Vortex line in a neutral finite-temperature superfluid Fermi gas

The structure of an isolated vortex in a dilute two-component neutral superfluid Fermi gas is studied within the context of self-consistent Bogoliubov-de Gennes theory. Various thermodynamic properties are calculated and the shift in the critical temperature due to the presence of the vortex is analyzed. The gapless excitations inside the vortex core are studied and a scheme to detect these states and thus the presence of the vortex is examined. The numerical results are compared with various analytical expressions when appropriate.Comment: 8 pages, 6 embedded figure

Atom-molecule equilibration in a degenerate Fermi gas with resonant interactions

We present a nonequilibrium kinetic theory describing atom-molecule population dynamics in a two-component Fermi gas with a Feshbach resonance. Key collision integrals emerge that govern the relaxation of the atom-molecule mixture to chemical and thermal equilibrium. Our focus is on the pseudogap regime where molecules form above the superfluid transition temperature. In this regime, we formulate a simple model for the atom-molecule population dynamics. The model predicts the saturation of molecule formation that has been observed in recent experiments, and indicates that a dramatic enhancement of the atom-molecule conversion efficiency occurs at low temperatures.Comment: Updated manuscript on July 5, 2004. Four pages with three embedded figure

Rapidity dependence of deuteron production in Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV

We have measured the distributions of protons and deuterons produced in high energy heavy ion Au+Au collisions at RHIC over a very wide range of transverse and longitudinal momentum. Near mid-rapidity we have also measured the distribution of anti-protons and anti-deuterons. We present our results in the context of coalescence models. In particular we extract the "volume of homogeneity" and the average phase-space density for protons and anti-protons. Near central rapidity the coalescence parameter $B_2(p_T)$ and the space averaged phase-space density $(p_T)$ are very similar for both protons and anti-protons. For protons we see little variation of either $B_2(p_T)$ or the space averaged phase-space density as the rapidity increases from 0 to 3. However both these quantities depend strongly on $p_T$ at all rapidities. These results are in contrast to lower energy data where the proton and anti-proton phase-space densities are different at $y$=0 and both $B_2$ and $f$ depend strongly on rapidity.Comment: Document updated after proofs received from PR

Rapidity and centrality dependence of particle production for identified hadrons in Cu+Cu collisions at sNN=200\sqrt{s_{NN}} = 200 GeV

The BRAHMS collaboration has measured transverse momentum spectra of pions, kaons, protons and antiprotons at rapidities 0 and 3 for Cu+Cu collisions at $\sqrt{s_{NN}} = 200$ GeV. As the collisions become more central the collective radial flow increases while the temperature of kinetic freeze-out decreases. The temperature is lower and the radial flow weaker at forward rapidity. Pion and kaon yields with transverse momenta between 1.5 and 2.5 GeV/c are suppressed for central collisions relative to scaled $p+p$ collisions. This suppression, which increases as the collisions become more central is consistent with jet quenching models and is also present with comparable magnitude at forward rapidity. At such rapidities initial state effects may also be present and persistence of the meson suppression to high rapidity may reflect a combination of jet quenching and nuclear shadowing. The ratio of protons to mesons increases as the collisions become more central and is largest at forward rapidities.Comment: 19 pages, 11 figures and 6 table

Collective ferromagnetism in two-component Fermi-degenerate gas trapped in finite potential

Spin asymmetry of the ground states is studied for the trapped spin-degenerate (two-component) gases of the fermionic atoms with the repulsive interaction between different components, and, for large particle number, the asymmetric (collective ferromagnetic) states are shown to be stable because it can be energetically favorable to increase the fermi energy of one component rather than the increase of the interaction energy between up-down components. We formulate the Thomas-Fermi equations and show the algebraic methods to solve them. From the Thomas-Fermi solutions, we find three kinds of ground states in finite system: 1) paramagnetic (spin-symmetric), 2) ferromagnetic (equilibrium) and 3) ferromagnetic (nonequilibrium) states. We show the density profiles and the critical atom numbers for these states obtained analytically, and, in ferromagnetic states, the spin-asymmetries are shown to occur in the central regions of the trapped gas, and grows up with increasing particle number. Based on the obtained results, we discuss the experimental conditions and current difficulties to realize the ferromagnetic states of the trapped atom gas, which should be overcome.Comment: submit to PR

Random-phase approximation study of collective excitations in the Bose-Fermi mixed condensate of alkali-metal gases

We perform Random Phase Approximation (RPA) study of collective excitations in the bose-fermi mixed degenerate gas of Alkali-metal atoms at T=0. The calculation is done by diagonalization in a model space composed of particle-hole type excitations from the ground state, the latter being obtained from the coupled Gross-Pitaevskii and Thomas-Fermi equations. We investigate strength distributions for different combinations of bose and fermi multipole ($L$) operators with $L=0,1,2,3$. Transition densities and dynamical structure factors are calculated for collective excitations. Comparison with the sum rule prediction for the collective frequency is given. Time dependent behavior of the system after an external impulse is studied.Comment: 28 pages, 13 figures, submitted to Phys. Rev.

Activity-dependent translation dynamically alters the proteome of the perisynaptic astrocyte process

Within eukaryotic cells, translation is regulated independent of transcription, enabling nuanced, localized, and rapid responses to stimuli. Neurons respond transcriptionally and translationally to synaptic activity. Although transcriptional responses are documented in astrocytes, here we test whether astrocytes have programmed translational responses. We show that seizure activity rapidly changes the transcripts on astrocyte ribosomes, some predicted to be downstream of BDNF signaling. In acute slices, we quantify the extent to which cues of neuronal activity activate translation in astrocytes and show that this translational response requires the presence of neurons, indicating that the response is non-cell autonomous. We also show that this induction of new translation extends into the periphery of astrocytes. Finally, synaptic proteomics show that new translation is required for changes that occur in perisynaptic astrocyte protein composition after fear conditioning. Regulation of translation in astrocytes by neuronal activity suggests an additional mechanism by which astrocytes may dynamically modulate nervous system functioning

Problem pušenja među mladima u Crnoj Gori - rezultati GYTS (Global Youth Tobacco Survey) istraživanja

Smoking is a burning healthcare and economy issue, especially in underdeveloped countries. The aim of this study was to determine the number of smokers among elementary school students in Montenegro and to assess the correlates of tobacco use. The study was done in 2003 using the World Health Organization Global Youth Tobacco Survey. Our data showed that children as young as ten years smoked. There were 3.6 % permanent smokers and one in three students (30.6 %) experimented with smoking. More than two thirds who smoked agreed that they should quit smoking, and three fourths tried to quit. This study has also shown that children talk too little about smoking in schools and are exposed to passive smoking at home and elsewhere. Activities to solve the elementary school smoking problem should include preventive programs to be introduced into regular school curricula because this is the only way to address the issue properly. In addition, legislation prohibiting indoor tobacco smoking should be implemented rigorously to protect children from passive smoking in public places.Pušenje duhana velik je zdravstveni i ekonomski problem, posebno u zemljama u razvoju. Istraživanje je provedeno radi utvrđivanja broja pušača u populaciji učenika osnovnih škola, kao i utvrđivanja stavova, znanja i ponašanja učenika u vezi s pušenjem. Istraživanje o potrošnji duhana kod djece u osnovnim školama u Crnoj Gori provedeno je 2003. godine po jedinstvenoj metodologiji Svjetske zdravstvene organizacije - Global Youth Tobacco Survey (GYTS). Podaci dobiveni istraživanjem pokazali su da u osnovnim školama Crne Gore postoji evidentan problem pušenja, i to već kod djece prije navršene desete godine života. U osnovnim školama postoji 3,6 % stalnih pušača, dok je jedan od troje (30,6 %) učenika eksperimentirao s cigaretama. Više od dvije trećine djece koja puše suglasno je da treba prestati s pušenjem, a tri četvrtine njih su pokušavale prestati s pušenjem. Osim toga, istraživanje je pokazalo da djeca malo govore u školama o problemu pušenja, da su osnovci konstantno izloženi utjecaju pasivnog pušenja u vlastitim kućama, kao i izvan kuće. Problem pušenja u osnovnim školama postoji i treba definirati aktivnosti za njegovo rješavanje. Prije svega, treba omogućiti uključivanje preventivnih programa u redovite obrazovne programe u školama, da bi se o problemu pušenja govorilo na adekvatan način. Također, mora se inicirati striktno provođenje “Zakona o ograničenju upotrebe duhanskih proizvoda” da bi djecu zaštitili od pasivnog pušenja