The effects of teacher attention on the attending behavior of two boys seated at adjacent desks were investigated. Baseline records were obtained of the appropriate attending behavior of two boys who were described as the most disruptive pupils in a second-grade classroom of a poverty area school. During the first experimental phase, the teacher systematically increased the amount of attention for appropriate attending in one of the pair, Edwin. This resulted in a dramatic increase in his attending rate and a lesser, though significant, increase in attending behavior of the second boy, Greg. During the second experimental phase, systematic attention for attending was instituted for Greg and was discontinued for Edwin. This resulted in further increases in attending by Greg and a reduction in attending by Edwin. A brief withdrawal of reinforcement for attending in both Greg and Edwin reduced attending levels for both. Following this reversal appropriate attending for both boys was systematically reinforced and attending returned to high levels.

In this paper, an experimental and theoretical study is carried out of crosstalk between nearest-neighbor devices within a backside-illuminated linear HgCdTe photovoltaic infrared sensing array. The dominant form of crosstalk that occurs in high performance photovoltaic arrays is associated with photogenerated minority carriers that diffuse laterally between adjacent devices within the array. To measure crosstalk, a scanning laser microscope is used to obtain a spatial map of spot-scan photoresponse at a temperature of 80K for individual p-on-n photovoltaic devices within the linear array. These experimental results are compared to calculations performed on a commercial two-dimensional device simulation package. The crosstalk measurements and calculations presented in this paper include results on mid-wavelength infrared planar device structures, as well as long-wavelength infrared mesa-isolated devices, which give measured crosstalk values of 6.2 and 8.3%, respectively. The results indicate that the device simulations are in good agreement with experimental results. Further simulations are carried out to determine the sensitivity of crosstalk to various material and device parameters such as epitaxial layer thickness (7 to 25 µm), illumination wavelength (1.047 to 11.0 µm), minority carrier diffusion length (8 to 90 µm), and diode pitch. It is found that the dominant feature influencing the value of crosstalk is the distance between the region of photogeneration and the collecting p-n junction.

The Visual and Infrared Mapping Spectrometer (VIMS) is a remote sensing instrument developed for the Cassini mission to Saturn by an international team representing the national space agencies of the United States, Italy, and France. A dual imaging spectrometer, VIMS' unique design consists of two optical systems boresighted and operating in tandem, coordinated by a common electronics unit. The combined optical system generates 352 two dimensional images (64 x 64 0.5 mrad pixels) simultaneously, each in a separate, contiguous waveband. These are combined by the electronics to produce "image cubes" in which each image pixel represents a spectrum spanning 0.3 to 5. 1 microns in 352 steps. VIMS images wifi be used to produce detailed spatial maps of the distribution of mineral and chemical species of Saturn's atmosphere, rings, and moons, and the atmosphere of Titan. At some wavelengths VIMS will penetrate Titan's atmosphere to map its surface, and image the night side of many Saturnian objects.

A comparison of photovoltaic HgCdTe/A1203, HgCdTe/CdZnTe, InGaAs/lnP and photoconductive GaAs/A1GaAs quantum well infrared photodetector (QWIP) detector technologies has been conducted at Rockwell by exploiting the ability to selectively hybridize disparate mosaic detector arrays to an assortment of silicon multiplexers. Hybrid FPA characteristics are reported as functions of operating temperature from 32.5K to room temperature and at photon backgrounds from 1 06 to mid-1016 photons/cm2-sec. The staring arrays range in size from about sixteen thousand to over a million pixels. Background-limited detectivities significantly exceeding 1014 cm4iEIW were achieved.

g Stockholm Observatory, SCFAB Astronomy, Stockholm (Sweden) h Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX (UK) i Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin2 (Ireland) ABSTRACTThe MIRI is the mid-IR (5-28µm) instrument for NGST and provides for imaging, cororographic, high-and lowresolution spectroscopic capabilities. Unlike to the other instruments on NGST, the MIRI must be cooled -to reduce the thermal background from the optics and because the detectors require an operating temperature of about 7k.. In this paper we summarise the science goals, the proposed overall opto-mechanical concept, the thermal design aspects, the detectors and the expected sensitivity of the instrument.