HST observations of the limb polarization of Titan

Titan is an excellent test case for detailed studies of the scattering polarization from thick hazy atmospheres. We present the first limb polarization measurements of Titan, which are compared as a test to our limb polarization models. Previously unpublished imaging polarimetry from the HST archive is presented which resolves the disk of Titan. We determine flux-weighted averages of the limb polarization and radial limb polarization profiles, and investigate the degradation and cancelation effects in the polarization signal due to the limited spatial resolution of our observations. Taking this into account we derive corrected values for the limb polarization in Titan. The results are compared with limb polarization models, using atmosphere and haze scattering parameters from the literature. In the wavelength bands between 250 nm and 2000 nm a strong limb polarization of about 2-7 % is detected with a position angle perpendicular to the limb. The fractional polarization is highest around 1 micron. As a first approximation, the polarization seems to be equally strong along the entire limb. The detected polarization is compatible with expectations from previous polarimetric observations taken with Voyager 2, Pioneer 11, and the Huygens probe. Our results indicate that ground-based monitoring measurements of the limb-polarization of Titan could be useful for investigating local haze properties and the impact of short-term and seasonal variations of the hazy atmosphere of Titan. Planets with hazy atmospheres similar to Titan are particularly good candidates for detection with the polarimetric mode of the upcoming planet finder instrument at the VLT. Therefore, a good knowledge of the polarization properties of Titan is also important for the search and investigation of extra-solar planets.Comment: 13 pages, 13 figures, accepted for publication in Astronomy & Astrophysic

Measurement of the earthshine polarization in the B, V, R, and I band as function of phase

The characterization of the polarimetric properties of the planet Earth is important for the interpretation of expected observations and the planning of future instruments. We present a multi-wavelengths and multi-phase set of benchmark values for the polarization signal of the integrated light from the planet Earth derived from new polarimetric observations of the earthshine back-scattered from the Moon's dark side. Using a new, specially designed wide field polarimeter we measured the fractional polarization of the earthshine in the B, V, R and I filters for Earth phase angles alpha between 30{\deg} and 110{\deg}. The phase dependence of the earthshine polarization is fitted by a function p x sin(alpha)^2. To determine the polarization of the planet Earth we correct our earthshine measurements by a polarization efficiency function for the lunar surface derived from measurements of lunar samples from the literature. The polarization of the earthshine decreases towards longer wavelengths and is about a factor 1.3 lower for the higher albedo highlands. For mare regions the measured maximum polarization is about 13 % at quadrature in the B band. The resulting fractional polarizations for Earth are 24.6 % for the B band, 19.1 % for the V band, 13.5 % for the R band, and 8.3 % for the I band. Together with literature values for the spectral reflectivity of Earth we obtain a contrast between the polarized flux of the Earth and the (total) flux of the Sun with an uncertainty of less than 20 % and we find that the best phase to detect an Earth twin is around an Earth phase alpha=65{\deg}. The polarimetric models of Earth-like planets from Stam (2008) are in qualitative agreement with our results but there are also significant differences which might guide more detailed computations.Comment: 14 pages, 14 figures, accepted for publication in Astronomy & Astrophysic

Development and sensitivity analysis of a model for assessing stratification and safety of Lake Nyos during artificial degassing

To prevent the recurrence of a disastrous eruption of carbon dioxide (CO2) from Lake Nyos, a degassing plan has been set up for the lake. Since there are concerns that the degassing of the lake may reduce the stability of the density stratification, there is an urgent need for a simulation tool to predict the evolution of the lake stratification in different scenarios. This paper describes the development of a numerical model to predict the CO2 and dissolved solids concentrations, and the temperature structure as well as the stability of the water column of Lake Nyos. The model is tested with profiles of CO2 concentrations and temperature taken in the years 1986 to 1996. It reproduces well the general mixing patterns observed in the lake. However, the intensity of the mixing tends to be overestimated in the epilimnion and underestimated in the monimolimnion. The overestimation of the mixing depth in the epilimnion is caused either by the parameterization of the k-epsilon model, or by the uncertainty in the calculation of the surface heat fluxes. The simulated mixing depth is highly sensitive to the surface heat fluxes, and errors in the mixing depth propagate from one year to the following. A precise simulation of the mixolimnion deepening therefore requires high accuracy in the meteorological forcing and the parameterization of the heat fluxes. Neither the meteorological data nor the formulae for the calculation of the heat fluxes are available with the necessary precision. Consequently, it will be indispensable to consider different forcing scenarios in the safety analysis in order to obtain robust boundary conditions for safe degassing. The input of temperature and CO2 to the lake bottom can be adequately simulated for the years 1986 to 1996 with a constant sublacustrine source of 18 l s−1 with a CO2 concentration of 0.395 mol l−1 and a temperature of 26 °C. The results of this study indicate that the model needs to be calibrated with more detailed field data before using it for its final purpose: the prediction of the stability and the safety of Lake Nyos during the degassing proces

An experimental determination of the scale length of N2O in the soil of a grassland

Concentration profiles of N2O in a grassland soil and dynamic response curves to disturbance of the soil concentration (relaxation curves) were measured with a new membrane tube technique. Diffusive properties of the soil were derived from 222Rn measurements. The mathematical analysis of the relaxation curves yielded N2O uptake rates U soil diffusivities Ds, scale lengths z*, and production rates P at different levels under the surface. The following ranges were found during 2 days of measurements: Ds = (0.4–5) × 10−7 m2 s−1, U = (1–20) × 10−4 s−1, z* = 0.7–2.8 cm, and P = 0.02–4.4 ppb s−1. These values were used to reproduce the measured N2O concentration profiles with a one-dimensional diffusive transport model of N2O in the soil air-filled pore space and to deduce flux profiles. Bidirectional fluxes occurred with small deposition fluxes up to a few ppt ms−1 during intensive growing phases of the grass. Uptake rates were high enough that N2O produced at greater depth did not reach the atmosphere

Systemic Capillary Leak Syndrome associated with hypovolemic shock and compartment syndrome. Use of transpulmonary thermodilution technique for volume management

Systemic Capillary Leak Syndrome (SCLS) is a rare disorder characterized by increased capillary hyperpermeability leading to hypovolemic shock due to a markedly increased shift of fluid and protein from the intravascular to the interstitial space. Hemoconcentration, hypoalbuminemia and a monoclonal gammopathy are characteristic laboratory findings. Here we present a patient who suffered from SCLS with hypovolemic shock and compartment syndrome of both lower legs and thighs. Volume and catecholamine management was guided using transpulmonary thermodilution. Extended hemodynamic monitoring for volume and catecholamine management as well as monitoring of muscle compartment pressure is of crucial importance in SCLS patients

Brominated Flame Retardants – Endocrine-Disrupting Chemicals in the Swiss Environment

Brominated flame retardants (BFR) are additives used to protect plastic materials and textiles against ignition. As some widely used BFR have chemical structures similar to well known endocrine disruptors such as polychlorinated biphenyls (PCB) or bisphenol A, adverse effects were also presumed for BFR. When the NRP50 programme started in 2001, the sparse knowledge on environmental behavior and toxicology of BFR did not allow a proper assessment of the risks associated with the widespread use of these chemicals. Therefore, we proposed to address questions such as the exposure of animals and humans, temporal trends in the environment as well as transformation and transport processes of BFR. Concentrations of BFR in wildlife and humans in Switzerland today pose no serious concerns for negative health effects according to the current knowledge on the toxicity of BFR. However, negative health effects cannot be ruled out in the future, since some BFR persist in the environment and their concentrations in freshwater lake sediments are increasing rapidly. The development of environmentally safe alternatives to these chemicals will be an important issue for the future

Durchseuchung, Durchimpfung und Risiko nach Alter für Covid-19 : Bereinigung und Interpretation von Häufigkeitsangaben im Phasenwechsel der Pandemie

Die Schweiz meldet im Juni 2021 weiterhin rückläufige Fallzahlen für Covid-19. Die Impfkampagne ist voll angelaufen, die Ärzteschaft spielt dabei eine wichtige Rolle. Die Quantifizierung des Covid-19-Risikos ist eine zentrale Voraussetzung für die Beratung von Patientinnen und Patienten wie auch für gezielte Schutzmassnahmen in bestimmten Bevölkerungsgruppen, so in der Armee

In Vitro Evaluation of Antimicrobial Activity of Minocycline Formulations for Topical Application in Periodontal Therapy.

Periodontal therapy using antimicrobials that are topically applied requires slow or controlled release devices. The in vitro antimicrobial activity of biodegradable polymer formulations that contain a new minocycline lipid complex (P-MLC) was evaluated. The new P-MLC formulations that contained 11.5% minocycline were compared with pure minocycline or an existing commercial formulation, which included determination of minimal inhibitory concentration (MIC) values against two oral bacteria and activity on six-species periodontal biofilm. Moreover, the flow of gingival crevicular fluid (GCF) was modeled up to 42 d and the obtained eluates were tested both for MIC values and inhibiting biofilm formation. In general, MICs of the P-MLC formulations were slightly increased as compared with pure minocycline. Biofilm formation was clearly inhibited by all tested formulations containing minocycline with no clear difference between them. In 3.5 d old biofilms, all formulations with 250 µg/mL minocycline decreased bacterial counts by 3 log10 and metabolic activity with no difference to pure antimicrobials. Eluates of experimental formulations showed superiority in antimicrobial activity. Eluates of one experimental formulation (P503-MLC) still inhibited biofilm formation at 28 d, with a reduction by 1.87 log10 colony forming units (CFU) vs. the untreated control. The new experimental formulations can easily be instilled in periodontal pockets and represent alternatives in local antimicrobials, and thus warrant further testing