Abstract: Method and arrangement for detecting the level of a liquid cryogen having a predetermined boiling point and which is being held in a container relative to the bottom of the container. The arrangement includes a container which receives the liquid cryogen and a longitudinal extending sensing member having a length extending from the bottom of the container to a level that is greater than any depth experienced for the liquid cryogen. The sensing member is vertically disposed in the container with one end in contact with the bottom of the container and the other end extending out of the liquid cryogen. The sensing member is composed of a high temperature superconductor material having a critical temperature that is higher than the predetermined boiling point of a selected cryogen. An electrical current is passed through the sensing member and the voltage drop across the sensing member is measured.

Abstract: A portable apparatus that may be employed to rapidly remove the limbs from the trunk of a tree passed through the apparatus. The apparatus incorporates a pair of semi-circular curved blades, with each blade mounted to an arm. A first arm is fixed to the base of the apparatus with the end of the second arm fitted to a crank shaft that is engaged in the end of the first arm permitting the cutting edge of the second arm to move towards or away from the cutting edge of the first arm in a curved path. A frame fixed to the structure guides a projection extending from the side of the second arm to limit the motion of the second arm with respect to the first arm and a hydraulic cylinder or spring is mounted to the structure to apply a bias force to the two arms so that each cutting edge will follow the tapered diameter of a tree trunk passed transversely to the arms, so as to cut the limbs from the tree trunk.