Persian Variations

The concept of variation is essential in geometric design. It is surprising that patterns very different may be variations of the same model. We define two families of pentagonal patterns with three kind of variations, and give some suggestions how to analyse these patterns and create in this style. We then search for self-similarity systems in a strict sense. Although from a systematic search, the two solutions proposed here can also generate some traditional 2-level patterns. In searching for subdivisions of the tiles into rhombuses, we found two solutions. Both can be compatible with the Binary Tiling (not with the Penrose Tiling). Then, using the concept of X-Tiles defined in a previous paper (Castera et al., http://castera.net/entrelacs/public/articles/Flying_Patterns.pdf, 2011), we find new relationship between the two families of pentagonal patterns. In the last chapter we show and comment some examples taken from traditional architecture in Iran, and infer a self-similar system for pattern with interlaces from a 2-level tiling in Isfahan. This paper reflect the point of view of a pattern designer.     

Study of the formation of complexes between DNA and esterified dairy proteins

Like with many naturally occurring basic proteins such as histones and lysozymes, plasmid DNA can interact with methylated α-lactalbumin (ALA) and methylated β-lactoglobulin (BLG) forming complexes. The stabilities of these complexes were tested at different pH, temperatures and salt concentrations, and after enzyme digestion with DNase I and pepsin. Incubation at 37°C for long periods (up to 24 h) allowed the interaction of DNA with low concentrations of esterified proteins to take place. High temperature treatment (100°C) for short periods of time enhanced complex formation after 5 min of heating in case of both DNA/methylated ALA and DNA/methylated BLG. The complex of DNA with methylated BLG was more stable than that of DNA and methylated ALA, when the thermal treatment at 100°C was extended to 10 min. Both complexes were formed in larger amounts and were more stable at acid pH (3–6). Generally, at acid pH, the concentration of the stable complex of DNA and methylated BLG was larger than that of the complex between DNA and methylated ALA. These complexes were still quite stable at very acid pH (1–2) but not at all at very basic pH (10–11). Formation and stability of studied complexes of DNA with esterified proteins were generally dependent on salt concentration. Magnesium chloride had the greatest inhibitory effect on the formation and the stability of these complexes while potassium acetate had the least. The inhibitory effect of KCl on both complex formation and stability was observed in the range 0.4–1.0 . The complexes between DNA and esterified milk proteins or lysozyme were more resistant to hydrolysis with DNase I than free non-complexed DNA. Surprisingly, the DNA/methylated ALA complex was more resistant to DNase I digestion than the DNA/methylated BLG or DNA/lysozyme complexes. All the studied proteins were resistant to pepsin when complexed with DNA.     

Thermal runaway analysis of a three-phase reactor for LCO hydrotreatment

Safety is a high-priority topic for the chemical industry to minimize the frequency and severity of accidents while keeping the productivity and quality of the production. The processes that may undergo thermal runaways due to exothermic reactions are at the heart of the risks of accidents. The study of such highly reactive systems is essential to achieve a safe and productive operation of existing processes and to ensure inherently safe new designs. It is well known that the stationary analysis with the van Heerden criterion must be satisfied, however, this is not sufficient to ensure reactor stability. Only dynamic analysis can provide an accurate answer concerning the safe operation of the reactor. Most of the reported stability studies are carried out for relatively simple systems (pseudo-homogeneous models, simple reaction schemes). This work presents the dynamic thermal stability study of a refining process (hydrotreatment of light cycle oils) carried out with real gasoils at industrial operating conditions. A 1D dynamic model that accurately represents the reactive system (gas–liquid–solid) was developed and validated with experimental pilot plant data. This mathematical model was used to perform the thermal stability analysis of the dynamic system using a perturbation method. The effect of the variation of the heat transfer coefficient on the thermal stability is presented. The spectral analysis of the eigenvalues indicating the stable/unstable behavior of the reactive system was compared with dynamic simulations. An excellent agreement was found between the simulations and the stability analysis. The case of oscillating behavior is also described. The frequencies of oscillation determined by the stability analysis are compared to the frequencies calculated by Fourier transform applied to the simulated signal. The reactor behavior and the oscillations features are accurately predicted with this stability analysis method.     

Effect of iron counter-ions on the redox properties of the Keggin-type molybdophosphoric heteropolyacid Part I. An experimental study on isobutane oxidation catalysts

Keggin-type molybdophosphoric heteropolyacid with protons partially substituted by iron cations in a bulk form (Fe_0.85H_0.45PMo₁₂O₄₀) or supported on the cesium salt (Cs₂Fe_0.2H_0.4PMo₁₂O₄₀) have been synthesized and characterized by different techniques like the Mössbauer spectroscopy and the electron spin resonance (ESR). The effect of iron on the redox and catalytic properties for the oxidation of isobutane into methacrylic acid (MAA) has also been studied. Iron has been shown to have a different effect whether acts as a counter-cation in the bulk acid or in the acid supported on the cesium salt. In the first case, it increases both the selectivity in methacrylic acid and methacrolein (MA) and the activity of the acid phase whereas in the second case, it increases only the selectivity. This difference has been explained by the existence of an electron transfer between iron and molybdenum occurring only in the bulk acid. This electron transfer was related to a combined hydration-oxidation mechanism which promotes the reducibility of the solid and consequently its catalytic activity.     

Influence of the Content and Distribution of Vanadium in the M1 Phase of the MoVTe(Sb)NbO Catalysts on their Catalytic Properties in Light Alkanes Oxidation

Phase-pure MoVTe(Sb)NbO mixed oxides, with an M1 structure, and various compositions were prepared, characterized and tested as catalysts for the oxidative dehydrogenation of ethane, in order to study the influence of vanadium content and its distribution over the crystallographic sites on the catalytic properties of these oxides. A linear variation in catalytic activity was observed, as a function of the total vanadium content. This property, which has already been demonstrated for propane oxidation, is shown to remain unaffected by the alkane reaction, the nature of the propene α-dehydrogenation elements (Te or Sb), the presence or absence of niobium. The use of XPS to study the surface composition of the catalysts allowed a direct proportionality to be established between the rate of ethane conversion and the V⁵⁺ surface content, thus explaining the first correlation observed with bulk V content. This result also emphasizes the fact that a maximum level of intrinsic catalytic activity can be found, and that high vanadium content might be detrimental to this activity, or to the stability of the catalysts. Finally, crystallographic data found in the literature are used to further interpret and discuss these results.     

Atomistic simulations of the optical absorption of type-II CdSe/ZnTe superlattices

We perform accurate tight binding simulations to design type-II short-period CdSe/ZnTe superlattices suited for photovoltaic applications. Absorption calculations demonstrate a very good agreement with optical results with threshold strongly depending on the chemical species near interfaces.     

MISTRAL: a myopic edge-preserving image restoration method, with application to astronomical adaptive-optics-corrected long-exposure images

Deconvolution is a necessary tool for the exploitation of a number of imaging instruments. We describe a deconvolution method developed in a Bayesian framework in the context of imaging through turbulence with adaptive optics. This method uses a noise model that accounts for both photonic and detector noises. It additionally contains a regularization term that is appropriate for objects that are a mix of sharp edges and smooth areas. Finally, it reckons with an imperfect knowledge of the point-spread function (PSF) by estimating the PSF jointly with the object under soft constraints rather than blindly (i.e., without constraints). These constraints are designed to embody our knowledge of the PSF. The implementation of this method is called MISTRAL. It is validated by simulations, and its effectiveness is illustrated by deconvolution results on experimental data taken on various adaptive optics systems and telescopes. Some of these deconvolutions have already been used to derive published astrophysical interpretations.     

A general framework for the evaluation of symbol recognition methods

Performance evaluation is receiving increasing interest in graphics recognition. In this paper, we discuss some questions regarding the definition of a general framework for evaluation of symbol recognition methods. The discussion is centered on three key elements in performance evaluation: test data, evaluation metrics and protocols of evaluation. As a result of this discussion we state some general principles to be taken into account for the definition of such a framework. Finally, we describe the application of this framework to the organization of the first contest on symbol recognition in GREC’03, along with the results obtained by the participants.