Static Retention of Dynamic Chiral Arrangements for Achiral Shear Thinning Metal–Organic Colloids

Chiral compounds are known to be important not only because they are the fundamental components of living organisms, but also for their unique chiroptical properties. In recent years, scientists have fabricated several chiral organic supramolecular aggregates by using chiral physical fields, such as vortex flow. Herein, the relationship between dynamic chiroptical properties and rheological nature is discussed, suggesting the shear thinning properties of non-Newtonian fluids might help colloidal particles adopt a chiral arrangement in vortices. Furthermore, the storage modulus of colloids could be increased by adding a linking agent, which successfully kept the dynamic chiroptical properties in the static state. Moreover, the salt effect on the host–guest interaction involved in the colloids was studied, the results suggested a significant enhancement of the transferred dynamic circular dichroism for the achiral guest molecule.     

DNA-directed formation of peptide bond: a model study toward DNA-programmed peptide ligation

A model study of DNA-directed peptide ligation has been developed by transferring fluorescent reporting group from small molecule thioester to a DNA strand (template DNA) in the presence of a thiol-functionalized DNA strand (auxiliary DNA), mimicking the Native Chemical Ligation (NCL) reaction. This DNA-directed transfer shows dependence on the sequence complementarity of the two DNA strands, with in situ generated 4-thiolphenylmethyl functionalized oligonucleotide as the auxiliary DNA strand, under mild basic condition (pH=8.5), and with tris(2-carboxyethyl) phosphine hydrochloride (TCEP) as a reducing agent. Reactions with different amino acid α-thioesters resulted in varied transfer efficiencies from glycine to α-substituted amino acids. This study has provided the basic foundation to use DNA-programmed chemistry toward the chemical synthesis or unnatural modification of protein molecules.     

Intermetallic Pt2Si：magnetron-sputtering preparation and electrocatalysis toward ethanol oxidation

Although most transition metals have been tested as the promoter to Pt for electrocatalysis toward fuel cell reactions,semi-conductor elements,such as Si,have hitherto not been examined.Here we report a simple synthesis of intermetallic Pt2Si electrode using magnetron sputtering and the electrocatalysis toward ethanol oxidation reaction（EOR）.In comparison to Pt,the intermetallic Pt2Si surface turns out to be much more active in catalyzing the EOR：the onset potential shifts negatively by 150 mV,and the current density at 0.6 V increases by a magnitude of one order.Such an enormous enhancement in EOR catalysis is ascribed to the promotion effects of Si,which can not only provide active surface oxygenated species to accelerate the removal of COads,but also strongly alter the electronic property of Pt,as clearly indicated by the core-level shift in XPS spectrum.     

A novel NH4OAc and CuBr(PPh3)3-induced intermolecular Pummerer-type reaction between free (NH)-indoles and dimethylsulfoxide: facile synthesis of 3-methylthiomethyl substituted indoles

A novel NH₄OAc/CuBr(PPh₃)₃-induced intermolecular Pummerer-type reaction between free (NH)-indoles and dimethylsulfoxide is first reported, which offers the 3-methylthiomethyl substituted indoles conveniently and efficiently.     

The Structural Fate of Individual Multicomponent Metal‐Oxide Nanoparticles in Polymer Nanoreactors

Multicomponent nanoparticles can be synthesized with either homogeneous or phase‐segregated architectures depending on the synthesis conditions and elements incorporated. To understand the parameters that determine their structural fate, multicomponent metal‐oxide nanoparticles consisting of combinations of Co, Ni, and Cu were synthesized by using scanning probe block copolymer lithography and characterized using correlated electron microscopy. These studies revealed that the miscibility, ratio of the metallic components, and the synthesis temperature determine the crystal structure and architecture of the nanoparticles. A Co‐Ni‐O system forms a rock salt structure largely owing to the miscibility of CoO and NiO, while Cu‐Ni‐O, which has large miscibility gaps, forms either homogeneous oxides, heterojunctions, or alloys depending on the annealing temperature and composition. Moreover, a higher‐ordered structure, Co‐Ni‐Cu‐O, was found to follow the behavior of lower ordered systems.     

近似周期时间序列分析（英文）

本文首先给出了近似周期时间序列概念,即:具有周期特征但是周期长度变化的时间序列.比如,太阳黑子序列具有11年左右的周期,但是其周期并不是11,而是在11左右变化,这就是一个近似周期序列.然后给出了提取近似周期趋势方法,并且提出了广义差分算子,这里提出的广义差分算子不仅可以消除时间序列的长期趋势和周期性,而且还可以消除近似周期性.最后,以太阳黑子序列为例说明了广义差分算子的应用.     

Flame‐retardant and mechanical properties of phenolic foams toughened with polyethylene glycol phosphates

Three kinds of polyethylene glycol phosphates (PEGPs) toughening agents were synthesized by esterification of phosphorus pentoxide (P₂O₅) with polyethylene glycol and characterized by Fourier transform infrared spectra and ³¹P nuclear magnetic resonance. A series of lightweight phenolic foams toughened with different loadings of PEGPs were prepared. Optical microscopy results show that the addition of PEGPs with small molecular weight PEG improves the structural homogeneity of phenolic foams obviously. The flame retardancy of toughened phenolic foams was evaluated by using UL 94, limiting oxygen index, and cone calorimeter. The results indicate that the incorporation of PEGPs not only increases the toughness of phenolic foams but also improves their flame retardancy. Moreover, the thermal stability of PEGPs and the toughened foams was investigated by thermogravimetric analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Study of Nonlinear Resonance Effect in Paul Trap

In this article, we investigated the nonlinear resonance effect in the Paul trap with a superimposed hexapole field, which was assumed as a perturbation to the quadrupole field. On the basis of the Poincare-Lighthill-Kuo (PLK) perturbation method, ion motional equation, known as nonlinear Mathieu equation (NME) was expressed as the addition of approximation equations in terms of perturbation order. We discussed the frequency characteristics of ion axial-radial (z-r) coupled motion in the nonlinear field, derived the expressions of ion trajectories and nonlinear resonance conditions, and found that the mechanism of nonlinear resonance is similar to the normal resonance. The frequency spectrum of ion motion in nonlinear field includes not only the natural frequency series but also nonlinear introduced frequency series, which provide the driving force for the nonlinear resonance. The nonlinear field and the nonlinear effects are inevitable in practical ion trap experiments. Our method provides better understanding of these nonlinear effects and would be helpful for the instrumentation for ion trap mass spectrometers.      

Simulation of Rarefied Gas Flows in Atmospheric Pressure Interfaces for Mass Spectrometry Systems

The understanding of the gas dynamics of the atmospheric pressure interface is very important for the development of mass spectrometry systems with high sensitivity. While the gas flows at high pressure (>1 Torr) and low pressure (<10^–3 Torr) stages are relatively well understood and could be modeled using continuum and molecular flows, respectively, the theoretical modeling or numeric simulation of gas flow through the transition pressure stage (1 to 10^–3 Torr) remains challenging. In this study, we used the direct simulation Monte Carlo (DMSC) method to develop the gas dynamic simulations for the continuous and discontinuous atmospheric pressure interfaces (API), with different focuses on the ion transfer by gas flows through a skimmer or directly from the atmospheric pressure to a vacuum stage, respectively. The impacts by the skimmer location in the continuous API and the temporal evolvement of the gas flow with a discontinuous API were characterized, which provide a solid base for the instrument design and performance improvement.

Preparation of Epoxy-Functionalized Magnetic Polymer Nanospheres for Magnetically Targeted Radiotherapy

Magnetic poly(styrene?methyl methacrylate-glycidyl methacrylate)/Fe₃O₄ nanospheres with epoxy groups were prepared by modified one-step mini-emulsion polymerization in the presence of Fe₃O₄ ferrofluids. The products were characterized by fourier-transform infrared spectrum, transmission electron microscopy, thermogravimetric analysis and vibrating sample magnetometer. After surface modification with diaminopropane, histidine was covalently linked to the amine group of magentic nanospheres using glutaraldehyde as crosslinker. Finally, the preliminary labeling study based on non-radioactive rhenium was carried out and the labeling efficiency reached 80.4%. Such magnetic nanospheres had promising potential in magnetically targeted radiotherapy of cancer.