Effects of adsorbed water and sample aging in air on the μN level adhesion force between Si(100) and silicon nitride

The microscale adhesion force of single crystal silicon (100) to silicon nitride was studied using a newly developed micro/nanoadhesion measurement apparatus. The effect of water adsorption on adhesion between clean surfaces and surfaces aged in air was determined. During experiments, varying relative humidity (RH) controlled water adsorption. Clean and aged samples showed measurably changed water adsorption and adhesion above 60% RH only, and aged samples showed more water adsorption and adhesion than clean ones above 90% RH. A contaminant film grew to a saturated thickness of about 6 Å over 50 days of aging, and the film changed surface chemistry which resulted in higher contact angle. The contaminated surface with higher contact angle exhibited more affinity for water and microadhesion on the molecular scale, which is contrary to the common interpretation of contact angle data. The divergence of water adsorption and adhesion force behavior between clean and aged samples above 90% RH may indicate that the Kelvin radius became comparable to a characteristic length on the contaminated surface at high RH. A molecular model is proposed in which the contaminant film provides porosity, which allows capillary condensation and the growth of a multilayer water film.     

Effect of surface chemistry on the tribological performance of a MEMS electrostatic lateral output motor

The effect of surface chemistry on the tribological performance and reliability of a MEMS lateral output motor is reported. Relative humidity (RH) and octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) coatings were used to change surface chemistry. Electrical and tribological performance of uncoated and OTS-coated motors were found to be dependent on RH. For uncoated motors, excessive wear of sliding contacts and welding (permanent adhesion) of static contacts were observed at 0.1% RH. Degradation of electrostatic force and high static friction (stiction) forces limited dynamic performance and reliability and caused device sticking at and above 70% RH. Around 50% RH, uncoated motors exhibited negligible wear, low adhesion, and a wear life at least three orders of magnitude longer than in the dry environment (experiments were stopped without failure after about one billion cycles). Water vapor behaved as a gas phase replenishable lubricant by providing a protective adsorbed film. The OTS coating broadened the operating envelope to 30–50% RH and reduced stiction, which allowed better dynamic performance at high RH. The OTS coating improved durability at 0.1% RH, but it was still poor. At high RH, stiction problems reoccurred when the OTS coating was worn away. By controlling and balancing surface chemistry (adsorbed water and OTS), excellent performance, low friction and wear, and excellent durability were attained with the lateral output motor.     

COX-2 Inhibition and Inhibition of Cytosolic Phospholipase A2 Increase CD36 Expression and Foam Cell Formation in THP-1 Cells

Cardiovascular safety of cyclooxygenase (COX)-2-selective inhibitors and nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) is of worldwide concern. COX-2 inhibitors and NSAIDs act by inhibiting arachidonic acid metabolism to prostaglandins. They confer a cardiovascular hazard manifested as an elevated risk of myocardial infarction. Mechanisms underlying these cardiovascular effects are uncertain. Here we determine whether interference with cytosolic phospholipase A2 (cPLA-2) or COX-2 through pharmacologic blockade or silencing RNA impacts expression of scavenger receptor CD36 and scavenger receptor A, both involved in cholesterol uptake in monocytes and macrophages. THP-1 human monocytes and human peripheral blood mononuclear cells were exposed to celecoxib, a COX-2 selective inhibitor currently in clinical use, and to arachidonyl trifluoromethyl ketone (AACOCF3), an arachidonic acid analog that selectively inhibits cPLA-2. Celecoxib and AACOCF3 each upregulated expression of CD36, but not scavenger receptor A, as determined by quantitative PCR and immunoblotting. Silencing of cPLA-2 or COX-2 had comparable effects to pharmacologic treatments. Oil red O staining revealed a profound increase in foam cell transformation of THP-1 macrophages exposed to either celecoxib or AACOCF3 (both 25 μM), supporting a role for the COX pathway in maintaining macrophage cholesterol homeostasis. Demonstration of disrupted cholesterol balance by AACOCF3 and celecoxib provides further evidence of the possible mechanism by which COX inhibition may promote lipid overload leading to atheromatous lesion formation and increased cardiovascular events.     

New process for the production of better quality rapeseed oil and meal: II. Detoxification and dehulling of rapeseeds — feasibility study

Feasibility studies have shown that a white, bland, defatted, thioglucoside-free flour can be prepared from rapeseed. The thioglucosides, the precursors of toxic principles, present in rapeseeds are removed by aqueous extraction. The key operations, boiling of the seed followed by wet-grinding and aqueous extraction, help in the removal of seed coat from the rapeseed. Although aqueous extraction results in the loss of solids, the quality of the end products is good and may offset the loss. Issued as No. 108 of the Food Research Institute.     

Investigation of heat pipe cooling in drilling applications.: part I: preliminary numerical analysis and verification

A combined numerical and experimental study is performed to analyze the feasibility of using heat pipe cooling in drilling applications. A parametric study is conducted to analyze the effect of different geometrical parameters expected for a heat pipe drill configuration, such as depth of the heat pipe within the drill, heat pipe diameter, heat flux input magnitude and length of the heat input zone. In this model, it is assumed that the drill is subjected to a static heat source which verifies the analysis and feasibility of using heat pipe cooling in drilling operations. The performance of the heat pipe drill model is approximated using a solid cylinder model of pure conduction. To validate the assumptions, numerical results are compared with experimental data that are based on the solid cylinder model. Both the numerical and experimental studies show that the use of a heat pipe in a drill can reduce the temperature field significantly. The results of this study can be used to define geometrical parameters for ‘optimal’ design and the setup for further analysis.     

Off-grid energy services for the poor: Introducing LED lighting in the Millennium Villages Project in Malawi

Lanterns that use light-emitting diodes (LEDs) powered by batteries, which are in turn charged by grid electricity or small solar panels, have emerged as a cost-competitive alternative to kerosene and other fuel-based lighting technologies, offering brighter light for longer duration at equal or lower cost over time. This paper presents lessons learned from the introduction of solar LED lanterns in rural Malawi. We discuss a market-based program using new and existing local commercial structures such as vendors and cooperatives to sell lanterns to village households without subsidy. The paper addresses issues of enterprise development, community interactions, and survey data on lighting use and expenditure patterns before and after LED lantern introduction. Households that purchased a lantern reported high levels of satisfaction with the LED lanterns as well as savings in annual kerosene expenditure comparable to the price of the lantern. These households also reported monthly incomes comparable to the price of the LED lanterns whereas non-adopters surveyed reported monthly incomes about half this level, suggesting a need for financing options to maximize adoption among poorer populations in rural areas. These results suggest that similar market based models of LED lighting technology dissemination have the potential to be replicated and scaled up in other off-grid regions in developing countries. However, viability of local cooperatives and supply chains for lantern products over the medium-to-long term remain to be assessed.     

Positive inotropic effect of the leaf extracts of parent and tissue culture plants of Coleus amboinicus on an isolated perfused frog heart preparation

The leaves of the indigenous plant Coleus amboinicus Lour (Lamiaceae) possess a characteristic aroma and are used in many food preparations to enhance the flavour. Apart from this, they also exhibit medicinal properties. Aqueous extracts of fresh leaves of C. amboinicus Lour. parent (CAP), as well as tissue culture-raised plants (CAT), showed a dose-dependent positive inotropic effect on isolated frog heart. The extracts of CAT showed higher activity. The responses to CAP and CAT (50–800 μg) were not affected in either way by propranolol, atropine, verapamil or imidazole. The responses to both CAP and CAT were inhibited after lowering sodium chloride concentration (from 111 to 55.6 mM) and potentiated after increasing sodium chloride concentration (from 111 to 222 mM). Lignocaine was found to inhibit the responses significantly. Thus, C. amboinicus induces a positive inotropic effect, possibly by increasing sodium influx, leading to greater intracellular availability of calcium.     

Magnesium levels in serum and erythrocytes of children from Kerala

BACKGROUND: Magnesium is required in higher quantities, during the phase of rapid growth, in children. Its level in the ground water in Kerala is low. This can cause magnesium deficiency especially in children from the lower socio-economic groups who also suffer from nutritional insufficiency. METHODS: We compared the serum and erythrocyte magnesium levels of school children from high and low (agricultural labourers and fisherfolk) socio-economic groups. These levels were determined using atomic absorption spectrophotometry. Body mass indices and haemoglobin levels were used as indirect measures of nutritional status. RESULTS: Serum and erythrocyte magnesium levels were significantly lower in both boys and girls from low socio-economic groups who also had lower body mass indices. CONCLUSION: Nutritional insufficiency is prevalent in children from the low socio-economic groups and is associated with low serum and erythrocyte magnesium levels.