A Predictive Model for Convective Flows Induced by Surface Reactivity Contrast

Concentration gradients in a fluid along a reactive surface due to contrast in surface reactivity generate convective flows. These flows result from contributions by electro and diffusio osmotic phenomena. In this study we have analyzed reactive patterns that release and consume protons, analogous to bimetallic catalytic conversion of peroxide. Here, we present a simple analytical model that accurately predicts the induced potentials and consequent velocities in such systems over a wide range of input parameters. Our model is tested against direct numerical solutions to the coupled Poisson, Nernst-Planck, and Navier-Stokes equations. Our analysis can be used to predict enhancement of mass transport and the resulting impact on overall catalytic conversion, and is also applicable to predicting the speed of catalytic nanomotors

Seasonal Predictions of Shoreline Change, Informed by Climate Indices

With sea level rise accelerating and coastal populations increasing, the requirement of coastal managers and scientists to produce accurate predictions of shoreline change is becoming ever more urgent. Waves are the primary driver of coastal evolution, and much of the interannual variability of the wave conditions in the Northeast Atlantic can be explained by broadscale patterns in atmospheric circulation. Two of the dominant climate indices that capture the wave climate in western Europe’s coastal regions are the ‘Western Europe Pressure Anomaly’ (WEPA) and ‘North Atlantic Oscillation’ (NAO). This study utilises a shoreline prediction model (ShoreFor) which is forced by synthetic waves to investigate whether forecasts can be improved when the synthetic wave generation algorithm is informed by relevant climate indices. The climate index-informed predictions were tested against a baseline case where no climate indices were considered over eight winter periods at Perranporth, UK. A simple adaption to the synthetic wave-generating process has allowed for monthly climate index values to be considered before producing the 103 random waves used to force the model. The results show that improved seasonal predictions of shoreline change are possible if climate indices are known a priori. For NAO, modest gains were made over the uninformed ShoreFor model, with a reduction in average root mean square error (RMSE) of 7% but an unchanged skill score. For WEPA, the gains were more significant, with the average RMSE 12% lower and skill score 5% higher. Highlighted is the importance of selecting an appropriate index for the site location. This work suggests that better forecasts of shoreline change could be gained from consideration of a priori knowledge of climatic indices in the generation of synthetic waves

Survival, transmission and control of Phoma koolunga in field pea seed and reaction of field pea genotypes to the pathogen

Little is known about the epidemiology of Phoma koolunga, a component of the ascochyta blight complex of field pea in southern Australia. The aims of this research were to investigate seed infection, efficacy of fungicides as seed dressings and the reaction of current field pea genotypes to this fungus. The frequency of isolation of P. koolunga from individual seed samples from South Australia, Victoria and Western Australia ranged from 0 to 6 %. Disease was transmitted to 98% of seedlings that emerged from artificially inoculated seeds (AIS) in growth room conditions. The necrotic index on seedlings that emerged from AIS at 8°C was greater than that for seedlings at 12, 16 and 20°C. P-Pickel T® and Jockey Stayer® were the most effective fungicides for reducing disease incidence and severity on seedlings emerged from AIS sown in soil and on germination paper, respectively. The response of 12 field pea genotypes to one isolate of P. koolunga was assessed by spraying plants with pycnidiospore suspension in controlled conditions and examining symptoms from 3 to 21 days post-inoculation (dpi). Genotypes Sturt, Morgan and Parafield showed more severe disease on the lowest three leaves than the other genotypes at 21 dpi. In another experiment, four genotypes of short, semi-leafless type field peas were inoculated with three isolates of P. koolunga which differed in virulence and assessed as described above. Kaspa showed significantly less disease than Morgan or WAPEA2211 at 21 dpi when inoculated with two of the three isolates tested. Isolates of P. koolunga differed in aggressiveness based on % leaf area diseased until 14 dpi, but differences were not significant at 21 dpi.M. Khani, J. A. Davidson, M. R. Sosnowski, E. S. Scot

Survival of Phoma koolunga, a causal agent of ascochyta blight, on field pea stubble or as pseudosclerotia in soil

Phoma koolunga is a recently recognized pathogen in the ascochyta blight complex of field pea (Pisum sativum). Unlike the other three ascochyta blight pathogens, survival of P. koolunga is poorly understood. Survival of this fungus was examined on field pea stubble and as pseudosclerotia on the surface of, and buried in, field soil. Pseudosclerotia were formed in plates containing potato dextrose agar (PDA) mixed with sand or amended with fluorocytocin. After 1 month, P. koolunga was recovered on amended PDA from 93% of stubble sections retrieved from the soil surface, 36% of buried stubble sections and 100% of pseudosclerotia buried in field soil, pasteurized or not. The frequency of recovery of P. koolunga decreased over time and the fungus was not recovered from stubble on the soil surface at 15 months, nor was it recovered from stubble buried in soil at 11 months or later, or from pseudosclerotia buried for 18 months. In a pot bioassay, most ascochyta blight lesions developed on plants inoculated with stubble retrieved from the soil surface after 1 month. Infectivity of the inoculum decreased over time. Disease on plants inoculated with stubble that had been buried or left on the soil surface for up to 6 and 5 months, respectively, and pseudosclerotia retrieved at 14 months and later from field soil did not differ from the non-inoculated control. These results suggest that field pea stubble may play a role in survival of P. koolunga, especially if it remains on the soil surface. In addition, pseudosclerotia were able to persist in soil and infect field pea plants into the next season.M. Khani, J. A. Davidson, M. R. Sosnowski and E. S. Scot

Electro-Osmotic Instability and Chaos near Ion-Selective Surfaces

We present a "fluid dynamics video" showing results from direct numerical simulations of electrokinetic transport in a binary electrolyte in two systems: (1) next to an ion-selective membrane and (2) around a metallic cylinder. The governing equations are the Poisson--Nernst--Planck and Navier--Stokes and our DNS resolves the time and length scales associated with the thin electric double layers. Our results show transition to chaotic dynamics when the applied voltage across the characteristic length scale is above a threshold of approximately 0.5 Volt. More details, in particular regarding system (1), are given in our paper [Druzgalski et al. POF 25, 110804 (2013)].Comment: 2 videos include

The Spring 1985 high precision baseline test of the JPL GPS-based geodetic system

The Spring 1985 High Precision Baseline Test (HPBT) was conducted. The HPBT was designed to meet a number of objectives. Foremost among these was the demonstration of a level of accuracy of 1 to 2:10 to the 7th power, or better, for baselines ranging in length up to several hundred kilometers. These objectives were all met with a high degree of success, with respect to the demonstration of system accuracy in particular. The results from six baselines ranging in length from 70 to 729 km were examined for repeatability and, in the case of three baselines, were compared to results from colocated VLBI systems. Repeatability was found to be 5:10 to the 8th power (RMS) for the north baseline coordinate, independent of baseline length, while for the east coordinate RMS repeatability was found to be larger than this by factors of 2 to 4. The GPS-based results were found to be in agreement with those from colocated VLBI measurements, when corrected for the physical separations of the VLBI and CPG antennas, at the level of 1 to 2:10 to the 7th power in all coordinates, independent of baseline length. The results for baseline repeatability are consistent with the current GPA error budget, but the GPS-VLBI intercomparisons disagree at a somewhat larger level than expected. It is hypothesized that these differences may result from errors in the local survey measurements used to correct for the separations of the GPS and VLBI antenna reference centers

Superoxide dismutase downregulation in osteoarthritis progression and end-stage disease

Oxidative stress is proposed as an important factor in osteoarthritis (OA). To investigate the expression of the three superoxide dismutase (SOD) antioxidant enzymes in OA. SOD expression was determined by real-time PCR and immunohistochemistry using human femoral head cartilage. SOD2 expression in Dunkin–Hartley guinea pig knee articular cartilage was determined by immunohistochemistry. The DNA methylation status of the SOD2 promoter was determined using bisulphite sequencing. RNA interference was used to determine the consequence of SOD2 depletion on the levels of reactive oxygen species (ROS) using MitoSOX and collagenases, matrix metalloproteinase 1 (MMP-1) and MMP-13, gene expression. All three SOD were abundantly expressed in human cartilage but were markedly downregulated in end-stage OA cartilage, especially SOD2. In the Dunkin–Hartley guinea pig spontaneous OA model, SOD2 expression was decreased in the medial tibial condyle cartilage before, and after, the development of OA-like lesions. The SOD2 promoter had significant DNA methylation alterations in OA cartilage. Depletion of SOD2 in chondrocytes increased ROS but decreased collagenase expression. This is the first comprehensive expression profile of all SOD genes in cartilage and, importantly, using an animal model, it has been shown that a reduction in SOD2 is associated with the earliest stages of OA. A decrease in SOD2 was found to be associated with an increase in ROS but a reduction of collagenase gene expression, demonstrating the complexities of ROS function

How safe is your playground? Analyzing soil in Scottish schools through a university outreach project

School pupils often perceive STEM subjects to be challenging; thus, in this project, an interactive, nationwide STEM investigation was designed to stimulate their interest. The “Soils in Scottish Schools” project provided teachers with a flexible package of resources to allow them to enhance the profile and understanding of soil science of their pupils. This package included presentations, experimental procedures, activities, and monthly newsletters which could be adapted to the particular learning environment of their pupils. In the focal point of the project, teachers were supported to encourage their pupils to collect samples from their school ground which were then analyzed for copper, lead, and zinc levels. This year-long project also afforded teachers with the opportunity to develop the pupils’ investigative skills through engagement with experiments in their own classrooms where they could engage with real data