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  • Articles  (76,221)
  • Articles: DFG German National Licenses  (76,221)
  • Springer  (76,221)
  • 1990-1994  (43,541)
  • 1980-1984  (32,680)
  • Physics  (76,221)
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  • Articles  (76,221)
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  • 1
    Electronic Resource
    Electronic Resource
    Indexed in current contents (1994)
    Springer
    Polymer bulletin 32 (1994), S. A3 
    Details
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308550
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanical properties of organosolv-lignin-filled thermoplastics (1994)
    Springer
    Polymer bulletin 32 (1994), S. 361-365 
    Details
    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 Organosolv lignin was used as organic filler for polypropylene (PP) and poly(ethene-co-vinylacetate) (EVA) containing 13wt-% vinylacetate. As a function of the lignin content, which was varied between 0 and 30wt-%, mechanical properties such as Young's modulus, yield stress, fracture stress, and elongation at break of the thermoplastic lignin-based compounds were measured. Both lignin-filled thermoplastics exhibit pronounced matrix reinforcement with increasing lignin content. Due to better interfacial adhesion between lignin and EVA, 30wt-% lignin addition to EVA doubles Young's modulus without sacrificing high elongation at break.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308549
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  • 3
    Electronic Resource
    Electronic Resource
    4-Vinylphthalic anhydride (1994)
    Springer
    Polymer bulletin 32 (1994), S. 373-380 
    Details
    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 4-Vinylphthalic anhydride can be prepared from phthalic acid via bromination and subsequent olefination (Heck-reaction). Homo- and copolymerization with styrene was accomplished using AIBN as initiator. The copolymer compositions were determined by infrared-spectroscopy. The copolymerization parameters are rs=0,15 and rVPA=3,09, the corresponding Q, e values of 4-vinylphthalic anhydride are estimated as Q=3,34 and e=0.09. Despite the fact that the molecular weights were rather low as a consequence of the reaction contions, the glass transition temperatures rise with increasing VPA content. The homopolymer has a glass transition temperature in the order of 226°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587877
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  • 4
    Electronic Resource
    Electronic Resource
    Homogeneous nucleation of the dispersed crystallisable component of immiscible polymer blends (1994)
    Springer
    Polymer bulletin 32 (1994), S. 471-477 
    Details
    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 Immiscible melt mixed blends of a crystallisable polyolefin (isotactic polypropylene, PP) and atactic polystyrene (PS) were prepared in a wide composition range. It was found that when PP is the major component in the blend its crystallisation behaviour is not affected by blending it with PS. However if PP is the minor component, it will be dispersed in the immiscible PS matrix, hence the nucleation mechanism changes from predominantly heterogeneous to predominantly homogeneous as long as the size of the dispersed PP droplets is below a critical value (of the order of 1–2 μm).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587890
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of glycidyl ethers modified by mesogenic units (1994)
    Springer
    Polymer bulletin 32 (1994), S. 529-536 
    Details
    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 New types of epoxy compounds containing biphenyl and azophenyl groups were synthesized. Model glycidyl ethers with one epoxy group were prepared to study the first reaction steps during the curing process. Diglycidyl ethers with or without a hexamethylene spacer were made to obtain epoxy networks. The structures of some intermediates and of the epoxy compounds synthesized were confirmed by Proton and Carbon-13 NMR spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00973898
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  • 6
    Electronic Resource
    Electronic Resource
    Anionic polymerization and copolymerization of cyclosiloxanes initiated by trimethylsilylmethyllithium (1994)
    Springer
    Polymer bulletin 32 (1994), S. 35-40 
    Details
    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 novel initiator, i.e. trimethylsilylmethyllithium has been successfully used for the ring opening polymerization of cyclosiloxanes, in toluene or in the bulk, in the presence of the cryptand [211] or DMSO. Suitable conditions have been found in which monomodal distributions of molecular weights are observed for homopolymers of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (V4) as well as for copolymers of V4 with D3 or D4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297411
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  • 7
    Electronic Resource
    Electronic Resource
    Editorial (1994)
    Springer
    Polymer bulletin 32 (1994), S. 1-2 
    Details
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297406
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  • 8
    Electronic Resource
    Electronic Resource
    Stereospecific propene polymerization with rac-[1,2-bis(η5-(9-fluorenyl))-1-phenylethane]zirconium dichloride/methylalumoxane (1994)
    Springer
    Polymer bulletin 32 (1994), S. 41-46 
    Details
    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 Methylalumoxane (MAO)-activated rac-[1,2-bis(η5-(9-fluorenyl))-1-phenylethane]zirconium dichloride (1) was used for propene polymerization at 30, 50, and 70°C and constant monomer concentration. The polypropene products are isotactic with stereoregularities depending on the polymerization temperature. The pentad distributions follow “enantiomorphic site statistics”, indicating stereocontrol being conducted by the chiral catalyst site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297412
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  • 9
    Electronic Resource
    Electronic Resource
    List of valid recommendations on macromolecular nomenclature (1994)
    Springer
    Polymer bulletin 32 (1994), S. 125-126 
    Details
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297424
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of a new styrene monomer: the 3-chloro-4-nitrostyrene (1994)
    Springer
    Polymer bulletin 33 (1994), S. 389-395 
    Details
    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 satisfactory synthesis route to a new monomer, the 3-chloro-4-nitrostyrene (3-CNS) is described. The results of free radical polymerisation experiments (limit of conversion, global kinetics) are reported by comparison with those of the isomer 4-chloro-3-nitrostyrene (4-CNS). They show the great influence of the nitro group position which markedly increases the reactivity of 3-CNS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293481
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  • 11
    Electronic Resource
    Electronic Resource
    Preparation of polystyrene poly(β-hydroxy nonanoate) graft copolymers (1994)
    Springer
    Polymer bulletin 33 (1994), S. 431-438 
    Details
    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 Poly(β-hydroxy nonanoate)-polystyrene graft copolymers were prepared by the reaction of active polystyrene containing peroxide group with poly(β-hydroxy nonanoate) at 80°C. Graft copolymers with a wide graft composition range depending on the amount of active polystyrene in the original mixture were produced and separated from the grafting product by fractional precipitation. NMR and IR spectra of the graft copolymers were containing the characteristic bands of the corresponding blocks. DSC curves of the graft copolymers had a large endotherm between 50 and 110°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293487
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  • 12
    Electronic Resource
    Electronic Resource
    Real-time small-angle synchrotron study of the crystallization kinetics of isotactic poly(1-hexadecene) (1994)
    Springer
    Polymer bulletin 33 (1994), S. 451-458 
    Details
    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 isothermal crystallization kinetics of the isotactic content of three poly(1-hexadecene) samples with different tacticity has been studied by real-time small-angle X-ray scattering using synchrotron radiation. The process was analyzed in terms of the Avrami equation. The value of the Avrami exponent was found to be approximately 1, suggesting instantaneous nucleation followed by rod-like growth. The results are compared with those previously obtained by differential scanning calorimetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293490
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  • 13
    Electronic Resource
    Electronic Resource
    Polymerization of styrene with diphenylzinc-butanone systems (1994)
    Springer
    Polymer bulletin 32 (1994), S. 367-371 
    Details
    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 the present work we report the results of the polymerization of styrene using diphenylzinc-butanone, Ph2Zn-MeCOEt. Our results indicate that these systems induce the polymerization of styrene reaching a larger conversion when the molar ratio MeCOEt/Ph2Zn=1,0. According to size exclusion chromatography, SEC, studies of the polystyrene obtained using the Ph2Zn-MeCOEt showed unimodal curves and have molecular weight distribution narrower than those obtained using the Ph2Zn-H2O system, suggesting a more simple reaction system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587876
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  • 14
    Electronic Resource
    Electronic Resource
    Poly(arylenecarbonate)s oligomers by carbonate interchange reaction of dimethyl carbonate with bisphenol-A (1994)
    Springer
    Polymer bulletin 32 (1994), S. 427-432 
    Details
    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 Fast atom bombardment mass spectrometry (FAB-MS) has been used to identify oligomers with different end groups obtained by the carbonate interchange reaction of bisphenol-A with dimethyl carbonate and the partial methanolysis of poly(bisphenol-A carbonate)s. Based on the FAB-MS data, a reaction pathway for the formation of compounds in the synthesized oligomers is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587884
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  • 15
    Electronic Resource
    Electronic Resource
    Semi-interpenetrating polymer networds produced with polyethylene terephthalate oligomer and unsaturated polyester resin (1994)
    Springer
    Polymer bulletin 32 (1994), S. 447-453 
    Details
    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 A series of semi-interpenetrating polymer networks (semi-IPN's) based on different compositions of an acyclic polyethylene terephthalate oligomer and unsaturated polyester resin (UP) were prepared. The oligomer was dissolved in the resin containing styrene crosslinker. Later this mixture was crosslinked at room temperature using methyl ethyl ketone peroxide catalyst and cobalt naphtanate as promoter. The tensile strength of the IPN's decreases as the concentration of oligomer increases, whereas, elongation to break increases. A characterization of the oligomer used is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587887
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  • 16
    Electronic Resource
    Electronic Resource
    Compatibilisation of polystyrene-polyolefin blends (1994)
    Springer
    Polymer bulletin 32 (1994), S. 479-485 
    Details
    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 impact properties of 1:1 polyolefin-polystyrene blends compatibilised with a series of hydrogenated styrene-butadiene block copolymers of various structures have been studied with a view to establishing a structure-property realationship. The most effective compatibiliser in this context appears to be a low molecular weight triblock (Kraton G1652). Addition of only 5% Kraton G1652 affords a ca. three-fold improvement in the impact strength for a 1:1 PP/PS blend over the uncompatibilised blend and leads to near HIPS impact strength for a 1:1 LDPE/PS blend. This compatibiliser is as effective as a high molecular weight tapered diblock and appears to be substantially more effective than either low molecular weight diblocks or a higher molecular weight triblock.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587891
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  • 17
    Electronic Resource
    Electronic Resource
    Metathesis copolymerization of chlorine-containing acetylenes with NBE catalyzed by MoCl5-n-Bu4Sn (1994)
    Springer
    Polymer bulletin 32 (1994), S. 517-524 
    Details
    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 the copolymerizations of 1-chloro-1-octyne (ClOc) and 1-chloro-2-phenylacetylene (ClPA) with norbornene (NBE) by MoCl5-n-Bu4Sn in toluene at-20°C, both comonomers were consumed simultaneously. The GPC curves of the copolymerization products were unimodal and identical irrespective of the RI and UV (290 nm) detectors. The13C NMR spectra of the products exhibited the presence of cross-propagating sequences. From these results, it is concluded that the copolymerization products are copolymers and not mixtures of homopolymers. The monomer reactivity ratios were: rClOc=0.69, rNBE=6.4; rClPA=1.0, rNBE=3.1. The more electron-donating the ring substituent of CiPA, the more reactive the ClPA in copolymerization with NBE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00973896
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  • 18
    Electronic Resource
    Electronic Resource
    Volume contents (1994)
    Springer
    Polymer bulletin 32 (1994), S. A5 
    Details
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297426
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  • 19
    Electronic Resource
    Electronic Resource
    Synthesis and properties of poly(diphenylacetylenes) having ether linkages (1994)
    Springer
    Polymer bulletin 32 (1994), S. 133-140 
    Details
    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 1-phenyl-2-(p-phenoxyphenyl)acetylene (p-PhODPA), 1-phenyl-2-(p-methoxyphenyl)acetylene, and 1-phenyl-2-(p-n-butoxyphenyl)acetylene was examined. These monomers polymerized with TaCl5-n-Bu4Sn to give methanol-insoluble polymers in over 60% yields. Poly(p-PhODPA) was a yellow solid completely soluble in toluene, CHCl3, etc., and its weight-average molecular weight was about 1.0x106 or higher. This polymer was thermally very stable (the onset temperature of weight loss in TGA in air was 420 °C). Its oxygen permeability coefficient (P o 2) was 37 barrers (P o 2/P n 2 2.2) and similar to that of natural rubber. In contrast, the other two polymers did not completely dissolve in any organic solvent, and their thermal stability was lower.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306379
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  • 20
    Electronic Resource
    Electronic Resource
    Homo- and copolymers of methacryloylmalodiethylester, synthesis and behaviour (1994)
    Springer
    Polymer bulletin 32 (1994), S. 141-147 
    Details
    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 Chelating polymers obtained by copolymerization of methacryl-oylmalodiethylester (MMDEt) with styrene, methylmethacrylate (MMA), N-vinylpyrrolidone (VPD) and N,N-dimethylacrylamide (DMAM) as well as the homopolymer of methacryloylmalodiethylester (MMDEt) have been investigated. Watersoluble chelating polymers derived from copolymerization with DMAM offer not only the possibility of a very fast removal of metal ions from aqueous solution, but are also insoluble after complexing certain metal ions and can therefore be separated by filtration. As additional investigations on the model acetyloylmalodiethylester (AMDEt) show, preferably hard metal ions such as Mg2+, Ca2+, Al3+ and Cu2+ with an ionic radius up to 1 Å are chelated by the enolic form of the β-ketodiester. The number of ligands for a metal ion corresponds to its valence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306380
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  • 21
    Electronic Resource
    Electronic Resource
    An analysis of the 1H- and 13C-NMR spectra of poly(3-bromostyrene) (1994)
    Springer
    Polymer bulletin 32 (1994), S. 207-214 
    Details
    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 300 MHz 1H-NMR spectrum of free radical initiated poly(3-bromostyrene) is similar to the 1H-NMR spectra of certain poly(vinyl heterocycles) and can be interpreted in a like manner. The 13C-NMR is typical of spectra for meta-substituted polystyrenes, with some of the carbon resonances showing a sensitivity to polymer stereochemistry. The spectra indicate that poly(3-bromostyrene) synthesized by free radical initiation is an atactic polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306390
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  • 22
    Electronic Resource
    Electronic Resource
    Effect of thermal molecular motion on pervaporation behavior of comb-shaped polymers with fluorocarbon side groups (1994)
    Springer
    Polymer bulletin 32 (1994), S. 193-200 
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    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 molecular motion of a series of comb-shaped polymers with heptadecafluorodecyl side chains (CF 8C2-) has been studied based on dynamic viscoelastic measurement. The main chain of comb-shaped polymers was poly(fumarate), poly(methacrylate), and poly(acrylate). Poly(fluoroalkylfumarate) with heptadecafluorodecyl group, P(CF 8C2-iPF) was amorphous polymer, whereas poly(acrylate) and poly(methacrylate) with CF 8C2-, P(CF 8C2-Acr) and P(CF 8C2-MAcr) showed mesomorphic behavior. The pervaporation behavior of water/organic mixtures through amorphous polymer, P(CF 8C2-iPF), and mesomorphic one, P(CF 8C2-Acr), were investigated. The distinct increase in permselectivity has been observed at the mesomorphic transition of P(CF 8C2-Acr).
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    URL: http://dx.doi.org/10.1007/BF00306388
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  • 23
    Electronic Resource
    Electronic Resource
    Synthesis of new donor-acceptor diarylacetylene chromophores and preparation of corresponding nonlinear optical side-chain polymers (1994)
    Springer
    Polymer bulletin 32 (1994), S. 265-272 
    Details
    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: Sammary New donor-acceptor substituted diarylacetylene hyperpolarizable chromophores bearing an amino group as donor and a methylsulfonyl group as acceptor at each extremities of an azatolane conjugated path have been designed to get a good nonlinearity-transparency trade-off, and synthesized. Corresponding methacrylate esters have been obtained then submitted to free radical polymerization, leading to novel side-chain nonlinear optical polymers and copolymers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308536
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  • 24
    Electronic Resource
    Electronic Resource
    Enthalpic interaction of diblock copolymers with immiscible polymer blend components (1994)
    Springer
    Polymer bulletin 32 (1994), S. 241-248 
    Details
    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 attempt is made to extend the model of Leibler for the emulsifying activity and interfacial properties of A-b-B diblock copolymers in incompatible blends of the homopolymers A and B-which are identical with the respective copolymer components- to enthalpically interacting C-b-D diblock copolymers, the block C being thermodynamically compatible with A and D with B. Due to the attractive enthalpic interaction the A/C-b-D/B compatibilized blends are promising for optimum phase adhesion (bold types for thermodynamically compatible partners). Thus, the extended model for a plane interfacial layer includes the enthalpic interaction of the compatible polymer pairs beside the entropic effects. The approach starts with the equillibrium supposition, not taking into consideration enthalpy driven migration effects of the block copolymer from the bulk to the interface, The model confirms a dominant role of the enthalpic interaction between blocks of the diblock copolymer and the respective homopolymers to the compatibilization of incompatible blend components. It is applicable also for blends compatibilized with block copolymers of unfavourable repulsive type interaction, A/C-b-D/B, and for blend systems with mixed type interactions, e. g. A/C-b-B/B or A/C-b-D/B.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306395
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  • 25
    Electronic Resource
    Electronic Resource
    A preliminary analysis of the high field 13C-NMR and 1H-NMR spectra of poly(2-thienyl vinyl ketone) (1994)
    Springer
    Polymer bulletin 32 (1994), S. 305-310 
    Details
    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 Poly(2-thienyl vinyl ketone) was synthesized via free radical initiation and its 300 H-NMR and 75.5 MHz 13C-NMR spectra were recorded and analyzed. The analysis showed that poly(2-thienyl vinyl ketone) is an atactic polymer.
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    URL: http://dx.doi.org/10.1007/BF00308541
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  • 26
    Electronic Resource
    Electronic Resource
    Electrical and third-order nonlinear optical properties of poly(2-fluoro-1,4-phenylenevinylene) and its copolymers (1994)
    Springer
    Polymer bulletin 33 (1994), S. 89-96 
    Details
    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 Poly(2-fluoro-1,4-phenylenevinylene), PFPV, and its copolymers have been synthesized via water soluble precursor route and their electrical and optical propreties were measured. It seems that electron-withdrawing fluorine substituent on phenylene ring increases the band-gap of PFPV and it affects electrical and optical properties. The conductivity values of FeCl3-doped drawn polymer films ranged from 10-1 to 101 Scm-1 depending on their composition, and were 10 times larger than those of undrawn ones. The χ(3) value for undrawn PFPV, using THG technique at 1907nm fundamental wavelength, was 4.76x10-12 esu.
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    URL: http://dx.doi.org/10.1007/BF00313478
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    A technique to measure the crystallinity of syndiotactic polystyrene using thermal analyses (1994)
    Springer
    Polymer bulletin 33 (1994), S. 109-112 
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    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 simple method for using differential scanning calorimeters to determine the crystallinity of syndiotactic polystyrene has been developed. Its validity was confirmed by use of infrared and x-ray analysis, as well as comparison to data from the literature. This method will be used to determine the effect of nucleating agents, shear stress, and temperature on the crystallization kinetics of syndiotactic polystyrene.
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    URL: http://dx.doi.org/10.1007/BF00313481
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    Polyether-modified fullerenes (1994)
    Springer
    Polymer bulletin 33 (1994), S. 175-182 
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    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: Summary Polyether-modified fullerenes have been prepared under mild conditions by reacting C60 or C70 in toluene with a precursor poly(oxyethylene) or poly(oxypropylene) polymer possessing amino end-groups. In the early stages of the interaction, soluble products are formed. Later, cross-linking proceeds between the polyfunctional fullerenes and the bifunctional polyethers. The non-crosslinked fullerene derivatives are soluble both in toluene and water; by evaporation of toluene, very adhesive films are formed.
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    Polysoap-induced polymerization of methyl methacrylate and styrene by poly(sodium alkyl 2-hydroxy-3-methacryloyloxypropyl phosphate)s in water (1994)
    Springer
    Polymer bulletin 33 (1994), S. 167-173 
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    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: Summary Poly(sodium alkyl 2-hydroxy-3-methacryloyloxypropyl phosphate)s as polysoap induced the radical polymerization of methyl methacrylate and styrene in the absence of an added radical initiator in water at 80°C. The polysoap having a C14 alkyl group showed the highest activity of all tested groups. The generalized initiation mechanism of the spontaneous polymerization in which the micellar aggregation state participates is discussed.
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    Poly(β-3-methylmalic acid): A new degradable functional polyester with two stereogenic centers in the main chain (1994)
    Springer
    Polymer bulletin 33 (1994), S. 149-158 
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    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: Summary Racemic ((3S,4R)-(3R,4S))-3-methyl-4-benzyloxycarbonyl-2-oxetanone has been prepared by a simple and reproductible method starting from a racemic mixture of threo-((2S,3S)-(2R,3R))-3-methylaspartic acid as chiral precursor. This α, β substituted β-lactone has been polymerized anionically, using tetraethylammonium benzoate as initiator, to yield high molecular weight and amorphous racemic threo-poly(β-benzyl-3-methylmalate). The catalytic cleavage of protecting benzyl ester groups has been conducted in different solvents and racemic threo-poly(β-3-methylmalic acid) has been obtained in N-methylpyrrolidone at room temperature. Racemic threo-poly(β-3-methylmalic acid-co-benzyl-β-3-methylmalate) has been prepared by heterogeneous H2/Pd charchoal catalyzed partial hydrogenolysis of the polymer precursor. Solubility of these different materials has been considered. Hydrolysis of threo-poly(β-3-methylmalic acid) has conducted to racemic threo-3-methylmalic acid. High resolution 13C NMR and selective INEPT NMR have been used for resonances assignment of polymers and copolymers. This new poly(β-hydroxy acid) type polyester expands the family of poly(β-malic acid) derivatives by opening the route for tailor making functional polystereoisomers with two stereogenic centers in the main chain and with the presence of an hydrophobic alkyl group and an hydrophilic carboxylic acid group in the macromolecule.
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    SERS evidence for existence of a critical concentration for polymer coil shrinking in poly(4-vinyl pyridine) solution (1994)
    Springer
    Polymer bulletin 33 (1994), S. 229-235 
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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 dependence of intensity of surface enhanced Raman scattering on the concentration of poly (4-vinyl pyridine) solutions was investigated. The spectral quality and the Raman scattering intensities of the enhanced spectra of poly (4-vinyl pyridine) adsorbed on nitric acid-roughened silver foil were inversely proportional to the concentration when it changed from semi-dilute to very dilute. The band intensity-concentration plot displays a turning point corresponding to the critical concentration for coil shrinkage. The observed phenomena are in accordance with Qian's proposal for the existence of C s for coil shrinkage in dilute solution.
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    Erratum (1994)
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    Polymer bulletin 33 (1994), S. 257-257 
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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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    URL: http://dx.doi.org/10.1007/BF00297364
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    Separation of poly(methyl methacrylate)s according to their tacticity (1994)
    Springer
    Polymer bulletin 32 (1994), S. 629-635 
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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 unconventional liquid chromatography of polymers under limiting conditions of their solubility was applied to poly(methyl methacrylate)s differing in their tacticity. The polymers were dissolved in thermodynamically good solvents and injected into an appropriate size exclusion chromatographic (SEC) column flushed with matched, moderately strong nonsolvents. The set of (limiting) conditions was found under which less soluble syndiotactic poly(methyl, methacrylate) moved along the column together with the zone of its initial solvent while better soluble isotactic poly(methyl methacrylate) was eluted according to the SEC mechanism. This indicates the potential of liquid chromatography under limiting conditions to characterize the tacticity of poly(methyl methacrylate)s.
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    Viscoelastic relaxations in poly(dimethylphenyl methacrylates) (1994)
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    Polymer bulletin 32 (1994), S. 675-678 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Dynamic mechanical properties of poly(dimethylphenyl methacrylátes) were studied considering the different positions of the methyl groups on the phenyl ring. In all cases a clear α relaxation can be observed which is associated to the polymer glass transition temperature (Tg). Nevertheless, at lower temperatures, viscoelastic activity is negligible. A correlation between the steric hindrance due to the methyl groups and the temperature at which the relaxation is detected, was established.
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    Relaxation processes in hyperbranched polyesters (1994)
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    Polymer bulletin 32 (1994), S. 679-685 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Dielectric permittivity and loss have been measured over the frequency range 10-2 Hz-10 kHz between 100 K and 350 K for samples of 50/50 mixtures of each of two hyperbranched polyesters, one five-generation hydroxy functional (5G-OH) and one threegeneration alkyl-terminated polymer (3G), with dielectrically inactive linear polyethylene. The thermal transitions of the hyperbranched polymers were studied with differential scanning calorimetry. Three relaxation transitions were found in 5G-OH: α, the glass-rubber transition and two subglass processes denoted β and γ showing Arrhenius temperature dependence both with an activation energy of 96±2kJ mol-1. The low temperature process could be assigned to motions of the terminal hydroxyl groups whereas β is due to reorientation of the ester groups. Sample 3G showed only a glass transition and one subglass process being assigned to reorientation of the ester groups. The high activation energy (202 kJ mol-1) of this process indicates that the ester groups are highly constrained in this polymer.
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    An X-ray photoelectron spectroscopy study of poly(methyl methacrylate) surface modified by 193-nm laser radiation (1994)
    Springer
    Polymer bulletin 33 (1994), S. 331-338 
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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 chemistry of poly(methyl methacrylate) subjected to 193-nm radiation, emitted by an argon-fluorine excimer laser, was studied by X-ray photoelectron spectroscopy. From the O/C atomic ratios measured at two different sampling depths, it is concluded that the role of depolymerization in the laser ablation process may be less important than previously suggested.
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    The application of miscibility parameter to the measurement of polymer-plasticizer compatibility (1994)
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    Polymer bulletin 33 (1994), S. 725-732 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly(vinyl butyral) (PVB)was found to precipitate from a clear plasticizer solution as it was cooled and this unique temperature (TP) (UCST) was noted. Poly(vinyl chloride) (PVC) did not precipitate and in this case the temperature at which it went into solution (TS) was noted. A quantity, referred to previously as the miscibility parameter (MP), is an excellent relative quantitative indicator of the miscibility of poly(vinyl butyral) and poly(vinyl chloride) with plasticizers as demonstrated from a correlation of MP with TP and Ts. Each polymer-plasticizer system is unique. A plot of MP vs. TP or TS for several polymer-plasticizer systems allows additional plasticizers to be evaluated for their plasticizing ability from calculated MP's without resorting to additional experimental measurements. The absolute level of MP acceptability is dictated by the application. For PVB, a copolymer which precipitates from a plasticizer/solvent, the interaction parameter chi(χ) is chi critical ( $$\chi _{cr} $$ ) at the TP of PVB in plasticizer. Since TP approximates the Θ temperature in the limit of molecular weight, the temperature of precipitation or Θ temperature, the solvent volume VS, and the $$\chi _{cr} $$ , define the theoretical MPcr as given by $$\frac{{(\chi _{cr} - 0.35)RT}}{{V_S }}$$ . All MPcr s were≈0.3 which represents the critical MP above which phase separation occurs. The low molecular weight plasticizers were estimated to drastically increase MPcr to about 1 for acceptable application compatibility and this value compares favorably with (PVB) acceptability for a wide range of plasticizer-PVB combinations based on a plasticizer DP of about 20.
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    Anisotropic friction on lamellar crystals of polyethylene by lateral force microscopy (1994)
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    Polymer bulletin 33 (1994), S. 459-464 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Frictional forces are very sensitive to the interface structure and the chemical and atomic structure of surfaces. It has been shown in the late 80′s (1) that lateral forces due to friction can be measured by atomic force microscopy (AFM) in the contact mode (2,3). This involves measurements which evoke vertical deflection of the AFM probe and observation of lateral forces which twist the AFM force sensor. A simultaneous detection of vertical deflection and twisting of the microcantilever can be done by using a four-sectored positional sensitive photodetector which measures the change in the deflection of a laser light reflected off the top of the microcantilever. The newest generation of SPM (Scanning Probe Microscope) equipment allows for simultaneous AFM and Lateral Force Microscopy (LFM) scans. There is ample evidence in the literature that contact-mode AFM can be used not only to investigate polymer morphology (4,5), but also to study polymer architecture from a true molecular perspective (6).
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    Structure and properties of styrene-divinylbenzene copolymers (1994)
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    Polymer bulletin 33 (1994), S. 487-491 
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    Notes: Abstract The influence of binary mixtures of heptane with different diluents on the porous structure of styrene-divinylbenzene (Sty-DVB) copolymers was investigated. It was found that the porosity produced by the diluent mixtures depends not only on the affinity of each diluent for the copolymer but also on the interaction of the diluent molecules with themselves. In this work it was observed that some polar aromatic solvents when mixed with heptane presented cosolvency effects. In general, the accessible pore volumes were higher than the fixed pore ones, indicating the formation of elastic internuclear chains.
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    The two-jet angular distribution probing virtual exotics at hadron colliders (1994)
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    The European physical journal 61 (1994), S. 91-95 
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    Topics: Physics
    Notes: Abstract Heavy virtual exotics, affecting the QCD quark-scattering amplitudes, can best be probed by the normalized two-jet angular distribution at the LHC, the SSC and the Fermilab Tevatron. As typical examples we considerSU(3) L ⊗SU(3) R axigluons andE 6 diquarks compared to the more familiar quark effective contact terms. We propose optimal jet pseudorapidity and invariant-mass cuts in order to enhance the signal at the future colliders. The discovery limits thus obtained, are studied in terms of energy and luminosity for each machine, comparatively.
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    The Higgs sector of the minimal supersymmetric standard model including radiative corrections (1994)
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    The European physical journal 61 (1994), S. 247-263 
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    Notes: Abstract We discuss the Higgs sector of the minimal supersymmetric standard model including effects of radiative corrections. The formalism is explained in detail for computing radiative corrections to the masses and the coupling constants of the Higgs bosons. The radiative corrections to the masses are studied in the on-shell renormalization scheme. The radiative corrections to the mixing angles between the two CP-even Higgs bosons and the Higgs self-coupling constants are investigated in a simple procedure. The explicit analytic expressions are given for the radiative corrections due to the loops containing the top and bottom quarks and their superpartners. Simple approximate formulae are derived from the analytic expressions obtained in the on-shell renormalization scheme. We numerically study the effects of radiative corrections on the mass of the lighter Higgs boson and the mixing angles between the two CP-even Higgs bosons.
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    The standard SU (2)×U(1) model in an external magnetic field at finite temperature and nonzero chemical potential (1994)
    Springer
    The European physical journal 61 (1994), S. 285-291 
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    Notes: Abstract The thermodynamic potential (TDP) of the boson sector of the Weinberg-Salam model in an external uniform magnetic field at finite temperature and nonzero chemical potential is calculated in one-loop approximation. In the high temperature limit with the use of Mellin summation technique explicit expressions for the thermodynamic potential are obtained to analyze its new minimum, different from the ordinary Higgs one. This new minimum is due to the root singularity in the oneloop expression for the TDP, originating as a consequence of the tachyonic mode in the spectrum of gauge boson in the magnetic field. It is demonstrated that in the high temperature limit the Higgs minimum possesses properties common with the ordinary superconductors and Abelian Higgs model. The influence of the magnetic field on the Higgs minimum is indirect and has a sufficiently complicated character. The presence of the non-zero chemical potential lowers the critical temperature leading to the disappearance of the Higgs minimum.
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    Meson properties from a bag model compared to lattice theory and heavy ion experiments (1994)
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    The European physical journal 61 (1994), S. 347-350 
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    Notes: Abstract A bag at temperature (T) with pressureB(T)=B(0)[1−(T/T c )4] is shown to be consistent with recent lattice data on the π and the ρ mesons. The limiting temperature,T l , of the pion bag from the Bekenstein entropy bound is lower than that of other mesons. This agrees with the thermal distribution of π,K and the ρ in heavy ion collisions, which (unlike proton-nucleus or pp data) show a marked difference inT of pion and other mesons in the mid-rapidity region.
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    Measurement of $$\Gamma (Z^0 \to b\bar b)/\Gamma (Z^0 \to hadrons)$$ using impact parameters and leptons (1994)
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    The European physical journal 61 (1994), S. 357-369 
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    Notes: Abstract A measurement of $$\Gamma _{b\bar b} /\Gamma _{had} \equiv \Gamma (Z^0 \to b\bar b)/\Gamma (Z^0 \to hadrons)$$ is presented using a “mixed tag” method involving the identification of $$Z^0 \to b\bar b$$ events by two different techniques. The first uses the large impact parameter of tracks emerging from the decay ofb-flavoured hadrons and the second their semi-leptonic decay. The identification efficiencies are measured from the data using all possible combinations of the two tags in opposite hemispheres. The method is therefore insensitive to Monte Carlo modelling of bottom quark production and ofb-flavoured hadron production and decay properties, and depends only weakly on the simulation of the detector. The data sample collected by OPAL at LEP in 1990 and 1991 is considered. The result is: $$\frac{{\Gamma _{b\bar b} }}{{\Gamma _{had} }} = 0.218 \pm 0.006(stat) \pm 0.007(syst) \pm 0.007(\Gamma _{c\bar c} /\Gamma _{had} ),$$ where the systematic uncertainty due to the charm quark partial width has been separated from the other systematic uncertainties. Combination with previous OPAL measurements gives: $$\frac{{\Gamma _{b\bar b} }}{{\Gamma _{had} }} = 0.220 \pm 0.004(stat) \pm 0.006(syst) \pm 0.006(\Gamma _{c\bar c} /\Gamma _{had} ),$$
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    Shape distortions of meson resonances produced in hadron interactions atP T≧2 GeV/c (1994)
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    The European physical journal 61 (1994), S. 371-381 
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    Notes: Abstract We study the shape of the invariant mass spectra of several resonances produced atP T≧2.0 GeV/c and observed through two-particle final states, namely thef 2(1270),K *(892), $$\bar K*(892)$$ ,K *(1430), and $$\bar K*(1430)$$ mesons. The data sample comes from π− Be interactions atP lab=150 GeV/c and 300 GeV/c which have been collected using the OMEGA spectrometer at CERN. We find that although these meson resonances have their masses and widths consistent with the corresponding world average values, their shapes are all subject to the same kind of distortion: their low-mass tail is enhanced while their high-mass tail is sharply cut. This observation indicates that meson resonances produced in the fragmentation of quarks and gluons are distorted by the same damping factor in a way which preserves their masses and lifetimes.
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    Properties of theη(1440) (1994)
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    The European physical journal 61 (1994), S. 425-431 
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    Notes: Abstract The phenomenology of the pseudoscalar η(1440) meson (also known as l) is discussed in a simplified η, η′ l mixing scheme in which the η is assumed to have no glueball component. The parameters of the model are quite well constrained from the η and η′ two-photon decays. First it is shown that the scheme is in rather good general agreement with (almost) all the available data. Then a number of testable predictions concerning decays involving the iota are made. The iota turns out to be largely a glueball in this model.
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    Stranger still: Kaon loops and strange quark matrix elements of the nucleon (1994)
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    The European physical journal 61 (1994), S. 433-440 
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    Notes: Abstract Intrinsic strangeness contributions to lowenergy strange quark matrix elements of the nucleon are modelled using kaon loops and meson-nucleon vertex functions taken from nucleon-nucleon and nucleon-hyperon scattering. A comparison with pion loop contributions to the nucleon electromagnetic (EM) form factors indicates the presence of significantSU(3)-breaking in the mean-square charge radii. As a numerical consequence, the kaon loop contribution to the mean square Dirac strangeness radius is significantly smaller than could be observed with parity-violating elastic $$\vec e$$ p experiments planned for CEBAF, while the contribution to the Sachs radius is large enough to be observed with PV electron scattering from (0+, 0) nuclei. Kaon loops generate a strange magnetic moment of the same scale as the isoscalar EM magnetic moment — a scale large enough to be observed at CEBAF — and a strange axial vector form factor having roughly one-third of the magnitude extracted from $$vp/\bar vp$$ elastic scattering. In the chiral limit, the loop contribution to the fraction of the nucleon's scalar density arising from strange quarks has roughly the same magnitude as the value extracted from analyses of∑ πN . The importance of satisfying the Ward-Takahashi Identity, not obeyed by previous calculations, is also illustrated, and the sensitivity of results to input parameters is analyzed.
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    The sigma term and the quark number operator in QCD (1994)
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    The European physical journal 61 (1994), S. 453-463 
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    Notes: Abstract We discuss the relationship of the forward matrix element of the operator $$\bar \psi \psi $$ , related to the so-called sigma term, to the quark number. We show that in the naive quark model in the canonical formalism these quantities coincide in the limit of small average quarkmomenta. In the QCD parton model defined through light-front quantization this result is preserved at leading perturbative order but it receives radiative corrections. We analyze the theoretical and phenomenological consequences of this result, which provides a bridge between a current algebra quantity, the sigma term, and a deepinelastic quantity, the parton number.
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    Dynamics of moving and spinning skyrmions (1994)
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    The European physical journal 61 (1994), S. 479-494 
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    Notes: Abstract We study the intermediate-and long-range forces between moving and spinning Skyrmions, employing two different methods. One uses a relativised product ansatz for the Skyrme fields, the other models Skyrmions as triplets of scalar dipoles. The methods lead to the same finite-dimensional Lagrangian dynamical system which may be interpreted as a point-particle approximation to Skyrmion dynamics. We discuss in detail the dynamics in the so-called attractive channel and the interaction between well-separated and rapidly spinning Skyrmions, and point out the resemblance between the latter and the one-pion exchange potential in nuclear physics.
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    Measurement of $$b\bar b$$ correlations at the CERN $$p\bar p$$ collider (1994)
    Springer
    The European physical journal 61 (1994), S. 41-52 
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    ISSN: 1434-6052
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    Topics: Physics
    Notes: Abstract We report on measurements of correlated $$b\bar b$$ production in $$p\bar p$$ collisions at $$\sqrt s = 630GeV$$ , using dimuon data to tag both theb and $$\bar b$$ quarks. Starting from an inclusive dimuon sample we obtain improved cross-sections for single inclusive beauty production and confirm our earlier results on $$B^0 - \bar B^0$$ mixing. From a study of $$b\bar b$$ correlations we derive explicit cross-sections for semi-differential $$b\bar b$$ production. We compare the measured cross-sections and correlations to $$\mathcal{O}\left( {\alpha _s^3 } \right)$$ QCD predictions and find good quantitative agreement. From the measured angular distributions we establish a size-able contribution from higher order QCD processes with a significance of about seven standard deviations. A large nonperturbative contribution to these higher order corrections is excluded.
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    A measurement of multi-jet rates in deep-inelastic scattering at HERA (1994)
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    The European physical journal 61 (1994), S. 59-66 
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    Topics: Physics
    Notes: Abstract Multi-jet production is observed in deep-inelastic electron proton scattering with the H1 detector at HERA. Jet rates for momentum transfers squared up to 500 GeV2 are determined using the JADE jet clustering algorithm. They are found to be in agreement with predictions from QCD based models.
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    Model-independent measurement ofω→ηγ decay branching ratio (1994)
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    The European physical journal 61 (1994), S. 35-40 
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    Topics: Physics
    Notes: Abstract The rare ηγ decay width of the ω-meson has been measured in a model-independent way, with ω produced in 38 GeV/c π− p charge-exchange. Large momentum transfer events have been selected in order to eliminate ω-ρ interference contribution. BR (ω→ηγ) =(8.3±2.1)·10−4. The gammas from ω→ηγ→3γ decay have been detected with the multiphoton spectrometer GAMS-2000 at the IHEP 70 GeV proton accelerator.
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    Measurements of the total cross section differenceΔσ Т innp transmission between 0.86 and 0.94 GeV (1994)
    Springer
    The European physical journal 61 (1994), S. 53-57 
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    Notes: Abstract We present results of the total cross section differenceΔσ Т obtained in transmission measurements at the energies 0.86, 0.88, 0.91 and 0.94 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was transmitted through the polarized Saclay frozen-spin proton target. The beam and target polarizations were oriented in the vertical direction. The present results agree with previous SATURNE measurements and improve the amplitude analysis in the forward direction.
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    Representation of osp (2, 2) q (2) andS-matrix of super sine-Gordon theory (1994)
    Springer
    The European physical journal 61 (1994), S. 105-108 
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    Notes: Abstract We investigate the representations of the osp (2, 2) q (2) algebra, which leads to theS-matrix of super sine-Gordon theory. TheS-matrix has been derived from supersymmetric conformal field theory with some assumptions. We show that the conjecturedS-matrix can be derived from the representation theory using a correspondence between the representations of osp (1, 2) q and those of sl(2) q .
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    On theO(1/N 2)β-function of the Nambu-Jona-Lasinio model with non-abelian chiral symmetry (1994)
    Springer
    The European physical journal 61 (1994), S. 115-124 
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    Notes: Abstract We present the formalism for computing the critical exponent corresponding to the β-function of the Nambu-Jona-Lasinio model withSU(M)×SU(M) continuous chiral symmetry atO(1/N 2) in a largeN expansion, whereN is the number of fermions. We find that the equations can only be solved for the caseM=2 and subsequently an analytic expression is then derived. This contrasting behavior between theM=2 andM〉2 cases, which appears first atO(1/N 2), is related to the fact that the anomalous dimensions of the bosonic fields are only equivalent forM=2.
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    Pseudoscalar glueball in terms of composite interpolating fields (1994)
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    The European physical journal 61 (1994), S. 147-155 
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    Notes: Abstract The pseudoscalar (PS) glueball is described with an account of the quark-gluon mixing and strict observation of the QCD local gauge and renormalization invariance. The lower limits on the mass and total width are established. The partial radiative decay widths and the PS-glueball production inJ/gY radiative decays are calculated. The consistency of the results with the η- and η′-meson data onJ/Ψ→PV decays is verified. On the basis of the results, the lower PS-glueball state may be identified with the upper iota state η(1490).
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    Soft photon production in the boost-invariant color-flux tube model (1994)
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    The European physical journal 61 (1994), S. 171-177 
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    Topics: Physics
    Notes: Abstract Starting from the classical expressions for emission of radiation we calculate soft photon production in the boost-invariant color-flux tube model. In the center-of-mass system of the initial tube we find that for large energies $$(\sqrt s \sim 20GeV)$$ the production of photons with frequencies: 20 MeV〈ω〈50 MeV, and emitted perpendicularly to the collision axis is strongly enhanced; it exceeds considerably production of photons given by the Low limit. For the emission more collinear with the collision axis and for decreasing ω the effect becomes weaker and, eventually, in the limit ω=0 we recover precisely the Low formula. We also find that for smaller energies $$(\sqrt s \sim 5GeV)$$ the emission of photons is well reproduced by the Low formula. Generally speaking, the observed enhancement is related to the existence of a large, i.e. extended in time, region of photon emission. This, in turn, results from the time dilation accompanying the space-time evolution of tubes. Strong time dilation effects follow from the boost-invariance of our model and, for larges, considerably enhance radiation of soft photons. By the same token, this enhancement decreases with decreasings, because dilation decreases.
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    Measurement of the photon structure functionF 2 γ in the reactione + e −→e + e −+hadrons at LEP (1994)
    Springer
    The European physical journal 61 (1994), S. 199-208 
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    Notes: Abstract We present measurements of the hadronic photon structure functionF 2 γ (x), in twoQ 2 ranges with mean values of 5.9 GeV2 and 14.7 GeV2. The data were taken by the OPAL experiment at LEP, with $$\sqrt s$$ close to theZ 0 mass and correspond to an integratede + e − luminosity of 44.8 pb−1. In the context of a QCD-based model we find the quark transverse momentum cutoff separating the vector meson dominance (VMD) and perturbative QCD regions to be 0.27±0.10 GeV. We confirm that there is a significant pointlike component of the photon when the probe photon hasQ 2〉4 GeV2. Our measurements extend to lower values ofx than any previous experiment, and no increase ofF 2 γ (x) is observed.
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    Studies of charged particle multiplicity inb quark events (1994)
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    The European physical journal 61 (1994), S. 209-221 
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    Notes: Abstract Using the distance from the average primary vertex to reconstructed secondary vertices in jets, samples of events withb purity varying from about 13% to 89% have been selected. The charged particle multiplicity in the hemispheres opposite those containing these jets has been studied as a function of theb purity of the events. Extrapolating to 0% and 100%b purity, values of the hemisphere charged particle multiplicity inZ 0→ $$b\bar b$$ events and in non- $$b\bar b$$ events have been measured to be $$\begin{gathered} \bar n_b = 11.71 \pm 0.03 \pm 0.18 \pm 0.21, \hfill \\ \bar n_{udsc} = 10.32 \pm 0.01 \pm 0.07 \pm 0.19. \hfill \\ \end{gathered}$$ The first error is statistical, the second systematic and the third is a common systematic error. The difference in charged particle multiplicity betweenb quark events and light (u, d, s) quark events has been measured and found to be $$\delta _{bl} = 3.02 \pm 0.05 \pm 0.79.$$ The result is compared to the predictions of MLLA QCD calculations. By studying the impact parameter distributions of charged particles in the hemispheres opposite these jets, the charged particle decay multiplicity ofB hadrons fromZ 0 decay, including particles fromK s 0 and Λ decay, has been measured to be $$\bar n^B = 5.51 \pm 0.05 \pm 0.51.$$ From the mean momentum of these decay products and separately from the number of primary charged particles perb event, the averagex E ofb flavoured hadrons has been measured to be $$\left\langle {x_E } \right\rangle _b = 0.693 \pm 0.003 \pm 0.030.$$
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    Semileptonic decays ofB mesons into excited charm mesons: Leading order and 1/m c contributions (1994)
    Springer
    The European physical journal 61 (1994), S. 293-296 
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    Notes: Abstract We use the heavy quark effective theory to investigate the form factors that describe the semileptonic decays of aB meson into excited daughter mesons. For an excited daughter meson with charm, a single form factor is needed at leading order, while five form factors and two dimensionful constants are needed to order 1/m c in the heavy quark expansion. For non-charmed final states, a total of four form factors are needed at leading order. For the processB→D * Xℓν, four form factors are also needed at leading order.
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    Quantum gases with internal symmetry revisited (1994)
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    The European physical journal 61 (1994), S. 297-301 
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    Notes: Abstract An analysis of an appearance of chemical potentials in thermodynamical systems with an internal symmetry is presented. Arguments are given that one should introduce also chemical potentials which are not related to internal symmetries. Condensation properties of the ideal gas are an example showing how the behaviour of the system depends on chemical potentials. There is also a possibility to use a chemical potential related to the particle number conservation as a tool to reproduce some properties of the hadronic matter formed in heavy ion collisions.
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    Derivation of the Wess-Zumino action for the generalized Schwinger model from the Batalin-Fradkin algorithm (1994)
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    The European physical journal 61 (1994), S. 317-322 
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    Notes: Abstract We apply the Batalin-Fradkin algorithm combined with the Batalin-Fradkin-Vilkovisky formalism to the generalized Schwinger model. We obtain the Becchi-Rouet-Stora-Tyutin invariant action showing that the auxiliary fields introduced in the algorithm turn into the Wess-Zumino scalar.
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    Similarity of hadron production inpp and heavy-ion collisions (1994)
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    The European physical journal 61 (1994), S. 341-345 
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    Notes: Abstract The characteristic features of pseudorapidity distributions of hadron production are investigated in terms of a geometrical parameterh≡(dn/dη)0/Φ, Φ being the phase space covered by the η distribution. It is found thath is about the same for the heavy-ion (HI) andpp collisions at the same energy, the same for π andK production and behaves ash∼E cm −1/3 . This similarity property yieldsK −/π−=0.041±0.004 andK +/K −=4.5±0.6 for HI collisions at 14.6 GeV/A in agreement with BNL experiments.
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    J/gy suppression as evidence for high densities in nuclear collisions (1994)
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    The European physical journal 61 (1994), S. 351-355 
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    Notes: Abstract We determine the hadron density necessary to account forJ/ψ suppression in nuclear collisions by absorption, including the effects of nuclear stopping andJ/ψ formation time. The suppression measured in central 200 GeV/A O-U and S-U collisions cannot be obtained from interactions of theJ/ψ with the primary nucleons alone. Absorption on primary and secondary hadrons can describe these data, however, provided the density of the secondaries is at least 0.8 fm−3, i.e., five times standard nuclear density.
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    Search forN ϕ (1960) baryon (1994)
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    The European physical journal 61 (1994), S. 399-405 
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    Notes: Abstract In the experiments at the SPHINX facility in the 70 GeV proton beam of the IHEP accelerator the diffractive production reactionsp+N→[Σ(1385)0 K +] +N andp+N→[Σ(1385)0 K +]+N+ (neutral particles) were studied. In the effective mass spectra of the [Σ(1385)0 K +] system in these processes there were no signals from the anomalously narrow baryon stateN ϕ (1960) which had been observed earlier in the measurement at the BIS-2 setup.
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    Direct measurements of shear-induced particle migration in suspensions of bimodal spheres (1994)
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    Rheologica acta 33 (1994), S. 185-192 
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    Keywords: Suspension ; particle migration ; demixing ; bimodal ; anisotropy ; concentration gradient
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A variety of studies reported in the literature have established that initially well mixed suspensions subjected to non-homogeneous shear flows attain an anisotropic particulate structure. It has also been shown that non-homogeneous shearing causes suspensions of unimodal spheres to demix, i.e., gradients in solids concentration are formed. The objective of this study was to determine the effect of non-homogeneous shear flows on suspensions of bimodal particles, and specifically, to determine if the solids concentration gradients which develop are accompanied by size segregation of the coarse with respect to the fine fraction. We used the simplest and most direct methods to determine the relative solids concentrations: visual observation of tracer particles in transparent suspensions and physical separation of the coarse and fine solid fractions. Three different types of non-homogeneous shear flows were examined, and in each case the data support two main conclusions: 1) suspended particles migrate from regions of high shear rate to regions of low shear rate, and 2) the coarse fraction of particles migrates much faster than the fine fraction, leading to size segregation of initially well-mixed suspensions. While the former conclusion is consistent with other studies reported in the literature, to our knowledge this paper provides the first data supporting and, to a limited extent, quantifying the latter conclusion.
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    Boundary conditions for contract lines in coextrusion flows (1994)
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    Rheologica acta 33 (1994), S. 241-241 
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    Topics: Chemistry and Pharmacology , Physics
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    Fractional complex modulus manifested in asphalts (1994)
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    Rheologica acta 33 (1994), S. 344-354 
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    Keywords: Complex modulus ; relaxation ; fractional relaxation modes ; asphalts
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract In recent years, a considerable effort has been made to develop a new generation of asphaltic materials based on a combination of polymers and asphalts. Regular and polymer-modified asphalts are studied via fractional relaxation processes, represented here by a fractional rational form of the complex modulus, G *. Basic properties of this complex modulus and the forms of generated constitutive equations are studied. Relaxation times of the model are related via a pseudospectrum to the phase angle lag.
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    Fractional relaxation and the time-temperature superposition principle (1994)
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    Rheologica acta 33 (1994), S. 337-343 
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    Keywords: Rheological models ; viscoelasticity ; fractional differentiation ; non-Debye relaxation ; thermo-rheological simplicity ; projection operator
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Relaxation processes in complex systems like polymers or other viscoelastic materials can be described by equations containing fractional differential or integral operators. In order to give a physical motivation for fractional order equations, the fractional relaxation is discussed in the framework of statistical mechanics. We show that fractional relaxation represents a special type of a non-Markovian process. Assuming a separation condition and the validity of the thermo-rheological principle, stating that a change of the temperature only influences the time scale but not the rheological functional form, it is shown that a fractional operator equation for the underlying relaxation process results.
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    A domain perturbation study of steady flow in a cone-and-plate rheometer of non-ideal geometry (1994)
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    Rheologica acta 33 (1994), S. 369-384 
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    Keywords: Cone-and-plate rheometer ; domain perturbation ; viscoelastic fluid ; secondary flow
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The method of domain perturbation developed by Joseph is used to calculate velocity and stress profiles in a slightly misaligned cone-and-plate rheometer where the cone is spinning and the plate is stationary. Results for a Newtonian fluid, a Criminale-Ericksen-Filbey fluid, an upper-convected Maxwell fluid, and a White-Metzner fluid are presented and compared with earlier results in which the cone is stationary and the plate is spinning (Dudgeon and Wedgewood, 1993). Streamlines calculated for the Newtonian fluid show a very small recirculation region near the stationary plate. Velocity and stress contours are symmetric around the plane of largest gap width. For the elastic fluids studied, streamlines are asymmetric. The fluid response lags where the fluid is dominated by memory effects. Much larger recirculation regions are calculated for fluids dominated by shear thinning. These recirculation regions contain a large fraction of the fluid in the apparatus and have the effect of changing the shape of the flow domain for the remaining fluid that rotates around the cone's axis. Elasticity also has a pronounced effect on the stress profile, indicating that the accuracy of the cone and plate may be compromised even for small mis-alignments.
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    Phase volume and size effects on the terminal relaxation of ABS melts (1994)
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    Rheologica acta 33 (1994), S. 446-453 
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    Keywords: ABS ; terminal relaxation ; gel point ; particle size ; interparticle distance
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The dynamical viscoelasticity of ABS melts with different particle size was investigated at various levels of rubbery phase contents. The effects of the rubber are more pronounced in the terminal zone: a transition from viscoelastic liquid to viscoelastic solid behavior was observed which can be interpreted as a physical gelation occurring at a critical rubbery phase content. This critical content resulted in being smaller in the case of smaller particles. A quantitative explanation of the experimental findings was proposed in terms of the average interparticle distance and overlapping of the chains grafted onto the neighboring rubber particles. The gel-like transition appeared to correspond to an approximately constant level of grafted chains overlapping.
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    A terminally anchored polymer chain in shear flow: Self-consistent velocity and segment density profiles (1994)
    Springer
    Rheologica acta 33 (1994), S. 485-505 
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    Keywords: Anchored bead-rod chain ; Brownian dynamics ; simulation ; shear flow ; surface bound polymer
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The behavior of a terminally anchored freely-jointed bead-rod chain, subjected to solvent shear flow, was investigated via Brownian dynamics simulations. Previous calculations have been improved by computing the segment density and fluid velocity profiles self-consistently. The segment density distributions, components of the radius of gyration, and chain attachment shear and normal stresses were found to be sensitive to low values of shear rate. Additionally, it was found that the thickness of a model polymer layer was a strong function of the shear rate, and that the functional dependence on shear rate changed dramatically as the chain length increased. For the longest chains studied, the thickness of the model polymer layer first increased as the shear rate increased, passed through a maximum, and then decreased at high shear rates, in accordance with experimental results in theta solvents. These results suggest that a dilute or semi-dilute layer model may explain hydrodynamic behavior previously thought to be due to the entanglements that occur in dense surface bound polymer layers.
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    Geometry dependence of the viscosity of a thermotropic LC-polymer measured by slit dies (1994)
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    Rheologica acta 33 (1994), S. 542-552 
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    Keywords: LC-polymers ; capillary rheometry ; slit die wall effect ; ordered texture ; Frank elasticity
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    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract This paper reports on geometry dependent viscosity curves of the biaxial thermotropic LC-Polymer Vectra B 950 measured with rectangular slit dies. The geometry dependence of the flow behaviour originates from the flow of two layers. The layer near the wall is highly flow oriented and free from defects. The layer in the bulk has an ordered texture. The thickness of the wall layer decreases with wall shear stress. Based on the Frank theory and the assumption that the core of a moving disclination is the smallest radius of distortion, the wall layer thickness is predicted and compared with experimental data.
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    Solidification behavior of the theta system 2-propanol/poly(n-butyl methacrylate) I. Influences of thermoreversible gelation on stationary flow (1994)
    Springer
    Rheologica acta 33 (1994), S. 159-164 
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    ISSN: 1435-1528
    Keywords: Zero shear viscosity ; polymer melts ; polymer solutions ; magnetoviscometer ; thermoreversible gelation ; glass transition temperatures ; critical molecular weight ; master curves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Zero shear viscosities, η0, were determined by means of a magnetoviscometer for melts of poly(n-butyl methacrylate) (M = 8.7 to 450 kg/mol, T =53.5 to 200°C) and for concentrated solutions of the highest molecular weight sample in isopropanol (T = 34.8 to 131.5 °C). Master curves can be constructed in both cases if the reference temperature is set proportional to the gelation temperature of the particular fluid. Special intersegmental interactions (eventually leading to thermoreversible gelation) can above all be felt in η0 (T) and in M c , the critical molecular weight determined in plots of log η0 vs. log M. As the temperature is lowered, the behavior changes from WLF to Arrhenius, and M c declines considerably. The former observation is explained by analogy to the transition from fragile to hard glasses resulting from increased crosslinking. The latter effect can also be rationalized in terms of a physical network reducing the molecular weight that is required for the formation of entanglements.
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    On the behavior of fine mud suspensions (1994)
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    Rheologica acta 33 (1994), S. 175-184 
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    ISSN: 1435-1528
    Keywords: Yield stress ; rheometry ; suspensions ; mud ; natural clay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Flows of natural mud-water mixtures are of great interest for industrial and civil engineering. But there is still no general agreement about the methods for determining the main rheological characteristics of these systems. We propose here an accurate rheological study of some natural mud-water mixtures. We first discuss the possible effects of changing various parameters such as temperature, pH, electrolyte concentration, solid concentration, clay type. The behavior of these muds appears to be very sensitive to most of these parameters and to be hardly predictable from a knowledge of their components. Then, we show that a Herschel-Bulkley model fits very well steady flow experimental data for a very large range of shear rates. We also suggest physical explanations of this model in agreement with our observations of behavior changes when some parameters change. The yield stress value of this model provides a good estimation of real yield stress which is a key parameter for mixture behavior. These considerations are very useful to characterize, predict, and compare various mud flows.
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    URL: http://dx.doi.org/10.1007/BF00437302
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    Error propagation in laser beam spatial parameters (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. 25-34 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have performed a propagation-of-errors analysis on two methods used to determine the spatial parameters of a laser beam. We measured diameters of a diode laser beam focused by a 993 mm focal length lens. Measurement uncertainties of less than 1% can result in uncertainties greater than 200% in locating the beam waist of the laser. We compare the inherent uncertainties in the spatial parameters as obtained by the two methods. Longer focal length lenses and lens position can reduce this magnification of uncertainty, but would require large propagation distances.
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    URL: http://dx.doi.org/10.1007/BF00573898
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    Splice loss in single- and twin-core buried channel waveguide devices (1994)
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    Optical and quantum electronics 26 (1994), S. 45-62 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We quantify the magnitude of the power loss incurred when a square-core buried channel waveguide (BCW) is spliced to a standard circular-core telecommunications fibre. With a view to minimizing the dissipated power, we show that a simple equal-core-area criterion provides an elegant means of determining the optimum core dimensions. This result is found to hold for more general BCW cross-sections that possess a reasonable degree of symmetry. The fundamental problems of waveguide misalignment and angular tilt are also investigated and their effect on splice loss is quantified. Our theoretical model is applied to both single- and twin-core waveguides.
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    URL: http://dx.doi.org/10.1007/BF00573900
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    Nonlinear optical interactions in dye-doped solids (1994)
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    Optical and quantum electronics 26 (1994), S. 1-23 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We present a brief review of non-linear optical investigations on dye-doped solids using low-power CW lasers. After a brief introduction to the photophysics of the dye molecules, we discuss specific nonlinear processes such as self-diffraction, optical phase conjugation, two-beam coupling and polarization gratings in these systems. The application potential of dye-doped solid devices is discussed.
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    URL: http://dx.doi.org/10.1007/BF00573897
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    Book review (1994)
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    Optical and quantum electronics 26 (1994), S. 1041-1042 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    URL: http://dx.doi.org/10.1007/BF00305004
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    Impact ionizing electroluminescence of a double barrier structure (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. 1033-1040 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The impact ionizing electroluminescence model of a unipolar double barrier structure has been developed. The electron density in the quantum well and the hole density generated in the collector region are based on electron current. The electroluminescence results from direct radiative recombination between the electrons and holes in the quantum well. The results show that a light on-off ratio of the electroluminescence can be obtained.
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    URL: http://dx.doi.org/10.1007/BF00305003
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    Phase-conjugate bistability and multistability in moving-grating operated orthogonally polarized pump four-wave mixing in photorefractives (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. 1019-1032 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We establish possible regions of bistability (BIST), multistability (MUST), hysteresis, self-oscillation (SO) and enhancement features of the phase-conjugate reflectivity (PCR) by use of moving-grating operation (MGO) in the orthogonally polarized pump four-wave mixing (OPP-FWM) geometry employing a photorefractive (PR) crystal (usually BaTiO3). Numerical evaluation of such PCR features has been presented as a function of parameters such as coupling strength (of complex gL and real g 0 L values), frequency-shift (Ω) owing to grating motion, the PR phase shift (øPR), and pump (r) and probe (q) intensity ratios. PCR results of this geometry are compared with those obtained from the regular (i.e. parallel-polarized pump) four-wave mixing (REG-FWM) geometry assuming the same set of parameters in both geometries. We find that the OPP geometry leads to a drastic PCR enhancement together with the appearance of a rich variety of multibranched solutions exhibiting BIST and MUST features of the PCR, particularly in the range 0.5 ≲ Ω ≲ 3 with values g 0L ∼ 10, r=1 and q ≲ 0.1 that are practically realizable. Nevertheless, this geometry sometimes offers the possibility of a PCR jump (from one stable state to the other), suggesting hysteresis caused by changing Ω only slightly. In the REG geometry, however, the PCR enhancement is less prominent, and also the BIST/MUST features rarely exist unless g 0 L becomes sufficiently large, say ∼ 20 or more.
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    URL: http://dx.doi.org/10.1007/BF00305002
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    Photoinduced dichroism and birefringence in films of Mordant Pure Yellow/poly(vinyl alcohol): simultaneous real-time investigations at two wavelengths (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. 1013-1018 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Photoinduced anisotropy in films of azo-dye Mordant Pure Yellow (MPY) dissolved in a polyvinyl alcohol matrix, is investigated. The photodichroism and photoinduced birefringence are measured in real time for two wavelengths, 488 nm (in the absorption band) and 633 nm (outside it), on excitation with an Ar+ laser beam. It is shown that strong dichroism is induced without changing the average optical density of the film, and the kinetic curves of the birefringence and the dichroism are substantially different. The conclusion is made that the photoprocesses of the dye molecules cause a reconstruction of the matrix.
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    URL: http://dx.doi.org/10.1007/BF00305001
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    On the possibility of mode-locking a dye laser by a fast saturable absorber (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. 79-85 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The problem of mode-locking a fully relaxing saturable (dye) laser medium by an instantaneously saturating (fast) absorber is theoretically considered when group velocity dispersion and Kerr-type nonlinearity are present. Off-resonant chirped solutions are found whose minimum duration is determined by the relative losses (saturable and nonsaturable) and by the saturation depth of the absorber. The addition of nonlinear elements can only broaden the stability range of the solution with respect to the group velocity dispersion.
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    URL: http://dx.doi.org/10.1007/BF00558143
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    Review of numerical and approximate methods for the modal analysis of general optical dielectric waveguides (1994)
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    Optical and quantum electronics 26 (1994), S. S113 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: AbstactAbstact This paper reviews numerical and approximate methods for the modal analysis of general optical dielectric waveguides with emphasis on recent developments. Six groups of methods are reviewed, covering (1) the finite-element method, (2) the finite-difference method, (3) the integral-equation method, (4) methods based on series expansion, (5) approximate methods based on separation of variables, and (6) methods that do not fit into the above groups, ranging from the specialized ones for analysing restricted classes of waveguides to the most general ones for analysing inhomogeneous, arbitrarily-shaped, anisotropic waveguides. Some suggestions with regard to the selection of methods for particular applications are given.
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    URL: http://dx.doi.org/10.1007/BF00384667
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    Computation of higher-order waveguide modes by imaginary-distance beam propagation method (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. S199 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstact Yevick and Hermansson presented an efficient numerical method for calculating fundamental modes of optical waveguides. We extend their technique to higher-order eigenmodes. Using a finite-difference beam propagation method, we obtain propagation constants and field profiles for the three lowest-order TE modes in an asymmetric rib waveguide.
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    URL: http://dx.doi.org/10.1007/BF00384673
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    Analysis of the eigenmodes of two coupled Ti: LiNbO3 optical waveguides and its application (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. S173 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstact Two kinds of trial solutions for the symmetric and antisymmetric modes of the parallel Ti: LiNbO3 waveguide structure are proposed and their parameters are determined by use of the variational method. Comparison with the results of the finite-element method and reported experimental results shows that the solutions composed of Hermite-Gaussian functions might achieve better accuracy. It is shown that the formulae established here are suited for both single waveguide structures and coupled waveguide structures. In addition, we discuss the optimal electrode design for the symmetric directional coupler switches with a zero waveguide spacing. It is found that the required drive voltage can be lowered by choosing a small electrode gap and an appropriate electrode width.
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    URL: http://dx.doi.org/10.1007/BF00384671
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    Simple finite-difference algorithm for calculating waveguide modes (1994)
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    Optical and quantum electronics 26 (1994), S. S151 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstact A simple algorithm for solving the finite-difference (FD) equations for the mode eigenvalues and field distributions of a linear waveguide is presented. By applying the discretized Helmholtz operator column-by-column to an index distribution defined on an N x N grid, a matrix whose size is only a few times N x N is obtained. This yields a reduction in computation time and space compared with the other classical FD approaches which involve an N 2 x N 2 matrix. Our method is tested against problems for which the exact solutions are known, and we find a high degree of accuracy. Despite the existence of fast algorithms for the treatment of the classical N 2 x N 2 matrix, our new algorithm presents some advantages over existing FD methods of comparable speed, including: the ability to find all the modes and associated field profiles, very high numerical stability, and no numerical approximations in the procedure. In addition, some general optimum expressions for the domain size and density of grid points which are consistent with the desired precision are provided, and apply to any FD method including ours.
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    Semiconductor waveguide directional couplers for coherent receivers (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. S529 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Optical waveguide 3-dB couplers integrated on semicondutors have been studied, designed and fabricated, using both bulk and diluted multi-quantum-well InGaAsP/InP-based materials, grown by MOCVD. The device structure is based on the two-mode interference (TMI) principle and is fully compatible for integration with the optoelectronic and electronic components of a coherent receiver. Bulk material couplers provide an output balanced within 0.05 dB per nanometer and an excess loss of 1.4 dB, compared to a straight guide, while coupling loss to a tapered-lensed single mode fibre is 4 dB. Improved coupling efficiency to single-mode fibres is achieved by use of moderately diluted multi-quantum-well waveguides, which include InGaAsP wells and InP barriers: coupling loss to a tapered-lensed single-mode fibre as low as 0.5 dB and excess loss of 1.8 dB are featured. Couplers fabricated with this waveguide structure have a balance sensitivity of 0.03 to 0.04 dB per nanometer. A moderately diluted multi-quantum-well 3-dB coupler has been permanently pigtailed and butt-coupled to a dual balanced PIN photoreceiver. This hybrid assembly was tested in a coherent transmission system at 155 and 622 Mbits-1 showing sensitivities, for 10-9 BER, of about-38.0 dBm and-28.8 dBm, respectively.
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    URL: http://dx.doi.org/10.1007/BF00306222
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    Design, modelling and implementation of the ATMOS project fibre delay line photonic switching matrix (1994)
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    Optical and quantum electronics 26 (1994), S. S497 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract This paper presents the fibre delay line switching matrix, a high-performance photonic system consisting of an electrically controlled optical high-speed transport network. This photonic matrix adopts the asynchronous transfer mode (ATM) technique and an internal self-routing architecture based on wavelength encoding, for cell routing and multiplexing. A set of output queues provides the buffering function. An extensive performance evaluation is presented, with reference to both the traffic throughput and technology feasibility. Numerical results have been obtained to evaluate optical performance and the implementation of a 4×4 demonstrator, supporting a 2.5 Gbit s-1 input/output rate, shows the feasibility of the matrix with state-of-the-art optical technology. Its high performance makes the fibre delay line switching matrix a strong candidate for implementing the core of future high-speed broadband ATM switches.
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    URL: http://dx.doi.org/10.1007/BF00306220
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    Tuneable fibre source for picosecond pulses around 1.55 μm with repetition rates up to 20 GHz (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. S547 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We report on the generation of picosecond optical pulses around 1.55 μm using a tuneable actively mode-locked erbium-doped fibre ring laser. Pulse widths of less than 10 ps have been achieved within the wavelength range 1518 to 1570 nm at a pulse repetition rate of 20 GHz. Pulse trains with lower repetition rates have been generated using electrical square-wave signals for driving the electrooptic modulator, resulting in 〈20 ps pulse widths. The implementation of an all polarization-preserving fibre ring cavity enabled stable and reproducible operation of the laser. Minimization of the overall ring dispersion offers tuneability at nearly constant repetition rate throughout the whole wavelength range. Simple analytic expressions are given that allow for optimization of the ring laser performance with respect to output power, relaxation oscillations and wavelength tuneability at constant repetition rate.
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    Space-charge-induced interband optical nonlinearities in asymmetric coupled quantum wells (1994)
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    Optical and quantum electronics 26 (1994), S. S565 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Space-charge-induced optical nonlinearities for asymmetric coupled quantum wells have been studied. Calculations for optimized AlGaAs structures show that a blue-shift of the band gap of 9 meV at a carrier density of 1012 cm-2 can be obtained. Experimental comparisons with a rectangular well show a large increase in room-temperature nonlinearities.
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    Erratum: ‘Succession of one-soliton pulses in the zero-dispersion region of silica optical fibres: the role of the phase difference between adjacent pulses’ (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. S583 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    URL: http://dx.doi.org/10.1007/BF00306227
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    Experimental determination of exponential parameters for multiphonon residual absorption in a ZBLAN: Er3+ fibre (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. S559 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Determination of exponential parameters for both Stokes and anti-Stokes sidebands by excitation of a ZBLAN: Er3+ fibre and bulk samples gives values of 9.4×10-3 cm and 14.1×10-3 cm, respectively. Observed values are larger than equivalent parameters usually found for nonradiative transitions. As examples, the measured parameters are used to determine the multiphonon sideband absorption between the 4I11/2 and the 4I13/2 electronic transitions of Er3+ and also between 1G4 and 3F4 of Pr3+. Available energy ranges for sideband pumping of distributed amplifiers are given as well as the minimum multiphonon background losses intrinsic to the rare-earth plus pure glass base combination.
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    Corrigendum: ‘Output power limitations in CW single transverse mode Nd:YAG lasers with a rod of large cross-section’ (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. S584 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    Optical fibre amplifiers: physical model and design issues (1994)
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    Optical and quantum electronics 26 (1994), S. 585-608 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The development of optical fibre amplifiers has caused an impressive evolution in optical telecommunications systems since the end of the 1980s. The widespread application of active fibre amplifiers requires accurate tools to design and simulate these devices in very different operating conditions. The present work describes some physical aspects of active fibre amplifiers and a numerical model for the analysis of active optical fibres that can be applied to investigate spatial and spectral properties of amplifiers for the transmission windows of optical fibre telecommunications. Finally, various design issues relevant to the investigation of optimal fibre design of silica, fluoride erbium-doped and fluoride praseodymium-doped fibres are discussed and illustrated by means of examples.
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    Measurement of beam quality degradation due to spherical aberration in a simple lens (1994)
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    Optical and quantum electronics 26 (1994), S. 629-632 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have measured the effect on laser beam quality factorM 2 of spherical aberration in a simple planoconvex lens. Theory predicts that the laser beam quality should remain essentially unchanged until the incident beam widthw exceeds a critical widthw q above which the beam quality will degrade rapidly, with theM 2 value increasing as (w/w q 4). We find good agreement between this theory and our experimental data.
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    Modelling and characterization of ferroelectric liquid crystal displays (1994)
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    Optical and quantum electronics 26 (1994), S. S571 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Modelling of liquid crystal displays is useful to predict their optical properties and dynamic behaviour. An integrated modelling system for ferroelectric liquid crystal displays has been developed. The system employs data from real FLC materials, polarizers, glasses, backlights, and colour filters, aiming to describe actual devices accurately. Optical transmission dependence on light wavelength and angle of incidence is obtained as a function of the liquid crystal director profile. This profile is in turn derived from energy minimization of bulk and glass surface conditioning contributions. The above static model has been extended to study sample switching in multiplexed displays. Usual slot times in actual displays are quite close to time response of FLC materials, hence no energy-minimized configurations are obtained upon switching. A dynamic model has been formulated to derive the director profile evolution with time, according to the employed driving scheme, and the rotational viscosity of the material. Predicted dynamic and optical results have been compared to experimental measurements on FLC test cells. It has been found that the behaviour of FLC cells depends on a large number of physical and optical parameters. Some of them may be obtained from FLC data sheets, and manufacturing conditions. Other parameters related to director profiles in relaxed states may be experimentally obtained by sample characterization through optical transmission measurements. A few little known parameters (e.g. specific elastic constants) remain; fortunately their influence on cell dynamics is low.
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    Influence of thermal fluctuation noise on two-wave mixing in saturable absorbers (1994)
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    Optical and quantum electronics 26 (1994), S. 633-640 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have extended the description of nonlinear optical two-wave mixing in a three-level saturable absorbing medium to include a noise contribution from thermally driven fluctuations in the real part of the refractive index. An effective gain factor is introduced to describe this influence on the signal beam and numerical data are given for ruby. These data, which include saturation, show that the influence of noise on the signal beam near the saturation gain value is more than ten times larger than that calculated using the theory for a Kerr medium for the same gain value.
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    Optical document security (1994)
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    Optical and quantum electronics 26 (1994), S. 645-646 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    URL: http://dx.doi.org/10.1007/BF00712925
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    Exact transcendental equation for scalar modes of rectangular dielectric waveguides (1994)
    Springer
    Optical and quantum electronics 26 (1994), S. 641-644 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Conclusion A Fourier operator method has been used to derive for the first time an exact closed-form eigenvalue equation for the scalar mode propagation constants of a buried rectangular dielectric waveguide. The new method has been implemented and the results used to determine the accuracy of the scalar finite-difference approach. It is hoped that the exact results obtained here may assist in the validation of the accuracy of the other numerical and semi-analytical methods.
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    URL: http://dx.doi.org/10.1007/BF00712924
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