8,675 research outputs found
Heavy-to-Light Form Factors in the Final Hadron Large Energy Limit: Covariant Quark Model Approach
We prove the full covariance of the heavy-to-light weak current matrix
elements based on the Bakamjian-Thomas construction of relativistic quark
models, in the heavy mass limit for the parent hadron and the large energy
limit for the daughter one. Moreover, this quark model representation of the
heavy-to-light form factors fulfills the general relations that were recently
argued to hold in the corresponding limit of QCD, namely that there are only
three independent form factors describing the B -> pi (rho) matrix elements, as
well as the factorized scaling law sqrt(M)z(E) of the form factors with respect
to the heavy mass M and large energy E. These results constitute another good
property of the quark models \`a la Bakamjian-Thomas, which were previously
shown to exhibit covariance and Isgur-Wise scaling in the heavy-to-heavy case.Comment: 11 pages, LaTex2e, no figur
Stably non-synchronizable maps of the plane
Pecora and Carroll presented a notion of synchronization where an
(n-1)-dimensional nonautonomous system is constructed from a given
-dimensional dynamical system by imposing the evolution of one coordinate.
They noticed that the resulting dynamics may be contracting even if the
original dynamics are not. It is easy to construct flows or maps such that no
coordinate has synchronizing properties, but this cannot be done in an open set
of linear maps or flows in , . In this paper we give examples of
real analytic homeomorphisms of such that the non-synchronizability is
stable in the sense that in a full neighborhood of the given map, no
homeomorphism is synchronizable
Quantitative analysis of the dripping and jetting regimes in co-flowing capillary jets
We study a liquid jet that breaks up into drops in an external co-flowing
liquid inside a confining microfluidic geometry. The jet breakup can occur
right after the nozzle in a phenomenon named dripping or through the generation
of a liquid jet that breaks up a long distance from the nozzle, which is called
jetting. Traditionally, these two regimes have been considered to reflect the
existence of two kinds of spatiotemporal instabilities of a fluid jet, the
dripping regime corresponding to an absolutely unstable jet and the jetting
regime to a convectively unstable jet. Here, we present quantitative
measurements of the dripping and jetting regimes, both in an unforced and a
forced state, and compare these measurements with recent theoretical studies of
spatiotemporal instability of a confined liquid jet in a co-flowing liquid. In
the unforced state, the frequency of oscillation and breakup of the liquid jet
is measured and compared to the theoretical predictions. The dominant frequency
of the jet oscillations as a function of the inner flow rate agrees
qualitatively with the theoretical predictions in the jetting regime but not in
the dripping regime. In the forced state, achieved with periodic laser heating,
the dripping regime is found to be insensitive to the perturbation and the
frequency of drop formation remains unaltered. The jetting regime, on the
contrary, amplifies the externally imposed frequency, which translates in the
formation of drops at the frequency imposed by the external forcing. In
conclusion, the dripping and jetting regimes are found to exhibit the main
features of absolutely and convectively unstable flows respectively, but the
frequency selection in the dripping regime is not ruled by the absolute
frequency predicted by the stability analysis.Comment: 10 pages, 12 figures, to appear in Physics of Fluid
Household Energy Utilization by the Elderly
A paper presented by Robert A. Bylund, Nelson L. LeRay and Charles O. Crawford to the United States Special Senate Committee on Aging on November 26, 1979
B0(t) -> DPP time-dependent Dalitz plots, CP-violating angles 2beta, 2beta+gamma, and discrete ambiguities
We study CP-violation in resonant three-body B -> DPP decays, where PP stands
for either Dpi, DK_S, pipi or piK_S. Analogously to the B -> 3pi channel and
the extraction of 2alpha, the first three channels are shown to measure
cos(2beta) in addition to sin(2beta), thus allowing to resolve the beta -> pi/2
-beta ambiguity, while the DpiK_S final state leads to a measurement of
2beta+gamma. The B0(t) -> D+D-pi0 channel via the interference between D**
orbitally excited resonances is taken as an example, although this
Cabibbo-suppressed decay suffers from irreducible penguin uncertainties. Then
two penguin-free and Cabibbo-dominant modes are proposed: B0(t) -> D+D-K_S with
the D_s** resonances, and B0(t) -> D0_CP pi+pi- with the D** plus the rho.
Finally, the B0(t) -> D+-pi-+K_S channel with the D_s** and K* resonances
provides a new clean method to measure the unusual angle 2beta+gamma. We
present in all cases a crude estimate of the number of cos(2beta) (respectively
2beta+gamma) sensitive events. We show that this number is an increasing
function of the resonance mass, a favorable situation compared to the more
extensively studied three-pion Dalitz plot. However, the poor detection
efficiency of the D mesons could pose a problem. As an annex and speculative
application of these Dalitz plot based methods, the penguin-dominated B0(t) ->
K_SK_SK_L decay also measures 2beta.Comment: 17 pages, 4 figures, Latex2e, graphicx. To appear in Phys. Lett. B.
This version includes an erratum sent to PLB: the wrong remark about untagged
events has been removed. Minor misprints in Eqs. (5), (9) and (24) correcte
Recommended from our members
Polymicrobial periodontal disease triggers a wide radius of effect and unique virome.
Periodontal disease is a microbially-mediated inflammatory disease of tooth-supporting tissues that leads to bone and tissue loss around teeth. Although bacterially-mediated mechanisms of alveolar bone destruction have been widely studied, the effects of a polymicrobial infection on the periodontal ligament and microbiome/virome have not been well explored. Therefore, the current investigation introduced a new mouse model of periodontal disease to examine the effects of a polymicrobial infection on periodontal ligament (PDL) properties, changes in bone loss, the host immune response, and the microbiome/virome using shotgun sequencing. Periodontal pathogens, namely Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Fusobacterium nucleatum were used as the polymicrobial oral inoculum in BALB/cByJ mice. The polymicrobial infection triggered significant alveolar bone loss, a heightened antibody response, an elevated cytokine immune response, a significant shift in viral diversity and virome composition, and a widening of the PDL space; the latter two findings have not been previously reported in periodontal disease models. Changes in the PDL space were present at sites far away from the site of insult, indicating that the polymicrobial radius of effect extends beyond the bone loss areas and site of initial infection and wider than previously appreciated. Associations were found between bone loss, specific viral and bacterial species, immune genes, and PDL space changes. These findings may have significant implications for the pathogenesis of periodontal disease and biomechanical properties of the periodontium. This new polymicrobial mouse model of periodontal disease in a common mouse strain is useful for evaluating the features of periodontal disease
Si and Mn Abundances in Damped Lya Systems with Low Dust Content
We have measured the abundances of Zn, Si, Mn, Cr, Fe, and Ni in three damped
Lyman alpha systems at redshifts z < 1 from high resolution echelle spectra of
QSOs recorded with the Keck I telescope. In all three cases the abundances of
Cr, Fe, and Ni relative to Zn indicate low levels of dust depletions. We
propose that when the proportion of refractory elements locked up in dust
grains is less than about 50 percent, it is plausible to assume an
approximately uniform level of depletion for all grain constituents and, by
applying a small dust correction, recover the intrisic abundances of Si and Mn.
We use this approach on a small sample of damped systems for which it is
appropriate, with the aim of comparing the metallicity dependence of the ratios
[Si/Fe] and [Mn/Fe] with analogous measurements in Milky Way stars. The main
conclusion is that the relative abundances of both elements in distant galaxies
are broadly in line with expectations based on Galactic data. Si displays a
mild enhancement at low metallicities, as expected for an alpha-capture
element, but there are also examples of near-solar [Si/Fe] at [Fe/H] < -1. The
underabundance of Mn at low metallicities is possibly even more pronounced than
that in metal-poor stars, and no absorption system has yet been found where
[Mn/Fe] is solar. The heterogeneous chemical properties of damped Lyman alpha
systems, evident even from this limited set of measurements, provide further
support for the conclusion from imaging studies that a varied population of
galaxies gives rise to this class of QSO absorbers.Comment: 29 pages, LaTex, 7 Postscript Figures. Accepted for Publication in
the Astrophysical Journa
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