Abstract: In a method of moulding gramophone records, the hole is formed by co-operating hole forming members which can extend into the mould cavity and which are pressed together at a position within the thickness of the record. One of the members is subsequently extended further and moves beyond this position, so that any web or flash which may be formed between the hole forming members is separated from the article after which the mould cavity opened and the article is removed. The machine described is for the injection moulding of gramophone records and one of the hole forming members is the nozzle tip of the injection nozzle. The other hole forming member is a counterpiece, which is the member which undergoes the further extension by pushing back the nozzle tip upon decompression of the mould cavity.

Abstract: In radiological apparatus, edge values derived by monitoring the radiation passed through a body along many co-planar paths are subjected to a transformation process, such as a convolution integral or Fourier transform process, in order to evaluate the absorption or transmission coefficients of the elements of a matrix of elements notionally delineated, in the plane of the paths, in the body. The values are inversely transformed to synthesize further edge values, and corresponding ones of the first mentioned and further edge values are compared to derive edge value error signals. The edge value error signals are indicative of errors in the evaluation of said coefficients and they are subjected to the aforementioned transformation process to derive therefrom individual correction signals for the various elements of the matrix.

Abstract: In a method of investigating a body of means of penetrating radiation such as X- or .gamma.- radiation, the energy of the radiation is chosen to be such that the radiation is scattered, rather than absorbed, by the body. The scattered radiation is detected by means of banks of detector means disposed on the opposite side of the body to the source, and the detector means include energy analyzing means to enable the angle of incidence thereon of scattered radiation to be determined.

Abstract: Apparatus is disclosed for providing a visual representation of the absorption or transmission coefficients of the elements of a two dimensional matrix of elements notionally defined in a cross-sectional plane through a body. The representation is in the form of an analogue display comprising superimposed lines of information scanned on the surface of a suitable screen, the brightness of each line being indicative of the absorption suffered by penetrating radiation on traversing a respective path through said plane of the body. The orientation of each scanned line depends on the orientation of the respective path with respect to the body.