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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 143-148 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Acoustic and optic phonons have been measured by Brillouin and Raman spectroscopies in LiNbO3 samples with different stoichiometries. Consequently, the elastic constants have been determined by Brillouin scattering as a function of the stoichiometry. The C44 elastic constant presents, as a function of the stoichiometry, a clear minimum for the [Li]/[Nb]=1 in the melt sample. This behavior must be related to the existence and competition of two kind of defects, i.e., extended defects induced when growing samples not at the congruent composition, and point defects present in nonstoichiometric samples. The optic phonons seem to be dominated by the point defects. The linear increase of the phonon lifetimes, with respect to an ideal stoichiometric sample, can be due to the scattering by the static imperfections and to an increase of the anharmonic scattering. Several Raman peaks, which appear when the [Li]/[Nb] ratio decreases, are related to the presence of Nb in antisites. The width of some particular phonons can be used to estimate the [Li]/[Nb] ratio whenever a line shape study and a good correction, taking into account the instrumental broadening, is carried out. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1881-1888 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The innovative method of combining specular and off-specular low-angle x-ray diffraction, along with the anomalous scattering effect, has been used to characterize magnetron-sputtered Co/Cu multilayers. The anomalous dispersion of Co is employed to increase the electron density contrast between the cobalt and copper layer. The use of a simulation program has been proven to be a straightforward and reliable method to analyze x-ray low-angle diffraction patterns in such a nonperfectly ordered metallic multilayer system. This method has been successfully applied to data obtained from synchrotron experiments and the results compared with those performed using a standard laboratory diffractometer. The combination of both specular and off-specular scans has ensured the obtention of a single set of simulation parameters for the structure of the multilayer and its interfaces. In addition, the off-specular scans have permitted us to confirm, in a rather complex system, the validity of the distorted wave born approximation. The mesoscopic structure of this multilayered system has been accurately and self-consistently characterized. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anatomia, histologia, embryologia 27 (1998), S. 0 
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The incidence and location of CD2+, CD4+, CD8+ and γ/δ T lymphocytes and IgM+ B lymphocytes were studied in the intestinal lymph nodes in 1-week, 1-month, 3-month and 7-month-old goats, using monoclonal antibodies and immuno-histochemical methods. The cortical area of the intestinal lymph nodes in 1-week-old animals contains only primary follicles occupied by IgM+ B lymphocytes and some CD2+CD4+ T lymphocytes. In goats older than 1 month, secondary follicles, that increased in number and size with age, were observed; the light zone of the germinal centre was occupied by IgM+ lymphocytes and some CD2+ and CD4+ T lymphocytes. In the other compartments of the lymph nodes, B lymphocytes were scarce, their number increasing with age in the medulla and diminishing in the paracortex. The numerous CD2+ T lymphocytes in the interfollicular area increased in number in the paracortical area of the 7-month-old goats, simultaneously with an increase in the MHC II+ dendritic cells and the CD4/CD8 ratio, which was greater than 1. The γ/δ T lymphocytes represented a minor subpopulation scattered through the lymph nodes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Anatomia, histologia, embryologia 28 (1999), S. 0 
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The distribution of B cells in the lymphoid organs of the goat was studied using a panel of 13 monoclonal antibodies (mAbs) developed against different markers for bovine B cells. Samples of mesenteric lymph nodes, jejunal and ileal Peyer’s patches, duodenum, jejunum, ileum, colon, caecum and rectum were taken from four 7-month-old male Murciano-granadina goats using the avidin-biotin-peroxidase (ABC) method on frozen sections as described by Hsu et al. (1981). The mAbs against immunoglobulins (Ig) recognized a large number of cells, particularly in the light zones of the germinative centres of the lymphoid follicles, regardless of the isotype against which they were directed. However, the greatest numbers of B cells in the germinative centres and outer coronas of the lymphoid follicles of the lymph node, spleen and Peyer’s patches were recognized by mAbs against the Lλ chain of Ig and against IgM. This was also the case in other locations where B cells were abundant, such as the medulla of the lymph node and the dome of the Peyer’s patches. These mAbs recognized not only B lymphocytes but also plasma cells, showing an intracytoplasmatic reaction (numerous in the spleen red pulp and the intestinal lamina propria when mAbs were used against the Lλ chain of the Ig, scarce in the intestinal lamina propria when used against IgM and scarce in spleen red pulp and numerous in the intestinal lamina propria when mAbs against IgA were used). The mAbs BAQ44 A, GC65 A and GB25 A are of interest because, besides marking cells in the B areas where lymphocytes show surface Ig, they give a positive reaction in areas where there are Ig− cells (the dark zone of the germinative centre) and do not immunostain plasma cells. Thus, these mAbs recognize a surface marker which is not an Ig.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Anatomia, histologia, embryologia 28 (1999), S. 0 
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We describe the ultrastructural characteristics of PRL cells with small secretory granules, immunostained with ovine antiserum, in adult Murciano-Granadina milking goats during anoestrus, the last third of gestation and lactation. This cell subtype is considered to comprise a stable population that decreases numerically during gestation and lactation, and that may change during these stages to show large granules.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spin dynamics in the condensed phases of ambient–pressure molecular oxygen (liquid, plastic–crystalline (γ−), magnetically disordered (β−) and fully ordered α−O 2 ) iS investigated by means of the concurrent use of neutron scattering and muon–spin relaxation. Above the α → β transition the magnetic dynamics is governed by fast paramagnetic fluctuations whose spectrum is determined from the S(Q,ω) dynamic structure factors accessible from inelastic neutron scattering. Such information is shown to provide a key to understand the non–trivial temperature dependence of longitudinal relaxation rates found in muon spin relaxation measurements. Recent neutron scattering measurements performed within the magnetically ordered α–phase under high–resolution conditions reveal the presence of a low–energy excitation of magnetic origin, unnoticed in a previous polarized–neutron experiment, which corresponds to the continuation to longer wavevectors of the spin–wave mode detected in antiferromagnetic resonance (AFMR) experiments carried out by optical means.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1572-994X
    Keywords: HIV-1 ; Vif ; nucleotide sequence ; variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have determined the nucleotide sequence of the HIV-1vif gene in viruses obtained from symptomatic patients of distinct risk groups in Madrid. The genetic diversity among the isolates was estimated in 4.6% (±1.4 standard deviation), a similar value to that obtained for thegag gene 3.9% (±0.8 standard deviation) andenv 4.1% (±1 standard deviation) (Rojas et al., Virus Res31, 331–342, 1994). Amino acid sequence analysis revealed the presence of hypermutable residues at positions 101 and 167, close to antigenically relevant sequential epitopes (comprising amino acids 87–94 and 172–178). Phylogenetic analysis supports the existence of two virus lineages circulating preferentially within different risk groups.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 324-329 
    ISSN: 0142-2421
    Keywords: Brillouin light scattering ; Si/Ge superlattices ; elastic constants ; surface acoustic waves ; supermodulus effect ; surface sound velocity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The elastic properties of Si/Ge strained-layer superlattices have been studied by means of Brillouin light scattering spectroscopy in order to verify the validity of the most reliable explanations for the so-called ‘supermodulus effect’. The superstructures, grown along the [001] direction, have composition modulation wavelengths ranging from 1.4 to 5.6 nm and Si/Ge ratios 1/1, 3/1, 4/1 and 1/4. The study has been carried out in three different stages: a check of the non-influence of the substrate on the determination of the elastic properties; the angular dependence of the surface sound velocity within the surface plane; the variation of the phase velocity with the modulation wavelength. No evidence of the anomalous supermodulus effect has been found in these superlattices, which can be explained on the basis of the latest theoretical predictions. In addition, the obtained data of hypersonic surface waves are in good agreement with previous results reported in Si and Ge pure single crystals. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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