University of Bern

About: University of Bern is a education organization based out in Bern, Switzerland. It is known for research contribution in the topics: Population & Medicine. The organization has 35422 authors who have published 79413 publications receiving 3125088 citations. The organization is also known as: Bern University & UNIBE.

67P/Churyumov-Gerasimenko, a Jupiter family comet with a high D/H ratio

Abstract: The provenance of water and organic compounds on Earth and other terrestrial planets has been discussed for a long time without reaching a consensus. One of the best means to distinguish between different scenarios is by determining the deuterium-to-hydrogen (D/H) ratios in the reservoirs for comets and Earth’s oceans. Here, we report the direct in situ measurement of the D/H ratio in the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA mass spectrometer aboard the European Space Agency’s Rosetta spacecraft, which is found to be (5.3 ± 0.7) × 10−4—that is, approximately three times the terrestrial value. Previous cometary measurements and our new finding suggest a wide range of D/H ratios in the water within Jupiter family objects and preclude the idea that this reservoir is solely composed of Earth ocean–like water.

Anterior femoroacetabular impingement after periacetabular osteotomy.

Abstract: As experience with the Bernese periacetabular osteotomy has grown, an unexpected observation in a group of patients has alerted the authors to the risk of a secondary impingement syndrome that may occur some time after the periacetabular osteotomy. This possibly may explain residual pain and limited range of motion in a larger group of patients. The impingement is produced by abutment of the femoral head or head to neck junction on the anterior rim of the properly aligned acetabulum. The symptoms are those of restricted flexion, and limited or absent internal rotation in flexion, with variable groin pain. Magnetic resonance imaging studies may reveal acetabular labral disease and adjacent cartilage damage associated with the impingement. Lack of anterior or anterolateral offset between the femoral neck and head results in neck to rim contact when the hip is flexed and/or internally rotated. Before the periacetabular osteotomy this is compensated by the lack of anterior acetabular coverage, but after proper correction the mismatch becomes apparent. The authors recently have devised a routine during the periacetabular osteotomy procedure whereby after the acetabular fragment is corrected into the desired position, the joint is opened, visually inspected, and palpated for impingement with the hip flexed and internally rotated. When necessary, a resection osteoplasty of the femoral neck to head junction is performed to improve the head and neck offset and reduce the anterior contact. This, in the short term, has provided satisfactory prevention of postoperative impingement.

Are invaders different? A conceptual framework of comparative approaches for assessing determinants of invasiveness.

Abstract: What determines invasiveness of alien organisms is among the most interesting and urgent questions in ecology. In attempts to answer this question, researchers compare invasive alien species either to native species or to non-invasive alien species, and this is done in either the introduced or native ranges. However, inferences that can be drawn from these comparisons differ considerably, and failure to recognize this could hamper the search for determinants of invasiveness. To increase awareness about this issue, we present a framework of the various comparisons that can be used to test for determinants of invasiveness, and the specific questions each comparison can address. Moreover, we discuss how different comparisons complement each other, and therefore should be used in concert. For progress in invasion biology, it is crucial to realize that different comparisons address different biological questions and that some questions can only be answered unambiguously by combining them.

Rayleigh scattering in the transit spectrum of HD 189733b

Abstract: The transit spectrum of the exoplanet HD 189733b has recently been obtained between 0.55 and 1.05 µm. Here we present an analysis of this spectrum. We develop first-order equations to interpret absorption spectra. In the case of HD 189733b, we show that the observed slope of the absorption as a function of wavelength is characteristic of extinction proportional to the inverse of the fourth power of the wavelength (∝λ −4 ). Assuming an extinction dominated by Rayleigh scattering, we derive an atmospheric temperature of 1340 ± 150 K. If molecular hydrogen is responsible for the Rayleigh scattering, the atmospheric pressure at the planetary characteristic radius of 0.1564 stellar radius must be 410 ± 30 mbar. However the preferred scenario is scattering by condensate particles. Using the Mie approximation, we find that the particles must have a low value for the imaginary part of the refraction index. We identify MgSiO3 as a possible abundant condensate whose particle size must be between ∼10 −2 and ∼10 −1 µm. For this condensate, assuming solar abundance, the pressure at 0.1564 stellar radius is found to be between a few microbars and few millibars, and the temperature is found to be in the range 1340–1540 K, and both depend on the particle size.

The EDC3 chronology for the EPICA Dome C ice core

Abstract: . The EPICA (European Project for Ice Coring in Antarctica) Dome C drilling in East Antarctica has now been completed to a depth of 3260 m, at only a few meters above bedrock. Here we present the new EDC3 chronology, which is based on the use of 1) a snow accumulation and mechanical flow model, and 2) a set of independent age markers along the core. These are obtained by pattern matching of recorded parameters to either absolutely dated paleoclimatic records, or to insolation variations. We show that this new time scale is in excellent agreement with the Dome Fuji and Vostok ice core time scales back to 100 kyr within 1 kyr. Discrepancies larger than 3 kyr arise during MIS 5.4, 5.5 and 6, which points to anomalies in either snow accumulation or mechanical flow during these time periods. We estimate that EDC3 gives accurate event durations within 20% (2σ) back to MIS11 and accurate absolute ages with a maximum uncertainty of 6 kyr back to 800 kyr.