Radiocarbon dioxide detection based on cavity ring-down spectroscopy and a quantum cascade laser

Monitoring of radiocarbon (C14) in carbon dioxide is demonstrated using mid-infrared spectroscopy and a quantum cascade laser. The measurement is based on cavity ring-down spectroscopy, and a high sensitivity is achieved with a simple setup. The instrument was tested using a standardized sample containing elevated levels of radiocarbon. Radiocarbon dioxide could be detected from samples with an isotopic ratio C14/C as low as 50 parts-per-trillion, corresponding to an activity of 5  kBq/m(3) in pure CO(2), or 2  Bq/m(3) in air after extraction of the CO(2) from an air sample. The instrument is simple, compact, and robust, making it the ideal tool for on-site measurements. It is aimed for monitoring radioactive gaseous emissions in a nuclear power environment, during the operation and decommissioning of nuclear power plants. Its high sensitivity also makes it the ideal tool for the detection of leaks in radioactive waste repositories.

Active control of the pointing of a multi-terawatt laser

The beam pointing of a multi-terawatt laser [corrected] is stabilized on a millisecond time scale using an active control system. Two piezo mirrors, two position sensing detectors, and a computer based optimization program ensure that both near- and far-field are stable, even during single shot operation. A standard deviation for the distribution of laser shots of 2.6 μ rad is achieved.

Laser-driven plasma waves in capillary tubes

The excitation of plasma waves over a length of up to 8 cm is demonstrated using laser guiding of intense laser pulses through hydrogen-filled glass capillary tubes. The plasma waves are diagnosed by spectral analysis of the transmitted laser radiation. The dependence of the spectral redshift-measured as a function of filling pressure, capillary tube length, and incident laser energy-is in excellent agreement with simulation results. The longitudinal accelerating field inferred from the simulations is in the range of 1-10 GV/m.

[Nonverbal communications and psychotherapy]

The authors review the research on non-verbal communications in therapy; they distinguish between psychoanalytic, psychiatric, phenomenological and ecosystemic approaches and compare their respective methodologies. They show that the structural approach is the most advanced as far as systematic description of non-verbal behavior is concerned and therefore is presently the most promising for the inference of the therapeutic process.

Evaluation of the antihypertensive effect of a beta-blocker with the aid of daily blood pressure profiles

The clinical efficacy of bopindolol, a new, long-acting beta-adrenoceptor blocking drug, in a dosage of 1-2 mg daily was compared with that of atenolol (50-100 mg daily) in 33 patients with mild or moderate arterial hypertension who were treated for a total period of 12 months. Both drugs lowered systolic and diastolic blood pressure to about the same extent, but atenolol caused a somewhat greater lowering of heart rate. Over 70% of patients receiving atenolol required a diuretic in addition, whereas only 55% of the bopindolol patients required a diuretic. Both drugs maintained 24-h blood pressure reduction with once-daily therapy, although circadian rhythm (recorded using a Remler device) tended to be lost during treatment with atenolol but not with bopindolol.