Growth and characterization of gold catalyzed SiGe nanowires and alternative metal-catalyzed Si nanowires

The growth of semiconductor (SC) nanowires (NW) by CVD using Au-catalyzed VLS process has been widely studied over the past few years. Among others SC, it is possible to grow pure Si or SiGe NW thanks to these techniques. Nevertheless, Au could deteriorate the electric properties of SC and the use of other metal catalysts will be mandatory if NW are to be designed for innovating electronic. First, this article's focus will be on SiGe NW's growth using Au catalyst. The authors managed to grow SiGe NW between 350 and 400°C. Ge concentration (x) in Si1-xGex NW has been successfully varied by modifying the gas flow ratio: R = GeH4/(SiH4 + GeH4). Characterization (by Raman spectroscopy and XRD) revealed concentrations varying from 0.2 to 0.46 on NW grown at 375°C, with R varying from 0.05 to 0.15. Second, the results of Si NW growths by CVD using alternatives catalysts such as platinum-, palladium- and nickel-silicides are presented. This study, carried out on a LPCVD furnace, aimed at defining Si NW growth conditions when using such catalysts. Since the growth temperatures investigated are lower than the eutectic temperatures of these Si-metal alloys, VSS growth is expected and observed. Different temperatures and HCl flow rates have been tested with the aim of minimizing 2D growth which induces an important tapering of the NW. Finally, mechanical characterization of single NW has been carried out using an AFM method developed at the LTM. It consists in measuring the deflection of an AFM tip while performing approach-retract curves at various positions along the length of a cantilevered NW. This approach allows the measurement of as-grown single NW's Young modulus and spring constant, and alleviates uncertainties inherent in single point measurement.     

Influence of dietary long-chain PUFA on premature baboon lung FA and dipalmitoyl PC composition

One of the major survival challenges of premature birth is production of lung surfactant. The lipid component of surfactant, dipalmitoyl PC (DPPC), increases in concentration in the period before normal term birth via a net shift in FA composition away from unsaturates. We investigated the influence of dietary DHA and arachidonic acid (AA) on lung FA composition and DPPC concentration in term and preterm baboons. Pregnant animals/neonates were randomized to one of four groups: breast-fed (B), term formula-fed (T⁻), preterm formulafed (P⁻), and preterm fed formula supplemented with DHA-AA (P⁺). Breast milk contained 0.68%wt DHA and the P⁺ group formula contained 0.61%wt DHA. In the preterm groups (P⁻ and P⁺), pregnant females received a course of antenatal corticosteroids. At the adjusted age of 4 wk, neonate lung tissue was harvested, and FA composition and DPPC were analyzed. Palmitate was ∼28%wt of lung total FA and no significant differences were found among the four treatment groups. In contrast, DPPC in the B group lung tissue was significantly greater than DPPC in the unsupplemented groups, but not compared with the P⁺ group. The B and P⁺ groups were not significantly different in DHA and AA, but were different compared with the unsupplemented (T, P⁻) groups. These results indicate that LCP supplementation increases lung DHA and AA, without compromising overall lung 16∶0 or DPPC. The shift in FA composition toward greater unsaturation in the groups consuming LCP supported improved surfactant lipid concentration in preterm neonate lungs.     

A Taguchi design approach for the enhancement of a detergent-biocompatible alkaline thermostable protease production by Streptomyces mutabilis strain TN-X30

The ability of microorganisms to grow at high temperature, alkaline pH, and high salinity makes them an attractive target for enzyme-production with several industrial applications. One strain TN-X30 has been selected as protease producer and identified as Streptomyces mutabilis after a phenotypic and molecular study. Its production of protease was improved using Taguchi L27 design. The strategy was carried out to identify the optimum levels and the interaction of the screened factors. Following this step, maximum protease activity (10,895 U/ml) was achieved after 6-days of incubation. The TN-X30 protease activity had an optimum of pH and temperature of 10 and 65°C, respectively. Thermodynamic parameters at 60°C were enthalpy 14.26 kJ/mol, entropy −220 J/mol/K, and Gibbs free energy 90.53 kJ/mol. TN-X30 protease production displayed a 16-fold increase reaching 175,000 U/ml in a 100-L fermentor. Furthermore, the lyophilization in presence of sorbitol enhanced the stability of the TN-X30 protease which remained active at 75% after 24-months of storage. The lyophilized TN-X30 protease exhibited exceptional stability indexes in presence of some known commercialized detergent components as NEODOL® 25-7, Dehydol® LT 7, Na₂ CMC, Galaxy LAS, Galaxy LES 70, Galaxy 110, Galaxy CAPB Plus, and Sulfacid K. The lyophilized enzyme also displayed high stability with respect to both solid and liquid detergents. Finally, TN-X30 protease exhibited remarkable destaining of blood, egg, and chocolate stained cloth pieces. These findings may promote TN-X30 protease for use as bioadditive in detergent formulation, thereby reducing environmental chemical threat.     

Attraction Modulated by Spacing of Pheromone Components and Anti-attractants in a Bark Beetle and a Moth

Orientation for insects in olfactory landscapes with high semiochemical diversity may be a challenging task. The partitioning of odor plumes into filaments that are interspersed with pockets of ‘clean air’ may help filament discrimination and upwind flight to attractive sources in the face of inhibitory signals. We studied the effect of distance between odor sources on trap catches of the beetle, Ips typographus, and the moth, Spodoptera littoralis. Insects were tested both to spatially separated pheromone components [cis-verbenol and 2-methyl-3-buten-2-ol for Ips; (Z,E)-9,11-tetradecadienyl acetate and (Z,E)-9,12-tetradecadienyl acetate for Spodoptera], and to separated pheromone and anti-attractant sources [non-host volatile (NHV) blend for Ips; (Z)-9-tetradecenyl acetate for Spodoptera]. Trap catch data were complemented with simulations of plume structure and plume overlap from two separated sources using a photo ionization detector and soap bubble generators. Trap catches of the beetle and the moth were both affected when odor sources in the respective traps were increasingly separated. However, this effect on trap catch occurred at smaller (roughly by an order of magnitude) odor source separation distances for the moth than for the beetle. This may reflect differences between the respective olfactory systems and central processing. For both species, the changes in trap catches in response to separation of pheromone components occurred at similar spacing distances as for separation of pheromone and anti-attractant sources. Overlap between two simulated plumes depended on distance between the two sources. In addition, the number of detected filaments and their concentration decreased with downwind distance. This implies that the response to separated odor sources in the two species might take place under different olfactory conditions. Deploying multiple sources of anti-attractant around a pheromone trap indicated long-distance (meter scale) effects of NHV on the beetle and a potential use for NHV in forest protection.     

Promising growth inhibitory potential of extracted natural silk sericin biopolymer against DEN-induced liver tumor in male mice

Silk sericin (SS), a protein biopolymer, is gaining an increasing attention in a variety of biomedical applications. Our objective was to identify the optimal extraction method yielding the highest silk protein content, to assess its chemical elemental composition, to characterize it, and to compare its conformation by X-ray diffraction and Fourier-transform infrared versus that of the commercial one. Herein, alkali and high temperature is the perfect approach. This study aimed further to test whether extracted SS could attenuate the adverse hepatotoxic effects induced by diethylnitrosamine (DEN) in mice. Animals were injected intraperitoneally once weekly for four consecutive weeks with physiological saline (0.9% NaCl), DEN (25 mg/kg), SS (1 g/kg) 90 min prior to DEN injection, melatonin (10 mg/kg) followed within 1 h with the administration of SS and 30 min later with DEN. The results confirmed the hepatotoxicity of DEN manifested by an increase in liver enzymes' activity, and pathological changes in the liver tissue. The combined use of SS and/or melatonin with DEN returned most of the parameters to values similar to the controls. Briefly, chemically characterized SS seems a valuable extract for further consideration as anti-carcinogenic agent. It has the potential to upgrade liver cancer chemotherapeutic agents.     

Effect of Nepheline Syenite Additives on the Technological Behavior of Ceramics and Porcelain Stoneware Tiles

To study the effect of the Egyptian nepheline syenite raw materials on the sinterability of the ceramic tiles, four batches with concentrations of nepheline syenite (0, 5, 10 and 15%) were prepared. The four batches were ground, mixed, shaped, pressed and fired at temperatures from 1160 °C to 1260 °C. Some technological behaviors of the samples were measured in dry, green state and after firing at 1260 °C; including densfication parameters. Phase composition and microstructural studies refered that mullite was the newly crystallized phase after firing set in a glassy matrix enriched in alkalis. Technological properties of the fired batches revealed that the higher firing temperature and higher nepheline syenite contents produced larger amounts of glassy phase, and consequently bulk density and linear shrinkage increased, while apparent porosity and water adsorption as well as whiteness of fired batches decreased. It is concluded that nepheline syenite could be successfully used as flux in ceramic tiles, while it is not accepted in the production of porcelain bodies because of their coloration.

     

Magnetic and Electrical Properties of Glass and Glass-Ceramics Based on Weathered Basalt

Silicon - A total of six glass batches (WB100-WB50) based primarily on weathered basalt with successive addition of bypass cement dust (with the weight content 0–50%) were melted at...     

Novel sensor-based tool wear monitoring approach for seamless implementation in high speed milling applications

A sensor-based hybrid processing approach for tool wear monitoring is presented to overcome the practical limitations of implementing state-of-the-art tool condition monitoring systems in milling processes. It extracts features from vibration signals that are insensitive to the variations in cutting conditions, tool path and interfering noises. A machine learning model was developed to accentuate features separation based on tool condition. Extensive experimental validation tests in high speed and conventional milling applications demonstrated the approach capability to achieve 98% accuracy and reduce system training by up to 97%. Such performance, practicality and accuracy have never been reached before in this application.     

Performance of ultrasonic – Treated nano-zeolites employed in the preparation of dimethyl ether

Catalytic dehydration of methanol to dimethyl ether was carried out over nano-zeolites and their modified samples via ultrasonic technique. Parent H-Beta and Parent H-Mordenite zeolites are used as synthesized and after sonication. H-Mordenite sonicated for 20 and 120 min whereas H-Beta sonicated for 20 min only. The reaction temperature was varied between 100 and 225 °C at three different contact times. The different catalyst samples were characterized using: XRD, FTIR, TEM, SEM and NH₃-TPD techniques. The results revealed that sonication of parent zeolite samples affects on the unit cell dimensions and their crystal size. FTIR-spectroscopic analysis indicated that sonication may decrease the pore opening and cause framework structure defects. TEM and SEM micrographs showed that sonication broke-up and re-ordered zeolite crystals with longer time resulted in a different morphology relative to parents and also change the particle size. Sonicated samples have a good performance in methanol dehydration with complete conversion and complete selectivity to dimethyl ether at lower temperature relative to the corresponding parent zeolites. TPD results indicated that the concentration of strong acid sites decreased in sonicated H-Mordenite samples leading to an increase of their catalytic activity and the selectivity to DME. On the other hand, ultrasonic treatment of H-Beta sample decreased its catalytic activity.     

Design∕Control Optimization of Cross‐Ply Laminates Under Buckling and Vibration

The optimal layer thicknesses and optimal feedback control function are determined for a symmetric, cross‐ply laminate. The objectives of the optimization are to maximize the biaxial buckling load (design objective) and to minimize the dynamic response to external disturbances (control objective) subject to a constraint on the expenditure of control energy. The design∕control problem is formulated as a multiobjective optimization problem by employing a performance index that combines the design and control objectives in a weighted sum. Numerical results are given for a laminate made of an advanced composite material. Comparisons of controlled and uncontrolled laminates as well as optimally designed and nonoptimal laminates indicate the benefits of treating the design and control problems in unified formulation. The implications of solving these two problems are discussed. The values of optimal design and control variables are given for a number of problem parameters.