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51.
We prove that any principal bundle on the affine line over a perfect field with a reductive group as structure group comes
from the base field by base change. 相似文献
52.
An improved pulse sequence for SLF experiments based on the magic sandwich (MS) scheme for homo-nuclear dipolar decoupling is proposed. The sequence incorporates a double MS, both on I and S spins and has been named as EXE-MS2. The proposed scheme which has a scaling factor of 1 is observed to be free from low intensity artifacts and provides better line-widths particularly for S spins labeled at multiple sites. The pulse sequence which has been applied on static oriented samples incorporates the EXE scheme where direct polarization of the S spin in the B(0) field is utilized in the place of polarization inversion and is observed to perform well without any loss of sensitivity while ensuring considerable reduction in rf power input into the sample. The EXE scheme has also been tested for solid samples under MAS. 相似文献
53.
Kumar A Jayakumar T Rao CB Sharma GK Rajkumar KV Raj B Arundhati P 《The Journal of the Acoustical Society of America》2008,124(2):911-917
This paper presents the first scientific investigation on the musical pillars of the Vitthala Temple at Hampi, India. The solid stone columns in these pillars produce audible sound, when struck with a finger. Systematic investigations on the acoustic characteristics of the musical pillars of mahamandapam (great stage) of the Vitthala Temple have been carried out. The 11 most popular pillars that produce sounds of specific musical instruments are considered for the investigations. The sound produced from these 11 most popular musical pillars was recorded systematically and different nondestructive testing techniques such as low frequency ultrasonic testing, impact echo testing, and in situ metallography were employed on the musical columns of these pillars. The peak frequencies in the amplitude spectrum of the sound produced from various columns in these pillars are correlated with the dimensional measurements and ultrasonic velocity determined using impact echo technique. The peak frequencies obtained experimentally have been found to have excellent correlation with the calculated flexural frequencies based on the dimensional measurements and ultrasonic velocities of the columns. 相似文献
54.
In electrospray ionization source hydrogen/deuterium exchange LC-MS and LC-MS/MS for characterization of metabolites 总被引:4,自引:0,他引:4
A new method is described for performing hydrogen/deuterium (H/D) exchange in an electrospray ionization (ESI) source. The use of liquid chromatography (LC)-mass spectrometer equipped with an ESI source and deuterium oxide (D2O) as the sheath liquid allows H/D exchange experiments to be performed on-line. This directly provides information for determining the number and position of exchangeable hydrogens, aiding in the elucidation of the structures of drug metabolites. To demonstrate the utility of this method, LC-mass spectrometry (MS) and LC-MS/MS experiments were performed using either H2O or D2O as sheath liquid on a matrix metalloprotease (MMP) inhibitor (PD 0200126) and its metabolites. Examination of the mass shift of the deuteriated molecule from that of the protonated molecule allowed the number of exchangeable protons to be determined. Interpretation of the production-spectra helped to determine the location of the exchanged protons and assisted in the assignment of the site(s) of modification for each metabolite. 相似文献
55.
Sajan D Binoy J Pradeep B Venkata Krishna K Kartha VB Hubert Joe I Jayakumar VS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(1-2):173-180
The single crystals of glycinium oxalate are grown by slow evaporation technique and vibrational spectral analysis is carried out using NIR-FT Raman and FT-IR spectra. The ab initio quantum computations are also performed at HF/6-31 G(d) level to derive the optimized geometry, atomic charges and vibrational frequencies of the glycinium oxalate molecule. Vibrational analysis indicates the presence of peculiar intermolecular C-H...O hydrogen bonding interaction producing "blue shift" of C-H stretching frequency. The vibrational spectra confirm the existence of NH3(+) in glycinium oxalate. Hydroxyl vibrations with different inter and intra molecular H-bonding are analysed, supported by computed results. 相似文献
56.
JM Taylor R Vaidhyanathan SS Iremonger GK Shimizu 《Journal of the American Chemical Society》2012,134(35):14338-14340
A new porous metal-organic framework (MOF), barium tetraethyl-1,3,6,8-pyrenetetraphosphonate (CALF-25), which contains a new phosphonate monoester ligand, was synthesized through a hydrothermal method. The MOF is a three-dimensional structure containing 4.6 ? × 3.9 ? rectangular one-dimensional pores lined with the ethyl ester groups from the ligand. The presence of the ethyl ester groups makes the pores hydrophobic in nature, as determined by the low heats of adsorption of CH(4), CO(2), and H(2)O (14.5, 23.9, and 45 kJ mol(-1), respectively) despite the polar and acidic barium phosphonate ester backbone. The ethyl ester groups within the pores also protect CALF-25 from decomposition by water vapor, with crystallinity and porosity being retained after exposure to harsh humid conditions (90% relative humidity at 353 K). The use of phosphonate esters as linkers for the construction of MOFs provides a method to protect hydrolytically susceptible coordination backbones through kinetic blocking. 相似文献
57.
Renganathan Jayakumar Shanmugam Jayashree Balumuri Annapurna Sundaram Seshadri 《Applied biochemistry and biotechnology》2012,168(7):1849-1866
This study describes the characterization and optimization of medium components for an extracellular detergent, surfactant, organic solvent and thermostable serine alkaline protease produced by alkaliphilic Bacillus pumilus MCAS8 strain isolated from Pulicat lake sediments, Tamil Nadu, India. The strain yielded maximum protease (2,214?U/ml) under optimized conditions: carbon source, citric acid??1.5?% (w/w); inducer, soyabean meal??2?% (w/w); pH?11.0; shaking condition 37?°C for 48?h. The enzyme had pH and temperature optima of 9.0 and 60?°C, respectively. The enzyme displayed the molecular mass of 36?kDa in sodium dodecyl sulphate?Cpolyacrylamide gel electrophoresis study and exhibited activity at a wide range of pH (6.0?C11.0) and thermostability (20?C70?°C). More than 70?% residual activity was observed when the enzyme was incubated with dithiothreitol, ethylenediaminetetraacetic acid, ethylene glycol tetraacetic acid and H2O2 for 30?min. The protease activity was also enhanced by divalent cations such as Ba2+, Ca2+ and Mg2+ and was strongly inhibited by Fe2+, Zn2+, Sr2+, Hg2+ and urea. The enzyme retained more than 50?% of its initial activity after pre-incubation for 1?h in the presence of 5?% (v/v) organic solvents such as dimethyl sulphoxide and acetone. The protease could hydrolyse various native proteinaceous substrates (1?%?w/v) such as bovine serum albumin, casein, skim milk, gelatine, azocasein and haemoglobin. Wash performance analysis of enzyme revealed that it could effectively remove blood stains from the cotton fabric, thus making it suitable to use as an effective detergent additive. The protease enzyme also exhibited promising result in the dehairing of goat skin. The potency of the eco-friendly enzyme without using any chemicals against washing and dehairing showed that the enzyme could be used for various industrial applications. 相似文献
58.
A new methodology has been established for identification of β-transus temperature in α + β and β titanium alloys by ultrasonic velocity measurements in a single specimen in one microstructural condition only. This methodology is based on a linear correlation obtained for the variation in β-transus temperature with ultrasonic longitudinal wave velocity in various titanium alloys specimens, β-heat-treated followed by water quenching. Furthermore, it has been demonstrated for the first time that ultrasonic velocity in α′ martensitic structure increases with the addition of α-stabilizing elements and decreases with the addition of β-stabilizing elements for α + β titanium-alloys. 相似文献
59.
Siva Rama Krishnan Balaji Devarajan Mutharasu Subramani Shanmugan N. Sankara Subramanian Kulathu Ramanathan 《Ionics》2010,16(4):351-360
LiSmxMn2–xO4 samples were synthesized via co-precipitation technique. The structural properties of the synthesized materials were studied
using X-ray diffraction analysis and it confirmed the cubic spinel structure for all the compounds. The lattice parameter
of LiMn2O4 was observed to be 8.2347 Ǻ and it decreased with Sm3+ concentration, due to the shrinkage in cell volume aided by higher binding energy between Sm-O bond. The SEM micrographs
were analyzed using Image processing software (Image-J) to ascertain the pore and grain properties. The microwave synthesis
had been observed to control the bulk grain formation and had yielded lesser porous and nanoparticles. The particle size distributions
obtained through photocross correlation laser diffraction analysis had shown that LiMn2O4 with 60 nm and Sm-doped compounds with ∼30 nm, respectively. The cyclic voltammetry studies had revealed the decrease in
electrocatalytic behavior in the initial cycle for compounds doped with Sm3+ ion. The initial capacities of LiMn2O4, LiSm0.05Mn1.95O4 and LiSm0.10Mn1.90O4 substituted compounds were observed to be 134.87 mAhg−1, 132.22 mAhg−1 and 126.41 mAhg−1, respectively. The cells were simulated using 1D model namely Dualfoil5.1 program. The simulated results coincide well with
the measured results. The cycle life studies reveal 93% capacity retention of samarium-0.05-doped samples when compared with
78.4% of the LiMn2O4. 相似文献
60.
Oleic acid (OA) coated stoichiometric NiCo (50:50) nanoparticles, with and without polyvinylpyrrolidone (PVP) coating, dispersible in aqueous and non aqueous media have been synthesized by a polyol process for the first time. Structural studies by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed the formation of an impurity free face centred cubic phase NiCo alloy. EDS analysis confirmed nearly 50:50 alloy composition. The magnetization, as a function of field and temperature, of these samples showed a soft ferromagnetic nature. The novelty of our method is that the particles are dispersible in non aqueous and aqueous media, which will facilitate preparation of films of these particles. 相似文献