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  • Articles  (133,531)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 645-647 
    ISSN: 1557-1947
    Keywords: EuBaSrCu3O7−δ superconductor ; Ca doping ; orthorhombicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The effect of Ca doping in EuBaSrCu3O7−δ has been investigated by X-ray diffraction, ac susceptibility, and electrical resistivity measurements. X-Ray diffraction analyses of the samples showed that up to 30 at.% Ca can be substituted for Sr in EuBaSrCu3O7−δ, which has orthorhombic symmetry. The orthorhombicity decreases with increase inx, in EuBaSr1−xCax Cu3O7−δ, the material becoming tetragonal atx=0.2. Ac susceptibility and dc electrical resistivity measurements as function of temperature from 10 to 300 K showed that the superconducting transition temperatureT c decreases monotonically from 84 to 75K as the Ca concentrationx increases from 0.0 to 0.3 The decrease inT c can be attributed to the structural change taking place in EuBaSrCu3O7 as a consequence of replacement of Sr by Ca.
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  • 2
    ISSN: 1557-1947
    Keywords: Superconductivity ; research opportunities ; state of the art
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract This report surveys the considerable progress made over the last five years—such as the marketing of superconducting quantum interference devices (SQUIDs), cellular wireless filter systems, and high current leads—and assesses needs and opportunities in the areas of fundamental science, materials development, thin film and device applications, and wire and bulk applications. It examines the challenges facing high-temperature superconductivity: from the need to understand the mechanism of high-temperature superconductivity and the unusual “normal” state to the need for new instrumentation for material characterization. Advances in thin film and bulk materials are reviewed, and obstacles impeding the commercialization of HTS materials are examined.
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  • 3
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    Journal of superconductivity and novel magnetism 10 (1997), S. 649-655 
    ISSN: 1557-1947
    Keywords: Single crystal of Bi2Sr2CaCu2O8 ; high-resolution electron microscopy ; low-temperature electron diffraction ; lattice anomaly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract High-resolution electron microscopy of a Bi2Sr2CaCu2O8 (Bi2212) single crystal prepared by the floating zone method shows that the single crystal is of high quality; there is no intergrowth faulting in the layered structure along thec-axis. Low-temperature selected area diffraction and convergent beam electron diffraction (CBED) studies of this high-quality single crystal show that there is no detectable change for both the point group symmetry of the basic structure and the modulated structure from room temperature to about 15 K. However, a lattice anomaly around 215 K was suggested by measuring the temperature dependence of the ratio between the cross-point distances of the HOLZ lines in high-index CBED patterns. The presence of the lattice anomaly was further confirmed by low-temperature X-ray diffraction.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 623-643 
    ISSN: 1557-1947
    Keywords: Superconductivity ; crystal field ; rare earth ; relaxation ; gap symmetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Neutron spectroscopy is a powerful tool to determine unambiguously the crystal-field (CF) potential in rare-earth (R) based high-T c superconducting materials. This technique provides detailed information on the electronic ground state of the R ions which is important to understand the thermodynamic magnetic properties as well as the observed coexistence between superconductivity and long-range magnetic ordering of the R ion sublattice at low temperatures. Moreover, the decay of the antiferromagnetic state of the parent compound as well as the evolution of the superconducting state upon doping can be directly and quantitatively monitored. It is found that the observed CF spectra separate into different local components whose spectral weights distinctly depend on the doping level, i.e., there is clear experimental evidence for cluster formation. The onset of superconductivity can be shown to result from percolation which means that the superconductivity is an inhomogeneous materials property. Since the linewidths of CF transitions directly probe the static electronic susceptibility, we discuss temperature-dependent experiments of the relaxation rate of CF excitations in both optimally doped and underdoped regimes. It is shown that there is clear evidence for the opening of an electronic gap in the normal state of underdoped superconductors. Furthermore, the relaxation behavior appears to be extremely dependent upon the energy at which the static susceptibility is being probed. The main observed features can be reproduced by considering a strongly anisotropic gap function.
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  • 5
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    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 663-668 
    ISSN: 1557-1947
    Keywords: Thermal diffusivity ; acoustic plasmons ; cobalt substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The thermal diffusivity κ(T) of the cobalt-substituted sintered YBCO system, YBa2Cu3−x Co x O7∮δ (x=0.0, 0.1), has been measured to, investigate, effects of atomic substitution and charge carrier concentration on the thermal diffusion processes. The thermal diffusivity was measured in the temperature range 35–300 K, using the transient-plane-source technique. The results show that, belowT c , the κ(T) values of the doped (x=0.1), samples are lower than the corresponding values for the undoped (x=0.0) samples. This may be due to the difference in the free-charge carrier concentrations of the two samples. A decoupling between the conducting Cu−O planes as a result, of Co-doping in the chain sites may contribute to additional decrease in the thermal diffusivity of the doped sample. An attempt was made to explain the rise in the thermal diffusivity belowT c by adopting a recent theoretical model based on the existence of weakly damped collective electron excitations of Bose type, with acoustic dispersion relation, (acoustic plasmons) inside the superconducting gap.
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  • 6
    ISSN: 1557-1947
    Keywords: High-T c superconductors ; order parameter ; Josephson junctions ; Josephson critical current ; pair symmetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An intrinsic gap depression at the superconductor-insulator interface due to the very short value of the coherence length in high-T c superconductors [HTS] is considered in the framework of a mixed (s+id)-wave pair symmetry for the order parameter ranging from pures to pured-wave. This gap depression acts as the main physical agent causing the relevant reduction ofI c (T)R n (T) values with respect to BCS expectations in HTS SIS Josephson junctions. Good agreement with various experimental data is obtained with both pures-wave and pured-wave symmetries of the order parameter, but with amounts of gap depression depending on the pair symmetry adopted. Regardless of the apir symmetry considered, these results prove the importance of the surface order-parameter depression in the correct interpretation of theI c (T)R n (T) data in HTS SIS junctions. In the case of a planar YBCO-based junction the use of the de Gennes condition allowed us to tentatively obtain an upper limit for the amount ofd-wave present in the gap of YBCO.
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  • 7
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    Springer
    Journal of superconductivity and novel magnetism 10 (1997), S. 669-672 
    ISSN: 1557-1947
    Keywords: Equation of state ; bulk modulus ; cohesive energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In the present paper the expression of cohesive energy and the bulk modulus as a function of volume are formulated for high-T c copper oxide superconductors. The model employed consists of long-range electrostatic Coulomb interaction and short-range overlap repulsion. The short-range overlap potential is considered in the Born-Landé inverse power form. The model, parameters of the Born-Landé model are calculated from the equilibrium condition and data of bulk modulus at room temperature. The computed values of pressure derivatives of bulk modulus atP=0 and the values of bulk modulus are found to be in very close agreement with experimental values for high-T c copper oxide and their nonsuperconducting parent compounds. It is also found that the quantity ΔU/U(V o) of these compounds increases with increasing hydrostistic pressure.
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  • 8
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    Journal of superconductivity and novel magnetism 10 (1997), S. 673-675 
    ISSN: 1557-1947
    Keywords: Cuprates ; van Hove singularity ; pseudo-gap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Several experimental features in the normal state of cuprates have been interpreted using a “pseudogap”. We show that these results may be explained by the band structure of the CuO2 planes in the metallic region, which exhibits, saddle points (van Hove singularities).
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  • 9
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    Polymer bulletin 36 (1996), S. 745-752 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Acrylamide/itaconic acid (AAm/IA) hydrogels prepared by irradiating with γ radiation were used in experiments on the adsorption of some cationic dyes such as basic red 9 (BR 9), basic green 4 (BG 4), cresyl violet (CV), and basic blue 20 (BB 20). Adsorption of the cationic dyes onto AAm/IA hydrogels is studied by batch adsorption technique. In the experiments of the adsorption, Langmiur type adsorption in the Giles classification system was found. Monolayer coverages for AAm/IA hydrogel-dye systems were calculated by using B point method. Adsorption studies indicated that monolayer coverages of AAm/IA hydrogel by these dyes were increased with following order; BB 20〉CV〉BR9〉BG 4.
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  • 10
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Styrene was polymerized using combined systems of diphenylzinc, Ph2Zn, and metallocene compounds activated by methylaluminoxane, MAO. From the various metallocenes employed bis (indenyl) zirconium dichloride, Ind2ZrCl2, [isopropyl (cyclopentadienyl) (1-fluorenyl)] zirconiumdichloride, i-Pr (Flu) (Cp) ZrCl2, and bis (cyclopentadienyl) titanium dichloride, Cp2TiCl2, produced the larger amounts of polymer. Ph2Zn-Cp2TiCl2-MAO system gave polystyrene, PSt, whose DSC analysis indicated a major endotherm peak at 256°C. A butanone insoluble fraction of the polymer was separated from the crude PSt. The proportion of insoluble polymer depends on the metallocene employed and on the conversion to polymer.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 37 (1996), S. 29-33 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Polymerization of propylene was carried out at 0°C in the presence of methyl methacrylate(MMA) or ethyl benzoate(EB) using rac-Et(Ind)2ZrMe2 or rac-Me2Si(Ind)2ZrMe2/Ph3CB(C6F5)4 as catalyst, which resulted in highly isotactic poly(propylene) with [mmmm]〉98%, Tm=160–161°C and very few 1,3- or 2,1 regioirregular units. With the use of an achiral zirconocene Cp2ZrMe2, a polymer with Tm=139°C was resulted as well. Base on these experimental fact that the zirconocene can form a C1-symmetrical complex with a Lewis base.
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  • 12
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    Polymer bulletin 37 (1996), S. 21-28 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary By using γ-butyrolactone (γ-BL) as the reaction media, highly active catalysts--light rare earth chloride-epoxidy-γ--BL-for the solution polymerization of ε-caprolactone, have been obtained for the first time. With these catalyst, PCL with molecular weight as his as 40x104(Mv) can be prepared at 60°C for 1.5 hr. The amount of epoxide in catalyst solution, catalyst aging temperature and time affect the catalyst activity significantly. The mechanism study shows that in γ-BL, the weakening of Ln-Cl bonds by the donation of coordinated γ-BL with Ln3+ and the homogenous effect promote the reaction between light rare earth chloride and epoxide. The produced rare earth alkoxide initiates CL polymerization via a ‘coordination-insertion’ mechanism with Acyl-oxygen bond cleavage.
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  • 13
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Triethoxysilane groups were covalently attached onto the surface of ethylene-vinyl alcohol (EVOH) copolymer film via a urethane linkage through reaction between the hydroxyl groups in EVOH and 3-isocyanatopropyltriethoxysilane in the presence of dibutyltin dilaurate as catalyst. This reaction was confirmed by ATR-IR and XPS analysis. XPS results also indicated that this reaction was not surface sensitive and the modified layer was at least 40 Å in depth. The modified film samples were further reacted with tetramethoxysilane (TMOS) for partial hydrolysis and condensation and XPS results showed a significant increase in the contents of oxygen and silicone on the surface which confirmed the above reaction.
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  • 14
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    Polymer bulletin 37 (1996), S. 59-65 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The title monomer was synthesized from the corresponding aldehyde via a Wittig reaction. The monomer was polymerized using free radical initiation and its high field 1H- and 13C-NMR spectra were recorded. When analyzed in terms of stereochemistry the spectra showed poly(6-vinyl-1,4-benzodioxane) is an atactic polymer when synthesized via free radical initiation.
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  • 15
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A resin containing 4-vinylpyridine and 2-acrylamidoglycolic acid was synthesized by radical polymerization with subsequent crosslinking by N,N′-methylene-bis-acrylamide. The resin was characterized by elemental analyses and FT-IR spectroscopy. The ability of this resin as well as both crosslinked homopolymers to bind Cu(II), Fe(II), Fe(III) and U(VI) was studied at different pHs depending on the metal ion. From pH=2 U(VI) was sorbed above 96% from an aqueous solution of 1.0 g/L. A dual sorption mechanism to U(VI) depending on the pH is suggested. The elution of the metal ions from the loaded resins was assayed with H2SO4 and Na2CO3.
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  • 16
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    Polymer bulletin 37 (1996), S. 199-206 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The photopolymerization of four analogous monomers: 2,2′-thiobisethanol diacrylate and its dimethacrylate plus 2,2′-oxybisethanol diacrylate and its dimethacrylate has been studied by isothermal differential scanning calorimetry (DSC) over a range of incident light intensities. The results obtained prove that the sulfide group accelerates polymerization both in the presence and absence of oxygen and enhances the conversion. The light intensity exponents for each monomer were determined and the mechanism of termination was discussed. The intensity exponents of sulfur-containing monomers are lower than their corresponding oxygen analogues, pointing to a greater participation of the bimolecular termination during their polymerization.
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  • 17
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Photoinitiated methyl methacrylate-ethylene glycol dimethacrylate (MMA/EGDM) copolymerization has been investigated in toluene at a monomer concentration of 35 w/v %. Diphenyl-2,4,6-trimethylbenzoylphosphine oxide (DPTPO) was used as a photoinitiator at 0.3 wt% concentration. Monomer conversions and the size distribution of the polymer molecules were measured as a function of the reaction time up to the onset of macrogelation. Compared to the photoinitiators benzoin or benzoin derivatives, gelation process proceeds at much higher rates in the presence of DPTPO. The size distribution curves obtained by size-exclusion chromatography (SEC) change from monomodal to bimodal distributions as the polymerization proceeds. Strongly bimodal SEC curves were obtained in the close vicinity of the gel point. This finding confirms the coagulation type gelation mechanism of compact primary particles. It also indicates that the present gelation theories cannot describe the structure dependent kinetics of free-radical crosslinking copolymerization.
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  • 18
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary FT-Raman spectroscopy of commercial amorphous and crystalline nylon 6–12 filaments subjected to various γ-radiation doses are presented. The results show that a difference exists in the interaction of γ-radiation with these polyamides, depending on the crystallinity which can be evaluated by measuring the CH-stretching/CH-bending Raman band intensity ratio as a function of applied γ-dose.
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  • 19
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Solid-state 13C NMR spectroscopy involving magic angle spinning (MAS) techniques with and without cross-polarization was employed for interaction studies in natural rubber (NR)/EVA and NR/mercapto-modified EVA (EVASH) blends. From arrayed of variable contact time spectra, the proton T1ϱ values were determined at short contact times to analyze the EVA or EVASH domains and longer contact times to investigate the interactions in the NR domains. Substantial changes have been observed when dicumyl peroxide was employed as curing agent in NR/EVASH and NR/EVA/EVASH blends.
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  • 20
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    Polymer bulletin 37 (1996), S. 229-235 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thermogravimetric analysis (TGA) has been shown to be a useful technique to determine the content of starch and other components that are usually present in blends of starch with synthetic polymers. However, some of these blends are composed of elements with an important superposition in their temperature degradation range. In these cases interpretation of the TGA results becomes quite difficult and usually important errors are committed in the determination of blend composition. We present here a method to improve the accuracy of the interpretation of TGA data. The analysis was developed to study blends containing starch, an ethylene-vinyl alcohol copolymer, and water plus glycerin as plasticizers. Using this procedure it is possible to predict blend composition with an error less than 3%, even when there is an appreciable superposition between the temperature degradation range of starch and poly(ethylene-co-vinyl alcohol). As the proposed method of analysis is quite general it may be extended to be used with other types of blends that give thermograms with similar characteristics to those described in this paper.
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  • 21
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The synthesis of polysulfone-polydimethylsiloxane (PSU-PDMS)linear block copolymers has been carried out in solution by condensation of chloro-terminated bisphenol A, diphenylsulfone and α, ω-di (hydrogensilyl)-polydimethylsiloxane with Si−C bond. 1H-NMR spectra of the block copolymers allow the estimation of siloxane and polysulfone ratio. The molecular weight of the polysulfone and polysiloxane oligomers and the block copolymers was determined by GPC. Thermogravimetric analysis indicates a thermal stability of block copolymers up to 400°C and allows estimation of the process activation energy. Microphase separation of the block copolymers was observed by differential scanning calorimetry (DSC).
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  • 22
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Aim of this work was to study the effectiveness of a novel oxazoline-functionalized polypropylene as a compatibilizer for PP/PBT and PP/PA6 blends. This polypropylene-based compatibilizer mixes well with the polypropylene and is capable of reacting with the carboxylic and amine end groups of PBT and PA6. Significant improvements in blend toughness were achieved without reduction in strength and stiffness. These effects were related to stabilized morphology of finely dispersed minor phase well attached to the matrix. The enhanced interfacial interactions between the two phases, in particular at high PBT content were evidenced by increased melt viscosity.
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  • 23
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    Polymer bulletin 37 (1996), S. 361-367 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The polyamides with aromatic rings in the main chain were synthesized by the solution polymerization of 4,4′-diphenylmethane diisocyanate and aliphatic dicarboxylic acid in the presence of catalyst. The thermal properties and the miscibility behaviours with polyamide-6,6 of these aromatic polyamides were studied. The aromatic polyamides synthesized with one kind of dicarboxylic acid had typical thermal properties of crystalline polymers, whereas those synthesized with the mixtures of dicarboxylic acids were not easily crystallized. The observed miscibility behaviours showed some differences from those predicted by binary interaction model.
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  • 24
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    Polymer bulletin 37 (1996), S. 369-376 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A series of aryl-aliphatic polyamides, copoly(4,4′-diaminobenzanilide-adipamide/2,6-naphthalamide)s, with feed mole ratios of adipic acid/2,6-naphthalene dicarboxylic acid of 1/9, 3/7, and 5/5 were synthesized. A new family of molecular composites based on the synthesized aryl-aliphatic polyamides and nylon 6 has been discovered. The molecular composites were found to have at least partial miscibility between aryl-aliphatic polyamides and nylon 6. Well-defined aryl-aliphatic polyamide microfibrils a few nanometers in diameter were observed in the molecular composites. 10 wt% aryl-aliphatic polyamide clearly promoted the toughness of nylon 6.
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  • 25
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    Polymer bulletin 37 (1996), S. 377-383 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A new type of coordination polyurethane was prepared by incorporating the transition metal ions into the pyridine containing thermoplastic polyurethane films. Then the metal ions dispersed in the polyurethane matrix were reduced by controlling the exposure of the metal sites to NaBH4 under mild condition. The reduction of the polyurethane metal complex films resulted in the production of amorphous ultrafine metal powders. The size of these powders was controlled by the content of the metal ions and the polarity of the polymer matrix. A polar polymer backbone and lower metal ion concentration favored to achieve a smaller particle. It was also found that the polymer chains prohibited the excessive aggregation of the metal atoms and have protective effect on the final metal powders.
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  • 26
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Crack-tip deformation has been investigated in pre-cracked samples of core-shell rubber particle modified epoxy resins with different degrees of crosslinking. Light cross linking resulted in cavitation of the modifier, the formation of croids and extensive crack-tip yielding, whereas these deformation mechanisms were suppressed at room T in highly crosslinked specimens. A zone of particle debonding was observed in these latter at high T, but this appeared detrimental to the toughness. Indeed it was possible to increase the toughness in this case by oxygen plasma treatment of the modifier particles.
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  • 27
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary An initiator for living free radical polymerization may be prepared by trapping the benzylic ethylbenzene radical with the stable 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) radical. The adduct, 2,2,6,6-tetramethyl-1-(1-phenethyloxy)piperidine (TMPEP), smoothly undergoes thermal fragmentation at temperatures approaching 140° C to afford an active carbon radical capable of initiating polymerization and a passive mediating nitroxyl radical to reversibly cap and preserve the propagating polymer chain.
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  • 28
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Association processes of D-fructose dehydrogenase (FDH) onto surfaces of liposomes which were composed of N-(5-dimethylamino-1-naphthalenesulfonyl)-L-α-dimyristoylphosphatidylethanolamide and L-α-dimyristoylphosphatidylcholine or L-α-dimyristoylphosphatidylglycerol (1:9) were investigated by the fluorescence stopped-flow technique. The association processes were divided into two relaxation processes: the faster process whose apparent rate constant monotonously increased with the concentration of FDH, and the slower process whose rate constant showed a saturation behavior. Taking the number of binding sites on the liposome surface into consideration, the corrected association rate constant of the faster process was 4.4% of the theoretical value for a binary collision, probably due to a disadvantageous surface-searching and dehydration processes on the liposome and protein surfaces. The Arrhenius plots of the rate constants both for the faster and slower steps showed a discontinuous change around the gel to liquid-crystal phase transition temperature of the liposomes. Strong influences of deformability of liposomes, and state of hydrating water molecules around polar heads, on the rate of association processes were suggested.
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  • 29
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    Polymer bulletin 37 (1996), S. 423-428 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Copolymers with 2-aceto-1,3-phenanthrenylene units in the chain have been directly prepared by Ru catalyzed step-growth copolymerization of 2-acetyl phenanthrene and α,ω-dienes such as 1,3-divinyltetramethyldisiloxane. Copolymers which incorporate 2-aceto-1,3-phenanthrenylene units possess higher TgS and increased thermal stability compared to analogous copolymers which have 2-aceto-5-phenyl-1,3-phenylene(biphenyl) or 2-aceto-1,3-phenylene units. Fluorescence spectra of these copolymers have been obtained.
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    ISSN: 1436-2449
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    Notes: Summary A new methodology is described for the synthesis of reactive polymers bearing triphenylphosphine dichloride groups by the use of triphosgene. These materials show high reactivity for the room temperature conversion of benzyl alcohol to benzyl chloride. In one hour, yields higher than 90% were achieved using reactive copolymers with up to 25 w% divinylbenzene (DVB). The functional groups can be easily and efficiently regenerated using 1.0 mol of triphosgene for every 2.6 moles of phosphine in the polymer. Preliminary results showed up to 40% conversion of benzyl alcohol in column reactions using regenerated polymers at 5 to 10 min contact times.
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  • 31
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The biosynthesis of poly (β-hydroxybutyrate) (PHB) byBacillus circulans was carried out through cultivation in nutrient broth in a single step. $$\overline {\text{M}} {\text{v}}$$ of polymer fractions soluble in chloroform were close to 2 x 105. IR,1H and13C NMR spectra of the isolated PHB were in agreement with the assumed structure of this poly-β-hydroxyester. NMR spectroscopy pointed out a high percentage of isotactic polymer, while differential scanning calorimetry showed that the PHB was crystalline.
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  • 32
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    Polymer bulletin 37 (1996), S. 437-442 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Graft copolymers of polyacrylonitrile (PAN) and poly(ethylene oxide) (PEO) were synthesized by radical copolymerization of acrylonitrile and methacrylate-headed poly(ethylene oxide) macromonomer. The macromonomer was prepared by reaction of methacryloyl chloride with PEO. The effects of solution concentration, initiator concentration and acrylonitrile/macromonomer molar ratio on the conversion, molecular weight and PEO branch content in the graft copolymer were studied. The graft copolymers were characterized by GPC, FTIR,13C-NMR and Kjeldhal method.
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  • 33
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    Polymer bulletin 37 (1996), S. 457-462 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The title vinyl thiophene monomer was synthesized by dehydration of the corresponding secondary alcohol. Free radical initiated copolymerizations with methyl methacrylate, styrene or isobutyl methacrylate were performed and the copolymer compositions were used in the calculation of reactivity ratios. The data was analyzed via a nonlinear least squares error-in-variables method. The 2,5-dimethyl-3-vinylthiophene was shown to have equal or slightly less reactivity than each of the monomers chosen as comonomers.
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  • 34
    ISSN: 1436-2449
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    Notes: Summary Alkylation of the methylene bridged tetrahydropyrimidine derivatives by chloromethylstyrene produces the bridged bis(4-vinylbenzyl)-1,4,5,6,-tetrahydropyrimidinium salts in high yields. Similar procedures are used to prepare 2-imidazolinium derivatives. The quaternary salts which support functional side groups of potential biomedical interest are characterized by means of spectroscopic methods. These monomers are readily polymerized free radically in solution of dimethyl formamide at moderate temperatures. The soluble and insoluble polymers containing 2-imidazolinium and 1,4,5,6-tetrahydropyrimidinium salts were found to exhibit antibacterial activites againstEscherichia coli.
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  • 35
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    Polymer bulletin 37 (1996), S. 463-468 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The parent polymer, poly(allylamine) as ligand polymer was employed to synthesize polychelates of heavy metal ions. The functional poly(allylamine) and its Ni(II), Co(II) and Cu(II) metal chelates were characterized by elemental analysis, FT-IR spectroscopy, TGA, and SEM. For the polychelates magnetic and conductivimetry studies were also carried out.
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  • 36
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    Polymer bulletin 37 (1996), S. 475-482 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A new chemically amplified polymeric imaging system based on polymers containingt-butylmalonate pendant groups has been demonstrated. Both the homopolymer of di-t-butyl (vinylbenzyl)benzylmalonate and its copolymer with styrene have been tested in coatings containing a photoacid generator. Imaging experiments confirm that the materials have very high sensitivities when exposed to UV radiation near 250nm.
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  • 37
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    Notes: Summary New pseudoaffinity chromatography supports were prepared and characterized from poly(sucrose acrylate) crosslinked with MDI or TDI and Cibacron Blue dye as ligand. Blue gels were useful in the retention of albumin and the results are reported.
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  • 38
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    Notes: Summary Copolymers of ethylene and 1-hexexe, 1-octene and 4-methyl-1-pentene were obtained using Et[In]2ZrCl2/MAO catalyst at various pressures. The increase of 1-hexene and 1-octene concentration in the feed increases catalyst activity(g/nZr.h.bar) and productivity(g/nZr.h). For 4-methyl-1-pentene the activity is independent on comonomer concentration. Increasing the ethylene pressure the productivity of the copolymerization increases and the activity shows a weak decay. Characterization of the copolymer shows that at higher pressure the cristallinity of the copolymers is higher due to lower comonomer incorporation. There is a good linear correlation of cristallinity with comonomer concentration in the feed for 1-hexene and 1-octene at a fixed pressure, but not for 4-methyl-1-pentene.
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  • 39
    ISSN: 1436-2449
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The present work deals with copolymerization of styrene (STY) and methyl methacrylate (MMA) catalysed by nickel acetylacetonate - Ni(acac) 2 , employing methylaluminoxane (MAO) as cocatalyst. This catalyst system presented low catalyst activities for STY homopolymerization and very high activities for MMA. It seems that the catalyst system based on Ni(acac) 2 /MAO is effective for the copolymerization of MMA and STY to give block copolymer but it also produced polystyrene and poly(methyl methacrylate) homopolymers. The polymers were characterized by 13 C NMR, GPC and FTIR. The polystyrene homopolymer was identified by IR and NMR analyses of the cyclohexane soluble fraction. The presence of absorption bands correspondent to carbonyl group and aromatic ring was observed in the IR spectrum of the acetic acid soluble part. This result is a clue that STY-MMA copolymer with low molecular weight was produced. The high molecular weight copolymer (acetic acid insoluble fraction) was also characterized by IR analysis which indicated the presence of characteristic absorption bands of carbonyl group and aromatic ring. These results were confirmed by 13 C NMR analysis.
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  • 40
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    Polymer bulletin 40 (1998), S. 555-562 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Four narrow-distribution samples of sodium hyaluronate with weight-average molecular weights M w of 3.8 × 103 to 1.1 × 104 in 0.02 and 0.1 M aqueous NaCl at 25°C have been studied by small-angle X-ray scattering. Data for their z-average radii of gyration 〈S2〉z 1/2 and particle scattering functions P(θ), together with previous 〈S2〉z data from light scattering for high molecular weights, are compared with relevant theories for the wormlike chain with or without excluded volume, using the parameters estimated previously from intrinsic viscosity ([η]) data. It is shown that for M w lower than 1.1 × 104, 〈S2〉z, P(θ), and [η] of the polysaccharide in the aqueous salts are all consistently explained by this model without excluded volume.
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  • 41
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    Notes: Summary Three new side chain liquid crystalline polythiiranes were prepared with new substituants on the mesogenic groups. Their thermotropic liquid crystalline behaviour was studied by the usual techniques (DSC, X-ray diffraction and polarized optical microscopy). Unlike the polyoxiranes described in the literature, the size of the terminal group has no influence on the nature of the mesophases of polythiiranes ; only slight changes of the transition temperatures were observed. In this series of polymers, a phase, denoted X, appeared at temperatures below the smectic E phase, and could not be identified by usual characterization techniques. An isothermal kinetic study for the smectic E / X phase transition resulted in an Avrami exponent close to 1, suggesting a one-dimensional ordering occurred during the transformation from the smectic phase. This result, combined with other observations, helped us to assign the X phase to the crystalline phase.
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  • 42
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    Polymer bulletin 40 (1998), S. 583-590 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Hybrid materials from Polyvinyl chloride (PVC) and titania were prepared using sol-gel technique. In-situ generation of titania network in the PVC matrix was carried out by introducing required amounts of tetrapropylorthotitanate (TPOT) followed by hydrolysis/condensation of TPOT in the matrix. Homogeneous and semi-transparent films were obtained by casting and solvent evaporation. Mechanical properties of these films up to 15 wt. % titania contents were studied. The results showed an increase in the Young's modulus, length at rupture and toughness of the unplasticised PVC. However, the tensile strength and stress at break point decreased with the addition of titania contents. Thermal stability of the material was studied using dehydrochlorination (DHCl) technique and thermogravimetric analysis. The PVC samples with small amount of titania were found to be more stable as compared with the pure PVC.
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  • 43
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    Notes: SUMMARY The sorption characteristics of benzene and cyclohexane vapours in the poly(urethane-urea) (PUU) with well defined structure were measured using an improved version of the Mc Bain's microbalance. The diffusion coefficients were calculated for the different vapour activities from the kinetics of solvent uptake, i.e. the sorption isotherms over time. Sorption and diffusion coefficients measured, showed a strong dependence of the applied vapour activity. The obtained transport parameters were discussed with regard to the polymer structure. Based on the sorption and diffusion data, the pervaporation performance of the PUU-based membrane in separation of the benzene/cyclohexane mixtures was predicted and compared with the experimental pervaporation characteristic.
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  • 44
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    Notes: Summary The polymerization of styrene with catalysts based on Ni(acac)2 supported on SiO2 and Al2O3 was investigated. Using catalysts based on MAO supported on silica, a highly isotactic polystyrene was obtained. Nevertheless, the Al2O3-supported catalyst can promote isospecific polymerization activated by common. alkyl aluminum compounds even by any prior support treatment with MAO.
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  • 45
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    Polymer bulletin 40 (1998), S. 701-706 
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    Notes: Summary A novel polymer having β,β-triketone unit in the main chain was prepared by polycondensation of triethylene glycol bis(p-butoxycarbonylphenyl) ether (1) with triethylene glycol bis(p-acetylacetophenyl) ether (4). The obtained polymer was soluble in CHCl3, DMF, and DMSO. The structure of the polymer was confirmed by 1H-NMR. Insoluble brownish yellow copper (II) chelate was obtained by adding a methanol solution of copper (II) acetate to a chloroform solution of the polymer. The IR analysis and the measurement of copper content by iodometric titration showed the quantitative formation of binuclear copper (II) complex.
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  • 46
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    Polymer bulletin 40 (1998), S. 715-720 
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    Notes: Summary Synthesis and polymerization behavior of 1-trimethylsiloxy- or 1-triphenylsiloxy-silacyclobutane derivatives were studied. These monomers gave polymers with reasonably high molecular weight by platinum catalyst like platinum 1,3-divinyl-1,1,3,3-tetramethyldisfloxane complex. Side-chain smectic, liquid crystalline polymer was obtained from 1-methyl-1-[3-{(4-cyanobiphenyl-4'-yl)oxy}propyl]dimethylsiloxysilacyclobutane. In the polymerization by butyllithium or phenyllithium, monomers corresponding to the amounts of the initiator were consumed, but no polymers were formed. Apparently, elimination of the trimethylsiloxy or triphenylsiloxy group occurred in the nucleophilic attack of the initiator or propagating species on the silicon atom of the monomer.
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  • 47
    ISSN: 1436-2449
    Keywords: (Keywords: lanthanocene; methylaluminoxane; polymerization; butadiene; isoprene; styrene.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The polymerization of butadiene(Bd), isoprene(Ip) and styrene(St) has been examined using the six catalyst systems composed of lanthanocene, (C5H9Cp)2NdCl(I), (C5H9Cp)2SmCl(II), (MeCp)2Sm OAr'(III), (Ind)2NdCl(IV), Me2Si(Ind)2NdCl(V) and (Flu)2NdCl(VI), and methylaluminoxane(MAO) respectively. All of them can be used to form the polyisoprene with molecular weights of 1 to 10 thousand and cis-1,4-unit contents of 41 to 47%. (I), (II) and (III) of them can be also used to form the polybutadiene with molecular weights of 10 to 20 thousand and cis-1,4-unit contents of 62 to 78%. In addition, the catalysts from (II) to (V) are still active for St polymerization and (II) of them gives a syndio -rich random polystyrene. It is noteworthy that (II) and (III) are active for homopolymerization of Bd, Ip and St in the same polymerization condition.
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  • 48
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    Polymer bulletin 40 (1998), S. 741-747 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this work, a series of 2,3-O-methylcellulose (MC) with different DS value were prepared. Its phase transition behavior in aqueous solution was studied in terms of DS value, concentration and molecular weight. The the following conclusions were obtained. (1) All the 2,3-O-MC samples show no sol-gel transition in aqueous solution despite the molecular weight. (2) No phase separation was observed for the 2,3-O-MCs with a DS value lower than 1.0, even when the temperature was raised to 95°C. (3) The precipitation temperature is surprisingly different between 2,3-O-MCs. and other MCs possessing comparable total DS value. (4) The precipitation temperature of 2,3-O-MCs depends on the molecular weight rather than on the concentration.
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  • 49
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    Notes: Summary Ultrahigh molecular weight polyacrylamides (PAAM) were obtained by plasma-induced polymerization in water solutions. The influenceof monomer concentration, sealing pressure, initiation time and post polymerization period on polymer yield and molecular weight were investigated. The viscosity and “screen factor” measurements, as well as the thermally stimulated depolarization currents spectroscopic data of the synthesized polymers, indicate good properties as efficient viscosity modifiers in displacement of fluids for enhance oil recovery (EOR).
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  • 50
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this report, the relaxation behavior of amorphous poly(ethylene terephthalate) (PET) in global chain orientation but nearly random segmental orientation (GOLR) state is studied by infrared dichroism, optical birefringence and hot shrinkage measurements at temperatures below or up PET's glass transition temperature, Tg. The results indicate that the difference in the relaxing rate between global chains and segments is at least in ∼ 102 times order above PET's Tg (∼ 84°C), with a rough approximation; while the sudden decrease of small Δn of the sample (∼ 10−4) upon being treated at about 85 ∼ 90°C, implies us that the small Δn is closely related with the orientation of global chains.
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    Polymer bulletin 41 (1998), S. 129-130 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 52
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    Notes: Summary New biomedical polyurethanes and a polyurethane urea based on Ε-caprolactone and 1,4-butanediisocyanate have been developed. On degradation, only non-toxic products are produced. The polyurethane urea with poly(Ε-caprolactone) soft segments and butanediisocyanate/butanediamine hard segments shows a high tensile strength, a high modulus and a high resistance to tearing but as a result of the strong interactions between the solvent and the polymer processing is difficult. When butanediamine is replaced by butanediol in the chain extension step, a processible polyurethane is obtained but the polymer lacks the desired mechanical properties for biomedical applications. By chain extending with a longer urethane diol block, a processible polymer was obtained with mechanical properties comparable to the polyurethane urea. This polyurethane has been made porous and can be used as a meniscal prosthesis.
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  • 53
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    Notes: Summary Catalytic 1,3-butadiene polymerization systems can be obtained with the new complex [NbO(C16H11O6 −)(C2O4 2−)] as a catalyst. When the catalysis occurs in a homogeneous medium (toluene as a solvent) in conjunction with AlEt2Cl, cis-1,4-polybutadiene is obtained. A remarkable inversion of stereoselectivity has been observed when the catalysis is carried out in a two phase system with the molten salt AlCl3.1-methyl-3-n-butyl-imidazolium chloride (MBIC) as a solvent and AlEt2Cl as a cocatalyst, giving the trans 1,4-polybutadiene.
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  • 54
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    Notes: Summary Highly branched aliphatic molecules have been used for the first time as tethers in the preparation of polymeric chiral stationary phases. Attachment of a specifically designed chiral selector to organic porous polymer beads through a branched linker substantially increases the enantioselectivity compared to that of the equivalent separation medium with a traditional linear tether.
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  • 55
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    Notes: Summary The EPR spectra of composite dextran and carboxymethyldextran gels were studied in order to identify the functional groups involved in copper(II) complexation depending on pH. The porous structure resulting from crosslinking of polymer chains of dextran, via epichlorohydrin, forces the immobilization of Cu2+ ions surrounded by different oxygen groups of the polymer gel matrix. The different polynuclear structures are postulated to be formed depending on the type of polysaccharide derivatives. The results indicate that carboxyl and deprotonated hydroxyl groups participate in the complex formation.
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  • 56
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    Notes: Summary Individual polystyrene (PS) and polyacrylonitrile (PAN) solutions in N,N-dimethylformamide (DMF) were studied by electronic absorption spectroscopy. Upon increasing the polymer concentration in the PS-DMF binary system a bathochromic shift of the band at about 260 nm was found. This spectral effect could be explained by an association of PS phenyl groups and/or by a complex formation between DMF and PS. The UV spectrum of PAN in DMF solution was interpreted in terms of the variety of possible donor-acceptor complex formations. The specific intermolecular interactions in the investigated binary liquid systems were discussed on the basis of the spectral data.
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  • 57
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    Notes: Summary Measurement of swelling is used to estimate the extent of cross-linking of latex particles prepared by emulsion polymerization. In this paper we report swelling data as a function of solvent activity for two latexes: (1) a poly(butylacrylate) (PBA) latex, and (2) a poly(isodecylacrylate) latex. In the latter case comparison is made between the swelling behavior of fully cross-linked, i.e., networks without free polymer chains, and partially cross-linked latexes. It is demonstrated that the equilibrium swelling properties are only slightly affected by the presence of uncross-linked chains. Swelling gives reliable results for the cross-link density only if the latex does not contain free chains.
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  • 58
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    Notes: Summary A correlation between interface strength and data of acoustic emission measurements in particle filled polymer composites was found. The method allows the evaluation of the interface strength in situ in polymer composite specimens at uniaxial loading. The measurements have shown that the tailored interface with the monomolecular tethered polymer layers of various grafting density change the mechanism of microdefect formation.
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    Meteorology and atmospheric physics 29 (1981), S. 57-70 
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Auf der landwirtschaftlichen Universität von Norwegen (59δ 40′N, 10δ 46′E) wurde mit vier verschiedenen Lysimetern die potentielle Evapotranspiration (PET) von Gerste und von kurzgeschnittenem Gras gemessen. Die Ergebnisse zeigen, daß in der aktiven Wachstumsperiode die PET von Gerste der PET von Gras gleich ist in Bestätigung der Tatsache, daß die Evapotranspiration von kurzer Vegetation in erster Linie durch meteorologische Faktoren beeinflußt wird, wenn die Wasserzufuhr nicht beschränkt ist. Mit der Formel von Priestley und Taylor PET =α Δ/Δ + γ R n, wo Δ den Abfall des Sättigungsdruckes mit der Temperatur,γ die Psychrometerkonstante undR n die Strahlungs. bilanz bedeuten, kann mit a gleich 1.25 die PET für zehntägige Perioden mit einer Genauigkeit von 10% geschätzt werden. Eine bessere Schätzung wird mit der Formel PET (mm pro 10 Tage) = −5,4 + 6,18 · 10−7 Δ/Δ + γ Rn (J/m2) erhalten.
    Notes: Summary Potential evapotranspiration (PET) from barley and short cut grass have been measured using four different lysimeters at the Agricultural University of Norway (59δ 40′N, 10δ 46′E). In the active growing season the results show that PET for barley is equal to PET for grass, confirming the fact that evapotranspiration is primarily controlled by meteorological factors for short vegetation when water supply is non-limiting. Using the Priestley-Taylor formula PET =α Δ/Δ + γ n, where Δ is the slope of the saturation pressure versus temperature curve,γ is the psychrometric constant andR n net radiation, PET can be estimated to an accuracy of 10% (67% level) for ten-day periods withα equal to 1.25. Even better estimates is obtained by using the formula PET (mm per 10 days) = − 5.4 + 6.18 · 10−7 Δ/Δ +γ R n (J/m2).
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    Meteorology and atmospheric physics 29 (1981), S. 89-97 
    ISSN: 1436-5065
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    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Ein Sonnenscheingeber und seine Eichung wird beschrieben. Er ist gekennzeichnet durch folgende Merkmale: Sein elektrischer Spannungsausgang liegt hoch (〉 4,5 V) für den Fall „Sonnenschein” und tief (〈 0,4 V) für den Fall „kein Sonnenschein” Seine Eichung auf eine Schwellwertintensität von 200 W/m2 folgt der Sonnenscheindefinition durch die World Meteorological Organization. Er erfordert keine nennenswerte Wartung und er enthält keine beweglichen Teile.
    Notes: Summary A sunshine monitor and its calibration is described. Its important characteristics are: it has an electrical DC level output which is high (〉 4.5 V) for “sunshine” and low (〈 0.4 V) for “no sunshine”; it is calibrated for a threshold sensitivity of 200 W/m2, which meets the sunshine definition of the World Meteorological Organization; it requires very little service and contains no moving parts.
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    Meteorology and atmospheric physics 29 (1981), S. 99-109 
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    Description / Table of Contents: Zusammenfassung Es wird gezeigt, daß auf Grund von Angaben in der Literatur die Konstanten für die statistische Beziehung zwischen der Globalstrahlung und der Sonnenscheindauer für Ostafrika nun hinreichend gesichert angegeben werden können. Werden die Unterschiede der Fehler bei der Datenerfassung mit anderen einfachen Meßmethoden der solaren Einstrahlung berücksichtigt, kann gezeigt werden, daß Campbell-Stokes Meßwerte gut geeignet sind zur Überprüfung, Kalibrierung oder zum zeitweisen Ersatz sonstiger Meßmethoden, wo in den Tropen keine geeichten Pyranometer verfügbar sind. Ein Beispiel wird gegeben für Gunn-Bellanis.
    Notes: Summary It is shown from literature research that constants in the statistical relationship between total global solar radiation and sunshine duration are now well established for East Africa. Taking into account the differences in data collection errors with other simple methods of solar radiation determination, we show Campbell-Stokes data to be suitable for checking, calibrating or temporarily replacing these other methods where no calibrated pyranometers are available in the tropics. An example is given for Gunn-Bellanis.
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    Meteorology and atmospheric physics 29 (1981), S. 129-135 
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    Description / Table of Contents: Zusammenfassung Es wurde die Globalstrahlung in GeU und GeMCap analysiert, womit es im Zusammenhang mit den thermo-pluviometrischen Angaben ermöglicht wurde, die klimatischen Charakteristiken eines am Meere gelegten Ortes (GeU) und eines auf den Appenninen gelegenen Ortes (GeMCap) zu beschreiben. Auf GeMCap weisen diese klimatischen Faktoren im Winter-Herbst einen kontinental-maritimen Charakter und im Frühling-Sommer einen streng kontinentalen Charakter auf.
    Notes: Summary It has been analysed the global solar radiation at GeU and GeMCap, that in connection with the thermo-pluviometric data has also allowed to outline the climatic characteristics of a coastal site (GeU) and of a site on Apennin ridge (GeMCap). At GeMCap these climatic parameters show a continental-maritime behaviour in winter-autumn and strictly continental feature in the remaining half year.
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    Meteorology and atmospheric physics 29 (1981), S. 111-128 
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    Description / Table of Contents: Zusammenfassung Der Zusammenhang zwischen Globalstrahlung und Sonnenscheindauer wird für 132 Stationen in Ostasien untersucht. Es zeigt sich, daß die Regressionskoeffizienten in der modifizierten ÅngströmgleichungQ/Qa = a + b n/N systematisch über das Gebiet verteilt sind, so daß sich niedrige Werte vona und hohe Werte vonb im Wintermaximum/Sommerminimum-Regime vonQ/Qa undn/N ergeben, hohe Werte vona und niedrige Werte vonb dagegen im Winterminimum/Sommermaximum-Regime vonQ/Qa undn/N anfallen. (Die Symbole werden in der Einleitung definiert.) Es ergibt sich daraus, daß Verteilungen der Regressionskoeffizienten eher an Terraingegebenheiten und an das lokale und jahreszeitliche Strahlungsklima geknüpft sind, das durch den vorherrschenden Wintermonsun, Baiu, kontrolliert wird, als an die geographische Breite und an Mittelwerte vonn/N.
    Notes: Summary The relationship between solar radiation and sunshine duration is studied for 132 stations in East Asia. Regression coefficientsa andb in the modified Ångström formulaQ/Qa = a + b n/N are found to be systematically distributed in the area with low values ofa and high values ofb in the winter maximum/summer minimum regime ofQ/Qa andn/N, and high values ofa and low values ofb in the winter minimum/summer maximum regime ofQ/Qa andn/N. This shows that the distribution of regression coefficients is more closely related to the local seasonal radiation climate controlled by the prevailing winter monsoon, Bain, and the terrain features rather than to latitude or meann/N.
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    Meteorology and atmospheric physics 29 (1981), S. 137-155 
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    Description / Table of Contents: Zusammenfassung Die Arbeit bringt eine Zusammenfassung der mit einem zweiteiligen Modell des täglichen Niederschlags zum Vergleich des Regenklimas von 11 Orten in einem Nord-Süd-Schnitt durch Westafrika erhaltenen Ergebnisse. Die Zahl der Regentage wurde gesondert von den Regenmengen analysiert. Es wurden Kurven der Wahrscheinlichkeit von Regen angepaßt; diese Kurven sind geographisch vereinbar. Die mittlere Länge der Trockenperioden und der Feuchteperioden variiert systematisch im Jahresgang. In der Regenzeit besteht ein nahezu konstantes mittleres Intervall von 4 Tagen zwischen dem Beginn aufeinanderfolgender Regenperioden. Regenmengen werden durch Gamma-Verteilungen beschrieben. Die mittlere Regenmenge pro Regentag ist verhältnismäßig konstant und die Änderung der Regenwahrscheinlichkeit ist daher die bedeutendste Komponente der jahreszeitlichen Änderung und der Differenzen zwischen den Orten.
    Notes: Summary This paper uses the concise summary obtained from a two part model of daily rainfall to compare the rainfall climate of eleven places on a north-south transect in West Africa. The number of rainy days is analysed separately from the amounts of rain. Curves are fitted to the probability of rain and these curves are geographically consistent. The mean length of dry spells and of wet spells vary systematically during the year. In the rainy season there is a nearly constant mean interval of about 4 days between the start of successive rainy spells. The amounts of rain are described by gamma distributions. The mean rainfall per rainy day is relatively constant and variation in the probability of rain is therefore the most important component of seasonal variation and of differences between places.
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    Meteorology and atmospheric physics 29 (1981), S. 167-179 
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    Description / Table of Contents: Zusammenfassung Es wurde die Abhängigkeit von feuchten und trockenen Tagen vom Zustand an vorhergehenden Tagen für sechs Stationen in Ost- und West-Afrika und in Südost-Asien untersucht. Während eine Anzahl von Untersuchungen in höheren Breiten darauf hinweisen, daß häufig nur der Zustand am vorhergehenden Tag in Betracht zu ziehen ist, zeigt das Ergebnis dieser Studie an, daß in den Tropen mindestens die zwei vorhergehenden Tage von Bedeutung sind. Für manche Stationen mag es angezeigt sein, in bestimmten Zeiten des Jahres die drei vorhergehenden Tage in Betracht zu ziehen.
    Notes: Summary Dependence of the occurrence of wet and dry days on the situation on previous days was tested for six stations in East and West Africa and South East Asia. Although a number of studies in higher latitudes suggest that often only the situation on the previous day needs to be taken into account, evidence from this pilot study indicates that in the tropics, at least the previous two days are important. For some stations at certain times of the year, it may be wise to consider the previous three days.
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    Meteorology and atmospheric physics 29 (1981), S. 157-166 
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    Description / Table of Contents: Summary This study, inspired by previous works, tries to establish a synthesis on a limited aspect: that is the variability of average precipitations over the Aegean Sea. Moreover, we consider variability parameters mostly used, as well as the most satisfactory technics for plotting this variability on the map.
    Abstract: Zusammenfassung In dieser Arbeit wird die Veränderlichkeit des Niederschlages im Ägäischen Meer zur Darstellung gebracht. Ferner werden die gebräuchlichsten Variabilitätsparameter und die am meisten befriedigenden Techniken der Kartendarstellung dieser Veränderlichkeit in Betracht gezogen.
    Notes: Résumé Cette étude qui s'inspire de travaux antérieurs tente d'établir une synthèse sur un aspect limité: selui de la variabilite des precipitations moyennes tombées dans la mer Egée. En outre, nous considérons les parameters de variabilite les plus utilisables, ainsi que les techniques les plus satisfaisantes pour la représentation cartographique de la variabilite.
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    Meteorology and atmospheric physics 29 (1981), S. 181-190 
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    Description / Table of Contents: Summary Windgustiness at the top of a tree which is relevant to tree vibrations within forests is described for a spruce forest (Ebersberger Forst near Munich) applying simple characteristic values of turbulence and gustiness.
    Notes: Zusammenfassung Bei der Untersuchung von Baumschwingungen innerhalb von Wäldern ist die Windböigkeit an der Baumoberhöhe von großer Bedeutung. Für einen Fichtenwald, den Ebersberger Forst bei München, wird sie mit einfachen Turbulenz- und Böigkeitskenngrößen beschrieben.
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    Meteorology and atmospheric physics 29 (1980), S. 197-204 
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    Description / Table of Contents: Zusammenfassung In früheren Untersuchungen langer atmosphärischer Wellen von niedriger Frequenz in der polaren Atmosphäre wurden Zylinderkoordinaten angewendet, wobei die Ebenez=0 die Erdoberfläche am Pole berührt. Dabei wurde mittels numerischer Beispiele gefunden, daß die in Zylinderkoordinaten erhaltenen Resultate gute Annäherungen an die mit Kugelkoordinaten berechneten darstellen. Hier wird gezeigt, daß die Formeln für die Wellenfrequenzen in beiden Koordinatensystemen angenähert gleich sind.
    Notes: Summary In earlier studies of long low-frequency atmospheric waves in the polar atmosphere a cyclindrical coordinate system had been used with the planez=0 tangential to the earth's surface at the pole. It had been found by numerical examples that the results obtained with a cylindrical coordinate system approximate quite well those obtained with a spherical coordinate system. Here, it is shown that the formulae for the wave frequencies in both coordinate systems are the same to a good degree of approximation.
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    Meteorology and atmospheric physics 29 (1980), S. 269-277 
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    Description / Table of Contents: Zusammenfassung Es werden die Auswirkungen der Einbeziehung der vertikalen Scherung in das Problem der stetigen Strömung einer nichtviskosen rotierenden und geschichteten Flüssigkeit um ein isoliertes topographisches Hindernis besprochen. Es wird gezeigt, daß bei Baroklinität in der fern von dem Hindernis ungestörten Strömung, bei dem hier betrachteten Parameterbereich, ein antizyklonaler an das Hindernis gebundener Wirbel erzeugt wird, ähnlich wie im Fall ohne Scherung aber mit durch die Scherung modifizierter Intensität. Im besonderen nimmt, wenn die Geschwindigkeit der Grundströmung mit der Höhe zunimmt, die Intensität des Wirbels im Vergleich zum barotropen Fall wegen der horizontalen Advektion potentieller Temperatur ab. Für den Fall einer geringen Größe der Hindernisse werden analytische Lösungen gebracht.
    Notes: Summary The effects of inclusion of vertical shear in the problem of steady flow of an inviscid, rotating and stratified fluid past isolated topography are discussed. It is shown that the presence of baroclinicity in the undisturbed flow far from the obstacle, in the parameter range considered here, produces an anti-cyclonic vortex bound to the obstacle, like in the unsheared case, but whose intensity is modified by the shear. In particular, if the velocity of basic flow increases with height, the intensity of the vortex is decreased with respect to the barotropic case, because of the horizontal advection of potential temperature. Analytical solutions are presented in the case of small amplitude obstacles.
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    Meteorology and atmospheric physics 29 (1980), S. 205-217 
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    Description / Table of Contents: Zusammenfassung Mit Hilfe approximierter ageostrophischer Windkomponenten und iterativer Integration in einem quasi Lagrangeschen System werden Trajektorien abgeleitet. Die Verifikation erfolgt an Hand der Verlagerung charakteristischer Wolkensysteme mittels Satellitenbilder.
    Notes: Summary Trajectories are computed with the help of approximated ageostrophic windcomponents and the iterative integration method in a quasi Lagrangian system. The displacement of distinctive cloud systems localized from satellite images is used for verification.
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    Meteorology and atmospheric physics 29 (1980), S. 219-233 
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    Description / Table of Contents: Zusammenfassung Es wird ein Parameter zur Feststellung des Minimalbereiches der übergeostrophischen Komponente der zonalen Strömung in einem westlichen Jet Stream aus der Bedingung bestimmt, daß eine geostrophische Bewegung nur in stabil geschichteten Medien möglich ist. Die Größe des übergeostrophischen Zonalwindes im Kerngebiet eines durchschnittlichen westlichen Jet Stream mittlerer Breiten wurde bei nahe von 60% der beobachteten zonalen Windgeschwindigkeit festgestellt. Die durch diese übergeostrophischen Zonalwindkomponenten verursachten nicht geostrophischen Querzirkulationen werden als thermisch indirekt und für die Entwicklung von einigen beobachteten Erscheinungen wie der Jet Stream Front, der Unterbrechung der nördlichen Tropopause quer zum Kern und der Clear air turbulence-Zonen in bestimmten Regionen eines westlichen Jet Stream als günstig erwiesen.
    Notes: Summary A parameter, for determining the minimum super-geostrophic component of zonal flow in a westerly jet stream, was identified, by invoking the condition that geostrophic motion is possible only in stably stratified media. The magnitude of super geostrophic zonal wind in the core region of an average mid-latitudinal westerly jet stream was found to be nearly 60% of the observed zonal wind speed. The non-geostrophic transverse circulations induced by this super-geostrophic zonal wind components were shown to be thermally indirect in nature and favourable for the formation of some of the observed features like jet stream front, break of the northern tropopause across the core and CAT (clear air turbulence) zones in certain regions of a westerly jet stream.
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    Meteorology and atmospheric physics 29 (1980), S. 249-267 
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    Description / Table of Contents: Zusammenfassung Mit Verwendung von in der zweiten Phase der Venezueler internationalen meteorologischen und hydrologischen Experimente (VIMHEX-1972) gesammelten Radar-Daten wurde eine Klassifikation von Unwettern in Böenlinien, in Gewittergruppen und in isolierten Gewittern vorgenommen. Die Verhältnisse in der nahen Umgebung während des Vorrückens dieser Typen von Unwetter werden untersucht. Die Modifikation der Umgebung wird, abgeleitet aus der trocken-statischen Energie, aus der feucht-statischen Energie, aus dem latenten Wärmegehalt und aus den relativen Winden, ebenfalls studiert und ein für die Unwetter entwickeltes Modell wird vorgelegt. Schließlich werden einige Aspekte der Bewegung der Unwettergebilde beschrieben.
    Notes: Summary A classification of storms in squall lines, thunderstorm clusters, and isolated thunderstorms was made using radar data collected during the second phase of the Venezuelan International Meteorological and Hydrological Experiments (VIMHEX-1972). The near-environmental conditions in advance of these types of storms are examined. The modification of the environment, as deduced from the dry static energy, moist static energy, latent heat content and relative winds is also studied, and a conceptual model for the storms is presented. Finally, some aspects of storm movement are described.
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    Meteorology and atmospheric physics 29 (1980), S. 235-247 
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    Description / Table of Contents: Zusammenfassung Die Untersuchung wurde an einem äquivalenten barotropen Modell zum Studium der Stabilität des meridionalen Windes im 200 mb-Niveau im Sommer in den Tropen durch-geführt. Das von Wiin-Nielsen für mittlere Breiten eingeführte äquivalente Modell wurde mit einigen Änderungen auch für die Tropen angenommen. Es wurde gefunden, daß der meridionale Wind einer Anzahl von überlagerten Rossby-Wellen äquivalent ist, so daß sich das Stabilitätsproblem der meridionalen Strömung auf das Stabilitätsproblem von Rossby-Wellen zurückführen läßt. In der vorliegenden Untersuchung wurde die Stabilität einer Rossby-Welle mit einer Störung, die einen zonalen Wind ergibt, geprüft. Es wurde gefunden, daß kurze Rossby-Wellen instabil sind, so daß die kurzen Rossby-Wellen ihre kinetische Energie auf den zonalen Wind übertragen. Das von Lorenz hinsichtlich der Instabilität der Rossby-Welle für mittlere Breiten gewonnene Ergebnis wurde mit dem äquivalenten barotropen Modell verbessert.
    Notes: Summary The present study is conducted in the equivalent barotropic model to study the stability of meridional wind at 200 mb level in tropics during summer. The equivalent barotropic model, which was introduced by Wiin-Nielsen [1] for midlatitude, is accepted for tropics after some possible changes. The meridional wind is found to be equivalent to a number of superposed dispersive Rossby waves, so the stability problem of meridional flow reduces to the stability problem of Rossby waves. In the present study, the stability of single Rossby wave is tested with a perturbation which gives zonal wind. It is found that the short Rossby waves are unstable, so the short Rossby waves release their kinetic energy to the zonal wind. Thus, the short waves of the spectral meridional flow release their kinetic energy to the zonal wind. For midlatitude, Lorenz's problem regarding the instability of Rossby wave is improved using the equivalent barotropic model.
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    Meteorology and atmospheric physics 29 (1980), S. 279-299 
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    Description / Table of Contents: Zusammenfassung Es werden die monatlichen und jahreszeitlichen Mittel, die Extreme und die Veränderlichkeit des Meereises der Süd-Hemisphäre aufgrund 5jähriger Beobachtungen untersucht. Seine Veränderlichkěit ist am größten in den geographischen Längen der Küsteneinbuchtungen der Antarktis; es wurde auch eine kleine aber allgemeine Abnahme seiner Ausdehnung in allen Jahreszeiten dieser Beobachtungsperiode festgestellt. Zum Maximum der Eisausdehnung (Juli bis November) nimmt das 5jährige Mittel der zonalen Westwinde im Norden des Eises mit zunehmender Eisausdehnung zu; in einzelnen Jahren besteht jedoch zum Maximum der Eisausdehnung keine deutliche Korrelation zwischen der zonal gemittelten Eisausdehnung und der Stärke der zonalen Westströmung im vorhergehenden oder folgenden Monat. Der Vergleich mit dem 5jährigen Mittel der Längenverteilung der atmosphärischen Druck-Maxima und Minima in der Breite des antarktischen Trogs weist allgemein auf Asymmetrien im Eisrand hin, derart, daß er in Gebieten mit häufigem Tiefdruck weiter nördlich liegt und veränderlicher ist und in Gebieten mit relativ hohem Druck weiter südlich liegt. Die Untersuchung einer spezifischen Längenzone zeigt, daß die Verteilung der Eisausdehnung deutlich regional ist und offenbar mit Änderungen in der kombinierten ozeanischen und atmosphärischen Zirkulation in den antarktischen Einbuchtungen in Beziehung steht.
    Notes: Summary The monthly and seasonal means, extremes and variability of the Southern Hemisphere sea ice are examined for a five year period. Its variability is found to be greatest in the longitudes of the Antarctic coastal embayments, and a small but general decline in extent at all seasons throughout the period is observed. At near maximum ice extent (July to November), the 5 year mean of the zonal westerlies to the north of the ice increases with increasing ice extent; however for individual years, at maximum ice extent, there is no clear correlation between zonally averaged ice extent and the strength of the zonal westerlies in the preceding or succeeding month. Comparison with the 5 year mean longitudinal pattern of atmospheric pressure maxima and minima at the latitude of the Antarctic trough points generally to asymmetries in the ice edge, such that it is further north and more variable in regions of frequent low pressure, and further south in regions of relatively high pressure. Examination of a specific longitudinal zone indicates that the pattern of ice extent is clearly regional, and apparently related to variations in the combined oceanic and atmospheric circulation particularly in the Antarctic embayments.
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    Meteorology and atmospheric physics 29 (1981), S. 215-228 
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    Description / Table of Contents: Zusammenfassung Es wird über die Anwendung der Hauptkomponentenanalyse zur Abgrenzung von Gebieten mit ähnlichen säkularen Tendenzen im Niederschlag berichtet. Eine Alternativmethode der Regionalisierung wird vorgeschlagen und auf eine Reihe von Beobachtungsdaten angewendet, die bereits früher mit der Hauptkomponentenanalyse analysiert worden ist.
    Notes: Summary The use of principal components analysis to delimit regions with similar secular trends in rainfall totals is reviewed. An alternative method of regionalization is proposed and is applied to a data set previously analysed using principal components analysis.
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    Meteorology and atmospheric physics 29 (1980), S. 327-332 
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    Description / Table of Contents: Zusammenfassung Die Maximalwellen energiereicher Erdbeben mit Herd in der oberen Kruste rufen im äußeren Schütterbereich häufig Resonanzeffekte hervor, die eine örtliche Steigerung der Bebenintensität zur Folge haben. Eine Bewertung solcher Intensitäten nach den gebräuchlichen makroseismischen Skalen ist derzeit nicht möglich. Geht man davon aus, daß die primären Bebenwirkungen an der Erdoberfläche eine Folge der vom Bebenherd abgestrahlten Schwingungsenergie sind und daß die makroseismische IntensitätI (oMSK oder MM) ein logarithmisches Maß für die Bebenwirkungen ist, dann gilt offenbarI=log10 E+const, wennE die örtliche Energiestromdichte (Flächendichte der seismischen Energie) ist. Während im Epizentralbereich wegen der Unregelmäßigkeit der Erdstöße ausgeprägte Resonanzeffekte fehlen, muß man in herdfernen Gebieten, wo die Sg-Maximalwellen des Bebens schon weitgehend harmonisch sind, bei schwingungsanfälligen dünnen Bodenschichten und/oder Bauwerken mit entsprechender Eigenperiode Resonanzschwingungen erwarten, die eine Anhebung der lokalen Bebenintensität um ΔI (oMSK oder MM) bewirken. Mit Hilfe von empirischen Näherungsformeln kann man zu einer Abschätzung dieser Intensitätssteigerung kommen. Sie beträgt ΔI=0,28M s+0,4, mitM s als Oberflächenwellen-Magnitude. Die von der Epizentraldistanz und Magnitude abhängigen Resonanzfrequenzen liegen in der Regel zwischen 0,5 und 2 Hz. Die denkbare Intensitätssteigerung durch Resonanz im Falle eines Bebens der Magnitude 4,0 (7,0) liegt bei 1,5° (2,4°) MSK oder MM. Daraus folgt z. B., daß viele der in Hochhäusern bemerkten und mitI=IIo bewerteten Beben eigentlich mitI=Io zu klassifizieren sind und daß das Anschlagen kleiner Glocken oder das Stehenbleiben von Pendeluhren am Rande des Schüttergebietes eines energiereichen Bebens nichtI=Vo (−VIo), sondernI=IIIo (−IVo) entspricht. Die 12teiligen makroseismischen Skalen sind daher in entsprechender Weise zu ergänzen.
    Notes: Summary In the epicentral area of an earthquake with the focus within the upper crust the rocking is irregular and therefore resonance effects are lacking, but far off the hypocentre, where theSg maximum waves are nearly sinusoidal, thin layers of soil and/or buildings with an appropriate natural period react with resonance oscillations, by which the local macroseismic intensity is increased by ΔI (oMSK or MM). The resonance frequencies — functions of magnitude and hypocentral distance — mostly range from 0.5 to 2 Hz. The increase of intensity can be assessed by the aid of the formula ΔI=0.28M s+0.4, found by the author (M s=surface wave magnitude). Hence, in case of an earthquake withM s=4.0 (7.0) the marginal increase of intensity by resonance amounts to 1.5° (2.4°) MSK or MM. This implies, e. g., that many earthquakes perceived in tall buildings and considered asI=IIo has to be classified asI=Ic correctly, and the ringing of small bells or the stopping of pendulum clocks in the outskirts of the shaken area of a strong earthquake corresponds toI=IIIo (−IVo), and not toI=Vo (−VIo). A valuation of such intensities by the aid of the usual macroseismic scales is not possible, and therefore these scales are to be supplemented in an appropriate way.
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    Meteorology and atmospheric physics 29 (1981), S. 229-237 
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    Topics: Geography , Physics
    Description / Table of Contents: Zusammenfassung Die Sichtbeobachtungsdaten der Periode 1968 bis 1972 in Phönix, Arizona, wurden analysiert, um zu zeigen, wie Änderungen im Laufe der Woche und im Tagesgang durch charakteristische Verunreinigungsquellenstärke und durch meteorologische Erscheinungen beeinflußt werden. Die Ergebnisse bilden eine Grundlage für künftige Untersuchungen zur Klärung von Nachwirkungen einer technologischen Modifikation von Verunreinigungscharakteristiken.
    Notes: Summary Visibility data for the period 1968–1972 at Phoenix, Arizona were analyzed to show how variations among days of the week and hours of the day may be influenced by both pollutant source strength characteristics and meteorological phenomena. The results form the basis for future studies designed to decipher subsequent effects of technological modification of pollutant characteristics.
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  • 78
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Polymerization behavior of δ-valerolactone (VL) with alkylsamarium (RSmI2) was studied, and its application to the block copolymerization of tetrahydrofuran (THF) with VL was examined. Polymerization of VL by butylsamarium gave the corresponding poly(VL) in good yield. The yield increased with increasing the concentration of VL and decreasing the polymerization temperature, resulting from the equilibrium between VL and poly(VL). The decrease in the molecular weight of poly(VL) by prolonging the polymerization time indicated the existence of back-biting reaction to form cyclic oligomers. The polymerization of VL with poly(THF)-macroanion obtained by the two-electron reduction of the propagation center of living poly(THF) with SmI2 led to the block copolymer of THF with VL. The initiation efficiency of VL-polymerization was almost quantitative, and the unit ratio of THF and VL-segments could be controlled by both the polymerization time of THF and the amounts of VL.
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  • 79
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary By using the redox reaction between Ce(IV) and terminal -CH2OH groups of polyethylene oxide(PEO), block copolymers composed of poly(N-isopropylacrylamide)(PNiPAAm) and poly(ethylene oxide) was prepared. The aqueous solution of the block copolymers exhibited thermal phase transition and the phase transition temperature of these block copolymers became higher than the PNiPAAm homopolymer.
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  • 80
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    Polymer bulletin 40 (1998), S. 469-476 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Liquid crystalline diols containing a biphenyl mesogenic core, methoxy or cyano terminal groups and spacers of various lengths were synthesized and used for the preparation of side-chain thermotropic polyurethanes. The structure of the synthesized diols and polymers was confirmed by elemental analysis, FTIR and NMR spectroscopy. Phase transition temperatures were studied by DSC, while optical textures were characterized by polarizing microscopy. A smectic type arrangement was found for the mesophases of all products.
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  • 81
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    Polymer bulletin 40 (1998), S. 485-490 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Brittle polylactide (PLA) was toughened by introducing 5 wt % of a poly(ɛ-caprolactone)(PCL) diol- and triol-based polyurethane (PU) network. The extent of cross-linking of the PU was varied by changing the ratio between diol and triol. The effects of the PU content and its crosslink density on the mechanical properties and the toughness of PU/PLA blends were investigated. Maximum toughness of PU/PLA blends, an order of magnitute higher than that of pure PLA, could be achieved by the use of a proper amount of PU and a proper extent of cross-linking.
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  • 82
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Effects of cyclization and ionic group contents on the termination rate of macroradicals formed at zero monomer conversion were investigated. For this purpose, the pregel regime of free-radical methyl methacrylate / ethylene glycol dimethacrylate (MMA/EGDM) and acrylamide / N,N'-methylenebisacrylamide (AAm/BAAm) copolymerization systems was studied by means of the dilatometric technique. To eliminate the chain-length dependent variation of the termination rates, different sets of experiments were carried out each at a fixed monomer and initiator concentration. At low crosslinker contents, the termination rate of zero-conversion macroradicals was enhanced in crosslinking copolymerizations compared to linear polymerization. This is due to the cyclization reactions which reduce the size of the macroradical coils and thus, enhance the termination rates due to the lowering of the thermodynamic excluded volume effect. As the amount of the crosslinker increases, an enhancement in the initial rate of polymerization is observed in all series of experiments, indicating that steric effects on segmental diffusion dominate at high crosslinker contents. The results also indicate a slower rate of termination of ionic macroradicals compared to the non-ionic radicals of the same molecular weight and points the significance of the thermodynamic excluded volume effect on rising the ionic group content.
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  • 83
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    Polymer bulletin 40 (1998), S. 525-532 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thermal stabilities of α,ω-hydroxypropyl, α,ω-hydroxybutyl, α,ω-2-hydroxypentyl and α,ω-hydroxyhexyl terminated polydimethylsiloxane (PDMS) oligomers were studied. Hydroxypropyl and hydroxybutyl terminated polydimethylsiloxane oligomers showed degradation upon heating, through the loss of functional end groups as determined by FT-IR spectroscopy and gel permeation chromatography. α,ω-Hydroxyhexyl and α,ω-2-hydroxypentyl terminated polydimethylsiloxane oligomers were stable under similar conditions. Instability of the end groups is due to the back biting of the terminal silicon in the PDMS by the primary hydroxyl oxygen, leading to the formation of 5 and 6 membered, stable, heterocylic compounds. Loss of end groups also resulted in a dramatic increase in the molecular weights of the oligomers produced, as determined by gel permeation chromatography.
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  • 84
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary. Functionalized oligo-ɛ-caprolactones synthesized by heterogeneous coordinated anionic ring opening polymerization (AROP) in protic conditions have been analyzed by mass spectrometry in order to investigate the molecular weight distribution as well as the possible occurrence of macrocycles. Mass spectra obtained from LSIMS revealed the presence of fragmentation products and some of them have been identified. Macrocycles were also detected. Nevertheless, ESI and MALDI-TOF spectrometries do not confirm the presence of macrocycles in the samples. The same results have been obtained by analysis of commercially available polycaprolactones.
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  • 85
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thin films of phase separated polystyrene-b-polyisoprene-b-polystyrene block copolymers were studied by tapping mode atomic force microscopy. The relative contrast in height and phase mode images of the phase separated regions was found to be very sensitive to changes in the operating conditions of the microscope. Contrast variations and reversals were observed for height and phase mode images as a function of the set-point amplitude ratio and drive frequency. No unique height or phase contrast was observed for the the tri-block copolymer system examined in this study.
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  • 86
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Dielectric constants of allyl methacrylate-methyl methacrylate copolymers are measured in toluene solution at a constant frequency of 2 MHz, within a wide temperature range (20–70°C). Soluble copolymers have been prepared by group transfer copolymerization. Dipole moments are calculated from Guggenheim-Smith equation. The effects of allyl group on the dipole moments of copolymers in a slightly polar medium are discussed.
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  • 87
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Influence of some aromatic amino acids (histidine, phenylalanine and tryptophan) on the swelling behavior of acrylamide/maleic acid hydrogel (AAm/MA) prepared by γ-radiation was investigated. Swelling tests of AAm/MA hydrogel were made in buffer solutions and amino acid solutions at various pH at 37°C. The pH values are ionization of α-carboxyl groups (pK'1), α-amino groups (pK'2) and, isoelectric points (pI) of amino acids. The swelling of AAm/MA hydrogel increased when pH values of solutions were increased. The value of equilibrium swelling of AAm/MA hydrogel was 1035% at pH 10 buffer, while it was 880% at pH 2 buffer. The values of equilibrium swelling of AAm/MA hydrogel in phenylalanine, tryptophan and histidine solutions varied among 1130–1245% at pH 10, while they were among 790–975% at pH 2. The rate constant of swelling, diffusional exponent, network parameter and, diffusion and intrinsic diffusion coefficient were calculated by swelling kinetics. Diffusion of the penetrants into the hydrogel was found to be non-Fickian character. The diffusion coefficients of the hydrogel varied between 3.33×10−6– 7.71×10−6 cm 2s−1, while the intrinsic diffusion coefficients waried between 4.03×10−6– 8.48×10−6 cm 2s−1.
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  • 88
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    Polymer bulletin 40 (1998), S. 599-605 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In order to characterize the low temperature relaxation of epoxy resin modified with amine-terminated butadiene acrylonitrile copolymers (ATBN), thermally stimulated current (TSC) and relaxation map analysis (RMA) were investigated. Four relaxation peaks at around −140, −100, −60 and 0°C were observed as the indication of γ-, β-relaxation of epoxy resin, Tg, new unknown peak of ATBN, respectively. The unknown peak at around 0°C was observed due to dipole orientation. The RMA data was showed that compensation temperature (Tc) and degree-of-disorder (DOD) were increased with increasing the content of acrylonitrile and ATBN, whereas the compensation time (τc) was decreased. It can be concluded that the cooperative molecular motion in cured epoxy resin was more active as the concentration of acrylonitrile and ATBN content increases.
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  • 89
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    Polymer bulletin 40 (1998), S. 639-645 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Bifunctional living polytetrahydrofuran (PTHF) was terminated with potassium salt of pyrrole to yield polymers with electrochemically active end groups. These polymers were employed in the second stage to obtain conducting polypyrrole/polytetrahydrofuran block copolymers with short and long polytetrahydrofuran segments by potentiostatic anodic polymerization of pyrrole in different electrolytic media. Syntheses of block copolymers were achieved in media where tetrabutylammonium fluoroborate, sodium perchlorate and sodium p-toluenesulfonate were used as the supporting electrolytes. Characterizations were based on DSC, TGA, SEM, FTIR, and CV analyses. No significant effect of the chain length of polytetrahydrofuran segments on the properties of the copolymers was observed; however, thermal, electrochemical behaviors, and surface morphologies of the films were greatly affected by the supporting electrolytes.
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  • 90
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The effects of molecular structure of graft copolymer on the interfacial properties are investigated using a Monte Carlo simulation. The interfacial activity is analyzed by calculating the surface coverage and the concentration profile of graft copolymer at the interface. At low interaction energy between two segments, the graft copolymer having fewer grafting sites and longer grafting chains locates better at the interface than the graft copolymer having more grafting sites and shorter grafting chain. At high interaction energy, this situation is reversed: the graft copolymer with more grafting sites locates better than the copolymer with fewer grafting sites.
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  • 91
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary CpTiCl2(OPri) was a very active catalyst for syndiotactic polymerization of styrene when activated with methyl aluminoxane (MAO). The catalyst activity and syndiospecificity of CpTiCl2(OPri)/MAO were about 107 g PS / mol Ti·mol S·h and about 95% respectively, both higher than those of CpTiCl3 / MAO.
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  • 92
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    Polymer bulletin 37 (1996), S. 729-735 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The cationic polymerizations of indene (Ind) and styrene (Sty) initiated by iodine (I2) in liquid sulfur dioxide (SO2) were investigated. Reactions involving Ind were characterized by termination by neutralization between the growing carbocationic species and the nucleophilic counteranion, at low temperature. Sty polymerization is also termination-dominated and gives low conversion at -20°C. High resolution gas chromatography coupled with mass spectrometry (HGC-MS) analysis of non polymeric material in the Sty polymerization suggested that initiation of Sty polymerization involves the formation of 1,2 diiodide adduct prior to initiation with HI.
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  • 93
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    Polymer bulletin 37 (1996), S. 743-749 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Novel, soluble 5-dimethylamino-1-naphthalenesulfonyl esters of cellulose (2) with a degree of substitution from 0.67 to 1.59 were prepared by esterification of cellulose dissolved in N,N-dimethylacetamide/LiCl solvent system and characterized by means of FTIR-as well as 1H and 13C NMR-spectroscopy. The remaining OH groups of 2 can be fully acetylated in pyridine using N,N-dimethylaminopyridine as a catalyst. The polymers show typical fluorescence and absorption spectra with absorptions at 217, 250 and 317 nm which are in good agreement with quantum chemical calculations.
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  • 94
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    Polymer bulletin 37 (1996), S. 759-763 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A very interesting part within the wide field of chemical reactions are-catalyzed reactions. To find an effective low cost catalyst for various applications is a primary goal of many workers. Polymer chemistry is able to provide systems with qualities not known for monomeric catalysts. Especially in heterogenic systems the use of polymeric catalysts has many advantages such as easy separation for reuse or low toxicity. A special type of heterogenic catalysis is the phase transfer catalysis. Comb polymers of poly(styrene) with oligo(ethylene oxide) side chains were investigated for their ability as phase transfer catalysts.
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  • 95
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Zn lactate, 3H2O and dehydrated Zn lactate were used as initiator to polymerize DL-lactide under various conditions. It is shown that the latter does polymerize DL-lactide up to high molecular weight at a slower rate than Sn octoate. Zn lactate being formed when lactic acid is allowed to react with Zn metal, it is believed that the active species in Zn metal initiation is Zn lactate. Comparison was made of the two poly(DL-lactide) initiated with Zn metal and Sn octoate respectively and selected to have almost similar characteristics. It is shown that degradation characteristics of the two polymers are different, especially water uptake and rate of heterogeneous degradation. It is further shown that residual Sn concentrated within the matrix remnants whereas the content in Zn remained constant according to degradation controlled release.
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  • 96
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Copolymers containing vinyltrimethylsilane and vinyltrimethoxysilane with N-vinyl-2-pyrrolidone at different compositions were synthesized and characterized. The reactivity ratios was estimated by using the classical Fineman-Ross and Kelen Tüdos linear fitting procedures. These parameters were also estimated through a computer program based on nonlinear minimization algorithm, starting from the r1 and r2 values obtained by the former procedures. The analysis of the results allow us to interpret the reactivity behaviour of these polymers in terms of the relative reactivity of the substiuents. The effect of the chemical structure of the polymer side group is discussed in terms of the different contributions to the stabilization of the radical intermediates.
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  • 97
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: SUMMARY The crosslinked poly(acrylamido glycolic acid) (180-250 µm) was used in the adsorption/desorption studies. Adsorption rate, capacity of the resin for the selected metal ions, i.e. Cd(III), Zn(II), Hg(II), Pb(II), and Cr(III) were investigated in aqueous media. At different pH values (1.0–5.0) very high adsorption was observed for Pb(II) at pH 3 and 5. The adsorption equilibrium was rapidly achieved in about 5–10 min. However, when the Pb(II) ions competed with Cd(II) (in the case of the adsorption from their binary mixture) the amount of adsorption for Pb(II) decreased. Desorption of Pb(II) was studied by using 1-4M HNO3 and 1-4M HClO4. High desorption ratios (more than 90%) were achieved in all cases. Adsorption/desorption cycles showed the possibility of repeated use of this resin.
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  • 98
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Telechelically bis(hydrodimethylsilyl)-functionalized oligo(dimethylsiloxane)s or aromatics were found to give polymers constituting of alternating disilylene and oligodimethylsiloxane or 4,4′-diylaromatics as repeating units by dehydrogenative coupling reaction in the presence of palladium dibenzylideneacetone complex. The same catalyst gave polysilylenes with trisiloxane pendant from 1,1-dihydro-1,3,3,5,5,7,7,7-octamethyltetrasiloxane.
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  • 99
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Nanosize poly(methyl methacrylate) (PMMA) microlatexes with high PMMA/surfactant ratio have been successfully prepared by a modified microemulsion polymerization, i.e., continuous and slow addition of monomer (MMA) to the polymerizing MMA microemulsion with mild stirring. Number-average diameters of 33–46 nm with narrow polydispersity (Dv/Dn= 1.1) and polymer content of 6–24 wt% were achieved using low levels of surfactant (dodecyltrimethylammonium bromide, DTAB) — less than 1 wt% of the reaction mixture. Particle diameter depended on polymerization temperature, MMA content, and concentrations of initiator and surfactant. Larger particles wereformed when temperature was too high, initiator concentration was too high, or surfactant concentration was too low.
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    Polymer bulletin 38 (1997), S. 23-25 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Hybrid particles have been synthesized from methyltriethoxysilane (MTEOS) by the sol-gel process. The particle size, size distribution, particle surface morphology conductivity and pH of the reaction solution at different reaction times were determined. Compared with tetraethyl orthosilicate (TEOS) and p-(chloromethyl)phenyl-trimethoxysilane (CMPTOS), MTEOS has a slower hydrolysis rate.
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