Polarization control in a vertical cavity surface emitting laser submitted to optical feedback

We study experimentally and theoretically two polarization effects in a vertical cavity surface emitting laser submitted to optical feedback. In a first experiment, we obtain flips between two linearly polarized laser modes up to a frequency of 50 MHz using an external cavity with a polarizer. In a second experiment, polarization self modulation is demonstrated up to a frequency of 2.6 GHz, using a quarter wave plate instead. Numerical calculations, based on a four levels model for the active medium, show a good agreement with the experiments.     

The effect of supercooling on crystallization of cocoa butter-vegetable oil blends

The solid fat content (SFC), Avrami index (n), crystallization rate (z), fractal dimension (D), and the pre-exponential term [log(γ)] were determined in blends of cocoa butter (CB) with canola oil or soybean oil crystallized at temperatures (T _Cr) between 9.5 and 13.5°C. The relationship of these parameters with the elasticity (G′) and yield stress (σ^*) values of the crystallized blends was investigated, considering the equilibrium melting temperature (T _M ^o) and the supercooling (i.e., T _Cr ^o−T _M ^o) present in the blends. In general, supercooling was higher in the CB/soybean oil blend [T _M ^o=65.8°C (±3.0°C)] than in the CB/canola oil blend [T _M ^o=33.7°C (±4.9°C)]. Therefore, under similar T _Cr values, higher SFC and z values (P<0.05) were obtained with the CB/soybean oil blend. However, independent of T _Cr TAG followed a spherulitic crystal growth mechanism in both blends. Supercooling calculated with melting temperatures from DSC thermograms explained the SFC and z behavior just within each blend. However, supercooling calculated with T _M ^o explained both the SFC and z behavior within each blend and between the blends. Thus, independent of the blend used, SFC described the behavior of G′_eq and σ^* and pointed out the presence of two supercooling regions. In the lower supercooling region, G′_eq and σ^* decreased as SFC increased between 20 and 23%. In this region, the crystal network structures were formed by a mixture of small β′ crystals and large β crystals. In contrast, in the higher supercooling region (24 to 27% SFC), G′_eq and σ^* had a direct relationship with SFC, and the crystal network structure was formed mainly by small β′ crystals. However, we could not find a particular relationship that described the overall behavior of G′_eq and σ^* as a function of D and independent of the system investigated.     

Developing Skype-Based Reference Services

ABSTRACT

Internet voice and video calling have demonstrated a dramatic rise in quality in the past several years and have quickly become communication technologies with a disruptive impact on society. Librarians, who regularly adopt such technologies in outreach and public services, should evaluate Web-calling programs as potential sources of innovative reference programming. This article describes the development of Skype video and Internet telephony pilot reference services at the Ohio University Libraries and considers the utility of Skype and VoIP in a library setting.     

Arm length dependency of Pt-decorated CdSe tetrapods on the performance of photocatalytic hydrogen generation

Pt-decorated CdSe tetrapods with different arm lengths were tested for the photocatalytic hydrogen generation reaction. Well-defined CdSe tetrapods with controlled wurtzite arm lengths were synthesized by the continuous precursor injection (CPI) approach. Pt nanocrystals with an extremely small size of ～1 nm were directly decorated on the overall surfaces of CdSe tetrapods. Ligand-exchanged Pt-decorated CdSe tetrapods with different arm lengths were employed as photocatalysts for photocatalytic hydrogen generation reaction in the presence of hole scavengers. Pt-decorated CdSe tetrapods with shorter arm length showed the highest photocatalytic efficiency, which is due to higher probability of charge separation.     

Processing mango stones for fat

Stones of mango fruit (Mangifera indica) were processed for recovery of fat and the fat refined. Mango kernel fat is potentially edible and can substitute for tallow and cacao butter. Mango kernal meal can be used as a sizing material and as a feed.     

Effects of viscous dissipation on slip-flow heat transfer in a micro annulus

This study deals numerically with the laminar slip-flow forced convection in a micro annulus with constant wall temperature. The solution takes the effects of viscous dissipation, velocity-slip and temperature-jump conditions at the surface into considerations. A hybrid application of the Laplace transformation technique and the local adaptive differential quadrature method (La-DQM) is used to solve the energy equation for the developing temperature field. Of interest are the effects of the Brinkman number Br, the Knudsen number Kn, and the radius ratio β of inner to outer cylinders on the temperature distribution and the Nusselt number.The results indicate that fully developed Nusselt number increases with an increase in the radius ratio β or a decrease in the Knudsen number Kn, but it is rather insensitive to the Brinkman number. The local Nusselt number in the thermal entrance region increases as Br increases. Comparisons are also made of the dimensionless temperature gradient at the outer cylinder between the present results and published data for the circular tube case β = 0, and the agreement is found out to be generally good.     

Effect of processing conditions and reactive compatibilizer on the morphology of injection molded modified poly(phenylene oxide)/polyamide‐6 blends

The effect of injection molding conditions and reactive compatibilization on the morphology of maleic anhydryde‐modified poly(phenylene oxide)/polyamide‐6 blends was investigated. The injection flow rate primarily influenced the position of the subskin layer, and the injection temperature affected the aspect ratio of the dispersed phase. A reduction of the sue of the dispersed phase occured during the converging flow in the barrel‐to‐sprue zone. The reactive compatibilization reduced the flow induced deformation, the coalescence and the breakup of particles and improved the dispersion of the minor phase.