Greek image of the Indian society

No abstrac

New Approximability Results for the Robust k-Median Problem

We consider a robust variant of the classical $k$-median problem, introduced by Anthony et al. \cite{AnthonyGGN10}. In the \emph{Robust $k$-Median problem}, we are given an $n$-vertex metric space $(V,d)$ and $m$ client sets $\set{S_i \subseteq V}_{i=1}^m$. The objective is to open a set $F \subseteq V$ of $k$ facilities such that the worst case connection cost over all client sets is minimized; in other words, minimize $\max_{i} \sum_{v \in S_i} d(F,v)$. Anthony et al.\ showed an $O(\log m)$ approximation algorithm for any metric and APX-hardness even in the case of uniform metric. In this paper, we show that their algorithm is nearly tight by providing $\Omega(\log m/ \log \log m)$ approximation hardness, unless ${\sf NP} \subseteq \bigcap_{\delta >0} {\sf DTIME}(2^{n^{\delta}})$. This hardness result holds even for uniform and line metrics. To our knowledge, this is one of the rare cases in which a problem on a line metric is hard to approximate to within logarithmic factor. We complement the hardness result by an experimental evaluation of different heuristics that shows that very simple heuristics achieve good approximations for realistic classes of instances.Comment: 19 page

Strong inapproximability of the shortest reset word

The \v{C}ern\'y conjecture states that every $n$-state synchronizing automaton has a reset word of length at most $(n-1)^2$. We study the hardness of finding short reset words. It is known that the exact version of the problem, i.e., finding the shortest reset word, is NP-hard and coNP-hard, and complete for the DP class, and that approximating the length of the shortest reset word within a factor of $O(\log n)$ is NP-hard [Gerbush and Heeringa, CIAA'10], even for the binary alphabet [Berlinkov, DLT'13]. We significantly improve on these results by showing that, for every $\epsilon>0$, it is NP-hard to approximate the length of the shortest reset word within a factor of $n^{1-\epsilon}$. This is essentially tight since a simple $O(n)$-approximation algorithm exists.Comment: extended abstract to appear in MFCS 201

A system for production of defective interfering particles in the absence of infectious influenza A virus

<div><p>Influenza A virus (IAV) infection poses a serious health threat and novel antiviral strategies are needed. Defective interfering particles (DIPs) can be generated in IAV infected cells due to errors of the viral polymerase and may suppress spread of wild type (wt) virus. The antiviral activity of DIPs is exerted by a DI genomic RNA segment that usually contains a large deletion and suppresses amplification of wt segments, potentially by competing for cellular and viral resources. DI-244 is a naturally occurring prototypic segment 1-derived DI RNA in which most of the PB2 open reading frame has been deleted and which is currently developed for antiviral therapy. At present, coinfection with wt virus is required for production of DI-244 particles which raises concerns regarding biosafety and may complicate interpretation of research results. Here, we show that cocultures of 293T and MDCK cell lines stably expressing codon optimized PB2 allow production of DI-244 particles solely from plasmids and in the absence of helper virus. Moreover, we demonstrate that infectivity of these particles can be quantified using MDCK-PB2 cells. Finally, we report that the DI-244 particles produced in this novel system exert potent antiviral activity against H1N1 and H3N2 IAV but not against the unrelated vesicular stomatitis virus. This is the first report of DIP production in the absence of infectious IAV and may spur efforts to develop DIPs for antiviral therapy.</p></div

Implementation of higher-order absorbing boundary conditions for the Einstein equations

We present an implementation of absorbing boundary conditions for the Einstein equations based on the recent work of Buchman and Sarbach. In this paper, we assume that spacetime may be linearized about Minkowski space close to the outer boundary, which is taken to be a coordinate sphere. We reformulate the boundary conditions as conditions on the gauge-invariant Regge-Wheeler-Zerilli scalars. Higher-order radial derivatives are eliminated by rewriting the boundary conditions as a system of ODEs for a set of auxiliary variables intrinsic to the boundary. From these we construct boundary data for a set of well-posed constraint-preserving boundary conditions for the Einstein equations in a first-order generalized harmonic formulation. This construction has direct applications to outer boundary conditions in simulations of isolated systems (e.g., binary black holes) as well as to the problem of Cauchy-perturbative matching. As a test problem for our numerical implementation, we consider linearized multipolar gravitational waves in TT gauge, with angular momentum numbers l=2 (Teukolsky waves), 3 and 4. We demonstrate that the perfectly absorbing boundary condition B_L of order L=l yields no spurious reflections to linear order in perturbation theory. This is in contrast to the lower-order absorbing boundary conditions B_L with L<l, which include the widely used freezing-Psi_0 boundary condition that imposes the vanishing of the Newman-Penrose scalar Psi_0.Comment: 25 pages, 9 figures. Minor clarifications. Final version to appear in Class. Quantum Grav

An Optimization Framework for “Build-or-Buy” Strategy for component Selection in a Fault Tolerant Modular Software System under Recovery Block Scheme

This paper discusses a framework that helps developers to decide whether to buy or build components of software architecture. Two optimization models have been proposed. First model is Bi-criteria optimization model based on decision variables in order to maximize the software reliability with simultaneous minimization of the overall cost of the system. The second optimization model deals with the issue of compatibility

Immune response to Japanese encephalitis virus in mother mice and their congenitally infected offspring

The immune response to Japanese encephalitis virus (JEV) was assessed in JEV-infected mice (mothers) and their offspring. The congenitally infected baby mice responded poorly in all assays for cell-mediated immunity. The total number of their splenic cells remained unaltered but the percentage of T cells was significantly reduced; a depressed delayed hypersensitivity response was seen against both homologous (JEV) and heterologous (sheep erythrocytes) antigens. In addition, significantly higher leukocyte migration inhibition (LMI) of spleen cells in the presence of specific antigen was observed. Adult mice infected during pregnancy demonstrated an impaired delayed hypersensitivity response to JEV antigen only. LMI was positive in mothers at 2 weeks post-partum, but not at later periods

Congenital granular cell lesion in newborn mandible

Congenital granular cell lesion (CGCL) is a rare non-neoplastic lesion found in newborns also known as Neumann’s tumor. This benign lesion occurs predominantly in females mostly as a single mass. The histogenesis and natural history of the lesion remains obscure. It arises from the mucosa of the gingiva, either from the maxillary or mandibular alveolar ridge. The lesion is more common in the maxillary alveolar ridge than the mandibular.The present report describes a case of congenital granular cell lesion in an eight-day-old female child who was born with a mass on the anterior mandibular alveolar ridge. The mass was protruding from her mouth and compromised feeding. A clinical diagnosis of teratoma was suggested. Histologically, cells of this lesion are identical to granular cell tumor (neuroectodermal type) and show intense diastase-resistant Periodic Acid Schiff positivity. Immunohistochemically, cells are positive for vimentin but negative for S-100 and desmin, thus suggesting that CGCL is possibly derived from primitive gingival mesenchymal cells rather than having schwannian origin.Key words: Congenital epulis, congenital granular cell lesion, immunohistochemistr

Transplacental Japanese encephalitis virus (JEV) infection in mice during consecutive pregnancies

Transplacental transmission of Japanese encephalitis virus (JEV) has been demonstrated in consecutive pregnancies of mice. Pregnant mice inoculated intraperitoneally with JEV transmit the virus to the foetus. When such female mice were mated again after 6 months, the virus could be isolated from the foetuses of the ensuing pregnancy. The incidence of abortion was increased significantly though the neonatal deaths were considerably less than during the first pregnancy. Intra-uterine infection occurred in spite of the presence of HAI antibodies against JEV in the preconceptional sera of the mice. The findings of the present study indicate the value of such a system for further investigations of the pathogenesis of JEV infection during pregnancy in humans

Characterization of Binary Constraint System Games

We consider a class of nonlocal games that are related to binary constraint systems (BCSs) in a manner similar to the games implicit in the work of Mermin [N.D. Mermin, "Simple unified form for the major no-hidden-variables theorems," Phys. Rev. Lett., 65(27):3373-3376, 1990], but generalized to n binary variables and m constraints. We show that, whenever there is a perfect entangled protocol for such a game, there exists a set of binary observables with commutations and products similar to those exhibited by Mermin. We also show how to derive upper bounds strictly below 1 for the the maximum entangled success probability of some BCS games. These results are partial progress towards a larger project to determine the computational complexity of deciding whether a given instance of a BCS game admits a perfect entangled strategy or not.Comment: Revised version corrects an error in the previous version of the proof of Theorem 1 that arises in the case of POVM measurement