The Rigidly Rotating Magnetosphere of Sigma Ori E

We attempt to characterize the observed variability of the magnetic helium-strong star sigma Ori E in terms of a recently developed rigidly rotating magnetosphere model. This model predicts the accumulation of circumstellar plasma in two co-rotating clouds, situated in magnetohydrostatic equilibrium at the intersection between magnetic and rotational equators. We find that the model can reproduce well the periodic modulations observed in the star's light curve, H alpha emission-line profile, and longitudinal field strength, confirming that it furnishes an essentially correct, quantitative description of the star's magnetically controlled circumstellar environment.Comment: 4 pages, 3 figures, accepted by Ap

Leader Election in Anonymous Rings: Franklin Goes Probabilistic

We present a probabilistic leader election algorithm for anonymous, bidirectional, asynchronous rings. It is based on an algorithm from Franklin, augmented with random identity selection, hop counters to detect identity clashes, and round numbers modulo 2. As a result, the algorithm is finite-state, so that various model checking techniques can be employed to verify its correctness, that is, eventually a unique leader is elected with probability one. We also sketch a formal correctness proof of the algorithm for rings with arbitrary size

The cost of accuracy in crop area estimation

Accuracy and cost of direct crop area measurement are compared with those of farmers' estimates after visual inspection, in this methodological study conducted in southern Mali. The observational error, the difference between the area measured and the area estimated, was first studied at the plot level. Average observational error or bias was -11% of the average area measured, indicating an average underestimation of plots by 11%. This observational error is strongly related to plot size, with smaller plots being overestimated and larger plots underestimated, in an approximately negative linear relationship. The observational error is also smaller for cotton fields than for cereals. The analysis was repeated at the farm level, where the bias in estimating the total area per farm was -8%. At this level, total error or accuracy was calculated by the relative total error (RTE), the square root of the mean square error, divided by the mean. The farmers' estimate was found to be less accurate (RTE=9.4% of the mean) than physical measurement (RTE=6.6%), but at a cost of only $370 as compared with$2328 (for a sample of 96 farms in 11 villages). The coefficient of variation (CV) of most surface variables was found to lie between 60% and 100%, and their relative bias (average observational error divided by the mean area) was between 2% and 10%. For crop area per farm, the physical measurement of plots resulted in a gain of accuracy of 2-4%, as compared with the farmers' estimate after visual inspection. A general model was developed in which these calculated parameters are used to predict the accuracy in future surveys and to compare the accuracy with the survey's cost. It is shown how the survey design can be optimized based on acceptable error, sample size and cost for each measurement technique. Simulations demonstrate that the total error for biased estimators, even for variables with small CVs, hardly decreases above sample sizes of 100-150 farmers

Consumer awareness and attitudes toward GM foods in Kenya

A survey of 604 consumers was conducted in Nairobi, Kenya, in November and December 2003, at three points of sale (supermarkets, kiosks, and posho mills) to determine consumer awareness and attitudes towards genetically modified (GM) foods. Above a third (38%) of the respondents were aware of GM crops, mostly from newspapers, television and radio. Others had learned about GM crops at school. Newspapers and television were more important to higher-income and more educated consumers. Consumers acknowledged the technology’s potential positive impacts, with more than 80% agreeing that it increases productivity. Sixty-eight percent said they would buy GM maize meal at the same price as their favorite brands, although many had concerns; half of the respondents feared that GM technology could lead to a loss of biodiversity and affect non-target insects; while more than one- third (37%) had concerns about the effects of GM food on human health. We conclude that GM technology has a role to play in food security in Kenya. However, consumers need more information about the technology, which can be provided through established sources of information. Finally, consumer attitudes should be studied regularly, and the survey population broadened to include rural consumers

Hyperspherical Formulation Of Impurity-Bound Excitons In Semiconductors

A hyperspherical formalism is shown to be an appropriate approach for the investigation of the three-particle complex corresponding to an exciton bound to a Coulomb center in a semiconductor. The ground- and excited-state potential curves and binding energies are calculated as a function of the mass ratio of the hole and electron, and the concept of a critical mass is discussed. The results that we have obtained are in very good agreement with variational calculations for several semiconductor materials

Developing Bt maize for resource-poor farmers – Recent advances in the IRMA project

This paper presents an overview of the advances in the IRMA project, which develops insect resistant maize varieties for resource-poor farmers, using both conventional breeding and genetic engineering. The project started in 1999 and is active in product development, impact assessment, andcommunication, all within the Kenya regulatory framework. So far, four application for introduction of tissue or commencement of field research were made to and approved by the National Biosafety Committee (NBC), and Bt maize leaves or seeds genes imported for testing against different stem borer species in bioassays on cut leaves in a biosafety laboratory, in potted plants in a Biosafety Greenhouse, and as whole plants in confined field trials in the Open Quarantine Station (OQS) at KARI Kiboko. All these biosafety facilities were specially built by the project for these evaluations. So far, good control has been realized against four of the five major stem borer species: Chilo partellus, Chilo orichalcociliellus, Eldana saccharina and Sesamia calamistis. Economic  impact assessment demonstrated that stem borers are major constraints and cause substantial losses. Resistant maizevarieties are likely to be adopted and to provide major returns to the investment if resistance against the economically most important species, Busseola fusca, can be found. Otherwise, returns would still be positive but small. Environmental impact research indicate that build-up of resistance against the Bt genes has not developed after that sufficient natural refugia exist in most areas, but suitable strategies acceptable to farmers need to be developed for some. Surveys, stakeholders meetings and other communications indicate that farmers, consumers and other stakeholders are cautiously optimistic about technology. Frequent interaction with the stakeholders and regulatory agencies assures a participative decision-making process and compliance with the strictest scientific and regulatorystandards

Mixed quark-nucleon phase in neutron stars and nuclear symmetry energy

The influence of the nuclear symmetry energy on the formation of a mixed quark-nucleon phase in neutron star cores is studied. We use simple parametrizations of the nuclear matter equation of state, and the bag model for the quark phase. The behavior of nucleon matter isobars, which is responsible for the existence of the mixed phase, is investigated. The role of the nuclear symmetry energy changes with the value of the bag constant B. For lower values of B the properties of the mixed phase do not depend strongly on the symmetry energy. For larger B we find that a critical pressure for the first quark droplets to form is strongly dependent on the nuclear symmetry energy, but the pressure at which last nucleons disappear is independent of it.Comment: 12 pages, 16 figures, Phys. Rev. C in pres

Estimates of Dietary Mineral Micronutrient Supply from Staple Cereals in Ethiopia at a District Level

Recent surveys have revealed substantial spatial variation in the micronutrient composition of cereals in Ethiopia, where a single national micronutrient concentration values for cereal grains are of limited use for estimating typical micronutrient intakes. We estimated the district-level dietary mineral supply of staple cereals, combining district-level cereal production and crop mineral composition data, assuming cereal consumption of 300 g capita−1 day−1 proportional to district-level production quantity of each cereal. We considered Barley (Hordeum vulgare L.), maize (Zea mays L.), sorghum (Sorghum bicolor (L.) Moench), teff (Eragrostis tef (Zuccagni) Trotter), and wheat (Triticum aestivum L.) consumption representing 93.5% of the total cereal production in the three major agrarian regions. On average, grain cereals can supply 146, 23, and 7.1 mg capita−1 day−1 of Ca, Fe, and Zn, respectively. In addition, the Se supply was 25 µg capita−1 day−1. Even at district-level, cereals differ by their mineral composition, causing a wide range of variation in their contribution to the daily dietary requirements, i.e., for an adult woman: 1–48% of Ca, 34–724% of Fe, 17–191% of Se, and 48–95% of Zn. There was considerable variability in the dietary supply of Ca, Fe, Se, and Zn from staple cereals between districts in Ethiopi