Design and evaluation of an optically triggered monolithic sampleand hold circuit using GaAs MESFET technology

The design and evaluation of an optically triggered, fully integrated sample and hold circuit (OS/H) is described. Measured results are presented that demonstrate operation of this circuit at 250 Ms/s and with effective resolution approaching 8 bits. The integrated circuit, which measures 2.1 mm×1.4 mm, is realized in -1.0-V threshold, 20-GHz ft GaAs MESFET technology, consumes approximately 200 mW of power, and requires one optical address. The OS/H will find applications in high precision, hybrid, and integrated signal processing systems where high speed, high levels of parallelism, and low timing jitter are important. Measured results of a series photoconducting (Auston switch) OS/H realized in the same technology are presented for comparison purposes     

The Effects of Cyclic Terminal Groups in 4-Aminoazo-benzene and Related Azo Dyes: Part 21—pKa Values of Some Monoazo Dyes Derived from

Basicity values have been determined for series of monoazo dyes incorporating a pyrrolidino or a piperidino moiety. In general, the pK_a value is found to decrease as the donor capacity of the terminal nitrogen atom decreases.The basicities of the 4'-substituted piperidinoazobenzenes decrease as the electron withdrawing strength of the 4'-substituent increases. However, the pK_a values of the related pyrrolidino compounds appear to be insensitive to the substituent.     

Regulation of the raffinose permease of Escherichia coli by the glucose-specific enzyme IIA of the phosphoenolpyruvate:sugar phosphotransferase system

In enteric bacteria, chromosomally encoded permeases specific for lactose, maltose, and melibiose are allosterically regulated by the glucose-specific enzyme IIA of the phosphotransferase system. We here demonstrate that the plasmid-encoded raffinose permease of enteric bacteria is similarly subject to this type of inhibition.     

The number of clonogenic cells in a mouse jejunal crypt

A study of eight deaths involving the benzodiazepine flunitrazepam was performed to assess the contribution of this drug to the fatalities. Coronial deaths in Victoria in the 2-year period to mid-1991 were selected in which either flunitrazepam or flunitrazepam and ethanol were the principal toxicological findings. All bodies were subject to a full autopsy by forensic pathologists, and a full toxicological examination. No significant pathology was found at autopsy in any case. Very high concentrations of 7-aminoflunitrazepam, a metabolite of flunitrazepam, were present in all cases. In four cases no other significant drug was detected, whereas in the other four cases there were significant concentrations of ethanol (mean 1.6 g/L). In these two groups of cases the concentrations of 7-aminoflunitrazepam were 0.45 mg/L and 0.16 mg/L, respectively. Only moderate levels of flunitrazepam were detected, suggesting that 7-aminoflunitrazepam is produced postmortem and may be an important marker of flunitrazepam usage. The causes of death in these eight cases were probably either flunitrazepam toxicity or a combination of flunitrazepam and ethanol toxicity. Only one case appeared likely to have been a suicide. Our observations in these cases suggest that flunitrazepam may cause death in the absence of other drugs or significant disease. The presence of ethanol reduces the amount of flunitrazepam needed to cause death.     

Humans: the missing link in manufacturing simulation?

Computer based discrete event simulation (DES) is one of the most commonly used aids for the design of automotive manufacturing systems. However, DES tools represent machines in extensive detail, while only representing workers as simple resources. This presents a problem when modelling systems with a highly manual work content, such as an assembly line. This paper describes research at Cranfield University, in collaboration with the Ford Motor Company, founded on the assumption that human variation is the cause of a large percentage of the disparity between simulation predictions and real world performance. The research aims to improve the accuracy and reliability of simulation prediction by including models of human factors.     

A semiautomated electron backscatter diffraction technique for extracting reliable twin statistics

A framework has been developed for extracting reliable twin statistics from a deformed microstructure using crystallographic twin identification techniques with spatially correlated electron backscatter diffraction (EBSD) data. The key features of this analysis are the use of the mathematical definition of twin relationships, the inclination of the common K ₁ plane at a twin boundary, and the correct identification of the parent orientation in a parent/twin pair. Methods for identifying the parent in a parent/twin pair will be briefly discussed and compared. Twin area fractions are then categorized by operative twin systems, number of active twin variants in each system, and corrected twin widths. These statistics are reported here for α-zirconium samples deformed in quasi-static four-point bend beams and in a 100 m/s Taylor cylinder impact test. Analysis of the statistics also begins to reveal the roles that deformation rate and relative orientation of the boundary conditions to the material’s symmetry axes play in determining the twinning activity that accommodates the imposed boundary conditions. These improved twin statistics can help quantify the deformation processes in materials that deform by twinning as well as serve to provide better validation of proposed models of the deformation processes.     

The Joint Evaluation Procedure for Active Substances contained in Plant Protection Products within the European Community – 10?Years of the ECCO-Project

Pflanzenschutzmittel müssen seit 1993 in den Mitgliedstaaten der Europ?ischen Gemeinschaft nach der Richtlinie 91/414/EWG des Rates bewertet und zugelassen werden. Das Programm zur Bewertung von alten Wirkstoffen (welche vor Juli 1993 auf dem Markt waren) beinhaltet mehrere Schritte und Stufen, die früher über einen Zeitraum von bis zu 10 Jahren zu bew?ltigen waren; heute sind dafür jedoch 15 Jahre vorgesehen. Das Programm wurde seit 1996 von der Europ?ischen Kommission mit Unterstützung des ECCO-Teams(European Community Co-Ordination) koordiniert. Das ECCO-Team bestand aus zwei Gruppen: eine im Pesticides Safety Directorate – PSD in York (Gro?britannien) und eine im Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL) bzw. vor November 2002 in der Biologischen Bundesanstalt für Land- und Forstwirtschaft in Braunschweig. Sie unterstüzten das Programm zur Bewertung von Wirkstoffen im Namen der Kommission in technischer und administrativer Hinsicht und zeichneten sich insbesondere für das ECCO Peer Review Programm (Expertenprüfungen) verantwortlich. Im November 2003 übernahm die Europ?ische Beh?rde für Lebensmittelsicherheit (EFSA) die Verantwortung für die wissenschaftliche überprüfung der von den Mitgliedstaaten erstellten Bewertungen durch Experten. Das ECCO-Team leistete jedoch weiterhin der Europ?ischen Kommission Unterstützung bei der Durchführung anderer Verfahrensaspekte, vor allem im Bereich der Managementaufgaben der Europ?ischen Kommission. Insgesamt war das Programm au?erordentlich erfolgreich. Es wurden für 162 Wirkstoffen zwischen 1996 und 2003 der Inhalt der von den Mitgliedstaaten erstellten Bewertungsberichte durch eine Expertengruppe diskutiert und füberprüft, was ma?geblich eine Entscheidungsfindung zur Akzeptabilitf?t dieser Wirkstoffe auf Gemeinschaftsebene erm?glicht hat.     

On Linear Copositive Lyapunov Functions and the Stability of Switched Positive Linear Systems

We consider the problem of common linear copositive Lyapunov function existence for positive switched linear systems. In particular, we present a necessary and sufficient condition for the existence of such a function for switched systems with two constituent linear time-invariant systems. Several applications of this result are also given.     

Biophysical Model of Larval Yellow Perch Advection and Settlement in Lake Michigan

Potential for large-scale physical transport processes to affect recruitment of Lake Michigan yellow perch (Perca flavescens) was studied by examining the variation in larval distribution, growth rate, and settlement during June–August 1998–2003 using a 3D particle transport model linked with an individual-based bioenergetics growth model. In all years, virtual larvae were released nearshore in southwestern Lake Michigan, a known and important spawning region for yellow perch. For any given year, the same circulation pattern and water temperature either promoted or reduced yellow perch settlement depending on the consumption rates and settlement size chosen in the growth model. Increased consumption increased the number of settled larvae and expanded the total area where larvae settled, whereas increased settlement size reduced the number of settled larvae and reduced the overall settlement area. Interannual variability in circulation patterns and water temperature also resulted in contrasting larval settlement rates, settlement locations, and size of settlement areas between years. Model predictions were most consistent with field observations of age-0 yellow perch from Illinois and Michigan waters when settlement was assumed to occur at 50 mm. Moreover, our model suggests that larvae originating from southwestern Lake Michigan can recruit anywhere within the southern basin and even in the northern basin. Future model improvement will require information on the relative contribution of various sectors to the larval pool, their distribution with reference to the hydrodynamic landscape, the feeding and growth of yellow perch during their pelagic phase, and the size at transition to demersal stage.