57,184 research outputs found
Double transverse spin asymmetry in the Drell-Yan process from Sivers functions
We show that the transverse double spin asymmetry (DSA) in the Drell-Yan
process contributed only from the Sivers functions can be picked out by the
weighting function
.
The asymmetry is proportional to the product of two Sivers functions from each
hadron . Using two sets of Sivers
functions extracted from the semi-inclusive deeply elastic scattering data at
HERMES, we estimate this asymmetry in the
Drell-Yan process which is possible to be performed in HESR at GSI. The
prediction of DSA in the Drell-Yan process contributed by the function
g_{1T}(x,\Vec k_T^2), which can be extracted by the weighting function
,
is also given at GSI.Comment: 6 latex pages, 2 figures, to appear in PR
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Privacy-Preserving iVector-Based Speaker Verification
This paper introduces an efficient algorithm to develop a privacy-preserving voice verification based on iVector and linear discriminant analysis techniques. This research considers a scenario in which users enrol their voice biometric to access different services (i.e., banking). Once enrolment is completed, users can verify themselves using their voice print instead of alphanumeric passwords. Since a voice print is unique for everyone, storing it with a third-party server raises several privacy concerns. To address this challenge, this paper proposes a novel technique based on randomization to carry out voice authentication, which allows the user to enrol and verify their voice in the randomized domain. To achieve this, the iVector-based voice verification technique has been redesigned to work on the randomized domain. The proposed algorithm is validated using a well-known speech dataset. The proposed algorithm neither compromises the authentication accuracy nor adds additional complexity due to the randomization operations
The Arches Cluster: Extended Structure and Tidal Radius
At a projected distance of ~26 pc from Sgr A*, the Arches cluster provides
insight to star formation in the extreme Galactic Center (GC) environment.
Despite its importance, many key properties such as the cluster's internal
structure and orbital history are not well known. We present an astrometric and
photometric study of the outer region of the Arches cluster (R > 6.25") using
HST WFC3IR. Using proper motions we calculate membership probabilities for
stars down to F153M = 20 mag (~2.5 M_sun) over a 120" x 120" field of view, an
area 144 times larger than previous astrometric studies of the cluster. We
construct the radial profile of the Arches to a radius of 75" (~3 pc at 8 kpc),
which can be well described by a single power law. From this profile we place a
3-sigma lower limit of 2.8 pc on the observed tidal radius, which is larger
than the predicted tidal radius (1 - 2.5 pc). Evidence of mass segregation is
observed throughout the cluster and no tidal tail structures are apparent along
the orbital path. The absence of breaks in the profile suggests that the Arches
has not likely experienced its closest approach to the GC between ~0.2 - 1 Myr
ago. If accurate, this constraint indicates that the cluster is on a prograde
orbit and is located front of the sky plane that intersects Sgr A*. However,
further simulations of clusters in the GC potential are required to interpret
the observed profile with more confidence.Comment: 24 pages (17-page main text, 7-page appendix), 24 figures, accepted
to Ap
Climate dynamics experiments using a GCM simulations
The study of surface-atmosphere interactions has begun with studies of the effect of altering the ocean and land boundaries. A ten year simulation of global climate using observed sea surface temperature anomalies has begun using the NCAR Community Climate Model (CCM1). The results for low resolution (R15) were computed for the first 8 years of the simulation and compared with the observed surface temperatures and the MSU (Microwave Sounding Unit) observations of tropospheric temperature. A simulation at higher resolution (T42) was done to ascertain the effect of interactive soil hydrology on the system response to an El Nino sea surface temperature perturbation. Initial analysis of this simulations was completed
On the discrete spectrum of quantum layers
Consider a quantum particle trapped between a curved layer of constant width
built over a complete, non-compact, smooth surface embedded in
. We assume that the surface is asymptotically flat in the sense
that the second fundamental form vanishes at infinity, and that the surface is
not totally geodesic. This geometric setting is known as a quantum layer. We
consider the quantum particle to be governed by the Dirichlet Laplacian as
Hamiltonian. Our work concerns the existence of bound states with energy
beneath the essential spectrum, which implies the existence of discrete
spectrum. We first prove that if the Gauss curvature is integrable, and the
surface is weakly -parabolic, then the discrete spectrum is non-empty.
This result implies that if the total Gauss curvature is non-positive, then the
discrete spectrum is non-empty. We next prove that if the Gauss curvature is
non-negative, then the discrete spectrum is non-empty. Finally, we prove that
if the surface is parabolic, then the discrete spectrum is non-empty if the
layer is sufficiently thin.Comment: Clarifications and corrections to previous version, conjecture from
previous version is proven here (Theorem 1.5), additional references include
The Quintuplet Cluster: Extended Structure and Tidal Radius
The Quintuplet star cluster is one of only three known young ( Myr)
massive (M M) clusters within pc of the Galactic
Center. In order to explore star cluster formation and evolution in this
extreme environment, we analyze the Quintuplet's dynamical structure. Using the
HST WFC3-IR instrument, we take astrometric and photometric observations of the
Quintuplet covering a field-of-view, which is times
larger than those of previous proper motion studies of the Quintuplet. We
generate a catalog of the Quintuplet region with multi-band, near-infrared
photometry, proper motions, and cluster membership probabilities for
stars. We present the radial density profile of candidate Quintuplet
cluster members with M out to pc from the cluster
center. A lower limit of pc is placed on the tidal radius,
indicating the lack of a tidal truncation within this radius range. Only weak
evidence for mass segregation is found, in contrast to the strong mass
segregation found in the Arches cluster, a second and slightly younger massive
cluster near the Galactic Center. It is possible that tidal stripping hampers a
mass segregation signature, though we find no evidence of spatial asymmetry.
Assuming that the Arches and Quintuplet formed with comparable extent, our
measurement of the Quintuplet's comparatively large core radius of
pc provides strong empirical evidence that young massive
clusters in the Galactic Center dissolve on a several Myr timescale.Comment: 25 pages (21-page main text, 4-page appendix), 18 figures, submitted
to Ap
Measuring the energy landscape roughness and the transition state location of biomolecules using single molecule mechanical unfolding experiments
Single molecule mechanical unfolding experiments are beginning to provide
profiles of the complex energy landscape of biomolecules. In order to obtain
reliable estimates of the energy landscape characteristics it is necessary to
combine the experimental measurements with sound theoretical models and
simulations. Here, we show how by using temperature as a variable in mechanical
unfolding of biomolecules in laser optical tweezer or AFM experiments the
roughness of the energy landscape can be measured without making any
assumptions about the underlying reaction oordinate. The efficacy of the
formalism is illustrated by reviewing experimental results that have directly
measured roughness in a protein-protein complex. The roughness model can also
be used to interpret experiments on forced-unfolding of proteins in which
temperature is varied. Estimates of other aspects of the energy landscape such
as free energy barriers or the transition state (TS) locations could depend on
the precise model used to analyze the experimental data. We illustrate the
inherent difficulties in obtaining the transition state location from loading
rate or force-dependent unfolding rates. Because the transition state moves as
the force or the loading rate is varied it is in general difficult to invert
the experimental data unless the curvature at the top of the one dimensional
free energy profile is large, i.e the barrier is sharp. The independence of the
TS location on force holds good only for brittle or hard biomolecules whereas
the TS location changes considerably if the molecule is soft or plastic. We
also comment on the usefulness of extension of the molecule as a surrogate
reaction coordinate especially in the context of force-quench refolding of
proteins and RNA.Comment: 44 pages, 7 figure
The orbital motion of the Quintuplet cluster - a common origin for the Arches and Quintuplet clusters?
We investigate the orbital motion of the Quintuplet cluster near the Galactic
center with the aim of constraining formation scenarios of young, massive star
clusters in nuclear environments. Three epochs of adaptive optics high-angular
resolution imaging with Keck/NIRC2 and VLT/NACO were obtained over a time
baseline of 5.8 years, delivering an astrometric accuracy of 0.5-1 mas/yr.
Proper motions were derived in the cluster reference frame and were used to
distinguish cluster members from the majority of field stars. Fitting the
cluster and field proper motion distributions with 2D gaussian models, we
derive the orbital motion of the cluster for the first time. The Quintuplet is
moving with a 2D velocity of 132 +/- 15 km/s with respect to the field along
the Galactic plane, which yields a 3D orbital velocity of 167 +/- 15 km/s when
combined with the previously known radial velocity. From a sample of 119 stars
measured in three epochs, we derive an upper limit to the velocity dispersion
in the core of the Quintuplet cluster of sigma_1D < 10 km/s. Knowledge of the
three velocity components of the Quintuplet allows us to model the cluster
orbit in the potential of the inner Galaxy. Comparing the Quintuplet's orbit
with the Arches orbit, we discuss the possibility that both clusters originated
in the same area of the central molecular zone. [abridged]Comment: 40 pages, 12 figures, accepted for publication in Ap
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