Ring-opening and Elimination Cooligomerization of Cyclic Carbonates and e-Caprolactone

Cyclic carbonates e.g. ethylene- and propylene carbonate undergo ring-opening polymerization （ROP） at elevated temperatures （ 〉 100 ℃ ） in the presence of initiators such as Lewis acids, bases, or transesterification catalysts to yield poly（ether carbonates） as outlined below. See Fig. 1.     

New Biodegradable Thermoplastic Multiblock Copolymers from Lactic Acid, ε-Caprolactone, Poly(Ethylene Oxide) and Toluene Diisocyanate

1 Introduction The interest in finding new biodegradable materials for applications in important areas has been motivated by environmental protection aspects. Foremost among the potentially biodegradable and biocompatible polymers, poly(lactic acid) and poly(ε-caprolactone) received considerable attention as their potential application in a wide range of biomedical and pharmaceutical areas was recognized.1IntroductionTheinterest infinding newbiodegradable materialsfor applicationsini mportant…     

Formation of ε-Fe_XN/BN magnetic nanocomposite and itsthermodynamic and kinetic analyses

A nanocomposite of nanometer-sized magnetic granular ε-Fe-XN embedded in a nonmagnetic amorphous boron nitride matrix was prepared by ball milling mixture of α-Fe and hexagonal boron nitride in argon atmosphere. The grain size of the ε-Fe-XN alloy was about 10-20 nm. The nitrogen concentration in the ε-Fe-XN alloy increases with extending milling time. Both thermodynamic calculation and the present experiment show that iron and nitrogen atoms have higher alloying driving force than iron and boron atoms. Analyses of thermodynamics and kinetics about formation of the ε-Fe-XN alloy suggested that the formation of the ε-Fe-XN alloy is related to amorphization of the hexagonal boron nitride and refinement of the α-Fe. It was found from the present experiment that a critical grain size of the α-Fe reacting with nitrogen in the amorphous boron nitride is about 8 nm.     

Analysis on the Reasons and the Elimination of Sexism in English Language

本文揭示并分析英语语言中广泛存在的性别歧视现象,以及提出规避性别歧视的可行方法。     

The Effect of Cyclic Stretching on Matrix Production, Mineralization and Differentiation of Osteoblasts

A four-point bending apparatus is used to investigate the effects of stretching on collagen synthesis, mineralization and differentiation of osteoblasts. Cells are stretched at 1500με for 24 hours. The responses of osteoblasts to mechanical signal of physiological stretching are evaluatedfrom three aspects: collagen production, extracellular inorganic calcium secretion and ALP activity. The results show that osteoblasts decrease the collagen synthesis, calcium secretion and ALP activity compared to the control cells (65.82 %, 73.51%, 48.10 96 respectively ), confirming that cyclic stretching at 1500με inhabits the ohvsiological activity of osteoblasts.     

Studies on the Nucleophilicity and Scavenge of Superoxide Ion by Cyclic Voltammetry

0　IntroductionManyevidencesshowthatsuperoxideionisrelatedtomanyhumandiseasessuchascancerandageing .Theinvestiga tiononsuperoxideionhasattractedmuchattentioninmanyfields.Manymethodshavebeenreportedforthestudyofsuper oxideionincludingelectronspinresonance ,chemiluminescence,liquidchromatographyandelectrochemicalmethods[1 3] .Comparingwithspectrometryandelectronspinresonance,electrochemicalmethodshavemoreadvantagessuchasdirectde tection ,highsensitivityandlowexpense .Therehavebeenmanyreportson…     

Enzyme-Mediated Hydrolysis of Poly（ethylene glycol）-Supported Carbonates

Enzymatic kinetic resolution of racemic alcohols or esters is known as a useful method for the preparation of optically active secondary alcohols. However, the work-up including the separation of the mixture of the remaining substrate and the resulting compound spend a lot of time and waste much amount of solvents. On the other hand, organic synthesis based on polymer supports has made rapid progress. Although the methodology is potentially useful for the easy separation of compounds obtained by the enzymatic reaction, there have been relatively few reports on enzymatic resolutions of using a polymer so far. We have noticed that using a watersoluble polymer could be suitable for enzymatic transformation. Here, we report the first example of an enzyme-mediated enantioseleetive hydrolysis of poly（ethylene glycol）（PEG）-supported substrates with a carbonate moiety to afford optically active compounds, and the method enables us to achieve the easy separation of the products. See Scheme 1.     

The General Technique of Selected Harmonics Elimination for Multilevel Converters

With the rapid developmentofeconomy,thereis a very large demand for power converters,especially for high power converters since the lowvoltage low power converter market becomes moreand more saturated.The converters for high powerhigh voltage applications are facing a new era inthe next decades,so many researchers have paidtheir attention on the converter structures,themost competitive one of which is the multilevelconverter. Selected harmonics elimination PWMtechniques for multilevel convert…     

Discussion of the Constitutive Relation on Cyclic Stress-Strain of Engineering Materials

Based on the experimental results and analysis of the cyclic deformation, there is an obvious yield stage on the cyclic stress-strain curve at the stage of small plastic deformation (in room or low temperatures). This phenomenon is similar to that of monotonic tensile curve case. But for the former the deformation amount at which the yield begins is much smaller than that for the latter. The cyclic stress-strain constitutive relation needs to be further studied according to the actual cyclic stress-strain curve. The conventional constitutive equation σ=Aεn is based on the results only corresponding to the cyclic strengthening stage. It is not appropriate for the stage of the small plastic deformation and the stage of yield.     

Properties of Surface Cyclic Oligomers Present on Polyester Fiber

The effects of different treatments, such as dry heat,wet heat, solvent vapor and ultrasonic, on propertiesof the cyclic oligomers on the surface of polyester fiberare studied. The components of surface oligomers areanalyzed through Thin-Layer Chromatograph. Theresult shows that: all of the treatment, especially     

Microwave-assisted ring-opening copolymerization of ε-caprolactone and 2-Phenyl-5,5-bis（oxymethyi） trimethylene carbonate

A series of polycarbonate copolymers were synthesized by microwave-assisted ring-opening polymerization of ε-caprolactone （CL） and 2-phenyl-5,5-bis（oxymethyl） trimethylene carbonate （PTC） with Tin （Ⅱ） 2-ethylhexanoate as a catalyst. These copolymers obtained were detected by 1H NMR, FT-IR, UV, gel permeation chromatography （GPC）, differential scanning calorimetry （DSC） and automatic contact angle meter. The influences of the feed molar ratio of monomers, catalyst concentration, reaction time and reaction temperature, as well as microwave irradiation power on the copolymerization process were also studied. In vitro degradation tests indicated that these polycarbonate copolymers possess the slow degradation rates and strong hydrophobicity. In vitro release profiles of 5-Fu from copolymers showed that copolymers have the steady drug release rates and good controlled release properties.     

Interactions between the nuclear matrix proteins and the 5'-flanking cis-acting elements of the human ε-globin gene

An erythroid-specific nuclear matrix protein (termed ε-NMPk) in K562 cells, which can specifically bind to the positive stage-specific regulatory element (ε-PRE Ⅱ , - 446- - 419 bp) upstream of the human ε-globin gene, has been identified by using gel mobility shift assay. Meanwhile, Southwestern blotting assay showed that the nuclear matrix protein ε-NMPk in K562, cells may be composed of two polypeptides ( ～ 40 ku). In addition, it is observed in the gel mobility shift assay that the nuclear matrix proteins from K562, HEL and Raji cells can bind to the silencer DNA ( - 392- - 177 bp) in the 5'-flanking sequence of human ε-globin gene respectively. However, the shift band K detected in K562 cells is different from shift band H/R in HEL and Raji cells, suggesting that a common nuclear matrix protein may exist in HEL and Raji cells. Results show that the nuclear matrix protein may play an important role in the regulation of the human ε-globin gene expression.     

Enolate chelating N-heterocyclic carbene complexes of Fe(II): Synthesis, structure and their catalytic activity for ring-opening polymerization of ε-caprolactone

The reaction of anhydrous FeBr2 with two equivalents of anionic N-heterocyclic carbene (NaL1 and NaL2), which are generated in situ by the reaction of the corresponding salt [4-R-C6H4COCH2{CH- (NCHCHNiPr)}Br] (R = OCH3, H2L1Br, 1; R = F, H2L2Br, 2) with two equivalents of NaN(SiMe3)2, affords bis-ligand Fe(II) complexes of L12Fe (3) and L22Fe (4) in high yield, respectively. Attempt to synthesize mono-ligand Fe(II) bromide by the 1:1 molar ratio of NaL to FeBr2 is unsuccessful, and the same com- plexes of 3 and 4 were obtained. Both 3 and 4 have been depicted by elemental analysis and X-ray structure determination. Preliminary studies show that both 3 and 4 can be used as single-component catalyst for the ring-opening polymerization of ε-caprolactone, and the catalytic activity of 3 is higher than that of 4.     

New Biodegradable Thermoplastic Multiblock Copolymers from Lactic Acid, 8-Caprolactone, Poly（Ethylene Oxide） and Toluene Diisocyanate

The interest in finding new biodegradable materials for applications in important areas has been motivated by environmental protection aspects. Foremost among the potentially biodegradable and biocompatible polymers, poly（lactic acid） and poly（ε-caprolactone） received considerable attention as their potential application in a wide range of biomedical and pharmaceutical areas was recognized.     

Synthesis and Characterizations of 1,4-butanediol( BDO )-Regulated Poly( ε-caprolactone)(PCL) Waterborne Polyurethane with Controlled Biodegradability for Medical Applications

Waterborne polyurethane(WBPU)with controlled biodegradability and biocompatibility was synthesized by using poly(ε-caprolactone)(PCL)as the polyglycol,isophorone diisocyanate(IPDI)as the isocyanate,2,2-bishydroxymethylbutyric acid(DMPA)as the chain extender and 1,4-butanediol(BDO)as the hard-segment regulating agent.We found that BDO content significantlyinfluencedmechanicalproperties,degradable performances and cyto-biocompatibility of PCL-WBPUs.Increasing the BDO content in PCL-WBPU enhanced its tensile strength and decreases strain.Enzymolysis and hydrolysis properties were also regulated by BDO content,but with different mechanisms.Cytobiocompatibility was evaluated with ATDC5 cells.The results show that the biodegradability of PCL-WBPU is significantly determined by BDO content,which exerts a serious influence on its polymer structure,leading to resultant degradable properties.     

Effects of lanthanum and gadolinium on proliferation and differentiation of primary osteoblasts

The effects of La3 and Gd3 on the proliferation, differentiation and adipogenic transdifferentiation of rat calvarial osteoblast-like cells (ROB cells) were evaluated by MTT method, measuring the activity of alkaline phosphatase (ALP) and Oil red O measurement. Both of La3 and Gd3 inhibited the proliferation of ROB cells at all concentrations (1×10-5, 1×10-6, 1×10-7, 1×10-8, 1×10-9 mol·L-1). La3 at concentration of 1×10-5mol·L-1 significantly increased the alkaline phosphatase activity of ROB cells up to 3 folds (P<0.01). However, the effects reversed to inhibit at other concentrations. Gd played a negative role in the alkaline phosphatase activity. La3 inhibited the adipogenic transdifferentiation of ROB cells at all concentrations in a dose-dependent way. However, Gd promoted the adipogenic transdifferentiation of ROB cells at 1×10 and 1×10 mol·L . These findings suggested that the effects of rare earth elements on the proliferation, differentiation and adipogenic transdifferentiation of ROB cells were dependent on their concentrations and species.     

Effects of lanthanum and gadolinium on proliferation and differentiation of primary osteoblasts

The effects of La³⁺ and Gd³⁺ on the proliferation, differentiation and adipogenic transdifferentiation of rat calvarial osteoblast-like cells (ROB cells) were evaluated by MTT method， measuring the activity of alkaline phosphatase (ALP) and Oil red O measurement. Both of La³⁺ and Gd³⁺ inhibited the proliferation of ROB cells at all concentrations (1×10^-5, 1×10^-6, 1×10^-7, 1×10^-8, 1×10^-9 mol?L^-1). La³⁺ at concentration of 1×10^-5 mol?L^-1 significantly increased the alkaline phosphatase activity of ROB cells up to 3 folds (P<0.01). However, the effects reversed to inhibit at other concentrations. Gd³⁺ played a negative role in the alkaline phosphatase activity. La³⁺ inhibited the adipogenic transdifferentiation of ROB cells at all concentrations in a dose-dependent way. However, Gd³⁺ promoted the adipogenic transdifferentiation of ROB cells at 1×10^-8 and 1×10^-9 mol?L^-1. These findings suggested that the effects of rare earth elements on the proliferation, differentiation and adipogenic transdifferentiation of ROB cells were dependent on their concentrations and species