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We present plane wave DFT calculations using van der Waals (vdW) functionals on the effects of surface coverage of Pt(111) by adsorbed benzene molecules. In particular, we study the variation of adsorption energy, preferred adsorption site and electronic structure of adsorbed benzene molecule over a range of surface coverage, including experimental saturation coverage value. We find that preferred site for adsorption changes and adsorption energy generally reduces as the surface coverage of benzene increases. Benzene molecules would preferably chemisorb until saturation coverage is attained and further form physisorbed layers on Pt(111) surface, similar to the results reported on Ni(111) and Ru(001). Benzene attains a tilted configuration with respect to the Pt(111) surface at higher coverage, in agreement with earlier experimental and theoretical data. [ABSTRACT FROM AUTHOR]

Bio Medical Image Detection is done by using the Image retrieval method. It analyzes the contents of the image rather than the metadata associated with the image. Here the input image passes through a series of tasks which is the classification task. A classification task involves with training and testing of data. For proper training and testing of data, SVM can be used. The goal of SVM is to produce a model which predicts target value of data instances in the testing set which are given as attributes. Actually, this work can provide the result values by doing the retrieving the medical image in high resolution. This work introduces the detection of medical images using Support Vector Machine. [ABSTRACT FROM AUTHOR]

Seed mediated routes for synthesis of nano particles are of much importance today as it enables fine tuning of the size and shape of the synthesized nanoparticles. Herein we have synthesized silver nanoparticles via seed mediated procedure using green synthesis method. This is done by chemical reduction of AgNO3 with Oxalis corniculata leaf broth. The morphology and optical properties of the particles were investigated using FESEM, AFM and UV- visible absorption spectroscopy. The crystallinity of the as prepared samples were analyzed using XRD. The SERS activities of these samples as substrates were tested with crystal violet molecule and are described in detail. [ABSTRACT FROM AUTHOR]

Nanocrystalline Pr2MoO6, a promising material for numerous optical applications, has been synthesized by modified combustion technique. Structural analysis of the sample was performed by powder X-ray diffraction (XRD). The XRD analysis revealed that the as prepared sample has single phase with tetragonal structure. XRD studies indicates that the complex ceramic perovskite phase is formed during the combustion process itself without the need of any post calcination process. The obtained lattice parameters are a=b-= 5.610 and c=11.843Å which is well agreeing with JCPDS file. The crystalline size calculated from XRD by using Scherrer formula was 26 nm. The particle size estimated from transmission electron microscopy was in the range 24-28nm. The optical properties of the sample were studied using ultraviolet UV-Visible absorption spectroscopy, which showed that the sample showed maximum absorption in ultraviolet region trailing towards violet region of visible region. The material band gap increases from 2.72eV to 3.01eV on annealing. The photoluminescence spectra showed intense emission in the blue region and a medium intense peak in the red region. Pr2MoO6 finds applications in the field of phosphors for LED, as laser host materials and in solid state lasers besides the normal optical and luminescent applications. [ABSTRACT FROM AUTHOR]

Nanocrystalline NiFe2O4, a promising material for temperature sensitive applications and in the field of electronics, has been synthesized by modified combustion technique. Structural analysis of the sample was performed by powder X-ray diffraction (XRD). The XRD analysis revealed that the as prepared sample has cubic spinel structure. The obtained lattice parameter is a=8.431A° which is well agreeing with JCPDS file. The crystalline size calculated from XRD by using Scherrer formula was 22 nm. FTIR analysis determine the chemical structure of the sample. The spectrum shows two main peaks, one main peak at 516cm−1 and a medium peak at 431cm−1. The optical properties of the sample were studied using ultraviolet UV- Visible absorption spectroscopy, which showed that the sample has maximum absorption in ultraviolet region with a step edge. The obtained band gap value is 4.74eV. These nano crystals could be sintered at a temperature of 945°C. The temperature coefficient of dielectric constant was -77.04ppm/°C. NiFe2O4 finds applications in solid oxide fuel cells, as a catalyst, magnetic storage system, site specific drug delivery and microwave devices. [ABSTRACT FROM AUTHOR]

In the present study copper oxide and magnesium oxide nanoparticles were synthesized using solution combustion method. Both samples were annealed at 500°C and 700°C to study the variations in properties attained with annealing temperature. Structural characterizations of all the synthesized samples were carried out using XRD and FTIR analysis. From XRD the formed metal oxides were confirmed to be CuO and MgO. Crystallite sizes of these oxides were calculated using Scherrer equation. FTIR confirmed the structure of metal oxides. All the four samples prepared in this work showed strong UV absorption which makes them suitable for anti UV applications such as anti UV glass, anti UV sunscreen, etc. Copper oxide nanoparticles showed visible range absorption in addition to UV range. The antimicrobial activity of all the synthesized nanoparticles were studied and compared. The selected microbes were B. cereus and E.coli. The results varied considerably. The results indicate that both nano metal oxides effective against gram negative bacterial strains. Activity was found to be highest for E.coli. Proper tuning of the nanoparticles is expected to improve its antimicrobial activity. [ABSTRACT FROM AUTHOR]

Silver quantum dots are prepared from aqueous AgNO3 solution by employing biological reduction using allium cepa extract under different compositions. The prepared quantum dots were analyzed experimentally by employing UV -visible Spectroscopy, HRTEM and FTIR techniques. The observed change in colour of mixture with composition is analyzed in detail. UV-visible experimental data was employed to calculate the optical band gap of different samples. Effective engineering of optical band gap is achieved by method of green synthesis. HRTEM analysis clearly indicated the formation of quantum dots through particles of spherical shape with average size of 10 nm. Crystallization of the obtained particles is confirmed as FCC of silver.FTIR measurements were carried out to identify the possible biomolecules responsible for capping and efficient stabilization of the Ag metal nanoparticles in the present study. [ABSTRACT FROM AUTHOR]

Scaling down to nanosize leads to structural and morphological reorientation of materials. Synthesis route plays a vital role in the modified characteristics of the material, be it physical or chemical. Morphological alteration becomes advantageous for materials which find application as catalysts, battery materials and sensors. Transition metal oxides especially spinel cobalt oxide is widely used as active materials for Li ion batteries, gas sensors and catalyst in many industrial reactions where surface morphology matters a lot. Substitution of Co ion with a similar one such as Zn results in modified surface morphology with less varied basic structure. Here the surface smoothening gradually increases with increase in the concentration incorporated Zn ion with less varied phase purity though a cost-effective chemical precipitation method. Blue shifted optical absorption also indicates the presence of Zn ion inhibits the growth of cobalt oxide nanoparticles. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis of nanoparticles of ReBa2NbO6 (Re=Y, Sm and Gd) using a modified single-step combustion process, for the first time. Structural conformation is done by means of XRD and vibrational spectroscopic analysis. The studies show that sample transforms from orthorhombic to cubic structure on annealing at 1000°C. The band gap and dielectric properties of the samples are also investigated. The samples are sintered in a temperature range of 1350-1400°C without any sintering aid. [ABSTRACT FROM AUTHOR]

Surface Plasmon Resonance (SPR) of silver nanostructures varies with its shape and size. In the present work silver nanoparticles, nanowires and nanocubes were synthesized by solvothermal method by reducing AgNO3 with ethylene glycol using PVP as the absorption agent and adding different amounts of NaCl to the solution. The size and shape of the nanostructures can be controlled by varying the concentration of NaCl and solvothermal growth duration. These nanostructures exhibiting different SPR properties are evaluated as SERS substrates using R6G molecules. The Raman signals are found to be enhanced in the presence of nanostructure SERS substrate. [ABSTRACT FROM AUTHOR]

Pyrochlores (A2B2O7) can exist in both ideal pyrochlore as well as defect fluorite structure depending upon the size difference between A and B ions. Gd2Zr2O7 having eight coordination for Gd3+ and six coordination for Zr4+ belongs to a class of ordered pyrochlore structure due to optimum size difference between (A) Gd3+ and (B) Zr4+. It indeed is a borderline compound that shows both pyrochlore and defect fluorite structure. Substitution of rare earth or transition metal at both Gd3+ and Zr4+ sit e can lead to change in local structure (symmetry, local chemical composition etc.) due to mismatch of ionic size and ionic radii. In the present work, Ce-substituted Gd2Zr2O7 system (Gd2-xCex) Zr2O7 (x = 0,2) is synthesized by the citrate based solution combustion method. The phase formation of the Ce-substituted Gd2Zr2O7 system is investigate by employing XRD. Our main aim is to provide an understanding of the contribution of crystallite size and microstrain to X-ray diffraction line broadening, which are analyzed by Williamson-Hall analysis (isotropic and anisotropic models) using elastic stiffness constants and young modulus. [ABSTRACT FROM AUTHOR]

Human existence on earth requires primary amenities among which water is the most important one not only for drinking purpose but for all the day to day activities. Clean water requirement is increasing day by with the increased population and industrial development. The industries, hospitals, hotels etc. uses plenty of pure water and sewage water not less in quantity is expelled out to the surrounding environment, mainly to the water bodies without any decontamination processes instigating adverse effects on the quality of naturally available water. This report focusses on the application of chemically synthesized cobalt oxide particles to reduce the bacterial load in sewage water and its size dependent activity. [ABSTRACT FROM AUTHOR]

Nanocrystalline BaAl2O4 has been successfully synthesized using a single step auto-ignition combustion route without the need of any calcination step. The structure and phase purity of the as-prepared powder were examined by powder X-ray diffraction technique (XRD). The XRD analysis revealed the hexagonal spinel structure of BaAl2O4 nanopowder and the lattice constant calculated from the XRD data is a = 5.2538Å and c=8.7947Å. The particle size of the as-prepared BaAl2O4 powder estimated from X-ray line broadening of the diffraction peak using Scherrer formula is 28 nm. The FT-lR spectroscopy showed that the as-prepared powder is phase pure. The particle size, distribution, shapes and degree of agglomeration of the as-prepared powder is studied by Transmission electron microscopy (TEM). The TEM studies on the powder morphology of the as-prepared powder obtained by the combustion method showed that the particles are of submicron size in the range 20-30 nm. The optical band gap of BaAl2O4 nanopowder was determined from UV-Vis spectroscopic measurements and the band gap energy of the material for direct allowed transitions were calculated to be 3.91eV which indicates that the material is a wide band gap semiconductor at room temperature. [ABSTRACT FROM AUTHOR]

The unique properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been attracting a wide variety of researches in material engineering. Enormous attention has been paid in this area due to their unique properties and potential applications in optoelectronics. In the group of these TMDCs, MoS2 is one of the most important one due to its tuneable properties. Nanostructured MoS2 are promising and desirable candidates as catalysts in hydrogen evolution reaction (HER). Platinum, the traditionally used catalyst for HER can be replaced by the earth abundant and cost effective MoS2 nanostructures. A simple route is adopted here for the synthesis of MoS2 quantum dots (MoS2 QDs) by using a single precursor in aqueous medium. The characterization studies of the prepared MoS2 QDs show the uniform size of the MoS2 QDs with an average size 3 nm. They exhibit excellent photoluminescence emission spectra with 553.3 nm peak. Polarisation graph with an overpotential of 463 mV at 10 mA Current, Tafel plot with a slope of 58 Mv / Dec and Nyquist plot with a charge transfer resistance of 878 ohms suggests it as an efficient catalyst for HER. [ABSTRACT FROM AUTHOR]

Bi2MoO6 nanoparticles were prepared by single step combustion method. Bi2MoO6 nanocrystals present a single shaped orthorhombic structure and their crystalline size 13nm. They were characterized by XRD, Photo luminescence [PL], UV and FTIR spectroscopy studies confirms the presence of highly crystalline Bi2MoO6 orthorhombic structure. FTIR analysis shows that the phase is pure with short range distortion. From UV-VIS spectra band gap obtained is 3.47eV. [ABSTRACT FROM AUTHOR]

The studies on ionospheric irregularities due to VHF and L band scintillations have great importance because of its application to GPS systems, communication, remote sensing etc. Many researchers are studying the impacts of ionospheric irregularities, their dependence on local time and seasonal aspects to understand the causative mechanisms behind these irregularities. Power spectral studies on scintillation is a very good tool to study the range of scale sizes of irregularities and their relative contribution to the scattered intensity. In the present work, the seasonal and latitudinal variations of power spectral parameter such as Fresnel frequency, drift of scintillation events were studied using the data derived from the receivers at equatorial trough station Trivandrum, near equatorial crest stations Hyderabad and Bangalore, far equatorial off crest stations Delhi and Kolkata during the year 2005. The seasonal and latitudinal variations of amplitude scintillation (S4 index), TEC depletion, were also studied. The data is obtained from receivers at these stations, as part of GAGAN(GPS Aided Geo Augmented Navigation)system. Strong scintillation events were not very frequent during the period of study. Scintillation occurrence is more in the pre midnight hours compared to post midnight hours and also scintillation event is more during equinox compared to other seasons. The latitudinal and range wise distributions of S4 index depict that during equinox most of the scintillations lie within the range 0.16-0.20 for Trivandrum; within 0.46-0.50 for Bangalore; within 0.21-0.25 for Hyderabad, Kolkata and Delhi. It is observed that the Fresnel frequency varied between 0.123Hz to 0.368 Hz during the period of study. The observed drift velocity varied between 33 m/s -138 m/s during the period of study. For stations Trivandrum, Hyderabad and Bangalore the most probable value of drift velocity is within the range 60-80 m/s during equinoctic period. During summer for station at Hyderabad most probable value of drift velocity is within the range 40-60 m/s, shows a decrease during summer. For the station Trivandrum and Kolkata most probable distribution is in within the range 80-100 m/s during summer. Observations at Bangalore shows an equal distribution in the ranges 40-60 m/s, 60-80 m/s and 80-100 m/s during summer. The preferential range of drift velocity falls within the range 60-100 m/s, which agrees with the previous results. In addition to this, the LT distributions of scintillation events were also compared. [ABSTRACT FROM AUTHOR]

TiO2 thin film nanostructures are prepared using pulsed laser deposition technique in reactive atmosphere. The obtained thin films are annealed at different temperatures to attain crystalline modifications. Optical properties of these quantum well nanostructures are studied using UV-visible spectroscopic analysis. Phase determination and structural analysis of the structures are conducted using GIXRD and micro Raman analysis. Morphological studies are conducted in detail, using SEM and AFM techniques. Effects of various growth parameters including different deposition and post deposition parameters are investigated. Well ordered, transparent TiO2 quantum wells are developed. [ABSTRACT FROM AUTHOR]

Visible-light-driven photocatalyst Ba2YBiO6 was successfully synthesized as nanoparticles by a low temperature sol-gel technique for the first time. X-ray diffraction (XRD) analysis revealed that the synthesized material has a complex cubic perovskite (A2BB'O6) structure. The phase purity of the nanopowder has been confirmed using thermal analysis (TG- DTA) and Fourier transform infrared spectroscopy (FT-IR). The morphological characterization of the nanopowder was performed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The TEM investigation confirmed the nanoscale (20–40 nm) nature of the powder. The SEM micrograph of the powder showed that the grain size ranges from 0.07 to 0.21 µm. The EDS pattern revealed the existence of Ba, Y, Bi and O without any noticeable impurities. The band gap energy of Ba2YBiO6 observed by UV–Vis diffuse reflectance spectroscopy (UV-Vis DRS) was 2.77eV. This indicated that Ba2YBiO6 might perform well as a photocatalyst in the visible light region. Photocatalytic activity of Ba2YBiO6 nanoparticles was investigated for the degradation of methyl orange and methylene blue under visible light irradiation. [ABSTRACT FROM AUTHOR]

Plasma bubbles are ionospheric irregularities that can often occur at night and finds equatorial ionosphere as the most favorable place for its onset. This study focusses on characterizing plasma bubble evolution using multifrequency Global Navigation Satellite Systems (GNSS) receiver system at Changanacherry (1.03°N,149.63 °E). Single station- multi satellite technique is employed here by tracking two geostationary Indian satellites GSAT-8 (PRN 127) and GSAT-10 (PRN-128) for the period from 2018 to 2020. Two events are taken for the study, each from the year 2019 (Event 1) and 2020 (Event 2). Based on the observations, morphological features of drift velocity, and East -West width of plasma bubbles were analyzed and compared. The relation between probable LT of occurrence of plasma bubbles and its drift velocity is also investigated. [ABSTRACT FROM AUTHOR]

The internal dynamics of the ionosphere exhibits nonlinear properties, which depends on external factors like incoming solar radiations and subsequent geomagnetic storms. Generally, different complexity tools such as Tsallis entropy, Rényi entropy, Lyapunov exponents, Correlation dimension, Hurst Exponent, Fractal dimension, and Beta Exponent are used to analyse the complex behaviour of the ionosphere. The present study focus on the variability in Tsallys entropy and Rényi entropy during the quiet time and storm time ionosphere. The variations in F layer peak electron density (foF2) and virtual height (h'F) during quiet and disturbed ionosphere over Japanese midlatitudes sector (Kokubunji 35.7°N, 139.5°E; 26.8°N magnetic latitude) in terms of non-extensive Tsallis and Rényi entropies were analysed. The variations in foF2 and h'F were reflected in the values of Tsallis and Rényi entropy with a characteristic decrease during storm time, compared to those of quiet periods. During storm time, the system tries to readjust itself by falling into a low entropy state or a state of higher degree of organization. The study includes events in different season and observed that the Tsallys entropy and Rényi entropy values do not show any significant changes with season. It is also noted that the decrease in values of Tsallys and Rényi entropy during major storms, are not proportional to the severity of geomagnetic storms. [ABSTRACT FROM AUTHOR]

The simultaneous observations of ionospheric EPBs over Indian equatorial stations Changanacherry and Trivandrum, for a period January 2016 to October 2017, using four constellations, namely SBAS, GPS, GLONASS, and GALILEO were presented here. The multistation-single satellite technique using satellites GSAT-8 (PRN 127) and GSAT-10 (PRN 128) of SBAS constellation was extended to observe S4 index time series of scintillation events/plasma bubbles to estimate ionospheric drift velocity (Vo) along the direction formed by the receiver base line, and random velocity (Vc) using full correlation analysis of peak value method. The satellites of GPS, GLONASS, and GALILEO constellations were utilized to estimate the corresponding depletion depth in TEC, its duration, rate of change of TEC Index (ROTI), S4 index and the elevation angle of satellites for the observed scintillation events/plasma bubbles. The maximum values of drift velocity and random velocity were reported during post sunset period using peak value method. The most probable range of east-west width of plasma bubbles was 100-150 km for both Changanacherry and Trivandrum. The probability of occurrence of plasma bubble was maximum during spring equinox followed by autumnal equinox. The rate of change of TEC (ROTI) has highest probable values well within the range 1.00-1.99 TECU/min for all constellations in Changanacherry. For Trivandrum, the most probable range of this quantity would be 0.00-0.99 TECU/min for GPS, and GALILEO, and 1.00-1.99 TECU/min for the GLONASS. The probable range of east-west velocity of plasma bubbles observed by PRN 127 (140.00-170.00 m/s) using the technique multistation-single satellite was matching with that for Changanacherry (140.00-170.00 m/s), and for Trivandrum (110.00-170.00 m/s), using the technique single station-multisatellite. The simultaneous observations of plasma bubbles using four constellations (both geostationary and non-geostationary satellites) incorporating different techniques is the new aspect of this study. [ABSTRACT FROM AUTHOR]

Exoplanetary systems are seen outside the solar system which may be similar or may vary drastically with the solar system. A comparative study between seventeen selected exoplanetary systems with solar system is carried out taking some physical parameters as probes with the hope that a clue to the habitable system outside the solar system can be found. Selected exoplanets are revolving around a Sun like star and have more than one confirmed planetary companions and all these are detected using transit method. The details about the exoplanets and the host stars are collected from the exoplanetary encyclopedia available online. One of the inferences got from the study is that most of the studied exoplanets are nearer to its host stars unlike the solar system. Ninety eight percent of the selected confirmed exoplanets are situated out of the habitable zone boundary of the host star and are at a high inclination with respect to their host stars. The characteristics of the selected exoplanetary systems show similarities as well as differences from the solar system planets. A modified and more general Bode-Titius empirical relation is also suggested, for predicting the position of hitherto undetected exoplanets. Obviously there is a broad array of enhancements which can be pursued following on this line of study. [ABSTRACT FROM AUTHOR]

Gamma ray attenuation studies play an important role in industry, agriculture, medicine, radiation dosimetry etc. In the present study, we have made an attempt to determine the linear attenuation coefficient for 662 keV gamma rays in pure coconut oil, in paraffin oil and in a mixture of both. From the experimentally obtained linear attenuation coefficients, mass attenuation coefficients were estimated and the corresponding effective atomic number values were determined by the polynomial interpolation method. No experimental studies of this type for oil samples have been reported so far. An advanced GR1-A USB powered gamma ray spectrometer was used in the studies. A narrow beam vertical geometry was employed. The study shows that with increase in the content of paraffin oil present in the coconut oil, an increase in the values of mass attenuation coefficient and a decrease in the effective atomic number take place. Also the mass attenuation coefficient of pure coconut oil (with an average value for weight fraction of different constituent fatty acids) was estimated by the mixture rule, using mass attenuation coefficient of constituent elements obtained from XCOM. The theoretical value is compared with the experimentally obtained mass attenuation coefficient of pure coconut oil and is found to be in good agreement. The results indicate that it can be used as a non-destructive technique for the investigation of adulteration in edible oils. [ABSTRACT FROM AUTHOR]

The fluctuation in the phase or amplitude of the radio signals as it transit the ionosphere is called scintillation. Nighttime scintillations are associated with F-region irregularities, while E-region irregularities produce daytime scintillations. In this work, characteristics of Earth's ionospheric amplitude scintillations on L1-Band of geostationary Indian satellites GSAT-8 (PRN 127) and GSAT-10 (PRN 128) over equatorial/low-latitude Indian stations under day and night sectors were comp ared. The scintillation data were recorded using GNSS receiver placed at Trivandrum, Bangalore, Hyderabad, Delhi, and Hanle during 2014. Both daytime and nighttime scintillation events over near equatorial trough station Trivandrum and off crest station Delhi show maximum probability of occurrence during equinox and during winter for near crest station, Hyderabad. For equatorial trough station Trivandrum, the daytime amplitude scintillations for both satellites were highest during afternoon/evening sectors 14:00-17:59 IST, whereas for near equatorial crest station Bangalore and off crest station Delhi, this would be during morning sector 06:00-09:59 IST. During nighttime, the amp litude scintillations observed by both the satellites were generally highest during post sunset (18:00-21:59 IST) hours for near trough station Trivandrum, near crest station Bangalore, and low-latitude station Hanle. The probability for strong amplitude scintillation events were highest over near crest station Hyderabad and off crest station Delhi. The present study indicates that there exists a poor correlation between magnetic activity and S4 index. [ABSTRACT FROM AUTHOR]

Zinc aluminate (ZnAl2O4) is a member of the spinel oxides having the general for AB2O4. It can be synthesized by many methods like co precipitation, sol-gel, combustion etc. Here the Solution Combustion Synthesis method is used for its synthesis, as it is simple, rapid and low cost method. The synthesized samples were annealed at four different temperatures. All the four samples were analyzed using XRD, SEM and FTIR. The result shows that annealing temperature affects the structure and morphology of the ZnAl2O4. [ABSTRACT FROM AUTHOR]

Nano-ceramics can be utilized for various applications like electronic, ionic, thermal, optical and catalytic. In particular, the combination of a relatively large portion of interfacial or grain boundary atoms along with the interactions of photons, electrons, or dislocations can lead to unusual mechanical and electrical behavior. New types of used ceramic powders are so called pyrochlores of the A2B2O7 general formula. In this work Sm2Zr2O7 oxides were synthesized through solution combustion synthesis. It has been identified as Samarium zirconium oxide, with a defect fluorite (Fm-3m cubic phase) structure. An important observation is that some of the Bragg peaks show asymmetric broadening due to strain. From Hall Williamson analysis, it is clear that there is a persistent increase in FWHM due to strain factor. Band gap energy of the sample was obtained from UV-Visible spectroscopic analysis. [ABSTRACT FROM AUTHOR]