The low-mass population in the young cluster Stock 8: Stellar properties and Initial Mass Function

The evolution of HII regions/supershells can trigger a new generation of stars/clusters at their peripheries, with environmental conditions that may affect the initial mass function, disk evolution and star formation efficiency. In this paper we study the stellar content and star formation processes in the young cluster Stock 8, which itself is thought to be formed during the expansion of a supershell. We present deep optical photometry along with JHK and 3.6, 4.5 {\mu}m photometry from UKIDSS and Spitzer-IRAC. We use multi-color criteria to identify the candidate young stellar objects in the region. Using evolutionary models, we obtain a median log(age) of ~6.5 (~3.0 Myr) with an observed age spread of ~0.25 dex for the cluster. Monte Carlo simulations of the population of Stock 8, based on estimates for the photometric uncertainty, differential reddening, binarity, and variability, indicate that these uncertainties introduce an age spread of ~0.15 dex. The intrinsic age spread in the cluster is ~0.2 dex. The fraction of young stellar objects surrounded by disk is ~35%. The K-band luminosity function of Stock 8 is similar to that of the Trapezium cluster. The IMF of Stock 8 has a Salpeter- like slope at >0.5 Msun and the IMF flattens and peaks at ~0.4 Msun, below which declines into the substellar regime. Although Stock 8 is surrounded by several massive stars, there seems to be no severe environmental effect in the form of IMF due to the proximity of massive stars around the cluster.Comment: Accepted for publication in Ap

Study of Bio-fertilizer Produced from Agro-waste (Sesame Straw) and Cow Dung Using Eisenia fetida and Perionyx sansibaricus in Arid Environment

In this study, an analysis of organic fertilizer of an agro-waste (Sesame straw) plus cow dung was carried out using an epigeic earthworm species Eisenia fetida and Perionyx sansibaricus. Sesame straw is abundantly produced after each harvesting of the crop in Kharif season in arid region of tropical India. The compost produced in presence and absence of earthworm exhibit significant (P0.05) changes in physicochemical properties respectively. In control bedding, the values of water holding capacity enhanced significantly (P<0.05) by 1.28 fold, while organic carbon and C/N ratio decreased significantly (P<0.05) by 19.93% and 31.25% respectively after 60 days of composting.Working of E. fetida in the bedding material showed significant (P<0.001) difference in the level of pH, electrical conductivity, water holding capacity, organic carbon, total nitrogen, C/N ratio, available phosphorous and available potassium. After 60 days of working of P. sansibaricus, these physicochemical properties of the bedding substrate also changed significantly (P<0.001). Analysis of vermibed showed a gradual increase in electrical conductivity, water holding capacity, total nitrogen, available phosphorus and available potassium by 1.51, 1.86, 1.95, 1.78 and 1.75 fold respectively. While the values of pH, organic carbon and C/N ratio declined by 9.30%, 41.80% and 71.48% respectively within 60 days of decomposition. Thus, E. fetida and P. sansibaricus can be applied for production of organic fertilizer of sesame chaff plus cow dung to fulfill the requirement of bio-fertilizers for organic farming and agro-waste management in arid environment

Majorization-Minimization based Hybrid Localization Method for High Precision Localization in Wireless Sensor Networks

This paper investigates the hybrid source localization problem using the four radio measurements - time of arrival (TOA), time difference of arrival (TDOA), received signal strength (RSS) and angle of arrival (AOA). First, after invoking tractable approximations in the RSS and AOA models, the maximum likelihood estimation (MLE) problem for the hybrid TOA-TDOA-RSS-AOA data model is derived. Then, in the MLE, which has the least-squares objective, weights determined using the range-based characteristics of the four heterogeneous measurements, are introduced. The resultant weighted least-squares problem obtained, which is non-smooth and non-convex, is solved using the principle of the majorization-minimization (MM), leading to an iterative algorithm that has a guaranteed convergence. The key feature of the proposed method is that it provides a unified framework where localization using any possible merger out of these four measurements can be implemented as per the requirement/application. Extensive numerical simulations are conducted to study the estimation efficiency of the proposed method. The proposed method employing all four measurements is compared against a conventionally used method and also against the proposed method employing only limited combinations of the four measurements. The results obtained indicate that the hybrid localization model improves the localization accuracy compared to the heterogeneous measurements. The integration of different measurements also yields good accuracy in the presence of non-line of sight (NLOS) errors

Characteristics of gravity waves generated in a convective and a non-convective environment revealed from hourly radiosonde observation under CPEA-II campaign

Analyses of hourly radiosonde data of temperature, wind, and relative humidity during four days (two with convection and two with no convection) as a part of an intensive observation period in CPEA-2 campaign over Koto Tabang (100.32° E, 0.20° S), Indonesia, are presented. Characteristics of gravity waves in terms of dominant wave frequencies at different heights and their vertical wavelengths are shown in the lower stratosphere during a convective and non-convective period. Gravity waves with periods ~10 h and ~4–5 h were found dominant near tropopause (a region of high stability) on all days of observation. Vertical propagation of gravity waves were seen modified near heights of the three identified strong wind shears (at ~16, 20, and 25 km heights) due to wave-mean flow interaction. Between 17 and 21 km heights, meridional wind fluctuations dominated over zonal wind, whereas from 22 to 30 km heights, wave fluctuations with periods ~3–5 h and ~8–10 h in zonal wind and temperature were highly associated, suggesting zonal orientation of wave propagation. Gravity waves from tropopause region to 30 km heights were analyzed. In general, vertical wavelength of 2–5 km dominated in all the mean-removed (~ weekly mean) wind and temperature hourly profiles. Computed vertical wavelength spectra are similar, in most of the cases, to the source spectra (1–16 km height) except that of zonal wind spectra, which is broad during active convection. Interestingly, during and after convection, gravity waves with short vertical wavelength (~2 km) and short period (~2–3 h) emerged, which were confined in the close vicinity of tropopause, and were not identified on non-convective days, suggesting convection to be the source for them. Some wave features near strong wind shear (at 25 km height) were also observed with short vertical wavelengths in both convective and non-convective days, suggesting wind shear to be the sole cause of generation and seemingly not associated with deep convection below. A drop in the temperature up to ~4–5 K (after removal of diurnal component) was observed at ~16 km height near a strong wind shear (~45–55 m s⁻¹ km⁻¹) during active period of convection

Soil Fertility under Grassland Compared to Other Land Uses in Acid Soil of Himachal Pradesh, India

In the last decades severe changes in land use occurred in tropical countries, due to increasing population and their demand for food resources. Forest land is rapidly converted into agriculture or pastureland which may cause significant changes in soil fertility. Land-use exerts significant effect on nutrient availability and may also influence secondary succession and biomass production (Lu et al., 2002). Nutrient cycling in agroforestry is in between natural forest ecosystems of the tropics and most of the agricultural systems with are ‘‘leaky’’ having higher nutrient losses. Research indicated that decline of soil organic matter may occur due to conversion of forest and grassland into agriculture (Ouattara et al., 2006). Tree growth is highly influenced by base cations (Ca, Mg, K, Na) concentration, cation exchange capacity, and concentrations of Al and Mn. Calcium and N are specifically important, as they are primary constituents of biomass and regulate cell function of many tree species. Base cations also help in alleviating the effects of Al toxicity in acid soil

Mesoscale convection system and occurrence of extreme low tropopause temperatures: observations over Asian summer monsoon region

The present study examines the process of how tropospheric air enters the stratosphere, particularly in association with tropical mesoscale convective systems (TMCS) which are considered to be one of the causative mechanisms for the observation of extremely low tropopause temperature over the tropics. The association between the phenomena of convection and the observation of extreme low tropopause temperature events is, therefore, examined over the Asian monsoon region using data from multiple platforms. Satellite observations show that the area of low outgoing long wave radiation (OLR), which is a proxy for the enhanced convection, is embedded with high altitude clouds top temperatures (&le;193 K). A detailed analysis of OLR and 100 hPa temperature shows that both are modulated by westward propagating Rossby waves with a period of ~15 days, indicating a close linkage between them. The process by which the tropospheric air enters the stratosphere may, in turn, be determined by how the areas of convection and low tropopause temperature (LTT) i.e. <I>T</I>&le;191 K are spatially located. In this context, the relative spatial distribution of low OLR and LTT areas is examined. Though, the locations of low OLR and LTT are noticed in the same broad area, the two do not always overlap, except for partial overlap in some cases. When there are multiple low OLR areas, the LTT area generally appears in between the low OLR areas. Implications of these observations are also discussed. The present analysis also shows that the horizontal mean winds have a role in the spatial distribution of low OLR and LTT

Oral human papillomavirus (HPV) infection in men who have sex with men: prevalence and lack of anogenital concordance.

To estimate the prevalence of oral detectable human papillomavirus (HPV) DNA in HIV-negative men who have sex with men (MSM) attending a sexual health clinic in London and concordance with anogenital HPV infection. Such data are important to improve our understanding of the epidemiology of oral HPV and the potential use of vaccines to prevent oropharyngeal cancers

Enhanced Room Temperature Coefficient of Resistance and Magneto-resistance of Ag-added La0.7Ca0.3-xBaxMnO3 Composites

In this paper we report an enhanced temperature coefficient of resistance (TCR) close to room temperature in La0.7Ca0.3-xBaxMnO3 + Agy (x = 0.10, 0.15 and y = 0.0 to 0.40) (LCBMO+Ag) composite manganites. The observed enhancement of TCR is attributed to the grain growth and opening of new conducting channels in the composites. Ag addition has also been found to enhance intra-granular magneto-resistance. Inter-granular MR, however, is seen to decrease with Ag addition. The enhanced TCR and MR at / near room temperature open up the possibility of the use of such materials as infrared bolometric and magnetic field sensors respectively.Comment: 22 pages of Text + Figs:comments/suggestions([email protected]