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Many novel materials are being actively considered for quantum information science and for realizing high-performance qubit operation at room temperature. It is known that deep defects in wide-band gap semiconductors can have spin states and long coherence times suitable for qubit operation. We theoretically investigate from ab-initio density functional theory (DFT) that the defect states in the hexagonal silicon carbide (4H-SiC) are potential qubit materials. The DFT supercell calculations were performed with the local-orbital and pseudopotential methods including hybrid exchange-correlation functionals. Di-vacancies in SiC supercells yielded defect levels in the gap consisting of closely spaced doublet just above the valence band edge, and higher levels in the band gap. The divacancy with a spin state of 1 is charge neutral. The divacancy is characterized by C-dangling bonds and a Si-dangling bonds. Jahn-teller distortions and formation energies as a function of the Fermi level and single photon interactions with these defect levels will be discussed. In contrast, the anti-site defects where C, Si are interchanged have high formation energies of 5.4 eV and have just a single shallow defect level close to the valence band edge, with no spin. We will compare results including the defect levels from both the electronic structure approaches.
The head and neck cancers as a whole are the most common cancers among males in India. Technological advancements have led to an improvement in radiation therapy (RT) techniques with subsequent reduction in normal tissue complications. To correct patient set-up errors, an off-line correction method like no action level (NAL) protocol may be used as a preferred protocol particularly for a busy department. The objectives of the study were to measure the translational set-up errors using kV cone-beam computed tomography (CBCT) in patients undergoing intensity modulated radiotherapy (IMRT) in head and neck cancers and also to optimise clinical target volume (CTV) to planning target volume (PTV) margin using NAL protocol.
Material and methods:
On the first 5 days of RT, patient’s position was verified by kV-CBCT and then weekly during the course of treatment. The comparison between the reference and kV-CBCT images was performed, and the shifts measured and recorded. The mean error from the initial five consecutive fractions was corrected on the sixth daily fraction. Displacements in all the directions were measured. The population systematic and random errors were determined and used to estimate PTV margins according to the van Herk formula.
A total of 322 images were analysed. Before correction, 15, 12 and 9% patients had systematic error ≥3 mm on X, Y and Z axes, but after correction this was reduced to 9, 0 and 0%. The total percentage of patients whose set-up margin was ≥5 mm before correction was 5, 6·25, 3·75%, but after correction it reduced to 1·88, 0, and 0·63%. The margins of total population were reduced to 63, 65 and 56% after correction on X, Y and Z axes, respectively.
A simple off-line NAL protocol can correct the set-up errors without daily on-line imaging in patients undergoing IMRT and hence acting as a resource sparing alternative. Five millimetre margin to CTVs was adequate and safe to overcome the problem of set-up errors in head and neck IMRT.
Binary Fe–Cu alloys are effective prototypes for investigating radiation-induced formation and growth of nanometric Cu-rich precipitates (CRPs) in nuclear reactor pressure vessels. In this report, the temporal evolution of CRPs during thermal aging of Fe–Cu binary alloys has been investigated by using complementary techniques such as atom probe tomography (APT) and small-angle neutron scattering (SANS). We report a detailed quantitative evolution of a rarely observed morphological transformation of Cu precipitates from spherical to ellipsoid with a significant change (approximately two times) in aspect ratio, an effect known to be associated with the 9R-3R structural transition of the precipitates. It is demonstrated through APT that the precipitates remain spherical up to 8 h, however, they subsequently convert to oblate ellipsoid upon further aging. SANS analysis also detected signs of this morphological transition in reciprocal space. Furthermore, SANS quantifies evolution of the precipitates and corroborates well with the APT results. Interestingly, the power-law exponent of the temporal evolution for mean size and number density agree reasonably well with the Lifshitz–Slyozov–Wagner model, in spite of the complex morphological evolution of the precipitates.
We develop experimentally and theoretically plasmonic and photonic crystals for enhancing thin film silicon solar cells. Thin film amorphous silicon (a-Si:H) solar cells suffer from decreased absorption of red and near-infrared photons, where the photon absorption length is large. Simulations predict maximal light absorption for a pitch of 700-800 nm for photonic crystal hole arrays in silver or ZnO/Ag back reflectors, with absorption increases of ~12%. The photonic crystal improves over the ideal randomly roughened back reflector (or the ‘4n2 limit’) at wavelengths near the band edge. We fabricated metallic photonic crystal back-reflectors using photolithography and reactive-ion etching. We conformally deposited a-Si:H solar cells on triangular lattice hole arrays of pitch 760 nm on silver back-reflectors. Electron microscopy demonstrates excellent long range periodicity and conformal a-Si:H growth. The measured quantum efficiency increases by 7-8 %, relative to a flat reflector reference device, with enhancement factors exceeding 6 at near-infrared wavelengths. The photonic crystal back reflector strongly diffracts light and increases optical path lengths of solar photons.
The partial coalescence dynamics of a compound drop in a liquid pool is numerically investigated. We study the effect of the ratio of the inner to outer radii
of the compound drop while maintaining a constant liquid volume in the outer shell of the compound droplet. It is observed that for small values of the radius ratio, the coalescence dynamics is similar to that of a ‘simple’ drop, but the partial coalescence is suppressed for large values of
. Increasing the value of
decreases the distance migrated by the inner bubble in the downward direction inside the pool. The location of the bubble after coalescence is found to play an important role in the pinch-off process of the satellite drop. The influence of the governing dimensionless parameters on the coalescence dynamics has also been investigated.
The availability of iodized salt in households remains low in Bangladesh, which calls for improving the salt iodization quality and its coverage. The present study assessed the socio-economic disparity in Bangladesh to characterize the availability of iodized salt at household level.
Associations between different socio-economic factors and availability of iodized salt at household level were explored using Bayesian mixed-effects logistic models after adjusting the district- and cluster-level random effects.
Results showed that 73·15 % of household salt samples were iodized to some extent although iodization level varied. According to the regression model, houses with young (adjusted odds ratio of posterior mean (OR) = 1·31; 95 % credible interval (CI) 1·09, 1·64) and educated (OR = 3·66; 95 % CI 3·25, 4·23) household heads had significantly higher likelihood of availability of iodized salt. In addition, iodized salt was less likely be found in poor and rural households, as urban households were 2·88 times (95 % CI 2·41, 3·34) more likely have iodized salt. Moreover, the regional locations of the households were an important component that contributed to the local iodized salt coverage. As per the district-wise distribution, the north-west part of Bangladesh and Cox’s Bazar in the far south seemed to lack household-level iodized salt.
Our findings suggest that iodized salt intervention should be promoted considering the area variations, which could potentially help policy makers to design interventions in the context of Bangladesh.
Discs of CoCuFeMnNi face centered cubic high entropy alloy were subjected to monotonic and cyclic high pressure torsion (HPT) in a single step and multiple steps of 5° forward and reverse cycle for 100° and 360° twist, respectively, under 5 GPa pressure at room temperature. It was observed that the 100° cyclic HPT sample shows the highest hardness at the periphery comparable to 360° monotonic HPT sample, while the cyclic 360° HPT sample shows the lowest hardness throughout the sample. High hardness of 100° cyclic HPT sample can be attributed to finer grain size and unstable dislocation substructure by continuous change in strain path from initial compression to forward–reverse torsion, while stable dislocation structure corresponding to shear contributes to increase in hardness from 100° to 360° for monotonic HPT sample. The unstable dislocation substructure promotes grain boundary migration–enabled grain growth leading to low hardness throughout the 360° cyclic HPT sample.
We present an information-based total-energy optimization method to produce nearly defect-free structural models of amorphous silicon. Using geometrical, structural, and topological information from disordered tetrahedral networks, we have shown that it is possible to generate structural configurations of amorphous silicon, which are superior than the models obtained from conventional reverse Monte Carlo and molecular dynamics simulations. The new data-driven hybrid approach presented here is capable of producing atomistic models with structural and electronic properties which are on a par with those obtained from the modified Wooten-Winer-Weaire (WWW) models of amorphous silicon. Structural, electronic, and thermodynamic properties of the hybrid models are compared with the best dynamical models obtained from using machine-intelligence-based algorithms and efficient classical molecular dynamics simulations, reported in the recent literature. We have shown that, together with the WWW models, our hybrid models represent one of the best structural models so far produced by total-energy-based Monte Carlo methods in conjunction with experimental diffraction data.
To investigate the prevalence and sociodemographic determinants of household-level mother–child double burden (MCDB) of malnutrition in Bangladesh.
The analysis was done using Bangladesh Demographic and Health Survey 2014 data. Multivariable logistic regression identified the sociodemographic factors associated with double-burden households.
Nationally representative cross-sectional survey.
A total of 5951 households were included in the analysis.
A coexistence of overweight or obese mother and underweight or stunted or wasted child (OWOBM/USWC) was found in 6·3 % households. The prevalence of overweight or obese mother and underweight child (OWOBM/UWC) was 3·8 %, of overweight or obese mother and stunted child (OWOBM/STC) was 4·7 %, and of overweight or obese mother and wasted child (OWOBM/WSC) was 1·7 %. Mother’s age 21–25 years at first birth, middle wealth index group, having two or three children and having four or more children showed statistically significant (P<0·05) associations with OWOBM/UWC. Households with mother’s age 21–25 years at first birth, middle wealth index group, no exposure to information media, having two or three children and having four or more children had higher odds of OWOBM/STC and OWOBM/USWC which were statistically significant (P<0·05). Delivery of child through caesarean section was significantly associated with OWOBM/USWC (P<0·05).
Although the prevalence of MCDB of malnutrition in Bangladesh is low, prevention programmes must consider the nutrition concerns of the entire household to prevent future risks. Such programmes also need to be tagged with family planning and increasing awareness through social and behaviour change counselling and exposure to information media.
The current work studied the effects of butyric acid (BA) supplementation on the growth performance, carcase characteristics, immunity, gut histology and serum biochemistry of broiler chicken. Four experimental diets were formulated: control, 20 mg bacitracin methylene di-salicylate/kg diet (BMD-supplemented), 3 g BA/kg diet and 4 g BA/kg diet. The results revealed higher body weight gain (BWG) in BA and BMD-supplemented groups. Only BMD supplementation increased the feed intake (FI) of birds, whereas BA supplementation improved feed efficiency. Expression of glucose transporter (GLUT5), sodium-dependent glucose transporter (SGLT1) and peptide transporter (PepT1) were up-regulated due to BMD and BA supplementation. However, at 21 days post-hatching SGLT1 expression in the BMD-supplemented group was down-regulated with respect to the BA-supplemented groups. The 4 g BA/kg diet yielded better humoral and cell-mediated immune responses than the other groups. No dietary effects were observed on carcase characteristics and histomorphometry of jejunum at 7 days post-hatching. However, at 42 days old, the 4 g BA/kg diet increased villus length and width significantly. There was a significant increase in serum protein, albumin, creatinine, aspartate aminotransaminase (AST), phosphorus and calcium due to BA supplementation. However, the reverse trend was observed in serum uric acid and cholesterol, where BA supplementation decreased both and BMD supplementation decreased uric acid levels only. Based on the results it was concluded that 4 g BA/kg diet supplementation in feed is optimal for desirable broiler production.
Unusual mafic rock fragments deposited in Plio-Pleistocene-aged marine sediments were recorded at Integrated Ocean Drilling Program (IODP) Site U1359, in Wilkes Land, East Antarctica. These fragments were identified from sediment layers deposited between c. 3 and 1.2 Ma, indicating a sustained supply during this time interval. Clinopyroxenes in these basalts are Al–Ti diopside–hedenbergite, uncommon in terrestrial magmatic rocks. A single strong peak in the Raman spectra of a phosphate-bearing mineral at 963 cm-1 supports the presence of merrillite. Although not conclusive, petrological traits and oxygen isotopic compositions also suggest that the fragments may be extra-terrestrial fragments affected by shock metamorphism. Nevertheless, it is concluded that the basaltic fragments incorporated in marine sediments at Site U1359 represent ice-rafted material supplied to the continental rise of East Antarctica, probably from the bedrocks near the proximal Ninnis Glacier. Further studies on Plio-Pleistocene sediments near Site U1359 are required to characterize the unusual mafic rocks described.
Cell morphology and relative density (ρrel) are two crucial intrinsic parameters controlling the mechanical properties of metal foams (MFs) and directly depend on their structure (closed/open-cell) and composition (affecting processing parameters). Here, we report on compressive studies of MFs of aluminum (Al) and 7075-T6 alloy processed via a customized route at strain rate, έ = 0.002 and 2.0 s−1. In both sets of MFs, the strength and apparent elastic modulus (E) monotonically increased with ρrel at both έ. At έ = 2.0 s−1, an increase in cell size (Cs) enhanced the strength of both sets of MFs, while at έ = 0.002 s−1, only the alloy foams showed strength increment. The densification strain (εd) of Al foams at έ = 0.002 s−1 monotonically decreased with increasing ρrel, whereas the alloy foams collapsed before the onset of densification. None of the MFs showed any particular trend of εd at έ = 2.0 s−1. The studies conclude that the mechanical properties of MFs with similar morphology, foam parameters, and processing route depend on έ and Cs. Absorption energy (W) and absorption efficiency (Im) of the two sets of MFs were also compared.
Using time-resolved laser-scanning confocal microscopy and ultrafast optical pump/THz probe spectroscopy, we measure photoluminescence (PL) and THz-conductivity in perovskite micro-crystals and films. PL quenching and lifetime variations occur from local heterogeneity. Ultrafast THz-spectra measure sharp quantum transitions from excitonic Rydberg states, providing weakly bound excitons with a binding energy of ~13.5 meV at low temperatures. Ab-initio electronic structure calculations give a direct band gap of 1.64 eV, a dielectric constant of ~18, heavy electrons, and light holes, resulting in weakly bound excitons, consistent with the binding energies from the experiment. The complementary spectroscopy and simulations reveal fundamental insights into perovskite light-matter interactions.
Dermatofibrosarcoma protuberans (DFSP) is a rare, locally aggressive soft tissue tumor commonly occurring in the trunk or extremities, lesser than 5% being located on the scalp. Surgery is the mainstay of management of this locally infiltrative cutaneous soft tissue sarcoma, with a high probability of recurrence if margin remains positive or inadequate. Adjuvant radiotherapy to a dose of 40–60 Gy decreases this chance of recurrence considerably. Radiotherapy is generally delivered by interstitial HDR brachytherapy, opposed photon or electron beam. We report a case of a 24 year old female, presenting with a small, painless nodule over right frontal area of scalp, diagnosed as DFSP post surgery with close margin that was treated with adjuvant radiation customized HDR surface mould brachytherapy with good local control and cosmesis.
A simple closed-form analytical formula is proposed to compute the probe reactance of an equilateral triangular patch antenna. The variation of the probe reactance with the variation of antenna dimension, substrate electrical parameters, and probe location is examined thoroughly. The computed values employing the present model show excellent agreement with experimental and simulation results.