One‐pot synthesis of (3‐sulfopropyl methacrylate potassium)‐silica hybrid monolith via thiol‐ene click chemistry for CEC

A novel (3‐sulfopropyl methacrylate potassium)‐silica hybrid monolithic column for CEC has been prepared by a simple one‐pot approach based on efficient thiol‐ene click chemistry. In this process, the polycondensation of hydrolyzed alkoxysilanes and in situ click reaction of vinyl groups on 3‐sulfopropyl methacrylate potassium and thiol groups on the precondensed siloxanes simultaneously occurred in a pretreated capillary. Homogeneous monolithic matrix with large through‐pores tightly bonded to the inner wall of the capillary was shown by optical microscope and SEM. The minimum plate height of this hybrid monolithic column was determined as 3.9 μm for thiourea. Anilines, alkylbenzenes, and phenols were well separated on this hybrid monolithic column by CEC, which indicated typical reversed‐phase and cation‐exchange chromatographic retention mechanisms of the column.     

Persistent photocatalysis of continuously flowing gas-phase nitric oxide using CaAl2O4:(Eu,Nd)/rutile phase TiO2−x N y composites

CaAl₂O₄:(Eu,Nd)/rutile phase TiO_2?x N _y composites were synthesized via a two-step method, i.e. a solvothermal reaction followed by a mechanochemical treatment. The photocatalytic deNO _x activity of the composites was evaluated under UV light (λ > 290 nm) irradiation and after turning off the UV light. It was confirmed that rutile phase TiO_2?x N _y nanoparticles could be uniformly dispersed on the surface of CaAl₂O₄:(Eu,Nd) after planetary ball milling treatment. The composites prepared by this two-step method had high photocatalytic activity and good prolonged catalysis time even after turning off the light.     

Wave motion analysis in arch structures via wavelet finite element method

The application of B-spline wavelet on interval (BSWI) finite element method for wave motion analysis in arch structures is presented in this paper. Instead of traditional polynomial interpolation, scaling functions at certain scales have been adopted to form the shape functions and construct wavelet-based elements. Different from other wavelet numerical methods adding wavelets directly, the element displacement field represented by the coefficients of wavelets expansions is transformed from wavelet space to physical space via the corresponding transformation matrix. The energy functional of the arch is obtained by the generalized shell theory, and the finite element model for wave motion analysis is constructed according to Hamilton's principle and the central difference method in time domain. Taking the practical application into account, damaged arch waveguides are also investigated. Proper analysis of the responses from structure damages allows one to indicate the location very precisely. This paper mainly focuses on the crack in structures. Based on Castigliano's theorem and the Pairs equation, the local flexibility of crack is formulated for BSWI element. Numerical experiments are performed to study the effect of wave propagations in arch waveguides, that is, frequency dispersion and mode spilt in the arch. The responses of the arch with cracks are simulated under the broad-band, narrow-band and chirp excitations. In order to estimate the spatial, time and frequency concentrations of responses, the reciprocal length, time-frequency transform and correlation coefficient are introduced in this investigation.     

Ga-vacancy-induced room-temperature ferromagnetic and adjusted-band-gap behaviors in GaN nanoparticles

Room-temperature ferromagnetism has been found in Ga-deficient GaN grown using the direct reaction of Ga \(_{2}\) O \(_{3}\) powder with NH \(_{3}\) gas. The observed magnetism in GaN induced by Ga vacancies is investigated both experimentally and theoretically. First-principles calculations reveal that the spontaneous spin polarization is created by the 3.0  \(\mu _\mathrm{B}\) local moment for GaN and magnetism originates from the polarization of the unpaired 2 \(p\) electrons of N surrounding the Ga vacancy. At the same time, the band gap can be also adjusted by changing the Ga-vacancy concentration.     

Base-Mediated Biginelli-Like Reaction Ignited by Aromatic Isocyanate: A Facile One-Pot Synthesis of N 4-Aryl-5-carboxyl-6-methyl Cytimidine Derivatives

The new three-component Biginelli reaction of aromatic isocyanate, ethyl acetoacetate, and substituted urea (or thiourea as well as guanidine) is described for the first time. In this reaction, N ⁴-aryl-5-carboxyl-6-methyl cytimidine derivatives were obtained in moderate to excellent yields by employing DBU as a highly effective catalyst. This methodology provides several advantages such as good functional group tolerance, excellent yields, atom efficiency, and experimental simplicity.     

光谱联合电泳法研究双酚A与肿瘤相关DNA的相互作用

研究双酚A与人类肿瘤相关DNA(抑癌基因p53 DNA和癌基因C-myc DNA)的相互作用。分别采用紫外、荧光和圆二色等光谱方法和聚丙烯酰胺凝胶电泳法研究了双酚A与人类肿瘤相关DNA(抑癌基因p53 DNA和癌基因C-myc DNA)的相互作用模式。其中紫外、荧光和圆二色滴定实验均表明了嵌插作用的存在,离子强度实验、KI猝灭对比实验和凝胶电泳实验证实了静电和嵌插作用的共同作用,可进一步影响DNA的双螺旋构象。     

Highly selective separation of aminoglycoside antibiotics on a zwitterionic Click TE‐Cys column

Hydrophilic interaction liquid chromatography has emerged as a valuable alternative approach to ion‐pair chromatography for the separation of aminoglycoside antibiotics in recent years. However, the resolution of structurally related aminoglycosides is a great challenge owing to the limited selectivity. In this work, a cysteine‐based zwitterionic stationary phase (named Click TE‐Cys) was utilized and compared with five commonly used hydrophilic interaction liquid chromatography columns. Click TE‐Cys displayed much better selectivity for structurally similar aminoglycosides. The retention behaviors of aminoglycosides were investigated in detail, revealing that low pH (2.7 or 3.0) and high buffer concentration (≥50 mM) were preferable for achieving good peak shape and selectivity. Effective resolution of ten aminoglycosides including spectinomycin, dihydrostreptomycin, streptomycin, gentamicin C1, gentamicin C2/C2a, gentamicin C1a, kanamycin, paromonycin, tobramycin, and neomycin was realized at optimized conditions. Additionally, spectinomycin and its related impurities were successfully resolved. The results indicated the great potential of the Click TE‐Cys column in the separation of aminoglycoside mixtures and related impurities.     

Mechanisms and kinetics for preparing carbohydrazide by reacting dimethyl carbonate with hydrazine: A theoretical study

The mechanism and kinetic modeling for preparing carbohydrazide from dimethyl carbonate and hydrazine has been declared. The geometries of all the stationary points (reactants, intermediates, transition states, and products) are optimized by using the B3LYP method with the cc‐pVDZ basis set, and the harmonic vibrational frequencies as well as infrared intensities are predicted with the same method. The minimum‐energy paths are obtained by using the intrinsic reaction coordinate (IRC) theory at the B3LYP/cc‐pVDZ level of theory with the step length 0.02 (amu)^1/2·bohr. The rate constants are evaluated by using the TST, TST/Eckart, and RRKM (T)/Eckart methods. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

β-Cyclodextrin and folic acid host–guest interaction binding parameters determined by Taylor dispersion analysis and affinity capillary electrophoresis

The thermodynamic properties of molecular recognition in host–guest inclusion complexes can be studied by Taylor dispersion analysis (TDA). Host–guest inclusion complexes have modest size, and it is possible to get convergent results fast, achieving greater certainty for the obtained thermodynamic properties. Cyclodextrins (CDs) and their derivatives can be used as drug carriers that can boost stability, solubility, and bioavailability of physiologically active substances. A simple and effective approach for assessing the binding properties of CD complexes that are critical in the early stages of drug and formulation development is needed to fully understand the process of CD and guest molecules’ complex formation. In this work, TDA was successfully used to rapidly determine interaction parameters, including binding constant and stoichiometry, between β-CD and folic acid (FA) along with the diffusivities of the free FA and its complex with β-CD. Additionally, the FA diffusion coefficient obtained by TDA was compared to the results previously obtained by nuclear magnetic resonance. Affinity capillary electrophoresis (ACE) was also used to compare the binding constants obtained by different methods. The results showed that the binding constants obtained by ACE were somewhat lower than those obtained by the two TDA procedures.