Anticipation of a non-aversive reaction time task facilitates the blink startle reflex

The conditions under which blink startle facilitation can be found in anticipation of a reaction time task were investigated to resolve inconsistent findings across previous studies. Four groups of participants (n = 64) were presented with two visual stimuli, one predicting a reaction time task (S+) and the second presented alone (S-). Participants were asked to make a speeded response to the offset of the S+ (S1 paradigm) or were asked to respond to a tactile stimulus presented at the offset of the S+ (S1-S2 paradigm). Half of the participants in each paradigm condition received performance feedback. Overall, blink latency shortening and magnitude facilitation were larger during S+ than during S-. More detailed analyses, however, found these differences to be reliable only in the Feedback conditions. Ratings of S+ pleasantness did not change across the experiment. Electrodermal responses to S+ were larger than to S- in all groups with differential electrodermal responding emerging earlier in the S1 paradigm. Taken together, the data support the notion that startle facilitation can occur during non-aversive Pavlovian conditioning. (C) 2002 Elsevier Science B.V. All rights reserved.

Trace organic compounds in the marine environment

Trace organic chemicals include a range of compounds which, due to a combination of their physico-chemical properties and toxicological implications, have been described as a serious threat to the biotic environment. A global treaty to regulate the manufacture and release of some of the most persistent trace chemicals has been promulgated and signed. The marine environment is an important sink for many trace chemicals, some of which accumulate in the marine food chain and in particular in marine mammals. With respect to the global distribution of trace organic chemicals, the levels of organohalogen compounds in the Southern Hemisphere are comparatively lower for a given environmental compartment and latitude compared to the Northern Hemisphere. A debate is currently evolving about the toxicity of alternative halogen substitutions such as bromine instead of chlorine and also of mixed halogen substitution. Recently a series of potentially natural bioaccumulative and persistent organohalogen chemicals have been found in marine mammals and turtles at levels in excess of those of anthropogenic trace organochlorines including PCBs and DDE. Little is known about the sources, behaviour and effects of natural trace organic chemicals. This manuscript presents an overview on the occurrence of trace organic chemicals in different compartments of the aquatic environment. Important knowledge gaps with regards to trace chemicals in the marine environment are presented. Crown Copyright (C) 2002 Published by Elsevier Science Ltd. All rights reserved.

Effects of paternal drinking, conduct disorder and childhood home environment on the development of alcohol use disorders in a Thai population

Aims To identify influences on the development of alcohol use disorders in a Thai population, particularly parental drinking and childhood environment. Design Case-control study. Setting A university hospital, a regional hospital and a community hospital in southern Thailand. Participants Ninety-one alcohol-dependents and 177 hazardous/harmful drinkers were recruited as cases and 144 non-or infrequent drinkers as controls. Measurements Data on parental drinking, family demographic characteristics, family activities, parental disciplinary practice, early religious life and conduct disorder were obtained using a structured interview questionnaire. The main outcome measure was the subject's classification as alcohol-dependent, hazardous/harmful drinker or non-/infrequent drinker. Findings A significant relationship was found between having a drinking father and the occurrence of hazardous/harmful drinking or alcohol dependence in the subjects. Childhood factors (conduct disorder and having been a temple boy, relative probability ratios, RPRs and 95% CI: 6.39, 2.81-14.55 and 2.21, 1.19-4.08, respectively) also significantly predicted alcohol dependence, while perceived poverty and ethnic alienation was reported less frequently by hazardous/harmful drinkers and alcohol-dependents (RPRS and 95% CIs = 0.34, 0.19-0.62 and 0.59, 0.38-0.93, respectively) than the controls. The relative probability ratio for the effect of the father's infrequent drinking on the son's alcohol dependence was 2.92 (95% CI = 1.42-6.02) and for the father's heavy or dependent drinking 2.84 (95% CI=1.31-6.15). Conclusions Being exposed to a light-drinking, father increases the risk of a son's alcohol use disorders exhibited either as hazardous-harmful or dependent drinking. However, exposure to a heavy- or dependent-drinking father is associated more uniquely with an increased risk of his son being alcohol-dependent. The extent to which this is seen in other cultures is worthy of exploration.

The work of fracture in uniaxial and biaxial oriented unplasticised polyvinylchloride pipes

In oriented unplasticised polyvinylchloride (uPVC) pipes, cracks propagate tangentially rather than through the wall as in conventional pipe. Notched impact, a modified peel test and the specific work of fracture approach have been used to measure fracture toughness of a conventionally extruded, a uniaxially oriented and a biaxially oriented uPVC pipe in different directions. The different failure mode for the oriented pipes was found to result from an order of magnitude increase in the fracture toughness for cracks propagating perpendicular to the orientation direction. Differences in the fracture toughness between the oriented pipes were also related to their molecular orientation. (C) 2002 Elsevier Science Ltd. All rights reserved.

Polarised infrared and differential scanning calorimetry studies on oriented vinyl pipe materials

The molecular orientation in a conventionally extruded PVC pipe, a uniaxially oriented PVC pipe and a biaxially oriented PVC pipe has been studied via Infrared dichroism. The degree of order or crystallinity has also been studied by Differential Scanning Calorimetry and also via Infrared Spectroscopy. The fundamental structural difference between the conventional and oriented pipes was that polymer chains were preferentially aligning in the hoop direction for oriented pipes whereas they were fairly isotropic in the conventional pipe with a slight preferential alignment in the axial direction. Analysis of the C-Cl stretching mode indicated that the uniaxially oriented pipe had much higher alignment of the C-Cl bond in the axial direction than the biaxial pipe, which correlates with higher fracture toughness for circumferential cracking in the biaxial pipe. Both DSC and Infrared spectroscopy detected little change in the crystallinity or order in the oriented pipes compared to the conventionally extruded pipes. (C) 2002 Kluwer Academic Publishers.

Exploring the learning potential of an artificial life simulation

CULTURE is an Artificial Life simulation that aims to provide primary school children with opportunities to become actively engaged in the high-order thinking processes of problem solving and critical thinking. A preliminary evaluation of CULTURE has found that it offers the freedom for children to take part in process-oriented learning experiences. Through providing children with opportunities to make inferences, validate results, explain discoveries and analyse situations, CULTURE encourages the development of high-order thinking skills. The evaluation found that CULTURE allows users to autonomously explore the important scientific concepts of life and living, and energy and change within a software environment that children find enjoyable and easy to use.

The influence of a concurrent cognitive task on the compensatory stepping response to a perturbation in balance-impaired and healthy elders

This study investigated the influence of a concurrent cognitive task on the compensatory stepping response in balance-impaired elders and the attentional demand of the stepping response. Kinetic, kinematic and neuromuscular measures of a forward recovery step were investigated in 15 young adults, 15 healthy elders and 13 balance-impaired elders in a single task (postural recovery only) and dual task (postural recovery and vocal reaction time task) situation. Results revealed that reaction times were longer in all subjects when performed concurrently with a compensatory step, they were longer for a step than an in-place response and longer for balance-impaired older adults compared with young adults. An interesting finding was that the latter group difference may be related to prioritization between the two tasks rather than attentional demand, as the older adults completed the step before the reaction time, whereas the young adults could perform both concurrently. Few differences in step characteristics were found between tasks, with the most notable being a delayed latency and reduced magnitude of the early automatic postural response in healthy and balance-impaired elders with a concurrent task. (C) 2002 Elsevier Science B.V. All rights reserved.

Structure of CcmG/DsbE at 1.14 angstrom resolution: High-fidelity reducing activity in an indiscriminately oxidizing environment

CcmG is unlike other periplasmic thioredoxin (TRX)like proteins in that it has a specific reducing activity in an oxidizing environment and a high fidelity of interaction. These two unusual properties are required for its role in c-type cytochrome maturation. The crystal structure of CcmG reveals a modified TRX fold with an unusually acidic active site and a groove formed from two inserts in the fold. Deletion of one of the groove-forming inserts disrupts c-type cytochrome formation. Two unique structural features of CcmG-an acidic active site and an adjacent groove-appear to be necessary to convert an indiscriminately binding scaffold, the TRX fold, into a highly specific redox protein.

Role of peripheral afference during acquisition of a complex coordination task

It has long been supposed that the interference observed in certain patterns of coordination is mediated, at least in part, by peripheral afference from the moving limbs. We manipulated the level of afferent input, arising from movement of the opposite limb, during the acquisition of a complex coordination task. Participants learned to generate flexion and extension movements of the right wrist, of 75degrees amplitude, that were a quarter cycle out of phase with a 1-Hz sinusoidal visual reference signal. On separate trials, the left wrist either was at rest, or was moved passively by a torque motor through 50degrees, 75degrees or 100degrees, in synchrony with the reference signal. Five acquisition sessions were conducted on successive days. A retention session was conducted I week later. Performance was initially superior when the opposite limb was moved passively than when it was static. The amplitude and frequency of active movement were lower in the static condition than in the driven conditions and the variation in the relative phase relation across trials was greater than in the driven conditions. In addition, the variability of amplitude, frequency and the relative phase relation during each trial was greater when the opposite limb was static than when driven. Similar effects were expressed in electromyograms. The most marked and consistent differences in the accuracy and consistency of performance (defined in terms of relative phase) were between the static condition and the condition in which the left wrist was moved through 50degrees. These outcomes were exhibited most prominently during initial exposure to the task. Increases in task performance during the acquisition period, as assessed by a number of kinematic variables, were generally well described by power functions. In addition, the recruitment of extensor carpi radialis (ECR), and the degree of co-contraction of flexor carpi radialis and ECR, decreased during acquisition. Our results indicate that, in an appropriate task context, afferent feedback from the opposite limb, even when out of phase with the focal movement, may have a positive influence upon the stability of coordination.

Effect of a control burn on lizards and their structural environment in a eucalypt open-forest

The composition of an open-forest lizard assemblage in eastern Australia was examined before and after a low-intensity controlled fire and concurrently compared with that in an adjoining unburnt area. The effect of fire on the available structural environment and the habitat used by two focal species, Carlia vivax and Lygisaurus foliorum, was also examined. Lizard species richness was unaffected by the controlled burn as was the abundance of most species. C. vivax was the only species to display a significant reduction in abundance after fire. While the low-intensity fire resulted in significant changes to the available structural environment, there were no compensatory shifts in the habitat preferences of either C. vivax or L. foliorum. The reduction in abundance of C. vivax was congruent with this species' avoidance of burnt areas. C. vivax displayed a non-random preference for ground cover and litter cover, which were reduced in burnt areas. Changes in the availability of preferred structural habitat features are likely to contribute to changes in the abundance of some lizard species. Therefore, even low-intensity disturbances can have an impact on lizard assemblages if critical habitat features are lost or become limiting.