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101.
Wear KA Laib A Stuber AP Reynolds JC 《The Journal of the Acoustical Society of America》2005,117(5):3319-3324
Biot's theory for elastic propagation in porous media has previously been shown to be useful for modeling the dependence of phase velocity on porosity in bovine cancellous bone in vitro. In the present study, Biot's theory is applied to measurements of porosity-dependent phase velocity in 53 human calcanea in vitro. Porosity was measured using microcomputed tomography for some samples (n = 23) and estimated based on bone mineral densitometry for the remaining samples (n = 30). The phase velocity at 500 kHz was measured in a water tank using a through-transmission technique. Biot's theory performed well for the prediction of the dependence of sound speed on porosity. The trend was quasilinear, but both the theory and experiment show similar slight curvature. The root mean square error (RMSE) of predicted versus measured sound speed was 15.8 m/s. 相似文献
102.
Mapping phosphorylation sites: a new strategy based on the use of isotopically labelled DTT and mass spectrometry 总被引:1,自引:0,他引:1
Amoresano A Marino G Cirulli C Quemeneur E 《European journal of mass spectrometry (Chichester, England)》2004,10(3):401-412
Phosphoproteomics, nowadays, represents a front line in functional proteomics as testified by the number of papers recently appearing in the literature. In an attempt to improve and simplify the methods so far suggested we have set up a simple isotope-coded approach to label and quantitate phospho-Ser/-Thr residues in protein mixtures. First of all, after appropriate oxidation of cysteine/cystine residues followed by tryptic hydrolysis, we have optimised and simplified the beta-elimination reaction to get the corresponding alkene moiety from the phosphate esters. This was achieved by (a) separating the elimination reaction from the addition reaction, (b) the use of Ba(OH)(2) as alkali reagent and (c) its further elimination by the simple addition of solid CO(2) to the peptide mixture. The Michael reaction was then performed, after the removal of BaCO(3) by centrifugation, by adding dithiothreitol (DTT) to the peptide mixture. Finally, the direct purification of the modified phosphopeptides was performed on a thiol-sepharose column. The availability of fully deuterated DTT, introducing a 6 Da difference with respect to the non-deuterated species, allows quantitation of the differential extent of signalling modification when analysed by matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) and liquid chromatography/mass spectrometry. The entire procedure has been set up by using bovine alpha-casein, and resulted in the identification of all the phosphorylated tryptic peptides, including the tetraphosphorylated peptides, which escaped all previously reported procedures 相似文献
103.
The systematic reduction of commonly used basis sets as a means to reduce computational cost is examined for a small test set of molecules, which includes H(2), CH(4), NH(3), H(2)O, HF, and HCN. Coupled cluster with single, double, and quasiperturbative triple excitations calculations were performed using both the correlation consistent basis sets, and a set of systematically reduced basis sets to examine both the impact of the reduction upon the accuracy of the structures and energies, and the computational cost savings achieved. The effect of several truncation scenarios upon basis set convergence is also examined. Overall, for the systems studied, a reduction can occur which preserves the well-established systematic convergence behavior of the correlation consistent basis sets. 相似文献
104.
Watson PJ Ciccia AH Weismer G 《The Journal of the Acoustical Society of America》2003,113(5):2812-2819
This study examined the relationship of speech breathing to other elements of speech production. It was hypothesized that initiating speech from different lung volumes would have an effect on different elements of the acoustic output. It was postulated that effects may be brought about by mechanical interaction as well as a dispersion of effort to mechanically unlinked elements of speech production, such as articulatory behavior. To this end, selected acoustic variables were studied in eight young healthy women who initiated speech from low, typical, and high lung volume levels. The acoustic variables studied were selected because they have been shown to be sensitive indicators of speech production performance. It was found that with increasing lung volume initiation levels, average sound pressure level, average fundamental frequency, and declination rate of fundamental frequency increased. It was also observed that vowel space was significantly smaller during low lung volume initiation levels relative to typical lung volume initiation levels. Vowel space reduction is discussed relative to "gaining down." 相似文献
105.
106.
The aim of this paper is to propose a stabilization technique in order to circumvent the two infsup conditions neededfor stability of the discretization of the three fields formulationfor domain decomposition methods (following the work of Brezzi& Marini (1993) Optimisation et Controle 8996). Realization of this technique in terms of wavelets is presented. Furthermore, the resulting discrete problem is shown to admitan asymptotically optimal preconditioner also based on wavelets.
Received 24 February, 1999. Revised 7 October, 1999.
* aivlis@ian.pv.cnr.it; http://www.ian.pv.cnr.it/~aivlis
kunoth@iam.un-bonn.de; http://www.iam.uni-bonn.de/~kunoth 相似文献
107.
Bogdan Constantinescu Angela Vasilescu Martin Radtke Uwe Reinholz Claire Pacheco Laurent Pichon Ernest Oberländer-Târnoveanu 《Applied Physics A: Materials Science & Processing》2012,109(2):395-402
A thorough microscopic investigation by SR XRF and micro-PIXE brings insight into the probable techniques used in the manufacture of thirteen Dacian gold bracelets, one of the most spectacular archaeological finds ever on the territory of Romania. 相似文献
108.
109.
Carlos F. Pedroso Julcemara G. de Oliveira Francinete R. Campos Alan G. Gon?alves Angela C. L. B. Trindade Roberto Pontarolo 《Chromatographia》2009,69(Z2):201-206
A simple RP–LC method for simultaneous quantification of losartan and amlodipine and separation of their degradation products
has been developed. For this purpose we tested appropriated mobile phase pH range, flow rate, temperature and different columns.
The method was validated with an ODS column. A gradient of acetonitrile and phosphate pH 3.0 buffer was utilized as mobile
phase. The linearity was determined at 50–150% level. Individual recoveries at 70–130% level ranged from 98.8 to 100.5% for
losartan and 96.4–101.2% for amlodipine. The robustness was also evaluated. Although losartan has much higher quantities than
amlodipine in commercial tablets, this method allowed simultaneous quantification for both drugs. 相似文献
110.