Cerenkov radiation by neutrinos in a supernova core

Neutrinos with a magnetic dipole moment propagating in a medium with a velocity larger than the phase velocity of light emit photons by the Cerenkov process. The Cerenkov radiation is a helicity flip process via which a left-handed neutrino in a supernova core may change into a sterile right-handed one and freestream out of the core. Assuming that the luminosity of the sterile right-handed neutrinos is less than 10^{53} ergs/sec gives an upper bound on the neutrino magnetic dipole moment \mu_\nu < 0.5 \times 10^{-13} \mu_B. This is two orders of magnitude more stringent than the previously established bounds on \mu_\nu from considerations of supernova cooling rate by right-handed neutrinos

The young cluster NGC 2282 : a multi-wavelength perspective

We present the analysis of the stellar content of NGC~2282, a young cluster in the Monoceros constellation, using deep optical $BVI$ and IPHAS photometry along with infrared (IR) data from UKIDSS and $Spitzer$-IRAC. Based on the stellar surface density analysis using nearest neighborhood method, the radius of the cluster is estimated as $\sim$ 3.15\arcmin. From optical spectroscopic analysis of 8 bright sources, we have classified three early B-type members in the cluster, which includes, HD 289120, a previously known B2V type star, a Herbig Ae/Be star (B0.5 Ve) and a B5 V star. From spectrophotometric analyses, the distance to the cluster has been estimated as $\sim$ 1.65 kpc. The $K$-band extinction map is estimated using nearest neighborhood technique, and the mean extinction within the cluster area is found to be A$_V$ $\sim$ 3.9 mag. Using IR colour-colour criteria and H$_\alpha$-emission properties, we have identified a total of 152 candidate young stellar objects (YSOs) in the region, of which, 75 are classified as Class II, 9 are Class I YSOs. Our YSO catalog also includes 50 H$_\alpha$-emission line sources, identified using slitless spectroscopy and IPHAS photometry data. Based on the optical and near-IR colour-magnitude diagram analyses, the cluster age has been estimated to be in the range of 2 $-$ 5 Myr, which is in agreement with the estimated age from disc fraction ($\sim$ 58\%). Masses of these YSOs are found to be $\sim$ 0.1$-$2.0 M$_\odot$. Spatial distribution of the candidate YSOs shows spherical morphology, more or less similar to the surface density map.Comment: 16 pages, 19 Figure

W40 region in the Gould Belt : An embedded cluster and H II region at the junction of filaments

We present a multiwavelength study of W40 star-forming region using IR observations in UKIRT JHK bands, Spitzer IRAC bands & Herschel PACS bands; 2.12 micron H2 narrow-band imaging; & radio observations from GMRT (610 & 1280 MHz), in a FoV of ~34'x40'. Spitzer observations along with NIR observations are used to identify 1162 Class II/III & 40 Class I sources in the FoV. The NN stellar surface density analysis shows that majority of these YSOs constitute the embedded cluster centered on the source IRS1A South. Some YSOs, predominantly younger population, are distributed along & trace the filamentary structures at lower stellar surface density. The cluster radius is obtained as 0.44pc - matching well with the extent of radio emission - with a peak density of 650pc^-2. The JHK data is used to map the extinction which is subsequently used to compute the cloud mass. It has resulted in 126 Msun & 71 Msun for the central cluster & the northern IRS5 region, respectively. H2 narrow-band imaging displays significant emission, which prominently resembles fluorescent emission arising at the borders of dense regions. Radio analysis shows this region as having blister morphology, with the radio peak coinciding with a protostellar source. Free-free emission SED analysis is used to obtain physical parameters of the overall region & the IRS5 sub-region. This multiwavelength scenario is suggestive of star formation having resulted from merging of multiple filaments to form a hub. Star formation seems to have taken place in two successive epochs, with the first epoch traced by the central cluster & the high-mass star(s) - followed by a second epoch which is spreading into the filaments as uncovered by the Class I sources & even younger protostellar sources along the filaments. The IRS5 HII region displays indications of swept-up material which has possibly led to the formation of protostars.Comment: 17 pages, 12 figures, 2 tables. Accepted for publication in The Astrophysical Journa

Histomorphological analysis of placental changes of pre-eclampsia patients in a tertiary care hospital of Puducherry, India

Background: Placenta is a dynamic tissue synthesized physiologically to serve as a nutrient source for developing fetus it is exposed to several changes in reaction to many toxemic conditions associated with pregnancies. Studies had proved that placental changes observed on histomorphology is directly proportional to reaction to hemodynamic compensatory mechanisms, thereby aiding the obstetricians to manage the sequelae of complications. Objective of this study was to study the placental histomorphology in pregnancies associated with pre-eclampsia and to quantitate the observed placental changes.Methods: The study comprised on 101 placental specimens obtained from department of obstetrics and gynecology, Mahatma Gandhi Medical College and Research Institute, Pondicherry. Toxemia of pregnancies were divided into mild, severe preeclampsia and eclampsia based on blood pressure. The 101 cases were divided as 4 groups: Group 1 (control group); Group 2 (mild preeclampsia); Group 3 (severe preeclampsia); Group 4 (eclampsia).Results: Among the 101 cases, 38 placentas were from uncomplicated full-term deliveries which constitutes the control group. The rest 63 placenta were from toxemia of pregnancies which constitutes the study group.Conclusions: The incidence of toxemic pregnancies and pre-eclamptic cases are on higher margin than assumed. Histomorphology examination of placenta plays a vital role in assessing etiopathogenesis and mechanism of toxemic pregnancies. This aids the obstetrician to further manage subsequent sequelae and fix the complication to significant proportion

Power system stability enhancment using UPFC damping controller

The rising of demand of power and difficulties of constructing a newly transmission network causes the power system to be complex and stressed. Due to the stress in the power system there is a chance of losing the stability following to the fault. When the fault occurs in the power system the whole system goes to severe transients. By using PSS and AVR we can easily stabilize the system. FACTS devices (i.e. TCSC, SVC, STATCOM, and UPFC) are extremely important to suppressing the power system oscillations for faults and it also increasing the damping of the system. The power electronic device named as UPFC which efficiently control the active and reactive power. This thesis reflects a novel control technique which is based on Fuzzy Logic technique to provide external controlling signal to UPFC which is mounted in a single-machine infinite bus system to suppress low frequency oscillations and also it describes the model of a UPFC with multi-machine system which is externally controlled by the signal which is generated by the newly proposed power flow controller to increase the stability of the system with occurrence of fault in which it connected. The proposed controller consists of Power oscillation damping controller and Proportional Integral Differential controller (POD & PID). The effectiveness of controller for suppressing oscillation due to change in mechanical input and excitation is examined by investigating their change in rotor angle and speed occurred in the SMIB system. FACTS devices are used the existing transmission system very efficiently with the specified stability margin

Star formation activity in the Galactic H II region Sh2-297

We present a multiwavelength study of the Galactic H II region Sh2-297, located in Canis Major OB1 complex. Optical spectroscopic observations are used to constrain the spectral type of ionizing star HD 53623 as B0V. The classical nature of this H II region is affirmed by the low values of electron density and emission measure, which are calculated to be 756 cm^-3 and 9.15 x 10^5 cm^-6 pc using the radio continuum observations at 610 and 1280 MHz, and VLA archival data at 1420 MHz. To understand local star formation, we identified the young stellar object (YSO) candidates in a region of area ~ 7.5' x 7.5' centered on Sh2-297 using grism slitless spectroscopy (to identify the Halpha emission line stars), and near infrared (NIR) observations. NIR YSO candidates are further classified into various evolutionary stages using color-color (CC) and color-magnitude (CM) diagrams, giving 50 red sources (H-K > 0.6) and 26 Class II-like sources. The mass and age range of the YSOs are estimated to be ~ 0.1 - 2 Msolar and 0.5 - 2 Myr using optical (V/V-I) and NIR (J/J-H) CM diagrams. The mean age of the YSOs is found to be ~ 1 Myr, which is of the order of dynamical age of 1.07 Myr of the H II region. Using the estimated range of visual extinction (1.1 - 25 mag) from literature and NIR data for the region, spectral energy distribution (SED) models have been implemented for selected YSOs which show masses and ages to be consistent with estimated values. The spatial distribution of YSOs shows an evolutionary sequence, suggesting triggered star formation in the region. The star formation seems to have propagated from the ionizing star towards the cold dark cloud LDN1657A located west of Sh2-297.Comment: 19 pages, 13 figures, 3 tables. Accepted for publication in The Astrophysical Journa

Studies on plasma processing of blue dust

A huge amount of blue dust is produced during mining operations of iron ore and mostly dumped at mines site. Till date no measure action is being taken for utilization of blue dust for extraction of metallic iron. Generally metallic iron is produced through BFO and DRI processes where particle/ore size and reductant is the most important factor considered for BF charge. The present piece of research work is aimed at use of blue dust for production of metallic iron. A newly emerging technology i.e. plasma smelting process is adopted for reduction of blue dust. Blue dust of average particle size about 100-150 micron is taken and carbon (pet coke) of 5, 10, 12, 15 and 20 percent is thoroughly mixed, used as feed material. It is charged to a 35 KW dc arc plasma furnace and smelted for different time lengths i.e. 10, 17 and 20min using argon and nitrogen, separately, as plasma forming gas. The degree of metallization, amount of recovery for all samples is measured. Maximum of 86% recovery and 98% metallization is achieved. It is observed that use of nitrogen as plasma forming gas increases the rate of recovery than that of argon plasma, due to high energy flux of nitrogen gas which increases the enthalpy due to its diatomicity. The X-ray diffraction analysis shows the presence of ferrite and cementite phases in the smelted product. Variation of microstructure is observed with the samples. The hardness measurement of different phases on the sample ensured the presence of ferrite, pearlite and cementite phases depending on smelting condition

The molecular complex associated with the Galactic HII region Sh2-90: a possible site of triggered star formation

We investigate the star formation activity in the molecular complex associated with the Galactic HII region Sh2-90, using radio-continuum maps obtained at 1280 MHz and 610 MHz, Herschel Hi-GAL observations at 70 -- 500 microns, and deep near-infrared observation at JHK bands, along with Spitzer observations. Sh2-90 presents a bubble morphology in the mid-IR (size ~ 0.9 pc x 1.6 pc). Radio observations suggest it is an evolved HII region with an electron density ~ 144 cm^-3, emission measure ~ 6.7 x 10^4 cm^-6 pc and a ionized mass ~ 55 Msun. From Hi-GAL observations it is found that the HII region is part of an elongated extended molecular cloud (size ~ 5.6 pc x 9.7 pc, H_2 column density >= 3 x 10^21 cm^-2 and dust temperature 18 -- 27 K) of total mass >= 1 x 10^4 Msun. We identify the ionizing cluster of Sh2-90, the main exciting star being an O8--O9 V star. Five cold dust clumps (mass ~ 8 -- 95 Msun), four mid-IR blobs around B stars, and a compact HII region are found at the edge of the bubble.The velocity information derived from CO (J=3-2) data cubes suggests that most of them are associated with the Sh2-90 region. 129 YSOs are identified (Class I, Class II, and near-IR excess sources). The majority of the YSOs are low mass (<= 3 Msun) sources and they are distributed mostly in the regions of high column density. Four candidate Class 0/I MYSOs have been found; they will possibly evolve to stars of mass >= 15 Msun. We suggest multi-generation star formation is present in the complex. From the evidences of interaction, the time scales involved and the evolutionary status of stellar/protostellar sources, we argue that the star formation at the immediate border/edges of Sh2-90 might have been triggered by the expanding HII region. However, several young sources in this complex are probably formed by some other processes.Comment: 22 pages, 22 figures, accepted for publication in Astronomy and Astrophysic