1,241 research outputs found
Directional characteristics of lunar thermal emission
Directional characteristics and brightness temperatures of thermal lunar emissio
Judging Corporate Directors by the Companies They Keep: Results from an Interactive Simulation About the Motivations of Corporate Directors
Exotic Invasive Elm Bark Beetle, \u3cem\u3eScolytus kirschii\u3c/em\u3e, Detected in South Africa
In February 2005, the exotic bark beetle, Scolytus kirschii (Curculionidae: Scolytinae), was detected infesting English elms (Ulmus procera) in Stellenbosch, South Africa. This appears to be the first report of an infestation of Scolytus species in this country. The presence of this beetle is of concern for several reasons. Scolytus kirschii is a serious pest of elms, capable of killing healthy trees, resulting in considerable economic impact. There also exists the possibility that the beetle may undergo a host switch to indigenous trees, with potentially serious ecological consequences. Furthermore, the beetle is capable of being the vector of the pathogens responsible for Dutch elm disease (DED), Ophiostoma ulmi and Ophiostoma novo-ulmi. None of the trees that we inspected in Stellenbosch exhibited symptoms or signs of DED. Isolations from infested host material likewise failed to detect these pathogens. Nonetheless, the damage to the trees by the beetles alone was sufficient to cause tree death. Future directions for research and management of the beetle in its new environment are discussed
Fungal phoenix rising from the ashes?
During May 2010, sporocarps of what appeared to be an Armillaria sp. were found in large clumps in historic Kirstenbosch Botanical Gardens on the foot of Table Mountain, Cape Town, South Africa. These sporocarps could be physically linked to the roots of unidentified dead trees and Protea spp. The aim of this study was to identify the Armillaria sp. found fruiting in Kirstenbosch. To achieve this goal isolates were made from the mycelium under the bark of dead roots linked to sporocarps. The ITS and IGS-1 regions were sequenced and compared to sequences of Armillaria spp. available on GenBank. Cladograms were generated using ITS sequences to determine the phylogenetic relationship of the isolates with other Armillaria spp. Sequence comparisons and phylogenetic analyses showed that the isolates represented A. mellea. They were also identical to isolates of this species previously discovered in the Company Gardens in South Africa and introduced from Europe apparently by the early Dutch Settlers. Armillaria mellea is alien and apparently invasive in Cape Town, fruits profusely and has the potential to spread to sensitive native forests on the foothills of the City
Bell inequality and CP violation in the neutral kaon system
For the entangled neutral kaon system we formulate a Bell inequality
sensitive to CP violation in mixing. Via this Bell inequality we obtain a bound
on the leptonic CP asymmetry which is violated by experimental data.
Furthermore, we connect the Bell inequality with a decoherence approach and
find a lower bound on the decoherence parameter which practically corresponds
to Furry's hypothesis.Comment: 10 pages, latex, no figure
Multi-gene phylogeny for Ophiostoma spp. reveals two new species from Protea infructescences
Ophiostoma represents a genus of fungi that are mostly
arthropod-dispersed and have a wide global distribution. The best known of
these fungi are carried by scolytine bark beetles that infest trees, but an
interesting guild of Ophiostoma spp. occurs in the infructescences of
Protea spp. native to South Africa. Phylogenetic relationships
between Ophiostoma spp. from Protea infructescences were
studied using DNA sequence data from the β-tubulin, 5.8S ITS (including
the flanking internal transcribed spacers 1 and 2) and the large subunit DNA
regions. Two new species, O. phasma sp. nov. and O.
palmiculminatum sp. nov. are described and compared with other
Ophiostoma spp. occurring in the same niche. Results of this study
have raised the number of Ophiostoma species from the infructescences
of serotinous Protea spp. in South Africa to five. Molecular data
also suggest that adaptation to the Protea infructescence niche by
Ophiostoma spp. has occurred independently more than once
Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize
Nitrogen fertilizer management can impact soil organic C (SOC) stocks in cereal-based cropping systems by regulating crop residue inputs and decomposition rates. However, the impact of long-term N fertilizer management, and associated changes in SOC quantity and quality, on the fate of N fertilizer inputs is uncertain. Using two 15-year N fertilizer rate experiments on continuous maize (Zea mays L.) in Iowa, which have generated gradients of SOC, we evaluated the legacy effects of N fertilizer inputs on the fate of added N. Across the historical N fertilizer rates, which ranged from 0 to 269 kg N ha−1 yr−1, we applied isotopically-labeled N fertilizer at the empirically-determined site-specific agronomic optimum rate (202 kg N ha−1 at the central location and 269 kg N ha−1 at the southern location) and measured fertilizer recovery in crop and soil pools, and, by difference, environmental losses. Crop fertilizer N recovery efficiency (NREcrop) at physiological maturity averaged 44% and 14% of applied N in central Iowa and southern Iowa, respectively (88 kg N ha−1 and 37 kg N ha−1, respectively). Despite these large differences in NREcrop, the response to historical N rate was remarkably similar across both locations: NREcrop was greatest at low and high historical N rates, and least at the intermediate rates. Decreasing NREcrop from low to intermediate historical N rates corresponded to a decline in early-season fertilizer N recovery in the relatively slow turnover topsoil mineral-associated organic matter pool (0–15 cm), while increasing NREcrop from intermediate to high historical N rates corresponded to an increase in early-season fertilizer N recovery in the relatively fast turnover topsoil particulate organic matter pool and an increase in crop yield potential. Despite the variation in NREcropalong the historical N rate gradient, we did not detect an effect of historical N rate on environmental losses during the growing season, which averaged 34% and 69% of fertilizer N inputs at the central and southern locations, respectively (69 kg N ha−1 and 185 kg N ha−1, respectively). Our results suggest that, while beneficial for SOC storage over the long term, fertilizing at the agronomic optimum N rate can lead to significant environmental N losses
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