bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diene‐based polymer nanoparticles: Preparation and direct catalytic latex hydrogenation
Authors: Wang Hui , Pan Qinmin , Rempel Garry L. 
Published: February 2012

AbstractThe diene‐based polymer nanoparticles represented by poly(butadiene‐co‐acrylonitrile) were prepared in the semibatch emulsion polymerization system using Gemini surfactant (GS) trimethylene‐1,3‐bis(dodecyldimethylammonium bromide) as the emulsifier. The nanoparticles within the range of 17–54 nm were achieved with narrow molecular weight and particle size distributions. A spherical morphology was observed for the produced nanoparticles. The effects of GS concentration on the particle size, molecular weight, polymerization conversion and solid content, and composition of copolymer were investigated. The semibatch process using monomeric and conventional surfactant sodium dodecyl sulfate (SDS) was compared. At the second stage of this study, the prepared unsaturated nanoparticles were employed as the substrates for the latex hydrogenation in the presence of Wilkinson's catalyst, that is, RhCl(P(C6H5)3)3. The effects of the particle size and catalyst concentration on the latex hydrogenation rate were investigated. The particle size is found to have a significant effect on the reaction rate. When the 17‐nm nanoparticles were used as the substrates, a high conversion of 95 mol % was obtained within 18 h using only 0.1 wt % RhCl(P(C6H5)3)3. The latex hydrogenation process was completely free of organic solvents. The present synthesis and following “green” hydrogenation process can be extended to latices made from semibatch emulsion containing other diene‐based polymers. This study shows great promise for decreasing the demanded quantity of expensive catalyst and eliminating the organic solvent in the hydrogenation process. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
AGET ATRP of water‐soluble PEGMA: Fast living radical polymerization mediated by iron catalyst
Authors: Miao Jie , He Weiwei , Zhang Lifen , Wang Yi , Cheng Zhenping , Zhu Xiulin 
Published: February 2012

AbstractIn this work, living radical polymerizations of a water‐soluble monomer poly(ethylene glycol) monomethyl ether methacylate (PEGMA) in bulk with low‐toxic iron catalyst system, including iron chloride hexahydrate and triphenylphosphine, were carried out successfully. Effect of reaction temperature and catalyst concentration on the polymerization of PEGMA was investigated. The polymerization kinetics showed the features of “living”/controlled radical polymerization. For example, Mn,GPC values of the resultant polymers increased linearly with monomer conversion. A faster polymerization of PEGMA could be obtained in the presence of a reducing agent Fe(0) wire or ascorbic acid. In the case of Fe(0) wire as the reducing agent, a monomer conversion of 80% was obtained in 80 min of reaction time at 90 °C, yielding a water‐soluble poly(PEGMA) with Mn = 65,500 g mol−1 and Mw/Mn = 1.39. The features of “living”/controlled radical polymerization of PEGMA were verified by analysis of chain‐end and chain‐extension experiments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
New selenium‐based iniferter agent for living free radical polymerization of styrene under UV irradiation
Authors: Zeng Jindong , Zhu* Jian , Zhang Zhengbiao , Pan Xiangqiang , Zhang Wei , Cheng Zhenping , Zhu* Xiulin 
Published: February 2012

AbstractP,P‐Diphenyl phosphinodiselenoic acid benzyl ester was synthesized and used as a mediator for the polymerization of styrene under UV–vis irradiation. Moderately controlled evidence was found: linear polymerization kinetics, linear evolution of molecular weight with monomer conversion, and relatively narrow molecular weight distribution (1.5–2.0). The structure of the obtained polymers was characterized using NMR and oxidative eliminaton. Based on polymerization results, an iniferter mechanism was proposed for the current polymerization system. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Monte carlo simulations of polydisperse polymers grafted on spherical surfaces
Authors: Dodd Paul M. , Jayaraman Arthi 
Published: February 2012

AbstractThis article presents effects of polydispersity in polymers grafted on spherical surfaces on grafted polymer chain conformations, grafted layer thickness, and free‐end monomer distribution within the grafted layer. At brush‐like grafting densities, as polydispersity index (PDI) increases, the scaling exponent of radius of gyration of grafted chains approaches that of a single chain grafted on the same nanoparticle, because polydispersity alleviates monomer crowding within the brush. At high PDI, the chains shorter than the number average chain length, Nn, have more compressed conformations, and the chains longer than Nn overall stretch less than in the monodisperse case. As seen in polydisperse flat brushes at high grafting densities, the grafted layer thickness on spherical nanoparticle increases with PDI. Polydispersity eliminates the region near the surface devoid of free‐end monomers seen in monodisperse cases, and it reduces the width of free‐end monomer distribution and shifts the free‐end monomer distribution close to the surface. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Vibrational analysis beyond the harmonicity from Ab initio molecular dynamics: Case of cytosine in its anhydrous and aqueous forms
Authors: Carbonniere Philippe , Thicoipe Sandrine , Very Thibault , Assfeld Xavier 
Published: February 2012

AbstractThis study provides the set of theoretical anharmonic fundamental transitions for cytosine in its anhydrous and hydrated forms from a vibrational analysis issuing from a time‐dependent approach. This evaluation is compared to the time‐independent VPT2 approach and to the experimental data available in the literature for the two forms. To investigate the vibrational property of a solute in a polar protic solvent, that is, the aqueous form of cytosine in this particular case, a practicable computational strategy to properly take into account the solvent effect is proposed. This is done by considering a combination of polarizable continuum model and of discrete solvent molecules model. The number of solvent molecules was chosen in such a way that the solute–solvent complex presents only one dominant stable conformer at 298 K. The quality of this combined solvent model is illustrated by comparing the structural and anharmonic vibrational properties achieved with those obtained from a purely implicit and purely explicit solvent model. © 2012 Wiley Periodicals, Inc. Int J Quantum Chem, 2012
Basis set and functional effects on excited‐state properties: Three bicyclic chromogens as working examples
Authors: Jacquemin Denis , Adamo Carlo 
Published: February 2012

AbstractWe have computed, at the time‐department density functional theory, TD‐DFT level of approximation, the ground‐ and excited‐state properties of three typical chromophores, namely indole, coumarin, and benzofurazan, using six functionals (B3LYP, B3P86, PBE0, BMK, BH&HLYP, and CAM‐B3LYP) and four atomic basis sets (BSs), the larger being 6‐311++G(2d,2p). It turned out that diffuse functions are necessary to obtain correct vertical transition energies. The selected functional mainly impacts on these energies, but the differences of vibrational energies between the ground‐ and excited‐states are almost BS and functional independent. The adiabatic gap estimated with total energies or with Gibbs free enthalpies are nearly the same provided the ZPVE effects are accounted for. Int J Quantum Chem, 2012. © 2012 Wiley Periodicals, Inc.
The adiabatic‐to‐diabatic transformation angle and topological phases for strongly interacting states: Solution with four states
Authors: Das Anita , Mukhopadhyay Debasis 
Published: February 2012

AbstractA few years back T. Vértesi et al. (J Phys Chem A 2005, 109, 3476) gave an elegant procedure to derive the adiabatic‐to‐diabatic transformation angle (ADT‐angle) for lowest two states, γ12, in presence of their interaction with the higher states. In this article, we explicitly solved the coupled differential equations involving the ADT‐angles describing the mixing of four interacting states for the first time to get all the ADT‐angles, γij's (including the γ12) associated with well‐defined topological phases. In application to a suitable configuration space (CS) of a molecular system, we have demonstrated well‐defined Berry phases (Berry M. V., R Soc London Ser A 1984, 45, 392) for an isolated system with as many as four strongly interacting states. © 2012 Wiley Periodicals, Inc.
Theoretical study on a series of push–pull molecules grafted on methacrylate copolymers serving for nonlinear optics
Authors: Derrar S. N. , Sekkal‐Rahal M. , Guemra K. , Derreumaux P. 
Published: February 2012

AbstractThe B3LYP functional combined with 6‐31G(d) basis set have been designated as the most appropriate for structural investigations of a new range of organic conjugated push–pull molecules containing numerous electron donor/acceptor couples in their ends. Second‐order Møller Plesset has been used to properly reproduce nonlinear optical (NLO) properties and to study the alkyl chain length effect of these systems. Satisfactory dynamic hyperpolarizabilities at the wavelength 1064 nm are obtained with values in the order of 11,500 × 10−30 esu. Then, the study has been extended to monomers generated by combination of the chromophores to either acryloyl chloride or 4‐hydroxy‐styrene sequences. Then, the obtained molecules have been grafted to a methyl methacrylate copolymeric chain, the resulting values of β(1064 nm) have been demonstrated to be sensitive to these modifications. © 2012 Wiley Periodicals, Inc. Int J Quantum Chem, 2012
Path integral approach to the calculation of reaction rates for a reaction coordinate coupled to a dual harmonic bath
Authors: Yang Yonggang , Kühn Oliver 
Published: February 2012

AbstractWe present a new method for the numerical calculation of canonical reaction rate constants in complex molecular systems, which is based on a path integral formulation of the flux–flux correlation function. Central is the partitioning of the total system into a relevant part coupled to a dual bath. The latter consists of two parts: First, there is a set of strongly coupled harmonic modes, describing, for example, intramolecular degrees of freedom. They are treated on the basis of a reaction surface Hamiltonian approach. Second, there is a set of bath modes mimicking an unspecific environment modeled by means of a continuous spectral density. After deriving general equations expressing the canonical rate constant in terms of appropriate influence functionals, several approximations are introduced to provide an efficient numerical implementation. Results for an initial application to the H‐transfer in 6‐aminofulvene‐1‐aldimine are discussed. © 2011 Wiley Periodicals, Inc.
Improvement of estradiol esters monitoring in bovine hair by dansylation and liquid chromatography/tandem mass spectrometry analysis in multiple reaction monitoring and precursor ion scan modes
Authors: Bichon E. , Béasse A. , Prevost S. , Christien S. , Courant F. , Monteau F. , Le Bizec B. 
Published: February 2012

RATIONALEThe control of forbidden anabolic practices in cattle in the European Union has become challenging since endogenous compounds such as estradiol derivatives can potentially be used as growth promoters. Due to the great difficulty in establishing a reference threshold value for endogenous steroids, the direct detection of steroid esters in hair is an efficient strategy for the detection of 'natural' steroid abuse in cattle.METHODSThe present study aimed to develop and validate according to the current European standards a specific liquid chromatography/tandem mass spectrometry (LC/MS/MS) analytical strategy to monitor estrogen esters in bovine hair. The analysis was performed by positive ion electrospray ionisation (ESI+) after dansylation. Two acquisition modes were then assessed: single reaction monitoring and precursor ion scanning.RESULTSThe results showed that the introduction of a dansylation step strongly improves the sensitivity of the detection of estradiol‐17‐esters by LC/(ESI+)‐MS/MS. The CCα values are in the range 1–10 ng g–1 after optimisation, except for estradiol decanoate for which the derivatisation is not efficient. In addition, this LC/MS/MS approach makes it possible to carry out a precursor ion scan to screen for the presence of these estradiol 17‐esters in hair samples.CONCLUSIONSBased on the specific product ions, i.e. m/z 255 in native conditions or m/z 171 after dansylation, this strategy has the advantage of detecting any (un)known estradiol ester and of giving access to the [M + H]+ ion of the suspected ester through only a single analysis. Copyright © 2012 John Wiley & Sons, Ltd.
Development of a liquid chromatographic method based on ultraviolet–visible and electrospray ionization mass spectrometric detection for the identification of nitrocatechols and related tracers in biomass burning atmospheric organic aerosol
Authors: Kitanovski Zoran , Grgić Irena , Yasmeen Farhat , Claeys Magda , Čusak Alen 
Published: February 2012

RATIONALEStudying the chemical composition of biomass burning aerosol (BBA) is very important in order to assess their impact on the climate and the biosphere. In the present study, we focus on the characterization of some newly recognized biomass burning aerosol tracers including methyl nitrocatechols, nitroguaiacols and 4‐nitrocatechol, but also on nitrophenols, methyl nitrophenols and nitrosalicylic acids, using liquid chromatography tandem mass spectrometry.METHODSFor the purpose of their separation and detection in atmospheric aerosol, a new chromatographic method was initially developed based on reversed‐phase chromatography coupled with ultraviolet/visible (UV/Vis) detection. The method was afterwards transferred to a liquid chromatography/electrospray ionization linear ion trap mass spectrometry (LC/ESI‐LITMS) system in order to identify the targeted analytes in winter aerosol from the city of Maribor, Slovenia, using their chromatographic retention times and characteristic (−)ESI product ion (MS2) spectra.RESULTSThe fragmentation patterns of analytes obtained with LITMS are presented. Additional nitro‐aromatic compounds (m/z 168 and 182) closely related to the targeted nitrocatechols and nitroguaiacols were detected in the aerosol. According to their MS2 spectra these compounds could be attributed to methyl homologues of methyl nitrocatechols and nitroguaiacols.CONCLUSIONSThe proposed LC/MS method results in a better separation and specificity for the targeted analytes. Several nitro‐aromatic compounds were detected in urban BBA. The LC/MS peak intensity of the newly detected methyl nitrocatechols and nitroguaiacols is comparable to that of the methyl nitrocatechols, which also qualifies them as suitable molecular tracers for secondary biomass burning aerosol. Copyright © 2012 John Wiley & Sons, Ltd.
Protein crystal content analysis by mass spectrometry and preliminary X‐ray diffraction of a lectin from Canavalia grandiflora seeds with modulatory role in inflammation
Authors: Simões Rafael Conceição , Rocha Bruno Anderson Matias , Bezerra Maria Julia Barbosa , Barroso‐Neto Ito Liberato , Pereira‐Junior Francisco Nascimento , da Mata Moura Raniere , Nascimento Kyria Santiago do , Nagano Celso Shiniti , Delatorre Plinio , de Freitas Pires Alana , Assreuy Ana Maria Sampaio , Sampaio Alexandre Holanda , Cavada Benildo Sousa 
Published: February 2012

RATIONALELectins are a family of proteins capable of deciphering the glycan code. Several authors have published works about crystallization and mass spectrometry analyses of ConA‐like lectins. However, mass spectrometry has never been used to characterize lectin crystal content. In this study, Canavalia grandiflora lectin (ConGF), a ConA‐like lectin, was crystallized, part of its primary structure sequenced and the pro‐inflammatory activity evaluated. In addition, the crystal content was analyzed by mass spectrometry.METHODSConGF was crystallized in the presence of X‐Man by hanging‐drop vapor diffusion at 293 K and the protein crystal content was analyzed by electrospray ionization in a SYNAPT HDMS mass spectrometer. Partial sequence was obtained by protein digestion with several proteolytic enzymes and the peptides sequenced by liquid chromatography/tandem mass spectrometry (LC/MS/MS). The pro‐inflammatory potential of ConGF was also evaluated in the model of rat paw edema.RESULTSThe protein crystals consist of mature α chain and β and γ fragments measuring 25 612 ± 2 Da, 12 962 ± 2 Da and 12 667 ± 2 Da, respectively. The crystal belongs to the orthorhombic space group I222 (unit cell parameters: a = 67.70, b = 55.90, c = 107.46 Å), assuming a monomer in the asymmetric unit. The solvent content was calculated as 43.50% and the protein content as 2.5 µg. Furthermore, a significant part of the primary structure (65.8%) was determined by mass spectrometry.CONCLUSIONSAs far as we know this is the first report of lectin crystal content characterized by mass spectrometry. Like other ConA‐like lectins, GonGF induced paw edema however differing in potency and duration. The observed pro‐inflammatory activity suggests that ConGF might be a useful tool in the study of inflammation processes and structure/function relationships. Copyright © 2012 John Wiley & Sons, Ltd.
The scaling window for a random graph with a given degree sequence
Authors: Hatami Hamed , Molloy Michael 
Published: February 2012

AbstractWe consider a random graph on a given degree sequence D, satisfying certain conditions. Molloy and Reed defined a parameter Q = Q(D) and proved that Q = 0 is the threshold for the random graph to have a giant component. We introduce a new parameter R = R(
\documentclass{article}\usepackage{mathrsfs, amsmath, amssymb}\pagestyle{empty}\begin{document}\begin{align*}\mathcal {D}\end{align*} \end{document}) and prove that if |Q| = O(n‐1/3R2/3) then, with high probability, the size of the largest component of the random graph will be of order Θ(n2/3R‐1/3). If |Q| is asymptotically larger than n‐1/3R2/3 then the size of the largest component is asymptotically smaller or larger than n2/3R‐1/3. Thus, we establish that the scaling window is |Q| = O(n‐1/3R2/3). © 2012 Wiley Periodicals, Inc. Random Struct. Alg., 2012
Fast simulation of large‐scale growth models
Authors: Friedrich Tobias , Levine Lionel 
Published: February 2012

AbstractWe give an algorithm that computes the final state of certain growth models without computing all intermediate states. Our technique is based on a “least action principle” which characterizes the odometer function of the growth process. Starting from an approximation for the odometer, we successively correct under‐ and overestimates and provably arrive at the correct final state. Internal diffusion‐limited aggregation (IDLA) is one of the models amenable to our technique. The boundary fluctuations in IDLA were recently proved to be at most logarithmic in the size of the growth cluster, but the constant in front of the logarithm is still not known. As an application of our method, we calculate the size of fluctuations over two orders of magnitude beyond previous simulations, and use the results to estimate this constant. © 2012 Wiley Periodicals, Inc. Random Struct. Alg., 2012
Current advances in Phi29 pRNA biology and its application in drug delivery
Authors: Ye Xin , Hemida Maged , Zhang Huifang M. , Hanson Paul , Ye Qiu , Yang Decheng 
Published: February 2012

AbstractBacteriophage 29 (Phi29) packaging RNA (pRNA) is one of the key components in the viral DNA‐packaging motor. It contains two functional domains facilitating the translocation of DNA into the viral capsid by interacting with other elements in the motor and promoting adenosine triphosphates hydrolysis. Through the connection between interlocking loops in adjacent pRNA monomers, pRNA functions in the form of multimer ring in the motor. Previous studies have addressed the unique structure and conformation of pRNA. However, there are different DNA‐packaging models proposed for the viral genome transportation mechanism. The DNA‐packaging ability and the unique features of pRNA have been attracting efforts to study its potential applications in nanotechnology. The pRNA has been proved to be a promising tool for delivering nucleic acid‐based therapeutic molecules by covalent linkage with ribozymes, small interfering RNAs, aptamers, and artificial microRNAs. The flexibility in constructing dimers, trimers, and hexamers enables the assembly of polyvalent nanoparticles to carry drug molecules for therapeutic purposes, cell ligands for target delivery, image detector for drug entry monitoring, and endosome disrupter for drug release. Besides these fascinating pharmacological advantages, pRNA‐based drug delivery has also been demonstrated to prolong the drug half life with minimal induction of immune response and toxicity. WIREs RNA 2012, 3:469–481. doi: 10.1002/wrna.1111This article is categorized under:

RNA Structure and Dynamics > RNA Structure, Dynamics, and Chemistry
RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems
RNA Processing > RNA Editing and Modification
RNA in Disease and Development > RNA in Disease
Systematic Review and Meta‐analysis of the Incidence of Incisional Hernia at the Site of Stoma Closure
Authors: Bhangu Aneel , Nepogodiev Dmitri , Futaba Kaori ,   West Midlands Research Collaborative
Published: February 2012

AbstractBackgroundThe incidence of incisional hernias at the site of stoma closure is surprisingly unclear. A review of the current literature was undertaken to determine how commonly this complication may occur and to assess the quality of evidence available.MethodsA systematic review was performed to identify studies reporting the incidence of incisional hernia after closure of an ileostomy or colostomy. Studies including children (<16 years old) and studies in which >10% of the total number were trauma patients were excluded.ResultsThirty‐four studies provided outcomes for 2,729 closed stomas. Median follow‐up time was 36 months but was only described in seven studies. Closure of loop ileostomies was the most commonly performed procedure (48%). The overall reported hernia rate was 7%, but with a wide range among studies (0–48%). Most studies based their hernia rates on retrospective clinical findings only. A separate analysis of three studies that were specifically designed to assess for stoma site hernias found the clinical hernia rate to be 30% (28/93) and the combined clinical/radiological hernia rate to be 35% (33/93). From 11 studies reporting reoperation rates, 51% of patients who developed a hernia required a surgical repair (34/66). There was a lower risk of hernia following reversal of ileostomy versus colostomy (odds ratio 0.28, 95% confidence interval 0.12–0.65).ConclusionsOne in three patients may develop a hernia after stoma closure, and around half of hernias that are detected require repair. Risk of hernia is greater after colostomy closure than after ileostomy closure. Clinical measures to reduce the development of these hernias warrant consideration.