Antigenic determinants of Staphylococcus aureus type 5 and type 8 capsular polysaccharide vaccines

Bacterial capsular polysaccharides (CP) are carbohydrate polymers comprised of repeating saccharide units. Several of these CP have side chains attached to their backbone structures. The side chains may include O-acetyl, phosphate, sialic acid, and other moieties. Those moieties represent the immunodominant epitopes and the most functional ones. The clinically significant Staphylococcus aureus type 5 CP (CP 5) and type 8 CP (CP 8) are comprised of a trisaccharide repeat unit with one O-acetyl group attached to each repeat unit. The immunogenicity of these CP and the functionality of antibodies to the backbone and the O-acetyl moieties were investigated. Immunization with the native CP conjugates (CP with 75% O-acetylation) elicited a high proportion of antibodies directed against the O-acetyl moiety. Nonetheless, all of the vaccinees produced antibodies to the backbone moieties as well. Conjugate vaccines made of de-O-acetylated CP elicited backbone antibodies only. Antibodies to both backbone and O-acetyl groups were found to be opsonic against S. aureus strains which varied in their O-acetyl content. Absorption studies with O-acetylated and de-O-acetylated CP showed that (i) native CP conjugates generated antibodies to both backbone and O-acetyl groups and (ii) O-acetylated isolates were opsonized by both populations of antibodies while the non-O-acetylated strains were predominantly opsonized by the backbone antibodies. These results suggest that S. aureus CP conjugate vaccines elicit multiple populations of antibodies with diverse specificities. Moreover, the antibodies of different specificities (backbone or O-acetyl) are all functional and efficient against the variations in bacterial CP that may occur among clinically significant S. aureus pathogenic isolates.     

Effect of Reynolds numbers on flow past four square cylinders in an in-line square configuration for different gap spacings

In this paper two-dimensional (2-D) numerical investigation of flow past four square cylinders in an in-line square configuration are performed using the lattice Boltzmann method. The gap spacing g = s/d is set at 1, 3 and 6 and Reynolds number ranging from Re = 60 to 175. We observed four distinct wake patterns: (i) a steady wake pattern (Re = 60 and g = 1); (ii) a stable shielding wake pattern (80 ≤ Re ≤ 175 and g = 1); (iii) a wiggling shielding wake pattern (60 ≤ Re ≤ 175 and g = 3) and (iv) a vortex shedding wake pattern (60 ≤ Re ≤ 175 and g = 6). At g = 1, the Reynolds number is observed to have a strong effect on the wake patterns. It is also found that at g = 1, the secondary cylinder interaction frequency significantly contributes for drag and lift coefficients signal. It is found that the primary vortex shedding frequency dominates the flow and the role of secondary cylinder interaction frequency almost vanish at g = 6. It is observed that the jet between the gaps strongly influenced the wake interaction for different gap spacing and Reynolds number combination. To fully understand the wake transformations the details vorticity contour visualization, power spectra of lift coefficient signal and time signal analysis of drag and lift coefficients also presented in this paper.     

A hybrid intelligent system to improve predictive accuracy for cache prefetching

Cache being the fastest medium in memory hierarchy has a vital role to play for fully exploiting available resources, concealing latencies in IO operations, languishing the impact of these latencies and hence in improving system response time. Despite plenty of efforts made, caches alone cannot comprehend larger storage requirements without prefetching. Cache prefetching is speculatively fetching data to restrain all delays. However, effective prefetching requires a strong prediction mechanism to load relevant data with higher degree of accuracy. In order to ameliorate the predictive performance of cache prefetching, we applied the hybrid of two AI approaches named case based reasoning (CBR) and artificial neural networks (ANN). CBR maintains the past experience and ANN are used in adaptation phase of CBR instead of employing static rule base. The novelty of technique in this domain is valued due to hybrid of two approaches as well as usage of suffix tree in populating the CBR’s case base. Suffix trees provide rich data patterns for populating case base and greatly enhanced the overall performance. A number of evaluations from different aspects with varying parameters are presented (along with some findings) where the efficacy of our technique is affirmed with improved predictive accuracy and reduced level of associated costs.     

Aspects of burr formation in bandsaw teeth manufactured by milling operation

Steel manufacturers and stockholders prefer bandsawing for cutting off raw materials compared to other techniques as it enjoys competitive advantages of higher accuracy of cut, better surface finish, lower kerf loss, better straightness of cut, long tool life and high metal removal rate. Along with the geometries of the bandsaw tooth, bandsaw cutting edge condition (e.g., edge sharpness and burr) significantly affects the cutting performance of a bandsaw. Currently the production of bandsaw is largely done by milling operation due to the scale of manufacturing and the economics of milling compared to other processes (e.g., grinding). Ideally, the bandsaw teeth should possess sharp cutting edges with no burr. In general, two types of burr are commonly seen in the bandsaw teeth manufactured by milling operation namely tooth tip burr and side burr. Current research undertaken at Northumbria University in collaboration with a major bandsaw producer is focused on the mechanism of burr formation in the bandsaw teeth. This paper briefly outlines the factors affecting the burr formation in bimetal (High Speed Steel edge wire and soft steel backing material) bandsaw teeth manufactured by milling process and suggests the necessary steps to be considered for manufacturing burr free bandsaw with sharp cutting edges. The investigation showed that flank wear in the milling cutter has a major influence on the side burr formation in the bandsaw teeth, whereas tooth tip burr was influenced by both flank wear and “V” type notch wear found at the crossover point on the flank face. It was also concluded that TiN coating on the milling cutter could control the burr formation in bandsaw teeth to some degree.     

Thermal and mechanical properties of SEBS-g-MA based inorganic composite materials

Organic-inorganic hybrids based on a triblock copolymer [polystyrene-b-poly (ethylene-ran-butylene)-b-polystyrene-g-maleic anhydride] (SEBS-g-MA) with silica and clay were prepared using sol-gel and solution intercalation methods respectively. Reinforcement in the first system was achieved by the in-situ hydrolysis/condensation of tetraethoxysilane in the copolymer matrix yielding hybrid materials. The interaction between organic and inorganic phases was developed through a coupling agent. In another system, copolymer was reinforced by organoclay and compatibility between copolymer and hydrophilic montmorillonite was achieved by intercalation of clay with dodecylamine which increased the organophilicity of the clay. Thin transparent films of these hybrids materials were characterized for their mechanical, thermal and thermomechanical behavior. The tensile strength of hybrids improved relative to the pure copolymer in all the systems. Dynamic mechanical thermal analysis carried out gave α-relaxation temperature associated with glass transition temperature (T_g). The results indicate a shift in T_g values with the addition of silica in the matrix, which suggests an increased interfacial interaction between organic and inorganic phases while this effect is less pronounced in polymer–clay system. Thermal decomposition temperatures of the hybrids were found in the range of 450–500 °C. The weights of the residues left at 700 °C were nearly proportional to the inorganic contents in the original hybrids.     

Cotton fabric dyeability assessment of floral extracts obtained from binary mixtures of Callistemon citrinus and Tagetes erecta L

Parameters affecting extraction of natural colorants from five binary mixtures of floral parts of Callistemon citrinus and Tagetes erecta L., like ratio of each flower in the binary mixture of powdered floral parts, amount of powdered binary mixture to liquor ratio and extraction time, were optimized for dyeing of cotton fabric. Optimum dyeing was obtained at 60°C with 70 g/L exhausting agent (Na₂SO₄), material to liquor ratio of 1:50 along with dyeing time of 100 min. The dyed fabric revealed good anti-bacterial activity and excellent ultraviolet protection factor (UPF).