Hemispheric Asymmetries in Cognitive Modeling: Connectionist Modeling of Unilateral Visual Neglect.

Neglect is an acquired cognitive disorder characterized by a lack of processing of one side of a stimulus or representational space. There are hemispheric asymmetries in its cause and in its effects, but implemented computational models of neglect have tended not to incorporate this fact. The authors report a series of neural network simulations of the line-bisection task. They test the hypothesis that simple, neuroanatomically realistic principles of connectivity in the nervous system can produce emergent behaviors that capture a wide range of quantitative and qualitative data observed in neglect patients presenting with general visuospatial neglect. They demonstrate that exploring low-level architectural principles in implemented computational models is both a productive avenue of research and offers the most parsimonious explanations of behaviors observed in patients. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effect of dietary restriction on cell-mediated immune responses in cattle infected with Mycobacterium bovis

Nine M. bovis-infected cattle on a diet deficient in both protein and energy for 133 days lost approximately 17% of their original body weight. However, dietary restriction did not result in any significant reduction in skin sensitivity to PPD, in vitro production of IFN-gamma or lymphocyte blastogenesis. The number of circulating BoCD4+ cells and B cells were similar in both the malnourished and the control cattle. However, significantly lower numbers (P < 0.01) of circulating BoCD2+ cells, BoCD8+ cells, WC1+ gamma delta T cells and ACT2+ cells were found in the malnourished cattle. With the exception of inorganic phosphate, the changes in plasma biochemical parameters were unremarkable.     

Association and colocalization of the Kvbeta1 and Kvbeta2 beta-subunits with Kv1 alpha-subunits in mammalian brain K+ channel complexes

The differential expression and association of cytoplasmic beta-subunits with pore-forming alpha-subunits may contribute significantly to the complexity and heterogeneity of voltage-gated K+ channels in excitable cells. Here we examined the association and colocalization of two mammalian beta-subunits, Kvbeta1 and Kvbeta2, with the K+ channel alpha-subunits Kv1.1, Kv1.2, Kv1.4, Kv1.6, and Kv2.1 in adult rat brain. Reciprocal coimmunoprecipitation experiments using subunit-specific antibodies indicated that Kvbeta1 and Kvbeta2 associate with all the Kv1 alpha-subunits examined, and with each other, but not with Kv2.1. A much larger portion of the total brain pool of Kv1-containing channel complexes was found associated with Kvbeta2 than with Kvbeta1. Single- and multiple-label immunohistochemical staining indicated that Kvbeta1 codistributes extensively with Kv1.1 and Kv1.4 in cortical interneurons, in the hippocampal perforant path and mossy fiber pathways, and in the globus pallidus and substantia nigra. Kvbeta2 codistributes extensively with Kv1.1 and Kv1.2 in all brain regions examined and was strikingly colocalized with these alpha-subunits in the juxtaparanodal region of nodes of Ranvier as well as in the axons and terminals of cerebellar basket cells. Taken together, these data provide a direct demonstration that Kvbeta1 and Kvbeta2 associate and colocalize with Kv1 alpha-subunits in native tissues and provide a biochemical and neuroanatomical basis for the differential contribution of Kv1 alpha- and beta-subunits to electrophysiologically diverse neuronal K+ currents.     

Survival and functional demonstration of interregional pathways in fore/midbrain slice explant cultures

An important general question in neurobiology concerns the development and expression of the rich context of neuronal phenotypes, especially in relation to the diverse patterns of connectivity. Organotypic cultures of brain slices may offer distinct advantages for such studies if such a preparation survives, maintains a wide diversity of neuronal phenotypes and displays appropriate synaptic connections between regions. To address these requirements, we utilized long-term organotypic cultures of intact horizontal slices of rat forebrain and midbrain and assessed a variety of markers of phenotype in combination with functional tests of connectivity. This explant preparation displayed a distinct viability requirement such that the greatest explant survival was seen in slices taken from pups of less than postnatal day 7 and was independent of N-methyl-D-aspartate channel blockade. The anatomical features of the major brain regions (e.g., neocortex, striatum, septum, hippocampus, diencephalon and midbrain) were observed in their normal boundaries. The presence of cholinergic and catecholaminergic neurons was demonstrated with acetylcholinesterase histochemistry and tyrosine hydroxylase immunohistochemistry. Labelled neurons displayed multiple, regionally-appropriate cytoarchitectures and, in some cases, could be seen to project to brain regions in a manner quite similar to that seen in vivo. Finally, the direct demonstration of spontaneous and evoked interregional excitatory synaptic transmission was made using whole-cell patch-clamp recordings from striatal neurons which revealed an intact glutamate-using corticostriatal pathway. This simple explant preparation appears to contain a rich diversity of neuronal types and synaptic organization. Therefore, this preparation appears to have several distinct advantages for basic neurobiologic research since it combines long-term culture viability and many features of mature brain including complex interregional neuronal systems.     

The effects of external loading on a yield tightened joint

If bolted assemblies are to perform adequately under service conditions it is vital that the clamp load on the joint should be as great as possible consistent with the design features of the joint. Furthermore, each fastener of the joint should exert the same clamping force if distortion and overloading are to be avoided. Recent research has shown that better consistency of clamping load can be achieved if the fasteners of the joint are tightened using a yield tightening technique rather than the more traditional torque control method. This paper examines the behaviour of fasteners tightened to yield under various conditions of lubrication. The behaviour of the yield tightened fastener under additional external loading is also examined. The results show that fasteners tightened to yield respond in an elastic manner under the initial application of an external load. It is also shown that under appropriate lubrication conditions a fastener can be repeatedly retightened to yield without failure occurring. It is felt that these results should be of particular interest to design and development engineers within industry in general and the machine tool industry in particular.     

Degradation dynamics and breakdown of MgO gate oxides

The degradation dynamics of magnesium oxide (MgO) layers in MOS structures has been investigated. It is shown that the shift of the conduction characteristics caused by both ramped and constant voltage stresses is well described by power-law models and that the signature of charge trapping is still visible even after the dielectric breakdown (BD) of the insulating film. The occurrence of progressive BD in 20-nm thick films is also reported.     

A Projection System for Real World Three-Dimensional Objects Using Spatial Light Modulators

We discuss a projection system for real world three-dimensional objects using spatial light modulators (SLM). An algorithm to encode the digital holograms of real world objects on to an SLM is presented. We present results from experiments to project holograms of real world holograms using a nematic liquid crystal SLM. We discuss the case when the pixel sizes of the charge-coupled device (CCD) and SLM used for recording the hologram and projection are different.