RESUMO
A polycrystalline 1.5% Ho: YAG fiber with a diameter of 31 µm was prepared. Surface roughness from grain boundary grooving was reduced by polishing, which decreased the fiber scattering coefficient from 76 m-1 to 35 m-1. Lasing tests were done on this fiber with a SF57 Schott glass cladding. Lasing was confirmed by spectrum narrowing with threshold pump power lower than 500 mW and a slope efficiency of 7%. To our knowledge, this is the first lasing demonstration from a small diameter polycrystalline ceramic fiber.
RESUMO
Infrared two-photon-pumped and cavity-enhanced frequency upconversion lasing has been achieved in a novel DNA-surfactant-chromophore complex (DSCC) gel system, which is a new step toward producing a biological laser. Once the focused intensity of the 150 fs and approximately 775 nm pump laser beam is higher than a certain threshold level, highly directional stimulated emission at approximately 582 nm wavelength can be observed from a 1 cm long DSCC complex gel cell. With cavity feedback provided by the two optical windows, the pump threshold can be further reduced, the highly directional output lasing can be greatly enhanced, and the output spectral linewidth can be reduced to less than 1/5 of the spontaneous fluorescence spectral bandwidth.
Assuntos
DNA/análise , Lasers , Medições Luminescentes/métodos , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Espectrometria de Fluorescência/métodos , Espectrofotometria Infravermelho/métodos , Tensoativos/análise , DNA/química , Corantes Fluorescentes , Tensoativos/químicaRESUMO
OBJECTIVE: To determine whether the pattern of cervical dilatation prior to caesarean section for 'failure to progress' can predict the outcome of subsequent labour. STUDY DESIGN: Single hospital case note review of 171 women delivered by caesarean section for failure to progress and subsequently delivering at the same hospital. Cervicograms were categorized into one of the four patterns by an assessor blinded to the subsequent outcome. Statistical analysis was done by analysis of variance. RESULTS: The incidence of vaginal delivery did not significantly differ between the groups. CONCLUSION: Categorisation of failure to progress by partographic abnormality does not predict subsequent successful vaginal delivery.
