Quasi-total omnidirectional light absorption in nanostructured gold films

A series of experiments and simulations have been performed to evidence the omnidirectional light absorption of planar gold structures containing a two-dimensional lattice of spherical beads or pores. We show that more than 90 % of incident light is absorbed at angles of incidence up to 65° for optimum values of the gold film thickness. We also report the tunability of the absorption wavelength by varying the size of the beads/pores.     

Développement d''un modèle en vue de la prédiction du rallumage d''un foyer de turboréacteur à haute altitudeDevelopment of a model to predict the ignition performance of a turbojet engine at high altitude

Within the context of turbojet engine re-ignition after in-flight extinction, a thermo-diffusive model has been developed to describe the electrical ignition, at low pressure and low temperature, of a cluster of fuel droplets. The model involves the resolution of the conservation equations of mass, species and energy. It also takes into account the various physical and chemical phenomena occurring during the ignition process. This Note presents the ignition model and preliminary results of this model applied to an experimental configuration. To cite this article: V. Quintilla et al., C. R. Mecanique 330 (2002) 811–818.     

An Insurance Risk Model with Parisian Implementation Delays

We consider a similar variant of the event ruin for a Lévy insurance risk process as in Czarna and Palmowski (J Appl Probab 48(4):984–1002, 2011) and Loeffen et al. (to appear, 2011) when the surplus process is allowed to spend time under a pre-specified default level before ruin is recognized. In these two articles, the ruin probability is examined when deterministic implementation delays are allowed. In this paper, we propose to capitalize on the idea of randomization and thus assume these delays are of a mixed Erlang nature. Together with the analytical interest of this problem, we will show through the development of new methodological tools that these stochastic delays lead to more explicit and computable results for various ruin-related quantities than their deterministic counterparts. Using the modern language of scale functions, we study the Laplace transform of this so-called Parisian time to ruin in an insurance risk model driven by a spectrally negative Lévy process of bounded variation. In the process, a generalization of the two-sided exit problem for this class of processes is further obtained.     

Relief distribution networks: a systematic review

In the last 20 years, Emergency Management has received increasing attention from the scientific community. Meanwhile, the study of relief distribution networks has become one of the most popular topics within the Emergency Management field. In fact, the number and variety of contributions devoted to the design or the management of relief distribution networks has exploded in the recent years, motivating the need for a structured and systematic analysis of the works on this specific topic. To this end, this paper presents a systematic review of contributions on relief distribution networks in response to disasters. Through a systematic and scientific methodology, it gathers and consolidates the published research works in a transparent and objective way. It pursues three goals. First, to conduct an up-to-date survey of the research in relief distribution networks focusing on the logistics aspects of the problem, which despite the number of previous reviews has been overlooked in the past. Second, to highlight the trends and the most promising challenges in the modeling and resolution approaches and, finally, to identify future research perspectives that need to be explored.     

Radical chain reduction of alkylboron compounds with catechols

The conversion of alkylboranes to the corresponding alkanes is classically per-formed via protonolysis of alkylboranes. This simple reaction requires the use of severe reaction conditions, that is, treatment with a carboxylic acid at high temperature (>150 °C). We report here a mild radical procedure for the transformation of organoboranes to alkanes. 4-tert-Butylcatechol, a well-established radical inhibitor and antioxidant, is acting as a source of hydrogen atoms. An efficient chain reaction is observed due to the exceptional reactivity of phenoxyl radicals toward alkylboranes. The reaction has been applied to a wide range of organoboron derivatives such as B-alkylcatecholboranes, trialkylboranes, pinacolboronates, and alkylboronic acids. Furthermore, the so far elusive rate constants for the hydrogen transfer between secondary alkyl radical and catechol derivatives have been experimentally determined. Interestingly, they are less than 1 order of magnitude slower than that of tin hydride at 80 °C, making catechols particularly attractive for a wide range of transformations involving C-C bond formation.     

From micro to nano reentrant structures: hysteresis on superomniphobic surfaces

The paper reports on the wetting characterization of two surfaces presenting reentrant shapes at micro- and nanoscale using low surface tension liquids (down to 28 mN/m). On the one hand, mushroom-like microstructures are fabricated by molding poly(dimethylsiloxane) (PDMS) onto a patterned sacrificial photoresist bilayer. On the other hand, zinc oxide nanostructures (ZnO NS) are synthesized by easy and fast chemical bath deposition technique. The PDMS and ZnO NS surfaces are then chemically modified with 1H,1H,2H,2H-perfluorodecyltrichlorosilane in vapor phase. Both PDMS and ZnO NS surfaces exhibit a large apparent contact angle (>150°) and contact angle hysteresis varying from 50° to a quasi-null value. This large discrepancy can be ascribed to the length scale and topography of the structures, promoting either a vertical imbibition or a lateral spreading within the roughness.     

Unsymmetrical Binding Modes of the HOPNO Inhibitor of Tyrosinase: From Model Complexes to the Enzyme

The deciphering of the binding mode of tyrosinase (Ty) inhibitors is essential to understand how to regulate the tyrosinase activity. In this paper, by combining experimental and theoretical methods, we studied an unsymmetrical tyrosinase functional model and its interaction with 2‐hydroxypyridine‐N‐oxide (HOPNO), a new and efficient competitive inhibitor for bacterial Ty. The tyrosinase model was a dinuclear copper complex bridged by a chelated ring with two different complexing arms (namely (bis(2‐ethylpyridyl)amino)methyl and (bis(2‐methylpyridyl)amino)methyl). The geometrical asymmetry of the complex induces an unsymmetrical binding of HOPNO. Comparisons have been made with the binding modes obtained on similar symmetrical complexes. Finally, by using quantum mechanics/molecular mechanics (QM/MM) calculations, we studied the binding mode in tyrosinase from a bacterial source. A new unsymmetrical binding mode was obtained, which was linked to the second coordination sphere of the enzyme.     

Synthesis and glycosidase inhibition properties of triazole-linked calixarene–iminosugar clusters

Calixarene–iminosugar derivatives bearing four 1-deoxynojirimycin units at the upper or lower rim of calix[4]arenes in a fixed cone conformation were synthesized by copper-catalyzed azide-alkyne cycloaddition (CuAAC) and their inhibitory activity was evaluated against five glycosidases. Modest but significant affinity enhancements of up to seven per 1-deoxynojirimycin unit over the monovalent iminosugar derivative were observed for the inhibition of Jack bean (Canavalia ensiformis) α-mannosidase. It was also demonstrated that the residual copper ions did not contribute to the inhibitory properties of the newly prepared calixarene-based multivalent iminosugars.