16,335 research outputs found
U-Spin Tests of the Standard Model and New Physics
Within the standard model, a relation involving branching ratios and direct
CP asymmetries holds for the B-decay pairs that are related by U-spin. The
violation of this relation indicates new physics (NP). In this paper, we assume
that the NP affects only the Delta S = 1 decays, and show that the NP operators
are generally the same as those appearing in B -> pi K decays. The fit to the
latest B -> pi K data shows that only one NP operator is sizeable. As a
consequence, the relation is expected to be violated for only one decay pair:
Bd -> K0 pi0 and Bs -> Kbar0 pi0.Comment: 12 pages, latex, no figures. References changed to follow MPL
guidelines; info added about U-spin breaking and small NP strong phases;
discussion added about final-state pi-K rescattering; analysis and
conclusions unaltere
Viscous dissipative effects in isotropic brane cosmology
We consider the dynamics of a viscous cosmological fluid in the generalized
Randall-Sundrum model for an isotropic brane. To describe the dissipative
effects we use the Israel-Hiscock-Stewart full causal thermodynamic theory. In
the limiting case of a stiff cosmological fluid with pressure equal to the
energy density, the general solution of the field equations can be obtained in
an exact parametric form for a cosmological fluid with constant bulk viscosity
and with a bulk viscosity coefficient proportional to the square root of the
energy density, respectively. The obtained solutions describe generally
non-inflationary brane worlds, starting from a singular state. During this
phase of evolution the comoving entropy of the Universe is an increasing
function of time, and thus a large amount of entropy is created in the brane
world due to viscous dissipative processes.Comment: 15 pages, 11 figure
Conflation of short identity-by-descent segments bias their inferred length distribution
Identity-by-descent (IBD) is a fundamental concept in genetics with many
applications. In a common definition, two haplotypes are said to contain an IBD
segment if they share a segment that is inherited from a recent shared common
ancestor without intervening recombination. Long IBD segments (> 1cM) can be
efficiently detected by a number of algorithms using high-density SNP array
data from a population sample. However, these approaches detect IBD based on
contiguous segments of identity-by-state, and such segments may exist due to
the conflation of smaller, nearby IBD segments. We quantified this effect using
coalescent simulations, finding that nearly 40% of inferred segments 1-2cM long
are results of conflations of two or more shorter segments, under demographic
scenarios typical for modern humans. This biases the inferred IBD segment
length distribution, and so can affect downstream inferences. We observed this
conflation effect universally across different IBD detection programs and human
demographic histories, and found inference of segments longer than 2cM to be
much more reliable (less than 5% conflation rate). As an example of how this
can negatively affect downstream analyses, we present and analyze a novel
estimator of the de novo mutation rate using IBD segments, and demonstrate that
the biased length distribution of the IBD segments due to conflation can lead
to inflated estimates if the conflation is not modeled. Understanding the
conflation effect in detail will make its correction in future methods more
tractable
The Impact of U.S. Trade Law on Government Policy Making in the Republic of China
Since President Reagan signed the Omnibus Trade Act on August 23, 1988, the U.S. government has completed a series of investigations according to the provisions of the Act. Consultations aimed at forcing its trading partners to adjust their trade- policies which are regarded as unfair to U.S. trade have also been held in the past ten months or so. Being one of the most important trading partners of the U.S. – both in terms of its overall trade volume and its surplus with the U.S. – the Republic of China on Taiwan (ROC) seems to have become a target of retaliatory measures implied in the Act. During the period from August of last year to this date, the U.S. has consulted intensively with the ROC on various trade issues. The possible implementation of the Trade Act seemed to have been implied throughout most of the talks. Therefore, the results of consultations often had an impact on the trade policy of the ROC. On the other hand, the adjustments that the ROC has made to cope with the new environment of the world economy have also been instrumental in formulating the ROC\u27s new trade policy. All in all, the ROC\u27s trade policy has been transformed, over the past twenty-five years, from an export-oriented one to the present one which encourages imports with a view toward balancing the two-way trade. In order to carry out this policy, the ROC has adopted a series of measures not only to expedite the liberalization of its market, but also to increase its purchases from the U.S
Assessment of the NPP VIIRS RVS for the Thermal Emissive Bands Using the First Pitch Maneuver Observations
The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key sensor carried on Suomi NPP (National Polar-orbiting Partnership) satellite (http://npp.gsfc.nasa.gov/viirs.html) (launched in October 2011). VIIRS sensor design draws on heritage instruments including AVHRR, OLS, SeaWiFS and MODIS. It has on-board calibration components including a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) for the reflective solar bands (RSB), a V-groove blackbody for the thermal emissive bands (TEB), and a space view (SV) port for background subtraction. These on-board calibrators are located at fixed scan angles. The VIIRS response versus scan angle (RVS) was characterized prelaunch in lab ambient conditions and is currently used to characterize the on-orbit response for all scan angles relative to the calibrator scan angle (SD for RSB and blackbody for TEB). Since the RVS is vitally important to the quality of calibrated radiance products, several independent studies were performed to analyze the prelaunch RVS measurement data. A spacecraft level pitch maneuver was scheduled during the first three months of intensive Cal/Val. The NPP pitch maneuver provided a rare opportunity for VIIRS to make observations of deep space over the entire range of scan angles, which can be used to characterize the TEB RVS. This study will provide our analysis of the pitch maneuver data and assessment of the derived TEB RVS. A comparison between the RVS determined by the pitch maneuver observations and prelaunch lab tests will be conducted for each band, detector, and half angle mirror (HAM) sid
Photorealistic 3D Model Reconstruction based on the Consistency of Object Surface Reflectance Measured by the Voxel Mask
Rotational Perturbations of Friedmann-Robertson-Walker Type Brane-World Cosmological Models
First order rotational perturbations of the Friedmann-Robertson-Walker metric
are considered in the framework of the brane-world cosmological models. A
rotation equation, relating the perturbations of the metric tensor to the
angular velocity of the matter on the brane is derived under the assumption of
slow rotation. The mathematical structure of the rotation equation imposes
strong restrictions on the temporal and spatial dependence of the brane matter
angular velocity. The study of the integrable cases of the rotation equation
leads to three distinct models, which are considered in detail. As a general
result we find that, similarly to the general relativistic case, the rotational
perturbations decay due to the expansion of the matter on the brane. One of the
obtained consistency conditions leads to a particular, purely inflationary
brane-world cosmological model, with the cosmological fluid obeying a
non-linear barotropic equation of state.Comment: 14 pages, 5 figures, REVTEX
Dielectric properties of interfacial water and distribution of ions at the air/water interface
This thesis covers several topics, including (i) the vibrational coupling of the H-O-H bending mode of bulk water, (ii) including the dielectric properties of interfacial water on sub-nanometer length scales, and the influence of interfacial dielectric on the surface water spectrum, and (iii) the distribution of ions at the air/water interface. Here, we employ the heterodyne-detected vibrational sum-frequency generation (HD-SFG) spectroscopy and polarization-resolved pump-probe IR measurement for studying the surface and bulk water, respectively. For bulk water, compared to O-H stretch vibration, information on energy transfer pathways from the H-O-H bending mode is lacking. Here, we reveal that the bend-to-bend coupling is much weaker than the stretch-to-stretch coupling. We find that the intramolecular bend-to-libration energy transfer (≈ 200 fs) takes place much faster than the intermolecular bend-to-bend coupling (≈ 1 ps). For water surface, HD-VSFG allows one to study the microscopic structure and dielectric environment of the interface. This so-called Fresnel factor correction can change the line shapes and absolute amplitudes of SFG spectra substantially. By comparing the experimental and simulated SFG spectra, we resolve the interfacial dielectric function with the angstrom-level depth resolution. Furthermore, we find that the impact of the vibrational coupling of water surface is largely suppressed due to the Fresnel factor. Next, we investigate the microscopic structure of electric double layer (EDL) created by the differential distribution of anions and cations at the interface. We find that small ions will not deplete from water surface but located in a subsurface region leading to a surface stratification
Spin Information from Vector-Meson Decay in Photoproduction
For the photoproduction of vector mesons, all single and double spin
observables involving vector meson two-body decays are defined consistently in
the center of mass. These definitions yield a procedure for
extracting physically meaningful single and double spin observables that are
subject to known rules concerning their angle and energy evolution. As part of
this analysis, we show that measuring the two-meson decay of a photoproduced
or does not determine the vector meson's vector polarization, but
only its tensor polarization. The vector meson decay into lepton pairs is also
insensitive to the vector meson's vector polarization, unless one measures the
spin of one of the leptons. Similar results are found for all double spin
observables which involve observation of vector meson decay. To access the
vector meson's vector polarization, one therefore needs to either measure the
spin of the decay leptons, make an analysis of the background interference
effects or relate the vector meson's vector polarization to other accessible
spin observables.Comment: 22 pages, 3 figure
- …