bluuebunny/crossref_metadata_2025 huggingface dataset:
Retardation effect of 1,1,4,4‐tetraphenyl‐2‐tetrazene in the radical polymerization of methyl methacrylate
Authors: Sugiyama Kazuo , Oda Tetsuo , Maeshima Toshihisa
Published: April 2003

The decomposition of 1,1,4,4‐tetraphenyl‐2‐tetrazene (TPT) was carried out in four aprotic solvents [acetonitrile, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and benezene]. ΔH≠ was found to decrease with increasing polarity of the solvent. The effect of TPT on the polymerization of methyl methacrylate (MMA) was also studied in the same solvents. TPT was found to be a retarder for the radical polymerization of MMA. The induction period is affected by the polarity of the medium. In addition, the chain‐transfer constant of TPT (CTPT) was calculated to be 5,40, 4,00, 2, 78, and 3, 96 for the polymerization of MMA in acetonitrile, DMSO, DMF, and benzene, respectively. The transition state of the chain‐transfer reaction seems to be influenced by the polarity of the solvent.
Concentration dependence of the dielectric behavior of poly(2‐methyl‐1‐pentene sulfone) in benzene solution
Authors: Araki Kazuo , Imamura Yoshio
Published: April 2003

Dielectric measurements over a wide frequency range (30 Hz to 3 MHz) were made on solutions of poly(2‐methyl‐1‐pentene sulfone) (PMPS) in benzene at various polymer mass fractions up to 40 wt.‐%. The dielectric relaxation time increased linearly with increasing polymer concentration. A breaking point in the plot of the relaxation time against the polymer concentration appeared at a critical polymer concentration. The dielectric behavior below and above the critical polymer concentration was interpreted on the basis of the theory of free volume effect. The observed dielectric relaxation time was analyzed by Fröhlich's theory, assuming two limiting relaxation times, τ1 and τ2. The lower limit, τ1, which corresponds to the segmental motion, was independent of the polymer concentration above the critical polymer concentration, but in contrast, the upper relaxation time corresponding to the motion of the molecule as a whole, τ2, depended strongly on the polymer concentration.
Quantitative analyse der selbstassoziation von hämoglobinmolekülen anhand der konzentrationsabhängigkeit der spektren
Authors: Burkhard Oswald , Barnikol Wolfgang K. R.
Published: April 2003

The dependence of the spectrum of oxygenated hemoglobin (Hb) on the Hb concentration was measured and it was found that Hb solutions do not obey Lambert‐Beer's law. The absorption coefficient depends clearly on the Hb concentration. As all external parameters were kept constant except Hb concentration, the only way to explain our result is to assume that Hb molecules undergo self association and that this self association is reflected in the behaviour of the absorption coefficient. To get parameters which are suited to describe the self association of Hb molecules, two models were used. The first model is based on the idea that Hb associates according to the following equation: Hb + Hb ⇌ (Hb)2. Hb represents a single Hb molecule (consisting of two α‐and two β‐chains) and (Hb)2 a complex of two Hb molecules. The second, more complicated model, takes into account higher associates of Hb molecules (like (Hb)3, (Hb)4, . . .). By using a least square fitting, it was possible to match experimental data and theoretical curves. Furthermore it became evident that at Hb concentrations, which are of physiological relevance, about 90% of the Hb molecules are involved in self association. The second model revealed that at those Hb concentrations there is a considerable portion of complexes which are composed of 10 or more Hb molecules.
Propylene polymerization on titanium‐magnesium catalysts determination of the number of active centers and propagation rate constants
Authors: Bukatov Gennadii D. , Shepelev Sergei H. , Zakharov Vladimir A. , Sergeev Sergei A. , Yermakov Yurii I.
Published: April 2003

By use of the quenching technique with 14CO and 14CO2 the number of active centers and the propagation rate constants (kp) were determined for the propylene polymerization on different titanium‐magnesium catalysts in the presence and absence of an organoaluminium cocatalyst. The kp values at 70°C were found to be 500–1000 1·mol−1·s−1, which were confirmed by independent data of molecular mass measurements of the isotatic polymer after a short polymerization time (5 s). Similar isotactic and atactic kpvalues were found. The maximum number of active centers for supported titanium‐magnesium catalysts can reach about 10% of the titanium content in the catalyst. The kp values of ethylene polymerization on catalysts active without an organoaluminium cocatalyst were also determined (≈ 104 l·mol−1·s−1 at 70°C).
Determination of unsaturated end groups in low molecular weight poly(vinyl chloride) by 1H NMR spectroscopy of the hydroxyphenyl substituted product
Authors: Bǎrboiu Virgil , Robilǎ Gabriela , Buruianǎ Emil , Caraculacu Adrian
Published: April 2003

Poly(vinyl chloride) of low molecular weight (the fraction extracted with a hexane/acetone mixture (vol.‐ratio 3:2)) was substituted by hydroxyphenyl groups and then analyzed by 1H NMR spectroscopy. It was established that the 1H NMR spectra of hydroxyphenyl substituted poly(vinyl chloride) prepared by removal of HCl, allows to determine the number of unsaturated end groups and to distinguish between the structures CHClCH2CHCHCH2Cl and CH2CHClCHCHCH2Cl, and even between their trans and cis forms. In addition the 1H NMR spectra of hydroxyphenyl substituted poly(vinyl chloride) prepared without removal of HCl allow to determine the total number of unsaturated end groups.
Über polyarylenalkenylene und polyheteroarylenaklenylene, 12. Synthesen und charakterisierung von poly(thieno[2,3‐b]thiophen‐2,5‐diylvinylenarylenvinylen)en, poly(thieno[3,2‐b]thiophen‐2,5‐diylvinylenarylenvinylen)en und einigen modellverbindungen
Authors: Koßmehl Gerhard , Beimling Peter , Manacke George
Published: April 2003

From Wittig‐reactions of thieno[2,3‐b]thiophene‐2,5‐dicarboxaldehyde (1) and thieno‐[3,2‐b]thiophene‐2,5‐carboxaldehyde (4) with “mono‐and bis Wittig‐salts” of the benzene and thiophene series two series of isomeric poly(thienothiophene‐2,5‐diylvinylenearylenevinylene)s 3a—c and 5a—c, and some model compounds 7a—c and 8a—c were obtained. Wittig‐reacaldehyde (11) with “mono‐and bis‐Wittig‐salts” gave two series more of model compounds 10a—c, 12a—c, 13a, c, 14a, c. The structure of all compounds were confirmed by elemental analyses, IR, and electronic spectra, and those of the model compounds additionally by mass spectra, and in case of sufficient solubility by 1 H NMR spectra. The electrical conductivities of all compounds and the thermooxidative degradation of the polymers were investigated.
Characterization of furfuryl alcohol oligomers by 1H and 13C NMR spectroscopy
Authors: Fawcett Allan Herbert , Dadamba Wilfred
Published: April 2003

The characterisation of the oligomers of furfuryl alcohol was performed using 13C NMR spectroscopy and high resolution 1H NMR spectroscopy. A shift parameter scheme for the 13C shifts of the furan ring was devised and utilised for the assignment of the shifts of the oligomers. An analysis of the chemical composition of several furfuryl alcohol resings produced with different catalysts was performed with the aid of the assignments.
Study of step‐growth polymerizations using epoxy‐carboxy reaction, 1. Study of the epoxy‐carboxy reaction on models in solvents of low or medium dielectric constants
Authors: Madec Pierre‐Jean , Maréchal Ernest
Published: April 2003

Due to its importance in the field of block‐polycondensation and of chemical modification, we carried out an extensive study of the epoxy‐carboxy reaction on models. This papier is related to the reaction of benzoic acid with 1‐phenoxy‐2,3‐epoxypropane in the presence of a basic catalyst, N,N‐dimethyldodecylamine. It is carried out in low polar solvents (xylene, chlorobenzene, and o‐dichlorobenzene); essential kinetic parameters are reported. From studies carried out under stoichiometric or non‐stoichiometric conditions a general rate equation (υ = k [acid]0.5 [epoxy] [amine]) is obtained. Kinetic relations are the same, no matter what the catalyst is: dimethyldodecylammonium benzoate or free amine. From these kinetic data it results that the overall mechanism involves two steps.
Study of step‐growth polymerizations using epoxy‐carboxy reaction, 3. General analysis of the results obtained on models in various solvents
Authors: Madec Pierre‐Jean , Maréchal Ernest
Published: April 2003

A global analysis of the kinetic results relating to a model reaction of epoxy‐carboxy polycondensation is reported. The model is the reaction of benzoic acid with 1‐phenoxy‐2,3‐epoxypropane carried out in the presence of N,N‐dimethyldodecylamine as catalyst. The hypothesis concerning the contribution of two competitive ractions as suggested in the two preceding parts of this series is subjected to a mathematical treatement. This allowed the determination of the rate constants of each reaction. All the kinetic characteristics obtained in a broad range of experimental conditions fit the reaction scheme, which is described in detail. Exceptions are found for borderline cases. The rate constants of the reaction of the classical dependence on dielectric constant and temperature. Activation parameters of each reaction are reported.
Kinetics of polymerization of alkyl cyanoacrylates by tertiary amines and phosphines
Authors: Pepper David Charles , Ryan Bernard
Published: April 2003

A theory of the overall rates and molecular weights in slowly‐initiated, non‐terminated polymerizations is developed for cases of complex initiation of alkyl cyanoacrylates by tertiary amines. Results with butyl cyanoacrylate (BCA) in the solvent THF, and five different amines (chiefly pyridine and derivatives) show widely differing overall rates. The theory, with the aid of previously determined initiation rate constants, permits the same value for the propagation rate constant (kp) to be derived in all cases, corroborated by values derived from the simpler overall kinetics of polymerisation initiated by Ph3P. The rate constant kp shows very slight temperature dependence, less than one order of magnitude between 20 and −80°C.
Glass transition and melting temperatures of random copolyesters of poly(ethylene terephthalate) with p‐hydroxybenzoic acid, 3
Authors: Balachandar M. , Balakrishnan T. , Kothandaraman H.
Published: April 2003

The glass transition temperature of the random copolyesters of poly(ethylene terephthalate) and p‐hydroxybenzoic acid prepared by molten state polycondensation increases with increasing concentration of p‐oxybenzoate units (oxy‐1,4‐phenylenecarbonyl units). The observed values of the glass transition temperature are compared with the values predicted from various empirical equations on the Tg's of copolymers and the concave Tg composition curve is explained in terms of the internal stiffening effect of the p‐oxybenzoate unit. The melting temperatures of the copolyesters vary with composition and show an eutectic phase diagram. The melting temperature and enthalpy of fusion of the homopolymer of p‐hydroxybenzoic acid were determined making use of Flory's equation on the melting point of a copolymer.
Reactions of macro‐ions resulting in the formation of block and graft copolymers. Grafting of polymers with aromatic groups
Authors: Kučera Miloslav , Salajka Zdeněk , Majerová Karla , Navrátil Milan
Published: April 2003

Grafting of poly(oxytetramethylene) (polytetrahydrofuran) chains containing living oxonium end groups onto polymers containing aromatic rings was investigated. The rate of grafting was found to be slow, but under favourable conditions several moles of polytetrahydrofuran can be grafted to one mole of polystryrene. Macrocations may also be grafted to the surface of in‐soluble polymers dispersed in a solution of grafting ions. This was proved by grafting living polytetrahydrofuran onto poly(phenylene oxide) or random poly(1‐butene‐co‐styrene). Macro‐cations can be prepared from an anionic living polymer via transformation of the growing centers. Thus, poly(dimethylsiloxane), whose original anionic centers were transformated into cationic ones, was grafted to polystyrene. Exchange reactions were found to take place in the living system on polytetrahydrofuran or poly(dimethylsiloxane) grafts, thus influencing their length. The graft copolymers are strong surfactants. Separation from their mixture with homo‐polymers by a repeated extraction of homopolymers with a solvent is difficult and sometimes impossible.
Molmassenverteilung und lösungszustand von linearen polyethylenen, 2. Vergleich von berechneten mit experimentell bestimmten streufunktionen
Authors: Böhm L. L. , Lanver U. , Lechner M. D. , Hertel P.
Published: April 2003

Scattering functions for linear polyethylenes were calculated, using different assumptions, and compared with experimentally determined scattering functions of the system polyethylene/decane. It is pointed out, that the polyethylene macromolecules in a good solvent can be treated as statistical coils with a non‐uniform expansion and a constant average expansion exponent ε and not as statistical coils with uniform expansion. Comparison of the experimentally determined and the calculated scattering functions yields a molar mass distribution of polyethylene which is in agreement with the results from GPC‐measurements within the limits of experimental error.
Morphology and properties of polybutadiene‐ and polyether‐polyurethane zwitterionomers
Authors: Yang Chang‐Zheng , Hwang Kirk K. S. , Cooper Stuart L.
Published: April 2003

Two series of polyurethane zwitterionomers based on 4,4′‐methylene‐di(phenyl isocyanate) (MDI), N‐methyl diethanolamine (MDEA)

Systematic IUPAC name: 2,2′‐(methylimino)diethanol.

, and either 1350 molecular weight hydroxyl terminated polybutadiene or 1000 molecular weight poly(tetramethylene oxide)

Systematic IUPAC name: poly(oxytetramethylene).

were synthesized. Zwitterionization was accomplished by quaternizing the tertiary amine of MDEA with 1,3‐pro‐panesultone. In Both series, IR analysis suggests that the sulfonate ion SO3− associates with the counter ion on the chain extender and the acidic hydrogen of the urethane linkage. Ammonium sulfonation shifts the soft segment Tg of polyether‐based material to lower temperatures suggesting that ionization improves microphase separation. The soft segment Tg of the polybutadiene system is unaffected by ionization. IR dichroism measurements show that with increasing ammonium sulfonation both the hard and soft segments in the polyether‐polyurethane zwitterionomers orient to a greater extent with deformation. In contrast, in the poly‐butadiene‐based zwitterionomers the orientability of the hard segment decreased with ionization while the soft segment showed significant chain alignment. Coupling the dichroism measurements to stress‐strain results suggests that the hard segment domains of the polyether‐polyurethane system possess more of an interconnected structure, while the polybutadiene‐poly‐urethane system contains hard segment domains which are largely isolated. The formation of different morphologies in the two systems of zwitterionomers may be due to the different interdomain surface tensions.
Structural studies on molecular complexes of polyethers, 1. Urea‐ethylene oxide oligomer complexes
Authors: Suehiro Kazuaki , Nagano Yoshiaki
Published: April 2003

Complexes of urea with ethylene oxide oligomeric mixtures were investigated by X‐ray diffraction, IR‐absorption, and differential scanning calorimetry. A new crystal modification (Form II) was found for the complexes of urea with ethylene oxide oligomers whose number average molecular weights ranged from 400 to 1000. The Form II complex has a tetragonal unit cell (a = 7,30 Å, c = 19,51 Å), containing eight molecules of urea and eight ethylene oxide units. This modification is metastable. A solid‐solid transition to the conventional Form I crystal occurs on heating up to a temperature between the melting points of both forms. The dependence of the melting points of these complexes on the molecular weight of the oligomers was also studied.
Synthèse et caractérisation de réticulats‐modèle de polyisoprène
Authors: Lutz Pierre , Herz Jean E. , Rempp Paul
Published: April 2003

Polyisoprene model‐networks were synthesized by an “endlinking” process: an efficient bifunctional initiator, developped recently, was used to polymerize isoprene to a bifunctional “living” precursor polymer. The living sites were subsequently used to initiate the polymerization of a small amount of divinylbenzene, whereby a model network is formed, the elastic chains of which are of known length and low polydispersity. Equilibrium swelling data and stretching moduli were measured. Unfortunately no reproducible results could be obtained on unswollen networks. Qualitative experience was obtained on the degree of association of lithium organic sites in benzene solution: the value of 2 is to be considered as plausible.
Crystallinity of methylene‐oxyethylene‐methylene triblock oligomers derived from pentadeca(ethylene glycol)
Authors: Teo Hoon Hong , Swales Timothy G. E. , Domszy Roman C. , Heatley Frank , Booth Colin
Published: April 2003

Block oligomers of the general formula CH3(CH2)nO[CH2CH2O]15(CH2)nCH3 where n + 1 = nc = 1 to 18 and 21 have been prepared. Both the oxyethylene and the methylene blocks are monodisperse. Examination of their crystallinity (by differential scanning calorimetry (DSC); X‐ray scattering; IR, Raman, and 1H NMR spectroscopy) shows two important structures I and II.

I: 3 ⩽ nc ⩽ 6: oxyethylene blocks crystalline, methylene blocks non‐crystalline;

II: 13 ⩽ nc ⩽ 18: oxyethylene and methylene blocks crystalline.

Samples with nc = 1 or 2 crystallise essentially as poly(oxyethylene). Samples with 7 ⩽ nc ⩽ 12 are intermediate in structure between I and II. Structure II has 7/2 helical oxyethylene blocks in high density crystalline layers, with a structure closely related to that of monoclinic poly(oxyethylene), and planar zig‐zag methylene blocks in low density crystalline layers. The oxyethylene helices are normal to the lamella end‐planes, or almost so, and the methylene planar zig‐zags are tilted. The enthalpies of fusion of the type II block oligomers show an even‐odd effect. There is evidence of chain folding in the block oligomer with nc = 21.
Viscosity and intrinsic viscosity/temperature relationships for dilute solutions of poly(2‐biphenylyl methacrylate) and poly(4‐biphenylyl methacrylate)
Authors: Hadjichristidis Nikos
Published: April 2003

The actual viscosity η and the intrinsic viscosity [η] of six fractions of poly(2‐biphenylyl methacrylate) {poly[1‐(2‐biphenylyloxycarbonyl)‐1‐methylethylene], (POB); weight average molecular weight M̄w: 4,0 · 104 to 1,42 · 106, polydispersity ratio M̄w/M̄n ≈ 1,4} and of three fractions of poly(4‐biphenylyl methacrylate) {poly[1‐(4‐biphenylyloxycarbonyl)‐1‐methyl‐ethylene], (PPB); M̄w : 8,1 · 104 to 5,3 · 105, M̄w/M̄n ∼ 1,4} in benzene have been determined at different temperatures between 20 and 60°C. Values of the apparent activation energy of the viscous flow Q and the pre‐exponential term A in the expression η = A · exp[Q/(RT)] have been obtained. Q varies with M̄w and concentration c according to Moore's equation: Q = Q0 + Ke · M · c, where Q0 refers to the solvent and Ke depends on polymer and solvent. The numerical value of Ke for POB and PPB is 1,6 · 10−4 (6,7 · 10−4) and ‐8,1 · 10−4 cal · dl · g−1 (‐3,4 · 10−3 J · dl · g−1), resp. From all polymethacrylates studied POB is the only polymer with a positive Ke value. The positive value of Ke for POB may possibly be related to the more extended form of POB in benzene and also may be connected, at least partly, with its low flexibility. The temperature coefficient of the unperturbed dimensions dln〈r02〉/dT for POB estimated from the viscosity data using the Burchard‐Stockmayer‐Fixman relation, is 0,14 · 10−3, much lower than for PPB (2,3 · 10−3 between 22 and 40°C and 1,2 · 10−3 between 40 and 60°C). The positive values of dln〈r02〉/dT indicate that extended conformations of these polymers in benzene must be associated with higher energies.
New experiments concerning the mechanism of solid‐state photopolymerization of 2,5‐distyrylpyrazine
Authors: Braun Hans‐Georg , Wegner Gerhard
Published: April 2003

The photoinduced formation of oligomers in single crystals of 2,5‐distyrylpyrazine (DSP) was investigated by X‐ray and electron diffraction techniques and also by gel permeation chromatography (GPC). The DSP crystals were characterized for the presence and nature of dislocations by dark‐field images and etch‐pit studies. Small angle grain boundaries were identified to be the prominent feature, but in general the crystals were highly perfect. A correlation between the sites of the defects and the formation of the photoproduct could not be detected. The oligomers formed in a solid‐solution under appropriate irradiation conditions. Thus, DSP oligomer of number average degree of polymerization P̄n = 3,2 in macroscopic single crystal texture was obtained for the first time using a laser light source at 478 nm. Deterioration of the single crystal texture of DSP usually observed during photopolymerization is explained as being caused by inhomogeneous light distribution which in turn causes an inhomogeneous product distribution with accumulation of large strain fields. These can be made visible by the multiplication of etch pits. Phase separation between oligomer and polymer is observed on further irradiation of the oligomer single crystals. The oligomer phase seems to play the role of an intermediate in the photopolymerization of DSP at wavelengths λ < 400 nm. The molecular weight distribution of the oligomers was studied by GPC. The data are only compatible with the assumption that the rate constant of dimerization is higher than that for the addition of a monomer to an already existing oligomer.
Synthèses de polysiloxanes organofonctionnels, 2. Les poly[(halométhylméthyl)siloxane]s et leurs modèles
Authors: Reyx Danièle , Guillaume Pierre
Published: April 2003

Heterogeneous linear polysiloxanes containing oxy[chloromethyl (or iodométhyl)méthyl]silanediyle, oxy(diméthyl)silanediyle, and oxy(methylvinyl)silanediyle units were prepared. Heterogeneously chloromethylated polysiloxanes were obtained by rearrangement of siloxane linkages in corresponding mixtures of polysiloxanes and oligocyclosiloxanes. Heterogeneously iodomethylated polysiloxanes were obtained by chlorine displacement in the previously chloromethylated polysiloxanes. The preparation of heterogeneously bromomethylated polysiloxanes is more difficult than that of the chloro and iodo derivatives. Their properties intervene between those of the chloromethylated and the iodomethylated products. Chlorine displacement leading to the bromomethylated derivatives, was studied on the bis(chloromethylated) disiloxane.
Synthesis, characterization, and kinetics of thermal degradation of copolyesters
Authors: Ponnusamy Ettigounder , Balakrishnan Thaikannu , Kothandaraman Harimurthi
Published: April 2003

Random terephthalate copolyesters of ethylene glycol and propylene glycol (1,2‐propanediol) with various contents of monomeric units of the diols were prepared by transesterification. The actual content of each monomeric unit in the copolyester was determined by 1H NMR. The thermal behaviour of the copolyesters was studied by differential thermal analysis. Kinetic order, heat and entropy of fusion, and activation energy for the thermal degradation of the copolyesters, were obtained.
High conversion copolymerization, 1. Kinetics of the copolymerization of styrene and maleic anhydride
Authors: Bartoň Jaroslav , Vašková Viera , Juraničová Viera , Mlynárová Mária
Published: April 2003

The copolymerization of styrene (S) with maleic anhydride (MAn) in 1,4‐dioxane at 60, 70 and 80°C up to high conversion (≈ 98%) was followed by differential scanning calorimetry. The rate of copolymerization increases up to 20 – 40% conversion of both monomers and then gradually decreases to zero. The increase in the copolymerization rate is more pronounced for equimolar ratios [S]/[MAn] as compared to ratios with an excess of S. For a given mole ratio of S and MAn the copolymerization rate in 1,4‐dioxane is higher at higher total monomer concentrations and/or at higher temperatures. The heat of copolymerization is 81,6 kj · mol−1 for the equimolar [S]/[MAn] mixture. For mixtures with [S]/[MAn] > 1 the heat of reaction is between 70 and 80 kj · mol−1. The limitingconversion of styrene for [S]/[MAn] = 1 is about 98%, and for [S]/[MAn] > 1 it is a function of the [S]/[MAn] ratio. Assuming exclusively the formation of an alternating S/MAn copolymer the following relation is derived.

for the ratio of the apparent rate constants of propagation k̄p, and termination k̄</t.
Synthèse de macromères à base de chlorures de vinyle et de vinylidène au moyen de télomères
Authors: Boutevin Bernard , Piétrasanta Yves , Taha Mohamed , Sarraf Tarek El
Published: April 2003

New macromers 4, 8, and 10, containing ester, alcohol, or acid functions, were prepared starting with vinyl chloride (CV) or vinylidene dichloride (CV2). The telomer 1, resulting from CV2 and CCI4 was telomerized with allyl acetate and the product was transformed into the acrylate 4 by hydrolysis of the reaction product and subsequent esterification. Macromers 8 and 10 were prepared from CV by radical telomerization with thioglycolic acid (7) and 2‐mercaptoethanol (9), respectively. Reactive double bonds were introduced into these macromers by reaction with acrylic acid, Vinyl chloroformate, methacryloyl chloride, or 2,3‐epoxypropyle methacrylate, leading to new macromers 12, 13, 14, and 15, respectively.
Propylene polymerization on titanium‐magnesium catalysts, 2. Study of catalyst formation
Authors: Sergeev Sergei A. , Bukatov Gennadii D. , Zakharov Vladimir A. , Moroz Ella M.
Published: April 2003

Formation of a supported titanium‐magnesium catalyst for propylene polymerization was studied using highly dispersed magnesium chloride (surface area ca. 100 m2/g). By means of X‐ray diffraction, chemical analysis, and measurement of the surface area it was found that: i) interaction of ethyl benzoate (EB) with MgCl2 results in the formation of a compound EBEB·MgCl2 (1:1 by mole); ii) milling of products nEB · MgCl2 (n < 1) results in the decomposition of the lattice of the compound EB · MgCl2 and in the decrease of the size of MgCl2 crystallites; iii) treatment of the product nEB · MgCl2 with titanium tetrachloride results in the removal of a part of EB in the form of an EB·TiCl4, complex from the support, the decomposition of the lattice of the compound EB·MgCi2 an increase of the size of the MgCl2 crystallites, and a sharp increase of the surface area; iv) a small amount of EB (EB/MgCl2 = 0,1 to 0,2) considerably increases the isoptacticity of polypropylene. The high activity of catalysts prepared by milling is due to a higher surface area of these catalysts compared to unmilled samples.
Polyarylenealkenylenes and polyheteroarylenealkenylenes, 15. Syntheses and electrical conductivities of alkoxylated poly(2,5‐thiophenediylvinylene‐1,4‐phenylenevinylene)s
Authors: Koßmehl Gerhard , Samandari Massoud
Published: April 2003

Poly(2,5‐thiophenediylvinylene‐1,4‐phenylenevinylene)s with one or two alkoxy groups as side chains of variable lenghts (8a, b and 9a – c) were prepared by Wittig‐reaction of 2,5‐thiophenedicarbaldehyde with the corresponding “bis(Wittig‐salt)s”. To establish the structure of the polymers, model compounds 10 and 11 were synthesized. Charge‐transfer (donor‐acceptor) complexes were prepared by iodine doping of the polyvinylenes 8 and 9. The room temperature conductivity, σ298K, of the original polymers was found to be increased by several orders of magnitude upon doping. It was not possible to remove all the iodine from the charge‐transfer complexes in vacuum.
Alternating copolymers of vinyl chloride and isobutylene with alkyl acrylates: Synthesis with an ethylaluminium dichloride catalyst and 13C NMR characterization
Authors: Florjańczyk Zbigniew , Kauran Witold , Langwald Norbert , Sitkowska Jadwiga
Published: April 2003

Copolymerizations of alkyl acrylates (alkyl: ethyl, butyl, isobutyl, tert‐butyl, and 2‐ethylhexyl) with vinyl chloride and isobutylene in the presence of catalytic amounts of C2H5AlCl2 were studied. Depending on the inonomer feed, equimolar or acrylate‐rich copolymers were obtained in most of these reactions. Only tert‐butyl acrylate does not produce any copolymers, due to its decomposition under the action of C2H5AICI2. 2‐Ethylhexyl acrylate forms with isobutylene only acrylate‐rich copolymers. By 13C NMR spectroscopy it could be shown that equimolar copolymers have an alternation structure.
Kristallisation und schmelzverhalten von fraktionen verzweigten polyethylens, 1. Darstellung und charakterisierung der fraktionen
Authors: Maderek Eugeniusz , Strobl Gert R.
Published: April 2003

A branched polyethylene with broad molecular weight distribution was separated into a series of fractions by fractional precipitation from dilute solution. The fractions were characterized by viscometric and density measurements, IR‐spectroscopy and calorimetry. The methyl group content and the density turned out as largely constant. Molecular weight effects show up in the melting behaviour. The main range of melting and the end of the melting curve shift to lower temperatures with decreasing molecular weight. Compared to the overall extension of the melting range these shifts are small. One has to conclude that polydispersity gives only a minor contribution to the broadening of the melting range, partial melting being mainly caused by the branches.
Aqueous gel permeation chromatography of electrolytes and polyelectrolytes, 2. Donnan salt exclusion effect
Authors: Kadokura Satoru , Miyamoto Takeaki , Inagaki Hiroshi
Published: April 2003

The salt exclusion of electrolytes and polyelectrolytes in aqueous GPC was investigated theoretically and experimentally, in order to elucidate the feasibility of GPC as a technique for measuring the Donnan salt exclusion parameter, Γ¯, of polyelectrolytes. Three simple salts different in the valency of the anion, i.e., sodium chloride, sodium sulfate and naphthalene‐1,3,6‐trisulfonic acid trisodium salt, were eluted with aqueous NaNO3 solution on a Sephadex G‐10 gel column. The experimental results were analyzed in terms of the Donnan equilibrium established on the gel, and the Γ¯ value of these simple salts was evaluated. It was found that the Γ¯ value from GPC was in good agreement with the theoretical value of 1/2 for an ideal case, showing that the colligative properties of electrolytes and polyelectrolytes such as Γ¯ can be accurately investigated by means of GPC. GPC experiments on the Donnan salt exclusion were further carried out for the heparin‐NaCl system by using a Sephadex G‐25 gel column. From the experimental data, the Γ¯ value of heparin was estimated.
Instantaneous shape and relative orientation of model chains as a function of their intermolecular separation
Authors: Olaj Oskar Friedrich , Zifferer Gerhard
Published: April 2003

Ensembles of self avoiding five‐way cubic lattice chains consisting of 50 segments were generated for athermal and θ‐conditions, and the instantaneous shape and the orientation of each chain were characterized by evaluation of the squared three axes L, L, and L of its equivalent ellipsoid and their orientation in space; the variation of these quantities within allowed pair configurations (relative to their values in isolated chains) was studied as a function of the separation R between the two centers of gravity of the two members of all isolated chain pairs, which could be formed from the ensemble. For small R (when R is smaller than the average radius of gyration of isolated chains 〈s2〉1/20) L, the squared longest axis of the equivalent ellipsoid, is strongly expanded for athermal as well as for θ‐conditions, while the squared two shortes axes, L and L, are much less enlarged or even decreased in this range, thus emphasizing the prolate character of the ellipsoids on approaching R = 0. Furthermore the angle between the two L3‐axes of the two chains forming a compatible pair is remarkably increased at vanishing separation (by ca. 10° in athermal systems and by ca. 7° in θ‐systems). Thus, chains forming compatible pairs at R = 0 not only have to increase their dimensions (as already described earlier) but also have to change their instantaneous shape (towards a still higher anisotropy of the equivalent ellipsoids) and their relative orientation (the longest axes L3 tend towards orthogonal orientation) in order to relieve the thermodynamic stress which they impose on each other. By integration of the effects over all separations the concentration dependence of all quantities was determined in the limit of zero concentration. Most quantities are subject to an appreciable, non‐zero concentration dependence. Contrary to most theoretical predictions this is also true for θ‐conditions.
Perméabilité des matériaux copolymères: modélisation moléculaire, 1. Essai d'application d'un modèle de percolation
Authors: Guyot Alain , d'Auriac Jean‐Christian Angles
Published: April 2003

The diffusion of small molecules across a copolymer membrane is simulated as a site percolation problem, assuming that in copolymers consisting of A and B units, B are active sites and A are inactive sites. Molecular modeling is conducted in three steps: (i) generation of a copolymer by a Monte‐Carlo process, taking into account the sequence distribution of the copolymer, (ii) organization of the material through a slipping process of the linear chain towards maximization of the dipolar interactions between the A units, and (iii) the site percolation itself. A quantitative application is carried out for acrylonitrile/methyl acrylate copolymers. The results show that the influence of the slipping process upon the internal organization of the material is most important.
Strategic planning in a turbulent environment: evidence from the oil majors
Authors: Grant Robert M.
Published: April 2003

The long‐running debate between the ‘rational design’ and ‘emergent process’ schools of strategy formation has involved caricatures of firms' strategic planning processes, but little empirical evidence of whether and how companies plan. Despite the presumption that environmental turbulence renders conventional strategic planning all but impossible, the evidence from the corporate sector suggests that reports of the demise of strategic planning are greatly exaggerated. The goal of this paper is to fill this empirical gap by describing the characteristics of the strategic planning systems of multinational, multibusiness companies faced with volatile, unpredictable business environments. In‐depth case studies of the planning systems of eight of the world's largest oil companies identified fundamental changes in the nature and role of strategic planning since the end of the 1970s. The findings point to a possible reconciliation of ‘design’ and ‘process’ approaches to strategy formulation. The study pointed to a process of planned emergence in which strategic planning systems provided a mechanism for coordinating decentralized strategy formulation within a structure of demanding performance targets and clear corporate guidelines. The study shows that these planning systems fostered adaptation and responsiveness, but showed limited innovation and analytical sophistication. Copyright © 2003 John Wiley & Sons, Ltd.
Prenatal ultrasound diagnosis and management of body stalk anomaly: analysis of nine singleton and two multiple pregnancies
Authors: Smrcek J. M. , Germer U. , Krokowski M. , Berg C. , Krapp M. , Geipel A. , Gembruch U.
Published: April 2003

Objective

To determine prenatal ultrasonographic features and management of fetuses with body stalk syndrome in singleton and multiple gestations.

Methods

In a retrospective chart analysis we reviewed all cases with body stalk anomaly diagnosed in our prenatal unit between 1994 and 2001. During this time period we adopted a uniform approach to the investigation of cases of body stalk anomaly, including amniocentesis or chorionic villus sampling (CVS) for fetal karyotyping. A general schematic sonographic examination was performed to search for fetal abnormalities and was followed by detailed two‐dimensional and color‐coded Doppler echocardiography. Nuchal translucency (NT) measurements were performed before 14 weeks of gestation. Postmortem examinations of fetuses were performed following termination by induction with prostaglandin.

Results

Eleven fetuses with body stalk anomaly were diagnosed, including two multiple pregnancies complicated by discordant body stalk anomaly. The typical ultrasonographic features were a major abdominal wall defect, severe kyphoscoliosis, limb abnormalities, neural tube defects, and a malformed, short umbilical cord with a single artery. None of the fetuses demonstrated craniofacial defects. All placentae that were examined showed evidence of persistence of the extra‐embryonic celomic cavity. NT measurements were abnormal in all cases. Fetal karyotyping was normal in ten cases. In one case CVS showed a mosaic trisomy 2 (46,XX/47,XX,+ 2). Selective fetocide was performed in one trichorionic–triamniotic triplet pregnancy in early gestation, which was followed by normal development of the remaining healthy dichorionic–diamniotic twins. In a monochorionic–diamniotic twin pregnancy with one affected fetus ultrasound surveillance showed the normal development of the unaffected twin.

Conclusions

We present a large series of body stalk anomaly, including multiple gestations, with thoraco‐ and/or abdominoplacental attachment and without craniofacial defects. This specific phenotype may be explained by embryonic maldevelopment. The typical features of body stalk anomaly can be detected by ultrasound by the end of the first trimester, which is important for patient management. Consequently, this anomaly should be distinguished from other fetal abdominal wall defects. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.
Elterliche Ungleichbehandlung in Kindheit und Jugend aus der Perspektive des mittleren Erwachsenenalters
Authors: Ferring Dieter , Boll Thomas , Filipp Sigrun-Heide
Published: April 2003

Zusammenfassung. Ausgehend von der Annahme, dass eine mit Blick auf Kindheit und Jugend erinnerte elterliche Ungleichbehandlung in späteren Lebensphasen noch bedeutsam sein kann, werden deren Struktur und Ausmaß bei Personen im mittleren Erwachsenenalter analysiert. Darüber hinaus werden equity-theoretische Vorhersagen über die potentiellen Folgen für die Beziehungsqualität zu Geschwister und Eltern überprüft. In einer Fragebogenstudie sollten N = 1208 Frauen und Männer im Alter zwischen 40 und 54 Jahren einschätzen, wie häufig sie selbst sowie ein ausgewähltes Geschwister während ihres Aufwachsens bestimmte Formen der elterlichen Behandlung durch Mutter und Vater erfahren haben. Faktorenanalysen der Differenzscores (Proband minus Geschwister) zeigten, dass in der retrospektiven Bewertung des Verhaltens beider Elternpersonen zwischen der differentiellen väterlichen resp. mütterlichen Unterstützung und Strenge unterschieden wurde. Über hierarchische Clusteranalysen der Skalenwerte konnte mit Blick auf das väterliche Verhalten eine Gruppe der “Gleichbehandelten“ (80.4% der Stichprobe), der “Benachteiligten“ (13.2%) und der “Bevorzugten“ (6.4%) ermittelt werden; hinsichtlich des mütterlichen Verhaltens zeigte sich ein Cluster der “Gleichbehandelten“ (87%) und der “Benachteiligten“ (13%). Zusammenhangsanalysen der Clustergruppenzugehörigkeit mit Indikatoren der aktuellen Beziehungsqualität zu den Eltern und dem Geschwister zeigten, dass die “Benachteiligten“ gegenüber den “Gleichbehandelten“ und “Bevorzugten“ eine geringere Verbundenheit/Nähe und Unterstützungsbereitschaft gegenüber Eltern und Geschwister berichteten.
The European Origins of “Personality Psychology”
Authors: Lombardo Giovanni Pietro , Foschi Renato
Published: April 2003

The year 1937 is remembered by historians of psychology as the year of the birth of personality psychology. This discipline emerged in the United States thanks to the work of several psychologists who came to organize its methodology and fundamental notions. Gordon Allport is the most important representative of this change within scientific psychology. This paper analyzes the continuity between “before” and “after” the foundation of the discipline and locates several important points of reference for the initial scientific research on personality. The aim of this essay is to reconstruct historically the contribution of some important lines of “European” psychological research that have had a remarkable influence both from the theoretical and methodological points of view on the scientific foundation of personality psychology studies in its modern developments.
Therapeutic vaccine for acute and chronic motor neuron diseases: Implications for amyotrophic lateral sclerosis
Authors: Angelov D. N. , Waibel S. , Guntinas-Lichius O. , Lenzen M. , Neiss W. F. , Tomov T. L. , Yoles E. , Kipnis J. , Schori H. , Reuter A. , Ludolph A. , Schwartz M.
Published: April 2003

Therapeutic vaccination with Copaxone (glatiramer acetate, Cop-1) protects motor neurons against acute and chronic degenerative conditions. In acute degeneration after facial nerve axotomy, the number of surviving motor neurons was almost two times higher in Cop-1-vaccinated mice than in nonvaccinated mice, or in mice injected with PBS emulsified in complete Freund's adjuvant (
P
< 0.05). In mice that express the mutant human gene Cu/Zn superoxide dismutase G93A (SOD1), and therefore simulate the chronic human motor neuron disease amyotrophic lateral sclerosis, Cop-1 vaccination prolonged life span compared to untreated matched controls, from 211 ± 7 days (
n
= 15) to 263 ± 8 days (
n
= 14;
P
< 0.0001). Our studies show that vaccination significantly improved motor activity. In line with the experimentally based concept of protective autoimmunity, these findings suggest that Cop-1 vaccination boosts the local immune response needed to combat destructive self-compounds associated with motor neuron death. Its differential action in CNS autoimmune diseases and neurodegenerative disorders, depending on the regimen used, allows its use as a therapy for either condition. Daily administration of Cop-1 is an approved treatment for multiple sclerosis. The protocol for non-autoimmune neurodegenerative diseases such as amyotrophic lateral sclerosis, remains to be established by future studies.
The high variance of AMPA receptor- and NMDA receptor-mediated responses at single hippocampal synapses: Evidence for multiquantal release
Authors: Conti Rossella , Lisman John
Published: April 2003

Most of our knowledge about transmission at central synapses has been obtained by studying populations of synapses, but some important properties of synapses can be determined only by studying them individually. An important issue is whether a presynaptic action potential causes, at most, a single vesicle to be released, or whether multiquantal transmission is possible. Previous work in the CA1 region has shown that the response to stimulation of a single axon can be highly variable, apparently because it is composed of a variable number of quantal elements (≈5 pA in amplitude). These quantal events have a low coefficient of variation (CV). Because the number of synaptic contacts involved is not known, the response could be because of uniquantal transmission at a varying number of synapses, or to multliquantal transmission at a single synapse. The former predicts that the CV at individual synapses should be small. We have used optical methods to measure the
N
-methyl-
d
-aspartate receptor-mediated Ca
2+
elevation at single active synapses. Our main finding is that the amplitude of nonfailure responses could be highly variable, having a CV as large as 0.63. In one fortuitous experiment, the optically studied synapse was the only active synapse, and we could therefore measure both its
N
-methyl-
d
-aspartate (NMDA) receptor- and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated signals. At this synapse, both signals varied over a 10-fold range and were highly correlated. These results strongly suggest that transmission at single CA1 synapses can be multiquantal. Furthermore, the individual quantal response is very far from saturation, allowing the effective summation of many quanta. The existence of multiquantal release has important implications for defining synaptic strength and understanding the mechanisms of synaptic plasticity.
Membrane potential fluorescence: A rapid and highly sensitive assay for nicotinic receptor channel function
Authors: Fitch Richard W. , Xiao Yingxian , Kellar Kenneth J. , Daly John W.
Published: April 2003

Seven cell lines expressing native and transfected nicotinic receptor subtypes were evaluated functionally by using fluorescent assays based on membrane potential and calcium dynamics with “no-wash” dye systems. Both assays provided the same rank orders of potency for (±)-epibatidine, 2
S
-(−)-nicotine, 7
R
,9
S
-(−)-cytisine, and 1,1-dimethyl-4-phenylpiperazinium in a cell line expressing rat α3β4 receptors. Nicotinic antagonists mecamylamine and dihydro-β-erythroidine inhibited responses in both assays. Both agonist and antagonist activity were assessed within the same experiment. Agonists seemed more potent in the membrane potential assay than in the calcium assay, whereas the converse was true for antagonists. The membrane potential assay afforded robust responses in K-177 cells expressing human α4β2 receptors, in IMR-32 and SH-SY5Y cells expressing human ganglionic receptors, and in TE-671 cells expressing human neuromuscular receptors. These lines gave weak to modest calcium responses. Moreover, membrane potential responses were obtained in cell lines expressing rat α4β2 and α4β4 receptors, which were devoid of calcium responses. Thus, membrane potential serves as a sensitive measure of nicotinic activity, and the resulting depolarization may be as important as calcium in cell signaling.
T cell leukemia I oncogene expression depends on the presence of Epstein–Barr virus in the virus- carrying Burkitt lymphoma lines
Authors: Kiss Csaba , Nishikawa Jun , Takada Kenzo , Trivedi Pankaj , Klein George , Szekely Laszlo
Published: April 2003

We used a modified subtractive suppression hybridization to identify cellular genes that show altered expression in Burkitt lymphomas (BLs) in the presence of Epstein–Barr virus (EBV). Comparison of the gene expression patterns of an EBV-negative clone of the originally EBV-positive BL line Akata, with its NeoR-EBV derivative, revealed a significant difference in the expression of the T cell leukemia 1 oncogene (TCL-1). Subsequent expression studies showed that the original EBV-positive Akata line and the EBV-reconstituted derivative expressed high levels of TCL-1, whereas the EBV-negative variant showed only a low level of expression. Two other independently established EBV-positive BLs (Mutu and OMA) that have also thrown off EBV showed a similar decrease in TCL-1 expression after virus loss. Reinfection with NeoR-EBV restored the TCL-1 expression levels in the EBV loss variants to as high a level as the originally EBV-positive lines. High-resolution immunostaining showed that TCL-1 was localized in both the cytoplasm and the nucleus. Our findings suggest that high expression of TCL-1 is necessary for the development of the BL phenotype. In view of the fact that germinal center B cells, regarded as the progenitors of BL, do not express TCL-1, we suggest that constitutive expression of this oncogene occurs by genetic or epigenetic changes in the EBV-negative BLs. In the originally EBV-positive BLs, the ability of the virus to switch on TCL-1 expression would obviate this need.