Electrical processes in heavy rain in the tropics

The thesis is based on research carried out in Sierra Leone over a period of several years. An asymmetric field mill and a 'wide-angle' shielded receiver have been developed for the measurement of electric field and precipitation current in tropical thunderstorms. A detailed field-mill theory is presented which analyses the effects of leakage currents, inadequate grounding, contact potentials, conduction current, 'pick-up' of fluctuating electric fields and noise in the amplifier. Principles are deduced for the optimum design of a precision field mill using either a phase sensitive detector or an asymmetric signal. Measurements of precipitation current and its response to step changes in the field show that turbulent diffusion of splash droplets probably constitutes an important, even dominant, electrical process in heavy rain. The response of precipitation current to a lightning flash, averaged over many flashes, is large and has a delay of a few seconds. From the analysis of various models considered as a mechanism to explain the results it is deduced that charge carried on splash droplets is being diffused upwards by turbulence, transported by wind and is itself precipitating into the rain receiver. An experiment was performed to measure the electric current due to evaporation. The results show that the current due to evaporation in the presence of an electric field is much smaller than that due to conduction in air. The observation of a 'warm' thunderstorm cloud is reported. A project was developed to make visual and electrical measurements simultaneously on the same cloud. A time lapse film of tropical clouds, together with some electric field measurements beneath them, are used to discuss the flow pattern associated with a tropical thunderstorm and the mechanism by which it becomes charged. Appendices include an analysis of the shielding effect of a vertical rod at ground potential, the description of some further instrumentation, including a data processing system designed by the author which uses a novel but effective method of detecting the occurrence of the peak of a signal, more detailed mathematical derivations of equations used in the main text and a filming schedule for the time-lapse photography

Working memory enhances target detection in the blind hemifield

Visual perception can be influenced by the content of working memory. Previous studies have shown this influence can be enough to improve unconscious visual discrimination in healthy participants and conscious visual discrimination in neuropsychological patients with extinction. Here, these findings are extended by examining the effects of holding an object in working memory on unconscious visual perception in a person with hemianopia. The results revealed significantly enhanced detection accuracy when there was an exact match between the colour and orientation of the discrimination target and the item in working memory. However, the facilitatory effect was greatly reduced when only colour or orientation was matched with the item being held in memory. A control experiment confirmed these effects were not due to visual priming. These results are consistent with the proposal that working memory guided perceptual facilitation is driven by signal enhancement. More broadly, the data are interpreted in terms of a biased competition account of visual perception

Neurocomputational mechanisms underlying emotional awareness: Insights afforded by deep active inference and their potential clinical relevance

Emotional awareness (EA) is recognized as clinically relevant to the vulnerability to, and maintenance of, psychiatric disorders. However, the neurocomputational processes that underwrite individual variations remain unclear. In this paper, we describe a deep (active) inference model that reproduces the cognitive-emotional processes and self-report behaviors associated with EA. We then present simulations to illustrate (seven) distinct mechanisms that (either alone or in combination) can produce phenomena – such as somatic misattribution, coarse-grained emotion conceptualization, and constrained reflective capacity – characteristic of low EA. Our simulations suggest that the clinical phenotype of impoverished EA can be reproduced by dissociable computational processes. The possibility that different processes are at work in different individuals suggests that they may benefit from distinct clinical interventions. As active inference makes particular predictions about the underlying neurobiology of such aberrant inference, we also discuss how this type of modelling could be used to design neuroimaging tasks to test predictions and identify which processes operate in different individuals – and provide a principled basis for personalized precision medicine

First record of verticillium wilt (Verticillium longisporum) in winter oilseed rape in the UK

Verticillium longisporum is an important pathogen of oilseed rape (OSR) and vegetable brassicas in several European countries, but has not been reported previously in the UK (Karapapa et al., 1997; Steventon et al., 2002). In 2007, Verticillium wilt was suspected in UK crops of winter OSR (W-OSR) on cv. Castille in Romney Marsh, Kent and on cv. Barrel near Hereford. At these two locations, 32 and 10% of the plants, respectively, appeared to be affected, but the presence of stem canker may have masked some infections. Symptoms were first seen as the crops began to ripen (seeds green-brown to brown, Growth Stage: 6,4-6,5) and included brown and dark grey vertical bands on the stems from soil level into the branches, and premature ripening of some branches (Fig. 1). Microsclerotia were observed on stem samples collected in the field (Fig. 2), suggesting V. longisporum as the causal agent. Cultures were prepared from field samples by immersing stem pieces in 5% sodium hypochlorite solution for one minute, washing twice in sterile distilled water and plating onto potato dextrose agar containing 25 mg/l streptomycin sulphate. Isolates from three plants per outbreak were identified morphologically as V. longisporum. Mean conidial dimensions (25 spores per isolate) were 8.80-9.65 μm (length) and 2.50-2.85 μm (width) and all isolates produced elongated microsclerotia, characters typical of V. longisporum (Karapapa et al., 1997). The identity was confirmed by PCR using species-specific primers (Steventon et al., 2002) and, as a member of the α sub-group, by direct sequencing of the amplicons from primer pairs ITS4-ITS5 and DB19-DB22 (Collins et al., 2003; 2005). Sequences for isolate 003 from Kent were deposited in GenBank (Accession Nos. HQ702376 and HQ702377). All isolates tested from 2008 and 2009 were identical with previously deposited sequences for European OSR isolates (e.g. AF363992 and AF363246 respectively). Pathogenicity was confirmed by inoculating three OSR cv. Castille seedlings per isolate using the root dip technique with 1 x 106 spores/ml (Karapapa et al., 1997) under heated glasshouse conditions at 19°C. Leaf yellowing and blackening of the leaf veins were found 26 days after inoculation (Fig. 3). Yellowing affecting the three oldest leaves increased for seven to nine days. After five weeks the final mean leaf area affected was 63-78% with no differences between isolates. No leaf yellowing occurred in the controls. After five weeks, V. longisporum was re-isolated from all the inoculated seedlings, but not from the non-inoculated controls. In June 2008, infection of W-OSR crops in different fields on the same farms was found on cv. Es Astrid in Kent (56% incidence) and on cv. Lioness in Hereford (15% incidence). The Kent farm had been growing W-OSR alternating with winter wheat for at least 10 years whilst the Hereford farm had grown W-OSR one year in four. These short rotations of OSR may be contributing to the appearance of this disease. This study confirms the identification of V. longisporum on any host in the UK, through molecular studies and detailed spore measurements that were not reported in an earlier review (Gladders, 2009). This pathogen occurs in several European countries and, since OSR may be traded freely, following a Defra consultation, no statutory plant health action is to be taken

From the Empire State to the North Star State: Voter Engagement in the 2016 Election

Voter engagement has the potential to be a fundamental part of social work practice and key to the professional socialization of social work students. This article describes a classroom-based voter engagement project conducted in two undergraduate social work programs in different U.S. states with significantly different voting laws. We describe the rationale, process of implementing the project, evaluation, and review the results in the context of the 2016 election. We suggest future research that can help develop best practices and methods for implementation of voter engagement in social work practice and education in the future

A Statement on the Appropriate Role for Research and Development in Climate Policy

This statement is issued by a group of economists and scientists which met at Stanford University on October 18, 2008 to discuss the role of research and development (R&D) in developing effective policies for addressing the adverse potential consequences of climate change. We believe that climate change is a serious issue that governments need to address. We also believe that research and development needs to be a central part of governments’ strategies for responding to this challenge. Solutions to manage long-term risks will require the development and global deployment of a range of technologies for energy supply and end-use, land-use, agriculture and adaptation that are not currently commercial. A key potential benefit of focused scientific and technological research and development investment is that it could dramatically reduce the cost of restricting greenhouse gas emissions by encouraging the development of more affordable, better performing technologies.

Masses, Luminosities, and Orbital Coplanarities of the mu Orionis Quadruple Star System from PHASES Differential Astrometry

mu Orionis was identified by spectroscopic studies as a quadruple star system. Seventeen high precision differential astrometry measurements of mu Ori have been collected by the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES). These show both the motion of the long period binary orbit and short period perturbations superimposed on that caused by each of the components in the long period system being themselves binaries. The new measurements enable the orientations of the long period binary and short period subsystems to be determined. Recent theoretical work predicts the distribution of relative inclinations between inner and outer orbits of hierarchical systems to peak near 40 and 140 degrees. The degree of coplanarity of this complex system is determined, and the angle between the planes of the A-B and Aa-Ab orbits is found to be 136.7 +/- 8.3 degrees, near the predicted distribution peak at 140 degrees; this result is discussed in the context of the handful of systems with established mutual inclinations. The system distance and masses for each component are obtained from a combined fit of the PHASES astrometry and archival radial velocity observations. The component masses have relative precisions of 5% (component Aa), 15% (Ab), and 1.4% (each of Ba and Bb). The median size of the minor axes of the uncertainty ellipses for the new measurements is 20 micro-arcseconds. Updated orbits for delta Equulei, kappa Pegasi, and V819 Herculis are also presented.Comment: 12 Pages, Accepted for publication in A