High power microsecond fiber laser at 1.5 mu m

In this work, we demonstrate a single frequency, high power fiber-laser system, operating at 1550 nm, generating controllable rectangular-shape mu s pulses. In order to control the amplified spontaneous emission content, and overcome the undesirable pulse steepening during the amplification, a new method with two seed sources operating at 1550 nm and 1560 nm are used in this system. The output power is about 35 W in CW mode, and the peak power is around 32 W in the pulsed mode. The repetition rate of the system is tunable between 50 Hz to 10 kHz, and the pulse duration is adjustable from 10 mu s to 100 mu s, with all on the fly electronically configurable design. The system demonstrates excellent long and short time stability, as well as spectral and spatial beam quality. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

High power microsecond fiber laser at 1.5 μm

© 2020 Optical Society of America.In this work, we demonstrate a single frequency, high power fiber-laser system, operating at 1550 nm, generating controllable rectangular-shape μs pulses. In order to control the amplified spontaneous emission content, and overcome the undesirable pulse steepening during the amplification, a new method with two seed sources operating at 1550 nm and 1560 nm are used in this system. The output power is about 35 W in CW mode, and the peak power is around 32 W in the pulsed mode. The repetition rate of the system is tunable between 50 Hz to 10 kHz, and the pulse duration is adjustable from 10 μs to 100 μs, with all on the fly electronically configurable design. The system demonstrates excellent long and short time stability, as well as spectral and spatial beam quality

Association of asthma-related symptoms with snoring and apnea and effect on health-related quality of life

Ekici, Arif B/0000-0001-6099-7066WOS: 000233508400040PubMed: 16304284Objectives: This study aimed to investigate the association of asthma-related symptoms with snoring and apnea, and to assess their effects on health-related quality of life (HRQL). Design: Population-based cross-sectional study. Subjects and methods: A total of 10,224 parents and grandparents of students from 14 randomly selected primary schools in city center were asked to answer questionnaires sent by their children. All subjects were questioned for asthma-related symptoms, sleep-related disorders (snoring and apnea), and for HRQL using the Respiratory Questionnaire, Sleep and Health Questionnaire, and Short Form-12 (SF-12) Health Survey, respectively. Results: The overall response rate to questionnaires was 97.7%, and all analysis was performed on 7,469 subjects (3,920 women and 3,549 men) who provided sufficient responses to questions. There were 2,713 subjects who reported asthma-related symptoms. The snoring and the observed apnea were more prevalent in subjects with asthma-related symptoms (54.0% vs 41.4%; odds ratio [OR], 1.7; 95% confidence interval [CI], 1.5 to 1.8; p < 0.001) than those without asthma-related symptoms (16.7% vs 7.0%; OR, 2.7; 95% CI, 2.3 to 3.1; p < 0.001), respectively. Asthma-related symptoms were found to be associated with snoring (OR, 1.5; 95% CI, 1.3 to 1.6; p < 0.001) and observed apnea (OR, 2.2; 95% CI, 1.8 to 2.5; p < 0.001) after adjusting for gender, age, body mass index, income, education, and smoking. Also, HRQL was found to be adversely affected by asthma-related symptoms, snoring, and observed apnea (beta = - 0.26, p < 0.001; beta = - 0.07, p < 0.001; and beta = - 0.08, p < 0.001, respectively, for SF-12 overall score) after adjusting for other confounding factors. Conclusion: Present data suggest that there is a link between the sleep-related breathing disorders and asthma-related symptoms. Moreover, the presence of snoring and observed apnea in individuals with asthma-related symptoms causes further impairment in HRQL. The effects on HRQL of coexistence of these three disorders should be supported by clinical studies

Multi-walled carbon nanotubes functionalized by carboxylic groups: Activation of TiO2 (anatase) and phosphate olivines (LiMnPO4; LiFePO4) for electrochemical Li-storage

Multi-walled carbon nanotubes functionalized by carboxylic groups, exhibit better affinity towards TiO2 (P90, Degussa) as compared to that of pristine nanotubes. Also the electrochemical performance of TiO2 is improved by nanotube networking, but the Li-storage capacity of TiO2 is unchanged. Whereas the composite of TiO2 with non-functionalized nanotubes demonstrates simple superposition of the behavior of pure components, the composite with functionalized nanotubes shows unique faradaic pseudocapacitance which is specific for this composite only. The surface functionalization of nanotubes enhances charge storage capacity and reversibility of a composite with LiMnPO4 (olivine), but mediates also the electrolyte breakdown at potentials >4.2 V. Whereas the electrochemical activation of LiMnPO4 (olivine) by functionalized nanotubes is quite modest, excellent performance was found for LiFePO4 (olivine) in composite materials containing only 2 wt% of functionalized nanotubes. (C) 2010 Elsevier B.V. All rights reserved

Understanding the surface chemistry of carbon nanotubes: Toward a rational design of Ru nanocatalysts

International audienceA comprehensive experimental and theoretical study of the surface chemistry of ruthenium nanoparticles supported on/in multi-walled carbon nanotubes (CNTs) is reported that could pave the way to the rational design of metal–carbon nanocomposites. It is shown that the oxidation of CNTs by nitric acid that creates various oxygen surface functional groups (SFGs) on the CNT external surface is a crucial step for metal grafting. In particular, it is demonstrated that carboxylic acid, carboxylic anhydride, and lactone groups act as anchoring centers for the Ru precursor, presumably as surface acetato ligands. The HNO3 treatment that also allows CNT opening contributes to the endohedral Ru deposition. The stability of Ru nanoparticles, modeled by a Ru13 cluster, on different adsorption sites follows the order: Gr-DV-(COOH)2 > Gr-DV > Gr (where DV is a double vacancy and Gr the graphene surface). It is evidenced that, after a high-temperature treatment performed in order to remove the SFGs, the Ru/CNT material can react with oxygen from air via a surface reconstruction reaction, which reforms a stable Ru-acetato interface. The mechanism of this reaction has been investigated by DFT. These Ru/CNT catalysts are extremely stable, keeping a mean particle size <2 nm, even after heating at 973 K under a hydrogen atmosphere

Understanding the surface chemistry of carbon nanotubes: Toward a rational design of Ru nanocatalysts

International audienceA comprehensive experimental and theoretical study of the surface chemistry of ruthenium nanoparticles supported on/in multi-walled carbon nanotubes (CNTs) is reported that could pave the way to the rational design of metal–carbon nanocomposites. It is shown that the oxidation of CNTs by nitric acid that creates various oxygen surface functional groups (SFGs) on the CNT external surface is a crucial step for metal grafting. In particular, it is demonstrated that carboxylic acid, carboxylic anhydride, and lactone groups act as anchoring centers for the Ru precursor, presumably as surface acetato ligands. The HNO3 treatment that also allows CNT opening contributes to the endohedral Ru deposition. The stability of Ru nanoparticles, modeled by a Ru13 cluster, on different adsorption sites follows the order: Gr-DV-(COOH)2 > Gr-DV > Gr (where DV is a double vacancy and Gr the graphene surface). It is evidenced that, after a high-temperature treatment performed in order to remove the SFGs, the Ru/CNT material can react with oxygen from air via a surface reconstruction reaction, which reforms a stable Ru-acetato interface. The mechanism of this reaction has been investigated by DFT. These Ru/CNT catalysts are extremely stable, keeping a mean particle size <2 nm, even after heating at 973 K under a hydrogen atmosphere