Showing papers by "Ajaya Kumar Singh published in 2016"

Upper Limits on the Rates of Binary Neutron Star and Neutron Star-Black Hole Mergers from Advanced LIGO’s First Observing Run

Abstract: We report here the non-detection of gravitational waves from the merger of binary–neutron star systems and neutron star–black hole systems during the first observing run of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). In particular, we searched for gravitational-wave signals from binary–neutron star systems with component masses $\in [1,3]\,{M}_{\odot }$ and component dimensionless spins <0.05. We also searched for neutron star–black hole systems with the same neutron star parameters, black hole mass $\in [2,99]\,{M}_{\odot }$, and no restriction on the black hole spin magnitude. We assess the sensitivity of the two LIGO detectors to these systems and find that they could have detected the merger of binary–neutron star systems with component mass distributions of 1.35 ± 0.13 M ⊙ at a volume-weighted average distance of ~70 Mpc, and for neutron star–black hole systems with neutron star masses of 1.4 M ⊙ and black hole masses of at least 5 M ⊙, a volume-weighted average distance of at least ~110 Mpc. From this we constrain with 90% confidence the merger rate to be less than 12,600 Gpc−3 yr−1 for binary–neutron star systems and less than 3600 Gpc−3 yr−1 for neutron star–black hole systems. We discuss the astrophysical implications of these results, which we find to be in conflict with only the most optimistic predictions. However, we find that if no detection of neutron star–binary mergers is made in the next two Advanced LIGO and Advanced Virgo observing runs we would place significant constraints on the merger rates. Finally, assuming a rate of ${10}_{-7}^{+20}$ Gpc−3 yr−1, short gamma-ray bursts beamed toward the Earth, and assuming that all short gamma-ray bursts have binary–neutron star (neutron star–black hole) progenitors, we can use our 90% confidence rate upper limits to constrain the beaming angle of the gamma-ray burst to be greater than $2\buildrel{\circ}\over{.} {3}_{-1.1}^{+1.7}$ ($4\buildrel{\circ}\over{.} {3}_{-1.9}^{+3.1}$).

Upper limits on the rates of binary neutron star and neutron-star--black-hole mergers from Advanced LIGO's first observing run

Abstract: We report here the non-detection of gravitational waves from the merger of binary neutron star systems and neutron-star--black-hole systems during the first observing run of Advanced LIGO. In particular we searched for gravitational wave signals from binary neutron star systems with component masses $\in [1,3] M_{\odot}$ and component dimensionless spins $< 0.05$. We also searched for neutron-star--black-hole systems with the same neutron star parameters, black hole mass $\in [2,99] M_{\odot}$ and no restriction on the black hole spin magnitude. We assess the sensitivity of the two LIGO detectors to these systems, and find that they could have detected the merger of binary neutron star systems with component mass distributions of $1.35\pm0.13 M_{\odot}$ at a volume-weighted average distance of $\sim$ 70Mpc, and for neutron-star--black-hole systems with neutron star masses of $1.4M_\odot$ and black hole masses of at least $5M_\odot$, a volume-weighted average distance of at least $\sim$ 110Mpc. From this we constrain with 90% confidence the merger rate to be less than 12,600 Gpc$^{-3}$yr$^{-1}$ for binary-neutron star systems and less than 3,600 Gpc$^{-3}$yr$^{-1}$ for neutron-star--black-hole systems. We find that if no detection of neutron-star binary mergers is made in the next two Advanced LIGO and Advanced Virgo observing runs we would place significant constraints on the merger rates. Finally, assuming a rate of $10^{+20}_{-7}$Gpc$^{-3}$yr$^{-1}$ short gamma ray bursts beamed towards the Earth and assuming that all short gamma-ray bursts have binary-neutron-star (neutron-star--black-hole) progenitors we can use our 90% confidence rate upper limits to constrain the beaming angle of the gamma-ray burst to be greater than ${2.3^{+1.7}_{-1.1}}^{\circ}$ (${4.3^{+3.1}_{-1.9}}^{\circ}$).

Glycine functionalized magnetic nanoparticle entrapped calcium alginate beads: A promising adsorbent for removal of Cu(II) ions

Abstract: Glycine functionalized magnetic nanoparticle entrapped calcium alginate beads (GFMNPECABs) were successfully prepared and used as a novel adsorbent for removal of Cu(II). The adsorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS) measurements, scanning electron microscopy (SEM), x-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) surface area analysis. Magnetic nanoparticles (MNPs) could be successfully functionalized by glycine and glycine functionalized magnetic nanoparticles (GFMNPs) could be entrapped into the alginate biopolymer. BET result showed specific high surface area and mesoporous structure of the adsorbent. The adsorption capacity of GFMNPECABs for Cu(II) ions evaluated by batch adsorption experiments showed maximum value of 120 mg/g at pH 6 in 160 min. Adsorption isotherms well fitted to different available models and data could be best described by Langmuir model. The adsorption kinetics followed pseudo second order model well. The thermodynamic studies showed exothermic and spontaneous nature of Cu(II) adsorption.

Silver Nanoparticle Entrapped Calcium-Alginate Beads for Fe(II) Removal via Adsorption

Abstract: Summary Silver nanoparticle entrapped calcium-alginate beads (AgNP-CAB) were successfully synthesized as adsorbent for effective removal of Fe(II) ions from aqueous solution. The adsorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Batch adsorption experiments were used to determine the adsorption capacity. The influence of various factors (such as temperature, pH, adsorbent dosage and contact time) on adsorption behaviour was investigated. The adsorbent thus developed showed higher uptake at pH 4, and adsorption the capacity decreased with increasing temperature. The kinetic results for the adsorption process were interpreted using pseudo-first order and pseudo-second order rate equations, as well as Elovich and intra-particle diffusion models. A good correlation with the pseudo-second order rate kinetics (R2 = 0.998) could be observed. Adsorption isotherms were fitted to Langmuir, Freundlich, Temkin and Harkins–Jura isotherms whereby the experimental data was found to best fitted for the Langmuir model. The maximum adsorption capacity of adsorbent was found to be 236.40 mg/g.

Kinetic study of oxidation of paracetamol by water-soluble colloidal MnO2 in the presence of an anionic surfactant

Abstract: The kinetics of the oxidation of paracetamol [PCM] by water-soluble colloidal MnO2 was investigated spectrophotometrically at 298 K in the absence and presence of an anionic surfactant, sodium dodecyl sulphate (SDS), in aqueous solution. The reaction was first order with respect to [MnO2], [PCM] and [H2SO4]. The effects of [Mn(II)], [salt], dielectric constant and ionic strength of the medium on the kinetics of the reaction have also been examined. Micelles of SDS in aqueous solution accelerated the reaction rate, and partitioning of MnO2 in favour of the micellar pseudophase was remarkable. The catalytic effect of SDS in aqueous solutions has been treated by well-defined mathematical (Tuncay), Menger and Portnoy, and Piszkiewicz models. The binding constant (7.59 × 10−2 mol−1 dm3), dissociation constant (32.43), rate constant in the micellar phase (5.15 × 104 s−1), cooperativity index (1.98) and various thermodynamic activation parameters have been evaluated, and on the basis of the observed kinetic data, possible reaction mechanism and rate law have been proposed.

Studies on Structural, Morphological and Optical Properties of Chemically Deposited CdS 1-x Se x Thin Films

Abstract: The thin films of CdS(1-x)Se(x) were successfully deposited over glass substrates by chemical bath deposition technique. Cadmium acetate, thiourea and sodium selenosulfate were used as source materials for Cd(2+), S(2-) and Se(2-) ions, while 2-mercaptoethanol was used as capping agent. The various deposition conditions such as precursor concentration, deposition temperature, pH and deposition time were optimized for the deposition of CdS(1-x)Se(x) thin films of good quality and the films were annealed at 200° and 300 °C. The structural, morphological, chemical and optical properties were examined by various characterization techniques and discussed in detail. The optical band gap of CdS(1-x)Se(x) thin film samples were estimated and found in the range from 2.11 to 1.79 eV for as-deposited and annealed thin films.

Hydrophilic ionic liquid-assisted control of the size and morphology of ZnO nanoparticles prepared by a chemical precipitation method

Abstract: ZnO nanoparticles (NPs) were prepared by a chemical precipitation method from zinc acetate dihydrate and NaOH using isopropanol as the reaction medium. The influence of an imidazolium-based hydrophilic ionic liquid (IL), 1-ethyl-3-methylimidazolium methylsulfate, [EMIM][MeSO4] at different concentrations on the size and morpholgy of ZnO NPs was investigated. The NPs were characterized by Fourier transform-infrared, energy dispersive X-ray and UV-visible spectroscopy, along with X-ray diffraction, particle size analysis, field emission scanning electron microscopy and high resolution transmission electron microscopy. Pure nanocrystalline ZnO with a hexagonal wurtzite phase was formed in the system. The particle size of the NPs varied in the range of 2–55 nm depending on the concentration of the IL used during preparation. With increasing concentration of [EMIM][MeSO4] the shape of the NPs also changed interestingly from spheres to flakes through nanorods. The use of the IL has been proved effective as a self directing agent and templating material for the successful preparation of ZnO nanostructures. Finally, the mechanism for preparation of ZnO NPs with controllable sizes and morphlogy has been established and the variation of size, shape and morphology has been explained in terms of hydrogen bonding –co–π–π* stacking interaction between the IL and NPs.

Micelle Catalyzed Oxidative Degradation of Paracetamol by Water Soluble Colloidal MnO2 in Acidic Medium

Abstract: The catalytic effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the MnO2-paracetamol (PCM) redox reaction has been examined spectrophotometrically in acidic medium at 298 K. The reaction demonstrates that the stoichiometric ratio of MnO2 and PCM is 1 : 1. The reaction exhibited first order kinetics with respect to [MnO2] and [PCM] but a negative fractional order was observed with respect to [H2SO4]. Various effects such as ionic strength, dielectric constant, [Mn(II)], [salts] and temperature have been studied. The catalytic effect of CTAB has been treated quantitatively by the well known Menger Portnoy and Piszkiewicz model. The values of binding constant (Ks), rate constant in the micellar phase (km), cooperativity index (n) and dissociation constant (KD) have also been calculated. From the several observations, a reaction mechanism has been proposed and the rate law has been derived. Applying the Arrhenius equation, various thermodynamic activation parameters have also be...

Oxidative degradation of norfloxacin by water soluble colloidal MnO 2 in the presence of cationic surfactant

Abstract: The oxidative degradation of norfloxacin (NOR) by water soluble colloidal MnO2 in alkaline medium has been studied spectrophotometrically in the absence and presence of cationic surfactant, cetyltrimethylammonium bromide (CTAB) at 298 K. The rate of reaction has been followed under pseudo-first order condition with respect to [MnO2]. Positive fractional order and negative fractional order are observed with respect to [NOR] and [NaOH] respectively in both aqueous and micellar media. The rate constant increases with decreasing dielectric constant of the medium in both the systems. The retardation effect observed by CTAB is discussed by well known Berezin’s model and from this model micelle binding constant has been computed. Using the Arrhenius equation, thermodynamic activation parameters have also been evaluated in both the media. On the basis of experimental results suitable mechanism and rate law are proposed.

Effect of Surfactants on Hydrolysis of Mono-N-ethyl-o-toluidine Phosphate

Abstract: Hydrolysis of phosphate ester (Mono-N-ethyl-o-toluidine phosphate) in the presence of different surfactants has been studied at 303 K. The rate of reaction has been found to be first-order and fractional order kinetics with respect to [substrate] and [HCl] respectively. The cationic micelles of cetyltrimethylammonium bromide (CTAB), anionic micelles of sodium dodecyl sulfate (SDS) and nonionic micelles of Brij-35 enhanced the rate of reaction to a maximum value and thereafter, the increase in concentration of surfactant decreased the reaction rate. The rate of reaction increased with increase of dielectric constant of the medium. The variation in the rate of hydrolysis by micelles was treated by considering the Menger-Portnoy, Piszkiewicz's and Berezin kinetic models. The various thermodynamic parameters have also been evaluated. The added salts viz KCl, KNO3, K2SO4 enhanced the rate of reaction in the presence of cationic, anionic and non-ionic micelles. The kinetic parameters i. e. micellar pha...

Synthesis, Morphological and Optical Properties of Nano-Crystalline Solid CuxS Thin Films

Abstract: Metal chalcogenide thin films of copper sulfide (CuxS) were grown on glass substrate using the chemical bath deposition. The CuxS thin film XRD studies reveal chalcocite low and covellite phases called as copper-rich and copper-poor form. The average grain size was calculated in the range of 8.87–69.65 nm. The optical band gap was estimated using Tauc's plot and found to be 3.02–4.06 eV. Optical properties exhibit that film find application in photovoltaic and photo thermal fields. AFM studies show formation of spherical shaped nanoparticle together with fine particles ranging 10 to 500 nm, evenly distributed showing homogeneity in polycrystalline thin film formation. SEM studies reveal spherical grain formation with cracks and pin holes at some places.