Carbon dynamics in a temperate grassland soil after 9 years exposure to elevated CO2 (Swiss FACE)

Elevated pCO₂ increases the net primary production, C/N ratio, and C input to the soil and hence provides opportunities to sequester CO₂-C in soils to mitigate anthropogenic CO₂. The Swiss 9 y grassland FACE (free air carbon-dioxide enrichment) experiment enabled us to explore the potential of elevated pCO₂ (60 Pa), plant species (Lolium perenne L. and Trifolium repens L.) and nitrogen fertilization (140 and 540 kg ha⁻¹ y⁻¹) on carbon sequestration and mineralization by a temperate grassland soil. Use of ¹³C in combination with respired CO₂ enabled the identification of the origins of active fractions of soil organic carbon. Elevated pCO₂ had no significant effect on total soil carbon, and total soil carbon was also independent of plant species and nitrogen fertilization. However, new (FACE-derived depleted ¹³C) input of carbon into the soil in the elevated pCO₂ treatments was dependent on nitrogen fertilization and plant species. New carbon input into the top 15 cm of soil from L. perennne high nitrogen (LPH), L. perenne low nitrogen (LPL) and T. repens low nitrogen (TRL) treatments during the 9 y elevated pCO₂ experiment was 9.3±2.0, 12.1±1.8 and 6.8±2.7 Mg C ha⁻¹, respectively. Fractions of FACE-derived carbon in less protected soil particles >53 μm in size were higher than in <53 μm particles. In addition, elevated pCO₂ increased CO₂ emission over the 118 d incubation by 55, 61 and 13% from undisturbed soil from LPH, LPL and TRL treatments, respectively; but only by 13, 36, and 18%, respectively, from disturbed soil (without roots). Higher input of new carbon led to increased decomposition of older soil organic matter (priming effect), which was driven by the quantity (mainly roots) of newly input carbon (L. perenne) as well as the quality of old soil carbon (e.g. higher recalcitrance in T. repens). Based on these results, the potential of well managed and established temperate grassland soils to sequester carbon under continued increasing concentrations of atmospheric CO₂ appears to be rather limited.     

Very long baseline interferometric observations made with an orbiting radio telescope

An orbiting spacecraft and ground observatories have been used to obtain interferometric observations of cosmic radio sources. The Tracking and Data Relay Satellite System (TDRSS) was used as the orbiting observatory in conjunction with two 64- meter radio telescopes at ground observatories, one in Australia and one in Japan. The quasars 1730-130 (NRAO 530), 1510-089, and 1741-038 were observed at a frequency of 2.3 gigahertz, and a maximum projected baseline of 1.4 earth diameters was achieved. All quasar observations for which valid data were acquired resulted in detected fringes. Many of the techniques proposed for a dedicated very long baseline interferometry observatory in space were used successfully in this experiment.     

Aqueous central cavity in aspartate transcarbamylase from Escherichia coli

A three-dimensional x-ray diffraction study of aspartate transcarbamylase to 5.5-angstrom resolution, with the aid of four isomorphous heavy atom derivatives, indicates the presence of a central aqueous cavity approximating an oblate spheroid about 25 by 50 by 50 angstroms in dimension, within a molecule about 90 by 110 by 110 angstroms in largest dimensions.     

Response of tomato (Solanum L. section Lycopersicon Mill.) germplasm to begomovirus inoculation under controlled and field conditions

Ninety-five tomato accessions belonging to the Vegetable Crops Germplasm Bank of the Federal University of Viçosa (BGH-UFV) were evaluated in a protected environment (biolistic inoculation under greenhouse conditions) and in the field (natural infection) for resistance to bipartite begomoviruses present in Brazil. Plants were assessed by the visual evaluation of symptoms, and viral infection was confirmed by non-radioactive molecular hybridization. Univariate statistical analyses and correlations were made between the traits. High and significant correlations were found between the percentages of visual symptoms and of viral replication, with values of 0.67 in the protected environment and 0.60 in the field. We concluded that under the protected environment, the accessions BGH-2144, BGH-2150, BGH-6878 and BGH-6881 displayed resistance to infection. Under field conditions with natural infection, the best results were obtained for the accessions BGH-2080 and BGH-6881. Only the BGH-6881 (Solanum peruvianum L.) accession excelled in both conditions; this resistance was attributed to the presence of the Ty-2 and Ty-3 resistance gene alleles in heterozygosity. In general, all of the accessions selected in both experimental conditions can serve as sources for the development of cultivars tolerant or resistant to the bipartite begomoviruses present in Brazil.     

Isotopic composition of old ground water from lake agassiz: implications for late pleistocene climate

A uniform oxygen isotope value of -25 per mil was obtained from old ground water at depths of 20 to 30 meters in a thick deposit of clay in the southern part of the glacial Lake Agassiz basin. The lake occupied parts of North Dakota and southern Manitoba at the end of the last glacial maximum and received water from the ice margin and the interior plains region of Canada. Ground water from thick late Pleistocene-age clay deposits elsewhere, a till in southern Saskatchewan, and a glaciolacustrine deposit in northern Ontario show the same value at similar depths. These sites are at about 50 degrees N latitude, span a distance of 2000 kilometers, and like the Lake Agassiz sites, have a ground-water velocity of less than a few millimeters per year. The value of -25 per mil is characteristic of meltwater impounded in the southern basin of Lake Agassiz. This value corresponds to an estimated air temperature of -16 degrees C, compared with the modern temperature of 0 degrees C for this area.     

Quantum coherence in an exchange-coupled dimer of single-molecule magnets

A multi- high-frequency electron paramagnetic resonance method is used to probe the magnetic excitations of a dimer of single-molecule magnets. The measured spectra display well-resolved quantum transitions involving coherent superposition states of both molecules. The behavior may be understood in terms of an isotropic superexchange coupling between pairs of single-molecule magnets, in analogy with several recently proposed quantum devices based on artificially fabricated quantum dots or clusters. These findings highlight the potential utility of supramolecular chemistry in the design of future quantum devices based on molecular nanomagnets.     

先进的陆地和海底管道涂覆技术

油气工业的快速发展给诸如在寒冷的气候和深水环境中、具有独特应用地位的管道涂覆技术的革新带来了巨大的挑战和机遇.突出强调了几种独特的、先进的并已经过证实的管道涂覆技术,这些技术适用于陆地和海底管道的保护,包括高效复合涂层系统(HPCC)、高强度钢粉末涂层低温涂覆技术和Thermotite稳流保证技术.给出了一些案例和收集的技术数据.