High average power diamond Raman laser.

We report a pulsed Raman laser at 1193 nm based on synthetic diamond crystals with a record output power of 24.5 W and a slope efficiency of 57%. We compared the performance of an anti-reflection coated crystal at normal incidence with a Brewster cut sample.

Extended sphere method for complete investigation of the phase-matching properties of sum- and difference-frequency generation.

We demonstrate the feasibility of a complete experimental investigation of the phase-matching properties of sum- and difference-frequency generation in a single crystal cut as a sphere over its entire transparency range. The class of the studied crystal is the only initial data that is required. This feasibility study was carried out with rubidium titanyl arsenate.

Efficient energy conversion for cubic third-harmonic generation that is phase matched in KTiOPO(4).

We demonstrate, for the first time to our knowledge, that efficient third-harmonic generation can be achieved with a cubic contribution much larger than the quadratic processes. An energy-conversion efficiency of 2.4% is achieved for cubic third-harmonic generation that is phase matched along the x axis of a KTiOPO(4) crystal by use of a picosecond fundamental laser emitting at 1618 nm.

Cylindrical KTiOPO(4) crystal for enhanced angular tunability of phase-matched optical parametric oscillators.

We demonstrate what is to our knowledge the first optical parametric oscillator (OPO) based on a cylindrical phase-matched nonlinear crystal. Experiments are performed with an uncoated KTiOPO(4) crystal cut as a cylinder with a diameter of 21.2 mm and a thickness of 5 mm.

Thermo-optical effect and saturation of nonlinear absorption induced by gray tracking in a 532-nm-pumped KTP optical parametric oscillator.

We present experiments that show that gray tracking modifies the parametric gain and the generated wavelengths of a KTP optical parametric oscillator pumped at 532 nm near degeneracy. These perturbations occur over a limited range of pump intensity. We propose a satisfactory model that takes into account photochromic damage, the thermo-optical effect, and the combined processes of creation and saturation of a two-photon absorber at 532 nm.

Widely and continuously tunable optical parametric oscillator based on a cylindrical periodically poled KTiOPO(4) crystal.

We report on what is to our knowledge the first realization of a quasi-phase-matched optical parametric oscillator (OPO) based on a crystal with a cylindrical shape. The main reason for interest in this device is its broad, continuous tuning. In experiments with a 1064-nm pump, the signal tuning range was equal to 525 nm (1515-2040 nm), and the corresponding idler was continuously tuned over 1340 nm (2220-3560 nm).

Four-wave mixing in nanosecond pulsed fiber amplifiers.

We present an experimental and theoretical analysis of four-wave mixing in nanosecond pulsed amplifiers based on double-clad ytterbium-doped fibers. This process leads to saturation of the amplified pulse energy at 1064 nm and to distortion of the spectral and temporal profiles. These behaviours are well described by a simple model considering both Raman and four-wave-mixing contributions.

Microchip-laser polarization control by destructive-interference resonant-grating mirror.

An output coupler comprising a resonant grating submirror monolithically associated with a standard multilayer submirror polarizes the emission of a Nd:YAG microchip laser linearly over its full emission bandwidth by intra-mirror destructive interference for the undesired polarization. A polarization extinction ratio of more than 25 dB is obtained up to 6.1microJ pulse energy.

Phase-matching and mitigation of four-wave mixing in fibers with positive gain.

We present a theoretical study of four-wave mixing interactions in fibers in the presence of gain. In contrast to passive fibers, positive gain at the pump wavelength leads to constructive generation of the signal and idler waves, even in the case of large phase-mismatch, so that FWM processes can be very efficient even in isotropic single-mode fibers with normal dispersion. We also propose simple ways to mitigate these parametric interactions by applying a controlled variation of the phase-mismatch along the fiber.

High-Power fiber amplifier with widely tunable repetition rate, fixed pulse duration, and multiple output wavelengths.

We report a pulsed, fiber-amplified microchip laser providing widely tunable repetition rate (7.1 - 27 kHz) with constant pulse duration (1.0 ns), pulse energy up to 0.

Iatrogenic Creutzfeldt-Jakob disease subsequent to dural graft: persisting risk after 1987.

The first case of Creutzfeldt-Jakob disease (CJD) related to the use of a dura mater graft of cadaveric origin was identified in 1987 and this procedure is now considered as one of the main causes of iatrogenic CJD. Although the decontamination procedure for the preparation of graft material was modified, the product was withdrawn from the market in many countries a few years later and replaced by synthetic material. In this context, two patients treated in our institution developed CJD following a cadaveric dural graft performed after cerebral and lumbar trauma.

Continuous tuning of a microlaser-pumped optical parametric generator by use of a cylindrical periodically poled lithium niobate crystal.

An optical parametric generator with a cylindrical periodically poled LiNbO3 crystal and a Nd:YAG commercial microchip pump laser yields continuous tuning of the emitted wavelengths over a broad spectral range (1.42-1.7 microm and 2.

[Ptosis and mastication disorders revealing concurrent myasthenia gravis and chronic polyradiculoneuritis].

Although myasthenia gravis (MG) has frequently been associated with other autoimmune disorders, it has only rarely been reported in conjunction with diseases of the nervous system. A 74-year-old patient with hypertension suddenly presented left unilateral ptosis and mastication disorders. Clinical examination showed a concomitant loss of strength distally and reduced deep tendon reflex.

Decrease in heart ventricular ejection fraction during multiple sclerosis.

Recent studies have shown that mitoxantrone is effective in patients with active multiple sclerosis (MS) and that cardiac monitoring is usually required. However, right and left ventricular ejection fractions (VEFs) have never been studied in MS patients as compared with control subjects. Radionuclide angiocardiography (RA) was performed to assess right and left VEFs at rest in 40 consecutive patients with active definite MS [15 men and 25 women; mean age 33.

[Recurrent syncope and Chiari malformation].

Downward herniation of the cerebellar tonsils through the foramen magnum (Chiari I malformation) is usually revealed by head and neck pain, often associated with brain-stem or spinal cord disturbances. Syncopes are rarely reported and may be difficult to link to their cause when they occur alone. We report two cases with brief and repetitive syncopes revealing a Chiari I malformation.

Sustained anxiety and 4-year progression of carotid atherosclerosis.

Several studies have shown that anxiety disorders are associated with a higher risk of coronary artery disease. However, the relationship between anxiety disorders and atherosclerosis has been studied to a lesser extent. The goal of this study was to examine whether high and stable trait anxiety was associated with the progression of atherosclerosis.

[Progressive multifocal leukoencephalopathy and pulmonary sarcoidosis].

An association of progressive multifocal leukoencephalopathy (PML) and sarcoidosis in a 47 year-old-woman is reported. This is the third case in which PML has been diagnosed by PCR. Clinical, biological and radiological features were in agreement with previous findings in immunologically suppressed patients.

[Late cerebrovascular complications of cardiac transplantation].

The occurrence of stroke after the post-operative period of cardiac transplantation is a rare event, and the role of the cardiac transplant in these patients, who often have various vascular risk factors, is unclear. We reviewed the clinical records of 303 consecutive patients with orthotopic cardiac transplantation performed from March 1985 to December 1996 and selected those who developed a stroke over the first 2 months postoperatively, in order to evaluate the frequency and the mechanisms of late cerebrovascular complications. Four patients had presented cerebral infarct and two intracranial hemorrhage.

[Analysis of neuropsychological disorders coupled with 99m Tc-HMPAO Spect in amyotrophic lateral sclerosis. Prospective study of 16 cases].

A prospective psychometric study was conducted in 16 patients who recently developed classic sporadic amyotrophic lateral sclerosis and had no signs of anxiety or depression. Tests included PM38, MMS, Rey word and Rey image tests, span, Stroop test, verbal fluency, Wisconsin test and London Tower test coupled with 99m Tc HMPAO tomography. Results demonstrated that the patients had no intellectual degradation nor visual constructive disorders but had disturbed verbal and visual memory with a reduced verbal fluency (particular bulbar forms), perseverance errors on the Wisconsin test (half of the cases) and an increased number of movements in the London Tower test.

Frontal type dementia preceding amyotrophic lateral sclerosis: a neuropsychological and SPECT study of five clinical cases.

Between 1993 and 1995, we observed five sporadic cases of frontotemporal dementia (FTD) which in all cases preceded the appearance of typical amyotrophic lateral sclerosis (ALS). The FTD rapidly became severe (within 12-18 months) and the delay between the presumed onset of mental change and ALS was short (12-26 months). The frontal dysfunction was characteristic (disinhibited, jocular, impatient, gluttonous, stereotypical gestures).

Combined effects of lipid peroxidation and antioxidant status on carotid atherosclerosis in a population aged 59-71 y: The EVA Study. Etude sur le Vieillisement Artériel.

There are few epidemiologic studies of the effects of lipid peroxidation and antioxidant status on atherosclerosis. The relation of lipid peroxidation evaluated by thiobarbituric acid-reactive substances (TBARS) and biological markers of antioxidant status to ultrasonographically assessed carotid atherosclerosis was examined from baseline data of a longitudinal study on cognitive and vascular aging (Etude sur le Vieillisement Artériel, the EVA Study). The study sample was composed of 1187 mean and women aged 59-71 y without any history of coronary artery disease or stroke.

[Frontal type dementia and amyotrophic lateral sclerosis. 3 cases with (HmPAO Tc99m) single-photon emission tomography study].

Three cases of rapid onset neuropsychological frontal dementia preceded the development of sporadic amyotrophic lateral sclerosis by 12 to 24 months. HmPAO Tc99m scintigraphy demonstrated hypoactivity in the cortex, predominantly in the frontal region. Three hypotheses are discussed: 1) coincidence between two degenerative diseases, Alzheimer's disease or Pick's disease and ALS; 2) an amyotrophic form of Creutzfeld Jakob disease; 3) pre-senile dementia associated with a motoneuron disease, a clinical pathology entity recently described by Mitzuyama.