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Mechanical joining and compression of the retinal edges during surgery for stage 3 or 4 idiopathic macular holes appears to yield a promising anatomic and functional result.

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Investigation of gas-sensitivity of sensor structures to hydrogen in a wide range of temperature, concentration and humidity of gas medium a b s t r a c t Response to H 2 of seven sensor structures of SnO 2 with various catalytic additives, made by thick-film technology, was investigated in a dry gas medium at a concentration of 200 ppm H 2 in a temperature range of 100-600 • C. Concentration dependence of six sensors (pure SnO 2 and doped with five catalytic additives: 3% Pd, 3% La 2 O 3 , 1% Pt + 3% Pd, 1% Sb 2 O 5 + 3% La 2 O 3 and 3% Pd with a support layer from Al 2 O 3 ) was investigated in a range of 1-19,700 ppm H 2 of different relative humidity (RH) in a range of 0-100% RH at two operating temperatures. The resistance and response of the sensors weakly depended on the humidity of the gas medium at RH ≥ 0 or 10%. Arithmetic mean values of response and resistance in the range of 0 (10)-100% RH were approximated by linear functions of log(S ma − 1) = B + n log C and log R ma = A + k log C, respectively.Based on the comparative analysis of experimental data (response to H 2 , reproducibility of indications, influence of humidity on the resistance and response, response threshold and a resistance drift in pure air), the best for H 2 detection were the two sensor structures of pure SnO 2 and SnO 2 + 3% La 2 O 3 , working at temperatures 500 • C and 450 • C, respectively. Formulas for resistance and response of these sensors were presented, which allowed estimation of H 2 concentration in air based on the measured parameters. Reproducibility of indications in the range of 1-19,700 ppm H 2 was within 4-10%. The response threshold was 0.08 ± 0.006 ppm H 2 in the mentioned range of humidity at the response equal to 1.1.The interpretation was given for the mechanism of interaction of H 2 with the catalytic surface of semiconductive sensors. The present sensors can be recommended as the primary transducer of H 2 concentration in air for the gas control devices.

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