24,761 research outputs found
Constraining and Dark Energy with Gamma-Ray Bursts
An relationship with a small
scatter for current -ray burst (GRB) data was recently reported, where
is the beaming-corrected -ray energy and
is the peak energy in the local observer frame. By considering this
relationship for a sample of 12 GRBs with known redshift, peak energy, and
break time of afterglow light curves, we constrain the mass density of the
universe and the nature of dark energy. We find that the mass density
(at the confident level) for a flat
universe with a cosmological constant, and the parameter of an assumed
static dark-energy equation of state ().
Our results are consistent with those from type Ia supernovae. A larger sample
established by the upcoming {\em Swift} satellite is expected to provide
further constraints.Comment: 8 pages including 4 figures, to appear in ApJ Letters, typos
correcte
Relaxed 2-D Principal Component Analysis by Norm for Face Recognition
A relaxed two dimensional principal component analysis (R2DPCA) approach is
proposed for face recognition. Different to the 2DPCA, 2DPCA- and G2DPCA,
the R2DPCA utilizes the label information (if known) of training samples to
calculate a relaxation vector and presents a weight to each subset of training
data. A new relaxed scatter matrix is defined and the computed projection axes
are able to increase the accuracy of face recognition. The optimal -norms
are selected in a reasonable range. Numerical experiments on practical face
databased indicate that the R2DPCA has high generalization ability and can
achieve a higher recognition rate than state-of-the-art methods.Comment: 19 pages, 11 figure
Nuclear charge-exchange excitations in localized covariant density functional theory
The recent progress in the studies of nuclear charge-exchange excitations
with localized covariant density functional theory is briefly presented, by
taking the fine structure of spin-dipole excitations in 16O as an example. It
is shown that the constraints introduced by the Fock terms of the relativistic
Hartree-Fock scheme into the particle-hole residual interactions are
straightforward and robust.Comment: 4 pages, 1 figure, Proceedings of INPC2013, Florence, Italy, 2-7 June
201
Effect of Different Supplement on Degradation of Dry Matter and Fiber of Untreated and Urea Treated Rice Straw in the Rumen of Sheep
The study was conducted to investigate the degradation of dry matter (DM) and neutral detergentfiber (NDF) of urea untreated (URS) and urea treated rice straw (TRS) incubated in the rumen of sheepfed different diet. Three fistulated sheep were fed on urea-treated rice straw basal diet with threesupplemental treatment diets which consisted of control diet (T0) mulberry and molasses; mulberry,rice bran and urea (T1); and rice bran and urea (T2). Either URS or TRS was placed in nylon bags andincubated in the rumen at 0, 8, 16, 24, 48 and 72 hours. Parameters recorded were degradation of DMand NDF, rumen pH, rumen ammonia. The results showed that DM degradability of URS of the diet T1was significantly lower than other diets. Similarly the URS degradability of rumen-insoluble fraction(b) of DM and NDF of T1 diet was significantly lower than those of T0 and T2 diet. DM and NDFdegradability of URS was not affected by diets. The rumen ammonia concentration of T1 and T2 wassignificantly higher than those T0, but still higher than critical ammonia concentration required forrumen microbial synthesis. These results suggest that different supplementations have no significanteffect on DM and NDF degradability of TRS
Comparison of TOMS retrievals and UVMRP measurements of surface spectral UV radiation in the United States
Surface noontime spectral ultraviolet (UV) irradiances during May-September of 2000–2004 from the total ozone mapping spectrometer (TOMS) satellite retrievals are systematically compared with the ground measurements at 27 climatological sites maintained by the USDA UV-B Monitoring and Research Program. The TOMS retrievals are evaluated by two cloud screening methods and local air quality conditions to determine their bias dependencies on spectral bands, cloudiness, aerosol loadings, and air pollution. Under clear-sky conditions, TOMS retrieval biases vary from −3.4% (underestimation) to 23.6% (overestimation). Averaged over all sites, the relative mean biases for 305, 311, 325, and 368 nm are respectively 15.4, 7.9, 7.6, and 7.0% (overestimation). The bias enhancement for 305 nm by approximately twice that of other bands likely results from absorption by gaseous pollutants (SO<sub>2</sub>, O<sub>3</sub>), and aerosols that are not included in the TOMS algorithm. For all bands, strong positive correlations of the TOMS biases are identified with aerosol optical depth, which explains nearly 50% of the variances of TOMS biases. The more restrictive in-situ cloud screening method reduces the biases by 3.4–3.9% averaged over all sites. This suggests that the TOMS biases from the in-situ cloud contamination may account for approximately 25% for 305 nm and 50% for other bands of the total bias. The correlation coefficients between total-sky and clear-sky biases across 27 sites are 0.92, 0.89, 0.83, and 0.78 for 305, 311, 325, and 368 nm, respectively. The results show that the spatial characteristics of the TOMS retrieval biases are systematic, representative of both clear and total-sky conditions
NMR evidence for Friedel-like oscillations in the CuO chains of ortho-II YBaCuO
Nuclear magnetic resonance (NMR) measurements of CuO chains of detwinned
Ortho-II YBaCuO (YBCO6.5) single crystals reveal unusual and
remarkable properties. The chain Cu resonance broadens significantly, but
gradually, on cooling from room temperature. The lineshape and its temperature
dependence are substantially different from that of a conventional spin/charge
density wave (S/CDW) phase transition. Instead, the line broadening is
attributed to small amplitude static spin and charge density oscillations with
spatially varying amplitudes connected with the ends of the finite length
chains. The influence of this CuO chain phenomenon is also clearly manifested
in the plane Cu NMR.Comment: 4 pages, 3 figures, refereed articl
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