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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4450-4451 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of "natural'' crystals as Bragg diffractors has been supplemented by the advent of artificial composition-modulated structures, that is, multilayers. The extension of optical systems using soft x rays to hard x rays is now supplemented by the synthesis of subnanometer repeat period multilayers. These structures consist of layering amorphous planes, each an atomic spacing thick, and may therefore be thought of as "amorphous crystals.''
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic coupling of the Fe layers in Fe/Si multilayers strongly depends on the morphology of the iron-silicide interlayer that forms during deposition. Antiferromagnetic interlayer coupling is only observed in Fe/Si multilayers with crystalline interlayers in the CsCl structure. Recently, it has been shown that single layers of Fe–Si in the CsCl structure can be grown epitaxially on Si over a range of stoichiometries. FeSi films are reported to be Kondo insulators below 50 K. We find evidence of a magnetic phase transition in antiferromagnetically coupled Fe/Si multilayers. Ms measured in a constant applied field of 50 kOe shows T3/2 behavior down to 10 K. However, M(T) at a lower constant field peaks around 50 K and decreases at lower temperature, indicating enhanced antiferromagnetic coupling or a phase transition. The remanent magnetization increases monotonically with decreasing temperature and has been explained by invoking thermally activated coupling. However, the saturation field also increases with decreasing temperature, indicating a stronger antiferromagnetic interaction. We explore the suggestion that the interlayer coupling is biquadratic in nature. Polarized neutron reflectometry has also been used to get a clearer picture of the complicated magnetic behavior of this multilayer system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 35 (2005), S. 0 
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background The composition of the intestinal flora in young children, if unfavourable, may increase the susceptibility to allergic disorders. Beneficial intestinal microbes originate from the maternal vaginal tract and thus are more likely to be transferred during vaginal births than during Caesarean sections (C-sections).Objective To determine whether children born by C-section have a different risk of allergic disorders compared with those delivered vaginally. We also tested the hypothesis that the risk of allergic disorders is highest for children born after ‘repeat C-sections’.Methods A retrospective cohort study of 8953 children aged 3–10 years. Children diagnosed with allergic rhinoconjunctivitis (AR), asthma, atopic dermatitis (AD), or food allergies were identified from the Kaiser Permanente Northwest Region electronic records. The children's sex, birth weight, birth order, postnatal exposure to antibiotics as well as the mothers' age, ethnicity, education, marital status, smoking status during pregnancy, and use of asthma or hayfever medications were identified through the mothers' medical records or through the Oregon Birth Registry.Results The risk of being diagnosed with AR was significantly higher in the children born by C-section than in those delivered vaginally: adjusted odds ratio (OR)=1.37%, 95% confidence interval (CI)=1.14–1.63. Delivery by C-section was also associated with the subsequent diagnosis of asthma (OR=1.24%, 95% CI=1.01–1.53); this association was gender specific, with a positive association restricted to girls (OR for asthma in girls: OR=1.53%, 95% CI=1.11–2.10; in boys: OR=1.08%, 95% CI=0.81–1.43). There was no significant association between mode of delivery and AD.If children born in a ‘repeat C-section’ were considered separately the risk of being diagnosed with AR increased further (OR=1.78%, 95% CI=1.34–2.37). The same increase was noted for asthma in girls (OR=1.83%, 95% CI=1.13–2.97) but not in boys.Conclusion Caesarean sections may be associated with an increased risk of developing AR in childhood.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5162-5168 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The utilization of W/C and W/B4C multilayer structures as Bragg diffractors rests in their reflective efficiency and dependability, both of which rely on the stability of the layered structure. The layers within the vapor deposited multilayers, often amorphous, are typically metastable, hence susceptible to thermally induced structural change. In fact, crystallization and compound formation are known to occur in annealed multilayer systems. In this study, multilayers of W/C and W/B4C were vacuum heat treated, then structurally examined. A comparison between the pre- and post-heat-treated structures of the two multilayer systems is accomplished using diffraction, depth profiling, and microscopy. Our results indicate structural stability in the W/B4C multilayers, after heat treatment, in comparison with structural degradation noted in the W/C system.
    Type of Medium: Electronic Resource
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