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31.
32.
A method is described for measuring the acoustic properties of an absorbent material and a duct/nozzle system (with or without airflow) in which a high voltage spark discharge is used as an impulse source of sound. The cross-spectra of the incident, reflected and transmitted acoustic pressure transients are analyzed by way of a FFT digital processor in the form of complex transfer functions. These transfer functions have a direct relationship to the termination impedance and radiation directivity. The impulse method has been justified by comparisons that show excellent agreement with data obtained from existing methods (both experimental and theoretical). 相似文献
33.
Grigoriev A Skorodumova NV Simak SI Wendin G Johansson B Ahuja R 《Physical review letters》2006,97(23):236807
The conductance of monoatomic gold wires containing 3-7 gold atoms has been obtained from ab initio calculations. The transmission is found to vary significantly depending on the wire stretching and the number of incorporated atoms. Such oscillations are determined by the electronic structure of the one-dimensional (1D) part of the wire between the contacts. Our results indicate that the conductivity of 1D wires can be suppressed without breaking the contact. 相似文献
34.
L. Huang L. Vitos B. Johansson R. Ahuja 《Journal of Physics and Chemistry of Solids》2010,71(8):1065-1068
The anomalous temperature dependence of elastic constant c44 for elements V, Nb, Ta, Pd, and Pt, has been calculated using first-principles theory. It is shown that the variation of elastic constant for simple elements can be approximated as the sum of thermal expansion and electronic components. The thermal expansion contributes the normal linearly decreasing effect to the elastic constant with temperature, while electronic contribution is determined by the unique character of electronic structure of elements and leads to the anomalous effect to the elastic constant with temperature. 相似文献
35.
36.
Actinide dioxides (ThO 2 , UO 2 , Pu 2 etc.) compounds have the CaF 2 -type structure at ambient pressure and temperature. Under high pressure, they exist in the PbCl 2 -type structure, belonging to space group Pnma [1]. We have studied crystal structures under high pressure in actinide dioxides by means of first-principles self-consistent total-energy calculations with the non-local Perdew, Burke and Ernzerhof (PBE) exchange correlation using the full-potential linear-muffin-tin-orbital (FPLMTO) method. The atomic equilibrium volume, bulk modulus and transition pressure for actinide dioxides were calculated, covering the full pressure range for which the mentioned experiments have been done [2]. 相似文献
37.
Ahuja R Singhal NK Ramanujam B Ravikumar M Rao CP 《The Journal of organic chemistry》2007,72(9):3430-3442
A galactosyl-naphthyl-imine-based derivative, 1-(beta-D-galactopyranosyl-1'-deoxy-1'-iminomethyl)-2-hydroxynaphthalene (GNI), and a galactosyl-naphthyl-amine-based derivative, 1-(galactopyranosyl-1'-deoxy-1'-aminomethyl)-2-hydroxynaphthalene (GNA), possessing an ONO binding core were studied for their recognition of naturally occurring amino acids using fluorescence and absorption spectroscopy, and the corresponding association constants were derived for the complexes formed. The complexes formed between GNI/GNA and amino acids were supported by electrospray ionization mass spectrometry (ESI/MS). The structures of the complexes were optimized by computational studies using density functional theory, and stabilization energies were computed for the complexes to substantiate the interactions present between GNI/GNA and amino acid. The interactions were found to be primarily hydrogen bonding in nature. These interactions are reminiscent of those present in the lectin-carbohydrate and glycosidase substrate. Thus, the carbohydrate moiety present in GNI shows high specificity toward the -COOH group of the amino acid, which may be relevant to such interactions present between the carbohydrates and the polypeptides. 相似文献
38.
Paecilomyces marquandii, a phosphate-solubilizing, starch-utilizing filamentous fungus, was immobilized on polyurethane foam (PUF). The immobilized
fungus was applied in a repeated batch (six batches) fermentation process to solubilize Hirapur rock phosphate. The fungus
was immobilized on PUF cubes and was used for phosphate solubilization in shake flask repeated batch cultivations. The fungus
was also immobilized on PUF sheet and utilized in an airlift bioreactor in a repeated batch process. Maximum soluble phosphate
(370 μg/ml) was recorded after third batch with 8 g rock phosphate/l. After 12 days of fermentation, a total production of
1,643 μg phosphate/ml was achieved. 相似文献
39.
Hao‐Hao Wang Yi‐Xiang J. Wang Prof. Ken Cham‐Fai Leung Prof. Doris W. T. Au Prof. Shouhu Xuan Dr. Chun‐Pong Chak Simon K. M. Lee Dr. Hui Sheng Dr. Ge Zhang Dr. Ling Qin Prof. James F. Griffith Prof. Anil T. Ahuja Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(45):12417-12425
Small polyhedral superparamagnetic iron oxide (SPIO) nanoparticles (<10 nm) coated with a thin layer of silica were prepared (SPIO@SiO2 and SPIO@SiO2‐NH2). Surface modification of the small polyhedral silica‐coated SPIO nanoparticles with amines led to substantially higher mesenchymal stem cell (MSC) labelling efficiency without the use of additional transfecting agents. Therefore, amine surface‐modified nanoparticles (SPIO@ SiO2‐NH2) appeared to be the preferred candidate for MSC labelling. In vitro studies demonstrated that controlled labelling of SPIO@SiO2 and SPIO@SiO2‐NH2 did not cause MSC death or proliferation inhibition. MSCs labelled with SPIO@SiO2‐NH2 nanoparticles retained differentiation potential and showed osteogenic, adipogenic and chondrogenic differentiations. The noncytotoxic polyhedral SPIO@SiO2‐NH2 nanoparticle‐labelled MSCs were successfully implanted in rabbit brain and erector spinae muscle, and demonstrated long‐lasting, durable MRI labelling efficacy after 8–12 weeks. 相似文献
40.
Pamita Bhandari Neeraj Kumar Bikram Singh Ajai P. Gupta Vijay K. Kaul Paramvir S. Ahuja 《Chromatographia》2009,69(3-4):221-227
A liquid chromatography method was developed and validated for the determination of picroside-I and picroside-II in herbal preparations containing Picrorhiza kurroa as one of the ingradients. Resolution of picrosides was achieved on a reversed phase (C-18) endcapped bidentate column by using a mobile phase of acetonitrile: water (25:75 v/v). The detection of picrosides was carried out at 270 nm. The method was validated for precision, accuracy and robustness according to the International Conference on Harmonization (ICH) guidelines and is applicable for the quality control of preparations containing P. kurroa. Analysis of samples in forced degradation proved it to be applicable for stability evaluation. The linear regression analysis data showed good linear relationship (r 2 = 0.9999 ± 0.0010 for picroside-I and 0.9997 ± 0.0012 for picroside-II) in the concentration range of 0.4–4.0 μg. The limit of detection and quantification for picroside-I and picroside-II were recorded to be 28.1 and 73.1 ng and 85.2 and 221.5 ng, respectively. Satisfactory recovery results were observed from the herbal preparations (97.5–100.5%). Intra- and inter- day precision of the method was acceptable, with relative standard deviation (%RSD) values in the range of 0.04–1.16% and 0.03–0.27%, respectively. 相似文献