Multi-epoch intra-night optical monitoring of 8 radio-quiet BL Lac candidates

For a new sample of 8 weak-line-quasars (WLQs) we report a sensitive search in 20 intranight monitoring sessions, for blazar-like optical flux variations on hour-like and longer time scale (day/month/year$-$like). The sample consists exclusively of the WLQs that are not radio$-$loud and have either been classified as `radio-weak probable BL Lac candidates' and/or are known to have exhibited at least one episode of large, blazar$-$like optical variability. Whereas only a hint of intra$-$night variability is seen for two of these WLQs, J104833.5$+$620305.0(z = 0.219) and J133219.6$+$622715.9 (z = 3.15), statistically significant inter$-$night variability at a few per cent level is detected for three of the sources, including the radio-intermediate WLQ J133219.6$+$622715.9 (z = 3.15) and the well known bona$-$fide radio$-$quiet WLQs J121221.5$+$534128.0 (z = 3.10) and WLQ J153259.9$-$003944.1 (z = 4.62). In the rest$-$frame, this variability is intra-day and in the far$-$UV band. On the time scale of a decade, we find for three of the WLQs large brightness changes, amounting to 1.655$\pm$0.009, 0.163$\pm$0.010 and 0.144$\pm$0.018 mag, for J104833.5$+$620305.0, J123743.1$+$630144.9 and J232428.4$+$144324.4, respectively. Whereas the latter two are confirmed radio-quiet WLQs, the extragalactic nature of J104833.5$+$620305.0 remains to be well established, thanks to the absence of any feature(s) in its available optical spectra. The present study forms a part of our ongoing campaign of intranight optical monitoring of radio quiet weak-line quasars, in order to improve the understanding of this enigmatic class of Active Galactic Nuclei and to look among them for a possible tiny, elusive population of radio-quiet BL Lacs.Comment: Accepted to MNRAS. 12 pages, 1 figure, 4 Tabl

Role of alcoholism in liver abscess

Background:This retrospective study was conducted on 108 patients to find the role of alcoholism in liver abscess. Methods:The present study was undertaken on patients both male and female admitted in surgical wards of Chennai medical college & hospital. 108 patients were taken up for the study from the surgical wards of the hospital over a period of 1½ year i.e., from January 2013 to June 2014.Results:The disease usually affects the males in the age group 25-55 years, alcoholism is found to be the chief predisposing factor. Following alcoholism, poor economic status & malnutrition also plays a vital role as predisposing factors in the formation of liver abscess. Among alcoholism also, consuming locally prepared alcohol plays a vital role, but the reason is still been unknown. Though Alcoholism is a predisposing factor, it has no role in the aetiology and the liver function tests also did not show much alteration. Improvement in radio diagnosis helps not only in diagnosis but also in the management. In complicated liver abscesses, the most common complication was found to be pleuropulmonary, followed by peritoneal and pericardial. With abscess remaining confined to the liver the case fatality rate is nil. Even in complicated cases, the case fatality rate is low. Comparison of the results of our study with various studies which are done all over the world are found be coinciding.Conclusion:From our study it was undoubtedly proved that alcoholism, mainly consuming locally prepared alcohol plays a major role as a predisposing factor for the formation of liver abscesses that is both amoebic as well as pyogenic liver abscess because of the adverse effects of alcohol over the Liver. It is also proven that Alcoholism is never an etiological factor for the formation of liver abscess.

Long term Ultra-Violet Variability of Seyfert galaxies

Flux variability is one of the defining characteristics of Seyfert galaxies, a class of active galactic nuclei (AGN). Though these variations are observed over a wide range of wavelengths, results on their flux variability characteristics in the ultra-violet (UV) band are very limited. We present here the long term UV flux variability characteristics of a sample of fourteen Seyfert galaxies using data from the International Ultraviolet Explorer acquired between 1978 and 1995. We found that all the sources showed flux variations with no statistically significant difference in the amplitude of UV flux variation between shorter and longer wavelengths. Also, the flux variations between different near-UV (NUV, 1850 - 3300 A) and far-UV (FUV, 1150 - 2000 A) passbands in the rest frames of the objects are correlated with no time lag. The data show indications of (i) a mild negative correlation of UV variability with bolometric luminosity and (ii) weak positive correlation between UV variability and black hole mass. At FUV, about 50% of the sources show a strong correlation between spectral indices and flux variations with a hardening when brightening behaviour, while for the remaining sources the correlation is moderate. In NUV, the sources do show a harder when brighter trend, however, the correlation is either weak or moderate.Comment: Accepted by Journal of Astrophysics and Astronom

Clinical study of multi nodular goitre in a rural hospital

Background: Worldwide, nodular goitre remains a problem of enormous magnitude affecting no less than 5% of the population. Neither a well formulated nor a simple procedure is available for the management of MNG. Hence the need for the present study. The aim was to study the various modes of presentation, the distribution with respect to age and sex, the usefulness of FNAC, and the complications of surgery.Methods: This was a prospective study of 50 cases of MNG during the period between April 2012 and March 2014, in Chennai medical college hospital with an adequate follow up to look for post op complications.Results: Majority of the patients were females with an M:F ratio of 15:1,with the commonest age group being 31-40 years. All patients presented with swelling in front of the neck, with other complaints being that of pain, discomfort, and features of hyperthyroidism in 6 patients. FNAC was done in all patients and was found to be 100% accurate. Majority of the patients were treated with total thyroidectomy followed by subtotal thyroidectomy. Complications included wound infection, post op bleeding and RLN palsy.Conclusion: FNAC is an invaluable and highly accurate tool in the diagnosis of MNG. Surgery - Total thyroidectomy was found to be an adequate and safe treatment for non- toxic MNG with minimal complications.

Night sky at the Indian Astronomical Observatory during 2000-2008

We present an analysis of the optical night sky brightness and extinction coefficient measurements in UBVRI at the Indian Astronomical Observatory (IAO), Hanle, during the period 2003-2008. They are obtained from an analysis of CCD images acquired at the 2 m Himalayan Chandra Telescope at IAO. Night sky brightness was estimated using 210 HFOSC images obtained on 47 nights and covering the declining phase of solar activity cycle-23. The zenith corrected values of the moonless night sky brightness in mag/square arcsecs are 22.14(U), 22.42(B), 21.28(V), 20.54(R) and 18.86(I) band. This shows that IAO is a dark site for optical observations. No clear dependency of sky brightness with solar activity is found. Extinction values at IAO are derived from an analysis of 1325 images over 58 nights. They are found to be 0.36 in U-band, 0.21 in B-band, 0.12 in V-band, 0.09 in R-band and 0.05 in I-band. On average, extinction during the summer months is slightly larger than that during the winter months. No clear evidence for a correlation between extinction in all bands and the average night time wind speed is found. Also presented here is the low resolution moonless optical night sky spectrum for IAO covering the wavelength range 3000-9300 \AA. Hanle region thus has the required characteristics of a good astronomical site in terms of night sky brightness and extinction, and could be a natural candidate site for any future large aperture Indian optical-infrared telescope(s).Comment: 18 pages, 7 figures, uses basi.cls, accepted for publication in Bulletin of the Astronomical Society of Indi

Simulation of 3-phase matrix converter using space vector modulation

This paper illustrates the simulation of 3-phase matrix converter using Space Vector Modulation (SVM). Variable AC output voltage engendered using matrix converter with bidirectional power switches controlled by appropriate switching pulse. The conventional PWM converter engenders switching common mode voltage across the load system terminals, which cause to common mode current and its leads to bearing failure in load drive. These problems can be rectified using SVM and which minimize the effect on the harmonic fluctuation in AC output voltage and stress on the power switch is reduced using bidirectional switch for proposed 3-phase matrix converter. The simulation results have been presented to validate the proposed system using matlab / simulink

Variable mass accretion and failed wind explain changing look phenomena in NGC 1365

Changing look active galactic nuclei (CLAGNs) show complex nature in their X-ray spectral shape and line of sight column density variation. The physical mechanisms responsible for these variations are unclear. Here, we study the spectral properties of a CLAGN, NGC\,1365 using combined {\it XMM-Newton} and {\it NuSTAR} observations to understand the CL behavior. The model fitted mass accretion rate varied between $0.003\pm 0.001$ and $0.009\pm0.002$ $\dot M_{\rm Edd}$ and the dynamic corona changed from $28\pm 3$ to $10\pm1$ $r_g$. We found that the variable absorption column density correlates with the mass accretion rate and the geometry of the corona. The derived wind velocity was sufficiently low compared to the escape velocity to drive the wind away from the disc for the epochs when column densities were high. This suggests that the high and variable absorption can be due to failed winds from the disc. Our estimated ratio of mass outflow to inflow rate from the inner region of the disc lies between $0.019\pm0.006$ and $0.12\pm0.04$. From spectral fitting of the combined data, we found the mass of the central black hole to be constant $4.38\pm0.34 - 4.51\pm0.29 \times10^{6} M_\odot$, consistent with earlier findings. The confidence contours of $N_H$ with other model parameters show that the model fitted parameters are robust and non-degenerate. Our study construed that the changing accretion rate, which is a fundamental physical quantity and the geometry of the corona driving the CL phenomena in NGC\,1365. The physical picture considered in this work connects both variable continuum and variable absorbing medium scenarios.Comment: 8 pages, 7 figures, 1 table, accepted for publication in A&A, comments welcom

Multiwavelength study of radio galaxy Pictor A: detection of western hotspot in far-UV and possible origin of high energy emissions

A comprehensive study of the nucleus and western hotspot of Pictor A is carried out using AstroSat observations, 13 years of Fermi, and archival Swift observations, along with other published data. We report the first detection of the western hotspot of Pictor A in the far-UV band using observations from AstroSat-UVIT. The broad-band SED of the western hotspot is explained by a multizone emission scenario where X-ray emission is caused by synchrotron emission process in the substructures embedded in the diffuse region, while the emission in radio to optical is caused by synchrotron emission process in the diffuse region. We do not notice any excess in the IR band and an additional zone (beyond 2-zone) is not required to account for the X-ray emission. Our broad-band spectro-temporal study and associated modelling of the core and hotspot of Pictor A suggests that (a) gamma-rays originate in the nuclear jet and not from the hotspot (b) X-ray emission from the core of Pictor A has nuclear jet-origin instead of previously reported disk-origin.Comment: 11 pages, 4 figures, Accepted for publication in MNRA