Beam conditions for radiation generated by an electromagnetic J 0-correlated Schell-model source

Based on the 2 x 2 (electric field) cross-spectral density matrix, a model for an electromagnetic J(0)-correlated Schell-model beam is given that is a generalization of the scalar J(0)-correlated Schell-model beam. The conditions that the matrix for the source to generate an electromagnetic J(0)-correlated Schell-model beam are obtained. The condition for the source to generate a scalar J(0)-correlated Schell-model beam can be considered as a special case. (C) 2008 Optical Society of America

Beam collimation of high-power laser diode array with graded-index fiber lens array

Graded-index (GRIN) fiber lens arrays are fabricated from commercial GRIN fibers to collimate a high-power laser diode array. The beam divergence angles are reduced to 4.2 and 14.7 mrad in the fast and slow axes, respectively. The influences of smile and fluctuation in fiber length are discussed. Using an aspherical focal lens system, about 74% power can be launched into a fiber with a numerical aperture (NA) of 0.22 and a core diameter of 400 mu m. (c) 2008 Society of Photo-Optical Instrumentation Engineers.

Relativistic force between fast electrons and planar targets

The full retarded electromagnetic force experienced by swift electrons moving parallel to planar boundaries is revisited, for both metallic and dielectric targets, with special emphasis on the consequences in electron microscopy experiments. The focus is placed on the sign of the transverse force experienced by the electron beam as a function of the impact parameter. For point probes, the force is found to be always attractive. The contribution of the induced magnetic field and the causality requirements of the target dielectric response, given by the Kramers-Kronig (K-K) relations, prove to be crucial issues at small impact parameters. For spatially extended probes, repulsive forces are predicted for close trajectories, in agreement with previous works. The force experienced by the target is also explored, with the finding that in insulators, the momentum associated to Cherenkov radiation (CR) is relevant at large impact parameters.

Ridge optical waveguide in an Er3+/Yb3+ co-doped phosphate glass produced by He+ ion implantation combined with Ar+ ion beam etching

This paper reports on the fabrication and characterization of a ridge optical waveguide in an Er3+/Yb3+ co-doped phosphate glass. The He+ ion implantation (at energy of 2.8 MeV) is first applied onto the sample to produce a planar waveguide substrate, and then Ar+ ion beam etching (at energy of 500 eV) is carried out to construct rib stripes on the sample surface that has been deposited by a specially designed photoresist mask. According to a reconstructed refractive index profile of the waveguide cross section, the modal distribution of the waveguide is simulated by applying a computer code based on the beam propagation method, which shows reasonable agreement with the experimentally observed waveguide mode by using the end-face coupling method. Simulation of the incident He ions at 2.8 MeV penetrating into the Er3+/Yb3+ co-doped phosphate glass substrate is also performed to provide helpful information on waveguide formation.

Self-organized microvoid array perpendicular to the femtosecond laser beam in CaF2 crystals

Microvoid arrays were self-organized when femtosecond laser beam was tightly focused at a fixed point inside CaF2 crystal sample. Except void array grown below the focal point which had been reported before, we found another void array grown vertical to the laser propagation direction. This result has potential application in the fabrication of integrated micro-optic elements and photonic crystals. The possible mechanism of the phenomenon was proposed and verified experimentally.

European Newspapers’ Digital Transition: New Products and New Audiences

The adaptation of traditional newspapers to new digital media and its interface, far from being a mere technical transformation, has contributed to a gradual change in the media themselves and their audiences. With a sample including the top general information pay newspaper in each of the 28 countries of the European Union, this research has carried out an analysis using 17 indicators divided in 4 categories. The aim is to identify the transformations that the implementation of digital media have brought to the top European newspapers. In general terms, the results show that most dailies have managed to keep their leadership also in online environment. Moreover, an emerging group of global media is growing up, based in preexisting national media. Digital and mobile media have contributed to the appearance of new consumption habits as well, where users read more superficially and sporadically. The audience uses several formats at a time, and digital devices already bring the biggest amount of users to many media. The Internet-created new information windows –search engines, social networks, etc. –are also contributing to the change in professional work routines.

White spot syndrome virus (WSSV) transmission risk through infected cooked shrimp products assessed by polymerase chain reaction (PCR) and bio-inoculation studies

The aim of the study was to evaluate the resistance of white spot syndrome virus (WSSV) in shrimps (Penaeus monodon) to the process of cooking. The cooking was carried out at 1000C six different durations 5, 10, 15, 20, 25 and 30 min. The presence of WSSV was tested by single step and nested polymerase chain reaction (PCR). In the single step PCR, the primers 1s5 & 1a16 and IK1 & IK2 were used. While in the nested PCR, primers IK1 &IK2 – IK3 & IK4 were used for the detection of WSSV. WSSV was detected in the single step PCR with the primers 1s5 and 1a16 and the nested PCR with the primers IK1 and IK2 – IK3 & IK4 from the cooked shrimp samples. The cooked shrimps, which gave positive results for WSSV by PCR, were further confirmed for the viability of WSSV by conducting the bio-inoculation studies. Mortality (100%) was observed within 123 h of intra-muscular post injection (P.I) into the live healthy WSSV-free shrimps (P. monodon). These results show that the WSSV survive the cooking process and even infected cooked shrimp products may pose a transmission risk for WSSV to the native shrimp farming systems.

Effect of crude oil and some petroleum products on Clarias Gariepinus fingerlings (Catfish: Claridae)

Ninety (90) hatchery bred fingerlings of Clarias gariepinus (mean weight: 0.96 ± 0.1g) were randomly placed in 15 plastic baths (25 litres each) at the Research laboratory and were exposed to different concentrations of oil products to determine their effects on the fish, to facilitate inferential deductions that will enhance effective aquatic environmental management. Three (3) replicate basins of 5 experimental treatments (crude oil, petrol oil, kerosene oil, engine oil and control) were used at a concentration of 1.25ml. L-1. The control experiment was devoid of oil treatment. Six (6) fingerlings were placed in each replicate basin, flooded with 20 litres of clean tap water and fed with nutrafin cichilid food, 2 times daily at 3% body weight. The results showed that the feeding behaviour and swimming performances of fish were reduced after 24 hours of the addition of the various oil pollutants. Mortality of fingerlings in the oiled basins increased as the hours of exposure increased (i.e. 24, 48, 72 and 96 hours). Recovery was not immediate in the treated basin while surviving fingerlings in the control basins grew up to post-fingerlings after 90 days (3 months). There were significant differences (P<0.01 and P<0.05) in the effect of crude oil and the petroleum products on the mortality rate of C. gariepinus when exposed to oil pollutants at 1.25ml. L-1 concentration

beam-shaping microstructure optical fiber

Microstructure optical fiber with uniform intensity distribution of the fundamental mode is proposed. The design guide line and characteristics of this kind fiber are demonstrated. The relationship between refractive index profile and structure parameters is investigated. The mechanism of forming uniform fundamental mode in these fibers is analyzed.