Low radio frequency signatures of ram pressure stripping in Virgo spiral NGC 4254

We report the detection of extended low radio frequency continuum emission beyond the optical disk of the spiral galaxy NGC 4254 using the Giant Metrewave Radio Telescope. NGC 4254, which has an almost face-on orientation, is located in the outskirts of the Virgo cluster. Since such extended emission is uncommon in low inclination galaxies, we believe it is a signature of magnetised plasma pushed out of the disk by ram pressure of the intracluster medium as NGC 4254 falls into the Virgo cluster. The detailed spectral index distribution across NGC 4254 shows that the steepest spectrum alpha < -1 (S propto nu^{alpha}) arises in the gas beyond the optical disk. This lends support to the ram pressure scenario by indicating that the extended emission is not from the disk gas but from matter which has been stripped by ram pressure. The steeper spectrum of the extended emission is reminiscent of haloes in edge-on galaxies. The sharp fall in intensity and enhanced polarization in the south of the galaxy, in addition to enhanced star formation reported by others provide evidence towards the efficacy of ram pressure on this galaxy. HI 21cm observations show that the gas in the north lags in rotation and hence is likely the atomic gas which is carried along with the wind. NGC 4254 is a particularly strong radio emitter with a power of 7x10^{22} Watts/Hz at 240 MHz. We find that the integrated spectrum of the galaxy flattens at lower frequencies and is well explained by an injection spectrum with alpha_0=-0.45+-0.12. We end by comparing published simulation results with our data and conclude that ram pressure stripping is likely to be a significant contributor to evolution of galaxies residing in X-ray poor groups and cluster outskirts.Comment: 10 pages, 7 figures (figures 1,2 and 4 are in jpg format) and 2 tables; Accepted for publication in MNRA

Geometry of good sets in n-fold Cartesian product

We propose here a multidimensional generalisation of the notion of link introduced in our previous papers and we discuss some consequences for simplicial measures and sums of function algebras.Comment: 17 pages, no figures, no table

R-PEKS: RBAC Enabled PEKS for Secure Access of Cloud Data

In the recent past, few works have been done by combining attribute-based access control with multi-user PEKS, i.e., public key encryption with keyword search. Such attribute enabled searchable encryption is most suitable for applications where the changing of privileges is done once in a while. However, to date, no efficient and secure scheme is available in the literature that is suitable for these applications where changing privileges are done frequently. In this paper our contributions are twofold. Firstly, we propose a new PEKS scheme for string search, which, unlike the previous constructions, is free from bi-linear mapping and is efficient by 97% compared to PEKS for string search proposed by Ray et.al in TrustCom 2017. Secondly, we introduce role based access control (RBAC) to multi-user PEKS, where an arbitrary group of users can search and access the encrypted files depending upon roles. We termed this integrated scheme as R-PEKS. The efficiency of R-PEKS over the PEKS scheme is up to 90%. We provide formal security proofs for the different components of R-PEKS and validate these schemes using a commercial dataset

On the origin of the various types of radio emission in GRS 1915+105

We investigate the association between the radio ``plateau'' states and the large superluminal flares in GRS 1915+105 and propose a qualitative scenario to explain this association. We identify several candidate superluminal flare events from available monitoring data on this source and analyze the contemporaneous RXTE pointed observations. We detect a strong correlation between the average X-ray flux during the ``plateau'' state and the total energy emitted in radio during the subsequent radio flare. We find that the sequence of events is similar for all large radio flares with a fast rise and exponential decay morphology. Based on these results, we propose a qualitative scenario in which the separating ejecta during the superluminal flares are observed due to the interaction of the matter blob ejected during the X-ray soft dips, with the steady jet already established during the ``plateau'' state. This picture can explain all types of radio emission observed from this source in terms of its X-ray emission characteristics.Comment: Corrected typo in the author names, contents unchanged, accepted in Ap

Stability of copper tolerance in Thiobacillus ferrooxidans

A strain of Thiobacillus ferrooxidans MAL-4-1 was adapted to grow at higher concentrations of copper by repeated subculturing in the presence of increasing levels of added cupric ions in 9K medium. The strains adapted to copper were found to be more efficient in bioleaching of copper from concentrates. When copper tolerant strains were back cultured repeatedly in 9K medium without cupric ions, the initially developed metal tolerance was observed to be lost. This indicates that the copper tolerance developed is stress-dependent and not a permanent trait of the adapted strain

Bayesian Inference for Volatility of Stock Prices

Lognormal distribution is widely used in the analysis of failure time data and stock prices. Maximum likelihood and Bayes estimator of the coefficient of variation of lognormal distribution along with confidence/credible intervals are developed. The utility of Bayes procedure is illustrated by analyzing prices of selected stocks

Study of Electrical and Thermal Behaviour of Li-ion Polymer Cells for Auxiliary Power Supply in Underwater Applications

Lithium  ion  polymer (Li-Po) battery technology is the latest technology for portable use and the most promising technology for exercise torpedoes. These batteries are technologically evolved from Lithium ion batteries. In this paper, extensive experimental studies on Li-Po cells which include studies on electrical characteristics during charge-discharge cycles, discharge at different C rates, self discharge throughout  charge stand, temperature profiles at the cathode and anode during the discharges, etc. are reported and discussed. The extensive electrical characterisation done on these cells indicates the capability of these cells for use as auxiliary power supply in underwater weapon applications.Defence Science Journal, 2012, 62(2), pp.127-131, DOI:http://dx.doi.org/10.14429/dsj.62.99