Effect of solvent volume on the physical properties of sprayed fluorine‐doped zinc oxide thin films

Fluorine‐doped zinc oxide (FZO) films were deposited from aged starting solutions having different solvent volumes (10, 20, 30, 40 and 50 ml) using a simplified spray pyrolysis technique. The electrical studies showed that the resistivity is minimum (4.68 × 10^–2 Ω cm) for lowest solvent volume (10 ml) and the value progressively increased with the increase in the solvent volume indicating that the fluorine incorporation increases with solvent volume. The systematic study clearly showed that the spray flux rate plays a crucial role in determining the electrical, optical, surface and structural properties of the FZO films. The optical transparency is found to be gradually increased (from 85 to 95%) as the volume of the solvent increases. The scanning electron microscope images depicted that the decrease in the spray flux rate caused an enhancement in the grain size. The X‐ray diffraction profile clearly showed that all the films have preferential orientation along the (002) plane with hexagonal wurtzite structure. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sono-leather technology with ultrasound: a boon for unit operations in leather processing - review of our research work at Central Leather Research Institute (CLRI), India

Ultrasound is a sound wave with a frequency above the human audible range of 16Hz to 16kHz. In recent years, numerous unit operations involving physical as well as chemical processes are reported to have been enhanced by ultrasonic irradiation. There have been benefits such as improvement in process efficiency, process time reduction, performing the processes under milder conditions and avoiding the use of some toxic chemicals to achieve cleaner processing. These could be a better way of augmentation for the processes as an advanced technique. The important point here is that ultrasonic irradiation is physical method activation rather than using chemical entities. Detailed studies have been made in the unit operations related to leather such as diffusion rate enhancement through porous leather matrix, cleaning, degreasing, tanning, dyeing, fatliquoring, oil-water emulsification process and solid-liquid tannin extraction from vegetable tanning materials as well as in precipitation reaction in wastewater treatment. The fundamental mechanism involved in these processes is ultrasonic cavitation in liquid media. In addition to this there also exist some process specific mechanisms for the enhancement of the processes. For instance, possible real-time reversible pore-size changes during ultrasound propagation through skin/leather matrix could be a reason for diffusion rate enhancement in leather processing as reported for the first time. Exhaustive scientific research work has been carried out in this area by our group working in Chemical Engineering Division of CLRI and most of these benefits have been proven with publications in valued peer-reviewed international journals. The overall results indicate that about 2-5-fold increase in the process efficiency due to ultrasound under the given process conditions for various unit operations with additional benefits. Scale-up studies are underway for converting these concepts in to a real viable larger scale operation. In the present paper, summary of our research findings from employing this technique in various unit operations such as cleaning, diffusion, emulsification, particle-size reduction, solid-liquid leaching (tannin and natural dye extraction) as well as precipitation has been presented.     

A tomographic PIV resolution study based on homogeneous isotropic turbulence DNS data

In order to accurately assess measurement resolution and measurement uncertainty in DPIV and TPIV measurements, a series of simulations were conducted based on the flow field from a homogeneous isotropic turbulence data set (Re _λ = 141). The effect of noise and spatial resolution was quantified by examining the local and global errors in the velocity, vorticity and dissipation fields in addition to other properties of interest such as the flow divergence, topological invariants and energy spectra. In order to accurately capture the instantaneous gradient fields and calculate sensitive quantities such as the dissipation rate, a minimum resolution of x/η = 3 is required, with smoothing recommended for the TPIV results to control the inherently higher noise levels. Comparing these results with experimental data showed that while the attenuation of velocity and gradient quantities was predicted well, higher noise levels in the experimental data led increased divergence.     

Nanoparticle aggregation due to dewetting of sandwiched buffer layers

The deposition of Au onto thin condensed volatile buffer layers produces small clusters. Sublimation of the buffer converts these clusters into compact or ramified structures, depending on the thickness of the buffer, in a process called buffer-layer-assisted growth. We have used bilayer structures of Xe on CO₂ or Xe on H₂O on amorphous carbon substrates to investigate effects of second layer dewetting and the impact of the initial particle size on aggregation. Compact particles formed by Xe desorption aggregate during removal of the CO₂ or H₂O layer but little aggregation occurs for ramified particles produced on Xe layers thicker than 100 ML. Instead, the large structures tend to break up on the CO₂ film, producing smaller, more compact particles. CO₂ and H₂O impurities in the Xe film significantly reduce particle coalescence and accelerate Xe dewetting.     

Gravitational charges,f-gravity and hadron masses

Two types of fundamental gravitational charges are suggested by quantization of the angular momentum (i.e. J=n?, wheren is an integer or half integer) occurring in the uncharged and charged Kerr metrics. These charges turn out to bee/√a ande/a, wheree is the unit electric charge anda the fine structure constant. The use of strong (f) gravity leads to corresponding fundamental massesM ₁(f) ～2.2×10^?24 g andM ₂(f)～2.3×10^?23 g. It is postulated that the hadrons are composed of these fundamental entities (christened oms here). Thus mesons arediomic particles and baryons aretriomic particles. This has a close resemblance to the quark model but here we deal with gravitational charges. The charges constituting hadrons are bound together by strong (f) gravity which is super strong compared to nuclear forces. Various hadron masses are obtained as the vibrational excitations of these composite units. The above model is capable of accounting for quantum numbers such as spin, baryon number, strangeness and isospin.     

CHARMM: A program for macromolecular energy,minimization, and dynamics calculations

CHARMM (Chemistry at HARvard Macromolecular Mechanics) is a highly flexible computer program which uses empirical energy functions to model macromolecular systems. The program can read or model build structures, energy minimize them by first- or second-derivative techniques, perform a normal mode or molecular dynamics simulation, and analyze the structural, equilibrium, and dynamic properties determined in these calculations. The operations that CHARMM can perform are described, and some implementation details are given. A set of parameters for the empirical energy function and a sample run are included.     

The laser gain characteristics of some substituted coumarins

A theoretical and experimental study has been made of the small signal gains of six coumarin dyes (DAMC, 4 MU, 7 HC, calcein blue, esculin and scopoletin) in a common solvent (ethanol), and the variation correlated with the different substituents in the coumarins. The relative variation in gain, taking the value for DAMC as the basis, is about 75% for 4 MU, 7 HC and calcein blue, 55% for esculin and 20% for scopoletin. The total tunable range for these dyes is from 430–530 nm. The higher gain in the case of DAMC is attributed to the relatively higher intramolecular charge transfer in this dye compared to the hydroxy-coumarins. The different substituents in the hydroxy-coumarins studied appear to have only a marginal influence on the gain.