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Rick Quax David A. M. C. van de Vijver Dineke Frentz Peter M. A. Sloot 《The European physical journal. Special topics》2013,222(6):1347-1358
The HIV-1 epidemic in Europe is primarily sustained by a dynamic topology of sexual interactions among MSM who have individual immune systems and behavior. This epidemiological process shapes the phylogeny of the virus population. Both fields of epidemic modeling and phylogenetics have a long history, however it remains difficult to use phylogenetic data to infer epidemiological parameters such as the structure of the sexual network and the per-act infectiousness. This is because phylogenetic data is necessarily incomplete and ambiguous. Here we show that the cluster-size distribution indeed contains information about epidemiological parameters using detailed numberical experiments. We simulate the HIV epidemic among MSM many times using the Monte Carlo method with all parameter values and their ranges taken from literature. For each simulation and the corresponding set of parameter values we calculate the likelihood of reproducing an observed cluster-size distribution. The result is an estimated likelihood distribution of all parameters from the phylogenetic data, in particular the structure of the sexual network, the per-act infectiousness, and the risk behavior reduction upon diagnosis. These likelihood distributions encode the knowledge provided by the observed cluster-size distrbution, which we quantify using information theory. Our work suggests that the growing body of genetic data of patients can be exploited to understand the underlying epidemiological process. 相似文献
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Magnetization processes at the surface of iron plates were investigated in a variable external field by means of Mössbauer emission and scattering spectroscopy of57Fe. It is shown that the 90? walls of closure domains do not move until an externally applied field reaches a certain value. The “starting” values of the field determined from the Mössbauer measurements agree with those at which a sudden decrease in the growth rate of the bulk magnetization starts. Blocking of the surface domain wall movement occurs in a layer of at least 10 Μm thickness. 相似文献
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In this paper we prove optimal interior regularity for solutions to the obstacle problem for a class of second order differential
operators of Kolmogorov type. We treat smooth obstacles as well as non-smooth obstacles. All our proofs follow the same line
of thought and are based on blow-ups, compactness, barriers and arguments by contradiction. The problem considered arises
in financial mathematics, when considering path-dependent derivative contracts with early exercise feature. 相似文献
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We have observed an infrared emission band at (4.69 ± 0.03)μ as a consequence of β-decay in molecular tritium at 25 K. This emission is due to β-recoil-induced vibrational excitation. 相似文献
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In this paper we continue the study initiated in [15] concerning the obstacle problem for a class of parabolic non-divergence operators structured on a set of vector fields X={X1,…,Xq} in Rn with C∞-coefficients satisfying Hörmander?s finite rank condition, i.e., the rank of Lie[X1,…,Xq] equals n at every point in Rn. In [15] we proved, under appropriate assumptions on the operator and the obstacle, the existence and uniqueness of strong solutions to a general obstacle problem. The main result of this paper is that we establish further regularity, in the interior as well as at the initial state, of strong solutions. Compared to [15] we in this paper assume, in addition, that there exists a homogeneous Lie group G=(Rn,°,δλ) such that X1,…,Xq are left translation invariant on G and such that X1,…,Xq are δλ-homogeneous of degree one. 相似文献
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