836 research outputs found
Domain Adaptation for Statistical Classifiers
The most basic assumption used in statistical learning theory is that
training data and test data are drawn from the same underlying distribution.
Unfortunately, in many applications, the "in-domain" test data is drawn from a
distribution that is related, but not identical, to the "out-of-domain"
distribution of the training data. We consider the common case in which labeled
out-of-domain data is plentiful, but labeled in-domain data is scarce. We
introduce a statistical formulation of this problem in terms of a simple
mixture model and present an instantiation of this framework to maximum entropy
classifiers and their linear chain counterparts. We present efficient inference
algorithms for this special case based on the technique of conditional
expectation maximization. Our experimental results show that our approach leads
to improved performance on three real world tasks on four different data sets
from the natural language processing domain
4U 1626-67 as seen by Suzaku before and after the 2008 torque reversal
Aims. The accretion-powered pulsar 4U 1626-67 experienced a new torque
reversal at the beginning of 2008, after about 18 years of steadily spinning
down. The main goal of the present work is to study this recent torque reversal
that occurred in 2008 February.
Methods. We present a spectral analysis of this source using two pointed
observations performed by Suzaku in 2006 March and in 2010 September.
Results. We confirm with Suzaku the presence of a strong emission-line
complex centered on 1 keV, with the strongest line being the hydrogen-like Ne
Ly-alpha at 1.025(3) keV. We were able to resolve this complex with up to seven
emission lines. A dramatic increase of the intensity of the Ne Ly-alpha line
after the 2008 torque reversal occurred, with the equivalent width of this line
reaching almost the same value measured by ASCA in 1993. We also report on the
detection of a cyclotron line feature centered at ~37 keV. In spite of the fact
that an increase of the X-ray luminosity (0.5-100 keV) of a factor of ~2.8
occurred between these two observations, no significant change in the energy of
the cyclotron line feature was observed. However, the intensity of the ~1 keV
line complex increased by an overall factor of ~8.
Conclusions. Our results favor a scenario in which the neutron star in 4U
1626-67 accretes material from a geometrically thin disk during both the
spin-up and spin-down phases.Comment: 7 pages, 5 figures and 2 tables. Accepted in A&
Thermal Benchmark and Power Benchmark Software
Power consumption and heat dissipation become key elements in the field of
high-end integrated circuits, especially those used in mobile and high-speed
applications, due to their increase of transistor count and clock frequencies.
Dynamic thermal management strategies have been proposed and implemented in
order to mitigate heat dissipation. However, there is a lack of a tool that can
be used to evaluate DTM strategies and thermal response of real life systems.
Therefore, in this paper we introduce and define the concepts of thermal
benchmark software and power benchmark software as a software application for
run-time system level thermal and power characterizationComment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Spectral and Timing Nature of the Symbiotic X-ray Binary 4U 1954+319: The Slowest Rotating Neutron Star in an X-ray Binary System
The symbiotic X-ray binary 4U 1954+319 is a rare system hosting a peculiar
neutron star (NS) and an M-type optical companion. Its ~5.4h NS spin period is
the longest among all known accretion-powered pulsars and exhibited large (~7%)
fluctuations over 8 years. A spin trend transition was detected with Swift/BAT
around an X-ray brightening in 2012. The source was in quiescent and bright
states before and after this outburst based on 60 ks Suzaku observations in
2011 and 2012. The observed continuum is well described by a Comptonized model
with the addition of a narrow 6.4 keV Fe Kalpha line during the outburst.
Spectral similarities to slowly rotating pulsars in high-mass X-ray binaries,
its high pulsed fraction (~60-80%), and the location in the Corbet diagram
favor high B-field (>~1e+12 G) over a weak field as in low-mass X-ray binaries.
The observed low X-ray luminosity (1e+33-1e+35 erg/s), probable wide orbit, and
a slow stellar wind of this SyXB make quasi-spherical accretion in the subsonic
settling regime a plausible model. Assuming a ~1e+13 G NS, this scheme can
explain the ~5.4 h equilibrium rotation without employing the magnetar-like
field (~1e+16 G) required in the disk accretion case. The time-scales of
multiple irregular flares (~50 s) can also be attributed to the free-fall time
from the Alfven shell for a ~1e+13 G field. A physical interpretation of SyXBs
beyond the canonical binary classifications is discussed.Comment: 20 pages, 18 figures, 3 tables, accepted for publication in the
Astrophysical Journa
Investigation of the Critical Behavior of the Critical Point of the Z2 Gauge Lattice
We investigate, through Monte-Carlo simulations, the nature of the second
order point in a (Bosonic) + gauge theory in four dimensions.
Detailed analysis of the critical exponents point to the Ising universality
class. Relevancy to extended models and possible Non-Gaussian behavior is
discussed.Comment: 4 pages, 6 figures, LaTe
Using Synchronic and Diachronic Relations for Summarizing Multiple Documents Describing Evolving Events
In this paper we present a fresh look at the problem of summarizing evolving
events from multiple sources. After a discussion concerning the nature of
evolving events we introduce a distinction between linearly and non-linearly
evolving events. We present then a general methodology for the automatic
creation of summaries from evolving events. At its heart lie the notions of
Synchronic and Diachronic cross-document Relations (SDRs), whose aim is the
identification of similarities and differences between sources, from a
synchronical and diachronical perspective. SDRs do not connect documents or
textual elements found therein, but structures one might call messages.
Applying this methodology will yield a set of messages and relations, SDRs,
connecting them, that is a graph which we call grid. We will show how such a
grid can be considered as the starting point of a Natural Language Generation
System. The methodology is evaluated in two case-studies, one for linearly
evolving events (descriptions of football matches) and another one for
non-linearly evolving events (terrorist incidents involving hostages). In both
cases we evaluate the results produced by our computational systems.Comment: 45 pages, 6 figures. To appear in the Journal of Intelligent
Information System
Cluster Algorithm for a Solid-On-Solid Model with Constraints
We adapt the VMR (valleys-to-mountains reflections) algorithm, originally
devised by us for simulations of SOS models, to the BCSOS model. It is the
first time that a cluster algorithm is used for a model with constraints. The
performance of this new algorithm is studied in detail in both phases of the
model, including a finite size scaling analysis of the autocorrelations.Comment: 10 pages, 3 figures appended as ps-file
Mutation of daf‐2 extends lifespan via tissue‐specific effectors that suppress distinct life‐limiting pathologies
In aging Caenorhabditis elegans, as in higher organisms, there is more than one cause of death. C. elegans exhibit early death with a swollen, infected pharynx (P death), and later death with pharyngeal atrophy (p death). Interventions that alter lifespan can differentially affect frequency and timing of each type of death, generating complex survival curve shapes. Here, we use mortality deconvolution analysis to investigate how reduction of insulin/IGF-1 signaling (IIS), which increases lifespan (the Age phenotype), affects different forms of death. All daf-2 insulin/IGF-1 receptor mutants exhibit increased lifespan in the p subpopulation (p Age), while pleiotropic class 2 daf-2 mutants show an additional marked reduction in P death frequency. The latter is promoted by pharyngeal expression of the IIS-regulated DAF-16 FOXO transcription factor, and at higher temperature by reduced pharyngeal pumping rate. Pharyngeal DAF-16 also promotes p Age in class 2 daf-2 mutants, revealing a previously unknown role for the pharynx in the regulation of aging. Necropsy analysis of daf-2 interactions with the daf-12 steroid receptor implies that previously described opposing effects of daf-12 on daf-2 longevity are attributable to internal hatching of larvae, rather than complex interactions between insulin/IGF-1 and steroid signaling. These findings support the view that wild-type IIS acts through multiple distinct mechanisms which promote different life-limiting pathologies, each of which contribute to late-life mortality. This study further demonstrates the utility of mortality deconvolution analysis to better understand the genetics of lifespan
Lattice Models
In this paper I construct lattice models with an underlying
superalgebra symmetry. I find new solutions to the graded Yang-Baxter equation.
These {\it trigonometric} -matrices depend on {\it three} continuous
parameters, the spectral parameter, the deformation parameter and the
parameter, , of the superalgebra. It must be emphasized that the
parameter is generic and the parameter does not correspond to the
`nilpotency' parameter of \cite{gs}. The rational limits are given; they also
depend on the parameter and this dependence cannot be rescaled away. I
give the Bethe ansatz solution of the lattice models built from some of these
-matrices, while for other matrices, due to the particular nature of the
representation theory of , I conjecture the result. The parameter
appears as a continuous generalized spin. Finally I briefly discuss the problem
of finding the ground state of these models.Comment: 19 pages, plain LaTeX, no figures. Minor changes (version accepted
for publication
New solutions to the Reflection Equation and the projecting method
New integrable boundary conditions for integrable quantum systems can be
constructed by tuning of scattering phases due to reflection at a boundary and
an adjacent impurity and subsequent projection onto sub-spaces. We illustrate
this mechanism by considering a gl(m<n)-impurity attached to an open
gl(n)-invariant quantum chain and a Kondo spin S coupled to the supersymmetric
t-J model.Comment: Latex2e, no figure
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