Towards the development of a novel bioinspired functional material: Synthesis and characterization of hybrid TiO2/DHICA-melanin nanoparticles

A large number of recent literature data focus on modification/modulation of surface chemistry of inorganic materials in order to improve their functional properties. Melanins, a wide class of natural pigments, are recently emerging as a powerful organic component for developing bioinspired active material for a large number of applications from organoelectronics to bioactive compounds.Here we report the use of the approach referred as “chimie douce”, involving in situ formation of the hybrids through reactions of precursors under mild conditions, to prepare novel hybrid functional architectures based on eumelanin like 5,6 dihydroxyindole-2-carboxylic acid (DHICA) polymer and TiO₂. Two synthesis procedures were carried out to get DHICA-melanin coated TiO₂ nanoparticles as well as mixed DHICA/TiO₂ hybrid nanostructures. Such systems were characterized through EPR, FT-IR and fluorescence spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and TEM microscopy in order to assess the effect of synthesis path as well as of DHICA content on structural, morphological and optical properties of TiO₂ nanostructures. In particular, EPR, FT-IR spectra and TGA analysis confirmed the presence of DHICA-melanin in these samples. TEM measurements indicated the formation of the nanoparticles having relatively narrow size distribution with average particle size of about 10 nm. DHICA-melanin does act as a morphological agent affecting morphology of hybrid nanostructures. XRD analysis proved that TiO₂ hybrid nanoparticles kept anatase structures for DHICA-melanin contents within the range of investigated compositions, i.e. up to 50% wt/wt.     

Antennal sensilla in an anophthalmic wood-dwelling species,Clinidium canaliculatum,Costa 1839 (Coleoptera,Rhysodidae)

The habit of feeding on slime moulds (Myxomycetes) commonly present in litter or dead wood requires specific morphological adaptations of the mouthparts and sensory structures involved in the search for habitat and food. In this study, the external morphology of antenna and its sensilla were studied using scanning electron microscopy in the saproxylic beetle, Clinidium canaliculatum, Costa 1839 (Coleoptera, Rhysodidae). Their moniliform antennae consist of a scape, pedicel, and nine flagellomeres. We identified seven different types of sensilla, according to their morphological characteristics: two types of sensilla chaetica (sc1 and 2), two types of sensilla basiconica (sb1 and 2), one type of sensilla campaniformia, one type of sensilla coeloconica, and Böhm sensilla. No sexual dimorphism was found regarding antennal morphology and sensilla type and distribution, except for the sensilla coeloconica. The functional role of these sensilla was discussed in relation to their external structure and distribution, and compared with the current knowledge on coleopteran sense organs. Results are basic information for further physiological and behavioral studies to identify their role in the selection of habitat, food, mates and oviposition sites.     

Wetting and interfacial phenomena of Ni‐Ta alloys on CVD‐SiC

When designing high‐temperature brazing processes for ceramic materials, the interfacial phenomena between the liquid media and the adjoining surfaces must be known to design reliable joints. In order to assess the feasibility of using Ta‐containing alloys for high‐temperature brazing of SiC‐based composites, the wetting of molten Ni‐Ta alloys on ultra‐pure chemical vapor deposited (CVD) SiC substrates has been investigated using the sessile drop technique. For all of the compositions and experimental conditions, good wetting was observed with fast spreading. The interfacial behavior is determined by the competition between the typical interfacial phenomena of the pure elements; specifically, either the dissolution of the ceramic phase by Ni or the formation of a new interfacial layer, TaC, by reaction between Ta and CVD‐SiC, which prevails depends on the relative amount of the single element in the alloy.     

Unilateral contact problems for cables

A cable (such as in a submarine energy-transmission line) is supposed to be subjected to given transversal loads and a given tension force, in the vicinity of a frictionless rigid ground of known profile. The search for its equilibrium configuration is a contact (unilateral support) problem of a special kind. The problem is studied here with reference to a finite difference discretization of the system, under the small deformation hypothesis. On this basis its formulation becomes a linear complementarity problem or, alternatively, a quadratic, strictly convex program. Extremum properties of the solution are established and interpreted in mechanical terms. A general monotonicity property of the equilibrium configuration under proportional loading is pointed out; precisely, it is proved that, despite the nonlinearity of the system, whatever the load distribution, as the load factor increases, in any point of the cable the possible contact reaction and the vertical distance from the obstacle will never decrease. Among the mathematical programming algorithms presently available, Cryer's systematic overrelaxation is found to be efficient for the numerical solution of large-size problems of the type in question. Some numerical experience is presented.     

Speaky for robots: the development of vocal interfaces for robotic applications

The currently available speech technologies on mobile devices achieve effective performance in terms of both reliability and the language they are able to capture. The availability of performant speech recognition engines may also support the deployment of vocal interfaces in consumer robots. However, the design and implementation of such interfaces still requires significant work. The language processing chain and the domain knowledge must be built for the specific features of the robotic platform, the deployment environment and the tasks to be performed. Hence, such interfaces are currently built in a completely ad hoc way. In this paper, we present a design methodology together with a support tool aiming to streamline and improve the implementation of dedicated vocal interfaces for robots. This work was developed within an experimental project called Speaky for Robots. We extend the existing vocal interface development framework to target robotic applications. The proposed solution is built using a bottom-up approach by refining the language processing chain through the development of vocal interfaces for different robotic platforms and domains. The proposed approach is validated both in experiments involving several research prototypes and in tests involving end-users.     

Strategies to Tackle Antimicrobial Resistance: The Example of Escherichia coli and Pseudomonas aeruginosa

Traditional antimicrobial treatments consist of drugs which target different essential functions in pathogens. Nevertheless, bacteria continue to evolve new mechanisms to evade this drug-mediated killing with surprising speed on the deployment of each new drug and antibiotic worldwide, a phenomenon called antimicrobial resistance (AMR). Nowadays, AMR represents a critical health threat, for which new medical interventions are urgently needed. By 2050, it is estimated that the leading cause of death will be through untreatable AMR pathogens. Although antibiotics remain a first-line treatment, non-antibiotic therapies such as prophylactic vaccines and therapeutic monoclonal antibodies (mAbs) are increasingly interesting alternatives to limit the spread of such antibiotic resistant microorganisms. For the discovery of new vaccines and mAbs, the search for effective antigens that are able to raise protective immune responses is a challenging undertaking. In this context, outer membrane vesicles (OMV) represent a promising approach, as they recapitulate the complete antigen repertoire that occurs on the surface of Gram-negative bacteria. In this review, we present Escherichia coli and Pseudomonas aeruginosa as specific examples of key AMR threats caused by Gram-negative bacteria and we discuss the current status of mAbs and vaccine approaches under development as well as how knowledge on OMV could benefit antigen discovery strategies.     

Evidence for the presence of a FAD pyrophosphatase and a FMN phosphohydrolase in yeast mitochondria: a possible role in flavin homeostasis

Despite the crucial roles of flavin cofactors in metabolism, we know little about the enzymes responsible for the turnover of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) and their subcellular localization. The mechanism by which mitochondria obtain their own flavin cofactors is an interesting point of investigation, because FMN and FAD are mainly located in mitochondria, where they act as redox cofactors of a number of dehydrogenases and oxidases that play a crucial function in both bioenergetics and cellular regulation. In this context, the capability of yeast mitochondria to metabolize externally added and endogenous FAD and FMN was investigated and use was made of purified and bioenergetically active mitochondria prepared starting from the Saccharomyces cerevisiae cell. To determine whether flavin metabolism can occur, the amounts of flavins in aliquots of neutralized perchloric extracts of both spheroplasts and mitochondria were measured by HPLC, and the competence of S. cerevisiae mitochondria to metabolize FAD and FMN was investigated both spectroscopically and via HPLC. FAD deadenylation and FMN dephosphorylation were studied with respect to dependence on substrate concentration, pH profile and inhibitor sensitivity. The existence of two novel mitochondrial FAD pyrophosphatase (diphosphatase) (EC 3.6.1.18) and FMN phosphohydrolase (EC 3.1.3.2) activities, which catalyse the reactions FAD + H₂O → FMN + AMP and FMN + H₂O → riboflavin + Pi respectively, is here shown by fractionation studies. Considering cytosolic riboflavin, FMN and FAD concentrations, as calculated by measuring both spheroplast and mitochondrial contents via HPLC, probably mitochondria play a major role in regulating the flavin pool in yeast and in relation to flavin homeostasis. Copyright © 2011 John Wiley & Sons, Ltd.