Deuterium solid echo line shape study of poly(ethylene oxide) dynamics in a blend with poly(methyl methacrylate)

Deuterium solid echo line shapes were measured on deuterated poly(ethylene oxide) (d₄PEO) in a blend with protonated poly(methyl methacrylate) to characterize chain dynamics of this component in the blend. Line shapes were observed as a function of temperature from 183 to 243 K and echo delay times from 10 to 100 μs on a blend containing 20 wt % d₄PEO. The line shapes and the associated relative intensities were quantitatively interpreted in terms of segmental motion and libration. The results of the interpretation are compared to an earlier study of deuterium spin‐lattice relaxation times over the temperature range of 313 to 413 K. A combined interpretation of both sets of data is developed based on bimodal distribution of correlation times that are separated by about 2 orders of magnitude in time. The faster mode is 30% of the correlation function with a stretched exponent near one while the slower mode is characterized by an exponent of 0.5. The source of the bimodal character is not revealed by the line shape and relaxation data but is consistent with the presence of two glass transition temperatures in this miscible blend and anomalous translational diffusion of diethyl ether through the blend. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2433–2444, 2005     

Metallocenes with Cp Ring-Fused to Chalcogen Heterocycles: Synthesis and Polymerization Results

Abstract

Substituted metallocene ligands containing cyclopentadiene ring fused to either selenophene or benzo[b]tellurophene were prepared following methods previously developed for analogs containing sulfur. 5-Methyl-4,5-dihydro-cyclopenta[b]-selenophen-6-one ( 2 ) and 3-Methyl-3,4-dihydro-benzo[b]cyclopenta[d]telluraphen-2-one ( 7 ) (major isomers) were prepared by polyphosphoric acid catalyzed Friedel-Crafts acylation/Nazarov cyclization of methacrylic acid onto selenophene and respectively benzo[b]tellurophene. Following reduction of the ketone to alcohol, then dehydration, the chalcogen-containing cyclopentadiene olefins were prepared. The olefins were deprotonated with n-butyllithium followed by either bridging with dichlorodimethylsilane, deprotonation and metallation, or deprotonation and direct metallation. In this manner, isomeric mixtures of –rac/-meso dimethylsilanediylbis(η⁵-5-Methyl-cyclopenta[b]selenophen-yl)zirconium dichloride ( 5 ) Bis(η^5?2-methyl-cyclopenta[b][1 Brintzinger, H. H., Fischer, D., Mülhaupt, R., Rieger, B. and Waymouth, R. 1995. Angew. Chem., 107: 1255[Crossref] , [Google Scholar]]benzotelluraphen-yl)zirconium dichloride ( 9 ) were prepared and characterized. Complexes formed active olefin polymerization catalyst when activated with methylalumoxane. Polymerization results with ethylene and propylene are included.     

Real-Time Monitoring of the Mechanical Properties of a Soy Protein and Rubber Polymer during its Production Using Transient Infrared Spectroscopy

Soy protein–based polymers offer promising performance properties, but their characteristics are sensitively dependent on production conditions, so on-line monitoring could help provide the needed control during production. Mid-infrared spectroscopy combined with partial least squares offer the needed analysis, but the opacity of many materials in the mid-infrared range limits its conventional application. Transient infrared spectroscopy is a method of acquiring mid-infrared spectra from moving streams in real time that avoids the opacity problem. We apply transient infrared spectroscopy to a polymer of soy protein and polyisoprene-graft-maleic anhydride–modified natural rubber during its compounding extrusion to measure tensile strength and Young's modulus.     

Duality, thermodynamics, and the linear programming problem in constraint-based models of metabolism

It is shown that the dual to the linear programming problem that arises in constraint-based models of metabolism can be given a thermodynamic interpretation in which the shadow prices are chemical potential analogues, and the objective is to minimize free energy consumption given a free energy drain corresponding to growth. The interpretation is distinct from conventional nonequilibrium thermodynamics, although it does satisfy a minimum entropy production principle. It can be used to motivate extensions of constraint-based modeling, for example, to microbial ecosystems.     

Arbitrary precision composite pulses for NMR quantum computing

We discuss the implementation of arbitrary precision composite pulses developed using the methods of Brown et al. [K.R. Brown, A.W. Harrow, I.L. Chuang, Arbitrarily accurate composite pulse sequences, Phys. Rev. A 70 (2004) 052318]. We give explicit results for pulse sequences designed to tackle both the simple case of pulse length errors and the more complex case of off-resonance errors. The results are developed in the context of NMR quantum computation, but could be applied more widely.     

The Effects of a Third Generation Combined Oral Contraceptive Pill on the Classical Singing Voice

The success of professional operatic singers depends upon the quality of their vocal mechanism. This is known to be sensitive to changes in the endocrine environment. Despite a widespread belief among singers that vocal quality changes according to the stage of the menstrual cycle, this has received little attention. In particular, the possibility that use of the contraceptive pill might stabilize vocal quality by "dampening" hormonal fluctuations has not previously been studied systematically. Here, we show that drospirenone containing oral contraceptive pill (Yasmin, Schering AG, West Sussex, UK) with antiandrogenic and antimineralocorticoid properties demonstrates a significant reduction in the irregularity of the pattern of vibration of the vocal folds during the performance of highly trained classical singers. This study constitutes the first double blind, randomized placebo controlled trial to assess the effects of the contraceptive pill on the patterns of vibration of the vocal folds during the performance of Western classical singing repertoire.     

Analysis of Organotin Compounds via a Thermabeam® LC–MS Interface

Selected organotin compounds, relating to antifouling paints, have been analysed using a particle beam interface system designed for use on liquid chromatography–mass spectrometry (LC–MS) instruments. The resultant mass spectra matched those obtained from conventional electron-impact (EI) techniques, and consistent data over several injections and different elution times were obtained. Data obtained from tributyltin, dibutyltin, monobutyltin, triphenyltin and diphenyltin (each as the chlorides) are presented. This interface has been shown to maintain sample and therefore spectral integrity for these compounds and is of potential use in further investigations relating to organotin environmental pollution.     

Hadamard's Finite Part

A systematic way of ascribing values to integrals which diverge at infinity is described. For integrals with algebraic or logarithmic behaviour it is akin to Hadamard's finite part for integrands which have singularities at finite points. The power of the method is illustrated by examples of particular integrals and the convolution of distributions which are beyond the range of standard theory. Both one-dimensional and multi-dimensional integrals are included. The theory also enables the definition of products of distributions which are considered normally to be too singular for multiplication.