Intracavity Raman lasers

Experimental and theoretical studies of intracavity Raman lasers are presented. Advantages of intracavity Raman lasers, particularly for low-emission cross section and broadly tunable vibronic gain media, are described. Experimental studies of a hydrogen gas Raman laser pumped inside the cavity of an alexandrite laser are presented. A theoretical model of the dynamics of a unidirectional intracavity Raman ring laser is developed and solved analytically. This model is adapted for simulation experiments     

The beat goes on: Rhythmic modulation of cortical potentials by imagined tapping.

A frequency analysis was used to tag cortical activity from imagined rhythmic movements. Participants synchronized overt and imagined taps with brief visual stimuli presented at a constant rate, alternating between left and right index fingers. Brain potentials were recorded from across the scalp and topographic maps made of their power at the alternation frequency between left and right taps. Two prominent power foci occurred in each hemisphere for both overt and imagined taps, one over sensorimotor cortex and the other over posterior parietal cortex, with homologous foci in opposite hemispheres arising from oscillations 180° out of phase. These findings demonstrate temporal isomorphism at a neural level between overt and imagined movements and illustrate a new approach to studying covert actions. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

交错BCH码在移动窄带图像信道中的性能研究

文章在详述ＢＣＨ码编译码过程的基础上，对交错ＢＣＨ码在移动瞧道压缩图像传输系统中的应用进行了计算机仿真，直观地显示出产错ＢＣＨ码在窄带图像传输系统中的优良性能，并为移动图像传输中码型的选用提供参考。     

Regioselective Alkoxylation of 2,2,4-Trimethyl-1,3-pentanediol

An efficient procedure for the regioselective synthesis of secondary alcohol alkoxylates from 2,2,4-trimethyl-1,3-pentanediol (TMPD) is described. TMPD was reacted with propylene oxide followed by ethylene oxide in the presence of a catalytic amount of alkali metal hydroxide to form secondary alcohol alkoxylates. Instead of a mixture of compounds resulting from the reaction of TMPD and propylene oxide, the primary hydroxyl group of the TMPD reacted to form predominantly 2,2,4-trimethyl-3-hydroxypentylpropoxylate as the major product. On further ethoxylation the less hindered secondary hydroxyl group of the 2,2,4-trimethyl-3-hydroxypentylpropoxylate reacted predominantly. ¹³C NMR indicated that the secondary hydroxyl group (96.2 mol%) of TMPD remained unreacted during alkoxylation.     

Studies of 1s2s 3S-1s2p 3P transitions in helium-like Ne8+ recoil ions using photographic spectroscopy

This work describes the application of the technique of photographic VUV spectroscopy to accurate measurement of the wavelength of the theoretically interesting 1s2s ³S₁-1s2p ³P₂ transition in helium-like Ne⁸⁺ in a recoil ion source. Good resolution is obtained, and a preliminary value of 124.815±0.002 nm is found for the wavelength.     

A comparative study on the processing, dielectric and electrical properties of PMN based solid solutions

Lead magnesium niobate (PMN) based binary with lead titanate (PT), lead iron niobate (PFN) and lead zinc niobate (PZN) and ternary with PZN-PT and PFN-PT solid solutions have been synthesized. In depth characterization using X-ray diffraction and SEM techniques have revealed the major perovskite phase formation. Amongst all the solid solutions, PMN-PZN-PT has given the highest values of permittivity as 19,740 and 23,700 withT _c as 34°C when sintered at 1080°C and 1180°C respectively on the one hand and on the other, PFN containing solid solutions exhibited distinct deviation from the relaxor behaviour.