Cepheid distance to the virgo cluster

HST data on Cepheid variables in one Virgo Cluster spiral galaxy is re-analyzed, taking into account flux-limited incompleteness in the sample and calibration of the period-luminosity relation in the relevant period range. Distance to the Virgo Cluster is estimated to be 19.6 ± 1.7 (random) ± 2.6 (systematic) Mpc.     

Congestion in large balanced multirate networks

In this paper, we obtain analytical approximations for various performance measures for a large fluid stochastic network that operates under a balanced fair bandwidth allocation policy. Balanced fairness results in the insensitivity of the stationary distribution of the number in the system to the precise distribution of file sizes. Balanced fairness has been shown to coincide with proportional fairness in large systems. The model we consider is that of servers operating under balanced fair rate allocations that are accessed by a large number of independent heterogeneous flows characterized by their arrival rate and general distributions of the file sizes; and a maximum service rate associated with each type of flow. The largeness of the system is parameterized by a scaling parameter that scales the arrival rates and capacity in such a way that the ratio is fixed. By exploiting a connection of the congestion probabilities with multirate Erlang loss systems, we use local limit large deviation methods to obtain accurate approximations as the scaling increases. The paper first discusses the single link case which is then extended to the case of a parking lot model that is a special case of tree networks.     

Selection of Suitable Combination of Nonfunctional Micellar Catalyst and Heteroaromatic Nitrogen Base as Promoter for Chromic Acid Oxidation of Ethanol to Acetaldehyde in Aqueous Medium at Room Temperature

The effect of the promoter and micellar catalyst on chromic acid on the oxidation of ethanol in aqueous acid media has been studied. Picolinic acid (PA), 1,10‐phenanthroline (phen), and 2,2′‐bipyridine (bipy) are used as promoters. Sodium dodecyl sulfate (SDS), cetyl pyridinium chloride (CPC), and Triton‐X‐100 (TX‐100) are tested as micellar catalysts. Hexavelent chromium is an active species in the absence of the promoter. In the presence of the heteroaromatic nitrogen bases used as the promoter, Cr(VI)–PA, Cr(VI)–bipy, and Cr(VI)–phen complexes have been proposed as the active oxidants. The time taken for completion of the reaction using different combinations of promoter and micellar catalysts are different. Although the rate is highest (12.5 times) in TX‐100 in the absence of the promoter, it is observed that the rate is almost 737 times faster for the combination of SDS and bipy compared to the unpromoted and uncatalyzed path. CPC inhibits the oxidation process. The observed acceleration and retardation of the rate of oxidation process has been explained on the basis of partitioning of the reactants in the micellar and aqueous phase. © 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 175–186, 2013     

Forward equations for reflected diffusions with jumps

In this paper we obtain the forward equations associated with the evolution of the density, if it exists, of reflected diffusions on the positive orthant with jumps which form a marked point process whose random jump measure possesses a stochastic intensity. These results generalize the so-called generalized Dynkin equations for piecewise deterministic jump processes due to Davis. We then consider the stationary case where the existence of a stochastic intensity is not needed. The techniques are based on local times and the use of random jump measures. We discuss the application of these results to problems arising in queuing and storage processes as well as stationary distributions of diffusions with delayed and jump reflections at the origin.This research was supported in part by the Quebec-France Cooperative Research Program and by the Natural Sciences and Engineering Research Council of Canada under Grant OGP 0042024.     

On the production mechanism of MF-HF radiopulses associated with large extensive air showers

Summary The existing theories on radio-emission from extensive air showers (EAS) are inadequate to explain the observed high fields associated with the emission of LF-MF-HF radiopulses. One of the attempts has been to explain the phenomenon in the light of the transition radiation (TR) mechanism from the excess negative charge of EAS on striking the ground. However, experimental data are very meagre. In order to concretise the theoretical basis of LF-MF-HF emission, experimental investigations on different aspects of radio-emission are essential. The present paper reports the experimental studies on radio-emission at some preselected frequencies (LF-HF) using a sophisticated data acquisition system. Results on i) variation of field strength with age parameter (S) for different primary energies (E _p) and different core distance (R), ii) lateral distribution of field strength for differentE _p andS and iii) frequency spectrum of radio-emission, are presented and analysed in the light of the TR mechanism.     

Non-static spherically symmetric clusters of particles in general relativity: I

In an ingenious way rotation (but no angular momentum) has been introduced in the case of spherical symmetry by Einstein, who has considered a stationary cluster of particles moving freely under the influence of the gravitational field produced by all of them together. The aim of the present work is to extend his idea to the non-static case, and it seems that under some circumstances instead of an indefinite gravitational collapse there is a minimum of the volume and a bouncing back.