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  • 1
    ISSN: 1432-0649
    Keywords: PACS: 42.15.Eq; 42.25.Bs; 42.40Pa; 42.60.Da; 42.65.k; 42.79Bh; 42.90.V
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. Chirped dielectric laser mirrors have been known for years as useful devices for broadband feedback and dispersion control in femtosecond pulse lasers. First we present a novel design technique referred to as frequency domain synthesis of chirped mirrors. These mirrors exhibit high reflectivity and nearly constant group delay over 150 THz supporting generation of sub-5-fs pulses in the visible. Afterwards, multi-cavity thin-film Gires–Tournois interferometers are introduced for the first time as an alternative approach to realize “negative dispersion mirrors”. These novel dielectric high reflectors exhibit reflectivities R〉99.97% and a negative group delay dispersion of −50±1 fs2 over a bandwidth of 56 THz. Dispersive properties originate from coupled resonances in multiple λ/2 cavities embedded in the layer structure. The general structure and performance of multi-cavity Gires–Tournois interferometers are compared to that of chirped dielectic mirrors and their distinct applications are discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:  Prior studies suggest that histamines may modulate the development of colorectal neoplasia.Aim:  To assess whether histamine receptor antagonist use was associated with adenoma formation.Methods:  Patients (n = 2366) were drawn from three adenoma chemoprevention trials. All underwent baseline colonoscopy with removal of adenoma(s) and were deemed free of remaining lesions; they were followed with surveillance colonoscopy. Medication use was assessed by questionnaire. Adjusted risk ratios for adenoma formation related to histamine receptor antagonist use (histamine H1 and H2 receptor, H1RA and H2RA) were determined using log linear models.Results:  In pooled analyses, H1RA exposure was not associated with subsequent adenoma risk (RR = 1.10; 95% CI 0.97–1.25) or multiple adenoma formation (RR = 0.85; 95% CI 0.67–1.07). H2RA use also was not associated with adenoma (RR = 0.90; 95% CI 0.77–1.06), or multiple adenoma (RR = 0.77; 95% CI 0.57–1.04) in the pooled analyses, but H2RA users in the first trial had a decreased risk of adenoma (RR = 0.70; 95% CI 0.48–1.03) and multiple adenoma (RR = 0.31; 95% CI 0.12–0.79).Conclusion:  H2RA use was associated with reduced risk for adenoma in one trial, but not in the pooled analyses. Further study would be warranted before undertaking randomized trials of H2RAs for adenoma chemoprevention.
    Type of Medium: Electronic Resource
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