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31.
[structure: see text] A new series of ligands with a novel phosphine-aminophosphine ligation design as depicted in structure 1 has been prepared on a ferrocenylethyl backbone. These BoPhoz ligands of structure 2 have afforded exceedingly high activity and enantioselectivity in the rhodium-catalyzed asymmetric hydrogenation of dehydro-alpha-amino acid derivatives, itaconic acids, and alpha-ketoesters. These air-stable ligands are readily prepared from cost-effective and non-pyrophoric intermediates. 相似文献
32.
Noninvasive measures of vocal fold activity are useful for describingnormal and disordered voice production. Measures of open and speed quotient from glottal airflow and electroglottographic (EGG) waveforms have been used to describe timing events associated with vocal fold vibration. To date, there has been little consistency in the measurement criteria used to calculate quotient values. In this study, criteria of 20% and 50% were applied to the AC amplitude of glottal airflow and inverted EGG waveforms for measurement of open quotient. Criteria of 20%, 50%, and 80%, and a midslope criterion that segmented the waveform between 20% and 80% of the waveform amplitude, were used for the calculation of speed quotient. Subjects produced waveforms at sound pressure levels (SPL) of 70, 75, 80 and 85 dB. Results indicated that approximations of open quotient obtained from the glottal airflow waveform significantly decreased using both the 20% and 50% criteria as SPL increased from 80 to 85 dB. No significant changes were found in open quotient from the EGG waveform as a function of SPL. Results of speed quotient measures from the glottal airflow and EGG waveforms showed a generally increasing trend as SPL increased, although the differences were not statistically significant. The data suggest that the signal type, measurement criterion and SPL must be considered in interpreting quotient measures. 相似文献
33.
G. G. Jayson T. A. Lawless D. Fairhurst 《Journal of Radioanalytical and Nuclear Chemistry》1981,64(1-2):327-335
A study has been made on the effect of pH upon the equilibrium adsorption capacity of triethyl phosphate, dimethyl phosphate
and orthophosphate on to activated carbon cloth. It is shown that for molecular phosphates no dependence upon pH exists, whilst
the adsorption of ionic phosphates exhibit a strong pH dependence. These adsorption trends may be explained in terms of pKa
values, ionic strength and the surface charge of the activated carbon cloth is aqueous solution. 相似文献
34.
W. N. Lawless 《Zeitschrift für Physik B Condensed Matter》1966,5(2):100-114
Calculations of dipole correlations and internal-energy densities are reported for dilute dipole systems in the NaCl and CsCl lattices. The tensorial dipole interaction potential is used in thermal averaging in a two-dipole approximation. Actual lattice geometries are taken into account in the three-dimensional spatial averages. The dipoles are assumed to have equilibrium orientations along [100] in the NaCl lattice, and along either [100] or [111] in the CsCl lattice. It is found thatlocal antiparallel ordering is favored in both lattices at low temperatures. Comparison with recent, low-temperature dielectric data indicates that relaxation mechanisms are as important as local antiparallel ordering in limiting theT ?1 increase of (??1)/(?+2) with decreasing temperature for OH? doped KCl. A simplified, nonequilibrium mechanism is studied whereby parallel-correlated dipoles with interaction energies greater than2 kT in absolute value become nonalignable and do not contribute to?. This mechanism together with antiparallel ordering are found to describe the experimental data satisfactorily; but additional relaxation mechanisms are indicated. The contribution of the dipole interactions to the specific heat is also calculated, and is in qualitative agreement with measured specific heat data for OH? doped KCl. 相似文献
35.
We study a type Ia supernova explosion using three-dimensional numerical simulations based on reactive fluid dynamics. We consider a delayed-detonation model that assumes a deflagration-to-detonation transition. In contrast with the pure deflagration model, the delayed-detonation model releases enough energy to account for a healthy explosion, and does not leave carbon, oxygen, and intermediate-mass elements in central parts of a white dwarf. This removes the key disagreement between simulations and observations, and makes a delayed detonation the mostly likely mechanism for type Ia supernovae. 相似文献
36.
Oganesyan VS Barclay JE Hardy SM Evans DJ Pickett CJ Jayasooriya UA 《Chemical communications (Cambridge, England)》2004,(2):214-215
The potential of NIS spectroscopy to study the iron-sulfur clusters in metalloproteins is illustrated using model compounds. The origin of the intense low energy transfer bands is discussed. 相似文献
37.
Nishaanthan Nadarajah Elaine Wong Ka Lun Lee Ampalavanapillai Nirmalathas 《Optics Communications》2007,273(1):246-251
A scheme for upstream transmission and local area network emulation in passive optical networks using a single reflective semiconductor optical amplifier placed at the customer premises is proposed and experimentally demonstrated. In this scheme, two optical carriers are delivered to the optical network units from the central office for the transmission of upstream and local area network signals, respectively. 相似文献
38.
We have directly resolved shock structures in pure aluminum in the first few hundred picoseconds subsequent to a dynamic load at peak stresses up to 43 GPa and strain rates in excess of 10(10) s(-1). For strong shocks we obtain peak stresses, strain rates, and rise times. From these data, we directly validate the invariance of the dissipative action in the strong shock regime, and by comparing with data obtained at much lower strain rates show that this invariance is observed over at least 5 orders of magnitude in the strain rate. Over the same range, we similarly validate the fourth-power scaling of the strain rate with the peak stress (the Swegle-Grady relation). 相似文献
39.
40.
Márcia R. S. Silva Mary C. F. Alves S. J. G. Lima L. E. B. Soledade Elaine C. Paris E. Longo A. G. Souza Iêda M. G. Santos 《Journal of Thermal Analysis and Calorimetry》2009,97(2):559-564
Sr(Ti,Nd)O3 was synthesized in order to evaluate the influence of the amount of neodymium on the thermal and structural properties of
SrTiO3. The synthesis was carried out using the polymeric precursor method. A small mass gain was observed for the SrTiO3 and SrTi0.98Nd0.02O3 samples accompanied by an exothermic peak in the DTA curves. Other steps at higher temperatures are assigned to the combustion
of the organic material and carbonate. Elimination of defects by previous calcination of the precursors is responsible by
the short and long range ordering of the perovskite. Cubic phase was obtained for undoped and doped SrTiO3. 相似文献