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151.
Val M. Runge Mark A. Osborne Michael L. Wood Samuel M. Wolpert Eddie Kwan Dean M. Kaufman 《Magnetic resonance imaging》1987,5(6):421-430
The angle between the straight axial plane and the orbito-meatal line was measured in 156 consecutive magnetic resonance examinations. Inconsistent head positioning caused this angle to vary by as much as 44 degrees. Careful positioning of the patient by the technologist can minimize this variability, leading potentially to improved image interpretation. To assess the merit of a standardized orientation for MR examinations of the head, straight axial and tilted axial MR scans were compared in 34 patients. The tilted images were obtained parallel to the orbito-meatal line and were found to be superior for visualization of the cerebellum. When correlative x-ray CTs are available or when an abnormality in the posterior fossa is suspected, tilted axial MR scans should be employed. 相似文献
152.
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154.
Dr. Jingjun Hao Prof. Arnold L. Rheingold Marzieh Kavand Dr. Kipp J. van Schooten Prof. Christoph Boehme Dr. Marçal Capdevila‐Cortada Prof. Juan J. Novoa Eva Wöss Prof. Günther Knör Prof. Joel S. Miller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(35):12312-12315
The reaction of 2,3,5,6‐tetracyanopyridine (TCNPy) and Cr(C6H6)2 forms diamagnetic σ‐[TCNPy]22? possessing a 1.572(3) Å intrafragment sp3–sp3 bond. This is in contrast to the structurally related 1,2,4,5‐tetracyanobenzene and 1,2,4,5‐tetracyanopyrazine that form π‐dimer dianions possessing long, multicenter bonds. 相似文献
155.
Maja Ponikvar-Svet Diana N. Zeiger Loryn R. Keating Joel F. Liebman 《Structural chemistry》2012,23(6):2019-2037
In the current review of the journal Structural Chemistry, the contents of the issues 1–3 for the calendar year 2012 are related to thermochemistry. A brief thermochemical commentary is added to the summary of each article. 相似文献
156.
The reaction of tetracyanoethylene (TCNE) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) with Fe(CO)(5) leads to formation of magnetically ordered materials of Fe[TCNE](2) (T(c) = 100 K) and Fe[TCNQ](2) (T(c) = 35 K) composition, respectively. In contrast, the reaction with 1,2-dichloro-5,6-dicyanobenzoquinone (DDQ) leads to a paramagnetic material. 相似文献
157.
A transition metal-catalyzed/Curtius rearrangement sequence toward the development of conformationally constrained alpha-Boc-aminophosphonates 2-6 is described. An approach using the versatile tert-butylphosphonoacetate moieties 1a and 1b to derive an array of mono- and bicyclic alpha-Boc-aminophosphonate systems is presented. Conformational constraint is incorporated using either the ring-closing metathesis reaction catalyzed by the first generation Grubbs catalyst or intramolecular cyclopropanation mediated by Rh2(OAc)4. Using the tert-butyl ester functionality in 1a or 1b as a potential amino group, the Curtius rearrangement provides an efficient route toward the target alpha-Boc-aminophosphonates. 相似文献
158.
Starting with the Vlasov-Boltzmann equation for a binary fluid mixture, we derive an equation for the velocity field u when the system is segregated into two phases (at low temperatures) with a sharp interface between them. u satisfies the incompressible Navier-Stokes equations together with a jump boundary condition for the pressure across the interface which, in turn, moves with a velocity given by the normal component of u. Numerical simulations of the Vlasov-Boltzmann equations for shear flows parallel and perpendicular to the interface in a phase segregated mixture support this analysis. We expect similar behavior in real fluid mixtures. 相似文献
159.
Onorato M Osborne AR Serio M Resio D Pushkarev A Zakharov VE Brandini C 《Physical review letters》2002,89(14):144501
We study the long-time evolution of deep-water ocean surface waves in order to better understand the behavior of the nonlinear interaction processes that need to be accurately predicted in numerical models of wind-generated ocean surface waves. Of particular interest are those nonlinear interactions which are predicted by weak turbulence theory to result in a wave energy spectrum of the form of [k](-2.5). We numerically implement the primitive Euler equations for surface waves and demonstrate agreement between weak turbulence theory and the numerical results. 相似文献
160.
Erickson JK Caldwell RR Steinhardt PJ Armendariz-Picon C Mukhanov V 《Physical review letters》2002,88(12):121301
Quintessence, a time-varying energy component that may account for the accelerated expansion of the universe, can be characterized by its equation of state and sound speed. In this paper, we show that if the quintessence density is at least 1% of the critical density at the surface of last scattering the cosmic microwave background anisotropy can distinguish between models whose sound speed is near the speed of light versus near zero, which could be useful in distinguishing competing candidates for dark energy. 相似文献