Effect of Processing Conditions on the Crystallization Behavior and Destabilization Kinetics of Oil-in-Water Emulsions

The objective of this research was to systematically study the effect of processing conditions on the crystallization behavior and destabilization mechanisms of oil-in-water emulsions. The effect of crystallization temperature (T _c) and homogenization conditions on both thermal behavior and destabilization mechanisms were analyzed. Results show that the crystallization of lipids present in the emulsions was inhibited when compared with bulk lipids as evidenced by a lower onset and peak temperature (T _on and T_p, respectively) in differential scanning calorimetry crystallization exotherms. The smaller the droplet size in the emulsion, the more significant the inhibition (lower T _on and T _p). Lower values of T _on and T _p were not necessarily indicators of emulsion stability. Homogenization conditions not only affected the T _on and T _p of crystallization but also the crystallization profile of the samples. Lipids present in emulsions with small droplets were crystallized and melted in a less fractionated manner when compared to lipids in bigger droplets or even to the bulk lipids. The amount of lipid crystallized as evidenced by enthalpy values, did not have a direct relationship with the emulsions stability. Although enthalpy values increased as T _c decreased, the destabilization kinetics did not follow the same tendency as evidenced by back scattering measurements.     

Diffusion soldering using a Gallium metallic paste as solder alloy: study of the phase formation systematics

In this work preliminary results are reported on the characterization of Pb-free joints produced by using a diffusion soldering method at a process temperature of 700 °C during 20 min. The solder alloy is a metallic paste involving Ga and Al and Ni powder, and the substrates are Cu and Ni. The dissolution and diffusion-reaction processes, which take place at the interfaces of the interconnection zone, have been investigated by means of SEM and EPMA. A solid solution and intermetallic compounds (IMCs) with high melting point form as layers almost free from defect, allowing service temperatures about 500 °C higher than the process temperature. The phase stability sequence starting from the Ni to the Cu interface is the following: α′-Ni₃Ga, γ-Cu₉Ga₄, β-Cu₃Ga and (Cu) solid solution of the Ga–Cu system. The relative reaction front displacement of the layers and the implications of the present findings for the applicability of the diffusion-soldering method are also discussed.     

An Optical Thermometer Exploiting Periodically Poled Lithium Niobate for Monitoring the Pantographs of High-Speed Trains

Optical thermometers have been widely investigated. Here, the temperature behavior of second harmonic generation (SHG) in periodically poled lithium niobate (PPLN) substrates is analyzed; indeed, the QPM tuning in PPLN devices and the obtained SHG efficiency depend on the crystal thermal expansion and dispersion, particularly in the case of guided propagation. Therefore, such devices are suitable to realize optical thermometers for demanding applications. This investigation originated with the request of a thermometer to be installed on the pantographs of high-speed trains. Therefore, it must be sturdy and reliable, but it has even to work in an EMD environment. The temperature behavior of the SHG was theoretically modeled and experimentally validated at 1550 nm, in both bulk propagation and APE channel waveguides. In the first case, by using a 10-mW source, which was obtained from a laser diode and a fiber amplifier, an accuracy of 0.3 degC was found. The pump power was about three orders of magnitude smaller in guided propagation. In view of testing on the trains, our investigation resulted in the design of a device without mechanical contacts with the input and output fibers. Since it works in free propagation, there are no serious alignment and packaging problems. The performances, which are expected to be the same of our tests, widely satisfy all the requirements for working effectively in a strongly hostile and EMD environment and for giving accurate measurements on a wide range of temperatures     

Correlation of analyte structures with biosensor responses using the detection of phenolic estrogens as a model

The apparent increase in hormone-induced cancers and disorders of the reproductive tract in wildlife and humans has led to a search for an accurate and reliable method for monitoring endocrine-disrupting chemicals (EDCs). This study presents a generic approach that may allow researchers to establish screening procedures for potential EDCs by correlating the analyte structures with biosensor responses and explain possible reaction mechanisms. A simple amperometric tyrosinase-based biosensor (Tyr-CPE) has been developed for the detection of phenolic EDCs. The investigation of the enzymatic oxidation of selected phenolic estrogens was first carried out using UV-vis spectroscopy. The result was used to correlate sensor responses to enzymatic activity. Natural phytoestrogen polyphenols, including resveratrol (RES), genistein (GEN), and quercetin (QRC), were compared with synthetic estrogens, for example, bisphenol A (BPhA), nonylphenol (NPh), and diethylstilbestrol (DES). The Tyr-CPE biosensor resulted in rapid, simple, and accurate measurement of phenolic estrogens with varying degrees of sensitivity, selectivity, and response times. The sensor responses have been evaluated for the detection of binary and tertiary mixtures of EDCs and natural estrogens. The results showed that BPhA could be successfully discriminated in a composite mixture containing NPh and DES at various ratios. In the case of natural phenolic estrogens GEN, RES, and QRC, the sensor allows the determination of a total phenolic content. The sensor was also validated for the detection of BPhA in a real environmental water sample, and the results was compared with standard ASTM method 9065. Mechanistically, our results indicated that the number of OH groups, the nature and the position of aryl ring substituents, or both could affect the detection limit and the biosensor sensitivity.     

Subsumptive general solutions and parametric general solutions of Post equations

In this paper we generalize Rudeanu’s results from [13] to Post algebras. We give a necessary and sufficient condition for the existence of a Post function f such that the set of solutions of equation f(x) = 0 is a given interval. We also prove that every Post transformation is the parametric solution of some consistent Post equation.