Contact process in disordered and periodic binary two-dimensional lattices.

The critical behavior of the contact process (CP) in disordered and periodic binary two-dimensional (2D) lattices is investigated numerically by means of Monte Carlo simulations as well as via an analytical approximation and standard mean field theory. Phase-separation lines calculated numerically are found to agree well with analytical predictions around the homogeneous point. For the disordered case, values of static scaling exponents obtained via quasistationary simulations are found to change with disorder strength. In particular, the finite-size scaling exponent of the density of infected sites approaches a value consistent with the existence of an infinite-randomness fixed point as conjectured before for the 2D disordered CP. At the same time, both dynamical and static scaling exponents are found to coincide with the values established for the homogeneous case thus confirming that the contact process in a heterogeneous environment belongs to the directed percolation universality class.

Supercritical series expansion for the contact process in heterogeneous and disordered environments.

The supercritical series expansion of the survival probability for the one-dimensional contact process in heterogeneous and disordered lattices is used for the evaluation of the loci of critical points and critical exponents beta . The heterogeneity and disorder are modeled by considering binary regular and irregular lattices of nodes characterized by different recovery rates and identical transmission rates. Two analytical approaches based on nested Padé approximants and partial differential approximants were used in the case of expansions with respect to two variables (two recovery rates) for the evaluation of the critical values and critical exponents. The critical exponents in heterogeneous systems are very close to those for the homogeneous contact process thus confirming that the contact process in periodic heterogeneous environment belongs to the directed percolation universality class. The disordered systems, in contrast, seem to have continuously varying critical exponents.

Contact process in heterogeneous and weakly disordered systems.

The critical behavior of the contact process (CP) in heterogeneous periodic and weakly disordered environments is investigated using the supercritical series expansion and Monte Carlo (MC) simulations. Phase-separation lines and critical exponents beta (from series expansion) and eta (from MC simulations) are calculated. A general analytical expression for the locus of critical points is suggested for the weak-disorder limit and confirmed by the series expansion analysis and the MC simulations. Our results for the critical exponents show that the CP in heterogeneous environments remains in the directed percolation universality class, while for environments with quenched disorder, the data are compatible with the scenario of continuously changing critical exponents.

Extinction of epidemics in lattice models with quenched disorder.

The extinction of the contact process for epidemics in lattice models with quenched disorder is analyzed in the limit of small density of infected sites. It is shown that the problem in such a regime can be mapped to the quantum-mechanical one characterized by the Anderson Hamiltonian for an electron in a random lattice. It is demonstrated both analytically (self-consistent mean field) and numerically (by direct diagonalization of the Hamiltonian and by means of cellular automata simulations) that disorder enhances the contact process, given the mean values of random parameters are not influenced by disorder.

Polymorphisms in the DLG5 and OCTN cation transporter genes in Crohn's disease.

BACKGROUND AND AIMS: Recent data suggest identification of causal genetic variants for inflammatory bowel disease in the DLG5 gene and in the organic cation transporter (OCTN) cluster, both situated in previously described linkage regions. PATIENTS AND METHODS: The polymorphisms in DLG5 (113 G-->A, 4136 C-->A, and DLG5_e26), SLC22A4 (1672 C-->T), and SLC22A5 (-207 G-->C) were assessed in 625 patients with Crohn's disease (CD), 363 patients with ulcerative colitis (UC), and 1012 healthy controls. Association with disease susceptibility, clinical phenotypes, and possible genetic interactions of these polymorphisms with disease associated CARD15/NOD2 mutations was analysed. RESULTS: No significant association of DLG5 polymorphisms with CD or UC was observed. Homozygosity for the OCTN-TC haplotype was associated with an increased CD risk (OR = 1.65), which was even greater in the presence of CARD15 mutations. Genotype-phenotype analysis revealed that this association was particularly strong in patients with colonic disease. The TC haplotype was associated with non-fistulising non-fibrostenotic disease, an earlier age of disease onset, and reduced need for surgery. CONCLUSION: Our observations argue against a role of DLG5 polymorphisms in the susceptibility for inflammatory bowel disease, whereas the OCTN polymorphisms are associated with CD. However, due to the comparable weak association observed herein, extended linkage disequilibrium analyses of these variants with the IBD5 haplotype tagged single nucleotide polymorphims might be advisable before definitive conclusions about their causative role in CD can be drawn.

[Expert opinion problems in the evaluation of osteomyelitis]. / Gutachterliche Probleme bei der Beurteilung von Osteomyelitiden.

Cases of osteomyelitis can be differentiated according to hematogenous (endogenous), and post-traumatic (exogenous) forms. Both types can lead to considerable permanent damage or recur even after a fairly long time. In the formulation of an expert opinion to assess cases of osteomyelitis, the foremost question concerns a possible error in treatment or clarification of a connection to a postulated trauma. The present article describes aspects of expert opinions on cases of osteomyelitis of the long bones, spinal column, and in children. In addition to potential claims for compensation for harm caused by permanent damage, other conceivable sequelae such as fistula carcinoma or amyloidosis are relevant for expert opinions. In contrast, substantiated clarification of the causality of a triggering traumatic event is essentially important for recognition of claims against accident insurance companies.

[Problems with expert opinion for the assessment of septic arthritis]. / Gutachterliche Probleme bei der Beurteilung von septischen Arthritiden.

Bacterial arthritis is a rare and usually protracted disease and complication which can cause substantial permanent damage. At the first indication of such an infection, rapid and efficient therapy is required. In general, after a rapid diagnosis and subsequent therapy in early stage of the disease, a complete cure should be effected. In the case of children timely diagnosis and therapy lead to a very good chance of cure. In the case of adults under 50 years, the chances of a cure after an infectious arthritis are still good to very good. For patients older than 50, however, the chances of permanent damage after a joint infection are high. Severe damage in the region of a joint frequently leads to the accusation of medical error. Due to the often undetermined reasons for an infection, common pre- and concurrent illnesses, the long course of the disease, and the often substantial long-term damage, it is necessary for the medical specialist asked for an expert opinion on the question of cause to be particularly careful. The expert must take into consideration not only the permanent damage but must also estimate the future consequences of the disease.

Analysis and verification of an analog VLSI incremental outer-product learning system.

An architecture is described for the microelectronic implementation of arbitrary outer-product learning rules in analog floating-gate CMOS matrix-vector multiplier networks. The weights are stored permanently on floating gates and are updated under uniform UV illumination with a general incremental analog four-quadrant outer-product learning scheme, performed locally on-chip by a single transistor per matrix element on average. From the mechanism of floating gate relaxation under UV radiation, the authors derive the learning parameters and their dependence on the illumination level and circuit parameters. It is shown that the weight increments consists of two parts: one term contains the outer product of two externally applied learning vectors; the other part represents a uniform weight decay, with time constant originating from the floating gate relaxation. The authors address the implementation of supervised and unsupervised learning algorithms with emphasis on the delta rule. Experimental results from a simple implementation of the delta rule on an 8x7 linear network are included.