Context flow: An alternative to conventional pipelined architectures

In an earlier paper [Topham, Omondi, and Ibbet 1988] we reviewed conventional approaches to the design of conventional pipelined architectures and concluded that the underlying limitations of these techniques necessitate radical alternatives. This paper discusses one such alternative,micromultiprogramming, and examines several implementation proposals based on this approach. The weaknesses of these proposals are highlighted, and it is argued that they can be eliminated within the unifying theory of context flow architectures. Implementations of uniprocessor and multiprocessor context flow architectures are considered.     

Implant dose monitoring by MOS C–V measurement

The most critical parameter for deep sub-micron MOS field effect transistors is the threshold voltage, which is highly dependent on processing specifically, the ion implanted channel dose. Monitoring the channel doping on product wafers is highly desirable and is a major issue for process engineers. MOS C–V methods are widely used for process ramp up and monitoring and MOS C–V doping profiling is an introduced method for monitoring of low dose implants. However, the failure of the depletion approximation in the near surface region implies that conventional MOS C–V measurements yield erroneous doping profiles in that region. Integrating MOS C–V doping profiles yields only a partial implant dose excluding the important near surface dose portion. Here, we report a new approach, which enables the determination of the entire implant dose, taking into account the crucial surface region. Moreover, the MOS threshold voltage can be obtained self-consistently. The method is also applicable to MOS structures with ultra thin gate oxides.     

Activation of multi-modal cortical areas underlies short-term memory

We wanted to examine whether there are cortical fields active in short-term retention of sensory information, independent of the sensory modality. To control for selective attention, response selection and motor output, the cortical activity during short-term memory (STM) tasks was compared with that during detection (DT) tasks. Using positron emission tomography and [15O]-butanol as a tracer, we measured the regional cerebral blood flow in ten subjects during three STM tasks in which the subjects had to keep in mind: (i) the pitch of tones; (ii) frequencies of a vibrating stylus; and (iii) luminance levels of a monochrome light. Another group of ten subjects undertook three tasks in which subjects detected changes in similar stimuli. Six cortical fields were significantly more activated during STM than during DT. These fields were activated irrespective of sensory modality, and were located in the left inferior frontal gyrus, right superior frontal gyrus, right inferior parietal cortex, anterior cingulate, left frontal operculum and right ventromedial prefrontal cortex. Since the DT tasks and the STM tasks differed only with respect to the STM component, we conclude that the neuronal activity specifically related to retention of the stimuli during the delays was located in these six multi-modal cortical areas. Since no differences were observed in the sensory-specific association cortices, the results indicate further that the activity in the sensory-specific association cortices due to selective attention is not different from the activity underlying short-term retention of sensory information.     

Optimized partitioning of unstructured finite element meshes

We address the problem of automatic partitioning of unstructured finite element meshes in the context of parallel numerical algorithms based on domain decomposition. A two-step approach is proposed, which combines a direct partitioning scheme with a non-deterministic procedure of combinatorial optimization. In contrast with previously published experiments with non-deterministic heuristics, the optimization step is shown to produce high-quality decompositions at a reasonable compute cost. We also show that the optimization approach can accommodate complex topological constraints and minimization objectives. This is illustrated by considering the particular case of topologically one-dimensional partitions, as well as load balancing of frontal subdomain solvers. Finally, the optimization procedure produces, in most cases, decompositions endowed with geometrically smooth interfaces. This contrasts with available partitioning schemes, and is crucial to some modern numerical techniques based on domain decomposition and a Lagrange multiplier treatment of the interface conditions.     

Is there a correlation in breast carcinomas between tumor size and number of tumor vessels detected by gadolinium-enhanced magnetic resonance mammography?

Tumor vessels are known as a sign of malignancy in breast tumors. Is there a correlation between tumor size and the number of vessels in cases of breast tumor examined by dynamic gadolinium (Gd)-enhanced MR imaging? Eighteen patients (mean age, 46±7 years) underwent dynamic Gd-enhanced MR imaging of the breast by three-dimensional gradient echo sequence using thin-layer technique (2.5 mm) at 1.5T. The dynamic study included one precontrast and four postcontrast sequences (every 90 seconds) in coronal slices. Postprocessing by subtraction method and reconstruction in both transverse and sagittal planes were performed. All carcinomas showed rapid Gd enhancement. Tumor size (0.5 to 31.5 cm³; mean, 6.3±3.7 cm³) and number of vessels (1 to 10; mean, 3±2.1) were detected in summation of all three directions. A significant correlation was found between number of vessels and tumor size (r=0.787,p≤0.01). Breast tumor size significantly correlated with the number of vessels detected by Gd-enhanced MR mammography. The introduced method is a further important step in differentiating a carcinoma from a benign lesion.     

High temperature crystallization of poly(ethylene terephthalate)

Annealing poly(ethylene terephthalate) (PET) at high temperature results in a crystalline phase stable to 10°C higher than the temperature previously regarded as the equilibrium melting point. Melting temperatures as high as 289°C can be attained, which is equivalent to the equilibrium melting point determined herein for PET. The high melting point and tendency to superheat suggest that the crystals possess a substantial extended chain structure, notwithstanding the magnitude of the infrared fold band.     

Ammoxidation of propene over antimony-vanadium-oxide catalysts

Antimony-vanadium-oxide catalysts were prepared with various Sb/V ratios and were used for propene ammoxidation. It was observed that antimony in excess of the amount required for forming SbVO₄ was required to have a catalyst that is selective to acrylonitrile formation. Characterisation of catalysts with FTIR revealed partial reduction of the oxidised phase Sb_0.92V_0.92O₄ upon use to form Sb_0.95V_1.05O₄. XPS data showed the surfaces of most selective catalysts to be further enriched with antimony in course of the catalytic reaction, thereby creating a surface structure that is selective. For acrylonitrile formation a yield of 55% was obtained at 90% of conversion. In propene oxidation, on the other hand, the yield for acrolein formation was limited to 20% due to consecutive combustion of the aldehyde.     

Ab initio studies of single-height Si(001) steps

We have studied the Si(001) surface with single-height steps by ab initio molecular dynamics simulations. Surface dimers were found to be unstable with respect to buckling for all geometries considered. However, the ground state reconstruction depends on the type of step. For the SA step, the c(2 × 4) geometry is induced by the step edge, while, for the SB step, the p(2 × 2) reconstruction is more stable. The binding sites and diffusion barriers for a single Si adatom were investigated via the adiabatic trajectory method. In agreement with other studies of the flat surface, fast diffusion takes place along the dimer rows. The local changes to buckling induced by the adatom are sizable and lead to changes in the activation barriers for diffusion, in particular for the path perpendicular to the dimer rows. We also investigated the diffusion of the adatom over the rebonded SB step. The calculations show that there is no additional barrier for the arrival of the adatom at the edge from the upper terrace, while a barrier of at least 1 eV exists for the arrival of the adatom from the lower edge. In step flow growth involving the rebonded SB step, most of the adatoms will thus arrive from the upper terrace.     

The relationship of structural ischemic brain damage to neurobehavioural deficit: The effect of postischemic MK-801.

Examined whether an N-methyl-D-aspartate antagonist (MK-801) would improve neurobehavioral performance (NBP) concomitant with a reduction in cell damage. 17 male rats received forebrain ischemia and then received MK-801 or no therapy. Six rats underwent a sham operation. Surviving Ss completed a learning-set task (LST) in a swimming pool paradigm. Brain tissue was analyzed. LST performance of MK-801 treated Ss approached that of sham-operated Ss over the course of testing and was significantly better than controls. MK-801 had no long-term detrimental effect on LST performance, and there was significantly less damage in major brain regions of MK-801 treated Ss. The histology correlated significantly with NBP. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)