The Design and Performance of a Distributed Flow Water-Cooled Solar Collector

Design of a flat plate collector which reduces the temperature differential between the absorber plate and the fluid is described. The reduced temperature differences are shown to yield increase collector performance. Flow characteristics of the collector are examined. Collector thermal performance is illustrated for typical operating and environmental conditions. A cost analysis is presented to demonstrate that material and assembly costs are substantially lower than for any collector presently on the market

Effects of external nutrient sources and extreme weather events on the nutrient budget of a Southern European coastal lagoon

The seasonal and annual nitrogen (N), phosphorus (P), and carbon (C) budgets of the mesotidal Ria Formosa lagoon, southern Portugal, were estimated to reveal the main inputs and outputs, the seasonal patterns, and how they may influence the ecological functioning of the system. The effects of extreme weather events such as long-lasting strong winds causing upwelling and strong rainfall were assessed. External nutrient inputs were quantified; ocean exchange was assessed in 24-h sampling campaigns, and final calculations were made using a hydrodynamic model of the lagoon. Rain and stream inputs were the main freshwater sources to the lagoon. However, wastewater treatment plant and groundwater discharges dominated nutrient input, together accounting for 98, 96, and 88 % of total C, N, and P input, respectively. Organic matter and nutrients were continuously exported to the ocean. This pattern was reversed following extreme events, such as strong winds in early summer that caused upwelling and after a period of heavy rainfall in late autumn. A principal component analysis (PCA) revealed that ammonium and organic N and C exchange were positively associated with temperature as opposed to pH and nitrate. These variables reflected mostly the benthic lagoon metabolism, whereas particulate P exchange was correlated to Chl a, indicating that this was more related to phytoplankton dynamics. The increase of stochastic events, as expected in climate change scenarios, may have strong effects on the ecological functioning of coastal lagoons, altering the C and nutrient budgets.Portuguese Science and Technology Foundation (FCT) [POCI/MAR/58427/2004, PPCDT/MAR/58427/2004]; Portuguese Science and Technology Foundation (FCT

Bacterioplankton dynamics in the Mondego estuary (Portugal)

In this work, the density of bacterioplankton and environmental parameters were monitored over a 11 month period (July 1999-June 2000), and also during one tidal cycle (15 June 2000), at two sampling stations, in the estuary of River Mondego. These data were treated by multivariate analyses methods in order to identify the key factors that control the dynamics of the bacterioplankton in the estuary. Bacterial dynamics were dominated by temporal gradients (annual seasons and tide-related) and less by the spatial structure of the estuary. Three main metabolic groups of bacterioplankton--aerobic heterotrophic bacteria, sulphate-reducing bacteria (SRB) and nitrate-reducing bacteria (NRB)--involved in the cycling of organic matter, were present in the water column of the estuary. Their relative abundance depended on the particular physical, chemical and biological environment. The abundance of aerobic heterotrophic bacteria, during the 11 month study, was modelled as a function of nitrate (the most important variable, with a negative effect), temperature, salinity and pH (with positive effects). SRB appeared to be limited to the water-sediment interface, where concentrations of sulphate and POM were greater. A competition between SRB and NRB for carbon has also been suggested.http://www.sciencedirect.com/science/article/B6VR3-4B6JTC7-8/1/1f5b2e8bcb56fdceb5fffe6f34b30e3

All-Electric Quantum Point Contact Spin Valve

This paper has been withdrawn by the author because in the main text some discussion parts were inadvertently added by mistake.Comment: This paper has been withdraw