Superficial fluoropolymer layers for efficient light-emitting diodes

Fluoropolymers are characterized by high chemical inertness and, when in solid state, by superficial dipoles due to the C–F bond where the charge density is strongly displaced. These two characteristics are exploited here for fine control of charge balance in organic light-emitting devices and for preventing electrochemical interaction between heterogeneous layers. The insertion of a thin layer of polytetrafluoroethylene, PTFE, at the interface between poly(ethylene dioxythiophene):poly(styrene sulfonic acid), PEDOT:PSS, and an electroluminescent polymer leads to improved device efficiency and longevity. The presence of the superficial dipole increases the effective work function of the anode and improves the charge balance which enhances the external quantum efficiency, EQE, of the devices by up to a factor of two without significant effects on the luminance levels. The insertion of the PTFE layer reduces the photoluminescence quenching at the PEDOT:PSS/polymer interface, however we show that the EQE enhancement is mainly due to a better confinement of minority carrier electrons in the active layer. The lifetime of the devices shows a remarkable increase correlated with the insertion of the PTFE layer. Such improvements are ascribed to the reduced electrochemical interaction between the electroluminescent polymer and PEDOT:PSS due to the chemically inert nature of PTFE. The PTFE acts as a chemical zipper of two heterogeneous media with the added functionality of control over the charge balance.     

High precision C AMS at CIRCE

The CIRCE AMS system started operation in March 2005. The measurement of isotopic ratios ¹⁴C/¹²C in samples of archaeological and environmental interest has rapidly attained high precision and accuracy levels in routine operation. The results of the intercomparison campaign in the framework of the VIRI program, as well as the outcome of a statistical analysis of the about 200 control measurements performed with standard samples, have shown the capability of the whole system for high precision measurements (δR/R < 0.3%), allowing systematic investigations in both archaeological and environmental sciences. ²⁶Al AMS has been implemented for the measurement of the astrophysically relevant ²⁵Mg(p,γ)²⁶Al reaction cross section, while a beam line is under construction for the measurement of actinides isotopic ratios.     

Enabling Human–Machine Interaction in Projected Virtual Environments Through Camera Tracking of Imperceptible Markers

Existing tracking methods designed for interacting with projection-based displays generally require visible artifacts to be introduced in the environment in order to guarantee effective stability and accuracy. For instance, in optical-oriented approaches, either the camera sensor or the reference pattern used for tracking are often located within the user's sight (or interfere with it), thus occluding portions of the scene or altering the perception of the virtual environment. Several ways to tackle these issues have been recently explored. Proposed approaches basically aim at making the presence of tracking references in the virtual space transparent to the user. However, such solutions introduce possibly critical constraints on required hardware or environment configuration. In this work, a novel tracking approach based on imperceptible fiducial markers is proposed. The approach relies on a hiding technique that allows digital images to be embedded in (and retrieved from) a projected scene by exploiting the properties of light polarization and additive color mixing. In particular, the virtual scene is obtained by overlapping the light beams of two projectors and by dealing with markers’ hiding via color compensation. A prototype setup has been deployed, where interaction with a flat surface projection environment has been evaluated in terms of tracking accuracy and artifacts avoidance performance by using a consumer camera equipped with a polarizing filter. Although the performed tests presented in this article represent only a preliminary and a partial evaluation of the proposed approach, they provided encouraging results indicating that the proposed technique could be possibly applied in more complex interaction scenarios still with limited hardware requirements.     

Proteins as biomarkers of oxidative/nitrosative stress in diseases: the contribution of redox proteomics

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) contribute to the pathogenesis and/or progression of several human diseases. Proteins are important molecular signposts of oxidative/nitrosative damage. However, it is generally unresolved whether the presence of oxidatively/nitrosatively modified proteins has a causal role or simply reflects secondary epiphenomena. Only direct identification and characterization of the modified protein(s) in a given pathophysiological condition can decipher the potential roles played by ROS/RNS-induced protein modifications. During the last few years, mass spectrometry (MS)-based technologies have contributed in a significant way to foster a better understanding of disease processes. The study of oxidative/nitrosative modifications, investigated by redox proteomics, is contributing to establish a relationship between pathological hallmarks of disease and protein structural and functional abnormalities. MS-based technologies promise a contribution in a new era of molecular medicine, especially in the discovery of diagnostic biomarkers of oxidative/nitrosative stress, enabling early detection of diseases. Indeed, identification and characterization of oxidatively/nitrosatively modified proteins in human diseases has just begun.     

Macroscopic electrical field distribution and field-induced surface stresses of needle-shaped field emitters

One major concern since the development of the field ion microscope is the mechanical strength of the specimens. The macroscopic shape of the imaging tip greatly influences field-induced stresses and there is merit in further study of this phenomenon from a classical perspective. Understanding the geometrical, as opposed to localized electronic, factors that affect the stress might improve the quality and success rate of atom probe experiments. This study uses macroscopic electrostatic principles and finite element modelling to investigate field-induced stresses in relation to the shape of the tip. Three two-dimensional idealized models are considered, namely hyperbolic, parabolic and sphere-on-orthogonal-cone; the shapes of which are compared to experimental tips prepared by electro-polishing. Three dimensional morphologies of both a nano-porous and single-crystal aluminium tip are measured using electron tomography to quantitatively test the assumption of cylindrical symmetry for electro-polished tips. The porous tip was prepared and studied to demonstrate a fragile specimen for which such finite element studies could determine potential mechanical failure, prior to any exhaustive atom probe investigation.     

Catalytic MTO-based C–H insertion reactions of hydrogen peroxide: an investigation on the polymeric support role in heterogeneous conditions

Polymer-supported methyltrioxorhenium (MTO) compounds are shown to act as efficient and selective catalysts for the oxy-functionalization of C–H bonds in representative hydrocarbon derivatives (leading to the corresponding alcohols or ketones), using H₂O₂ as oxidant. The different supports used for the heterogenation of MTO, such as poly(4-vinylpyridine), poly(4-vinylpyridine)-N-oxide and polystyrene resins, all showed different catalytic behaviour in terms of substrate conversion and product yield, depending on the experimental conditions used. It is noteworthy that the novel heterogeneous catalysts were found to be stable, it being possible to effect their recover and recycle at least five times without appreciable loss of activity.     

Development of smooth finishes in electrostatic fluidized bed (EFB) coating process of high-performance thermoplastic powders (PPA 571 H)

This paper deals with the analysis of the evolution of the surface morphology of metal substrates coated with high-performance thermoplastic powders, namely PPA 571 H, by using electrostatic fluidized bed (EFB) process. Attention has been particularly focused on the relationship between baking time and temperature of EFB coated substrates and the morphological characteristics of the resulting polymeric films.

First, thermal behaviour of PPA 571 H polymeric powders was characterized by using standard calorimetric techniques. Accordingly, PPA 571 H melting kinetic was experimentally deduced. Based upon experimental findings, predictive analytical model was also developed and employed to trace ‘iso-conversion’ curves out.

Second, metal substrates, made from low carbon steel (AISI 1040), were EFB coated and baked at several baking time and temperatures. Combined analyses of scanning electron and confocal microscopes were led to measure the evolution of the films surface morphology under different baking conditions. Accordingly, a relationship between film morphologies and melting degree was sought. Consistent trends of roughness parameters versus baking parameters were found, with smoother finishes of the polymeric films being achieved for higher degrees of melting, that is, for higher baking temperature and time. Full maps and related analytical models of the finishing levels according to baking parameters were also built up, hence providing first useful indications to powder coaters on how to best deal with their settings.     

Enzymatic Conversion of Unnatural Amino Acids by Yeast D‐Amino Acid Oxidase

Unnatural amino acids, particularly synthetic α‐amino acids, are becoming crucial tools for modern drug discovery research. In particular, this application requires enantiomerically pure isomers. In this work we report on the resolution of racemic mixtures of the amino acids d,l ‐naphthylalanine and d,l ‐naphthylglycine by using a natural enzyme, D ‐amino acid oxidase from the yeast Rhodotorula gracilis. A significant improvement of the bioconversion is obtained using a single‐point mutant enzyme designed by a rational approach. With this D ‐amino acid oxidase variant the complete resolution of all the unnatural amino acids tested was obtained: in this case, the bioconversion requires a shorter time and a lower amount of biocatalyst compared to the wild‐type enzyme. The simultaneous production of the corresponding α‐keto acid, a possible precursor of the amino acid in the L ‐form, improves the significance of the procedure.     

Fiber diffraction study of spicules from marine sponges

A synchrotron radiation fiber diffraction structural study of the axial filament of siliceous spicules from two species of marine sponges (the Demosponge Geodia cydonium and the Hexactinellid Scolymastra joubini) was carried out. The sharpness of the spots in the diffraction patterns indicated that the protein units in the filament of both samples were highly organized. A possible explanation is that the arrangement of the protein units is similar to that of the pores in highly ordered siliceous mesoporous materials. Nevertheless, the diffraction patterns are quite different for the two types of spicules. The pattern of G. cydonium is consistent with a regular 2D hexagonal lattice of protein units in the direction perpendicular to the spicule axis, with a repeating distance of 5.8 nm; the units are linked to form fibers along the axis. The pattern of S. joubini indicates the presence of two different 2D lattices in which the repeating protein units are inclined by +50 degrees and -50 degrees with respect to the elongation axis; the distance between the units increases to 8.4 nm. This 2D model is consistent with hexagonal packing of spirally oriented cylindrical protein units elongated along the filament axis.