The speed of conversion of infrared (IR) images by a planar semiconductor gas discharge system into the visible range has been investigated. Argon or nitrogen are used in the discharge gap having an electrode distance of 100 μm. Using pulse radiation from an IR laser to excite the system, we have shown that the characteristic response time of the device with the cryogenic discharge in the gap can lie in the submicrosecond range. This characteristic of the system can be applied for a fast IR imaging at a rate higher than 106 frame/s.

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Transient phenomena which accompany the breakdown of gas in a semiconductor-gas discharge (SGD) system with 100 μm interelectrode distance have been studied experimentally and with numerical calculations. This system serves as the basis for an image converter operating in the infrared (IR) spectral region. The experiments are done for a cryogenic discharge in helium at a temperature close to that of liquid nitrogen. Depending on specific experimental conditions, oscillatory or aperiodic modes approaching to the steady-state current are observed after breakdown has been induced by a step-like voltage pulse. Numerical calculations of transient phenomena were performed for experimental conditions within the framework of the Townsend model, taking into account direct ionization, Penning ionization and secondary emission of electrons from the cathode. The main features of discharge kinetics obtained are in accordance with experimental data. At the same time, with the steady-state discharge current density varying from j= 1×10−4 A/cm2 to 7×10−2 A/cm2, inconsistencies between experimental and theoretical results are observed. A possible reason for this discrepancy is related to the complex process of secondary ionization at the cathode under the conditions of a cryogenic discharge and to the dependence of the secondary electron emission factor on current density, that has been neglected in constructing the model. The results obtained are considered from the viewpoint of the response time of gas-discharge IR image converters.

Twelve femoral heads (two normal, four after fracture and six osteo-arthritic) were obtained at surgery or autopsy. Circumferential slices were obtained and five separate areas were analyzed in each for ash content; histological-histochemical grading of the severity of the cartilage changes; and quantitative morphometric analyses to establish the percentage of trabecular area, osteoblastic area and osteoclastic area. Analyses were performed to compare weight-bearing and non-weight-bearing areas of the femoral heads and to determine correlations between the bony and cartilaginous alterations. The data obtained showed wide variations in all parameters in the osteoarthritic specimens but consistently more marked cartilage and bony changes in the weight-bearing areas. Bone structures and metabolic parameters were distinctly increased for the osteoarthrities, differing significantly from both normal and fracture control groups. The bony change correlated directly with the severity of the cartilage lesions, as determined by the histological-histochemical grade.