bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid cyclic oxidation tests, using joule heating of wire and foil materials
Authors: Nicholls J. R. , Rose T. , Hojda R.
Published: January 2006

As part of a programme to establish a thermal cyclic oxidation test standard for metallic materials at elevated temperatures (COTEST) a programme of work has been undertaken on the rapid cyclic oxidation of wire and foil materials, using Joule heating.

By way of introduction, alternative technologies for rapid thermal cyclic tests are reviewed. Following this the benefits of adopting a modified existing ASTM standard is discussed. The aims of the project were, first, to define a suitable test matrix to evaluate the effect of critical material parameters, to undertake the test to a prescribe standard and then evaluate the performance of materials under rapid thermal cycling, using Joule heating. The performance of the testing methodology is assessed using two materials, Kanthal A1 (reference temperature 1250°C) and Alloy 800 (reference temperature 1000°C). In this paper tests on Kanthal A1 at 1200, 1250 and 1300°C are reported. These tests have been undertaken in laboratory air. Other parameters include the upper dwell time (2, 5 and 10 min), the lower dwell time (constant at 2 min) and specimen geometry. Kanthal A1 material was available as 0.4 mm diameter wire, 0.7 mm diameter wire and 70 μm × 1.25 mm ribbon.

The results of these tests were analysed statistically using a 3 × 3 × 3 test matrix with triplicate repeat specimens. The lifetime of the wire or foil samples could be measured using either of two parameters: 1) the number of cycles to failure or the accumulated hot time to failure (accumulated upper dwell time). The cyclic lifetime was critically dependent on temperature, hot dwell time and sample geometry.

For these rapid cycle tests on Kanthal A1 wire and foil cycle life decreased with increase in temperature and increase in hot dwell time. The wire/foil endurance (accumulated hot time to failure) decreased slightly with increase in temperature, but increased with hot dwell time (fewer cycles). The endurance of foil samples was shorter than wire samples. Thus for wire/foil endurance only hot dwell time was a statistically significant parameter, over the temperature range studied.
Thermo‐mechanical fatigue – the route to standardisation (“TMF‐Standard” project)
Authors: Beck T. , Hähner P. , Kühn H.‐J. , Rae C. , Affeldt E. E. , Andersson H. , Köster A. , Marchionni M.
Published: January 2006

Thermo‐mechanical fatigue (TMF) data are needed for dimensioning of safety‐critical parts, e.g. in power generation and in transportation by air, rail and road, and for designing of components, which operate at higher levels of efficiency and safety for longer periods of time. However, the current lack of a validated international standard for TMF leads to non‐reproducibility of TMF data with negative implications on the design and economy of operation of many components. While a preliminary draft TMF standard has been written under the auspices of the International Standards Organisation (ISO), the “TMF‐STANDARD” project addresses this issue at the European level, within the GROWTH programme of Framework Programme 5 funded by the European Commission.

The R&D work in the TMF‐Standard project has been started with the preparation of an inventory of institutions in the EU and the pre‐accession states that perform TMF testing, and the testing methods and procedures which they apply. Afterwards, extensive pre‐normative testing work has been carried out, the results of which have been considered in the drafting of a preliminary Code‐of‐Practice (CoP) that forms the base for the current validation round robin testing. The results of the validation tests are going to be subjected to statistical analysis, in order to substantiate the formulation of a validated CoP on strain‐controlled TMF testing. The present paper summarizes the main objectives and achievements obtained so far within the TMF‐Standard project, and gives an outlook on the further activities of the project.
Evaluation of high‐temperature corrosion life using temperature gradient corrosion test with thermal cycle component in waste combustion environments
Authors: Kawahara Y.
Published: January 2006

In energy conversion facilities such as boilers and pyrolysis reactors that burn waste, fossil fuel, biomass and other materials, many corrosion factors, such as gas temperature and fluctuations in gas temperature, the condition of deposits, and gas composition, influence the high‐temperature corrosion rate of materials in a complex manner. In order to evaluate the corrosion behavior and corrosion life time of materials rapidly and accurately, a temperature gradient corrosion test (TGT) was developed and applied to waste incineration environments.

The TGT with thermal cycle was carried out without corrosive deposits in order to investigate the basic effect of gas temperature and fluctuation on corrosion behavior, especially in terms of the stability of protective oxide layers. As a result, it was clarified that gas temperature enhances the environmental factors such as the deposition rate of ash and penetration of corrosive species, while thermal cycle mainly enhances material factors such as the breakdown of protective scales.

Furthermore, three application case studies of TGTs for corrosion life estimation were carried out with a comparison between TGT and field corrosion data. From these studies, a good correspondence of corrosion rates between TGTs and field tests was obtained. This correspondence of corrosion rate was explained by the breakdown of the protective oxide layer and the penetration of corrosive species in a corrosion front.

The reproducibility and applicability of TGTs in the evaluation of the corrosion life time of materials were clarified based on the consideration of various corrosion mechanisms.
Accelerated cyclic oxidation testing protocols for thermal barrier coatings and alumina‐forming alloys and coatings
Authors: Stiger M. J. , Meier G. H. , Pettit F. S. , Ma Q. , Beuth J. L. , Lance M. J.
Published: January 2006

The oxide spallation resistance of oxide scales and ceramic thermal barrier coatings is a key design factor for developing high‐temperature alloy systems.

Determination of the lifetimes of such alloy and coating systems is highly desirable. However, as improved systems are developed, lifetimes become so long that the time required to test a system to failure becomes prohibitive. Therefore, reliable protocols for accelerated testing and lifetime prediction are needed. This paper describes two attempts at developing such protocols. The first involves modification of the NASA COSP model to predict cyclic oxidation behavior of alloys and metallic coatings and the incorporation of acoustic emission data into this model. The second involves use of an indentation technique to induce spalling of thermal barrier coatings (TBCs) after short‐term thermal exposures.

The first effort involves using the COSP Model, developed at NASA, as the basis for the prediction of oxide spallation. Acoustic emission measurements are used in an attempt to obtain critical parameters in the model from short‐time experiments for a variety of alloys and coatings which rely on alumina scales for oxidation resistance. The model is then used to predict the lives of these alloys and coatings when subjected to cyclic oxidation at 1100°C.

A principal concern with ceramic thermal barrier coatings (TBCs) used in gas turbines is their loss of adhesion during service, leading to coating spallation. In this paper, an overview is given of an indentation test for brittle coatings on ductile substrates which is used to quantify decreases in interfacial toughness of TBC systems due to cyclic high‐temperature exposures. The indentation test involves penetration of the TBC and the oxide layer below it, inducing plastic straining in the underlying metal bond coat and superalloy substrate. The indentation strains cause an axisymmetric delamination of the TBC and oxide layers. Measurement of the extent of the delamination, coupled with finite‐element modeling, provides a measure of the adherence of the coating. Test results are presented tracking the loss of interfacial toughness for EBPVD TBC systems cyclically exposed at 1100°C.
Reactive Blending of Aromatic Polyesters: Thermal Behaviour of Co‐precipitated Mixtures PTT/PET
Authors: Castellano Maila , Turturro Antonio , Valenti Barbara , Avagliano Alessandra , Costa Giovanna
Published: January 2006

Summary: Due to its unique combination of properties, PTT is a promising material for textile fibre and engineering thermoplastic applications, both as neat polymer and in formulated products. To bring down the cost yet keeping some of its advantageous properties it seems interesting to apply PTT in blends and particularly with PET. We consider here the effect of composition and reaction time on co‐precipitated mixtures PTT/PET, in terms of melting and crystallization behaviour, solution properties and morphology. Blends of various compositions were prepared from mixed solutions, kept in the DSC at 280 °C for different times (0–120 min) and analysed during a successive cooling‐heating cycle. A single Tg was detected for each composition, indicative of miscibility in the glassy state. Melting temperatures, at fixed composition, decrease with increasing treatment time. Mixtures rich in one component show a single Tm, whereas two distinct peaks were observed for the 50/50 blend; on increasing the treatment time some transesterification takes place, evidenced by the melting peak broadening and merging together. The overall crystallinity developed when transesterification plays a role strongly depends on composition: it is inhibited for the 50/50 mixture on cooling, though it can be induced to some extent by reheating or holding during cooling, whereas in one component‐rich blends the main effect is a reduction of the crystallization temperature. Isothermal crystallizations were also carried out as a function of the composition and of the residence time in the molten state; crystallization rate decreases with increasing holding time in the melt. Morphology of PTT and PTT‐rich mixtures under the adopted crystallization conditions exhibits typical banded spherulites, whose growth rate and band spacing vary with melt holding time; moreover, less regular concentric circles develop on increasing residence time at 280 °C.

Spherulitic texture developed at 198 °C after 60 min storage at 280 °C by a PTT/PET 90/10 mixture.

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Spherulitic texture developed at 198 °C after 60 min storage at 280 °C by a PTT/PET 90/10 mixture.
Study of Comicellization of Diblock Copolymers in a Selective Solvent
Authors: Pleštil Josef , Koňák Čestmír , Hu Xuesong , Lal Jyotsana
Published: January 2006

Summary: The size, aggregation number and other quantities which characterize the formation of micelles in a bidisperse solution of block copolymers which are chemically identical but have different block asymmetries has been studied in a selective solvent using LS and SANS techniques. Experimental results for the comicellization of two chemically identical block copolymers (high molecular weight, PS‐PI, and a low molecular weight dPS‐PI with a deuterated PS block) and two slightly incompatible copolymers (high molecular weight PS‐HPI, and dPS‐PI) in decane, a selective solvent for PI, are reported. Individually, each of the PS‐HPI and PS‐PI copolymers formed micelles with a PS core, which were stable over the entire temperature range covered by the experiments (25–70 °C). The small copolymer, dPS‐PI, formed micelles with a highly swollen core at low temperatures and was molecularly dispersed above the critical micelle temperature (47 °C). Comicellization was observed for both pairs of copolymers studied over a broad range of mixing ratios. The mixed micelles were comprised of large copolymer (PS‐HPI or PS‐PI) and a portion of the small copolymer (dPS‐PI). The amount of adsorbed dPS‐PI copolymer increased with increasing weight fraction of this copolymer and decreased with increasing temperature. The critical comicellization temperature was estimated as 70 and 60 °C for the comicelles based on PS‐HPI and PS‐PI copolymers, respectively. The SANS data suggest that the small copolymer does not form a shell coating the PS core of the initial micelle, but is instead incorporated into the core where it forms a layer of mixed dPS and PS chains.

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First Poly(2‐oxazoline)s with Pendant Amino Groups
Authors: Cesana Sonia , Auernheimer Jörg , Jordan Rainer , Kessler Horst , Nuyken Oskar
Published: January 2006

Summary: A new 2‐oxazoline monomer with a Boc protected amino function, 2‐[N‐Boc‐5‐aminopentyl]‐2‐oxazoline; (Boc‐AmOx), was synthesized from commercially available compounds. With an initiator salt system (N‐methyl‐2‐methyl‐2‐oxazolinium triflate; MeOxOTf), the monomer could be converted via living cationic ring‐opening polymerization to well‐defined homopolymers with narrow molar mass distributions and targeted polymer chain length. After a quantitative deprotection, poly(2‐oxazoline)s with pendant amino functions were obtained. In order to vary the polymer functional group density and solubility of the polymer, copolymerization with different monomer ratios of Boc‐AmOx and 2‐ethyl‐2‐oxazoline (EtOx) was performed. Ex‐situ NMR spectroscopy studies verified the randomness of the cationic copolymerization. The accessibility of the pendant amino side functions was confirmed in polymer analog thiourea formation with different isothiocyanates, such as benzyl isothiocyanate (BzNCS), or a fluorescence dye, tetramethyl rhodamine isothiocyanate (TRITC). A cross‐linking reaction with a bifunctional isothiocyanate (Ph(NCS)2) resulted in poly(2‐oxazoline) hydrogels.

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Insights into Bridging Flocculation
Authors: Fellows Christopher M. , Doherty William O. S.
Published: January 2006

The phenomenon of bridging flocculation is very widely encountered in many industrial applications, but is rarely explained with any clarity. In this paper, a cohesive mechanistic model is used to explain the extraordinary effectiveness of bridging flocculation and to guide a body of work on synthesis and application of cationic polymers for the cane sugar industry.
Fluorocarbon End‐functionalized Polymers from Poly(arylether) Dendritic Initiators
Authors: Narrainen A. Pillay , Hutchings L. R. , Feast W. J. , Thompson R. L. , Ansari I. A. , Clarke N.
Published: January 2006

Fréchet‐type poly(arylether) first and second generation (G1 and G2 respectively) dendrons were prepared from 1‐(bromomethyl)‐3,5‐bis(trifluoromethyl)benzene. The latter and the brominated versions of the two dendrons were successfully employed in the copper mediated living radical polymerization (LRP) of styrene‐d8 giving polymers of predictable molecular weights and narrow polydispersities. Contact angle measurements and ion beam analysis were used to explore the adsorption of these materials to the air‐polymer surface in blended films with unfunctionalized hydrogenous polystyrene. Although contact angle analysis indicated only modest changes in the hydrophobicity and lipophobicity of the surface, ion beam analysis clearly showed the formation of an excess layer of dendron functionalized polymer at the exposed surface that increased with increasing fluorine content.
Microscopic and Molecular Insights into Heterogeneous Phase Degradation of Agars and Carrageenans by Marine Bacterial Galactanases
Authors: Helbert William , Nyvall‐Collen Pi , Michel Gurvan , Czjzek Mirjam
Published: January 2006

Agars and carrageenans are sulfated galactans and are the main matrix component of the cell wall of red algae. They form gels made of a 3D network of fibres built by the aggregation of polysaccharide double‐helices. Agarases and carrageenase are enzymes produced by marine bacteria involved in the conversion of algal biomass. We have analyzed the structures and the modes of action of these enzymes adapted to the degradation of anionic polysaccharides in heterogeneous phase. We found that κ‐ and ι‐carrageenases proceed via an endo‐processive mode of action as it was already described for other enzymes active on neutral polysaccharides (cellulose, starch).
Investigation of the Reaction Between Benzophenone and Trimethylaluminium: A Source of Novel Aluminic Activator for Single‐site Olefin Polymerization Catalysts
Authors: Dalet Thomas , Cramail Henri , Deffieux Alain
Published: January 2006

The reaction between benzophenone and TMA was investigated in details at 20 °C for different TMA/benzophenone (r) ratios. For r = 2, a heterodimer µ‐(1,1‐diphenylethoxy)‐µ‐methyl‐tetramethyldialuminium (B) is only formed. The latter was found able to activate MeDIP(2,6‐iPrPh)2FeCl2 catalyst towards ethylene polymerization. Such catalytic system leads to the formation of high molar mass polyethylene with a broad molar mass distribution, without the presence of oligomers, that is attributed to a strong reduction of the transfer reaction to TMA.
Structure and Properties of Nanocomposites Based on SBS Block Copolymer and Alumina
Authors: Adhikari R. , Henning S. , Lebek W. , Godehardt R. , Ilisch S. , Michler G. H.
Published: January 2006

The addition of inorganic filler into commodity plastics has a long history. Today, polymer composites based on nanosized filler are popular among polymer scientists from academia and industries due to their ability to enhance a number of physical properties. In this work, we investigate the dispersion and reinforcing effect of alumina nanoparticles using a polystyrene‐polybutadiene based block copolymer (SBS) and organically modified alumina nanofiller. With the aid of solution casting procedures, polymer composites with good dispersion of nanoparticles could be produced. It has been demonstrated that with suitably coated nanoparticles, polymer composites with optimum dispersion of nanofiller ensuring marked reinforcement effect can be achieved.
Catalytic and Optical Behavior of Polymer Embedded Metal Nanoparticles
Authors: Ciardelli Francesco , Pertici Paolo , Vitulli Giovanni , Giaiacopi Simone , Ruggeri Giacomo , Pucci Andrea
Published: January 2006

Very small metal aggregates (nanoaggregates) embedded in an inert polymer matrix, which simply stabilizes the nanodispersion, show unique catalytic and optical behaviour.

Indeed Ru‐nanoparticles in vinyl‐aromatic polymers or polyphosphazenes display an enhanced reactivity for hydrogenation of different groups, such as aromatic rings, keto and nitro groups, oximes and nitriles which are converted into the corresponding saturated derivatives under mild conditions.

The optical properties of terthiophenethiol‐coated gold nanoparticles in UHMWPE (concentration lower than 4 wt.%) are characterized by poor dichroism due to their centrosymmetric structure. High dichroism (R = 30 at 400 nm, DR = 30) is on the contrary recorded for the terthiophene band showing the chromophores to be sensitive to mechanical orientation also when complexed with gold. On the other hand, nanocomposites based on polymers containing vinyl alcohol units and dispersed gold nanoparticles with average diameter ranging from 3 to 20 nm have been efficiently prepared by an UV photo‐reduction process. Uniaxial drawing of the irradiated Au/polymer nanocomposites favours the anisotropic distribution of packed assemblies of gold particles, providing oriented films with polarization‐dependent tunable optical properties.
Characterization of Polymers by Liquid Chromatography
Authors: Held Daniela , Kilz Peter
Published: January 2006

Liquid chromatography (LC) is well established for the comprehensive characterization of complex macromolecules with multiple distributions. Hyphenated chromatographic methods in their various forms are currently one of the most promising and powerful methods for the fractionation and characterization of complex sample mixtures in different property coordinates. Modern detector technologies open up new ways to investigate various properties with high sensitivity even in the low concentration ranges used in chromatography. This paper discusses possibilities and applications for the advanced characterization of macromolecules.
Biopolymers from the Mauritian Marine Environment
Authors: Jhurry D. , Bhaw‐Luximon A. , Mardamootoo T. , Ramanjooloo A.
Published: January 2006

To the best of our knowledge, the extraction of biopolymers from algae and seaweeds still remains untapped. Prior studies in this area have been limited to a taxonomic survey of algae and seaweeds found around our coastal regions. In this paper, we report on the extraction of biopolymers from Hypnea, Eucheuma and Gracilaria species collected around the coastal regions of Mauritius. Various extraction conditions were used and their effects on yield and structure of the corresponding biopolymers were investigated. The extracted polysaccharides were characterized by a combination of IR, NMR, SEC, viscometry and elemental analyses. These revealed that polysaccharide extracted from Gracilaria is a highly methylated agar and Hypnea/Eucheuma contain κ‐carrageenan.
New Chromatographic and Hyphenated Techniques for Hydrophilic Copolymers
Authors: Pasch Harald , Adler Martina , Knecht Daniela , Rittig Frank , Lange Ronald
Published: January 2006

Most synthetic polymers are distributed in more than one parameter of molecular heterogeneity. For hydrophobic copolymers there are different chromatographic techniques available to analyse these distributions. As a result of the increasing interest in hydrophilic polymers and copolymers new chromatographic techniques are developed for the characterization of these polymers as well. However, very frequently these polymers contain highly polar or charged functional groups making them soluble only in aqueous mobile phases. There are several problems related to the use of aqueous mobile phases in polymer chromatography. Even the SEC analysis of such copolymers is not straightforward. As for HPLC in aqueous mobile phases, there are only a few applications in the literature so far. In addition to the fact that only a very limited number of stationary phases is available for aqueous HPLC of polymers, the interactions of polyelectrolytes in such chromatographic systems are not well understood.

The present paper addresses the problems related to the application of SEC and HPLC in aqueous mobile phases. For graft copolymers with a polyethylene oxide backbone, e.g. PEG‐g‐polymethacrylic acid and PEG‐g‐polyvinyl alcohol, it will be shown that methods can be developed that give accurate molar mass and chemical composition information. Two‐dimensional chromatography where aqueous HPLC and SEC are coupled on‐line will be shown to be the most powerful analysis tool for the analysis of such copolymers. The hyphenation of the chromatographic separation techniques with spectroscopic detection techniques provides further insight into the molecular complexity of these copolymers.
The Progress of Ageing of Lignin‐containing Paper Induced by Light and its Relation to Chemiluminescence – Temperature Runs
Authors: Rychlý Jozef , Matisová‐Rychlá Lyda , Bukovský Vladimír , Pleteníková Martina , Vrška Milan
Published: January 2006

Lignin‐containing papers from different sources and of different age were irradiated by the visible light and the progress of the degradation reaction was followed by non‐isothermal chemiluminescence method. Kinetic data obtained for papers degraded in oxygen were compared with double fold endurance test and carbonyl groups concentration. The effect of lignin on degradation of cellulose after deacidification treatment of the paper by methoxymagnesium methylcarbonate (MMMC) was ascertained and a mechanism of co‐oxidation of lignin and cellulose in originally alkaline conditions was outlined.
Properties of a Water‐Soluble Paclitaxel Conjugate in Aqueous Solution and its Interaction with Serum Albumin
Authors: Hess M. , Jo B.‐W. , Wermeckes B. , Dehne S. , Sohn J.‐S. , Wunderlich S. , Zähres M.
Published: January 2006

A summary of the most recent investigations of conformation and solution properties of a polymer conjugate of the anti‐cancer drug paclitaxel is given. First results of spectroscopic studies of interaction with model proteins in the solid state and in solution are discussed.
Improvements in Polysaccharides for use as Blood Plasma Expanders
Authors: Kulicke W.‐M. , Heinze T.
Published: January 2006

Modern blood plasma volume expanders consist of water‐soluble polysaccharides that are compatible with the human body. They are more effective for the treatment of intravasal volume deficiency compared to synthetic polymers. These colloidal blood plasma volume expanders, for example pullulan, dextran or hydroxyethyl starch (HES) are used in blood isotonic electrolyte solutions. HES has the lowest tendency to remain in the liver or other organs of the human body in comparison to other expanders.

The knowledge of the molar mass and coil dimensions as well as their distribution are essential, since products of low molar masses do not have the desired effect and parts of large molar masses can lead to an anaphylactic shock. Injection of HES enhances the microcirculation and leads to a better oxygen transport into the tissue and the muscle. Because of this, HES was identified as a doping agent in 02/2002. In addition to this it will be shown that starch acetates have an even better physiological compatibility and are an interesting alternative to HES. We will present investigations on the shelf life of a new acetyl starch, which may be an alternative to the blood plasma expanders used to date.
Polymerization of ε‐Caprolactone and its Copolymerization with γ‐Butyrolactone using Metal Complexes
Authors: Bhaw‐Luximon Archana , Jhurry Dhanjay , Motala‐Timol Shaheen , Lochee Yemanlall
Published: January 2006

Solution polymerization of ε‐caprolactone (ε‐CL) was performed using four different initiators namely: tin(II) octanoate (Sn(Oct)2)/ethanolamine, aluminium Schiff's base complex‐HAPENAlOiPr, lithium diisopropyl amide (LDA) and aluminium isopropoxide. The reaction conditions varied with the initiator used. LDA gave rise to the most rapid polymerization with the highest amount of cyclic species as detected by 13C NMR. However, no cyclic species were detected when HAPENAlOiPr was used as initiator. The tin(II) octanoate/ethanolamine system lead to an α,ω‐dihydroxy‐polycaprolactone (PCL). The copolymerization of ε‐CL was then performed with the hard to oligomerize γ‐butyrolactone using the four initiators. GPC (Gel Permeation Chromatography) analyses showed the formation of copolymers. The highest incorporation of polybutyrolactone (PBL) in the copolymer was obtained using HAPENAlOiPr as evidenced by 1H NMR. 13C NMR indicated the presence of pseudoperiodic random copolymers with short blocks of PCL whose block length varied with initiator used. The longest and shortest block length were obtained using Sn(Oct)2 and HAPENAlOiPr respectively as calculated from 13C NMR. The reactivity ratios were determined using the Finemann‐Ross method at low conversion with HAPENAlOiPr as initiator. The values obtained, rCL = 19.4 and rBL = 0.11, confirmed the presence of long blocks of CL units in the copolymer.
Kinetic Study of the Al‐Schiff's Base Initiated Polymerization of ε‐caprolactone and Synthesis of Graft Poly(methylmethacrylate‐g‐caprolactone)
Authors: Motala‐Timol Shaheen , Bhaw‐Luximon Archana , Jhurry Dhanjay
Published: January 2006

Graft copolymers of polycaprolactone (PCL) on polymethacrylate (PMMA) backbone have been successfully synthesized and characterized by SEC, 1H and 13C NMR spectroscopy. The strategy used consisted of polymerizing ε‐CL, followed by end‐functionalization of the resulting PCL using methacryloyl chloride. Free radical polymerization of the methacryl double bond lead to the C‐C polymer backbone and an overall graft copolymer. The polymerization of ε‐caprolactone was achieved using Al‐Schiff's base isopropoxide (HAPENAlOiPr) in DCM at ambient temperature. SEC and MALDI analysis of the polymers confirmed that mostly linear chains were obtained with the Al initiator, up until high monomer conversion. The low molar mass PCL was then end‐capped with a methacryloyl group, in a quantitative manner, as evidenced by 1H NMR. The macromonomer thus obtained was copolymerized in small proportions with methyl methacrylate by conventional free radical polymerization and atom transfer radical polymerization (ATRP). Analysis of the products by NMR and SEC showed the presence of true graft copolymers and the absence of homopolymers.
Polydioxanone Polymers for Annuloplasty in Valve Repair
Authors: Kalangos Afksendiyos
Published: January 2006

The Kalangos biodegradable ring® was recently developed fpr mitral and tricuspid annuloplasty to allow for flexibility, remodeling and preservation of growth potential of the native annulus. In this article, the results of the experimental trials carried out to assess its safety and potential advantages will be discussed.
Molecular Watchmaking: ab initio Emulsion Polymerization by RAFT‐controlled Self‐assembly
Authors: Sprong Ewan , Leswin Joost S.K. , Lamb David J. , Ferguson Christopher J. , Hawkett Brian S. , Pham Binh T.T. , Nguyen Duc , Such Christopher H. , Serelis Algirdas K. , Gilbert Robert G.
Published: January 2006

Controlled radical polymerization using RAFT has the potential to make polymers with virtually any desired molecular architecture. For this to be implemented on an industrial scale, it must be performed by polymerization in disperse media. However, simply adding a RAFT agent to a conventional emulsion polymerization recipe leads to a loss of molecular weight control and formation of coagulum, probably because of nucleation in droplets, which is normally an unlikely phenomenon in emulsion polymerizations. Recently, a method has been devised for implementing RAFT in ab initio emulsion polymerization that avoids droplets in the particle formation stage. The molecular weight distribution of the polymer thus formed shows that molecular weight control is maintained throughout the polymerization. A model is developed to predict the particle size formed in this new type of emulsion polymerization. The new methodology enables synthesis of novel dispersions where molecular architecture can be precisely controlled, such as structured core‐shell particles.
Change in Physico‐chemical Properties of PMMA and PS by Copolymerization with an Anionic Amphiphilic Comonomer: Sodium 11‐(methacryloyloxy) undecanylsulfate (MET)
Authors: Hartmann P. C. , Lupo M. , Weber W. , Sanderson R. D.
Published: January 2006

Sodium 11‐(methacryloyloxy) undecanylsulfate (MET) monomer units were incorporated in polystyrene (PS) and poly(methyl methacrylate) (PMMA) by free radical copolymerization in solution with styrene and methyl methacrylate, respectively. Experimental compositions, thermal degradations, average molecular weights, glass transitions and affinities for moisture were experimentally determined for copolymers of various compositions. Both styrene and methyl methacrylate copolymerized well with MET. An increase in the moisture affinity and a change in the glass transition were observed with increasing MET content in the respective copolymers.
Effects of Laplace Pressure on Propagation and Termination in Aqueous Heterogeneous Free Radical Polymerization
Authors: Zetterlund Per B. , Okubo Masayoshi
Published: January 2006

Summary: The influence of the Laplace pressure in polymer emulsion particles during aqueous heterogeneous free radical polymerization on the polymerization kinetics has been investigated. Calculations were carried out based on experimentally reported pressure dependences of propagation and termination rate coefficients. The results suggest that in most cases the effects are not likely to be significant, although under conditions of very small particles (diameter <20 nm) and high interfacial tensions effects of the order of a few percent on propagation (increase in rate) and termination (decrease in rate) were predicted.

(kp/kt0.5)/(kp/kt0.5)0 as a function of particle radius as a result of the Laplace pressure.

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(kp/kt0.5)/(kp/kt0.5)0 as a function of particle radius as a result of the Laplace pressure.
Differential impairment of the sudomotor and nociceptor axon‐reflex in diabetic peripheral neuropathy
Authors: Berghoff Martin , Kilo Sonja , Hilz Max J. , Freeman Roy
Published: January 2006

It is not known whether C‐fiber functional subclasses are differentially affected by diabetes mellitus or whether the patterns of C‐fiber dysfunction are different between type 1 and type 2 diabetes. We therefore examined efferent sympathetic sudomotor and primary afferent nociceptor C‐fiber function in diabetic patients. Acetylcholine (10%) was used to evoke C‐fiber (axon‐reflex)–mediated responses. The nociceptor (flare) response was measured using a laser Doppler device. The sudomotor response was quantified with silastic imprints. The nociceptor C‐fiber–mediated flare response was reduced in type 2 diabetic patients (P < 0.008) but was similar to controls in type 1 diabetic patients. The sympathetic C‐fiber–mediated responses, including sweat volume (P < 0.05) and the number of activated sweat glands (P = 0.003), were increased in patients with type 1 diabetes. There also was a trend toward a larger axon‐reflex sweat area in patients with type 1 diabetes (P = 0.09). No differences in these sweat responses were found in patients with type 2 diabetes compared to controls. These findings suggest that the functional abnormalities in diabetic peripheral neuropathy are not homogeneous and that C‐fiber subclasses are differentially affected in type 1 and 2 diabetes mellitus. Muscle Nerve, 2006
Dose‐dependent separation of the hypertrophic and myotoxic effects of the β2‐adrenergic receptor agonist clenbuterol in rat striated muscles
Authors: Burniston Jatin G. , Clark William A. , Tan Lip‐Bun , Goldspink David F.
Published: January 2006

Muscle growth in response to large doses (milligrams per kilogram) of β2‐adrenergic receptor agonists has been reported consistently. However, such doses may also induce myocyte death in the heart and skeletal muscles and hence may not be safe doses for humans. We report the hypertrophic and myotoxic effects of different doses of clenbuterol. Rats were infused with clenbuterol (range, 1 μg to 1 mg.kg−1) for 14 days. Muscle protein content, myofiber cross‐sectional area, and myocyte death were then investigated. Infusions of ≥10 μg.kg−1.d−1 of clenbuterol significantly (P < 0.05) increased the protein content of the heart (12%–15%), soleus (12%), plantaris (18%–29%), and tibialis anterior (11%–22%) muscles, with concomitant myofiber hypertrophy. Larger doses (100 μg or 1 mg) induced significant (P < 0.05) myocyte death in the soleus (peak 0.2 ± 0.1% apoptosis), diaphragm (peak 0.15 ± 0.1% apoptosis), and plantaris (peak 0.3 ± 0.05% necrosis), and significantly increased the area fraction of collagen in the myocardium. These data show that the low dose of 10 μg.kg−1.d−1 can be used in rats to investigate the anabolic effects of clenbuterol in the absence of myocyte death. Muscle Nerve, 2006
An integer programming approach to routing in daisy networks
Authors: Becker Johanna , Csizmadia Zsolt , Galtier Jérôme , Laugier Alexandre , Szabó Jácint , Szegő László
Published: January 2006

We are concerned with routing problems arising in special kinds of SDH networks, called daisy networks. Beside the capacity constraints, some disjoint edge‐sets of the network, called arcs, are also prescribed. Our goal is to find a routing of the demands satisfying the capacities with the additional constraint that whenever a path (with value 1) enters an arc then it uses capacity 1 on all edges of that arc. We consider two types of arc‐systems and give algorithms and computational results of integer programming formulations. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 47(2), 116–121 2006
Changes within maturing neurons limit axonal regeneration in the developing spinal cord
Authors: Blackmore Murray , Letourneau Paul C.
Published: January 2006

Embryonic birds and mammals display a remarkable ability to regenerate axons after spinal injury, but then lose this ability during a discrete developmental transition. To explain this transition, previous research has emphasized the emergence of myelin and other inhibitory factors in the environment of the spinal cord. However, research in other CNS tracts suggests an important role for neuron‐intrinsic limitations to axon regeneration. Here we re‐examine this issue quantitatively in the hindbrain‐spinal projection of the embryonic chick. Using heterochronic cocultures we show that maturation of the spinal cord environment causes a 55% reduction in axon regeneration, while maturation of hindbrain neurons causes a 90% reduction. We further show that young neurons transplanted in vivo into older spinal cord can regenerate axons into myelinated white matter, while older axons regenerate poorly and have reduced growth cone motility on a variety of growth‐permissive ligands in vitro, including laminin, L1, and N‐cadherin. Finally, we use video analysis of living growth cones to directly document an age‐dependent decline in the motility of brainstem axons. These data show that developmental changes in both the spinal cord environment and in brainstem neurons can reduce regeneration, but that the effect of the environment is only partial, while changes in neurons by themselves cause a nearly complete reduction in regeneration. We conclude that maturational events within neurons are a primary cause for the failure of axon regeneration in the spinal cord. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006
Cytoplasmic domain of protocadherin‐α enhances homophilic interactions and recognizes cytoskeletal elements
Authors: Triana‐Baltzer Gallen B. , Blank Martina
Published: January 2006

Cell adhesion molecules of the protocadherin‐α (pcdh‐α), ‐β, and ‐γ families have been proposed to be synaptic specifiers. Pcdh‐α and ‐γ family members localize in part to synapses, and deletion of all pcdh‐γs in mouse affects synaptogenesis. Little is known, however, about the binding specificities and intracellular signaling of protocadherins. Using heterologous expression of tagged constructs, immunostaining, and biotinylation of surface components followed by Western blots we demonstrate that pcdh‐αs undergo homophilic interactions that are significantly enhanced by the cytoplasmic domain. Pcdh‐αs cloned from chick ciliary ganglion have one of two cytoplasmic constant regions (A‐ and B‐types). Screening a yeast two‐hybrid library of ciliary ganglion cDNA with the A‐type domain yielded a fragment of neurofilament M (NFM); screening with B‐type domain yielded a fragment of the actin‐bundling protein fascin. Cotransfection of HEK cells with the constructs indicated that the NFM and A‐type fragments codistributed as did the fascin and B‐type fragments, and the latter could be coimmunoprecipitated. Antibody‐induced clustering of full‐length pcdh‐αs on the surface of transfected HEK cells induced coclustering of the interacting NFM fragment. Native full‐length NFM in tissue extracts bound specifically to the A‐type domain on beads, while native full‐length fascin in tissue extracts specifically coimmunoprecipitated with pcdh‐α. Immunostaining neurons demonstrated codistribution of full‐length pcdh‐α with both NFM and actin filaments. These findings suggest cytoskeletal links for pcdh‐αs and identify candidate targets. They also demonstrate homophilic interactions for pcdh‐αs as described for classical cadherins. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006
Genome‐wideP‐element screen forDrosophilasynaptogenesis mutants
Authors: Liebl Faith L.W. , Werner Kristen M. , Sheng Qi , Karr Julie E. , McCabe Brian D. , Featherstone David E.
Published: January 2006

A molecular understanding of synaptogenesis is a critical step toward the goal of understanding how brains “wire themselves up,” and then “rewire” during development and experience. Recent genomic and molecular advances have made it possible to study synaptogenesis on a genomic scale. Here, we describe the results of a screen for genes involved in formation and development of the glutamatergicDrosophilaneuromuscular junction (NMJ). We screened 2185P‐element transposon mutants representing insertions in ≈16% of the entireDrosophilagenome. We first identified recessive lethal mutants, based on the hypothesis that mutations causing severe disruptions in synaptogenesis are likely to be lethal. Two hundred twenty (10%) of all insertions were homozygous lethal. Two hundred five (93%) of these lethal mutants developed at least through late embryogenesis and formed neuromusculature. We examined embryonic/larval NMJs in 202 of these homozygous mutants using immunocytochemistry and confocal microscopy. We identified and classified 88 mutants with altered NMJ morphology. Insertion loci in these mutants encode several different types of proteins, including ATP‐ and GTPases, cytoskeletal regulators, cell adhesion molecules, kinases, phosphatases, RNA regulators, regulators of protein formation, transcription factors, and transporters. Thirteen percent of insertions are in genes that encode proteins of novel or unknown function. Complementation tests and RT‐PCR assays suggest that approximately 51% of the insertion lines carry background mutations. Our results reveal that synaptogenesis requires the coordinated action of many different types of proteins—perhaps as much as 44% of the entire genome—and that transposon mutageneses carry important caveats that must be respected when interpreting results generated using this method. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006
Kinesin‐2 differentially regulates the anterograde axonal transports of acetylcholinesterase and choline acetyltransferase in Drosophila
Authors: Baqri Rehan , Charan Rakshita , Schimmelpfeng Kristina , Chavan Swati , Ray Krishanu
Published: January 2006

Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) are involved in acetylcholine synthesis and degradation at pre‐ and postsynaptic compartments, respectively. Here we show that their anterograde transport in Drosophila larval ganglion is microtubule‐dependent and occurs in two different time profiles. AChE transport is constitutive while that of ChAT occurs in a brief pulse during third instar larva stage. Mutations in the kinesin‐2 motor subunit Klp64D and separate siRNA‐mediated knock‐outs of all the three kinesin‐2 subunits disrupt the ChAT and AChE transports, and these antigens accumulate in discrete nonoverlapping punctae in neuronal cell bodies and axons. Quantification analysis further showed that mutations in Klp64D could independently affect the anterograde transport of AChE even before that of ChAT. Finally, ChAT and AChE were coimmunoprecipitated with the kinesin‐2 subunits but not with each other. Altogether, these suggest that kinesin‐2 independently transports AChE and ChAT within the same axon. It also implies that cargo availability could regulate the rate and frequency of transports by kinesin motors. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006
Second and third malignant solid tumor in a girl with ovarian Sertoli–Leydig tumor
Authors: Panagiotou John P. , Polychronopoulou Sophia , Sofou Kalliopi , VanVliet‐Constantinidou Catherine , Papandreou Evangelos , Haidas Stavros
Published: January 2006

We report a Sertoli–Leydig cell (SLC) tumor of the right ovary in a 10‐year‐old girl, which was dealt with surgical removal. Three months after resection, she presented with a new episode of acute abdomen because of an abdominal mass, which histologically was compatible with an undifferentiated embryonal rhabdomyosarcoma. Chemotherapy, according to SIOP‐??? 89 protocol, was administered additionally to radiotherapy (3,960 cGy). Three years after completing treatment, the patient developed a painful swelling at her left upper arm. The diagnosis was Ewing sarcoma of the humerus, which was confirmed by identification of the typical 11; 22 translocation on cytogenetic and molecular analysis of the tumor tissue. The patient died 14 months from Ewing diagnosis due to progressive disease. Pediatr Blood Cancer © 2006 Wiley‐Liss, Inc.
Optic pathway gliomas
Authors: Jahraus Christopher D. , Tarbell Nancy J.
Published: January 2006

Optic pathway gliomas represent approximately 5% of all pediatric intracranial tumors. While these tumors are most frequently low grade astrocytomas, they follow a highly variable clinical course, and accordingly, there is much debate regarding their optimal management. Their propensity to occur in very young children and infants further complicates selection of therapy. Historically, surgery and radiotherapy have played a primary role in management, however, in the last 15 years, chemotherapy has evolved into the first‐line treatment of choice. Nonetheless, chemotherapy frequently fails, but serves to delay implementation of radiotherapy or surgery until the child has progressed neuropsychologically. An overall favorable prognosis for this tumor emphasizes the need for careful selection of therapy. Herein, we review the major features of optic pathway glioma, including epidemiology, pathology, therapeutic interventions, outcome, and treatment sequelae. Pediatr Blood Cancer © 2006 Wiley‐Liss, Inc.
Pediatric primary leptomeningeal lymphoma treated without cranial radiotherapy
Authors: Taga Takashi , Sakaue Yuko , Anzai Yuko , Takeuchi Yoshihiro , Ohta Shigeru
Published: January 2006

We report a case of primary leptomenigeal lymphoma (PLML) in an 11‐year‐old boy presenting with headache, vomiting, and diplopia. The patient was treated on an advanced non‐Hodgkin lymphoma protocol with systemic/intrathecal chemotherapy without cranial radiotherapy. He remains in complete remission 33 months after treatment. Pediatr Blood Cancer © 2006 Wiley‐Liss, Inc.
Weighing the risks of G‐CSF administration, leukopheresis, and standard marrow harvest: Ethical and safety considerations for normal pediatric hematopoietic cell donors
Authors: Pulsipher Michael A. , Nagler Arnon , Iannone Robert , Nelson Robert M.
Published: January 2006

Background

Granulocyte colony stimulating factor (G‐CSF) is used for collection of hematopoietic cells in most adult and a smaller but significant percentage of pediatric normal donor harvests. Short and long‐term risks of G‐CSF administration and leukopheresis are not well understood in the pediatric population.

Procedure

Literature review including observations from the IBMTR, NMDP, EBMT, German Donor Registry, and the authors' work.

Results

G‐CSF causes temporary discomfort in a minority of younger donors. Rare serious side effects of G‐CSF have yet to be reported in children. To date, an increase in hematological malignancies after short‐term G‐CSF use has not been detected in adult donors and no cases have been reported in children. Reported complications of leukopheresis in children are rare and minor, but donors <20 kg may be exposed to allogeneic blood products. Pediatric aged donors vary widely in their ability to assent or consent to the risks of a donation procedure. There are key regulations and ethical imperitives, which must be addressed in deciding which donation procedures are appropriate for minors.

Conclusions

While short term administration of G‐CSF and leukopheresis appear to be safe and effective procedures when used to assist in collection of a hematopoietic cell graft from a normal pediatric donor, institutions adding or substituting one or both of these procedures for standard marrow donation must decide whether the donor should be considered a research subject, and if so, whether the new procedures are a minor increase over minimal risk. Because these procedures are being performed on and off study at many pediatric centers, a comprehensive study addressing donor safety could help clarify risks of rare adverse events. Pediatr Blood Cancer 2006, 46:422–433. © 2006 Wiley‐Liss, Inc.