bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and characterization of semifluorinated polymers and block copolymers
Authors: Pospiech Doris , Komber Hartmut , Voigt Dieter , Jehnichen Dieter , Häußler Liane , Gottwald Antje , Kollig Wolfram , Eckstein Kathrin , Baier Angela , Grundke Karina
Published: October 2003

The goal of the investigation presented here was to evaluate the influence of semifluorinated side chains on the bulk structure and the surface properties of polysulfones with different chain structure. Thus, segmented block copolymers consisting of polysulfone and semifluorinated aromatic polyester segments as well as polysulfones having semifluorinated side chains randomly distributed over the polymer backbone were synthesized and characterized. Oxydecylperfluorodecyl side chains were used because of their strong tendency for self‐organization. The influence of the chain architecture on the self‐organization as well as on the surface properties, particularly the wetting behavior, was examined. It could be shown that despite of the higher self‐organizing tendency of block copolymers the surface properties of both polymer types are comparable and depend only on the concentration of side chains.
Synthesis of well‐defined poly(p‐benzamide) from chain‐growth polycondensation and its application to block copolymers
Authors: Yokozawa Tsutomu , Ogawa Miyuki , Sekino Atsushi , Sugi Ryuji , Yokoyama Akihiro
Published: October 2003

Poly(p‐benzamide) with a defined molecular weight and a low polydispersity and block copolymers containing this well‐defined aramide was synthesized. Phenyl 4‐(4‐octyloxybenzylamino)benzoate (1b) polymerized at room temperature in the presence of base and phenyl 4‐nitrobenzoate (2a) as an initiator in a chain‐growth polycondensation manner to give well‐defined aromatic polyamides having the 4‐octyloxybenzyl groups as a protecting group on nitrogen in an amide. It was confirmed by a model reaction that deprotection of this protecting group proceeded completely with trifluoroacetic acid (TFA) without breaking the amide linkage. The utility of this approach to poly(p‐benzamide) with a low polydispersity was demonstrated by the synthesis of block copolymers of poly(p‐benzamide) and poly(N‐octyl‐p‐benzamide) or poly(ethylene glycol). The SEM images of the supramolecular assemblies of the former block copolymer showed μm‐sized bundles and aggregates of flake structures.
Cyclizations in hyperbranched aliphatic polyesters and polyamides
Authors: Chikh Linda , Arnaud Xavier , Guillermain Céline , Tessier Martine , Fradet Alain
Published: October 2003

Hyperbranched aliphatic polyesters of 2,2′‐bis‐(hydroxymethyl) propanoic acid and hyperbranched aliphatic polyamides obtained from new carboxy‐ and amino‐functionalized caprolactams were studied by NMR spectroscopy and MALDI‐TOF mass spectrometry. Ring‐chain equilibria taking place through intramolecular hydroxy‐ester, carboxy‐amide or amine‐amide interchanges and leading to the formation of cyclic branches or end‐groups were found to exert a predominant influence on the molar mass of these hyperbranched polymers. A number of intra‐ or intermolecular side reactions, such as the formation of ethers in polyesters and the formation of anhydrides, imides, amidines and secondary amines in polyamides were also detected and resulted in polymer crosslinking on prolonged heating. The existence of such ring‐chain equilibria and side‐reactions make the control of hyperbranched polymer structure much more difficult than generally accepted.
Lyotropic para‐linked aromatic poly(amic ethyl ester)s
Authors: Neuber Christian , Giesa Reiner , Schmidt Hans‐Werner
Published: October 2003

The synthesis, characterization and application of lyotropic precursor polymers for polyimides, poly(amic ethyl ester)s (PAE) are presented. By the use of non‐coplanar and para‐linked monomers, rigid‐rod PAEs are synthesized in a typical polycondensation reaction yielding liquid crystalline solutions at concentrations of 30‐40 wt% in NMP at 100°C. These lyotropic solutions permit for the first time the fabrication of orientation PAE layers by shear which are thermally converted to the corresponding polyimide. The bulk orientation in the thin films is characterized by spectroscopic methods. In addition the lyotropic solution is spun into fibers in a dry‐jet wet spinning process. The obtained fiber orientation is characterized by tensile tests and wide angle X‐ray scattering.
Liquid crystalline thermosets from dimeric LC epoxy resins cured with primary and tertiary amines
Authors: Ribera David , Mantecón Ana , Serra Angels
Published: October 2003

Liquid crystalline thermosets (LCTs) were prepared by curing difunctional LC dimeric epoxy monomers with imine moieties in the mesogenic core and central spacers of different length. Primary diamines or tertiary amines were used as curing agents obtaining materials with different characteristics. The results obtained were related to the mesogen structure, since dipolar moments in the mesogenic cores affect the ability to form ordered networks.
Polymer design for thermally stable polyimides with low dielectric constant
Authors: Goto Kohei , Akiike Toshiyuki , Inoue Yasutake , Matsubara Minoru
Published: October 2003

We successfully prepared a series of thermally stable polyimides (PIs) with low dielectric constant (k) by introducing bulky diphenyl fluorenylidene moieties in backbone. The lowest k was found to be 2.77 among non‐fluorinated PIs and 2.35 among fluorinated ones. In order to prove the lowest limit of k in PIs, we prepared soluble and thermally stable polyarylenes (PArs) without polar imide linkage with the same aromatic moieties by coupling polymerization. The lowest k was 2.7 without fluorine (F) and 2.2 with F atom, which showed also promising for low k materials. From these results, PIs we prepared were estimated to the lowest k values among PIs. On the basis of statistics on these results, we could express contour lines of k as a function of imide concentration and F content with high correlation factor (r= 0.96) in PIs and PArs.
New organosoluble polyimides with low dielectric constants derived from bis[4‐(2‐trifluoromethyl‐4‐aminophenoxy)phenyl] diphenylmethylene
Authors: Liaw Der‐Jang , Tseng Wen‐Tsung
Published: October 2003

A new kink diamine with trifluoromethyl group on either side, bis[4‐(2‐trifluoromethyl‐4‐aminophenoxy)phenyl]diphenylmethane(BTFAPDM), was reacted with various aromatic dianhydrides to prepare polyimides via poly (amic acid) precursors followed by thermal or chemical imidization. Polyimides were prepared using 3,3′, 4,4′‐biphenyltetracarboxylic dianhydride(1), 4,4′‐oxydiphthalic anhydride(2), 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (3), 4,4′‐sulfonyldiphthalic anhydride(4), and 4,4′‐hexafluoroisopropylidene‐diphathalic anhydride(5). The fluoro‐polyimides exhibited low dielectric constants between 2.46 and 2.98, light color, and excellent high solubility. They exhibited glass transition temperatures between 227 and 253°C, and possessed a coefficient of thermal expansion (CTE) of 60‐88 ppm/°C. Polymers PI‐2, PI‐3, PI‐4, PI‐5 showed excellent solubility in the organic solvents: N‐methyl‐2‐pyrrolidinone (NMP), N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridkie and tetrahydrofuran (THF). Inherent viscosity of the polyimides were found to range between 0.58 and 0.72 dLg‐1. Thermogravimetric analysis of the polyimides revealed a high thermal stability decomposition temperature in excess of 500°C in nitrogen. Temperature at 10 % weight loss was found to be in the range 506‐563°C and 498‐557°C in nitrogen and air, respectively. The polyimide films had a tensile strength in the range 75‐87 MPa; tensile modulus, 1.5‐2.2 GPa; and elongation at break, 6‐7%.
HALS in polyamide 6 polymerization
Authors: Filippini Fantoni Roberto , Sanfilippo Giorgio
Published: October 2003

The use of Hindered Amine Light Stabilizers (HALS) directly in polyamide 6 polymerization can cause some problems. The following two problems were the focus of our project:

1) We investigated, from a theoretical point of view, the results of introducing directly one of the precursors of HALS into polyamide 6 polymerization. For the investigation, 4 amino‐2,2,6,6‐tetramethylpiperidine (triaceton‐diamine or TAD) was chosen. We considered the TAD chain‐ending effects and their influence on the total amount of amino chain‐endings that can be titrated, a parameter of primary importance in the fibre field.

2) We examined the amide interchange reaction in the case of an HALS containing two amide groups, using a product available on the market, N,N′‐bis(tetramethyl‐4‐piperidyl)isophtalamide. In this case we were able to generate a couple of equations that allows one to calculate the quantity of amide interchanged HALS. This was done by comparing the results (molecular weight and chain‐endings analysis) of polymerization with and without HALS.
Transfer molding imide resins based on 2,3,3′,4′‐biphenyltetracarboxylic dianhydride
Authors: Smith J.G. , Connell J.W. , Hergenrother P.M. , Ford L.A. , Criss J.M.
Published: October 2003

Phenylethynyl containing imide oligomers have been under investigation as part of an effort to develop resins for non‐autoclave composite fabrication processes such as resin transfer molding (RTM). These high performance/high temperature composites are potentially useful on advanced aerospace vehicles such as reusable launch vehicles (RLVs). New phenylethynyl terminated imide oligomers (PETI) based upon 2,3,3′,4′‐biphenyltetracarboxylic dianhydride (a‐BPDA) were prepared and characterized primarily by rheological behavior and cured glass transition temperature (Tg). In comparison to resins from the symmetrical isomer (3,3′,4,4′‐biphenyltetracarboxylic dianhydride, s‐BPDA), a‐BPDA afforded corresponding resins with lower melt viscosities and upon curing, higher Tgs. Several resins exhibited an attractive combination of properties such as low and stable melt viscosities required for RTM composite fabrication, high cured Tgs, and moderate toughness. One resin (P10) was used to fabricate flat, void free laminates by RTM. The laminates exhibited high mechanical properties at temperatures to 288°C. The chemistry and physical properties of these new PETIs and the laminate properties of one composition are discussed.
Synthesis and characterisation of polyketanils with ether linkages
Authors: Sęk Danuta , Iwan Agnieszka , Kasperczyk Janusz , Janeczek Henryk
Published: October 2003

A series of polyketanils from four diketones with pendant aromatic groups (i.e. dibenzoyl, p‐dibenzoylbenzene, p‐disebacoylbenzene and trans‐1,2‐dibenzoylethylene) and two diamines with flexibilizing ether linkages [4,4′‐diaminediphenyl ether, 4,4′‐(1,3phenylenedioxy)dianiline] has been synthesized using melt polycondensation (180°C, 24h). Spectral and thermal properties of the polyketanils before and after protonation with 1,2‐(di‐2‐ethylhexyl)ester of sulfophthalic acid (DEHEPSA) were investigated.
Engineering with metallo‐supramolecular polymers: linear coordination polymers and networks
Authors: Schmatloch S. , Schubert U.S.
Published: October 2003

Here we demonstrate the synthesis of telechelics with different spacer units and different numbers of metal‐complexing units, like α‐methoxy‐ω‐(2,2′:6′,2″‐terpyrid‐4′‐yl)‐poly(ethylenoxide)78 (1), bis(2,2′:6′,2″‐terpyrid‐4′‐yl) di(ethylene glycol) (2), bis(2,2′:6′,2″‐terpyrid‐4′‐yl)‐poly(ethylene oxide)180 (3) and tris[(2,2′:6′,2″‐terpyrid‐4′‐yl)‐oligo (ethylenoxy‐)3.33]glycerin (4) utilizing 4‐chloro‐2,2′:6′,2″‐terpyridine. The complexation behaviour of a variety of metal‐salts towards the telechelics was studied and different supramolecular architectures were investigated, such as symmetric polymeric complexes and linear coordination polymers. Furthermore, attempts have been undertaken to prepare metallo‐supramolecular cross‐linked systems.
Condensation polymers containing silicon and germanium in the main chain
Authors: Tagle Luis H.
Published: October 2003

Poly(carbonates), poly(thiocarbonates) and poly(esteres) containing silicon and/or germanium in the main chain were obtained under phase transfer conditions. Polymers were synthesized in a biphasic system NaOH/CH2Cl2 at 20°C using several phase transfer catalysts, and characterized by IR and 1H and 13C NMR. The results were evaluated by the yields and the inherent viscosity values. The process was effective observing an increase of both parameters in comparison with the essays without catalyst. The increases depended of the nature of the polymer and the catalyst. In poly(ester) synthesis there was an increase of these parameters when the NaOH concentration was increased due to a salting out effect of the diphenolate from the aqueous phase to the organic one. Also poly(amides) containing silicon or germanium were synthesized by solution polymerization.
Aromatic polymers with side oxadiazole rings as luminescent materials in LEDs
Authors: Bruma Maria , Hamciuc Elena , Schulz Burkhard , Köpnick Thomas , Kaminorz Yvette , Robison Jenifer
Published: October 2003

Aromatic polyamides and polyazomethines with side oxadiazole rings have been synthesized by using aromatic diamines containing pendent substituted oxadiazole groups and a diacid chloride having diphenylsilane or hexafluoroisopropylidene, or an aromatic dialdehyde with fluorene unit, respectively. These polymers were easily soluble in amidic solvents. Very thin films which were deposited from polymer solutions onto silicon wafers exhibited smooth, pinhole‐free surface in atomic force microscopy investigations. The polymers showed high thermal stability with decomposition temperature being above 400°C. Some of them exhibited blue photoluminescence, in the range of 450‐480 nm, making them promising candidates for future use as high performance materials in the construction of light emitting devices.
Smart nanocomposite polymer gels
Authors: Varga Zsolt , Fehér József , Filipcsei Genovéva , Zrínyi Miklós
Published: October 2003

The combination of polymers with nanomaterials displays novel and often enhanced properties compared to the traditional materials. They can open up possibilities for new technological applications. The magnetic polymer gel represents a new type of composites consisting of small magnetic particles, usually from the nanometer range to the micron range, dispersed in a highly elastic polymeric gel matrix. Combination of magnetic and elastic properties leads to a number of striking phenomena that are exhibited in response to impressed magnetic fields. Giant deformational effects, high elasticity, anisotropic properties, temporary reinforcement and quick response to magnetic field open new opportunities for using such materials for various applications.
Study of the interaction polymer/organic solvents/salt in microporous PVdF separator for lithium batteries
Authors: Saunier J. , Alloin F. , Sanchez J‐Y.
Published: October 2003

Interactions between microporous PVdF and polar liquid electrolytes have been investigated. PVdF separators are an attractive alternative to microporous apolar polyolefins, such as polyethylene, whose poor wetting by these electrolytes induces a significant resistivity increase in lithium batteries. The swelling study of polymer/electrolyte interactions has shown that the resistivity increase induced by microporous PVdF is moderate and will enable the electrolyte composition to be optimized. Existence of a shut‐down effect is an asset for the battery safety.
Swelling, elasticity and structure of hydrogels prepared via bis‐macromonomers of poly(ethylene oxide)
Authors: Dubrovskii Sergey A. , Lagutina Marina A. , Vasiljev Vitalij V.
Published: October 2003

The effect of swelling on the shear modulus was studied for hydrogels prepared by radical polymerization of methacrylate‐terminated poly(ethylene oxide) (PEO) bis‐macromonomers of different molecular weight. Gels made of long chains (M = 12000 or 6000) display classical softening upon swelling, whereas gels made of shorter chains (M = 4000 or 2000) remain rigid or even stiffen. The abnormal behaviour is explained by a specific character of network junctions presented by polymethacrylate chains in which each unit is linked with a PEO network chain. It is assumed that the interactions among densely grafted PEO chains result in their stretching on polymerization and non‐affine deformation on swelling, which stiffen the gel. This is verified by the data on copolymer (macromonomers ‐ 2‐hydroxyethyl methacrylate) gels that have lesser densities of PEO chains attached to the junctions and show weaker stiffening on swelling. The osmotic pressure of gels was estimated from the swelling pressure and shear modulus. Similar to the mixing pressure of equivalent PEO solutions, it varies as the 9/4 power of polymer concentration. At the same time, it is lower than the mixing pressure. This indicates that the junctions make only quantitative changes in the osmotic properties of macromonomer chains.
H‐bond in chitosan‐based hydrogels
Authors: Xin Meihua , Li Mingchun , Yao Kangde
Published: October 2003

N‐alkyl chitosan derivatives, including N‐ethyl, butyl, heptyl and lauryl forms were prepared via Schiff's base intermediates. The study of H‐bonds in chitosan‐based hydrogel was performed by DSC, NMR, XKD and PALS. The content of unfrozen bound water increases with increasing length of the alkyl side chain and the degree of substitution. The X‐ray diffraction peak centered at 2θ=26.5° is sensitive to water. The free volume enhances in the order, chitosan (CS) < N‐ethyl CS < N‐butyl CS < N‐heptyl CS << N‐lauryl CS. Moreover the free volume of the derivatives decreases as water content rises but the situation of chitosan is opposite. The dynamic properties of water molecules within the networks were studied through the variation of the proton line width in the 1H‐NMR spectrum. The proton line width of the water peak of N‐alkyl chitosan increases in the sequence, N‐ethyl CS < N‐butyl CS < N‐heptyl CS < N‐lauryl CS. The same results arise from the spin‐lattice relaxation time (T1) for these N‐alkyl chitosan derivatives.
Controlled‐release of drugs from cross‐linked polymers containing cubane as a crosslinking agent
Authors: Mahkam Mehrdad
Published: October 2003

Two anti‐inflammatory drugs, indomethacin and aspirin together with cubane‐1, 4‐dicarboxylic acid (CDA) were covalently linked with 2‐hydroxyethyl methacrylate (HEMA). The drug‐linked HEMA (indomethacin‐linked HEMA) is abbreviated as HI, aspirin‐linked HEMA as HA and cubane‐1, 4‐dicarboxylic acid (CDA) linked to two HEMA group is the cross‐linking agent (CA). A difunctional spacer group was introduced between the drugs and acrylic moiety of the monomer through a hydrolyzable ester linkage. Free radical cross‐linking polymerization of the monomers with drug effect was carried out in dioxane solution at various CA ratios, using AIBN as initiator in the temperature range 60‐70°C. The compositions of the cross‐linked three‐dimensional polymers were determined by FT‐IR spectroscopy. The glass transition temperature (Tg) of the network polymers was determined calorimetrically. The hydrolysis of drug‐polymer conjugates was carried out in cellophane membrane dialysis bags containing an aqueous buffer solution (pH 8 and pH 1) at 37°C. Detection of the hydrolysis product by UV spectroscopy shows that the drugs were released by hydrolysis of the ester bond located between the drug and spacer group.
Properties of simple models of polymer networks. A Monte Carlo simulation
Authors: Sikorski Andrzej , Romiszowski Piotr
Published: October 2003

A model polymer network was constructed from branched chains. Each chain was built on a simple cubic lattice forming a star‐branched polymer consisting of f = 3 arms of equal lengths. The fragment of network under consideration consisted of 1, 2 and 3 star polymers with different topology of connections. The only potential used was excluded volume (athermal chains). The properties of the network were determined by the means of computer simulations using the classical Metropolis sampling algorithm (local micromodifications of chain conformation). The behaviour of linear chains of the same molecular weight was also studied as a state of reference. The influence of attaching the next star‐branched chain to the network on its static and dynamic properties was studied. The short‐time dynamic behaviour of chain fragments was determined and discussed.
Water sorption properties of poly(ethyl acrylate‐co‐hydroxyethyl methacrylate) macroporous hydrogels
Authors: Vidaurre Ana , Castilla Cortázar Isabel , Meseguer José María
Published: October 2003

Synthetic porous hydrogels are becoming more and more important in the field of biomaterials. Different studies demonstrate that the porous structure promotes the colonisation of living cells and improves the biocompatibility of the implants. The macroporous structure allows not only the control of cellular ingrowth morphology but also the mechanical integration and the regulation of nutrient and hydraulic flow in the hydrogel. In this work poly(ethyl acrylate‐co‐hydroxyethyl methacrylate) (PEA/PHEMA) copolymers were polymerized using 2% of ethylene glycol dimethacrylate as cross‐linking agent and azoiso‐botyronitrile as initiator. Five samples were prepared with the EA/HEMA weight ratios of 75/25, 50/50, 25/75 and pure PEA and PHEMA polymers, obtaining different degrees of hydrophilicity. The macroporous structure was obtained by adding poly(acrylonitrile) fibres to the monomers. After polymerization the fibres were eliminated by dissolution in dimethyl formamide. The holes are cylinders of approximately 40μm diameter and are all, more or less, in the same direction, although they are not uniformly distributed. Water sorption isotherms and diffusion properties of the macroporous samples are compared with the samples without holes.
NMR study of the synthesis of 17O‐enriched acetic acid by hydrolysis of acetic anhydride with 17O‐enriched water
Authors: Hultman Heidi M. , Djanashvili Kristina , Peters Joop A.
Published: October 2003

17O‐enriched acetic acid (2.5% in 17O) was synthesized by hydrolysis of acetic anhydride with 17O‐enriched water. The reaction was monitored by 17O and 1H NMR spectroscopy. Acetic anhydride, 17O‐enriched in both the ether and the carbonyl oxygens, was observed as an intermediate. This can be ascribed to competition between acetic acid and water for nucleophilic attack on acetic anhydride. Copyright © 2003 John Wiley & Sons, Ltd.
Non‐empirical calculations of NMR indirect carbon‐carbon coupling constants. Part 5: Bridged bicycloalkanes
Authors: Krivdin Leonid B.
Published: October 2003

All possible J(C,C) of the bicarbocyclic frameworks together with J(C,H) and J(H,H) at bridgeheads in the series of six bridged bicycloalkanes, bicyclo[1.1.0]butane, bicyclo[2.1.0]pentane, bicyclo[3.1.0]hexane, bicyclo[2.2.0]hexane, bicyclo[3.2.0]heptane and bicyclo[3.3.0]octane, were calculated at the SOPPA level with correlation consistent Dunning sets cc‐pVTZ‐Cs augmented with inner core s‐functions and locally dense Sauer sets aug‐cc‐pVTZ‐J augmented with tight s‐functions and rationalized in terms of the multipath coupling mechanism and hybridization effects explaining many interesting structural trends. Copyright © 2003 John Wiley & Sons, Ltd.
25R/25S stereochemistry of spirostane‐type steroidal sapogenins and steroidal saponins via chemical shift of geminal protons of ring‐F
Authors: Agrawal Pawan K.
Published: October 2003

A method based on the differences among the 1H NMR chemical shifts of geminal protons of ring‐F methylene resonances (H2‐23, H2‐24 and H2‐26) is proposed for ascertaining the 25R/25S stereochemistry of ring‐F unsubstituted spirostane‐type steroidal sapogenins and steroidal saponins. Copyright © 2003 John Wiley & Sons, Ltd.
A new coumarin from Perezia hebeclada
Authors: Hernández‐Carlos Beatriz , Burgueño‐Tapia Eleuterio , Joseph‐Nathan Pedro
Published: October 2003

Methanol extracts from Perezia hebeclada roots yielded the new 8‐β‐D‐glucopyranosyloxy‐4‐methoxy‐5‐methylcoumarin (1) together with the known 4‐β‐D‐glucopyranosyloxy‐5‐methylcoumarin (2). Their structures were determined and verified, respectively, by MS and NMR studies, including 1D and 2D experiments. Two 13C NMR signals of the sugar residue of 2 were reassigned. Copyright © 2003 John Wiley & Sons, Ltd.
Assignment of 1H and 13C NMR data for diethyl 2‐ and 8‐quinolylmethylphosphonates and their palladium(II) dihalide complexes
Authors: Marinić Željko , Ćurić Manda , Vikić‐Topić Dražen , Tušek‐Božić Ljerka
Published: October 2003

1H and 13C NMR spectral data for diethyl 2‐ and 8‐quinolylmethylphosphonates (L) and their palladium(II) dihalide complexes, trans‐[PdL2X2] (L = 2‐dqmp, 8‐dqmp; X = Cl, Br), are presented. The NMR analysis was performed on the basis of one‐ and two‐dimensional homo‐ and heteronuclear experiments including 1H, 13C, APT, 1H–1H COSY, 1H–13C COSY, HMQC and HMBC techniques. Copyright © 2003 John Wiley & Sons, Ltd.
Structure elucidation of [1,3]oxazolo[4,5‐e][2,1]benzisoxazole and naphtho[1,2‐d][1,3]‐ and phenanthro[9,10‐d]oxazoles using gradient selected gHMBC, gHMQC and gHMQC‐TOCSY NMR techniques
Authors: Katritzky Alan R. , Akhmedov Novruz G. , Wang Zuoquan , Roznyatovsky Vitaly A. , Shestopalov Aleksandr A. , Dennis Hall C.
Published: October 2003

Structure elucidation of compounds in the benzisoxazole series (1–6) and naphtho[1,2‐d][1,3]‐ (7–10) and phenanthro[9,10‐d][1,3]oxazole (11–14) series was accomplished using extensive 2D NMR spectroscopic studies including 1H–1H COSY, long‐ range 1H–1H COSY, 1H–13C COSY, gHMQC, gHMBC and gHMQC‐TOCSY experiments. The distinction between oxazole and isoxazole rings was made on the basis of the magnitude of heteronuclear one‐bond 1JC2, H2 (or 1JC3, H3) coupling constants. Complete analysis of the 1H NMR spectra of 11–14 was achieved by iterative calculations. Gradient selected gHMQC‐TOCSY spectra of phenanthro[9,10‐d][1,3]oxazoles 11–14 were obtained at different mixing times (12, 24, 36, 48 and 80 ms) to identify the spin system where the protons of phenanthrene ring at H‐5, H‐6 and at H‐9 and H‐7 and H‐8 were highly overlapping. Copyright © 2003 John Wiley & Sons, Ltd.
Occurrence of A‐waves in F‐wave studies of healthy nerves
Authors: Puksa Leena , Stålberg Erik , Falck Björn
Published: October 2003

A‐waves are compound muscle action potentials that follow the M‐wave with a constant shape and latency; usually they are detected during F‐wave studies. A large reference value database for F‐wave parameters from the median, ulnar, peroneal, and tibial nerves was collected from 121–196 subjects aged 14 to 95 years without known pathology involving the studied nerves. From this material, we studied retrospectively the occurrence of A‐waves. To be included, an A‐wave had to be clearly discriminated from the baseline in at least 8 of 20 traces with a jitter of less than 0.5 ms. A‐waves occurred in 25% of the tibial nerves studied and 14% of the peroneal nerves but in only 2% of median and ulnar nerves. In the peroneal and tibial nerves, the frequency of A‐waves increased with age, suggesting that A‐waves may be related to normal age‐related mild neuropathic changes of alpha motor neurons. Thus, A‐waves are frequently found in lower‐extremity nerves in healthy subjects and less commonly in upper‐extremity nerves. Their presence must therefore be interpreted with caution and cannot be taken as necessarily indicative of abnormality. Muscle Nerve 28: 626–629, 2003
Peripheral nerve fascicles: Anatomy and clinical relevance
Authors: Stewart John D.
Published: October 2003

Within a peripheral nerve, the individual nerve fibers are grouped together in fascicles. Whether there is somatotopic organization within these fascicles has long been of interest, the subject of many investigations, and somewhat controversial. Evidence from diverse sources now points to important somatotopic clustering of nerve fibers within most of the length of the nerve. Information is lacking regarding proximal segments, particularly the plexus and spinal nerve root levels. As a result of this somatotopic arrangement, partial focal nerve lesions can produce restricted clinical deficits that defy the classic rules of localization. Examples of such restricted nerve lesions are provided in this review. Recognition of fascicle somatotopy is also important in the surgical approach to disorders of peripheral nerves. Muscle Nerve 28: 525–541, 2003
Melas with point mutations involving tRNALeu (A3243G) and tRNAGlu(A14693g)
Authors: Tzen Chin‐Yuan , Thajeb Peterus , Wu Tsu‐Yen , Chen Shiu‐Ching
Published: October 2003

The syndrome of mitochondrial encephalomyopathy, lactic acidosis, and stroke‐like episode (MELAS) is typically associated with a single point mutation in the mitochondrial genome (mtDNA). Because mtDNA is known to have a higher mutation rate than nuclear DNA, we speculate that some patients with MELAS syndrome may harbor more than one mutation in mtDNA. For this purpose, mtDNA extracted from muscle containing dysmorphic mitochondria from a 32‐year‐old man with MELAS was sequenced in its entirety to identify all possible mutations. The result showed a homoplasmic A14693G and a heteroplasmic A3243G. The A14693G transition was not present in 205 unrelated control individuals, was not seen in 76 species randomly selected from GenBank, and appears to disrupt the base pairing within the T‐loop of mtDNA tRNAGlu. His asymptomatic siblings' blood showed wild‐type at these positions, whereas the blood of the patient's oligosymptomatic diabetic mother had a heteroplasmic A14693G and an apparent homoplasmic wild‐type A3243, suggesting an association of A14693G with diabetes mellitus. This case demonstrates the importance of sequencing the mtDNA in its entirety to evaluate the molecular basis of mitochondriopathy. Muscle Nerve 28: 575–581, 2003
Vasomotor dysfunction in carpal tunnel syndrome
Authors: Wilder‐Smith Einar P.V. , Fook‐Chong Stephanie , Chew Soh Eng , Chow Adeline , Guo Yaling
Published: October 2003

Little attention has been paid to small‐fiber dysfunction in carpal tunnel syndrome (CTS) although its symptoms are common. This study investigates vasomotor dysfunction, which is controlled by small nerve fibers, in patients with CTS compared with control subjects. Vasomotor function was quantified by measuring, with laser Doppler velocimetry, skin vasoconstriction induced by a eutectic mixture of local anesthetic (EMLA) cream over digit tips 3, 4, and 5. Hands with CTS (n = 32) compared with controls (n = 19) demonstrated significantly reduced vasoconstriction in digits 3 and 4, but not digit 5. A blood flow ratio (digit 3/5) of less than 0.73 identified CTS in 69% with 68% specificity. Testing for vasomotor dysfunction in CTS allows for more comprehensive neurophysiological testing, which is heavily biased towards large nerve fibers. Muscle Nerve 28: 582–586, 2003
Strength training in older women: Early and late changes in whole muscle and single cells
Authors: Frontera Walter R. , Hughes Virginia A. , Krivickas Lisa S. , Kim Sang‐Kyu , Foldvari Mona , Roubenoff Ronenn
Published: October 2003

In order to examine the relative contribution of neural‐ and muscle‐based adaptation to strength training, we studied early (2 weeks) and later (12 weeks) effects of strength training on muscle size and strength and type I single‐fiber size and contractility in 14 elderly women (aged 68–79 years) and seven young controls. Older subjects were randomized to training (n= 7) or control (n= 7) groups. Strength did not change, but whole muscle size increased significantly after 2 weeks. After 12 weeks, strength, whole muscle size, and specific force all increased. No changes occurred in the control group. In single fibers, no changes in size and contractility were noted after 2 weeks, but specific force was higher in the training group after 12 weeks. Early adaptations to strength training in elderly women cannot be attributed to changes at the cellular level and therefore occur primarily in the central nervous system. Later, cellular adaptations in specific force track closely whole muscle changes. Muscle Nerve 28: 601–608, 2003
Role of intertendinous connections in distribution of force in the human extensor digitorum muscle
Authors: Keen Douglas A. , Fuglevand Andrew J.
Published: October 2003

The human extensor digitorum (ED) muscle gives rise distally to multiple tendons that insert onto and extend digits 2–5. It has been shown previously that the spike‐triggered average forces of motor units in ED are broadly distributed across many tendons. Such force dispersion may result from linkages between the distal tendons of ED and may limit the ability to move the fingers independently. The purpose of this study, therefore, was to determine the extent to which the connections between tendons of ED distribute force across the fingers. Stimulation of ED muscle fibers was performed at 107 different sites in four subjects. The isometric force exerted on digits 2–5 resulting from the stimulation was measured separately. Stimulus‐triggered averaging of each of the four force channels yielded the force contribution to each of the digits due to the stimulation at each site. A selectivity index from 0 (a site that distributes force equally across the fingers) to 1.0 (a site that produces force on a single finger) was computed to describe the distribution of force across the four fingers. The selectivity index resulting from electrical stimulation of ED averaged 0.70 ± 0.21. These selectivity index values were significantly greater (P < 0.001) than those obtained for single motor units using spike‐triggered averaging. These findings suggest that linkages between the distal tendons of ED probably play only a minor role in distributing force across the fingers and, therefore, other factors must be primarily responsible for the inability to move the fingers independently. Muscle Nerve 28: 614–622, 2003
The peripheral nerve complications of human immunodeficiency virus (HIV) infection
Authors: Brew B. J.
Published: October 2003

Peripheral nerve complications occurring in patients with human immunodeficiency virus (HIV) infection are frequent and challenging. This review discusses these various complications according to the degree of advancement of HIV disease. Particular emphasis is placed upon emerging causes of neuropathy found in the context of HIV disease, such as infection with hepatitis C and human T‐lymphotropic virus type I, as well as neuropathies related to antiretroviral medications. Muscle Nerve 28: 542–552, 2003
Irreversible Markov processes for phylogenetic models
Authors: Bohl Erich , Lancaster Peter
Published: October 2003

A frequently used model in phylogenetics uses a discrete Markov process to model molecular drift as a cause of evolutionary diversification. Predictions are often based on eigenvalue computations which, we argue, only make sense if the process is reversible. Since there is no evidence (to our knowledge) to support the reversible nature of the process, a re‐examination is made of the model and necessary algorithms with emphasis on irreversible processes. The paper includes careful discussion of the underlying Markov processes, careful distinction between the properties of reversible and irreversible processes (including earlier widely accepted analysis) all in the language of linear algebra, a new least squares approach to data adjustments, and numerical examples. Copyright © 2003 John Wiley & Sons, Ltd.
Nested tetrahedral grids and strengthened C.B.S. inequality
Authors: Blaheta Radim
Published: October 2003

The paper deals with nested two‐level decompositions of 3D domains into tetrahedra and the corresponding spaces of continuous piecewise linear finite element (FE) functions. The decomposition of the fine grid FE space into the coarse grid FE space and its complement can be used for the construction of various multi‐level iterative methods and preconditioners, which are efficient for the finite element solution of boundary value problems (BVP) in the considered domains. The constant in the strengthened Cauchy–Bunyakowski–Schwarz (C.B.S.) inequality for the coarse grid FE space and its complement determines the efficiency of these multi‐level methods and preconditioners. From this reason, this constant is investigated in this paper for the case of BVP with anisotropic Laplacian or elasticity operators. Special emphasis is given on getting universal estimates of the C.B.S. inequality constant, which are valid for all kinds of physical or discretization anisotropy. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical validation of solutions of saddle point matrix equations
Authors: Chen Xiaojun , Hashimoto Kouji
Published: October 2003

A numerical validation method for verifying the accuracy of approximate solutions of saddle point matrix equations is presented and analysed. The method only requires iterative solutions of two symmetric positive definite linear systems. Moreover, it is shown that preconditioning can be used to improve the error bounds. The method is illustrated by several examples derived from mixed finite element discretization of the Stokes equations. Preliminary numerical results indicate that the method is efficient. Copyright © 2003 John Wiley & Sons, Ltd.
Theory and numerics of geometrically non‐linear open system mechanics
Authors: Kuhl E. , Steinmann P.
Published: October 2003

The present contribution aims at deriving a general theoretical and numerical framework for open system thermodynamics. The balance equations for open systems differ from the classical balance equations by additional terms arising from possible local changes in mass. In contrast to existing formulations, these changes not only originate from additional mass sources or sinks but also from a possible in‐ or outflux of matter. Constitutive equations for the mass source and the mass flux are discussed for the particular model problem of bone remodelling in hard tissue mechanics. Particular emphasis is dedicated to the spatial discretization of the coupled system of the balance of mass and momentum. To this end we suggest a geometrically non‐linear monolithic finite element based solution technique introducing the density and the deformation map as primary unknowns. It is supplemented by the consistent linearization of the governing equations. The resulting algorithm is validated qualitatively for classical examples from structural mechanics as well as for biomechanical applications with particular focus on the functional adaption of bones. It turns out that, owing to the additional incorporation of the mass flux, the proposed model is able to simulate size effects typically encountered in microstructural materials such as open‐pored cellular solids, e.g. bones. Copyright © 2003 John Wiley & Sons, Ltd.
Parallel multipole implementation of the generalized Helmholtz decomposition for solving viscous flow problems
Authors: Brown Mary J. , Mammoli Andrea A. , Ingber Marc S.
Published: October 2003

The evaluation of a domain integral is the dominant bottleneck in the numerical solution of viscous flow problems by vorticity methods, which otherwise demonstrate distinct advantages over primitive variable methods. By applying a Barnes–Hut multipole acceleration technique, the operation count for the integration is reduced from O(N2) to O(NlogN), while the memory requirements are reduced from O(N2) to O(N). The algorithmic parameters that are necessary to achieve such scaling are described. The parallelization of the algorithm is crucial if the method is to be applied to realistic problems. A parallelization procedure which achieves almost perfect scaling is shown. Finally, numerical experiments on a driven cavity benchmark problem are performed. The actual increase in performance and reduction in storage requirements match theoretical predictions well, and the scalability of the procedure is very good. Copyright © 2003 John Wiley Sons, Ltd.
Analysis of 3D problems using a new enhanced strain hexahedral element
Authors: Areias P. M. A. , César de Sá J. M. A. , António C. A. Conceição , Fernandes A. A.
Published: October 2003

The now classical enhanced strain technique, employed with success for more than 10 years in solid, both 2D and 3D and shell finite elements, is here explored in a versatile 3D low‐order element which is identified as HIS. The quest for accurate results in a wide range of problems, from solid analysis including near‐incompressibility to the analysis of locking‐prone beam and shell bending problems leads to a general 3D element. This element, put here to test in various contexts, is found to be suitable in the analysis of both linear problems and general non‐linear problems including finite strain plasticity. The formulation is based on the enrichment of the deformation gradient and approximations to the shape function material derivatives. Both the equilibrium equations and their variation are completely exposed and deduced, from which internal forces and consistent tangent stiffness follow. A stabilizing term is included, in a simple and natural form. Two sets of examples are detailed: the accuracy tests in the linear elastic regime and several finite strain tests. Some examples involve finite strain plasticity. In both sets the element behaves very well, as is illustrated in numerous examples. Copyright © 2003 John Wiley & Sons, Ltd.
An empirical evaluation of school‐based prevention programs that involve parents
Authors: Shepard Jon , Carlson John S.
Published: October 2003

The purpose of this review article is to provide education professionals with an overview of the current state of research in the area of school‐based prevention programs that involve parents in project objectives and methods. Prevention programs utilizing home‐school collaborative efforts cited within the literature were reviewed in the context of criteria espoused as demonstrating empirical support (Chambless et al., 1998; Lonigan, Elbert, & Bennett Johnson, 1998). To examine the state of the literature, 20 school‐based prevention programs that involved parents and were published between 1989 and 2001 were reviewed. Characteristics related to best practices in home–school collaboration (Christenson, Rounds, & Franklin, 1992). Parent involvement and methodological rigor are examined. A brief review of programs meeting “well‐established” and “probably efficacious” criteria are presented and discussed within the context of future research and practice related to meaningfully involving parents in school‐based prevention programs. © 2003 Wiley Periodicals, Inc. Psychol Schs 40: 641–656, 2003.
Relaxation and guided imagery: A school‐based intervention for children with asthma
Authors: Peck Heather L. , Bray Melissa A. , Kehle Thomas J.
Published: October 2003

Asthma, a disease of the respiratory system, is the most common chronic medical condition among children. School‐aged children with asthma evidence increased absenteeism, decreased school performance, restriction of various activities, poor peer relationships, and emotional and behavioral difficulties. Asthma can be triggered and exacerbated by emotions and stress, and therefore, it has been treated with psychological interventions. Relaxation and guided imagery (RGI), an intervention based on the theoretical position that the mind and body interact in determining health, has been shown to be effective in improving mental and physical health outcomes with a myriad of medical conditions, yet it has not been adequately studied with childhood asthma. This investigation analyzed the effect of RGI on lung function [forced expiratory volume in 1 second (FEV1) and forced expiratory flow 25–75 (FEF25–75)] and anxiety by employing a multiple baseline design across four middle school students with asthma. With the introduction of the intervention, it was found that FEV1 improved and anxiety decreased in all students. FEF25–75 improved in three of the four participants. The effect sizes for the four participants ranged from −0.98 to −1.88 for FEV1, 0.20 to −1.93 for FEF25–75, and 2.19 to 4.06 for anxiety. © 2003 Wiley Periodicals, Inc. Psychol Schs 40: 657–675, 2003.
Does rational persuasion influence potential consultees?
Authors: Truscott Stephen D. , Richardson Robert D. , Cohen Celina , Frank Alicia , Palmeri Deanna
Published: October 2003

Success in collaborative school‐based consultation depends on whether teachers implement interventions suggested by consultants. In business literature, Rational Persuasion (RP) has been identified as one potentially effective way to influence consultee perceptions about proposed interventions. RP includes intervention information, why it is important to decide to use the intervention, and potential objections to the intervention with arguments against those objections. The influence of these RP elements on potential school‐based consultees has not been studied. This preliminary analog study investigated whether presenting RP importance and objections for behavioral interventions influenced teachers' ratings of acceptability, effectiveness, and commitment‐to‐implement. Participants included 71 teachers enrolled in graduate education courses. The within‐subject design included three video vignettes of each of three conditions for three different behavioral interventions (total of nine possible videos, three presented to each group). Results suggest that the influence of RP on acceptability, perceived effectiveness, and commitment‐to‐implement ratings was inconsistent. Implications for research and practice are discussed. © 2003 Wiley Periodicals, Inc. Psychol Schs 40: 627–640, 2003.
Effect of Scale and Confinement on Gap Tests for Liquid Explosives
Authors: Jetté François‐Xavier , Yoshinaka Akio C. , Higgins Andrew J. , Zhang Fan
Published: October 2003

The factors influencing initiation of detonation in gap tests for liquid explosives are investigated experimentally. A calibrated donor charge (nitromethane) and PMMA attenuator disk arrangement are used to transmit shocks of known strength (2–10 GPa) into a test explosive of nitromethane sensitized with 5% diethylenetriamine. The test explosive is contained in capsules of different wall materials (PVC, Teflon, aluminum), and the dimensions of the charges vary from 25 mm to 100 mm in diameter. For the small‐scale charges, the presence of the confining wall of the test capsule is seen to have a pronounced effect on the detonation initiation. Certain wall materials (PVC, Teflon) exhibit a multi‐valued critical gap thickness, meaning that a weaker shock may result in initiation while a stronger shock does not. The effect of the wall materials could not be correlated with their acoustic or shock impedance, and the only way to eliminate these effects was to make the diameter of the test charge larger than the donor charge. When the size of the donor charge was increased, the critical pressure required for initiation decreased. These results could be correlated to “ideal” shock initiation experiments that use flyer plates as shock sources assuming that lateral rarefactions quench detonation initiation if they reach the central axis of the charge before the onset of detonation is complete.
Modelling Powder Compaction and Mixture Laws
Authors: Lamy Peggy , Brunet Luc , Erre René , Stempfer Berthe
Published: October 2003

The purpose of this paper is related to the improvement of the manufacturing processes of pyrotechnic compositions by determining the relative influence of physical properties on the compressibility and the cohesion. The Heckel‐Gonthier four parameter model is used to assess the powder compressibility. This relationship is generally applied to the compression of pharmaceutical powders, but we show a good correlation with the behaviour of pyrotechnic compositions. The compact cohesion is assessed by the cohesion index and the breaking resistance. This study demonstrates that the mean diameter, generally used as a parameter to describe the particle size, is less reliable than the dispersion index. This approach makes it possible to formulate mixing behaviour laws that can reduce the required number of experiments to assess a new composition.