Removal of the high-potential [4Fe-4S] center of the beta-subunit from Escherichia coli nitrate reductase. Physiological, biochemical, and EPR characterization of site-directed mutated enzymes

The beta-subunit of the nitrate reductase of Escherichia coli contains four groups of Cys residues (I-IV) which are thought to bind the single [3Fe-4S] center and the three [4Fe-4S] centers. The first or second Cys residue of group I was substituted by site-directed mutagenesis with Ala or Ser. Physiological, biochemical, and EPR studies were performed on the mutated enzymes. With small variations, the properties of these mutant enzymes do not differ from one another. They were found to be as abundant and as stably bound to the membrane as the native enzyme, provided the gamma-subunit was present. Although physiological activity was reduced, it was sufficient to allow growth on nitrate. The study of variations in EPR intensity as a function of the redox potential indicated that these enzymes only contained three iron-sulfur centers instead of the usual four in the native enzyme. Spectral EPR analysis showed that the [4Fe-4S] center of high redox potential (center 1, +80 mV) was missing. The loss of this center did not affect the stable integration of the other three centers. The data presented here are in total contrast to those we have reported for each of the other three centers (centers 2-4), the loss of which was detrimental to the integration of all centers and to the integration of the molybdenum cofactor (Augier et al., in press). Taken together, our results demonstrated that the first and second Cys residues of group I are the ligands of the [4Fe-4S] center (center 1, +80 mV) and that this center participates in electron transfer, but is dispensable. On the basis of these results, it is proposed that the [3Fe-4S] center (center 2, +60 mV) also plays a biological role and that in the native enzyme both high-potential centers, centers 1 and 2, contribute independently and in parallel to the electron transfer to the molybdenum cofactor.     

On-chip signature analyser for analogue circuit testing

The authors propose a technique for on-chip analogue response compaction to implement self-test capabilities in analogue circuits. The integration function is identified as a powerful analogue compression scheme and op-amp-based implementations are proposed for both single and multiple-input analysers. Validations show that an improved fault coverage can be achieved     

A Library for Self-Adjusting Computation

We present a Standard ML library for writing programs that automatically adjust to changes to their data. The library combines modifiable references and memoization to achieve efficient updates. We describe an implementation of the library and apply it to the problem of maintaining the convex hull of a dynamically changing set of points. Our experiments show that the overhead of the library is small, and that self-adjusting programs can adjust to small changes three-orders of magnitude faster than recomputing from scratch. The implementation relies on invariants that could be enforced by a modal type system. We show, using an existing language, abstract interfaces for modifiable references and for memoization that ensure the same safety properties without the use of modal types. The interface for memoization, however, does not scale well, suggesting a language-based approach to be preferable after all.     

Robox at Expo.02: A large-scale installation of personal robots

In this paper we present Robox, a mobile robot designed for operation in a mass exhibition and the experience we made with its installation at the Swiss National Exhibition Expo.02. Robox is a fully autonomous mobile platform with unique multi-modal interaction capabilities, a novel approach to global localization using multiple Gaussian hypotheses, and a powerful obstacle avoidance. Eleven Robox ran for 12 hours daily from May 15 to October 20, 2002, traveling more than 3315 km and interacting with 686,000 visitors.     

Effects of chronic haloperidol and intermittent cocaine administration on behavior elicited by apomorphine.

Relatively little is known about the behavioral or neurophysiological effects resulting from the concurrent administration of haloperidol and cocaine. To investigate this drug interaction the effects of chronic, daily administration of haloperidol, intermittent cocaine injections, or the combination of both drug treatments on locomotion and stereotypy elicited by apomorphine in rats (Rattus norvegicus) were compared. The results indicated that, in comparison to treatment with either drug alone, the combination of daily haloperidol and intermittent injections of cocaine produced unique behavioral effects. Rats coadministered both drugs exhibited significant increases in apomorphine-induced locomotion that were maintained throughout the 64 days following suspension of drug treatment. These results are discussed in terms of the possible neurophysiological mechanisms underlying the observed behavioral changes and are related to the consequences of psychostimulant abuse in human neuroleptic treated populations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling the Random Parameters Effects in a Non-Split Model of Gate Oxide Short

This paper presents a new model for gate-to-channel GOS defects. The transistors used in digital cell library are usually designed with a minimum-size. This new model permits to handle minimal-length transistors allowing the simulation of GOS defects in realistic digital circuits. Based on the electrical analysis of the defect behavior, a comprehensive method for the model construction is detailed. It is shown that the behavior of the proposed model matches in a satisfactory way the behavior of a defective transistor including the random parameters of the defect.