Solar thermal electric power systems: Comparison of line-focus collectors

Three types of line-focusing collectors: parabolic though, fixed slats with movable absorber and movable slats with fixed absorber, are evaluated to find those systems that are capable of producing the lowest costs of electrical energy. Minimum costs per kW-hr are found using sequential optimization techniques that consider variations in rim angle, reflectance, aperture width, length, orientation, tracking, contour error, slat width, slat curvature, tangent slat angle, slope, installation methods, materials, fabrication methods, absorptance, emittance, cover transmittance, field shape, layout, pipe sizes, insulation thicknesses and turbine-generator-cooling lower efficiencies and designs. This approach provides a uniform treatment of both cost and performance for a solar thermal electric power system. This uniform treatment of solar thermal electric power systems for all collector types insures that valid comparisons are made.     

Preliminary reference levels in interventional cardiology

This article describes the European DIMOND approach to defining reference levels (RLs) for radiation doses delivered to patients during two types of invasive cardiology procedures, namely coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA). Representative centres of six European countries recorded patients' doses in terms of dose-area product (DAP), fluoroscopy time and number of radiographic exposures, using X-ray equipment that has been subject to constancy testing. In addition, a DAP trigger level for cardiac procedures which should alert the operator to possible skin injury, was set to 300 Gyxcm2. The estimation of maximum skin dose was recommended in the event that a DAP trigger level was likely to be exceeded. The proposed RLs for CA and PTCA were for DAP 45 Gyxcm2 and 75 Gyxcm2, for fluoroscopy time 7.5 min and 17 min and for number of frames 1250 and 1300, respectively. The proposed RLs should be considered as a first approach to help in the optimisation of these procedures. More studies are required to establish certain "tolerances" from the proposed levels taking into account the complexity of the procedure and the patient's size.     

Processing-morphology relationships of compatibilized polyolefin/polyamide blends

The emulsifying effect of a polyethylene-based ionomer on the phase size/composition relationship was studied for polypropylene/polyamide and polyethylene/polyamide blends. The particle size measured for the uncompatibilized blends increased with minor phase concentration, particularly as the region of dual phase continuity was approached. This relationship was less pronounced when ionomer was added, and the dimensions of the dispersed phase were significantly reduced. A narrowing of the region of dual phase continuity was observed due to the addition of ionomer. An increase in the torque measured during melt blending in a Brabender mixing chamber resulted when ionomer was added, due to the increase in the interactions at the interface. The particle size determined for the uncompatibilized blends increased with viscosity ratio. The effect was also less pronounced for the compatibilized blends. From these observations, it was possible to conclude that the effect of interfacial modification on morphology predominates over that of composition and viscosity ratio. The effects were interpreted in terms of the reduction of interfacial mobility due to the compatibilization.     

Area and volume conservation among the elderly: Assessment and training.

Conducted 2 studies to examine whether the elderly maintain the competence to adequately solve problems of logical thinking. In the 1st study the performance of 60 noninstitutionalized middle-class elderly females was assessed on area and volume conservation tasks. On overall performance only 33.3% of the Ss were classified as conservers. In the 2nd study a training paradigm was used to determine whether simple verbal feedback activated the strategies required for adequate performance on conservation tasks. 22 Ss who failed at least 2 conservation tasks in the assessment study were administered a 20-trial training procedure. Half of these Ss received simple verbal feedback following each response, while half received no feedback. Results on an immediate posttest indicated that the feedback group performed significantly better than the control group on the near transfer posttest task and on the majority of far transfer tasks. The results are discussed in terms of a distinction between competence and performance. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phylogenetic and physiological diversity of sulphate-reducing bacteria isolated from a salt marsh sediment

Xenopus blastula cells activate different mesodermal genes as a concentration-dependent response to activin, which behaves like a morphogen. To understand how cells recognize morphogen concentration, we have bound naturally labeled activin to cells and related this to choice of gene activation. We find that the increasing occupancy of a single receptor type can cause cells to switch gene expression. Cells sense ligand concentration by the absolute number of occupied receptors per cell (100 and 300 molecules of bound activin induce Xbra and Xgsc, respectively, i.e., 2% and 6% of the total receptors) and not by a ratio of occupied to unoccupied receptors. The long duration of occupancy explains a previously described ratchet effect. Our results suggest a new concept of morphogen gradient formation and interpretation that is particularly well suited to the needs of early development.     

Implementation of service systems on the shop-floor level in financial service companies. Empirical evidence from Australia and Germany

This article presents the practices of Australian and German financial service providers regarding the implementation of shop-floor control within different types of service systems. The results delivered in this article should serve as a guideline for future research to develop and adapt methods for shop-floor control in financial service systems. Interviews with 25 experts from the Australian and German financial services industry reveal novel insights into the practice of shop-floor control, suggesting that methods and concepts from manufacturing are only used to a limited extent for shop-floor control. Shop-floor control is mostly used to react quickly to unexpected deviations due to a low usage of forecasts and information systems. Thus, there seems to be improvement potential in the financial services industry in comparison with in the manufacturing industry in terms of shop-floor control. Further research within the production research area should use the empirical insights to test and adapt existing methods and to develop new ones, taking cultural differences into account.     

Optimal scan for time-varying tomography. I. Theoretical analysisand fundamental limitations

The authors consider the tomographic reconstruction of objects with spatially localized temporal variation, such as a thorax cross section with a beating heart. The conventional scan format, in which projections are taken progressively around the object, requires high and sometimes infeasible scan rates to avoid motion artifacts in the reconstructed images. The authors formulate the problem of data acquisition as a time-sequential sampling problem of spatially and temporally bandlimited signals, where only one view can be taken at a time, but the time interval between successive views is independent of their angular separation. These conditions, naturally satisfied in magnetic resonance imaging and in X-ray CT using the Imatron system, can also be satisfied by a conventional system with a continuously and rapidly spinning gantry with source pulsing. Theoretical analysis, which includes tight performance bounds, shows that by using an optimally scrambled angular sampling order, the required scan rate can be lowered as much as four times, while preserving image quality. The analysis also greatly simplifies the design of the optimum scan pattern by reducing it to a constrained geometric packing problem.