Search Results - (Author, Cooperation:D. Nayak)

2014-05-03

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Base Sequence ; Codon, Initiator/*genetics ; Consensus Sequence ; DNA-Directed RNA Polymerases/metabolism ; Escherichia coli/*genetics/*metabolism ; *Gene Expression Regulation, Bacterial ; Peptide Chain Initiation, Translational/*genetics ; *Regulatory Elements, Transcriptional ; *Transcription, Genetic

2013-12-10

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Administration, Topical ; Animals ; Antioxidants/administration & dosage/therapeutic use ; Astrocytes/pathology ; Brain/drug effects/pathology ; Brain Injuries/*complications/diagnosis/drug therapy/*pathology ; Cell Death/drug effects ; Disease Models, Animal ; Encephalitis/complications/drug therapy/*pathology/*prevention & control ; Glasgow Coma Scale ; Glutathione/administration & dosage/therapeutic use ; Humans ; Intracranial Hemorrhages/complications/diagnosis ; Male ; Meninges/drug effects/pathology ; Mice ; Microglia/cytology/drug effects/physiology ; Neuroprotective Agents/administration & dosage/therapeutic use ; Neutrophils/drug effects/physiology ; Purinergic P2 Receptor Antagonists/administration & ; dosage/pharmacology/therapeutic use ; Rats ; Rats, Sprague-Dawley ; Reactive Oxygen Species/metabolism ; Receptors, Purinergic P2/metabolism ; Receptors, Purinergic P2X7/metabolism ; Skull/metabolism

1089-7550

AIP Digital Archive

Physics

The experimental results of a molecular-beam epitaxy grown Si/GeSi p-n heterojunction are reported. It is found that the current flow in these p-n heterojunctions shows a nonideality factor of about 1.5 at room temperature and 2.35 at liquid nitrogen temperature. The nonideal behavior of the Si/GeSi p-n heterojunction is attributed to the charges that are trapped at the heterointerface. Annealing the samples at temperatures higher than the growth temperature results in an increase in the density of defects as well as an increase in the nonideal current. C-V measurements were employed to further investigate the behavior of the charges that are trapped in the interface. From C-V measurements under reverse bias it is found that increasing the annealing time and temperature increases the density of interface traps. In addition, a charge density of about 1012 cm−2 is found to be present at the Si/GeSi interface for the as-grown sample and increases with increasing annealing time and temperature.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Thin oxide on strained Si1−xGex surface has been grown using a nonelectron cyclotron resonance mode microwave plasma at low temperatures (150–200 °C). An optimized post-oxidation and post-metal annealing cycle has resulted in very low fixed oxide charge density (1.78×1010/cm2) and moderately low interface trap density (2.9×1011/cm2 eV). A controlled in situ hydrogen-plasma treatment to Si1−xGex has been found to be useful in improving the electrical properties of the oxide. The high electron injection phenomena of metal oxide semiconductor capacitors has been used for charge trapping studies of sites normally present in the SiGe oxides. From the position and the extent of current ledge observed as a function of ramped gate voltage, the capture cross section and the total number of traps have been determined. © 1995 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The electrical and chemical properties of the interfaces of thin oxides grown on strained GexSi1−x layers are analyzed in detail using capacitance-voltage measurements and Auger electron spectroscopy. It is found that the electrical properties (interface states and fixed oxide charges) of the interface depend on various parameters such as oxidation temperature, oxidation time, Ge distribution near the interface, and Ge distribution in the entire epilayer. The Ge distribution at the interface can be described using concentration-dependent diffusivity of Ge in the epilayer. The electrical properties are improved with the increase in oxidation temperature, but for a given oxidation temperature, the quality of the interface degrades with the increase in oxidation time. At a very high oxidation temperature the Ge distribution in the entire epilayer is altered due to the high diffusivity of Ge.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A cold-wall rapid thermal processor is used for the wet oxidation of the commensurately grown GexSi1−x layers on Si substrates. The rate of oxidation of the GexSi1−x layer is found to be significantly higher than that of pure Si, and the oxidation rate increases with the increase in the Ge content in GexSi1−x layer. The oxidation rate of GexSi1−x appears to decrease with increasing oxidation time for the time-temperature cycles considered here. Employing high-frequency and quasi-static capacitance-voltage measurements, it is found that a fixed negative oxide charge density in the range of 1011– 1012/cm2 and the interface trap level density (in the mid-gap region) of about 1012/cm2 eV are present. Further, the density of this fixed interface charge at the SiO2/GeSi interface is found to increase with the Ge concentration in the commensurately grown GeSi layers.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The experimental results of the rapid thermal oxidation in the initial oxidation regime of molecular beam epitaxy grown GeSi strained layers are reported. It is shown that the dry oxidation rate of GeSi is the same as that of Si at different temperatures. After a very short initial time (∼10 s), the oxide thickness appears to be a linear function of time, which suggests that the kinetics of oxide growth during dry oxidation is limited by surface reaction controlled mechanisms. Further, the oxidation rate in the thin oxide regime is not affected by the Ge content up to 20% in the GeSi strained layer for dry oxidation. Using secondary-ion mass spectrometry, it is found that Ge is completely rejected out of the SiO2 layer which is formed during oxidation, and a Ge-rich layer is formed at the SiO2/GeSi interface. A significant amount of Ge is found to diffuse into the underlying GeSi layer during the growth of thin oxide films.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Microwave plasma oxidation of strained Si1−xGex layer has been carried out at low temperatures (150–200 °C). The chemical properties of the oxide investigated by x-ray photoelectron spectroscopy show the formation of single phase mixed oxides consisting a SiO2 and GeO2, without any Ge pileup on the surface or at the substrate-oxide interface. Electrical properties of the oxides show a moderately low value of fixed oxide charge and interface trap density. Grown oxides exhibit low leakage current (10−8 A/cm2) and high breakdown strength (5–10 MV/cm), and are useful for a gate dielectric in metal–oxide semiconductor field effect transistor.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Electronic Resource

1077-3118

AIP Digital Archive

Physics

A study of the photoluminescence properties of Si/SiGe/Si quantum wells grown on separation by oxygen implantation (SIMOX) substrate by gas source molecular beam epitaxy is presented. Intense photoluminescence and carrier confinement in the quantum well are demonstrated. It is found that buried SiO2 isolates the top silicon on insulator from the back Si of SIMOX, and alters the photoluminescence properties of SIMOX compared to those of bulk Si. The SOI layer is found to be free of any strain. A SiO2/Si/SiO2 optical cavity is proposed by depositing SiO2 on SIMOX. A substantial enhancement of the photoluminescence intensity of SiGe quantum well is found, which is attributed to the optical confinement of incident beam in the cavity.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

An enhancement-mode p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) is fabricated on a strained Si layer for the first time. A biaxial strain in a thin Si layer is produced by pseudomorphically growing this layer on a Ge0.25Si0.75 buffer layer which is grown on a Si substrate. At higher magnitude of gate bias, channel mobility of a strained Si PMOSFET has been found to be 50% higher than that of an identically processed conventional Si PMOSFET.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Intense photoluminescence (PL) was observed from a new class of Si-based quantum well structures (QWs), that is, neighboring confinement structure (NCS). NCS consists of a single pair of tensile-strained-Si layer and a compressive-strained Si1−yGey layer sandwiched by completely relaxed Si1−xGex ( layers. In spite of the indirect band structure in real and k spaces, radiative recombination was enhanced compared with not only type-II strained-Si/relaxed-Si1−xGex QWs but also type-I strained-Si1−yGey/relaxed-Si1−xGex QWs. PL without phonon participation was found to dominate the spectrum possibly due to the effective carrier confinement for both electrons and holes. Quantum confinement effect was clearly observed by varying the well width, showing that the expected band alignment is realized. © 1995 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Integration of strained Si1−xGex/Si quantum wells (QWs) in a vertical cavity is demonstrated on a Si substrate with a buried-oxide using gas source Si molecular beam epitaxy. Spontaneous emission from the SiGe QW is found to be spectrally coupled to the longitudinal modes of a vertical cavity with buried oxide/Si and top Si/air interface mirrors, which is in excellent agreement with separate reflectance measurements. In addition, clear oscillations were observed in photoluminescence excitation spectra for photon energies even above the Si band gap, demonstrating cavity modulation of the incident light absorption. © 1994 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Electron cyclotron resonance plasma oxidation of strained Si on relaxed Si1−xGex buffer layers in O2 ambient at room temperature is reported. The electrical properties of grown oxide have been characterized and compared with thermally grown oxides using a metal-oxide semiconductor structure. At a low field, the accumulation of holes in the buried Si1−xGex layer, due to the type-II band offset, has been observed. The experimental results from thermally grown oxides have been compared with the simulation results obtained using a heterostructure Poisson solver. © 1997 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Microwave plasma oxidation (below 200 °C) of strained Si on relaxed Si1−xGex buffer layers in N2O ambient is reported. The electrical properties of grown oxide have been characterized using a metal-oxide-semiconductor structure. Fixed oxide charge density and mid-gap interface state density are found to be 6×1010 cm−2 and 1.2×1011 cm−2 eV−1, respectively. The oxide on strained-Si samples has exhibited hole trapping behavior and moderately low interface state generation on constant current stressing. © 1997 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Microwave N2O plasma oxidation of strained Si1−xGex layers at low temperature (〈200 °C) is reported. The hole confinement in accumulation in a metal oxide semiconductor (MOS)-gated SiGe/Si heterostructure has been confirmed by both simulation and experiments. Electrical properties are also discussed. © 1996 American Institute of Physics.

Electronic Resource

1432-0789

Azospirillum lipoferum inoculation ; Rice yield ; Acetylene reduction assay ; 15N feeding and dilution techniques

Springer Online Journal Archives 1860-2000

Biology

Geosciences

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Summary A spontaneous mutant ofAzospirillum lipoferum, resistant to streptomycin and rifampicin, was inoculated into the soil immediately before and 10 days after transplanting of rice (Oryza sativa L.). Two rice varieties with high and low nitrogen-fixing supporting traits, Hua-chou-chi-mo-mor (Hua) and OS4, were used for the plant bacterial interaction study. The effect of inoculation on growth and grain and dry matter yields was evaluated in relation to nitrogen fixation, by in situ acetylene reduction assay,15N2 feeding and15N dilution techniques. A survey of the population of marker bacteria at maximum tillering, booting and heading revealed poor effectivety. The population of nativeAzospirillum followed no definite pattern. Acetylene-reducing activity (ARA) did not differ due to inoculation at two early stages but decreased in the inoculated plants at heading. In contrast, inoculation increased tiller number, plant height of Hua and early reproductive growth of both varieties. Grain yield of both varieties significantly increased along with the dry matter. Total N also increased in inoculated plants, which was less compared with dry matter increase.15N2 feeding of OS4 at heading showed more15N2 incorporation in the control than in the inoculated plants. The ARA,15N and N balance studies did not provide clear evidence that the promotion of growth and nitrogen uptake was due to higher N2 fixation.

Electronic Resource

0165-1781

Fluphenazine ; decanoate ; minimal dosage ; outcome ; schizophrenia

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Medicine

Electronic Resource

1432-072X

Rice root ; Culture ; Association ; Spirillum sp. ; Nitrogen-fixing efficiency ; Combined nitrogen

Springer Online Journal Archives 1860-2000

Biology

Abstract Nitrogen fixation by Spirillum sp. obtained from the roots of rice plants grown at different levels of combined nitrogen was studied. The roots of rice plants exposed to low levels of combined nitrogen (20–40 kg N/ha) harboured Spirillum sp. possessing higher nitrogen-fixing efficiency as compared to the cultures from plants receiving 60–100 kg N/ha. More-over, the nitrogen-fixing efficiency of these Spirillum spp. varied with age of the plant, irrespective of the dosage of combined nitrogen.

Electronic Resource

1573-5036

Combined nitrogen ; 15N2 incorporation ; Rhizosphere soil ; Rice straw amendment ; Variety

Springer Online Journal Archives 1860-2000

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Summary Heterotrophic nitrogen fixation by rhizosphere soil samples from 20 rice cultivars grown under uniform field conditions was estimated employing15N-tracer technique. Rhizosphere soil samples from different rice cultivars showed striking differences with regard to their ability to incorporate15N2. Rhizosphere samples from rice straw-amended (3 and 6 tons/ha) soil exhibited more pronounced nitrogen-fixing activity than the samples from unamended soil; while the activity of the rhizosphere samples from soils receiving combined nitrogen (40 and 80 kg N/ha) was relatively low. However, the inhibitory effect of combined nitrogen was not expressed in the presence of rice straw at 6 tons/ha. Results suggest that plant variety, application of combined nitrogen and organic matter influence the rhizosphere nitrogen fixation.

Electronic Resource