Reduction of Context Switches due to Task Synchronization in Uniprocessor and Multiprocessor Platform

The problem of frequent context switches in multitasking is a real scheduling overhead which wastes extra CPU cycles, memory and causes much delay in scheduling. This paper focuses on reducing the context switches that result due to blocking when jobs are required to synchronize. The Priority Ceiling Protocol (PCP) is used to synchronize the tasks in uniprocessor as well as multiprocessor platforms. The jobs are scheduled using Earliest Deadline First (EDF) policy. The simulation results show that the context switches are reduced by about 20% on an average using our technique of avoiding context switches due to blocking

Non-affine deformation in microstructure selection in solids: I. Molecular dynamics

We study the nucleation dynamics and microstructure selection in a model two-dimensional solid undergoing a square to rhombic transformation, using coarse-grained molecular dynamics (MD) simulations. We find a range of microstructures depending on the depth of quench. The transformations are accompanied by the creation of transient and localized non-affine zones (NAZ), which evolve with the rapidly moving parent-product interface. These plastic regions are created beyond a threshold stress, at a rate proportional to the local stress. We show that the dynamics of NAZs determines the selection of microstructure, including the ferrite and martensite

Effect of city pollution and its cleansing treatments on hair

With the increasing pollution in urban areas, so has the demand for anti-pollution hair care products. Hair care manufacturers are introducing formularies to fight particulate matter pollution by prevention and treatment/cleansing. The claims are often written in the product descriptions on the webpage, and not boldly displayed on the container. This opens the door for claims substantiation testing. This paper will outline the TRI Princeton test protocol designed to study the effect of city air-borne pollutants on hair and their resultant effects on quality of hair. Please click Additional Files below to see the full abstract

Sphingosine-1-phosphate promotes the differentiation of adipose-derived stem cells into endothelial nitric oxide synthase (eNOS) expressing endothelial-like cells.

BACKGROUND: Adipose tissue provides a readily available source of autologous stem cells. Adipose-derived stem cells (ASCs) have been proposed as a source for endothelial cell substitutes for lining the luminal surface of tissue engineered bypass grafts. Endothelial nitric oxide synthase (eNOS) is a key protein in endothelial cell function. Currently, endothelial differentiation from ASCs is limited by poor eNOS expression. The goal of this study was to investigate the role of three molecules, sphingosine-1-phosphate (S1P), bradykinin, and prostaglandin-E1 (PGE1) in ASC endothelial differentiation. Endothelial differentiation markers (CD31, vWF and eNOS) were used to evaluate the level of ASCs differentiation capability. RESULTS: ASCs demonstrated differentiation capability toward to adipose, osteocyte and endothelial like cell phenotypes. Bradykinin, S1P and PGE were used to promote differentiation of ASCs to an endothelial phenotype. Real-time PCR showed that all three molecules induced significantly greater expression of endothelial differentiation markers CD31, vWF and eNOS than untreated cells. Among the three molecules, S1P showed the highest up-regulation on endothelial differentiation markers. Immunostaining confirmed presence of more eNOS in cells treated with S1P than the other groups. Cell growth measurements by MTT assay, cell counting and EdU DNA incorporation suggest that S1P promotes cell growth during ASCs endothelial differentiation. The S1P1 receptor was expressed in ASC-differentiated endothelial cells and S1P induced up-regulation of PI3K. CONCLUSIONS: S1P up-regulates endothelial cell markers including eNOS in ASCs differentiated to endothelial like cells. This up-regulation appears to be mediated by the up-regulation of PI3K via S1P1 receptor. ASCs treated with S1P offer promising use as endothelial cell substitutes for tissue engineered vascular grafts and vascular networks

Design and fabrication of a hydroformed absorber for an evacuated flat plate solar collector

The concept of an evacuated flat plate collector was proposed over 40 years ago but, despite its professed advantages, very few manufacturers have developed commercial versions. The absorber is a key component of a flat plate collector: in the context of an evacuated panel, absorber design poses a number of technical challenges. A flooded panel absorber has been designed for use in evacuated flat plate solar collectors. The aim was to obtain higher efficiency, in a low out-gassing material, than would be possible using a conventional serpentine tube design. Initial plans for a micro-channel plate were modified when optimisation analysis showed that a flooded panel could achieve as good performance with easier fabrication. The absorber plate is made from hydroformed stainless steel sheets welded together and features an array of through-holes for the glass supporting pillars with the square panel sub-divided into two rectangles connected in series for ease of fabrication and better flow distribution. The coolant flow was modelled in Star-CCM+. FEM simulations based on tensile test data informed the choice of sheet thickness and weld radius around the holes to withstand the 1 bar pressure differential. Hydroforming is an effective method for producing sheet metal components, e.g. plates for heat exchangers or solar absorbers. As a thermal engineering experimental technique, the tooling is significantly cheaper than press tools since the mould does not need a matching die. In a research context, the ability to form plates in-house and explore profile and tooling options at low cost is very useful and might find application in other fields such as experimental heat exchangers. A hydroforming facility was built using 85 mm thick steel sheet and a 25 MPa hydraulic pump. This proved highly effective at forming 0.7 mm stainless steel sheet. A total of eight absorbers were fabricated and successfully leak tested using helium. Two variants were made: one kind for use in enclosures with a metallic rear tray, the other for enclosures with glass on both sides. The collector efficiency factor is estimated to be 3% higher than for commercial tube-on-plate designs

An evacuated enclosure design for solar thermal energy applications

Flat-plate solar thermal collector technology when coupled with vacuum enclosure technology has potential to supply clean energy efficiently for use in applications including residential water and space heating. This paper focuses on the design of vacuum enclosures for flat-plate solar collectors with specific reference to vacuum enclosures designed for thin micro-channel solar absorber plates (thickness < 10mm). The expectations, requirements and applications of these solar collectors are discussed along with a description of an enclosure concept under consideration. Potential seal materials are identified and their limitations discussed. Finite element modelling results are presented and conclusions made regarding design parameter selection