Design of a highly stable, high-conversion-efficiency pumping source for optical parametric amplifier by extending efficient crystal length

The objective of this study is to improve the stability of pumping source of optical parametric amplifier. Analysis by simulation leads to the conclusion that the stability of the second harmonic can be improved by using properly the intensity of fundamental light and corresponding length of the crystal. By the method of the noncollinear two-pass second harmonic or the tandem second harmonic, the efficient crystal length is extended to a proper value, and the stability of the second harmonic output has been improved two times more than that for the fundamental light, and the conversion-efficiency is about 70% in experiment. When the variation of the fundamental light is about 10%, the variation of the second harmonic intensity has been controlled within 5%. (c) 2006 Elsevier Ltd. All rights reserved.

Magnetic Cross-Linked Enzyme Aggregates (mCLEAs) of Candida antarctica Lipase: An Efficient and Stable Biocatalyst for Biodiesel Synthesis

Enzyme-catalyzed production of biodiesel is the object of extensive research due to the global shortage of fossil fuels and increased environmental concerns. Herein we report the preparation and main characteristics of a novel biocatalyst consisting of Cross-Linked Enzyme Aggregates (CLEAs) of Candida antarctica lipase B (CALB) which are covalently bound to magnetic nanoparticles, and tackle its use for the synthesis of biodiesel from non-edible vegetable and waste frying oils. For this purpose, insolubilized CALB was covalently cross-linked to magnetic nanoparticles of magnetite which the surface was functionalized with –NH2 groups. The resulting biocatalyst combines the relevant catalytic properties of CLEAs (as great stability and feasibility for their reutilization) and the magnetic character, and thus the final product (mCLEAs) are superparamagnetic particles of a robust catalyst which is more stable than the free enzyme, easily recoverable from the reaction medium and reusable for new catalytic cycles. We have studied the main properties of this biocatalyst and we have assessed its utility to catalyze transesterification reactions to obtain biodiesel from non-edible vegetable oils including unrefined soybean, jatropha and cameline, as well as waste frying oil. Using 1% mCLEAs (w/w of oil) conversions near 80% were routinely obtained at 30°C after 24 h of reaction, this value rising to 92% after 72 h. Moreover, the magnetic biocatalyst can be easily recovered from the reaction mixture and reused for at least ten consecutive cycles of 24 h without apparent loss of activity. The obtained results suggest that mCLEAs prepared from CALB can become a powerful biocatalyst for application at industrial scale with better performance than those currently available.

Fast and Efficient Neural Conversion of Human Hematopoietic Cells

Neurons obtained directly from human somatic cells hold great promise for disease modeling and drug screening. Available protocols rely on overexpression of transcription factors using integrative vectors and are often slow, complex, and inefficient. We report a fast and efficient approach for generating induced neural cells (iNCs) directly from human hematopoietic cells using Sendai virus. Upon SOX2 and c-MYC expression, CD133-positive cord blood cells rapidly adopt a neuroepithelial morphology and exhibit high expansion capacity. Under defined neurogenic culture conditions, they express mature neuronal markers and fire spontaneous action potentials that can be modulated with neurotransmitters. SOX2 and c-MYC are also sufficient to convert peripheral blood mononuclear cells into iNCs. However, the conversion process is less efficient and resulting iNCs have limited expansion capacity and electrophysiological activity upon differentiation. Our study demonstrates rapid and efficient generation of iNCs from hematopoietic cells while underscoring the impact of target cells on conversion efficiency.

Contributions to the efficient use of general purpose coprocessors: kernel density estimation as case study

142 p.

Efficient electronic implementations of adaptive systems for ambient intelligence environments

183 p.

Highly efficient Nd:YAG ceramic CW laser with 59.8% slope-efficiency

In this paper, a highly efficient Ti:sapphire end-pumped 1 at.-% Nd:YAG ceramic laser that is comparable in efficiency with Nd:YAG single crystal lasers has been developed. Optical absorption and emission spectra for Nd:YAG ceramics have been measured. With 673-mW pumping, 295-mW laser output at 1064 nm has been obtained. The laser threshold is only 13 mW. Deducted the transmitted light, the corresponding optical-to-optical conversion efficiency is 58.4%. The lasing characteristics of Nd:YAG ceramic are nearly equal to those of Nd:YAG single crystal.

Highly efficient diode side-pumped Nd : YAG ceramic laser with 210W output power

We developed a highly efficient diode side-pumped Nd:YAG ceramic laser with a diffusive reflector as an optical pump cavity. A maximum output power of 211.6W was obtained with an optical -to- optical conversion efficiency of 48.7%. This corresponds to the highest conversion efficiency in the side-pumped ceramic rod. Thermal effects of the Nd:YAG ceramic rod were analyzed in detail through the measurements of laser output powers and beam profiles near the critically unstable region. A M-2 beam quality factor of 18.7 was obtained at the maximum laser output power. (c) 2006 Elsevier Ltd. All rights reserved.

Efficient excitations of radially and azimuthally polarized Nd 3+:YAG ceramic microchip laser by use of subwavelength multilayer concentric gratings composed of Nb2O5/SiO2

Cylindrical vector beams were produced from laser diode end-pumped Nd:YAG ceramic microchip laser by use of two types of subwavelength multilayer gratings as the axisymmetric-polarization output couplers respectively. The grating mirrors are composed of high- and low-refractive-index (Nb2O5/SiO2) layers alternately while each layer is shaped into triangle and concentric corrugations. For radially polarized laser output, the beam power reached 610mW with a polarization extinction ratio ( PER) of 61: 1 and a slope efficiency of 68.2%; for azimuthally polarized laser output, the beam power reached 626mW with a PER of 58: 1 and a slope efficiency of 47.6%. In both cases, the laser beams had near-diffraction limited quality. Small differences of beam power, PER and slope efficiency between radially and azimuthally polarized laser outputs were not critical, and could be minimized by further optimized adjustment to laser cavity and the reflectances of respective grating mirrors. The results manifested, by use of the photonic crystal gratings mirrors and end-pumped microchip laser configuration, CVBs can be generated efficiently with high modal symmetry and polarization purity. (C) 2008 Optical Society of America.