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[en] The incidence of varicose veins in lower limbs is increasing in the Indian subcontinent. With the advent of radiofrequency ablation (RFA), an effective minimally invasive technique is now available to treat varicose veins. RFA can be performed with either unipolar or bipolar probes. We present a simple technique for bipolar radiofrequency-induced thermotherapy of the great saphenous vein. This can be a safe and effective alternative to surgical procedures
[en] The average pulse profiles of PSR 0809 + 74 recorded simultaneously at 25, 20, and 17 MHz show positions conforming to the dispersion law, with no perceptible superdispersion delay. The dispersion measure is 5.752 + or - 0.005/cu cm pc. 9 references
[en] Recent discoveries of dispersed, non-periodic impulsive radio signals with single-dish radio telescopes have sparked significant interest in exploring the relatively uncharted space of fast transient radio signals. Here we describe V-FASTR, an experiment to perform a blind search for fast transient radio signals using the Very Long Baseline Array (VLBA). The experiment runs entirely in a commensal mode, alongside normal VLBA observations and operations. It is made possible by the features and flexibility of the DiFX software correlator that is used to process VLBA data. Using the VLBA for this type of experiment offers significant advantages over single-dish experiments, including a larger field of view, the ability to easily distinguish local radio-frequency interference from real signals, and the possibility to localize detected events on the sky to milliarcsecond accuracy. We describe our software pipeline, which accepts short integration (∼ ms) spectrometer data from each antenna in real time during correlation and performs an incoherent dedispersion separately for each antenna, over a range of trial dispersion measures. The dedispersed data are processed by a sophisticated detector and candidate events are recorded. At the end of the correlation, small snippets of the raw data at the time of the events are stored for further analysis. We present the results of our event detection pipeline from some test observations of the pulsars B0329+54 and B0531+21 (the Crab pulsar).
[en] Scattering of mobile-phone base-stations within populated areas is a source of some misscomfortableness to many people. As there is no one agreed on safety level for the MPE for RF/MW all over the world, measurements of radiation emitted from base-stations is a necessity. In this work we screened out some mobile-phone base-stations inside and outside Khartoum city in Sudan. Measurements were done indoor and outdoor to maximum horizontal distance of about 300 m from the base of the base-stations. Results obtained were then compared to the maximum and minimum MPE values admitted in different countries in the world. The maximum MPE value (i.e- 0.57 mW/cm2) consider only the thermal effects of the RF/MW, while other values tend to reduce the exposure limits to as minimum as possible for safety considerations (considering non-thermal effects). Some of the values obtained were consistent with some reported biological effects. We recommended the removal of some base-stations from sensitive areas like schools, kindergardens, hostels, hospitals, etc. (author)
[en] A review is given of current understanding of the Orion A complex. Although not fully understood, the optically visible HII region and background molecular cloud have been intensely studied. HI regions are also associated with the complex. An attempt is made to explain the observed carbon recombination lines from Orion A in terms of two such regions, a foreground cloud observed in absorption at 21-cm, and the interface between the HII region and the molecular cloud. The coefficients of departure from local thermodynamic equilibrium within the proposed source regions are calculated with consideration of the effects of the radio continuum radiation from the HII region on the level populations of the atomic states, including the effects of the previously neglected parallel Δn parallel greater than 1 radiatively induced transitions. The uncertainties in the collisional cross sections and their effects are discussed. Observations were made of the 85α and 107β lines of carbon with the 140-ft telescope at Green Bank (and incidentally detected corresponding lines due to heavier-than-carbon elements). The present and earlier observations are analyzed with that instrument to support the contention that the source is multiple and to determine the conditions within the component regions. The radial velocities are used to identify the sources as the foreground cloud and background interface, and the ratios of the intensities of alpha lines to beta lines of the same frequencies are used to infer electron densities and temperatures within the regions of origin. The resulting model is then tested against the observed dependence of alpha line intensities on frequency and the agreement is discussed. A fitting to observations gives more precise information on the geometry and cloud conditions, and further research is suggested
[en] The radio source Sgr A has been mapped with the Very Large Array (VLA) at 6 and 20 cm with an angular resolution of 5'' x 8'' arc. In agreement with the earlier 'WORST' map, the non-thermal source Sgr A East shows a shell structure, while the thermal source Sgr A West shows a spiral-like morphology. The authors suggest that Sgr A East is a supernova remnant (SNR) near the galactic centre. Its surface brightness is the third largest in our galaxy after Cas A and the Crab Nebula. The diameter is 9 pc and the source fits the surface-brightness diameter relationship of Clark and Caswell (1976) if a distance of 10 kpc is assumed. (Auth.)
[en] Searching for dispersed radio pulses in interferometric data is of great scientific interest, but poses a formidable computational burden. Here, we present two efficient, new antenna-coherent solutions: The Chirpolator and The Chimageator. We describe the equations governing both techniques and propose a number of novel optimizations. We compare the implementation costs of our techniques with classical methods using three criteria: the operation rates (1) before and (2) after the integrate-and-dump stage, and (3) the data rate directly after the integrate-and-dump stage. When compared with classical methods, our techniques excel in the regime of sparse arrays, where they both require substantially lower data rates, and The Chirpolator requires a much lower post-integrator operation rate. In general, our techniques require more pre-integrator operations than the classical ones. We argue that the data and operation rates required by our techniques are better matched to future supercomputer architectures, where the arithmetic capability is outstripping the bandwidth capability. Our techniques are, therefore, viable candidates for deploying on future interferometers such as the Square Kilometer Array.