691 research outputs found
Potential for an Arctic-breeding migratory bird to adjust spring migration phenology to Arctic amplification
Shapes, contact angles, and line tensions of droplets on cylinders
Using an interface displacement model we calculate the shapes of
nanometer-size liquid droplets on homogeneous cylindrical surfaces. We
determine effective contact angles and line tensions, the latter defined as
excess free energies per unit length associated with the two contact lines at
the ends of the droplet. The dependences of these quantities on the cylinder
radius and on the volume of the droplets are analyzed.Comment: 26 pages, RevTeX, 10 Figure
Enhanced Mucosal Antibody Production and Protection against Respiratory Infections Following an Orally Administered Bacterial Extract
Secondary bacterial infections following influenza infection are a pressing problem facing respiratory medicine. Although antibiotic treatment has been highly successful over recent decades, fatalities due to secondary bacterial infections remain one of the leading causes of death associated with influenza. We have assessed whether administration of a bacterial extract alone is sufficient to potentiate immune responses and protect against primary infection with influenza, and secondary infections with either Streptococcus pneumoniae or Klebsiella pneumoniae in mice. We show that oral administration with the bacterial extract, OM-85, leads to a maturation of dendritic cells and B-cells characterized by increases in MHC II, CD86, and CD40, and a reduction in ICOSL. Improved immune responsiveness against influenza virus reduced the threshold of susceptibility to secondary bacterial infections, and thus protected the mice. The protection was associated with enhanced polyclonal B-cell activation and release of antibodies that were effective at neutralizing the virus. Taken together, these data show that oral administration of bacterial extracts provides sufficient mucosal immune stimulation to protect mice against a respiratory tract viral infection and associated sequelae
Observation of the Holstein shift in high superconductors with thermal modulation reflectometry
We use the experimental technique of thermal modulation reflectometry to
study the relatively small temperature dependence of the optical conductivity
of superconductors. Due to a large cancellation of systematic errors, this
technique is shown to a be very sensitive probe of small changes in
reflectivity. We analyze thermal modulation reflection spectra of single
crystals and epitaxially grown thin films of YBaCuO and
obtain the function in the normal state, as well as
the superconductivity induced changes in reflectivity. We present detailed
model calculations, based on the Eliashberg-Migdal extension of the BCS model,
which show good qualitative and quantitative agreement with the experimental
spectra. VSGD.93.12.thComment: 6 pages, figures on request. Revtex, version 2, Materials Science
Center Internal Report Number VSGD.93.12.t
The Localization Transition of the Two-Dimensional Lorentz Model
We investigate the dynamics of a single tracer particle performing Brownian
motion in a two-dimensional course of randomly distributed hard obstacles. At a
certain critical obstacle density, the motion of the tracer becomes anomalous
over many decades in time, which is rationalized in terms of an underlying
percolation transition of the void space. In the vicinity of this critical
density the dynamics follows the anomalous one up to a crossover time scale
where the motion becomes either diffusive or localized. We analyze the scaling
behavior of the time-dependent diffusion coefficient D(t) including corrections
to scaling. Away from the critical density, D(t) exhibits universal
hydrodynamic long-time tails both in the diffusive as well as in the localized
phase.Comment: 13 pages, 7 figures
Lattice Study of the Decay B^0-bar -> rho^+ l^- nu_l-bar: Model-Independent Determination of |V_{ub}|
We present results of a lattice computation of the vector and axial-vector
current matrix elements relevant for the semileptonic decay B^0-bar -> rho^+
l^- nu_l-bar. The computations are performed in the quenched approximation of
lattice QCD on a 24^3 x 48 lattice at beta = 6.2, using an O(a) improved
fermionic action. Our principal result is for the differential decay rate,
dGamma/dq^2, for the decay B^0-bar -> rho^+ l^- nu_l-bar in a region beyond the
charm threshold, allowing a model-independent extraction of |V_{ub}| from
experimental measurements. Heavy quark symmetry relations between radiative and
semileptonic decays of B-bar mesons into light vector mesons are also
discussed.Comment: 22 pages LaTeX-209 (dependent on settings in a4.sty), 23 PostScript
figures included with epsf.sty. Complete PostScript file including figures
available at http://wwwhep.phys.soton.ac.uk/hepwww/papers/shep9518
Enhancement of low-mass dileptons in heavy-ion collisions
Using a relativistic transport model for the expansion stage of S+Au
collisions at 200 GeV/nucleon, we show that the recently observed enhancement
of low-mass dileptons by the CERES collaboration can be explained by the
decrease of vector meson masses in hot and dense hadronic matter.Comment: 12 pages, RevTeX, 3 figures available from [email protected]
Strangeness nuclear physics: a critical review on selected topics
Selected topics in strangeness nuclear physics are critically reviewed. This
includes production, structure and weak decay of --Hypernuclei, the
nuclear interaction and the possible existence of bound
states in nuclei. Perspectives for future studies on these issues are also
outlined.Comment: 63 pages, 51 figures, accepted for publication on European Physical
Journal
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