Arecibo observations of Parkes multibeam pulsars

The on-going Parkes multibeam survey has been astoundingly successful (Manchesteret al. 2001), and its discovery of over 600 pulsars has opened up new avenues for probing the Galaxy’s electron content and magnetic field. Here we report on recent observations made with the Arecibo 305-m telescope, where 80 distant, high dispersion measure pulsars (of which 35 are from the multibeam survey) were studied at multiple frequency bands in the range 0.4–2.4 GHz, in order to determine their scattering properties, rotation measures and spectral indices. The results will be used to meet a variety of science goals; viz., creating an improved model of the electron density, mapping out the Galactic magnetic field, and modeling the pulsar population.     

Scope of high-frequency time keeping in searches for short-period gamma-ray sources

This paper presents a novel technique to derive the absolute time of occurrence of an event with an accuracy of < 200 μs by adapting the HF time synchronization technique to correct for the aging rate and the frequency drift of a temperature-controlled quartz frequency standard. The propagation delay suffered by the HF time signals has been estimated by monitoring the clock error with respect to time signals from five broadcast stations located at distances in the range 500–3700 km from Gulmarg. Using simulated data, we further show the viability of this technique in permitting periodicity searches on timescales of ≥5 milliseconds in cosmic gamma-ray data An erratum to this article is available at .     

PGE and isotopic characteristics of Shergol and Suru Valley Ophiolites,Western Ladakh: Implications for supra-subduction tectonics along Indus Suture Zone

Present study reports the PGE-geochemistry of mantle peridotites and Nd-isotope geochemistry of arc related mafic rocks from the Indus Suture Zone (ISZ), western Ladakh. The total PGE concentration of the Shergol and Suru Valley peridotites (∑PGE = 96–180 ppb) is much higher than that of the primitive mantle and global ophiolitic mantle peridotites. The studied peridotites show concave upward PGE-distribution patterns with higher palladium-group PGE/Iridium-group PGE ratios (i.e., 0.8–2.9) suggesting that the partial melting is not the sole factor responsible for the evolution of these peridotites. The observed PGE-distribution patterns are distinct from residual/refractory mantle peridotites, which have concave downward or flat PGE-distribution patterns. Relative enrichment of palladium-group PGE as well as other whole-rock incompatible elements (e.g., LILE and LREE) and higher Pd/Ir ratio (1.1–5.9) reflects that these peridotites have experienced fluid/melt interaction in a supra-subduction zone (SSZ) tectonic setting. Also, the Shergol mafic intrusives and Dras mafic volcanics, associated with the studied peridotites, have high ¹⁴³Nd/¹⁴⁴Nd ratios (i.e., 0.512908–0.513078 and 0.512901–0.512977, respectively) and positive ε_Nd(t) (calculated for t = 140 Ma) values (i.e., +5.3 to +8.6 and + 5.1 to +6.6, respectively), indicating derivation from depleted mantle sources within an intra-oceanic arc setting, similar to Spongtang and Nidar ophiolites from other parts of Ladakh Himalaya. The transition from SSZ-type Shergol and Suru Valley peridotites to Early Cretaceous tholeiitic Shergol mafic intrusives followed by tholeiitic to calc-alkaline Dras mafic volcanics within the Neo-Tethys Ocean exhibit characteristics of subduction initiation mechanism analogous to the Izu-Bonin-Mariana arc system within western Pacific.     

Biodegradation of polyvinyl alcohol-low linear density polyethylene-blended plastic film by consortium of marine benthic vibrios

Marine bacteria, Vibrio alginolyticus and Vibrio parahemolyticus isolated from sediments were evaluated for their ability as a consortia, to degrade polyvinyl alcohol-low linear density polyethylene (PVA-LLDPE)-blended plastic films in shake flask conditions at 120 rpm at 37 °C over 15 weeks. Results indicated that relatively 20 % decrease in tensile strength of the film could be achieved with 25 and 30 % blend of PVA in the PVA-LLDPE plastic film compared to other ratios. Micrographs obtained with scanning electron microscope showed visible cracks and grooves on the surface of the PVA-LLDPE blend film after 15 weeks of incubation with bacterial consortium. The decrease in tensile strength of the PVA-blended plastic films after treatment and the results of the scanning electron microscopic analysis evidence that the consortium could cause degradation of PVA-LLDPE plastic blends compared to suitable controls. This is the first report on polyvinyl alcohol degrading Vibrio sp. from marine sediments and its application in microbial degradation of polyvinyl alcohol-low linear density polyethylene plastic blends. The study indicated potential of marine benthic vibrios that have novel enzymes and unique characteristics for application in bioremediation and solid waste management particularly in handling synthetic polymers such as PVA-blended plastic films.     

Mapping of Soil Micronutrients in Kashmir Agricultural Landscape Using Ordinary Kriging and Indicator Approach

Soil nutrient maps based on intensive soil sampling are useful to adopt site-specific management practices. Geostatistical methods have been widely used to determine the spatial correlation and the range of spatial dependence at different sampling scales. If spatial dependence is detected, the modeled semivariograms can then be used to map the interested variable by kriging, an interpolation method that produces unbiased estimates with minimal estimation variance. The objectives of this paper were to examine and map the spatial distribution of the soil micronutrients Cu, Zn, Fe and Mn on an agricultural area in Kupwara, J&K, under temperate climatic conditions. The ordinary kriging was first used to determine the values for the non-sampled locations, and then the indicator approach was used to transform the micronutrient content values into binary values having the mean values of each nutrient as the threshold content. All four elements analyzed showed spatial dependence using the indicator semivariograms. The strength of spatial dependence was assessed using the values of nugget effect and range from the semivariogram, the fitted range values decreased in the order Zn > Cu > Mn > Fe. The spatial dependence of the combination of two or more of the studied micronutrients was also examined using indicator semivariograms. In opposition to spatial analysis of individual microelements, indicator semivariograms obtained for the binary coding of the variables showed a great nugget effect value or a low proportion of sill. The maps for each nutrient obtained using indicator kriging showed some similarity in the spatial distribution, suggesting the delimitation of uniform management areas.     

Reservoir induced landslide at Assar,Jammu and Kashmir: A case study

In February 2009, a huge landslide occurred at Assar in Doda district of Jammu and Kashmir state. The slide triggered after the reservoir level of the Baglihar dam increased from initial water level of 850 m to 870 m. The impounding of reservoir water created high angle scarps at number of fossil slide sites on either side of the river within the reservoir area. One such scarp (about 250 m long) at Assar caused a huge landslide washing out about 150 m road stretch. The sliding material is dominated by finer fraction (71.5 %) of micaceous silty sand and coarser fraction of gravel to boulder size. Over saturation of the slope forming material, weak rocks and high absorption and swelling nature of the soil, high slope angle and toe cutting by the water are the main reasons that triggered this slide.     

Vertical structure of orographic precipitating clouds observed over south Asia during summer monsoon season

Orography profoundly influences seasonal rainfall amount in several places in south Asia by affecting rain intensity and duration. One of the fundamental questions concerning orographic rainfall is nature of the associated precipitating clouds in the absence of synoptic forcing. It is believed that these clouds are not very deep, however, there is not much information in the literature on their vertical structure. The present study explores the vertical structure of precipitating clouds associated with orographic features in south Asia using data collected with the precipitation radar on board the Tropical Rainfall Measuring Mission satellite. Two types of precipitating clouds have been defined based on cloud echo top height, namely, shallow echo-top cloud and medium echo-top cloud. In both, radar reflectivity factor is at least 30 dBZ at 1.5 km altitude, and tops of shallow and medium echo-top clouds lie below 4.5 km and between 4.5 and 8 km, respectively. The Western Ghats contains the highest fraction of the shallow echo-top clouds followed by the adjacent eastern Arabian Sea, while the Khasi Hills in Meghalaya and Cardamom Mountains in Cambodia contain the least fraction of them. Average vertical profiles of shallow echo-top clouds are similar in different mountainous areas while regional differences are observed in the medium echo-top clouds. Below 3 km, precipitation liquid water content in medium echo-top clouds is the highest over the Western Ghats and the eastern Arabian Sea. The average precipitation liquid water content increases by \(0.16\,\hbox { gm m}^{-3}\) for shallow echo-top clouds between 3 and 1.5 km altitude, while the corresponding increase for medium echo-top clouds is in 0.05–0.08 \(\hbox { gm m}^{-3}\) range.     

VRI photometry of M67 for CCD standardization at 2.3m VBT

We present the results from CCD photometry in theV, R andI bands, of the ‘Dipper Asterism’ region of the open cluster M67 based on observations carried out at the prime focus of the 2.3 m Vainu Bappu Telescope of the Vainu Bappu Observatory, Kavalur. The CCD parameters like the system gain and the readout noise are measured using several flatfield frames taken through the standardI filter. The CCD chip is calibrated using the photometric standards in the field and linear colour transformation relations are derived. Also a few newVRI photometric measurements are reported for the members of the cluster.     

A search for the millisecond pulsar in Cygnus X-3

Atmospheric Cerenkov data, recorded at Gulmarg, India, during the 2-year period 1988–1989 in the direction of Cygnus X-3, have been searched for the presence of a periodic pulsar modulation, employing both the Rayleigh power and the epoch-folding ( ²) techniques. No evidence is found for pulsations at either 12.59 ms or 9.22 ms, the two period values around which the detection of pulsed signals has been reported by three atmospheric Cerenkov groups, but not by at least two other groups, including one using a higher-sensitivity Cerenkov imaging telescope.     

On the marine atmospheric boundary layer characteristics over Bay of Bengal and Arabian Sea during the Integrated Campaign for Aerosols,gases and Radiation Budget (ICARB)

Detailed measurements were carried out in the Marine Atmospheric Boundary Layer (MABL) during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) which covered both Arabian Sea and Bay of Bengal during March to May 2006. In this paper, we present the meteorological observations made during this campaign. The latitudinal variation of the surface layer turbulent fluxes is also described in detail.