Correlation among QPO frequencies and Quiescence-state Duration in Black Hole Candidate GRS 1915+105

We discover a definite correlation between the frequency of the quasi-periodic oscillations (QPO) in quiescence states and the duration of the quiescence state of the transient X-ray source GRS 1915+105. We find that while the QPO frequency can be explained with the oscillation of shocks in accretion flows, the switching of burst to quiescence states (and vice versa) and their duration can be explained by assuming an outflow from the post-shock region. The duration of the quiescence state is inversely related to the QPO-frequency. We derive this relation. We also find the correlation between the observed low ($\sim 0.001-0.01$Hz) and the intermediate (1-10Hz) QPO frequencies. Our analytical solutions are verified by analyzing several days of public-domain data from RXTE.Comment: Latex, 13 pages with 3 figures; Accepted for Publication in Astrophysical Journal Letter

On the source of QPO of the black hole candidate GRS1915+105: some new observations and their interpretation

A few classes of the light curve of the black hole candidate GRS 1915+105 have been analyzed in detail. We discover that unlike the previous findings, QPOs occasionally occur even in the so-called `On' or softer states. Such findings may require a revision of the accretion/wind scenario of the black hole candidates. We conjecture that considerable winds which is produced in `Off' states, cool down due to Comptonization, and falls back to the disk and creating an excess accretion rate to produce the so-called `On' state. After the drainage of the excess matter, the disk goes back to the `Off' state. Our findings strengthen the shock oscillation model for QPOs.Comment: MNRAS style. MNRAS (To appear

Efficacy of curative applications of submicron chitosan dispersions on anthracnose intensity and vegetative growth of dragon fruit plants

The antifungal potential of submicron chitosan dispersions (SCD) and its effect on the vegetative growth of dragon fruit plants were studied under field conditions. There was a reduction in disease incidence (15.65%) with a severity score of 1.60 in plants treated with SCD of 600 nm droplet size of 1.0% chitosan compared to the control plants. Moreover, a significant increase was also observed among the treatments in terms of number of shoots per cutting, stem diameter and shoot length. However, the highest number of shoots (19), maximum stem diameter (0.23 m) and maximum stem length (2.80 m) were observed in plants treated with SCD of 600 nm droplet size of 1.0% chitosan. Similarly, chlorophyll content were also high in plants receiving SCD of 600 nm droplet size of 1.0% chitosan. Therefore, it can be concluded from the results that, instead of applying chitosan in the conventional form, it can be more effective as an antifungal agent as well as plant growth enhancer when applied in the form of submicron dispersions

Effectiveness of submicron chitosan dispersions in controlling anthracnose and maintaining quality of dragon fruit

Conventional chitosan (CC) and submicron chitosan dispersions (SCD) were evaluated for the control of postharvest anthracnose and maintenance of quality of dragon fruit during storage at 10 ± 2 °C and 80 ± 5% RH for 28 days. All the chitosan treatments significantly reduced anthracnose symptoms, resulting in a reduction of disease development and thereby maintained the quality of fresh fruit for extended periods. SCD at 1.0% with 600 nm droplet size gave the best result in that it delayed the onset of disease and maintained the quality of dragon fruit for up to 28 days of storage. It can be concluded from the present investigation that SCD have potential to be used as an antifungal agent to control postharvest anthracnose and maintain quality of dragon fruit during storage

Characterization of MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces

In this study, MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces under ambient condition were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The radiation fluence used was 0.5 J/cm2 at a pulse repetition rate of 25 MHz with 1 ms interaction time. SEM analysis of the irradiated surfaces showed self-assembled intermingled weblike nanofibrous structure in and around the laser-irradiated spots. Further TEM investigation on this nanostructure revealed that the nanofibrous structure is formed due to aggregation of Au-Si/Si nanoparticles. The XRD peaks at 32.2°, 39.7°, and 62.5° were identified as (200), (211), and (321) reflections, respectively, corresponding to gold silicide. In addition, the observed chemical shift of Au 4f and Si 2p lines in XPS spectrum of the irradiated surface illustrated the presence of gold silicide at the irradiated surface. The generation of Si/Au-Si alloy fibrous nanoparticles aggregate is explained by the nucleation and subsequent condensation of vapor in the plasma plume during irradiation and expulsion of molten material due to high plasma pressure