Angle-tuned type II external-cavity frequency doubling without temperature stabilization.

We report frequency doubling of a low-power cw diode laser at 1064 nm in an external ring cavity by use of an angle-tuned KTP type II crystal. We demonstrate a new setup that requires no temperature stabilization of the crystal. An intracavity lambda/2 plate rotates the polarization of the fundamental after each cavity round trip by 90 degrees; this provides the two eigenpolarizations of the crystal required for a type II nonlinear process. As a result, it is possible to maintain the resonance condition by use of a standard locking circuit.

Use of the A1- and the A2-sequences to modulate continuous-wave pseudorandom noise lidar.

The A1-sequences and the A2-sequences have been proposed to replace the M-sequence that is generally used to modulate continuous-wave pseudorandom noise lidar. These new sequences, under two hypotheses, provide a reduction in the background noise, which is especially significant in noisy conditions when one uses M-sequences. We show that one of these two hypotheses is not verified for cloudy atmospheric conditions. Thus, the A1- and the A2-sequences cannot be used for such conditions.

Accuracy limitations on Brillouin lidar measurements of temperature and sound speed in the ocean.

There are five mutually dependent variables relevant to Brillouin lidar measurements of temperature and sound speed in the ocean; they are (1) the Brillouin shift, (2) the sound speed, (3) the index of refraction, (4) the temperature, and (5) the salinity. We use three well-known relations to analyze rigorously the interdependence of these five variables. Clearly, a Brillouin shift measurement does not provide a stand-alone determination of temperature or sound speed; one more variable or one more relation must be known. The use of mean values of salinity that have been obtained by an analysis of a large set of historical in situ data is considered for this additional relation.

In vivo measurement of dye concentration using an evanescent-wave optical sensor.

A miniaturised evanescent-wave optical sensor is proposed for in vivo measurement of dye concentrations. It enables a continuous monitoring of the optical-dye attenuation or fluorescence spectra between 380 and 650 nm. The sensor is constructed with polished fibres: the cladding of a single-mode fibre is removed by longitudinal polishing. The proximity of the core to the medium favours penetration of the evanescent part of the modal field into the bio fluid. The dimensions of the probe permit several potential applications: for example, insertion into hypodermic needles for spectroscopic analysis of tissues and blood. In the paper, a gastro-enterologic application of the sensor introduced into a catheter is reported. In vivo tests demonstrate the feasibility of quantitative measurement of dye clearance in the gastro-oesophageal tract.

Assessment of the lactulose-mannitol test in Crohn's disease.

The mannitol-lactulose intestinal permeability test was evaluated in 100 healthy controls and 47 patients with Crohn's disease. These patients were further separated into three subgroups of increased activity (Harvey-Bradshaw index) and in two subgroups, with elective colonic lesions and associated ileal and colonic lesions. Results were given as percentages of urinary recoveries for mannitol (M), lactulose (L), and L/M ratio. As a whole, patients with Crohn's disease have lower mean M and higher mean L and mean L/M ratios than controls. The magnitude of alterations in M, L, and L/M increased with activity. The sensitivity of the test, however, reached interesting figures (67%:L and 86%:L/M) only in subgroup III which was composed of relapsing patients. Mean M was lower in patients with associated ileal lesion but, whatever the criterion (M, L, or L/M), the test does not provide any clue for the detection of a possible infraclinical associated ileal localisation.

[Terminal constipation caused by abdominopelvic asynchrony: analysis of etiological, clinical, manometric data and therapeutic results after rehabilitation by biofeedback]. / Constipation terminale par asynchronisme abdomino-pelvien: analyse des données étiologiques, cliniques, manométriques, et des résultats thérapeutiques après rééducation par biofeedback.

The aim of this study was to describe the etiological, clinical, rectoanal manometric findings as well as the results of biofeedback therapy in a series of 65 patients (34 males, 31 females, aged between 5 and 77 years) presenting with severe primary constipation due to pelvic abdominal asynchronism. Pelvic abdominal asynchronism was statistically more frequent in males during childhood and in female patients during adult life (p less than 0.005). This study disclosed a high frequency of psychogenic factors in the onset of pelvic abdominal asynchronism (26 p. 100) as well as a high frequency of soiling (46.2 p. 100) in constipated patients. In 36.2 p. 100 of cases, pelvic abdominal asynchronism was the only abnormality. In contrast, in most of the patients, asynchronism was associated with miscellaneous rectoanal disorders: increased anal closure pressure (43.3 p. 100), decreased anal closure pressure (11.8 p. 100), impaired rectal conscious sensitivity (11.7 p. 100), and increased rectal compliance (31 p. 100). This study demonstrated that when high-fiber diet and laxatives fail, biofeedback therapy is a very interesting alternative, providing 80 p. 100 of good results in selected cases. However, we were unable to find any clinical or manometric parameters predictive of results of treatment. Follow-up studies are needed to determine long-term results of biofeedback training.