The prevalence of allergic rhinitis, a common respiratory disorder, may be rapidly increasing. Epidemiological studies, however, indicate little about its association with climatic factors and air pollution. The relationship between trafficrelated air pollutants and allergic rhinitis in middle-school students was therefore investigated.In a nationwide survey of middle-school students in Taiwan conducted in 1995/1996, the lifetime prevalence of physician-diagnosed allergic rhinitis and typical symptoms of allergic rhinitis were compared with air-monitoring station data on temperature, relative humidity, sulphur dioxide (SO 2 ), nitrogen oxides (NOx), ozone (O 3 ), carbon monoxide (CO) and particulate matter with a 50% cut-off aerodynamic diameter of 10 mm (PM10).A .2)%. The prevalence of physician-diagnosed allergic rhinitis was 28.6 and 19.5% in males and females, respectively, with prevalence of questionnaire-determined allergic rhinitis 42.4 and 34.0%. After adjustment for age, parental education and history of atopic eczema, physician-diagnosed allergic rhinitis was found to be associated with higher nonsummer (September-May) warmth and traffic-related air pollutants, including CO, NOx and O 3 . Questionnaire-determined allergic rhinitis correlated only with traffic-related air pollutants.Nonsummer warmth and traffic-related air pollution, probably mediated through exposure to common allergens such as dust mites, are possible risk factors for allergic rhinitis in middle-school-aged children. Eur Respir J 2003; 21: 964-970.
With a Gaussian-like broadband light source from high brightness Ce 3+ :YAG single-clad crystal fiber, a full-field optical coherence tomography using a home-designed Mirau objective realized high quality images of in vivo and excised skin tissues. With a 40 × silicone-oilimmersion Mirau objective, the achieved spatial resolutions in axial and lateral directions were 0.9 and 0.51 μm, respectively. Such a high spatial resolution enables the separation of lamellar structure of the full epidermis in both the cross-sectional and en face planes. The number of layers of stratum corneum and its thickness were quantitatively measured. This label free and non-invasive optical probe could be useful for evaluating the water barrier of skin tissue in clinics. As a preliminary in vivo experiment, the blood vessel in dermis was also observed, and the flowing of the red blood cells and location of the melanocyte were traced.
A novel double-clad Cr4+:YAG crystal fiber is demonstrated by use of a codrawing laser-heated pedestal growth method. Up to 10 dB of gross gain at a wavelength of 1.52 microm is achieved at a pump power of 0.83 W, which, to our knowledge, is the first Cr4+-doped fiber amplifier in the optical fiber communication band.
We report what we believe to be the first demonstration of a room-temperature, continuous-wave Cr(4+):Y(3)Al(5)O(12) (Cr(4+):YAG) double-clad crystal fiber laser grown by the codrawing laser heated pedestal growth method. The threshold is below 100 mW, which is a factor of 4 lower than previously reported Cr(4+)-doped lasers. A slope efficiency of 6.9% was obtained, and is in good agreement with the numerical simulation. In additional to small core diameter, the low-threshold lasing is made possible by the low propagation loss of 0.08 dB/cm and the high crystallinity of the core.
A two‐dimensional simulation was employed to study the melt/air and melt/solid interface shapes of the miniature molten zone formed in a laser‐heated pedestal growth (LHPG) system. Using a non‐orthogonal body‐fitting grid system with the control‐volume finite‐difference method, the interface shape can be determined both efficiently and accurately. During stable growth, the dependence of the molten‐zone length and shape on the heating CO2 laser is examined in detail under both the maximum and the minimum allowed powers with various growth speeds. The effect of gravity on the miniature molten zone is also simulated and the possibility of horizontally oriented LHPG is revealed. Such a horizontal system is good for the growth of long crystal fibers.
We report on the first fabrication of a Cr-doped fiber using a drawing-tower method with Cr:YAG as the core of the preform. Both Cr3+ and Cr4+ ions coexist in the Cr-doped fiber, and the amplified spontaneous emission (ASE) spectrum shows a broadband emission of 1.2 to 1.55 mum which can not be realized by using currently available fiber amplifiers. This indicates that the new Cr-doped fibers have the potential for being used as a broadband fiber amplifier to cover the bandwidth of the entire 1.3-1.6 mum range which exhibit 300 nm usable spectral bands.
The fabrication of a Cr-doped fiber using a drawing-tower method with Cr:YAG as the core of the preform is presented. The Cr-doped YAG preform was fabricated by a rod-in-tube method. By employing a negative pressure control in drawing-tower technique on the YAG preform, the Cr-doped fibers with a better core circularity and uniformity, and good interface between core and cladding were fabricated. The amplified spontaneous emission spectrum showed a broadband emission of 1.2 to 1.6 mum with the output power density about a few nW/nm. The results indicate that this new Cr-doped fiber may be used as a broadband fiber amplifier to cover the bandwidths in the whole 1.3-1.6 mum range of low-loss and lowdispersion windows of silica fibers.
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