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Abstract  

This work began with the side chain of ginsenoside Rg1 which was acetylized with Ac2O-Pyr and oxidized by OsO4 and NaIO4 to give ginsenoside Rg1 aldehyde(2), which was further converted into an unsaturated ester(3) by Wittig-Horner reaction. The unsaturated ester(3) was treated with N2H4 and HNO2 to yield Rg1 azide(4) which was directly conjugated with BSA to give immunogen: ginsenoside Rg1-BSA conjugate(5). This azide(4) was conjugated with tyramine to give ginsenoside Rg1-tyramine conjugate which was labelled with free Na125I by CH-T to yield125I-labeled antigen: gensenoside Rg1-125I-tyramine(6). The labelling rate was 40%–50% and specific activity was 3.0–4.0 MBq/g.

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Abstract  

Upon
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$(\bar M_n )$$ \end{document}
of the grafted poly(methyl methacrylate) (PMMA) side chains was in the range of 430 000 (for a dose of 10 kGy) and practically independent of grafting degree. However, the number of branches per graft copolymer molecule increases from 0.3 to 0.8 when the degree of grafting increases from 32% to 88%. Similarly, the radiation yield, i.e. the number of branches formed per 100 eV of energy absorbed in the substrate polymer increases from 0.75 to 1.94. The value and meaning of molecular weight of graft copolymer is discussed along with the mechanism of polymer chain termination.
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Abstract  

Positron annihilation lifetime measurements of PMMA, PEMA, PiPMA, PnPMA and PnBMA were performed in the temperature range between 15 and 300 K, where , and relaxational transitions occur for these polyalkylmethacrylates. The variations of free volume size and content calculated from the longest lifetime component against temperature are correlated to the results obtained by dielectric, viscoelastic and dynamic mechanical relaxation data of the polymers. The variations of free volume sizes and contents, apparent free volume fraction and size distribution of the polyalkylmethacrylates are well correlated with the rotational transitions of side chains. The location of free volumes, in which positronium annihilates can be estimated near the vicinity of alkyl groups bound to oxygen atom of side ester chains.

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Abstract  

Despite substantial progress in analytical techniques for polymer characterization, a realistic picture of branching structure in industrial polymers still remains at large. Using a number of assumptions, structure-based constitutive models can distinguish between linear and branched structures in a qualitative sense. More detail on branching architecture, such as the number and length of side chains, the sequence in which they exist on the backbone and their contribution to polymer chain relaxation is more or less unknown. In the current study, elongational behavior of four commercial polyolefins is compared using the predictions of the MSF (molecular stress function) theory. The results will then be used to analyze the branching in a group of strain-hardening polypropylenes synthesized using single site catalyst.

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Journal of Flow Chemistry
Authors: Michael S. Placzek, Jessica M. Chmielecki, Connor Houghton, Alyssa Calder, Charlotte Wiles, and Graham B. Jones

Abstract

Continuous-flow methodologies have been applied to the synthesis of a number of fluorinated alkynyl arenes and heteroarenes. Through a series of optimizations reagent stoichiometry and reaction time were improved and substrate specificity was interrogated. Using optimized conditions under copper-free Sonogashira type couplings readily available arene building blocks were derivatized with fluoroalkynyl side chains in <10 min. Given the rapidity of the process and the enhanced purity profile of the products an immediate application of the work is in the development of 18F labeled versions of the agents for subsequent use in positron emission tomography (PET) imaging. A homolog of the Alzheimer's disease imaging agent Fallypride® was prepared using the methodology and additional analogs was identified.

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Summary The mixing state of amphiphilic di-block copolymers consisted of poly(ethylene oxide) and poly(methacrylate) having azobenzene moieties in the side chains p(EO)114pMA(Az)24 and poly(ethylene oxide) p(EO)114 was investigated from the viewpoints of isothermal crystallization and nano-scale ordered structure. The chemical potential, which required establishing the constant crystal growth rate, decreased with the p(EO) content up to 60%. The hexagonal packed cylinder structure was observed for the blends with the p(EO) content up to 60% and the lattice spacing of (100) and (110) planes increased with the p(EO) content up to 60%. The blends of amphiphilic p(EO)114pMA(Az)24 and p(EO)114 were miscible without in the p(EO) content below 60%.

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Abstract  

Phase transition process of PEOm-b-PMA(Az)n was investigated by the simultaneous DSC-XRD measurement using the synchrotron radiation facility. Four endothermic DSC peaks were observed during heating process. These DSC peaks were assigned to the melting of PEO, the transition from SmX, which is a mixture of super-cooled SmC and crystal, to SmC, from SmC to SmA, and from SmA to isotropic liquid state as determined by XRD profiles. In SmC phase, the liner expansion coefficient calculated from the spacing variation of the smectic layer distance was larger than that of the other phases. This result reflected the fact azobenzene moieties in the long-side chains of PMA(Az)n forming the smectic layers and then they were tilted and stood up during the heating process.

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Összehasonlító vizsgálatokat végeztünk 13 gyomirtó szer hatóanyagán azok fotobomlási folyamatainak tanulmányozására. Mivel a spontán alapfolyamatok megfigyelése volt a célunk, nem használtunk adalékanyagokat. Bár a természetben a növényvédő szerek számtalan, a bomlásukat befolyásoló anyaggal találkoznak, a kutatás e fázisában ezeknek a hatásoknak a vizsgálata nem volt célunk. A vizsgálatok alapján felvázoltuk az egyes hatóanyagok bomlási sémáját és a bomlás időbeli lefutását. Megállapítottuk, hogy valamennyi vizsgált vegyület jól mérhető fotoaktivitást mutatott vizsgálati körülményeink között, valamint hogy a legtöbb vegyület bomlásterméke kevésbé környezetidegen, mint az eredeti vegyület volt.

Nem hagyhatjuk azonban figyelmen kívül, hogy természetes körülmények között a talajban számos egyéb folyamat is lejátszódik, a vizsgált vegyületek — elsősorban bázikus jellegű — nitrogénatomján a mikrobiális folyamatok hatására N-oxidáció is bekövetkezhet. Ez egyrészt közvetlenül nitrozovegyületek kialakulásához vezethet, amelyek már magukban is igen toxikusak és karcinogének. A talajban előforduló nitrit- és különösen a nagy mennyiségű nitrátionokkal ezek a nitrozovegyületek tovább is reagálhatnak, és ez a folyamat a fokozottan agresszív karcinogén N-nitrózaminok keletkezéséhez vezethet. Mivel ezek a folyamatok talajtípus függőek, további vizsgálatuk elengedhetetlen.

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Summary Thermally induced structural transformation of fibrous hydrogen-bonded molecular assemblage formed from an amphoteric pyridinecarboxylic acid of 6-[2-propyl- 4-(4-pyridylazo)phenoxy]hexanoic acid (C5PR) was studied using differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermogravimetry (TG). The organized fibrous morphology formed in an aqueous solution was stable at temperatures below 150°C. The ordered crystalline solid phase (K1) of the original fibrous material altered to a disordered crystalline solid phase (K2) at 150°C and subsequently to an isotropic phase (I) at 172°C. In the isotropic state, the C5PR molecule was slowly decomposed by decarboxylation. Once the molecular assemblage was subjected to the mesophase by heating, another ordered crystalline solid phase (K3) appeared reversibly at 17°C. The heat budget analyses by DSC indicated that a conformational entropy change such as the side-chain propyl group and the main-chain pentamethylene unit in the hydrogen-bonded molecular assemblage took place between the two ordered crystalline solid phases K1 and K3.

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Abstract  

Bis [(ω-(4′-cyanobiphenyl)-4-yl)oxy-n-alkyl]norborn-5-ene-2,3-dicarboxylate was polymerised via ring opening metathesis polymerisation (ROMP). Two disubstituted polynorbornene derivatives both of cis configuration with different length of the side-chain were studied. Differential scanning calorimetry (DSC) was used to study the effect of thermal history on the assignment of the glass transition event associated with the biaxial orientation of a smectic phase. Glass transition temperatures, the change of isobaric specific heats at Tg and the enthalpies of isotropisation were calculated. The DSC traces only show the classic step-wise change in Tg in some cases, giving the evidence that the amorphous domains are constrained and highly restricted in movement due to the morphology developed as a result of the biaxial stretching. Based on the literature data of mono- and disubstituted polynorbornene derivatives and our calorimetric experiments, the shape of Tg dependence on number of (CH2) units is interpreted. The origin of this shape is discussed.

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