Quasi-stationary multiple stimulated Raman generation in the visible using optical fibers

Several orders of stimulated Raman scattering (SRS) in monomode and multimode fibers have been observed. The relatively low power in the visible used in the quasi-stationary regime permitted observation of sharply defined Stokes and anti-Stokes spectral lines without any continua. Results of pump-to-Stokes power conversion in a monomode fiber indicate a striking equivalence between pump power and fiber length. The dependence of multiple SRS generation/amplification with these parameters is investigated up to the limit of near total pump extinction. We propose a qualitative explanation of these facts, although a detailed theory of nonlinear behavior of fibers is wanting. Parametric four-photon mixing is again confirmed to account for the generation of stimulated anti-Stokes radiation in multimode fibers and its absolute absence in monomode fibers.     

Quasi-elastic light scattering of carnauba wax in the liquid phase: dynamics 2

Quasi-elastic light scattering of carnauba wax in the liquid phase is obtained in a heterodyne setup, and dynamic processes are analyzed through electrophoresis. Nonspherical polar clusters are found, containing a net electrical charge. An applied square-wave electric field induces drift and rotation of these clusters.These effects are dependent on strength and frequency of the applied electric field. At 373 K and in the low frequency limit the local electric field strength is approximately 70 times the strength of the applied one. This enhancement is believed to be caused by collective orientation of the clusters. The electrophoretic mobility is 1.1 X 10(-12) m2/V sec in the high frequency limit and 7.4 X 10(-11) m2/V sec in the low frequency limit. The electric dipole moment is 6.3 X 10(-16) N(-1/2) m(-1/2) where N is the cluster density/cubic meter and the net charge is about one or two elementary charges.     

Preparation and characterization of new niobophosphate glasses in the Li2O-Nb2O5-CaO-P2O5 system

In the present work we describe the synthesis, spectroscopy, thermal and chemical durability properties of the vitreous system Li₂O-Nb₂O₅-CaO-P₂O₅ (LNCP). Investigations of the short-range order by Fourier transform infrared, Raman, UV-VIS and ³¹P MAS-NMR spectroscopies suggest that the network former glass consists of Nb octahedra linked to pyro/orthophosphate units through Nb—O—P bonds. The presence of modifier cations (Li⁺ and Ca²⁺) promotes depolymerization of the P—O—P chains, yielding pyro/orthophosphate units. The presence of this kind of structure accounts for the improvement of the chemical durability at low pH when the Nb content in the LNCP glass composition is high. The density and linear refractive indices of LNCP glasses increased linearly as the Nb₂O₅/P₂O₅ molar ratio increased, as a consequence of P₂O₅ substitution by Nb₂O₅ as the glassformer. The dependence of the glass transition temperature, the softening temperature and the crystallization temperature on the Nb₂O₅/P₂O₅ ratio exhibits the same behavior. On the other hand, the thermal expansion coefficient decreases with the increased Nb₂O₅/P₂O₅ ratio.     

Functional and comparative study of lingual papillae in four species of bear (Ursidae) by scanning electron microscopy

The eight current species of bear (Ursidae) are widely distributed throughout Europe, Asia, and America. They are mainly encountered in the northern hemisphere, except for the spectacled bear and the sun bear, which are also found in the south of the equator. Adaptations of the masticatory apparatus (teeth, tongue, and musculature) to diet are one of the factors that imply the greatest structural changes in the cranium. This diet may be carnivorous, herbivorous, melliferous, or insectivorous, with one type of food predominating according to the time of year. The way in which food is eaten determines the morphology of the lingual surface; generally speaking, all bears put their mouth to the food, which, initially, they lick or they let the food stick to their tongue, as occurs when insects are eaten. As in all mammals, a distinction can be made between mechanical and gustatory papillae and the development and distribution of which depend on the species and their eating habits. In this study of the complete tongues of four species of adult bears, we describe the morphology of the lingual surfaces, the different types of papillae, their characteristics, and topographic distribution. It was seen that there were five main types of lingual papillae: filiform, conical, fungiform, foliate, and vallate. Morphology of the microgrooves and pores was similar to that observed in other mammals. In general, there were no great differences among the four species of bears studied, perhaps due to the similarity in the kind of food they consume in captivity.     

R&R (repeatability and reproducibility) gage study applied on gaps’ measurements of aircraft assemblies made by a laser technology device

This paper presents the competitive advantages when a type of laser instrument is applied in the aircraft production environment. This contribution reports the winnings that could be achieved when measurements made by a laser technology are done. This proposed application comprises a modern and suitable resource that contributes to a higher performance and relevant gains in competitiveness for the companies. It can provide a high level of accuracy, flexibility, productivity, quality and speed on the manufacturing floor. A case study, based on a statistics gage named repeatability and reproducibility method, is done to demonstrate the gained advantages and benefits when the laser device is used. This study aims to evaluate and compare the variability of measurements between a manual instrument of measurement and a laser instrument during aircraft production processes and its relevant quality issues for the business.     

Effect of grain and secondary phase morphologies in the mechanical and damping behavior of Al7075 alloys

The present study evaluates the role of the microstructure in the static and dynamic mechanical behavior of as-cast Al7075 alloy promoted by ultrasonic treatment (US) during solidification. The characterization of samples revealed that US treatment promoted grain and intermetallics refinement, changed the shape of the intermetallic phases (equilibrium phases of soluble M and/or T (Al, Cu, Mg, Zn) and their insoluble Al-Cu-Fe compounds) and lead to their uniform distribution along the grain boundaries. Consequently, the mechanical properties and damping capacity above critical strain values were enhanced by comparison with values obtained for castings produced without US vibration. This results suggest that the grain and secondary phases refinement by US can be a promising solution to process materials to obtain high damping and high strength characteristics.     

The effect of ultrasonic irradiation on the crystallinity of nano-hydroxyapatite produced via the wet chemical method

Nanohydroxyapatite (nHAp) powders were produced via aqueous precipitation by adopting four different experimental conditions, assisted or non-assisted by ultrasound irradiation (UI). The nHAp powders were characterized by X-ray diffraction, energy-dispersive X-ray fluorescence, Raman and attenuated total reflection Fourier transform infrared spectroscopies, which showed typical surface chemical compositions of nHAp. Analysis found strong connections between UI and the crystallization process, crystal growth properties, as well as correlations between calcination and substitution reactions.     

Spray drying conditions for orange juice incorporated with lactic acid bacteria

This work aimed to develop an orange juice powder by spray drying with lactic acid bacteria (Lactobacillus plantarum 299v and Pediococcus acidilactici HA‐6111‐2), testing their survival both during drying and storage (room temperature and 4 °C). Initially, the best conditions for spray drying were chosen to allow the best survival of each LAB: (i) inlet air temperature of 120 °C and (ii) 0.5:2 ratio of the orange juice soluble solids and drying agent added (prebiotics: 10 DE maltodextrin or gum Arabic). Survival of LAB was not affected by drying process, and it was higher when cultures were stored at 4 °C. A slightly higher protection was conferred by 10 DE maltodextrin, in the case of L. plantarum and at 4 °C. Pediococcus acidilactici was more resistant during storage at 4 °C, with logarithmic reductions lower than 1 log‐unit. It was demonstrated that it is possible to produce a functional nondairy product, orange juice powder supplemented with prebiotic compounds, containing viable LAB for at least 7 months, when stored at 4 °C.