654 research outputs found
Sort by
Catalytic Behavior of Nickel Nanoparticles Stabilized by Lower Alkyl Ammonium Bromide in Aqueous Medium
No full textHeterogeneous synthesis of monodisperse pure nickel nanoparticles in aqueous medium has been carried out using cetyltrimethylammonium bromide and a lower alkylammonium bromide mixture of tetraethylammonium bromide and tetrabutylammonium bromide. The presence of cetyltrimethylammonium bromide alone results in the formation of a mixture of nickel hydroxide and nickel nanoparticles. The particles have been characterized using TEM, EDS, XRD, TGA-DSC and FTIR. The analysis showed that particles are spherical in shape, monodisperse, face-centered-cubic with average size about 15 nm and are stable in air up to 325 °C. The nanoparticles have been used as a solid phase catalyst for the reduction ofp-nitrophenol in the presence of hydrazine hydrate as reducing agent at different temperatures under varying conditions. The reduction process has been monitored by UV-vis analysis. The present study showed that nanoparticles are not poisoned after their repeated use in reduction of p-nitrophenol to p-aminophenol. TEM analysis also confirms that nanoparticles are stable in the dispersed medium for longer times
Knife-edge diffraction pattern as an interference phenomenon: An experimental reality
No full textThis paper demonstrates that a knife-edge diffraction pattern is, indeed, due to the interference of two superimposing waves: the geometrical wave and the boundary diffraction wave. Within the framework of boundary diffraction wave theory it is shown that this diffraction pattern can easily be broadened in such a manner that a single fringe covers the whole field of view. At this point the system converges to a schlieren diffraction interferometer and could be used for the study of phase objects using diffraction-limited optics. Experimental observations show that the method bears a similarity to that of any known two-beam interferometer, e.g. Mach-Zehnder interferometer. The experimental details have been presented and the results are compared with a two-beam holographic interferometer and a point diffraction interferometer
A Set of EEG Parameters to Predict Clinically Anesthetized State in Humans for Halothane Anesthesia
No full textThis article evaluates all the EEG parameters suggested in the literature that undergo changes due to anaesthetic dose, and suggests a set of EEG parameters that act as best signatures of anaesthetic state of a patient. This set of EEG parameters is validated by an artificial neural network
Performance Characteristics of Indigenously Developed 24-Bit Seismic Data Recorder for Earthquake Seismology
Get PDFThis paper describes long term performance of CSIO developed seismic data acquisition tested on local, regional and distant earthquakes in comparison with imported data acquisition system. Waveform data is cross-correlated to test the similarity and validate the results. Two major earthquakes have been considered for cross-correlation procedure and the results have been analyzed and explained. CSIO developed 24-bit seismic data recorder has been explained
DNA Immobilization Chemical Interference due to Aggregates Study by Dip and Drop Approach
No full textIn the present manuscript, we report the studies and observations for chemical interference due to aggregates formation during covalent immobilization of thiolated λ-DNA between gold microelectrodes. Dip and Drop approaches were employed to study DNA immobilization using thiolated oligos (oligoA 5′ GGGCGGCGACCT 3′ and oligoB 5′ AGGTCGCCGCCC 3′). As a result of aggregation, less interference was observed in Dip approach as compared to Drop approach. Atomic Force Microscopy (AFM) analysis of piranha treated gold surface revealed 47.5% increase in height roughness, contributing in interference by creating active sites. Cyclic voltammetry (CV) studies ascertain the multitude of adsorption states existing in long strand of DNA on surface. Surface coverage was found to be ∼ 72% (1.35 × 1010 molecules/cm2), and ∼ 42% (7.89 × 109 molecules/ cm2) in Dip and Drop approach, respectively. Dip approach can be used as a measure to minimize interference due to aggregation
Interferometric Moire Pattern Encoded Security Holograms with Concealed Phase Object
No full textThis paper describes an interferometry-based scheme for concealing phase objects in a security hologram. The decoding process is based on geometrical moiré technique and requires a key for hologram authenticity verification. Decoding process is straightforward and could be carried out in white light, making it suitable for validation of security holograms. The method is described and experimental results are presented
Preventive Maintenance of Molecular Beam Epitaxy (MBE) Machine for the Growth of III-V Compound Semiconductors
No full textMolecular Beam Epitaxy (MBE) is a technique for growing epitaxial films by directing beams of atoms or molecules created by thermal evaporation onto a clean heated substrate under Ultra High Vacuum (UHV) conditions. Although the process appears to be simple, MBE machines are quite complex. The maintenance requirements are arduous and toilsome. Several practical problems have to be addressed in order to consistently maintain the UHV required for depositing low defect and high quality epilayers. Because of the accurate control and precise repeatability of doping and thickness required to produce epilayers for device applications, machine performance over a period of time must be maintained. This paper highlights the problems and issues being faced for proper maintenance of Molecular Beam Epitaxy System
Design Consideration for the AbsoluteTesting Approach of Aspherics using Combined Diffractive Optical Elements
No full textAspheric optical surfaces are often tested using diffractive optics as null elements. For precise measurements, the errors caused by the diffractive optical element must be calibrated. Recently, we reported first experimental results of a three position quasi-absolute test for rotationally invariant aspherics by using combined-diffractive optical elements (combo-DOEs). Here we investigate the effects of the DOE substrate errors on the proposed calibration procedure and present a set of criteria for designing an optimized combo-DOE. It is demonstrated that this optimized design enhances the overall consistency of the procedure. Furthermore, the rotationally varying part of the surface deviations is compared with the rotationally varying deviations obtained by an N-position averaging procedure and is found to be in good agreement
Design & Development of IR technique Based Snow Surface Temperature Measuring Probe
Get PDFThis paper presents design and development of IR probe, developed first time in India, which is used to measure snow surface temperature without contact with snow. The design can operate round the clock in harsh weather conditions in snow bound areas (–40 °C to +50 °C) with high relative humidity and wind speed (200 km/h). This instrument has been installed in Siachen region, J & K region and interfaced with Data Collection Platform. The recorded temperature data is being transmitted hourly through satellite from Siachen and J & K region to central base station at SASE, Chandigarh. This instrument can measure temperature (– 40 °C to +100 °C) with the resolution of 0.1 °C and consumes low power. This paper mainly describes the characteristics of IR rays, basic principle involved in designing and principle of operation
Macroelectrode Fabrication Using Laser Scissors.
No full textToday laser microdissection system or laser scissor is frequently used for isolation of single chromosome, nucleus, cell, tissue etc. Here we fabricated the gold microelectrodes having a gap spacing of less than 3 μm using this system. A 500 Å thickness of gold was coated on standard glass slide. A UV-laser (λ 337 nm) of 4 ns pulse duration having an energy of 22 μJ is sufficient to cold ablate the gold, was used for fabrication of gold electrodes on the above slides. Microstructures up to the resolution limit (0.25 μm) of optical microscope can be fabricated using this cold ablation by laser