Liquid chromatographic resolution of racemic rasagiline and its analogues on a chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid

A liquid chromatographic chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid was applied to the resolution of 15 analytes, including racemic rasagiline, a chiral drug for the treatment of Parkinson's disease, and its analogues. The composition of mobile phase was optimized to be ethanol/acetonitrile/acetic acid/triethylamine (80:20:0.2:0.3, v/v/v/v) by evaluating the chromatographic results for the resolution of five selected analytes under various mobile phase conditions. Under the optimized mobile phase conditions, racemic rasagiline was resolved quite well with a separation factor of 1.48 and resolution of 2.71 and its 14 analogues were also resolved reasonably well with separation factors of 1.06–1.54 and resolutions of 0.54–2.11. Among 15 analytes, racemic rasagiline was resolved best except for just one analyte. The analyte structure–enantioselectivity relationship indicated that racemic rasagiline has the most appropriate structural characteristics for resolution on the chiral stationary phase.     

Bistable stochastic biochemical networks: highly specific systems with few chemicals

In this paper we describe a class of stochastic biochemical systems exhibiting bistable behavior, in the sense that the invariant measure associated to the system is concentrated near two different classes of states of the system. We develop methods that allow us to describe the behavior of the invariant measure in some suitable asymptotic limits, as well as the switching times for the transitions between the states close to each of the states with high probability. Due to the discrete character of the problem, switching times cannot be computed using the classical Kramers’ formula, and alternative methods are required.     

Short time deposition of TiO2 nanoparticles on SiC as photocatalysts for the degradation of organic dyes

The deposition of TiO₂ nanoparticles on SiC was carried out by mechanical milling under different conditions. SiC–TiO₂ samples were used as photocatalysts for the degradation of organic dyes such as methylene blue and rhodamine B. A short time deposition of TiO₂ nanoparticles was observed during mechanical milling (2 min at 200 rpm) to cover the SiC particles. The presence of SiC and TiO₂ (anatase and rutile) was confirmed by means of X-ray diffraction after thermal treatment at 450 °C. The deposition of TiO₂ on SiC was corroborated by scanning electron microscopy analysis; the thickness of the thin layer of TiO₂ deposited on SiC increases as the proportion of TiO₂ increases. The energy band gap values obtained for these compounds were around 3.0 eV. SiC–TiO₂ photocatalysts prepared by mechanical milling exhibited better activity under UV-light irradiation for the degradation of methylene blue and rhodamine B than commercial TiO₂ powder (titania P25).     

Dynamic output feedback consensus of continuous‐time networked multiagent systems

This article addresses the dynamic output feedback consensus problem of continuous‐time networked multiagent systems. Both a fixed topology and Markovian switching topologies are considered. The consensus algorithms are on the base of the output information of each agent's itself and its neighbors. Some sufficient conditions for consensus of multiagent systems are obtained in forms of bilinear matrix inequalities. The algorithm based on the homotopy continuation method is given to compute the feasible controller gains. Numerical simulations are given to show the effectiveness of the proposed results. © 2014 Wiley Periodicals, Inc. Complexity 20: 35–42, 2015     

Cyclized oligomer of tetracyanoquinodimethane-tetrathiafulvalene (TCNQ-TTF): a versatile macrocyclic molecule by DFT calculations

Journal of Inclusion Phenomena and Macrocyclic Chemistry - The combination of the electron donor and acceptor into a donor–acceptor system can transform the intermolecular charge transfer...     

Upgrading Solid Digestate from Anaerobic Digestion of Agricultural Waste as Performance Enhancer for Starch-Based Mulching Biofilm

Developing a green and sustainable method to upgrade biogas wastes into high value-added products is attracting more and more public attention. The application of solid residues as a performance enhancer in the manufacture of biofilms is a prospective way to replace conventional plastic based on fossil fuel. In this work, solid digestates from the anaerobic digestion of agricultural wastes, such as straw, cattle and chicken manures, were pretreated by an ultrasonic thermo-alkaline treatment to remove the nonfunctional compositions and then incorporated in plasticized starch paste to prepare mulching biofilms by the solution casting method. The results indicated that solid digestate particles dispersed homogenously in the starch matrix and gradually aggregated under the action of a hydrogen bond, leading to a transformation of the composites to a high crystalline structure. Consequently, the composite biofilm showed a higher tensile strength, elastic modulus, glass transition temperature and degradation temperature compared to the pure starch-based film. The light, water and GHG (greenhouse gas) barrier properties of the biofilm were also reinforced by the addition of solid digestates, performing well in sustaining the soil quality and minimizing N₂O or CH₄ emissions. As such, recycling solid digestates into a biodegradable plastic substitute not only creates a new business opportunity by producing high-performance biofilms but also reduces the environmental risk caused by biogas waste and plastics pollution.     

Failure analysis of Cu(In,Ga)Se2 photovoltaic modules: degradation mechanism of Cu(In,Ga)Se2 solar cells under harsh environmental conditions

High‐temperature‐induced and humidity‐induced degradation behaviors were investigated through the failure analysis of encapsulated Cu(In,Ga)Se₂ (CIGS) modules and non‐encapsulated CIGS cells. After being exposed to high temperature (85 °C) for 1000 h, the efficiency loss of CIGS modules and the resistivities of the aluminum‐doped zinc oxide (AZO) layer, CIGS layer, and Mo layer were slightly increased. After damp heat (DH) testing (85 °C/85% RH), the efficiency of some modules decreased significantly accompanied by discoloration, and in these areas, the resistivity of the AZO layers increased markedly. The causes of degradation of CIGS cells after high temperature and DH tests were suggested through X‐ray photoelectron spectroscopy analysis. The high‐temperature‐induced degradation behaviors were revealed to be increases in series resistance of the CIGS cells, due to the adsorption of oxygen on the AZO, CIGS, and Mo layers. The degradation behavior after DH (85 °C/85% RH) exposure was caused by the adsorption of oxygen, as well as the generation of Zn(OH)₂ due to water molecules. In particular, the humidity‐induced degradation behavior in discolored CIGS modules was ascribed to the generation of Zn(OH)₂ and carboxylic acids in the AZO layer, due to a chemical reaction between the AZO, ethylene‐vinyl acetate copolymer, and water. Copyright © 2014 John Wiley & Sons, Ltd.     

Preparation and thermal properties of poly[acrylonitrile-co-(β-methylhydrogen itaconate)] used as carbon fiber precursor

In order to replace terpolymer with bipolymer, a bifunctional comonomer β-methylhydrogen itaconate (MHI) containing carboxyl group and ester group was synthesized to prepare poly[acrylonitrile-co-(β-methylhydrogen itaconate)] [P(AN-co-MHI)] bipolymers used as carbon fiber precursor for improving the stabilization and spinnability at the same time. The P(AN-co-MHI) bipolymers with different monomer feed ratios were characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The results show that both the polymerization conversion and molecular mass of P(AN-co-MHI) reduce with the increasing MHI amounts in the feed due to the larger molecular volume of MHI than acrylonitrile (AN). The monomer reactivity ratios were calculated by Fineman–Ross and Kelen–Tüdõs methods, the results show good agreement and MHI possesses higher reactivity than AN. Two parameters $ E_{\text{s}} = A_{{1,629\,{\text{cm}}^{ - 1} }} /A_{{2,244\,{\text{cm}}^{ - 1} }} $ and $ SI = (I_{0} - I_{\text{S}} )/I_{0} $ were defined to evaluate the extent of stabilization, and the activation energy (E _a) of the cyclization was calculated by Kissinger method and Ozawa method. The FTIR, XRD, and DSC results show that P(AN-co-MHI) bipolymers exhibit significantly improved stabilization characteristics than PAN homopolymer, such as larger extent of stabilization, lower initiation temperature, and smaller E _a of cyclization, which is attributed to the ionic initiation by MHI comonomer and it is beneficial to preparing high-performance carbon fiber.     

Copper‐Catalyzed Three‐Component Azidotrifluoromethylation/Difunctionalization of Alkenes

A novel three‐component strategy for the azidotrifluoromethylation of alkenes has been presented here. The reaction proceeded smoothly under gentle temperature and gave the bifunctional olefins in high yields. Furthermore, 1,3‐dipolar reactions between azide‐containing products and phenylacetylene revealed great potential in molecular modification by using this method.     

A Sm(III) Coordination Polymer Containing 2,5-Furandicarboxylic Acid: Crystal Structure and Recognition of Oxalate in Water

Crystallography Reports - The {[Sm2(FDC)2](FDC) · 10H2O}n complex, where H2FDC is a 2,5-furandicarboxylic acid, has been prepared by hydrothermal reaction and structurally characterized by...