Search Results - (Author, Cooperation:V. Sundaram)

2018-05-02

Nature Publishing Group (NPG)

2041-1723

Biology

Chemistry and Pharmacology

Natural Sciences in General

Physics

2014-11-21

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Cell Line ; Chromatin/genetics/metabolism ; Conserved Sequence/*genetics ; Enhancer Elements, Genetic/genetics ; Genome/*genetics ; *Genomics ; Humans ; Mice ; Polymorphism, Single Nucleotide/genetics ; Regulatory Sequences, Nucleic Acid/*genetics ; Transcription Factors/*metabolism

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] Varagu (Tamil), kodo, kodaka (Hindustani), Paspalum scrobiculatum (Linn.), is a millet largely used by the working and poorer classes of people in all parts of India as a staple article of food. More than 300,000 tons of this millet is produced in the Madras Presidency alone. In 1946, when rice ...

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We report here the diffusion behavior of zinc in n-type GaSb in the temperature range of 450–540 °C. The diffusion was carried out in a closed box system using a zinc-gallium source. The diffusion profiles were obtained using secondary ion mass spectrometry. From the diffusion profiles, concentration dependent diffusion coefficients were calculated using Boltzman–Montano analysis. These data have been qualitatively interpreted in terms of the interstitial-substitutional diffusion model originally proposed for zinc diffusion in GaAs. Finally, diffused junction GaSb solar cells were fabricated and their performance evaluated.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We report a high-efficiency PpinN GaAs/AlGaAs waveguide phase modulator for high-speed operations. By introducing p- and n-GaAs layers beside the intrinsic GaAs layer of a P-i-N double heterostructure, the absorption edge-related effect, hardly used in P-i-N phase modulators, is utilized. We demonstrate a high phase shift efficiency of 37.5°/V mm at 1.3 μm wavelength. Although this corresponds to the highest expeirmental value reported for reverse-biased GaAs/AlGaAs phase modulators, our device operates with a low junction and a very low dynamic capacitance.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

High quality, intentionally doped (both p and n type) gallium arsenide layers have been grown using trimethylgallium and tertiary butylarsine in a low-pressure metalorganic chemical vapor deposition reactor. Using an alternate arsenic source, namely, tertiary butylarsine, a concentrator GaAs solar cell has been fabricated. Under 37 sun, air mass 1.5 illumination, the cell had an open-circuit voltage of 1.095 V, a fill factor of 83%, and an overall efficiency of 18.5%.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Depending on the deposition conditions, amorphous SixHy alloy films prepared by planar rf reactive magnetron sputtering exhibit one of three types of microstructure: (i) type A with no discernible microstructural features down to the 20-A(ring) level and with a smooth uniform density; (ii) type B consisting of high-density regions of 50–200-A(ring) lateral dimensions separated by a low-density network; and (iii) a two-level (type C) microstructure consisting of 300–500-A(ring) dimensions columns separated by a pronounced low-density network. The columns, in turn, are composed of 50–200-A(ring) dimension high-density regions interspersed with low-density network. The Si-2p level in these alloy films, determined by x-ray photoelectron spectroscopy, is observed to be strongly influenced by the microstructure of the film. A shift in the Si-2p level, systematically varying with the hydrogen concentration, is observed in alloy films with type B and type C microstructures. No shift is observed, irrespective of the hydrogen concentration, in alloy films with type A microstructure. The photoelectron spectra are examined in the light of the vibrational spectra of the films as measured by Fourier transform infrared techniques. The dependence of the Si-2p level shift on the microstructure and the variation with hydrogen concentration are explained qualitatively in terms of the differences in the silicon–hydrogen bonding in amorphous SixHy films with dissimilar microstructures.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The fabrication of GaSb infrared-sensitive photovoltaic cells designed to boost the energy-conversion efficiency in tandem solar cell stacks is reported. Located behind GaAs solar-cells in 50× concentrated light configurations, these GaSb cells will boost the stack efficiency by 6.5 percentage points for space (AM0) and 7.0 percentage points for terrestrial (AM1.5D) applications. Assuming a GaAs cell efficiency of 26.7% (AM1.5D, 50×) as recently reported, the GaAs on GaSb stack efficiency will be 33.7%. Reduced series resistance in future GaSb cells will allow tandem-stack energy-conversion efficiencies over 35%.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Se-passivated n-GaAs(001) surfaces prepared in a metalorganic chemical vapor desposition reactor have been investigated by means of x-ray photoelectron spectroscopy, low-energy electron diffraction, and x-ray photoelectron diffraction. The band bending of these free surfaces was as low as ∼0.1 eV, indicating excellent passivation. It was found that Se undergoes an anion exchange reaction with As to depths of at least five atomic layers. This result suggests that the reduction of surface states is brought about by the formation of a GaAsxSe1−x/GaAs heterojunction interface of very high structural quality.

Electronic Resource

0022-0248

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Geosciences

Physics

Electronic Resource

0022-0248

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Geosciences

Physics

Electronic Resource

1438-2385

Springer Online Journal Archives 1860-2000

Process Engineering, Biotechnology, Nutrition Technology

Summary We describe a new, fully enzymic determination for glycerol in beverages, making use of an immobilized glycerol dehydrogenase nylon-tube reactor. The method, that is automated by adaptation onto a continous-flow system, is specific and reliable with high precision, reducing the cost of analysis immensely.

Zusammenfassung Eine neue, vollenzymatische Bestimmungsmethode für Glycerin in Getränken unter Verwendung an Nylon gebundener Glycerin Dehydrogenase wird beschrieben. Die automatisierte Methode, die auf ein Durchflußanalysensystem adaptiert wurde, ist spezifisch, präzise, zuverlässig und führt zu einer erheblichen Kostenreduzierung.

Electronic Resource

1435-1536

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Electronic Resource

0021-8995

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

1 Ill.

Electronic Resource

0021-8995

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

A method is developed to estimate the composition of a powder mixture using breadths of over-lapping x-ray diffraction (XRD) lines. The application of the method is illustrated for analyzing blends of cotton and jute.

4 Ill.

Electronic Resource

0021-8995

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Enzymolysis of cotton cellulose in their never-dried state, belonging to all the four cultivated species of cotton, was carried out with the enzyme derived from penicillium funiculosum F4. Hydrolysis to reducing sugars was almost complete for all the cottons in 6 h, though glucose percentage varied. X-ray characterizations of the residues obtained, which were both after enzyme and acid hydrolysis, showed significant differences between both hydrolyses, as well as differences in the behavior of different cotton fibers towards enzyme action. These differences have been attributed to the different structural organization of cellulose in the secondary cell wall of cotton fibers.

3 Ill.

Electronic Resource

0021-8995

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

In the present investigation, we have made a systematic study of the induced crystallization in never-dried cotton fiber, by allowing it to desiccate under different conditions of humidity and temperature. The resulting structural changes have been followed using x-ray diffraction and infrared absorption techniques. A slow rate of drying coupled with a high temperature was more conducive for maximum crystallization. Analysis of the effect of temperature on the induced crystallization showed possible existence of a thermal transition in cellulose around 30°C. The induced crystallization brought about by slow drying as well as those produced using intercrystalline swelling agents, have been shown to be resulting from a proper channelization of the interfibrillar mobility existing in the never-dried fibers.

4 Ill.

Electronic Resource

0021-8995

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

5 Ill.

Electronic Resource

0142-2421

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Physics

An In0.71Ga0.29As0.63P0.37/In0.97Ga 0.03 As0.10P0.90 liquid phase epitaxy (LPE) grown low lattice mismatch (δa/a ≤ 0.03%) interface has been profiled using 1 keV argon ions incident at 50° to sample surface normal in a commercial Varian Auger system. It was found that an interface width of 160 Å from P (120 eV) Auger peak intensities.

2 Ill.

Electronic Resource

0449-296X

Physics ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

The nature and behavior of free radicals induced in acetylated cotton celluloses irradiated with γ-rays have been studied by electron spin resonance (ESR) spectroscopy. Dehydrogenation and deacetylation appear to be responsible for the free radicals observed from samples irradiated at 77°K. The degree of substitution enhanced the yield of acetyl radicals when the samples were irradiated at 77°K and adversely affected the overall radical concentration when irradiation was done at 300°K. In addition, the ESR spectra of samples irradiated under vacuum at 300°K were more intense than those obtained from samples irradiated in air. The nature, yield, and post-irradiation behavior of the primary radicals are discussed in the light of the ultimate chemical effects observed.

5 Ill.

Electronic Resource