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81.
Adams GJ Greene J Vick GW Harrist R Kimball KT Karmonik C Ballantyne CM Insull W Morrisett JD 《Magnetic resonance imaging》2004,22(9):1249-1258
BACKGROUND AND PURPOSE: Magnetic resonance imaging (MRI) can accurately and reproducibly measure the volume of atherosclerotic plaque in human carotid arteries. Atherosclerotic plaques may either progress or regress over time, depending on individual risk factors and treatment regimens. This study was designed to determine if regression or progression of human carotid atherosclerosis in patients receiving statin therapy over 24 months can be detected by high-resolution MRI. METHODS: In 11 subjects who had undergone unilateral carotid endarterectomy and were on statin therapy, volumes for total carotid artery, concentric wall (normal wall), eccentric wall (plaque), and lumen were quantified at 0, 16 and 24 months using a 1.5-T human imager equipped with 6-cm phased array coils. RESULTS: The interobserver mean coefficient of variation (CV) was lowest for the lumen volume (3.1%) and highest for the plaque volume (9.8%). The interscan mean CV was lowest for the total artery volume (3.2%) and highest for the plaque volume (9.9%). As much as 26% regression and 35% progression were observed in individual subject's carotid artery eccentric wall (plaque) volumes over time. Mean eccentric wall volume increased 5% by 16 months and 8% by 24 months. Mean total wall volume increased slightly at both 16 and 24 months (+1.2% and +1.8%). CONCLUSIONS: High-resolution MRI provides a noninvasive reproducible method of tracking changes in carotid atherosclerosis. This pilot study detected changes in individual subjects at both 16 and 24 months. MRI tracking of changes in atherosclerotic plaques should prove useful in assessing vascular disease risk and monitoring the efficacy of interventions designed to induce regression or retard progression. 相似文献
82.
Direct numerical simulations are used to examine the locking of quantized superfluid vortices and normal fluid vorticity in evolving turbulent flows. The superfluid is driven by the normal fluid, which undergoes either a decaying Taylor-Green flow or a linearly forced homogeneous isotropic turbulent flow, although the back reaction of the superfluid on the normal fluid flow is omitted. Using correlation functions and wavelet transforms, we present numerical and visual evidence for vortex locking on length scales above the intervortex spacing. 相似文献
83.
The contents of issues 3 and 4 of Structural Chemistry from the calendar year 2018 are summarized in the present review. A brief thermochemical commentary and recommendations for future research have been added to the summary of each paper.
相似文献84.
Optimization Letters - Differential evolution (de) is a popular population-based meta-heuristic that has been successfully used in complex optimization problems. Premature convergence is one of the... 相似文献
85.
The B → X (2870–3100 Å) and D → X (2250–2370 Å) band systems of 136Xe35Cl are photographed and vibrationally analyzed. A simultaneous least-squares fit of 41 band-heads in the B-X system and 35 in D-X yields, in part, the following constants (in cm?1): TeB = 32 405.8, TeD = 42 347.9, ωeB = 194.75, ωeD = 204.34, ωeX = 26.22. The ground state dissociation energy (″e) is estimated to be 281 ± 10 cm?1. Potential curves are derived for all three states through Franck-Condon calculations. From these curves the D-state internuclear distance is 0.09 ± .02 Å smaller than the B-state distance. 相似文献
86.
An optimization approach for planning daily drayage operations 总被引:1,自引:0,他引:1
Yetkin Ileri Mokhtar Bazaraa Ted Gifford George Nemhauser Joel Sokol Erick Wikum 《Central European Journal of Operations Research》2006,14(2):141-156
Daily drayage operations involve moving loaded or empty equipment between customer locations and rail ramps. Our goal is to
minimize the cost of daily drayage operations in a region on a given day. Drayage orders are generally pickup and delivery
requests with time windows. The repositioning of empty equipment may also be required in order to facilitate loaded movements.
The drayage orders are satisfied by a heterogeneous fleet of drivers. Driver routes must satisfy various operational constraints.
We present an optimization methodology for finding cost-effective schedules for regional daily drayage operations. The core
of the formulation is a set partitioning model whose columns represent routes. Routes are added to the formulation by column
generation. We present numerical results for real-world data which demonstrate that our methodology produces low cost solutions
in a reasonably short time. 相似文献
87.
Joel Kamnitzer 《Advances in Mathematics》2007,215(1):66-93
In an earlier work, we proved that MV polytopes parameterize both Lusztig's canonical basis and the Mirkovi?-Vilonen cycles on the affine Grassmannian. Each of these sets has a crystal structure (due to Kashiwara-Lusztig on the canonical basis side and due to Braverman-Finkelberg-Gaitsgory on the MV cycles side). We show that these two crystal structures agree. As an application, we consider a conjecture of Anderson-Mirkovi? which describes the BFG crystal structure on the level of MV polytopes. We prove their conjecture for sln and give a counterexample for sp6. Finally we explain how Kashiwara data can be recovered from MV polytopes. 相似文献
88.
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
89.
90.
In this paper, we show that massless Dirac waves in the Schwarzschild geometry decay to zero at a rate t ?2λ , where λ = 1, 2, . . . is the angular momentum. Our technique is to use Chandrasekhar’s separation of variables whereby the Dirac equations split into two sets of wave equations. For the first set, we show that the wave decays as t ?2λ . For the second set, in general, the solutions tend to some explicit profile at the rate t ?2λ . The decay rate of solutions of Dirac equations is achieved by showing that the coefficient of the explicit profile is exactly zero. The key ingredients in the proof of the decay rate of solutions for the first set of wave equations are an energy estimate used to show the absence of bound states and zero energy resonance and the analysis of the spectral representation of the solutions. The proof of asymptotic behavior for the solutions of the second set of wave equations relies on careful analysis of the Green’s functions for time independent Schrödinger equations associated with these wave equations. 相似文献