The Measurement of Fundamental Constants (Metrology) and Its Effect on Scientific and Technical Progress
It is perhaps appropriate that in this year 1975, which marks the centenary of the Systeme Metrique and that of the Bureau International des Poids et Mesures, scientific activity in the field of Metrology appears to be flourishing. This is witnessed on the one hand by the number, range and quality of the contributions to this Symposium and, on the other, by the importance which most of the 44 Governments affiliated to the BIPM attach both to their Basic Laboratories and to the network of technical centers engaged in developing measuring methods and in disseminating their results to all levels of the various branches of industry. Should this state of affairs be considered a happy but ephemeral stage in the march of science, or does it represent a tendency of fundamental importance in the evolution of science and technology ? Enough is now known about the history of civilization for us to affirm that, even since the Renaissance, Metrology has payed an ever greater part in both scientific and civic activities.
AC Josephson Effect Determination of e/h: A Standard of Electrochemical Potential Based on Macroscopic Quantum Phase Coherence in Superconductors
Abstract : An ac Josephson effect determination of e/h with significantly improved accuracy is reported. The precision of the measurement is determined by uncertainties associated with the comparison of a Josephson device voltage with the emf of an electrochemical standard cell voltage reference and is about 3 parts in 10 to the 8th power. This precision was made possible by use of Josephson devices at voltages above 10 mV and design and construction of two special voltage comparator instruments. The fabrication and operation of the Josephson devices and the design and performance of the voltage comparators are discussed.
CLINICAL TRIALS OF THE ABDOMINAL LEFT VENTRICULAR ASSIST DEVICE (ALVAD): PROGRESS REPORT.
An abdominal left ventricular assist device (ALVAD) is undergoing controlled clinical trials in our institution. The ALVAD is pneumatically-actuated, synchronously or asynchronously with an external console and is interposed between the apex of the left ventricle and the infrarenal abdominal aorta. It is an order of magnitude more effective than conventional intraaortic balloon pumping. Thus far, we have implanted this pump in 21 patients (15 males and six females). The average age has been 50. The duration of cardiopulmonary bypass with intensive pharmacologic support and IABP until ALVAD implantation has been nearly 4 hours. The plasma hemoglobins prior to ALVAD implantation have averaged 168 mg%. The platelet counts at implantation have averaged 68,000 mm(3). The average duration of ALVAD support has been in excess of one day and the longest trial extended for one week. We have been able to remove the pump after ventricular recovery in two instances and effected cardiac allografting in one instance of ALVAD dependency. We have found that (1) the profoundly depressed left (and right) ventricles can recover if totally supported with this device; (2) the device can function in the presence of ventricular fibrillation and/or standstill; (3) the device can effectively replace both left and right ventricular function in the presence of normal pulmonary vascular resistance and microcirculatory hemodynamics; and (4) in the presence of impending multiple organ failure, procrastination in use is to be avoided.