3,749 research outputs found
Isospin Breaking and -> Decay
We study decay up to including all orders of the chiral
expansion and one-loop level of mesons in formlism of chiral constituent quark
model. This G-parity forbidden decay is caused by and
electromagnetic interaction of mesons. We illustrate that in the formlism both
nonresonant contact interaction and resonance exchange contribute to
this process, and the contribution from resonance exchange is dominant.
We obtain that transition matrix element is
MeV, and
isospin breaking parameter is MeV at energy scale .Comment: Revtex file, 16 pages, four eps figur
Continuum-particle hybrid coupling for mass, momentum and energy transfers in unsteady fluid flow
The aim of hybrid methods in simulations is to communicate regions with
disparate time and length scales. Here, a fluid described at the atomistic
level within an inner region P is coupled to an outer region C described by
continuum fluid dynamics. The matching of both descriptions of matter is made
across an overlapping region and, in general, consists of a two-way coupling
scheme (C->P and P->C) which conveys mass, momentum and energy fluxes. The
contribution of the hybrid scheme hereby presented is two-fold: first it treats
unsteady flows and, more importantly, it handles energy exchange between both C
and P regions. The implementation of the C->P coupling is tested here using
steady and unsteady flows with different rates of mass, momentum and energy
exchange. In particular, relaxing flows described by linear hydrodynamics
(transversal and longitudinal waves) are most enlightening as they comprise the
whole set of hydrodynamic modes. Applying the hybrid coupling scheme after the
onset of an initial perturbation, the cell-averaged Fourier components of the
flow variables in the P region (velocity, density, internal energy, temperature
and pressure) evolve in excellent agreement with the hydrodynamic trends. It is
also shown that the scheme preserves the correct rate of entropy production. We
discuss some general requirements on the coarse-grained length and time scales
arising from both the characteristic microscopic and hydrodynamic scales.Comment: LaTex, 12 pages, 9 figure
Untangling Source-To-Sink Geochemical Signals in a ~3.5 Ga Martian Lake: Sedimentology and Geochemistry of the Murray Formation
Sedimentary rocks are historical archives of planetary surface processes; their grains, textures, and chemistry integrate the effects of source terrains, paleoclimatic conditions, weathering and transport processes, authigenic mineral precipitation, and diagenesis, which records groundwater chemistry through time. Source to Sink basin analysis seeks to constrain the influence of each of these different signals through sedimentary and geochemical analyses. Here, we use Mars Science Laboratory (MSL) Curiosity rover images and geochemical and mineralogical data from a traverse across a portion of the Murray formationthe lowermost unit exposed in the Gale crater central moundto begin to constrain the aspects of the source to sink system that formed this Martian mudstone between 3.7 and 3.2 Ga
Realâlife experience in switching to new extended halfâlife products at European haemophilia centres
The concept of replacement therapy in haemophilia is changing significantly thanks to the switch from standard products to extended halfâlife products. These novel drugs are showing beneficial effects overcoming current prophylaxis limitations by reducing the infusion frequency, maintaining a higher trough level to ensure a lower risk of bleeding, and making treatment significantly less distressing to patients by improving the quality of life. Realâlife data on the efficacy of novel drugs and their impact on routine management of haemophilia A and B patients are still limited. This manuscript reports the results of a European survey conducted by the European Association for Haemophilia and Allied Disorders (EAHAD) at the beginning of 2018 on the clinical management of patients using extended halfâlife recombinant FVIII and FIX fusion products, since at the time of the survey none of the PEGylated products were available yet. We report data on the efficacy of these novel drugs by 33 European haemophilia centres that have already switched to extended halfâlife fusion products, showing a significant reduction in the number of infusions and a satisfactory trough levels in the clinical care of haemophilia patients, with a greater impact for haemophilia B
Ginsparg-Wilson Pions Scattering in a Sea of Staggered Quarks
We calculate isospin 2 pion-pion scattering in chiral perturbation theory for
a partially quenched, mixed action theory with Ginsparg-Wilson valence quarks
and staggered sea quarks. We point out that for some scattering channels, the
power-law volume dependence of two pion states in nonunitary theories such as
partially quenched or mixed action QCD is identical to that of QCD. Thus one
can extract infinite volume scattering parameters from mixed action
simulations. We then determine the scattering length for both 2 and 2+1 sea
quarks in the isospin limit. The scattering length, when expressed in terms of
the pion mass and the decay constant measured on the lattice, has no
contributions from mixed valence-sea mesons, thus it does not depend upon the
parameter, C_Mix, that appears in the chiral Lagrangian of the mixed theory. In
addition, the contributions which nominally arise from operators appearing in
the mixed action O(a^2 m_q) Lagrangian exactly cancel when the scattering
length is written in this form. This is in contrast to the scattering length
expressed in terms of the bare parameters of the chiral Lagrangian, which
explicitly exhibits all the sicknesses and lattice spacing dependence allowed
by a partially quenched mixed action theory. These results hold for both 2 and
2+1 flavors of sea quarks.Comment: 27 pages, 3 figures. Mistakes corrected in Eqs. (37), (42). Improved
discussion in section 4 and related results in Eqs. (33), (37), (40) and
(42). Added references. Version to be published in PR
Hydrogen atom in phase space. The Kirkwood-Rihaczek representation
We present a phase-space representation of the hydrogen atom using the
Kirkwood-Rikaczek distribution function. This distribution allows us to obtain
analytical results, which is quite unique because an exact analytical form of
the Wigner functions corresponding to the atom states is not known. We show how
the Kirkwood-Rihaczek distribution reflects properties of the hydrogen atom
wave functions in position and momentum representations.Comment: 5 pages (and 5 figures
Virtual guidance: a new technique to empower point-of-care ultrasound in remote or extreme environments
Higher meson resonances in and
The role of higher meson resonances with spin 1 and 2 is investigated
quantitatively in the decay processes of and
. Among the higher resonances, we find that the
tensor meson can give a nontrivial contribution especially to the
decay process. When the contribution is
combined with the processes involving the vector and scalar meson intermediate
states, a good agreement with the recent measurements is achieved for both
decays. The effect of the is found to be sizable at the
intermediate photon energies and may be verified by precise measurements of the
recoil photon spectrum of the decay. The
dependence of the decay widths on various models for the - mixing
in the literature is also investigated.Comment: 16 pages, REVTeX, 6 figures, revised version, to appear in Phys. Rev.
The Star Clusters in the Starburst Irregular Galaxy NGC 1569
We examine star clusters in the irregular, starburst galaxy NGC 1569 from HST
images. In addition to the two known super star clusters, we identify 45 other
clusters that are compact but resolved. Integrated UVI colors of the clusters
span a large range, and suggest that ages range from 3 Myrs to 1 Gyr. However,
most of the clusters were formed at the tail end of the recent starburst.
Numerous clusters in addition to the know super star clusters are similar in
luminosity to a small globular cluster. We examined the radial surface
brightness of four of the clusters. Their half-light radii and core radii are
in the range observed in present-day globular clusters. Therefore, conditions
that produced the recent starburst have also been those necessary for producing
compact, bright star clusters.
We examine resolved stars in the outer parts of the two super star clusters.
Cluster A is dominated by bright blue stars with a small population of red
supergiants. Sub-components A1 and A2 have similar colors and a two-dimensional
color map does not offer evidence that one component is dominated by red
supergiants and the other not. The contradiction of the presence of red super-
giants with Wolf-Rayet stars may instead not be a contradiction at all since
there coexistence in a coeval population is not inconsistent with the evolution
of massive stars. Cluster B is dominated by red supergiants, and this is
confirmed by the presence of the stellar CO absorption feature in an integrated
spectrum. The various age indicators are consistent with a picture in which
cluster B is of order 10--20 Myrs old, and cluster A is >4-5 Myrs old.Comment: To be published in AJ, November 200
Dynamics of a tagged particle in the asymmetric exclusion process with the step initial condition
The one-dimensional totally asymmetric simple exclusion process (TASEP) is
considered. We study the time evolution property of a tagged particle in TASEP
with the step-type initial condition. Calculated is the multi-time joint
distribution function of its position. Using the relation of the dynamics of
TASEP to the Schur process, we show that the function is represented as the
Fredholm determinant. We also study the scaling limit. The universality of the
largest eigenvalue in the random matrix theory is realized in the limit. When
the hopping rates of all particles are the same, it is found that the joint
distribution function converges to that of the Airy process after the time at
which the particle begins to move. On the other hand, when there are several
particles with small hopping rate in front of a tagged particle, the limiting
process changes at a certain time from the Airy process to the process of the
largest eigenvalue in the Hermitian multi-matrix model with external sources.Comment: 48 pages, 8 figure
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