Robust utility maximization with nonlinear continuous semimartingales

In this paper we study a robust utility maximization problem in continuous time under model uncertainty. The model uncertainty is governed by a continuous semimartingale with uncertain local characteristics. Here, the differential characteristics are prescribed by a set-valued function that depends on time and path. We show that the robust utility maximization problem is in duality with a conjugate problem, and we study the existence of optimal portfolios for logarithmic, exponential and power utilities.Comment: To appear in "Mathematics and Financial Economics

Markov selections and Feller properties of nonlinear diffusions

In this paper we study a family of nonlinear (conditional) expectations that can be understood as a diffusion with uncertain local characteristics. Here, the differential characteristics are prescribed by a set-valued function that depends on time and path in a Markovian way. We establish its Feller properties and examine how to linearize the associated sublinear Markovian semigroup. In particular, we observe a novel smoothing effect of nonlinear semigroups in frameworks which carry enough randomness. Furthermore, we link the value function corresponding to the semigroup to a nonlinear Kolmogorov equation

Off-axis reflection zone plate for quantitative soft x-ray source characterization

A compact system for high-resolution spectroscopy and quantitative photon flux and brilliance measurements of pulsed soft x-ray sources is described. The calibrated system combines a novel elliptical off-axis reflection zone plate with charge-coupled device detection for simultaneous spectral and spatial measurements. Experiments on a water-window droplet-target laser-plasma source demonstrate lambda/Delta lambda greater than or equal to 1000 spectral resolution and absolute flux and brilliance measurements. (C) 1997 American Institute of Physics

High genetic diversity among Mycobacterium tuberculosis complex strains from Sierra Leone

<p>Abstract</p> <p>Background</p> <p>Among tuberculosis (TB) high incidence regions, Sub-Saharan Africa is particularly affected with approx. 1.6 million new cases every year. Besides this dramatic situation, data on the diversity of <it>Mycobacterium tuberculosis </it>complex (MTBC) strains causing this epidemic in this area are only sparsely available. Here we analyzed the population structure of strains from Sierra Leone with a special focus on the prevalence of <it>M. africanum</it>.</p> <p>Results</p> <p>A total of 97 strains isolated from smear positive cases registered for re-treatment in the Western Area and Kenema districts in years 2003/2004 were investigated by susceptibility testing (first line drugs) and molecular typing (IS<it>6110 </it>fingerprinting, spoligotyping, and MIRU-VNTR typing).</p> <p>Among the strains analyzed, 32 were resistant to isoniazid, and 11 were multidrug resistant (at least resistant to isoniazid and rifampin). The population diversity was high with two previously described <it>M. africanum </it>lineages (West African-1, n = 6; West African-2, n = 17) and seven <it>M. tuberculosis </it>lineages (Haarlem, n = 14; LAM, n = 15; EAI, n = 4; Beijing, n = 4; S-type, n = 4, X-type, n = 1; Cameroon, n = 4). Furthermore, two new <it>M. tuberculosis </it>genotypes Sierra Leone-1 (n = 7) and -2 (n = 10) were found. Strain classification according to a 7 bp deletion in pks1/15 revealed that the majority of <it>M. tuberculosis </it>strains belonged to the Euro American lineage (66 out of 74).</p> <p>Conclusion</p> <p>Resistance rates in Sierra Leone have reached an alarming level. The population structure of MTBC strains shows an intriguing diversity raising the question of possible consequences for TB epidemic and for the introduction of new diagnostic tests or treatment strategies in West Africa.</p