RESUMO
In this paper, we design aperiodic gratings based on orientation-patterned gallium arsenide (OP-GaAs) for converting 2.1 µm pump laser radiation into long-wave infrared (8-12 µm) in an idler-efficiency-enhanced scheme. These single OP-GaAs gratings placed in an optical parametric oscillator (OPO) or an optical parametric generator (OPG) can simultaneously phase match two optical parametric amplification (OPA) processes, OPA 1 and OPA 2. We use two design methods that allow simultaneous phase matching of two arbitrary χ(2) processes and also free adjustment of their relative strength. The first aperiodic grating design method (Method 1) relies on generating a grating structure that has domain walls located at the zeros of the summation of two cosine functions, each of which has a spatial frequency that equals one of the phase-mismatch terms of the two processes. Some of the domain walls are discarded considering the minimum domain length that is achievable in the production process. In this paper, we propose a second design method (Method 2) that relies on discretizing the crystal length with sample lengths that are much smaller than the minimum domain length and testing each sample's contribution in such a way that the sign of the nonlinearity maximizes the magnitude sum of the real and imaginary parts of the Fourier transform of the grating function at the relevant phase mismatches. Method 2 produces a similar performance as Method 1 in terms of the maximization of the height of either Fourier peak located at the relevant phase mismatch while allowing an adjustable relative height for the two peaks. To our knowledge, this is the first time that aperiodic OP-GaAs gratings have been proposed for efficient long-wave infrared beam generation based on simultaneous phase matching.
RESUMO
BACKGROUND/AIMS: Sequential therapy is one of the recent answers given to the problem of increasing antibiotic resistance and decreasing eradication rates of Helicobacter pylori infection. The aim of this study is to compare the ornidazole-based sequentialtherapy with the standard triple therapy in Helicobacter pylori eradication. MATERIALS AND METHODS: Children aged 4-18 years diagnosed with Helicobacter pylori infection based on histology and at least one of 13 C urea breath test and rapid urease test positivity were included in the study. Children were randomized to standard triple therapy with amoxicillin, clarithromycin, and lansoprazole for 14 days and sequential therapy with amoxicillin and lansoprazole for the first 5 days and clarithromycin, ornidazole and lansoprazole for another 5 days in 2:3 randomization. At the end of the treatment, families were contacted by phone, and side effects of and the compliance to the treatment were noted. Patients were requested to do 13 C urea breath test 6-8 weeks after the treatment. RESULTS: Sixty-one children were included for the final analysis. Per-protocol eradication rates were 48.6% for sequential therapy group and 54.2% for standard triple therapy group. Intention to treat eradication rates were 40.9% and 46.0%, respectively. There were no differences between eradication rates in the two study groups. Side effect rates were also similar between the two groups. CONCLUSIONS: Ornidazole-based sequential therapy did not show any superiority compared to the standard triple treatment in children with Helicobacter pylori infection.
