Annealing studies and electrical properties of SnS-based solar cells

Thin films of SnS (tin sulphide) were thermally evaporated onto glass and CdS/ITO (cadmium sulphide/indium tin oxide) coated glass substrates and then annealed in vacuum with the aim of optimising them for use in photovoltaic solar cell device structures. The chemical and physical properties of the layers were determined using scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffraction, and transmittance versus wavelength measurements. “Superstrate configuration” devices were also made using indium tin oxide as the transparent conductive oxide, thermally evaporated cadmium sulphide as the buffer layer and evaporated copper/indium as the back contact material. Capacitance-voltage data are given for the fabricated devices. Capacitance- voltage, spectral response and I-V data are given for the fabricated devices

Extreme nonlinear electrodynamics in metamaterials with very small linear dielectric permittivity

We consider a sub-wavelength periodic layered medium whose slabs are filled by arbitrary linear metamaterials and standard nonlinear Kerr media and we show that the homogenized medium behaves as a Kerr medium whose parameters can assume values not available in standard materials. Exploiting such a parameter availability, we focus on the situation where the linear relative dielectric permittivity is very small thus allowing the observation of the extreme nonlinear regime where the nonlinear polarization is comparable with or even greater than the linear part of the overall dielectric response. The behavior of the electromagnetic field in the extreme nonlinear regime is very peculiar and characterized by novel features as, for example, the transverse power flow reversing. In order to probe the novel regime, we consider a class of fields (transverse magnetic nonlinear guided waves) admitting full analytical description and we show that these waves are allowed to propagate even in media with $\epsilon0$ since the nonlinear polarization produces a positive overall effective permittivity. The considered nonlinear waves exhibit, in addition to the mentioned features, a number of interesting properties like hyper-focusing induced by the phase difference between the field components.Comment: 12 pages, 7 figure

Plasmon polaritons in photonic superlattices containing a left-handed material

We analyze one-dimensional photonic superlattices which alternate layers of air and a left-handed material. We assume Drude-type dispersive responses for the dielectric permittivity and magnetic permeability of the left-handed material. Maxwell's equations and the transfer-matrix technique are used to derive the dispersion relation for the propagation of obliquely incident optical fields. The photonic dispersion indicates that the growth-direction component of the electric (or magnetic) field leads to the propagation of electric (or magnetic) plasmon polaritons, for either TE or TM configurations. Furthermore, we show that if the plasma frequency is chosen within the photonic $=0$ zeroth-order bandgap, the coupling of light with plasmons weakens considerably. As light propagation is forbidden in that particular frequency region, the plasmon-polariton mode reduces to a pure plasmon mode.Comment: 4 pages, 4 figure

Transverse power flow reversing of confined waves in extreme nonlinear metamaterials

We theoretically prove that electromagnetic beams propagating through a nonlinear cubic metamaterial can exhibit a power flow whose direction reverses its sign along the transverse profile. This effect is peculiar of the hitherto unexplored extreme nonlinear regime where the nonlinear response is comparable or even greater than the linear contribution, a condition achievable even at relatively small intensities. We propose a possible metamaterial structure able to support the extreme conditions where the polarization cubic nonlinear contribution does not act as a mere perturbation of the linear part

Probing the frictional properties of soft materials at the nanoscale

The understanding of friction in soft materials is of increasing importance due to the demands of industries such as healthcare, biomedical, food and personal care, the incorporation of soft materials into technology, and in the study of interacting biological interfaces. Many of these processes occur at the nanoscale, but even at micrometer length scales there are fundamental aspects of tribology that remain poorly understood. With the advent of Friction Force Microscopy (FFM), there have been many fundamental insights into tribological phenomena, such as ‘stick-slip’ and ‘super-lubricity’ at the atomic scale. This review examines the growing field of soft tribology, the experimental aspects of FFM and its underlying theory. Moving to the nanoscale changes the contact mechanics which govern adhesive forces, which in turn play a pivotal role in friction, along with deformation of the soft interface, and dissipative phenomena. We examine recent progress and future prospects in soft nanotribology

Developing Satellite-derived Estimates of Surface Moisture Status

Recent research has shown that the combination of spectral vegetation indices with thermal infrared observations may provide an effective method for parameterizing surface processes at large spatial scales. In this paper, we explore the remotely sensed surface temperature (Ts)/normalized difference vegetation index (NDVI) relationship regarding a) influence of biome type on the slope of Ts/NDVI, b) automating the definition of the relationship so that the surface moisture status can he compared with Ts/NDVI at continental scales. The analysis was carded out using 1) NOAA Advanced Very High Resolution Radiometer (AVHRR) data over a 300-km × 300-km area in western Montana under various land-use practices (grass, crops, and forests), 2) Earth Resources Observations Systems Data Center continental United States biweekly composite AVHRR data. A strong negative relationship was observed between NDVI and Ts over all biome types. The similarity of the Ts/NDVI relationships over different biomes indicated that fraction of vegetation cover has strong influence on the spatial variability of Ts. A substantial change in the Ts/NDVI relationship was observed over forests between wet and dry days. In comparison, no change was observed over irrigated crops. Results from the automated approach agreed well with those using manual selection. At continental scales, the slope of Ts/NDVI is strongly correlated to crop-moisture index values indicating that Ts/NDVI relation is sensitive to surface moisture conditions. Upon further development, this relationship may be useful for parameterizing surface moisture conditions in climate models, decomposition studies, and fire weather monitoring

A study of serum magnesium, calcium and phosphorus level, and cognition in the elderly population of South India

Introduction: Different studies have shown the role of micro and macronutrients on cognitive function. Macronutrients have been involved in many metabolic activities of the body including oxidation and reduction reactions in the central nervous system. This involvement of macronutrients in the activities of central nervous system indicates its role in cognition. The present study is designed to know the role of macronutrients and its relation with cognition by using biological samples.Materials and methods: A total of 337 subjects with a mean age of 49 participated in the cross sectional study fromdifferent parts ofKerala state in India. Individuals participating in this studywere administered a series of neuropsychological test batteries with major emphasis on 7-min screen test. All test procedures were administered by standard protocol after a written consent was obtained from the participating subjects. Analysis of macronutrients level of magnesium, calcium and phosphorus was done by using serum samples and the data obtained were then statistically analyzed using SPSS software version 17.Results: The macronutrients magnesium, calcium and phosphorus were found to be significantly related to the cognitive score. Increasing magnesiumand calciumlevel was associated with higher cognitive score (P<0.0031 and 0.001 respectively), while lower phosphorus level was significantly associated with lower composite score (P<0.001).Conclusion: The results of our study give us an expression that macronutrients such as calcium, magnesium and phosphorus may be associated with cognitive function in elderly population of our state. But further studies on a larger population are required to come out with a definite conclusion

The effect of gain saturation in a gain compensated perfect lens

The transmission of evanescent waves in a gain-compensated perfect lens is discussed. In particular, the impact of gain saturation is included in the analysis, and a method for calculating the fields of such nonlinear systems is developed. Gain compensation clearly improves the resolution; however, a number of nonideal effects arise as a result of gain saturation. The resolution associated with the lens is strongly dependent on the saturation constant of the active medium.Comment: to appear in J. Opt. Soc. Am.

A MODIFIED C-DUMP CONVERTER FOR PMSM MACHINE USED IN A FLYWHEEL ENERGY STORAGE SYSTEM

This paper presents a modified C-dump converter for permanent magnetic synchronous (PMSM) machine used in the flywheel energy storage system. The converter can realize the energy bidirectional flowing and has the capability to recover the energy extracted from the turnoff phase of the PMSM machine. The principle of operation, modeling, and control strategy of the system has been investigated in the paper. Simulation and experimental results of the proposed system are also presented and discussed