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61.
Tziveleka LA Kontoyianni C Sideratou Z Tsiourvas D Paleos CM 《Macromolecular bioscience》2006,6(2):161-169
Multifunctional hyperbranched polyether polyols bearing protective poly(ethylene glycol) (PEG) chains with or without the folate targeting ligand at their end have been prepared. Solubilization in these polymers of a fluorescent probe, pyrene, and an anticancer drug, tamoxifen, was physicochemically investigated. It was found that PEG chains attached at the surface of these hyperbranched polymers, in addition to their well-established protective role, enhance the encapsulation efficiency of the polymers. The release of pyrene and tamoxifen observed upon addition of sodium chloride is, in most of the cases, significant only at concentrations exceeding the physiological extracellular concentration. Thus, a significant amount of the probe or drug remains solubilized inside the carriers, which is an encouraging result if the polymers are to be used for drug delivery. 相似文献
62.
The zero total angular momentum (J = 0) S matrix elements, calculated using a time-dependent wave packet method for the Cl (2P) + H2 reaction on two different potential energy surfaces, have been matrix transformed to the stereodirected and Gauss-Legendre discrete variable representations. Although the results in the two representations are (as expected) quantitatively different with respect to the angular selectivity and specificity of the reactive process, the qualitative similarity has allowed us to draw for the first time conclusions with respect to some characteristics of the potential energy surface. 相似文献
63.
Athanasekos L Vasileiadis M Tsigara A Kaminska E Piotrowska A Alexandropoulos D Sigalas MM Vainos NA 《Optics letters》2010,35(23):4003-4005
We designed and fabricated multilayer metal/metal-oxide surface relief diffractive grating structures by growing alternating Pt and SnO(x) layers. Optical interrogation at 633 nm reveals the temperature dependence of their reflection and transmission diffractive effects. This function is explored here in the context of a remote, spatially localized, photonic temperature sensing operation, achieving sensitivity of 10% per °C for the zeroth-order in the transmission mode. The experimental demonstration is found to be in good agreement with the results of rigorous coupled wave analysis of the composite metal/metal-oxide element. 相似文献
64.
Mathematical Programming - The last decade witnessed an explosion in the availability of data for operations research applications. Motivated by this growing availability, we propose a novel schema... 相似文献
65.
Characteristic parameter sets and limits of circulant Hermitian polygon transformations 总被引:1,自引:0,他引:1
Polygon transformations based on taking the apices of similar triangles constructed on the sides of an initial polygon are analyzed as well as the limit polygons obtained by iteratively applying such transformations. In contrast to other approaches, this is done with respect to two construction parameters representing a base angle and an apex perpendicular subdivision ratio. Furthermore, a combined transformation leading to circulant Hermitian matrices is proposed, which eliminates the rotational effect of the basic transformation. A finite set of characteristic parameter subdomains is derived for which the sequence converges to specific eigenpolygons. Otherwise, limit polygons turn out to be linear combinations of up to three eigenpolygons. This leads to a full classification of circulant Hermitian similar triangles based polygon transformations and their limit polygons. As a byproduct classical results as Napoleon’s theorem and the Petr-Douglas-Neumann theorem can be easily deduced. 相似文献
66.
We propose both robust and data-driven approaches to a fluid model of call centers that incorporates random arrival rates with abandonment to determine staff levels and dynamic routing policies. We test the resulting models with real data obtained from the call center of a US bank. Computational results show that the robust fluid model is significantly more tractable as compared to the data-driven one and produces overall better solutions to call centers in most experiments. 相似文献
67.
This paper investigates whether productive inefficiency measured as the distance from the industry’s ‘best practice’ frontier is an important ex-ante predictor of business failure. We use samples of French textiles, wood and paper products, computers and R&D companies to obtain efficiency estimates for individual firms in each industry. These efficiency measures are derived from a directional technology distance function constructed empirically using non-parametric data envelopment analysis (DEA) methods. Estimating binary and ordered logit regression models we find that productive efficiency has significant explanatory power in predicting the likelihood of default over and above the effect of standard financial indicators. 相似文献
68.
We consider random walk on a mildly random environment on finite transitive d-regular graphs of increasing girth. After scaling and centering, the analytic spectrum of the transition matrix converges in distribution to a Gaussian noise. An interesting phenomenon occurs at d = 2: as the limit graph changes from a regular tree to the integers, the noise becomes localized. The graphs of the noise covariance structure for d = 4, 3, 2.1 from above. 相似文献
69.
We introduce the Conditional Mutual Information (CMI) for the estimation of the Markov chain order. For a Markov chain of K symbols, we define CMI of order m, Ic(m), as the mutual information of two variables in the chain being m time steps apart, conditioning on the intermediate variables of the chain. We find approximate analytic significance limits based on the estimation bias of CMI and develop a randomization significance test of Ic(m), where the randomized symbol sequences are formed by random permutation of the components of the original symbol sequence. The significance test is applied for increasing m and the Markov chain order is estimated by the last order for which the null hypothesis is rejected. We present the appropriateness of CMI-testing on Monte Carlo simulations and compare it to the Akaike and Bayesian information criteria, the maximal fluctuation method (Peres–Shields estimator) and a likelihood ratio test for increasing orders using ?-divergence. The order criterion of CMI-testing turns out to be superior for orders larger than one, but its effectiveness for large orders depends on data availability. In view of the results from the simulations, we interpret the estimated orders by the CMI-testing and the other criteria on genes and intergenic regions of DNA chains. 相似文献
70.
Dimitris Koukoulopoulos 《Geometric And Functional Analysis》2013,23(5):1569-1630
Let f be a completely multiplicative function that assumes values inside the unit disc. We show that if ${\sum_{n \leq x}f(n)\ll x/(\rm log x)^A}$ ∑ n ≤ x f ( n ) ? x / ( l o g x ) A , ${x \geq 2}$ x ≥ 2 , for some A > 2, then either f(p) is small on average or f pretends to be ${\mu(n)n^{it}}$ μ ( n ) n i t for some t. 相似文献