Blocked and overshadowed stimuli are weakened in their ability to serve as blockers and second-order reinforcers in Pavlovian fear conditioning

The ability of a blocked or overshadowed conditioned stimulus (CS) to serve as (a) blocker or (b) a 2nd-order reinforcer in Pavlovian fear conditioning was tested in 152 albino rats. CS-evoked suppression of barpressing for food was the index of conditioned fear. Experiments 1 and 2 showed that an overshadowed CS was weakened in its ability to serve as a blocker. In Experiment 2, a blocked CS was similarly weakened. Experiment 3 showed that an overshadowed and blocked CS was weakened in its ability to serve as a 2nd-order reinforcer. Experiments 4 and 5 failed to restore the blocking ability of blocked (Experiment 4) or overshadowed (Experiment 5) CSs by extinguishing the CSs that had blocked or overshadowed them. Results favor a learning-deficit view of blocking and overshadowing.     

A method for measuring work interference in surgical teams

To enhance surgical systems we need to manage the performance of the teams that comprise them. To do this we must measure the properties and processes of teams and account for the demands and conditions of their work. Recent research shows that observation is a potentially valuable method of measurement, but its potential application in surgery remains unclear. In this study of laparoscopic cholecystectomy, an observer applied observational measures of teamwork in the operating theatre and recorded intra-operative interference from observed distraction and interruption. Results showed that it was feasible to observe a broad scope of teamwork and to reveal the frequency and source of work interference. However, the measures were necessarily selective and so limited in their analysis of the conditions and events that might interfere with the collective work in surgery. Such measures may however prove useful when applied in conjunction with other methods of measurement and utilised as performance feedback data.     

Quantifying self-heating effects with scaling in globally strained Si MOSFETs

Electrical results are presented for deep submicron strained Si MOSFETs fabricated on both thick and thin SiGe strain relaxed buffers, SRBs. For the first time thin SRB devices are shown to offer the same performance enhancements as thick SRB devices. The reduction in performance enhancement with device scaling widely reported in the literature has also been investigated. Correcting for dynamic self-heating effects using ac measurements, the enhancements seen in long channel devices are maintained down to short channel lengths, demonstrating the scalability of SRB technology. Thermal resistances have been measured experimentally and compared with analytical models. The thermal resistance for devices on the thin SRBs is reduced by 50% compared with devices on thick SRBs. Finally, a comparison of self-heating effects in MOSFETs fabricated on SOI and Si_0.8Ge_0.2 SRBs provides insight into the challenges ahead as power densities continue to increase.     

Effect of hydrogen on dislocation nucleation in alloy 718

In situ electrochemical nanoindentation has been used to study the effect of hydrogen on the nanomechanical response of Alloy 718. Observations show that hardness increase as a result of hydrogen charging. Also, the hydrogen charging gives a reduced pop-in load and pop-in width. This is related to a reduction in the energy needed for dislocation nucleation and the mobility of the dislocations in the presence of hydrogen. Two grains with different orientations has been tested here. The pop-in load and width obtained in the (101) orientation was more affected by the presence of hydrogen than those achieved in the (111) oriented grain.     

Effect of low‐dose irradiation on shelf life and microbiological safety of sliced carrot

Minimally processed non‐irradiated carrots (sliced) exhibited diverse microflora at initial level. During storage, bacterial number increased with the presence of pathogenic bacteria accompanied by a loss of total solids. On the other hand γ‐irradiation at an optimal dose of 2 kGy offered a pathogen‐free, hygienic product with insignificant losses in nutrients such as in sucrose, total carotenes and ascorbic acid content in comparison to controls and 2‐ to 4‐fold increased in shelf‐life at refrigeration temperature. The D₁₀ values of pathogens like Escherichia coli and Yersinia enterocolitica in carrot paste were in a lower range (0.12–0.26 kGy) compared with that of Listeria monocytogenes (0.3–0.5 kGy). The validity of the processing treatment (2 kGy) was challenged by artificially inoculating Listeria monocytogenes in the product. Thus, minimally processed carrots (sliced) are amenable to radiation treatment for extended storage stability and microbial safety. Copyright © 2005 Society of Chemical Industry     

Comments on ‘A necessary and sufficient condition for the positive-detiniteness of interval symmetric matrices’

The main results obtained recently by Shi and Gao are already known and can be strengthened.     

Intermolecular cleavage by UmuD-like enzymes: identification of residues required for cleavage and substrate specificity

The UmuD-like proteins are best characterized for their role in damage-induced SOS mutagenesis. An essential step in this process is the enzymatic self-processing of the UmuD-like proteins. This reaction is thought to occur either via an intramolecular or intermolecular self-cleavage mechanism. Here, we demonstrate that it can also occur via an heterologous intermolecular cleavage reaction. The Escherichia coli UmuD enzyme demonstrated the broadest substrate specificity, cleaving both E. coli and Salmonella typhimurium UmuD substrates in vivo. In comparison, the wild-type S. typhimurium UmuD (UmuDSt) and MucA enzymes catalyzed intermolecular self-cleavage, but did not facilitate heterologous cleavage. Heterologous cleavage by the UmuDSt enzyme was, however, observed with chimeric UmuD substrates that possess residues 30-55 of UmuDSt. We have further localized the residue predominantly responsible for UmuDSt-catalyzed heterologous cleavage to Ser50 in the substrate molecule. We hypothesize that changes at this residue affect the positioning of the cleavage site of a substrate molecule within the catalytic cleft of the UmuDSt enzyme by affecting the formation of a so-called UmuD "filament-dimer". This hypothesis is further supported by the observation that mutations known to disrupt an E. coli UmuD' filament dimer also block intermolecular UmuDEc cleavage.