Integration of electrostatic and fluid dynamics within a dust devil

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94610/1/jgre2050.pd

Applications of electrified dust and dust devil electrodynamics to Martian atmospheric electricity

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kVm-1 to 100 kVm-1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m-1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)-MicroARES (Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ measurements

Colorimetric Estimation of Ni(II) Ions in Aqueous Solution

A rapid and accurate colorimetric method has been proposed for the estimation of nickel(II) in aqueous solution. It is found that nickel(II) ions have maximum absorbance at 393 nm in distilled water and in aqueous sucrose solution (0.3 mol dm-3). In both case, the Beer’s law was obeyed over the range from 0.04 to 0.08 mol dm -3 of nickel(II).The value of molar absorpitivity was constant 5.13±0.03 mol dm-3. This method is more rapid than the existing spectrophotometeric methods for the estimation of nickel(II). The variation in the results obtained by the method is ±2.1%

Low field room temperature magnetism and band gap modifications in Sm doped SnO2

The structural, optical and magnetic properties of pure and Sm doped SnO2 nanoparticles synthesized in aqueous solution by a low cost chemical co-precipitation method without using any stabilizing agent have been reported. X-ray diffraction analysis reveals that the crystallite size of SnO2 decreases with the increase of Sm doping into the SnO2 matrix. The calculated value of optical band gap of undoped SnO2 nanoparticles is calculated to be 2.65 eV and it anomalously increases with the increase of Sm3+ concentration. The band gap of undoped SnO2 nanoparticles is found to be lower than those reported for bulk SnO2 (3.6 eV) that may be due to the presence of defects, oxygen vacancies and non-stoichiometry of SnO2 nanoparticles. All the undoped and Sm doped SnO2 nanoparticles show weak room temperature magnetism in the range of applied low magnetic field region of 2000 Oe due to the presence of defects and oxygen vacancies. All the samples exhibit negative magnetic susceptibility for the applied magnetic field higher than 2000 Oe. The strong optical absorption with weak magnetic properties at room temperature may serve the SnO2 nanomaterials as a potential candidate for many DMS, spintronics, and optoelectronics based applications

Variation in Ground Electric Field due to Various Forms of Intracloud Lightning Discharges

104-109The calculations for instantaneous and total changes in ground electric field due to various forms of intracloud lightning discharges are presented. To place in perspective the significance of the individual form of intra cloud discharge, three possible cases, namely, propagation of positive, negative and complex streamers have been studied separately. The important aspects of thunderclouds such as spatially inhomogeneous charge distribution, redistribution of charge due to propagation of streamers, and concept of finite dimensions of streamers and thunderclouds have been taken into account. The present study points out the incapability of the electric field variation dependent hypothesis to distinguish between a negative and a complex streamer because both these streamers produce negative changes in ground electric field. Our theoretical findings suggest that a more convincing hypothesis to classify the nature of intracloud discharges should incorporate magnitudes of electric field variations along with the nature of electric field changes. Plots of total electric field change against distance of observing point show a reasonable agreement with the observed magnitude variations and electric field sign reversal distances at ground

Magnetic and electrical properties of manganese and cadmium co-substituted lithium ferrites

Manganese and cadmium co-substituted lithium ferrite having the general formulae Li0.35Cd0.3MnxFe2.35−xO4 + 0.10 wt% Bi2O3 with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 has been prepared by standard ceramic technique. M–H curves of all samples have been determined by using vibrating sample magnetometer (VSM). The highest saturation magnetization 79 emu/g is observed in Li0.35Cd0.3Fe2.35O4 (Mn = 0) and it decreases with increase in manganese content in the compound. It is observed that the value of initial permeability increases to maximum value ∼230 for Mn = 0.4 and then decreases with further increase in Mn contents. The dc resistivity of all samples is found in the range of 107 Ω cm

Multifunctional behaviour of nanostructured Pb0.7Sr0.3(Fe0.012Ti0.988)O3 thin film

Structural, magnetic, electrical and optical properties of the Pb0.7Sr0.3(Fe0.012Ti0.988)O3 (PSFT) thin film have been studied. The PSFT solution was prepared by the sol–gel combined metallo-organic decomposition method and deposited on Si, Pt/Ti/SiO2/Si and fused quartz substrates by the spin-coating technique. The superparamagnetic relaxation between bulk nanoparticles and film nanograins has been done. The insulating gaps between the PSFT nanograins made symmetrically coupled plasmon modes and explored their potential in magneto-optic data storage, light generation, microscopy and bio-photonics

Dielectric properties of nanocrystalline Pb0.8Sr0.2TiO3 thin films at different annealing temperature

Nanocrystalline Pb0.8Sr0.2TiO3 (PST20) thin films have been synthesized by metallo-organic decomposition (MOD) technique and deposited on Pt/Ti/SiO2/Si substrates at different annealing temperatures of 550–750 °C. The X-ray diffraction (XRD) confirms the distorted tetragonal perovskite phase in PST20 films. The average grain's size varies from 35 nm to 46 nm as the annealing temperature increases from 650 °C to 750 °C as revealed by atomic force microscopy. At 550 °C, the film shows low crystallization with incomplete perovskite structure. The study of dielectric properties of PST20 films is aimed at electrically tunable applications and to observe ferroelectric behaviors of PST20 films. The film annealed at 650 °C shows large dielectric constant and higher tunability than the films annealed at 550 °C and 750 °C. The values of dielectric constant and tan δ at 1 MHz are 272 and 0.005, respectively, and tunability is ∼66% for PST20 film annealed at 650 °C. The dispersionless dielectric properties are observed up to high frequency ∼8 MHz. The results suggest that the growth of uniform, dense and nano-sized grains in PST film makes it suitable for higher frequency device applications and electrically tunable devices