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  • Articles  (18,849)
  • Springer  (16,373)
  • American Association for the Advancement of Science (AAAS)  (2,476)
  • American Association of Petroleum Geologists (AAPG)
  • Emerald
  • Frontiers Media
  • 2020-2022
  • 1995-1999  (18,849)
  • 1995  (18,849)
  • Physics  (18,849)
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  • Articles  (18,849)
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  • 2020-2022
  • 1995-1999  (18,849)
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  • 1
    Electronic Resource
    Electronic Resource
    Crystallization of water in swollen poly(vinyl alcohol)-poly(vinyl pyrrolidone) blends (1995)
    Springer
    Polymer bulletin 35 (1995), S. 649-652 
    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 Water molecules sorbed in pure poly(vinyl alcohol) and poly(vinyl pyrrolidone), as well as in their blends is found to be only partially crystallizable. The fraction of noncrystalizable water is shown to vary with the blend composition. Such variation is explained by the newly proposed Tg-regulation effect when the swollen blend materials is cooled down. A part of the sorbed water cannot crystallize due to the fact that during cooling the amorphous polmer-water phase is frozen before the water crystallization temperature is reached.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324121
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  • 2
    Electronic Resource
    Electronic Resource
    Study of siloxane-modified epoxy resin using thermally stimulated current (1995)
    Springer
    Polymer bulletin 35 (1995), S. 641-648 
    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 low temperature relaxation of epoxy resin modified with siloxane oligomers was investigated by using thermally stimulated current (TSC) and relaxation map analysis (RMA). The β-relaxation of epoxy resin and the glass transition temperature of siloxane oligomer were folded and shifted to higher temperature as the concentration of trifluoropropyl (TFP) in siloxane oligomer increased. In the systems containing over 50% of TFP a new relaxation peak due to the dipole orientation was observed at around-45°C. As the concentration of TFP increased the compensation temperature (Tc) and the degree-of-disorder (DOD) were increased while the compensation time, τc was decreased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324120
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  • 3
    Electronic Resource
    Electronic Resource
    Cationic oligomerization of 3-methylene-p-menth-4(8)-ene and 2-methyl-3-methylene-5-isopropylbicyclo [3.1.01,5] hexane (1995)
    Springer
    Polymer bulletin 35 (1995), S. 653-658 
    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 title monomers were synthesized via Wittig reaction from thujone and pugelone. The monomers were found to react rapidly with cationic initiators at temperatures from -15° to 22°C. The products of these reactions were found to be low molecular weight oligomers. The reaction temperature, presence of solvent or initiator type and concentration seemed to have some effect on the molecular weights of the products obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294945
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and chelating properties of poly[(N,N-dicarboxymethyl)allylamine] derived from poly(allylamine) (1995)
    Springer
    Polymer bulletin 35 (1995), S. 659-663 
    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[(N,N-dicarboxymethyl)allylamine] as a water-soluble polymeric chelating agent was prepared by carboxymethylation of poly(allylamine) (PAA) with chloroacetic acid or bromoacetic acid. The 1H-NMR, IR, and elementary analyses showed that the iminodiacetic group was introduced quantitatively into the amino group of PAA. Chelating properties of this polymeric chelating agent toward Cu2+, Ni2+, Zn2+, and Ba2+ were examined by potentiometric titration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294946
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  • 5
    Electronic Resource
    Electronic Resource
    Copolymerization of N-vinyl phthalamide with acrylate and methacrylate monomers and preliminary analysis of the stereochemistry of poly(N-vinyl phthalamide) (1995)
    Springer
    Polymer bulletin 35 (1995), S. 665-670 
    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 N-Vinyl phthalamide was copolymerized with methyl methacrylate, isobutyl methacrylate or butyl acrylate. The copolymerizations were initiated free radically and it was necessary to conduct the polymerizations in solution or else insoluble products would result. In most cases the polymerizations preceded to relatively high conversions in a short time. The conversions necessitated the use of high conversion methods to calculate the reactivity ratios. The N-vinyl phthalamide was found to be the less reactive monomer in all cases. As part of this study, poly(N-vinyl phthalamide) homopolymer was synthesized by free radical initiation. While the 1H-NMR spectrum yield very little information concerning polymer stereochemistry, the methine carbon resonance in the 13C-NMR spectrum displayed a sensitivity to polymer stereochemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294947
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  • 6
    Electronic Resource
    Electronic Resource
    Cyclopolymerization of cinnamate ester derivatives of alkyl α-(hydroxymethyl) acrylates (1995)
    Springer
    Polymer bulletin 35 (1995), S. 671-676 
    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 Three new monomers for cyclopolymerization were synthesized using phase transfer catalysis of ethyl α-(chloromethyl) acrylate (ECMA), t-butyl α-(bromomethyl) acrylate (TBBMA) and isobornyl α-(bromomethyl)acrylate (IBBMA) with cinnamic acid sodium salt. Bulk and solution polymerization at 70–80°C using AIBN gave soluble cyclopolymers with Mn=13650 and Mw=36540 for the ethyl ester, Mn=47700 and Mw=86900 for the t-butyl ester and Mn=3500 and Mw=4650 for the isobornyl ester monomer. The ester polymerizabilities decreased with increasing substituent bulkiness. FTIR spectra showed ca 30 to 93% cyclic units depending on the concentration of the monomer used in polymerizations. DSC thermograms showed that alkyl group size had little effect on Tg's, with values of 151°C, 156°C, and 164°C for the ethyl, t-butyl and isobornyl esters, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294948
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of poly(tetrahydrofuran-b-ε-caprolactone) macromonomer via the Sml2-induced transformation (1995)
    Springer
    Polymer bulletin 35 (1995), S. 683-689 
    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 well-defined macromonomer consisting of different types of monomers in polymerization mechanisms was synthesized for the first time through the SmI2-induced transformation. The macromonomer, ω-methacryloylpoly-(tetrahydrofuran-b-ε-caprolactone), was prepared by the reaction of methacryloyl chloride with living poly(tetrahydrofuran-b-ε-caprolactone) [poly(THF-b-CL)] which was obtained by the two-electron reduction of the cationic growing center of poly(THF) by samarium iodide (SmI2) followed by the polymerization of CL. 1H NMR analysis indicated the quantitative introduction of the methacryloyl group onto the polymer end. The molecular weight distribution of the macromonomer was relatively narrow, and the unit ratio of THF to CL could be controlled by both polymerization time of THF and the amount of CL, resulting from the living nature of both CL- and THF-polymerizations. Radical copolymerization of the produced macromonomers with methyl methacrylate in the presence of AIBN resulted in a polymethacrylate backbone grafted with poly(THF-b-CL) block copolymers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294950
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis and electrical properties of poly[2-(2-(4-trifluoromethyl)phenyl)ethenyl-1,4-phenylenevinylene] and PPV copolymers (1995)
    Springer
    Polymer bulletin 35 (1995), S. 697-704 
    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-(2-(4-(trifluoromethyl)phenyl)ethenyl)-5-methoxy-1,4-phenylenevinylene] (PFEMPV) and a series of PPV copolymers containing 1,4-phenylenevinylene (PV) units were synthesized through a water-soluble precursor route, and their electrical and third-order nonlinear optical properties were studied. The PFEMPV films could not be doped with I2, but FeCl3-doped films showed an electrical conductivity of 5.0x10-4 S/cm. The conductivities of FeCl3-doped copolymer films ranged from 2.0x10-3 to 2.0 S/cm depending on their copolymer compositions. The third-order nonlinear optical susceptibility, χ(3)(−ω;ω,ω,−ω), was also investigated by the degenerate four wave mixing technique at 602 nm. The χ(3) value of PFEMPV was 6.9x10-11 esu. The photoluminescence spectrum of PFEMPV shows its emission maximum at 550 nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294952
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  • 9
    Electronic Resource
    Electronic Resource
    A novel and versatile method for the synthesis of soluble fullerenated polymers (1995)
    Springer
    Polymer bulletin 35 (1995), S. 705-710 
    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 new route for the preparation of soluble fullerenated polymer through the reaction of carbanion intermediates of polymers with fullerenes, particularly C60, is demonstrated. Confirmation of the covalent attachment of C60 to the polystyrene backbone is by a variety of techniques such as UV-Vis, FT-IR, TGA, SEM and 13C NMR etc. The product, which has a visibly brownish yellow cast when compared with the unreacted polymer, is soluble in some common organic solvents. The thermal stability of pure polystyrene is enhanced by C60-chemical modification, and no bonds within the carbon sphere are broken.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294953
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  • 10
    Electronic Resource
    Electronic Resource
    Analysis of the 1H-NMR and 13C-NMR spectra of poly(3-methyl-1-vinylpyrazole) (1995)
    Springer
    Polymer bulletin 35 (1995), S. 711-718 
    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 title monomer was polymerized in solution via free radical initiation. The polymer's 300 MHz 1H-NMR and 75.5 MHz 13C-NMR spectra were recorded and analyzed in terms of polymer stereochemistry. Most of the resonances in both the 1H-NMR and 13C-NMR spectra showed multiplicity consistent with sensitivity to polymer stereochemistry. However the 13C-NMR spectrum proved somewhat easier to interpret. The analysis of both the 1H-NMR and 13C-NMR spectra very strongly indicate that poly(3-methyl-1-vinylpyrazole) is an atactic polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294954
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  • 11
    Electronic Resource
    Electronic Resource
    A comparative study of etching enamel by acid and laser (1995)
    Springer
    Lasers in medical science 10 (1995), S. 37-42 
    Details
    ISSN: 1435-604X
    Keywords: Enamel ; Etch ; Laser ; Acid ; Nd-YAG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Acid etching is regarded as one of the main means of providing additional retention in aesthetic dentistry. Alternative methods of achieving bonding to tooth tissue which have been proposed include laser etching. Conflicting results on bond strength to enamel have been reported for laser etching. Here the tensile bond strength of composite resin to acid- and laser-etched enamel was measured and the topographical differences between the surfaces were evaluated using the scanning electron microscope. The laser used was a pulsed Nd-YAG laser at 10 pulses per second with a pulse length of 150μs, 80mJ pulse−1, 1.064μm wavelength. The results obtained indicate that the bond strength of laser-etched enamel was significantly lower than that of acid-etched enamel. In this study the difference may be attributable to the chromophore used. Variations in the rate of traverse of the laser tip across the surface did not appear to produce significant alterations in the bond strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02133162
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  • 12
    Electronic Resource
    Electronic Resource
    Laserthermia kills acidotic cancer cells more effectively than conventional hyperthermia (1995)
    Springer
    Lasers in medical science 10 (1995), S. 31-36 
    Details
    ISSN: 1435-604X
    Keywords: Embryonal carcinoma ; F9 cells ; Laser ; Hyperthermia ; Nigericin ; Acidosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The aim of this study was to investigate how acidosis affects the sensitivity of F9 embryonal carcinoma cells to conventionally induced hyperthermia and Nd-YAG laser-induced laserthermia. Nigericin, a polyether ionophore, was used to reduce the intracellular pH to 6.8, while the control cells were maintained at a physiological pH of 7.4. Acidosis increased the heat sensitivity significantly. After the water bath only 75% of the acidotic F9S1 cells were viable, whereas all of the control cells at pH 7.4 survived. When the laser was used, the difference was even more pronounced. Only 9% of the acidotic cells were viable after a 2-min treatment and 0.2% after a 4-min treatment. At physiological pH a 2-min treatment left 41% of the cells viable and a 4-min treatment 2%. This study showed that laserthermia is significantly more effective in killing cells with low intracellular pH than it is in killing cells with normal intracellular pH. The core of a tumour is often acidotic and thus radioresistant. It is suggested that laserthermia could be a good choice when treating acidotic radioresistant cancer cells, and its effect as an adjuvant to radiation therapy should be investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02133161
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  • 13
    Electronic Resource
    Electronic Resource
    Diode lasers: Experimental and clinical review (1995)
    Springer
    Lasers in medical science 10 (1995), S. 157-163 
    Details
    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Diode lasers are now capable of delivering up to 60 W of power down thin optical fibres, and their medical applications have increased considerably over the past 5 years. Most of the recent experimental and clinical work has been performed using the 805 nm diode laser wavelength, which is more heavily absorbed and is less penetrating than the 1064 nm Nd-YAG wavelength in most tissues. In contact and non-contact mode, the overall tissue effects from the diode laser are similar to the Nd-YAG laser, but with interstitial therapy the 805 nm wavelength produces significantly greater necrosis than the 1064 nm wavelength. Experimental work has established the effectiveness of the diode laser and clinical work has confirmed its suitability for a wide variety of procedures. Diode lasers have the major advantages of being small, compact, portable, efficient, easy to use and virtually maintenance free; they are likely to replace more cumbersome lasers for many medical applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02133326
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  • 14
    Electronic Resource
    Electronic Resource
    Transmyocardial revascularization (1995)
    Springer
    Lasers in medical science 10 (1995), S. 83-91 
    Details
    ISSN: 1435-604X
    Keywords: Transmyocardial revascularization ; Lasers ; Coronary artery disease ; Ischaemia ; Tissue hibernation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Transmyocardial revascularization (TMR) is a puncture technique proposed as a solution for patients with coronary artery disease who cannot be efficiently treated with the standard revascularization procedures such as bypass surgery or percutaneous transluminal coronary angioplasty (PTCA). The studies presented in this review have investigated the use of lasers to revascularize ischaemic myocardium. Needle puncture methods are also briefly described. The results from experimental studies are not conclusive but the encouraging clinical reports raise further questions about the mechanism of angina relief.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02150845
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  • 15
    Electronic Resource
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    The effect of the illumination time when treating port-wine stains (1995)
    Springer
    Lasers in medical science 10 (1995), S. 93-104 
    Details
    ISSN: 1435-604X
    Keywords: Copper vapour laser ; Electron microscopy ; Illumination time ; Numerical modelling ; Optimal treatment ; Port-wine stain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract This paper reports the electron microscopy results obtained from two patients who were treated with 5 W of yellow (578 nm) light from a copper vapour laser with an illumination time of 3.6 ms and a 0.3 mm spot diameter. The endpoint of treatment was transient blanching. Following treatment, erythema was observed. There was minimal damage to the epidermis and non-vascular tissue such as the nerve fibres. There was severe damage to the endothelial cells of the ectatic vessels. Twenty-four hours after treatment, platelet activation and collagen were present, indicating that these vessels were no longer viable. Theoretical calculations are used to determine the flow of heat within and away from a 50μm diameter vessel. From this, heating of the entire vessel is shown to occur with illumination times of 4 ms, with minimal heating of the non-vascular tissue. Shorter illuminations do not heat the entire vessel, while the use of longer illumination times will cause excessive damage to the surrounding non-vascular tissue. Illumination times close to 4 ms must be regarded as optimal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02150846
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  • 16
    Electronic Resource
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    Photodynamic therapy to the oral cavity, tongue and larynx: a canine normal tissue tolerance study (1995)
    Springer
    Lasers in medical science 10 (1995), S. 13-18 
    Details
    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Larynx ; Oval cavity ; Light dose rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy (PDT) has the potential to treat early carcinomas of the oral cavity and larynx while preserving normal tissue. However, normal tissues retain the photosensitizing agents and may be activated by high light fluence and dose rates resulting in normal tissue necrosis. The effects of varying dose rates of light delivery on various tissues in the upper aerodigestive tract have not been evaluated to date and are necessary to determine a ‘therapeutic light dose range’ that will result in selective tumour necrosis. Thirty adult mongrel dogs received intravenous Photofrin, 2 mg kg−1, 48 h prior to PDT treatment. Photodynamic therapy was administered to the tongue, buccal mucosa and larynx with a microlens fibre and implantable cylindrical diffuser at various dose rates from 20 to 125 J cm−2 at 150 mW cm−2. At the same dose rate of light delivery, the tongue was the most sensitive organ, followed by the buccal mucosa, and last by the larynx. The differential tissue effect of identical dose rates of therapy must be taken into account when administering PDT so that selective tumour necrosis with normal tissue preservation may be achieved. This study indicates the need to perform evaluations of the effect of PDT on other tissue types in an animal model with each new photosensitizer prior to administering PDT to those areas in humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02133158
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  • 17
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    The relevance of pulse repetition rate and radiant exposure to the neurophysiological effects of low-intensity laser (820 nm/pulsed wave) irradiation upon skin temperature and antidromic conduction latencies in the human median nerve (1995)
    Springer
    Lasers in medical science 10 (1995), S. 253-259 
    Details
    ISSN: 1435-604X
    Keywords: Nerve conduction ; Laser therapy ; Skin temperature ; Biostimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The effects of low-intensity near-infra-red laser irradiation (820 nm; 1.5 and 9.0 J cm−2; pulsed at 12 Hz, 73 Hz and 5 kHz) upon peripheral neurophysiology and skin temperature were investigated using antidromic conduction studies in the human median nerve in vivo. Healthy human volunteers (n = 90) were recruited and allocated randomly to either a control group (n=10) or one of eight experimental groups (two radiant exposures, 1.5 J cm−2 and 9.0 J cm−2 at one of three pulse repetition rates, 12 Hz, 73 Hz or 5 kHz, in addition to a placebo group for each radiant exposure;n = 10 all groups). Analysis of variance (ANOVA) demonstrated a significant (p≤0.05) decrease in skin temperature following irradiation at the lowest radiant exposure (1.5 J cm−2) combined with pulse repetition rates of 73 Hz and 5 kHz, with the greatest effect at 73 Hz. These changes in skin temperature were coupled with increases in negative peak latency (NPL); ie changes in NPL were inversely related to changes in skin temperature. However, in contrast to the authors' previous findings using continuous wave (CW) laser irradiation, differences in NPL were not found to be significant. These findings, therefore, provide little evidence of the neuro-physiological effects of low-intensity infra-red irradiation at the dosage levels and pulse repetition rates used here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02133617
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  • 18
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    Laser Doppler velocimetry in retinal arteries of infants (1995)
    Springer
    Lasers in medical science 10 (1995), S. 267-272 
    Details
    ISSN: 1435-604X
    Keywords: Blood flow pulsatility ; Human infants ; Laser Doppler velocimetry ; Retinal blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The present study was conducted to assess the feasibility of laser Doppler velocimetry in young infants, as a prelude to ultimately undertaking such measurements in premature infants. A portable, unidirectional laser Doppler velocimeter was developed based on a Kowa RC-2 hand-held fundus camera. Six infants between 1 and 21 weeks of age were studied. Relative red blood cell velocity (δfmax) at the centre of retinal arteries was measured over approximately 10 heart cycles. A pulsatility parameter (P=1−δfmax.dia/δfmax.sys), a summary index of vascular status, was determined from the average diastolic and systolic values of δfmax. Velocity waveforms were obtained in four of the six infants. Arterial pulsatility for the group was 0.63±0.13. Precise non-invasive measurement of arterial red blood cell velocity waveforms in young infants was achieved. The high signal-to-noise ratio and temporal resolution of this data suggest that relative measurements of retinal blood flow may permit assessment of haemodynamic changes in premature infants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02133619
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  • 19
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    Polymer-solvent interaction parameter for poly(4-hydroxystyrene) by IGC (1995)
    Springer
    Polymer bulletin 34 (1995), S. 677-684 
    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 polymer-solvent interaction parameter, χ12, was determined for poly(4-hydroxystyrene) (P4HS) at 443 and 463 K, by inverse gas chromatography (IGC) using several probes. The partial molar heat of mixing at infinite dilution in the polymer was also calculated. The solubility parameter δ2 of P4HS has been obtained by using the method developed by DiPaola-Baranyi and Guillet. Moreover using the equation-of-state theory the contact interaction energy, X12, was also determined. The variation of the interaction parameters were correlated with the size and kinds of atoms present in the molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00423368
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  • 20
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    Emulsion polymerization of styrene in the presence of carbohydrate-based amphiphiles (1995)
    Springer
    Polymer bulletin 34 (1995), S. 691-698 
    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 Novel amphiphilic N-alkyl-, N-decenyl-, and N-alkyl-N'-methyl-semicarbazones of maltose and maltotriose with CnH2n+1 alkyl chains and n=8,9,10,11,12,16 were applied as emulsifiers in styrene emulsion polymerization. Surfactant properties, emulsion polymerization, and rheology were examined as a function of amphiphile molecular architectures. Both critical micelle concentration and average polystyrene particle size increased with decreasing alkyl chain length. Using N-methyl-N-[11-(acryloylamino)-undecanoyl]-glucamine comonomer in a starved feed emulsion polymerization process, it was possible to prepare uniform polystyrene latex with glucamide surface.
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    URL: http://dx.doi.org/10.1007/BF00423370
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  • 21
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    A comparison of the PVCILO calculated stabilization energies of the DA complexes of N-phenylmaleimide and 4-phenyl-1,2,4-triazoline-3,5-dione with methyl vinyl ether (1995)
    Springer
    Polymer bulletin 34 (1995), S. 685-690 
    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 PVCILO method has been used to compare the stabilization energies of the electron donor electron acceptor complexes between methyl vinyl ether as donor and the enophiles, 4-phenyl 1-1,2,4-triazoline-3,5-dione (1) and N-phenylmaleimide (2), respectively, as acceptor. A stabilization energry difference in favor of the more reactive 1 was obtained, which is being interpreted as an explanation for the enhanced rate of reaction of 1 vs 2, often by factors 〉104.
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    URL: http://dx.doi.org/10.1007/BF00423369
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  • 22
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    Influence of the final extent of reaction on the structure of model polydimethylsiloxane networks obtained by the end-linking hydrosilation reaction (1995)
    Springer
    Polymer bulletin 35 (1995), S. 279-284 
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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 Model silicone networks obtained by hydrosilation of vinyl terminated polydimethylsiloxane chains have been used extensively to verify molecular theories of rubber elasticity. In these networks, the maximum extent of reaction obtained during cross linking considerably affects their final structure. The degree of completion of the hydrosilation reaction depends on the concentration of reactive groups. A recursive approach and kinetic data from the literature are used to show that, for this particular reaction, perfect networks, i.e. those with high concentration of elastically active network chains, are only obtained when a relatively high concentration of reactive groups is present in the system. This critical concentration corresponds in a bulk reaction to polydimethylsiloxane chains with a number average molecular weight lower than 10,000.
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    URL: http://dx.doi.org/10.1007/BF00963124
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    Copolymerization without initiator ofN-(2-hydroxyethyl)ethyleneimine with succinic anhydride (1995)
    Springer
    Polymer bulletin 35 (1995), S. 271-277 
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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 Copolymers of N-(2-hydroxyethyl)ethyleneimine and succinic anhydride without initiator were prepared under different experimental conditions. The composition of the copolymers was determined by elemental analyses and1H-NMR spectroscopy. From the results of FT-IR and1H-NMR spectroscopy a scheme of copolymerization via zwitterion is presented which includes an esterification reaction of the pendant hydroxylic groups.
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    URL: http://dx.doi.org/10.1007/BF00963123
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  • 24
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    Synthesis and characterization of ethylene-1-hexene copolymers using homogeneous Ziegler-Natta catalysts (1995)
    Springer
    Polymer bulletin 35 (1995), S. 299-306 
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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 This study investigated the copolymerization of ethylene with 1-hexene using the homogeneous Et[Ind]2ZrCl2 and [Ind]2ZrCl2 catalysts. The Et[Ind]2ZrCl2 catalyst gave a higher catalytic activity than the [Ind]2ZrCl2 and also showed a better incorporation of 1-hexene for the same comonomer concentration in the feed. Thermal analysis (DSC) and viscosity measurements showed that an increase of the 1-hexene incorporated in the copolymer results in a decrease of the melting point, crystallinity and molecular weight of the polymer formed. The reactivity ratios for ethylene and 1-hexene confirmed the more successful incorporation of the comonomer for the polymerization catalyzed by Et[Ind]2ZrCl2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00963127
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  • 25
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    Modified poly(ethyleneimine) supports for vanadium, molybdenum, and rhenium removal (1995)
    Springer
    Polymer bulletin 35 (1995), S. 337-343 
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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 Sorption characteristics of modified poly(ethyleneimine) supports which contain ammonium, carboxymethyl or phosphonomethyl groups have been determined for uptake of molybdenum(VI), rhenium(VII) and vanadium(V). Results suggest the separation of rhenium(VII) toward molybdenum(VI) from loaded N-carboxymethl derivative by selective elution with 1M sulfuric or perchloric acid. Moreover, vanadium(V) should be also selectively eluted from molybdenum(VI), iron(II) or iron(III).
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    URL: http://dx.doi.org/10.1007/BF00963132
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  • 26
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    Effects of molecular weight on morphology and electrooptical properties of polymethylmethacrylate/liquid crystal composites fabricated by a solvent-induced phase separation method (1995)
    Springer
    Polymer bulletin 35 (1995), S. 365-370 
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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 The relationship between the electrooptical properties, morphology and molecular weight of polymethylmethacrylate (PMMA) in PMMA/liquid crystal composite films is clarified. The LC droplet size has decreased with increasing molecular weight of PMMA. The threshold voltage has increased with increasing molecular weight of PMMA in good agreement with a equation of Doaneet al, qualitatively. Electrooptical response characteristics have included fast and slow mode. Thermal motion of PMMA at the interface between PMMA and LC seems to affect response time.
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    URL: http://dx.doi.org/10.1007/BF00963136
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  • 27
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    Synthesis, characterization and properties of polyimides from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and imidazole-blocked 2,5-bis[(n-alkyloxy)methyl]-1,4-benzenediisocyanates (1995)
    Springer
    Polymer bulletin 35 (1995), S. 423-430 
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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 By the solution condensation of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) with imidazole-blocked 2,5-bis[(n-alkyloxy)methyl]-1,4-benzenediisocyanates (Cm-BDIs) a series of aromatic polyimides (Cm-BP-PIs) having flexible (n-alkyoxy)methyl (-CH2O-n-CmH2m+1, m=4, 6, 8) side chains were prepared and characterized by IR- and 1H-NMR spectroscopy and their properties were measured and discussed in respect to the effects of side chains. Inherent viscosities of the polymers were in the 0.23–0.34 dL/g range. All the polymers were highly soluble in N,N′-dimethylpropyleneura(DMPU) and C6- and C8-BP-PIs even in CHCl3 at room temperature. UV-VIS spectra showed that the π-electrons are delocalized along the main chain. TGA studies showed a two-step pyrolysis behavior and in DSC Tg's of C4-, C6- and C8-BP-PIs were determined to be 184, 135 and 127 °C, respectively. Wide-angle X-ray diffractometry for as-polymerized samples revealed a quite low crystallinity with only loosely developed layered structure.
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    URL: http://dx.doi.org/10.1007/BF00297607
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  • 28
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    Preparation and characterization of poly(2,6-dimethyl-1,4-phenylene oxide) and Nylon 6 graft copolymer (1995)
    Springer
    Polymer bulletin 35 (1995), S. 407-413 
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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 poly(2,6-dimethyl-1,4-phenylene oxide) (PPO, 1) macroinitiator having carbonylcaprolactam groups was prepared through metalation of methyl group of PPO and subsequent modification to introduce carboxyl group, acid chloride group, and finally carbonylcaprolactam group. Anionic ring opening copolymerization of ɛ-caprolactam took place onto the macroinitiator to give a graft copolymer of PPO and Nylon 6. The structure of intermediate materials and the graft copolymer were characterized by 1H NMR, 13C NMR, and IR spectroscopy. Glass transition temperatures and melting temperatures of these materials are also reported. It is found that the copolymer has a microphase-separated morphology even with segment molecular weight as low as 3000.
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    URL: http://dx.doi.org/10.1007/BF00297605
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  • 29
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    Preparation and thermal characterisation of some new liquid crystalline copolymers involving a spacer unit based on vinylacetic acid (1995)
    Springer
    Polymer bulletin 35 (1995), S. 435-440 
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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 Three series of new liquid crystalline (LC) copolymers having a polysiloxane backbone and two different mesogenic pendant groups, one involving a vinylacetic acid moiety in the spacer, have been synthesised. Thermal characterisation of these polymeers has allowed comparison of behaviour between a number of different copolymer systems. It was found that increasing amounts of the vinylacetic acid moiety lowered the clearing points (Ti) of the copolymers in an almost linear fashion whilst also inhibiting crystallinity in these polymers.
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    URL: http://dx.doi.org/10.1007/BF00297609
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  • 30
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    In-situ photopolymerization of an oriented chiral liquid crystal acrylate in an electric field (1995)
    Springer
    Polymer bulletin 34 (1995), S. 7-12 
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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 The effect of an external electric field on the photopolymerization rate of chiral liquid crystalline 4-acryloyloxy-undecanloxy-4'-[S(-)-2-methylbutyloxy]-biphenyl (monomer (I)) was studied using FT-IR. The orientation behavior of the thermally polymerized polyacrylate of monomer (I) under an electric field was observed by POM. The results showed that in-situ photopolymerization of the oriented monomer (I) under the application of an electric field proceeded at a higher rate than in the absence of an electric field and can fix mesogenic orientation.
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    URL: http://dx.doi.org/10.1007/BF00294880
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  • 31
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    Effect of PVC on low-polar isobutylene polymerization in the presence of BCl3 (1995)
    Springer
    Polymer bulletin 34 (1995), S. 183-189 
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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 The isobutylene polymerizations in the presence of BCl3 were carried out in dichloromethane ([M]=7 mol/l) at-20°C in the presence and absence of PVC. The products of polymerizations in the absence of PVC are oligoisobutylenes with a narrow molecular weight distribution $${\text{(}}\mathop M\limits^{\_\_\_} _{\text{W}} /\mathop M\limits^{\_\_\_} _{\text{n}} \approx {\text{1}}{\text{.3, }}\mathop M\limits^{\_\_\_} _{\text{n}} \approx {\text{2700)}}$$ ; their structure was analyzed by 1H-NMR spectroscopy. In addition to the signals assigned to known unsaturated terminal structures [δ 4.62 and 4.82-CH2C(CH3)=CH2, 5.12-CH=C(CH3)2], a new intense signal was found at δ 5.09 ppm and assigned to the structure-CH=C(CH3)CH2CH3. A mixture of isobutylene homopolymers $${\text{(}}\mathop M\limits^{\_\_\_} _{\text{n}} \approx {\text{2700, 15000)}}$$ and PVC grafted with isobutylene (approx. 9.5% wt. isobutylene grafted) is formed in the presence of PVC.
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    URL: http://dx.doi.org/10.1007/BF00316394
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  • 32
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    A novel free radical interfacial copolymerization (1995)
    Springer
    Polymer bulletin 34 (1995), S. 295-300 
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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 Free radical interfacial copolymerization which is carried out by means of an amphiphilic bifunctional initiator as a novel polymerization method was proposed for the first time. For utilizing the new polymerization method, an amphiphilic bifunctional initiator, palmitoyl (3-carboxy propionyl) sebacoyl diperoxide (PSD), was synthesized and further used to initiate the free radical interfacial copolymerization of acrylamide (AM) with n-butyl methacrylate (n-BMA) which gave the amphiphilic PAM/PnBMA block copolymers. The resulting PAM/PnBMA block copolymers were purified by solvent extraction and characterized by elemental analysis, solubility, IR and DSC.
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    URL: http://dx.doi.org/10.1007/BF00294147
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  • 33
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    An investigation of microstructure of styrene-methacrylonitrile copolymers by FT-IR spectroscopy (1995)
    Springer
    Polymer bulletin 34 (1995), S. 323-330 
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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 The microstructure of styrene-methacrylonitrile copolymers has been investigated by FT-IR spectroscopy. The CN bond stretching frequency was shifted to a higher value with an increase in the methacrylonitrile (MAN) content in the copolymers. There was no linear relationship between the CN frequency and the diad fraction of MAN-MAN linkages in the copolymer chain, as reported previously for styrene-acrylonitrile copolymers. Different methods for the copolymer sample preparation can cause differences in the shifts in the CN frequency. This suggests that the polymer morphology plays an important role. A study of blends of poly(methacrylonitrile) (PMAN) with polystyrene has shown that the CN frequency is shifted to a higher value with an increase of the PMAN composition of the blends.
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    URL: http://dx.doi.org/10.1007/BF00294151
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  • 34
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    Oxidation and colour development in AES resins (1995)
    Springer
    Polymer bulletin 34 (1995), S. 353-359 
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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 The structural changes connected with the beginning of colour development during thermal oxidation of a AES polymer blend have been investigated. The yellowing behaviour of AES has been compared with that of the different components of the blend, and the influence of oxygen partial pressure on the polymer degradation has been determined. Colour changes have been shown to be correlated with the early stages of oxidation, and at the same time the different stabilities of the blend components were verified.
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    URL: http://dx.doi.org/10.1007/BF00294155
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  • 35
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    Synthesis of a polynorbornene containing 3,5-di-TERT-butyl-4-hydroxybenzoyl group (1995)
    Springer
    Polymer bulletin 34 (1995), S. 385-391 
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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 new polynorbornene derivative was synthesized by ring-opening metathesis polymerization (ROMP) of 5- {[(3,5-di-t-butyl-4-hydroxy-benzoyl)oxy]methyl}-2-norbornene (BHBN) using Ru- and Os-based catalysts. The structure and properties of the poly(BHBN) were characterized by NMR, IR, DTA, DSC, and GPC. It was shown that ROMP leads to the formation of high molecular weight polynor-bornene derivatives containing the stabilizing group.
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    URL: http://dx.doi.org/10.1007/BF00306230
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  • 36
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    Copolymerization of ethylene and 1-octadecene with the Cp2ZrCl2/MAO and Cp2HfCl2/MAO catalyst systems (1995)
    Springer
    Polymer bulletin 34 (1995), S. 413-418 
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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 The comparison of the copolymers obtained with the Cp2ZrCl2/MAO and Cp2HfCl2/MAO catalyst systems showed that the catalyst having hafnocene was much more reactive towards 1-octadecene than zirconocene. The comonomer concentration had to be three times higher in the zirconocene copolymerization than in the hafnocene copolymerization when the level of 6 mol-% was reached. Although the hafnocene catalyst was more reactive towards 1-octadecene, the molecular weights were higher than in the copolymers obtained with the zirconocene catalyst. The total activity of the zirconocene was 10 times higher than with the hafnocene catalyst. With the zirconocene catalyst the activity towards ethylene was constantly increasing by increasing the comonomer concentration but stayed nearly constant with the hafnocene catalyst. It seemed that there is no rate enhancement effect upon comonomer addition with the hafnocene catalyst.
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    URL: http://dx.doi.org/10.1007/BF00306234
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  • 37
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    Segmented liquid crystalline copolyesters and blending with poly(ethylene terephthalate) (1995)
    Springer
    Polymer bulletin 34 (1995), S. 441-447 
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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 series of segmented copolyesters with semi-regular structure was synthesized. In these copolymers, fully aromatic triad hard segments-HB-T-HB-, acting as mesogenic units, are linked each other by poly(ethylene terephthalate) (PET) segments with different average chain lengths as flexible spacers. The liquid crystallinity of the copolymers, i.e. the meso-phase forming ability, was studied against length of the spacer. In subsequent blending of these copolymers with PET matrix, results were compared with those from a commercial TLCP of PHB/PET random copolyester. Better mechanical properties were gained as expected since the compatibility of the segmented liquid crystalline copolyesters with the matrix is believed to be improved.
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    URL: http://dx.doi.org/10.1007/BF00306238
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  • 38
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    Preliminary analysis of the 13C-NMR spectrum of poly(3-vinyl furan) (1995)
    Springer
    Polymer bulletin 34 (1995), S. 449-454 
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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 Poly(3-vinyl furan) was synthesized in bulk by free radical initiation. The polymerization was quite sluggish with long polymerization times resulting in relatively low yields of product. The 75.5 MHz 13C-NMR spectrum could be analyzed in terms of stereochemistry even though signal/noise ratios were not optimum. The analysis indicates that poly(3-vinyl furan) (3VF), synthesized by free radical initiation, is an atactic polymer.
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    URL: http://dx.doi.org/10.1007/BF00306239
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  • 39
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    Wide-angle X-ray scattering studies on polyethylene at low temperatures (1995)
    Springer
    Polymer bulletin 34 (1995), S. 477-483 
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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 Linear polyethylene (Lupolen 6041 D) and a polyethylene fraction (PE 2000) were investigated by WAXS at temperatures 8 K〈T〈293 K. From the position and integral widths of the reflections the lattice constants (and expansion coefficients) and lattice distortions are determined. Lattice distortions are of the strain type, induced by inherent stresses. They increase with decreasing temperature up to ∼50 K and then to lower temperatures a decrease is observed. This is explained by the decrease of the thermal expansion coefficients. For PE 2000 for some reflections a minimum in the integral widths at T∼38 K occurs. The explanation of this effect is given by the occurence of a stress induced martensitic transformation (orthorhombic to monoclinic) of part of the material. The corresponding weak reflections are observed.
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    URL: http://dx.doi.org/10.1007/BF00306243
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  • 40
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    Miscibility of poly(α-methyl styrene-co-methacrylic acid) with alkyl methacrylate-co-4-vinylpyridine copolymers (1995)
    Springer
    Polymer bulletin 34 (1995), S. 485-491 
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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 The miscibility of blends of poly(α-methyl styrene-co-methacrylic acid) (PαMSMA) with various alkyl methacrylate polymers or poly(alkyl methacrylate-co-4-vinylpyridine) was studied by differential scanning calorimetry and Fourier transform infra red spectroscopy. PαMSMA is immiscible with poly(methyl methacrylate), poly(ethyl methacrylate) and poly(n-butyl methacrylate). The introduction of 4-vinylpyridine by random free radical copolymerization within these alkyl methacrylate polymer chains enhanced the miscibility of these copolymers with PαMSMA as a result of specific interactions that occurred between the carboxylic and pyridine groups, evidenced from the significant changes observed by FTIR in the carboxyl and pyridine ring regions. The density of interacting groups required for miscible blends depends on the size of the pendant group.
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  • 41
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    Alkoxy-substituted liquid-crystalline aromatic copolyesters (1995)
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    Polymer bulletin 34 (1995), S. 503-508 
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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 Rigid rod copolyesters derived from 2,5-bis(pentyloxy)terephthaloyl dichloride (3), 4,4′-dihy-droxybiphenyl (4) and trans-1,4-dihydroxycyclohexane (5) were synthesized and their thermal behavior analysed. The structures were characterized by 1H-NMR, GPC and elemental analyses; their thermal behavior was studied by DSC measurements, microscopy under polarized light and thermogravimetric analyses. The composition of the copolyesters with 30, 50 and 70 mol % 5 was not as expected, due to the differing reactivities of the diols 4 and 5 during the polycondensation. This led to the existence of two species of polyesters from one reaction mixture. The higher the content of 5 in the polymer, the lower the molecular weight. By increasing the amount of 5, the thermal stabilities and melting points decrease drastically, whereas the solubility increases. The copolyesters 6a-g show only a low ability to form fibres which are brittle and break very easily.
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  • 42
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    Synthesis and polymerization of unsaturated monomers with OH groups in their structure: 2-(hydroxyethyleneoxyterephthaloyloxy) ethyl acrylate (1995)
    Springer
    Polymer bulletin 34 (1995), S. 509-514 
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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 The synthesis and polymerization of new unsaturated monomers derived from acrylic acid and an aliphatic-aromatic glycol is reported. Values of kp/kt 1/2 were obtained for the monoacrylate monomer and compared with those found for other acrylic monomers. The thermal properties of the starting glycol (Bis[2-hydroxyethyl]terephthalate), monomers (monoacrylate and diacrylate) and linear polymer were determined by calorimetric techniques. The results show the influence of intermolecular interactions (hydrogen bondings) on these properties.
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    Studies on diacetylenic vinyl compounds (1995)
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    Polymer bulletin 34 (1995), S. 547-554 
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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 Three alka-3,5-diynylmethacrylate and 1,8-Bis(methacryloxy)octa-3-5-dyine were synthesized and their polymerization in the molten state was studied. 3,5-Octadiynylene-1,8-dimethacrylate, which was the only one that was solid at room temperature, was not light sensitive in the solid state. All the monomers underwent rapid polymerization at 140 °C. The DSC and IR-spectra indicated that the polymerization of the vinyl and diacetylenic groups takes place simultaneously. An optically highly transparent, yellow-orange glass was obtained.
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  • 44
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    Influence of thermal history on the mechanical properties of thermotropic poly(triethylene glycol p,p′-bibenzoate) (1995)
    Springer
    Polymer bulletin 34 (1995), S. 635-641 
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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 The influence of thermal history on the mechanical properties of thermotropic poly(triethylene glycol p,p'-bibenzoate) has been studied. The mechanical parameters of three samples of this polyester with different thermal histories have been determined at two deformation rates (1 and 10 cm/min) and two drawing temperatures (23 and 50°C), showing the influence of the thermal and mechanical histories on the stress-strain plots. The phase state and the degree of crystallinity of the samples also affect the mechanical parameters (Young modulus, yield stress and deformation at break).
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  • 45
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    An analysis of the 1H-NMR and 13C-NMR spectra of poly(2-methyl-N-vinyl imidazole) (1995)
    Springer
    Polymer bulletin 34 (1995), S. 455-460 
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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 The title monomer was polymerized via free radical initiation. The polymerization proved very rapid, yielding quantitative conversion in ∼ 5–10 min. Most of the polymer proved to be insoluble in any solvent tried, but good quality 1H-NMR and 13C-NMR spectra could be obtained from the soluble fraction. The soluble fraction of the polymer proved to have an atactic stereochemistry.
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    Synthesis and characterization of polystyrene-polyester liquid crystalline block copolymers (1995)
    Springer
    Polymer bulletin 34 (1995), S. 531-537 
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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 Liquid crystalline (LC) block copolymers comprising polystyrene and LC polyester blocks were obtained by a three-step procedure. In a first step, hydroxyl-terminated oligoesters were obtained by polycondensation reaction of methylhydroquinone and 4,4′-dicarboxy-1, 10-dibenzoyloxydecane in pyridine solution in the presence of tosyl chloride and dimethylformamide. Hydroxyl-terminated oligoesters were then further polymerized with 4,4′-azo-bis(4-cyanopentanoyl chloride) to form azo-macroinitiators which, in a third step, were employed in the free-radical polymerization of styrene to form block copolymers. The thermal and LC properties of the copolymers are presented and discussed in terms of the dependence upon the molecular weight of the polystyrene block.
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    URL: http://dx.doi.org/10.1007/BF00423348
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    Synthesis and characterization of poly(dioxynaphthylene-1,4-dicarbonylnaphthylene)s with various isomeric naphthylene links (1995)
    Springer
    Polymer bulletin 35 (1995), S. 251-258 
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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 Six all-naphthylene polyesters were prepared by the condensation of 1,4-naphthalenedicarboxylic acid (NA) chloride with 1,4-, 1,5-, 1,6-, 2,3-, 2,6-, and 2,7-naphthalenediol (ND) isomers and effects of the isomerism of NDs on structure and properties of the polyesters were investigated. The polymers-1,4,-1,5 and-2,6 with more or less linear ND link were insoluble and the others with bent ND link were soluble in the mixed solvent from phenol/p-chlorophenol/1,1,2,2-tetrachloroethane(TCE). The polymer-2,6 with the most linear ND link did not show a Tg and the highest decomposition initiation temperature(TD) and Tg's and TD's of the other polymers were only marginally dependent on their structures. The polymer-2,3 is believed to have a macrocyclic structure consisting of four to six monomer units and the polymer-1,6 is amorphous in its stable chain conformation, while all the other polymers are semicrystalline. The polymers-1,4and-1,5 exhibited an irreversible crystal-to-crystal transition at 380 and 320°C, respectively, whereas the polymer-2,6 a reversible one at 240°C. The polymer-2,7 exhibited an irreversible crystal-to-amorphous transition at 360°C.
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    URL: http://dx.doi.org/10.1007/BF00963120
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    Synthesis and thermal properties of polyamide 6 (A)-polyimide (B) block copolymers of ABA type (1995)
    Springer
    Polymer bulletin 35 (1995), S. 441-448 
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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 Polyimides (PI) having different molecular weights were prepared by condensation of oxydiphthalic anhydride with 9,9-bis-(4-aminophenyl)fluorene in nitrobenzene solution at 180°C. These polyimides carried two amino chain ends which allowed us to fix polycaprolactam chains (PA6) to obtain PA6-PI-PA6 type copolymers. The elemental analysis and infrared spectroscopic determination gave the proportion of PA6 (or PI) in the copolymers. The studies of thermal properties-DSC and TGA-allowed us to characterize the copolymers.
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    Preliminary analysis of the 1H-NMR and 13C-NMR spectra of poly(2-vinylpyrazine) (1995)
    Springer
    Polymer bulletin 35 (1995), S. 465-471 
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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 The title polymer was synthesized by free radical initiation. The 1H-NMR and 13C-NMR spectra revealed several resonances that were sensitive to polymer stereosequence distribution. Analysis of these resonances showed that free radical initiated poly (2-vinyl pyrazine) is an atactic polymer, a result consistent with data accumulated for other poly vinylheterocycle initiated free radically.
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    Analysis of the 1H-NMR and 13C-NMR spectra of poly(5-vinyl-2,2′-bithiophene) (1995)
    Springer
    Polymer bulletin 35 (1995), S. 473-480 
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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 The title polymer was synthesized by free radical initiation in bulk and its 1H-NMR and 13C-NMR spectra were recorded and analyzed in terms of polymer stereochemistry. The aliphatic region of the proton spectrum shows an unusual multiplicity due to stereochemical sensitivity and the resonances of several of the ring carbons displayed a sensitivity to higher order stereosequences. The analysis of these spectra showed that poly(5-vinyl-2,2′-thiophene) is an atactic polymer.
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    The Calibration of fibre optic probes used for light dosimetry measurements during photodynamic therapy (1995)
    Springer
    Lasers in medical science 10 (1995), S. 19-24 
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    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Light dosimetry ; Fibre optic probes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract We describe the calibration of fibre optic probes used to perform in vivo light dosimetry studies during the treatment of skin lesions by photodynamic therapy. Results from six individual detectors show that the linearity of the calibration and the calculated radiant energy fluence rate within a liquid phantom are independent of the type and sensitivity of the probe. The method of calibration is also shown to yield the optical interaction coefficients of the phantom.
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    Non-PDT Uses of lasers in oncology (1995)
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    Lasers in medical science 10 (1995), S. 3-8 
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    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The use of therapeutic lasers depends on four basic laser-tissue interactions; photothermal, photochemical (PDT), mechanical and ablative. There is no place for mechanical and ablative interactions in oncology; PDT will be the subject of a further review and the subject of this review is therefore the photothermal reaction. Thermal lasers have been in routine use in oncology for the last 10–15 years. These lasers, emitting in the visible or infra-red parts of the spectrum, are used to produce three basic effects; hyperthermia, coagulation and vaporization. Other energy sources beside lasers can also be used to produce these tissue effects but lasers seem to possess certain basic advantages. In comparison with monopolar or bipolar diathermy and heater probes, lasers can deliver more power, more accurately at the target tissue with better control of damage and a wider range of effects. In comparison with microwave and ultrasound therapy, lasers are again more precise and can be used with more compact and accurate delivery devices. In gastroenterological surgery (as opposed to endoscopy), neurosurgery and gynaecology, laser light can be delivered via a handpiece to cut and coagulate. In ENT and also some applications of gynaecology lasers can also be used via a microscope. In endoscopic surgery laser light is delivered through an optical fibre within the endoscope—this for the time being precludes the use of the CO2 laser for these applications. More recently, the laser fibre can be placed directly within tumour tissue for interstitial thermal therapy of liver metastases, pancreatic tumours and brain tumours. The future use of thermal lasers in oncology depends very much on the results of properly controlled comparative studies against PDT and non-laser thermal devices; in addition their use may well be widened to include some curative procedures; up until now their use has very much been restricted to palliative therapy except where they are used as an adjunctive cutting device alongside conventional curative surgery.
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    Endoscopic Nd-YAG laser therapy of gastric polyposis (1995)
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    Lasers in medical science 10 (1995), S. 189-192 
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    ISSN: 1435-604X
    Keywords: Stomach ; Polyposis ; Nd-YAG laser ; Therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Thirteen patients with gastric polyposis (113 polyps) were treated by endoscopic Nd-YAG laser irradiation. Among them there were five cases with adenomas, six with hyperplastic polyps and two with inflammatory polyps. Ninety-six polyps were 〈1 cm, 13 polyps were ⩾ 1 cm, and four polyps were ⩾ 2 cm. In the patient who had the largest number of lesions, 22 polyps were found at endoscopic examination. All but two patients were regularly followed up endoscopically for 2–5 years after treatment and showed no sign of recurrence. Mild bleeding occurred in three cases. No perforation or any other serious complications occurred. The results were encouraging. It is concluded that endoscopic Nd-YAG laser ablation of gastric polyposis is effective, simple to perform, safe and deserves recommendation.
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    Granular cell abrikossoff tumours of the larynx and tongue treated with the carbon dioxide (CO2) laser (1995)
    Springer
    Lasers in medical science 10 (1995), S. 213-216 
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    ISSN: 1435-604X
    Keywords: Granular cell tumours ; CO2 Laser treatment ; Electron microscopic examinations ; Tongue ; Larynx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Seven cases of granular cell Abrikossoff tumours of the larynx and tongue are reported: four in the tongue and three in the larynx. All of these tumours were removed with the carbon dioxide (CO2) laser. The anatomical site of the origin and clinical features of granular cell tumours (GCT) are not specific. Histological, light microscopic, electron microscopic (EM) and immunohistochemical studies are required for diagnosis. The histogenesis and cellular derivation of GCTs is still controversial. The biological potential and lack of cellular atypia define a benign process. However, it is important to take into account that these tumours have ill-defined borders without a capsule. Radiation therapy has proved ineffective in the past. Surgical excision with a wide margin is required. Because of numerous advantages, for example, no bleeding, no oedema, minimal pain and quick recovery, CO2 laser removal is the treatment of choice. The authors have not seen any recurrence or complications.
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    Laser energy threshold for thermal vascular injury in a port-wine stain skin model (1995)
    Springer
    Lasers in medical science 10 (1995), S. 231-234 
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    ISSN: 1435-604X
    Keywords: Port-wine stain ; Blood vessel ; Pulse duration ; Energy threshold ; Selective photothermolysis ; Monte Carlo ; Thermal diffusion ; Vascular injury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Monte Carlo simulation of laser energy deposition in a port-wine stain (PWS) skin model and numerical solution of the thermal diffusion equation have been used to calculate threshold energies for thermal injury of PWS blood vessels for different vessel sizes and laser pulse durations. It has been assumed that an average vessel temperature rise of 65
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    The effect of helium-neon laser irradiation on in vitro maturation and fertilization of immature bovine oocytes (1995)
    Springer
    Lasers in medical science 10 (1995), S. 113-119 
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    ISSN: 1435-604X
    Keywords: Radiation effects ; In vitro maturation ; In vitro fertilization ; HeNe laser irradiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A study was made of the effects of low power laser irradiation on in vitro oocyte maturation rates and subsequent fertilization of immature bovine oocytes. Immature bovine oocytes from cows sacrificed at a slaughterhouse were irradiated with Helium-Neon laser (HeNe laser) irradiation at an energy density of 0.4 and 2.0 J cm−2. An oocyte group was left untreated, serving as control group. All oocytes were matured and fertilized in TCM-199 medium supplemented with 20% fetal calf serum (FCS). Maturation and fertilization rates obtained in the irradiated oocytes group were lower (p〈0.001 andp〈0.05, respectively) than those of the control group. Furthermore, the laser-treated oocytes showed important degenerative changes on both cytoplasm and chromosomes in comparison with untreated control oocytes which showed a homogenous cytoplasm and disperse chromosomes. It is concluded that the application of HeNe laser irradiation at 0.4 and 2.0 J cm−2 energy densities has a detrimental effect on in vitro maturation and fertilization process of immature bovine oocytes.
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    Development of an alternative light source to lasers for photodynamic therapy: 2. Comparative in vivo tumour response characteristics (1995)
    Springer
    Lasers in medical science 10 (1995), S. 121-126 
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    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Haematoporphyrin derivative ; In vivo ; Laser ; Light source ; Murine tumour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The performance of a low cost, table-top/portable light source was tested against an argon ion pumped dye laser for in vivo photodynamic therapy (PDT). The prototype delivers up to 1 W via a 4 mm flexible lightguide within a 30 nm bandwidth centred at any wavelength from 300 nm to 1200 nm at fluence rates of up to 8 W cm−2. An in situ bioassay using regrowth delay of tumour T50/80 was used to quantify the relative efficacy of the prototype with a laser. The tumours were sensitized with haematoporphyrin derivative (HpD) and externally irradiated. There was no significant difference in the response of the tumour to treatment between the two light sources (p = 0.69). Mean growth delays ranged from 2 days (light dose 10 J cm−2) to 20 days (light dose 100 J cm−2). The estimate for the difference in means (laser minus prototype growth delay) was only 0.66 days and was not statistically significant. This in vivo study demonstrates that the prototype is equivalent to a laser in PDT effect. The device has low capital/running cost, is simple to use and is one of the most powerful, spectrally efficient non-laser PDT sources available.
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    Construction, quality assurance and calibration of spherical isotropic fibre optic light diffusers (1995)
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    Lasers in medical science 10 (1995), S. 137-147 
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    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Isotropic fibre optic light diffusers ; Construction of diffusers ; Quality assurance of diffusers ; Calibration of diffusers ; Goniometer ; Integrating sphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Spherical isotropic fibre optic light diffusers are used in photodynamic therapy either as a light source or as a light detector. The construction of light diffusers using different materials is described, viz. an optical method involving local polymerization of a dental fissure sealant, which is referred to as the Henderson method, and a second method using plastic or ceramic pre-fabricated spheres. Quality tests necessary for reliable clinical use are presented for the mechanical strength, output power and isotropy. The maximum pull-off force and blow-off output power for the different kinds of diffusers were determined. The calibration procedures are given for measurement of the output power and wavelength of the light emitted by a diffuser and for measurement of the fluence rate by a light-detecting diffuser, using a compact integrating sphere device. With all types of diffusers described, an isotropy can be obtained of better than ± 20% measured over a 320° angle for spheres as small as ≈ 1 mm. Larger ceramic diffusers are particularly suitable for delivering high output powers. A 3-mm-diameter ceramic diffuser mounted on a 600-μm-core fibre can emit up to ≈ 5 W of continuous wave (CW) visible light in air. Diffusers used for light detection can measure the light fluence rate in tissue with ≈15% accuracy or better if calibration factors are determined for each individual probe.
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    Editorial (1995)
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    Lasers in medical science 10 (1995), S. 155-155 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
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    URL: http://dx.doi.org/10.1007/BF02133325
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    Holmium-YAG Laser ablation characteristics in calvarial lamellar and cortical bone: The role of water and tissue micro-architecture (1995)
    Springer
    Lasers in medical science 10 (1995), S. 181-188 
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    ISSN: 1435-604X
    Keywords: Bone histology ; Holmium-YAG laser ; Infra-red lasers ; Laser surgery ; Photo ablation ; Otology ; Stapes ; Otosclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The effect of tissue micro-architecture and water content on ablation rates in bone is examined. Precisely machined and prepared porcine calvarial lamellar and cortical bone were ablated with a Holmium-YAG laser (λ=2.1Μm). Lamellar and cortical bone differ substantially in their tissue micro-architecture. Both are porous hard tissues, which differ predominantly in size and distribution of pores within the bone matrix. These hard tissues were ablated under physiological (wet) and chemically dehydrated conditions. The ablation rates over the range of energy densities examined assumes many linear characteristics. Ablation rate (as a function of fluence) is considerably higher for dehydrated cortical bone (4.7Μm cm2 J−1) compared to fresh cortical bone (1.49Μm cm2 J−1). This trend is also observed in lamellar bone (2.31Μm cm2 J−1 for wet and 0.37Μm cm2 J−1 for dry). Under both physiological and dehydrated conditions, cortical bone was ablated faster. Mechanisms accounting for these observations are discussed.
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    Interstitial laser thermotherapy: Comparison between bare fibre and sapphire probe (1995)
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    Lasers in medical science 10 (1995), S. 193-200 
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    ISSN: 1435-604X
    Keywords: Nd-YAG laser ; Hyperthermia ; Light penetration ; Temperature distribution ; Feedback control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A sapphire probe and a bare fibre were compared with respect to temperature control and distribution and light fluence in interstitial laser thermotherapy. Experiments were performed in processed liver using an Nd-YAG laser and output power levels of 1–4 W. The temperature was controlled at a distance of 10 mm using a feedback circuit with an automatic thermometry system and thermistor probes. With the sapphire probe, carbonization was rare at power levels of 1–2 W but was observed in half of the experiments at 3 W and in all experiments at 4 W. Using the bare fibre, carbonization was seen in almost all experiments. Absence of carbonization was associated with a moderate decrease in the penetration of light and excellent control of the temperature, whereas carbonization led to rapid impairment of light penetration and temperature control. In addition, the temperature gradient was smaller with the sapphire probe than with the bare fibre or when carbonization was absent. It is concluded that a diffuser tip, such as the sapphire probe, may be preferable to the bare fibre for interstitial laser thermotherapy because it gives a smaller temperature gradient and helps to avoid carbonization which results in preserved light penetration and improved temperature control.
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    Surgical removal of dorsal wrist ganglion with a new laser scalpel (1995)
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    Lasers in medical science 10 (1995), S. 217-221 
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    ISSN: 1435-604X
    Keywords: Laser scalpel ; Nd-YAG laser ; Wrist ganglion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A novel laser scalpel, consisting of a clad conically-sculptured silica tip (core diameter: 600Μm; end diameter: 150Μm transmitting radiation from a 10 W CW Nd-YAG laser, was used for the excision of a dorsal wrist ganglion. The dynamic range of this instrument (17–57 kW cm−2) easily suffices for the cutting of soft tissues, which feature is combined with impressive haemostatic properties, thus obviating the need for tourniquet control. Morphological examination of the excised ganglion reveals a peripheral zone of heat-damaged collagenoius tissue containing vessel profiles which show signs of thermally-induced blood flow stasis.
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    Analysis of laser effects on chromosomal structure by fluorescence in situ hybridization and image cytometry: Methodological approach for precise microdissection (1995)
    Springer
    Lasers in medical science 10 (1995), S. 261-266 
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    ISSN: 1435-604X
    Keywords: Chromosome ; Laser ; Image cytometry ; Fluorescence in situ hybridization ; Microdissection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Laser effects on human chromosomes have been studied with an image cytometer using an argon ion laser emitted beam at 488 nm, with a 50 mW power. The smallest laser spot was of 0.2Μm. Aiming of the laser beam was controlled by a computer. Irradiated and non-irradiated chromosomal fragments were analysed by measuring the fluorescence intensity of propidium iodide and by fluorescence in situ hybridization (FISH) with fluorescein biotinylated Alu polymerase chain reaction products. No propidium iodide staining or FISH could be observed on irradiated chromosome fragments indicating total elimination of DNA by the laser beam. The non-irradiated fragments of chromosome showed Alu hybridization similar to control metaphase spreads, suggesting that the DNA structure remained intact. This methodological approach could be used to carry out precise and rapid microdissection of chromosomes.
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    New laser literature (1995)
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    Lasers in medical science 10 (1995), S. 287-289 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
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    URL: http://dx.doi.org/10.1007/BF02133623
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    Can intra-uterine mortality be reduced in Nd-YAG laser treatment of Twin-Twin Transfusion Syndrome? An analysis (1995)
    Springer
    Lasers in medical science 10 (1995), S. 283-286 
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    ISSN: 1435-604X
    Keywords: Twin-Twin Transfusion Syndrome ; Haemodynamics ; Intra-uterine laser coagulation ; ND-YAG laser treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Recent studies have shown that laser therapy can reduce the mortality and morbidity associated with Twin-Twin Transfusion Syndrome in the second trimester of pregnancy. The purpose of this paper is to analyse current treatment strategies using laser surgery, and to suggest ways in which fetal mortality may be further reduced.
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    Phase separation effects in the rheology of aqueous solutions of hydroxypropylcellulose (1995)
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    Rheologica acta 34 (1995), S. 137-146 
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    ISSN: 1435-1528
    Keywords: Rheology ; hydroxypropylcellulose ; liquid crystalline polymers ; phase separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Aqueous solutions of hydroxypropylcellulose (HPC) have been widely used as a model system to study liquid crystalline behavior in polymers. The HPC limiting concentration for mesophase formation in water is about 40% wt, quite independent of molecular weight. Most rheo-optical investigations have been carried out in the concentration range from 50% to 65% wt, on the assumption that only the liquid crystalline phase was present. In this study, by using video-enhanced contrast light microscopy, we show that an isotropic phase in form of tiny droplets is also present at concentrations up to 60% wt, both in quiescent and in sheared samples at room temperature. The isotropic phase can be made to disappear by lowering the temperature. The effects of phase separation on the rheology of the HPC/water system are studied by measuring viscosity as a function of temperature and concentration. A slope of Region I of the viscosity curve close to −0.5 is found only at low temperatures, when the sample is fully anisotropic, whereas an anomalous dependence of the viscosity on temperature is observed when phase separation is significant. This study shows that special care is needed when interpreting experimental results from the HPC/water system in terms of theories for liquid crystalline polymers.
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    Solidification behavior of the theta system 2-propanol/poly(n-butyl methacrylate) (1995)
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    Rheologica acta 34 (1995), S. 172-181 
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    ISSN: 1435-1528
    Keywords: Thermoreversible gelation ; glass transition ; viscosity ; storage modulus ; loss modulus ; activation energies of flow ; entanglement molecular weights ; poly(n-butyl methacrylate) ; 2-propanol ; concentration and temperature influences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Thermoreversible gelation of the system 2-propanol/poly (n-butyl methacrylate) — as detected by D'SC or dielectric experiments — does not manifest itself in a straightforward manner in the dynamic-mechanical properties. Its occurrence can, however, be seen in many ways: i) For constant composition of the system and a reference temperature lower than T gel, the storage modulus G′ is larger than the loss modulus G″ in the glass transition zone of the master curve and both vary in an almost parallel manner with the angular frequency ω over almost two decades (whereas this feature is normally found for other gelling systems within the rubber plateau or the flow region). ii) The entanglement molecular weight obtained from G″max is markedly less max than the entanglement molecular weight in the melt divided by ϕ2, the volume fraction of the polymer. iii) The temperature influences change from WLF like to Arrhenius-like behavior as T is lowered in the case of highly concentrated polymer solutions; analogous considerations hold true as ϕ2 is increased at constant T. iv) For sufficiently low temperatures, the activation energy of flow exhibits a maximum in the concentration range where the gelation is — according to DSC experiments — most pronounced. Like with ordinary non-gelling systems it is possible to construct master curves. On the basis of Graessley's theory identical dependencies are obtained for the variation of the entanglement parts of the stationary viscosity with shear rate and for the dependence of the entanglement part of the complex viscosity on the frequency ω of oscillation. Zero shear viscosity and limiting value of the complex viscosity for vanishing ω as a function of ϕ2 match smoothly and exhibit two points of inflection.
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    A note on the tan δ(T) peak as a glass transition indicator in biosolids (1995)
    Springer
    Rheologica acta 34 (1995), S. 215-220 
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    ISSN: 1435-1528
    Keywords: Glass transition ; complex modulus ; biopolymers ; solid foods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The plasticization of many biosolids can take place over a fairly broad temperature range. The resulting loss of stiffness is primarily expressed by a drastic drop of G′(T) whose magnitude is usually higher than G″(T) by one or two orders of magnitude. Both G′(T) and G″(T) have characteristic properties that can vary widely among biomaterials. Consequently, the tan δ(T) peak need not be a mark of the transition center and it can be observed at temperatures where different materials have undergone a very different degree of plasticization as judged by the magnitude of G′(T). This is demonstrated by computer simulations using typical functions that describe G′(T) and G″(T) at the glass transition region and with published data on the dynamic mechanical behavior of a variety of biosolids.
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    On the rheological modeling of viscoelastic polymer liquids with stable constitutive equations (1995)
    Springer
    Rheologica acta 34 (1995), S. 259-273 
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    ISSN: 1435-1528
    Keywords: Constitutive equations ; viscoelasticity-stability constraints ; simple flows
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Various approaches to the theology of polymer solutions and melts have resulted in an overabundance of constitutive equations (CEs). None of these equations can describe the entire set of available rheological data in a consistent fashion, even for simple flows. Additionally, almost all the CEs suggested in the literature have recently been determined to be unstable in either the Hadamard or dissipative sense without any physical reason. In this paper, we attempt to describe simple flow data for LDPE Melt I/IUPAC A/IUPAC X, HDPE II. PS I, PIB P-20 and PIB L-80 with a certain class of differential CEs, while complying with the global isothermal stability constraints. For simplicity, only one or two nonlinear parameters additional to the discretized linear viscoelastic spectra are introduced for the description of data.
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    The electrorheological property of a polyaniline-coated copolystyrene particle suspension (1995)
    Springer
    Rheologica acta 34 (1995), S. 298-302 
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    ISSN: 1435-1528
    Keywords: Electrorheology ; polyaniline-coated copolystyrene particle ; silicone oil ; suspension ; dispersibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Polyaniline-coated copoly (styrene styrenesulphonate) (PSS) particles were prepared by oxidative polymerization of aniline hydrochloride using ammonium persulphate in the presence of anionic PSS particles. Polyanilinecoated PSS particles were found to be higher dispersibility than polyaniline itself in an organic solvent. A suspension of polyanilinecoated PSS particle in silicone oil was found to exhibit high performance at higher temperature without the necessity for water.
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    Yield stress and maximum packing fraction of concentrated suspensions (1995)
    Springer
    Rheologica acta 34 (1995), S. 544-561 
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    ISSN: 1435-1528
    Keywords: Concentrated suspension ; maximum packing fraction ; yield stress ; suspension structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The yield stress and features of the structure of concentrated suspensions based on silica flour, with particles of average diameter around 4 μm, were investigated in terms of a phenomenological model. The yield stress of a concentrated suspension of known solid volume concentration is estimated by employing a shear-dependent maximum packing fraction Φ m which is obtained by model fitting equilibrium viscosity data, and by incorporating a first-order kinetic equation. The model proposed was examined by using several mineral suspensions in which silica flour was mixed with metal oxide particles so that microstructural features of the suspensions could be adjusted. A cocoa fat suspension was also used as a test sample having radically different chemistry. The agreement between the model prediction and independently obtained experimental evidence is acceptable. Furthermore, a qualitative explanation is obtained by a scaling analysis in an effort to relate the model parameters with the suspension structure that stems from interactions among the suspension constituents.
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    Determination of yield stress fluid behaviour from inclined plane test (1995)
    Springer
    Rheologica acta 34 (1995), S. 534-543 
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    ISSN: 1435-1528
    Keywords: Yield stress fluid ; rheological behaviour ; mud suspensions ; inclined plane ; rheometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The aim of this paper is to determine precisely under which conditions an inclined plane can be used as a rheometer, which could represent a practical and rapid technique for various types of industrial or natural viscoplastic coarse suspensions. We first examine its efficiency and relevancy for determining fluid yield stress in a straight way by measuring the deepest fluid layer able to stay on the inclined plane. We have made experiments with different materials (clay-water suspensions) whose yield stress ranged from 35 to 90 Pa, using 1 m long open rectangular channels with a slope ranging from 10 to 30° and a width ranging from 5 to 25 cm. Our procedure involved measuring the final fluid depth far from edges a long time after the end of the slow gravity-induced emptying of a dam placed upstream. The fluid yield stress was also estimated independently by fitting a Herschel-Bulkley model to simple shear rheometry data obtained within a relatively wide shear rate range. A good agreement between inclined rectangular channel tests and independent usual rheometrical tests is obtained even for aspect ratios (flow depth to channel width ratio) as large as 1 when one assumes that, when the fluid has stopped, the side and bottom wall shear stresses are equal to the fluid yield stress. These results prove the efficiency of the inclined plane test for determining yield stress when appropriate experimental precautions are taken for both tests. In addition we examine the possibility of determining the simple shear flow curve of a mud suspension from fluid depth, velocity and discharge measurements of different steady flows in a wide open channel (8 m long; 60 cm wide) equipped with a recirculating system. The results obtained from inclined plane tests are in good agreement with independent rheometrical data (with torsional geometries). However it is technically difficult to cover a wide shear rate range from the inclined plane technique since this requires a rather wide channel flow rate range.
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    Steady and dynamic shear properties of non-aqueous drag-reducing polymer solutions (1995)
    Springer
    Rheologica acta 34 (1995), S. 586-600 
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    ISSN: 1435-1528
    Keywords: Non-aqueous drag reducers ; steady and dynamic shear properties ; temperature and concentration effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The steady and dynamic shear properties of two non-aqueous drag-reducers (a medium molecular weight polyisobutylene and a commercial organic drag-reducer) in kerosene solutions over a wide range of temperature and concentration were presented. The intrinsic and zero-shear viscosity results were used to identify the concentrate regimes of these solutions. A characteristic time constant λ0, which was based on the spring-bead model for dilute solutions, was employed as the scaling parameter for both steady-shear and dynamic data over a wide range of concentration and temperature. The inadequacy of the Graessley reduced-variable method in the dilute region was illustrated. The shear-thinning behaviour of these polymer solutions could be described by the Carreau model. The dynamic data followed the Zimm and Rouse-like behaviour in the low and high frequency limits. The Cox-Merz rule was obeyed in the low shear rate and frequency regions. The Carreau and the zero-frequency Maxwell time constants appeared to be related to λ0 by a constant factor over a wide range of polymer concentrations. The finding provides a method for extrapolating viscoelastic information into the drag reduction regime, and could be useful for interpretation of drag reduction results.
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    Determination of critical molecular weight for entangled macromolecules using the tensile strength data (1995)
    Springer
    Rheologica acta 34 (1995), S. 578-585 
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    ISSN: 1435-1528
    Keywords: Critical molecular weight ; entanglements ; tensile strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The multivariable power dependence of polymer properties on molecular characteristics (Dobkowski, 1981) has been applied to molecular weight dependence of tensile strength, and the known equation of Flory (1945) has been extended taking polydispersity of polymers into account. Constant parameters of the relevant regression equations have been calculated using experimental data on tensile strength and molecular weight averagesM n andM w of polystyrene (PS) and polycarbonate (PC). Then, the critical molecular weight for entanglementsM c has been obtained from the following relationship:A=Kσ∞ M cwhereA and σ∞ are parameters of the extended Flory equation for the tensile strength, and the constantK = 2 is assumed for linear polymers. It has been found thatM c of injection and compression moulded PS is equal to 34000 and 37350g/mole, respectively, whileM c of injection moulded PC equals to 5000 g/mole. The values ofM c calculated from the polymer tensile strength are consistent with published data obtained by other methods and with the computer modeling calculations. Branched polymers have only qualitatively been discussed. Dimensionless equations have been proposed for tensile strength characteristics for polymer materials. The described procedure can be suggested as applicable to various polymers for the determination of theirM c values. However, more experimental data on another polymer materials will be necessary to support hitherto obtained results.
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    A sensitive dynamic viscometer for measuring the complex shear modulus in a steady shear flow using the method of orthogonal superposition (1995)
    Springer
    Rheologica acta 34 (1995), S. 606-621 
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    ISSN: 1435-1528
    Keywords: Superimposed oscillations ; complex viscosity ; complex shear modulus ; nearly viscometric flow ; dynamic viscometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A new instrument to carry out complex viscosity measurements in equilibrium and in a steady shear flow has been developed. A small amplitude harmonic excitation is superimposed orthogonally to the steady shear rate component. It is realized by a thin-walled cylinder, which oscillates in the axial direction in a rotating annular cup. The cylinder is suspended from a spring and guided by an air bearing. The spring, which itself is attached to an axially oscillating exciter, has been designed especially for a low linear and a large torsional spring constant. The motion of the cylinder and exciter is recorded and analysed. The applicable frequency ranges from 0.001 up to 50 Hz, the steady shear rate from 0.001 up to 100 s-1 and the oscillatory shear amplitude from 3 down to 0.003. The temperature can be set and controlled between 5° and 70°C. The instrument is suited for viscosities in the range from 0.3 mPas up to 1 Pas. Considering this, the range and sensitivity with respect to existing instruments has been extended significantly. Besides a description of the instrument much attention has been paid in this paper to the theoretical background of orthogonal super-position in frames of the simple fluid theory. Also the measurement range and calibration of the instrument as well as the accuracy of the obtainable results are discussed. At last some demonstration measurements on both a polymer solution and an ordering latex, dispersion are presented.
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    Modelling of self-aligned total internal reflection waveguide mirrors: an interlaboratory comparison (1995)
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    Optical and quantum electronics 27 (1995), S. 935-942 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Results of modelling of light propagation in 45° self-aligned total internal reflection rib waveguide mirrors on InP substrate are compared. Six laboratories participated in the comparison with the following six modelling methods: the standard fast-Fouriertransform beam propagation method (BPM), the standard finite-difference (FD) BPM using the Crank-Nicholson scheme (two laboratories), the FD-BPM with the correction for the slowly varying envelope approximation, the method of lines, the eigenmode expansion and propagation method, and a simple method based on the field overlap. All the laboratories used the effective-index method to reduce the three-dimensional problem to two dimensions. The differences among the results obtained by different methods are briefly discussed and qualitatively compared to measured values.
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    New developments of a beam propagation algorithm based on the method of lines (1995)
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    Optical and quantum electronics 27 (1995), S. 943-950 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An extension of a beam propagation algorithm based on the method of lines is presented. Cylindrical coordinates are used to analyse taper structures. The results are compared with those using Cartesian coordinates. The numerical effort is reduced and better convergence is obtained. The field distribution and the power flow for a slab guide taper are presented.
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    An FD-BPM with adaptive mesh for longitudinally varying optical structures (1995)
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    Optical and quantum electronics 27 (1995), S. 951-959 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A finite difference beam propagation method (FD-BPM) algorithm using an adaptive mesh is proposed for optimal use of computer memory and minimization of CPU times in three-dimensional longitudinally varying guiding structures. Preliminary results confirming its feasibility and the advantages of the new algorithm both in CPU and computer memory requirements are described in a 2D case using a Y-junction.
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    Efficient interface conditions for the semi-vectorial finite-difference beam propagation method (1995)
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    Optical and quantum electronics 27 (1995), S. 961-975 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Efficient interface conditions (EICs) are derived for the propagation equation using the slowly varying envelope approximation for the dominant electric field component. At the interface between two different media, the two lateral second derivatives in the discretized propagation equation are adapted such that the discretized modal field equation is correct up to second order in the lateral grid spacing. Since the error term is then of the order of the lateral grid spacing, our EICs are first-order EICs. These interface conditions are compared with well-known zero-order EICs derived by Stern and Kim and Ramaswamy. It is shown that the first-order EICs yield faster convergence to the exact effective index value as the lateral grid spacing is decreased than do the zero-order EICs. It turns out that our EICs are very much like those derived by Vassallo. Using essentially the same method, he derived EICs of second and first order for the field component respectively parallel and perpendicular, to the interface. Hence the accuracy of his EICs is one order higher for the field component parallel to the interface, although it introduces an extra asymmetry in the propagation matrix.
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    Radiation field propagation in low-contrast single-mode optical waveguides (1995)
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    Optical and quantum electronics 27 (1995), S. 977-985 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In short waveguides used in integrated optical circuits, the radiation field is often present in the guiding region of a waveguide as well as the guided modes. We show that this can be investigated efficiently by extracting the radiation part from the total input field and simulating its evolution along the waveguide by use of the beam propagation method. The results are presented for a single-mode waveguide and a waveguide junction excited by a Gaussian beam. For a noncentred excitation, a considerable fraction of the radiation power is still in the guiding region after propagation over several tens of micrometres, and can be coupled to guided modes past the junction.
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    Second-mode cutoff in rectangular-core couplers using the Fourier decomposition method (1995)
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    Optical and quantum electronics 27 (1995), S. 987-994 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract By transforming the infinitex-y plane onto the unit square and using two-dimensional Fourier series expansions, the modal fields and propagation constants of dielectric waveguides can be accurately determined within the scalar (weak-guidance) regime. In particular, the method gives cutoffV-values directly. By applying the technique to symmetric and asymmetric rectangular-core couplers, the second-mode cutoffV-value is determined numerically as a function of both the centre-to-centre core separation and the core aspect ratios. Approximate analytical expressions are derived from the exact numerical data which give the cutoff values to within 2.5%.
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    Determination and stability analysis of the supermodes in nonlinear directional couplers through a variational approach (1995)
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    Optical and quantum electronics 27 (1995), S. 1015-1026 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The even and the odd supermodes of nonlinear directional couplers are determined by means of a variational approach; both slab and channel nonlinear couplers are considered. The validity of the solutions given by the analytical method and their stability properties are analysed through numerical integration of the governing equations. It is shown that channel nonlinear directional couplers improve the stability of the eigenmodes.
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    Study of acid-base dye laser systems (1995)
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    Optical and quantum electronics 27 (1995), S. 1027-1051 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Rate equations with temporal, spectral and spatial dependences are derived to obtain the characteristics of the laser emission of dye molecules that undergo acid-base processes. The model has been tested to reproduce the experimental results of the laser emission due to the monoprotonated species of 4-amino-7-phenyl-8H-pyrazino[2,3-c]-1,2,6-thiadiazine 2,2-dioxide in acetonitrile. Numerical solution of the rate equations is performed to predict general lasing characteristics of acid-base dye laser systems. The temporal evolution and the superficial density of output energy of both a neutral and a base species are studied as a function of the pumping energy and the acidity of the solution. Cases of equilibrium or nonequilibrium in the excited state and overlap or nonoverlap between fluorescence and absorption bands of the different species are considered. The possibility of simultaneous lasing of both species at two different frequencies is discussed.
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    The general approach to mode-locking mechanism analysis for CW solid-state lasers with a nonlinear Fabry-Pérot interferometer (1995)
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    Optical and quantum electronics 27 (1995), S. 1061-1068 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The effective mode locking of a CW solid-state laser with a nonlinear Fabry-Pérot interferometer with a period matched to that of the main cavity period (mode locking by additional cavity, or coupled-cavity mode locking) is considered. The main features of the ultra-short pulse generation obtained on the basis of numerical simulations in the framework of the fluctuation model are interpreted using an analysis of nonlinear reflectivity of the interferometer. A correlation between parameter ranges for effective mode locking and self-consistent solutions of the system describing the CW ultra-short pulse generation allows one to explain a ‘discrete’ range character. A new mode-locking regime has been described and the influence of interferometer bistability on the mode-locking efficiency has been evaluated.
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    Local fields in single-mode helical fibres (1995)
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    Optical and quantum electronics 27 (1995), S. 1069-1074 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The scalar local-field wave equations in helical fibres are derived and, with the aid of a special mathematical treatment, solved approximately in a local coordinate system—the Serret-Frenet frame from the Maxwell's equations. Two basic results are obtained: (1) The local modes in a single-mode helical fibre are circularly polarized. (2) The difference of the propagation constants between the two fundamental modes is 2τ, where τ is the torsion. They agree well with the known experimental measurements.
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    Optical and quantum electronics 27 (1995), S. 1081-1086 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    Laser welding with filler wire (1995)
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    Optical and quantum electronics 27 (1995), S. 1181-1191 
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    ISSN: 1572-817X
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract New applications such as welding of material combinations and the ability to fill opening gaps between the workpieces offer new prospects for laser beam welding processes with filler wire. To guarantee good quality, vertical distance variations between wire tip and weld pool are, above all, not permissible as this causes globular metal transfer and would accordingly result in strongly rippled, unclean welds. A process-internal signal, recorded by a sensor, helps to solve this problem. The automatic tracking of the vertical wire position is possible on-line via a controller. In this way, the running process can be optimized and a consistently good weld quality can be achieved.
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    Lasers for materials processing: specifications and trends (1995)
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    Optical and quantum electronics 27 (1995), S. 1089-1102 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An overview is given of the types of lasers dominating the field of laser materials processing. The most prominent lasers in this field are the CO2 and the Nd: YAG laser. The domain of CO2 lasers is applications which demand high laser powers (up to 30 kW are available at present), whereas the domain of Nd:YAG lasers is micro-machining applications. In the kilowatt range of laser output power, the two types of lasers are in competition. New diffusion-cooled CO2 laser systems are capable of output laser powers of several kilowatts, with good beam qualities, while still being quite compact. The output power and beam quality of Nd:YAG lasers has been improved in recent years, so that Nd:YAG lasers are now an alternative to CO2 lasers even in the kilowatt range. This is especially true for applications that demand optical fibre transmission of the laser beam, which is possible with Nd:YAG laser light but not with the longerwavelength light emitted by CO2 lasers. The main problem in solid-state lasers such as Nd:YAG is the thermal lensing effect and damage due to thermal stresses. In order to reduce thermal loading, cooling has to be enhanced. Several alternative geometries have been proposed to reduce thermal loading and, by this, thermal lensing effects. There are now slab and tube geometries which allow much higher output powers than the conventionally used laser rods. A very new scheme proposes a thin slab whose cooled side is also used as one of the laser mirrors, so that thermal gradients occur mainly in the direction of the beam propagation and not perpendicular to it, as is the case in the other geometries. As well as CO2 and Nd:YAG lasers, semiconductor laser diodes are very promising for direct use of the emitted light or as pump sources for Nd:YAG and other solid-state lasers. When packaging together thousands of single laser diodes, output powers of several kilowatts can be realized. Major problems are collimation of the highly divergent laser beams and cooling of the laser diode bars.
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    Optical and quantum electronics 27 (1995), S. 639-642 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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    Optical and quantum electronics 27 (1995), S. 699-704 
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    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 91
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    Modulation of luminescence intensity in anisotropic crystals under excitation by ultrashort pulses (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 725-734 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The theoretical description of excitation of anisotropic colour centres under the action of ultrashort laser pulses in a birefringent crystal is considered. Peculiarities of spaceperiodic modulation phenomena caused by nonsteadiness of excitation have been studied. It is shown that space-periodic modulation is observed under conditions of overlap of ordinary and extraordinary pulse components. Possible ways of utilizing this phenomenon in new methods of ultrashort pulse duration measurement and determination of the orientation of anisotropic quantum systems in crystals are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00576723
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  • 92
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    A novel probe for an evanescent wave fibre-optic absorption sensor (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 747-753 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A novel, highly sensitive probe consisting of a uniform region sandwiched between two linear tapers for an evanescent wave fibre-optic absorption sensor is proposed. The diameter of the uniform region is chosen to be equal to the minimum allowed diameter of the taper's output end. The first taper is used to bring the angles of the rays in the input fibre close to the critical angle of the sensing region while the second taper reconverts the angles into their initial values so that they can propagate in the output fibre. It has been shown that the sensitivity of the sensor depends on the length of the uniform region of the probe, the refractive index of the fluid and the numerical aperture of the fibre. The sensitivity increases with increase in the length of the uniform region and also with decrease in the numerical aperture of the fibre. In addition, the sensitivity of the proposed probe can be further increased by launching the selected rays into the input fibre.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00576726
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  • 93
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    Analysis of TEM00 laser beam quality degradation caused by a birefringent Nd: YAG rod (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 777-783 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The effects produced by a birefringent rod on the beam quality factor,M infr sup2 , of a Gaussian TEM00 laser beam are studied. Analytical expressions for the beam parameters at the output plane of a rod amplifier are derived. The theory predicts that the beam quality degrades rapidly with the heat power dissipated in the rod.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567553
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  • 94
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    Spatial-temporal coupling in a grating-pair pulse compression system analysed by matrix optics (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 785-798 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The coupling between spatial and temporal parameters of ultrashort pulsed beams propagating through a dispersive system is treated by a 6×6 matrix formalism. A typical grating-pair system which is commonly used in pulsed beam compression is analysed in detail. Numerical examples show that the spatial-temporal coupling becomes severe under some conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567554
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  • 95
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    Announcement (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 828-828 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567559
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  • 96
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    Nonlinearities in semiconductor laser amplifiers (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 1-13 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract This review discusses the physical mechanisms of absorptive and dispersive nonlinearity in amplifiers resulting from interband and intraband electron transitions, with an assessment of the relative strengths and response times of these nonlinearities. Where appropriate, the potential applications of these nonlinearities in optical networks are also indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431029
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  • 97
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    Limitations in the perturbation analysis of bent finite-clad fibres and waveguides (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 15-33 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The transverse shift in the field distribution and the correction to the propagation constant of the fundamental and symmetric cladding modes on bent finite-clad single-mode fibres and slab waveguides are evaluated from perturbation theory for effective index values extending below the cladding index. Analytical results are derived in both geometries for the step-profile that are valid within the overall limitations of the theory. However, it is found that, for the fibre geometry only, the method breaks down at certain discrete wavelengths because of degeneracies that occur between the HE12 (LP02) and TE01 (LP11) mode propagation constants.
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    URL: http://dx.doi.org/10.1007/BF00431030
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  • 98
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    Fabrication and characterization of double-diffused waveguides (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 43-48 
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    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An experimental study of two-step Ag+/Na+ ion exchange in BK-7 glass substrates in molten solutions consisting of AgNO3/NaNO3 mixtures is presented. This paper describes a method for evaluating the measured mode index spectra and the index profile of double-diffused semiburied waveguides. They are first diffused at 320°C in 2% melt and are then converted to semiburied waveguides by a second diffusion step consisting of a short-time reimmersion in a 0.25% melt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431032
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  • 99
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    Doubling of the spatial frequency during recording of holographic gratings in dye-sensitized dichromated gelatin (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 35-41 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Theoretical and experimental investigations are reported on spatial frequency doubling of holographic gratings, recorded with two linear orthogonal polarizations in dyesensitized dichromated gelatin. This frequency doubling is caused by photoinduced isotropic changes in the optical parameters of the material that depend on the polarization state of the irradiating light. The dependence of the diffraction efficiency on the composition, exposure and spatial frequency of the recorded gratings is investigated in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431031
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  • 100
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    Why variational approximation reduces solition switching in nonlinear couplers to the CW case (1995)
    Springer
    Optical and quantum electronics 27 (1995), S. 49-57 
    Details
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Use of the variational approximation to describe soliton propagation in a nonlinear optical coupler is shown formally to reduce the problem to one with the same form as CW operation of a coupler, albeit with a different form of nonlinearity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431033
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