Hypercube sandwich approach to conferencing

This paper presents a novel cascaded conference network that provides distributed processing and signal transmission among members of disjoint sets of generic send/receive devices called conferees. It assumes an online request model in which idle groups of conferees may request the formation of a conference interconnection. Once a conference is established, all conferees remain connected until the entire conference is dissolved. The Hypercube Sandwich Network (HSN) consists of two components. A bidirectional permutation network is used for routing purposes to and from a hypercube of special processing elements for the purpose of conference formation. The HSN achieves strictly nonblocking performance for N conferees using O(Nlog N) processing elements, and this is shown to be tight to within a log ^1/4 N factor. Previous constructions required a quadratic number of processing elements for strictly nonblocking performance or could only provide wide-sense nonblocking conferencing. If the stronger requirement is made that the communication delay is logarithmic in the conference size, a simple algorithm is presented for wide-sense nonblocking conferencing in an HSN with O(N log N) processing elements.An earlier version of this paper was presented at the 1995 International Conference on Parallel Processing Techniques and Applications.     

Innervation of cerebral blood vessels: morphology, plasticity, age-related, and Alzheimer's disease-related neurodegeneration

The light microscopical and ultrastructural morphology of the innervation of the major cerebral arteries and pial vessels is described, including the origins of the different groups of nerve fibres and their characteristic neurotransmitter phenotype. Species and region specific variations are described and novel data regarding the parasympathetic innervation of cerebral vessels are presented. The dynamic nature, or plasticity, of cerebrovascular innervation is emphasized in describing changes affecting particular subpopulations of neurons during normal ageing and in Alzheimer's disease. The molecular controls on plasticity are discussed with particular reference to target-associated factors such as the neurotrophins and their neuronal receptors, as well as extracellular matrix related factors such as laminin. Hypotheses are presented regarding the principal extrinsic and intrinsic influences on plasticity of the cerebrovascular innervation.     

Technical report: Initial experiences with an experimental solid-state universal digital X-ray image detector

This paper presents a brief technical evaluation and first review of clinical experiences with an experimental direct digital X-ray image detector designed to support both dynamic and snap-shot imaging. Derivatives of this type of image detector can potentially fulfil the majority of the fluoroscopic and radiographic imaging requirements of clinical radiology departments, and initial results suggest that imaging systems using the new technology will provide a high quality dose-efficient solution to the search for a universal digital X-ray image detector.     

Follow-up study of maladapting school children seen by nonprofessionals.

Examined whether children, seen 2-5 yr. earlier by nonprofessional child aides for school maladaptation problems, maintained short-term gains over time. Follow-up interviews, exploring the child's subsequent educational and interpersonal career, were held with mothers of 36 such children. Both mothers and interviewers independently rated change over the intervening time period along 9 salient educational and interpersonal dimensions. Ratings of the 2 groups were in substantial agreement. Both judged significant educational and interpersonal growth to have occurred. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Single wire model of high gradient magnetic separation processes I

A rate equation is being developed to model the buildup of single-sized, weakly magnetic particles on a single ferromagnetic cylindrical wire. The equation relates the rate of buildup on the wire to the fraction of the incoming particles that are captured and the portion of the particles that are carried away by the fluid stream. The theoretical predictions and experimental results generally agree well for a range of field values, flow rates, and particle concentrations. A more accurate model of the collection process will enable development of more accurate models for arrays and entire filters.     

The use of 2D and 3D displays for shape-understanding versus relative-position tasks

Research on when and how to use three-dimensional (3D) perspective views on flat screens for operational tasks such as air traffic control is complex. We propose a functional distinction between tasks: those that require shape understanding versus those that require precise judgments of relative position. The distortions inherent in 3D displays hamper judging relative positions, whereas the integration of dimensions in 3D displays facilitates shape understanding. We confirmed these hypotheses with two initial experiments involving simple block shapes. The shape-understanding tasks were identification or mental rotation. The relative-position tasks were locating shadows and determining directions and distances between objects. We then extended the results to four experiments involving complex natural terrain. We compare our distinction with the integral/separable task distinction of Haskel and Wickens (1993). Applications for this research include displays for air traffic control, geoplots for military command and control, and potentially, any display of 3D information.     

Exploration of alloy 441 chemistry for solid oxide fuel cell interconnect application

Alloy 441 stainless steel (UNS S 44100) is being considered for application as an SOFC interconnect material. There are several advantages to the selection of this alloy over other iron-based or nickel-based alloys: first and foremost alloy 441ss is a production alloy which is both low in cost and readily available. Second, the coefficient of thermal expansion (CTE) more closely matches the CTE of the adjoining ceramic components of the fuel cell. Third, this alloy forms the Laves phase at typical SOFC operating temperatures of 600-800 °C. It is thought that the Laves phase preferentially consumes the Si present in the alloy microstructure. As a result it has been postulated that the long-term area specific resistance (ASR) performance degradation often seen with other ferritic stainless steels, which is associated with the formation of electrically resistive Si-rich oxide subscales, may be avoidable with alloy 441ss. In this paper we explore the physical metallurgy of alloy 441, combining computational thermodynamics with experimental verification, and discuss the results with regards to Laves phase formation under SOFC operating conditions. We show that the incorporation of the Laves phase into the microstructure cannot in itself remove sufficient Si from the ferritic matrix in order to completely avoid the formation of Si-rich oxide subscales. However, the thickness, morphology, and continuity of the Si-rich subscale that forms in this alloy is modified in comparison to non-Laves forming ferritic stainless steel alloys and therefore may not be as detrimental to long-term SOFC performance.