bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conversion of 3‐aminopropionamide and 3‐alkylaminopropionamides into acrylamide in model systems
Authors: Zamora Rosario , Delgado Rosa M. , Hidalgo Francisco J. 
Published: September 2009

AbstractCarbonyl compounds have been shown to play a major role in the conversion of asparagine into acrylamide. However, it is unclear at this point if its role is only restricted to the decarboxylation of the amino acid or if carbonyl compounds also play a role in the deamination reaction of the decarboxylated intermediates 3‐aminopropionamide and 3‐(alkylamino)propionamides. This study describes the deamination reaction of 3‐aminopropionamide and 3‐(alkylamino)propionamides (benzyl, phenylethyl, butyl, and octyl) in model systems and in the presence, or not, of different carbonyl compounds (alkadienals, alkenals, and alkanals). All these reactions were mainly produced at almost neutral or basic pH values. In addition, the reaction yields and the activation energies not only depended on the type of aminopropionamide involved but also on the water activity (aw) and in the presence, or not, of carbonyl compounds. However, there was not a clear correlation among the activation energies calculated for the different deamination reactions and the yields of acrylamide obtained; therefore, suggesting the existence of diverse pathways by which 3‐aminopropionamide and 3‐(alkylamino)propionamides are converted into acrylamide. In addition, these reactions are also competing with other carbonyl–amine reactions when carbonyl compounds are present. All these results suggest that the type of the intermediate aminopropionamide involved is going to play a major role in both the amount of acrylamide produced and the conditions required for its formation. On the other hand, the role of carbonyl compounds in the acrylamide produced, but not in the activation energy of the reactions implicated, seems to be more limited than either the type of amine or the aw. A detailed analysis of the type of the intermediate aminopropionamide formed in foods may help to define strategies for mitigating the formation of this food toxicant.
PAX5 activates the transcription of the human telomerase reverse transcriptase gene in B cells
Authors: Bougel Stéphanie , Renaud Stéphanie , Braunschweig Richard , Loukinov Dmitri , Morse III Herbert C , Bosman Fred T. , Lobanenkov Victor , Benhattar Jean 
Published: September 2009

AbstractTelomerase is an RNA‐dependent DNA polymerase that synthesizes telomeric DNA. Its activity is not detectable in most somatic cells but it is reactivated during tumorigenesis. In most cancers, the combination of hTERT hypermethylation and hypomethylation of a short promoter region is permissive for low‐level hTERT transcription. Activated and malignant lymphocytes express high telomerase activity, through a mechanism that seems methylation‐independent. The aim of this study was to determine which mechanism is involved in the enhanced expression of hTERT in lymphoid cells. Our data confirm that in B cells, some T cell lymphomas and non‐neoplastic lymph nodes, the hTERT promoter is unmethylated. Binding sites for the B cell‐specific transcription factor PAX5 were identified downstream of the ATG translational start site through EMSA and ChIP experiments. ChIP assays indicated that the transcriptional activation of hTERT by PAX5 does not involve repression of CTCF binding. In a B cell lymphoma cell line, siRNA‐induced knockdown of PAX5 expression repressed hTERT transcription. Moreover, ectopic expression of PAX5 in a telomerase‐negative normal fibroblast cell line was found to be sufficient to activate hTERT expression. These data show that activation of hTERT in telomerase‐positive B cells is due to a methylation‐independent mechanism in which PAX5 plays an important role. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Pediatric rhabdomyosarcoma in Morocco
Authors: Hessissen Laila , Kanouni Lamya , Kili Amina , Nachef Mohamed Nacer , El Khorassani Mohamed , Benjaafar Noureddine , Khattab Mohamed , El Gueddari Brahim El Khalil 
Published: September 2009

AbstractBackgroundRhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in the first two decades of life. There is, however, a paucity of reports on the pattern of its occurrence in Africa. This study analyses the epidemiological pattern, clinical features, histology, and outcome in Moroccan children presenting with RMS.MethodsWe retrospectively studied 100 consecutive cases of histologically proven RMS in previously untreated children <15 years old followed at the Pediatric Oncology Unit of the Children's Hospital of Rabat from January 1995 to December 2004.ResultsRMS represented 5% of all the patients treated for cancer during this period. The male/female ratio was 2:1 with a mean age at diagnosis of 5 years. The embryonal subtype was the most frequent (73%) and the head and neck was the most common site of disease, followed by the genito‐urinary tract and limbs. Chemotherapy was used in all patients; 44% also had a radical surgery and 23% radiation therapy. The event‐free survival (EFS) at 10 years was 39% with relapse as the first cause of treatment failure. The overall survival at 10 years was 70%. The rate of treatment abandonment was 37%.ConclusionEpidemiology and clinical features of RMS in Moroccan children does not differ from others countries. However, EFS is lower than that reported elsewhere due to occasional lack of availability of drugs, inadequate local control, and abandonment. Pediatr Blood Cancer 2010; 54:25–28. © 2009 Wiley‐Liss, Inc.
Design, synthesis and polymerization of highly branched pseudodendrimers through tandem reactions
Authors: Wang Junyan , Johnson Dave M 
Published: September 2009

AbstractBACKGROUND: Pseudodendrimers are hyperbranched polymers which are isomeric with dendrimers, that is, each repeat unit is either fully reacted or only singly reacted. The careful design of an ABB′ monomer leads to higher branching by virtue of tandem reactions that increase the reactivity of linear units during polymerization, leading to fully reacted repeat units. The resulting polymers are predicted to be very highly branched, and in the optimum case, pseudodendrimers.RESULTS: Our work shows that 6‐amino‐3‐bromophthalide leads to a highly branched polymer via bromohydrin decomposition during polymerization, giving polymers of M̄ = of 3000 and a polydispersity index of 1.03. Our findings indicate a degree of branching of 0.84. The synthesis of similar polymers using different techniques confirms our proposed intermediate.CONCLUSION: We have demonstrated a new class of hyperbranched polymers which are highly branched, and may be considered pseudodendrimers. Copyright © 2009 Society of Chemical Industry
Cationic polymerization of styrene involving ionization of the CCl bond in ionic liquid/SO2 mixture
Authors: Baśko Małgorzata , Biedroń Tadeusz , Kubisa Przemysław 
Published: September 2009

AbstractThere has been a recent upsurge in interest in use of ionic liquids as reaction media for various chemical processes. Until recently, ionic liquids were considered as highly polar solvents. Our earlier investigation indicated that cationic polymerization of styrene initiated by aryl (alkyl) chlorides in ionic liquids may proceed even in the absence of coinitiator (Lewis acid). Polymerization, however, did not conform to controlled polymerization scheme. More recently, it has been claimed that ionic liquids are not as polar as it was previously assumed. Independently, high solubility of sulfur dioxide in ionic liquids was noticed. As sulfur dioxide displays a high ionizing power toward organic halides, we applied ionic liquid/sulfur dioxide mixture as a solvent in cationic polymerization of styrene initiated by aryl (alkyl) chlorides. Results show that in this reaction medium ionization of the CCl bond is facilitated, and the contribution of chain transfer reaction can be reduced as compared with polymerization in ionic liquid alone. Ionization of the CCl bond, however, is still not sufficiently fast to ensure conditions of controlled polymerization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5251–5257, 2009
Polyisobutylene‐based polyurethanes. III. Polyurethanes containing PIB/PTMO soft co‐segments
Authors: Erdodi Gabor , Kang Jungmee , Kennedy Joseph P. , Yilgor Emel , Yilgor Iskender 
Published: September 2009

AbstractThe synthesis, characterization, and structure–property behavior of polyurethanes containing polyisobutylene (PIB)/poly(tetramethylene oxide) (PTMO) soft co‐segments and bis(4‐isocyanatocyclohexyl)methane (HMDI)/hexanediol (HDO) hard segments is presented. The mechanical (stress/strain, hardness, and hysteresis) properties of these novel polyurethanes were investigated over a broad composition range. PIB‐based polyurethanes with HMDI/HDO hard segments showed better mechanical properties than earlier polyurethanes containing highly crystalline hard segments. The addition of moderate amounts (20% by weight) of PTMO significantly increased both tensile strengths and elongation. In the presence of larger amounts of PIB, these polyurethanes are expected to possess oxidative/hydrolytic/enzymatic stabilities superior to commercially available polyurethanes. These polyurethanes are softer and exhibit hysteresis superior to or comparable with conventional polyurethanes. According to initial thermal studies, these materials show good melt processibility. Overall, the mechanical properties of PIB based hybrid polyurethanes are similar to commercially important polyurethane type biomaterials. Our results show that the incorporation of PTMO segments to PIB‐based polyurethanes significantly improves elastomeric properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5278–5290, 2009
Synthesis and white electroluminescent properties of multicomponent copolymers containing polyfluorene, oligo(phenylenevinylene), and porphyrin derivatives
Authors: Li Hui , Xiang Na , Wang Lei , Zhao Bin , Shen Ping , Lu Junjian , Tan Songting 
Published: September 2009

AbstractTwo novel multicomponent copolymers (P1 and P2) containing polyfluorene (PF), oligo(phenylenevinylene) (OPV), and porphyrin (Por) derivatives were synthesized according to the Suzuki polymerization method. The structures, optical, and electrochemical properties of the two model compounds (OPV and Por) and multicomponent copolymers were characterized by 1H NMR, FTIR, elemental analysis, UV–vis spectroscopy, photoluminescence, and cyclic voltammetry, respectively. Both of the copolymers exhibit thermotropic liquid crystalline properties and represent the characteristic Schlieren textures in a wide temperature range. Electroluminescence spectra of these copolymers exhibit broadband emissions covering the entire visible region from 400 to 700 nm. The single layer polymer light emitting diodes device based on P2 with a configuration of indium tin oxide/poly(ethylenedioxythiophene):poly(styrenesulfonic acid)/polymers/Ca/Al emits white light with the Commission Internationale de l′Eclairage chromaticity coordinates of (0.29, 0.30), maximum brightness of 443 cd/m2. The white‐light‐emitting devices based on the novel multicomponent copolymers exhibit low turn‐on voltage, and good color stability at different driving voltages as well. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5291–5303, 2009
High performance polymer field‐effect transistors based on polythiophene derivative with conjugated side chain
Authors: He Youjun , Wu Weiping , Liu Yunqi , Li Yongfang 
Published: September 2009

AbstractPoly(3‐[2‐(5‐hexyl‐2‐thienyl) ethenyl]‐2,2′‐bithiophene) (P2, see Scheme 1) with conjugated thienylvinyl side chain was synthesized by copolymerization of the thiophene units with and without conjugated side chain with Pd‐catalyzed Stille coupling method. For comparison, P1 with the hexyl side chain instead of conjugated side chain was also synthesized. P2 film shows broad absorption in the visible region with absorption edge at about 700 nm. The solution‐processed polymer field‐effect transistors were fabricated and characterized with bottom gate/top contact geometry. The organic field‐effect transistors (OFET) based on P2 showed an average hole mobility of about 0.034 cm2/Vs (the highest value reached 0.061 cm2/Vs) upon annealing at about 180 °C for 30 min, with a threshold voltage of −1.15 V and an on/off ratio of 104 with n‐octadecyltrichlorosilane (OTS) modified SiO2 substrate. In comparison, the OFET based on P1 displayed a hole mobility of 8.9 × 10–4 cm2/Vs and an on/off ratio of 104 with OTS modified SiO2 substrate. The results indicate that the polythiophene derivative with conjugated thienylvinyl side chain is a promising polymer for the application in polymer field‐effect transistors. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5304–5312, 2009
Poly(cyclohexene oxide)/clay nanocomposites by photoinitiated cationic polymerization via activated monomer mechanism
Authors: Oral Ayhan , Tasdelen Mehmet Atilla , Demirel Adem Levent , Yagci Yusuf 
Published: September 2009

AbstractPoly(cyclohexene oxide) (PCHO)/clay nanocomposites were prepared by in situ photoinitiated activated monomer cationic polymerization. The polymerization of cyclohexene oxide through the interlayer galleries of the clay can provide distribution of the clay layers in the polymer matrix homogenously and results in the formation of PCHO/clay nanocomposites. The exfoliated structures were characterized by X‐ray diffraction spectroscopy, thermogravimetric analysis, transmission electron microscopy, and atomic force microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5328–5335, 2009
Synthesis and characterization of new low bandgap polyfluorene copolymers for bulk heterojunction solar cells
Authors: Hsu Steve Lien‐Chung , Lin Yu‐Chen , Lee Rong‐Fong , Sivakumar Chinnaiah , Chen Jen‐Sue , Chou Wei‐Yang 
Published: September 2009

AbstractTwo new low bandgap alternating polyfluorene copolymers based on dioctylfluorene and donor‐acceptor‐donor monomers have been synthesized via a Suzuki polymerization reaction. The resulting copolymers have low optical bandgaps at 1.99–1.98 eV. The bulk heterojunction polymer solar cells were fabricated with the conjugated polymers as the electron donor and 6.6‐phenyl C61‐butyric acid methyl ester as the electron acceptor. The power conversion efficiencies of the solar cells based on copolymers 1 and 2 are 0.37 and 0.42%, respectively, under the illumination of AM 1.5, 100 mW/cm2. The results indicate that the two copolymers are promising conjugated polymers for polymer solar cells. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5336–5343, 2009
An efficient approach to synthesize polysaccharides‐graft‐poly(p‐dioxanone) copolymers as potential drug carriers
Authors: Lu Fang , Wang Xiu‐Li , Chen Si‐Chong , Yang Ke‐Ke , Wang Yu‐Zhong 
Published: September 2009

AbstractStarch and poly(p‐dioxanone) (PPDO) are the natural and synthetic biodegradable and biocompatible polymers, respectively. Their copolymers can find extensive applications in biomedical materials. However, it is very difficult to synthesize starch‐graft‐PPDO copolymers in common organic solvents with very good solubility. In this article, well‐defined polysaccharides‐graft‐poly(p‐dioxanone) (SAn‐PPDO) copolymers were successfully synthesized via the ring‐opening polymerization of p‐dioxanone (PDO) with an acetylated starch (SA) initiator and a Sn(Oct)2 catalyst in bulk. The copolymers were characterized via Fourier transform infrared spectroscopy, 1H NMR, gel permeation chromatography, thermogravimetric analysis (TG), differential scanning calorimetry, and wide angle x‐ray diffraction. The in vitro degradation results showed that the introduction of SA segments into the backbone chains of the copolymers led to an enhancement of the degradation rate, and the degradation rate of SAn‐PPDO increased with the increase of SA wt %. Microspheres with an average volume diameter of 20 μm, which will have potential applications in controlled release of drugs, were successfully prepared by using these new copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5344–5353, 2009
Incorporation of poly(2‐acrylamido‐2‐methyl‐N‐propanesulfonic acid) segments into block and brush copolymers by ATRP
Authors: McCullough Lynne A. , Dufour Bruno , Matyjaszewski Krzysztof 
Published: September 2009

Abstract2‐Acrylamido‐2‐methyl‐N‐propanesulfonic acid (AMPSA) was successfully polymerized via atom transfer radical polymerization (ATRP) using a copper chloride/2,2′‐bipyridine (bpy) catalyst complex afterin situneutralization of the acidic proton in AMPSA with tri(n‐butyl)amine (TBA). A 5 mol % excess of TBA was required to completely neutralize the acid and prevent protonation of the bpy ligand, as well as to avoid side reactions caused by large excess of TBA. The use of activators generated by electron transfer (AGET) ATRP with ascorbic acid as reducing agent resulted in both increased conversion of the AMPSA monomer during polymerization (up to 50% with a 0.8 [ascorbic acid]/[Cu(II)] ratio) and much shorter polymerization times (<30 min). Block copolymers and molecular brushes containing AMPSA side chains were prepared using this method, and the solution and surface behavior of these materials were investigated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5386–5396, 2009
Photoluminescence behaviors of organic soluble DNA bearing carbazole and pyrene derivatives as side‐chain substituents and effect of the copolymer structure on the Förster energy transfer process
Authors: Lee U Ra , Lee Jung Eun , Cho Min Ju , Kim Kyung Hwan , Kwon Young Wan , Jin Jung‐Il , Choi Dong Hoon 
Published: September 2009

AbstractOrganic soluble DNA bearing two different fluorophores in the side chain was prepared by reacting purified DNA with the cationic molecules 9‐(12‐bromododecyl)‐9H‐carbazole and (E)‐1‐(4‐(12‐bromododecyloxy)styryl)pyrene in water. Two homopolymers (CzDNA and PyDNA) and random copolymers (CzDNA‐co‐PyDNA) were prepared successfully. The absorption and photoluminescence (PL) behavior of CzDNA‐co‐PyDNA with pyrene derivative concentrations was investigated. As reference, we employed a guest‐host system and polymer blends using DNA homopolymers. The Förster energy transfer process was investigated in three different DNA systems. The DNA copolymer system showed much better energy transfer efficiency than the other DNA systems. The copolymers were mixed with 2‐{2‐[2‐(4‐diethylamino‐phenyl)‐vinyl]‐6‐methyl‐pyran‐4‐ylidene}‐malononitrile (DCM) at an optimum concentration. At low DCM concentration (0.3 wt %), undesired emissions were observed due to an incomplete energy transfer process from excited pyrene moieties. At high DCM concentration (5.0 wt %), red emissions were predominant; this is attributed to an efficient Förster energy transfer process. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5416–5425, 2009
Ionomers for proton exchange membrane fuel cells by sulfonation of novel dendritic multiblock copoly(ether‐sulfone)s
Authors: Matsumura Sumiko , Hlil Antisar R. , Al‐Souz Mohammed A. K. , Gaudet Julie , Guay Daniel , Hay Allan S. 
Published: September 2009

AbstractThe synthesis and properties of the first examples of dendritic multiblock coPESs, bearing sulfonated dendritic clusters, that form strong membranes are described. End‐capped dendritic multiblock coPESs with various average block lengths (n = 50–80) were synthesized by two‐step reactions. The synthesis of dendritic blocks consisting of difunctional dendritic block and monofunctional dendritic end‐group was accomplished by an aromatic nucleophilic substitution reaction of hexakis(4‐(4‐fluorophenylsulfonyl)phenyl)benzene with varying amounts of 1‐(4‐hydroxyphenyl)‐2,3,4,5,6‐pentaphenylbenzene, which provides a number of pendant phenyl rings as postsulfonation sites. Polycondensation of a controlled molar ratio between 4,4′‐dihydroxybenzophenone and bis(4‐fluorophenyl)sulfone monomers was carried out in the presence of the difunctional and monofunctional dendritic blocks in sulfolane at 215 °C for 3.5 h. Essentially six sulfonic acid groups were introduced into each hexaphenylbenzene moiety on the dendritic blocks by reaction with a large excess of chlorosulfonic acid, followed by hydrolysis with KOH aqueous solution. The introduction of longer average blocks (n = 60–80) into the dendritic PESs improved the mechanical properties of the resulting sulfonated dendritic PES membranes. At a level of IEC (0.92–1.26 meq/g) similar to Nafion (0.91 meq/g), PES membranes showed proton conductivities (58–67 mS/cm) comparable with that of Nafion (99 mS/cm). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5461–5473, 2009
Cylindrical molecular brushes with a loose grafting density
Authors: Deng Guohua , Chen Yongming 
Published: September 2009

AbstractA cylindrical molecular brush with a low graft density was synthesized by two steps. Firstly, free radical alternating copolymerization of styrene (St) and N‐[2‐(2‐bromoisobutyryloxy)ethyl] maleimide (BiBEMI) gave a macroinitiator where pendant initiating sites for atom transfer radical polymerization (ATRP) being positioned along the backbone with an interval of four CC bonds. The backbone‐to‐be with an alternating sequence was verified by elemental analysis (EA). Secondly, grafting poly(tert‐butyl acrylate) chains from the macroinitiator by ATRP produced the novel molecular brush. Size exclusion chromatography, static light scattering (SLS), and 1H NMR and atomic force microscopy (AFM) were used to characterize the macroinitiator and the molecular brush. The results show that the backbone contains an average 730 repeat units (1 repeat unit = a pair of St and BiBEMI) and the absolute molecular weight of the brush, Mw,SLS, was 4.88 × 106 Da. The brush reveals a number average length Ln to be 96 nm under AFM observation on carbon coated mica, corresponding to the length per main chain monomer unit (Lunit) of 0.066 nm, indicating a less extended conformation due to the low grafting density. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5527–5533, 2009