Cold forming of plastics part I. Draw forming of thermoplastic sheets

An experimental procedure is outlined to examine the potential of thermoplastic sheets in draw forming. Experiments carried out on a variety of materials indicate that the following requirements must be fulfilled for a thermoplastic sheet to be cold formable: (1) The glass transition of polymer should be above ambient temperature and above the temperature of forming, (2) tensile elongation at break should equal or exceed 30%, (3) ratio of tensile to compressive yield stress should equal or exceed 1.6 and (4) sheet must not yield locally (neck) when strained in tension. An experimental method has been developed to determine the compressive, friction and bending forces which oppose the drawing force exerted by the punch. It is shown that the compressive force is, in most cases, largest. A stress analysis is carried out leading to an expression correlating the maximum depth of draw as a function of basic properties of sheets such as tensile strength (S_t*) and compressive yield stress (S_c). The effect of rolling on drawability is examined and interpreted in terms of the ratio S_t*/S_c. The cold formed items have a lower heat distortion temperature than their thermoformed counterparts.     

New brown chlorobacteria Prosthecochloris phaeoasteroidea nov. sp

Two strains of new photosynthetic bacteria were isolated from salt meromictic lakes Mogilnoye and Faro. The bacteria are abligate phototrophic anaerobic cultures which utilize H2S as an electron donor by oxidizing it to elementary sulphur and sulphates. Sulphur is liberated outside the cell. The cultures contain bacteriochlorophyll e and carotenoids of the isorenierathene type. Photosynthetic structures are represented by chlorobium-vesicles. According to these properties, the cultures belong to the Chlorobiaceae family. The bacteria have no gas vacuoles. The cells form 10--20 apophyses-prosthecae which is typical of the Prostheocochloris genus. The new strains differ from Prosthecochloris aestuarii by the brown colour of the cell suspension, the composition of pigments, and ecology. They are classed as a new species Prostheocochloris phaeoasteroidea nov. sp. Diagnosis of the new species is presented.     

The study reports on a case of habitual dislocation of the hip-joint in a 6-year-old girl (author''s transl)

During the operative reposition the capsule was found extremely wide, and extended capsular fibrosis was exhibited. Resection of an ovoid capsular segment and a double capsular suture, secured by superfixation of the m. rectus tendon, resulted in a stabile hip-joint position.     

Antiorthostatic hypokinesia as a method of weightlessness simulation

Physiological effects seen in eight test subjects during a 5-d bedrest experiment in the head-down position (0,-4,-8,-12degrees) were studied. It was shown that the antiorthostatic hypokinesia at -12degrees could reproduce physiological responses shown by space crewmembers more closely than recumbent bedrest. Our observations help to stimulate an acute stage of human adaptation to the weightless state and to assess the part played by gravity-induced blood redistribution in the development of physiological changes.     

Renal carcinoma in the dog

Thirty-three cases of canine renal carcinoma reported between 1907 and 1972 are reviewed, and clinical and pathological features of nine other cases seen in Bristol between 1966 and 1975 are described. Clinical features frequently include nonspecific signs of anorexia and weight loss. The age range of affected dogs varies from 3 to 15 years, with a mean of 7.1 years. Male dogs appear to be affected more frequently than females, but there is no breed predilection. The clinical behaviour of canine renal carcinoma is variable, with 4 years the longest survival time after nephrectomy. The primary tumours characteristically are large and unilateral and occupy most of one pole of a kidney. Metastatic spread can involve a wide range of organs, the commonest being lymph nodes and lung. Solid, tubular and papillary patterns are common. Clear cell carcinoma is uncommon.     

Phenomenology of explosions of hydrocarbon gas-air mixtures in the atmosphere

This paper discusses the phenomenology of explosions of hydrocarbon gas-air mixtures. In general, after deflagration-type ignition such air-gas mixtures reach velocities in the free atmosphere of only a few m/sec to the order of 10 m/sec. These velocities are not sufficient to induce the transition from the combustion process to a detonative process.     

Ischemic necroses of the colon and rectum following alloplastic vessel substitution of the abdominal aorta

Arterial insufficiency to the colon and rectum followed by ischemic necrosis of this bowel portion is considered to be a rare complication after resection of abdominal aortic aneurysms and alloplastic replacement of the abdominal aorta in arterial occlusive disease. The main symptom is diarrhea and mucus or blood in stool. Sigmoidoscopic examination is of diagnostic value; the treatment of choice has to be colostomy and resection. A causative factor for the development of large bowel necrosis is diminution of collateral blood supply, which is discussed in detail.