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981.
Thomas S. C. MacDonald William S. Price R. Dean Astumian Jonathon E. Beves 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19040-19043
Intriguing reports of enhanced diffusion in enzymes and molecular catalysts have spurred significant interest in experimental and theoretical investigations, and the mechanism of this phenomenon is the topic of lively debate. Here we use time‐resolved diffusion NMR methods to measure the diffusion coefficients (D) of small molecule species involved in chemical reactions with high temporal resolution. We show the enhanced diffusion of small molecules cannot be explained by reaction velocity, and that apparent measurements of enhanced diffusion by small molecules appear to be caused by bulk fluid flow processes such as convection. 相似文献
982.
Using quantum-mechanical simulations based on density-functional perturbation theory, we address the problem of stability of MgSiO3 perovskite to decomposition into MgO and SiO2 at pressures and temperatures of the Earth's lower mantle. We show that MgSiO3 perovskite (and its post-perovskite phase) is more stable than the mixture of oxides throughout the pressure-temperature regime of the Earth's mantle. Structural stability and lattice dynamics of phases in the system MgO-SiO2 are discussed. 相似文献
983.
Cross-linked reverse micelle-palladium catalysts are effective and stable cross-coupling catalysts; cross-linking is crucial for stability. 相似文献
984.
Probing dipeptide trans/cis stereochemistry using pH control of thiopeptide analogues, and application to the PepT1 transporter 总被引:2,自引:0,他引:2
Bailey PD Boyd CA Collier ID Kellett GL Meredith D Morgan KM Pettecrew R Price RA 《Organic & biomolecular chemistry》2005,3(22):4038-4039
The stereochemistry of thiodipeptides of proline [e.g. Ala-Psi[CS-N]-Pro] can be controlled using pH, allowing the trans-preference for substrates of the peptide transporter PepT1 to be confirmed. 相似文献
985.
Five prolinol-based chiral auxilaries have been compared for the stereoselective synthesis of gamma-butyrolactones via the sequence of N-acylation, C(alpha)()-allylation, and iodolactonization under both solution-phase and solid-phase conditions. Comparisons of stereoselectivity of both the C(alpha)()-allylation and iodolactonization processes indicate that incorporation of a non-C(2)-symmetric auxiliary as a polymer cross-link gives results superior to those obtained either in solution or with other non-C(2)-symmetric auxiliaries and comparable to those observed using a polymer-supported pseudo-C(2)-symmetric auxiliary. 相似文献
986.
Price GJ Ashokkumar M Cowan TD Grieser F 《Chemical communications (Cambridge, England)》2002,(16):1740-1741
The quenching of sonoluminescence from aqueous solutions by acrylic and methacrylic acids is dependent on whether the acid is ionised in solution, as controlled by the pH, but also by the frequency of ultrasound used. 相似文献
987.
Mackinnon AJ Sentoku Y Patel PK Price DW Hatchett S Key MH Andersen C Snavely R Freeman RR 《Physical review letters》2002,88(21):215006
MeV-proton production from solid targets irradiated by 100-fs laser pulses at intensities above 1x10(20) W cm(-2) has been studied as a function of initial target thickness. For foils 100 microm thick the proton beam was characterized by an energy spectrum of temperature 1.4 MeV with a cutoff at 6.5 MeV. When the target thickness was reduced to 3 microm the temperature was 3.2+/-0.3 MeV with a cutoff at 24 MeV. These observations are consistent with modeling showing an enhanced density of MeV electrons at the rear surface for the thinnest targets, which predicts an increased acceleration and higher proton energies. 相似文献
988.
Practical low-noise stretched-pulse Yb(3+)-doped fiber laser 总被引:19,自引:0,他引:19
Lefort L Price JH Richardson DJ Spüler GJ Paschotta R Keller U Fry AR Weston J 《Optics letters》2002,27(5):291-293
We report on the development of what we consider to be a practical and highly stable stretched-pulse laser based on Yb(3+) -doped silica fiber. The Fabry-Perot cavity uses nonlinear polarization rotation as the mode-locking mechanism, and a semiconductor saturable-absorber mirror to ensure robust self-starting and incorporates a diffraction grating pair to compensate for the normal dispersion of the fiber. Use of a single-mode grating-stabilized telecommunications-qualified pump laser diode ensures reliable, low-noise operation (~0.05% amplitude fluctuations at 10-Hz measurement bandwidth). The laser generates high-quality, 60-pJ pulses of <110-fs duration at a repetition rate of ~54 MHz (3-mW average power). 相似文献
989.
990.