Photonic and omnidirectional band gap engineering in stack of exponential graded index material and negative index material

We have investigated the photonic band gaps (PBG) and omnidirectional band gaps in one-dimensional photonic crystals made up of alternate layer of exponential graded index material and negative index material. We have considered the influence of material properties, geometrical parameters and material composition on the PBG and omnidirectional band gap. Results show that the parameters of exponential graded index material and negative index material can change the photonic and omnidirectional band structures remarkably. Number and bandwidth of PBG increases with increasing the negative index material layer thicknesses while thicknesses of graded index layer only have an effect on the bandwidth of PBGs. The bandwidth of PBG also depends on grading profile parameter of exponential graded index layers and bandwidth can be tuned with increase the value of grading profile parameter. This work can facilitate the design of filters and reflectors, and provide the basic understanding of the influence of graded index materials and metamaterials on the PBG properties.     

Structural transformation from Mn3O4 nanorods to nanoparticles and band gap tuning via Zn doping

Synthesis of undoped and Zn doped hausmannite Mn₃O₄ nanorods was achieved through a simple hydrothermal route. Scanning electron microscopic studies showed that due to in situ Zn doping a structural deformation from Mn₃O₄ nanorods to a mixture of Mn₃O₄ nanorods and nanoparticles occurred. The amount of nanoparticles in the mixture increased with the increase of doping percentage. X-ray diffraction studies, transmission electron microscopy and selected area electron diffraction pattern revealed that both the nanorods and the nanoparticles were hausmannite Mn₃O₄. X-ray photoelectron spectroscopic studies confirmed successful zinc doping in Mn₃O₄. Microscopic studies revealed that the average diameters of Mn₃O₄ nanorods and nanoparticles were of 200 nm and 70 nm, respectively. The possible growth mechanism and the reasons behind the formation of nanoparticles along with nanorods are discussed briefly. UV–vis spectroscopic studies showed a continuous increase in the energy bandgap of Mn₃O₄ with the increase in Zn doping percentage.     

Small Pd cluster adsorbed double vacancy defect graphene sheet for hydrogen storage: A first-principles study

Stability and electronic properties of small Pd_n clusters (n = 1–5), adsorbed on different types of double vacancy (DV) defect graphene sheets are thoroughly investigated by both density functional theory (DFT) and molecular dynamics (MD). Defect bridge sites of DV(555-777) defect graphene sheet are identified to be the most favorable for Pd₄ cluster adsorption. MD calculations, performed using a canonical ensemble, showed this system to be highly stable up to 800 K. Much better hybridization between C 2p and Pd 4d and 5s orbitals near Fermi level as well as higher charge transfer to graphene sheet was found to be the governing reason for enhanced stability of Pd₄ cluster on DV(555-777) defect site. Comparative analysis of H₂ storage on Pd₄ cluster adsorbed pristine and DV(555-777) defect graphene sheet showed, while adsorption energy/H₂ molecule for both cases lie well within desirable energy window for a hydrogen storage media, the later is much more efficient energetically as distorted in plane sp² hybridization reduces the saturations of C–C bonds in the defect regions, making more electron density available for bonding; which leads to higher net charge gain of Pd₄ cluster and higher charge sharing with H₂ molecule.     

First principles study of the electronic and magnetic properties of semi-Heusler alloys NiXSb (X = Ti, V, Cr and Mn)

The electronic density of states (DOS), magnetic moments and band structure of semi-Heusler alloy NiXSb (where X = Ti, V, Cr and Mn) has been studied by using the first principles full-potential linearized augmented plane wave method (FP-LAPW) based on density functional theory (DFT). For the exchange and correlation potential generalized-gradient approximation (GGA) is used. From the observations, NiTiSb shows the possibility of half-metallic ferromagnet (HMF) behavior with a band gap of 0.53 eV and an effective moment of 0.35 μ_B. The alloys like NiVSb, NiCrSb and NiMnSb are HMF with band gap of 0.49 eV, 0.38 eV and 0.48 eV and an effective moment of 1.995 μ_B, 3.01 μ_B and 3.99 μ_B respectively. DOS and band structure result shows the 3d states of Ni overlap with 3d states of X atoms suggesting hybridization between them. The exchange-splitting of Ni-3d and X-3d state electrons lead to localized spin moment which determines the HMF behavior of NiXSb. The results obtained are compared and found to be in close agreement with the available data.     

Internal migration in contemporary nepal: Models which internalize development policies

ABSTRACT A set of models is developed to assess at the interdistrict level the relative importance of economic, demographic, social and government policy determinants of internal migration in Nepal. The first "proximate" model and the second "structural" model estimates are generated using ordinary least squares regression and specification error is investigated by spatial autocorrelation tests of the residuals of each model in its reduced form. These two models are developed to extract the important variables. Finally, to formalize and evaluate empirically the linkages between the "proximate" and "structural" determinants, a simultaneous equation model is developed using three stage generalized least squares regression.     

Trajectory of Affordances: Insights from a case of telemedicine in Nepal

Although Affordance Theory has become increasingly influential in the Information Systems (IS) literature, the exact process through which the affordances of IT are actualised is less studied. In this paper, we build on a realist ontology of affordance and an interpretive epistemology of how affordances are perceived and actualised to trace the process of actualisation. On the basis of insights drawn from a case study of a telemedicine project in a remote mountainous region of Nepal, we develop a concept, which we call the “Trajectory of Affordances.” Trajectory of Affordances captures the complex relations between affordances of IT and the role of goal‐oriented actors who perceive and then play a vital role in actualising them, using capabilities that are enabled by facilitating conditions to take the necessary action. Trajectory of Affordances shows that the affordances of IT can travel from perception to actualisation through multiple paths, sometimes clustering together, and in the process, often lead to the emergence of new affordances.     

Lyophilization of unit dose pharmaceutical dosage forms

A lyophilization process for a pharmaceutical unit dosage form was developed which comprised a container closed with an impermeable membrane pierced with one or more holes through which the material in the container can be lyophilized. The hole or holes in the membrane have to be sufficiently large to allow water vapor to escape but small to ensure that the material is kept within the container. Lyophilization from sealed, perforated, unit-dose package has shown to be feasible. The technique offers a novel convenient means of lyophilizing nonsterile products in their primary pack and increases the potential for the development of lyophilized formulations for nonparenteral applications.