Chlorinated organics from chlorine used in water treatment

The contribution from impurities in chlorine to levels of chlorinated organics found in potable water after chlorination was investigated. Techniques for sampling of chlorine and gas chromatography (GC) determination of chlorinated organics in chlorine are described. The detection limits were better than 1 ppm for each of chloromethane, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, hexachloroethane, hexachloropropane and hexachlorobenzene in chlorine. With the exception of chloroform which occasionally accounted for nearly 1 μg l⁻¹ in water, the levels of the nine compounds in chlorine accounted for less than 0.1 μg l⁻¹ of each compound in chlorinated water from 10 Canadian treatment plants. The occurrence of these nine and 28 additional chlorinated organics previously detected in water supplies was determined by aid of liquid-liquid extraction of water samples. Seven compounds, including chloroform, carbon tetrachloride, trichloroethylene and tetrachloroethylene were detected, usually at levels ranging from 0.1 to 1 μg l⁻¹ in chlorinated water from the treatment plant.     

6Gbit/s multiplexer and regenerating demultiplexer ICs for optical transmission systems based on a standard bipolar technology

Time-division 4:1 multiplexing and 1:4 demultiplexing as well as signal regeneration are important functions in high-speed optical fibre transmission systems. It has been shown by experiments that these tasks can be solved up to about 6Gbit/s by using monolithic integrated circuits fabricated with a 2 ?m standard bipolar technology.     

Mechanical stability of rigid rod polymer fibres under the influence of compression and temperature

This work presents a mathematical model for the compressive strength of a rigid rod polymer fibre based on an approach describing the fibre fibril as an end-loaded column on an elastic base. Also, it is suggested that the model of elastic stability of the coated fibre includes the influence of thermal stresses. A good agreement with experimental data is received. From this model one can propose that if an interfibrilar matrix material is incorporated in the fibre, at a small volume fraction of about a few per cent, this material may have a pronounced influence on the fibre's compressive strength.     

Exercise hemodynamics in small (< or = 21 mm) aortic valve prostheses assessed by Doppler echocardiography

Exercise Doppler echocardiography was used to assess hemodynamics in 25 patients with a < or = 21 mm aortic valve prosthesis (14 with a Medtronic-Hall 21 mm valve, three with a Medtronic-Hall 20 mm valve, three with a Sorin 21 mm valve, one with a Duromedics 21 mm valve, and four with a Carpentier-Edwards 21 mm valve). A symptom-limited upright bicycle exercise test was performed, and Doppler gradients were recorded during exercise. Gradients increased with exercise from 30 +/- 8/16 +/- 4 mm Hg (peak/mean) at rest to 46 +/- 12/24 +/- 7 mm Hg during exercise; both p < 0.001. Mean exercise gradient exceeded 30 mm Hg in five patients, and the highest mean gradient recorded was 37 mm Hg. Within the group of mechanical valves, gradients at exercise were similar for different types of valves. A linear relationship was found between gradients at rest and during exercise (peak r = 0.75, mean r = 0.77; both p < 0.001). Additional findings were midventricular velocities exceeding 1.5 m/sec in late systole in 10 patients (40%) and intraventricular flow (> or = 0.2 m/sec) toward the apex during isovolumic relaxation in 11 patients (44%). The patients with these velocity patterns had significantly smaller left ventricular cavities (end-diastolic diameter 39.8 +/- 4.8 vs 46.5 +/- 4.2 mm, p < 0.01; end-systolic diameter 24.2 +/- 3.0 vs 28.5 +/- 4.5 mm, p = 0.013).(ABSTRACT TRUNCATED AT 250 WORDS)