47,628 research outputs found

    Boundedness of Pseudodifferential Operators on Banach Function Spaces

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    We show that if the Hardy-Littlewood maximal operator is bounded on a separable Banach function space X(Rn)X(\mathbb{R}^n) and on its associate space Xā€²(Rn)X'(\mathbb{R}^n), then a pseudodifferential operator Opā”(a)\operatorname{Op}(a) is bounded on X(Rn)X(\mathbb{R}^n) whenever the symbol aa belongs to the H\"ormander class SĻ,Ī“n(Ļāˆ’1)S_{\rho,\delta}^{n(\rho-1)} with 0<Ļā‰¤10<\rho\le 1, 0ā‰¤Ī“<10\le\delta<1 or to the the Miyachi class SĻ,Ī“n(Ļāˆ’1)(Ļ°,n)S_{\rho,\delta}^{n(\rho-1)}(\varkappa,n) with 0ā‰¤Ī“ā‰¤Ļā‰¤10\le\delta\le\rho\le 1, 0ā‰¤Ī“00\le\delta0. This result is applied to the case of variable Lebesgue spaces Lp(ā‹…)(Rn)L^{p(\cdot)}(\mathbb{R}^n).Comment: To appear in a special volume of Operator Theory: Advances and Applications dedicated to Ant\'onio Ferreira dos Santo

    Complexity and Inapproximability Results for Parallel Task Scheduling and Strip Packing

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    We study the Parallel Task Scheduling problem Pmāˆ£sizejāˆ£Cmaxā”Pm|size_j|C_{\max} with a constant number of machines. This problem is known to be strongly NP-complete for each mā‰„5m \geq 5, while it is solvable in pseudo-polynomial time for each mā‰¤3m \leq 3. We give a positive answer to the long-standing open question whether this problem is strongly NPNP-complete for m=4m=4. As a second result, we improve the lower bound of 1211\frac{12}{11} for approximating pseudo-polynomial Strip Packing to 54\frac{5}{4}. Since the best known approximation algorithm for this problem has a ratio of 43+Īµ\frac{4}{3} + \varepsilon, this result narrows the gap between approximation ratio and inapproximability result by a significant step. Both results are proven by a reduction from the strongly NPNP-complete problem 3-Partition

    An output-sensitive algorithm for the minimization of 2-dimensional String Covers

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    String covers are a powerful tool for analyzing the quasi-periodicity of 1-dimensional data and find applications in automata theory, computational biology, coding and the analysis of transactional data. A \emph{cover} of a string TT is a string CC for which every letter of TT lies within some occurrence of CC. String covers have been generalized in many ways, leading to \emph{k-covers}, \emph{Ī»\lambda-covers}, \emph{approximate covers} and were studied in different contexts such as \emph{indeterminate strings}. In this paper we generalize string covers to the context of 2-dimensional data, such as images. We show how they can be used for the extraction of textures from images and identification of primitive cells in lattice data. This has interesting applications in image compression, procedural terrain generation and crystallography

    L-Arginine promotes gut hormone release and reduces food intake in rodents

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    Aims: To investigate the anorectic effect of Lā€arginine (Lā€Arg) in rodents. Methods: We investigated the effects of Lā€Arg on food intake, and the role of the anorectic gut hormones glucagonā€like peptideā€1 (GLPā€1) and peptide YY (PYY), the Gā€proteinā€coupled receptor family C group 6 member A (GPRC6A) and the vagus nerve in mediating these effects in rodents. Results: Oral gavage of Lā€Arg reduced food intake in rodents, and chronically reduced cumulative food intake in dietā€induced obese mice. Lack of the GPRC6A in mice and subdiaphragmatic vagal deafferentation in rats did not influence these anorectic effects. Lā€Arg stimulated GLPā€1 and PYY release in vitro and in vivo. Pharmacological blockade of GLPā€1 and PYY receptors did not influence the anorectic effect of Lā€Arg. Lā€Argā€mediated PYY release modulated net ion transport across the gut mucosa. Intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) administration of Lā€Arg suppressed food intake in rats. Conclusions: Lā€Arg reduced food intake and stimulated gut hormone release in rodents. The anorectic effect of Lā€Arg is unlikely to be mediated by GLPā€1 and PYY, does not require GPRC6A signalling and is not mediated via the vagus. I.c.v. and i.p. administration of Lā€Arg suppressed food intake in rats, suggesting that Lā€Arg may act on the brain to influence food intake. Further work is required to determine the mechanisms by which Lā€Arg suppresses food intake and its utility in the treatment of obesity

    Dwarf Nova V1040 Centauri and Variable Stars in its Vicinity

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    We present the results of a photometric campaign of the dwarf nova V1040 Cen. The light curve shows two normal outbursts with recurrence time ~ 40 days and amplitude ~ 2.5 mag. Quiescence data show oscillations with periods in the range ~ 0.1 days (2.4 h) to ~ 0.5 days (12 h) of unknown origin. We measured the orbital period of V1040 Cen to be P_orb=0.060458(80) days (1.451+-0.002 h). Based on the M_v-P_orb relation we found the distance of V1040 Cen to be 137+-31 pc. In this paper we also report the detection of eleven new variable stars in the field of the monitored dwarf nova.Comment: 7 figures and 2 tables, accepted for publication in Acta Astronomic

    A Goal-based Framework for Contextual Requirements Modeling and Analysis

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    Requirements Engineering (RE) research often ignores, or presumes a uniform nature of the context in which the system operates. This assumption is no longer valid in emerging computing paradigms, such as ambient, pervasive and ubiquitous computing, where it is essential to monitor and adapt to an inherently varying context. Besides influencing the software, context may influence stakeholders' goals and their choices to meet them. In this paper, we propose a goal-oriented RE modeling and reasoning framework for systems operating in varying contexts. We introduce contextual goal models to relate goals and contexts; context analysis to refine contexts and identify ways to verify them; reasoning techniques to derive requirements reflecting the context and users priorities at runtime; and finally, design time reasoning techniques to derive requirements for a system to be developed at minimum cost and valid in all considered contexts. We illustrate and evaluate our approach through a case study about a museum-guide mobile information system

    Graphene-based photovoltaic cells for near-field thermal energy conversion

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    Thermophotovoltaic devices are energy-conversion systems generating an electric current from the thermal photons radiated by a hot body. In far field, the efficiency of these systems is limited by the thermodynamic Schockley-Queisser limit corresponding to the case where the source is a black body. On the other hand, in near field, the heat flux which can be transferred to a photovoltaic cell can be several orders of magnitude larger because of the contribution of evanescent photons. This is particularly true when the source supports surface polaritons. Unfortunately, in the infrared where these systems operate, the mismatch between the surface-mode frequency and the semiconductor gap reduces drastically the potential of this technology. Here we show that graphene-based hybrid photovoltaic cells can significantly enhance the generated power paving the way to a promising technology for an intensive production of electricity from waste heat.Comment: 5 pages, 4 figure

    Prediction of the Atomization Energy of Molecules Using Coulomb Matrix and Atomic Composition in a Bayesian Regularized Neural Networks

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    Exact calculation of electronic properties of molecules is a fundamental step for intelligent and rational compounds and materials design. The intrinsically graph-like and non-vectorial nature of molecular data generates a unique and challenging machine learning problem. In this paper we embrace a learning from scratch approach where the quantum mechanical electronic properties of molecules are predicted directly from the raw molecular geometry, similar to some recent works. But, unlike these previous endeavors, our study suggests a benefit from combining molecular geometry embedded in the Coulomb matrix with the atomic composition of molecules. Using the new combined features in a Bayesian regularized neural networks, our results improve well-known results from the literature on the QM7 dataset from a mean absolute error of 3.51 kcal/mol down to 3.0 kcal/mol.Comment: Under review ICANN 201
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