2,133 research outputs found
Analysis of Two-Body Decays of Charmed Baryons Using the Quark-Diagram Scheme
We give a general formulation of the quark-diagram scheme for the nonleptonic
weak decays of baryons. We apply it to all the decays of the antitriplet and
sextet charmed baryons and express their decay amplitudes in terms of the
quark-diagram amplitudes. We have also given parametrizations for the effects
of final-state interactions. For SU(3) violation effects, we only parametrize
those in the horizontal -loop quark diagrams whose contributions are solely
due to SU(3)-violation effects. In the absence of all these effects, there are
many relations among various decay modes. Some of the relations are valid even
in the presence of final-state interactions when each decay amplitude in the
relation contains only a single phase shift. All these relations provide useful
frameworks to compare with future experiments and to find out the effects of
final-state interactions and SU(3) symmetry violations.Comment: 28 pages, 20 Tables in landscape form, 4 figures. Main changes are:
(i) some errors in the Tables and in the relations between the quark-diagram
amplitudes of this paper and those of Ref.[10] are corrected, (ii)
improvements are made in the presentation so that comparisons with previous
works and what have been done to include SU(3) breaking and final-state
interactions are more clearly stated; to appear in the Physical Review
Laurent series expansion of a class of massive scalar one-loop integrals up to {\cal O}(\ep^2) in terms of multiple polylogarithms
In a recent paper we have presented results for a set of massive scalar
one-loop master integrals needed in the NNLO parton model description of the
hadroproduction of heavy flavors. The one--loop integrals were evaluated in
n=4-2\ep dimension and the results were presented in terms of a Laurent
series expansion up to {\cal O}(\ep^2). We found that some of the \ep^2
coefficients contain a new class of functions which we termed the
functions. The functions are defined in terms of one--dimensional integrals
involving products of logarithm and dilogarithm functions. In this paper we
derive a complete set of algebraic relations that allow one to convert the
functions of our previous approach to a sum of classical and multiple
polylogarithms. Using these results we are now able to present the \ep^2
coefficients of the one-loop master integrals in terms of classical and
multiple polylogarithms.Comment: 32 pages, Latex, references added, matches published versio
Inclusive Semileptonic Decays in QCD Including Lepton Mass Effects
Starting from an Operator Product Expansion in the Heavy Quark Effective
Theory up to order 1/m_b^2 we calculate the inclusive semileptonic decays of
unpolarized bottom hadrons including lepton mass effects. We calculate the
differential decay spectra d\Gamma/(dE_\tau ), and the total decay rate for B
meson decays to final states containing a \tau lepton.Comment: 16 pages + 4 figs. appended in uuencoded form, LaTeX, MZ-TH/93-3
SU(3)_flavor analysis of two-body weak decays of charmed baryons
We study two-body weak decays of charmed baryons \Lambda_c and \Xi_c into an
octet or decuplet baryon and a pseudoscalar meson employing the SU(3) flavor
symmetry. Using certain measured Cabibbo-favored modes, we fix the reduced
amplitudes and predict the branching ratios of various decays of charmed
baryons in the Cabibbo-enhanced, -suppressed and -doubly suppressed modes.Comment: 25 pages, No figure, Phys. Rev. D (to appear
Consequence of reputation in an open-ended Naming Game
We study a modified version of the Naming Game, a recently introduced model
which describes how shared vocabulary can emerge spontaneously in a population
without any central control. In particular, we introduce a new mechanism that
allows a continuous interchange with the external inventory of words. A novel
playing strategy, influenced by the hierarchical structure that individuals'
reputation defines in the community, is implemented. We analyze how these
features influence the convergence times, the cognitive efforts of the agents
and the scaling behavior in memory and time.Comment: 6 pages, 6 figure
Quark and Pole Models of Nonleptonic Decays of Charmed Baryons
Quark and pole models of nonleptonic decays of charmed baryons are analysed
from the point of view of their symmetry properties. The symmetry structure of
the parity conserving amplitudes that corresponds to the contribution of the
ground-state intermediate baryons is shown to differ from the one hitherto
employed in the symmetry approach. It is pointed out that the "subtraction" of
sea quark effects in hyperon decays leads to an estimate of -exchange
contributions in charmed baryon decays that is significantly smaller than
naively expected on the basis of . An constraint questioning
the reliability of the factorization technique is exhibited. Finally, a
successful fit to the available data is presented.Comment: 25 pages, LATEX, 1643/PH IFJ Krako
Cabibbo-allowed nonleptonic weak decays of charmed baryons
Cabibbo-allowed nonleptonic weak decays of charmed baryons
\lamc,~\xin,~\xip and into an octet baryon and a pseudoscalar
meson are analyzed. The nonfactorizable contributions are evaluated under pole
approximation, and it turns out that the -wave amplitudes are dominated by
the low-lying \halfm resonances, while -wave ones governed by the
ground-state \halfp poles. The MIT bag model is employed to calculate the
coupling constants, form factors and baryon matrix elements. Our conclusions
are: (i) waves are no longer dominated by commutator terms; the
current-algebra method is certainly not applicable to parity-violating
amplitudes, (ii) nonfactorizable exchange effects are generally important;
they can be comparable to and somtimes even dominate over factorizable
contributions, depending on the decay modes under consideration, (iii)
large- approximation for factorizable amplitudes also works in the heavy
baryon sector and it accounts for the color nonsuppression of \lamc\ri
p\bar{K}^0 relative to \lamc\ri\Lambda\pi^+, (iv) a measurement of the decay
rate and the sign of the asymmetry parameter of certain proposed decay
modes will help discern various models; especially the sign of in
\lamc\ri\Sigma\pi decays can be used to unambiguously differentiate recent
theoretical schemes from current algebra, and (v) waves are the dominant
contributions to the decays \lamc\ri\Xi^0 K^+ and \xin\ri\Sigma^+ K^-, but
they are subject to a large cancellation; this renders present theoretical
predictions on these two channels unreliable.Comment: PHYZZX, 31 pages, 3 tables, IP-ASTP-10-93, ITP-SB-93-2
Conventions spreading in open-ended systems
We introduce a simple open-ended model that describes the emergence of a
shared vocabulary. The ordering transition toward consensus is generated only
by an agreement mechanism. This interaction defines a finite and small number
of states, despite each individual having the ability to invent an unlimited
number of new words. The existence of a phase transition is studied by
analyzing the convergence times, the cognitive efforts of the agents and the
scaling behavior in memory and timeComment: 11 pages, 5 figure
Two-body Cabibbo-suppressed Decays of Charmed Baryons into Vector Mesons and into Photons
The heavy quark effective theory and the factorization approximation are used
to treat the Cabibbo-suppressed decays of charmed baryons to vector mesons,
,
and . The input from two recent experimental results on
decays allows the estimation of the branching ratios for these modes, which
turn out to be between and . The long distance contribution
of these transitions via vector meson dominance to the radiative weak processes
, and
leads to quite small branching ratios,
; the larger value holds if a sum rule between the coupling
constants of the vector mesons is broken.Comment: 11 pages, latex, no figure
A folyamatos szubkután glükózmonitorizálás szerepe az intenzív terápiában
A kritikus állapotú betegek stressz-hyperglykaemiájának értékelése az elmúlt évtizedben jelentősen megváltozott. A vércukor szoros kontrolljának mortalitást csökkentő hatását igazolta több jelentős vizsgálat, ugyanakkor az ezt célzó inzulinkezelés megnöveli a hypoglykaemia kockázatát, amely független mortalitási tényező lehet. A hypoglykaemia szempontjából kiemelt jelentőségű a gyermekpopuláció, a fejlődő idegrendszer miatt. Ezek alapján joggal merül fel a vércukorváltozások intenzív osztályos monitorizálásának igénye, különösen gyermek betegeknél. A hagyományos, vérmintából történő vércukor-meghatározások nem tesznek lehetővé kellően szoros monitorizálást. A cukorbetegek számára kifejlesztett, a szövet közti glükóz meghatározásán alapuló módszerek (continuous glucose monitoring) jó alternatívát jelenthetnek az intenzív osztályos monitorizálásra, amennyiben felmérjük a rendszer korlátait. A mérés a szövet közti folyadékban történik, így a szöveti perfúzió változásai zavarhatják a pontosságát. A folyamatos glükózmonitoring módszer intenzív osztályos alkalmazását jelenleg még nem javasolják, amíg a rendszer megbízhatóságáról nem áll rendelkezésre elegendő adat. Összefoglaló közleményükben a szerzők a magyar klinikai gyakorlatban elterjedt Medtronic folyamatos szubkután glükózmonitorizáló rendszert értékelik, részben saját eredményeik alapján. Orv. Hetil., 2013, 154, 1043–1048.
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Critical care associated with stress hyperglycaemia has gained a new view in the last decade since the demonstration of the beneficial effects of strong glycaemic control on the mortality in intensive care units. Strong glycaemic control may, however, induce hypoglycaemia, resulting in increased mortality, too. Pediatric population has an increased risk of hypoglycaemia because of the developing central nervous system. In this view there is a strong need for close monitoring of glucose levels in intensive care units. The subcutaneous continuous glucose monitoring developed for diabetes care is an alternative for this purpose instead of regular blood glucose measurements. It is important to know the limitations of subcutaneous continuous glucose monitoring in intensive care. Decreased tissue perfusion may disturb the results of subcutaneous continuous glucose monitoring, because the measurement occurs in interstitial fluid. The routine use of subcutaneous continuous glucose monitoring in intensive care units is not recommended yet until sufficient data on the reliability of the system are available. The Medtronic subcutaneous continuous glucose monitoring system is evaluated in the review partly based on the authors own results. Orv. Hetil., 2013, 154, 1043–1048
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