8,292 research outputs found
Testing the Standard Model by precision measurement of the weak charges of quarks
In a global analysis of the latest parity-violating electron scattering
measurements on nuclear targets, we demonstrate a significant improvement in
the experimental knowledge of the weak neutral-current lepton-quark
interactions at low energy. The precision of this new result, combined with
earlier atomic parity-violation measurements, places tight constraints on the
size of possible contributions from physics beyond the Standard Model.
Consequently, this result improves the lower-bound on the scale of relevant new
physics to ~1 TeV.Comment: 4 pages, 3 figures; v2: further details on extraction of electroweak
parameters, new figur
Grassland Research: Goals for the Future
Our goal as scientists must be to provide sufficient food for the world’s population, while returning sufficient income for effort to the food producer. It has been established elsewhere in the conference that pasture-based systems can return high milk production per hectare at low input cost, but are limited to highly fertile, temperate regions with evenly dispersed rainfall patterns and moderate maximum and minimum temperatures. There should be two goals of grazing research in the future; to sustain or improve the profitability of current grazing production systems, and to develop plant and animal varieties that allow grazing in currently less suitable environments. Both of these goals can, and will be achieved through improvements in biotechnology
Quantum turbulence at finite temperature: the two-fluids cascade
To model isotropic homogeneous quantum turbulence in superfluid helium, we
have performed Direct Numerical Simulations (DNS) of two fluids (the normal
fluid and the superfluid) coupled by mutual friction. We have found evidence of
strong locking of superfluid and normal fluid along the turbulent cascade, from
the large scale structures where only one fluid is forced down to the vorticity
structures at small scales. We have determined the residual slip velocity
between the two fluids, and, for each fluid, the relative balance of inertial,
viscous and friction forces along the scales. Our calculations show that the
classical relation between energy injection and dissipation scale is not valid
in quantum turbulence, but we have been able to derive a temperature--dependent
superfluid analogous relation. Finally, we discuss our DNS results in terms of
the current understanding of quantum turbulence, including the value of the
effective kinematic viscosity
Morphology and Redshifts of Extremely Red Galaxies in the GOODS/CDFS deep ISAAC field
We present the photometric redshift distribution of a sample of 198 Extremely
Red Galaxies (ERGs) with Ks3.92 (Vega), selected by Roche et al.
in 50.4 sq. arcmin of the Chandra Deep Field South (CDFS). The sample has been
obtained using ISAAC-VLT and ACS-HST GOODS public data. We also show the
results of a morphological study of the 72 brightest ERGs in the z band (z<25,
AB).Comment: 2 pages, 2 figures. To appear in the proceedings of the ESO/USM/MPE
Workshop "Multiwavelength Mapping of Galaxy Formation and Evolution", Venice,
October 13-16, 200
The X-ray Transient XTE J2012+381
We present optical and infrared observations of the soft X-ray transient
(SXT) XTE J2012+381 and identify the optical counterpart with a faint red star
heavily blended with a brighter foreground star. The fainter star is coincident
with the radio counterpart and appears to show weak H alpha emission and to
have faded between observations. The RXTE/ASM lightcurve of XTE J2012+381 is
unusual for an SXT in that after an extended linear decay, it settled into a
plateau state for about 40 days before undergoing a weak mini-outburst. We
discuss the nature of the object and suggest similarities to long orbital
period SXTs.Comment: 5 pages, 7 postscript figures included, uses mn.sty. Accepted for
publication in MNRA
Vortex density spectrum of quantum turbulence
The fluctuations of the vortex density in a turbulent quantum fluid are
deduced from local second-sound attenuation measurements. These measurements
are performed with a micromachined open-cavity resonator inserted across a flow
of turbulent He-II near 1.6 K. The power spectrum of the measured vortex line
density is compatible with a (-5/3) power law. The physical interpretation,
still open, is discussed.Comment: Submitted to Europhys. Let
Extracting nucleon strange and anapole form factors from world data
The complete world set of parity violating electron scattering data up to
Q^2~0.3 GeV^2 is analysed. We extract the current experimental determination of
the strange electric and magnetic form factors of the proton, as well as the
weak axial form factors of the proton and neutron, at Q^2 = 0.1 GeV^2. Within
experimental uncertainties, we find that the strange form factors are
consistent with zero, as are the anapole contributions to the axial form
factors. Nevertheless, the correlation between the strange and anapole
contributions suggest that there is only a small probability that these form
factors all vanish simultaneously.Comment: 4 pages, 3 figs; v2: version to appear in PR
Effects of magnetic field and disorder on electronic properties of Carbon Nanotubes
Electronic properties of metallic and semiconducting carbon nanotubes are
investigated in presence of magnetic field perpendicular to the CN-axis, and
disorder introduced through energy site randomness. The magnetic field field is
shown to induce a metal-insulator transition (MIT) in absence of disorder, and
surprisingly disorder does not affect significantly the MIT. These results may
find confirmation through tunneling experimentsComment: 4 pages, 6 figures. Phys. Rev. B (in press
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