Chromosome aberration analysis in radiotherapy patients and simulated partial body exposures: biological dosimetry for non-uniform exposures

Chromosome aberration analysis was carried out in peripheral blood lymphocytes of cancer patients following radiotherapy of lungs, cervix and spine. Radiotherapy in the pelvic region involving large doses (6 Gy) showed an overdispersed distribution of dicentrics. However, when the doses were fractionated (three fractions of 2 Gy) distribution was found to be near Poisson. Spine irradiation covering almost all the lymphocytes pools, indicated a Poisson distribution. The data show that depending on the sites of exposure, the distribution of dicentrics in cells varies and hence there is a non-uniform distribution of lymphocytes in the body. The average dose to the lymphocytes was found to be one sixth of the partial body dose. Based on the non-Poisson distribution of aberrations, the fraction of lymphocytes irradiated, mean dose to the fraction and part of the body exposed was calculated in a case of acute 6 Gy pelvic irradiation. The fraction of cells irradiated was calculated to be 4.11% and the portion of the body exposed was approximately 16.8%. The dose to the irradiated fraction was found to be 5.4 Gy, which is in agreement with the given dose of 6 Gy. In simulated exposures the u values increased systematically with the decrease in fraction of irradiated cells and the calculated dose to the fraction was also in good agreement with the true dose.     

Nonresonant Microwave Absorption in Bi2212 Single Crystal: Second Peak and Microwave Power Dependence

Nonresonant microwave absorption (NMA) measurements were carried out at liquid-nitrogen temperature on a high quality Bi2212 single crystal, as a function of microwave power in three mutual orientations of crystal ab plane, dc field (H_dc), and microwave magnetic field (H_w). NMA line shapes in Bi2212 crystal are complicated with a narrow peak (P₁ peak) located near zero field, followed by a much broader second peak (P₂ peak) in the particular orientations. More excitingly, we show that the P₂ peak qualitatively evolves as a function of microwave power in the orientation of H_dc ab plane, plane, and H_dc H_w. In this configuration, as the microwave power is progressively increased, the broad P₂ peak first gets smeared off and then a multiple peak structure appears, which develops into another narrower second peak (P_s-peak) at high enough microwave powers. In the orientation of plane, H_w ab plane, and H_dc H_w, we report for the first time the appearance and disappearance of a new second peak (P₂-like peak) as a function of microwave power.     

LC-MS/MS Determination of Organophosphorus Pesticide Residues in Coconut Water

A simple and specific analytical method based on solid phase extraction (SPE), and liquid chromatography–electrospray ionization–tandem mass spectrometry (LC-ESI-MS/MS) operated in multipule reaction monitoring (MRM) mode with dynamic time segment acquisition windows, was developed to determine organophosphorus pesticide residues (acephate, monocrotophos, dimethoate, malaoxon, dichlorvos, malathion, phenthoate, parathion-ethyl, chlorfenvinfos, quinalphos, diazinon, phosalone, profenofos, ethion, chlorpyrifos) in tender coconut water. The method was observed to be linear with lower limit of detections ranged from 0.1 to 1.5 ng/mL (measured at S/N ratio 5:1) and limit of qunatitation 0.5 to 2.0 ng/mL (measured at S/N ratio 10:1) for all studied pesticides. The intra- and inter-day assay accuracies calculated at four concentration levels in six replicates (n?=?6) were in the range of 80 % to 115 % with relative standard deviations (RSD) below 15 %. The percentage recoveries of all the analysed pesticides were in the range of 86.8 % to 107.6 % and the calculated RSD values were below 12 %. The developed method was applied to determine pesticide residues in natural tender coconut water samples. The results showed the presence of malathion ranging from 24 to 45 ng/L concentrations in some natural tender coconut water samples collected from various local market places in and around Hyderabad, Andhra Pradesh, India.     

Frequency-dependent distortions of composite triple beat inlightwave CATV transmission systems

The frequency-dependent distortion of composite triple beat (CTB) for analog AM multichannel lightwave transmission systems is studied. A modified circuit model which takes into account the small signal behavior of the leakage path is developed, and it is shown that it is adequate to describe the measured frequency-dependent behavior of CTB in a 42-channel load lightwave CATV (cable television) transmission system using a cap-mesa buried-heterostructure (CMBH) distributed-feedback (DFB) laser inside the transmitter module     

Buck-boost converter feedback controller design via evolutionary search

Buck-boost converters are switched power converters. The model of the converter system varies from the ON state to the OFF state and hence traditional methods of controller design based on approximate transfer function models do not yield good dynamic response at different operating points of the converter system. This article attempts to design a feedback controller for a buck-boost type dc–dc converter using a genetic algorithm. The feedback controller design is perceived as an optimisation problem and a robust controller is estimated through an evolutionary search. Extensive simulation and experimental results provided in the article show the effectiveness of the new approach.     

Performance evaluation of a novel sampling-based texture synthesis technique using different sized patches

We propose a novel sampling-based texture synthesis algorithm called Multipatch, which improves on the results of previous sampling-based algorithms by using patches of different size, and by minimizing global pasting errors. A key feature of the proposed algorithm is that it always converges to a local minimum. Multipatch, the patchwork algorithm, and Wei and Levoy’s multi-resolution texture synthesis algorithm, which is based on a tree-structured vector quantization method, are statistically analyzed and subjectively evaluated. The results of simulations show that the patchwork algorithm yields a perceptually acceptable texture in a shorter expected running time than the other two algorithms; however, Multipatch is the most efficient in terms of obtaining a good quality texture image.     

Design framework for dimethyl ether (DME) production from coal and biomass-derived syngas via simulation approach

A comprehensive thermodynamic study was conducted to evaluate the comparative efficacy of methanol and dimethyl ether (DME) synthesis using CO₂ rich syngas feed. The first part of our study included assessing the relative performances of the methanol synthesis system, two step DME synthesis system, and one step DME synthesis system in terms of the CO_x conversion and product yield (methanol/DME) based on the Gibbs free energy minimization approach. The wide range of composition of CO₂-enriched syngas feed produced by the coal and biomass gasification was simulated using Aspen Plus and the following evaluation parameters were analyzed for a broad parameter range: reaction temperature (180–280°C), reaction pressure (10–80 bar), stoichiometry number (SN) (0–11), and CO₂/(CO₂ + CO) molar feed ratio (0–1) for isothermal as well as adiabatic conditions. Based on the equilibrium yield, one-step DME synthesis was discovered as the most viable process to utilize the co-gasification derived syngas effectively. In the second part of our study, the overall process efficiency was inspected through the process design of 1 tonnes per day (TPD) DME plant inclusive of heat integration, resulting in significant CO₂ abatement and DME production with high product purity and minimum energy consumption. Consequently, one-step DME production via CO₂-enriched syngas obtained through the coal or biomass gasification process is identified as the leading technology based on energy utilization and CO₂ abatement.     

Perspectives on SnSe-based thin film solar cells: a comprehensive review

Currently, selenium (Se)-based compound semiconductors (CISe, CIGSe and CZTSe) are considered as the active materials in the photovoltaic world. However, these materials exhibit couple of issues related to stoichiometry maintenance and scarcity of their constituent elements (In, Ga), which limit their massive production for future energy demands. These issues could be rectified by introducing a non-toxic, inexpensive and earth-abundant binary material. One such material is a tin monoselenide (SnSe), which exhibits a high chemical stability along with attractive physical properties namely, suitable band gap (1.3 eV), high absorption coefficient (10⁵ cm^?1) and p-type conductivity. These properties indicate SnSe as a competitive substitute in place of conventional absorbers in thin film solar cells. Despite of its remarkable properties, only a few reports were published on the fabrication of SnSe-based solar cells with poor efficiency (≤1 %). This indicates a need to review on the physical properties of SnSe and its device structures in a deeper sense. In this context, the present review describes the different methods of preparation of SnSe films and their physical properties along with the details of photovoltaic device fabrication. We highlighted the different factors that are limiting the efficiency of SnSe solar cells, and a few suggestions were included to overcome these problems for further improvement of these cells. This review will enrich and stimulate the readers to further investigate the growth of SnSe thin films and their devices, for the development of >20 % efficient SnSe solar cells.     

Kinetic studies of sulfuric acid decomposition over Al–Fe2O3 catalyst in the sulfur-iodine cycle for hydrogen production

The decomposition of H₂SO₄ to produce SO₂ is the reaction with the highest energy demand in the sulfur-iodine cycle and it shows a large kinetic barrier. In the present study, alumina supported iron (III) oxide has been chosen for a detailed kinetic study. Experiments were carried out in the temperature range of 1023 K–1173 K using space hour velocities in the range of 0.146–0.731 kmol/kg-h in a quartz tube double stage continuous flow fixed bed reactor with 98% sulfuric acid feed over alumina supported Fe₂O₃ catalyst, nitrogen as inert carrier gas. From the homogeneous kinetic analysis, the apparent activation energy (E_A) was found to be 138.6 kJ/mol. This high activation energy indicates that the experiments were conducted in a kinetic controlled regime. The catalyst was well characterized by XRD, BET, TPR/TPO, SEM and FT-IR before and after reaction.