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  • 1
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The migration ofTrichobilharzia ocellata schistosomula in the duck host and the accidental mouse host was studied by the detection of [75Se]-methionine in radiolabelled cercariae using autoradiography of compressed host tissues and by the recovery of schistosomula following the mincing and incubation of host tissues. Exposure via duck feet (30 min) and mouse tails (60 min) resulted in low infection rates: 3.9% in the duck and 3.1% in the mouse. However, when mice were infected via the abdominal skin using the ring method, 25% of the cercariae were recovered in the skin. In the duck, schistosomula left the skin within 3 days post-infection (p.i.) and were detected in the lungs between days 2 and 4 p.i. Thereafter, only few radioactive foci were found in the liver, kidney and intestine. In the mouse, schistosomula were detected in the lungs within 10 h and for up to 6 days p.i., and some foci were detected in the liver and intestine on days 2–5 p.i. On days 3–4 p.i., 36% of the detectable parasites in the mouse (91 foci in 10 mice) had migrated from the skin to other organs. Living schistosomula could be extracted from mouse skin and lungs only until day 4 p.i. The schistosomula ofT. ocellata migrate faster within their vertebrate hosts than do those ofSchistosoma mansoni, indicating that the former may use other transformation and immune-evasion mechanisms.
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2357-2359 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The process of surface relief grating formation was inspected by atomic force microscopy after short-pulse exposure with counter-rotating circularly polarized laser light of 488 nm on a polymer film containing an azobenzene side-chain homopolymer (pDR1M, TG=129 °C). During light inscription, the grating formation was probed by time-resolved visible scattering with red laser light. The efficiency of grating formation depends on the pulse length of blue light exposure. The shortest pulse length of 2 s did not create a permanent surface relief. After 5 s, a speckled surface modification starts rising and the surface relief becomes more and more uniform with a sinusoidal shape for longer exposure. The experimental findings reveal the individual addressing of azobenzene side groups by the actinic light providing a local lateral force via molecular trans-cis and cis-trans isomerization which subsequently causes grating formation. © 2001 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1366-1370 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A lateral surface grating has been prepared by holographic photolithography followed by wet chemical etching on a slightly misaligned GaAs [001] substrate. The structural parameters were investigated before and after thermal annealing by triple-axis high resolution x-ray diffraction (HRXRD) and scanning electron microscopy (SEM). In particular HRXRD was used to collect reciprocal space maps providing periodicity and shape of the grating. After overgrowth of the free standing nanostructure with AlxGa1−xAs the HRXRD technique fails. Only first order grating truncation rods remain in the (004) HRXRD map. They disappear completely running asymmetric reflections. On the other hand SEM at the cleavage plane reveals the perfection of the overgrowth process and the smoothness of the sample surface. Thus nondestructive analysis of the buried lateral nanostructure was performed by triple-axis x-ray grazing incidence diffraction using synchrotron radiation. This method is exclusively sensitive to the lateral strain profile and provides the possibility of depth resolution. Using two complementary in-plane reflections we found lateral strain modulation within the GaAlAs overlayer accompanied by a compositional modulation with the same period as the grating itself. This periodicity still appears close below the sample surface. © 1998 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2601-2606 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The depth profile of the chemical composition in InxGa1−xAs single quantum wells (SQWs), epitaxially grown onto a GaAs[001] substrate and covered by a GaAs cap layer, has been determined by use of grazing incidence diffraction (GID). This method allows the scattering signal from the SQW to be enhanced and the scattering depth to be tailored. The coherently illuminated area is large, due to the small incident angle αi; this makes GID a unique technique for investigating buried thin layers over a lateral length scale of several microns. In the case of very thin SQWs the measurements could be described assuming a Gaussian-like distribution of the In content with depth. The broad In profile seen using this method is in contrast with the sharp monolayer signal achieved by photoluminescence measurements. This can be explained by the assumption of a terracelike In distribution and the very different lateral integration length of both experiments. For thicker SQWs we could verify that at least one of the two interfaces is not sharp but shows a gradient in the chemical composition. © 1997 American Institute of Physics.
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  • 5
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Möglichkeiten und Grenzen der Strukturaufklärung an Langmuir-Blodgett Filmen mittels symmetrischer Reflexion von Röntgenstrahlen werden anhand des Beispiels einer Stearinsäure-Multischicht beschrieben. Drei verschiedene Techniken der Elektronendichteprofil-Bestimmung werden verglichen: eine Fourier-Methode, eine Patterson-Methode und Modellrechnungen. Dabei wird die Bedeutung der a priori-Information bei der Auswahl des günstigsten Strukturmodells hervorgehoben.
    Notes: The possibilities and limits of structure refinement of Langmuir-Blodgett films by means of symmetrical reflection of X-rays are described using the example of a stearic acid multilayer. Three different techniques for the determination of the electron density profile from reflectivity data are compared: a Fourier method, a Patterson method, and model calculations. The important role of the a priori information for finding the best structure model is outlined.
    Additional Material: 6 Ill.
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  • 6
    ISSN: 0921-4526
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 7
    ISSN: 0921-4526
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 8
    ISSN: 0040-6090
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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  • 9
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Langmuir-Blodgett (LB) multilayer systems are found to be inhomogeneous in morphology and structure. The most characteristic feature of these multilayer films is the appearance of three-dimensional domains in which the molecules arrange themselves as a result of the film transfer onto the substrate. A series of lead arachidate (PbA2) LB multilayers have been prepared as model systems to study the dependence of film morphology on the pH value in the subphase. Atomic force microscopy (AFM) and two different x-ray scattering methods [specular (XSR) and diffuse (XDS) x-ray reflectometry] have been used to investigate the intrinsic interface properties, such as the vertical electron density profile and lateral distribution of head groups and chains, as well as the microscopic description of the interface structure, thus providing an overall picture of the investigated multilayers. With AFM, discrete height variations of domains with minimum step widths of one double layer independent of the salt concentration in the films were observed. The lateral domain size shows a dependence on pH. It was found to be maximum at pH=4.2 (pure acid) but minimum at pH 7.0 (maximum salt content). The AFM pictures were treated by a statistical analysis to extract quantities that can be compared with the x-ray results. A considerable number of Bragg maxima were observed in XSR. The vertical correlation length LZ was calculated from the angular width of Bragg maxima along 2θ and was found to vary with pH value. It follows, in general, the tendency of the domain sizes, being maximum at pH=4.8 and minimum at pH=7.0, respectively. The lateral correlation length LX has been evaluated via XDS from the half widths Δω measured by rocking the sample across a fixed 2θ. It decreases for increasing pH. LX was compared with the respective quantity of the AFM analysis. Estimated by XDS, the correlation lengths for inner interfaces and domains complement one another with the lateral length scales resulting from AFM analysis of the surface. © 1999 American Institute of Physics.
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  • 10
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Focused Ga+ ion beam implantation was used to define a laterally periodic modulation of the electronic band gap in a GaAs/Ga0.97In0.03As/Al0.2Ga0.8As/GaAs [001] multiquantum well structure. The samples were investigated as-implanted and after a rapid thermal annealing (60 s at 650 and 800 °C) by means of x-ray grazing-incidence diffraction. The method provides a separate inspection of the induced strain and the damage profiles as a function of depth below the sample surface. For samples with an ion dose of 5×1013 cm−2, we found a nearly uniform lateral strain amplitude of about 2×10−3 up to the maximum information depth of about 500 nm. It was accompanied by the appearance of structural defects. Rapid thermal annealing at 650 °C has reduced the strain amplitude by a factor of five as well as the density of volume defects. The maximum strain amplitude were found in a depth of about 100 nm. After rapid thermal annealing at 800 °C, the strain has disappeared. © 2000 American Institute of Physics.
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