Evanescent tunneling of an effective surface plasmon excited by convection electrons

We introduce the subwavelength transmission of an effective surface plasmon beyond the light zone via the proximity interaction of convection electrons with a metal grating. A comparative analysis of dielectric homogenization and a finite-difference-time-domain simulation shows that out-of-phase-like modes (pi modes) have strong transmission below the cutoff frequency relying on the parametric condition of structural dimension and electronic energy. The synchronous spatial field and charge distribution of the pi mode system confirms the evanescent tunneling effect of the electron-coupled plasmons.     

Changes of microflora in high pressure treated Indian white prawn (Fenneropenaeus indicus)

ABSTRACT

This study was to investigate the piezotolerance and diversity indices of microflora of Indian white prawn (Fenneropenaeus indicus) after high pressure (HP)-treatment. Indian white prawns subjected to HP-treatments and its effect was studied up to species level and compared with unpressurized samples. The bacterium was identified by using bacterial identification schemes, biochemical tests and API kits (bioMérieux, Marcyl’Etoile, France). Diversity analysis was performed using PRIMER (Plymouth Routines in Multivariate Research) software v 5.2.2. The significant elimination of microflora was found to be proportional with the pressure level. In the case of spore formers, mere destruction was noticed after HP-treatment. Arthrobacter spp., Listeria grayi and Corynebacterium spp. were the most piezotolerant bacteria in HP-treated samples. Diversity indices revealed a significant reduction of microflora of Indian white prawn. The apparent reduction of microflora with pressure level was clearly evident from the diversity indices; moreover a diminished piezotolerance of Gram negative spoilage bacteria was also observed.     

On the occurrence of polytypism in single crystal CdTe thin films

Cadmium telluride thin films have been found to exhibit polytypism. The polytypes are formed when the as grown amorphous CdTe thin films undergo amorphous to crystalline transformation. The transformed single crystal regions correspond to different polytypes. Besides the well known zinc blende type 3 C cubic phase and less often found wurtzite type 2 H phase, four new polytypes (5 H, 6 H, 6 R and 15 R) the only ones known to-date have been found in the present investigation. In addition to the new polytypes, a new structural variant has also been found. This has the same ‘c’ parameter as that of the 2 H phase but has its ‘a’ lattice parameter as ‘a₀ \documentclass{article}\pagestyle{empty}\begin{document}$ a_{\rm o} \sqrt {3} $\end{document}’ (a₀ being the common lattice parameter of the polytypes). A feasible mechanism making the formation of polytypes intelligible has been suggested.     

Two-dimensional cell parameters measurement of nematic liquid crystal using optical interferometry and Fourier transform fringe analysis technique

We report a method for the measurement of nematic liquid crystal (NLC) cell parameters i.e., switching voltage, birefringence, retardation, dielectric anisotropy, average tilt angle and change in refractive index with applied DC voltage to LC material. The proposed method is based on optical interferometry and Fourier transform fringe analysis technique, in which we obtain 2-dimensional (2D) phase map of the interferograms as a function of applied voltage. Mach-Zehnder interferometer (MZI) was used for the study of cell parameters and interferograms were recorded at different applied DC voltages to NLC cell using CCD camera. From the phase map, 2D-refractive index distribution of the LC cell with applied voltage was reconstructed. Analytical equations are derived based on optical interferometry and then solved to obtain cell parameters. The present method is fast and can give 2D-cell parameters from only two quick interferograms.     

AWG and EDFA based optical packet switch using feedback shared loop buffer memory

Optical packet switching provides high speed, data rate/format transparency, efficient use of bandwidth and flexibility. The major problem in the implementation of “all-optical” switching is contention which occurs when two or more packets arrive at the same time for the same destination. To resolve the contention, we have proposed an optical packet switch architecture based on WDM loop buffer memory in the feedback configuration. In that architecture, the contending packets are stored in a loop buffer module, and routed in the free time slots. The buffering duration in the recirculating loop is limited by a circulation limit. The analysis was been done to obtain the maximum number of allowed circulations. This paper proposes improved version of that optical packet switch architecture, to increase the number of maximum allowed circulations. The modification is done either by adding an extra erbium doped fiber amplifier (EDFA) in the original switch or by replacing the core space switch with arrayed waveguide grating (AWG). The performance analysis has been done by the simulations.     

Effect of substrate texture on the growth of hematite nanowires

The effect of texture of iron foil substrate on the growth of hematite nanowires by annealing method has been investigated in detail. Three substrates of different textures were prepared from a [2 0 0] oriented iron foil by some simple processes. The hematite nanowires on these substrates were synthesized by annealing iron foil at 700 °C in moist oxygen. The growth pattern of nanowires on these substrates showed that the growth of hematite nanowires depends strongly on the iron substrate texture and [1 1 0] oriented iron grains are necessary for their growth. The samples were characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction (XRD), Electron Back Scatter Diffraction (EBSD) and Raman Spectroscopy. We have also tried to explain the various observations on the mechanism of growth. Mainly, the presence of water vapor significantly enhanced the formation of hematite nanowires which resulted in a very dense and aligned growth of nanowires on the substrate areas of favorable texture. Finally, the study proved the substrate texture to be a powerful tool to control growth of nanowires and can be used efficiently for patterning and large scale synthesis of the nanowires.     

Electron and positron impact excitation of hydrogen from the initially excited 22S state to 32S and 32P states

The total and differential cross sections for the electron and positron impact excitation of hydrogen from its initially excited metastable 2²S state to 3²S and 3²P states are reported. A distorted-wave approximation theory is used for the calculation. The angular correlation parameters, Ly and alignment angle are also reported for 2²S-3²P excitation. For comparison, similar first Born results are also obtained. Interesting features are noted on comparing our distorted wave results with the first Born results as well as with the other available results forn ²S andn ²P (n=2,3) excitations from the ground 1²S state of hydrogen.     

Aes study of the segregation behaviour of silicon in high-silicon steel during oxidation

The segregation behaviour of silicon during oxidation of a high-silicon steel has been investigated by AES. The results show that silicon seems to have two states of oxidation: one leading to the formation of SiO_x and iron oxides when the oxidation and the following heat treatments in vacuum are performed below 500°C and the other occurring at temperatures higher than 500°C, leading to the formation of SiO₂ and segregation of this species toward the surface without oxidation of iron.     

On the variable-charge Coulomb-projected Born approximation

Total cross-sections for electron impact excitation of 1¹ S – 2³ S transition in helium have been calculated using variable-charge Coulomb-projected Born approximation and also using a distorted wave model in which the prior form of theT-matrix is used. The comparison of the two sets of results enables us to make certain observations about the suitability of the variable-charge Coulomb-projected Born approximation.