Probing the time course of nonlinear discriminations during human electrodermal conditioning

Animal-based theories of Pavlovian conditioning propose that patterning discriminations are solved using unique cues or immediate configuring. Recent studies with humans, however, provided evidence that in positive and negative patterning two different rules are utilized. The present experiment was designed to provide further support for this proposal by tracking the time course of the allocation of cognitive resources. One group was trained in a positive patterning; schedule (A-, B-, AB+) and a second in a negative patterning schedule (A+, B+, AB-). Electrodermal responses and secondary task probe reaction time were measured. In negative patterning, reaction times were slower during reinforced stimuli than during non-reinforced stimuli at both probe positions while there were no differences in positive patterning. These results support the assumption that negative patterning is solved using a rule that is more complex and requires more resources than does the rule employed to solve positive patterning. (C) 2001 Elsevier Science (USA).

Cue competition between elementary trained stimuli: US miscuing, interference, and US omission

The present series of experiments was designed to assess whether rule-based accounts of Pavlovian learning can account for cue competition effects observed after elemental training. All experiments involved initial differential conditioning training with A-US and B alone presentations. Miscuing refers to the fact that responding to A is impaired after one B-US presentation whereas interference is the impairment of responding to A after presentation of C-US pairings. Omission refers to the effects on B of A alone presentations. Experiments 1-2a provided clear evidence for miscuing whereas interference was not found after 1, 5 or 10 C-US pairings. Moreover, Experiments 3 and 3a found only weak evidence for interference in an A-US, B I C-US, D I A design used previously to show the effect. Experiments 4 and 5 failed to find any effect of US omission after one or five omission trials. The present results indicate that miscuing is more robust than is the interference effect. Moreover, the asymmetrical effects of US miscuing and US omission are difficult to accommodate within rule-based accounts of Pavlovian conditioning. (C) 2002 Elsevier Science (USA). All rights reserved.

Simulating growth, development, and yield of tillering pearl millet. III. Biomass accumulation and partitioning

Pearl millet landraces from Rajasthan, India, yield significantly less than improved cultivars under optimum growing conditions, but not under stressed conditions. To successfully develop a simulation model for pearl millet, capable of capturing such genotype x environment (G x E) interactions for grain yield, we need to understand the causes of the observed yield interaction. The aim of this paper is to quantify the key parameters that determine the accumulation and partitioning of biomass: the,light extinction coefficient, radiation use efficiency (RUE), pattern of dry matter allocation to the leaf blades, the determination of grain number, and the rate and duration of dry matter accumulation into individual grains. We used data on improved cultivars and landraces, obtained from both published and unpublished sources collected at ICRISAT, Patancheru, India. Where possible, the effects of cultivar and axis (main shoot vs. tillers) on these parameters were analysed, as previous research suggested that G x E interactions for grain yield are associated with differences in tillering habit. Our results indicated there were no cultivar differences in extinction coefficient, RUE, and biomass partitioning before anthesis, and differences between axes in biomass partitioning were negligible. This indicates there was no basis for cultivar differences in the potential grain yield. Landraces, however, produced consistently less grain yield for a given rate of dry matter accumulation at anthesis than did improved cultivars. This was caused by a combination of low grain number and small grain size. The latter was predominantly due to a lower grain growth rate, as genotypic differences in the duration of grain filling were relatively small. Main shoot and tillers also had a similar duration of grain filling. The low grain yield of the landraces was associated with profuse nodal tillering, supporting the hypothesis that grain yield was below the potential yield that could be supported by assimilate availability. We hypothesise this is a survival strategy, which enhances the prospects to escape the effects of stress around anthesis. (C) 2002 E.J. van Oosterom. Published by Elsevier Science B.V. All rights reserved.

Haemodynamic response to TENS applied to upper thoracic nerve roots in normal subjects

This study investigated the haemodynamic response to the 90-minute application of 85 Hz transcutaneous electrical nerve stimulation (TENS) to the T1 and T5 nerve roots. Comparison was made between 20 healthy subjects who had TENS stimulation and a separate group of 20 healthy subjects who rested for 90 minutes. Pulse and blood pressure were measured just prior to the start of TENS stimulation, after 30 minutes of stimulation, and after 90 minutes of stimulation (immediately after stopping TENS) or at completion of the rest time depending on group allocation. The rate pressure product was calculated from the pulse and systolic blood pressure data. Multivariate repeated measures analysis showed a significant group effect for TENS (p = 0.048). Univariate repeated measures analyses showed a significant group by time effect due to TENS on systolic blood pressure over the 90-minute time period (p = 0.028). Separate group repeated measures ANOVA showed a significant decline in heart rate (p = 0.000), systolic blood pressure (p = 0.013) and rate pressure product (p = 0.000) for the TENS group, while the control resting group showed a significant decline in heart rate only (p = 0.04). The application of 85 Hz TENS to the upper thoracic nerve roots causes no adverse haemodynamic effects in healthy subjects.

Linking physiological and architectural models of cotton

Despite the strong influence of plant architecture on crop yield, most crop models either ignore it or deal with it in a very rudimentary way. This paper demonstrates the feasibility of linking a model that simulates the morphogenesis and resultant architecture of individual cotton plants with a crop model that simulates the effects of environmental factors on critical physiological processes and resulting yield in cotton. First the varietal parameters of the models were made concordant. Then routines were developed to allocate the flower buds produced each day by the crop model amongst the potential positions generated by the architectural model. This allocation is done according to a set of heuristic rules. The final weight of individual bolls and the shedding of buds and fruit caused by water, N, and C stresses are processed in a similar manner. Observations of the positions of harvestable fruits, both within and between plants, made under a variety of agronomic conditions that had resulted in a broad range of plant architectures were compared to those predicted by the model with the same environmental inputs. As illustrated by comparisons of plant maps, the linked models performed reasonably well, though performance of the fruiting point allocation and shedding algorithms could probably be improved by further analysis of the spatial relationships of retained fruit. (C) 2002 Elsevier Science Ltd. All rights reserved.

Sexual dysfunction in the Australian population

AIM: To describe the prevalence and forms of sexual dysfunction experienced by Australians, and compare these with people in the United States. METHODS: A cross sectional, telephone interview survey of a randomly selected sample of men (n = 876) and women (n = 908) aged between 18 and 59 years on the electoral roll in all states and territories of Australia (response rate = 61%) was conducted between November 1999 and April 2000. RESULTS: Large proportions of Australian men (55.0%) and women (60.5%) reported at least one sexual problem within the preceding year. More serious sexual dysfunction (> 3 symptoms) was observed in 13.2% of men and 19.7% of women. DISCUSSION: Australia and the USA are similar with regard to the high rate of symptoms of sexual dysfunction observed in the population. The low rate of treatment points to both patient and doctor reluctance to discuss sexual performance and practices.

Effects of soil water availability on water use efficiency of Eucalyptus cloeziana and Eucalyptus argophloia plants

Effects of soil water availability on transpiration efficiency (WUET), instantaneous water use efficiency (WUEi) and carbon isotope composition (delta(13)C) were investigated in 7-month-old plants of humid coastal (Gympie) and dry inland ( Hungry Hills) provenances of Eucalyptus cloeziana F. Muell. and in a dry inland provenance of E. argophloia Blakely (Chinchilla), supplied with 100 (W-100), 70 (W-70) and 50% (W-50) of their water requirements. At W-100, WUET of the three provenances were not significantly different but as available soil moisture decreased, E. argophloia produced greater biomass and demonstrated significantly higher WUET than either E. cloeziana provenance. Midday WUEi was not significantly affected by watering regime within each provenance but was lowest in E. argophloia. A decrease in soil water availability caused a consistent increase in delta(13)C values in all three provenances; however, delta(13)C values of E. argophloia in all three water regimes were significantly lower than those of E. cloeziana provenances, which did not differ significantly from each other. For all three provenances, delta(13)C was not correlated with WUEi but height and root collar diameter were negatively correlated to delta(13)C. There was little evidence of differences in delta(13)C, WUET and WUEi between E. cloeziana provenances but clear differences between E. cloeziana and E. argophloia. The high WUET, low WUEi and low delta(13)C for E. argophloia may have implications in the selection of Eucalyptus provenances for commercial forestry in low-rainfall regions.

Evidence and information for health policy: a decade of change

Over the past decade or so, there has been increasing demand for greater clarity about the major causes of disease and injury, how these differentially affect populations, and how they are changing. In part, this demand has been motivated by resource constraints and a realisation that better health is possible with more informed allocation of resources. At the same time, there has been a change in the way population health and its determinants are quantified, with a much closer integration of the quantitative population sciences (such as epidemiology, demography and health economics) to strengthen and broaden the evidence base for healthcare policy.