Localization–delocalization phenomena in a cyclic box

The localization–delocalization of a particle in a cyclic box is studied by examination of its Shannon information entropy and standard deviation. These results are compared to the particle in a box model, in ground and also in excited states. We show how a cyclic symmetry imposes that the ground state is more delocalized in the cyclic box as compared to the particle in a box. However, excited states in both models exhibit the same localization. The differences between the Shannon entropy and the standard deviation are discussed and the analysis is then extended to consider multiple particles in both models.     

Methanol Decomposition in a Water–Methanol Equimolar Mixture on a Nickel-Promoted Copper–Zinc–Cement Catalyst

Methanol decomposition in a water–methanol equimolar mixture is studied in the presence of a nickel-promoted copper–zinc–cement catalyst. Methanol decomposition at 200–300°C on the oxide and reduced forms of the catalyst yields a gas with an H₂/CO ratio close to two. The use of an equimolar CH₃OH–H₂O mixture under analogous conditions enables obtaining gaseous products with a hydrogen concentration up to 75 vol %.     

Oxidative dehydrogenation of ethane over a Mo–V–Nb–Te–O mixed-oxide catalyst in a cyclic mode

The oxidative dehydrogenation of ethane (ODE) into ethylene over a Mo–V–Nb–Te–O mixedoxide catalyst in a cyclic mode with alternate feeding of ethane and air has been investigated. The amount of oxide-phase oxygen involved in the reaction has been estimated by titrating the oxygen of the active phase of the catalyst with ethane. The reactivity of this oxygen increases with an increasing temperature. The amount active oxygen involved in ODE at 360–400°C is 0.2–0.6 mmol/g.     

Roton excitations in Bose–Einstein condensates and a fluid–solid transition

Several authors have recently discussed the existence of roton excitations in Bose–Einstein condensates (BECs) and considered how a roton dip in the dispersion curve of elementary excitations may be related to the formation of a spatially modulated ground state. Here attention is drawn to a theoretical study of Minguzzi et al. on interatomic correlations in a BEC from dipole–dipole interactions induced by laser light of increasing intensity. Attractive interactions in superfluid ⁴He and repulsive interactions in ‘untuned’ BECs are then compared and contrasted, the experiments of Woods and Cowley and of Greiner et al. providing the focus respectively. It is stressed that, contrary to a very recent assertion by Nazario and Santiago, ⁴He is crucially different from BECs at the lowest temperatures.     

Cellulose in NaOH–water based solvents: a review

The article is a critical review of all aspects of the dissolution of cellulose in NaOH-based aqueous solutions: from the background properties of the solvent itself, to the mechanisms of cellulose fibre swelling and dissolution, solution structure and properties and influence of additives and, finally, to the properties of various materials (fibres, films, aerogels, composites and interpenetrated networks) prepared from these solutions. A historical evolution of the research on this topic is presented. The pros and cons of NaOH-based aqueous solvent for cellulose are summarised and some prospects are suggested.     

Receptor–ligand interactions in a reconstituted bilayer lipid membrane

A simple method is described to reconstitute membrane receptors into bilayer lipid membranes (BLMs). After reconstitution, the receptor still retains its ligand activity. Furthermore, the relationship between receptor–ligand interactions and electrical properties of reconstituted BLMs such as membrane capacitance (C_m) and membrane resistance (R_m) was studied. When glycophorin in erythrocyte and asialoglycoprotein in hepatocyte were taken as examples, it was found that the resistance of reconstituted BLM decreased when adding blood type monoclonal antibody or the solutions of galactose, respectively, and the decrease is ligand-concentration dependent; however, the membrane capacitance was not influenced. This provides a simple, practical approach to determining the interactions between the receptor and its ligand.     

Coordination-Induced Band Gap Reduction in a Metal–Organic Framework

Herein, we report on the synthesis of a microporous, three-dimensional phosphonate metal–organic framework (MOF) with the composition Cu₃(H₅-MTPPA)₂ ⋅ 2 NMP (H₈-MTPPA=methane tetra-p-phenylphosphonic acid and NMP=N-methyl-2-pyrrolidone). This MOF, termed TUB1, has a unique one-dimensional inorganic building unit composed of square planar and distorted trigonal bipyramidal copper atoms. It possesses a (calculated) BET surface area of 766.2 m²/g after removal of the solvents from the voids. The Tauc plot for TUB1 yields indirect and direct band gaps of 2.4 eV and 2.7 eV, respectively. DFT calculations reveal the existence of two spin-dependent gaps of 2.60 eV and 0.48 eV for the alpha and beta spins, respectively, with the lowest unoccupied crystal orbital for both gaps predominantly residing on the square planar copper atoms. The projected density of states suggests that the presence of the square planar copper atoms reduces the overall band gap of TUB1, as the beta-gap for the trigonal bipyramidal copper atoms is 3.72 eV.     

High Compression-Induced Conductivity in a Layered Cu–Br Perovskite

We show that the onset pressure for appreciable conductivity in layered copper-halide perovskites can decrease by ca. 50 GPa upon replacement of Cl with Br. Layered Cu–Cl perovskites require pressures >50 GPa to show a conductivity of 10⁻⁴ S cm⁻¹, whereas here a Cu–Br congener, (EA)₂CuBr₄ (EA=ethylammonium), exhibits conductivity as high as 2×10⁻³ S cm⁻¹ at only 2.6 GPa, and 0.17 S cm⁻¹ at 59 GPa. Substitution of higher-energy Br 4p for Cl 3p orbitals lowers the charge-transfer band gap of the perovskite by 0.9 eV. This 1.7 eV band gap decreases to 0.3 eV at 65 GPa. High-pressure X-ray diffraction, optical absorption, and transport measurements, and density functional theory calculations allow us to track compression-induced structural and electronic changes. The notable enhancement of the Br perovskite's electronic response to pressure may be attributed to more diffuse Br valence orbitals relative to Cl orbitals. This work brings the compression-induced conductivity of Cu-halide perovskites to more technologically accessible pressures.     

Cooperative binding of an anticancer drug in a guest–host–protein assembly

The supramolecular formation of an anticancer drug (6-mercaptopurine (6-MP)) in an acetate buffer solution was demonstrated through a host–guest interaction with the macrocyclic host cucurbit[7]uril (Q[7]) and bovine serum albumin (BSA). With the help of ultraviolet absorption and fluorescence spectroscopy, it was shown that a binary complex formed between 6-MP and Q[7] and/or BSA, and a specific binding interaction took place between 6-MP and Q[7] in the presence of BSA. The inclusion constants and thermodynamic parameters were determined at different temperatures. The data suggested that the formation of the binary 6-MP–Q[7] complex was driven by enthalpy in the presence of an unfavourable entropy, which was attributed to the van der Waals and hydrophobic interactions. The fluorescence quenching of BSA by 6-MP was a result of the formation of the 6-MP–BSA complex. This quenching occurred by a static quenching mechanism, and hydrophobic forces played predominant roles in the binding process. Moreover, the absorption data suggested that the interaction between 6-MP and Q[7] or BSA was a competitive process. In addition, the effect of 6-MP on BSA conformation was investigated by synchronous and 3D fluorescence spectra.     

Limiting Current Densities in a System with Cation-Exchange Membrane MK-100 Rotating in a Glycine–HCl Solution

Limiting diffusion current densities in an electromembrane system (EMS) comprising cation-exchange membrane MK-100 and a glycine solution containing hydrochloric acid are studied on a rotating membrane disk. The dependence of the limiting current density at a given rotation rate of the disk on the equilibrium volume concentrations of glycine cations and protons in solution is described by a regression model. The diffusion fluxes of these cations in the EMS are shown to be independent.     

The B–H–B bridging interaction in B-substituted oxazaborolidine–borane complexes: a theoretical study

Ten oxazaborolidine–borane complexes, nine among them boron-substituted (B–R, R=CH₃, CF₃, and OCH₃), are carefully analysed using quantum-chemistry methods to determine their equilibrium geometries and the corresponding oxazaborolidine–borane interaction energies. It is observed that in all B-trifluoromethyl substituted oxazaborolidine–borane complexes and in one B-methyl substituted complex the B–H–B bond is formed and the interaction energies are 1.5–2.5 times as large as in other investigated complexes. We believe that the presented results may be helpful in experimental recognition of oxazaborolidine–borane complexes which may appear, inter alia, as reaction intermediates.     

Li–Yorke chaos in a coupled lattice system related with Belusov–Zhabotinskii reaction

Garca Guirao and Lampart (J Math Chem 48:66–71, 2010; J Math Chem 48:159–164, 2010) said that for non-zero couplings constant, the lattice dynamical system is more complicated. Motivated by this, in this paper, we prove that this coupled map lattice system is Li–Yorke chaotic for coupling constant ${0 < \epsilon <1 }$ .     

GC–MPI–MS of Pentachlorodibenzofurans in Flue Gas Using a UV Picosecond Laser

Pentachlorodibenzofurans (pentaCDFs) are measured by means of gas chromatography combined with multiphoton ionization–mass spectrometry (GC–MPI–MS) using a picosecond Nd:YAG laser (266 nm) as an ionization source. In this study, the pre-treated sample was collected from flue gas in an incinerator. The pentaCDF isomers in the environment were determined, for the first time, by GC–MPI–MS. In addition, the details of the fragment patterns of mono—pentaCDFs were discussed, resulting in the detection of M⁺–COCl as a major fragment ion for all of them. On the other hand, the fragment peak of M⁺–Cl was quite small, suggesting that a molecular ion (e.g., tetraCDF⁺) can easily be identified without any interference by the M⁺–Cl fragment ion (e.g., pentaCDF⁺–Cl).     

SPE and LC–ESI–MS for Quantitative Analysis of Mitiglinide in Human Plasma in a Bioequivalence Study

Liquid chromatography–electrospray ionization mass spectrometry has been used for rapid, selective, and sensitive quantitative analysis of mitiglinide in human plasma. Sample pretreatment involved solid-phase extraction from plasma with gliclazide as internal standard. Separation was performed on a C₁₈ column (150 × 2.0 mm) with 71:29 (v/v) acetonitrile–water (containing 0.1% formic acid and 0.2 mmol L^?1 ammonium acetate) as mobile phase at a flow rate of 0.2 mL min^?1. The method was validated then successfully applied to a clinical bioequivalence study of mitiglinide in 20 healthy volunteers after oral administration.     

Catalytic hydrogenation of itaconic acid in a biotinylated Pyrphos–rhodium(I) system in a protein cavity

The construction of a chiral catalyst system embedded at a specific site in a protein has been studied. The preparation of the biotinylated Pyrphos–Rh(I) complex attached to the binding site in avidin and its application to the asymmetric hydrogenation of itaconic acid have been investigated. By introducing the chiral Pyrphos–Rh(I) moiety into the constrained environment of the protein cavity it was found that the enantioselectivity of the system was significantly influenced by the tertiary conformation within the avidin cavity. The effects of reaction conditions such as temperature, hydrogen pressure, and the pH value of the buffer on enantioselectivity are reported.     

Electrochemical oxidation of aniline in a silica sol–gel matrix

Electrochemical oxidation of aniline encapsulated in a silica solid electrolyte prepared by a sol–gel process yielded products that were dependent on the pore size. An acid-catalyzed process that used tetramethyl orthosilicate as the precursor and aniline as a dopant yielded the silica. When the aging time was limited to one day so that a mesoporous solid was obtained, the potentiodynamic oxidation of aniline at a carbon fiber electrode resulted in the formation of polyaniline. With aging times of 3–5 days, microporous silica was obtained. In this electrolyte, the formation of dimers and other oligomers was observed by cyclic voltammetry. Evidence for these products was the presence of a quasi-reversible redox couple at 0.2 V vs Ag/AgCl that was previously related to oligomeric aniline by Raman spectroscopy. The results supported the hypothesis that the pore structure of sol–gel electrolytes can influence the pathways of electrode reactions therein.     

Analytical Electron Microscopy in a Discontinuous Precipitated Cu–In Alloy

The morphology and kinetics of the discontinuous precipitation reaction in a Cu-4.5 at.% In alloy were studied by means of analytical electron microscopy. Upon discontinuous precipitation an /(Cu₇In₃) lamellar two-phase microstructure was observed, where is the In-depleted solid solution and the precipitate phase. Indium concentration profiles were determined parallel to the moving reaction front for individual lamellae. A local analysis was applied to characterize the kinetics of the discontinuous precipitation reaction and allowed the determination of the local grain-boundary diffusivity.