1,317 research outputs found

    Staying afloat on Neurath's boat - Heuristics for sequential causal learning

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    Causal models are key to flexible and efficient exploitation of the environment. However, learning causal structure is hard, with massive spaces of possible models, hard-to-compute marginals and the need to integrate diverse evidence over many instances. We report on two experiments in which participants learnt about probabilistic causal systems involving three and four variables from sequences of interventions. Participants were broadly successful, albeit exhibiting sequential dependence and floundering under high background noise. We capture their behavior with a simple model, based on the “Neurath’s ship” metaphor for scientific progress, that neither maintains a probability distribution, nor computes exact likelihoods

    General practice ethnicity data: evaluation of a tool

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    INTRODUCTION: There is evidence that the collection of ethnicity data in New Zealand primary care is variable and that data recording in practices does not always align with the procedures outlined in the Ethnicity Data Protocols for the Health and Disability Sector. In 2010, The Ministry of Health funded the development of a tool to audit the collection of ethnicity data in primary care. The aim of this study was to pilot the Ethnicity Data Audit Tool (EAT) in general practice. The goal was to evaluate the tool and identify recommendations for its improvement. METHODS: Eight general practices in the Waitemata District Health Board region participated in the EAT pilot. Feedback about the pilot process was gathered by questionnaires and interviews, to gain an understanding of practices’ experiences in using the tool. Questionnaire and interview data were analysed using a simple analytical framework and a general inductive method. FINDINGS: General practice receptionists, practice managers and general practitioners participated in the pilot. Participants found the pilot process challenging but enlightening. The majority felt that the EAT was a useful quality improvement tool for handling patient ethnicity data. Larger practices were the most positive about the tool. CONCLUSION: The findings suggest that, with minor improvements to the toolkit, the EAT has the potential to lead to significant improvements in the quality of ethnicity data collection and recording in New Zealand general practices. Other system-level factors also need to be addressed

    Talc-dominated seafloor deposits reveal a new class of hydrothermal system

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    The Von Damm Vent Field (VDVF) is located on the flanks of the Mid-Cayman Spreading Centre, 13?km west of the axial rift, within a gabbro and peridotite basement. Unlike any other active vent field, hydrothermal precipitates at the VDVF comprise 85–90% by volume of the magnesium silicate mineral, talc. Hydrothermal fluids vent from a 3-m high, 1-m diameter chimney and other orifices at up to 215?°C with low metal concentrations, intermediate pH (5.8) and high concentrations (667?mmol?kg?1) of chloride relative to seawater. Here we show that the VDVF vent fluid is generated by interaction of seawater with a mafic and ultramafic basement which precipitates talc on mixing with seawater. The heat flux at the VDVF is measured at 487±101?MW, comparable to the most powerful magma-driven hydrothermal systems known, and may represent a significant mode of off-axis oceanic crustal cooling not previously recognized or accounted for in global models

    Proton transfer reactions of N-aryl triazolium salts: unusual ortho-substituent effects

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    Previous studies of the C(3)-hydrogen/deuterium exchange reactions of the triazolium ion conjugate acids of triazolyl N-heterocyclic carbenes revealed a change of mechanism under acidic conditions with N1-protonation to a dicationic salt. Interestingly, the data suggested an increase in pKaN1 in the presence of a N-pentafluorophenyl substituent relative to other N-aryl substituents with hydrogens or methyl substituents rather than fluorines at the ortho-positions. To probe the presence of an apparent donor effect of a N-pentafluorophenyl substituent, which differs from the more common electron withdrawing effect of this group, we have studied the analogous deuterium exchange reactions of four triazolium salts with heteroatoms or heteroatom substituents in the 2-position and/or 6-position of the N-aryl ring. These include triazolium salts with N-2,4,6-tribromophenyl 11, N-2,6-dichlorophenyl 12, N-2-pyridyl 13 and N-2-pyrimidinyl 14 substituents. The log kex – pD profiles for 11, 12 and 14 were found to show similar trends at lower pDs as for the previously studied N-pentafluorophenyl triazolium salt, hence supporting the presence an apparent donor effect on pKaN1. Surprisingly, the log kex – pD profile for N-pyridyl salt 13 uniquely showed acid catalysis at lower pDs. We propose herein that this data is best explained by invoking an intramolecular general base role for the N-(2-pyridyl) substituent in conjunction with N1-protonation on the triazolium ring. Finally, the second order rate constants for deuteroxide ion catalysed C(3)-H/D exchange (kDO, M−1 s−1), which could be obtained from data at pDs >1.5, were used to provide estimates of C(3)-carbon acid pKaC3 values for the four triazolium salts 11, 12, 13, 14

    Grape Heterogeneity Index: Assessment of Overall Grape Heterogeneity Using an Aggregation of Multiple Indicators

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    Uniform grape maturity can be sought by producers to minimise underripe and/or overripe proportions of fruit and limit any undesirable effects on wine quality. Considering that grape heterogeneity is a multifaceted phenomenon, a composite index summarising overall grape heterogeneity was developed to benefit vineyard management and harvest date decisions. A grape heterogeneity index (GHI) was constructed by aggregating the sum of absolute residuals multiplied by the range of values from measurements of total soluble solids, pH, fresh weight, total tannins, absorbance at 520 nm (red colour), 3-isobutyl-2-methoxypyrazine, and malic acid. Management of grape heterogeneity was also studied, using Cabernet Sauvignon grapes grown under four viticultural regimes (normal/low crop load, full/deficit irrigation) during the 2019/2020 and 2020/2021 seasons. Comparisons of GHI scores showed grape variability decreased throughout ripening in both vintages, then significantly increased at the harvest time point in 2020, but plateaued on sample dates nearing the harvest date in 2021. Irrigation and crop load had no effect on grape heterogeneity by the time of harvest in both vintages. Larger vine yield, leaf area index, and pruning weight significantly increased GHI score early in ripening, but no significant relationship was found at the time of harvest. Differences in the Ravaz index, normalised difference vegetation index, and soil electrical conductivity did not significantly change the GHI score.Claire E. J. Armstrong, Pietro Previtali, Paul K. Boss, Vinay Pagay, Robert G. V. Bramley, and David W. Jeffer

    The formation of gold-rich seafloor sulfide deposits: Evidence from the Beebe Hydrothermal Vent Field, Cayman Trough

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    The Beebe vent field (BVF) in the Cayman Trough has built an auriferous massive sulfide deposit on the ultra-slow spreading mid-Cayman spreading centre. The genesis of auriferous sulfide deposits at mid-ocean ridges is not fully understood, although there is a growing recognition that slow and ultra-slow spreading centres are conducive to gold mineralization. Analysis of hydrothermal precipitates from the BVF indicates that the highest gold contents are present within “beehive diffusers”, which have developed a highly porous pyrrhotite framework. The beehive structure allows vent fluids to effuse slowly, while allowing ingress of seawater to cool the fluid. The prevalence of pyrrhotite in the beehive samples, lack of sulfates, association between pyrrhotite and gold grains, and results of thermodynamic modelling, suggests gold precipitation occurred under highly reduced conditions even during mixing with seawater. In contrast, high temperature chimneys, with a single orifice, maintain high temperatures to the primary vent orifice and much of the gold is lost to seawater. Despite this, both chimney types are relatively gold enriched, which points to a further underlying cause for high gold at the BVF such as interaction of hydrothermal fluids with ultramafic lithologies in the basement. The final gold composition of the deposit is partially controlled by loss of gold during mass-wasting of the material, with gold depletion most prevalent in blocks formed at beehive-type chimneys. The BVF demonstrates that the overall gold content of a massive sulfide deposit is the sum of basement, precipitation, and surface processes
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