Far-infrared photo-conductivity of electrons in an array of nano-structured antidots

We present far-infrared (FIR) photo-conductivity measurements for a two-dimensional electron gas in an array of nano-structured antidots. We detect, resistively and spectrally resolved, both the magnetoplasmon and the edge-magnetoplasmon modes. Temperature-dependent measurements demonstrates that both modes contribute to the photo resistance by heating the electron gas via resonant absorption of the FIR radiation. Influences of spin effect and phonon bands on the collective excitations in the antidot lattice are observed.Comment: 5 pages, 3 figure

Geographic genetic structure of Iberian columbines (gen. Aquilegia)

Southern European columbines (genus Aquilegia)are involved in active processes of diversification, and the Iberian Peninsula offers a privileged observatory to witness the process. Studies on Iberian columbines have provided significant advances on species diversification,but we still lack a complete perspective of the genetic diversification in the Iberian scenario. This work explores how genetic diversity of the genus Aquilegia is geographically structured across the Iberian Peninsula. We used Bayesian clustering methods, principal coordinates analyses, and NJ phenograms to assess the genetic relationships among 285 individuals from 62 locations and detect the main lineages. Genetic diversity of Iberian columbines consists of five geographically structured lineages, corresponding to different Iberian taxa. Differentiation among lineages shows particularly complex admixture patterns at Northeast and highly homogeneous toward Northwest and Southeast. This geographic genetic structure suggests the existence of incomplete lineage sorting and interspecific hybridization as could be expected in recent processes of diversification under the influence of quaternary postglacial migrations. This scenario is consistent with what is proposed by the most recent studies on European and Iberian columbines, which point to geographic isolation and divergent selection by habitat specialization as the main diversification drivers of the Iberian Aquilegia complex

Microbial diversity in waters, sediments and microbial mats evaluated using fatty acid-based methods

The review summarises recent advances towards a greater comprehensive assessment of microbial diversity in aquatic environments using the fatty acid methyl esters and phospholipid fatty acids approaches. These methods are commonly used in microbial ecology because they do not require the culturing of micro-organisms, are quantitative and reproducible and provide valuable information regarding the structure of entire microbial communities. Because some fatty acids are associated with taxonomic and functional groups of micro-organisms, they allow particular groups of micro-organisms to be distinguished. The integration of fatty acid-based methods with stable isotopes, RNA and DNA analyses enhances our knowledge of the role of micro-organisms in global nutrient cycles, functional activity and phylogenetic lineages within microbial communities. Additionally, the analysis of fatty acid profiles enables the shifts in the microbial diversity in pristine and contaminated environments to be monitored. The main objective of this review is to present the use of lipid-based approaches for the characterisation of microbial communities in water columns, sediments and biomats

Guided optical modes in randomly textured ZnO thin films imaged by near-field scanning optical microscopy

We report on near-field optical imaging of light transmission through textured zinc oxide (ZnO) thin films grown on glass substrates. Such ZnO layers are commonly used as a transparent conducting oxide for the front contacts in thin-film solar cells. To increase the quantum efficiency of such solar cells, the ZnO surface is randomly textured, resulting in a higher light scattering and promoting light trapping. Here, we study these phenomena microscopically by imaging the local optical mode profiles in such thin films. Our results give clear evidence for the interconversion of propagating and guided evanescent modes. Such information, which cannot be extracted from more conventional far-field optical studies, may prove helpful in further optimizing the efficiencies of thin-film optoelectronic devices

Observations of a mass occurrene of Macoma balthica larvae in midsummer

In 1995 the seasonal development of concentrations of both phytoplankton and larvae of the bivalve Macoma balthica was studied in the coastal zone behind the back-barrier island of Spiekeroog (German Wadden Sea). In July=August larvaereached maximum concentrations of about 1000 to 4200 ind.

FP7-CHEETAH Project Knowledge Exchange Portal: an Advanced Tool to Efficiently Bring Information to the European Photovoltaic RTD Community

FP7-CHEETAH is a combined collaborative project (CP) and coordination and support action (CSA) funded under the European Commission’s 7th Framework program and coordinated by ECN, NL with the aims to solve specific R&D issues and to overcome fragmentation of European PV R&D by intensifying the collaboration between R&D providers and industry to accelerate the industrialization of innovations. The project is also tightly linked to the EERA-PV Joint Program. The CHEETAH Knowledge Exchange Area Portal (KEAP), in parallel to the project web site and other dissemination activities (newsletter, communication, etc), constitutes the pillar of the project to distribute information in a uniform and simple way. It is based on several very efficient ICT procedures by operating from the collection to management of information by dynamic data base matrix: any uploaded information is linked to all others. All interested browsers/readers can have efficient access to any stored data thanks to the utilization of a search engine/query keywords and user friendly graphic interfaces. Based on the implementation of SOPHi@webinar platform, the portal also offers its own e-learning platform. CHEETAH KEAP represents for its peculiarities a major breakthrough in the field with highly innovative contents and a substantial improvement in comparison with the state of the art of knowledge exchange on PV RTD

The impact of intermediate reflectors on light absorption in tandem solar cells with randomly textured surfaces

The impact of dielectric intermediate reflectors on the light absorption in the top cell of an a-Si:H/mu c-Si:H tandem solar cell comprising randomly textured surfaces was investigated by rigorous diffraction theory. Despite the strong light scattering, we found Fabry-Perot oscillations for the absorption with a decreasing modulation for an increasing thickness of the intermediate layer, a larger oscillation period when compared to thin films and a homogenization of the absorption profile. Optimized intermediate reflectors generate an absorption enhancement in the a-Si:H film, which varies between a factor of 2 and more than 3 for wavelengths of strong and weak absorption, respectively