Effect Of Pressure Variation Research Articles

EFFECTS OF CO2 ON PARAMECIUM MULTIMICRONUCLEATUM.

SYNOPSIS. Experiments were undertaken to examine and to quantitate the effect of CO2 upon movement, contractile vacuole activity, cellular volume and shape, and survival of Paramecium multimicronucleatum. Paramecia tolerated pressures of CO* up to 1 atmosphere for at least 24 hours. Above 1 atmosphere survival was inversely related to pressure of CO2. Increasing CO2 tensions slowed forward movement and altered length and width of the spiral paths. Pulsation rates of anterior contractile vacuoles diminished as the CO2 pressure increased. At 20 psi of CO2 vacuoles ceased to function. Paramecia retained their volume and shape when exposed to high CO2 tensions. Removal of CO2 from the medium decreased speed and length of spirals and caused an increase in cellular volume. These effects of pressure variation of “CO” are examined in terms of the ability of COS to expand the volume of hydrocarbons upon dissolving into these compounds and in terms of bicarbonate competing for cations at the cell membrane.

Aetiology and pathology of beat knee.

The object of this study was to determine the mechanism of the production of beat knee and its relation to pathological findings. A clinical study was made among 598 coal-face workers at one large colliery: 579 were examined of whom 233 showed evidence of past or present beat knee. A considerable preponderance of non-inflammatory lesions, most commonly in the prepatellar bursa, was demonstrated. It was concluded that the single common factor in the causation of non-inflammatory or acute recurrent bursitis was the trauma of kneeling. Experimental investigation of the pressures exerted showed great variations in the pressure on the knee as a whole and on different parts of its weight-bearing surfaces. The view that these localized and extreme variations in pressure may lead to rupture of a vessel found confirmation in the aspiration of blood from the bursae of 29 out of 30 patients. Histological sections from chronically enlarged bursae showed intense fibrosis in the wall of the bursa and sometimes deposition of haemosiderin. In the management of a new case of acute simple bursitis immediate aspiration of the blood and the instillation of hyalase proved successful in all 12 cases. Aspiration was also successful in certain cases of acute recurrent simple bursitis. Surgical removal of chronically enlarged fibrotic bursae allowed eight out of 12 patients to return to the coal-face. It is suggested that in order to reduce the incidence of beat knee the use of a knee pad that will not only protect the skin of the front of the knee from trauma by coal particles but will also cushion the knee from the effects of extreme variations in pressure may be desirable.

Flame propagation: the effect of pressure variation on burning velocities

The burning velocity of mixtures of methane, propane, ethylene and propylene with air are determined under constant-pressure conditions in a tube of rectangular section at pressures from ½ to 9 atm. For methane and also for propane, the effect of mixture strength was also investigated. Schlieren photographs of the passage of the combustion wave were obtained. The conditions leading to vibrations and to turbulence in the flame front, and also to change in the shape of the surface of the advancing flame, were investigated. The burning velocity was obtained from measurements of the speed of uniform movement and the flame area. A special valve maintained communication with an atmosphere of nitrogen during passage of the flame so as to maintain the pressure constant. The results are compared with other measurements. The pressure exponent is about 0·5 for methane and for other gases approximately 0·3, but there is some variation with change of mixture strength; the richer mixtures are less affected by pressure. The results indicate that both heat and diffusion (particularly of hydrogen atoms) play a part in flame propagation.

OCULAR EFFECTS OF ALTITUDE FLYING AND OF DEEP SEA DIVING

The subject assigned refers primarily to changes brought about by alterations in atmospheric pressure and in partial pressure of oxygen, to rapid and severe changes in temperature and to protection of the eyes against glare, air blast, dust and flying debris. Changes in atmos1 pheric pressure in flying are within the range between the pressure at sea level (1 atmosphere—about 15 pounds per square inch [1,050 Gm. per square centimeter], or 760 mm. of mercury) and a pressure of about ⅙ atmosphere (2½ pounds per square inch [170 Gm. per square centimeter], or 127 mm. of mercury) at the maximum altitudes now attainable by military aircraft. Pressures encountered in deep sea diving can also be expressed in terms of pressure at sea level. These pressures range from 1 to 6, 7 or 8 atmospheres. The physiologic effects of variations in pressure are brought about in several ways : By

Mechanics of Hydraulic-Turbine Pressure Regulation

Abstract Problems of pressure control or the pressure variations resulting from the action of the governor complicate calculations of hydraulic turbines. This paper describes mechanical means whereby desired field results can be obtained under existing conditions of operation and of pipe-line characteristics. Calculations, formulas, and examples of speed and pressure control take up such points as closing gates, passing through position of static balance of turbine gates, formulas for speed regulation, effect of pressure variations on speed, and calculations of pressure rises in pipe lines.