1,613 research outputs found
Determination of the strange quark mass from Cabibbo-suppressed tau decays with resummed perturbation theory in an effective scheme
We present an analysis of the m_s^2-corrections to Cabibbo-suppressed tau
lepton decays employing contour improved resummation within an effective scheme
which is an essential new feature as compared to previous analyses. The whole
perturbative QCD dynamics of the tau-system is described by the beta-function
of the effective coupling constant and by two gamma-functions for the effective
mass parameters of the strange quark in different spin channels. We analyze the
stability of our results with regard to high-order terms in the perturbative
expansion of the renormalization group functions. A numerical value for the
strange quark mass in the MS scheme is extracted m_s(M_\tau)=130\pm 27_{exp}\pm
9_{th} MeV. After running to the scale 1 GeV this translates into m_s(1
GeV)=176 \pm 37_{exp}\pm 13_{th} MeV.Comment: 32 pages, latex, 4 postscript figures, revised version to appear in
European Physical Journal C, discussion of the choice of the moments added,
some errors correcte
Asymptotic structure of perturbative series for lepton decay observables: corrections
In a previous paper we performed an analysis of asymptotic structure of
perturbation theory series for semileptonic -lepton decays in massless
limit. We extend our analysis to the Cabibbo suppressed decay
modes of the lepton. In particular we address the problem of
corrections to theoretical formulas. The properties of the asymptotic behavior
of the finite order perturbation theory series for the coefficient functions of
the corrections are studied.Comment: 25 page
Asymptotic structure of perturbative series for tau lepton observables
We analyze tau lepton decay observables, namely moments of the hadronic
spectral density in the finite energy interval (0,M_\tau), within finite order
perturbation theory including \alpha_s^4 corrections. The start of asymptotic
growth of perturbation theory series is found at this order in a scheme
invariant manner. We establish the ultimate accuracy of finite order
perturbation theory predictions and discuss the construction of optimal
observables.Comment: 21 page
Timing and Potential Drivers of Symbiont Selection in the Early Life Stages of the Massive Starlet Coral Siderastrea siderea
The ability of corals to build reefs can be attributed to their relationship with single-celled algae of the familySymbiodiniaceae.Through the process of photosynthesis, these algae can provide their coral hosts with over 90% of their daily energy requirements. Most coral species acquire multiple species of symbionts from the surrounding water during their larval stage or immediately after settling. However, over time, the coral will select a dominant symbiont speciesthat can depend on the local environment. Until this study, the size or age of the coral at which this transition from multiple Symbiodiniaceaespecies to one dominant species occurs has remained uncertain. Likewise, it was unclear whether the selection of Symbiodiniaceaespeciesis influenced by the environment. The environmental conditions and symbiont composition of one hundred and eighteen juvenile Siderastrea siderea were assessed across four sites in Broward County, Florida. Presuming newly settled corals acquire multiple symbionts and then select just one dominant species, it was determined that the transition from multiple symbiont speciesto one dominant species in Siderastrea sidereaoccurs in the single polyp stage, between the time of settlement and approximately 4 to 6 months of age. The results also suggest that the selection of these dominant symbiont speciesis influenced by the environment, and that juveniles commonly select the same species as adults inhabiting similar environmental conditions. The selection of symbionts homologous to adult corals combined with environmental influences may be an early indicator of acclimatization in Siderastrea siderea
Constitutional Law - Fifth Amendment - Right of Defendant in Denaturalization Proceedings to Refuse to Testify
The United States as plaintiff instituted denaturalization proceedings alleging that deliberately false statements were made by defendant at the time of his naturalization. No affidavit showing good cause for such suit, required by section 340 (a) of the Immigration and Nationality Act of 1952, was filed with the original complaint although one was filed with a later amended complaint. When plaintiff sought to take defendant\u27s deposition pursuant to rule 26, Federal Rules of Civil Procedure, defendant appeared for the examination but refused to be sworn. He was taken before the district court which directed that he be sworn, and he again refused. From a conviction of contempt defendant appealed, alleging that jurisdiction did not attach since the required affidavit was filed after the original complaint, and that pre-trial discovery procedures should not be applied to denaturalization proceedings since, as a defendant in such a proceeding, he was privileged to refuse to take the stand at all. The Second Circuit affirmed, holding that the affidavit could permissibly be filed with an amended complaint, and that denaturalization proceedings are not sufficiently criminal in their nature to entitle a defendant to refuse to take the stand. On certiorari to the United States Supreme Court, held, reversed per curiam. An affidavit showing good cause is a prerequisite to the initiation of denaturalization proceedings. The affidavit must be filed with the complaint when the proceedings are instituted. Matles v. United States, 26 U.S. Law Week 3282 (1958)
Negligence - Last Clear Chance - Evidence Insufficient as a Matter of Law
Plaintiff, having fallen asleep at night at the side of a narrow dirt road, was run over by defendant\u27s automobile. He alleged that defendant was negligent in operating a vehicle at an excessive speed without proper lights. Defendant pleaded that plaintiff was contributorily negligent by being asleep in the road, and plaintiff then replied that defendant had the last clear chance to avoid the injury. On appeal from a judgment of involuntary nonsuit, held, affirmed, three justices dissenting. The plaintiff, by falling asleep at the side or in the middle of the road, was contributorily negligent as a matter of law, and the evidence was insufficient to allow a jury to conclude that the defendant had an opportunity to avoid the accident after he discovered or should have discovered the plaintiff\u27s perilous position. Barnes v. Horney, (N.C. 1958) 101 S.E. (2d) 315
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