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Megawatt peak power from a Mamyshev oscillator.

ABSTRACT: We demonstrate a fiber source with the best performance from an ultrafast fiber oscillator to date. The ring-cavity Mamyshev oscillator produces ~50-nJ and ~40-fs pulses. The peak power is an order of magnitude higher than that of previous lasers with similar fiber mode area. This performance is achieved by designing the oscillator to support parabolic pulse formation which enables the management of unprecedented nonlinear phase shifts. Experimental results are limited by available pump power. Numerical simulations reveal key aspects of the pulse evolution, and realistically suggest that (after external compression) peak powers that approach 10 MW are possible from ordinary single-mode fiber. The combination of practical features such as environmental stability, established previously, with the performance described here make the Mamyshev oscillator extremely attractive for applications.

SUBMITTER: Liu Z

PROVIDER: S-EPMC6181231 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Megawatt peak power from a Mamyshev oscillator.

Liu Zhanwei Z Ziegler Zachary M ZM Wright Logan G LG Wise Frank W FW

Optica 20170601 6

We demonstrate a fiber source with the best performance from an ultrafast fiber oscillator to date. The ring-cavity Mamyshev oscillator produces ~50-nJ and ~40-fs pulses. The peak power is an order of magnitude higher than that of previous lasers with similar fiber mode area. This performance is achieved by designing the oscillator to support parabolic pulse formation which enables the management of unprecedented nonlinear phase shifts. Experimental results are limited by available pump power. N ...[more]

PMID: 30320157

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Project description:Key pointsRespiratory muscle function declines with ageing, contributing to breathing complications in the elderly. Here we report greater in vitro respiratory muscle contractile function in old mice receiving supplemental NaNO3 for 14 days compared with age-matched controls. Myofibrillar protein phosphorylation, which enhances contractile function, did not change in our study - a finding inconsistent with the hypothesis that this post-translational modification is a mechanism for dietary nitrate to improve muscle contractile function. Nitrate supplementation did not change the abundance of calcium-handling proteins in the diaphragm of old mice, in contrast with findings from the limb muscles of young mice in previous studies. Our findings suggest that nitrate supplementation enhances myofibrillar protein function without affecting the phosphorylation status of key myofibrillar proteins.AbstractInspiratory muscle (diaphragm) function declines with age, contributing to ventilatory dysfunction, impaired airway clearance, and overall decreased quality of life. Diaphragm isotonic and isometric contractile properties are reduced with ageing, including maximal specific force, shortening velocity and peak power. Contractile properties of limb muscle in both humans and rodents can be improved by dietary nitrate supplementation, but effects on the diaphragm and mechanisms behind these improvements remain poorly understood. One potential explanation underlying the nitrate effects on contractile properties is increased phosphorylation of myofibrillar proteins, a downstream outcome of nitrate reduction to nitrite and nitric oxide. We hypothesized that dietary nitrate supplementation would improve diaphragm contractile properties in aged mice. To test our hypothesis, we measured the diaphragm function of old (24 months) mice allocated to 1 mm NaNO3 in drinking water for 14 days (n = 8) or untreated water (n = 6). The maximal rate of isometric force development (∼30%) and peak power (40%) increased with nitrate supplementation (P < 0.05). There were no differences in the phosphorylation status of key myofibrillar proteins and abundance of Ca2+-release proteins in nitrate vs. control animals. In general, our study demonstrates improved diaphragm contractile function with dietary nitrate supplementation and supports the use of this strategy to improve inspiratory function in ageing populations. Additionally, our findings suggest that dietary nitrate improves diaphragm contractile properties independent of changes in abundance of Ca2+-release proteins or phosphorylation of myofibrillar proteins.

Project description:Background and objectives: This study aimed to determine the cut-off values of the following three respiratory pressure meters; the voluntary peak cough flow (PCF), maximal expiratory pressure (MEP) and maximal inspiratory pressure (MIP); associated with post-stroke dysphagia and assess which of these parameters show good diagnostic properties associated with post-stroke dysphagia. Materials and Methods: Retrospective analysis of a prospectively maintained database. Records of patients with first-ever diagnosed dysphagia attributable to cerebrovascular disease, who had performed spirometry measurements for the PCF, MIP and MEP. Results: From a total of 237 stroke patients, 163 patients were diagnosed with dysphagia. Those with dysphagia had significantly lower PCF values than those without dysphagia (116.3 ± 75.3 vs. 219.4 ± 91.8 L/min, p < 0.001). In addition, the former group also had lower MIP (30.5 ± 24.7 vs. 41.6 ± 25.7 cmH2O, p = 0.0002) and MEP (41.0 ± 27.9 vs. 62.8 ± 32.3 cmH2O, p < 0.001) values than the latter group. The receiver operating characteristic curve analysis showed that the PCF cut-off value of 151 L/min (area under the receiver operating characteristic curve [AUC] 0.81; sensitivity 72%; specificity 78.8%) was associated with post-stroke dysphagia. The optimum MEP and MIP cut-off were 38 cmH2O (AUC 0.70, sensitivity 58%; specificity 77.7%) and 20 cmH2O (AUC 0.65, sensitivity 49%; specificity 84%). PCF showed the highest AUC results. Results from the univariate analysis indicated that PCF values of ≤151 L/min increased risk of dysphagia by 9.51-fold (4.96-18.23). Multivariable analysis showed that after controlling of other clinical factor, the PCFs at this cut-off value still showed increased risk of by 4.19 (2.02-83.69) but this was not observed with the MIPs or MEPs. Conclusions: Our study has provided cut-off values that are associated with increased risk of dysphagia. Among the three parameters, PCF showed increased association with post-stroke dysphagia.

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Megawatt peak power from a Mamyshev oscillator.

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Megawatt peak power from a Mamyshev oscillator.

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