Emission from Bow Shocks of Beamed Gamma-Ray Bursts

Beamed gamma-ray burst (GRB) sources produce a bow shock in their gaseous environment. The emitted flux from this bow shock may dominate over the direct emission from the jet for lines of sight which are outside the angular radius of the jet emission, theta. The event rate for these lines of sight is increased by a factor of 260*(theta/5_degrees)^{-2}. For typical GRB parameters, we find that the bow shock emission from a jet with half-angle of about 5 degrees is visible out to tens of Mpc in the radio and hundreds of Mpc in the X-rays. If GRBs are linked to supernovae, studies of peculiar supernovae in the local universe should reveal this non-thermal bow shock emission for weeks to months following the explosion.Comment: ApJ, submitted, 15 pages, 3 figure

CCD photometric and mass function study of 9 young Large Magellanic Cloud star clusters

We present CCD photometric and mass function study of 9 young Large Magellanic Cloud star clusters namely NGC 1767, NGC 1994, NGC 2002, NGC 2003, NGC 2006, SL 538, NGC 2011, NGC 2098 and NGC 2136. The BVRI data reaching down to V ~ 21 mag, are collected from 3.5-meter NTT/EFOSC2 in sub-arcsec seeing conditions. For NGC 1767, NGC 1994, NGC 2002, NGC 2003, NGC 2011 and NGC 2136, broad band photometric CCD data are presented for the first time. Seven of the 9 clusters have ages between 16 to 25 Myr while remaining two clusters have ages $32\pm4$ Myr (NGC 2098) and $90\pm10$ Myr (NGC 2136). For 7 younger clusters, the age estimates based on a recent model and the integrated spectra are found to be systematically lower ($\sim$ 10 Myr) from the present estimate. In the mass range of $\sim 2 - 12$ $M_{\odot}$, the MF slopes for 8 out of nine clusters were found to be similar with the value of $\gamma$ ranging from $-1.90\pm0.16$ to $-2.28\pm0.21$. For NGC 1767 it is flatter with $\gamma = -1.23\pm0.27$. Mass segregation effects are observed for NGC 2002, NGC 2006, NGC 2136 and NGC 2098. This is consistent with the findings of Kontizas et al. for NGC 2098. Presence of mass segregation in these clusters could be an imprint of star formation process as their ages are significantly smaller than their dynamical evolution time. Mean MF slope of $\gamma = -2.22\pm0.16$ derived for a sample of 25 young ($\le 100$ Myr) dynamically unevolved LMC stellar systems provide support for the universality of IMF in the intermediate mass range $\sim 2-12 M_{\odot}$.Comment: To appear in MNRA

Work probability distribution and tossing a biased coin

We show that the rare events present in dissipated work that enters Jarzynski equality, when mapped appropriately to the phenomenon of large deviations found in a biased coin toss, are enough to yield a quantitative work probability distribution for Jarzynski equality. This allows us to propose a recipe for constructing work probability distribution independent of the details of any relevant system. The underlying framework, developed herein, is expected to be of use in modelling other physical phenomena where rare events play an important role.Comment: 6 pages, 4 figures

Purification, crystallization and preliminary X-ray studies of Mycobacterium tuberculosis RRF

The ribosome recycling factor from Mycobacterium tuberculosis has been crystallized. The monoclinic crystals, with 52.5% solvent content, contain one protein molecule in the asymmetric unit

Jet break time -- flux density relationship and constraints on physical parameters of GRB afterglows

We derive a relation between the flux density $F_{\nu,j}$ at the light-curve break of a gamma-ray burst (GRB) afterglow and the break time $t_{j}$. The break is due to the transition from the spherical-like to jet-like evolution of the afterglow, when the Lorentz factor of the jet equals the inverse of the initial half-opening angle, i.e., $\gamma=1/\theta_0$. We show that this relation indeed behaves as $F_{\nu,j}\propto t_{j}^{-p}$ among GRBs for the slow-cooling case, where $p$ is the power-law index of electron distribution. A statistical analysis of the optical jet breaks of nine GRBs gives $p=2.10\pm 0.21$, which is consistent with the shock acceleration theory. The value of $p$ derived in this way is different from the observed temporal index $\alpha_2$ ($F_{\nu}\propto t^{-\alpha_{2}}$) of the late-time light curve after $t_{j}$, which suffers several uncertainties from the unclear hydrodynamics of the sideways expansion and exhibits a large dispersion. Our results not only confirm that the remnants of GRBs are standard candles, but also provide the first evidence that the physical parameters of relativistic shocks are universal, with the favored values $\epsilon_{e}\sim 0.1$ and $\epsilon_{B}\sim 10^{-3}$.Comment: 11 pages including 3 color figure

Signatures of two-dimensionalisation of 3D turbulence in presence of rotation

A reason has been given for the inverse energy cascade in the two-dimensionalised rapidly rotating 3D incompressible turbulence. For such system, literature shows a possibility of the exponent of wavenumber in the energy spectrum's relation to lie between -2 and -3. We argue the existence of a more strict range of -2 to -7/3 for the exponent in the case of rapidly rotating turbulence which is in accordance with the recent experiments. Also, a rigorous derivation for the two point third order structure function has been provided helping one to argue that even with slow rotation one gets, though dominated, a spectrum with the exponent -2.87, thereby hinting at the initiation of the two-dimensionalisation effect with rotation.Comment: An extended and typos-corrected version of the earlier submissio

Performance Analysis of Two Receiver Arrangements for Wireless Battery Charging System

Two different arrangements for Wireless Battery Charging Systems (WBCSs) with a series-parallel resonant topology have been analyzed in this paper. The first arrangement charges the battery by controlling the receiver-side rectifier current and voltage without a chopper, while the second arrangement charges it with a chopper while keeping the chopper input voltage constant. The comparison of these two arrangements is made based on their performance on various figures of merit, such as the sizing factor of both the supply voltage source and receiver coil, overall system efficiency, power-transfer ratio, receiver efficiency, and cost estimation. Later, the simulated study is verified by the experimental setup designed to charge the electric vehicle

Coherent amplitudon generation in K_0.3MoO_3 through ultrafast inter-band quasi particle decay

The charge density wave system K_0.3MoO_3 has been studied using variable energy pump-probe spectroscopy, ellipsometry, and inelastic light scattering. The observed transient reflectivity response exhibits quite a complex behavior, containing contributions due to quasi particle excitations, coherent amplitudons and phonons, and heating effects. The generation of coherent amplitudons is discussed in terms of relaxation of photo-excited quasi particles, and is found to be resonant with the interband plasmon frequency. Two additional coherent excitations observed in the transients are assigned to zone-folding modes of the charge density wave state