Identification of a component of Drosophila polar granules

Information necessary for the formation of pole cells, precursors of the germ line, is provided maternally and localized to the posterior pole of the Drosophila egg. The maternal origin and posterior localization of polar granules suggest that they may be associated with pole cell determinants. We have generated an antibody (Mab46F11) against polar granules. In oocytes and early embryos, the Mab46F11 antigen is sharply localized to the posterior embryonic pole. In pole cells, it becomes associated with nuclear bodies within, and nuage around, the nucleus. Immunoreactivity remains associated with cells of the germ line throughout the life cycle of both males and females. This antibody recognizes a 72-74 X 10^(3) Mr protein and is useful both as a pole lineage marker and in biochemical studies of polar granules

Trypanosoma equiperdum in the horse : a neglected threat?

Dourine is a contagious disease caused by Trypanosoma equiperdum that is transmitted directly from animal to animal during coitus. Dourine is known as an important disease in many countries, and it threatens equidae worldwide. It is reported to be widespread in South America, Eastern Europe, Russia, Mongolia, Namibia and Ethiopia. The disease can be carried to various parts of the world through the transportation of infected animals and semen. Since knowledge of the prepatent infectiousness of a recently infected animal is lacking, introduction of the disease is in principle an ever-present threat. Definitive diagnosis depends on the identification of the parasite by means of direct microscopy. This is rarely possible in practice and therefore, diagnosis in the field is based on the observation of typical clinical signs, together with serological tests. This paper is an endeavour to review briefly and compile information on the appearance and importance of Dourine in terms of its epidemiological and clinical features, as well as on its diagnosis, treatment and prognosis

Critical Dynamics of a Two-dimensional Superfluid near a Non-Thermal Fixed Point

Critical dynamics of an ultracold Bose gas far from equilibrium is studied in two spatial dimensions. Superfluid turbulence is created by quenching the equilibrium state close to zero temperature. Instead of immediately re-thermalizing, the system approaches a meta-stable transient state, characterized as a non-thermal fixed point. A focus is set on the vortex density and vortex-antivortex correlations which characterize the evolution towards the non-thermal fixed point and the departure to final (quasi-)condensation. Two distinct power-law regimes in the vortex-density decay are found and discussed in terms of a vortex binding-unbinding transition and a kinetic description of vortex scattering. A possible relation to decaying turbulence in classical fluids is pointed out. By comparing the results to equilibrium studies of a two-dimensional Bose gas, an intuitive understanding of the location of the non-thermal fixed point in a reduced phase space is developed.Comment: 11 pages, 13 figures; PRA versio

Pressure-induced changes in the optical properties of quasi-one-dimensional β\beta-Na0.33_{0.33}V2_2O5_5

The pressure-induced changes in the optical properties of $\beta$-Na$_{0.33}$V$_2$O$_5$ single crystals at room temperature were studied by polarization-dependent Raman and far-infrared reflectivity measurements under high pressure. From the changes in the Raman- and infrared-active phonon modes in the pressure range 9 - 12 GPa a transfer of charge between the different V sites can be inferred. The importance of electron-phonon coupling in the low-pressure regime is discussed.Comment: 7 pages, 5 figure

Controlled epitaxial graphene growth within amorphous carbon corrals

Structured growth of high quality graphene is necessary for technological development of carbon based electronics. Specifically, control of the bunching and placement of surface steps under epitaxial graphene on SiC is an important consideration for graphene device production. We demonstrate lithographically patterned evaporated amorphous carbon corrals as a method to pin SiC surface steps. Evaporated amorphous carbon is an ideal step-flow barrier on SiC due to its chemical compatibility with graphene growth and its structural stability at high temperatures, as well as its patternability. The amorphous carbon is deposited in vacuum on SiC prior to graphene growth. In the graphene furnace at temperatures above 1200$^\circ$C, mobile SiC steps accumulate at these amorphous carbon barriers, forming an aligned step free region for graphene growth at temperatures above 1330$^\circ$C. AFM imaging and Raman spectroscopy support the formation of quality step-free graphene sheets grown on SiC with the step morphology aligned to the carbon grid

Effects of CMB temperature uncertainties on cosmological parameter estimation

We estimate the effect of the experimental uncertainty in the measurement of the temperature of the cosmic microwave background (CMB) on the extraction of cosmological parameters from future CMB surveys. We find that even for an ideal experiment limited only by cosmic variance up to l = 2500 for both the temperature and polarisation measurements, the projected cosmological parameter errors are remarkably robust against the uncertainty of 1 mK in the FIRAS instrument's CMB temperature monopole measurement. The maximum degradation in sensitivity is 20%, for the baryon density estimate, relative to the case in which the monopole is known infinitely well. While this degradation is acceptable, we note that reducing the uncertainty in the current temperature measurement by a factor of five will bring it down to the per cent level. We also estimate the effect of the uncertainty in the dipole temperature measurement. Assuming the overall calibration of the data to be dominated by the dipole error of 0.2% from FIRAS, the sensitivity degradation is insignificant and does not exceed 10% in any parameter direction.Comment: 12 pages, 2 figures, uses iopart.cls, v2: added discussion of CMB dipole uncertainty, version accepted by JCA

Nonequilibrium Kondo Effect in a Quantum Dot Coupled to Ferromagnetic Leads

We study the Kondo effect in the electron transport through a quantum dot coupled to ferromagnetic leads, using a real-time diagrammatic technique which provides a systematic description of the nonequilibrium dynamics of a system with strong local electron correlations. We evaluate the theory in an extension of the `resonant tunneling approximation', introduced earlier, by introducing the self-energy of the off-diagonal component of the reduced propagator in spin space. In this way we develop a charge and spin conserving approximation that accounts not only for Kondo correlations but also for the spin splitting and spin accumulation out of equilibrium. We show that the Kondo resonances, split by the applied bias voltage, may be spin polarized. A left-right asymmetry in the coupling strength and/or spin polarization of the electrodes significantly affects both the spin accumulation and the weight of the split Kondo resonances out of equilibrium. The effects are observable in the nonlinear differential conductance. We also discuss the influence of decoherence on the Kondo resonance in the frame of the real-time formulation.Comment: 13 pages, 13 figure

Ionization of clusters in strong X-ray laser pulses

The effect of intense X-ray laser interaction on argon clusters is studied theoretically with a mixed quantum/classical approach. In comparison to a single atom we find that ionization of the cluster is suppressed, which is in striking contrast to the observed behavior of rare-gas clusters in intense optical laser pulses. We have identified two effects responsible for this phenomenon: A high space charge of the cluster in combination with a small quiver amplitude and delocalization of electrons in the cluster. We elucidate their impact for different field strengths and cluster sizes.Comment: 4 pages, 4 figure

A stochastic perturbation of inviscid flows

We prove existence and regularity of the stochastic flows used in the stochastic Lagrangian formulation of the incompressible Navier-Stokes equations (with periodic boundary conditions), and consequently obtain a \holderspace{k}{\alpha} local existence result for the Navier-Stokes equations. Our estimates are independent of viscosity, allowing us to consider the inviscid limit. We show that as $\nu \to 0$, solutions of the stochastic Lagrangian formulation (with periodic boundary conditions) converge to solutions of the Euler equations at the rate of $O(\sqrt{\nu t})$.Comment: 13 pages, no figures

Experimental joint signal-idler quasi-distributions and photon-number statistics for mesoscopic twin beams

Joint signal-idler photoelectron distributions of twin beams containing several tens of photons per mode have been measured recently. Exploiting a microscopic quantum theory for joint quasi-distributions in parametric down-conversion developed earlier we characterize properties of twin beams in terms of quasi-distributions using experimental data. Negative values as well as oscillating behaviour in quantum region are characteristic for the subsequently determined joint signal-idler quasi-distributions of integrated intensities. Also the conditional and difference photon-number distributions are shown to be sub-Poissonian and sub-shot-noise, respectively.Comment: 7 pages, 6 figure