45,457 research outputs found
Single-Transverse Spin Asymmetry in Dijet Correlations at Hadron Colliders
We present a phenomenological study of the single-transverse spin asymmetry
in azimuthal correlations of two jets produced nearly "back-to-back" in pp
collisions at RHIC. We properly take into account the initial- and final-state
interactions of partons that can generate this asymmetry in QCD
hard-scattering. Using distribution functions fitted to the existing
single-spin data, we make predictions for various weighted single-spin
asymmetries in dijet correlations that are now readily testable at RHIC.Comment: 14 pages, 2 figure
Reply to "Comment on `Resilience of gated avalanche photodiodes against bright illumination attacks in quantum cryptography'"
This is a Reply to the Comment by Lydersen et al. [arXiv: 1106.3756v1]
Reconstruction from Radon projections and orthogonal expansion on a ball
The relation between Radon transform and orthogonal expansions of a function
on the unit ball in \RR^d is exploited. A compact formula for the partial
sums of the expansion is given in terms of the Radon transform, which leads to
algorithms for image reconstruction from Radon data. The relation between
orthogonal expansion and the singular value decomposition of the Radon
transform is also exploited.Comment: 15 page
Origin of the X-ray Emission in the Nuclei of FR Is
We investigate the X-ray origin in FRIs using the multi-waveband high
resolution data of eight FR I sources, which have very low Eddington ratios. We
fit their multi-waveband spectrum using a coupled accretion-jet model. We find
that X-ray emission in the source with the highest L_X (~1.8*10^-4 L_Edd) is
from the advection-dominated accretion flow (ADAF). Four sources with moderate
L_X(~several*10^-6 L_Edd) are complicated. The X-ray emission of one FR I is
from the jet, and the other three is from the sum of the jet and ADAF. The
X-ray emission in the three least luminous sources (L_X<1.0*10^-6L_Edd) is
dominated by the jet. These results roughly support the predictions of Yuan and
Cui(2005) where they predict that when the X-ray luminosity of the system is
below a critical value, the X-radiation will not be dominated by the emission
from the ADAF any longer, but by the jet. We also find that the accretion rates
in four sources must be higher than the Bondi rates, which implies that other
fuel supply (e.g., stellar winds) inside the Bondi radius should be important.Comment: 6 pages. To published in Journal of Physics, in proceedings of "The
Universe under the Microscope - Astrophysics at High Angular Resolution" (Bad
Honnef, Germany, April 2008), eds. R. Schoedel, A. Eckart, S. Pfalzner, and
E. Ro
Dielectric properties and lattice dynamics of alpha-PbO2-type TiO2: The role of soft phonon modes in pressure-induced phase transition to baddeleyite-type TiO2
Dielectric tensor and lattice dynamics of alpha-PbO2-type TiO2 have been
investigated using the density functional perturbation theory, with a focus on
responses of the vibrational frequencies to pressure. The calculated Raman
spectra under different pressures are in good agreement with available
experimental results and the symmetry assignments of the Raman peaks of
alpha-PbO2-type TiO2 are given for the first time. In addition, we identified
two anomalously IR-active soft phonon modes, B1u and B3u, respectively, around
200 cm-1 which have not been observed in high pressure experiments. Comparison
of the phonon dispersions at 0 and 10 GPa reveals that softening of phonon
modes also occurs for the zone-boundary modes. The B1u and B3u modes play an
important role in transformation from the alpha-PbO2-type phase to baddeleyite
phase. The significant relaxations of the oxygen atoms from the Ti4 plane in
the Ti2O2Ti2 complex of the baddeleyite phase are directly correlated to the
oxygen displacements along the directions given by the eigenvectors of the soft
B1u and B3u modes in the alpha-PbO2-type phase.Comment: 8 pages, 9 figure
First-principles Calculations of Engineered Surface Spin Structures
The engineered spin structures recently built and measured in scanning
tunneling microscope experiments are calculated using density functional
theory. By determining the precise local structure around the surface
impurities, we find the Mn atoms can form molecular structures with the binding
surface, behaving like surface molecular magnets. The spin structures are
confirmed to be antiferromagnetic, and the exchange couplings are calculated
within 8% of the experimental values simply by collinear-spin GGA+U
calculations. We can also explain why the exchange couplings significantly
change with different impurity binding sites from the determined local
structure. The bond polarity is studied by calculating the atomic charges with
and without the Mn adatoms
Star Formation and Dust Extinction Properties of Local Galaxies as seen from AKARI and GALEX
An accurate estimation of the star formation-related properties of galaxies
is crucial for understanding the evolution of galaxies. In galaxies,
ultraviolet (UV) light emitted by recently formed massive stars is attenuated
by dust, which is also produced by star formation (SF) activity, and is
reemitted at mid- and far- infrared (IR) wavelengths. In this study, we
investigate the star formation rate (SFR) and dust extinction using UV and IR
data. We selected local galaxies which are detected at AKARI FIS 90 um and
matched the IRAS IIFSCz 60 um select catalog. We measured FUV and NUV flux
densities from GALEX images. We examined the SF and extinction of Local
galaxies using four bands of AKARI. Then, we calculated FUV and total IR
luminosities, and obtained the SF luminosity, L_{SF}, the total luminosity
related to star formation activity, and the SFR. We find that in most galaxies,
L_{SF} is dominated by L_{dust}. We also find that galaxies with higher SF
activity have a higher fraction of their SF hidden by dust. In fact, the SF of
galaxies with SFRs >20 M_{sun}/yr is almost completely hidden by dust. Our
results boast a significantly higher precision with respect to previously
published works, due to the use of much larger object samples from the AKARI
and GALEX all sky surveys.Comment: 9 pages, 12 figures, accepted for publication in Earth, Planets, and
Space, A few minor corrections, and a reference adde
Avoiding the Detector Blinding Attack on Quantum Cryptography
We show the detector blinding attack by Lydersen et al [1] will be
ineffective on most single photon avalanche photodiodes (APDs) and certainly
ineffective on any detectors that are operated correctly. The attack is only
successful if a redundant resistor is included in series with the APD, or if
the detector discrimination levels are set inappropriately
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