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1.
The purpose of this study was to use dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to search for systematic intratumor heterogeneity in blood perfusion in human melanoma xenografts growing intradermally in BALB/c-nu/nu mice. Six xenografted tumors of an amelanotic human melanoma line (A-07) were included in the study. DCE-MRI was performed daily for 5 days by using spoiled-gradient recalled sequences. Tumor images of E.F (E is initial extraction fraction and F is perfusion) were produced by subjecting DCE-MRI data to Kety analysis. E.F was used as a measure of tumor blood perfusion, since comparative studies have shown that E.F is closely related to blood perfusion in A-07 tumors. The E.F images indicated that the intratumor heterogeneity in blood perfusion was similar in all investigated tumors. The blood perfusion was low in the center of the tumors and increased toward the tumor periphery in the dorsal and ventral direction by a factor of 3-4, but not in the lateral and medial direction. The magnitude of the heterogeneity increased by a factor of approximately 2 during tumor growth. In conclusion, intradermal human melanoma xenografts show significant systematic intratumor heterogeneity in blood perfusion.  相似文献   
2.
We give an equivariant version of Packer and Rieffel’s theorem on sufficient conditions for the existence of orthonormal wavelets in projective multiresolution analysis. Suppose that the scaling functions are invariant with respect to some finite group action. We give sufficient conditions for the existence of wavelets with similar invariance. Research supported in part by the Research Council of Norway, project number NFR 154077/420. Some of the final work was also done with the support from the project NFR 170620/V30.  相似文献   
3.
A Heuristic for Moment-Matching Scenario Generation   总被引:1,自引:0,他引:1  
In stochastic programming models we always face the problem of how to represent the random variables. This is particularly difficult with multidimensional distributions. We present an algorithm that produces a discrete joint distribution consistent with specified values of the first four marginal moments and correlations. The joint distribution is constructed by decomposing the multivariate problem into univariate ones, and using an iterative procedure that combines simulation, Cholesky decomposition and various transformations to achieve the correct correlations without changing the marginal moments.With the algorithm, we can generate 1000 one-period scenarios for 12 random variables in 16 seconds, and for 20 random variables in 48 seconds, on a Pentium III machine.  相似文献   
4.
This paper considers a maritime inventory routing problem faced by a major cement producer. A heterogeneous fleet of bulk ships transport multiple non-mixable cement products from producing factories to regional silo stations along the coast of Norway. Inventory constraints are present both at the factories and the silos, and there are upper and lower limits for all inventories. The ship fleet capacity is limited, and in peak periods the demand for cement products at the silos exceeds the fleet capacity. In addition, constraints regarding the capacity of the ships’ cargo holds, the depth of the ports and the fact that different cement products cannot be mixed must be taken into consideration. A construction heuristic embedded in a genetic algorithmic framework is developed. The approach adopted is used to solve real instances of the problem within reasonable solution time and with good quality solutions.  相似文献   
5.
The observation of isolated positive and negative charges, but not isolated magnetic north and south poles, is an old puzzle. Instead, evidence of effective magnetic monopoles has been found in the abstract momentum space. Apart from Hall-related effects, few observable consequences of these abstract monopoles are known. Here, we show that it is possible to manipulate the monopoles by external magnetic fields and probe them by universal conductance fluctuation measurements in ferromagnets with strong spin-orbit coupling. The observed fluctuations are not noise, but reproducible quasiperiodic oscillations as a function of magnetization direction, a novel Berry phase fingerprint of the magnetic monopoles.  相似文献   
6.
Motivated by the multivariate wavelet theory, and by the spectral theory of transfer operators, we construct an abstract affine structure and a multiresolution associated to a matrix-valued weight. We describe the one-to-one correspondence between the commutant of this structure and the fixed points of the transfer operator. We show how the covariant representation can be realized on if the weight satisfies some low-pass condition.   相似文献   
7.
We analyze matrix-valued transfer operators. We prove that the fixed points of transfer operators form a finite-dimensional C-algebra. For matrix weights satisfying a low-pass condition we identify the minimal projections in this algebra as correlations of scaling functions, i.e., limits of cascade algorithms.  相似文献   
8.
Transient separation of the individual components in a multicomponent liquid mixture in a thermogravitational column can be used to determine the thermal and molecular diffusion coefficients. Two models of the transient behavior are developed. First, a classical model where density only depends on temperature. Second, a general model where the compositional effect on density is also taken into account. Diffusion coefficients can be determined by fitting experimental data to either model. The procedure is demonstrated for a ternary liquid mixture. The results reveal that the classical model is very unreliable even though composition variation only contributes to the total buoyancy by one-third. Diffusion coefficients can be obtained reliably from the general model provided the experimental noise does not exceed +/-1% of steady-state separation. This level of accuracy in composition measurements is achievable.  相似文献   
9.
We review research on ship routing and scheduling and related problems during the new millennium and provide four basic models in this domain. The volume of research in this area about doubles every decade as does the number of research outlets. We have found over a hundred new refereed papers on this topic during the last decade. Problems of wider scope have been addressed as well as more specialized ones. However, complex critical problems remain wide open and provide challenging opportunities for future research.  相似文献   
10.
We have developed the theory for using the deflection of laser beams of various wavelengths to determine molecular and thermal diffusion coefficients in multicomponent mixtures. In the past, simultaneous determination of molecular and thermal diffusion coefficients have only been achieved for binaries. Our procedure is faster and more accurate than the current techniques to determine molecular diffusion coefficients. The analysis for an N-component mixture requires deflections from (N - 1) beams of different wavelengths. We show in an example that the molecular and thermal diffusion coefficients can be determined reliably in a ternary mixture.  相似文献   
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