bluuebunny/crossref_metadata_2025_split huggingface dataset:
Upper and lower critical solution temperatures in 1‐octanol solutions of polyethylene
Authors: Muraoka Yoichiro , Inagaki Hiroshi , Suzuki Hidematsu 
Published: April 2007

AbstractCloud points of 1‐octanol solutions of four linear polyethylene samples having different molecular weights were measured visually in both regions of the upper and lower critical solution temperatures (UCST and LCST). From the (temperature, polymer weight fraction) phase diagrams drawn, the UCST and LCST were determined. These data were plotted according to Shultz and Flory, to yield the results of ΘU = 444 K and ψ1,U = 1.16 for the UCSTS and ΘL = 621 K and ψ1,L = −5.4 for the LCSTs. Here, Θ is the Flory theta temperature, ψ1 is the entropy of dilution parameter, and the subscripts U and L refer to the UCST and LCST respectively. The interaction parameter χ1 of the present solutions over the temperature range from ΘU to ΘL was first estimated according to the Eichinger version of the classical lattice theory. Secondly, the Flory and the Patterson polymer solution theories were applied in order to obtain the information on each contribution of cohesive energy and free volume to χ1(T) separately. It was found that the final results significantly depend upon the reference temperature at which the equation‐of‐state parameters are determined. This finding suggests that the temperature reduction in the Foory theory is inadequate.
Ultrasonic attenuation and adiabatic compressibility of polyethyleneoxide‐water mixtures
Authors: Pethrick Richard A. , Poh B. T. 
Published: April 2007

AbstractUltrasonic attenuation and velocity measurements are reported at 2MHz over a temperature range from 293 to 353K for mixtures of polyethylene oxide and water for concentrations from 0 to 100%. The ultrasonic attenuation in the mixtures was observed to be lower than that in the ideal solution. This implies that the structural distribution in the system is changing with concentration. Studies of the compressibility of water indicate the existence of a minimum at approximately 343K. Introduction of polyethylene oxide leads to a shift of the minimum to lower temperature. These data are interpreted in terms of changes in the structure of water and the interaction of the polymer with water.
Dielectric and physico‐mechanical properties of butyl rubber loaded with some white fillers
Authors: Hanna Faika F. , Yehia Abbas A. , Hakim Itedal K. , Bishai Augenie M. , Saad Azima L. G. 
Published: April 2007

AbstractA systematic dielectric study over the frequency region from 0.06 to 300kHz has been carried out on butyl rubber loaded with one of six white fillers namely talc, calcium carbonate, dolomite, barytes, kaolin and silica in increasing quantities at room temperature. A low frequency loss term whose maximum lies around 104Hz for all samples is noticed and is attributed to Maxwell‐Wagner losses arising from the interfacial polarisation due to the presence of the ingredients added stepwise to raw rubber. These losses are found to increase by the addition of filler and the cause of this increase is interpreted.
Soluble synthetic polymers as targetable agents for intracellular drug release
Authors: Lloyd John B. , Duncan Ruth , Pratten Margaret K. 
Published: April 2007

AbstractSoluble synthetic polymers have potential as targetable drug delivery and release agents. Copolymers of 2‐hydroxypropylmethacrylamide with oligopeptide side‐chains have been used to demonstrate the attachment of drug analogues by covalent linkages susceptible to hydrolysis by lysosomal enzymes but stable in plasma. Targeting of polymers to particular sites has been illustrated by making use of the substrate specificity of adsorptive pinocytosis.
Release of ergotamine from poly (2‐hydroxyethyl Methacrylate)
Authors: Huglin Malcolm B. , Sloan David J. 
Published: April 2007

AbstractThe release of the alkaloid ergotamine from thin discs of poly(2‐hydroxyethyl methacrylate) [PHEMA] into an aqueous buffered medium has been effected under sink conditions and monitored by fluorescence spectroscopy. The process was found to be diffusion controlled, the fraction of available drug released being linear in (time)1/2 during the initial stages. The influences of disc thickness, drug load and temperature were investigated and yielded 2.0 (± 1.0) × 10−13 m2 s−1 for the diffusion coefficient of ergotamine through the swollen gel at 310K and a value of 69 ± 5 kJ mol−1 for the activation energy of diffusion. For the uptake of aqueous buffer alone into PHEMA the corresponding values were ca 100 times greater and three times smaller respectively.
The automation of a torsional braid analyser, interfaced with an apple microcomputer
Authors: Cowie John M. G. , Ferguson Roderick 
Published: April 2007

AbstractThe automation of a torsional braid analyser by interfacing with an Apple II microcomputer is described. The use of an analogue to digital convertor is discussed together with appropriate mathematical procedures for carrying out the subsequent on‐line data processing. Finally, the advantages of this automated system for obtaining thermomechanical spectra of polymeric materials, as compared with the previous method of data collection and analysis, are discussed.
Recent trends in the stabilisation of polymers
Authors: Scott Gerald 
Published: April 2007

AbstractPolymers are subject to oxidation during processing due to the application of mechanical stress (shear) which leads to the scission of the polymer backbone and the formation of initiating macroalkyl radicals. Under the conditions of low oxygen concentration in commercial mixing operations, a catalytic redox antioxidant mechanism can operate which involves the alternating oxidation of alkyl radicals and reduction of alkylperoxyl radicals.‘Stable’ free radicals (A) notably phenoxyl and nitroxyl radicals and inorganic radicals such as I are very effective melt stabilisers for polyolefins because of their ability to undergo reversible oxidation and reduction. magnified imageA similar mechaism has been shown to operate during the mechano‐oxidation of rubbers in service (fatigue) and during the photo‐oxidation of polyolefins.
The structures of polydienes prepared anionically in tetrahydrofuran in the presence of sterically hindered lewis acids II ‐ polyisoprene and trimesityl boron
Authors: Bres Philippe , Richards David H. , Stewart Malcolm J. , Viguier Michele 
Published: April 2007

AbstractThe presence of the sterically hindered Lewis acid, trimesityl boron, during the anionic polymerisation of isoprene is shown to affect the structure of the resulting polymer only marginally. This behaviour contrasts with its effect when the monomer is butadiene. The principal change is an increase in 1,4‐content at the expense of 1,2‐structure, with the proportion of 3,4‐structure remaining unaffected. These results are explained in terms of the isomeric forms of the propagating anion.
Positron annihilation and X‐ray diffraction studies of cellulose and some derivatives
Authors: Doyle Stephen , Malhotra Bansi D. , Peacock Norman , Pethrick Richard A. 
Published: April 2007

AbstractPositron lifetime measurements are reported over a temperature range from 290 to 380K on cellulose and certain of its derivatives. The lifetime spectra were resolved into three components each attributed to a different mode of positron annihilation in the polymer. The longest lifetime component is associated with the decay of ortho‐positronium and is a function of the average cavity distribution in the sample. It is observed that significant differences exist in the lifetimes of positrons in cellulose and its derivatives which can be interpreted as evidence for changes in the free volume distribution in these materials. Comparison of positron decay in samples of cellulose acetate prepared at both room temperature and elevated temperature indicate that the phenomena of gelation in this material is accompanied by a reduction of free volume. The correlation of such observations with the dynamic properties of these polymers is discussed.
The isolation and characterisation of grafts from glass surfaces and their immiscibility with homopolymer
Authors: Eastmond Geoffrey C. , Mucciariello Gennaro 
Published: April 2007

AbstractA procedure for photochemically detaching, isolating and characterising grafts (produced by a method developed previously by the authors) from glass surfaces is described. Preliminary results indicate that the molecular weights and molecular weight distributions can be varied through control of the kinetics of graft formation; our previous studies are seen to have produced a high surface coverage of grafts of high molecular weight. A thermodynamic argument is developed to explain the immiscibility of grafts with free homopolymer for high surface coverage by grafts from which it is seen that the immiscibility is entropy‐driven. Comparisons are drawn between our previous studies and relevant studies by other workers and apparent anomolies are explained.
Electron beam lithography — influence of molecular characteristics on the performance of positive resists
Authors: Sharma Varinder K. , Affrossman Stanley , Pethrick Richard A. 
Published: April 2007

AbstractPolymers are widely used as resists in electron beam lithography. This paper is concerned with theoretical modelling of the electron beam lithographic process and establishing criteria which need to be satisfied for a polymer to behave as a good positive resist. The effects of molecular weight, tacticity, solvent selection and sequence structure are discussed. Criteria are presented upon which the design of a new resist material may be based.
Spacial arrangement of poly(vinylacetate) synthesised by matrix polymerisation
Authors: Bezdadea Mariana , Leanca Mihai 
Published: April 2007

AbstractThe tactic structure of PVAc synthesised by matrix polymerisation was reported. At temperatures below 0°C, for a ratio, matrix to monomer, equal to 3, a higher packing degree of the macromolecular chains was obtained. The third peak of the X‐ray diffraction spectra of matrix samples suggests the existence of isotactic polymer.
Mechanochemically initiated polymerisations. 12. Spectral and thermal characterisation of some products obtained by vibratory milling of benzene and pyridine
Authors: Oprea Cleopatra Vasiliu , Popa Marcel , Cascaval Constantin N. 
Published: April 2007

AbstractVibratory milling is used to open the aromatic ring of compounds such as benzene and pyridine and this is followed by concatenation of the structural units. The products obtained form both the soluble fractions in methanol, i.e. dimethylformamide and the insoluble fraction, the latter being found in the prevalent amount. Analysis of the soluble fractions by infrared spectroscopy (i.r.) and pyrolysis‐gas chromatography (p.‐g.c.) conforms their linear structure of the polyenic type with some short crosslinkings and a great sensitivity to the action of atmospheric oxygen.
Properties of (BA)n‐B type block copolymers of butadiene and dimethyl itaconate prepared using macroazonitrile initiators
Authors: Cowie John M. G. , Yazdani‐Pedrarn Mehrdad 
Published: April 2007

AbstractMulti‐block copolymers of the (BA)n‐B type, where A is poly(dimethyl itaconate) and B is polybutadiene, were synthesised using a macroazonitrile initiator. This was prepared by the reaction of 4, 4′ azobis (4‐cyanopentanoyl chloride) with hydroxyl terminated polybutadienes. and subsequent decomposition of the azo group in the presence of dimethyl itaconate monomer yielded the block copolymer. Measurement of their glass transition temperatures revealed that the copolymers formed two phases. The dynamic thermomechanical properties were measured and this demonstrated that in the temperature range 290–400K, the glassy poly(dimethyl itaconate) blocks acted as crosslinking sites for the elastomeric polybutadiene blocks and that the materials behaved like typical elastoplastic block copolymers. Property variation was obtained when the ratio of polybutadiene to poly(dimethyl itaconate) in the copolymers was altered.
Molecular weight averages and distributions of unsaturated polyesters: Their effect on the properties of styrene‐crosslinked networks
Authors: Douglas William E. , Ghotra Joginder S. , Ho Dawn , Pritchard Geoffrey 
Published: April 2007

AbstractUnsaturated polyesters have been synthesised and modified to determine the effect of number‐average molecular weight (M̄n) and molecular weight distribution (MWD) on the following properties of the polyesters after crosslinking with styrene: (i) water absorption, (ii) initial mechanical properties and (iii) property retention after immersion The most important factor was found to be the very low molecular weight ‘tail’ which adversely affected behaviour in several respects. Above a certain M̄n, initial mechanical properties were insensitive to the variables mentioned, but mechanical property retention after immersion closely reflected the water absorption behaviour by its dependence on the average chain length and the low molecular weight constituents. The importance of removing such constituents is apparent.
Reform in statistical education
Authors: Huck Schuyler W. 
Published: April 2007

AbstractTwo questions are considered in this article: (a) What should professionals in school psychology do in an effort to stay current with developments in applied statistics? (b) What should they do with their existing knowledge to move from surface understanding of statistics to deep understanding? Written for school psychologists who have completed their formal education, this article examines the way in which four kinds of relatively new technological tools—Java applets, electronic discussion groups, blogs, and online books, tutors, and courses—can help professionals increase their knowledge and understanding of statistical concepts and procedures. Because new statistical procedures, over time, enter the arsenal of applied researchers, and given that the National Association of School Psychologists explicitly states that continuing professional development in research is an expectation, the information presented here shows school psychologists that there are useful and efficient ways for them to “keep current” with advances in applied statistics. © 2007 Wiley Periodicals, Inc. Psychol Schs 44: 527–533, 2007.
NF‐kappaB in the lungs of premature rabbits during mechanical ventilation—comparison between conventional mechanical ventilation (CMV) and high‐frequency oscillation (HFO)
Authors: Oba Kunihiro , Yamashita Hiroko , Waragai Aki , Kawano Toshio 
Published: March 2007

AbstractThe purpose of this study is to compare pulmonary nuclear factor‐kappaB (NF‐kappaB) activity of conventional mechanical ventilation (CMV) with that of high‐frequency oscillation (HFO) in premature rabbit lungs. For surfactant‐depleted model, we used premature rabbits in order to exclude the effect of lung lavage on the activation of NF‐kappaB. The premature rabbits were delivered at a gestational age of 27 days by hysterotomy. Both modes of the ventilator were set at the same MAP and FiO2. We used animals that had PCO2 levels of approximately 50‐mmHg. Animals were sacrificed after 1‐hr ventilation with CMV or HFO. Then activity of pulmonary NF‐kappaB was assessed. We observed that NF‐kappaB activity was higher in the lungs of CMV compared with those of HFO, as measured by Western blot analysis. The activity level of NF‐kappaB in the lungs measured by ELISA was significantly higher in CMV group than in HFO group. We conclude that a higher level of NF‐kappaB activation was associated with CMV when compared to HFO. Pediatr Pulmonol. 2007; 42:446–451. © 2007 Wiley‐Liss, Inc.
A model of restriction endonuclease MvaI in complex with DNA: A template for interpretation of experimental data and a guide for specificity engineering
Authors: Kosinski Jan , Kubareva Elena , Bujnicki Janusz M. 
Published: April 2007

AbstractR.MvaI is a Type II restriction enzyme (REase), which specifically recognizes the pentanucleotide DNA sequence 5′‐CCWGG‐3′ (W indicates A or T). It belongs to a family of enzymes, which recognize related sequences, including 5′‐CCSGG‐3′ (S indicates G or C) in the case of R.BcnI, or 5′‐CCNGG‐3′ (where N indicates any nucleoside) in the case of R.ScrFI. REases from this family hydrolyze the phosphodiester bond in the DNA between the 2nd and 3rd base in both strands, thereby generating a double strand break with 5′‐protruding single nucleotides. So far, no crystal structures of REases with similar cleavage patterns have been solved. Characterization of sequence‐structure‐function relationships in this family would facilitate understanding of evolution of sequence specificity among REases and could aid in engineering of enzymes with new specificities. However, sequences of R.MvaI or its homologs show no significant similarity to any proteins with known structures, thus precluding straightforward comparative modeling. We used a fold recognition approach to identify a remote relationship between R.MvaI and the structure of DNA repair enzyme MutH, which belongs to the PD‐(D/E)XK superfamily together with many other REases. We constructed a homology model of R.MvaI and used it to predict functionally important amino acid residues and the mode of interaction with the DNA. In particular, we predict that only one active site of R.MvaI interacts with the DNA target at a time, and the cleavage of both strands (5′‐CCAGG‐3′ and 5′‐CCTGG‐3′) is achieved by two independent catalytic events. The model is in good agreement with the available experimental data and will serve as a template for further analyses of R.MvaI, R.BcnI, R.ScrFI and other related enzymes. Proteins 2007. © 2007 Wiley‐Liss, Inc.
“Chemistry for all, instead of chemistry just for the elite”: Lessons learned from detracked chemistry classrooms
Authors: Watanabe Maika , Nunes Nicole , Mebane Sheryl , Scalise Kathleen , Claesgens Jennifer 
Published: March 2007

AbstractWithin the already limited literature on instructional practices in detracked classrooms, there are even fewer research‐based studies of detracked science classrooms. This article attempts to address this gap in the research literature, delving into the unique challenges and instructional responses to teaching detracked science. The authors report on a case study of two chemistry teachers' heterogeneous classrooms at a racially diverse, public high school in California, where all students have been required to take chemistry since the school's founding in 1994. The authors highlight the following four beliefs and instructional practices that were instrumental in teachers' successful efforts to teach detracked chemistry classes: (1) teachers' true belief in a developmental conception of ability and intelligence; (2) a focus on an inquiry‐based pedagogical approach to chemistry foregrounding real‐world contexts; (3) a focus on teaching students study skills; and (4) a strong sense of community in the classroom, where students are held responsible for their own and each other's learning. To illustrate each of these findings, the authors select vivid examples from fieldnotes of classroom observations as well as interviews of teachers and students that make clear how teachers enacted and students experienced these elements in chemistry classrooms. © 2007 Wiley Periodicals, Inc.Sci Ed91:683–709, 2007
Statistical tests with accurate size and power for balanced linear mixed models
Authors: Muller Keith E. , Edwards Lloyd J. , Simpson Sean L. , Taylor Douglas J. 
Published: March 2007

AbstractThe convenience of linear mixed models for Gaussian data has led to their widespread use. Unfortunately, standard mixed model tests often have greatly inflated test size in small samples. Many applications with correlated outcomes in medical imaging and other fields have simple properties which do not require the generality of a mixed model. Alternately, stating the special cases as a general linear multivariate model allows analysing them with either the univariate or multivariate approach to repeated measures (UNIREP, MULTIREP). Even in small samples, an appropriate UNIREP or MULTIREP test always controls test size and has a good power approximation, in sharp contrast to mixed model tests. Hence, mixed model tests should never be used when one of the UNIREP tests (uncorrected, Huynh–Feldt, Geisser–Greenhouse, Box conservative) or MULTIREP tests (Wilks, Hotelling–Lawley, Roy's, Pillai–Bartlett) apply. Convenient methods give exact power for the uncorrected and Box conservative tests. Simulations demonstrate that new power approximations for all four UNIREP tests eliminate most inaccuracy in existing methods. In turn, free software implements the approximations to give a better choice of sample size. Two repeated measures power analyses illustrate the methods. The examples highlight the advantages of examining the entire response surface of power as a function of sample size, mean differences, and variability. Copyright © 2007 John Wiley & Sons, Ltd.
Renaissance in chiroptical spectroscopic methods for molecular structure determination
Authors: Polavarapu Prasad L. 
Published: March 2007

AbstractTwo of the chiroptical spectroscopic methods, namely optical rotatory dispersion (ORD) and electronic circular dichroism (ECD), have been around for several decades. But their use in determining the absolute configuration and predominant conformation is gaining renewed interest with the availability of quantum mechanical methods for predicting ORD and ECD. Two other methods, namely vibrational circular dichroism (VCD) and vibrational Raman optical activity (VROA), are relatively new and offer convenient approaches for deducing the structural information in chiral molecules. With the availability of quantum mechanical programs for predicting VCD and VROA, these methods have attracted numerous new researchers to this area. This review summarizes the latest developments in these four areas and provides examples where more than one method has been used to confirm the information obtained from individual methods. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 125–136; 2007: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20117
4. Management of the infertile couple in tertiary care, part 1
Authors: Mcclure Neil 
Published: March 2007

AbstractAs well as all the investigations and services offered by secondary care, the tertiary care unit provides advanced fertility surgery and, in particular, assisted reproductive technologies (ARTs). In the first part of this article, Professor McClure discusses ovarian hyperstimulation and subsequent oocyte retrieval, which are the cornerstone of therapy for couples undergoing ARTs. He also outlines how sperm is collected and prepared for use in assisted conception techniques. For those couples who are unable to produce their own gametes, most ART units offer donor sperm and donor oocytes. Copyright © 2007 Wiley Interface Ltd
Nonequilibrium transitions in thermotropic phases of eicosenoic acid methyl esters
Authors: Chang S. P. , Rothfus J. A. 
Published: March 2007

AbstractMethyl esters ofcis‐5‐eicosenoic (5‐EAME) andcis‐11‐eicosenoic (11‐EAME) acids from the seed oil ofLimnanthes alba (Meadowfoam) exhibit a degree of thermotropic polymorphism unobserved with shorter and longer chainlength monoenic methyl esters. 5‐EAME freezes at 264 K and melts at 266 K if cooled no lower than 215 K. 11‐EAME freezes at 239 K and melts at 255 K if cooled at no lower than 240 K. Solids cooled to lower temperatures undergo phase transformation to highermelting polymorphs (274 K, 5‐EAME; 262 K, 11‐EAME), and samples often exhibit double melting endotherms. Quantities of each high‐melting phase vary with time at temperatures below characteristic initiation temperatures. Highly temperature‐sensitive phase conversions suggest low temperature nucleation, followed by crystal growth and conversion, as reheating allows molecular motion. Once formed, both high‐melting phases melt with essentially the same melting entropy. Thermodynamic and kinetic analyses imply that differences exhibited by the isomeric esters derive from aliphatic configuration distal to the double bond.