QUANTUM CASCADE LASER: from 3 to 26 mum

Absorption spectroscopy of gases and liquids is amongst the most widely used methods to measure molecular concentrations. It is used in various fields, amongst them are industrial leak testing, medical analysis and surgery, process control and monitoring. Trace gas analysis of low-mass molecules is preferably performed in the mid-IR wavelength region, where the line strength for many molecules are high. With the QCL, invented in 1994, this spectral range has a laser source that delivers sufficient output power in continuous-wave operation. The semiconductor laser is robust and operates in a wide temperature range. This work is dedicated to explore the capabilities of QCLs and improve their performance in the wavelength region from 3 to 26 mum. Our active region simulations are based on a Density Matrix model. The choice of basis wavefunctions is verified and a method to find the optimal injection barrier is presented. The influence of different interface roughness models is discussed. Our model agrees well with the full quantum Non-Equilibrium Green’s Function model and with experiments. In this thesis we explore the short wavelength boundary of QCLs. Lasing emission around 3.3 mum requires highly strained active region material. We investigate in detail active region designs, growth optimization, the impact of intervalley scattering and interface roughness. We present a device emitting at 3.4 mum with dissipation values of only 250 mW and threshold currents as low as 16 mA in pulsed operation. A boxcar experiment with a 5.6 ms long pulse shows stable spectral behaviour of DFB devices, an important requirement for spectroscopic applications. We perform genetic optimizations of devices in the range from 4 to 26 mum and investigate active region design parameters. The optimizations are performed on ”seed” designs of published devices and designs from our own group. The current record design in wallplug efficiency for 9 mum is optimized. The design was extracted from literature and processed along with the optimized structure. Comparing the measurements, we improve the slope efficiency from 1.9 to 2.5 W/A, the wallplug efficiency from 9 to 12 % and the dynamical range from 1.5 to 2.1. For all optimizations, the seed and optimized structures are compared, resulting in some common strategies for optimization. The active region designs are explored experimentally as single stacks and broadband designs. Heterogeneous stacking is discussed and application examples for DFB, external cavity and comb operation are shown. An attempt for spectral coverage of a full octave is presented. We show laser emission spanning from 1090 to 1960 cm-1 at 80 K

Vulnerability to Freshwater Changes in the Inuit Settlement Region of Nunatsiavut, Labrador: A Case Study from Rigolet

Drawing on vulnerability approaches from the climate change literature, this paper explores the vulnerability of residents of the community of Rigolet, Nunatsiavut, Labrador, to changes in freshwater. Our approach emphasizes local preferences and values. We analyze the results from 89 household interviews (88% response) and targeted interviews in Rigolet to consider the human experience of climate variability and change. Residents report that changes in the spatial and temporal distribution of freshwater are currently challenging their ability to access preferred drinking water and food sources and are adding to the financial barriers that restrict their time spent on the land. The results of our study suggest that Rigolet residents are successfully adapting to existing freshwater changes in their watershed, though these adaptations have not come without sacrifice. The adaptive capacity of Rigolet residents has been supported by resource flexibility and experience-based knowledge of freshwater variability within their watershed, among other factors. Findings suggest that the exposure of sub-Arctic and Arctic communities to freshwater changes and their capacity to adapt are largely shaped by the lifeways of residents and the manner and degree to which they are dependent on local freshwater systems.Cet article explore la vulnérabilité des résidents de Rigolet, au Nunatsiavut, Labrador, vis-à-vis des changements caractérisant l’eau douce en s’appuyant sur les approches de vulnérabilité puisées dans la documentation sur le changement climatique. Notre démarche met l’accent sur les préférences et les valeurs locales. Nous analysons les résultats de 89 entrevues réalisées auprès de divers ménages (taux de réponse de 88 %) et d’entrevues ciblées effectuées à Rigolet afin de considérer la réaction de l’être humain vis-à-vis de la variabilité et du changement climatique. Les résidents signalent que les changements enregistrés sur le plan de la répartition spatiale et temporelle de l’eau douce leur posent des difficultés pour ce qui est de l’accès à leurs sources préférées d’eau potable et de nourriture, ce qui a également pour effet d’amplifier les obstacles financiers, car ils restreignent le temps qu’ils passent sur la terre. Les résultats de notre étude suggèrent que les résidents de Rigolet réussissent à s’adapter aux changements caractérisant l’eau douce au sein de leur bassin hydrographique, mais que ces adaptations ne se sont pas faites sans sacrifices. La capacité d’adaptation des résidents de Rigolet a notamment été facilitée par la flexibilité des ressources et les connaissances de la variabilité de l’eau douce découlant de l’expérience au sein même de leur bassin hydrographique. Nos observations laissent entendre que les changements en matière d’eau douce que connaissent les communautés subarctiques et arctiques de même que leur capacité d’adaptation sont largement attribuables aux modes de vie des résidents et à la manière et au degré dont ils dépendent des réseaux d’eau douce de la région

Callosal Connections of Primary Visual Cortex Predict the Spatial Spreading of Binocular Rivalry Across the Visual Hemifields

In binocular rivalry, presentation of different images to the separate eyes leads to conscious perception alternating between the two possible interpretations every few seconds. During perceptual transitions, a stimulus emerging into dominance can spread in a wave-like manner across the visual field. These traveling waves of rivalry dominance have been successfully related to the cortical magnification properties and functional activity of early visual areas, including the primary visual cortex (V1). Curiously however, these traveling waves undergo a delay when passing from one hemifield to another. In the current study, we used diffusion tensor imaging (DTI) to investigate whether the strength of interhemispheric connections between the left and right visual cortex might be related to the delay of traveling waves across hemifields. We measured the delay in traveling wave times (ΔTWT) in 19 participants and repeated this test 6 weeks later to evaluate the reliability of our behavioral measures. We found large interindividual variability but also good test–retest reliability for individual measures of ΔTWT. Using DTI in connection with fiber tractography, we identified parts of the corpus callosum connecting functionally defined visual areas V1–V3. We found that individual differences in ΔTWT was reliably predicted by the diffusion properties of transcallosal fibers connecting left and right V1, but observed no such effect for neighboring transcallosal visual fibers connecting V2 and V3. Our results demonstrate that the anatomical characteristics of topographically specific transcallosal connections predict the individual delay of interhemispheric traveling waves, providing further evidence that V1 is an important site for neural processes underlying binocular rivalry

Technikfolgenabschätzung und Akzeptanz in der Abfallwirtschaft

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The effect of ε-aminocaproic acid on blood product requirement, outcome and thromboelastography parameters in severely thrombocytopenic dogs

Background: No treatment other than platelet administration is known to protect against spontaneous hemorrhage in thrombocytopenic dogs. Objectives: Primary: determine if treatment with ε-aminocaproic acid (EACA) decreases the requirement for blood transfusions and improves outcome in dogs with severe thrombocytopenia. Secondary: find evidence of hyperfibrinolysis and determine the effect EACA administration on rapid (rTEG) and tissue plasminogen activator-spiked (tPA-rTEG) thromboelastography parameters. Animals: Twenty-seven dogs with severe thrombocytopenia were treated with EACA, and data from an additional 33 were obtained from the hospital database as historical control (HC) cohort. Methods: Single arm clinical trial with HCs. The EACA group dogs received EACA (100 mg/kg IV followed by a constant-rate infusion [CRI] of 400 mg/kg/24 hours). Thromboelastography before and during EACA infusion, hospitalization days, number of transfusions, and mortality were compared. Results: No difference was found in number of transfusions per dog (median, interquartile range; 1, 0-2.5 vs 0.9, 0-2; P =.5) and hospitalization days (4, 4-6 vs 4.5, 3.75-6; P =.83) between HC and EACA groups, respectively, and no difference in survival was identified by log-rank analysis (P =.15). Maximum amplitude on both rTEG and tPA-rTEG increased after EACA administration (rTEG baseline: 23.6, 9.6-38.9; post-EACA: 27.3, 19.8-43.2; P &lt;.001; tPA-rTEG baseline: 23, 10.9-37.2; post-EACA: 24.7, 16.7-44.8; P &lt;.002). Conclusions and Clinical Importance: Although EACA increased clot strength, there was no effect on outcome. Treatment with EACA at this dosage cannot be recommended as a routine treatment but may be considered for dogs with severe ongoing hemorrhage.</p

Was ist Gegenstand des Faches Christliche Sozialethik? Bericht über die 3. Tagung des Forum Sozialethik

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