Isolation of Photosystem II Reaction Center Complexes from Plants

18 Pags. The definitive version is available at: http://www.springerlink.com/content/1064-3745/Methods to isolate and purify 6- and 5-Chl D1/D2/Cyt b559 photosystem II (PSII) reaction center (RC) complexes from plants are presented, and the advantages and disadvantages of each procedure are discussed. One of the simpler 6-Chl procedures and a procedure for isolating 5-Chl complexes are described in detail. Furthermore, a rapid procedure that produces relatively large amounts of less pure 6-Chl material (i.e., more nonpigmented protein) is also described. Criteria to assess the purity of PSII RC preparations are presented, and problems associated with each of the isolation procedures are discussed.This work was supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Science, U.S. Department of Energy (MS) and by the MCYT of Spain (Grant BFU2005-04722-C02-01 and AGL2008-00377) to RP.Peer reviewe

We All Know How, Don’t We? On the Role of Scrum in IT-Offshoring

Part 2: Creating Value through Software DevelopmentInternational audienceOffshoring in the IT-industry involves dual interactions between a mother company and an external supplier, often viewed with an implicit perspective from the mother company. This article review general off shoring and IT offshoring literature, focusing on the proliferation of a globally available set of routines; Scrum and Agile. Two cases are studied; a small company and short process and a large mother company with a long process. The interactions of the set ups shows that global concepts like Scrum and Agile are far from a common platform. The “well known” concepts are locally shaped and the enterprises have mixed experiences

Experiments and Modeling of Electrochemical Impedance Spectroscopy on Pressurized SOFC

For this contribution a combined experimental and modeling approach was used. Impedance measurements were performed on a five-cell anode-supported SOFC short stack at pressures between 1 and 8 bar. Each cell has an active area of 84 cm². Impedance spectra were taken at OCV and increasing current densities up to 25 A. The multi-scale model used for the simulations is based on an in-house software [4] and is representing the system including the electrochemical reactions on the surface of the electrodes, gas transport within the porous electrodes and in the gas channels on cell level and the thermal coupling of five cells to include temperature-related effects on stack level. The model was validated with current/voltage characteristics and impedance measurements in a wide range of operating condition

Fuel Variation in a pressurized SOFC

The demand for electrical energy is growing continually. In order to meet this demand in future, power plants with high efficiency and low emissions are needed. For example a hybrid power plant consisting of an SOFC system combined with a gas turbine which offers electrical efficiencies of up to 60% at a wide range of applications from kW to MW. One major advantage of this combination is that it can be operated amongst others on natural gas from the existing grid. Efficiencies have been shown to be highest if the SOFC subsystem is pressurized. This and the requirements due to the interaction with the gas turbine lead to a need to exactly understand the behavior of SOFC at elevated pressures. The German Aerospace Center (DLR) is aiming to demonstrate stable operation of such a hybrid power plant and is currently examining the behavior, requirements and limits of the subsystems at elevated pressure. A test rig for the examination of pressurized SOFC exists at DLR to examine various planar stack designs at elevated pressure which has so far been used to asses the influence of pressure on performance with different fuels at different temperatures as well as operational limits at elevated pressures. Experimental results have been used for validation of a cell model which allows for a thorough interpretation of the experimental data. This contribution summarizes the advances made within the last years concerning the experimental examination and the complementary simulation of pressurized SOFC at DLR

Effect of pressure on internal reforming in SOFC

The increasing demand for electrical energy requires the development of power plants with high efficiencies and low emissions. Hybrid power plants consisting of an SOFC system coupled with a gas turbine promise to fulfil both requirements reaching electrical efficiencies above 60% [1]. They can also be used for a large range of applications from several 10 kW to multiple MW and can use natural gas from the existing grid. The German Aerospace Center (DLR) is aiming at the demonstration of the stable operation of a hybrid power plant in the 50 kW class in which the SOFC will be operated at elevated pressures. For the realisation of the power plant the effects of pressure on SOFC has to be understood, therefore the behaviour of SOFC at pressures ranging from 1 to 8 bar with varying fuel gas composition (H2/N2 mixture and reformate gases with different methane content) and different temperatures was examined experimentally in a specially designed setup [2]. Current-voltage characteristics and gas analysis at the anode were performed to examine the influence of pressure on OCV, power density at constant voltage and constant current as well as on gas composition at the cell for different fuels. Power density increases of up to 70% were found. Simulations were used to better understand the experimentally obtained results