Dissolved organic nutrient uptake by riverine phytoplankton varies along a gradient of nutrient enrichment

The concentration of dissolved organic matter (DOM) in freshwaters is increasing in large areas of the world. In addition to carbon, DOM contains nitrogen and phosphorus and there is growing concern that these organic nutrients may be bioavailable and contribute to eutrophication. However, relatively few studies have assessed the potential for dissolved organic nitrogen (DON) or dissolved organic phosphorus (DOP) compounds to be bioavailable to natural river phytoplankton communities at different locations or times. Temporal and spatial variations in uptake, relative to environmental characteristics were examined at six riverine sites in two contrasting catchments in the UK. This study also examined how the uptake by riverine phytoplankton of four DON and four DOP compounds commonly found in rivers, varied with concentration. Total nitrogen (TN) and phosphorus (TP) concentrations, the proportion of inorganic nutrient species, and nutrient limitation varied temporally and spatially, as did the potential for DON and DOP uptake. All eight of the DOM compounds tested were bioavailable, but to different extents. Organic nutrient use depended on the concentration of the organic compound supplied, with simple compounds (urea and glucose-6-phosphate) supporting algal growth even at very low concentrations. DON use was negatively correlated with the TN and ammonia concentration and DOP use was negatively correlated with soluble reactive phosphorus (SRP) and dissolved organic carbon (DOC) concentration. The evidence indicates that DOM in rivers has been overlooked as a potential source of nutrients to phytoplankton and therefore as an agent of eutrophication

Synthesis, structure and magnetic properties ofβ-MnO2nanorods

We present synthesis, structure and magnetic properties of structurally well-ordered single-crystalline β-MnO2nanorods of 50–100 nm diameter and several µm length. Thorough structural characterization shows that the basic β-MnO2material is covered by a thin surface layer (∼2.5 nm) of α-Mn2O3phase with a reduced Mn valence that adds its own magnetic signal to the total magnetization of the β-MnO2nanorods. The relatively complicated temperature-dependent magnetism of the nanorods can be explained in terms of a superposition of bulk magnetic properties of spatially segregated β-MnO2and α-Mn2O3constituent phases and the soft ferromagnetism of the thin interface layer between these two phases

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics

The state of Esthwaite Water in 2010

1. Esthwaite Water is one of the most nutrient-enriched lakes in the English Lake District, but the enrichment has mainly occurred in the last 50 years and in particular since the establishment of the wastewater treatment works (WwTW) at Hawkshead in 1973 and a fish farm on the lake in 1981. The fish cages were removed from the lake in November 2009 and recent upgrades have been made to the WwTW. This report describes the conditions and water quality at Esthwaite Water in 2010, places them into the context of recent conditions and assesses evidence for any change. 2. The seasonal temperature and stratification cycle was typical with surface water reaching nearly 20 °C and the bottom temperature only 10 °C. Stratification lasted for about 180 days from the beginning of April to mid-October. 3. The average alkalinity was 0.43 equiv m-3 placing Esthwaite Water in the medium alkalinity category of the Water Framework Directive. 4. Nutrients showed typical seasonal patterns. Total phosphorus was relatively conservative with peaks during time of high phytoplankton biomass and an average concentration of 21.4 mg m-3. Soluble reactive phosphorus had peak concentrations of about 12 mg m-3 at the start of the year but fell rapidly in March to the limit of detection, 0.6 mg m-3, and the concentration remained low for most of the summer and only increased on the breakdown of stratification in autumn. Silica concentrations also fell rapidly in spring as is was removed by the growing spring diatoms. Nitrate was the dominant form of nitrogen and fell more slowly than phosphorus and silica and reached minima of 30 mg m-3 that could indicate a short-period of nitrogen limitation in an otherwise phosphorus-limited lake. 5. The phytoplankton produced a spring bloom of about 16 mg m-3 comprising mainly diatom and an extensive summer bloom of cyanobacteria that reached 35 mg m-3 that did not decline until the beginning of November. The annual average concentration was 15.6 mg m-3. 6. The phytoplankton had a major effect on the light climate with Secchi depth minim of 1.5 m in August. The annual average light attenuation coefficient of about 0.87 m-1 would allow macrophyte colonisation down to between 2 and 4.3 m depending on species. 7. Nine species of crustacean zooplankton were recorded with an early summer peak population in May dominated by Daphnia hyalina/galeata. Later in the year, smaller bodied Bosmina longirostris and Ceriodaphnia quadrangula produced a population peak in mid September. 8. Statistical comparisons of the monthly-average and annual-average values of various water quality parameters in 2010 and the previous ten years showed encouraging changes. Statistically significant reduction in concentration in 2010 compared to the previous ten years were found for: (i) total phosphorus in ten months and as an annual average; (ii) soluble reactive phosphorus in 4 months and as an annual average; (iii) nitrate in eight months and as an annual average. This led to statistically significant reductions in the concentration of chlorophyll a in eight months and as annnual average and increases in Secchi depth in five months and as an annual average. The minimum concentrations of oxygen at depth were essentially unchanged and the density of zooplankton was lower in some months. 9. The current ecological status of Esthwaite Water under the Water Framework Directive is ‘Moderate’ for both total phosphorus and chlorophyll a. In previous years, the ecological status was close to the Moderate: Poor boundary for both measures. This underlines the necessity of the programme of measures that are currently underway on the lake. 10. While these results are extremely encouraging, weather patterns can lead to periods of improvement and worsening in water quality so continued monitoring is essential. Furthermore, some of these improvements started to be evident in 2009 (concentrations of total phosphorus, soluble reactive phosphorus and nitrate) and so in order to be able, confidently, to link these to management changes, it is very to obtain more information on waste-water handling at the Hawkshead WwTW and the stocking densities and feeding regime of the fish farm on the lake

Battery research at Argonne National Laboratory

Argonne National Laboratory (ANL) has, for many years, been engaged in battery-related R and D programs for DOE and the transportation industry. In particular, from 1973 to 1995, ANL played a pioneering role in the technological development of the high-temperature (400 C) lithium-iron disulfide battery. With the emphasis of battery research moving away from high temperature systems toward ambient temperature lithium-based systems for the longer term, ANL has redirected its efforts toward the development of a lithium-polymer battery (60--80 C operation) and room temperature systems based on lithium-ion technologies. ANL`s lithium-polymer battery program is supported by the US Advanced Battery Consortium (USABC), 3M and Hydro-Quebec, and the lithium-ion battery R and D efforts by US industry and by DOE

An investigation of spinel-related and orthorhombic LiMn0₂ cathodes for rechargeable lithium batteries

Cathode materials that have been synthesized by reduction of lithium-manganese-oxide and manganese-oxide precursors with hydrogen at 300 to 350°C and with carbon at 600°C have been evaluated in rechargeable lithium cells. The cathodes which initially have a composition close to LiMnO₂ contain structures related to the lithiated-spinel phase Li₂[Mn₂]0₄ and/or orthorhombic LiMnO₂. The orthorhombic LiMnO₂ component transforms gradually to a spinel structure on cycling. These cathodes are significantly more tolerant to repeated lithium insertion and extraction, when cycled over both the 4 and 3 V regions, than a standard Liₓ[Mn₂]0₄ spinel electrode (0 < x < 2)

Structural stability of LiMn{sub 2}O{sub 4} electrodes for lithium batteries

the structural stability of LiMn{sub 2}O{sub 4}, which is of interest as an insertion electrode for rechargeable lithium batteries, is discussed with respect to processing techniques, composition, the Li- Mn-O phase diagram, and electrochemical behavior. Particular attention is paid to processing conditions that result in the formation of lithium-magnesium-oxide spinel products in which Mn{sup 2+} ions partially occupy the tetrahedral sites of the spinel structure. The electrochemical behavior of electron beam and rf magnetron sputtered thin film electrodes suggests the existence of partially inverse Li{sub 1-x}Mn{sub 2} O{sub 4} spinel structures during an initial charge to 5.3 volts