Analysis of a resonant-cavity enhanced GaAs/AlGaAs MSMphotodetector

The authors have developed a 2-D device simulator for heterostructure metal-semiconductor-metal (MSM) photodetectors. They have incorporated a model of multilayer optics into the simulator and used it to analyze the temporal response of a resonant-cavity enhanced heterostructure with a confining buffer layer and a distributed Bragg reflector (DBR). The authors show that through fine tuning the layer thicknesses, optical resonance enhancement of the light absorption can be obtained     

A cholera toxin-sensitive guanyl nucleotide binding protein mediates the movement of pituitary luteinizing hormone into a releasable pool: loss of this event is associated with the onset of homologous desensitization to gonadotropin-releasing hormone

Cholera toxin (CTX; 5 micrograms/ml), but not pertussis toxin (100 ng/ml), when preincubated with pituitary cells for 18 h, enhances the percentage of cellular LH released in response to continuous or pulsatile administration of 5 x 10(-9) M GnRH. This effect occurs without increasing total (intracellular plus extracellular) LH, indicating that it is best explained by redistribution of LH from a nonreleasable to a releasable pool. This site of action is consistent with the observation that CTX-pretreated cells are also sensitized to stimulation of LH release by the Ca2+ ionophore A23187. The observations that CTX stimulates the production of cAMP in these cells and that the sensitizing action of CTX is mimicked by (Bu)2cAMP (1 mM) are consistent with the view that a CTX-stimulated guanyl nucleotide binding protein, capable of activating adenylyl cyclase, is mediating this sensitization. We used a perifused cell system to show that the movement of LH into a releasable pool is lost with the onset of homologous desensitization due to high pulse frequency or constant administration of GnRH (5 x 10(-9) M, continuous or a pulse each 15 min). Sensitization to CTX is restored by stimulation with a high concentration of GnRH (10(-6) M) or by resetting the pulse frequency to the rate measured in vivo (a pulse each 90 min). Both of these treatments also circumvent the desensitized state, restoring LH release. These results identify a novel lesion associated with the development of desensitization in the gonadotrope and support the role of a CTX-sensitive guanyl nucleotide binding protein in regulation of pituitary responsiveness to GnRH.     

Invasiveness of LiTaO/sub 3/ and GaAs probes in external E-O sampling

Disturbances of signals on a coplanar waveguide (CPW) induced by the presence of LiTaO/sub 3/ and GaAs electrooptic probes in external electrooptic (EO) sampling have been simulated and compared quantitatively. The finite-difference-time-domain method is used to simulate the full wave field around a coplanar waveguide on a GaAs substrate in an external EO sampling configuration. The results indicate that the induced signal disturbance, or invasiveness, of a LiTaO/sub 3/ probe is almost ten times that of a GaAs probe in terms of the magnitude of S/sub 11/, but that LiTaO/sub 3/ yields about two times the EO response for a given S/sub 11/ and optical probing wavelength. The transparency of LiTaO/sub 3/ to shorter wavelengths, however, allows an even higher sensitivity for this material relative to GaAs. The results suggest that these probes do not exhibit significant invasiveness (magnitude of S/sub 11/ smaller than -40 dB), if they are removed from contact by the distance of CPWs center conductor width.<>     

Dynamic workflow analysis in a multiuser task context

With the ongoing development of computer‐mediated collaboration environments, computer‐supported collaborative work (CSCW) systems are at hand. An emerging theme is the treatment of dynamic groups. The interest in this article is in the automated construction of dynamic policies for workflow situations in cooperative environments. The system described in this article operates on the events that are recorded in solving workflow problems. These are analyzed in order to derive policies that may be used to guide future cooperative activities.     

Large signal mwSPICE model of DMOS transistor

A new large signal mwSPICE model is presented for the DMOS device. The model describes the device accurately in all regions of operation, and can be scaled with respect to gate width and length. Predicted DC, small and large signal RF performances are in good agreement with measured values.<>     

Language bindings to XML

By preserving application semantics, XML bindings improve program specification, verification, and optimization. We compare two standard binding solutions - namely, the Simple API for XML (SAX) and the Document Object Model (DOM) API - and two novel approaches: Sun's JAXB architecture and our Strathclyde Novel Architecture for Querying XML (SNAQue).