HII Regions, Embedded Protostars, and Starless Cores in Sharpless 2-157

We present arcsecond resolution 1.4mm observations of the high mass star forming region, Sharpless 2-157, that reveal the cool dust associated with the first stages of star formation. These data are compared with archival images at optical, infrared, and radio wavelengths, and complemented with new arcsecond resolution mid-infrared data. We identify a dusty young HII region, numerous infrared sources within the cluster envelope, and four starless condensations. Three of the cores lie in a line to the south of the cluster peak, but the most massive one is right at the center and associated with a jumble of bright radio and infrared sources. This presents an interesting juxtaposition of high and low mass star formation within the same cluster which we compare with similar observations of other high mass star forming regions and discuss in the context of cluster formation theory.Comment: accepted to ApJ; 6 pages, 3 figure

Resolving distance ambiguities towards 6.7 GHz methanol masers

Distances to most star forming regions are determined using kinematics, through the assumption that the observed radial velocity arises from the motion of the source with respect to the Sun resulting from the differential rotation of Galaxy. The primary challenge associated with the application of this technique in the inner Galaxy is the kinematic distance ambiguity. In this work, we aim to resolve the kinematic distance ambiguity towards a sample of 6.7 GHz methanol masers, which are signposts of the early stages of massive star formation. We measured 21 cm HI absorption spectra using the Very Large Array in C and CnB configurations. A comparison of the maximum velocity of HI absorption with the source velocity and tangent point velocity was used to resolve the kinematic distance ambiguity. We resolved the distance ambiguity towards 41 sources. Distance determinations that are in conflict with previous measurements are discussed. The NE2001 spiral arm model is broadly consistent with the locations of the star forming complexes. We find that the use of vertical scale height arguments to resolve the distance ambiguity can lead to erroneous classifications for a significant fraction of sources.Comment: Accepted by Astronomy & Astrophysic

The Arecibo Methanol Maser Galactic Plane Survey - III: Distances and Luminosities

We derive kinematic distances to the 86 6.7 GHz methanol masers discovered in the Arecibo Methanol Maser Galactic Plane Survey. The systemic velocities of the sources were derived from 13CO (J=2-1), CS (J=5-4), and NH3 observations made with the ARO Submillimeter Telescope, the APEX telescope, and the Effelsberg 100 m telescope, respectively. Kinematic distance ambiguities were resolved using HI self-absorption with HI data from the VLA Galactic Plane Survey. We observe roughly three times as many sources at the far distance compared to the near distance. The vertical distribution of the sources has a scale height of ~ 30 pc, and is much lower than that of the Galactic thin disk. We use the distances derived in this work to determine the luminosity function of 6.7 GHz maser emission. The luminosity function has a peak at approximately 10^{-6} L_sun. Assuming that this luminosity function applies, the methanol maser population in the Large Magellanic Cloud and M33 is at least 4 and 14 times smaller, respectively, than in our Galaxy.Comment: Accepted by Ap

Optical properties of AlGaN nanowires synthesized via ion beam techniques

AlGaN plays a vital role in hetero-structure high electron mobility transistor by employing a two-dimensional electron gas and as electron blocking layer in the multi quantum well light emitting diodes. Nevertheless, the incorporation of Al in GaN for the formation of AlGaN alloy is limited by the diffusion barrier formed by instant nitridation of Al adatoms by reactive atomic N. Incorporation of Al above the miscibility limit, however can be achieved by ion beam technique. The well known ion beam mixing (IBM) technique was carried out with the help of Ar+ irradiation for different fluences. A novel approach was also adopted for the synthesis of AlGaN by the process of post irradiation diffusion (PID) as a comparative study with the IBM technique. The optical investigations of AlGaN nanowires, synthesized via two different methods of ion beam processing are reported. The effect of irradiation fluence and post irradiation annealing temperature on the random alloy formation were studied by the vibrational and photoluminescence (PL) spectroscopic studies. Vibrational studies show one-mode phonon behavior corresponding to longitudinal optical (LO) mode of A1 symmetry (A1(LO)) for the wurtzite phase of AlGaN nanowires in the random alloy model. Maximum Al atomic percentage ~6.3-6.7% was calculated with the help of band bowing formalism from the Raman spectral analysis for samples synthesized in IBM and PID processes. PL studies show the extent of defects present in these samples

Investigations on the Flexural Strength and the Effect of b/h and l/b ratio on the Carbon Fiber Reinforced Epoxy Laminated Composites

In present day the use of fiber reinforced composites is increased remarkably in the various sectors of industries owing to its relative advantages especially in industries like aeronotics, automobile, ship buildingand in chemical industries, where the major emphasis is on weight reduction with a subtantial increase in the mechanical strengt h of the component with enhanced durabli ty by having properties like corrosive resistance, anti reactive to various acidic reactions and to with stand various climatic and temperature conditions.In this context carbon fibre reinforced laminated composites exhibit excellent mechanical properties.Investigation of various properties is difficult in composite materials because of its complex behavior further it is very difficult to evaluate the behavior of fiber laminated composites because of its enhanced complexity,evaluation of properties in composites is difficult with the addition of the fiber (carbon fiber)into the matrix. in this paper an investigation on the flexural properties of the carbon fiber reinforced laminates is carried out and the effect of bredth(b)to thickness(t)and the influence of the of length(l)to breadth(b),Aspect ratiois being evaluated and appropriate conclusions are drawn

The Arecibo Methanol Maser Galactic Plane Survey-IV: Accurate Astrometry and Source Morphologies

We present accurate absolute astrometry of 6.7 GHz methanol masers detected in the Arecibo Methanol Maser Galactic Plane Survey using MERLIN and the Expanded Very Large Array (EVLA). We estimate the absolute astrometry to be accurate to better than 15 and 80 milliarcseconds for the MERLIN and EVLA observations respectively. We also derive the morphologies of the maser emission distributions for sources stronger than ~ 1 Jy. The median spatial extent along the major axis of the regions showing maser emission is ~ 775 AU. We find a majority of methanol maser morphologies to be complex with some sources previously determined to have regular morphologies in fact being embedded within larger structures. This suggests that some maser spots do not have a compact core, which leads them being resolved in high angular resolution observations. This also casts doubt on interpretations of the origin of methanol maser emission solely based on source morphologies. We also investigate the association of methanol masers with mid-infrared emission and find very close correspondence between methanol masers and 24 micron point sources. This adds further credence to theoretical models that predict methanol masers to be pumped by warm dust emission and firmly reinforces the finding that Class II methanol masers are unambiguous tracers of embedded high-mass protostars.Comment: Accepted by Ap

The Arecibo Methanol Maser Galactic Plane Survey - II: Statistical and Multi-wavelength Counterpart Analysis

We present an analysis of the properties of the 6.7 GHz methanol maser sample detected in the Arecibo Methanol Maser Galactic Plane Survey. The distribution of the masers in the Galaxy, and statistics of their multi-wavelength counterparts is consistent with the hypothesis of 6.7 GHz maser emission being associated with massive young stellar objects. Using the detection statistics of our survey, we estimate the minimum number of methanol masers in the Galaxy to be 1275. The l-v diagram of the sample shows the tangent point of the Carina-Sagittarius spiral arm to be around 49.6 degrees, and suggests occurrence of massive star formation along the extension of the Crux-Scutum arm. A Gaussian component analysis of the maser spectra shows the mean line-width to be 0.38 km/s which is more than a factor of two larger than what has been reported in the literature. We also find no evidence that faint methanol masers have different properties than those of their bright counterparts.Comment: Accepted by ApJ; Revised footnote number 3 on page 8 based on private communicatio

Woman Entrepreneurship Through SHGs in Tamil Nadu, India

Entrepreneurship development and income generating activities are a feasible solution for empowering women. It generates income and also provides flexible working hours according to the needs of home makers. Economic independence is the need of the hour. Participation in income generating activities helps in the overall empowerment of women. Empowering women through education, ideas, consciousness, mobilization and participatory approach can enable them to take their own decisions, make them selfreliant and self-confident. Although women are taking on important positions in the business sector, they continue to face barriers to their entrepreneurial activities, compared to their male counterparts. Women still have to struggle with their traditional role in order to balance career and household responsibilities. They have to endure negative social value and cultural bias that lead to unfair perceptions about their ability to operate a business and legal constraints also limit the pursuit of economic independence by women