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排序方式: 共有197条查询结果,搜索用时 15 毫秒
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Excitation transfer between the two components of a dye mixture has allowed a near IR dye laser to be pumped by a nitrogen laser. Several dye mixtures were employed to achieve lasing at all wavelengths within the range 6400–7720 Å. The output pulse powers were in excess of 10 kW over most of this range. 相似文献
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Aubrey D. Calhoun Kaki R. Lung Terence A. Nile Leon L. Stokes Scott C. Smith 《Transition Metal Chemistry》1983,8(6):365-368
Summary The catalytic activity of rhodium complexes for the hydrosilylation of substrates such as alkenes, 1,3-dienes, 1-alkynes, or ketones, is enhanced by the addition of organic oxidizing agents, such ast-butyl hydroperoxide, hydrogen peroxide, orm-chloroperbenzoic acid. Similar enhancement is found for the Group VIA hexacarbonyls in the hydrosilylation of 1,3-dienes. 相似文献
66.
Accurate quantitation has been demonstrated on many different types of mass spectrometer. However, quantitative applications of Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) have been limited. In this study, the quantitative potential of FTICRMS has been investigated using an exact matching isotope dilution method for the determination of creatinine in serum. Creatinine is an important clinical biomarker and its measurement is used as an assessment of renal function. The quantitation of creatinine was selected because a high-accuracy high-performance liquid chromatography/mass spectrometry (HPLC/MS) determination using a triple quadrupole mass spectrometer has already been successfully developed in-house. Therefore, a direct comparison of the quantitative capability of FTICRMS could be made against an established method. The accuracy of the quantitation of creatinine was found to be equivalent to that obtained using LC/MS. However, the expanded measurement uncertainty (k = 2) was larger, at 6%, when using FTICRMS compared with 1% when using HPLC/MS with the triple quadrupole mass spectrometer. 相似文献
67.
There is currently significant interest in all-ceramic dental restorations due to the demand to replace metals as the primary load-bearing tooth restorative material. A promising non-metallic material for such restorations is fluorcanasite, a chain-silicate glass-ceramic that is castable using conventional dental metal-casting techniques and which exhibits enhanced fracture toughness and flexural strength compared with currently available resin-bonded ceramics. Unfortunately, because of its relatively low silica content, it exhibits poor chemical durability. The aim of this study was to assess the influence of compositional changes on the formation and chemical solubility of the fluorcanasite forming glass, crystalline phase and residual glass. To this end, mixed-alkali compositions have been investigated and it has been shown that the solubility of the glass is a function of the alkali species present in the glass. By changing the alkali ratio of the fluorcanasite forming glass from 0.33 ([K]/[K + Na]) of the base composition derived from stoichiometry to 0.47, it was possible to reduce the chemical solubility of the fluorcanasite material significantly. The addition of extra CaF2 to refine the grain structure resulted in a decrease in the durability of the material, making it currently unacceptable for dental applications. The glass-ceramic exhibits a minimum chemical solubility at the composition K7/Na8. The residual glass may have a slightly elevated K content compared to the original glass. The addition of extra CaF2 to refine the grain structure resulted in an unacceptable decrease in the durability of the material. 相似文献
68.
G. M. Chechin O. A. Lavrova V. P. Sakhnenko H. T. Stokes D. M. Hatch 《Physics of the Solid State》2002,44(3):581-584
A new type of nonlinear (anharmonic) excitations—bushes of vibrational modes—in physical systems with point or space symmetry is discussed. All infrared-active and Raman-active bushes for C60 fullerene are found by means of special group-theoretical methods. 相似文献
69.
Abbasi RU Abu-Zayyad T Amann JF Archbold G Bellido JA Belov K Belz JW Bergman DR Cao Z Clay RW Cooper MD Dai H Dawson BR Everett AA Fedorova YA Girard JH Gray RC Hanlon WF Hoffman CM Holzscheiter MH Hüntemeyer P Jones BF Jui CC Kieda DB Kim K Kirn MA Loh EC Manago N Marek LJ Martens K Martin G Matthews JA Matthews JN Meyer JR Moore SA Morrison P Moosman AN Mumford JR Munro MW Painter CA Perera L Reil K Riehle R Roberts M Sarracino JS Sasaki M Schnetzer SR Shen P Simpson KM Sinnis G Smith JD 《Physical review letters》2004,92(15):151101
We have measured the cosmic ray spectrum above 10(17.2) eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources. 相似文献
70.
Trinkle DR Hennig RG Srinivasan SG Hatch DM Jones MD Stokes HT Albers RC Wilkins JW 《Physical review letters》2003,91(2):025701
We propose a new direct mechanism for the pressure driven alpha-->omega martensitic transformation in pure titanium. A systematic algorithm enumerates all possible pathways whose energy barriers are evaluated. A new, homogeneous pathway emerges with a barrier at least 4 times lower than other pathways. The pathway is shown to be favorable in any nucleation model. 相似文献