517 research outputs found
Collective dynamics of fermion clouds in cigar-shaped traps
The propagation of zero sound in a spin-polarized Fermi gas under harmonic
confinement is studied as a function of the mean-field interactions with a
second Fermi gas. A local-density treatment is compared with the numerical
solution of the Vlasov-Landau equations for the propagation of density
distortions in a trapped two-component Fermi gas at temperature T=0.2 Tf. The
response of the gas to the sudden creation of a sharp hole at its centre is
also studied numerically.Comment: 15 pages, 6 figure
Time-dependent linear response of an inhomogeneous Bose superfluid: Microscopic theory and connection to current-density functional theory
The dynamics of a confined fluid of Bose atoms is treated within the linear
response regime, with a view to establishing a current-density functional
formalism for an inhomogeneous superfluid state. After evaluating in full
detail a simplified case of an external coupling to the density and phase of
the condensate, the theory is extended to include the coupling to the total
current density. The Kohn-Sham response functions of the condensate and all the
exchange-correlation kernels for the superfluid are introduced from the
microscopic equations of motion and are expressed in a physically transparent
way through functional derivatives of correlation functions. A microscopic
formula for the superfluid density is derived and used to introduce a
generalized hydrodynamic approach for a weakly inhomogeneous two-fluid model in
isothermal conditions. Local-density expressions are thereby derived for the
velocities of first and second sound in the weakly inhomogeneous superfluid and
for visco-elastic functions describing the transition from the hydrodynamic to
the collisionless regime. Landau's hydrodynamic theory and known results in
Green's functions language are recovered in the limiting case of a homogeneous
superfluid.Comment: 25 pages, no figures, Postscript fil
Explicit finite-difference and direct-simulation-MonteCarlo method for the dynamics of mixed Bose-condensate and cold-atom clouds
We present a new numerical method for studying the dynamics of quantum fluids
composed of a Bose-Einstein condensate and a cloud of bosonic or fermionic
atoms in a mean-field approximation. It combines an explicit time-marching
algorithm, previously developed for Bose-Einstein condensates in a harmonic or
optical-lattice potential, with a particle-in-cell MonteCarlo approach to the
equation of motion for the one-body Wigner distribution function in the
cold-atom cloud. The method is tested against known analytical results on the
free expansion of a fermion cloud from a cylindrical harmonic trap and is
validated by examining how the expansion of the fermionic cloud is affected by
the simultaneous expansion of a condensate. We then present wholly original
calculations on a condensate and a thermal cloud inside a harmonic well and a
superposed optical lattice, by addressing the free expansion of the two
components and their oscillations under an applied harmonic force. These
results are discussed in the light of relevant theories and experiments.Comment: 33 pages, 13 figures, 1 tabl
HUBUNGAN DUKUNGAN KELUARGA DENGAN TINGKAT DEPRESI PADA NARAPIDANA NAPZA DI RUTAN KELAS IIB KAJHU ACEH BESAR
Banda Ace
Possible origins of macroscopic left-right asymmetry in organisms
I consider the microscopic mechanisms by which a particular left-right (L/R)
asymmetry is generated at the organism level from the microscopic handedness of
cytoskeletal molecules. In light of a fundamental symmetry principle, the
typical pattern-formation mechanisms of diffusion plus regulation cannot
implement the "right-hand rule"; at the microscopic level, the cell's
cytoskeleton of chiral filaments seems always to be involved, usually in
collective states driven by polymerization forces or molecular motors. It seems
particularly easy for handedness to emerge in a shear or rotation in the
background of an effectively two-dimensional system, such as the cell membrane
or a layer of cells, as this requires no pre-existing axis apart from the layer
normal. I detail a scenario involving actin/myosin layers in snails and in C.
elegans, and also one about the microtubule layer in plant cells. I also survey
the other examples that I am aware of, such as the emergence of handedness such
as the emergence of handedness in neurons, in eukaryote cell motility, and in
non-flagellated bacteria.Comment: 42 pages, 6 figures, resubmitted to J. Stat. Phys. special issue.
Major rewrite, rearranged sections/subsections, new Fig 3 + 6, new physics in
Sec 2.4 and 3.4.1, added Sec 5 and subsections of Sec
Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea
An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site
of the ANTARES neutrino telescope near Toulon, France, thus providing a unique
opportunity to compare high-resolution acoustic and optical observations
between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward
vertical currents of magnitudes up to 0.03 m s-1 in late winter and early
spring 2006. In the same period, observations were made of enhanced levels of
acoustic reflection, interpreted as suspended particles including zooplankton,
by a factor of about 10 and of horizontal currents reaching 0.35 m s-1. These
observations coincided with high light levels detected by the telescope,
interpreted as increased bioluminescence. During winter 2006 deep dense-water
formation occurred in the Ligurian subbasin, thus providing a possible
explanation for these observations. However, the 10-20 days quasi-periodic
episodes of high levels of acoustic reflection, light and large vertical
currents continuing into the summer are not direct evidence of this process. It
is hypothesized that the main process allowing for suspended material to be
moved vertically later in the year is local advection, linked with topographic
boundary current instabilities along the rim of the 'Northern Current'.Comment: 30 pages, 7 figure
Model-independent search for CP violation in D0âKâK+ÏâÏ+ and D0âÏâÏ+Ï+Ïâ decays
A search for CP violation in the phase-space structures of D0 and View the MathML source decays to the final states KâK+ÏâÏ+ and ÏâÏ+Ï+Ïâ is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fbâ1 collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the KâK+ÏâÏ+ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the ÏâÏ+Ï+Ïâ final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity
Search for the lepton-flavor-violating decays Bs0âe±Όâ and B0âe±Όâ
A search for the lepton-flavor-violating decays Bs0âe±Όâ and B0âe±Όâ is performed with a data sample, corresponding to an integrated luminosity of 1.0ââfb-1 of pp collisions at âs=7ââTeV, collected by the LHCb experiment. The observed number of Bs0âe±Όâ and B0âe±Όâ candidates is consistent with background expectations. Upper limits on the branching fractions of both decays are determined to be B(Bs0âe±Όâ)101ââTeV/c2 and MLQ(B0âe±Όâ)>126ââTeV/c2 at 95% C.L., and are a factor of 2 higher than the previous bounds
flavour tagging using charm decays at the LHCb experiment
An algorithm is described for tagging the flavour content at production of
neutral mesons in the LHCb experiment. The algorithm exploits the
correlation of the flavour of a meson with the charge of a reconstructed
secondary charm hadron from the decay of the other hadron produced in the
proton-proton collision. Charm hadron candidates are identified in a number of
fully or partially reconstructed Cabibbo-favoured decay modes. The algorithm is
calibrated on the self-tagged decay modes and using of data collected by the LHCb
experiment at centre-of-mass energies of and
. Its tagging power on these samples of
decays is .Comment: All figures and tables, along with any supplementary material and
additional information, are available at
http://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-027.htm
Branching fraction and CP asymmetry of the decays B+âK0SÏ+ and B+âK0SK+
An analysis of B+ â K0
SÏ+ and B+ â K0
S K+ decays is performed with the LHCb experiment. The pp
collision data used correspond to integrated luminosities of 1 fbâ1 and 2 fbâ1 collected at centre-ofmass
energies of
â
s = 7 TeV and
â
s = 8 TeV, respectively. The ratio of branching fractions and the
direct CP asymmetries are measured to be B(B+ â K0
S K+
)/B(B+ â K0
SÏ+
) = 0.064 ± 0.009 (stat.) ±
0.004 (syst.), ACP(B+ â K0
SÏ+
) = â0.022 ± 0.025 (stat.) ± 0.010 (syst.) and ACP(B+ â K0
S K+
) =
â0.21 ± 0.14 (stat.) ± 0.01 (syst.). The data sample taken at
â
s = 7 TeV is used to search for
B+
c
â K0
S K+ decays and results in the upper limit ( fc · B(B+
c
â K0
S K+
))/( fu · B(B+ â K0
SÏ+
)) <
5.8 Ă 10â2 at 90% confidence level, where fc and fu denote the hadronisation fractions of a ÂŻb
quark
into a B+
c or a B+ meson, respectively
- âŠ