bluuebunny/crossref_metadata_2025_split huggingface dataset:
Monodisperse stereoregular poly(methyl methacrylate) by anionic polymerization. II
Authors: Roig A. , Figueruelo J. E. , Llano E. 
Published: September 2014

AbstractAnionic polymerization of poly(methyl methacrylate) in solvating media (THF, glyme, pyridine), using as initiators complexes of the type organic—alkali metal(biphenyl—sodium, biphenyl—lithium), is described, leading to stereoregular and monodisperse polymers. Polymerization is carried out in a vacuum line system, all solvents being previously purified with the same type of complexes used in the polymerization reaction; monomer is purified with benzil—sodium. All transfers are made through sealed ampules. The polymers obtained were fractionated and found to have very narrow molecular weight distributions. All polymers are mainly syndiotactic and their NMR spectra allow the steric composition to be determined, which goes up to 97% syndiotactic. The polymerization can be described by a single parameter governing the probabilities of isotactic and syndiotactic placements, as predicted by the Coleman and Fox theory.
Some solution properties of polyoxymethylenes
Authors: Grassie N. , Roche R. S. 
Published: September 2014

AbstractPerfluoroacetone hydrate (PFAH) is a useful nondegrading solvent for high molecular weight polyoxymethylenes (POM) at ordinary temperatures. Infrared spectroscopic measurements on mixtures of low molecular weight POM diisopropyl ethers and PFAH in carbon tetrachloride solution give evidence of specific polymer—solvent interactions involving hydrogen bonds. Although the viscosity behavior of POM in PFAH and PFAH—H2O mixtures conforms to the Huggins equation, the values of the Huggins constant are not consistent with the values expected on theoretical grounds. Much more satisfactory values are obtained by application of the Schulz—Blaschke viscosity relationship.
On the mechanism of thermo‐oxidative degradation of cellulose ethers
Authors: Kozmina O. P. 
Published: September 2014

AbstractCellulose and alcohol ethers of aliphatic series, benzyl, allyl cellulose and other ethers containing labile hydrogen atoms were shown to undergo thermo‐oxidative degradation owing to the formation of peroxide in the ether groups and to their decomposition with the removal of the corresponding aldehydes, alcohols, alkylhydroperoxides, and other products and the break of the pyranose cycle. This has been established by the method of labeled atoms. It was also shown that the peroxide groups in ethers are partially transformed into the corresponding ester groups. The reaction of ethyl cellulose with oxygen was investigated in greater detail. Kinetic data on the formation of ether peroxides and of the products of their decomposition are given. Cellulose ethers and esters in whose ether and ester groups the labile hydrogen atoms are absent (tritylcellulose, pivalinates, benzoates, etc.) are much more resistant to thermo‐oxidative degradation.
Methode d'Etude Cinétique des Réactions de Polymérisation Anionique
Authors: Guyot Alain , Vialle Jean , Le Doan T. , Tho Pham Quang 
Published: September 2014

AbstractBeside the usual reactants, the reaction medium of polymerization contains two inert compounds IM and IC, which act as internal standards of concentration corresponding, respectively, to the monomer M and the organometallic catalyst RMe. At given time intervals, small liquid samples are picked up and injected into a vaporization cell together with small amounts of water or alcohol. Then a part of the gaseous mixture is analyzed by gas chromatography. The consumption of the monomer and of the catalyst are obtained from the measurements of the ratios of the areas under the peaks M and IM, and RH and IC. Some results are given for the polymerizations of vinyl chloride with an organomagnesium catalyst and of isoprene with n‐butyllithium.
Synthesis of new ferrocene‐containing polymers
Authors: Paushkin Ya. M. , Vishnyakova T. P. , Machus F. F. , Sokolinskaya F. A. , Golubeva I. A. 
Published: September 2014

AbstractSix new polymers based on ferrocene and its derivatives have been synthesized and their electrophysical properties investigated. The polymers were prepared by various methods. In polymerization of acetylferrocene oxime and difulvene of 1,1′‐diacetyl‐ferrocene the yield of polymers was 90%. In the direct interaction of ferrocene and hexamethylene diisocyanate, poly(ferrocenylene polyamide) resulted in 73% yield. The polycondensation of ferrocene both with phthalic anhydride and with carbamyl chloride, and that of acetylferrocene with ammonium bicarbonate, in the presence of zinc chloride gave new ferrocenic polymers with a system of conjugated bonds. All produced polymers were coloured powders partly soluble in organic solvents. In the direct interaction of ferrocene and carbamyl chloride (in the form of a complex with zinc chloride) (poly‐(ferrocenyl nitrile), not described previously, has been obtained. By polycondensation of acetylferrocene and ammonium bicarbonate the insoluble polymers and oligomer of molecular weight 480 and m.p. 145‐150°C. containing two hydroxy groups have been prepared. The presence of CN bonds in poly(ferrocenyl nitrile) and the products of polycondensation of acetyl‐ and 1,1,‐diacetylferrocene with ammonium bicarbonate has been confirmed by the complexing effect of CN bonds with a silver salt. Silver extraction due to the complex formation has been 0.62 g./g. of the polymer. The prepared polymers produced a narrow one‐component signal in the ESR spectrum at spin concentration of 10−7–1019 spins/g. which confirms the presence of conjugated double bonds in the polymers. The electrical conductivity temperature plot obeyed the exponential law. The values of conductivities were 11−12 to 10−8 ohm−1‐cm.−1, and activation energies—0.72‐0.049 e.v.
Die Parakristalline Struktur von Polyäthylen‐Einkristallen
Authors: Calleja F. J. Baltá , Hosemann R. , Wilke W. 
Published: September 2014

AbstractThe increase in integral width of (110), (220) and (330) reflections of linear polyethylene single crystals crystallized from 0.05% n‐xylene solution demonstrates the existence of paracrystalline lattice defects in crystalline regions. The g value describing the statistical distance fluctuations of (110) planes is g = 1.88% and 2.14%, the particle size vertical to the chain direction D = 299 and 331 A., respectively, for Hostalen G and Lupolen 6011‐H, respectively, the two polyethylene materials investigated. It is not possible to explain the increase in line width by the occurrence of lattice strains.
Tracer study of stereospecific butadiene polymerization initiated by rh catalyst in water emulsion
Authors: Sokolov V. N. , Babitskii B. D. , Kormer V. A. , Poddubnyi I. Ya. , Chesnokova N. N. 
Published: September 2014

AbstractStereospecific polymerization of butadiene with different rhodium compounds in water medium has been studied using the tracer method. Water is shown to play an active part in both the initiation and termination stages as evidenced by the presence of groups in polymers. The OH−, Cl− polar groups of the polymer are found to be allylic. It has been shown for the case of rhodium‐acetate complex, using the kinetic isotope effect method that termination of polymer chains occurs through water proton addition. A coordinated mechanism through π‐allylic complexes has been proposed for the polymerization of butadiene with rhodium catalysts. It has been assumed that the initiation stage is a π‐allylic complex forming reaction, propagation of polymer chains occurring through the monomer molecules introduction between a metal atom and organic ligand.
Polymerization of butadiene with π‐allylic catalysts
Authors: Kormer V. A. , Babitskii B. D. , Lobach M. I. , Chesnokova N. N. 
Published: September 2014

AbstractThe polymerization of butadiene‐1,3 with π‐allylic nickel complexes has been studied. π‐Allyl(crotyl) nickel halides themselves are shown to initiate stereospecific polymerization. The stereospecificity of the catalysts is determined by the nature of halogen bonded to metal. In the presence of chlorine complexes cis‐1,4‐polybutadienes are obtained, the iodine ones giving trans‐1,4‐polybutadienes.Lewis acids change the stereospecificity of π‐crotyl nickel bromide and iodide, favoring cis‐1,4‐structure formation.The polymerization of butadiene with rhodium compounds has been investigated. The experimental evidence indicates that the polymerization involves π‐allylic complexes.An attempt is made to explain the mechanism of polymer chain unit formation on the basis of π‐allylic structure of active sites in diene polymerization by transition metal compounds.
Contribution à l'Étude du Fluage des Copolymères Polyesters Linéaires Insaturés—Styrolène
Authors: Rosso Jean‐Claude , Persoz Bernard 
Published: September 2014

AbstractThe experiments dealt with a series of succino‐fumarates of diethylene glycol whose crosslinking, obtained by copolymerization with styrene, is adjusted by varying the percentage of fumaric and succinic acids. The overall results in tensile creep in the transition zone have provided for each of the compounds a master curve for creep and a time‐temperature relation of the Williams, Landel, and Ferry type. These master curves may be expressed in terms of general equations function of time, of the number of portions of network chains between two crosslinking junctures and of the percentage in styrene.
Transport of cationic depolarizers through polybase monolayers adsorbed on the mercury surface
Authors: Miller Israel R. , Frei Yael F. , Bach Diana 
Published: September 2014

AbstractThe permselectivity of the ultrathin charged membranes to transport of identically charged ions and the structure of adsorbed polyelectrolyte monolayers from the measured transport was investigated. The ion transport was measured by means of the electrical current resulting from the electroreduction of the cationic depolarizers (Cd++, Cu++), diffusing to the surface. The diffusion of the ionic depolarizers to the mercury surface is impeded by the equally charged layer of polybases to an extent depending on their concentration and their structure in the surface and on the concentration of the supporting electrolyte in the bulk. The impeding effect of the adsorbed polybase monolayers was obtained from the ordinary polarographic diffusion current measurements and also from the current–time curves during the lifetime of single mercury droplets at selected constant potentials. The current–time curves also provide a means for determination of the diffusion coefficients or of the surface concentrations of the polybases.
The kinetics of the polyisoprene formation initiated with lithium organyl
Authors: Sinn H. , Bandermann F. 
Published: September 2014

AbstractThe kinetics of polyisoprene formation have been investigated in n‐heptane, diethylether, and in mixtures of these two solvents. Li‐butyl (LiB) or Li‐poly‐isoprenyl (LiR) was used as an initiator. The time–conversion curves for isoprene [M] are described by the following equations:

and

[LiR] and [LiB] means the concentration of monomer forms of the highly self‐associated Li‐organyls. To evaluate these from the analytically found concentration, equations and functions are given. No ionic picture for the reaction mechanism can be derived from the discussion of the found reaction rates and equilibrium constants. Furthermore, conductivity measurements have been done on Li‐butyl in n‐heptane. The found values for molar conductivity between 10−5 to 10−4 [cm.2/mole‐1 Ω] in the concentration ranges 10−6 to 10−2 [moles/liter] fulfill laws derived for 1 − α ≅ 1 (α = degree of ionic dissociation).
A three‐thermistor ebulliometer
Authors: Daniels T. , Lehrle R. S. 
Published: September 2014

AbstractComparison of the performance of one‐, two‐, and three‐thermistor ebulliometers has shown that the three‐thermistor design is preferable. In this apparatus two of the three thermistors are sited in the vapor phase, and the other receives liquid effluent from the vapor‐lift pump. Temperature gradients in the apparatus have been measured, and optimum sites for the thermistors chosen on this basis. Other aspects of design, including that of the vapor‐lift pump, are discussed. This type of instrument allows measurements corresponding to the boiling point of solvent to be repeated even when the boiler contains solution. By this means any effects of drift are eliminated. The sensitivity of the instrument is comparable with that of two‐thermistor instruments (useful molecular weight range up to ca. 40,000, at which the predicted uncertainty is less than 10% for studies up to 2% concentration); the advantage of the design is that measurements are made with greater speed and facility because of improved stability and repro‐ducibility. Examples of the application of the apparatus to some problems of interest in polymer chemistry are included. These include: (a) estimation of solvent of crystallization in diphenylpicrylhydrazyl, (b) an examination of oligomeric products from chloroprene polymerizations, and (c) direct molecular weight measurements on low molecular weight polymers (MW range 1000‐30,000). The results are compared with independent estimations.
Fractionnement et Distribution Moléculaire du Diacétate de Polyoxyméthylène
Authors: Dick Richard , Sack Henri , Benoit Henri 
Published: September 2014

AbstractThe fractionation of a polyoxymethylene, stabilized by controlled degradation with acetolysis, has been carried out by two techniques: fractional precipitation and fractional dissolution. Infrared spectroscopy combined with end‐group analysis and intrinsic viscosity measurements in aniline at 116.5°C. have been used for the identification of the fractions. The results follow a Mark‐Houwink‐Sakurada viscosity law and permit the determination of the molecular weight distribution.
Kinetics of radical polymerization. XVIII. Inhibition of radical polymerization with quinones
Authors: Simándi T. L. , Tüdös F. , Turcsányi B. 
Published: September 2014

AbstractThe inhibitory effect of multiring quinones on the polymerization of styrene was examined. The logarithm of the relative reactivity of quinones also contains, besides a member which reflects the changes in the oxidation‐reduction potential, a member corresponding to the changes in resonance energy which accompany quinoid r̊ benzenoid structural transformation. The observation that the experimental values of the stoichiometric coefficient are generally much smaller than the theoretical ones can be interpreted by the aid of the hot‐radical hypothesis.
The structure and flexibility of stereoregular macromolecules. The model of statistical zigzag chain
Authors: Birshtein T. M. , Ptitsyn O. B. 
Published: September 2014

AbstractThe statistical zigzag chain model is proposed for a description of the conformational properties of macromolecules. The lengths of the segments in such a model are statistically distributed. The short‐range order in regular regions (segments) of chain is similar to one‐dimensional, long‐range order in a crystalline chain, which corresponds to the minimum of the intramolecular potential energy. The equivalence is not completely due to asymmetrical vibrations of monomer units about the positions of energy minimum. The flexibility of the statistical zigzag chain is characterized by the mean length of regular regions and by the relative orientation of the neighboring regular regions. For the macromolecules with the helical short‐range order, the latter is determined by an angle between the axes of the neighboring helical regions. It is shown that comparision of experimental values of mean square end‐to‐end dimensions and dipole moments permit both parameters of the model to be obtained. The results of calculation of the conformational characteristics of isotactic vinyl chains by means of the statistical zigzag chain model are very similar to those of the rigorous theory, based on the matrix method of the Ising model. The relative contributions of rotational isomerization and rotational vibrations to the statistical coiling of chains and to the temperature dependence of their mean dimensions are discussed.
Addition des Carbènes sur les cis‐1,4 Polyisoprènes et sur des Polymères Analogues
Authors: Pinazzi Christian , Levesque Guy 
Published: September 2014

AbstractThe action of dihalocarbenes upon polyisoprenes and polybutadienes leads in some cases to the nearly complete disappearance of the carbon‐carbon double bonds, which are replaced by gem‐dihalocyclopropane units. Most of the macromolecules so obtained have a quite remarkable stability to heat and resistance to many reagents. Generally dichlorocarbene yields more complete reactions than the dibromocarbene does, because the solubility is less diminished. The structure of the macromolecular compounds prepared is partly based on spectrographic data (IR, NMR). The structures proposed have been proven by a detailed study on organic models such as 4‐methyl 3‐heptene, dihydromyrcene, and squalene. Their gem‐dihalocyclopropane derivatives have been obtained by employing a procedure similar to the one used for macromolecular polyenes. Phenylchlorocarbene and phenylmercaptocarbene have also been reacted with polyisoprenes. The reactions with these carbenes lead easily to macromolecular compounds in which the carbon‐carbon double bonds are almost all replaced by cyclo‐propanes, Phenylcyclopropane derivatives show a rather high solubility in usual solvents, which allows them to be studied by the classic methods of fractionation and molecular weight determination. Finally, via Skattebol's works, the transformation of dihalocyclopropane macromolecules to polycumulenes could be realized. This reaction, also performed on organic models, shows difficulties which have not all been overcome. During the reaction changing polycyclopropanes to polycumulenes, the length of the macromolecular chain is theoretically increased by the regular insertion of a carbon atom for each isoprene unit initially present.
Characterisation and inhibition studies of Helicoverpa armigera (Hübner) gut α‐amylase
Authors: Kaur Rimaljeet , Gupta Anil K , Taggar Gaurav K 
Published: September 2014

AbstractBACKGROUNDThe survival of a devastating pest, Helicoverpa armigera, is mainly dependent on the availability of α‐amylase. Therefore, characterising H. armigera α‐amylase and targeting it with effective inhibitors could aid in reducing its damaging effects.RESULTSH. armigera gut possessed four isozymes of α‐amylase. The molecular weight of the major purified isozyme ranged from 79 to 81 kDa. The purified enzyme was identified to be α‐amylase on the basis of products formed from starch. The optimum pH and temperature were 10.0 and 50 °C respectively. The activation energy was 5.7 kcal mol−1. The enzyme showed high activity with starch and amylopectin, whereas dextrins were poor substrates. The Michaelis constant Km with starch, amylose and amylopectin was 0.45, 1.23 and 0.11 mg mL−1 respectively. ZnSO4, FeSO4, CuSO4, citric acid, oxalic acid and salicylic acid were potent inhibitors. ZnSO4, salicylic acid and pigeonpea α‐amylase inhibitor (∼21.0 kDa) acted primarily as competitive inhibitors, FeSO4 and citric acid displayed mainly anticompetitive behaviour, while CuSO4 and oxalic acid behaved mainly as non‐competitive inhibitors.CONCLUSIONSThe identification of effective ecofriendly inhibitors could help in managing H. armigera infestation. © 2014 Society of Chemical Industry
Semiparametric hidden Markov models: identifiability and estimation
Authors: Dannemann Jörn , Holzmann Hajo , Leister Anna 
Published: September 2014

We review the theory on semiparametric hidden Markov models (HMMs), that is,HMMsfor which the state‐dependent distributions are not fully parametrically, but rather semi‐ or nonparametrically specified. We start by reviewing identifiability in such models, where by exploiting the dependence much stronger results can be achieved than for independent finite mixtures. We also discuss estimation, in particular in an algorithmic fashion by using appropriate versions or modifications of the Baum‐Welch (orEM) algorithm. We present some simulation results and give an application to modeling bivariate financial time series, where we compare parametric with nonparametric fits for the state‐dependent distributions as well as the resulting state‐decoding.WIREs Comput Stat2014, 6:418–425. doi: 10.1002/wics.1326This article is categorized under:Applications of Computational Statistics > Computational FinanceStatistical and Graphical Methods of Data Analysis > EM AlgorithmStatistical and Graphical Methods of Data Analysis > Modeling Methods and AlgorithmsStatistical Models > Model Selection
Comparison of 3D and 4D Monte Carlo optimization in robotic tracking stereotactic body radiotherapy of lung cancer
Authors: Chan Mark K.H. , Werner Rene , Ayadi Miriam , Blanck Oliver 
Published: September 2014

Abstract
Purpose
To investigate the adequacy of three-dimensional (3D) Monte Carlo (MC) optimization (3DMCO) and the potential of four-dimensional (4D) dose renormalization (4DMCrenorm) and optimization (4DMCO) for CyberKnife (Accuray Inc., Sunnyvale, CA) radiotherapy planning in lung cancer.

Materials and methods
For 20 lung tumors, 3DMCO and 4DMCO plans were generated with planning target volume (PTV5 mm) = gross tumor volume (GTV) plus 5 mm, assuming 3 mm for tracking errors (PTV3 mm) and 2 mm for residual organ deformations. Three fractions of 60 Gy were prescribed to ≥ 95 % of the PTV5 mm. Each 3DMCO plan was recalculated by 4D MC dose calculation (4DMCrecal) to assess the dosimetric impact of organ deformations. The 4DMCrecal plans were renormalized (4DMCrenorm) to 95 % dose coverage of the PTV5 mm for comparisons with the 4DMCO plans. A 3DMCO plan was considered adequate if the 4DMCrecal plan showed ≥ 95 % of the PTV3 mm receiving 60 Gy and doses to other organs at risk (OARs) were below the limits.

Results
In seven lesions, 3DMCO was inadequate, providing < 95 % dose coverage to the PTV3 mm. Comparison of 4DMCrecal and 3DMCO plans showed that organ deformations resulted in lower OAR doses. Renormalizing the 4DMCrecal plans could produce OAR doses higher than the tolerances in some 4DMCrenorm plans. Dose conformity of the 4DMCrenorm plans was inferior to that of the 3DMCO and 4DMCO plans. The 4DMCO plans did not always achieve OAR dose reductions compared to 3DMCO and 4DMCrenorm plans.

Conclusion
This study indicates that 3DMCO with 2 mm margins for organ deformations may be inadequate for Cyberknife-based lung stereotactic body radiotherapy (SBRT). Renormalizing the 4DMCrecal plans could produce degraded dose conformity and increased OAR doses; 4DMCO can resolve this problem.
Genetic Counseling for Fanconi Anemia: Crosslinking Disciplines
Authors: Zierhut Heather A. , Tryon Rebecca , Sanborn Erica M. 
Published: September 2014

AbstractFanconi anemia (FA) is the most common of the inherited bone marrow failure syndromes with an incidence of approximately 1/100,000 to 1/200,000 live births. FA is a genetically complex and phenotypically heterogeneous condition involving birth defects, bone marrow failure, and cancer predisposition. This rare disease became well known in the genetic counseling community in 2002, when it was identified that biallelic mutations in BRCA2 can cause FA. Knowledge gained from the growing association between FA and breast cancer pathways has brought even more light to the complex genetic issues that arise when counseling families affected by this disease. Genetic counseling issues surrounding a diagnosis of FA affect many different disciplines. This review will serve as a way to cross‐link the various topics important to genetic counselors that arise throughout the life of a patient with FA. Issues covered will include: an overview of FA, phenotypic presentation, management and treatment, the genetics and inheritance of FA, cytogenetic and molecular testing options, and the risks to family members of an individual with FA.