First Results From Sleuth: The Palomar Planet Finder

We discuss preliminary results from our first search campaign for transiting planets performed using Sleuth, an automated 10 cm telescope with a 6 degree square field of view. We monitored a field in Hercules for 40 clear nights between UT 2003 May 10 and July 01, and obtained an rms precision (per 15-min average) over the entire data set of better than 1% on the brightest 2026 stars, and better than 1.5% on the brightest 3865 stars. We identified no strong candidates in the Hercules field. We conducted a blind test of our ability to recover transiting systems by injecting signals into our data and measuring the recovery rate as a function of transit depth and orbital period. About 85% of transit signals with a depth of 0.02 mag were recovered. However, only 50% of transit signals with a depth of 0.01 mag were recovered. We expect that the number of stars for which we can search for transiting planets will increase substantially for our current field in Andromeda, due to the lower Galactic latitude of the field

On Lundh's percolation difussion

A collection of spherical obstacles in the ball in Euclidean space is said to be avoidable for Brownian motion if there is a positive probability that Brownian motion diffusing from some point in the ball will avoid all the obstacles and reach the boundary of the ball. The centres of the spherical obstacles are generated according to a Poisson point process while the radius of an obstacle is a deterministic function depending only on the distance from the obstacle's centre to the centre of the ball. Lundh has given the name percolation diffusion to this process if avoidable configurations are generated with positive probability. An integral condition for percolation diffusion is derived in terms of the intensity of the Poisson point process and the function that determines the radii of the obstacles

Weed economic thresholds : Useful agronomic tool or pipe dream?

L'intérêt pour des approches de lutte contre les mauvaises herbes plus ration nelles et objectives s'est considérablement accru au Canada et ailleurs. Les questions de coût/bénéfices, les préoccupations environnementales et le développement de la résistance aux herbicides ont semé le doute sur la pertinence et la possibilité de poursuivre l'utilisation préventive des herbicides. Le concept de seuil d'intervention économique pour les mauvaises herbes et le concept plus large de lutte intégrée présentent un potentiel important comme outils agronomiques pratiques dans les systèmes de production canadiens. Un grand nombre d'expériences ont été menées afin de déterminer l'impact des mauvaises herbes sur le rendement des cultures, mais les modèles développés à partir de ces études ont été peu mis en pratique. Les contraintes à la mise en pratique de ces concepts comprennent l'absence de protocoles d'échantillonnage réalistes afin de déterminer l'impact des mauvaises herbes sur les cultures sur de vastes étendues, ainsi qu'un manque de renseignements sur les implications à long terme de la production de graines par les mauvaises herbes non contrôlées. Les malherbologistes qui mènent des expériences sur l'interférence causée par les mauvaises herbes devraient mieux définir leurs objectifs et devraient fournir des directives sur la façon dont leurs résultats peuvent être utilisés à la ferme. L'accent devrait être placé sur l'effet des cultures sur les mauvaises herbes plutôt que sur l'effet des mauvaises herbes sur les cultures. Une meilleure coordination des activités de recherche des malherbologistes s'impose. La mise en place de protocoles standards pour les études à long terme entre les sites et les années augmenterait la pertinence et la précision des modèles d'interférence, et pourrait conduire au développement de systèmes d'aide à la décision conviviaux et adaptés spécifiquement à la prise de décisions rationnelles de lutte contre les mauvaises herbes dans les systèmes canadiens de production des cultures. Le développement de tels systèmes sera essentiel à la mise en place de seuils d'intervention et de méthodes de lutte intégrée contre les mauvaises herbes.Interest in more rational and objective approaches to weed management has increased considerably in Canada and elsewhere. Cost/benefit issues, environmental concerns, and the development of weed resistance to herbicides have cast doubt on the rationality and sustainability of prophylactic herbicide use. The concept of an economic threshold for weeds and the broader concept of integrated weed management have considerable potential as practical agronomic tools in Canadian crop production Systems. A large number of experiments have been conducted to determine the impact of weeds on crop yield, but the models developed from these studies have been put to little practical use. Constraints to the practical implementation of these concepts include a lack of realistic sampling procedures to assess the impact of weeds on crops over large areas, and a lack of information on the long-term implications of seed production by uncontrolled weeds. Weed ecologists conducting weed interference experiments should define their objectives better, and should provide guidelines on how their findings can be used at the farm level. Emphasis should be placed on the effects of the crop on the weed rather than the weed on the crop. There is also a need for greater coordination of research activities among weed ecologists. The establishment of standard protocols for long-term studies across locations and years would enhance the relevance and precision of weed interference models, and lead to the development of user- friendly decision support Systems specifically adapted to aiding rational weed management decisions in Canadian crop production Systems. The development of such Systems will be essential to the implementation of weed thresholds and integrated weed management

Ecotoxicological effects of polyethylene microplastics, with and without adsorbed contaminants, on the clam Scrobicularia plana (da Costa, 1778) using a multi-biomarker approach

The potentially detrimental impacts of plastic debris on the marine biota are numerous and diverse with deleterious physical effects recorded. Microplastics, defined as plastic particles ≤ 5mm, are of particular concern due to their ubiquitous distribution in the marine environment. Low density polyethylene accounts for ~17% of European plastic production, with use dominated by the packaging industry. This study investigated the ecotoxicological effects of exposure of low density polyethylene microplastics, with and without added contaminants, in gill tissues and haemocytes of the peppery furrow shell clam, Scrobicularia plana. Environmentally relevant concentrations of contaminants, benzo[a]pyrene, oxybenzone, and perfluorooctane sulfonic acid, were adsorbed to microplastics to evaluate the potential role of plastic particles as a source of chemical contamination once ingested. S. plana were exposed to microplastics at a concentration of 1 mgL-1 for 14 days. To clarify any effects of exposure, a set of biomarkers were employed, including the quantification of antioxidant (superoxide dismutase, catalase, glutathione peroxidase) and biotransformation (glutathione-S-transferases) enzyme activities, oxidative damage (lipid peroxidation levels), genotoxicity (single and double strand DNA breaks) and neurotoxicity (acetylcholinesterase activity). Neither a genotoxic nor an inhibitory neurotoxic effect was recorded. The dominant response in catalase and glutathione-S-transferase was attributed to virgin microplastics, suggesting the observed effects were due to physical ingestion and the potential mechanical injuries that result. Superoxide dismutase and lipid peroxidation, showed an increase in activity in contaminated microplastic treatments relative to virgin microplastic, suggesting a synergistic effect of physical ingestion and chemical exposure. A reduction in glutathione peroxidase activity was observed in contaminated microplastic treatments, compared to virgin microplastic, indicating an antagonistic effect may have occurred. Further analysis is needed to confirm the bioavailability of microplastics and that the observed biomarker responses are a result of microplastic exposure, and chemical exposure in the case of superoxide dismutase and lipid peroxidation

Magnetic field effects on the density of states of orthorhombic superconductors

The quasiparticle density of states in a two-dimensional d-wave superconductor depends on the orientation of the in-plane external magnetic field H. This is because. in the region of the gap nodes, the Doppler shift due to the circulating supercurrents around a vortex depend on the direction of H. For a tetragonal system the induced pattern is four-fold symmetric and, at zero energy, the density of states exhibits minima along the node directions. But YBa_2C_3O_{6.95} is orthorhombic because of the chains and the pattern becomes two-fold symmetric with the position of the minima occuring when H is oriented along the Fermi velocity at a node on the Fermi surface. The effect of impurity scattering in the Born and unitary limit is discussed.Comment: 24 pages, 11 Figure

The Broadband Infrared Emission Spectrum of the Exoplanet TrES-3

We use the Spitzer Space Telescope to estimate the dayside thermal emission of the exoplanet TrES-3 integrated in the 3.6, 4.5, 5.8, and 8.0 micron bandpasses of the Infrared Array Camera (IRAC) instrument. We observe two secondary eclipses and find relative eclipse depths of 0.00346 +/- 0.00035, 0.00372 +/- 0.00054, 0.00449 +/- 0.00097, and 0.00475 +/- 0.00046, respectively in the 4 IRAC bandpasses. We combine our results with the earlier K band measurement of De Mooij et al. (2009), and compare them with models of the planetary emission. We find that the planet does not require the presence of an inversion layer in the high atmosphere. This is the first very strongly irradiated planet that does not have a temperature inversion, which indicates that stellar or planetary characteristics other than temperature have an important impact on temperature inversion. De Mooij & Snellen (2009) also detected a possible slight offset in the timing of the secondary eclipse in K band. However, based on our 4 Spitzer channels, we place a 3sigma upper limit of |ecos(w)| < 0.0056 where e is the planets orbital eccentricity and w is the longitude of the periastron. This result strongly indicates that the orbit is circular, as expected from tidal circularization theory.Comment: Accepted by Ap

A Capability Maturity Model to assess Government ICT4D Policy

The efforts of a Government to provide ICTs in a developing country are mostly well intended but not always successful. To establish why this happens can be a complex process. Influencing government initiatives are a variety of inhibitors, enablers and influences ranging from the diversity of stakeholders and their cultures and history, to skill levels, existing infrastructure, economic conditions, access, prejudice and politics, and language. All these factors need to be understood and managed before current or future initiatives can hope to be successful. To this end, the purpose of this paper was to develop a Capability Maturity Model for use as a conceptual framework to advance the understanding of researchers and practitioners of Governmental ICT4D policy, and the implementation of that policy. This paper sets up a theoretical model with four levels of maturity, each level consisting of five dimensions. Each of the five dimensions are then discussed and, finally, the use and contribution of the model is outlined