Synthesis of Nanostructured Tin Oxide (SnO2) Powders and Thin Films Prepared by Sol-Gel Method

Nanocrystalline SnO2 powder was successfully prepared by using simple sol-gel technique. The sol-gel obtained was washed and calcinated at 400 C to obtain the SnO2 nano-powder. The structural property of (SnO2) nanocrystalline powder was investigated by using X-ray diffraction (XRD) technique. The optical properties were studied using Uv-Vis Spectroscopy, by recording the absorbance and transmittance spectra. The XRD pattern of the as-prepared sample demonstrated the formation of a rutile structure of SnO2 nanocrystallites. The Scanning Electron Microscopic (SEM) analysis showed a homogeneous distribution of quite small grains over scanned area. The Uv-Vis absorbance spectra also showed a characteristic peak of absorbance at 312 nm corresponding to SnO2. The energy band gap measurement for nanocrystalline SnO2 thin film was done from the graph of variation of (hν)2 versus hν. The measured value of optical bandgap energies for SnO2 thin film is 3.78 eV. The results show that the transmittance of the synthesized SnO2 film is 78 % in the spectral range 350 nm to 800 nm

Synthesis of Nanostructured Tin Oxide (SnO2) Powders and Thin Films Prepared by Sol-Gel Method

Nanocrystalline SnO2 powder was successfully prepared by using simple sol-gel technique. The sol-gel obtained was washed and calcinated at 400 C to obtain the SnO2 nano-powder. The structural property of (SnO2) nanocrystalline powder was investigated by using X-ray diffraction (XRD) technique. The optical properties were studied using Uv-Vis Spectroscopy, by recording the absorbance and transmittance spectra. The XRD pattern of the as-prepared sample demonstrated the formation of a rutile structure of SnO2 nanocrystallites. The Scanning Electron Microscopic (SEM) analysis showed a homogeneous distribution of quite small grains over scanned area. The Uv-Vis absorbance spectra also showed a characteristic peak of absorbance at 312 nm corresponding to SnO2. The energy band gap measurement for nanocrystalline SnO2 thin film was done from the graph of variation of (hν)2 versus hν. The measured value of optical bandgap energies for SnO2 thin film is 3.78 eV. The results show that the transmittance of the synthesized SnO2 film is 78 % in the spectral range 350 nm to 800 nm

Growth of CaF2 buffer on Si using low energy cluster beam deposition technique and study of its properties

International audienc

Peak effect in a superconducting DyBa2Cu3O7-y film at microwave frequencies

We report the observation of a peak in the microwave (9.55 GHz) surface resistance in an epitaxial DyBa2Cu3O7-y superconducting film in magnetic fields (parallel to the c axis) ranging between 0.2 to 0.9 Tesla. Such a peak is absent in the measurements done in zero-field. The temperature and field dependence of the peak suggests that this peak could be associated with the peak effect phenomenon reflecting the order-disorder transformation in the flux-line lattice. A strong dependence of this peak effect at frequencies close to the depinning frequency of the flux line lattice is observed.Comment: 1 text, 4 figures (all postscript) to be published in Phys. Rev.

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

All-sky search for long-duration gravitational wave transients with initial LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

On the progenitor of binary neutron star merger GW170817

On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy's star formation history, provided the stellar populations are older than 1 Gyr