A procedure to construct exact solutions of nonlinear evolution equations

In this paper, we implemented the functional variable method for the exact solutions of the Zakharov?CKuznetsov-modified equal-width (ZK-MEW), the modified Benjamin?CBona?CMahony (mBBM) and the modified KdV?CKadomtsev?CPetviashvili (KdV?CKP) equations. By using this scheme, we found some exact solutions of the above-mentioned equations. The obtained solutions include solitary wave solutions, periodic wave solutions and combined formal solutions. The functional variable method presents a wider applicability for handling nonlinear wave equations.     

不同[Cu]/[In]比例的CuInS2薄膜的特性

采用连续离子层吸附与反应方法在玻璃基板上按照不同[Cu]/[In]的比例制备了CuInS₂薄膜,并在400 °C退火30 min. 对薄膜的晶体结构和晶粒尺寸用X射线衍射方法进行了表征,原子力显微镜测定薄膜的表面形貌. 研究不同的[Cu]/[In]比例对薄膜光学和电学性能的影响. 采用直流两探针法在300～470 °C测定CuInS₂薄膜的电阻率,随着[Cu]/[In]比例的增加,电阻率值越来越低. 溶液中[Cu]/[In]的比例明显影响CuInS₂薄膜的结构、电学和光学特性.     

Fast fluorescence switching within hydrophilic supramolecular assemblies

We designed a supramolecular strategy to modulate fluorescence in water under optical control. It is based on the entrapment of fluorophore-photochrome dyads within the hydrophobic interior of an amphiphilic polymer. The polymeric envelope around the dyads protects them from the aqueous environment, while imposing hydrophilic character on the overall supramolecular construct. In the resulting assemblies, the photochromic component can be operated reversibly on a microsecond timescale under the influence of ultraviolet stimulations. In turn, the reversible transformations control the emission intensity of the adjacent fluorophore. As a result, the fluorescence of such nanostructured constructs can be photomodulated for hundreds of cycles in water with microsecond switching speeds. Thus, our protocol for fast fluorescence switching in aqueous solutions can eventually lead to the realization of functional probes for the investigation of biological samples.     

Simulation and micro-fabrication of optically switchable split ring resonators

The effect of conductivity variation as a proposed method for the investigation of photoconductive switching properties of split ring resonators (SRRs) is simulated. Three different systems that are applicable under certain fabrication and/or optical excitation conditions are described. The simulated transmission spectrum indicates that for a large range of dark conductivity values, complete switching of the SRR resonance is possible. One of the simulated systems, involving split ring resonators on Si substrate, was fabricated and characterized. The transmission spectrum of that system was measured, with the Si in its high-resistivity state, and a −60 dB dip between 108 and 115 GHz, due to SRRs magnetic resonance, was observed.     

A parametric study on biphasic medium conditions for the enantioselective production of naproxen by <Emphasis Type="Italic">Candida rugosa</Emphasis> lipase

A parametric study to increase the enantioselectivity of Candida rugosa lipase (CRL) toward S-Naproxen production by the hydrolysis of racemic Naproxen methyl ester in an aqueous-organic biphasic batch system was carried out. Effects of organic solvent type, aqueous phase/organic solvent volume ratio, agitation rate, concentrations of the substrate and the enzyme, pH of the aqueous phase, and temperature on the en antiomeric excess for the product (ee_p), on the enantiomeric ratio (E) and on the conversion (x) were evaluated. Employing isooctane as the solvent resulted in higher ee_p, E, and x than those obtained in hexane, cyclohexane, and toluene. The higher the volume ratio of aqueous phase/organic solvent employed, the higher the conversion and enantioselectivity achieved. The increase in agitation rate increased the hydrolysis rate. Higher concentration of racemic Naproxen methyl ester than 10 mg/mL decreased both the conversion and enantioselectivity. The increase in crude CRL concentration resulted in enhancement of x, but the decrease of fee_p and E. Acidic pH led to higher conversion and enantioselectivity than the medium and alkaline pH values. A further increase in temperature to over 45°C decreased the conversion and enantioselectivity. The highest enantiomeric ratio achieved in the S-Naproxen production was E=171.1, with x=49.8% and ee_p=95.7%.     

An efficient and selective enzymatic oxidation system for the synthesis of enantiomerically pure D-tert-leucine

[reaction: see text] d-tert-Leucine was prepared with an enantiomeric excess of >99% by an enzyme-catalyzed oxidative resolution of the racemic mixture of dl-tert-leucine with use of leucine dehydrogenase. The l-amino acid was oxidized completely due to coupling of the primary reaction with a highly efficient irreversible NAD(+)-regenerating step by NADH oxidase.     

Preparation and characterization of In<Subscript>2</Subscript>S<Subscript>3</Subscript> semiconductor thin films using the sol–gel method

This study describes the In₂S₃ semiconductor thin film coating on glass substrate by sol–gel method. The In₂S₃ thin film samples were prepared and examined by the X-ray diffraction (XRD), the UV–visible optical absorption and transmission study, and the Scanning Electron Microscope (SEM) image analyses. The XRD analysis results show that the In₂S₃ semiconductor thin films prepared by sol–gel method is formed at T~360–520 °C temperature interval. Band gap energy and optical absorption spectrum analysis of the In₂S₃ thin films reveal that Eg~2.51 eV for the In₂S₃ thin films. According to the EDX result the film was In-rich with the In/S = 1.42 ratio. The thickness of prepared In₂S₃ layer is about 400 nm.     

Novel dinuclear and polynuclear copper(II)-pyrazine-2,3-dicarboxylate supramolecular complexes with 1,3-propanediamine, N,N,N′,N′-tetramethylethylenediamine and 2,2′-bipyridine

Three novel Cu(II)-pyrazine-2,3-dicarboxylate complexes with 1,3-propanediamine (pen), [Cu₂(μ-pzdc)₂(pen)₂] · 2H₂O (1), N,N,N′,N′-tetramethylethylenediamine (tmen), {[Cu(μ-pzdc)(tmen)] · H₂O}_n(2), and 2,2′-bipyridine (bipy), {[Cu(μ-pzdc)(bipy)]·H₂O}_n(3) have been synthesized and characterized by means of elemental and thermal analyses, magnetic susceptibilities, IR and UV/vis spectroscopic studies. The molecular structures of dinuclear (1) and polynuclear (2 and 3) complexes have been determined by the single crystal X-ray diffraction technique. The pyrazine-2,3-dicarboxylate acts as a bridging ligand through oxygen atom of carboxylate group and N atom of pyrazine ring and one oxygen atom of neighboring carboxylate. It links the Cu(II) ions to generate a distorted square pyramidal geometry forming a one-dimensional (1D) chain. Adjacent chains of 1 and 2 are then mutually linked via hydrogen bonding interactions, which are further assembled to form a two and three-dimensional network, respectively. The chains of complex 3 are further constructed to form three-dimensional framework by hydrogen bonding, C–H?π and ring?ring stacking interactions. In the complexes, Cu(II) ions have distorted square pyramidal geometry. Thermal analyses properties and thermal decomposition mechanism of complexes have been investigated by using thermal analyses techniques (TG, DTG and DTA).     

Synthesis,Characterization, and Spectroscopic Properties of Hexa(4-Bromo-2-Formyl-Phenoxy)Cyclotriphosphazene and Hexa(4-Chloro-2-Formyl-Phenoxy)Cyclotriphosphazene and Fully Substituted Cyclotriphosphazene Derivatives Bearing a Schiff Base at Room Temperature

Abstract

Hexa(4-bromo-2-formyl-phenoxy)cyclotriphosphazene (2) and hexa(4-chloro-2- formyl-phenoxy)cyclotriphosphazene (3) were obtained from the reactions of hexachloro- cyclotriphosphazene (1) with 5-bromosalicylaldehyde and 5-chlorosalicylaldehyde in the presence of (C₂H₅)₃N and K₂CO₃ at room temperature, respectively. The new two organocyclotriphosphazenes bearing formyl groups were reacted with 4-cyano aniline, 2-phenyl aniline, 4-aceto aniline, 5-chloro-2-hydroxy aniline, 2-hydroxy aniline, 4-hydroxy aniline, 2-(4-morpholino)ethyl amine, 4-carboxy aniline, 4-carbomoyl aniline, 2-mercapto aniline, and 5-amino isoquonoline to prepare cyclotriphosphazene derivatives containing a Schiff base at room temperature. However, fully phenoxy-substituted cyclotriphosphazenes containing a Schiff base were isolated from the reactions of the compound 2 and 3 with 5-chloro-2-hydroxy aniline, 2-hydroxy aniline, 4-hydroxy aniline, and 2-(4-morpholino)ethyl amine. The structures of the synthesized compounds were characterized by elemental analysis, IR, and NMR (¹H, ¹³C, ³¹P) spectroscopy. According to the results of the analysis, all synthesized compounds were found to be fully substituted organocyclotriphosphazenes, such as hexa[4-bromo-2-(5-chloro-2-hydroxy-pheyliminomethyl)phenoxy]cyclotriphosphaze (2a). All cyclotriphosphazene derivatives synthesized gave fluorescence emission peaks in range between 300 nm and 410 nm.