A PSP-Based Small-Signal MOSFET Model for Both Quasi-Static and Nonquasi-Static Operations

In this paper, a small-signal MOSFET model is described, which takes the local effects of both velocity saturation and transverse mobility reduction into account. The model is based on the PSP model and is valid for both quasi-static and nonquasi-static (NQS) operations. Recently, it has been found that, in the presence of velocity saturation, the low-frequency capacitances cannot be determined from the Ward-Dutton charge-partitioning scheme. By use of the small-signal model developed in this paper, it is demonstrated that, in the presence of velocity saturation, no terminal drain and source charges exist, from which the capacitances can be derived. The small-signal model enables the determination of the correct capacitive behavior in the presence of velocity saturation. Furthermore, it is demonstrated how the small-signal model can be used to determine the number of collocation points needed in the large-signal NQS PSP model. Finally, inclusion of the local variation of mobility reduction due to the vertical electrical fields provides insight into the approach commonly applied in compact modeling, where these fields are replaced by global ones depending on the terminal voltages only.     

Catalytic combustion in a domestic natural gas burner

Gastec and Vaillant developed a boiler in which the combustion is catalytically stabilised as well as a completely catalytic boiler. The catalytically stabilised boiler emitted about 5 ppm NO_x and 0 ppm CO. In this boiler the burner is replaced by a metal honeycomb. The honeycomb is partly coated with a catalyst washcoat. The coated part is at the flame side of the honeycomb. The coated length of the channels is an important parameter. A too long coating results in CO emissions, a too short coating in higher NO_x emissions.

The catalytic boiler emitted 0 ppm NO_x, 0 ppm CO and 0 ppm CH₄. The gas is combusted catalytically in two metal honeycombs. Most gas is converted in the first few millimetres from the entrance of the monolith. The heat that is produced is radiated to a heat exchanger. The remaining honeycomb and the secondary honeycomb convert the rest of the methane.

Comparing these boilers, the completely catalytic boiler shows lower emissions and a lower sensitivity to the gas quality. The partly catalytic burner is more reliable and can use a conventional security system. Production and development costs are thus smaller.     

CHEMICAL AND TECHNICAL ASPECTS OF HYDROFORMYLATION OF OLEFINS WITH SUPPORTED LIQUID-PHASE RHODIUM CATALYSTS

Supported liquid-phase catalysts containing RhH(CO)(PPH₃)₃ dissolved in PPH₃ are used in the gas-phase hydroformylation of several olefins. Their activity in the hydroformylation of ethylene, propylene and the butenes is reported.

Various physicochemical aspects of the rhodium SLP catalysts, such as the adsorptive withdrawal of the rhodium complexes by the supports, the activity of the rhodium complexes at the gas-liquid interface and the solubility of the reactants and products in the liquid part of the catalysts, are discussed.

The results are presented of a bench-scale process study of the hydroformylation of propylene, from which the design parameters of a future plant are calculated.     

Visualization of Three Sclerotiniaceae Species Pathogenic on Onion Reveals Distinct Biology and Infection Strategies

Botrytis squamosa, Botrytis aclada, and Sclerotium cepivorum are three fungal species of the family Sclerotiniaceae that are pathogenic on onion. Despite their close relatedness, these fungi cause very distinct diseases, respectively called leaf blight, neck rot, and white rot, which pose serious threats to onion cultivation. The infection biology of neck rot and white rot in particular is poorly understood. In this study, we used GFP-expressing transformants of all three fungi to visualize the early phases of infection. B. squamosa entered onion leaves by growing either through stomata or into anticlinal walls of onion epidermal cells. B. aclada, known to cause post-harvest rot and spoilage of onion bulbs, did not penetrate the leaf surface but instead formed superficial colonies which produced new conidia. S. cepivorum entered onion roots via infection cushions and appressorium-like structures. In the non-host tomato, S. cepivorum also produced appressorium-like structures and infection cushions, but upon prolonged contact with the non-host the infection structures died. With this study, we have gained understanding in the infection biology and strategy of each of these onion pathogens. Moreover, by comparing the infection mechanisms we were able to increase insight into how these closely related fungi can cause such different diseases.     

2,2'-Dithiobisbenzamides and 2-benzisothiazolones, two new classes of antiretroviral agents: SAR and mechanistic considerations

Substituted 2,2'-dithiobisbenzamides and 2-benzisothiazolones were prepared and shown to possess low microM activity with high therapeutic indices against HIV-1, HIV-2 and SIV in cell culture. The mechanism of antiviral action was determined to be directed toward the nucleocapsid protein (NCp7), which contains two zinc fingers and plays vital roles in the viral life cycle. The "active sulfides" of this study cause the extrusion of zinc from these zinc fingers. Structure-activity relationships of the 2,2'-dithiobisbenzamides reveal that the disulfide bond and the ortho benzamide functional groups are essential for activity, with the best compounds having a carboxylic acid, carboxamide, or sulfonamide substituent. The 2-benzisothiazolones are formed from the disulfides both chemically and in vivo and their SAR mimics that of the 2,2'-dithiobisbenzamides. The antiviral activity of the disulfides may require cyclization to the isothiazolones. Two agents, PD 159206 and PD 161374, which showed good antiviral activity, physical properties, and excellent pharmacokinetics in mice, were selected for advanced studies.