Disambiguating Visual Motion by Form-Motion Interaction—a Computational Model

The neural mechanisms underlying motion segregation and integration still remain unclear to a large extent. Local motion estimates often are ambiguous in the lack of form features, such as corners or junctions. Furthermore, even in the presence of such features, local motion estimates may be wrong if they were generated near occlusions or from transparent objects. Here, a neural model of visual motion processing is presented that involves early stages of the cortical dorsal and ventral pathways. We investigate the computational mechanisms of V1-MT feedforward and feedback processing in the perception of coherent shape motion. In particular, we demonstrate how modulatory MT-V1 feedback helps to stabilize localized feature signals at, e.g. corners, and to disambiguate initial flow estimates that signal ambiguous movement due to the aperture problem for single shapes. In cluttered environments with multiple moving objects partial occlusions may occur which, in turn, generate erroneous motion signals at points of overlapping form. Intrinsic-extrinsic region boundaries are indicated by local T-junctions of possibly any orientation and spatial configuration. Such junctions generate strong localized feature tracking signals that inject erroneous motion directions into the integration process. We describe a simple local mechanism of excitatory form-motion interaction that modifies spurious motion cues at T-junctions. In concert with local competitive-cooperative mechanisms of the motion pathway the motion signals are subsequently segregated into coherent representations of moving shapes. Computer simulations demonstrate the competency of the proposed neural model.     

Juvenile transfer to adult courts: A look at the prototypes for dangerousness sophistication-maturity and amenability to treatment through a legal lens.

Juvenile court judges are often required to make distinctions as to whether certain adolescents should remain in the juvenile justice system or be transferred to adult courts. Typically, 3 broad factors weigh into juvenile court judges' decision making: (a) the level of danger the juvenile poses to the community, (b) the level of sophistication-maturity of the juvenile, and (c) the extent to which the juvenile is viewed as treatable. In an earlier study, knowledge of forensic and child psychologists was tapped to elucidate core characteristics related to the transfer process (R. T. Salekin et al, 2001). The current study augments that investigation. Judges provided (a) their perspective regarding the core criteria for dangerousness, sophistication-maturity, and amenability to treatment, and (b) data on the core characteristics of juveniles who were evaluated and subsequently judged to be appropriate for transfer to adult criminal courts. Policy implications for this increasingly critical interface between law and psychology are threefold: (a) Individualized assessments are key; (b) the adoption of a national standard for transfer to adult court is required; and (c) the development of treatment programs to improve the socialization of youth is necessary. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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When to use bit-wise neutrality

Representation techniques are important issues when designing successful evolutionary algorithms. Within this field the use of neutrality plays an important role. We examine the use of bit-wise neutrality introduced by Poli and López (2007) from a theoretical point of view and show that this mechanism only enhances mutation-based evolutionary algorithms if not the same number of genotypic bits for each phenotypic bit is used. Using different numbers of genotypic bits for the bits in the phenome we point out by rigorous runtime analyses that it may reduce the optimization time significantly.     

A dynamic mesh refinement technique for Lattice Boltzmann simulations on octree-like grids

In this contribution, we present our new adaptive Lattice Boltzmann implementation within the Peano framework, with special focus on nanoscale particle transport problems. With the continuum hypothesis not holding anymore on these small scales, new physical effects—such as Brownian fluctuations—need to be incorporated. We explain the overall layout of the application, including memory layout and access, and shortly review the adaptive algorithm. The scheme is validated by different benchmark computations in two and three dimensions. An extension to dynamically changing grids and a spatially adaptive approach to fluctuating hydrodynamics, allowing for the thermalisation of the fluid in particular regions of interest, is proposed. Both dynamic adaptivity and adaptive fluctuating hydrodynamics are validated separately in simulations of particle transport problems. The application of this scheme to an oscillating particle in a nanopore illustrates the importance of Brownian fluctuations in such setups.     

Ant Colony Optimization and the minimum spanning tree problem

Ant Colony Optimization (ACO) is a kind of metaheuristic that has become very popular for solving problems from combinatorial optimization. Solutions for a given problem are constructed by a random walk on a so-called construction graph. This random walk can be influenced by heuristic information about the problem. In contrast to many successful applications, the theoretical foundation of this kind of metaheuristic is rather weak. Theoretical investigations with respect to the runtime behavior of ACO algorithms have been started only recently for the optimization of pseudo-Boolean functions.We present the first comprehensive rigorous analysis of a simple ACO algorithm for a combinatorial optimization problem. In our investigations, we consider the minimum spanning tree (MST) problem and examine the effect of two construction graphs with respect to the runtime behavior. The choice of the construction graph in an ACO algorithm seems to be crucial for the success of such an algorithm. First, we take the input graph itself as the construction graph and analyze the use of a construction procedure that is similar to Broder’s algorithm for choosing a spanning tree uniformly at random. After that, a more incremental construction procedure is analyzed. It turns out that this procedure is superior to the Broder-based algorithm and produces additionally in a constant number of iterations an MST, if the influence of the heuristic information is large enough.     

Mycotoxins in breakfast cereals from the Canadian retail market: A 3-year survey

One hundred and fifty-six samples of breakfast cereals were collected from the Canadian retail marketplace over a 3-year period. The samples were analysed for the mycotoxins deoxynivalenol, nivalenol, HT-2 toxin, zearalenone, ochratoxin A, and fumonisins B₁ and B₂ to contribute to dietary exposure estimates in support of the development of Canadian guidelines for selected mycotoxins in foods. The samples included corn-, oat-, wheat- and rice-based cereals, as well as mixed-grain cereals, and were primarily from North American processors. Overall, deoxynivalenol was the most frequently detected mycotoxin  — it was detected in over 40% of all samples analysed. Fumonisins and ochratoxin A were each detected in over 30% of all samples. Zearalenone was detected in over 20% of all samples. Nivalenol and HT-2 toxin were each detected in only one sample. The survey clearly demonstrated regular occurrence of low levels of multiple mycotoxins in breakfast cereals on the Canadian market.