Ring-type plasmon resonance in metallic nanoshells

A simple, approximate theoretical model of surface plasmon resonance in two-dimensional metal nanoshells is developed. The model is based on the concept of short-range surface plasmons propagating around closed circular metal nanotubes. In this model, the plasmon resonance in a metal nanotube is treated as a propagating, self-interfering plasmonic wave, in a ring-type resonance, at plasmonic wavelengths matching an integer fraction of the nanotube's effective circumference. The model is validated by detailed computer simulations based on the finite-difference time-domain method and is shown to be in full agreement with the widely used plasmon hybridization model, which is based on the quasi-static approximation.     

Small animal PET image super-resolution using Tikhonov and modified total variation regularisation

Positron emission tomography (PET) is an imaging procedure used mainly in the diagnosis and treatment of diseases. PET is also used in the preclinical research studies of small animals. However, researchers may have difficulty interpreting the particularly low-resolution images obtained via this procedure. This paper presents a new method of increasing the resolution of PET images through the use of super-resolution techniques. Aside from being resistant to the noise and other degradations that plague PET images, our proposed algorithm is also capable of preserving important structures (e.g. lesions). To this end, the proposed objective function includes a term based on the modified total variation model which allows the user to preserve texture and to deal with noise without incurring the artefacts that typically arise when the total variation norm is used. The present study shows the effectiveness of the method in recovering structures and details and indicates that, in most cases, it outperforms other state-of-the-art methods.     

Microstructure and mechanical properties of Mg-5Li-1Al sheets prepared by accumulative roll bonding

Ultrafine-grain and high-strength Mg-5Li-1Al sheets were prepared by accumulative roll bonding (ARB) process. Evolution of microstructure and mechanical properties of ARB-processed Mg-5Li-1Al sheets was investigated.Results show that, during ARB process, the evolution of deformation mechanism of t Mg-5Li-1Al alloy is as follows: twinning deformation, shear deformation, forming macro shear zone, and finally dynamic recrystallization (DRX). The grain refining mechanism changes from twin DRX to rotation DRX. With the increase in ARB cycles, strength of the Mg-5Li-1Al sheets is enhanced, whilst elongation varies slightly. With the increase in rolling cycles, anisotropy of mechanical properties decreases. It is conclusive that strain hardening and grain refinement dominate the strengthening mechanism of Mg-5Li-1Al alloy.     

Optimal attacks on qubit-based Quantum Key Recycling

Quantum Key Recycling (QKR) is a quantum cryptographic primitive that allows one to reuse keys in an unconditionally secure way. By removing the need to repeatedly generate new keys, it improves communication efficiency. ?kori? and de Vries recently proposed a QKR scheme based on 8-state encoding (four bases). It does not require quantum computers for encryption/decryption but only single-qubit operations. We provide a missing ingredient in the security analysis of this scheme in the case of noisy channels: accurate upper bounds on the required amount of privacy amplification. We determine optimal attacks against the message and against the key, for 8-state encoding as well as 4-state and 6-state conjugate coding. We provide results in terms of min-entropy loss as well as accessible (Shannon) information. We show that the Shannon entropy analysis for 8-state encoding reduces to the analysis of quantum key distribution, whereas 4-state and 6-state suffer from additional leaks that make them less effective. From the optimal attacks we compute the required amount of privacy amplification and hence the achievable communication rate (useful information per qubit) of qubit-based QKR. Overall, 8-state encoding yields the highest communication rates.     

A correlation model to compute the incidence angle modifier and to estimate its effect on collectible solar radiation

Radiation transmittance and absorptance of materials vary according to the angle of incidence of the incoming solar radiation. Therefore, the efficiency of most solar converters (thermal or photovoltaic) at a given radiation amount is a function of the sun's position through the angle of incidence. This problem is accounted for by the Incidence Angle Modifier, which is considered in this paper. An analytic expression for the incidence angle modifier, based on meteorological data or on geographic and geometric parameters, has been developed; this expression includes the effect of beam and diffuse radiation as well as the global influence. A comparison between measured data and computed from our model has given a very good correlation, the results being within a ±3% of difference for horizontal and tilted planes, and within ±17% for vertical surfaces, on average. The method also computes the collectible solar energy within a 5% error for thresholds up to 300 W m⁻². The method has been validated for more than 30 locations of south and west Europe.     

Towards the integration of dark- and photo-fermentative waste treatment. 2. Optimization of starch-dependent fermentative hydrogen production

Eight natural microbial consortia collected from different sites were tested for dark, hydrogen production during starch degradation. The most active consortium was from silo pit liquid under mesophilic (37 °C) conditions. The fermentation medium for this consortium was optimized (Fe, NH₄⁺, phosphates, peptone, and starch content) for both dark fermentation and for subsequent purple photosynthetic bacterial H₂ photoproduction [Laurinavichene TV, Tekucheva DN, Laurinavichius KS, Ghirardi ML, Seibert M, Tsygankov AA. Towards the integration of dark and photo fermentative waste treatment. 1. Hydrogen photoproduction by purple bacterium Rhodobacter capsulatus using potential products of starch fermentation. Int J Hydrogen Energy 2008;33(23):7020–26], in the presence of the spent dark, fermentation effluent. The addition of Zn (10 mg L⁻¹), as a methanogenesis inhibitor that does not inhibit purple bacteria at this concentration, also did not inhibit dark, fermentative H₂ production. The influence of various fermentation end products at different concentrations (up to 30 g L⁻¹) on dark, H₂ production was also examined. Added lactate stimulated, but added isobutyrate and butanol strongly inhibited gas production. Under optimal conditions the fermentation of starch (30 g L⁻¹) resulted in 5.7 L H₂ L⁻¹ of culture (1.6 mol H₂ per mole of hexose) with the co-production mainly of butyrate and acetate.     

Morphological and adhesive properties of polypyrrole films synthesized by sonoelectrochemical technique

This paper presents electrochemical synthesis of polypyrrole films under high frequency sonication. The films are characterized in terms of adhesion and surface morphology. Comparison to classical electrosynthesized polypyrrole films is made. In particular, the use of high frequency sonication (500 kHz) during electrodeposition of polypyrrole on Si was reported for the first time. Chronocoulometry was used for polymer films electrosynthesis on Si substrates. Influence of polymer thickness on the rugosity, morphology and adhesion force properties was studied. Scanning Electron Microscopy and mechanical probe profiling showed that sonication led to less rough and more homogeneous surface structure. Adhesion force properties of polypyrrole films were also studied by means of force–distance curves obtained by atomic force microscopy. For polymer films obtained in the absence of sonication, adhesion forces decreases with increase in polymer thickness. On the contrary, for polymer films obtained under sonication, the adhesion of the films decreased when the polymer thickness decreased.     

Persönlichkeit 2.0

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