Chromatic Influence of Value Resin Composites

Clinical Relevance Value resin composites used to replace enamel can induce a brightness decrease in stratified composite restoration techniques.

Vt-Shift Compensating Amorphous Silicon Pixel Circuits for Flexible OLED Displays

ABSTRACTIn this paper, we present design considerations pertinent to amorphous silicon pixel circuits for mechanically flexible active matrix display applications. We describe both circuit topologies and pixel architectures that are amenable to surface emissive pixels in a-Si:H technology. Metastable shifts in the a-Si:H material characteristics after prolonged gate bias or mechanical stress are manifested in the form of increasing TFT threshold voltages and varying mobilities. As a result, the TFT drive current and consequently the OLED brightness decrease, and the pixel eventually turns off. The circuits presented here compensate for this decrease in current through the use of current programming and feedback, and allow for stable OLED brightness over longer time periods. They also enable the implementation of high aperture ratio (close to 100%), low leakage current, surface emissive OLED pixels. Results show that the circuits provide higher linearity and dynamic range than currently available pixel circuits while minimizing the pixel area. Charge injection effects at the gate of the drive TFT have been reduced by using smaller switching TFTs, along with circuit topologies that provide in-pixel current gain. All circuits meet the speed requirements of a QVGA 60 Hz refresh rate display, and occupy less than 300um x 300um area.

Covering of cometary nucleus by refractory crust and its evolution into asteroid-like body

From the established dependence of the brightness decrease of a short-period comet dependence on the perihelion distance of its orbit it follows that part of the surface of these cometary nuclei gradually covers by a refractory crust. The results of cometary nucleus simulation show that at constant insolation energy the crust thickness is proportional to the square root of the insolation time and the ice sublimation rate is inversely proportional to the crust thickness. From laboratory experiments resulted the thermal regime, the gas productivity of the nucleus, covering of the nucleus by the crust, and the tempo of evolution of a short-period comet into the asteroid-like body studied.

The Photometric and Spectral Variability of the Planetary Nebula IC 4997

Among the planetary nebulae showing noticeable long-time variations of brightness (see our foregoing contributed paper; Astron. Circ. USSR, No. 1430, 3, 1986, and earlier publications) the young stellar planetary IC 4997 is the most prominent. Our photoelectric observations revealed its rather surprising behaviour. During 1968–85 its total UBV-brightness was monotonously decreasing, especially in filter V: the reduction of the value Δv amounted ∼ 0m.5–0m.6. The colour indices of the planetary showed that during the observation period the object as a whole, became definitely bluer. In 1985–86 our observations revealed an unexpected stop of mentioned brightness decrease, but in 1987 the object appeared to start brightening.

Interplanetary Shock Waves from McMath Region 11976 During Its Passage in August 1972

(J. Geophys. Res.). The August 1972 events provided an excellent opportunity for synthesizing a variety of observations in a coordinated fashion for the purpose of improving flare-shock associations, and our understanding of interplanetary shock propagation and solar wind interaction with planets and comets. These observations included the usual sudden commencements of magnetic storms at Earth; preliminary shock data from Heos-2, Prognoz-1 and Prognoz-2 (at Earth) and the radially-aligned Pioneers 9 (0.77 AU) and 10 (2.2 AU) located about 45° east of the Sun–Earth axis; solar radio types II and IV (as reported in World Data Center A's UAG Report 28, 1973, and this Symposium); discrete radio source scintillations in the solar wind; and the more speculative ideas regarding the solar wind's interaction with planets and comets. In the last case, Jupiter and Comet P/Schwassmann-Wachmann I exhibited non-Io-associated radio emission and a brightness increase, respectively, as a possible result of shock waves from the flare and/or coronal ejection activity initiated on 1972 June 15. During the August events, Comet P/Giacobini-Zinner exhibited statistically-significant sudden brightness decrease following its perihelion on 1972 August 4 at 1 AU approximately 57° west of the Sun–Earth axis.