Two-dimensional dynamic simulations of DFB lasers and MOPAs

Due to the complex lateral structure of Distributed Feedback lasers (DFB) and Master Oscillator Power Amplifiers (MOPAs), one-dimensional methods like the classical Transfer Matrix Method (TMM) are not suitable for simulating the optical wave in these devices. Therefore, we applied Trigonometric Finite Wave Elements (TFWE) that generalize the TMM in two or three dimensions. By coupling the dynamic wave equation with simplified temperature and drift-diffusion models, we can simulate the dynamic behavior of DFB lasers and MOPAs. Furthermore, by Fourier transformation, we can calculate the modes of the laser cavity and the corresponding wavelengths. By this approach, the influence of injection current and temperature on the resulting modes and output power can be analyzed in detail.     

Voice problems as side effects of inhaled corticosteroids in asthma patients—a prevalence study

Voice disturbances in asthma patients may be caused by inhaled corticosteroids. In order to study the prevalence of such voice disturbances, a questionnaire was delivered to asthma patients at three asthma and allergy departments in Stockholm. The questionnaire consisted of 25 questions concerning the asthma disease symptoms, medication, voice function, and voice disturbances. A total of 350 questionnaires were delivered. Response frequency was 80%. There was a significant positive correlation between inhalation of cortison and voice disturbances. Most of the patients complained about hoarseness, followed by throat clearing, a lump in the throat, loss of voice, and less frequently, throat pain. There were no significantly differences between men and women. Elderly had more voice problems than young persons. Patients with voice-demanding professions had more problems than patients who used their voice to a lesser extent during the working day. There was a significant positive correlation between high cortison doses and voice problems as well as between voice problems and acid regurgitation.     

Glottal closure, transglottal airflow, and voice quality in healthy middle-aged women

Seventeen healthy women, 45 to 61 years old, were examined using videofiberstroboscopy during phonation at three loudness levels. Two phoniatricians evaluated glottal closure using category and ratio scales. Transglottal airflow was studied by inverse filtering of the oral airflow signal recorded in a flow mask (Glottal Enterprises System) during the spoken phrase /ba:pa:pa:pa:p/ at three loudness levels. Subglottal pressure was estimated from the intraoral pressure during p occlusion. Running speech and the repeated /pa:/ syllables were perceptually evaluated by three speech pathologists regarding breathiness, hypo-, and hyperfunction, using continuous scales. Incomplete glottal closure was found in 35 of 46 phonations (76%). The degree of glottal closure increased significantly with raised loudness. Half of the women closed the glottis completely during loud phonation. Posterior glottal chink (PGC) was the most common gap configuration and was found in 28 of 46 phonations (61%). One third of the PGCs were in the cartilaginous glottis (PGCc) only. Two thirds extended into the membranous portion (PGCm); most of these occurred during soft phonation. Peak flow, peak-to-peak (AC) flow, and the maximum rate of change for the flow in the closing phase increased significantly with raised loudness. Minimum flow decreased significantly from normal to loud voice. Breathiness decreased with increased loudness. The results suggest that the incomplete closure patterns PGCc and PGCm during soft phonation ought primarily to be regarded as normal for Swedish women in this age group.     

Synthesis and structural characterization of the isomuscarines

Four diastereomers of 2-[(trimethylammonium)-methyl]-5-methyltetrahydrofuran-3-ol, trivially named isomuscarine, allo-isomuscarine, epi-isomuscarine, and epiallo-isomuscarine, were prepared as bromide salts from 2,4-like and 2,4-unlike diastereomers of 3-(4-hydroxyhex-5-en-2-oxy)-4-methylthiazole-2(3H)-thione. The strategy for constructing the tetrahydrofuran nucleus of the isomuscarines uses alkenoxyl radical 5-exo-bromocyclization, occurring 2,3-cis-selectively for the 2,4-like-4-hydroxyhex-5-en-2-oxyl radical, and 2,3-trans-selectively for the 2,4-unlike diastereomer. A fraction of 4-hydroxyhex-5-en-2-oxyl radicals cyclizes 6-endo-selectively providing 5-bromo-2-methyltetrahydropyran-4-ols in yields between 3 and 15%. Substituting trimethylamine for bromide in 5-exo-bromocyclized products furnishes isomuscarine bromides, which were structurally characterized by X-ray diffraction and NMR-spectroscopy.     

Resonant infrared laser-induced desorption of methane condensed on NaCl(100): isotope mixture experiments

Resonantly enhanced infrared laser-induced desorption of methane condensed on a single-crystal NaCl(100) surface is observed after excitation with the widely tunable infrared laser output of the free-electron laser at the free-electron laser for infrared experiments facility using mass spectroscopic detection and time-of-flight analysis. Desorption of methane is observed only when the exciting light is in resonance with an internal vibrational mode of the molecule. Different intramolecular modes of the three methane isotopologues under study--CH(4), CD(4), and CD(3)H--are excited; the degenerate deformation mode nu(4) is observed for CH(4) and CD(4) at 7.69 and 10.11 microm, respectively, as well as the nu(2) and nu(4) modes of CD(3)H at 7.79, 9.75, and 9.98 microm. The desorption signals for the pure layers of these different methane isotopologues as well as for different mixtures of two of these are investigated as a function of the infrared wavelength and the laser fluence. The desorption behavior for pure and mixed layers is compared and the underlying desorption mechanism is discussed.     

Asymptotic periodicity of recurrent flows in infinite networks

We consider a transport process on an infinite network and, using the corresponding flow semigroup as in Dorn (Semigroup Forum 76:341–356, 2008), investigate its long term behavior. Combining methods from functional analysis, graph theory and stochastics, we are able to characterize the networks for which the flow semigroup converges strongly to a periodic group.