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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5251-5258 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structure of lamellar phases of symmetric AB diblock copolymers in a thin film is investigated. We quantitatively compare the composition profiles and profiles of individual segments in self-consistent field calculations with Monte Carlo simulations in the bond fluctuation model for chain length N=32 and χN=30. Three film thicknesses are investigated, corresponding to parallel oriented lamellae with 2 and 4 interfaces and a perpendicular oriented morphology. Taking account of capillary waves, we find good quantitative agreement between the Monte Carlo simulations and the self-consistent field calculations. However, the fluctuations of the local interfacial position are strongly suppressed by confinement and mutual interactions between lamellae. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 5370-5379 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By means of extensive Monte Carlo simulations of the bond fluctuation model, we study the effect of adding AB diblock copolymers on the properties of an interface between demixed homopolymer phases. The parameters are chosen such that the homopolymers are strongly segregated, and the whole range of copolymer concentrations in the two phase coexistence region is scanned. We compare the "mushroom" regime, in which copolymers are diluted and do not interact with each other, with the "wet brush" regime, where copolymers overlap and stretch, but are still swollen by the homopolymers. A "dry brush" regime is never entered for our choice of chain lengths. "Intrinsic" profiles are calculated using a block analysis method introduced by us in earlier work. We discuss density profiles, orientational profiles, and contact number profiles. In general, the features of the profiles are similar at all copolymer concentrations, however, the profiles in the concentrated regime are much broader than in the dilute regime. The results compare well with self-consistent field calculations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 5241-5250 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We investigate the phase behavior of symmetric AB diblock copolymers confined into a thin film. The film boundaries are parallel, impenetrable and attract the A component of the diblock copolymer. Using a self-consistent field technique [M. W. Matsen, J. Chem. Phys. 106, 7781 (1997)], we study the ordered phases as a function of incompatibility χ and film thickness in the framework of the Gaussian chain model. For large film thickness and small incompatibility, we find first order transitions between phases with different number of lamellae which are parallel oriented to the film boundaries. At high incompatibility or small film thickness, transitions between parallel oriented and perpendicular oriented lamellae occur. We compare the self-consistent field calculations to Monte Carlo simulations of the bond fluctuation model for chain length N=32. In the simulations we quench several systems from χN=0 to χN=30 and monitor the morphology into which the diblock copolymers assemble. Three film thicknesses are investigated, corresponding to parallel oriented lamellae with 2 and 4 interfaces and a perpendicular oriented morphology. Good agreement between self-consistent field calculations and Monte Carlo simulations is found. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 1221-1229 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the effect of surface fields on the interfacial properties of a binary polymer melt confined between two parallel walls. Each wall attracts a different component of the blend by a nonretarded van der Waals potential. An interface which runs parallel to the surfaces is stabilized in the center of the film. Using extensive Monte Carlo simulations we study the interfacial properties as a function of the film thickness, the strength of the surface forces, and the lateral size over which the profiles across the film are averaged. We find evidence for capillary wave broadening of the apparent interfacial profiles. However, the apparent interfacial width cannot be described quantitatively by a simple logarithmic dependence on the film thickness. The Monte Carlo simulations reveal that the surface fields give rise to an additional reduction of the intrinsic interfacial width and an increase of the effective interfacial tension upon decreasing the film thickness. These modifications of the intrinsic interfacial properties are confirmed by self-consistent field calculations. Taking account of the thickness dependence of the intrinsic interfacial properties and the capillary wave broadening, we can describe our simulation results quantitatively. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 32 (1999), S. 1127-1133 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A complete image of the helical arrangement of cellulose fibrils in the S2 layer of adjacent wood cells of Picea abies (Norwegian spruce) was obtained by applying position-resolved synchrotron X-ray microdiffraction on cells in cross section. In contrast to conventional fiber diffraction studies, the incident beam was parallel to the longitudinal cell axis, resulting in a glancing angle μ far from 90° with respect to the cellulose fibrils. This special choice of diffraction geometry allowed us to take advantage of an asymmetry effect in the two-dimensional diffraction patterns arising from the curvature of the Ewald sphere to obtain information on the local orientation of the cellulose fibrils. The small size of the beam, smaller than the thickness of a single cell wall, allowed mesh scans over intact transverse sections of adjacent wood cells with a microscopic position resolution. The scan yielded a map of diffraction patterns that could readily serve as a microscopic image. Each of the diffraction patterns was then used to evaluate the local orientation of the cellulose fibrils at the actual beam position. The combination of these results gave an image of cellulose fibrils forming (Z) helices in several adjacent wood cells.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we ...
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0630
    Keywords: PACS: 61.72.Hh; 61.72.Ww; 61.80.Jh; 66.30.Jt; 79.20.Wc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: 6 Li+ ions were implanted into PMMA at high flux up to fluences of 1×1015 cm-2 under angles of 0° to 70° towards the surface normal. The Li depth distributions were determined by means of neutron depth profiling, and compared with theoretical simulations. The three-dimensional Li distribution was reconstructed from the one-dimensional depth profiles by means of a tomographic technique. It turned out that the measured Li depth distributions can be described by a superposition of Gaussian and exponential functions. This points at considerable Li mobility during or after the ion implantation, with trapping in unsaturable traps in the ion-irradiated region which roughly follow the electronic energy transfer distribution. The Li redistribution is more pronounced along the track direction than transversely to it. The normalized Li distributions in various implantation directions were fed into our tomographic program to reconstruct the three-dimensional distribution of the deposited lithium. As expected, the lithium preferentially distributes along the ion tracks. This work is another hint that mobility of implanted ions in solids does not proceed isotropically, but is strongly influenced by the radiation-damage distributions.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0649
    Keywords: PACS: 42.65 H; 42.30; 07.07.D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. In this article, we demonstrate the capability of a two-beam coupling photorefractive optical novelty filter of detecting changes in the amplitude or phase of optical images. These changes may either be continuous or discrete in time. The performance of the two-beam coupling novelty filter is investigated and expressions for the output contrast corresponding to phase and amplitude changes based on a novel, simple interference model of two-beam coupling are derived. These expressions are verified by experimental results on the novelty contrast, revealing that the amplitude contrast is not described correctly by the commonly accepted coupled-wave theory. The novelty filter was applied to the detection of temporally continuous phase changes provided by a gas flow and moving microscopic objects. A novel scheme for image subtraction is also demonstrated, showing the novelty filter’s ability to detect temporally discrete changes.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1433-0385
    Keywords: Key words: Surgical mesh ; Incisional hernia ; Complication ; Stereography ; Polypropylene. ; Schlüsselwörter: Netze ; Narbenhernie ; Polypropylen ; Komplikationen ; Stereographie.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung. Die Reparation von Narbenhernien machen eine großflächige präperitoneale Implantation alloplastischen Materials erforderlich. Die Menge und Struktur des eingebrachten Materials bestimmen aber das Ausmaß der induzierten unelastischen Narbenfläche und die Rate lokaler Wundkomplikationen. Dies macht eine Minimierung der alloplastischen Implantate wünschenswert. In einer prospektiven randomisierten Studie an 65 Patienten wurden die Frühergebnisse nach Implantation eines minimierten, leichtgewichtigen Netzes (26,8 g/m2 Polypropylen) mit 5 mm Maschengröße einerseits und einem schwergewichtigen, üblichen Netz (90,2 g/m2 Polypropylen) kleiner Porengröße (0,8 mm) andererseits verglichen. Als Parameter dienten die sonographische Seromrate und -menge, die subjektiven Mißempfindungen, die körperliche Aktivität, die Bauchwandmotorik mittels 3-D-Stereographie und die histologischen Veränderungen, soweit wegen akzidentieller Reoperation sich die Möglichkeit zur Probeentnahme ergab. Hierbei fand sich eine deutliche Reduktion der Serome, Mißempfindungen und Bewegungsstörungen sowie eine objektive Verbesserung der Bauchfunktionen mittels 3-D-Stereographie für das minimierte Polypropylen-Netz. Dies geht in der histologischen Auswertung mit einer geringeren Entzündungs- und Narbenreaktion, d. h. einer früheren Gewebsintegration des alloplastischen Materials, einher. Bis auf ein Rezidiv waren keine weiteren Komplikationen festzustellen.
    Notes: Summary. Repair of incisional hernias requires the extensive implantation of alloplastic materials. The extent of the scar tissue is markedly regulated by the amount and structure of the incorporated material and is responsible for the increased rate of local wound complications. Correspondingly, minimization of the alloplastic implants should be favorable. In a randomized, prospective clinical study, the early results were compared after implantation of either a minimized, low-weight (26.8 g/m2) mesh with a pore size of 5 mm or a common, heavy-weight (90.2 g/m2 polypropylene) mesh with a pore size of 0.8 mm. Indicators for clinical suitability were the rate and volume of seroma, subjective paraesthesia, physical capability, abdominal wall compliance, and the histologically analyzed tissue reaction of samples removed on the occasion of revision operations. As result, the optimized, low-weight mesh showed a remarkable decrease in the rate of seroma, patient complaints, less restriction of abdominal wall mobility, and improved abdominal wall compliance as verified by 3D stereography. These clinical findings corresponded to a pronounced decrease in inflammation and scar reaction, indicating improved incorporation of the alloplastic material. No other major complications except for one recurrence have been found.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Monatsschrift Kinderheilkunde 147 (1999), S. 1106-1110 
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Thrombose ; Thrombolyse ; Rekombinanter Gewebeplasminogenaktivator ; Streptokinase ; Urokinase ; Key words Thrombosis ; Thrombolysis ; Recombinant Plasminogen-Activator ; Streptokinase ; Urokinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Thrombolysis therapy in childhood and adolescence has brought about numerous case reports, but no controlled studies over dosage and duration of therapy have been published to date. We report about an adolescent female patient with massive pelvic and leg vein thrombosis that underwent thrombolysis therapy. Loss of the affected leg was imminent. A novelty in this field, two fibrinolytic agents (recombinant tissue plasminogen-activator, as well as streptokinase) were employed simultaneously with success. Discussion: In thrombolysis therapy without success the use of two fibrinolytic agents should be considered.
    Notes: Zusammenfassung Über Thrombolysetherapien bei der Behandlung von Thrombosen im Kindes- und Jugendalter gibt es bereits viele Fallberichte, jedoch noch keine kontrollierten Studien über Dosierung und Therapiedauer des Thrombolytikums. Wir berichten über eine Thrombolysetherapie bei einer massiven Becken- und Beinvenenthrombose einer jugendlichen Patientin, bei der erstmals bei drohendem Verlust des betroffenen Beins 2 Fibrinolytika (rekombinanter Gewebeplasminogenaktivator lokal und Streptokinase systemisch) zeitgleich erfolgreich eingesetzt wurden. Diskussion: Bei einer erfolglosen Lysetherapie einer bedrohlichen Bein- und Beckenvenenthrombose sollte der kombinierte Einsatz zweier Fibrinolytika erwogen werden.
    Type of Medium: Electronic Resource
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