Enhancement of Growth and Grain Yield of Rice in Nutrient Deficient Soils by Rice Probiotic Bacteria

Plant associated bacteria are promising alternatives to chemical fertilizers for plant growth and yield improvement in an eco-friendly manner. In this study, rice associated bacteria were isolated and assessed for mineral phosphate solubilizationand indole-3-acetic acid (IAA) production activity in vitro. Six promising strains, which were tentatively identified as phylotaxon Pseudochrobactrum sp. (BRRh-1), Burkholderia sp. (BRRh-2), Burkholderia sp. (BRRh-3), Burkholderia sp. (BRRh-4), Pseudomonas aeruginosa (BRRh-5 and BRRh-6) based on their 16S rRNA gene phylogeny, exhibited significant phosphate solubilizing activity in National Botanical Research Institute phosphate growth medium, and BRRh-4 displayed the highest phosphate solubilizing activity, followed by BRRh-5. The pH of the culture broth declined, resulting in increase of growth rate of bacteria at pH 7, which might be due to organic acid secretion by the strains. In presence of L-tryptophan, five isolates synthesized IAA and the maximum IAA was produced by BRRh-2, followed by BRRh-1. Application of two most efficient phosphate solubilizing isolates BRRh-4 and BRRh-5 by root dipping (colonization) of seedling and spraying at the flowering stage significantly enhanced the growth and grain yield of rice variety BRRI dhan-29. Interestingly, application of both strains with 50% of recommended nitrogen, phosphorus and potassium fertilizers produced equivalent or higher grain yield of rice compared to the control grown with full recommended fertilizer doses, which suggests that these strains may have the potential to be used as bioinoculants for sustainable rice production

Using the Active Collimator and Shield Assembly of an EXIST-Type Mission as a Gamma-Ray Burst Spectrometer

The Energetic X-ray Imaging Survey Telescope (EXIST) is a mission design concept that uses coded masks seen by Cadmium Zinc Telluride (CZT) detectors to register hard X-rays in the energy region from 10 keV to 600 keV. A partially active or fully active anti-coincidence shield/collimator with a total area of between 15 and 35 square meters will be used to define the field of view of the CZT detectors and to suppress the background of cosmic-ray-induced events. In this paper, we describe the use of a sodium activated cesium iodide shield/collimator to detect gamma-ray bursts (GRBs) and to measure their energy spectra in the energy range from 100 keV up to 10 MeV. We use the code GEANT4 to simulate the interactions of photons and cosmic rays with the spacecraft and instrument and the code DETECT2000 to simulate the optical properties of the scintillation detectors. The shield collimator achieves a nu-F-nu sensitivity of 3 x 10^(-9) erg cm^(-2) s^(-1) and 2 x 10^(-8) erg cm^(-2) s^(-1) at 100 keV and 600 keV, respectively. The sensitivity is well matched to that of the coded mask telescope. The broad energy coverage of an EXIST-type mission with active shields will constrain the peak of the spectral energy distribution (SED) for a large number of GRBs. The measurement of the SED peak may be key for determining photometric GRB redshifts and for using GRBs as cosmological probes.Comment: 20 pages, 10 Figures, Accepted May 19, 2006 A&

The optical counterpart to gamma-ray burst GRB970228 observed using the Hubble Space Telescope

Although more than 2,000 astronomical gamma-ray bursts (GRBs) have been detected, and numerous models proposed to explain their occurrence, they have remained enigmatic owing to the lack of an obvious counterpart at other wavelengths. The recent ground-based detection of a transient source in the vicinity of GRB 970228 may therefore have provided a breakthrough. The optical counterpart appears to be embedded in an extended source which, if a galaxy as has been suggested, would lend weight to those models that place GRBs at cosmological distances. Here we report the observations using the Hubble Space Telescope of the transient counterpart and extended source 26 and 39 days after the initial gamma-ray outburst. We find that the counterpart has faded since the initial detection (and continues to fade), but the extended source exhibits no significant change in brightness between the two dates of observations reported here. The size and apparent constancy between the two epochs of HST observations imply that it is extragalactic, but its faintness makes a definitive statement about its nature difficult. Nevertheless, the decay profile of the transient source is consistent with a popular impulsive-fireball model, which assumes a merger between two neutron stars in a distant galaxy.Comment: 11 pages + 2 figures. To appear in Nature (29 May 1997 issue

The chaperone protein clusterin may serve as a cerebrospinal fluid biomarker for chronic spinal cord disorders in the dog

Chronic spinal cord dysfunction occurs in dogs as a consequence of diverse aetiologies, including long-standing spinal cord compression and insidious neurodegenerative conditions. One such neurodegenerative condition is canine degenerative myelopathy (DM), which clinically is a challenge to differentiate from other chronic spinal cord conditions. Although the clinical diagnosis of DM can be strengthened by the identification of the Sod1 mutations that are observed in affected dogs, genetic analysis alone is insufficient to provide a definitive diagnosis. There is a requirement to identify biomarkers that can differentiate conditions with a similar clinical presentation, thus facilitating patient diagnostic and management strategies. A comparison of the cerebrospinal fluid (CSF) protein gel electrophoresis profile between idiopathic epilepsy (IE) and DM identified a protein band that was more prominent in DM. This band was subsequently found to contain a multifunctional protein clusterin (apolipoprotein J) that is protective against endoplasmic reticulum (ER) stress-mediated apoptosis, oxidative stress, and also serves as an extracellular chaperone influencing protein aggregation. Western blot analysis of CSF clusterin confirmed elevated levels in DM compared to IE (p < 0.05). Analysis of spinal cord tissue from DM and control material found that clusterin expression was evident in neurons and that the clusterin mRNA levels from tissue extracts were elevated in DM compared to the control. The plasma clusterin levels was comparable between these groups. However, a comparison of clusterin CSF levels in a number of neurological conditions found that clusterin was elevated in both DM and chronic intervertebral disc disease (cIVDD) but not in meningoencephalitis and IE. These findings indicate that clusterin may potentially serve as a marker for chronic spinal cord disease in the dog; however, additional markers are required to differentiate DM from a concurrent condition such as cIVDD

IR Contamination in Galactic X-Ray Novae

The most widely used means of measuring the mass of black holes in Galactic binaries - specifically the X-ray novae - involves both radial velocity measurements of the secondary star, and photometric measurements of its ellipsoidal variability. The latter is important in constraining the inclination and mass ratio, and requires as direct a measure of the flux of the secondary as possible. Up to now, such measurements have been preferentially carried out in the NIR (1 -- 2.5$\mu m$), where the flux from the cooler secondary is expected to dominate over that from the accretion disc. However, here we present evidence of a significant non-stellar contribution to the NIR flux in many of those quiescent X-ray novae that are thought to contain a black hole primary. We discuss origins of this excess and the effect of such contamination on Galactic black hole mass measurements.Comment: 9 pages, 4 figures, 2 tables, accepted for publication in MNRA

Cluster Lenses

Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects - probing the properties of the background lensed galaxy population - which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe - as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy. In this review, we present the basics of cluster lensing and provide a current status report of the field.Comment: About 120 pages - Published in Open Access at: http://www.springerlink.com/content/j183018170485723/ . arXiv admin note: text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author