Thermal analysis of CuMg alloys deformed by equal channel angular pressing

Journal of Thermal Analysis and Calorimetry - The thermal behavior of two copper alloys, with 0.2 and 0.5 mass % of Mg, was analyzed after severe plastic deformation processing by Equal Channel...     

Botanical Characterization of Guiera senegalensis Leaves

Guiera senegalensis J. F. Gmel. (Combretaceae) is one of the most important West African medicinal plants, often used to treat a variety of microbial infections. The most frequently used plant part is the leaf, its medicinal use being corroborated by several in vitro antimicrobial activity studies. However, quality criteria for pharmaceutical use, including botanical identification, are not yet determined. Aiming the establishment of such criteria, the present work deepens today's knowledge on G. senegalensis leaf morphology and anatomy, the anatomical characters of both leaf transversal section and powdered leaves being hereby presented for the first time. The most useful characters for identification purposes are leaf isobilateral organization, with similar upper and lower surfaces and a palisade parenchyma on both surfaces; trichome insertion points on both epidermis, surrounded by polar arrangements of cells; tomentose indumentum on the upper epidermis consisting of compartmented and uniseriated trichomes with long, curved, or straight terminal cells; brown scales, isolated or inserted into the epidermis, formed by radially arranged cells surrounding a central cell, with a more or less circular form and a conspicuous base; calcium oxalate cluster crystals, isolated or inserted into the palisade parenchyma and absent in lateral veins.     

Determination of 3-MCPD by GC-MS/MS with PTV-LV injector used for a survey of Spanish foodstuffs

3-Monochloropropane-1,2-diol (3-MCPD) is the most common chemical contaminant of the group of chloropropanols. It can occur in foods and food ingredients at low levels as a result of processing, migration from packaging materials during storage and domestic cooking. A sensitive method for determination of 3-MCPD in foodstuffs using programmable temperature vaporization (PTV) with large-volume injection (LVI) gas chromatography (GC) with tandem mass spectrometry detection (MS/MS) has been developed and optimized. The optimization of the injection and detection parameters was carried out using statistical experimental design. A Plackett-Burman design was used to estimate the influence of resonance excitation voltage (REV), isolation time (IT), excitation time (ET), ion source temperature (IST), and electron energy (EE) on the analytical response in the ion trap mass spectrometer (ITMS). Only REV was found to have a statically significant effect. On the other hand, a central composite design was used to optimize the settings of injection temperature (T(inlet)), vaporization temperature (T(vap)), vaporization time (t(vap)) and flow (Flow). The optimized method has an instrumental limit of detection (signal-to-noise ratio 3:1) of 0.044 ng mL(-1). From Valencian, Spain, supermarkets 94 samples of foods were surveyed for 3-MCPD. Using the optimized method levels higher than the limit established for soy sauce by the European Union were found in some samples. The estimated daily intake of 3-MCPD throughout the investigated foodstuffs for adults and children was found about 0.005 and 0.01%, respectively, of the established provisional tolerable daily intake.     

Diversity oriented microwave-assisted synthesis of (-)-steganacin aza-analogues

A novel microwave-assisted, highly efficient protocol for the synthesis of hitherto unknown aza-analogues of (-)-Steganacin, a naturally occurring bisbenzocyclooctadiene lignan lactone with potent antileukemic and tubulin polymerization inhibitory activity, has been developed. Focused microwave irradiation is demonstrated to be highly beneficial in promoting the three crucial steps of the sequence to effect the final ring closure: the Suzuki-Miyaura reaction, Cu-mediated A3-coupling, as well as the intramolecular Huisgen 1,3-dipolar cycloaddition.     

Ionic Liquid Crystalline Calixarene with Photo-Switchable Proton Conduction

We have developed a new strategy for the preparation of a light-responsive ionic liquid crystal (LC) that shows photo-switchable proton conduction. The ionic LC consists of a bowl-shaped calix[4]arene core ionically functionalized with azobenzene moieties. The non-covalent architectures were obtained by the formation of ionic salts between the carboxylic acid group of an azo-derivative and the terminal amine groups of a calixarene core. The presence of ionic salts results in a hierarchical self-assembly process that extends to the formation of a nanostructured lamellar LC arrangement (smectic A phase). In this LC phase, the ionic LC calixarene is able to display proton conductive properties, since the ionic nanosegregated areas (formed by the ionic pairs) generate the continuous channels that favor proton transport. The optical and photo-responsive properties were studied by UV-Vis spectroscopy, demonstrating that the azobenzene moieties of the ionic LC undergo reversible (E)-to-(Z) isomerization by irradiation with UV light. Interestingly, this (E)-to-(Z) photoisomerization results in a decrease of the proton conductivity values since the bent-shaped (Z)-isomer disrupts the lamellar LC phase. This isomerization process is totally reversible and leads to an ionic LC material with unique photo-switchable proton conductive properties.     

Effect of iron salt on the color removal of water containing the azo-dye reactive blue 69 using photo-assisted Fe(II)/H2O2 and Fe(III)/H2O2 systems

The effect of chloride, sulfate and nitrate anions on the color removal of water containing the azo-dye reactive blue 69 (RB69) in acidic solution, by using photo-assisted Fenton process with Fe(II)/H₂O₂ and Fe(III)/H₂O₂ systems was investigated. Experiments were conducted in a batch reactor irradiated during 5 h with a domestic 15 W lamp with emission in the visible spectra. Experimental results showed color disappearance in the first 5 min of reaction in the photo-assisted process for all of the different salts, greatly enhancing the reaction rate with respect to the corresponding systems under dark conditions. The exception of the general trend was the Fe₂(SO₄)₃/H₂O₂/UV system, where the decolorization process is slower probably because the oxidative species generated by rupture of Fe(III)–peroxo complexes are less reactive. Total organic matter depletion and mineralization of the effluent were also tested during the experimental runs by means of total organic carbon (TOC) showing that, for most of the photo-assisted experiments high mineralization was reached after 3 h of reaction.     

Nitrosylation of Nitric‐Oxide‐Sensing Regulatory Proteins Containing [4Fe‐4S] Clusters Gives Rise to Multiple Iron–Nitrosyl Complexes

The reaction of protein‐bound iron–sulfur (Fe‐S) clusters with nitric oxide (NO) plays key roles in NO‐mediated toxicity and signaling. Elucidation of the mechanism of the reaction of NO with DNA regulatory proteins that contain Fe‐S clusters has been hampered by a lack of information about the nature of the iron‐nitrosyl products formed. Herein, we report nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) calculations that identify NO reaction products in WhiD and NsrR, regulatory proteins that use a [4Fe‐4S] cluster to sense NO. This work reveals that nitrosylation yields multiple products structurally related to Roussin's Red Ester (RRE, [Fe₂(NO)₄(Cys)₂]) and Roussin's Black Salt (RBS, [Fe₄(NO)₇S₃]. In the latter case, the absence of ³²S/³⁴S shifts in the Fe?S region of the NRVS spectra suggest that a new species, Roussin's Black Ester (RBE), may be formed, in which one or more of the sulfide ligands is replaced by Cys thiolates.