Abstract: Disclosed is a method of producing cubic boron nitride, which comprises the steps of subjecting to a pressure of from 40 to 70 kilobars and to a temperature of from 1100.degree. to 2000.degree. C. a charge including hexagonal boron nitride and a conversion initiator selected from the group consisting of alkali and alkaline earth metals and borides of the foregoing metals, doping the charge with crystallohydrate in the form of a compound selected from the group consisting of sulfur-, halogen- or nitrogen-containing salts and their mixtures incorporating at least 5 molecules of crystallization water. According to another embodiment, the aforesaid charge is doped with a member selected from the group consisting of alkali metal hydroxide or alkaline earth metal hydroxide.

Abstract: An artificial heart comprising at least one blood circulating pump having a transparent housing divided into two chambers by a diaphragm. One of the chambers is a hydraulic chamber having an inlet valve and an outlet valve which are connected to the circulatory system; the other chamber is a pneumatic chamber provided with a nipple for the intake and discharge of gas. The pump's pneumatic chamber has a transparent conductive coating, for example, of gold, applied onto the internal wall of said pneumatic chamber. Said coating and the surface of the blood circulating in the hydraulic chamber make up a capacitor whose capacity varies due to changes in the volume of the hydraulic chamber. Said capacitor serves as a blood volume transducer. The artificial heart includes a system for controlling the supply of gas to and the discharge of gas from the pneumatic chamber of said pump. The control system comprises an element which is sensitive to variations in the blood volume. Said sensitive element is an RC bridge.