32,891 research outputs found
Anytime Control using Input Sequences with Markovian Processor Availability
We study an anytime control algorithm for situations where the processing
resources available for control are time-varying in an a priori unknown
fashion. Thus, at times, processing resources are insufficient to calculate
control inputs. To address this issue, the algorithm calculates sequences of
tentative future control inputs whenever possible, which are then buffered for
possible future use. We assume that the processor availability is correlated so
that the number of control inputs calculated at any time step is described by a
Markov chain. Using a Lyapunov function based approach we derive sufficient
conditions for stochastic stability of the closed loop.Comment: IEEE Transactions on Automatic Control, to be publishe
Stochastic Stability of Event-triggered Anytime Control
We investigate control of a non-linear process when communication and
processing capabilities are limited. The sensor communicates with a controller
node through an erasure channel which introduces i.i.d. packet dropouts.
Processor availability for control is random and, at times, insufficient to
calculate plant inputs. To make efficient use of communication and processing
resources, the sensor only transmits when the plant state lies outside a
bounded target set. Control calculations are triggered by the received data. If
a plant state measurement is successfully received and while the processor is
available for control, the algorithm recursively calculates a sequence of
tentative plant inputs, which are stored in a buffer for potential future use.
This safeguards for time-steps when the processor is unavailable for control.
We derive sufficient conditions on system parameters for stochastic stability
of the closed loop and illustrate performance gains through numerical studies.Comment: IEEE Transactions on Automatic Control, under revie
Positive solutions for nonlinear m-point Eigenvalue problems
In this paper, we are concerned with determining values of lambda, for which there exist positive solutions of the nonlinear eigenvalue problem [GRAPHICS] where a, b, c, d is an element of [0, infinity), xi(i) is an element of (0, 1), alpha(i), beta(i) is an element of [0 infinity) (for i is an element of {1, ..., m - 2}) are given constants, p, q is an element of C ([0, 1], (0, infinity)), h is an element of C ([0, 1], [0, infinity)), and f is an element of C ([0, infinity), [0, infinity)) satisfying some suitable conditions. Our proofs are based on Guo-Krasnoselskii fixed point theorem. (C) 2004 Elsevier Inc. All rights reserved
Review article: the global emergence of Helicobacter pylori antibiotic resistance.
BackgroundHelicobacter pylori is one of the most prevalent global pathogens and can lead to gastrointestinal disease including peptic ulcers, gastric marginal zone lymphoma and gastric carcinoma.AimTo review recent trends in H. pylori antibiotic resistance rates, and to discuss diagnostics and treatment paradigms.MethodsA PubMed literature search using the following keywords: Helicobacter pylori, antibiotic resistance, clarithromycin, levofloxacin, metronidazole, prevalence, susceptibility testing.ResultsThe prevalence of bacterial antibiotic resistance is regionally variable and appears to be markedly increasing with time in many countries. Concordantly, the antimicrobial eradication rate of H. pylori has been declining globally. In particular, clarithromycin resistance has been rapidly increasing in many countries over the past decade, with rates as high as approximately 30% in Japan and Italy, 50% in China and 40% in Turkey; whereas resistance rates are much lower in Sweden and Taiwan, at approximately 15%; there are limited data in the USA. Other antibiotics show similar trends, although less pronounced.ConclusionsSince the choice of empiric therapies should be predicated on accurate information regarding antibiotic resistance rates, there is a critical need for determination of current rates at a local scale, and perhaps in individual patients. Such information would not only guide selection of appropriate empiric antibiotic therapy but also inform the development of better methods to identify H. pylori antibiotic resistance at diagnosis. Patient-specific tailoring of effective antibiotic treatment strategies may lead to reduced treatment failures and less antibiotic resistance
Canonical Demon Monte Carlo Renormalization Group
We describe a new method to compute renormalized coupling constants in a
Monte Carlo renormalization group calculation. The method can be used for a
general class of models, e.g., lattice spin or gauge models. The basic idea is
to simulate a joint system of block spins and canonical demons. In contrast to
the Microcanonical Renormalization Group invented by Creutz et al. our method
does not suffer from systematical errors stemming from a simultaneous use of
two different ensembles. We present numerical results for the nonlinear
-model.Comment: LaTeX file, 7 pages, preprints CERN TH.7330/94, MS-TPI-
Systematic decay studies of even-even ^Nd, ^Gd, ^Hg and ^Pb isotopes
The alpha and cluster decay properties of the ^Nd, ^Gd,
^Hg and ^Pb even-even isotopes in the two mass regions A =
130-158 and A = 180-198 are analysed using the Coulomb and Proximity Potential
Model. On examining the clusters at corresponding points in the cold valleys
(points with same A_2) of the various isotopes of a particular nucleus we find
that at certain mass numbers of the parent nuclei, the clusters emitted are
getting shifted to the next lower atomic number. It is interesting to see that
the change in clusters appears at those isotopes where a change in shape is
occurring correspondingly. Such a change of clusters with shape change is
studied for the first time in cluster decay. The alpha decay half lives of
these nuclei are computed and these are compared with the available
experimental alpha decay data. It is seen that the two are in good agreement.
On making a comparison of the alpha half lives of the normal deformed and super
deformed nuclei, it can be seen that the normal deformed ^Nd, ^Hg
and ^Pb nuclei are found to be better alpha emitters than the super
deformed (in excited state) ^Nd, ^Hg and ^Pb nuclei. The
cluster decay studies reveal that as the atomic number of the parent nuclei
increases the N \neq Z cluster emissions become equally or more probable than
the N=Z emissions. On the whole the alpha and cluster emissions are more
probable from the parents in the heavier mass region (A=180-198) than from the
parents in the lighter mass region (A= 130-158). The effect of quadrupole
({\beta}_2) and hexadecapole ({\beta}_4) deformations of parent and fragments
on half life times are also studied.Comment: 42 pages,19 figure
Information-Theoretic Bounds for Multiround Function Computation in Collocated Networks
We study the limits of communication efficiency for function computation in
collocated networks within the framework of multi-terminal block source coding
theory. With the goal of computing a desired function of sources at a sink,
nodes interact with each other through a sequence of error-free, network-wide
broadcasts of finite-rate messages. For any function of independent sources, we
derive a computable characterization of the set of all feasible message coding
rates - the rate region - in terms of single-letter information measures. We
show that when computing symmetric functions of binary sources, the sink will
inevitably learn certain additional information which is not demanded in
computing the function. This conceptual understanding leads to new improved
bounds for the minimum sum-rate. The new bounds are shown to be orderwise
better than those based on cut-sets as the network scales. The scaling law of
the minimum sum-rate is explored for different classes of symmetric functions
and source parameters.Comment: 9 pages. A 5-page version without appendices was submitted to IEEE
International Symposium on Information Theory (ISIT), 2009. This version
contains complete proofs as appendice
RGS10 shapes the hemostatic response to injury through its differential effects on intracellular signaling by platelet agonists.
Platelets express ≥2 members of the regulators of G protein signaling (RGS) family. Here, we have focused on the most abundant, RGS10, examining its impact on the hemostatic response in vivo and the mechanisms involved. We have previously shown that the hemostatic thrombi formed in response to penetrating injuries consist of a core of fully activated densely packed platelets overlaid by a shell of less-activated platelets responding to adenosine 5\u27-diphosphate (ADP) and thromboxane A2 (TxA2). Hemostatic thrombi formed in RGS10-/- mice were larger than in controls, with the increase due to expansion of the shell but not the core. Clot retraction was slower, and average packing density was reduced. Deleting RGS10 had agonist-specific effects on signaling. There was a leftward shift in the dose/response curve for the thrombin receptor (PAR4) agonist peptide AYPGKF but no increase in the maximum response. This contrasted with ADP and TxA2, both of which evoked considerably greater maximum responses in RGS10-/- platelets with enhanced Gq- and Gi-mediated signaling. Shape change, which is G13-mediated, was unaffected. Finally, we found that free RGS10 levels in platelets are actively regulated. In resting platelets, RGS10 was bound to 2 scaffold proteins: spinophilin and 14-3-3γ. Platelet activation caused an increase in free RGS10, as did the endothelium-derived platelet antagonist prostacyclin. Collectively, these observations show that RGS10 serves as an actively regulated node on the platelet signaling network, helping to produce smaller and more densely packed hemostatic thrombi with a greater proportion of fully activated platelets
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