bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic MR assessment of the anorectal angle and puborectalis muscle in pediatric patients with anismus: Technique and feasibility
Authors: Chu Winnie C.W. , Tam Yuk‐him , Lam Wynnie W.M. , Ng Alex W.H. , Sit Frances , Yeung Chung‐kwong
Published: April 2007

Purpose

To assess the feasibility of dynamic breath‐hold MRI for evaluating changes in the anorectal angle and movements of the pelvic‐floor musculature (puborectalis) during resting and straining states in pediatric patients presenting with anismus.

Materials and Methods

Six pediatric patients (7–13 years old) with chronic constipation and manometric evidence of anismus were assessed by dynamic breath‐hold MRI. Changes in the anorectal angle, the degree of pelvic‐floor descent, and the thickness and length of the puborectalis muscles were measured during rest and straining. The findings were compared with those obtained in six age‐ and sex‐matched controls.

Results

The children with anismus had a smaller anorectal angle during straining, and the angle decreased from rest to defecation. The puborectalis also became paradoxically shortened and thickened during straining in the anismus group. There were significant differences between the two groups in terms of the change of degree of the anorectal angle, and the thickness and length of the puborectalis muscle during straining.

Conclusion

Fast dynamic MRI is feasible for evaluating pelvic‐floor movement in pediatric patients. Preliminary results suggest that children with anismus have a smaller anorectal angle and a different puborectalis configuration compared to controls. J. Magn. Reson. Imaging 2007. © 2007 Wiley‐Liss, Inc.
Combining Krylov subspace methods and identification‐based methods for model order reduction
Authors: Heres P. J. , Deschrijver D. , Schilders W. H. A. , Dhaene T.
Published: April 2007

Many different techniques to reduce the dimensions of a model have been proposed in the near past. Krylov subspace methods are relatively cheap, but generate non‐optimal models. In this paper a combination of Krylov subspace methods and orthonormal vector fitting (OVF) is proposed. In that way a compact model for a large model can be generated. In the first step, a Krylov subspace method reduces the large model to a model of medium size, then a compact model is derived with OVF as a second step. Copyright © 2007 John Wiley & Sons, Ltd.
2‐methoxyestradiol induces apoptosis and cell cycle arrest in human chondrosarcoma cells
Authors: Fong Yi‐Chin , Yang Wei‐Hong , Hsu Sheng‐Feng , Hsu Horng‐Chaung , Tseng Kuo‐Fung , Hsu Chin‐Jung , Lee Chun‐Yi , Scully Sean P.
Published: April 2007

2‐Methoxyestradiol (2ME) is an endogenous metabolite with estrogen receptor‐independent anti‐tumor activity. The current study seeks to determine the mechanism of anti‐tumor activity of 2ME on human chondrosarcoma. 2ME caused a time‐ and dose‐dependent cytotoxity in chondrosarcoma cells, while primary chondrocytes were minimally affected. Cells accumulated in G0/G1 phase in response to 2ME and DAPI stain indicated an induction of apoptosis. Bax, Cytochrome C, and Caspase‐3 protein expression were increased, while p53 expression was decreased. A higher Bax/Bcl‐2 ratio followed 2ME treatment. 2ME has a potentially promising role as a systemic therapy of chondrosarcoma when the mechanism of action is better delineated. Published by Wiley Periodicals, Inc. J Orthop Res 25:1106–1114, 2007
Nuclear excitation by the atomic electron rescattering in a laser field
Authors: Kornev A S , Zon B A
Published: April 2007

Excitation of low-lying nuclear levels by inelastic scattering of laser-accelerated electrons was considered. The process has a threshold dependence on the laser intensity. The estimates give a short-term activity of certain isotopes up to 103Cu for 10-fs laser pulses with energy 3 J for concentration of this isotope in the target about 1020cm-3.
Global minimum and orthogonality in Cp‐classes
Authors: Mecheri Salah
Published: April 2007

In this paper we use recent results [14] to establish various characterizations of the global minimum of the map Fψ : U → ℝ+ defined by Fψ (X) = ‖ψ (X)‖p (1 < p < ∞) where ψ: U → Cp is a map defined by ψ (X) = S +ϕ (X), with ϕ: B (H) → B (H) a linear map and S ∈ Cp , and U = {X ∈ B (H): ϕ (X) ∈ Cp }. Further, we apply these results to characterize the operators which are orthogonal to the range of elementary operators. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the structure of the essential spectrum for the three‐particle Schrödinger operators on lattices
Authors: Albeverio Sergio , Lakaev Saidakhmat N. , Muminov Zahriddin I.
Published: April 2007

A system of three quantum particles on the three‐dimensional lattice ℤ3 with arbitrary dispersion functions having not necessarily compact support and interacting via short‐range pair potentials is considered. The energy operators of the systems of the two‐and three‐particles on the lattice ℤ3 in the coordinate and momentum representations are described as bounded self‐adjoint operators on the corresponding Hilbert spaces. For all sufficiently small values of the two‐particle quasi‐momentum k ∈ (–π, π ]3 the finiteness of the number of eigenvalues of the two‐particle discrete Schrödinger operator hα (k) below the continuous spectrum is established. The location of the essential spectrum of the three‐particle discrete Schrödinger operator H (K), K ∈ (–π,π ]3 being the three‐particle quasi‐momentum, is described by means of the spectrum of the two‐particle discrete Schrödinger operator hα (k), k ∈ (–π, π ]3. It is established that the essential spectrum of the three‐particle discrete Schrödinger operator H (K), K ∈ (–π, π ]3, consists of finitely many bounded closed intervals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lp estimates of solutions tomixed boundary value problems for the Stokes system in polyhedral domains
Authors: Maz'ya V. , Rossmann J.
Published: April 2007

A mixed boundary value problem for the Stokes system in a polyhedral domain is considered. Here different boundary conditions (in particular, Dirichlet, Neumann, free surface conditions) are prescribed on the faces of the polyhedron. The authors prove the existence of solutions in (weighted and non‐weighted) Lp Sobolev spaces and obtain regularity assertions for weak solutions. The results are based on point estimates of Green's matrix. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A hierarchical analysis of the green consciousness of the Egyptian consumer
Authors: Mostafa Mohamed M.
Published: April 2007

This study investigates the influence of various cultural values and psychological factors on the green purchase behavior of Egyptian consumers. Using a large sample of 1093 consumers, a conceptual model has been developed. The survey results provide reasonable support for the validity of the proposed model. Specifically, the findings from the structural equation model confirm the influence of the consumers' natural environment orientation, ecological knowledge, and environmental concern on their attitudes towards green purchase. Consumers' attitudes toward green purchase, in turn, are also found to affect their actual green purchase behavior via the mediator role of green purchase intention. However, one of the other important findings suggests that the link between intention and actual purchase is weak. In other words, on a declarative level, more and more consumers in Egypt express their concern over the ecological situation and declare their willingness to contribute somehow to the protection of environment by buying green products. However, in reality this concern may not be manifested consistently. © 2007 Wiley Periodicals, Inc.
Chemoenzymatic Synthesis of Amylose‐Grafted Chitosan
Authors: Matsuda Shun‐ichi , Kaneko Yoshiro , Kadokawa Jun‐ichi
Published: April 2007

An amylose‐grafted chitosan has been synthesized by a chemoenzymatic method according to the following two reactions. First, maltoheptaose is introduced to chitosan by a reductive amination using sodium cyanotrihydroborate in a mixed solvent of 1.0 mol · L−1 aqueous acetic acid and methanol at room temperature to produce a maltoheptaose‐grafted chitosan that has a well‐defined molecular structure. A phosphorylase‐catalyzed enzymatic polymerization of α‐D‐glucose 1‐phosphate is then performed from the maltoheptaose‐grafted chitosan to obtain the amylose‐grafted chitosan. This material does not dissolve in any solvent, e.g., aqueous acetic acid and dimethyl sufoxide, which are good solvents for chitosan and amylose, respectively.

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A Facile Route to Synthesize Highly Uniform Nanocapsules: Use of Amphiphilic Poly(acrylic acid)‐block‐polystyrene RAFT Agents to Interfacially Confine Miniemulsion Polymerization
Authors: Lu Fujun , Luo Yingwu , Li Bogeng
Published: April 2007

Miniemulsion polymerization with an amphiphilic poly(acrylic acid)‐block‐polystyrene reversible addition–fragmentation chain transfer agent as a surfactant and polymerization mediator is used to synthesize highly uniform nanocapsules. The nanocapsules with uniform structures, which include particle size, shell thickness, and shape symmetry, could be achieved by the post‐addition of a small amount of sodium dodecyl sulfate. Although the solid particles seem unavoidable, the ‘pure’ uniform core–shell structures are easily collected by centrifugation.

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Polysorbate 80 as a Tool: Synthesis of Gold Nanoparticles
Authors: Premkumar Thathan , Kim Dongsik , Lee Kyungjae , Geckeler Kurt E.
Published: April 2007

The preparation of metal nanoparticles generally requires the use of mostly toxic reducing agents according to state‐of‐the‐art procedures. Here, we report that polysorbate 80, a polymeric nonionic surfactant, when reacted with a gold salt in water at room temperature, yields well‐dispersed gold nanoparticles. Furthermore, we could control the particle size by simply altering concentration or temperature. The synthetic procedure presented here is easy, inexpensive, straightforward, and user‐friendly.

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Ductile‐to‐Semiductile Transition in PP‐MWNT Nanocomposites
Authors: Satapathy Bhabani K. , Ganß Martin , Weidisch Roland , Pötschke Petra , Jehnichen Dieter , Keller Thomas , Jandt Klaus D.
Published: April 2007

A ductile‐to‐semiductile transition in the crack resistance behaviour of PP/MWNT composites is discussed, using an essential work of fracture approach based on a post yield fracture mechanics concept and its possible interrelation to the structural attributes studied by TEM, SEM, and WAXD. A maximum in the non‐essential work of fracture is observed at 0.5 wt.‐% MWNT content, which demonstrates the enhanced resistance to crack propagation compared to pure PP, followed by a sharp decline with the increase in MWNT content to 1.5 wt.‐%, which reveals a ductile‐to‐semiductile transition. Fracture kinetic studies present a qualitative picture of the nature of such a transition in terms of a) switch over from non‐steady (in pure PP) to steady‐state crack tip opening displacement rate (in nanocomposites), and b) a ductile‐to‐semiductile transition; largely as a result of delayed‐yielding of the nanocomposites.

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Stabilization of Silver Nanoparticles by Polyelectrolytes and Poly(ethylene glycol)
Authors: Radziuk Darya , Skirtach Andre , Sukhorukov Gleb , Shchukin Dmitry , Möhwald Helmuth
Published: April 2007

Silver nanoparticles of 23 nm size were formed by chemical reduction of silver nitrate in excess of aqueous sodium borohydride. To examine the aggregation behavior in NaCl solutions, they were coated with poly(diallyldimethylammonium chloride), poly(allylamine hydrochloride) and poly(ethylene glycol) by layer‐by‐layer assembly. Silver nanoparticles coated with PDADMAC of both high and low molecular weight revealed the lowest stability independent of salt concentration. Silver nanoparticles coated with PAH and PEG are stable in 0.1 or 0.01 M NaCl, whereas addition of 0.5 M NaCl destroys the colloidal solution. The destruction of silver agglomerates and the increase of monodispersity in the case of PEG coated silver nanoparticles were observed after heating at 90 °C. In contrast, uncoated silver nanoparticles readily agglomerate and precipitate even after heating at 65 °C.

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Applications of mass spectrometry for the structural characterization of recombinant protein pharmaceuticals
Authors: Srebalus Barnes Catherine A. , Lim Amareth
Published: April 2007

Therapeutic proteins produced using recombinant DNA technologies are generally complex, heterogeneous, and subject to a variety of enzymatic or chemical modifications during expression, purification, and long‐term storage. The use of mass spectrometry (MS) for the evaluation of recombinant protein sequence and structure provides detailed information regarding amino acid modifications and sequence alterations that have the potential to affect the safety and activity of therapeutic protein products. General MS approaches for the characterization of recombinant therapeutic protein products will be reviewed with particular attention given to the standard MS tools available in most biotechnology laboratories. A number of recent examples will be used to illustrate the utility of MS strategies for evaluation of recombinant protein heterogeneity resulting from post‐translational modifications (PTMs), sequence variations generated from proteolysis or transcriptional/translational errors, and degradation products which are formed during processing or final product storage. Specific attention will be given to the MS characterization of monoclonal antibodies as a model system for large, glycosylated, recombinant proteins. Detailed examples highlighting the use of MS for the analysis of monoclonal antibody glycosylation, deamidation, and disulfide mapping will be used to illustrate the application of these techniques to a wide variety of heterogeneous therapeutic protein products. The potential use of MS to support the selection of cell line/clone selection and formulation development for therapeutic antibody products will also be discussed. © 2007 Wiley Periodicals, Inc., Mass Spec Rev
Increase of the trophoblast giant cells with prolactin‐releasing peptide (PrRP) receptor expression in p53‐null mice
Authors: Komatsu Daisuke , Abe Takumi , Sano Yoshihiro , Shimazaki Kiyoe , Tomita Motowo , Kanayama Naohiro , Takahashi Katsuhiko
Published: April 2007

Trophoblast giant cells in the mouse placentas are polyploid cells that form as a result of endoreduplication. The giant cells form the outermost layer of the extraembryonic compartment and produce a number of pregnancy‐specific hormones, including prolactin family members. Here we demonstrate that trophoblast giant cells are increased, and display upregulation of prolactin releasing peptide (PrRP) receptor in the p53‐null (p53−/−) embryonic placentas. At day 13.5 of gestation, the weight of p53−/− placentas was less than that of both wild‐type and p53+/− placentas. In p53−/− placentas, the spongiotrophoblast layer was significantly decreased in thickness, and the trophoblast giant cells were observed not only in the outer layer of placentas but in both the spongiotrophoblast layer and the labyrinthine layer. The giant cells spread over the spongiotrophoblast and labyrinthine layer in p53−/− placentas displayed more intensive expression of immunoreactive PrRP receptor than in wild‐type placentas. Previous studies indicated that the association between PrRP and PrRP receptor physiologically involves in the expression and secretion of the peptide hormones, including prolactin and growth hormones. These results suggest that p53 may regulate the differentiation of trophoblast giant cells, and may control the physiological PrRP stimuli in mouse placentas. Mol. Reprod. Dev. 74: 1089–1094, 2007. © 2007 Wiley‐Liss, Inc.
Protein kinase C activity in mouse eggs regulates gamete membrane interaction
Authors: Akabane Hiroto , Fan Jun , Zheng Xuehai , Zhu Guo‐Zhang
Published: April 2007

Gamete membrane interaction is critical to initiate the development of a new organism. The signaling pathways governing this event, however, are poorly understood. In this report, we provide the first evidence that protein kinase C activity in mouse eggs plays a crucial role in the regulation of this process. Stimulating PKC activity in mouse eggs by phorbol 12‐myristate 13‐acetate (PMA) drastically inhibited the egg's membrane ability to bind and fuse with sperm. Surprisingly, this significant reduction of gamete membrane interaction was also observed in eggs treated with the PKC inhibitors staurosporine and calphostin c. In further analysis, we found that while no change of egg actin cytoskeleton was detected after either PMA or calphostin c treatment, the structural morphology of egg surface microvilli was severely altered in the PMA‐treated eggs, but not in the calphostin c‐treated eggs. Moreover, sperm, which bound but did not fuse with the eggs treated with the anti‐CD9 antibody KMC8, were liberated from the egg membrane after PMA, but not calphostin c, treatment. Taken together, these results suggest that egg PKC may be precisely balanced to regulate gamete membrane interaction in a biphasic mode, and this biphasic regulation is executed through two different mechanisms. Mol. Reprod. Dev. 74: 1465–1472, 2007. © 2007 Wiley‐Liss, Inc.
Presumptive pre‐sertoli cells express genes involved in cell proliferation and cell signalling during a critical window in early testis differentiation
Authors: Cory Aron T. , Boyer Alexandre , Pilon Nicolas , Lussier Jacques G. , Silversides David W.
Published: April 2007

In mammals, the pre‐Sertoli cell of the male genital ridge is the first cell type to display sex specific differentiation and differential gene expression. The genetic cascade driving the differentiationof pre‐Sertoli cells and ultimately testis formationis beginning to be unravelled, but many questions remain. A better understanding of the transcriptome of pre‐Sertoli cells immediately after sex determination is essential in order to further understand this differentiationprocess. A mouse model expressing Red Fluorescent Protein (RFP) under the control of a hybrid mouse/pig SRY promoter (HybSRYp‐RFP) was used to purify cells from embryonic day 12.0 (e12.0) male genital ridges. To compare the transcriptomes of HybSRYp‐RFP cell populations versus age matched whole female genital ridges, RNA was extracted and used to generate molecular probes that were hybridized onto Affymetrix Mouse Genome 430 2.0 micro‐arrays. The expression of genes considered markers for pre‐Sertoli cells, including Sox9, Mis, Dhh and Fgf9 were identified within the HybSRYp‐RFP expressing cell population, while markers for germ cells (Oct4, SSEA‐1) and endothelial cells (Ntrk3) were not identified. In contrast, markers for ovarian somatic cell expression, including Fst and Bmp2, were identified as overexpressed within the ovarian cell population. In a general fashion, genes identified as 2.5‐fold over expressed in HybSRYp‐RFP expressing cells coded notably for cell signalling and extra cellular proteins. The expression of Sox10, Stc2, Fgf18, Fgf13 and Wnt6 were further characterized via whole mount in situ hybridization (WISH) on male and female genital ridges between e11.5 and e14.5. Sox10, Fgf18, Fgf13 and Stc2 gene expression was detected within the male genital ridges while Wnt6 was found diffusely within both the male and female genital ridges. These data represent the earliest comprehensive microarray expression analysis of purified presumptive pre‐Sertoli cells available to date. Mol. Reprod. Dev. 74: 1491–1504, 2007. © 2007 Wiley‐Liss, Inc.
Aging study of linseed oil resin/styrene thermosets and their composites with wood flour
Authors: Mosiewicki Mirna A , Rojas Oscar , Sibaja María R , Borrajo Julio , Aranguren Mirta I
Published: April 2007

The changes in the properties of new crosslinked polymers based on renewable resources and their derived composites have been monitored as a function of time; this knowledge being necessary to estimate their behavior in final applications. Rigid thermoset polymers prepared by free radical polymerization of resins obtained from linseed oil and styrene and composites reinforced with wood flour were evaluated in different environmental conditions and at different times after their preparation. The action of atmospheric oxygen on the unsaturated groups in fatty acids produces chemical changes in these polymers, which affect the properties of the cured materials. These changes were analyzed using Fourier transform infrared spectroscopy, dynamic mechanical analysis and mechanical testing. An increase in the modulus with time was observed during exposure of the samples to dry conditions, or humid environments (60% relative humidity), with or without UV irradiation. The reaction with oxygen appears to be accelerated when the materials are subjected to UV irradiation, showing a large effect on the glass transition temperature. Copyright © 2007 Society of Chemical Industry
A study of the thermodynamic properties of the system polystyrene‐ethylcyclohexane by the light scattering method
Authors: Kratochvil Jaroslav , Sedléček Blahoslav
Published: April 2007

The thermodynamic properties of the system polystyrene‐ethylcyclohexane (temperature 70°C) were examined between 57 and 80°C for weight fractions of the polymer 0‐0.16. Scholte's light scattering method was used for this purpose. The results are presented in the form of the temperature and concentration dependence of the interaction parameter of the Flory‐Huggins equation. The interaction function thus obtained has been tested by comparing calculated and experimental spinodals. The given system has been compared with a pseudoideal solution in order to discuss the pronounced concentration dependence of the interaction parameter and its dependence on molecular weight.
Liquid‐liquid phase separation in multicomponenent polymer systems: XV thermodynamic aspects of polymer compatibility
Authors: Koningsveld R. , Kleintjens L. A.
Published: April 2007

Cloud‐point curves in mixtures of short‐chain polymers often have irregular shapes, showing shoulders or two maxima. Limits of the thermodynamic stability as measured by Pulse Induced Critical Scattering also appear to be bimodal in such cases. A possible explanation of this phenomenon might be that the constituent molecules influence each other's chain flexibility, the more flexible chains becoming less flexible upon addition of stiffer ones, and vice versa. Such a feature is incorporated i.a. in Huggins' new theory in which orientational entropy correction terms relate the average randomness of orientation of a segment with respect to the preceding one in the chain to the surroundings of the segment.
Interaction between polymers in dilute solutions of two polymers in a single solvent measured by light scattering and the compatibility of polymers
Authors: Kratochvil Pavel , Straková Dagmar , Tuzar Zdeněk
Published: April 2007

The intensity of light scattered from dilute solutions of mixtures of two nonidentical polymers in a single solvent was measured. The parameter A24 characterising the thermo‐dynamic interaction of two nonidentical polymer molecules in solution was calculated for several systems polymer 2 ‐ polymer 4 ‐ solvent. For chemically strongly different polymers, A24 is independent of molecular weights of the polymers and probably also of solvent. A24 is related to the compatibility of both polymers and decreases contrary to expectation with increasing chemical difference between polymers 2 and 4.
On the second virial coefficient for solutions of polystyrene mixtures
Authors: Suzuki Hidematsu
Published: April 2007

Light scattering measurements were carried out on several standard polystyrenes and their binary mixtures in benzene and in 2‐butanone. Their second virial coefficients, B2, were determined as a function of the polymer composition. It was revealed that for some pairs of mixtures whose components differ greatly in size, a minimum in B2 is observed, whereas a maximum is expected theoretically. The reasons for this phenomenon are discussed and interpreted in terms of the characteristics of the samples in solution and by considering the non‐negligible contribution of the attractive forces.
Cyclohexane‐polystyrene revisited
Authors: Kleintjens Ludo A. , Koningsveld Ronald , Chermin Hubert A. G. , Huggins Maurice L.
Published: April 2007

A semi‐empirical interaction function previously used in the quantitative description of critical miscibility data for the system cyclohexane/polystyrene is reconsidered in terms of molecular parameters. The empirical part of the function has approximately the same magnitude as correction terms which, owing to the dependence of the average randomness of orientation of molecules and polymer segments on the composition of the liquid, have to be applied to the combinatory entropy of mixing. Such a treatment largely ignores excess volume effects. These have been quantitatively dealt with by Flory et al., who had to bring in an empirical entropy correction whose order of magnitude may prove to be compatible with the orientational entropy contributions mentioned above. A full treatment in terms of molecular parameters seems within reach, but this will have to take the variation of the segment density distribution with concentration into account.
Reactive polymers XIV. Hydrolysis of the epoxide groups of the copolymer glycidylmethacrylate — ethylenedimethacrylate
Authors: Hrudková Hana , Švec František , Kálal Jaroslav
Published: April 2007

Hydrolysis of the epoxide groups of the copolymer glycidylmethacrylate ‐ ethylenedi‐methacrylate in variously concentrated sulphuric acid solutions was studied. An approximate activation energy of hydrolysis, 41 kJ mol−1, was determined from the temperature dependences. For the sake of comparison the effect of pH on the degree of hydrolysis over the whole range of pH values was examined, and the importance of the results with respect to other reactions of the copolymer used was discussed.
Poly(mono n‐alkyl itaconic acid esters): Their preparation and some physical properties
Authors: Cowie John M. G. , Haq Zia
Published: April 2007

A series of poly(mono n‐alkyl itaconic acid esters), with ester chain lengths varying from methyl to decyl, were prepared by emulsion polymerisation. The materials are all hard brittle glassy polymers at ambient temperatures and undergo a dehydration reaction in the range 430 K to 450 K. Dynamic mechanical measurements showed the presence of at least three other damping maxima: an Δ‐transition at 90−95 K, a δ‐transition at 190–200 K and a γ‐transition at 240–260 K. The ε is associated with motion in the hydrocarbon part of the side chain, while the δ and γ transitions are associated with relaxations involving the carboxyl and alkoxycarbonyl groups respectively. Glass transitions were only detectable in higher esters. The thermal stability of the polymers is also briefly discussed.
Some aspects of the thermal stability of poly(alkyl itaconic acid esters)
Authors: Cowie John M. G. , Haq Zia
Published: April 2007

The thermal stability of members of several series of polyitaconates has been assessed using thermogravimetric and thermal volatilisation techniques. From these data general degradation patterns have been established. The poly (di‐n‐alkyl itaconates) are stable up to 570K before chain breakdown occurs. The poly(mono‐n‐alkyl itaconates) are less stable and undergo a dehydration/de‐esterification reaction at 430K which results in the formation of anhydride structures. This reaction can be suppressed by the formation of the salts. In the copolymers, salt formation also leads to increased stability but the range of copolymers studied was too restricted to draw general conclusions about their thermal behaviour.
Kinetics of the epitaxy and the over‐growth of polyoxymethylene from molten state on needle‐like single‐crystals
Authors: Iguchi Masatoshi , Watanabe Yasushi
Published: April 2007

Kinetic studies have been made on the over‐crystallisation of polyoxymethylene on needle‐like crystals, which takes place cylindrically around the needles by forming a pile of lamellar crystallites, using the ordinary spherulitic crystallisation as reference. The growth kinetics were investigated, by means of microscopy and differential scanning calorimetry (DSC), and the resultant structure was examined by small‐angle X‐ray scattering and melting temperature measurements. The discontinuity found for their theoretical plot was assumed to be attributable to the difference in the type of crystallisation. The lamellar surface free energies obtained for the over‐growth were smaller than those for the spherulitic growth, i.e., σe = 42.1 and σs = 2.94 erg/cm2 against σe = 53.4 and σs = 4.97 erg/cm2. The epitaxy effect was elucidated from the analysis of DSC curves during cooling and the combined free‐energy, σeσs = 89.4 erg2/cm4, was estimated for the initial deposit on the needle surface.
Eutectic solidification of the quasi binary system of isotactic polypropylene and 1, 2,4, 5‐tetrachlorobenzene
Authors: Smith P. , Alberda Ekenstein G. O. R. Van , Pennings A. J.
Published: April 2007

This paper describes a study on eutectic solidification of the quasi binary system of un‐fractionated isotactic polypropylene and the faceted growing diluent 1,2,4,5‐tetrachlorobenzene. According to the Flory‐Huggins theory of melting point depression the phase diagram of the present system does not exhibit a eutectic point for equilibrium conditions. However, under experimental circumstances a simple “eutectic‐type phase diagram” was found, in which the location of the eutectic point was determined by kinetics to a large extent. The very nature of the eutectic solidification process was found to depend critically on the rate of cooling. At cooling rates lower than 0.5°C/ min the simultaneous crystallisation of the polypropylene and the tetrachlorobenzene proceeded in an uncoupled manner, producing a microstructure consisting of randomly mixed polypropylene spherulites and diluent needles with a characteristic dimension of about 0.1 mm. At speeds of cooling exceeding 0.5°C/min coupled growth of the polymer and the solvent occurred, forming a unique eutectic microstructure of curved diluent crystals homogeneously dispersed in a polymer matrix. The transverse dimension of these particular tetrachlorobenzene crystals was found to be in the micron range.
Copolymers of 4‐vinyl pyridine with fluorinated acrylates: Part II ‐ the evaluation of some cationic derivatives as detergent aids
Authors: Carson Phillip A. , Fennah Geoffrey , Bevan Geoffrey
Published: April 2007

Cationic derivatives of the title copolymers are water‐soluble, materials which adsorb onto fabrics when applied from aqueous solution and render the substrate oleophobic and hence more resistant to staining by oily soils. The effects of the polymer finish on soil‐removal and redeposition during washing are discussed.
The effect of fibre surface treatment, resin type and fabrication process on the interlaminar shear strength of carbon fibre composites
Authors: Judd Nigel C. W.
Published: April 2007

Some data related to the preparation of carbon fibre composites is summarised.

A limited investigation concerned with presenting markedly different fibre surfaces to the resin by coating with metals and stearic acid is also described.

There are carbon fibre surface treatments which lead to improved shear strength, but it is not clear how they are affecting the fibre surface. It also seems likely that some facets of the processing technique can have a large effect on composite quality as indicated by shear strength measurements.

The difficulties in interpreting results and identifying sources of variability points to the advisability of statistically planned experiments to assess the significance of changes when investigating possible materials and processing improvements.
Implication of solvent structure in the interaction of poly (vinylalcohol) and short chain monohydric alcohols
Authors: Wardlaw Graham C. , Humphrey Stephen , Eagland Donald
Published: April 2007

Viscosity and density data have been obtained for aqueous solutions of a monodisperse sample of 90% hydrolysed poly (vinylalcohol) PvOH and for solutions of PvOH in short chain alcohol/water mixtures. The results are interpreted in terms of a ‘dynamic’ flowing volume and a ‘static’ partial molar volume for the macromolecule. Changes in the size of the dynamic and static volumes of the polymer in alcohol/water solvent mixtures are shown to correlate closely with reported changes in the degree of solvent structure. A tentative explanation of the role of solvent structure in the solution behaviour of the polymer is proposed.
Studies on pectins I. Light‐scattering and w
Authors: Smith Janet E. , Stainsby George
Published: April 2007

An enzyme digestion technique for obtaining the scatter from pectin molecules in solution is described and evaluated. Weight average molecular weights, w, calculated from the pectin scatter, are considerably higher than literature values obtained via sedimentation equilibrium experiments, but the present results are preferred. Limited comparison with a number average value, n, obtained osmometrically, suggests that pectins can be extremely poly disperse with w/n = 11, for example. The relationship of intrinsic viscosity to molecular weight is a complex function of composition.
Crystallization of polyethylene oxide III
Authors: Afifi‐Effat Amr M. , Hay James N.
Published: April 2007

The crystallisation kinetics of high molecular weight fractions of polyethylene oxide have been measured dilatometrically and also with a polarising light microscope. In general, marked deviations from the Avrami equation with exponent of 3.0 are observed which cannot alone be accounted for either in terms of rejection of low molecular weight molecules or secondary crystallisation by which crystal perfection occurs. Anomalies in nucleation, and the presence of induction periods, are present, which can account for the apparent low values of the Avrami exponent, i.e. 2.0.
Influence of orientation on polyester fibres
Authors: Brody Harry
Published: April 2007

The technological applications and the associated molecular mechanisms of various levels of orientation in polyester fibres are discussed. The inherent birefringence of these fibres is high and therefore the orientation is easily measurable, while their behaviour is very sensitive to small changes in orientation. In particular, practical properties such as strength, productivity and ease of bulking are very dependent on the spun yarn orientation before the drawing operation takes place, but for completely different reasons. Polyester fibres can be pretreated in terms of orientation in such a way that an extremely high spontaneous extension can be obtained, a property which can be used for bulking. It is shown that variations in low levels of orientation can have profound industrial implications.
Studies on the gel—sol transition and some gel characteristics of photographic gelatine
Authors: Tar Ildikó , Fodor Zsolt , Wolfram Ervin
Published: April 2007

Studies have been made on gelatine gels containing inorganic salts and ionic surfactants, with the aim of learning about factors that influence the structural make‐up of hydrogels. Gel‐sol transition temperature, Tm, was studied by a micro capillary‐visco‐meter, gel‐elasticity, E, by applying unidirectional compression and gel‐hardness (rigidity), H, by using Röths micro penetrometer. An attempt was made to describe the results quantitatively. The equation lg Tm = k c + b was found to fit the data on gelation and analogous equations proved to be valid for both the E vs. c and the H vs. c relations. This is true for the different chlorides in the whole concentration‐range studied, but for sulphates over a limited concentration range only. The specific effect of the latter reveals itself mostly in the changes of Tm and H. As ΔH was not altered significantly by the cosolutes used it is concluded that ΔS plays the essential role in the described effects.
Emulsion polymerisation of styrene in the presence of hydrocarbon diluents
Authors: Blackley David C. , Haynes Alan C.
Published: April 2007

Results are given for the effects of four hydrocarbon diluents (benzene, toluene, ethylbenzene and cyclohexane) upon the rate of emulsion polymerisation of styrene at 50°C, upon the particle size of the resultant latex, and upon the intrinsic viscosity of the polymer produced. The aromatic diluents were found to have a much greater effect in reducing the rate of polymerisation than can be accounted for by mere dilution of the monomer. For these diluents, the rate of polymerisation is approximately third order in initial concentration of monomer in the oil phase as a whole. Cyclohexane is far less effective as a retarder of polymerisation, the rate being approximately first order in monomer concentration in the oil phase. Particle size determinations indicate that the reductions in rate are due primarily to a reduction in the rate of polymerisation at each locus, rather than to a reduction in the number of reaction loci. The intrinsic viscosity of the polymer produced tends to fall with the rate of polymerisation. These observations are consistent with the view that aromatic diluents cause severe retardation of polymerisation because they diminish the Trommsdorff ‘gel’ effect at the reaction loci. This view is in turn shown to be consistent with a reaction mechanism in which, in the case of styrene‐rich systems at least, the growing polymer particles do not attain equilibrium with the monomer droplets.
Charge‐transfer complexes as polymerisation inhibitors: III. Studies on the mechanism of inhibition and retardation of styrene polymerisation by N, N‐dimethylaniline‐chloranil complexes
Authors: Yassin Ahmady A. , Rizk Nadia A.
Published: April 2007

The mechanism of inhibition and retardation of the sensitised polymerisation of styrene has been investigated using the charge‐transfer complexes of N, N‐dimethylaniline (DMA) with chloranil. The results support the idea that the inhibition reactions involve electron‐transfer from the growing chains to the quinone to form polymeric cations and semiquinone anions. The latter are the actual inhibiting species and the inhibiting efficiency is determined by the extent to which they are found as kinetically independent species in the polymerising system. The inhibition reactions should accordingly be considered as oxidation‐reduction processes in which the growing chains are the electron‐donors.
Theory of neck development in tensile tests on thermoplastics
Authors: Mills Nigel J.
Published: April 2007

A one‐dimensional finite element model is used to relate the constitutive equation of a thermoplastic with the phenomena observed when it is tensile tested. Predictions are made of the temperature distribution in a propagating neck, and in particular PVC is shown to be liable to thermal fracture in fast tensile tests. The neck geometry is shown to be an important factor in stable, high speed, neck propagation.
Mechanical properties of polystyrene/ethylene‐propylene copolymer blends
Authors: Barentsen Willem , Heijdenrijk Paul J. , Heikens Derk , Piet Piet
Published: April 2007

Some mechanical properties of blends of polystyrene (PS) and ethylene‐propylene‐rubber (EP) were derived from stress‐strain and impact measurements. The strength and impact properties are improved by adding EP‐g‐PS graftcopolymer, prepared by reacting PS with EP, to the blends. It is assumed that the EP‐g‐PS graftcopolymer acts as an adhesive at the interface between the thermoplast and the rubber phases. The addition of the graftcopolymer reduces the dimensions of the dispersed rubber particles.

High values of impact strength at reasonable values of tensile moduli could be reached by replacing EP for a smaller or larger part by EP‐g‐PS copolymer.

These kinds of EP‐modified PS blends had much higher impact values than those of comparable PS blends containing low density polyethylene (1 dPE) and 1dPE‐g‐PS graftcopolymer or this graftcopolymer only. It seems attractive to ascribe these results to the non‐crystallinity of the PE‐g‐PS as compared with the crystallinity of 1dPE in 1dPE and in 1dPE‐g‐PS. However some caution seems recommendable as EP‐modified PS fractures with microshear whereas, the PE‐modified PS shows crazing.
The effect of rolling on the mechanical properties of polymers with phenylene groups in the main chain
Authors: Macnulty Basil J.
Published: April 2007

The changes occurring, in mechanical properties particularly, when polymers with phenylene groups in the main chain are subjected to uniaxial rolling have been investigated. All properties can be enhanced by the process under the correct conditions. The anisotropy of the specimens at various reduction ratios have also been measured and an explanation of the behaviour on a molecular basis is suggested.
Variation of yield stress with orientation in oriented polyethylene
Authors: Burnay Suzana G. , Groves Geoffrey W.
Published: April 2007

High density polyethylene with a single crystal texture has been used to examine the variation of yield stress with orientation in both tension and compression. The Coulomb yield criterion, which has previously been applied to yield data in oriented polyethylene, must be rejected since the experimental data can only be fitted over a limited range of orientation in tension only. The von Mises criterion, as modified by Hill 12 for anisotropic materials, appears to give a reasonably good fit to the tensile data. However, further consideration of the theory with respect to the compressive data shows that the criterion is not applicable. The pressure dependent yield criterion proposed by Caddell et al13 also appears unable to predict the experimentally observed tensile and compressive behaviour. A three‐part criterion previously applied to fibre‐composites 11 gives a good fit to the tensile data; this model also predicts the changeover from ductile to brittle behaviour observed in tensile specimens with θ > 70d̀ (θ is the angle between the tensile axis and the molecular axis). None of the yield criteria examined have been able to explain satisfactorily the lack of any marked degree of anisotropy in compression.
Fracture of particulate filled polymers
Authors: Kendall Kevin
Published: April 2007

The addition of particulate mineral fillers to polymers confers certain mechanical property improvements automatically. Stiffness increases, creep diminishes and distortion at elevated temperatures is often reduced. However, the fracture energy of a polymer, as measured in impact, cracking or tearing tests, may vary quite unpredictably when filler is incorporated. In some special cases the fracture energy increases when small amounts of filler are added although it falls away again at higher volume loadings. This enhancement of polymer toughness by filler is an example of reinforcement. More generally the addition of filler causes a continuous and drastic reduction in fracture energy, resulting in a brittle, weak product.

This paper seeks to explain the common degrading effect of filler on polymer fracture energy by considering the progress of a crack through the composite material. The crack travels through regions of polymer and also along the interfaces between polymer and filler. Experiment demonstrates that, although fracture of the polymer regions absorbs considerable energy, fracture of the interfaces usually requires very little. These weak interfaces do not resist cracking and are the cause of brittleness in particulate filled systems.

This idea was quantified for thermoplastics such as low density polyethylene and poly (methylmethacrylate) filled with colloidal silica by twin‐roll milling. Where the interfacial adhesive energy was much smaller than the polymer fracture energy, the composite toughness dropped as predicted when filler was added. The particle size, the nature or dispersion of the filler, and the crystallinity of the polymer used, had little influence on this phenomenon, as pointed out theoretically.

The crucial parameters influencing the fracture energy of the filled polymer were found to be the volume fraction of filler and the interfacial adhesion between polymer and filler. By chemical treatments the adhesive energy between filler and polymer was raised until the interface was almost as tough as the polymer itself. In this case the filled polymer showed good fracture toughness, lending further support to the theory.
The short and long term performance of polymers in different environments
Authors: Andrews Edgar H.
Published: April 2007

The behaviour of polymeric solids in contact with different environments is considered. A thermodynamic viewpoint is adopted and worked out in terms of chemical reactions, physical processes and the interaction between the two.

It is shown that chemical attack alone does not normally cause serious loss of physical properties, but that a combination of chemical and physical (or physico‐chemical) interactions between polymer and environment can lead to rapid deterioration.

An understanding of these processes, and their synergistic effects, is essential in designing against environmental failure.
Relationship between structure and mechanical properties in rubber‐toughened epoxy resins
Authors: Bucknall Clive B. , Yoshii Toshiya
Published: April 2007

Toughened polymers were prepared by adding CTBN rubbers to DGEBA‐type epoxy resins. Structure was varied by altering the type and concentration of hardener, the initial molecular weight of the resin, the amount of Bisphenol A added, and the conditions of cure. Electron microscopy showed that these factors affected both particle size and degree of phase separation: rapid curing inhibited phase separation, and produced small particles. Increasing the molecular weight of the resin, either directly or by reaction with Bisphenol A, improved phase separation. Dynamic mechanical measurements of rubber phase volume proved possible, although Tg of the CTBN rubber coincided with a β process in the epoxy resin. Fracture resistance, measured by GIC, increased linearly with rubber phase volume. Creep and yield behaviour were also affected by the degree of phase separation.
Unsolved problems in the fracture of homogeneous thermoplastic
Authors: Haward Robert N.
Published: April 2007

The steps which occur when a homogeneous polymer breaks are considered with reference to plane strain and plane stress conditions. Under plane strain fracture generally seems to take place by cavitation and crazing, though the reason for the different measured energies of crack propagation are not well understood. Other obscure steps concern the basic reason for crazing and the mechanism of craze separation. The mechanism by which polymer separates after yielding by a simultaneous process of crack propagation and plastic straining is also largely unknown as is the reason why non strain softening uniformly extending polymers appear to generate dispersed voids.

Only the thermal fracture process seems to raise no fundamental difficulties.
The influence of liquid environmental media on the mechanical behaviour of thermoplastics
Authors: Pütz Dieter , Menges Georg
Published: April 2007

Thermoplastic materials, having a high chemical stability, are used on a very large scale in corrosive environmental media. Nevertheless, in many cases unexpected failure occurs, since valid construction guide‐lines are missing.

For this reason, in the present work a deformation‐related dimensioning criterion is presented, based on the appearance of first irreversible material‐damage.

Further, the sorption‐, swelling‐, short‐term‐ and creep‐behaviour of PMMA in the presence of distilled water are described and discussed. Finally, mathematical and graphical procedures for the determination of the creep‐strain under different loading and environmental conditions are shown and explained.