Permanent bending and alignment of ZnO nanowires

Ion beams can be used to permanently bend and re-align nanowires after growth. We have irradiated ZnO nanowires with energetic ions, achieving bending and alignment in different directions. Not only the bending of single nanowires is studied in detail, but also the simultaneous alignment of large ensembles of ZnO nanowires. Computer simulations reveal how the bending is initiated by ion beam induced damage. Detailed structural characterization identifies dislocations to relax stresses and make the bending and alignment permanent, even surviving annealing procedures.     

Foam formation in oxidic pool with application to MCCI real material experiments

Void fraction is an important parameter in molten core concrete interaction (MCCI) study of PWR since it controls the swollen level of the corium pool, the interaction surface between the pool and the concrete and, in turn, the concrete erosion velocity. In recent MCCI real material experiments (OECD-MCCI, VULCANO), it seems that very high void fraction (higher than 50%) might have been obtained leading to low erosion velocity of concrete (e.g. CCI-4) and significant concrete erosion of the upper part of the test section (e.g. CCI-2 and CCI-4). Such void fraction cannot presently be predicted with classical void fraction correlations (e.g. Zuber and Findlay), so that a different phenomenon related to the formation of foam in oxidic pool during core concrete interaction could be considered. The main purpose of this paper is to propose an analysis of MCCI experiments taking into account the foam formation resulting from gas released from concrete in corium pool with SiO₂ and CaO. The first part of this paper is devoted to a review of the available experimental and modeling work performed in the frame of the metallurgical industry R&D. Two of these models have been implemented in the TOLBIAC-ICB code (CEA/EDF) which has then been used to simulate real material MCCI experiments of the OECD-MCCI project, CCI-2 and CCI-3. In the second part of this paper, it will be seen that foam formation could explain some of the phenomena observed in these experiments such as the strong ablation of the upper part of the cavity in Limestone Common Sand (LCS) concrete tests.     

Synthesis and action of the cyclic AMP antagonist, prostaglandylinositol cyclic phosphate (cyclic PIP), in Dictyostelium discoideum

PURPOSE: To examine the incidence of and risk factors for retinal detachment during a 10-year follow-up on intracapsular cataract extraction (ICCE). METHODS: Retrospective analysis of medical records of 1041 eyes operated on with ICCE in the years 1984-86. A complete follow-up was achieved, and actuarial methods were used in the risk assessment. The risk time averaged 82 months. RESULTS: Twenty-two (2.1%) eyes developed retinal detachment; half of the cases occurred during the first postoperative year, but new cases emerged throughout the period. The cumulative incidence of RD amounted to 2.8%; 95% confidence interval: 1.5-4.2%. Multivariate Cox regression analysis identified younger age at surgery (relative risk for each 10-year increase in age=0.6; 95% confidence interval: 0.39-0.95) and male gender (relative risk=2.5; 95% confidence interval 1.04-6.04) as significant risk factors for RD. Eleven eyes, 50% of eyes with RD and 1% of the total number of eyes, lost useful vision in spite of retinal surgery. CONCLUSION: Even though the risk for both RD and an unfavourable result following retinal surgery may be smaller using contemporary surgical techniques, the present study indicates a substantial morbidity following cataract surgery, when a sufficiently long observation period is considered.     

Sideband evolution from spontaneous into amplified emission in a free electron laser

A theoretical study of the evolution of sidebands, originating from large-scale (nonlinear) oscillations in the electron dynamics, is reported for a combined wiggler and guide field system operating near magnetoresonance. These sidebands, already existent in the spectrum of spontaneous emission, are followed up through small signal gain computations, and are finally recovered in the simulations of the nonlinear saturation process. A comparison with a radiation spectrum of an experiment done at the Naval Research Laboratory (NRL) shows good agreement. This indicates that the sidebands, observed in the experiment at saturation power level, are essentially due to the specific structure of the spectrum of spontaneous emission.     

Fractal analysis of pores

The fractal interpretation of porosimeter measurements leads to simple expressions which allow one to evaluate both cumulative pore volumes and surface areas over a range of three orders of magnitude. The pore system often consists of differently fractal regions which are superimposed on each other.

Investigated were activated charcoals, lignite coke, ashes, gas purification agents and zeolites. In all cases, the fractal analysis showed fractal dimensions D between 2 and 3.     

NMR investigations on molecular transport in ZSM-5 type zeolites containing structural defects

NMR spectroscopy is used to study the transport properties in ZSM-5 type zeolites containing structural irregularities. Using methane as a probe molecule, the structural distortions in polycrystalline aggregates are found to lead to an enhanced molecular mobility. After coking, molecular mobility is more reduced than in the monocrystalline specimen. This finding is explained by a preferential coke deposition in the secondary pore system. A variation of the concentration of non-acidic OH groups (silanol groups) indicating non-intact Si---O---Si bonds as structural defects of the pentasil structure, leads to characteristic changes in the sorption and diffusion properties of water. Bronsted acid sites are probed by methane self-diffusion measurements after chemisorption of ammonia and pyridine.     

Fluorescent‐based tandem white OLEDs designed for display and solid‐state‐lighting applications

Abstract— Highly efficient tandem white OLEDs based on fluorescent materials were developed for display and solid‐state‐lighting (SSL) applications. In both cases, the white OLED must have high power efficiency and long lifetime, but there are a number of attributes unique to each application that also must be considered. Tandem OLED technology has been demonstrated as an effective approach to increase luminance, extend OLED lifetime, and allow for use of different emitters in the individual stacks for tuning the emission spectrum to achieve desired performance. Here, examples of bottom‐emission tandem white OLEDs based on small‐molecule fluorescent emitters designed for displays and for SSL applications are reported. A two‐stack tandem white OLED designed for display applications achieved 36.5‐cd/A luminance efficiency, 8500K color temperature, and lifetime estimated to exceed 50,000 hours at 1000 cd/m². This performance is expected to meet the specifications for large AMOLED displays. A two‐stack tandem white OLED designed for SSL applications achieved 20‐lm/W power efficiency, 38‐cd/A luminance efficiency, 3500K color temperature, and lifetime estimated to exceed 140,000 hours at 1000 cd/m². With the use of proven light‐extraction techniques, it is estimated that this tandem device will exceed 40 lm/W with more than 500,000‐hour lifetime, performance that should be sufficient for first‐generation lighting products.     

Sustainable development: How to weigh both economical and ecological cost? A new strategy for a combined optimization

Sustainable development attempts a combined optimization of ecological, economical and social development. One task, then, is to measure progress in these terms, i.e. to weigh, e.g. economical against ecological advantages. We have developed and tested a method that combines at least the most essential criteria of ecological and economical development, i.e. the ecological cost derived from ecobalance studies and the economical cost derived from life‐cycle cost calculations. The method consists of improving lower‐cost products as long as they are cheaper than their alternatives. These improved products, which cost the same or less, are then compared in an ecobalance study with the alternatives. In many cases these improved products show by far the best ecological results and cost no more than the alternatives. They thus have the highest optimization potential both from an economical and ecological point of view. A strategy that strives towards sustainable development optimizes rare economical and ecological resources in an ecoefficient way. One formulation of such a strategy: Use lower‐cost products and improve them by using all or part of the price difference relative to their alternatives; these optimized products are very often much better when comparing ecobalance results, and not more expensive than their alternatives. This is shown to be the case for PVC windows compared both to wood and aluminum windows. An alternate method, the monetarizing of ecological impacts, is briefly discussed.