Abstract: This invention relates generally to a novel process for preparing 5-deazariboflavins by the cyclization of the corresponding 6-(N-substituted arylamino)uracils with trialkylorthoformate in the presence of a strong acid catalyst. An improved process for preparing the uracil intermediate is also disclosed. More particularly, it is concerned with the process for preparing 5-deazariboflavin by cyclizing 6-[3,4-dimethyl-N-(D-ribityl)anilino[uracil with trialkylorthoformate in the presence of a strong acid catalyst and hydrolyzing the resulting alkoxymethylene derivative. The corresponding uracil intermediate is prepared by reacting 6-chlorouracil with N-D-ribityl-3,4-xylidine.5-Deazariboflavins having the general Formula (I) herein below: ##STR1## wherein R.sub.7 is hydrogen or methyl, R.sub.8 is methyl, hydroxy or acyloxy and R.sub.

Abstract: A method of automatically maintaining a selected spacing for a plasma arc cutting torch form a workpiece is disclosed which takes advantage of the fact that at any given setting of a plasma arc power supply the current in the arc varies inversely and the voltage across the arc varies directly in relation to the spacing of the plasma arc torch from the workpiece when new material in the workpiece is presented to the plasma arc at an essentially constant rate and which includes the step of automatically compensating for variations in the rate at which new material is presented to the arc.

Abstract: A method of automatically maintaining a selected spacing for a plasma arc torch from a workpiece is disclosed which takes advantage of the fact that at any given setting of a plasma arc power supply the current in the arc varies inversely and the voltage across the arc varies directly in relation to the spacing of the plasma arc torch from the workpiece. According to such method, the current and voltage of the power supply for the torch are sensed in operation, a signal representative of each comparable to the other is generated and one of such signals is inverted with respect to the other of such signals. The signals are then summed with each other and with a third comparable selectively adjustable signal and the difference signal is used to control the spacing of the torch from the workpiece.