Streptococcus thermophilus strains: Multifunctional lactic acid bacteria

Streptococcus thermophilus has “Generally Recognized as Safe” status and is extensively used for the manufacture of several important fermented dairy foods, including yoghurt and some cheese varieties (Swiss, Limburger, Brick). S. thermophilus also has a number of functional activities such as production of extracellular polysaccharides, bacteriocins and vitamins. In addition, it also has potential as a probiotic, as demonstrated by various health effects, transient survival, and moderate adherence in the gastrointestinal tract. Therefore, the natural diversity among S. thermophilus strains with respect to their capacity to produce different metabolites has the potential to be exploited beyond fermentation for lactic acid production.     

Mechanical properties of mica‐filled PBT/ABAS composites

Tensile properties and Izod impact strength of mica‐filled composites of poly(butylene terephthlate) (PBT)/polyacrylonitrile‐butyl acrylate‐styrene (ABAS) were studied at mica concentration range 0 to 0.14 volume fraction, (?_f). Tensile properties such as tensile modulus, strength, and breaking strain were normalized by dividing the data with the crystallinity (%) of the major component PBT in the composites and the matrix blends. The normalized relative tensile properties were compared with simple models to evaluate the interphase interactions between the matrix (i.e. PBT/ABAS blend) and the dispersed phase mica. Mica reinforced the blend increasing the tensile modulus and strength with mica concentration while the strain‐at‐break was increased marginally up to ?_f = 0.04 and decreased beyond this ?_f. The impact strength, however, decreased with increase in ?_f due to enhanced matrix stiffening and lack of plastic deformation of the matrix. Scanning electron microscopic studies revealed good dispersion of mica in the composites. The effect of surface treatment with a zirconate coupling agent, NZ‐97, on the above properties has also been examined. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Transmission of shear waves through a self-reinforced layer sandwiched between two inhomogeneous viscoelastic half-spaces

A problem of reflection and transmission of plane SH-wave through a perfectly conducting self-reinforced elastic layer interposed between two vertically inhomogeneous viscoelastic solid half-spaces has been studied in this paper. The heterogeneity in the half-spaces is taken exponentially varying along vertical direction. Expressions of reflection and transmission coefficients are obtained in closed form and it is found that these coefficients depend on the angle of incidence, inhomogeneity parameters of the half-spaces and on the reinforcement parameters of the sandwiched layer. These coefficients are computed for a specific model against the angle of incidence for different values of inhomogeneity parameters of the half-spaces and for reinforcement parameter of the layer. The results have been presented graphically. The problem studied by Borcherdt [Reflection and refraction of type-II SH waves in elastic and anelastic media. Bulletin of the Seismological Society of America 1977;67:43–67] has been reduced as a special case.     

Hot forging behavior of nickel based superalloys under elevated temperatures

Thermomechanical behaviors of superalloys at high temperatures and constant strain rates related dynamic microstructural changes are studied in this article by means of the commentaries of thermomechanic graphs and microdublex changes. Thermomechanic and microdynamic deformation characteristics based on test data are presented by a methodology for superalloys which are consolidated by hot isostatic pressure (HIP) operation. It is assumed that true stress which is caused deformation, changes depending on thermomechanical behaviors such as; strain, strain rate, absolute temperature, activation energy, diffusion mechanism, grain size, microdynamic behaviors and structural parameters of the material. In this study, a detailed investigation of thermomechanical and microdynamical behaviors of powder metallurgy (PM) Rene 95 is carried on by the attribution of experimental data.     

Integral-type generalizations of operators obtained from certain multivariate polynomials

Abstract In this work, we mainly focus on the Kantorovich-type (integral-type) generalizations of the positive linear operators obtained from the Chan-Chyan-Srivastava multivariable polynomials. Using the notion of A-statistical convergence, we obtain various approximation theorems including a statistical Korovkin-type result and rates of A-statistical convergence with the help of the modulus of continuity, Lipschitz class functionals and Peetre’s K-functionals. We also introduce an sth order generalization of our approximating operators. Keywords. Chan-Chyan-Srivastava multivariable polynomials, Korovkin approximation theorem, Kantorovich-type operators, A-statistical convergence, modulus of continuity, Lipschitz class functional, Peetre’s K-functional Mathematics Subject Classification (2000): Primary: 41A25; 41A36, Secondary: 33C45     

Elastic-plastic J and COD estimation schemes for throughwall circumferentially cracked elbow under in-plane closing moment

Leak-before-break (LBB) assessment of primary heat transport piping of nuclear reactors involves detailed fracture assessment of pipes and elbows with postulated throughwall cracks. Fracture assessment requires the calculation of elastic-plastic J-integral and crack opening displacement (COD)¹ for these piping components. Analytical estimation schemes to evaluate elastic-plastic J-integral and COD simplify the calculations. These types of estimation schemes are available for pipes with various crack configurations subjected to different types of loading. However, no such schemes are available for throughwall circumferentially cracked elbow (or pipe bend), an important component for LBB analysis. In this paper, simple J and COD estimation schemes are proposed for throughwall circumferentially cracked elbow subjected to closing bending moment. The ovalisation of elbow cross-section has a significant bearing on its fracture behavior. Therefore, unlike conventional deformation theory plasticity analysis, incremental flow theory is adopted considering both material and geometric non-linearities in the development of the proposed estimation schemes. Although it violates Ilyushin’s theorem, it has been shown that the resulting estimation schemes is still reasonably accurate for engineering purposes. Finally, experimental/numerical validation has been provided by comparing the J-integral and COD between numerical/test data and predictions of the proposed estimation schemes.     

Shape, wear & mechanical properties of spray formed hypoeutectic Al-Si alloys

Manufacturing process through spray forming leads to give near-net-shape and fine grain microstructure. In this process Si particles, which are not distributed uniformly in conventional casting process, are distributed uniformly throughout the casting. In the present study disc shape spray form castings were made of Al-6.91Si and Al-10.1Si alloys, and then their shape, wear and mechanical properties were studied. The shape of the deposit was observed to be the most uniform at 30o inclination angle of the substrate. The hardness and tensile strength value of spray formed alloys shows the increment in the mechanical property in contrast to as cast alloys. The wearing properties of Al-10.1Si alloy were found to be better than that of the Al-6.91Si alloy.     

Evaluation of flyash-filled and aramid fibre reinforced hybrid polymer matrix composites (PMC) for friction braking applications

Flyash-filled and aramid fibre reinforced phenolic based hybrid polymer matrix composites (PMC) were fabricated followed by their characterization and tribo-evaluation. The friction-fade and friction-recovery behaviour has been rigorously evaluated as a function of in situ braking induced temperature rise in the disc at the braking interface on a Krauss friction testing machine as per the ECE regulations. The fade behaviour has been observed to be highly dependent on the weight fraction of resin i.e. followed a consistent decrease with the decrease in the flyash content, whereas the frictional fluctuations (μ_max − μ_min) has been observed to decrease with the increase in flyash content. A higher recovery response is registered when the flyash content is 80 wt.%. The analysis of friction performance has revealed that the fade and static friction response are the major determinants of overall frictional response. Wear analysis has revealed that material integrity and temperature rise of the disc decide the wear behaviour. Worn surface morphology investigation using SEM has revealed that the dynamics of formation–destruction of contact-patches (friction-layers) and topographical attributes largely influence the friction and wear performance of such composite brake-pads.     

Energetic and exergetic performance investigation of the Bigadic Geothermal District Heating System in Turkey

In this study a comprehensive performance analysis of the Bigadic Geothermal District Heating System (GDHS) in Balikesir, Turkey is performed through thermodynamic assessment in terms of energy and exergy efficiencies. The actual thermal data taken from the Technical Department of the GDHS are utilized in the analysis to determine the exergy destructions in each component of the system and the overall energy and exergy efficiencies of the system for two reference temperatures taken as 15.6 °C for November (e.g., case 1) and 11 °C for December (e.g., case 2). The energy and exergy flow diagrams are clearly drawn to illustrate how much destructions/losses take place in addition to the inputs and outputs. The average energy and exergy efficiencies are found to be 30% and 36% for case 1, and 40% and 49% for case 2, respectively. The key reason as to why the exergy efficiencies are higher is because the heat recovery option is used through the reinjection processes which make use of waste heat. A parametric study is also conducted to show how energy and exergy flows change with the environment temperature. The results are expected to be helpful to researchers and engineers in the area.     

Indirect electrochemical treatment of bisphenol A in water via electrochemically generated Fenton's reagent

Bisphenol A (BPA) has been treated with electrochemically generated Fenton's reagent in aqueous medium. Hydroxyl radicals that were formed in Fenton's reagent reacted with the organic substrate producing two different isomers of monohydroxylated product and, upon successive hydroxylation, mainly one dihydroxylated product. Further hydroxylation first degraded one of the aromatic rings, and the side chain thus formed was then cleaved off the other aromatic ring. The second aromatic ring was also degraded upon successive hydroxylations. Small saturated and unsaturated aliphatic acids were the last products prior to mineralization. It was found that use of cuprous/cupric ion pair resulted a faster conversion of BPA and faster mineralization when compared using ferrous/ferric ions, but this happened at the expence of excess electrical charge utilized for an equivalent conversion or mineralization. Degradation by using ferrous/ferric ions was more efficient than cuprous/cupric ions case in terms of total mineralization versus charge utilized, and a mineralization of 82% had been achieved by applying 107.8 mF of charge to a 0.7 mM BPA solution of 0.200 dm3. The rate constant of the monohydroxylation of BPA in the presence of ferrous/ferric ions had been determined as 1.0 x 10(10) M(-1) s(-1) where BPA and salicylic acid competitively reacted with hydroxyl radicals in aqueous medium with the initial concentrations of Fe2+, BPA, and SA of 1.0, 0.5, and 0.5 mM, respectively. In a similar experiment where the initial concentrations of Cu2+, BPA, and SA were 1.0, 0.5, and 0.5 mM, respectively, the corresponding rate constant was determined to be the same as the rate constant obtained for Fe2+ (i.e., 1.0 x 10(10) M(-1) s(-1)). While the use of Cu2+ cannot be advised for processing BPA and similar substrates by using the electro-Fenton technique for both technical and economical reasons, the use of [Fe2+]/[BPA]0 values in the range 3-4 will be sufficient to achieve an efficient mineralization of BPA and similar substrates by the electro-Fenton process in aqueous medium.