Analysis of natural red dyes (cochineal) in textiles of historical importance using HPLC and multivariate data analysis

A new analytical approach based on high-performance liquid chromatography with diode array detector (HPLC-DAD) and multivariate data analysis was applied and assessed for analyzing the red dye extracted from cochineal insects, used in precious historical textiles. The most widely used method of analysis involves quantification of specific minor compounds (markers), using HPLC-DAD. However, variation in the cochineal markers concentration, use of aggressive dye extraction methods and poor resolution of HPLC chromatograms can compromise the identification of the precise insect species used in the textiles. In this study, a soft extraction method combined with a new dye recovery treatment was developed, capable of yielding HPLC chromatograms with good resolution, for the first time, for historical cochineal-dyed textiles. After principal components analysis (PCA) and mass spectrometry (MS), it was possible to identify the cochineal species used in these textiles, in contrast to the accepted method of analysis. In order to compare both methodologies, 7 cochineal species and 63 historical cochineal insect specimens were analyzed using the two approaches, and then compared with the results for 15 historical textiles in order to assess their applicability to real complex samples. The methodology developed here was shown to provide more accurate and consistent information than the traditional method. Almost all of the historical textiles were dyed with Porphyrophora sp. insects. These results emphasize the importance of adopting the proposed methodology for future research on cochineal (and related red dyes). Mild extraction methods and HPLC-DAD/MSⁿ analysis yield distinctive profiles, which, in combination with a PCA reference database, are a powerful tool for identifying red insect dyes.     

Existence of a Weak Solution in L p to the Vortex-Wave System

The vortex-wave system is a coupling of the two-dimensional vorticity equation with the point-vortex system. It is a model for the motion of a finite number of concentrated vortices moving in a distributed vorticity background. In this article, we prove existence of a weak solution to this system with an initial background vorticity in L ^p , p>2, up to the time of first collision of point vortices.     

Photochemistry and vibrational spectra of matrix-isolated methyl 4-chloro-5-phenylisoxazole-3-carboxylate

Methyl 4-chloro-5-phenylisoxazole-3-carboxylate (MCPIC) has been synthesized, isolated in low temperature argon and xenon matrices, and studied by FTIR spectroscopy. The characterization of the low energy conformers of MCPIC was made by undertaking a systematic investigation of the DFT(B3LYP)/6-311++G(d,p) potential energy surface of the molecule. The theoretical calculations predicted the existence of three low energy conformers. Two of them (I and II) were observed experimentally in the cryogenic matrices. The third one (III) was found to be converted into conformer II during deposition of the matrices, a result that is in agreement with the predicted low III → II energy barrier (<0.3 kJ mol(-1)). In situ UV irradiation (λ > 235 nm) of matrix-isolated MCPIC yielded as final photoproduct the corresponding oxazole (methyl 4-chloro-5-phenyl-1,3-oxazole-2-carboxylate). Identification of the azirine and nitrile-ylide intermediates in the spectra of the irradiated matrices confirmed their mechanistic relevance in the isoxazole → oxazole photoisomerization.     

Study of the thermal behavior of Al(III) and In(III)-diclofenac complexes in solid state

The Al and In-diclofenac compounds were prepared. Thermogravimetry (TG) and X-ray diffraction powder patterns were used to characterize these compounds. Details concerning the dehydration and thermal decomposition as well as data of kinetic parameters have been described here. The kinetic studies of these stages were evaluated from several heating rates with mass sample of 2 and 5 mg in open crucibles under nitrogen atmosphere. The results of the present study improve the knowledge on these compounds including their dehydration and thermal stability. The obtained data leads to a dependence on the sample mass, which results in two kinetic behavior patterns.     

Evaluation of a glycerol derived biofuel by thermal analysis

This work describes thermal analysis evaluation of a glycerol derived compound (fatty acid esters of (2,2-dimethyl-1,3-dioxolan-4-yl) methanol) developed to work as a biofuel. Mixtures of these ketal–glyceryl esters with fatty acid methyl esters typical of soybean biodiesel were prepared and evaluated in relation to biodiesel critical thermal properties such as temperature of crystallization, thermal stability and volatilization measured by differential scanning calorimetry and thermogravimetric analysis. The volatility of the products containing fatty acid methyl esters and (2,2-dimethyl-1,3-dioxolan-4-yl) methyl esters could be predicted by thermogravimetric analyses conducted in nitrogen that avoided time consuming distillation and greatly reduced material expenditure.     

Effect of alkyl chain length and hydroxyl group functionalization on the surface properties of imidazolium ionic liquids

Properties of the surface of ionic liquids, such as surface tension, ordering, and charge and density profiles, were studied using molecular simulation. Two types of modification in the molecular structure of imidazolium cations were studied: the length of the alkyl side chain and the presence of a polar hydroxyl group at the end of the side chain. Four ionic liquids were considered: 1-ethyl-3-methylimidazolium tetrafluoroborate, [C(2)C(1)im][BF(4)]; 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate, [C(2)OHC(1)im][BF(4)]; 1-octyl-3-methylimidazolium tetrafluoroborate, [C(8)C(1)im][BF(4)] and 1-(8-hydroxyoctyl)-3-methylimidazolium tetrafluoroborate, [C(8)OHC(1)im][BF(4)]. The surface tension was calculated using both mechanical and thermodynamic definitions, with consistent treatment of the long-range corrections. The simulations reproduce the available experimental values of surface tension with a maximum deviation of ±10%. This energetic characterization of the interface is completed by microscopic structural analysis of orientational ordering at the interface and density profiles along the direction normal to the interface. The presence of the hydroxyl group modifies the local structure at the interface, leading to a less organized liquid phase. The results allow us to relate the surface tension to the structural ordering at the liquid-vacuum interface.     

Two-dimensional incompressible viscous flow around a small obstacle

In this work we study the asymptotic behavior of viscous incompressible 2D flow in the exterior of a small material obstacle. We fix the initial vorticity ω₀ and the circulation γ of the initial flow around the obstacle. We prove that, if γ is sufficiently small, the limit flow satisfies the full-plane Navier–Stokes system, with initial vorticity ω₀ + γδ, where δ is the standard Dirac measure. The result should be contrasted with the corresponding inviscid result obtained by the authors in Iftimie et al. (Comm. Part. Differ. Eqn. 28, 349–379 (2003)), where the effect of the small obstacle appears in the coefficients of the PDE and not only in the initial data. The main ingredients of the proof are L ^p − L ^q estimates for the Stokes operator in an exterior domain, a priori estimates inspired on Kato’s fixed point method, energy estimates, renormalization and interpolation.     

Monitoring of structures or mechanical components by an acoustoultrasonic signature technique

This paper describes a methodology for adapting the acoustoultrasonic technique for use in monitoring structures or mechanical components. As a practical example, the adaptation of the technique for monitoring fatigue tests on front suspension arms is considered. From this particular example, it will be shown that the procedure is suitable for application to more general cases. The results of a number of fatigue tests carried out at the Fiat Research Center on a typical component test rig are also presented.     

Optimal discrete Morse functions for 2-manifolds

Morse theory is a powerful tool in its applications to computational topology, computer graphics and geometric modeling. It was originally formulated for smooth manifolds. Recently, Robin Forman formulated a version of this theory for discrete structures such as cell complexes. It opens up several categories of interesting objects (particularly meshes) to applications of Morse theory. Once a Morse function has been defined on a manifold, then information about its topology can be deduced from its critical elements. The main objective of this paper is to introduce a linear algorithm to define optimal discrete Morse functions on discrete 2-manifolds, where optimality entails having the least number of critical elements. The algorithm presented is also extended to general finite cell complexes of dimension at most 2, with no guarantee of optimality.