Requirements-Level Semantics and Model Checking of Object-Oriented Statecharts

In this paper we define a requirements-level execution semantics for object-oriented statecharts and show how properties of a system specified by these statecharts can be model checked using tool support for model checkers. Our execution semantics is requirements-level because it uses the perfect technology assumption, which abstracts from limitations imposed by an implementation. Statecharts describe object life cycles. Our semantics includes synchronous and asynchronous communication between objects and creation and deletion of objects. Our tool support presents a graphical front-end to model checkers, making these tools usable to people who are not specialists in model checking. The model-checking approach presented in this paper is embedded in an informal but precise method for software requirements and design. We discuss some of our experiences with model checking. Correspondence and offprint requests to: Rik Eshuis, Department of Computer Science, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. Email: eshuis@cs.utwente.nl     

Rigorous electromagnetic analysis of dipole emission in periodically corrugated layers: the grating-assisted resonant-cavity light-emitting diode

We study the grating-assisted light-emitting diode, an LED design for high brightness based on a resonant cavity containing one- or two-dimensionally periodically corrugated layers (grating). We give in detail a generally applicable electromagnetic analysis based on the rigorous coupled-wave theory to calculate the extraction efficiency of spontaneous emission in a periodically corrugated layer structure. This general model is then specified on the grating-assisted resonant-cavity LED, showing simulated efficiencies of more than 40%.     

Visualizing business data with generalized treemaps

Business data is often presented using simple business graphics. These familiar visualizations are effective for providing overviews, but fall short for the presentation of large amounts of detailed information. Treemaps can provide such detail, but are often not easy to understand. We present how standard treemap algorithms can be adapted such that the results mimic familiar business graphics. Specifically, we present the use of different layout algorithms per level, a number of variations of the squarified algorithm, the use of variable borders, and the use of non-rectangular shapes. The combined use of these leads to histograms, pie charts and a variety of other styles     

Improving Multipath Radiosity with Bundles of Parallel Lines

Monte Carlo approaches use random lines to distribute the light power in the scene but the cost of creating a set of random single lines is very costly. In this paper, we present several software and hardware techniques in order to reduce the computational cost of the generation of random single lines by using bundles of parallel lines. The bundle of parallel lines is simulated with a general purpose polygon filling algorithm, like the painter's algorithm. We also present two graphics hardware implementations. The first approach uses two depth buffers in order to represent stochastically a bundle of parallel global lines. The second one uses multiple depth buffers and the aim is to exploit coherence between projection planes for each iteration. All algorithms were implemented with the multipath method.     

Generating Color Palettes using Intuitive Parameters

Color is widely used in data visualization to show data values. The proper selection of colors is critical to convey information correctly. In this paper, we present a technique for generating univariate lightness ordered palettes. These are specified via intuitive input parameters that are used define the appearance of the palette: number of colors, hue, lightness, saturation, contrast and hue range. The settings of the parameters are used to generate curves through CIELUV color space. This color space is used in order to correctly translate the requirements in terms of perceptual properties to a set of colors. The presented palette generation method enables users to specify palettes that have these perceptual properties, such as perceived order, equal perceived distance and equal importance. The technique has been integrated in Magna View, a system for multivariate data visualization.     

The effect of phosphorus on the HDN reaction of piperidine,decahydroquinoline and ortho-propylaniline over Ni-MoS2/Al2O3 catalysts

The hydrodenitrogenation (HDN) of piperidine, decahydroquinoline (DHQ) and orthopropylaniline (OPA) has been studied over NiMo(P)/Al₂O₃ catalysts at 593 K and 3.0 MPa in order to understand the effect of phosphorus on the elementary HDN reaction steps. Phosphorus exhibited a negative effect on the HDN of piperidine and DHQ, both on the C-N bond cleavage reaction and on the subsequent hydrogenation reaction of alkene to alkane. A P/Al₂O₃ catalyst showed no HDN activity at all, neither with piperidine, nor with DHQ. A positive effect of phosphorus was observed in the HDN of OPA, where hydrogenation of the aromatic ring is needed and is rate limiting. It is suggested that introduction of phosphorus to NiMo/Al₂O₃ catalysts on the one hand decreases the available support surface area, and as a consequence the dispersion of the Ni-Mo-S phase and thus the capacity for C-N bond breaking and olefin hydrogenation. On the other hand, phosphorus induces either new or more active sites for the hydrogenation of aromatics.     

Validation of multiparametric MRI by histopathology after nephrectomy: a case study

Magnetic Resonance Materials in Physics, Biology and Medicine - Renal multiparametric MRI (mpMRI) is a promising tool to monitor renal allograft health to enable timely treatment of chronic...     

Compact Slanted Grating Couplers Between Optical Fiber and InP–InGaAsP Waveguides

We present theoretical and experimental results for compact slanted gratings for vertical coupling between single-mode fiber and InP-InGaAsP waveguides. The maximum calculated coupling efficiency is 59%. We have measured a coupling efficiency of 16% for a 10-mum-long slanted grating     

The effects of fluorine, phosphate and chelating agents on hydrotreating catalysts and catalysis

The effects of fluorine, phosphate and chelating agents on hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) are reviewed. All three additives enhance the activity of NiMo/Al₂O₃ catalysts in HDN but have only a slightly positive or even a negative effect on the HDS activity of CoMo/Al₂O₃ and NiMo/Al₂O₃ catalysts. The positive effect on HDN is due to the enhancement of the hydrogenation of aromatic rings. On the other hand, these three additives diminish the rates of C–N bond breaking and alkene hydrogenation reactions.

All three additives are hard basic ligands that may interact strongly with hard acids such as coordinatively unsaturated Al³⁺ cations on the alumina surface. A strong interaction with the alumina support has several effects. First, molybdate and tungstate anions are no longer strongly bonded to the support and are predominantly present as polyanions, which can be easily sulfided to MoS₂ and WS₂ crystallites. The weaker interaction with the smaller support surface also leads to larger MoS₂ and WS₂ crystallites with a lower dispersion. Second, the Ni²⁺ and Co²⁺ cations will also interact more weakly with the alumina, and this makes the formation of Ni and Co promoter atoms in the catalytically active Ni–Mo–S and Co–Mo–S phases more efficient. Third, the weaker interaction of Mo and W with the support leads to a higher stacking of the MoS₂ and WS₂ crystallites and, thus, to the more active type II Ni–Mo–S and Co–Mo–S phases. The increased stacking is beneficial for geometrically demanding reactions such as the hydrogenation of aromatics. For less demanding reactions, such as alkene hydrogenation, aliphatic C–N bond breaking and thiophene HDS, the loss in dispersion is important.     

Titanium dioxide nanoparticles induce oxidative stress and DNA-adduct formation but not DNA-breakage in human lung cells

Titanium dioxide (TiO₂), also known as titanium (IV) oxide or anatase, is the naturally occurring oxide of titanium. It is also one of the most commercially used form. To date, no parameter has been set for the average ambient air concentration of TiO₂ nanoparticles (NP) by any regulatory agency. Previously conducted studies had established these nanoparticles to be mainly non-cyto- and -genotoxic, although they had been found to generate free radicals both acellularly (specially through photocatalytic activity) and intracellularly. The present study determines the role of TiO₂-NP (anatase, ∅ < 100 nm) using several parameters such as cyto- and genotoxicity, DNA-adduct formation and generation of free radicals following its uptake by human lung cells in vitro. For comparison, iron containing nanoparticles (hematite, Fe₂O₃, ∅ < 100 nm) were used. The results of this study showed that both types of NP were located in the cytosol near the nucleus. No particles were found inside the nucleus, in mitochondria or ribosomes. Human lung fibroblasts (IMR-90) were more sensitive regarding cyto- and genotoxic effects caused by the NP than human bronchial epithelial cells (BEAS-2B). In contrast to hematite NP, TiO₂-NP did not induce DNA-breakage measured by the Comet-assay in both cell types. Generation of reactive oxygen species (ROS) was measured acellularly (without any photocatalytic activity) as well as intracellularly for both types of particles, however, the iron-containing NP needed special reducing conditions before pronounced radical generation. A high level of DNA adduct formation (8-OHdG) was observed in IMR-90 cells exposed to TiO₂-NP, but not in cells exposed to hematite NP. Our study demonstrates different modes of action for TiO₂- and Fe₂O₃-NP. Whereas TiO₂-NP were able to generate elevated amounts of free radicals, which induced indirect genotoxicity mainly by DNA-adduct formation, Fe₂O₃-NP were clastogenic (induction of DNA-breakage) and required reducing conditions for radical formation.