简介:Weobservedthecharacteristicsofwhitematterfibersandgraymatterinmultiplesclerosispatients,toidentifychangesindiffusiontensorimagingfractionalanisotropyvaluesfollowingwhitematterfiberinjury.Weanalyzedthecorrelationbetweenfractionalanisotropyvaluesandchangesinwhole-braingraymattervolume.Theparticipantsincluded20patientswithrelapsing-remittingmultiplesclerosisand20healthyvolunteersascontrols.Allsubjectsunderwentheadmagneticresonanceimaginganddiffusiontensorimaging.Ourresultsrevealedthatfractionalanisotropyvaluesdecreasedandgraymattervolumeswerereducedinthegenuandspleniumofcorpuscallosum,leftanteriorthalamicradiation,hippocampus,uncinatefasciculus,rightcorticospinaltract,bilateralcingulategyri,andinferiorlongitudinalfasciculusinmultiplesclerosispatients.Graymattervolumesweresignificantlydifferentbetweenthetwogroupsintherightfrontallobe(superiorfrontal,middlefrontal,precentral,andorbitalgyri),rightparietallobe(postcentralandinferiorparietalgyri),righttemporallobe(caudatenucleus),rightoccipitallobe(middleoccipitalgyrus),rightinsula,rightparahippocampalgyrus,andleftcingulategyrus.Thevoxelsizesofatrophicgraymatterpositivelycorrelatedwithfractionalanisotropyvaluesinwhitematterassociationfibersinthepatientgroup.Thesefindingssuggestthatwhitematterfiberbundlesareextensivelyinjuredinmultiplesclerosispatients.Themainareasofgraymatteratrophyinmultiplesclerosisarethefrontallobe,parietallobe,caudatenucleus,parahippocampalgyrus,andcingulategyrus.Graymatteratrophyisstronglyassociatedwithwhitematterinjuryinmultiplesclerosispatients,particularlywithinjurytoassociationfibers.
简介:Inrecentdevelopmentsinchemistryandgeneticengineering,thehumbleresearcherdealingwiththeoriginoflifefindsher(him)selfinagreyareaoftacklingsomethingthatevendoesnotyethaveacleardefinitionagreedupon.Aseriesofchemicalstepsisdescribedtobeconsideredasthelife-nonlifetransition,ifoneadherestotheminimalisticdefinition:lifeisself-reproductionwithvariations.ThefullyartificialRNAsystemchosenfortheexplorationcorrespondssequence-wisetothereconstructedinitialtripletrepeats,presumablycorrespondingtotheearliestprotein-codingmolecules.Thedemonstratedoccurrenceofthemismatches(variations)inotherwisecomplementarysyntheses("self-reproduction"),inthisRNAsystem,opensanexperimentalandconceptualperspectivetoexploretheoriginoflife(anditsdefinition),ontheapparentedgeoftheorigin.
简介:重点词汇1.mattern.问题;事情What’sthematter?=What’sthetrouble?=What’swrong?怎么了?出什么事了?用于询问某人有什么病或某人遇到什么麻烦、问题。其后跟询问对象时,与介词with连用。What’sthematterwithyou?你怎么了?2.liev.(lay)躺;平躺lie是动词,意为'躺',过去式和过去分词分别为lay和lain,现在分词为lying。Ifoundhewaslyingontheground.我发现他躺在地上。lie还有'位于'的意思。Atempleliesonthetopofthemountain.一座寺庙位于山顶。
简介:Thepaperrepresentsarigoroustreatmentoftheunderlyingquantumtheory,notjustinwordsbutprovidingtheunderlyingtechnicaldetails,astowhymatteroccupiessolargeavolumeanditsintimateconnectionwiththePauliexclusionprinciple,asmoreandmorematterisputtogether,aswellasofthecontractionorshrinkageof'bosonicmatter',uponcollapse,forwhichthePauliexclusionisabolished.Fromthederivedexplicitboundsofintegralsofpowersoftheparticlenumberdensities,explicitboundsonprobabilitiesoftheoccurrencesoftheeventsjustdescribedareextracted.Theseprobabilitiesleadonetoinferthechangeofthe'size'orextensionofsuchmatter,uponexpansionorcontraction,respectively,astheircontentisincreased.
简介:Inthescenariowherethedarkmatter(DM)particlesχχˉpairannihilatethrougharesonanceparticleR,theconstraintfromDMrelicdensitymakesthecorrespondingcrosssectionforDM-nucleielasticscatteringextremelysmall,andcanbebelowtheneutrinobackgroundinducedbythecoherentneutrino-nucleiscattering,whichmakestheDMparticlebeyondthereachoftheconventionalDMdirectdetectionexperiments.WepresentanimprovedanalyticalcalculationoftheDMrelicdensityinthecaseofresonantDMannihilationfors-andp-wavecasesandinvesitgatetheconditionfortheDM-nucleiscatteringcrosssectiontobeabovetheneutrinobackground.WeshowthatinHiggs-portaltypemodels,forDMparticleswiths-waveannihilation,thespin-independentDM-nucleusscatteringcrosssectionisproportionaltoΓR/mR,theratioofthedecaywidthandthemassofR.ForatypicalDMparticlemass~50GeV,theconditionleadstoΓR/mR≥O(10-4).Inp-waveannihilationcase,thespin-independentscatteringcrosssectionisinsensitivetoΓR/mR,andisalwaysabovetheneutrinobackground,aslongastheDMparticleislighterthanthetopquark.TherealsingletDMmodelisdiscussedasaconcreteexample.