The transition temperature of the dilute interacting Bose gas

We show that the critical temperature of a uniform dilute Bose gas must increase linearly with the s-wave scattering length describing the repulsion between the particles. Because of infrared divergences, the magnitude of the shift cannot be obtained from perturbation theory, even in the weak coupling regime; rather, it is proportional to the size of the critical region in momentum space. By means of a self-consistent calculation of the quasiparticle spectrum at low momenta at the transition, we find an estimate of the effect in reasonable agreement with numerical simulations.Comment: 4 pages, Revtex, to be published in Physical Review Letter

Effect of Repeated Administration of hCG on Ovarian Response in PMSG-superovulated Ouled Djellal Ewes (Algeria)

The objective of this study was to evaluate the effect of repeated administration of hCG on ovarian response in PMSG-superovulated ewes. Intravaginal pessaries containing 40 mg fluorogestone acetate (FGA) were inserted in all ewes (n=9) and remained in situ for 14 days. Two days prior to pessary removal, all ewes were treated with 1000 IU of PMSG. On the day of sponge removal (day 0), the females were randomly assigned to 2 treatments. The first group (n=3) did not receive any hCG, while the second group (n=6) treated inter-muscular with hCG (500 IU) during days 0-2. On day 8, laparotomy was performed to assess numbers of corpora lutea (CL) and anovulatory follicles (AF). Blood samples were collected for analysis of serum progesterone (P4) using radioimmunoassay (RIA) method. The results obtained for first and second group was in number of CL (6.33±1.15 and 10.50±5.54), number of AF (2 ±3.46 and 4.16±5.70), then the levels of P4 (5.75± 4.45 and 13.22±6.80 ng/ml), respectively. These results indicate that the repeated administration of hCG post-sponge removal increases number of CL and improves luteal function in ewes after PMSG-superovulatory treatment

Preparation and analysis of a two-components breath figure at the nanoscale

International audienceSolid/liquid two-components Ga-Pb structures in isolated nanometer sized particles have been produced and studied by electron microscopy. Production is based on the breath figure technique and we investigate the way the two components are distributed. We clearly identify two growth regimes associated with the two different ways a Pb atom incorporates into a Ga nanodrop. Using TEM and SEM, the shape and microstructure of the nanoparticles are studied and the results obtained are in good agreement with the proposed model. The experimental technique used appears to be appropriate to produce Pb nanocrystals in liquid Ga nano-containers

Estrogens promote misfolded proinsulin degradation to protect insulin production and delay diabetes

Summary: Conjugated estrogens (CE) delay the onset of type 2 diabetes (T2D) in postmenopausal women, but the mechanism is unclear. In T2D, the endoplasmic reticulum (ER) fails to promote proinsulin folding and, in failing to do so, promotes ER stress and β cell dysfunction. We show that CE prevent insulin-deficient diabetes in male and in female Akita mice using a model of misfolded proinsulin. CE stabilize the ER-associated protein degradation (ERAD) system and promote misfolded proinsulin proteasomal degradation. This involves activation of nuclear and membrane estrogen receptor-α (ERα), promoting transcriptional repression and proteasomal degradation of the ubiquitin-conjugating enzyme and ERAD degrader, UBC6e. The selective ERα modulator bazedoxifene mimics CE protection of β cells in females but not in males. : Estrogens prevent diabetes in women, but the mechanism is poorly understood. Xu et al. report that estrogens activate the endoplasmic-reticulum-associated protein degradation pathway, which promotes misfolded proinsulin degradation, suppresses endoplasmic reticulum stress, and protects insulin secretion in mice and in human pancreatic β cells. Keywords: estrogens, beta cell, islet, endoplasmic reticulum stress, proinsulin misfolding, diabetes, bazedoxifene, sex dimorphism, ERAD, SER

An Experimental and Theoretical Study of Nitrogen-Broadened Acetylene Lines

We present experimental nitrogen-broadening coefficients derived from Voigt profiles of isotropic Raman Q-lines measured in the 2 band of acetylene (C2H2) at 150 K and 298 K, and compare them to theoretical values obtained through calculations that were carried out specifically for this work. Namely, full classical calculations based on Gordon's approach, two kinds of semi-classical calculations based on Robert Bonamy method as well as full quantum dynamical calculations were performed. All the computations employed exactly the same ab initio potential energy surface for the C2H2N2 system which is, to our knowledge, the most realistic, accurate and up-to-date one. The resulting calculated collisional half-widths are in good agreement with the experimental ones only for the full classical and quantum dynamical methods. In addition, we have performed similar calculations for IR absorption lines and compared the results to bibliographic values. Results obtained with the full classical method are again in good agreement with the available room temperature experimental data. The quantum dynamical close-coupling calculations are too time consuming to provide a complete set of values and therefore have been performed only for the R(0) line of C2H2. The broadening coefficient obtained for this line at 173 K and 297 K also compares quite well with the available experimental data. The traditional Robert Bonamy semi-classical formalism, however, strongly overestimates the values of half-width for both Qand R-lines. The refined semi-classical Robert Bonamy method, first proposed for the calculations of pressure broadening coefficients of isotropic Raman lines, is also used for IR lines. By using this improved model that takes into account effects from line coupling, the calculated semi-classical widths are significantly reduced and closer to the measured ones

Magnetic polarons in weakly doped high-Tc superconductors

We consider a spin Hamiltonian describing $d$-$d$ exchange interactions between localized spins $d$ of a finite antiferromagnet as well as $p$-$d$ interactions between a conducting hole ($p$) and localized spins. The spin Hamiltonian is solved numerically with use of Lanczos method of diagonalization. We conclude that $p$-$d$ exchange interaction leads to localization of magnetic polarons. Quantum fluctuations of the antiferromagnet strengthen this effect and make the formation of polarons localized in one site possible even for weak $p$-$d$ coupling. Total energy calculations, including the kinetic energy, do not change essentially the phase diagram of magnetic polarons formation. For parameters reasonable for high-$T_c$ superconductors either a polaron localized on one lattice cell or a small ferron can form. For reasonable values of the dielectric function and $p$-$d$ coupling, the contributions of magnetic and phonon terms in the formation of a polaron in weakly doped high-$T_c$ materials are comparable.Comment: revised, revtex-4, 12 pages 8 eps figure

Acoustic Events in the Solar Atmosphere from Hinode/SOT NFI observations

We investigate the properties of acoustic events (AEs), defined as spatially concentrated and short duration energy flux, in the quiet sun using observations of a 2D field of view (FOV) with high spatial and temporal resolution provided by the Solar Optical Telescope (SOT) onboard \textit{Hinode}. Line profiles of Fe \textsc{i} 557.6 nm were recorded by the Narrow band Filter Imager (NFI) on a $82" \times 82"$ FOV during 75 min with a time step of 28.75 s and 0.08$"$ pixel size. Vertical velocities were computed at three atmospheric levels (80, 130 and 180 km) using the bisector technique allowing the determination of energy flux in the range 3-10 mHz using two complementary methods (Hilbert transform and Fourier power spectra). Horizontal velocities were computed using local correlation tracking (LCT) of continuum intensities providing divergences. The net energy flux is upward. In the range 3-10 mHz, a full FOV space and time averaged flux of 2700 W m$^{-2}$ (lower layer 80-130 km) and 2000 W m$^{-2}$ (upper layer 130-180 km) is concentrated in less than 1% of the solar surface in the form of narrow (0.3$"$) AE. Their total duration (including rise and decay) is of the order of $10^{3}$ s. Inside each AE, the mean flux is $1.6 10^{5}$ W m$^{-2}$ (lower layer) and $1.2 10^{5}$ W m$^{-2}$ (upper). Each event carries an average energy (flux integrated over space and time) of $2.5 10^{19}$ J (lower layer) to $1.9 10^{19}$ J (upper). More than $10^{6}$ events could exist permanently on the Sun, with a birth and decay rate of 3500 s$^{-1}$. Most events occur in intergranular lanes, downward velocity regions, and areas of converging motions.Comment: 18 pages, 10 figure

Oxygen-isotope effect on the in-plane penetration depth in cuprate superconductors

Muon-spin rotation (muSR) studies of the oxygen isotope (^{16}O/^{18}O) effect (OIE) on the in-plane magnetic field penetration depth lambda_{ab} in cuprate high-temperature superconductors (HTS) are presented. First, the doping dependence of the OIE on the transition temperature T_c in various HTS is briefly discussed. It is observed that different cuprate families show a similar doping dependence of the OIE on T_c. Then, bulk muSR, low-energy muSR, and magnetization studies of the total and site-selective OIE on lambda_{ab} are described in some detail. A substantial OIE on lambda_{ab} was observed in various cuprate families at all doping levels, suggesting that cuprate HTS are non-adiabatic superconductors. The experiments clearly demonstrate that the total OIE on T_c and lambda_{ab} arise from the oxygen sites within the superconducting CuO_2 planes, demonstrating that the phonon modes involving the movement of planar oxygen are dominantly coupled to the supercarriers. Finally, it is shown that the OIE on T_c and lambda_{ab} exhibit a relation that appears to be generic for different families of cuprate HTS. The observation of these unusual isotope effects implies that lattice effects play an essential role in cuprate HTS and have to be considered in any realistic model of high-temperature superconductivity.Comment: 22 pages, 12 figures. To be published in a special issue of J. Phys. Cond. Ma

Challenging assumptions of the enlargement literature : the impact of the EU on human and minority rights in Macedonia

This article argues that from the very start of the transition process in Macedonia, a fusion of concerns about security and democratisation locked local nationalist elites and international organisations intoa political dynamic that prioritised security over democratisation. This dynamic resulted in little progress in the implementation of human and minority rights until 2009, despite heavy EU involvement in Macedonia after the internal warfare of 2001. The effects of this informally institutionalised relationship have been overlooked by scholarship on EU enlargement towards Eastern Europe, which has made generalisations based on assumptions relevant to the democratisation of countries in Eastern Europe, but not the Western Balkans

Nonequilibrium molecular dynamics simulation of rapid directional solidification

We present the results of non-equilibrium molecular dynamics simulations for the growth of a solid binary alloy from its liquid phase. The regime of high pulling velocities, $V$, for which there is a progressive transition from solute segregation to solute trapping, is considered. In the segregation regime, we recover the exponential form of the concentration profile within the liquid phase. Solute trapping is shown to settle in progressively as $V$ is increased and our results are in good agreement with the theoretical predictions of Aziz [J. Appl. Phys. {\bf 53}, 1158 (1981)]. In addition, the fluid advection velocity is shown to remain directly proportional to $V$, even at the highest velocities considered here ($V\simeq10$ms$^{-1}$).Comment: Submitted to Phys. Rev.