these calls respond with increased vigilance, promoting predator detection and evasion, but in doing so, lose time from foraging. That loss can be minimized if alarm call recipients discriminate among signalers, and weight their response accordingly. For juvenile ground squirrels, we predicted that the trade-off between foraging and vigilance could be optimized via selective response to alarm calls emitted by their own dam, and/or neighboring colony members over calls broad- cast by less familiar conspecifics. Alarm calls of adult female Richardson＇s ground squirrels were elicited in the field using a predator model and recorded on digital audio tape. Free-living focal juveniles were subjected to playbacks of a call of their mother, and on a separate occasion a call from either another adult female from their own colony, or an adult female from another colony. Neither immediate postural responses and escape behavior, nor the duration of vigilance manifested by juveniles differed with exposure to alarm calls of the three adult female signaler types. Thus, juveniles did not respond preferentially to alarm calls emitted by their mothers or colony members, likely reflecting the high cost of ignoring alarm signals where receivers have had limited opportunity to establish past signaler reliability [Current Zoology 58 （5）： 773-780, 2012].

关键词： Alarm Signal Communication Maternal Call Recognition Signal Reliability Ground Squirrel Social Discrimination

Effect of calcination temperature on steam reforming activity of Ni-based pyrochlore catalysts

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journal of Rare Earths 2020年第7期38卷 711-718,I0002页

作者： Daniel j.Haynes Dushyant Shekhawat David Berry Amitava Roy james j.Spivey National Energy Technology Laboratory U.S.Department of Energy3610 Collins Ferry RdMorgantownWV26507 USA Louisiana State University Cain Department of Chemical Engineering3307 Patrick Taylor HallBaton RougeLA70803USA

This work served as the second part of a study evaluating the effect of calcination temperature(700-1000℃) on Ni-based lanthanum zirconate pyrochlore catalysts for methane steam reforming.A previous study(Haynes et ***.2017(43) 16744) provided a thorough characterization of the material properties for the catalysts used here,and this study focuses on the evaluation of catalytic *** activity was assessed by two different experimental studies:the effect of reaction temperature using a temperature programmed surface reaction(TPSR),and the effect of reaction *** results demonstrate a complex interaction between the Ni particles and surface LaOx species under the methane steam reforming ***,the material calcined at the lowest temperature(700℃) possesses the highest activity and selectivity,which is attributed to smaller and more welldispersed Ni particles on the surface,and,more importantly,a lesser degree La enrichment at the *** catalysts were deactivated by steam to NiO under all conditions tested,but at certain low reaction pressure(p=0.23 MPa) conditions the materials calcined at 700-900℃ are able to completely recover equilibrium activity in-situ that is then robust and stable under both low and high reaction pressures(p=1.8 MPa) suggesting the formation of a synergistic relationship between Ni and La for syngas ***,exposure of a fresh material to high reaction pressures leads to a rapid and irreversible loss in both CH4 conversion and syngas selectivity whether in the fresh(no pretreatment),or pretreated(steam,H2 or Ar only at 800℃) form for any *** mechanism for deactivation appears to be due to the presence of LaOx species that become mobile,possibly by the formation of La-OH,and covers the active Ni particles and inhibits sites responsible for the CH4 decomposition.

关键词： Nickel Pyrochlore Methane Steam reforming Catalyst Lanthanum enrichment

Hydrogen for a Net-Zero Carbon World

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Engineering 2023年第10期29卷 8-10页

作者： Nigel P.Brandon james j.Brandon Faculty of Engineering Imperial College LondonSouth Kensington CampusLondon SW72AZUK The First Element Ltd. London N17GUUK

*** hydrogen?The concept of the“hydrogen economy”was first coined by *** Bockris during a talk he gave in 1970 at the General Motors Technical ***’s talk introduced the vision of a world economy in which energy was... 详细信息

关键词： hydrogen Carbon economy