A state space analysis of propose-and-revise

A central research topic in the area of knowledge engineering is the reuse of problem-solving methods for developing knowledge based systems. For being able to reuse a problem-solving method it is important to know under which restrictions a problem-solving method is appropriate to solve a given problem. This paper describes the problem-solving method propose-and-revise as well as the way this problem-solving method searches in its problem space for a solution. A quantitative analysis of the efficiency of this search process is given. Additionally, task and domain specific properties and restrictions and their influence on the efficiency of the search process are considered. For these purposes an instance of the problem-solving method is transformed to a corresponding instance of a Stanford Research Institute Problem Solver (STRIPS) planning system. Then the problem-solving method is considered as an additional control strategy for such a planning system. By this way the various insights and analysis results which are available in the area of planning systems may be exploited for the analysis of problem-solving methods. ©1999 John Wiley & Sons, Inc.     

Flow mixing inside a control-rod guide tube – Experimental tests and CFD simulations

This paper covers a combined experimental and computational effort carried out at Vattenfall Research & Development AB in order to study the thermal mixing in the annular region between a top tube and a control-rod stem. The low frequency thermal fluctuations in this region can result in problems with thermal fatigue and have caused cracks in the control-rod stems of several nuclear reactors ( [Kobayashi et al., 2009] and [0070] ).The flow in the vertical annular region formed by the top tube and the control-rod stem is characterized by the mixing of hot bypass flow with cold crud-removal flow. The crud-removal flow is flowing upwards along the control-rod stem, and the warmer bypass flow is entering through eight horizontal holes positioned in the lower part of the guide tube and four holes in the upper part of the top tube, forming jets.Two full-scale models of a control rod, including the control-rod stem and the guide tube, were constructed. The first model, designed to work at atmospheric conditions, was made of Plexiglass, in order to be able to visualize the mixing process, whereas the second one was made of steel to allow for a higher temperature difference between the two flows, and the heating of the top tube.CFD simulations of the case at atmospheric conditions were also carried out.Both the experiments and the simulations showed that the mixing region between the cold crud-removal flow and the warm bypass flow is dominated by large flow structures coming from above. The process is characterized by low frequency, high amplitude temperature fluctuations. The process is basically hydrodynamic, caused by the downward transport of flow structures originated at the upper bypass inlets. The damping thermal effects through buoyancy is of secondary importance, as also the scaling analysis shows, however a slight damping of the temperature fluctuations can be seen due to natural convection due to a pre-heating of the cold crud-removal flow. The comparison between numerical and experimental results shows a rather good agreement, indicating that experiments with plant conditions are not necessary since, through the existing scaling laws and CFD calculations, the obtained results may be extrapolated to plant conditions.The problem of conjugate heat transfer has not yet been addressed experimentally since complex and difficult measurements of the heat transfer have to be carried out. These types of measurements, along with corresponding CFD calculations, constitute one of the main challenges to be dealt with in ongoing work.     

Reflective bistable nematic displays (BiNem®) fabricated by standard manufacturing equipment

Abstract— Bistable liquid‐crystal displays have been developed by using BiNem® technology. In this paper, the BiNem® principle, addressing, power consumption, reflective mode, and manufacturing process will be described, and performance of the latest displays will be discussed. We will show that this technology has simultaneously low power consumption due to bistability, very good visual quality, passive‐addressing mode, and a manufacturing process compatible with STN mass‐production equipment.     

Bone marrow failure by cytomegalovirus is associated with an in vivo deficiency in the expression of essential stromal hemopoietin genes

Bone marrow (BM) failure associated with cytomegalovirus (CMV) infection is a feared complication after clinical BM transplantation. Experiments in long-term BM cultures have indicated that BM stromal cells (BMSC) are targets of productive CMV infection, but an in situ infection of BM stroma remained to be documented, and the pathomechanism is open to question. Here we describe a murine in vivo model of lethal CMV aplastic anemia (CMV-AA). The reconstitution of hematopoietic progenitor cells expressing stem cell factor (SCF) receptor was found to be defective in CMV-AA. While murine CMV replication in permissive parenchymal tissues is cytolytic, the hematopoietic cord was found to be a site of very limited virus production with foci of reticular BMSC expressing the intranuclear viral IE1 protein, but with only a few BMSC positive for viral genome in the in situ hybridization. XX-XY BM chimeras were established in order to quantitate Y-chromosome-tagged BMSC by a PCR specific for the male-sex-determining gene Tdy. This approach revealed that murine CMV infection is not associated with a significant loss of BMSC. Despite the physical integrity of the stromal network, the functional integrity of the stroma was impaired. While housekeeping genes were expressed normally in BMSC of infected mice, the expression of genes encoding the essential hemopoietins SCF, granulocyte colony-stimulating factor, and interleukin-6 was markedly reduced. In conclusion, the mechanism of BM failure is not a stromal lesion but an insufficient stromal function. These findings explain CMV-AA as a manifestation of multiple hemopoietin deficiency.     

Control of cytomegalovirus in bone marrow transplantation chimeras lacking the prevailing antigen-presenting molecule in recipient tissues rests primarily on recipient-derived CD8 T cells

Cytomegalovirus (CMV) infection during the transient immunodeficiency after bone marrow transplantation (BMT) develops into disease unless antiviral CD8 T cells are restored in due course. Histoincompatibility between donor and recipient is associated with increased risk. Complications may include a rejection response against the foreign major histocompatibility complex (MHC) antigens and a lack of antiviral control resulting from a misfit between donor-derived T cells and the antigenic viral peptides presented in recipient tissues. Here we have established a murine model of CMV disease after experimental BMT performed across a single MHC class I disparity. Specifically, BALB/c bone marrow cells expressing the prevailing antigen-presenting molecule Ld were transplanted into the Ld gene deletion mutant BALB/c-H-2(dm2), an experimental setting that entails a selective risk of host-versus-graft but not graft-versus-host response. The reconstituted T-cell population proved to be chimeric in that it consisted of Ld-positive donor-derived and Ld-negative recipient-derived cells. Pulmonary infiltrates did not include cytolytic T cells directed against Ld. This finding implies that the infection did not trigger a host-versus-graft response. Notably, upon adoptive transfer, donor-derived CD8 T cells preferentially protected tissues of donor genotype, whereas recipient-derived CD8 T cells protected tissues of either genotype. We infer from these data that the focus on immunodominant antigens presented by Ld within the donor cell population distracted the donor T cells from protecting recipient tissues and that protection in the chimeras was therefore primarily based on recipient T cells. As a consequence, T-cell chimerism after BMT should give a positive prognosis with respect to control of CMV.     

Parafoveal processing of word n + 2 during reading: Do the preceding words matter?

We used the boundary paradigm (Rayner, 1975) to test two hypotheses that might explain why no conclusive evidence has been found for the existence of n + 2 preprocessing effects. In Experiment 1, we tested whether parafoveal processing of the second word to the right of fixation (n + 2) takes place only when the preceding word (n + 1) is very short (Angele, Slattery, Yang, Kliegl, & Rayner, 2008); word n + 1 was always a three-letter word. Before crossing the boundary, preview for both words n + 1 and n + 2 was either incorrect or correct. In a third condition, only the preview for word n + 1 was incorrect. In Experiment 2, we tested whether word frequency of the preboundary word (n) had an influence on the presence of preview benefit and parafoveal-on-foveal effects. Additionally, Experiment 2 contained a condition in which only preview of n + 2 was incorrect. Our findings suggest that effects of parafoveal n + 2 preprocessing are not modulated by either n + 1 word length or n frequency. Furthermore, we did not observe any evidence of parafoveal lexical preprocessing of word n + 2 in either experiment. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Finishing high precision quartz balls

This paper describes a four cup lapping machine for finishing balls of 40 mm diameter to a roundness of 10^?6 diameters or better. The spring loaded lapping cups are spaced tetrahedrally for maximum size and uniform distribution over the ball surface. A four cam control mechanism switches the sense of rotation of the four lapping motors in such a way that the ball rotates about a different axis at each switching. This achieves good uniformity in lapping action. Motor rotation combinations which would produce a ball rotation in or near to a cup axis are avoided. Lapping tests have produced roundness of $\text{25 × 10}{}^{\mathrm{?6}}\text{mm}$