Direct detection of the asteroidal YORP effect

The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect is believed to alter the spin states of small bodies in the solar system. However, evidence for the effect has so far been indirect. We report precise optical photometric observations of a small near-Earth asteroid, (54509) 2000 PH5, acquired over 4 years. We found that the asteroid has been continuously increasing its rotation rate omega over this period by domega/dt = 2.0 (+/-0.2) x 10(-4) degrees per day squared. We simulated the asteroid's close Earth approaches from 2001 to 2005, showing that gravitational torques cannot explain the observed spin rate increase. Dynamical simulations suggest that 2000 PH5 may reach a rotation period of approximately 20 seconds toward the end of its expected lifetime.     

Structural insights into the assembly of the type III secretion needle complex

Type III secretion systems (TTSSs) mediate translocation of virulence factors into host cells. We report the 17-angstrom resolution structures of a central component of Salmonella typhimurium TTSS, the needle complex, and its assembly precursor, the bacterial envelope-anchored base. Both the base and the fully assembled needle complex adopted multiple oligomeric states in vivo, and needle assembly was accompanied by recruitment of the protein PrgJ as a structural component of the base. Moreover, conformational changes during needle assembly created scaffolds for anchoring both PrgJ and the needle substructure and may provide the basis for substrate-specificity switching during type III secretion.     

夏大豆群体结构对不同类型品种产量及农艺性状的影响

在南方地区选择不同类型的代表品种，研究不同密度及同密度下不同株行距配置对大豆产量的影响，结果显示：密度与株行距配置显著地影响产量，品种类型不同，其对密度要求不同，主茎结荚型品种密度以３．０万株／亩为宜，而分枝型品种以１．０－１．５万株／亩为宜，相同密度下株行距愈接近，则产量愈高，因而建议均匀种植。文中分析讨论了密度对产量影响的原因，并对结论的应用作了讨论。     

Biological activity of natural phytoecdysteroids from Ajuga iva against the sweetpotato whitefly Bemisia tabaci and the persea mite Oligonychus perseae

BACKGROUND: Ecdysteroids are steroid hormones that control moulting and govern several changes during metamorphoses in arthropods. The discovery of the same molecules (phytoecdysteroids) in several plant species displayed a wide array of rather beneficial agricultural impact. Many representatives of the genus Ajuga plants contain phytoecdysteroids with a 5β‐7‐ene‐6‐one system exhibiting physiological activities in insects. RESULTS: By means of chromatographic (silica gel column, TLC) and LC‐MS, two major ecdysteroids (20‐hydroxyecdysone and cyasterone) have been isolated and identified from Israeli carpet bugle Ajuga iva (L.) Schreber (Lamiales: Lamiaceae) plants. Ajuga iva extract fractionated on the silica gel column yielded two fractions that showed high activity against the sweetpotato whitefly Bemisis tabaci and the persea mite Oligonychus perseae. A dose of 5 mg AI L^?1 of the purely identified A. iva ecdysterone significantly reduced fecundity, fertility and survival of these pests, while commercial 20‐hydroxyecdysone at the same dose had lesser effects. CONCLUSION: The results demonstrate considerable efficacy of natural phytoecdysteroids against major agricultural pests, and suggests that these materials should be considered for potential development of friendly control agents. Copyright © 2011 Society of Chemical Industry     

Soil Contamination in Dumps on the Karstic Areas from the Plateaus (Southeast of Madrid, Spain)

After over 10 years of accumulation of residues in the studied dumps near Madrid, it has been registered low or moderate heavy metals concentrations on the surrounding area. Only occasionally, some rubbish dumps contain significant quantities of Cu, Ni, Zn and Pb. The concentration levels of Pb, Ni, Zn and Cu are safe when they are compared with the surrounding areas levels of heavy metals. The aim of this paper is the analysis of pollutants existing around in the dumps located at the sides of the plateaus of the central valley of the Tajo River (provinces of Madrid and Toledo, Spain). The high karstification rate of the upper layer of these tablelands and the existence of numerous dumps on them (even on their slopes) make these areas vulnerable to heavy metal pollution. However, after several years of use, the concentration of pollutants only reaches moderate values in the studied areas. Dumping materials were collected at four rubbish dumps. The mineralogical composition of the materials were analysed by XRD. Sequential extraction procedure was applied for speciation of the metal forms in the collected samples. Concentrations of Zn, Pb, Ni, Cu, Cr and Cd in extracts were determined by AAS. The studied samples showed high carbonate concentration. Contamination processes are combined there with weathering processes. Heavy metals concentration in control samples (gypsum, limestones, red soils and colluviums) were compared with samples of the studied dump in order to evaluate the pollution level. Concentrations of Zn, Pb, Ni and Cu were variable. The contamination was elevated for samples in depth in relation with weathering process of heavy metals.     

Heavy Metal Pollution in Soils Around the Abandoned Mine Sites of the Iberian Pyrite Belt (Southwest Spain)

This paper investigates the pollution load of selected trace elements in 32 soil samples collected around 21 different mining areas of the Iberian Pyrite Belt (Southwest Spain), integrating chemical data with soil parameters to help understand the partitioning and mobility of pollutants. The minesoils are depleted in acid neutralising minerals and show limiting physicochemical properties, including low pH values and very high anomalies of potentially hazardous metals. The total concentrations of As (up to 1,560 mg kg^?1) and certain heavy metals (up to 2,874 mg kg^?1 Cu, 6,500 mg kg^?1 Pb, 6,890 mg kg^?1 Zn, 62 mg kg^?1 Hg and 22 mg kg^?1 Cd) are two orders of magnitude above the soil background values. The close association of Cd and Zn with the carbonate content in lime-amended minesoils suggests metal immobilisation through adsorption and/or co-precipitation mechanisms, after acid neutralisation, whereas As and Pb are similarly partitioned into the soil and mostly associated with iron oxy-hydroxides.     

A decision support approach for cane supply management within a sugar mill area

Increased competition between agri-food supply chains has strained relationships between farmers and processing factories while reducing individual profit margins. Decisions at different levels of the supply chain can no longer be considered independently, since they may influence profitability throughout the supply chain. This paper presents a decision support approach based on the MAGI^® simulation tool, which aims to facilitate discussion and negotiation between stakeholders while collectively exploring satisfactory solutions.The simulation tool helps sugarcane growers and millers in designing and assessing new ways of organizing cane supply management within a mill area. It addresses key issues such as restructuring mill areas or changing cane delivery allocation rules in order to increase total sugar production and total net revenue at the mill area level. This approach has been implemented for two mills in Réunion and one mill in South Africa. Simulations showed that sugar gains may be obtained by rearranging supply scheduling according to quality-based zoning within a mill area. Discussions led to further studies regarding the practicality of the best scenarios. MAGI^® is now available as freeware for testing in different settings.     

Soil pollution by mining activities in Andalusia (South Spain)—the role of Mineralogy and Geochemistry in three case studies

Purpose

Geochemical and mineralogical studies of soils potentially polluted by trace elements are basic to find the source of pollution, to understand the behavior of the contaminants in the environment, and to propose remediation and reclamation actions. This work reviews the role of the Mineralogy and Geochemistry to assess the hazard of soil contamination by trace elements in mining areas, focusing on three different case studies carried out in the Andalusian community (South Spain), with a Mediterranean temperate climate.

Materials and methods

Two significant mining districts were selected for this work: the Linares-La Carolina (Pb-Zn ores) and the Riotinto (Iberian Pyrite Belt, IPB) mining areas. Another case study was the Guadiamar basin, which soil was polluted by the spill produced in 1998 by the breakage of a mine tailing impoundment in Aznalcóllar mines (IPB). Soils, mine waste, and secondary precipitates were studied to approach the source of the pollution and the fate of the contaminants. Chemical composition (major and trace elements), soil parameters, and mineralogy of all materials selected were studied. In addition, the bioavailability of trace elements was determined by different methods.

Results and discussion

Pyrite and secondary phases are the main sources of pollution in the Riotinto area. Their stability is a key factor in the release of trace elements. The availability of trace elements in soils was lower in unpolluted leptosols than in contaminated orchards. In Linares-La Carolina, a severe pollution by Pb and a high availability (10–70% extracted with EDTA) were found. In Guadiamar basin, the residual pyrite sludge continues releasing trace elements to soil. Cd and Zn were mobile at pH <?6 and As at pH >?8, and Pb was quite immobile. Cd, Zn, and Pb can be coprecipitated by carbonates while As is mainly adsorbed by clays and iron oxyhydroxides.

Conclusions

The geochemical studies of soils polluted by mining activities allow to evaluate the availability of trace elements and their retention in soils. Therefore, geochemical and mineralogical studies are necessary for the assessment of soil pollution and remediation actions.