A cluster pair : A3532 and A3530

We present a detailed study of a close pair of clusters of galaxies, A3532 and A3530, and their environments. The \textit{Chandra} X-ray image of A3532 reveals presence of substructures on scales of $\sim$20$^{\prime\prime}$ in its core. XMM-Newton maps of the clusters show excess X-ray emission from an overlapping region between them. Spectrally determined projected temperature and entropy maps do not show any signs of cluster scale mergers either in the overlapping region or in any of the clusters. In A3532, however, some signs of the presence of galaxy scale mergers are visible e.g., anisotropic temperature variations in the projected thermodynamic maps, a wide angled tailed (WAT) radio source in the brighter nucleus of its dumbbell Brightest Cluster Galaxy (BCG), and a candidate X-ray cavity coincident with the northwestern extension of the WAT source in the low-frequency radio observations. The northwestern extension in A3532 seems either a part of the WAT or an unrelated diffuse source in A3532 or in the background. There is an indication that the cool core in A3532 has been disrupted by the central AGN activity. A reanalysis of the redshift data reinforces the close proximity of the clusters. The excess emission in the overlapping region appears to be a result of tidal interactions as the two clusters approach each other for the first time. However, we can not rule out the possibility of the excess being due to the chance superposition of their X-ray halos.Comment: Accepted for publication in the Astrophysical Journa

IMPACT OF ICT IN COLLEGE LIBRARIES OF ASSAM FOR PROMOTING HIGHER EDUCATION WITH SPECIAL REFERENCE TO LAKHIMPUR DISTRICT.

Library plays a vital role in academic institutions of higher learning. In the 21st century information technology has revolutionized the field of library and information science globally. In this context the present study is aimed to see the status of under graduate colleges of Assam and their attached libraries with special reference to Lakhimpur district of the state of Assam. It is found that library activities in these institutions of higher learning are lagging behind reason of which is lack of initiative to upgrade the library facilities up to date using modern technologies. Due to this the satisfaction level of users is much lower and might cause harm to the society

A Review on Different Control Techniques Used for Pitch Control of Horizontal Axis Wind Turbine

In wind turbine technology, the pitch control mechanism of blades is a very important factor for the efficient power output of a wind turbine. Various control techniques can be implemented for pitch control. This paper deals with the study and review of different control methodologies used by the researchers and engineers to control the pitch angle of the blades of a horizontal axis wind turbine to optimize the power in low rated wind speed. This paper involves the study of PI, PID, Fuzzy logic control, Sliding mode control and Adaptive control methodologies

Extragalactic sources with asymmetric radio structure I. Observations of 17 sources

We present total-intensity and linear-polarization observations with the Very Large Array (VLA) at λ6 and 2 cm of 17 sources, almost all of which were suspected to have extended emission only on one side of the nucleus. Five of them are still one-sided, three appear unresolved, while seven have radio lobes on both sides of the nucleus. The outer components in the double-lobed sources, however, have significantly different surface brightness or are very asymmetrically located with respect to the nucleus

The 25 November 1988 Saguenay, Quebec, Earthquake: Source Parameters and the Attenuation of Strong Ground Motion

The Saguenay earthquake of 25 November 1988 occurred close to the southern margin of the Saguenay Graben in southern Quebec. It was caused by almost purely dip-slip faulting centered at a depth of 26 km with a P axis oriented northeast-southwest. This faulting mechanism is similar to those of the larger historical earthquakes in eastern North America, but the focal depth is substantially greater than all but one of these events. The seismic moment estimated from regional PnI waves and teleseismic long-period body waves is 5 × 10^(24) dyne-cm., corresponding to a moment magnitude of 5.8. The source duration of the earthquake is estimated to be 1.8 sec, corresponding to a stress drop of 160 bars, which is not significantly higher than the average stress drop of 120 bars estimated from previous large earthquakes in eastern North America. In order to simultaneously match the recorded ground motion amplitudes of strong-motion acceleration, strong-motion velocity, and teleseismic short-period and long-period body waves, it is necessary to use a source function having a complex shape that implies the presence of asperities and larger local stress drops. The large set of strong-motion recordings of the Saguenay earthquake has been used to validate a procedure for estimating strong ground motion attenuation based on a simple wave propagation model. The most important feature of the recorded strong motions is that their peak amplitudes do not decay significantly with distance inside 120 km, but then decay abruptly beyond 120 km. Profiles of recorded accelerograms with absolute times indicate that at distances beyond 64 km the peak ground motions are due to strong postcritical reflections from velocity gradients in the lower crust. The principal shear-wave arrivals and the variation of their peak amplitudes with distance were reproduced in synthetic seismograms generated using a regional crustal structure model. The critical distances for the postcritical reflections were short because of the deep focal depth of the event, causing the elevation of ground motion amplitudes out to 120 km. Similar studies of earthquakes in other regions of eastern North America indicate that the strength of the postcritical reflections, and the distance ranges over which they are dominant, are controlled by the focal depth and crustal structure. Regional variations in crustal structure thus give rise to predictable regional variations in strong ground motion attenuation

XRD and FT-IR investigations of sub-bituminous Assam coals

Two coal samples collected from Makum coal field, Assam, India were studied by XRD and FT-IR techniques. The X-ray diffractogram shows the existence of some crystalline carbons in Assam coals as proven by the appearance of peaks. The radial distribution functional (RDF) method was applied for the determination of structural aspects of the coals. The study indicates that the coals are lignite in type and there is no evidence of graphite-like structures. The maximum in the G(r) plots of function of radial distribution of atoms (FRDA) relates to different distances between carbon atoms of aliphatic chains. The first significant maximum relates to the C-C bond (type C-CH=CH-C), the second maximum relates to the distance between carbon atoms of aliphatic chains that are located across one carbon atom. The curve intensity profiles obtained from FRDA show quite regular molecular packets for this coal. The coals were found to be lignite in nature. FT-IR study shows the presence of aliphatic carbon, C=O and C-O stretching associated with -OH and -NH stretching vibrations. Kaolinite and quartz were also found to be major minerals in Assam coals by FTIR spectroscopy. The difference in intensities of carbonyl groups of the coal samples is likely to relate with the rank. © Indian Academy of Sciences

FT-IR spectroscopic investigation of high sulphur assam coals and their solvent-extracts

The FT-IR spectroscopic techniques were used to understand the structural feature of four samples of high sulphur Assam coals and their extracts in polar solvents. Pyridine, N, N-Dimethyl Acetamide and Ethyl Acetate were used for extraction of the coals at their reflux temperatures in a Soxhlet apparatus. The difference-FT-IR spectroscopic technique was used to characterize the compositions of extracts. The extracts were found to contain characteristic absorption bands of original coals. Both aromatic and aliphatic C-H stretching bands were observed in the spectra of extracts. The spectral interpretations of the extracts closely resembled the parent coal structures. The relative transmittances of characteristic bands in extract spectrum suggest that the distribution of functional groups in coals were somewhat effected due to the interaction with the solvents. The spectra show some depletion of bands along with increase in some regions. The information regarding the structure of coal and extracts obtained by this method are qualitative in nature but very much useful in coal utilizations. © Geol. Soc. India