Determination of the anchoring constant for a compensated binary cholesteric mixture

The optical transmission and the electric power was simultaneously recorded for the binary compensated cholesteric mixture cholesteryl chloride + cholesteryl nonanoate (70:30 molar). The values of the critical voltages U₁ and U₂ (at which the planar texture changes into a conic focal one, and the cholesteric-nematic transition take place) at different temperatures were obtained. The temperature dependence of the anchoring constant is determined.     

Recent developments in the formation and structure of tin-iron oxides by laser pyrolysis

Complex oxides demonstrate specific electric and magnetic properties which make them suitable for a wide variety of applications, including dilute magnetic semiconductors for spin electronics. A tin-iron oxide Sn_1−xFe_xO₂ nanoparticulate material has been successfully synthesized by using the laser pyrolysis of tetramethyl tin-iron pentacarbonyl-air mixtures. Fe doping of SnO₂ nanoparticles has been varied systematically in the 3-10 at% range. As determined by EDAX, the Fe/Sn ratio (in at%) in powders varied between 0.14 and 0.64. XRD studies of Sn_1−xFe_xO₂ nanoscale powders, revealed only structurally modified SnO₂ due to the incorporation of Fe into the lattice mainly by substitutional changes. The substitution of Fe³⁺ in the Sn⁴⁺ positions (Fe³⁺ has smaller ionic radius as compared to the ionic radius of 0.69 Å for Sn⁴⁺) with the formation of a mixed oxide Sn_1−xFe_xO₂ is suggested. A lattice contraction consistent with the determined Fe/Sn atomic ratios was observed. The nanoparticle size decreases with the Fe doping (about 7 nm for the highest Fe content). Temperature dependent ⁵⁷Fe Mössbauer spectroscopy data point to the additional presence of defected Fe³⁺-based oxide nanoclusters with blocking temperatures below 60 K. A new Fe phase presenting magnetic order at substantially higher temperatures was evidenced and assigned to a new type of magnetism relating to the dispersed Fe ions into the SnO₂ matrix.     

The Influence of Temperature,Storage Conditions,pH, and Ionic Strength on the Antioxidant Activity and Color Parameters of Rowan Berry Extracts

Recent trends in the food industry combined with novel methods in agriculture could transform rowan into a valuable raw material with potential technological applications. Thus, the aim of this research was to investigate the content of bioactive compounds in its fruits and to assess the color and antioxidant stability of the extracts prepared from such fruits during various thermal treatments and at different pH and ionic strength values. Various spectrophotometric methods, HPLC, and capillary electrophoresis were used to quantify the concentrations of bioactive compounds—polyphenols, carotenoids, organic acids, and to assess antioxidant activity and color. The results show that rowan berries contain circa 1.34–1.47 g/100 g of polyphenols among which include catechin, epicatechin, ferulic acid methyl ester, procyanidin B1, etc.; ca 21.65 mg/100 g of carotenoids including zeaxanthin, β-cryptoxanthin, all-trans-β-carotene, and various organic acids such as malic, citric, and succinic, which result in a high antioxidant activity of 5.8 mmol TE/100 g. Results also showed that antioxidant activity exhibited high stability when the extract was subjected to various thermal treatments, pHs, and ionic strengths, while color was mainly impacted negatively when a temperature of 100 °C was employed. This data confirms the technological potential of this traditional, yet often overlooked species.     

Photopyroelectric (PPE) Spectroscopy of Surface Reflectance for Nd2−xCexCuo4 Single Crystals

The relevance of the sample surface reflectance Rs when applying the photopyroelectric technique is demonstrated and, based on this, a method for determining Rs spectra of opaque samples, is presented. Measurements were done on single crystals of Nd₂CuO₄ and Nd_1.97Ce_0.03CuO₄ and the results were found in good agreement with the data obtained by optical methods.     

On the sonic composites subjected to severe acoustic loads

Transformation acoustics opens a new avenue towards the fabrication of a new class of sonic composites with scatterers made of auxetic materials embedded in the epoxy matrix. The design of the acoustic scatterers is based on the property of Helmoltz equations to be invariant under coordinate transformations, i.e. a specific spatial compression is equivalent to a variation of the material parameters in the original space. In this paper, the noise suppression for a wide full band-gap of frequencies is discussed for spherical shell scatterers made of auxetic materials. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Evaluating the biological potential of some new cobalt (II) complexes with acrylate and benzimidazole derivatives

This paper presents the synthesis, physico‐chemical and biological properties of four new coordination compounds with mixed ligands: acrylate ion (acr) and benzimidazole/benzimidazole derivatives with the general formula [Co(L) ₂ (acr) ₂ ]·nH ₂ O [ (1) L: benzimidazole (HBzIm), n: 0.5; (2) L: 2‐methylbenzimidazole (2‐MeBzIm), n: 0.5; (3) L: 5‐methylbenzimidazole (5‐MeBzIm), n: 0; (4) L: 5,6‐dimethylbenzimidazole (5,6‐Me₂BzIm), n: 0]. Their chemical formulae were achieved correlating the chemical analysis with mass spectrometry data, the ligands coordination modes were assigned by Fourier transform‐infrared measurements, and the trigonal bipyramidal geometry of cobalt ion in complexes was assigned by data correlation of UV–Vis‐NIR spectra and magnetic moments measurements. Single‐crystal X‐ray diffraction reveals a mononuclear structure with a pentacoordinated cobalt (II) ion, connected to two acrylato coordinated in different modes and two unidentate 5,6‐dimethylbenzimidazole ligands for compound (4) . The biological tests were performed against several microbial strains, the cytotoxicity was evaluated on HCT8 cellular lines and the cell cycle analysis was performed on HT29 cellular lines. Microbiological assays indicated that Co (II) complexes present a very good to good activity against Candida albicans 1760, Enterococcus faecium E5, Bacillus subtilis ATCC 6683 and Escherichia coli ATCC 25922. Predictive pharmacokinetic (ADME), toxicity and drug‐likeness profiles were evaluated for Co (II) complexes. Our results highlight that Co (II) complexes depicted in the present study are suitable to be used as efficient pharmacological agents.     

Thermal and mineralogical investigations of historical ceramic

The selected sample for this study represents a piece of pavement ceramics from a private collection. The ceramic (approximately XVIIIth century) comes from Campania region, Naples province. A chemical, mineralogical and morphological characterization of a Campagna ceramic piece received from a particular collection has been performed. Inductively coupled plasma-atomic emission spectroscopy—(ICP-AES) was used for the determination of Al₂O₃, CaO, Fe₂O₃, K₂O, MgO, MnO, Na₂O, and TiO₂ as major constituents and Cu, Cr, Ni, Pb, and Zn as minor and trace selected elements. There is a very important characterization method used for the control of the reaction process and of the properties of the materials obtained. Physical and mineralogical analyses were made by using the thermal behavior (thermogravimetric analysis (TG) and differential thermal analysis (DTG)) and X-ray diffraction spectrometry for the mineralogical composition. The results of these analyses allow the establishment of conclusions about several aspects of their manufacture, the origin of the raw materials and their provenance (local or imported). They provide information supporting certain archeological hypothesis. The performed analysis revealed some very interesting characteristics: lower amount of silica and increased concentration of alumina, the presence of calcium in relatively low concentration (Ca-poor ceramic) and a mineralogical composition.     

Magnetite‐polylactic acid core–shell nanoparticles by ring‐opening polymerization under microwave irradiation

The synthesis of magnetic core–shell nanoparticles consisting of magnetite cores surface‐functionalized by glycolic acid covered by polylactic acid was performed by applying the “grafting‐from” strategy, where the polymerization is initiated from the particle surface. The surface initiated ring‐opening polymerization of D,L ‐lactide was initiated by tin (II) 2‐ethylhexanoate using microwave irradiation. Core–shell nanoparticles of high colloidal stability in water were obtained in this way. The morphology of the magnetic core–shell nanostructure was determined by transmission electron microscopy, and the chemical structure was elucidated by Fourier transform infrared spectroscopy (FTIR) and X‐ray photoelectron spectroscopy. Magnetic measurements revealed superparamagnetic behavior and high magnetization values. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Histamine detection using functionalized porphyrin as electrochemical mediator

This study reports on deposition of asymmetrical substituted meso-phenyl porphyrin, 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin (CPTPP) thin films by matrix-assisted pulsed laser evaporation (MAPLE) on screen-printed electrodes, aiming for histamine detection. Raman spectrometry confirmed that CPTPP chemical structure was preserved in MAPLE-deposited thin films at 200 mJ/cm² laser fluence. Atomic force microscopy topography revealed that MAPLE-deposited thin films have a better coverage on the working electrode made of carbon compared to the ones obtained by dropcasting. Cyclic voltammetry demonstrated that CPTPP is an appropriate mediator for histamine detection in trichloroacetic acid solution. We proved that MAPLE serves as a soft technique in fabrication of porphyrin thin films and patterns.     

Differential systems with Fuchsian linear part: Correction and linearization, normal forms and multiple orthogonal polynomials

Differential systems with a Fuchsian linear part are studied in regions including all the singularities in the complex plane of these equations. Such systems are not necessarily analytically equivalent to their linear part (they are not linearizable) and obstructions are found as a unique nonlinear correction after which the system becomes formally linearizable.More generally, normal forms are found.The corrections and the normal forms are found constructively. Expansions in multiple orthogonal polynomials and their generalization to matrix-valued polynomials are instrumental to these constructions.