Abstract: A silicon-containing step ladder polymer comprising a unit represented by the following general formula (I): ##STR1## a unit represented by the following general formula (II): ##STR2## and a unit represented by the following general formula (III): ##STR3## where R.sup.1 represents a hydrocarbon or fluorine-substituted hydrocarbon group, R.sup.2 represents hydrogen or a trialkyl siloxy group, and R.sup.3 and R.sup.4 which may be identical or different with each other represent individually hydrocarbon or fluorine-substituted hydrocarbon groups, the molar ratio of the unit (I) to the unit (II) is between 5:1-100:1 and the molar ratio of the unit (III) to the total amount of the unit (I)+unit (II) is between 1:5-1:100, as well as a process for producing such polymer.

Abstract: A guest-host type liquid crystal display device not requiring the use of external polarizers, comprises: at least two guest-host type liquid crystal cells which are superimposed one upon another, two of which are constructed in a manner that the liquid crystal molecules contained in these two cells and located close to the boundary between the two cells are aligned in a direction parallel to the plane of the boundary, but that the direction of alignment of the molecules in one of these two cells is perpendicular to that in the other cell when a voltage is applied to both cells, or alternatively when no voltage is applied to both cells, or alternatively when a voltage is applied to only one of these two cells.

Abstract: A rotatable cutter head for a pit boring machine used in reverse circulation drilling. The cutter head has cutter arrays including rotary cutters and drag cutters and disposed radially and circumferentially spaced positions on the cutter head, the drag cutters having the cutting ends lying generally in a conical plane having the axis coaxial with the axis of rotation of the cutter head. The rotary cutters each have cutting teeth around the circumference thereof and each tooth has an inclined side face lying in a further conical plane the central axis of which is coaxial with the axis of rotation of the rotary cutter, the inclined side face of each tooth facing generally along the inclination of the conical plane in which the cutting ends of the drag cutters lie, and the tip of each cutting tooth of each rotary cutter projecting beyond the plane in which the cutting ends of the drag cutters lie.

Abstract: A swivel joint to be located at the upper end of a drill string in reverse circulation drills to support loads occurring on the drill string, the swivel joint including a fixed outer housing, a center housing rotatably mounted in the outer housing through bearings, a hollow inner housing vertically slidably fitted in the center housing, and an upper lid fixedly mounted on the outer housing to close the inner and center housings, the inner housing having at the upper and lower ends thereof flanged projections extending toward the center housing to restrict the range of the vertical sliding movement of the inner housing and being, after imposition and release of a downward thrust, slid upward within a range defined by a spacing between the flanged projection at the lower end of the inner housing and the lower end of the center housing subject to an upward thrust acting thereon, thereby preventing transmission of the upward thrust to the outer housing.

Abstract: A method of determining a depth of an accumulation of snow in which the water-equivalent depth of an accumulation of snow is determined from the count of survival neutrons of cosmic rays after passing through an accumulation of snow.