A Linear Image Reconstruction Framework Based on Sobolev Type Inner Products

Exploration of information content of features that are present in images has led to the development of several reconstruction algorithms. These algorithms aim for a reconstruction from the features that is visually close to the image from which the features are extracted. Degrees of freedom that are not fixed by the constraints are disambiguated with the help of a so-called prior (i.e. a user defined model). We propose a linear reconstruction framework that generalizes a previously proposed scheme. The algorithm greatly reduces the complexity of the reconstruction process compared to non-linear methods. As an example we propose a specific prior and apply it to the reconstruction from singular points. The reconstruction is visually more attractive and has a smaller 핃₂-error than the reconstructions obtained by previously proposed linear methods. Bart Jansen, Frans Kanters and Remco Duits are joint main authors of this article.     

Solution‐Processed Organic Tandem Solar Cells

A solution‐processed polymer tandem cell fabricated by stacking two single cells in series is demonstrated. The two bulk‐heterojunction subcells have complementary absorption maxima at λ_max ～ 850 nm and λ_max ～ 550 nm, respectively. A composite middle electrode is applied that serves both as a charge‐recombination center and as a protecting layer for the first cell during spin‐coating of the second cell. The subcells are electronically coupled in series, which leads to a high open‐circuit voltage of 1.4 V, equal to the sum of each subcell. The layer thickness of the first (bottom) cell is tuned to maximize the optical absorption of the second (top) cell. The performance of the tandem cell is presently limited by the relatively low photocurrent generation in the small‐bandgap polymer of the top cell. The combination of our tandem architecture with more efficient small‐bandgap materials will enable the realization of highly efficient organic solar cells in the near future.     

27-GHz bandwidth high-speed monolithic integrated optoelectronicphotoreceiver consisting of a waveguide fed photodiode and anInAlAs/InGaAs-HFET traveling wave amplifier

A monolithic integrated photoreceiver for 1.55-μm wavelength has been designed for operation in a 20-Gb/s synchronous digital hierarchy system (SDH/SONET), based on a new integration concept. The optoelectronic integrated circuit (OEIC) receiver combines a waveguide-integrated PIN-photodiode and a traveling wave amplifier in coplanar waveguide layout with four InAlAs/InGaAs/InP-HFETs (0.7-μm gate length). The receiver demonstrates a bandwidth of 27 GHz with a low frequency transimpedance of 40 dBΩ. This is, to our knowledge, the highest bandwidth ever reported for a monolithic integrated photoreceiver on InP. Furthermore, a receiver sensitivity of -12 dBm in the fiber (20 Gb/s, BER=10^-9) and an overall optical input dynamic range of 27 dB is achieved. Optical time domain multiplex (TDM) system experiments of the receiver packaged in a module show an excellently shaped eye pattern for 20 Gb/s and an overall sensitivity of -30.5 dBm (BER=10^-9) [including erbium doped fiber amplifiers (EDFA)]     

Incorporating design rules into the LIGA technology applied to a fourier transformation spectrometer

For very complex systems made with the LIGA technology, manufacturing and subsequently yield problems may arise if the aspects of the manufacturing are not already considered in the design process. To enable the designers to make manufacturable designs collections of design rules as could be found in [1] are very useful. The rules can be utilized to make better, more production oriented designs, which will ease manufacturing and subsequently boost the yield. As an example the following paper presents a novel miniaturized Fourier Transformation Spectrometer which was designed following design recommendations that can be found in the literature. The applied rules are explained and the obtained results are discussed. We observed a very high yield in the pure LIGA process steps and an outstanding robustness of the integrated electromagnetic actuator.     

Using the biotic ligand model for predicting the acute sensitivity of cladoceran dominated communities to copper in natural surface waters

In this study, the acute copper sensitivity of field-collected cladoceran species was determined using their natural surface waters and a standard reconstituted test water as test medium. A total of 43 species were collected on two occasions from six different sites, representing different water types and chemistries in Europe. The collected species belonged to four different families (Daphniidae, Bosminidae, Macrothricidae, Chydoridae) and 11 different genera (Daphnia, Ctenodaphnia, Ceriodaphnia, Simocephalus, Scapholeberis, Alona, Acroperus, Chydorus, Eurycercus, Disparalona, Pleuroxus). In acute experiments with immobilization as end point, the 48-h median effective concentrations (48-h EC50) for the cladoceran species ranged from 5.30 to 70.6 microg of Cu L(-1) in standard test water and from 9.60 to 853 microg of Cu L(-1) in natural waters. The mean site sensitivity (the geometric mean of 48-h EC50 values of species within a community) ranged from 10.1 to 27.4 microg of Cu L(-1) in standard water and from 16.4 to 281 microg of Cu L(-1) in natural water. This indicates that bioavailability is more importantthan inter-community (species composition) differences in determining the variability of copper toxicity across different aquatic systems. For the four surface waters that had a pH within the range for which the acute Daphnia magna biotic ligand model (BLM) has previously been successfully validated, the BLM predicted 48-h EC50 values for 27 of the 28 tested cladoceran species within factor of 2 of the observed values. For the same sites, all community sensitivities were predicted within a factor of 2.3. The BLM was clearly over-protective for the two acidic surface waters tested. Hence, the BLM can be considered a valuable tool for estimating the potentially harmful effects of copperto natural cladoceran communities, but more research will be needed for acidic surface waters.     

Mass transfer at gas evolving electrodes

To elucidate the mechanism of the mass transfer at a gas evolving electrode, the thickness of the diffusion layer δ has been determined as a function of the volume rate of the gas evolution ν, for both hydrogen and oxygen evolving electrodes in alkaline solution. The effect of electrode material, alkaline concentrations, roughness, position and disk diameter of the electrode, gas pressure and of temperature upon the δ/gn relation is given. A low absolute value of the slope of the log δ/log ν, of about 0.3 is found experimentally when no coalescence of gas bubbles occurs and a high one, that is about 0.9 when coalescence occurs frequently. It has been concluded from the experimental results that the mass transfer can be explained on the basis of the hydrodynamic model when no coalescence of gas bubbles occurs and on that of the penetration model when coalescence occurs frequently.     

Growth and energy generation by Enterococcus faecium FAIR-E 198 during citrate metabolism

Citrate metabolism by Enterococcus faecium FAIR-E 198, isolated from Greek Feta cheese, was studied in various growth media containing citrate either in the presence of glucose, or as the sole carbon source, both under aerobic and anaerobic conditions. In de Man-Rogosa-Sharpe (MRS) broth with increasing citrate concentrations, cometabolism of citrate and glucose took place. Glucose was stoichiometrically converted into lactate, while citrate into acetate. Glucose consumption and biomass yield were enhanced with increasing initial citrate concentrations, even though maximum specific growth rate was not. When citrate was used as the sole carbon source in increasing initial concentrations, the main end product was acetate. Small amounts of lactate, formate, ethanol, and acetoin were also produced. In all cases, no significant differences were observed between aerobic and anaerobic conditions. However, when citrate was used as sole carbon source, formate production was favored in the absence of oxygen. The present work shows that E. faecium is able to utilize citrate in synthetic media, either in the presence of glucose or as the sole carbon source, resulting in energy production and the formation of aroma compounds.     

Direct observation of dipolar chains in iron ferrofluids by cryogenic electron microscopy

A key issue in research on ferrofluids (dispersions of magnetic colloids) is the effect of dipolar interactions on their structure and phase behaviour, which is not only important for practical applications but gives fundamental insight in dipolar fluids in general. In 1970, de Gennes and Pincus predicted a Van der Waals-like phase diagram and the presence of linear chains of particles in ferrofluids in zero magnetic field. Despite many experimental studies, no direct evidence of the existence of linear chains of dipoles has been reported in the absence of magnetic field, although simulations clearly show the presence of chain-like structures. Here, we show in situ linear dipolar structures in ferrofluids in zero field, visualized on the particle level by electron cryo-microscopy on thin, vitrified films of organic dispersions of monodisperse metallic iron particles. On systematically increasing the particle size, we find an abrupt transition from separate particles to randomly oriented linear aggregates and branched chains or networks. When vitrified in a permanent magnetic field, these chains align and form thick elongated structures, indicating lateral attraction between parallel dipole chains. These findings show that the experimental model used is well suited to study the structural properties of dipolar particle systems.