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排序方式: 共有1632条查询结果,搜索用时 15 毫秒
1.
Yi-Min Wang Hua Lee Dipali V. Apte 《International journal of imaging systems and technology》1992,4(3):201-206
The matrix pencil (MP) method, based on the singular value decomposition (SVD), is applied to quantitative NMR spectroscopy. Its relationship to other SVD-based methods is also presented. Simulations and applications are given to demonstrate the capability of superior performance.©1993 John Wiley & Sons Inc 相似文献
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A 6-year-old white female was found to have an adenoid cystic carcinoma originating in a lacrimal gland. Eighteen months following diagnosis, the tumor recurred. Conservative surgery has been the sole mode of therapy. To date, after four operations and quadrimenstral imaging surveillance, there is no sign of disease progression. Our purpose is to record the unusual occurrence of an adenoid cystic carcinoma of the lacrimal gland in a child. An interim report, 32 months after diagnosis, is presented. 相似文献
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We have investigated gate oxide degradation in metal-oxide-semiconductor (MOS) devices as a function of high-field constant-current stress for charge injection from both gate and substrate. The two polarities are asymmetric: gate injection, where the substrate Si-SiO2 interface is the collecting electrode for the energetic electrons, shows a higher rate of interface-state generation (ΔDit) and lower charge-to-breakdown Qbd. Thus the collecting electrode interface, which suffers primary damage, emerges as a critical degradation site in addition to the injecting electrode interface, which has been the traditional focus. Consistent with a physical-damage model of breakdown, we demonstrate that interfacial degradation is an important precursor of breakdown, and that the nature of breakdown-related damage is physical, such as trap-generation by broken bonds 相似文献
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Angiogenesis is an important component of the development of chronic inflammatory diseases such as rheumatoid arthritis. It is known that clinically used anti-rheumatic drugs exert, in part, effects on the angiogenic response. Little work, however, has investigated the potential of experimental angiostatic therapies in chronic inflammatory disease models. The effect of one such angiostatic treatment, cortisone combined with heparin, was tested in an in vivo model of granuloma-mediated cartilage degradation. Angiostatic treatment significantly retarded the growth of granulomatous tissue, mononuclear cell influx into the granuloma, and the degradation of juxtaposed cartilage. This correlated with a decrease in the vascularity of the granulomatous tissue. Modulation of this component of pathogenesis of "angiogenesis-dependent disease" may be useful as a new therapeutic approach. 相似文献
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Two new methods of activation were developed to graft enzymes on collegen films. They involved chemical modifications of surface groups of collagen either by Woodward's reagent "K" or by EDC, a water-soluble derivative of carbodiimide. EDC was a better coupling agent and a detailed study was conducted with this agent. It could be used either in a global method of activation and coupling, or in a two-step procedure of activation of collagen, followed by spontaneous coupling of enzyme. All enzymes tested were successfully bound: malate dehydrogenase, lactate dehydrogenase, aspartate aminotransferase, urease, creatine kinase, hexokinase. The influence on the yield of grafted enzyme, of pretreatment of films, time and temperature of EDC activation, concentration of EDC and enzyme, protecting agents was studied. Stability of enzyme activity on storage was greatly increased after grafting. A co-grafted dual system creatine kinase/heoxkinase, was achieved which exhibited a good efficiency. A striking renaturing process at 0-4degreesC after thermal denaturation, was observed with hexokinase. 相似文献
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D. Kumar R. D. Vispute O. Aboelfotoh S. Oktyabrsky K. Jagannadham J. Narayan P. R. Apte R. Pinto 《Journal of Electronic Materials》1996,25(11):1760-1766
Metallization of high-Tc superconductors using low resistivity metal oxides and Cu-Ge alloys has been investigated on high quality pulsed laser deposited
epitaxial YBa2Cu3O7-x (YBCO) films. Epitaxial LaNiO3 (LNO) thin films have been grown on YBCO films at 700°C using pulsed laser deposition. The specific resistivity of LNO was
measured to be 50 μΩ-cm at 300K which decreases to 19 μΩ-cm at 100K indicating good metallicity of the LNO films. The contact
resistance of LNO-YBCO thin film interface was found to be reasonably low (of the order of 10-4Ω-cm2 at 77K) which suggests that the interface formed between the two films is quite clean and LNO can emerge as a promising metal
electrode-material to YBCO films. A preliminary investigation related to the compatibility of Cu3Ge alloy as a contact metallization material to YBCO films is discussed. The usage of other oxide based low resistivity materials
such as SrRuO3 (SRO) and SrVO3 (SVO) for metallization of high-Tc YBCO superconductor films is also discussed. 相似文献
9.
G.R. Olbright R.P. Bryan W.S. Fu R. Apte D.M. Bloom Y.H. Lee 《Photonics Technology Letters, IEEE》1991,3(9):779-781
The authors report the measurement of the laser linewidth, wavelength tunability, and generation of microwave frequencies between individually addressable elements of a vertical-cavity GaAs quantum-well surface-emitting laser diode array (lasing in the wavelength range 850-865 nm). Using heterodyne techniques, the authors obtain a deconvolved 65 MHz laser linewidth from the 109 MHz beat signal. The laser linewidth corresponds to a semiconductor laser linewidth enhancement factor alpha =5.7, which is in excellent agreement with that obtained independently from optical gain measurements and corresponding calculated refractive index changes. The authors measured heterodyne beat frequencies of 2-20 GHz. The bandwidth was limited by the microwave amplifiers. A simple calculation shows that a tuning range of 65 MHz to 3 THz can be achieved.<> 相似文献
10.
1. The 129 MHz (non-proton decoupled) and 36.4 MHz (proton decoupled) 31P NMR spectra arising from unsonicated aqueous dispersions of well defined species of phospholipid have been investigated. The phospholipids employed (and the parameters varied) include phosphatidylcholine (temperature), phosphatidylethanolamine (temperature), phosphatidic acid (temperature and p2H) and phosphatidylglycerol (temperature, p2H and Ca2+ (or Mg2+)) concentration. 2. At p2H = 7 the 31 P MNR spectra arising from saturated species of phosphatidylcholine, phosphatidylethanolamine and phosphatidylglycerol become progressively broader as the temperature is reduced below the phase transition, demonstrating reduced motion in the phosphate region of the polar headgroup. 3. In the liquid crystalline state at p2H = 7 the molecular dipolar order parameters obtained for saturated species of phosphatidylcholine, phosphatidylethanolamine and phosphatidylglycerol and very similar, and are independent of the acyl chain length for species derived from lauric and myristic acid. Thus the motion in the methylene-phosphate-methylene region is similar for these different liquid crystaline phospholipid species. 4. The 31 P NMR spectra of aqueous dispersions of 14:0/14:0 phosphatidic acid display anomalous temperature and p2H dependences. The effective chemical shift anistropy (delta v CSA EFF) at 5 degrees C varies from 71 ppm at p2H = 8.5 to 38 ppm at p2H = 2.5. Further, the motion in the phosphate region is relatively insensitive to the gel or liquid crystalline nature of the hydrocarbon chains. 5. The addition of 40 mol% Ca2+ (or Mg2+) to saturated species of phosphatidylglycerol causes an increase of approx. 20 degrees C in the hydrocarbon phase transition temperature as indicated by 31 P NMR. Equimolar concentrations of Ca2+ increase the transition temperature by approx. 70 degrees C, and no 31P NMR signal could be observed for the very condensed precipitate formed below this temperature. In the liquid crystalline state the motion in the phosphate region of the polar headgroup is not significantly affected by the presence of Ca+ or Mg2+. 6. The 31P NMR spectra obtained from 18 : 1c/18 : 1c phosphatidylethanolamine are consistent with a phase transition from a lamellar to an hexagonal (HII) phase in the region 10-15 degrees C. 7. The observed narrowing of the 31 P NMR spectra of aqueous dispersions of phospholipids as the temperature is raised toward the hydrocarbon transition temperature is discussed in terms of the "pretransition" observed in calorimetric studies. 相似文献