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A novel free-standing and flexible counter electrode for dye solar cells has been developed by conveniently transferring a vertically aligned carbon nanotube forest onto an oxygen-plasma-treated flexible, free-standing and conductive nanocomposite foil. Vertically aligned carbon nanotubes were first grown onto an aluminium foil by chemical vapour deposition and then transferred to the nanocomposite surface by hot pressing. The most meaningful electrochemical parameters have been quantitatively analyzed by means of electrochemical impedance spectroscopy and cyclic voltammetry in order to elucidate how the implementation of the anisotropic carbon nanotube top layer impacts the ultimate catalytic performances of the plate. Such an engineered counter electrode is able to guarantee a fast and effective reduction of the iodide-based electrolyte as well as to provide a solar conversion efficiency that is comparable with a typical Pt/TCO-coated rigid counter electrode. A photocurrent density higher than 13.36 mA cm−2 along with a solar conversion efficiency of 7.26% have been reported for the dye solar cell mounting a counter-electrode based on vertically aligned carbon nanotubes implanted onto a conductive nanocomposite plate.

Geostatistical techniques were applied and a series of spatial indicators were calculated (occupation, aggregation, location, dispersion, spatial autocorrelation and overlap) to characterize the spatial distributions of European anchovy and sardine during summer. Two ecosystems were compared for this purpose, both located in the Mediterranean Sea: the Strait of Sicily (upwelling area) and the North Aegean Sea (continental shelf area, influenced by freshwater). Although the biomass of anchovy and sardine presented high interannual variability in both areas, the location of the centres of gravity and the main spatial patches of their populations were very similar between years. The size of the patches representing the dominant part of the abundance (80%) was mostly ecosystem- and species-specific. Occupation (area of presence) appears to be shaped by the extent of suitable habitats in each ecosystem whereas aggregation patterns (how the populations are distributed within the area of presence) were species-specific and related to levels of population biomass. In the upwelling area, both species showed consistently higher occupation values compared to the continental shelf area. Certain characteristics of the spatial distribution of sardine (e.g. spreading area, overlapping with anchovy) differed substantially between the two ecosystems. Principal component analysis of geostatistical and spatial indicators revealed that biomass was significantly related to a suite of, rather than single, spatial indicators. At the spatial scale of our study, strong correlations emerged between biomass and the first principal component axis with highly positive loadings for occupation, aggregation and patchiness, independently of species and ecosystem. Overlapping between anchovy and sardine increased with the increase of sardine biomass but decreased with the increase of anchovy. This contrasting pattern was attributed to the location of the respective major patches combined with the specific occupation patterns of the two species. The potential use of spatial indices as auxiliary stock monitoring indicators is discussed.

The combination of photonics and silicon technology is a great challenge because of the potentiality of coupling electronics and optical functions on a single chip. Silicon nanocrystals are promising in various areas of photonics especially for light-emitting functionality and for photovoltaic cells. This review describes the recent achievements and remaining challenges of Si photonics with emphasis on the perspectives of Si nanoscale materials. Many of the results and properties can be simulated and understood based on theoretical studies. However, some of the key questions like the light-emitting mechanism are subjects of intense debates despite a remarkable progress in the recent years. Even more complex and important is to move the known experimental observations towards practical applications. The demonstrated devices and approaches are often too complex and/or have too low efficiency. However, the challenge to combine optical and electrical functions on a chip is very strong, and we expect more research activity in the field of Si nanophotonics in the future.

Rapid population growth invokes the need for a vast amount of water conservation. Many centralized water treatment systems will reach their limits and face difficulties to provide clean industrial water to rural areas. The infrastructure for water distribution is dilapidated in many regions and only little of the wastewater is currently being recycled. One solution could be the expansion of decentralized membrane bioreactor (MBR) systems in peri-urban areas. MBR achieves excellent water qualities, whereas the comparatively high energy consumption is the main drawback. Therefore, MBR plants need to be optimized in their specific energy consumption to obtain a high degree of self-sufficiency for decentralized locations. There is a dire need for innovative controlling strategies and efficient coupling with energy supply systems through novel applications. This chapter will highlight the basic approaches to reduce the MBR's overall energy consumption and ways to establish sustainable, autonomous operations without sacrificing the process quality.

AbstractThe Law of the Sea and regional and national laws and agreements require exploited populations or stocks to be managed so that they can produce maximum sustainable yields. However, exploitation level and stock status are unknown for most stocks because the data required for full stock assessments are missing. This study presents a new method [abundance maximum sustainable yields (AMSY)] that estimates relative population size when no catch data are available using time series of catch-per-unit-effort or other relative abundance indices as the main input. AMSY predictions for relative stock size were not significantly different from the “true” values when compared with simulated data. Also, they were not significantly different from relative stock size estimated by data-rich models in 88% of the comparisons within 140 real stocks. Application of AMSY to 38 data-poor stocks showed the suitability of the method and led to the first assessments for 23 species. Given the lack of catch data as input, AMSY estimates of exploitation come with wide margins of uncertainty, which may not be suitable for management. However, AMSY seems to be well suited for estimating productivity as well as relative stock size and may, therefore, aid in the management of data-poor stocks.

In the anodisation of Nb in acidic fluoride solutions or warm aqueous alkali, and in that of Mo in concentrated phosphoric acid, impedance spectroscopy provides evidence that 3D film growth proceeds already during the active–passive transition. Indeed, linear potential dependences of both the inverse of the high-frequency capacitance and of the product of the high-frequency resistance times the steady-state current are observed already below the peak potential. Simultaneously, a pseudo-inductive loop at intermediate frequencies is detected in the impedance spectra. In the present paper, we propose a kinetic model for the interpretation of these data. The model assumes that the metal is covered with a non-stoichiometric oxide containing at least two oxidation states of the cation. The processes of oxidative dissolution of the lower valence cations and their transformation to cations of higher valence, leading to passivation, explain the shape of the I–E curve. These processes are limited by both charge transfer at the film–solution (F/S) interface and transport of cation vacancies through the film. Thickening of the oxide film is assumed to proceed simultaneously, and is limited by transport of oxygen vacancies accelerated by an interfacial charge of cation vacancies.

Concentrating Solar Power (CSP) is considered to be one of the most promising and sustainable technologies for electricity production in the future, and as efficiency of solar thermal systems rapidly increases with increasing working temperature, the big challenge for future is to develop novel solutions for solar receivers. In this framework, Ultra-High Temperature Ceramics (UHTCs) are mainly studied as thermal protection materials for aerospace and military applications, but their peculiar properties (very high melting points and good thermo-mechanical properties at high temperatures) can be advantageously exploited to increase the operating temperature of thermodynamic solar plants in concentrating solar power systems. This work is devoted to the study and characterization of the spectral reflectance of hafnium and zirconium diborides containing MoSi2 as secondary phase in order to evaluate their potential as novel solar absorbers. To assess the spectral selectivity properties, room-temperature hemispherical reflectance spectra were measured from the UV wavelength region to the mid-infrared, considering different levels of porosity for each system, in order to understand how porosity affect spectral reflectance. Moreover, for zirconium diboride and hafnium diboride composites containing 10vol% of MoSi2 sintering aid, the thermal emittance was measured in the 1100-1400K temperature range in PROMES-CNRS solar furnace. Data obtained were compared with spectral characteristics and high temperature emittance of a monolithic silicon carbide. (C) 2013 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license