OM-VPE grown materials for high efficiency solar cells

Organometallic sources are available for all the III-V elements and a variety of dopants; thus it is possible to use the technique to grow a wide variety of semiconductor compounds. AlGaAsSb and AlGaInAs alloys for multijunction monolithic solar cells were grown by OM-VPE. While the effort concentrated on terrestrial applications, the success of OM-VPE grown GaAs/AlGaAs concentrator solar cells (23% at 400 suns) demonstrates that OM-VPE is suitable for growing high efficiency solar cells in large quantities for space applications. In addition, OM-VPE offers the potential for substantial cost reduction of photovoltaic devices with scale up and automation and due to high process yield from reproducible, uniform epitaxial growths with excellent surface morphology

Solitary waves in a two-dimensional nonlinear Dirac equation: from discrete to continuum

In the present work, we explore a nonlinear Dirac equation motivated as the continuum limit of a binary waveguide array model. We approach the problem both from a near-continuum perspective as well as from a highly discrete one. Starting from the former, we see that the continuum Dirac solitons can be continued for all values of the discretization (coupling) parameter, down to the uncoupled (so-called anti-continuum) limit where they result in a 9-site configuration. We also consider configurations with 1- or 2-sites at the anti-continuum limit and continue them to large couplings, finding that they also persist. For all the obtained solutions, we examine not only the existence, but also the spectral stability through a linearization analysis and finally consider prototypical examples of the dynamics for a selected number of cases for which the solutions are found to be unstable

Precise time and frequency intercomparison between NPL, India and PTB, Federal Republic of Germany via satellite symphonie-1

A time and frequency intercomparison experiment conducted using Earth stations in New Delhi, India and Raisting, FRG is described. The NPL clock was placed at New Delhi Earth Station and the Raisting Clock was calibrated with PTB/Primary standard via LORAN-C and travelling clocks. The random uncertainity of time comparisons, represented by two sample Allan Variance sigma (30 seconds), was less than 10 nanoseconds. The relative frequency difference between the NPL and Raisting Clocks, SNPL, RAIS, as measured over the 44 days period was found to be -15.7 x 10 to the -13th power. The relative frequency difference between PTB Primary Standard and Raisting Clock, SPTB, RAIS, during this period, was measured to be -22.8 x 10 to the -13th power. The relative frequency difference between NPL clock and PTB Primary Standard, SNPL, PTB, thus, is +7.1 x 10 to the -13th power. The clock rate (UTC, India) of +7.1 + or - 0.5 x 10 to the -13th power, agrees well with that obtained via VLF phase measurements over one year period and with USNO travelling clock time comparisons made in September, 1980

Non-fusion joining of aluminium

JOINING of aluminium is now a well established techn-ology. Successful joining can be done by TIG and MIG welding, pressure welding processes, brazing and solde-ring processes. Conventional fusion processes of joining aluminium are well known and are widely used in India by all major fabricators. On the other hand, though non-fusion joining processes like soldering, brazing and pressure welding have wide field of applications the correct process and material required are not very well known ; as such there is a specific need in India, at present, to disseminate the knowledge on joining of aluminium especially by these processes which a small fabricator can handle

Thermally Induced Local Failures in Quasi-One-Dimensional Systems: Collapse in Carbon Nanotubes, Necking in Nanowires and Opening of Bubbles in DNA

We present a general framework to explore thermally activated failures in quasi one dimensional systems. We apply it to the collapse of carbon nanotubes, the formation of bottlenecks in nanowires, both of which limit conductance, and the opening of local regions or "bubbles" of base pairs in strands of DNA that are relevant for transcription and danaturation. We predict an exponential behavior for the probability of the opening of bubbles in DNA, the average distance between flattened regions of a nanotube or necking in a nanowire as a monotonically decreasing function of temperature, and compute a temperature below which these events become extremely rare. These findings are difficult to obtain numerically, however, they could be accessible experimentally.Comment: 4 pages, 2 figures, to be submitte

Management of red rust thrips, Chaetanophothripssignipennis (Bagnall) in banana

The commercial value of banana is mainly affected by red rust thrips, Chaetanophothripssignipennis(Bagnall) during fruiting phase at maturity. In this context, the trial was framed at F.R.S., N.A.U., Gandevi under ICAR-AICRP (Fruits) programme. The three years data on efficacy of bio-rational pesticides for management of red rust thrips revealed that bud injection of imidacloprid (0.3 ml/ 500 ml water) @ 1 ml/bud exhibited lowest unblemished fruits up to 8.37% over conventional spraying (20.72%) and bunch sleeving method (42.83%). The comparable results on fruit damage (14.83%) was observed with bud injection of azadirachtin (1%) (5 ml/l water) @ 2 ml/bud over conventional spray. The merit of technology furnished higher no. of unblemished fruits (<10%) and original peel superficial appearance remains impassive under bud injection technique with higher benefit cost ratio with very low dose of pesticide provide financial profit to growers and traders. Besides, imidacloprid residue was not detected in harvested fruits and there is no other technology available to remove this malady of banan

Phase ordering and shape deformation of two-phase membranes

Within a coupled-field Ginzburg-Landau model we study analytically phase separation and accompanying shape deformation on a two-phase elastic membrane in simple geometries such as cylinders, spheres and tori. Using an exact periodic domain wall solution we solve for the shape and phase ordering field, and estimate the degree of deformation of the membrane. The results are pertinent to a preferential phase separation in regions of differing curvature on a variety of vesicles.Comment: 4 pages, submitted to PR