Fiber-based source of 500 kW mid-infrared solitons.

Fiber-based sources delivering high-energy few-cycle pulses at high repetition rates are currently being developed in the near-infrared spectral range, thanks to the wide availability of telecommunication-grade optical fibers and components. Similar sources in the middle-wave infrared (mid-IR) spectral domain, however, are scarce, although such sources are of high interest for applications such as high-precision frequency metrology and molecular spectroscopy or as a seed source to reach further into the mid-IR via coherent nonlinear processes. Here we report on the design of a fiber-based source of 50-nJ energy 90 fs duration pulses up to 2950 nm, corresponding to 500 kW peak power. To obtain this level of peak power we exploit multi-solitonic fission and soliton self-frequency shift in large mode area fibers excited by picosecond pulses emitted at 2 µm from a megahertz repetition rate fiber laser. We leverage mature silica-based fiber technology up to 2.4 µm and restrict the use of fluoride fiber to the very last frequency-shifting stage. The level of instantaneous power and ultra-short duration achieved in this Letter pave the way to all-fiber format generation of an ultra-broadband coherent continuum in the mid-IR with profound implications for applications such as high-resolution molecular spectroscopy and imaging.

Generation of 35 kW peak power 80 fs pulses at 2.9 µm from a fully fusion-spliced fiber laser.

Tunable femtosecond light sources in the short wave and middle wave infrared regions are of utmost importance for various applications ranging from multiphoton microscopy, mid-infrared supercontinuum generation to high-harmonic generation. We report on an all-fusion-spliced fiber laser emitting 80 fs pulses up to 2.9 µm with 35 kW peak power. The laser is based on Raman self-frequency shift effect from 1560 nm up to 3000 nm in germanium-doped fibers fabricated by the widespread modified chemical vapor deposition process.

Early post-stroke physical conditioning in hemiplegic patients: A preliminary study.

OBJECTIVE: To establish the value of an early post-stroke evaluation of cardiorespiratory fitness in hemiparetic patients using a one-leg cycling exercise test and to analyze the impact of an adapted physical activity programme 12 weeks after the stroke. PROTOCOL: Eighteen hemiparetic stroke patients participated in the study. The subjects were randomly assigned to one of two groups: the control group (CG) underwent 4 weeks of conventional rehabilitation, whereas the training group (TG) performed additional physical exercises. The initial evaluation (T1) was carried out after 1 week of exercise and the final evaluation (T2) was performed after 28 days. Both evaluations consisted of maximal graded tests performed with the valid leg, followed by completion of a questionnaire on personal autonomy in activities of daily living (ADL). RESULTS: In the CG group, we recorded a 4 to 8% increase in peak oxygen uptake (VO2 peak). There was no significant increase in peak power output (Wpeak). However, the TG displayed significantly (P<0.05) greater peak values than those recorded on study entry (Wpeak: +30%, VO2 peak: +20%). The TG showed a statistically significant improvement in the Barthel and Katz ADL scale scores, whereas the pre- and post-rehabilitation values did not differ significantly in the CG. However, there was no correlation between the Barthel/Katz scale scores and Wpeak. CONCLUSION: Evaluation of cardiorespiratory fitness by using the valid leg seems to be feasible in hemiplegic patients 1 month post-stroke. Early post-stroke physical training appears to be needed to limit the negative effects of functional hypoactivity.

Development of a surface ionization source for the SPIRAL 2 project.

Development of new radioactive beams, and thus of new target ion sources (TISs) for isotope-separator-on-line production systems are in progress at GANIL for the SPIRAL 2 project. The efficiency and time response measurements of each step in the production process are crucial to predict and maximize the available yields, in particular, for short lived isotopes. This paper presents a method for measuring these quantities that makes use of a stable alkali chopped beam of controlled intensity. This method was applied to surface ionization source test for high efficiency. Results of recent experiments are presented that include ionization efficiency measurements for Cs, Rb, K, Na, and Li with a graphite and rhenium ionizer and dwell time of these alkalis on graphite. The results enabled to design a first surface ionization source prototype which will be installed in the SPIRAL 2 TIS.

Direct 1+ --> N+ conversion of stable alkali ions using an electron cyclotron resonance ion source.

The production of radioactive ions using the Isotope Separation On-Line method gives rise, in most cases, to singly charged ions. In order to perform experiments with postaccelerated radioactive ion beams, these ions have to be multicharged. We describe here a new compact design for a charge breeder that will be coupled to the production target of SPIRAL1 at GANIL. We present recent results obtained offline with stable alkali ions (Na, K, Rb, and Cs) on the SIRa test bench. Particularly, 1(+) to N(+) conversion efficiencies and conversion times are presented. Several points have been identified for the improvements of the present performances.

Short-term effect of pudendal nerve electrical stimulation on detrusor hyperreflexia in spinal cord injury patients: importance of current strength.

Twenty patients with chronic suprasacral spinal cord injury presenting with detrusor hyperreflexia were examined. In a preliminary study in ten patients we investigated the reproducibility of bladder capacity through the repetition of three cystometries. The effect of electrical stimulation (ES) on detrusor hyperreflexia was then investigated in ten patients during three consecutive cystometries, the first one without ES (baseline) and the other two with continuous ES of the dorsal penile or clitoris nerve via surface electrodes. Parameters of stimulation were 5 Hz frequency, 0.50 msec pulse duration, and stimulation strength of 1 and 2 times the bulbocavernosus reflex threshold. No significant differences in bladder capacity were found between the three consecutive cystometries without ES (respectively 97.0 ml, 101.5 ml and 105.6 ml). A current at the bulbocavernosus threshold (mean 24.4 mA) failed to induce a significant increase in bladder capacity compared to baseline (173.0 ml vs 155.5 ml, P = 0.17) whereas a current of twice the bulbocavernosus threshold (mean 48.9 mA) was highly significant (318.5 ml vs 155.5 ml, P < 0.007). ES of twice the threshold resulted in perineal contraction in all of the patients, the threshold ES never did. Our results emphasise the decisive roles of perineal contraction and of current strength for achieving short-term bladder inhibition in spinal cord injury patients. The carry-over effect may also be dependent on the current strength. If so, maximal pudendal ES could represent an alternative procedure in the treatment of detrusor hyperreflexia in these patients.