First-Order Phase Transitions and Hysteresis

A simple phase-field model for first-order phase transitions with hysteresis is proposed. It describes both temperature- and stress-induced transitions between austenitic and (oriented) martensitic regimes in a shape memory alloy (SMA). Finally, numerical simulations of local paths of the system are performed in the (ε,σ) and (ε,θ) planes, respectively, when either stress or temperature cyclic processes are considered and phase diffusion is neglected.     

Multivariate Optimization and Validation of a CZE Method for the Analysis of Pridinol Mesylate and Meloxicam in Tablets

A capillary zone electrophoresis method for the simultaneous determination of pridinol mesylate (PRI) and meloxicam (MEL) employing epinastine hydrochloride and piroxicam as internal standards, was developed and optimized employing experimental design and response surface methodologies. The separation was optimally achieved in less than 2 min at 30 kV in an uncoated fused-silica capillary (41.4 cm × 75 ??m I.D.), employing an 18 mmol L^?1 sodium phosphate buffer solution (pH 5.90) at 25 °C. Samples were injected in hydrodynamic mode (50 mbar, 5 s) and the analytes were spectrophotometrically detected at 200 nm. Method robustness was demonstrated by ANOVA of determinations performed under conditions slightly different from the optimum. The method was validated regarding separation selectivity (peak purity factors > 0.99), linearity and range (PRI = 17.6?C31.4 mg L^?1; MEL = 66.5?C122.5 mg L^?1), accuracy (PRI = 100.2?C101.9%; MEL = 98.9?C100.7%) and precision. The RSD values obtained were ??1.3% for injection repeatability and ??1.9% for intra-day precision. The limits of detection (1.0 and 0.9 mg L^?1) and quantification (3.3 and 16.5 mg L^?1) of PRI and MEL, respectively, were also determined. The method was successfully applied to the determination of both drugs in three brands of tablet formulations. No statistically significant differences were observed when these results were compared with those of a RP-HPLC method.     

Temperature-dependent structure of methyltributylammonium bis(trifluoromethylsulfonyl)amide: X ray scattering and simulations

We report the combined results of computational and x ray scattering studies of amorphous methyltributylammonium bis(trifluoromethylsulfonyl)amide as a function of temperature. These studies included the temperature range for the normal isotropic liquid, a deeply supercooled liquid and the glass. The low q peaks in the range from 0.3 to 1.5 A(-1) in the structure function of this liquid can be properly accounted for by correlations between first and second nearest neighbors. The lowest q peak can be assigned to real space correlations between ions of the same charge, while the second peak arises mostly from nearest neighbors of opposite charge. Peaks at larger q values are mostly intramolecular in nature. While our simulated structure functions provide an excellent match to our experimental results and our experimental findings agree with previous studies reported for this liquid, the prior interpretation of the experimental data in terms of an interdigitated smectic A phase is not supported by our simulations. In this work, we introduce a set of general theoretical partitions of real and reciprocal space correlations that allow for unambiguous analysis of all intra- and interionic contributions to the structure function and coherent scattering intensity. We find that the intermolecular contributions to the x ray scattering intensity are dominated by the anions and cross terms between cations and anions for this ionic liquid.     

Photostability of Octyl‐P‐Methoxy Cinnamate in O/W Emulsions and in SLNs Vehicled in the Emulsions

The photochemical degradation of the sunscreen p‐octyl‐methoxy‐cinnamate (OMC) was studied in different media: Finsolv TN (a fluid ester), O/W emulsion and gel‐emulsion. OMC photolysis was performed using an UVB lamp and the degradation kinetic was studied in presence of various initial concentration of the active. The study was performed comparing the naked to the SLNs form of the active and the experiments were monitored with HPLC/UV‐VIS apparatus. Results suggest that lower is the concentration of the UVB sunscreen in the formulations more pronounced is its photodegradation rate. In all the cases the inglobation of OMC into SLNs leads to an over additive UV‐blocking effect.     

Synthesis of Benzo[b]thiophene Carboxamides Connected to 4‐Arylpiperazines through a Benzylic Spacer: Potential Ligands with 5‐HT1A Binding Affinity

New benzothiophene arylpiperazine derivatives 8 (a–f) were synthesized as potential serotoninergic agents with 5‐HT_1A receptor affinity. Preparation of the derivatives was performed by treating N‐[2‐(chloromethyl)phenyl]‐4,7‐dimethoxybenzo[b]thiophene‐2‐carboxamide (7) with a series of substituted 4‐arylpiperazines.     

Preparation of β-Silyl-α,β-unsaturated Esters and 3-Silyl Allyl Alcohols

Acylsilanes react with lithium α-silyl ester enolates to provide β-silyl-α,β-unsaturated esters having predominantly the (Z) geometry. These esters were reacted with Grignard reagents and with lithium aluminum hydride to give the corresponding (Z) 3-silyl allyl alcohols.     

On modeling the dissolution of sedimentary rocks in acidic environments. An overview of selected mathematical methods with presentation of a case study

Different environmental processes utilize calcium carbonate and sedimentary rocks, for instance sedimentary rocks are used for water purification as filters and utilized also for acid remediation of process waters before being discarded. Additionally sedimentary rocks are used in another very important environmental process, wet Flue Gas Desulfurization. In this process, limestone and carbonates in general play one important role because of their dissolution and provision of the necessary amount of calcium ions used for the precipitation of gypsum. The objective of this study is to present in a first place an overview of a reduced number of specific theoretical and empirical mathematical models applied to the dissolution of carbonates in acidic environments with provision of additional developments and details, secondly a case study was presented where a suitable time of exposure and surface diffusivity obtained analytically by different methods well describe the experimental results. There were justifications for this choice. The experimental data and the related mathematical modeling were performed considering transient conditions. In the present work diverse raw materials were tested in order to reveal their suitability for wet Flue Gas Desulfurization. The research was focused on products from $\text{ CO }_{2}$ CO 2 fixation processes materials as well as other types of limestone samples. In this way it was found that also waste materials from different environmental processes, like $\text{ CO }_{2}$ CO 2 fixation can be used for Flue Gas Desulfurization.     

Pulse Respirometry in Two-Phase Partitioning Bioreactors: Case Study of Terephthalic Acid Biodegradation

Two-phase partitioning bioreactors (TPPBs) are based on the addition of an organic phase, often called vector, to a bioreactor in order to increase mass transfer of oxygen or gaseous substrates from the gaseous phase to the aqueous phase. In TPPBs, like in any other reactor design, the characterization of the bioprocess is often required for design, control, and operation purposes. Pulse respirometry is a method that allows for microbial processes characterization through the determination of several stoichiometric and kinetic parameters with relatively little experimental effort. Despite its interest and its previous application in countless applications, pulse respirometry has never been applied in TPPBs. In this work, pulse respirometry was assessed in a model TPPB degrading terephthalic acid and using Elvax? as solid vector to enhance oxygen transfer. The results indicated that the addition of 10 to 20 % Elvax increased oxygen transfer by up to 97 %, compared to control with no vector. Pulse respirometry was successfully applied and allowed for the determination of the growth yield, the substrate affinity constant, and the maximum growth rate, within other. It is concluded that pulse respirometry is a useful method, not only for the characterization of processes in TPPBs but also for the selection of a vector within several brands commercially available.