Experimental (X-ray Diffraction,UV–Vis Spectroscopy) and DFT Studies of 1-Ethyl-3-methylquinoxaline-2-thione

Russian Journal of Physical Chemistry A - In this paper, we present the experimental and theoretical investigation of 1-ethyl-3-methylquinoxaline-2-thione, molecule exhibiting an important...     

Generation of Organozinc Reagents by Nickel Diazadiene Complex Catalyzed Zinc Insertion into Aryl Sulfonates

The generation of arylzinc reagents (ArZnX) by direct insertion of zinc into the C−X bond of ArX electrophiles has typically been restricted to iodides and bromides. The insertions of zinc dust into the C−O bonds of various aryl sulfonates (tosylates, mesylates, triflates, sulfamates), or into the C−X bonds of other moderate electrophiles (X=Cl, SMe) are catalyzed by a simple NiCl₂–1,4-diazadiene catalyst system, in which 1,4-diazadiene (DAD) stands for diacetyl diimines, phenanthroline, bipyridine and related ligands. Catalytic zincation in DMF or NMP solution at room temperature now provides arylzinc sulfonates, which undergo typical catalytic cross-coupling or electrophilic substitution reactions.     

Carboxymethylcellulose obtained by ethanol/water organosolv process under acid conditions

Sugar cane bagasse pulps were obtained by ethanol/water organosolv process under acid and alkaline conditions. The best condition of acid pulping for the sugarcane bagasse was 0.02 mol/L sulfuric acid at 160 degrees C, for 1 h, whereas the best condition for alkaline pulping was 5% sodium hydroxide (base pulp) at 160 degrees C, for 3 h. For the residual lignin removal, the acid and alkaline pulps were submitted to a chemical bleaching using sodium chlorite. Pulps under acid and alkaline conditions bleached with sodium chlorite presented viscosities of 3.6 and 7.8 mPa x s, respectively, and mu-kappa numbers of 1.1 and 2.4, respectively. The pulp under acid condition, bleached with sodium chlorite was used to obtain carboxymethylcellulose (CMC). CMC yield was 35% (pulp based), showing mass gain after the carboxymethylation reaction corresponding to 23.6% of substitution or 0.70 groups -CH(2) COONa per unit of glucose residue. The infrared spectra showed the CMC characteristic bands and by the infrared technique it was possible to obtain a substitution degree (0.63), similar to the substitution degree calculated by mass gain (0.70).     

Récréations et mathématiques mondaines au XVIII siècle: le cas de Guyot

In this paper, we study the most popular book of recreational mathematics published in the second half of the 18th century: The Nouvelles Récréations by Guyot. We indicate the motivations of the author, a simple postman, and the conditions which led him to write this book. We describe the spirit of the book and the public at which it aims. The success of the Nouvelles Récréations illustrates the rise of a science in polite society whose main goal is to amaze and amuse. Then, we examine the place of mathematics in this project and analyze the repertoire of problems and tricks. We focus on problems of combinatorics proposed by Guyot, like anagrams and card shuffles, which inspired some real mathematical work on the part of Monge and Gergonne.     

Oriented immobilization and electron transfer to the cytochrome c oxidase

Direct electron transfer to cytochrome c oxidase (CcO) is investigated as a function of packing density of the surface layer. This is varied by the surface concentration of chelator molecules when the enzyme is immobilized on the electrode using the his-tag technology. Chelator molecules with a terminal nitrilotriacetic acid group are synthesized ex situ in contrast to in situ synthesis used in a previous work. Self-assembled monolayers of the chelator mixed at different mole fractions with a dilution molecule are prepared to bind the CcO after complex formation with Ni²⁺ ions. The CcO, which is immobilized in the solubilized form, is then reconstituted into a protein-tethered bilayer lipid membrane (ptBLM). Varying the mixing ratio of chelator to dilution molecules enabled us to control the packing density of CcO residing in the ptBLM. Subtle differences in the architecture of the protein/lipid layers revealed by surface-enhanced IR absorption spectroscopy are considered to be essential for an effective electron transfer. Cyclic voltammograms are measured under anaerobic conditions at different scan rates and analyzed by means of a model which describes the transfer of four electrons to CcO in the ptBLM. The rate constants thus obtained show a marked dependence on the packing density.     

Simulated annealing and density functional theory calculations of structural and energetic properties of the ammonium chloride clusters (NH4Cl)n, (NH4+)(NH4Cl)n, and (Cl-)(NH4Cl)n, n = 1-13

Simulated annealing Monte Carlo conformer searches using the "mag-walking" algorithm are employed to locate the global minima of molecular clusters of ammonium chloride of the types (NH(4)Cl)(n), (NH(4)(+))(NH(4)Cl)(n), and (Cl(-))(NH(4)Cl)(n) with n = 1-13. The M06-2X density functional theory method is used to refine and predict the structures, energies, and thermodynamic properties of the neutral, cation, and anion clusters. For selected small clusters, the resulting structures are compared to those obtained from a variety of models and basis sets, including RI-MP2 and B3LYP calculations. M06-2X calculations predict enhanced stability of the (NH(4)(+))(NH(4)Cl)(n) clusters when n = 3, 6, 8, and 13. This prediction corresponds favorably to anomalies previously observed in thermospray mass spectroscopy experiments. The (NH(4)Cl)(n) clusters show alternations in stability between even and odd values of n. Clusters of the type (Cl(-))(NH(4)Cl)(n) display a magic number distribution different from that of the cation clusters, with enhanced stability predicted for n = 2, 6, and 11. None of the observed cluster structures resemble the room-temperature CsCl structure of NH(4)Cl(s), which is consistent with previous work. Numerous clusters have structures reminiscent of the higher-temperature, rock-salt phase of the solid ammonium halides.     

Biomedical Imaging Using Synchrotron Radiation: Experience at the Biomedical Imaging and Therapy (BMIT) Facility at the Canadian Light Source

The Biomedical Imaging and Therapy (BMIT) beamlines at the Canadian Light Source (CLS) comprise a multi-modality synchrotron imaging facility capable of imaging objects with 2–200 μm resolution with beam sizes up to ~200 mm wide and ~10 mm high in the experimental hutches [1 T. W. Wysokinski, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 775, 1–4 (2015).[Crossref], [Web of Science ®] , [Google Scholar]–3 T. W. Wysokinski, Nucl Instr Meth Phys Res A 582, 73–76 (2007).[Crossref], [Web of Science ®] , [Google Scholar]]. BMIT hosts two beamlines, a bend magnet 05B1-1 and an insertion device 05ID-2, with capabilities to apply absorption imaging, in-line phase contrast imaging (PCI), analyzer-based imaging (ABI) or diffraction-enhanced imaging (DEI), and K-Edge Subtraction (KES) imaging. Talbot or grating interferometry is under development.     

Comparison of active and passive environmental sampling for safeguards applications

Towards development of electrical conductivity based sensors for online detection of formation of third phase during reprocessing of Pu rich spent nuclear fuels, laboratory studies were carried out using U⁴⁺ solutions in various experimental conditions. Third phases were generated by extracting U⁴⁺ from nitric acid medium by 1.09 M TBP at different A/O (A: aqueous, O: organic) ratios. The results of this study indicate that the third phase is nearly 100–300 times more conducting than lean organic phase and saturated phase. The higher conductivity of third phase as compared to that of other two phases is explained based on the principle of reverse micelle formation and charge movement between the micro emulsion globules by percolation phenomenon.     

Nanocarbon Paste Electrodes

The electrochemical behaviour of carbon paste electrodes prepared using nanocarbon and mineral oil was investigated and the results contrasted with different carbon and carbon pastes electrodes. The composition of carbon paste was studied by performing cyclic voltammetry performed in 0.1 M KCl solution in the presence of 4.0 mM Ru(NH₃)₆Cl₃, a well‐characterized redox system commonly used to test the electrode behaviour. After optimisation of the paste composition, the sensors chosen were tested for the analysis and characterization of three different systems: Ru(NH₃)₆^3+/2+, FcCH₂OH/FcCH₂OH⁺ and acetaminophen. The ability to obtain high quality voltammetry from the nanocarbon electrode was demonstrated and simulation of the voltammetry allowed the extraction of electrode kinetic parameters with high precision.