排序方式: 共有4条查询结果,搜索用时 0 毫秒
1
1.
Applications of molecular dynamics simulations coupled with Harris functional approximation to argon
Chengteh Lee Xiping Long Ilene Carpenter Shep Smithline George Fitzgerald 《International journal of quantum chemistry》1994,49(4):527-537
We have demonstrated molecular dynamics simulations using a combination of the classical molecular dynamics with density functional theory for argon clusters. Three different molecular dynamics schemes, which differ in their treatment of the potential energy and forces, have been carried out. The first uses a Lennard-Jones potential. In the second, the potential is computed using the Harris functional, and in the third, a combination of Lennard-Jones and Harris functional potentials is used. In addition to direct examination of the trajectories, the velocity autocorrelation function and its power spectrum have been computed to demonstrate the agreement between these three methods. The present studies show that a scheme that used a combination of model potentials and density functional theory provides a very useful tool for the dynamics simulation of systems that contain some fragments in which the analytical model potentials are not available. © 1994 John Wiley & Sons, Inc. 相似文献
2.
The ratio of inorganic phosphate to phosphocreatine (Pi:PCr) is a validated marker of mitochondrial function in human muscle. The magnetic resonance imaging rapid acquisition with relaxation enhancement (RARE) pulse sequence can acquire phosphorus-31 (31P) images with higher spatial and temporal resolution than traditional spectroscopic methods, which can then be used to create Pi:PCr ratio maps of muscle regions. While the 31P RARE method produces images that reflect the content of the 31P metabolites, it has been limited to producing an image of only one chemical shift in a scan. This increases the scan time required to acquire images of multiple chemical shifts as well as the likelihood of generating inaccurate Pi:PCr maps due to gross motion. This work is a preliminary study to demonstrate the feasibility of acquiring Pi and PCr images in a single scan by interleaving Pi and PCr chemical shift acquisitions using a chemically selective radiofrequency excitation pulse. The chemical selectivity of the excitation pulse evaluated and the Pi:PCr maps generated using the interleaved Pi and PCr acquisition method with the subject at rest and during exercise are compared to those generated using separate Pi and PCr acquisition scans. A paired t test indicated that the resulting Pi:PCr ratios for the exercised forearm muscle regions were not significantly different between the separate Pi and PCr acquisition method (3.18±1.53) (mean±standard deviation) and the interleaved acquisition method (3.41±1.66). This work demonstrates the feasibility of creating Pi:PCr ratio maps in human muscle with Pi and PCr images acquired simultaneously by interleaving between the Pi and PCr resonances in a single scan. 相似文献
3.
Adam NE Alexander JP Berkelman K Cassel DG Duboscq JE Ecklund KM Ehrlich R Fields L Gibbons L Gray R Gray SW Hartill DL Heltsley BK Hertz D Jones CD Kandaswamy J Kreinick DL Kuznetsov VE Mahlke-Krüger H Meyer TO Onyisi PU Patterson JR Peterson D Pivarski J Riley D Ryd A Sadoff AJ Schwarthoff H Shi X Stroiney S Sun WM Wilksen T Weinberger M Athar SB Patel R Potlia V Stoeck H Yelton J Rubin P Cawlfield C Eisenstein BI Karliner I Kim D Lowrey N Naik P Sedlack C Selen M White EJ Wiss J Shepherd MR 《Physical review letters》2006,97(25):251801
We present measurements of the inclusive branching fractions for the decays D+-->Xe+ nu(e) and D0-->Xe+ nu(e), using 281 pb(-1) of data collected on the psi(3770) resonance with the CLEO-c detector. We find B(D0-->Xe+ nu(e)) = (6.46+/-0.17+/-0.13)% and B(D+-->Xe+ nu(e)) = (16.13+/-0.20+/-0.33)%. Using the known D meson lifetimes, we obtain the ratio Gamma(D+)sl/Gamma(D0)sl = 0.985+/-0.028+/-0.015, confirming isospin invariance at the level of 3%. The positron momentum spectra from D+ and D0 have consistent shapes. 相似文献
4.
1