Electronic Spectra of Iron Pnictide Superconductors: Influence of Multi-orbitals Hopping and Hund’s Coupling

We present a theoretical study of the electronic spectral function of iron-pnictide superconductors like LaFeAs(O, F) material. We have attempted two-band tight-binding model Hamiltonian containing various orbitals hopping energies, intra- and inter-band electronic correlations and Hund’s coupling energy in Fe 3d orbitals. The expression of a single particle spectral function within BCS-mean-field Green’s function approach for superconducting state of iron pnictides is obtained. The spectral function at different points of the Brillouin zone is numerically calculated for extended s-wave pairing symmetry as a function of various model parameters applicable for these systems. It is pointed out through numerical analysis that on increasing nearest-neighbor hopping (t ₁) between (d _xz /d _yz ) σ-orbitals, the spectral function A(k,ω) shifts towards the Fermi level and provides favorable conditions for band splitting effects in the form of two well separated peaks in the electronic spectral as observed in iron pnictides angle-resolved photoemission spectroscopic (ARPES) measurements. On increasing t ₂ (nearest-neighbor hopping between d _xz /d _yz π-orbitals), the spectral function shows prominent peak with increase in spectral weight close to the Fermi level at the (π,0) and (0,0) points of the Brillouin zone, while the quasi-particle peak shifts away from the Fermi level at the (π,π) point with decreased spectral weight. The bonding peak of spectral function get suppressed while the antibonding spectral peak becomes prominent with increasing t ₃ (next nearest-neighbor hopping between same orbitals of d _xz /d _yz ) at (π,π) of the Brillouin zone. Further, intra-band Coulomb correlations shift the spectral peak downward with respect to Fermi level along with suppression of the spectral weight. The Hund’s coupling term try to pile up spectral weight close to Fermi level and support to stabilize superconducting state in these systems. The variation of the spectral function within the two-band model is in qualitative accordance with existing ARPES measurements and theoretical investigations in iron-pnictide superconductors.     

Evaluation of Bulk Mechanical Properties of Selected Lead-Free Solders in Tension and in Shear

Lead-free solders are fast emerging as better alternatives to Sn-Pb solders. The reliability of a soldered joint to withstand imposed stresses in an assembly is decided by its mechanical properties. The present work is about the investigation of tensile and shear properties of four binary eutectic alloys Sn-3.5Ag, Sn-58Bi, Sn-0.7Cu, Sn-9Zn and a ternary alloy Sn-57Bi-1.3Zn in comparison with conventional Sn-38Pb alloy. It is observed that the lead-free solders have better mechanical properties than the latter. SEM studies of tensile and shear fracture show ductile dimples circular in tension and parabolic in shear modes supporting the mechanical behavior of the alloys investigated. Eutectic alloys Sn-Ag, Sn-Zn, and Sn-Cu form potential substitutes for Sn-Pb for electronic interconnects exposed to high temperatures, while Sn-Bi and Sn-Bi-Zn are attractive alternatives in addressing the need of lower processing temperatures in printed circuit boards and other applications.     

Load Forecasting Technique for System Expansion in Isolated Area Using Time Invariant Socio-Economic Factors of Identical Agglomerations

Load forecasting is a critical issue for operational planning as well as grid expansion to ensure an uninterruptable electric power system. Being a small but densely populated country in South Asia, Bangladesh has many isolated places which are not connected to national grid yet. If concern authority opts to expand grid to those areas, they need reliable demand data for designing and dimensioning of different power system entities, e.g., capacity, overhead line capacity, tie line capacity, spinning reserve, load-shedding scheduling, etc., for reliable operation and to prevent possible obligatory redesigning. This paper represents an analysis to forecast the electricity demand of an isolated island in Bangladesh where past history of electrical load demand is not available. The analysis is based on the identification of factors, e.g., population, literacy rate, per capita income, occupation, communication, etc., on which electrical load growth of an area depends. Data has been collected from the targeted isolated area and form a grid connected area which is similar to target area from social and geographical perspective. Weights of those factors on load have been calculated by matrix inversion. Demand of the new area is forecasted using these weights factors by matrix multiplication.     

Zingiber officinale extract exhibits antidiabetic potential via modulating glucose uptake, protein glycation and inhibiting adipocyte differentiation: an in vitro study

BACKGROUND: Ginger, the rhizome of Zingiber officinale Roscoe (Zingiberaceae), a perennial herbaceous plant is native to Southern Asia. Study was aimed to evaluate antioxidant and antidiabetic potential of ginger extract and its characterization. Possible mode of action to elicit antidiabetic activity was also evaluated. METHODS AND RESULTS: Ethyl acetate extract of ginger (EAG) was evaluated for its antioxidant activity in terms of DPPH radical scavenging potential with an IC₅₀ value of 4.59 µg/ml. Antidiabetic activity of EAG was evaluated by estimating antiglycation potential (IC₅₀ 290.84 µg/ml). HPLC profiling of EAG revealed the presence of phenolic components, gingerol and shoagol as major constituents. After determining sub‐toxic concentration of EAG (50 µg/ml), efficacy of extract to enhance glucose uptake in cell lines were checked in L6 mouse myoblast and myotubes. EAG was effective at 5 µg/ml concentration in both cases. Antibody based studies in treated cells revealed the effect of EAG in expressing Glut 4 in cell surface membrane compared to control. CONCLUSION: The antidiabetic effect of ginger was experimentally proved in the study and has concluded that the activity is initiated by antioxidant, antiglycation and potential to express or transport Glut4 receptors from internal vesicles. Copyright © 2012 Society of Chemical Industry     

Properties of Arrowroot Starch Treated with Aqueous HCl at Ambient Temperature

Arrowroot starch was acid-treated using 2.2 M HCl at 29 to 30° C for durations of 0 to 72 h, and properties of the control and modified samples were compared. Increasing length of acid treatment produced a progressive decline in amylose blue value, intrinsic viscosity, and swelling power, as well as an increase in free sugars and solubility. Differential scanning calorimetry (DSC) studies highlighted changes effected by acid-treatment in the gelatinization behavior of the starch samples. Gel permeation chromatography (GPC) studies on 32- and 72-h acid-treated samples indicated a greater proportion of dextrins with a higher percentage of reducing sugars, compared to the control. While X-ray diffraction data suggested minor changes in the crystal phase impacted by acid-treatment, in vitro digestibility of both control and acid-treated samples did not show any appreciable change in overall patterns.     

Tobacco use in India: prevalence and predictors of smoking and chewing in a national cross sectional household survey

Objective: To estimate the prevalence and the socioeconomic and demographic correlates of tobacco consumption in India.

Design: Cross sectional, nationally representative population based household survey.

Subjects: 315 598 individuals 15 years or older from 91 196 households were sampled in National Family Health Survey-2 (1998–99). Data on tobacco consumption were elicited from household informants.

Measures and methods: Prevalence of current smoking and current chewing of tobacco were used as outcome measures. Simple and two way cross tabulations and multivariate logistic regression analysis were the main analytical methods.

Results: Thirty per cent of the population 15 years or older—47% men and 14% of women—either smoked or chewed tobacco, which translates to almost 195 million people—154 million men and 41million women in India. However, the prevalence may be underestimated by almost 11% and 1.5% for chewing tobacco among men and women, respectively, and by 5% and 0.5% for smoking among men and women, respectively, because of use of household informants. Tobacco consumption was significantly higher in poor, less educated, scheduled castes and scheduled tribe populations. The prevalence of tobacco consumption increased up to the age of 50 years and then levelled or declined. The prevalence of smoking and chewing also varied widely between different states and had a strong association with individual's sociocultural characteristics.

Conclusion: The findings of the study highlight that an agenda to improve health outcomes among the poor in India must include effective interventions to control tobacco use. Failure to do so would most likely result in doubling the burden of diseases—both communicable and non-communicable—among India's teeming poor. There is a need for periodical surveys using more consistent definitions of tobacco use and eliciting information on different types of tobacco consumed. The study also suggests a need to adjust the prevalence estimates based on household informants

     

Suppression of floatability of pyrite in coal processing by carrier microencapsulation

Carrier microencapsulation, CME, is a technique to form a thin layer of metal oxide or hydroxide on pyrite surface using a water soluble organic carrier combined with metal ions. The present study investigated the effect of CME using a tris-catecholato complex of Si⁴⁺, Si(cat)₃²⁻ on pyrite-coal separation by dynamic bubble pick-up experiments and Hallimond tube flotation experiments using coal, pyrite, and a coal-pyrite mixture. The mineral samples were treated in 0-5 mol m^− 3 Si(cat)₃²⁻ solutions at pH 4-9 at treatment times of 1-24 h. Dynamic bubble pick-up experiments showed that CME treatment converted the pyrite surface from hydrophobic to hydrophilic but did not affect coal's hydrophobic surface. The results of the Hallimond tube flotation experiments of a coal-pyrite mixture at pH 7-9 in the presence of kerosene as a collector showed that pyrite floatability was selectively suppressed after 1 h CME treatment with 0.5 mol^− 3 Si(cat)₃²⁻ while both coal and pyrite were floated without the treatment. This indicates that CME treatment is effective in suppressing pyrite floatability in coal-pyrite flotation.     

Kinetic studies on the esterification of free fatty acids in jatropha oil

Kinetic studies have been carried out on the esterification of free fatty acids (FFAs) in jatropha oil with methanol in the presence of sulphuric acid catalyst at 5 and 10 wt% concentrations relative to free fatty acids (0.4–0.8 wt% relative to oil) and methanol–FFA mole ratios ranging from 20:1 to 80:1. It has been found that a 60:1 methanol–FFA mole ratio and 5 wt% catalyst at 60°C and 500 rpm or above provided a final acid value lower than 1 mg KOH/g oil within 60 min. A kinetic model has been proposed with second‐order kinetics for both the forward and backward reactions. The effect of temperature on the reaction rate constants and equilibrium constant has been determined using Arrhenius and von't Hoff equations, respectively. The heat of reaction was found to be ?11.102 kJ/mol.     

Studies on High Density Polyethylene in the Far-field Region in Ultrasonic Welding of Plastics

Polyethylene (PE) is an extremely versatile plastic and has the largest sales turnover than other plastics. With new uses for PE, researchers continue to find innovative technologies to process and join the material. Ultrasonic welding is one such process that is rapidly emerging as a major joining process for thermoplastics because of its reliability, ease of operation, fastness, and economic feasibility. Amorphous polymers are ideal materials for ultrasonic welding, but semicrystalline polymers are difficult to weld in the far-field region. This paper deals with the far field welding of semicrystalline polymer/high-density polyethylene (HDPE). The temperature distribution has been modeled for varying lengths of the specimen using Ansys to predict the temperature spikes, which can be related to the performance of the joints achieved. Experimental work studied the temperature at the joint interface and the variation in tensile strength for different lengths of the specimen.