3,434 research outputs found
Local Rademacher complexities
We propose new bounds on the error of learning algorithms in terms of a
data-dependent notion of complexity. The estimates we establish give optimal
rates and are based on a local and empirical version of Rademacher averages, in
the sense that the Rademacher averages are computed from the data, on a subset
of functions with small empirical error. We present some applications to
classification and prediction with convex function classes, and with kernel
classes in particular.Comment: Published at http://dx.doi.org/10.1214/009053605000000282 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org
B006 Effects of losartan in an experimental model of metabolic syndrome
IntroductionA large body of experimental and clinical evidence indicates that some AT1 receptor antagonists may have beneficial metabolic effects in addition to their well-known cardiovascular actions. Whether or not these metabolic effects are related to additional PPARγ agonist activity of some AT1 antagonists is still under debate. Therefore, the aim of the present study was to check the cardiovascular and metabolic effects of losartan lacking any PPAR agonist activity in a suitable experimental model of metabolic syndrome, namely SHHF rats (Spontaneously Hypertensive, Heart Failure). These rats exhibit obesity, hypertension, dyslipidemia and glucose intolerance. They lack leptin receptors. WKY and SH rats were considered as control of SHHF rats.MethodsLosartan was delivered in the drinking water (10mg/kg/day during 3 months) to 12-week-old male rats. Cardiovascular and metabolic parameters were measured at the end of the treatment and compared to those of untreated SHHF rats at the same age. Intravenous glucose tolerance tests (IVGTT) were also performed. Total cholesterol, LDL, HDL, triglycerides and glucose were measured on plasma samples (0,5ml) taken from caudal veins. Blood pressure was measured (right femoral artery) under pentobarbital anaesthesia (60mg/kg, ip).Mean values±SEM are presented. P values < 0.05 were considered significant. Unpaired Student¡¦s t-tests were used for intergroup comparisons.ResultsEffects of a 3-month treatment are shown in the previous table (SHHF rats).* : p<0.05Losartan impaired significantly glucose tolerance in SHHF rats.The treatment had no significant metabolic effect in WKY and SH rats.ConclusionOur study showed that, at an antihypertensive dose, losartan impaired glucose tolerance, fasted glycaemia, plasma triglycerides and free fatty acids in SHHF rats whereas it had no significant metabolic effect in WKY and SH rats
The hidden burden of adult allergic rhinitis : UK healthcare resource utilisation survey
Funding Funding for this survey was provided by Meda Pharma.Peer reviewedPublisher PD
A Cost-based Optimizer for Gradient Descent Optimization
As the use of machine learning (ML) permeates into diverse application
domains, there is an urgent need to support a declarative framework for ML.
Ideally, a user will specify an ML task in a high-level and easy-to-use
language and the framework will invoke the appropriate algorithms and system
configurations to execute it. An important observation towards designing such a
framework is that many ML tasks can be expressed as mathematical optimization
problems, which take a specific form. Furthermore, these optimization problems
can be efficiently solved using variations of the gradient descent (GD)
algorithm. Thus, to decouple a user specification of an ML task from its
execution, a key component is a GD optimizer. We propose a cost-based GD
optimizer that selects the best GD plan for a given ML task. To build our
optimizer, we introduce a set of abstract operators for expressing GD
algorithms and propose a novel approach to estimate the number of iterations a
GD algorithm requires to converge. Extensive experiments on real and synthetic
datasets show that our optimizer not only chooses the best GD plan but also
allows for optimizations that achieve orders of magnitude performance speed-up.Comment: Accepted at SIGMOD 201
The Dynamics of Sharpness-Aware Minimization: Bouncing Across Ravines and Drifting Towards Wide Minima
We consider Sharpness-Aware Minimization (SAM), a gradient-based optimization
method for deep networks that has exhibited performance improvements on image
and language prediction problems. We show that when SAM is applied with a
convex quadratic objective, for most random initializations it converges to a
cycle that oscillates between either side of the minimum in the direction with
the largest curvature, and we provide bounds on the rate of convergence.
In the non-quadratic case, we show that such oscillations effectively perform
gradient descent, with a smaller step-size, on the spectral norm of the
Hessian. In such cases, SAM's update may be regarded as a third derivative --
the derivative of the Hessian in the leading eigenvector direction -- that
encourages drift toward wider minima.Comment: 30 page
A Case Study in Matching Test and Proof Coverage
AbstractThis paper studies the complementarity of test and deductive proof processes for Java programs specified in JML (Java Modeling Language). The proof of a program may be long and difficult, especially when automatic provers give up. When a theorem is not automatically proved, there are two possibilities: either the theorem is correct and there are not enough pieces of information to deal with the proof, or the theorem is incorrect. In order to discriminate between those two alternatives, testing techniques can be used. Here, we present experiments around the use of the JACK tool to prove Java programs annotated with JML assertions. When JACK fails to decide proof obligations, we use a combinatorial testing tool, TOBIAS, to produce large test suites that exercise the unproved program parts. The key issue is to establish the relevance of the test suite with respect to the unproved proof obligations. Therefore, we use code coverage techniques: our approach takes advantage of the statement orientation of the JACK tool to compare the statements involved in the unproved proof obligations and the statements covered by the test suite. Finally, we ensure our confidence within the test suites, by evaluating them on mutant program killing exercises. These techniques have been put into practice and are illustrated by a simple case study
First experimental demonstration of temporal hypertelescope operation with a laboratory prototype
In this paper, we report the first experimental demonstration of a Temporal
HyperTelescope (THT). Our breadboard including 8 telescopes is firstly tested
in a manual cophasing configuration on a 1D object. The Point Spread Function
(PSF) is measured and exhibits a dynamics in the range of 300. A quantitative
analysis of the potential biases demonstrates that this limitation is related
to the residual phase fluctuation on each interferometric arm. Secondly, an
unbalanced binary star is imaged demonstrating the imaging capability of THT.
In addition, 2D PSF is recorded even if the telescope array is not optimized
for this purpose.Comment: Accepted for publication in MNRAS. 11 pages, 25 figure
Self-aligned silicidation of surround gate vertical MOSFETs for low cost RF applications
We report for the first time a CMOS-compatible silicidation technology for surround-gate vertical MOSFETs. The technology uses a double spacer comprising a polysilicon spacer for the surround gate and a nitride spacer for silicidation and is successfully integrated with a Fillet Local OXidation (FILOX) process, which thereby delivers low overlap capacitance and high drive-current vertical devices. Silicided 80-nm vertical n-channel devices fabricated using 0.5-?m lithography are compared with nonsilicided devices. A source–drain (S/D) activation anneal of 30 s at 1100 ?C is shown to deliver a channel length of 80 nm, and the silicidation gives a 60% improvement in drive current in comparison with nonsilicided devices. The silicided devices exhibit a subthreshold slope (S) of 87 mV/dec and a drain-induced barrier lowering (DIBL) of 80 mV/V, compared with 86 mV/dec and 60 mV/V for nonsilicided devices. S-parameter measurements on the 80-nm vertical nMOS devices give an fT of 20 GHz, which is approximately two times higher than expected for comparable lateral MOSFETs fabricated using the same 0.5-?m lithography. Issues associated with silicidation down the pillar sidewall are investigated by reducing the activation anneal time to bring the silicided region closer to the p-n junction at the top of the pillar. In this situation, nonlinear transistor turn-on is observed in drain-on-top operation and dramatically degraded drive current in source-on-top operation. This behavior is interpreted using mixed-mode simulations, which show that a Schottky contact is formed around the perimeter of the pillar when the silicided contact penetrates too close to the top S/D junction down the side of the pillar
Mesoscale acid deposition modeling studies
The work performed in support of the EPA/DOE MADS (Mesoscale Acid Deposition) Project included the development of meteorological data bases for the initialization of chemistry models, the testing and implementation of new planetary boundary layer parameterization schemes in the MASS model, the simulation of transport and precipitation for MADS case studies employing the MASS model, and the use of the TASS model in the simulation of cloud statistics and the complex transport of conservative tracers within simulated cumuloform clouds. The work performed in support of the NASA/FAA Wind Shear Program included the use of the TASS model in the simulation of the dynamical processes within convective cloud systems, the analyses of the sensitivity of microburst intensity and general characteristics as a function of the atmospheric environment within which they are formed, comparisons of TASS model microburst simulation results to observed data sets, and the generation of simulated wind shear data bases for use by the aviation meteorological community in the evaluation of flight hazards caused by microbursts
Scaling of the atmosphere of self-avoiding walks
The number of free sites next to the end of a self-avoiding walk is known as
the atmosphere. The average atmosphere can be related to the number of
configurations. Here we study the distribution of atmospheres as a function of
length and how the number of walks of fixed atmosphere scale. Certain bounds on
these numbers can be proved. We use Monte Carlo estimates to verify our
conjectures. Of particular interest are walks that have zero atmosphere, which
are known as trapped. We demonstrate that these walks scale in the same way as
the full set of self-avoiding walks, barring an overall constant factor
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