Optimization of a holographic memory setup using an LCD and a PVA-based photopolymer

Holographic data pages were stored in a polyvinyl alcohol (PVA)/acrylamide (AA) photopolymer. This material is formed of AA photopolymers which are considered interesting materials for recording holographic memories. A liquid crystal device was used to modify the object beam and store the data pages in the material. During the storage process, some parameters like exposure time, beam ratio and reading beam intensity were controlled to obtain high image quality after the reconstruction process. The bit error rate (BER) was calculated fitting the histograms of the images to determine what parameters improve the quality of the images.     

Thermal diffusivity study of cheese fats by thermal lens detection

In this paper we used thermal lens spectrometry to determine the thermal diffusivity of cheese fats. We have used equal concentrations of cheese fats from oaxaca, chihuahua, gouda, manchego and mozzarella cheeses at 42°C temperature. The two lasers mismatched mode experimental configuration was used with a He-Ne laser, as a probe beam and an Ar⁺ laser as the excitation one. The characteristic time constant of the transient thermal lens was obtained by fitting the theoretical expression to the experimental data in order to obtain the thermal diffusivity of the cheese fat samples. This measured thermal property may contribute to a better understanding of the cheese fats quality, which is very important in food industry.     

Synthesis of heterocyclic compounds. XXIV. Synthesis of pyridines from β-substituted α-phenylacrylonitriles

The reaction of malononitrile with α-phenylcinnamonitriles in ethanolic sodium ethanethiolate is studied as a convenient route to 2-amino-4-aryl-5-cyano-6-ethylthio-3-phenyl-3,4-dihydropyridines ( 5 ) and the corresponding pyridines 6 . From the study of the structure of 5a (Ar = Ph) we can conclude that this cyclization reaction proceeds via a site-selective addition of the ethanethiolate to the cyano group i of the 1,3-tricarbonitrile ( 2 ).     

Three-dimensional recomposition of the absorption field inside a nonbuoyant sooting flame

A remote scanning retrieval method was developed to investigate the soot layer produced by a laminar diffusion flame established over a flat plate burner in microgravity. Experiments were conducted during parabolic flights. This original application of an inverse problem leads to the three-dimensional recomposition by layers of the absorption field inside the flame. This technique provides a well-defined flame length that substitutes for other subjective definitions associated with emissions.     

Synthesis and structural characterization of Ba(Ln2/3B1/3)O3 (Ln=Dy, Gd and Sm; B=Mo or W) complex perovskites

We describe in this work the synthesis and crystal structure of five rare earth and Mo(VI) or W(VI) containing complex perovskites. The compounds studied are Ba(Dy_2/3Mo_1/3)O₃, Ba(Dy_2/3W_1/3)O₃, Ba(Gd_2/3Mo_1/3)O₃, Ba(Gd_2/3W_1/3)O₃ and Ba(Sm_2/3W_1/3)O₃ and were prepared starting from solutions, by the polymeric precursors method. Structural characterization by HREM, SAED and powder XRD revealed the five compounds to be ordered cubic perovskites, SG Fm-3m (225), with a cell parameter double of that of a simple perovskite cell and increasing as the size of the trivalent lanthanide ion increases (Dy<Gd<Sm).     

Liquid-vapor isotherm in a closed single-component system with droplets or bubbles in smooth crevices

A thermodynamic model in order to study a single-component system where droplets or bubbles are inside smooth crevices is presented. Liquid-vapor interface curvature radius can change its sign as the droplet or bubble volume change. The results suggest that there is always dispersed phase inside smooth crevices of microscopic dimensions, even in the expected single-phase region. Thus, the occurrence of an anti-ripening phenomenon is predicted from a microscopic point of view; meanwhile the occurrence of a ripening phenomenon is energetically favorable at a macroscopic scale. The relevance of these results on the heterogeneous nucleation process is analyzed.     

A finite strain contact model for mixed lubricated surfaces in forming processes

For an accurate simulation of forming processes, it is of paramount importance to model the different lubrication regimes that can develop at the contact interface. These might vary from zone to zone of the forming piece, and from one regime to another, resulting in forces of different nature and magnitude. In these cases, the use of the classical Coulomb friction law will be clearly not sufficient to capture, in a suitable manner, the variety of forces applied on the forming piece.     

Stochastic uniform observability of linear differential equations with multiplicative noise

The aim of this paper is to give a deterministic characterization of the uniform observability property of linear differential equations with multiplicative white noise in infinite dimensions. We also investigate the properties of a class of perturbed evolution operators and we used these properties to give a new representation of the covariance operators associated to the mild solutions of the investigated stochastic differential equations. The obtained results play an important role in obtaining necessary and sufficient conditions for the stochastic uniform observability property.