A new device for objective assessment of skin type in Caucasians by violet light reflectance

In the present study, we tested a new device called skin phototype diagnosis (SPD) built for the purpose of objectively determining skin phototype. We compared its performance with that of phototype determinations according to Fitzpatrick method and on tristimulus colorimetry (Minolta CR-200). Our population consisted of 100 subjects of Caucasian race (60 female, 40 male; mean age 33 years). Skin colour was measured with both devices (SPD and Minolta CR-200) on the medial surface of the arm (constitutional skin colour). Our study showed that the SPD gave a better representation of Fitzpatrick phototype, showing 89% concordance (evaluated by classification matrix) as against the 71% concordance of the L(*)a(*)b(*) and Yxy colorimetric systems. The present results are important because evaluation of phototype with the SPD device is easy, fast, objective and reliable. Moreover, this instrument has potential applications in cosmetology and in photodermatology.     

Microscopical characterization of nanocapsules templated on ionic crystals and biological cells toward biomedical applications

Nanocapsules, fuzzy assemblies of polyelectrolyte, represent a comparatively new class of colloids with controlled nanostructure and tunable properties. Due to the fact that the core as well as the dissolution influences the wall texture and the properties of the hollow capsules, the use of carbonate crystals as template is most convenient. Yeast cells constitute as a core candidate as well. They are a good system for testing the protective ability of shells and the permeability of the walls with respect to the needs of biological systems, namely, feeding and stability against attacks. The main features of the nanocapsules have been studied by two-photon, confocal, and atomic force microscopy. Nanocapsules are of biomedical interest because they can be used, for example, for the controlled release and targeting of drugs as well as for the protection of enzymes, proteins, and foreign cells.     

Auger Electron Spectroscopy Analysis of Cross-Section Surface of Oxidized Titanium Carbide Single Crystal

A TiC monocrystal was heated by three thermal cycles with isotherm at 1108 K while exposed to Ar/O₂ mixtures respectively with O₂ contents of 239, 1.0, and 324 ppm. The reactivity was detected with a homemade device based on two identical solid electrolyte oxygen sensors connected to a quadrupole mass spectrometer (QMS). The oxidized sample was cleaved by impact bending under high vacuum and the cross section investigated by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM) techniques. Both area and profile AES spectra were acquired by using a 70 nm diameter beam. Spectral changes have been analyzed to identify chemical species present at the TiC/TiO₂ interface. A model for high-temperature oxidation of TiC has been proposed. It implies oxygen diffusion through a protective TiO₂ layer and the existence of two inner interfaces: TiC/TiC_{1− x} O _x and TiC_{1− x} O _x /TiO₂.     

An electrothermal functional model of the microwave FET suitable for nonlinear simulation

This article introduces a CAD-oriented functional model of the microwave FET depending on temperature as an additional state variable in addition to the usual gate and drain voltages. The model is fully conservative and non-quasistatic, and thus considerably more advanced than other currently available empirical models. A novel parameter extraction strategy allows the simultaneous determination of the voltage and temperature dependence of the constitutive relations, making use of a set of DC measurements and bias-dependent scattering matrices obtained at a single ambient temperature. The model can be coupled to a harmonic-balance algorithm for the efficient electrothermal simulation of temperature-dependent nonlinear microwave circuits, which the authors discussed in a previous article.     

Interaction of polyelectrolytes and their composites with living cells

Since the layer-wise polyelectrolyte deposition offers the opportunity to modify surfaces for biomedical applications, interactions and toxicity between polyelectrolytes and living cells become interesting. The aim of the present work is to determine the different factors such as contact area, charge, and transplantation site that influence the cell reaction to a specific polymer. We found that toxicity is influenced by all these factors and cannot be tested easily in a model.     

Nanocapsules with functionalized surfaces and walls

With the possibility of creating and handling nanometer-sized objects, it became popular to dream of future miniaturized tools allowing completely new applications in medicine and technology. Mother nature created during evolution many such self-assembled highly sophisticated and robust objects, and it is very tempting to modify them for other purposes: artificial cells as intelligent submarines floating in the bloodstream attacking cancer cells, single-molecule detection and manipulation allowing the bottom-up construction of devices, and so on. Nanobiotechnology became a hot topic and significant budgets have been attributed to it. However, caution has to be paid that unrealistic dreams might have a fairly negative effect on the taxpayer seeing unkept promises. In this paper, we explore the possibilities of using biological substances in material science.     

Design and bioproduction of a recombinant multi(bio)functional elastin-like protein polymer containing cell adhesion sequences for tissue engineering purposes

Genetic engineering techniques were used to design and biosynthesise an extracellular matrix (ECM) analogue. This was designed with a well-defined molecular architecture comprising different functional domains. The structural base is a elastin-derived repeating unit, which confers an adequate elastic characteristic. Some of these elastin domains have been modified to contain lysine; this amino acid can be used for crosslinking purposes. The polymer also contain periodically spaced fibronectin CS5 domains enclosing the well-known cell attachment sequence REDV. Finally, the polymer has target sequences for proteolitic action. These sequences are those found in the natural elastin and are introduced to help in the bioabsorption of the polymer. In addition, these proteolitic sequences were chosen in a way that, after proteolitic action, the released fragments will be bioactive. These fragments are expected to promote cell proliferation activity, angiogenesis and other bioactivities of interest for tissue growing, repairing and healing. After purification, the resulting polymers proved to be of high purity and correct sequence. Glutaraldehyde has shown to be a cross-linking agent for this polymer, yielding insoluble hydrogel matrices. This work is framed in a long term project aimed to exploit the power of genetic engineering for the design and bioproduction of complex ECM analogues showing the rich complexity and multi (bio)functionality of the natural matrix.     

Life model based on space-charge quantities for HVDC polymeric cables subjected to voltage-polarity inversions

This paper illustrates a new model that enables the estimation of life of polymeric insulation subjected to DC stress, both in the presence and in the absence of voltage polarity inversions. The derivation of the model parameters is based on the results of space charge measurements and accelerated life tests realized at constant DC stress, which allows the characterization of the performance of insulating materials under DC electrical stress to be carried out in short times. The expected life of a cable in service can be evaluated by means of this model, provided that the rate of voltage inversions expected during its life is known or estimated. The model is applied here to results of tests carried out on polyethylene-based materials for cable insulation, and model parameters are calculated resorting to two different approaches. A satisfactory fitting of life test results is achieved, thus confirming the validity of the proposed model.