Acid-base cooperativity of heterogeneous catalyst containing acidic framework and sterically hindered base for aldol condensation

A bifunctional heterogeneous catalyst containing two mutually incompatible acidic and basic sites,which exhibits cooperative catalytic behavior in the aldol condensation of acetone and various aldehydes,was synthesized by postgrafting of 1,5,7- triazabicyclo[4.4.0]dec-5-ene(TBD,a sterically hindered organic base) onto Al-MCM-41 molecular sieve.     

一个极限定理

本文给出一个与同余和有关的极限定理,它在计算机模式识别中有应用。     

On three-phase boundary motion and the singular limit of a vector-valued Ginzburg-Landau equation

We present a formal asymptotic analysis which suggests a model for three-phase boundary motion as a singular limit of a vector-valued Ginzburg-Landau equation. We prove short-time existence and uniqueness of solutions for this model, that is, for a system of three-phase boundaries undergoing curvature motion with assigned angle conditions at the meeting point. Such models pertain to grain-boundary motion in alloys. The method we use, based on linearization about the initial conditions, applies to a wide class of parabolic systems. We illustrate this further by its application to an eutectic solidification problem.     

Copper and amine free Sonogashira cross-coupling reaction catalyzed by efficient diphosphane-palladium catalyst

The commercially available diphosphane ligand MeO-BIPHEP was first investigated in the palladium-catalyzed Sonogashira reaction in the absence of copper and amine.The coupling of various aryl bromides and aryl chlorides with phenylacetylene gave moderate to excellent yields.     

Preparation and characterization of cross-linked β-cyclodextrin polymer/Fe_3O_4 composite nanoparticles with core-shell structures

Cross-linkedβ-cyclodextrin polymer/Fe₃O₄ composite nanoparticles with core-shell structures were prepared via cross linking reaction on the surface of carboxymethylβ-cyclodextrin（CM-β-CD） modified Fe₃O₄ nanoparticles inβ-cyclodextrin alkaline solution by using epichlorohydrin as crosslinking agent.The morphology,structure and magnetic properties of the prepared composite nanoparticles were investigated by transmission electron microscopy（TEM）,Fourier transform infrared（FTIR） spectrometry,X-ray diffraction（XRD） measurement,thermogravimetric analysis（TGA） and Vibrating sample magnetometry （VSM）,respectively.     

Electrochemically induced anatase inhibits bacterial colonization on Titanium Grade 2 and Ti6Al4V alloy for dental and orthopedic devices

Bacterial contamination of implanted devices is a common cause of their failure. The aim of the present study was to assess the capability of electrochemical procedures to: (a) promote the formation of anatase on the surface of commercially pure Grade 2 Ti and Ti Grade 5 (Ti6Al4V) alloy; (b) inhibit in vitro biofilm formation of Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus mutans and Porphyromonas gingivalis and oral plaque in vivo, (c) preserve favorable response of osteoblasts and fibroblasts to materials surfaces. Ti Grade 2 and Ti Grade 5 were respectively anodized at two different voltages: 90 and 130V for pure titanium; 100 and 120V for Ti6Al4V alloy. Surface characterization was performed by scanning electron microscopy (SEM) equipped with EDS probe, laser profilometry and X-ray diffractometry. Bacterial adhesion characterization was performed either in vitro and in vivo in patients. Osteoblast and fibroblast response was evaluated by metabolic activity assessment. The higher voltage applied in the anodization treatment of pure titanium (130V) and Ti6Al4V alloy (120V) surfaces, compared to the untreated pure titanium and Ti6Al4V and to lower voltage treatments, resulted in a greater decrease in bacterial attachment and biofilm formation in both in vitro and in vivo experiments. In contrast, the high voltage treatments were found to promote osteoblasts and fibroblasts proliferation. The observations indicated that the experimented high voltage anodization treatments may contribute to preserve the tissue integration and reduce bacteria colonization of titanium and titanium alloy for implantable applications.     

Insights on the mechanism for synthesis of methylenedianiline from aniline and formaldehyde through HPLC-MS and isotope tracer studies

The mechanism for synthesis of 4,4-methylenedianiline(MDA) via condensation reaction of aniline with formaldehyde has been studied extensively in this paper.The intermediate and by-products were isolated and identified.The combination of isotope labeling and HPLC-MS characterizations disclosed that the reaction proceeded through an S_N2 reaction mechanism.Moreover,the effect of aniline/formaldehyde molar ratio on the formation of MDA was investigated.This work would be of significance to understand the reaction mechanism deeply and provide valuable information for further improving the yield of desired product.     

Anionic synthesis of binary random in-chain multi-functionalized poly(styrene/butadiene/isoprene and dimethyl [4-phenylvinyl)-phenyl]silane)(PS-DPESiH,PB-DPESiH,PI-DPESiH) copolymers

The binary random in-chain silyl-hydride multi-functionalized poly(styrene/butadiene/isoprene and dimethyl[4-(1-phenylvinyl) phenyl]silane)(PS-DPESiH,PB-DPESiH,PI-DPESiH) copolymers were successfully synthesized.These functionalized copolymers were prepared in hexane with n-BuLi as the initiator at 50℃for 4 h.The silyl-hydride groups were introduced into polymer backbones quantitatively by living anionic polymerization.The copolymers were determined through ’H NMR,size exclusion chromatography(SEC) and differential scanning calorimetry(DSC) techniques,while the number of silyl-hydride groups was calculated and discussed.