On the Excess Dispersion in the Polarization Position Angle of Pulsar Radio Emission

The polarization position angles (PA) of pulsar radio emission occupy a distribution that can be much wider than what is expected from the average linear polarization and the off-pulse instrumental noise. Contrary to our limited understanding of the emission mechanism, the excess dispersion in PA implies that pulsar PAs vary in a random fashion. An eigenvalue analysis of the measured Stokes parameters is developed to determine the origin of the excess PA dispersion. The analysis is applied to sensitive, well-calibrated polarization observations of PSR B1929+10 and PSR B2020+28. The analysis clarifies the origin of polarization fluctuations in the emission and reveals that the excess PA dispersion is caused by the isotropic inflation of the data point cluster formed by the measured Stokes parameters. The inflation of the cluster is not consistent with random fluctuations in PA, as might be expected from random changes in the orientation of the magnetic field lines in the emission region or from stochastic Faraday rotation in either the pulsar magnetosphere or the interstellar medium. The inflation of the cluster, and thus the excess PA dispersion, is attributed to randomly polarized radiation in the received pulsar signal. The analysis also indicates that orthogonal polarization modes (OPM) occur where the radio emission is heavily modulated. In fact, OPM may only occur where the modulation index exceeds a critical value of about 0.3.Comment: Accepted for publication in Ap

The oil sardine fishery along northern Tamil Nadu coast with a note on unusually heavy landings at Cuddalore,Pazhayar and Kaveripattinam

The Indian Oil sardine, Sardinella longiceps is one of the important exploited fishery resources along the Tamil Nadu. The bulk of oil sardine were landed along the coast by the bag-net, Eda valai while lesser quantities were caught by the gill nets, Kavala valai and Thattakavala valai. Unusually heavy landings of oil sardine by the Eda valai units have been recorded at Cuddalore and Pazhayar fisheries harbours and Kaveripattinam during certain months of the period, 1989-'90. Abundance of juvenile oil sardines of the size group 110 - 114 mm was noticed during May - June, '90 at Pazhayar and in July at Kaveripattinam. Larger size groups of 175 - 179 mm predominated in September, '89 whereas in the same period of the succeeding year, 165 – 169 mm length groups supported the fishery. The unprecedented heavy landings of the oil sardine in most of the centers did not benefit the fishermen monetarily to any significant extent. Due to lack of demand for fresh fish, the bulk of catches was sun dried. Oil sardine catches are obtained along the east coast of India in areas close to harbours, backwaters and river mouths and this discontinuous distribution of fish appears to indicate its affinity, particularly juvenile phase, to areas where there is admixture of fresh and brackish water

The ASCA Spectrum of the Vela Pulsar Jet

ROSAT observations of the Vela pulsar and its surroundings revealed a collimated X-ray feature almost 45' in length (Markwardt & Ogelman 1995), interpreted as the signature ``cocoon'' of a one-sided jet from the Vela pulsar. We report on a new ASCA observation of the Vela pulsar jet at its head, the point where the jet is believed to interact with the supernova remnant. The head is clearly detected, and its X-ray spectrum is remarkably similar to the surrounding supernova remnant spectrum, extending to X-ray energies of at least 7 keV. A ROSAT+ASCA spectrum can be fit by two-component emission models but not standard one-component models. The lower energy component is thermal and has a temperature of 0.29+/-0.03 keV (1 sigma); the higher energy component can be fit by either a thermal component of temperature ~4 keV or a power law with photon index ~2.0. Compared to the ROSAT-only results, the mechanical properties of the jet and its cocoon do not change much. If the observed spectrum is that of a hot jet cocoon, then the speed of the jet is at least 800 km s^-1, depending on the angle of inclination. The mechanical power driving the jet is >10^36 erg s^-1, and the mass flow rate at the head is > 10^-6 M_sun yr^-1. We conclude that the jet must be entraining material all along its length in order to generate such a large mass flow rate. We also explore the possibility that the cocoon emission is synchrotron radiation instead of thermal.Comment: 12 pages, LaTeX in AAS v4.0 preprint style, two PS figures, accepted for publication in the ApJ Letter

The Sasa-Satsuma higher order nonlinear Schrodinger equation and its bilinearization and multi-soliton solutions

Higher order and multicomponent generalizations of the nonlinear Schrodinger equation are important in various applications, e.g., in optics. One of these equations, the integrable Sasa-Satsuma equation, has particularly interesting soliton solutions. Unfortunately the construction of multi-soliton solutions to this equation presents difficulties due to its complicated bilinearization. We discuss briefly some previous attempts and then give the correct bilinearization based on the interpretation of the Sasa-Satsuma equation as a reduction of the three-component Kadomtsev-Petvishvili hierarchy. In the process we also get bilinearizations and multi-soliton formulae for a two component generalization of the Sasa-Satsuma equation (the Yajima-Oikawa-Tasgal-Potasek model), and for a (2+1)-dimensional generalization.Comment: 13 pages in RevTex, added reference

Influence of process variables on precursor and carbon fibres

Special grade acrylic fibres have been developed from PAN-co-methyl acrylate. The effect of molecular weight and distribution have heen studied in relation to precursor and carbon fibre propcrties. The influence of process variables such as coagulation bath temperature, stretching, etc. on strength and modulus of fibres have been studied

Results from the first Argo float deployed by India

Argo is a revolutionary concept in ocean observation system that envisages real-time sampling of the temperature and salinity profiles of the global oceans at an approximate spatial resolution of 300 km, once in ten days. Argo float is an autonomous drifting profiler that pops up and down in the ocean from the surface up to 2000 m, measuring two most important physical properties of the water column, viz. temperature and salinity as a function of pressure (depth). Moreover, it can provide an estimate of currents both at the surface and at the parking depth in near-real time. India is an active participant in the Argo programme and has already deployed 31 out of 150 proposed floats. In this article, we describe the data received from the first Argo float deployed by India in the southeastern Arabian Sea. The data demonstrate that the temperature and salinity profiles from Argo floats present possibilities for oceanographic studies and spatial and temporal scales that had been hitherto impossibl

Application of Data Mining In Marketing

One of the most important problems in modern finance is finding efficient ways to summarize and visualize the stock market data to give individuals or institutions useful information about the market behavior for investment decisions. The enormous amount of valuable data generated by the stock market has attracted researchers to explore this problem domain using different methodologies. Potential significant benefits of solving these problems motivated extensive research for years. The research in data mining has gained a high attraction due to the importance of its applications and the increasing generation information. This paper provides an overview of application of data mining techniques such as decision tree. Also, this paper reveals progressive applications in addition to existing gap and less considered area and determines the future works for researchers.Comment: 06 Pages, 02 Figures, 01 Table, Volume 2, Issue