WO3–EDA hybrid nanoplates and nanowires: synthesis, characterization, formation mechanism and thermal decomposition

Previously the WO3–EDA hybrid material was obtained only from solvothermal reactions.</p

QuantUM: Quantitative Safety Analysis of UML Models

When developing a safety-critical system it is essential to obtain an assessment of different design alternatives. In particular, an early safety assessment of the architectural design of a system is desirable. In spite of the plethora of available formal quantitative analysis methods it is still difficult for software and system architects to integrate these techniques into their every day work. This is mainly due to the lack of methods that can be directly applied to architecture level models, for instance given as UML diagrams. Also, it is necessary that the description methods used do not require a profound knowledge of formal methods. Our approach bridges this gap and improves the integration of quantitative safety analysis methods into the development process. All inputs of the analysis are specified at the level of a UML model. This model is then automatically translated into the analysis model, and the results of the analysis are consequently represented on the level of the UML model. Thus the analysis model and the formal methods used during the analysis are hidden from the user. We illustrate the usefulness of our approach using an industrial strength case study.Comment: In Proceedings QAPL 2011, arXiv:1107.074

Unique determination of “subatomic” contrast by imaging covalent backbonding

The origin of so-called “subatomic” resolution in dynamic force microscopy has remained controversial since its first observation in 2000. A number of detailed experimental and theoretical studies have identified different possible physicochemical mechanisms potentially giving rise to subatomic contrast. In this study, for the first time we are able to assign the origin of a specific instance of subatomic contrast as being due to the back bonding of a surface atom in the tip−sample junction

Component-wise incremental LTL model checking

Efficient symbolic and explicit-state model checking approaches have been developed for the verification of linear time temporal logic (LTL) properties. Several attempts have been made to combine the advantages of the various algorithms. Model checking LTL properties usually poses two challenges: one must compute the synchronous product of the state space and the automaton model of the desired property, then look for counterexamples that is reduced to finding strongly connected components (SCCs) in the state space of the product. In case of concurrent systems, where the phenomenon of state space explosion often prevents the successful verification, the so-called saturation algorithm has proved its efficiency in state space exploration. This paper proposes a new approach that leverages the saturation algorithm both as an iteration strategy constructing the product directly, as well as in a new fixed-point computation algorithm to find strongly connected components on-the-fly by incrementally processing the components of the model. Complementing the search for SCCs, explicit techniques and component-wise abstractions are used to prove the absence of counterexamples. The resulting on-the-fly, incremental LTL model checking algorithm proved to scale well with the size of models, as the evaluation on models of the Model Checking Contest suggests

Synthesis and characterization of triangulene

Triangulene, the smallest triplet-ground-state polybenzenoid (also known as Clar's hydrocarbon), has been an enigmatic molecule ever since its existence was first hypothesized1. Despite containing an even number of carbons (22, in six fused benzene rings), it is not possible to draw Kekulé-style resonant structures for the whole molecule: any attempt results in two unpaired valence electrons2. Synthesis and characterization of unsubstituted triangulene has not been achieved because of its extreme reactivity1, although the addition of substituents has allowed the stabilization and synthesis of the triangulene core3, 4 and verification of the triplet ground state via electron paramagnetic resonance measurements5. Here we show the on-surface generation of unsubstituted triangulene that consists of six fused benzene rings. The tip of a combined scanning tunnelling and atomic force microscope (STM/AFM) was used to dehydrogenate precursor molecules. STM measurements in combination with density functional theory (DFT) calculations confirmed that triangulene keeps its free-molecule properties on the surface, whereas AFM measurements resolved its planar, threefold symmetric molecular structure. The unique topology of such non-Kekulé hydrocarbons results in open-shell π-conjugated graphene fragments6 that give rise to high-spin ground states, potentially useful in organic spintronic devices7, 8. Our generation method renders manifold experiments possible to investigate triangulene and related open-shell fragments at the single-molecule level

Oxygen reduction reaction features in neutral media on glassy carbon electrode functionalized by chemically prepared gold nanoparticles

Gold nanoparticles (AuNPs) were prepared by chemical route using 4 different protocols by varying reducer, stabilizing agent and solvent mixture. The obtained AuNPs were characterized by transmission electronic microscopy (TEM), UV-Visible and zeta potential measurements. From these latter surface charge densities were calculated to evidence the effect of the solvent mixture on AuNPs stability. The AuNPs were then deposited onto glassy carbon (GC) electrodes by drop-casting and the resulting deposits were characterized by cyclic voltammetry (CV) in H2SO4 and field emission gun scanning electron microscopy (FEG-SEM). The electrochemical kinetic parameters of the 4 different modified electrodes towards oxygen reduction reaction (ORR) in neutral NaCl-NaHCO3 media (0.15 M / 0.028 M, pH 7.4) were evaluated by rotating disk electrode voltammetry and subsequent Koutecky-Levich treatment. Contrary to what we previously obtained with electrodeposited AuNPs [Gotti et al., Electrochim. Acta 2014], the highest cathodic transfer coefficients were not obtained on the smallest particles, highlighting the influence of the stabilizing ligand together with the deposits morphology on the ORR kinetics

The role of reactive surface sites and complexation by humic acids in the interaction of clay mineral and iron oxide particles

Aggregation and dispersion of mineral particles spontaneously take place under changing environmental conditions in natural systems. The structure of particle network in soils, the retardation or release of colloidal particles, and their mobility and transport are inherently influenced by natural organic matter bound to the mineral matrix. Since the surface properties of clay mineral and metal oxide particles, and the electrified mineral-water interfaces play a major role in formation, structure and strength of aggregates, any surface modification, especially by polyanionic organic complexants such as humic substances, has a significant affect on particle interaction in a mineral assemblage. The permanently and/or conditionally charged clay minerals (montmorillonite and kaolinite) and iron oxides (hematite and magnetite), as known major mineral components in natural waters, were selected for studying their surface charge characteristics and pH dependent interactions. We discuss how the surface charge correlates with particle aggregation through some characteristic examples for homo and heterocoagulation of similar and dissimilar mineral particles under acidic condition (at pH similar to4) in the dilute and concentrated systems studied by means of light scattering and theology, respectively. The adsorption of a brown coal derived humic acid, and its influence on the surface charge character and particle aggregation of clay and iron oxide particles were also studied in dilute and concentrated suspensions. Humic acids can be bound to the most reactive surface sites of clay and oxide particles, i.e. to Al-OH mainly at the edges of clay lamellae, and to Fe-OH on iron oxides, in surface complexation reaction, therefore their role in particle aggregation is specific. Relations between surface complexation, surface charge modification, and particle aggregation in pure and mixed montmorillonite-iron oxide systems are explained. (C) 2003 Elsevier Ltd. All rights reserved