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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 41 (1985), S. 434-440 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The Fourier diffraction method of Warren-Averbach, developed to measure external stress-induced strains of polycrystalline materials, can also be applied to analyse internal distortions of microparacrystals. In one case a function that is proportional to the distance p2 can be obtained whilst in the second case a function proportional to |p| in the physical space can be derived. More complicated problems arise when both types of distortions occur at the same time, which happens if microparacrystals are exposed to external stresses. This is discussed here for examples of unannealed extruded polyethylene and composite material such as carbon resin fibres. The Warren plot shows that the microparacrystals under investigation suffer rheological transformations, which can no longer be explained by a convolution integral of the reflection profiles with the distribution function of their mean net-plane distance s. The measured function of p can satisfactorily be derived from an empirically detected formula being applied to the convolution product of reciprocal values of the two distortions 1/g2p and 1/ε2p2, the physical meaning of which still remains an open question.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 506-513 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Very thin equatorial small-angle scattering of Cu Kα radiation is observed from metallic wires, glass fibres and hard elastic polypropylene which can be explained quantitatively as a refraction phenomenon if the excess refractive indices n = 1 - ε of the samples are smaller than unity. For Cu Kα radiation and SiO2 glass ε has a value of 7.2 × 10-6. The intensity Is of reflection within a total reflection angle δ = 3.8 × 10-3 = 13' is negligibly small compared with the intensity of refraction IB. In addition to refraction, diffraction by gaps and holes in strained polypropylene was observed. The scattering of 60 μm particles of Li-Ba silicate glass powders [Nau & Brückner (1971). Kolloid Z. Z. Polym. 244, 223-233] can be explained by transforming the observed scattering of spheres to cylinders yielding the refraction IB as calculated.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 446-447 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The absorption of X-rays scattered by isotropic random multiphase materials is shown theoretically to depend not only on volume fraction, linear absorption coefficient and mean particle size of each phase but also on the shape of the scattering particles. The absorption effect is remarkably enhanced with increasing polydispersity and irregularity of the scattering phase.
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  • 4
    ISSN: 1435-1536
    Keywords: Phasediagram ; phospholipids ; calorimetry ; freeze-fracture electronmicroscopy ; NMR ; 31Pdemixing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Differential-scanning-calorimetry, freeze-fracture electron microscopy, and31P-NMR spectroscopy were used to study the lyotropic and thermotropic properties of the system dihexadecylphosphatidylcholine/dihexadecylphosphatidic acid/water/ NaOH in dispersion with excess water at pH=14. The phase diagram showed that both phospholipids are demixed nearly completely in the gel phase. The coexistence of theP β′ and theB β-phase in the mixtures was pointed out in the freeze-fracture electron micrographs by the “ripple structure” (P β′-phase) and by the lamellar structure (B β-phase).
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  • 5
    ISSN: 1432-0649
    Keywords: PACS: 42.60.Da; 42.60.Jf; 42.60.LH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We present a kHz-rate all-solid-state Ti:sapphire oscillator–amplifier system producing 1.8 mJ sub-20 fs pulses using a single multipass amplifier stage pumped by ≈10 mJ pulses. Compensation for gain narrowing and high-order dispersion is provided by chirped dielectric multilayer optics. The focused peak intensity approaches 1018 W/cm2, making this compact high-repetition-rate source attractive for a wide range of high-field applications.
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  • 6
    ISSN: 1432-0649
    Keywords: PACS: 42.79.Gn; 42.65.Ky; 42.50.Hz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 15  W/cm2. The high resistance of fused silica to damage in the sub-10-fs regime allows stable reproducible operation without degradation of the capillary waveguide. In preliminary experiments, we demonstrate kHz-repetition-rate guided-wave high-harmonic generation in helium down to the 10-nm range. The reported experiments open up the way to realizing high-field interactions with plane-wave excitation at intensity levels in excess of 1015 W/cm2 under well-controlled conditions.
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  • 7
    ISSN: 1432-0649
    Keywords: PACS: 42.65.Re
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
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  • 8
    ISSN: 1432-0649
    Keywords: PACS: 42.65.Ky; 41.50.+h; 42.50.Hz; 42.65.Re
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We have investigated the use of sub-10-fs near-infrared laser pulses to generate high-order harmonic radiation efficiently in the wavelength region between 30 to 10 nm. The ultrashort rise time of the driver pulses allows harmonics to be produced at low ionization levels and hence to grow coherently over propagation lengths becoming comparable to the XUV absorption lengths in the noble gas medium. As a result, absorption-limited harmonic generation has been extended to the 10-nm range for the first time. Harmonic conversion efficiencies of (3–4)×10−8 in the range of 10–13 nm in neon and some two orders of magnitude higher at around 30 nm in argon have been obtained in simple gas tube targets under these conditions. Preliminary focusing tests with 13-nm harmonic radiation have been carried out with a specially designed zoneplate and a spherical Mo/Si multilayer mirror and have resulted in spot sizes of about 2 microns. Our experiments aim at paving the way to nonlinear optics in the soft-X-ray regime.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 259 (1981), S. 1161-1169 
    ISSN: 1435-1536
    Keywords: a-Gesetz ; Festkörperphysik ; Mikroparakristalle ; Quasi-Gleichgewicht ; Reflexprofilanalyse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary A correct analysis of wide angle scattering of noncrystalline materials proves that most of them consist of microparacrystals and obey thea-law. The physical interpretation of this law is given by the limited flexibility of the chemical binding and leads to a theoretical calculation of the statistical size distribution of an ensemble of microparacrystals. Their theoretically calculated line profiles agree within the error of experiment with the reflections 110 and 220 of an extruded polyethylene sample annealed 4 days at 111 °C. This is a direct proof that macromolecules aggregate in a quasi-equilibrium state, which is unknown in conventional solid state physics. The importance of these results for colloid science is pointed out -in this work.
    Notes: Zusammenfassung Eine adäquate Analyse der Weitwinkelprofile nichtkristalliner Substanzen beweist, daß sie meist aus Mikroparakristallen aufgebaut sind und dema-Gesetz gehorchen. Die physikalische Erklärung hierfür ergibt sich aus der begrenzten Flexibilität der chemischen Bindung und führt auf eine theoretische Berechnung der Größenverteilung (Polydispersität) eines Ensembles von Mikroparakristallen. Ein Vergleich mit einem bei 111 °C getemperten extrudierten Polyäthylenstab führt auf befriedigende Übereinstimmung mit der Rechnung und beweist, daß sich die Makromoleküle in einem neuartigen Quasi-Gleichgewichtszustand aggregiert haben, der in der heutigen Festkörperphysik unbekannt ist. Auf die Bedeutung der Ergebnisse für die Kolloidwissenschaft wird hingewiesen.
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  • 10
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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