Performance testing of a linear fresnel reflector

Results of optical and thermal performance evaluation tests conducted on a prototype linear Fresnel reflector system fabricated using locally available material are presented in this paper.     

Decentralized semaphore support in a virtual shared-memory system

Distributed shared memory has increasingly become a desirable programming model on which to program multicomputer systems. Such systems strike a balance between the performance attainable in distributed-memory multiprocessors and the ease of programming on shared-memory systems. In shared-memory systems, concurrent tasks communicate through shared variables, and synchronization of access to shared data is an important issue. Semaphores have been traditionally used to provide this synchronization. In this paper we propose a decentralized scheme to support semaphores in a virtual shared-memory system. Our method of grouping semaphores into semaphore pages and caching a semaphore at a processor on demand eliminates the reliability problems and bottlenecks associated with centralized schemes. We compare the performance of our scheme with a centralized implementation of semaphores and conclude that our system performs better under high semaphore access rates as well as larger numbers of processors.     

Potential antifilarial activity of roots of Asparagus adscendens Roxb, against Setaria cervi in vitro

The effect of dipole-dipole cross correlations on the net nuclear Overhauser effect (NOE) has been analyzed here for realistic systems by extending the three-spin calculations to four and five spins in order to account for additional cross correlations and spin diffusion. These have been compared with the addition of leakage terms to the three-spin system. The additional spins enhance cross-correlation effects on one hand but on the other act as supplementary relaxation pathways for the magnetization to diffuse. This analysis shows that for a linear array of spins in the long-correlation limit, dipole-dipole cross correlations increase net NOE, while spin diffusion decreases it, and that the cumulative effect is a reduced effect of cross correlations. In other geometries and correlation limits, the effect of cross correlations on net NOE is generally small.     

Optimization of thermal interface materials for electronics cooling applications

Thermal interface materials (TIMs) are used in electronics cooling applications to decrease the thermal contact resistance between surfaces in contact. A methodology to determine the optimal volume fraction of filler particles in TIMs for minimizing the thermal contact resistance is presented. The method uses finite element analysis to solve the coupled thermo-mechanical problem. It is shown that there exists an optimal filler volume fraction which depends not only on the distribution of the filler particles in a TIM but also on the thickness of the TIM layer, the contact pressure and the shape and the size of the filler particles. A contact resistance alleviation factor is defined to quantify the effect of these parameters on the contact conductance with the use of TIMs. For the filler and matrix materials considered-platelet-shaped boron nitride filler particles in a silicone matrix-the maximum observed enhancement in contact conductance with the use of TIMs was by a factor of as much as nine.     

The effect of financing decisions on the choice of manufacturing technologies

This paper demonstrates the importance of jointly considering financing and technology choices when making manufacturing investments. We show that considerable value can be added to investments through financing decisions, and that the gains due to financing are sensitive to technology choice. A model of financing and technology choice is presented that considers differences in cost structure and product flexibility, and applies it to an example involving flexible manufacturing systems (FMSs). Three main results emerge. First, optimal financing decisions are different for different technologies and the choice of technology can change when financing and technology decisions are made simultaneously. Second, if one technology's fixed and variable costs are lower or its initial investment higher than another technology's the former has higher value added due to financing. Since empirical data shows that FMS and conventional technologies have this pattern, ignoring the benefits of debt financing leads to undervaluation of new technology. Third, product flexibility can add considerable value through its effect on financing decisions because product flexibility reduces variability of cash flows. A major conclusion is that financing and technology choice are long-term strategic decisions that should be made jointly. Firms that make these decisions separately, not considering the effect of one on the other, may make suboptimal technology decisions.     

Elevated plasma osteopontin in metastatic breast cancer associated with increased tumor burden and decreased survival

Osteopontin (OPN) is a secreted, integrin-binding phosphoprotein that has been implicated in both normal and pathological processes; qualitative increases in OPN blood levels have been reported in a small number of patients with metastatic tumors of various kinds. We measured plasma OPN levels in 70 women with known metastatic breast carcinoma, 44 patient controls who were on follow-up after completion of adjuvant treatment for early breast cancer, and 35 normal volunteers. The median plasma OPN of patients with metastatic disease was 142 microgram/liter (range, 38-1312 microgram/liter) and was significantly different (P < 0.0001, Mann Whitney U test) from both control groups (medians, 60 and 47 microgram/liter; ranges, 15-117 and 22-122 microgram/liter). Furthermore, we found that increasing plasma OPN is associated with shorter survival (P < 0.001) when patients were grouped in terciles for plasma OPN. This was also demonstrated when using a Cox proportional hazards model. Median plasma OPN levels were significantly increased for three or more sites of involvement (median, 232 microgram/liter; n = 13) versus 1 or 2 metastatic sites (medians, 129 and 130 microgram/liter; n = 29 and 28, respectively). Plasma OPN levels were correlated with other biochemical markers related to the extent of disease, such as serum alkaline phosphatase, aspartate succinate aminotransaminase, and albumin (r = 0.81, 0.62, and -0.56, respectively; all P < 0.001). This study demonstrates a statistically significant elevation in plasma OPN in the majority ( approximately 70%) of a large series of patients with metastatic breast cancer when compared (95th percentile) to healthy women or patients who had completed adjuvant treatment for early-stage breast cancer. Furthermore, this is the first study to demonstrate that higher OPN levels in patients with metastatic breast cancer may be associated with an increased number of involved sites and decreased survival.     

Atherosclerosis: are dairy products safe?

The role of lipids, particularly saturated fats, in the development of atherosclerosis and other heart diseases has been widely accepted. It is generally recommended that animal food products, namely, eggs, meat and dairy products, especially butter, butteroil, ghee, cheese, etc, which contain high levels of saturated fatty acids, should be minimized in the diet. The diet-heart issue and the role of fats in the development of atherosclerosis are reviewed with emphasis on the need to explore other factors which significantly affect the circulation of blood. It is concluded that it is not the type of fat but the balance of dietary components that contributes to the development of atherosclerosis.     

Reactive blends of epoxy resin (DGEBA) crosslinked by anionically polymerized polycaprolactam. II. Mechanical and electrical properties

Various reactive blends of diglycidyl ether of bisphenol A (DGEBA)/polycaprolactam were synthesized by anionic polymerization at 140°C, conducted by sodium hydride catalyst, a strong base, along with N‐acetyl caprolactam as a cocatalyst. The experiments were performed to study the effect of composition on the mechanical and electrical properties of the reactive blends, such as tensile properties, flexural properties, Izod impact strength, Rockwell hardness, and volume resistivity. It was observed that the DGEBA was crosslinked by the polycaprolactam through the rapid reaction of the oxirane group with amide nitrogen. The heat of reaction and heat‐deflection temperature of the reactive blends increased with increasing DGEBA content from 50 to 80 wt %, and increased dramatically above 70 wt % DGEBA content. The mechanical and electrical properties of the reactive blends increased with increasing DGEBA content from 50 to 80 wt %. Substantial increases in these properties were observed above 70 wt % DGEBA content in the reactive blends. SEM studies revealed that the reactive blends show a multiphase system with an increase in the DGEBA content from 50 to 80 wt % as the mixing of the two phases increased. The reactive blend Ep₈₀Ca₂₀, with 80 wt % DGEBA content, resembles a single‐phase system because of better mixing of the two phases; as a result, this reactive blend showed the highest mechanical and electrical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 537–549, 2005