Pressure Reduction Method Research Articles

Accuracy of reproducing the unit pressure by absolute pressure-reduction in a high or ultrahigh vacuum

1. The measurement equation of the pressure-reduction method has been analyzed theoretically. The necessary corrections have been noted; methods for determining these errors have been described; and such a determination has been illustrated. 2. The error of an apparatus intended for reproducing the unit of pressure by the pressure-reduction method has been evaluated. 3. The errors involved in a theoretical account of the conductance of apertures have been studied. 4. The total relative rms error of the apparatus of [2] for reproducing the unit pressure in the range 10−3–10−6 N/m2 is no greater than 2.5–3%.

Absolute method for dynamic reproduction of small pressures

1. Theoretical investigations have shown the possibility of measuring high vacuum by the pressure-reduction method. 2. The equipment produced by us provides a reproduction by the above method of small absolute pressures from 10−2 to 10−4N/m2. 3. The relative root-mean-square error of the equipment does not exceed 5% of the measured pressure. 4. The calibration of ionization-gauge transducers by the pressure-reduction method has confirmed the results obtained in calibrating them with the compression single-capillary manometer [12]. The calibration errors are approximately of the same order as those obtained in calibrating by means of a compression manometer. 5. The above dynamic method of reproducing small pressures has distinct possibilities for measuring considerably lower pressures than those attained at the present time and, in this respect, it is preferable to the mercury compression-manometer method. 6. Equipment used for implementing the above dynamic pressure-reduction method can serve as a reference absolute manometer within its pressure range.

Drug therapy of hypertension. V. Observations on the results with ganglion-blocking agents given in combination with Rauwolfia and chlorothiazide.

During the past 10 years many different drugs with direct and indirect actions upon the sympathetic nervous system have been used for the treatment of diastolic hypertension. Some of these drugs produce a central depressant effect on the hypothalamus with a secondary inhibition of the medullary vasomotor center; others exert their action at peripheral sites by blocking the release of levarterenol or depressing the neuroeffector site within the arteriolar walls. A third group of drugs exert their antihypertensive effect by depressing the autonomic ganglia. It now appears that the use of ganglion-blocking agents in combination with central depressant drugs and diuretics is the most effective method of blood pressure reduction in patients with moderate and severe diastolic blood pressure elevation. The first available ganglion-blocking agent for the treatment of hypertension was tetraethyl ammonium 1-4 ; subsequently a variety of other ganglioplegic drugs were introduced. 5-35 All of these compounds produce their

Treatment of hypertension in the ambulatory patient

Blood pressure elevation of adequate severity and for a prolonged period of time will definitely produce vascular changes in the brain, the heart, and the kidneys. The more severe the hypertension, the more marked these changes will be in the kidneys. Effective reduction of blood pressure may completely arrest these vascular changes regardless of the method used for blood pressure reduction. Although the changes are arrested, renal function rarely returns to normal. Hypertension aggravates and hastens the development of arteriosclerosis. Reducing the blood pressure arrests this hastening process, but still arteriosclerosis progresses just as it does in the normotensive individual. The method of blood pressure reduction is probably not important, insofar as arresting the vascular changes associated with hypertension is concerned. The important thing is that the blood pressure be reduced effectively. This the surgeon can do, particularly when he employs concurrent medical therapy. We would concur with this approach just as long as the blood pressure is severe enough to warrant surgical therapy and the surgeon is proficient at doing sympathectomies. On the other hand, when the psychiatrist, or the general practitioner, or the internist who carries psychiatric overtones, can “talk the blood pressure down,” this is good therapy. Unfortunately, being neither psychiatrist nor surgeon, we prefer to use drugs and our results using psychotherapy (and placebo) have been poor. Any drug therapeutic program that is effective in bringing the blood pressure to a normal or relatively normal levels, is an effective therapeutic program. Generally speaking, our program has been one of polypharmacy in which we attempt to deplete body sodium with chlorothiazide. This drug is continued indefinitely as a background medication for all antihypertensive drugs. This is probably the most effective measure for blood pressure reduction. Then the sympathetic nervous system is blocked by different methods. The centrally acting drugs are used first. The most common ones are rauwolfia and hydralazine. Usually in milder cases rauwolfia is given an initial trial alone and if the patient needs additional therapy, he may receive hydralazine (Apresoline). In the moderatelysevere cases, we give a therapeutic trial of hydralazine with rauwolfia. For the more severe cases when the diastolic blood pressure is fixed above 120 to 130 mm Hg, we use ganglionic blocking agents, such as mecamylamine or pentolinium.

VAPOUR PRESSURES OF SODIUM ALUMINATE SOLUTIONS

There are many reports on researches concerning the equilibrium of sodium aluminate solutions, but few reports have been published from the thermodynamic point of view. because theyare metastable and easilt over saturated with respect to Al(OH, )3. In order to contribute to this part of research, the following experiments and calculations of the equation were carried out.One of the writers (Kitajima) obtained the values of vapour pressures of caustic soda solutions and sodium aluminate solutions (containing a small amount of impurities) by the pressure reduction method with variations of temperature 40, 60, 80, 100°C (t); Na2O concentration 100, 200, 300g/l (n); and Al2O3/Na2O mol ratio 0-0.6(m).From these observed results, the other writer (Mitsugi) obtained the following experimental equation with the above variables t, n, and m. The experimental values of the vapour pressure of caustic soda solutions, however, were corrected according to those based on the Int. Crit. Table and the relation was studied from the temperature variation of the activity of water.P=Pw-4.02•10-3e0.04317t.n1.149+3.72t.10-3-2•9t2.10-5-3.24me0.0223t-6mnt4.8×10-11Pw shows the vapour pressure of pure water at t°C. As to the accuracy of the equation, calculated values for caustic soda solutions of various temperatures and concentrationes were compared with those based on the Int crit. Table, and the accuracy was found to be ±2mm Hg, and in case of sodium aluminate solutions, the standard deviation. between the observed values was calculated for solutions of various temperatures, the result being as follows;