Selective electrooxidation of uric acid in presence of ascorbic acid at a room temperature ionic liquid/nickel hexacyanoferarrate nanoparticles composite electrode

A novel amperometric sensor for the determination of uric acid was fabricated using room temperature ionic liquid and nickel hexacyanoferrate nanoparticle composite which was immobilized on paraffin wax impregnated graphite electrode. The nickel hexacyanoferrate nanoparticle was characterized by UV-vis, X-ray diffraction and field emission scanning electron microscopy. The electrochemical behavior of the modified electrode was investigated in detail by electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. Various experimental parameters influencing the electrochemical behavior of the modified electrode were optimized by varying the supporting electrolyte, scan rate and pH. The apparent electron transfer rate constant (K(s)) and charge transfer coefficient (α) of the modified electrode were found to be 1.358(± 0.02)cm/s and 0.65, respectively from cyclic voltammetry. The sensor exhibited an excellent electrocatalytic activity towards the oxidation of uric acid. The interference from ascorbic acid was easily overcome by coating the modified electrode with PEDOT layer. Under optimal condition, the determination range for uric acid is from 1.0 × 10(-6)M to 2.6 × 10(-3)M and the detection limit was 3.3 × 10(-7)M (3σ). The proposed method has been used for the determination of uric acid in human urine samples.     

Semiconductor cadmium sulphide nanoparticles as matrices for peptides and as co-matrices for the analysis of large proteins in matrix-assisted laser desorption/ionization reflectron and linear time-of-flight mass spectrometry

The use of semiconductor cadmium sulphide nanoparticles (CdS NPs) capped with 4-aminothiophenol (ATP) and 11-mercaptoundecanoic acid (MUA) is described for the first time as matrices and as co-matrices for the analysis of peptides and proteins in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied for the characterization of functionalized CdS NPs. The synthesized CdS-ATP and CdS-MUA NPs exhibit uniform size distribution with diameter of 15-25 nm and 20-30 nm, respectively. The -NH(2) (ATP) and -COOH (MUA) groups modified on the surfaces of CdS NPs provide ionizable moieties for efficient transfer of protons during the desorption/ionization of analytes. The functionalized CdS NPs have desirable properties for the analysis of peptides in reflectron MALDI-TOF-MS with suppressed background noise and increased mass resolution (4-13-fold) in linear MALDI-TOF-MS. The application of CdS-MUA NPs and SA as the co-matrices in MALDI-MS is demonstrated for the analysis of hydrophobic proteins from soybean.     

Effect of binary phase plate on incident radially polarized hollow Gaussian beam

Effect of a pure binary phase filter on the three-dimensional light intensity distributions in focal region is theoretically investigated in this paper. The results show that the proposed binary phase filter may induce flat top profile with large depth of focus and reduced focal spot by properly adjusting the geometrical parameters of the binary phase filter of incident radially polarized hollow Gaussian beam (HGB) beam. On the other hand, the HGB beam benefits the most from the use of an annulus. Such kind of system is potentially useful for lithography, imaging, optical data storage, optical trapping, optical excitation of molecules, or coupling to optical fibers.     

Tight focusing of partially coherent radially polarized beam with high NA lens axicon

Tight focusing of radially polarized partially coherent vortex beam over a high numerical aperture lens axicon system is introduced and its propagation properties are studied based on vectorial Debye theory. The effect of propagation parameters on the intensity distribution, the polarization property and the coherent property of the beam is illustrated analytically and numerically. It is shown that the correlation length and maximal NA angle has a significant influence on the intensity profile.     

Experiments to Explore the Mechanisms of Heat Transfer in Nanocrystalline Alumina/Water Nanofluid under Laminar and Turbulent Flow Conditions

Abstract

Heat transfer characteristics of water-based nanocrystalline alumina (Al₂O₃) nanofluids flowing through a uniformly heated tube under a fully developed laminar and turbulent flow regime is investigated experimentally in the present work to explore the heat transfer mechanism in nanofluids. In a laminar flow, the increase in Nusselt number was attributed to the thermophysical properties of the nanofluid. The movement of nanoparticles, along with the turbulent eddies in the turbulent core region and diffusion mechanism, such as thermophoresis, in the laminar sublayer are believed to be the reasons for enhanced heat transfer in turbulent region. The compatibility of Al₂O₃/water nanofluids was also examined by monitoring its color.     

Area spectrum and thermodynamics of KS black holes in Hořava gravity

We investigate the area spectrum of Kehagias–Sfetsos black hole in Ho?ava–Lifshitz gravity via modified adiabatic invariant $I=\oint p_i d q_i$ I = ∮ p i d q i and Bohr–Sommerfeld quantization rule. We find that the area spectrum is equally spaced with a spacing of $ \Delta A=4 \pi l_p ^2$ Δ A = 4 π l p 2 . We have also studied the thermodynamic behavior of KS black hole by deriving different thermodynamic quantities.     

Theoretical analysis for the transient behaviour of radiative cooling of cavities in superconducting LINAC cryomodule

For the superconducting linear accelerator program, three cryomodules each houses eight superconducting cavities were successfully developed at IUAC, New Delhi. In each cryomodule, the cold mass at 4.2 K is surrounded by the liquid nitrogen cooled thermal shield maintained at 100 K. Three stages of cooling namely, radiation cooling followed by liquid nitrogen pre-cooling and finally liquid helium (LHe) cooling, are followed to reduce the temperature of cold mass from 300 to 4.2 K. The cold mass at 4.2 K consists of cavities, LHe vessel and the support structure. The temperature of cavity and helium vessel reaches to 210–220 K in 40 h of time by the natural radiation from the thermal shield. The radiative cooling rates for the cavities, helium vessel and support structure are found to be 3.0, 4.0 and 2.0 K/h respectively. A detailed analytical calculation has been done to understand the transient cool-down phenomenon for each component and compared with the experimental measured values. The experimental values are in agreement with the analytical data within 5 % variation considering the correction factor of radiation funneling. This paper presents the role of different thermal parameters like shield temperature, conduction load and radiation funneling area in the transient radiative cool-down behaviour of different components.     

Study on propagation properties of a radially polarized partially coherent dark hollow beam through a high numerical aperture lens

In recent years the partially coherent beams have attracted very much due to novel properties and its applications. In this paper the tight focusing properties of radially polarized partially coherent dark hollow beam (DHB) through a high numerical aperture lens are investigated numerically based on vectorial Debye theory in detail. The result shows that the optical intensity distribution in the focal region directly fluctuates due to small change in coherence length and high numerical aperture angle of the focused radially polarized partially coherent DHB.     

Growth,optical, mechanical,dielectric and theoretical properties of picolinium maleate NLO single crystal

Nonlinear optical single crystals of picolinium maleate (PM) were grown by slow evaporation method. The grown crystal was subjected to single crystal X-ray diffraction analysis to confirm that the crystal belongs to the monoclinic crystal structure with space group P2₁/c. The optical transmission range of the grown crystal was measured by UV–Vis–NIR region with the lower cut-off wavelength as 330 nm. The optical bandgap is found to be 3.75 eV. Mechanical strength of the grown crystal was analyzed using Vickers microhardness tester. Dielectric constant and dielectric loss of picolinium maleate are measured in the frequency range from 50 Hz to 5 MHz at different temperatures. Further, electronic properties, such as valence electron plasma energy, Penn gap, Fermi energy and electronic polarizability of the grown crystal have been estimated.