Showing papers by "University of Fribourg published in 2023"

A Single Nucleotide Variant in the PPARγ-homolog <i>Eip75B</i> Affects Fecundity in <i>Drosophila</i>

Abstract: Single nucleotide polymorphisms are the most common type of genetic variation, but how these variants contribute to the adaptation of complex phenotypes is largely unknown. Experimental evolution and genome-wide association studies have demonstrated that variation in the PPARγ-homolog Eip75B has associated with longevity and life-history differences in the fruit fly Drosophila melanogaster. Using RNAi knockdown, we first demonstrate that reduced expression of Eip75B in adult flies affects lifespan, egg-laying rate, and egg volume. We then tested the effects of a naturally occurring SNP within a cis-regulatory domain of Eip75B by applying two complementary approaches: a Mendelian randomization approach using lines of the Drosophila Genetic Reference Panel, and allelic replacement using precise CRISPR/Cas9-induced genome editing. Our experiments reveal that this natural polymorphism has a significant pleiotropic effect on fecundity and egg-to-adult viability, but not on longevity or other life-history traits. Our results provide a rare functional validation at the nucleotide level and identify a natural allelic variant affecting fitness and life-history adaptation.

Phylogeographic and Morphological Analysis of Botrylloides niger Herdman, 1886 from the Northeastern Mediterranean Sea

Abstract: Botrylloides niger (class Ascidiacea) is an invasive marine filter-feeding invertebrate that is believed to originate from the West Atlantic region. This species of colonial tunicate has been observed in several locations along the coasts of Israel and around the Suez Canal, but it has not yet been reported on the coasts of the Northeastern Mediterranean Sea (NEMS), suggesting an ongoing Lessepsian migration. However, the extent of this invasion might be concealed by reports of other potentially misidentified species of Botrylloides, given that the strong morphological similarities within this genus renders taxonomical identification particularly challenging. In this study, we performed a phylogeographic and morphological analysis of B. niger in the NEMS. We collected 238 samples from 8 sampling stations covering 824 km of the coastlines of NEMS. We reported 14 different morphotypes, of which the orange-brown, orange, and brown-striped morphs were the most abundant. Using the mitochondrial cytochrome C oxidase I (COI) as a DNA barcode marker, we identified 4 haplotypes. The COI haplotypes clustered with the reference B. niger sequences from GenBank and differed significantly from the sister Botrylloides species. We confirmed our identification using three additional barcoding markers (Histone 3, 18S rRNA, and 28S rRNA), which all matched with over 99% similarity to reference sequences. In addition, we monitored a station for a year and conducted a temporal analysis of the collected colonies. The colonies were absent during the winter and spring, while new colonies were established in the summer and expanded during autumn. We performed demographic population analysis on our spatial data that identified a possible population subdivision at a sampling site, which might have been caused by local freshwater input. Herein, we present the first report on the presence of Botrylloides niger in the NEMS. This study represents a key step toward understanding the diversity and the propagation of this highly invasive species of colonial ascidians, both within the Mediterranean basin as well as globally.

Human Stem Cell-Derived Cardiac Organoid-Like Structures: Generation and Applications

Abstract: Since 2017, the interest in cardiac organoids has flourished. Their critical benefit relies on the three-dimensional organization and multicellular composition that mimic cardiac tissue structure and complexity. Stem cells, particularly pluripotent stem cells, fundamentally contributed to creating cardiac organoids. Indeed, the differentiation of stem cells into various cardiac cells, including cardiomyocytes, endothelial cells, cardiac fibroblasts, or macrophages, is essential for the incorporation of multiple cell lineages. Furthermore, the spatial organization allows modeling cell-to-cell communication and the interaction of the cells with the extracellular matrix as major features for cell differentiation and function. Stem cell-derived cardiac organoids aim at multiple applications such as studying cardiac development and diseases, elaborating novel therapies, screening therapeutic drugs, and testing for toxicity. In addition, patient-specific stem cell-derived cardiac organoids drive and empower precision medicine. We review here the different types of cardiac organoids, focusing on the human cardiac organoids engineered from pluripotent stem cells. Then, we introduce their different applications in fundamental and applied biology and biomedicine.

Federalism and conflict resolution: mixed success?

Abstract: There has been increasing interest in using federalism as a tool of conflict resolution. The vast majority of federal systems that emerged in recent decades has come out of countries that witnessed violent conflict and authoritarian rule. Bosnia and Herzegovina (1995), Nigeria (1997), Sudan (2005), Iraq (2005), and Nepal (2015) are important examples. As federalism is more and more used to end violent conflicts, preserve the territorial integrity of states facing increasing self-governance pressures from different groups, and providing a framework for democratization in a post-authoritarian society, the federal structures that can be found in these countries are becoming ever-more complex. Teaching federalism and conflict resolution therefore requires a distinct focus on the theoretical challenges involved, as well as the willingness and ability to use a variety of case studies to highlight how federalism can contribute to peace and democracy, while at the same time keeping in mind the challenges in federalism's use as a tool of conflict resolution.

Atmospheric drivers of melt-related ice speed-up events on the Russell Glacier in Southwest Greenland

Abstract: Abstract. The Greenland ice sheet is a major contributor to current and projected sea level rise in the warming climate. However, uncertainties in Greenland’s contribution to future sea level rise remain, partly due to challenges in constraining the role of ice dynamics. One process that has the potential to indirectly affect the mass budget of the ice sheet are transient ice accelerations, or ice speed-up events, lasting from one day to a week and triggered by overloading the subglacial drainage system with an increase in water supply. In this study, we identify melt-induced ice speed-up events at the Russell Glacier, Southwest Greenland, in order to analyse synoptic patterns driving these events. The short-term speed-up events are identified from daily ice velocity time series collected from six GPS stations along the glacier, for each summer (May–September) from 2009 to 2012. In total, 45 ice speed-up events are identified, of which 36 are considered melt-induced events where melt is derived from two in-situ observational datasets and one regional climate model forced by ERA5 reanalysis. 16 out of the 45 speed-up events co-occur with lake drainage events, and only four are linked with extreme rainfall events. The 36 melt-induced speed-up events occur during synoptic patterns that can be grouped into three main clusters: (1) patterns that resemble atmospheric rivers with a landfall in Southwest Greenland, (2) patterns with anticyclonic blockings centred over Southwest Greenland, and (3) patterns that show low pressure systems centred either south or southeast of Greenland. Out of these clusters, the one resembling atmospheric river patterns is linked to the strongest speed-up events induced by a 2–3 day continuously increasing surface melt driven by anomalously high sensible heat flux and incoming longwave radiation. In the other two clusters, the net shortwave radiation dominates the contribution to the melt energy. As the frequency and intensity of these weather patterns may change in the warming climate, so may the frequency and intensity of ice speed-up events, ultimately altering the mass loss of the ice sheet.

Energy: Adaptation

Abstract: For most of their evolutionary history, humans have been faced with frequent periods of food scarcity and famine, specific nutrient deficiencies and sometimes food abundance. In such a lifestyle of famine-and-feast, it is conceivable that adaptive mechanisms—operating through adjustments in energy expenditure and in management of the body's main energy-containing compartments (fat and protein)—have evolved as key control systems in the regulation of body weight. What are these control systems, and how they function to enable the human body to adapt to nutritional stresses and to achieve weight homeostasis is the focus of this article.

Rapid warming and degradation of mountain permafrost in Norway and Iceland

Abstract: Abstract. With the EU-funded PACE project in the turn of this century, several deep boreholes (100 m +) were drilled in European mountain sites, including mainland Norway, Svalbard and Sweden. During other projects from c. 2004 and the International Polar Year (IPY) period in 2006/07, several additional boreholes were drilled in different sites in both Norway and Iceland, measuring temperatures along both altitudinal and latitudinal gradients. At most sites, multi-temporal geophysical soundings are available using seismic and electrical resistivity tomography (ERT). Here we study the development of permafrost and ground temperatures in mainland Norway and Iceland based on these data sets. We document that permafrost in is warming at an high rate, including the development of taliks in both Norway and Iceland in response to climate change during the last 20 years. At most sites ground surface temperature (GST) is apparently increasing stronger than surface air temperature (SAT). Changing snow conditions appear to be the most important factor for the higher GST rates. Modelling exercises also indicate that the talik development can by explained both by higher air temperatures and increasing snow cover.

Cosmic-ray neutron production and propagation inside snow packs characterized by multi-particle Monte Carlo simulations

Abstract: Cosmic-ray neutron sensors buried below a snow pack provide a passive and autonomous monitoring technique of snow water equivalent (SWE). The effective neutron flux is attenuated inside the snow volume resulting in an inverse relationship between neutron intensity and the water equivalent of the snow column above the sensor. Neutrons are moderated and absorbed within the snow. Simultaneously, highly energetic cosmic rays produce further neutrons via spallation and evaporation processes. A comprehensive assessment of the neutron flux therefore requires multi-particle simulations which involve all relevant incoming particle species and transient particles from cosmic-ray showers which play a crucial role in neutron production.In our study, we used the Monte Carlo toolkit MCNP6 and validated its high-energy evaporation and spallation models against a measured data set of a neutron intensity profile in water. Based on that we fitted analytical functions to a large variety of simulation setups that describe the neutron intensity as a function of SWE and the moisture content of the soil below the sensor. Moreover, single-particle tracking revealed that the radial footprint of the method does not exceed few meters for detectors below thick snow layers. In the case of shallow snow, however, the diffusive long-range neutron flux in the atmosphere may penetrate through the snow pack to the buried sensor and thereby increases the influence of distant objects. Since the diffusive flux is further sensitive to the atmospheric water content, we developed an air humidity correction tailored to snow-buried neutron detectors.In general, the study aims at a holistic understanding of neutron production and transport processes in snow and the adjacent soil and air volumes in order to improve SWE monitoring by buried cosmic-ray neutron sensors and compares the simulation results to field data.

Histoire de la France féodale

Abstract: Programme de l’annee 2008-2009 : I. Les eveques dans la guerre feodale. — II. Questions diverses.

Energy balance

Abstract: Energy expenditure is less effective than food intake as a quantitative control mechanism of energy balance equilibrium. The mechanisms underlying long-term energy balance and body weight are complex and they involve both endogenous (e.g., genetic, hormonal) and exogenous factors (e.g., nutrition and physical activity behavior) ultimately aimed at correcting the deviations in tissue storage/mobilization and hence contributing to body weight maintenance. Small, repetitive energy and fat imbalances over short/middle terms (days, weeks), if not fully compensated, will ultimately lead to body weight and body fat changes. Underfeeding leads to negative energy/fat balance and body weight loss, resulting into an adaptive decrease in energy expenditure to moderate total tissue losses.

Modelling lateral meltwater flow atop the GreenlandIce Sheet’s near-surface ice slabs

Abstract: The Greenland ice sheet is losing mass. Thereby, the location of the runoff limit, the highest elevation from which meltwater finds its way off the ice sheet, plays an important role. Above the runoff limit all meltwater refreezes and does not contribute to mass loss. In recent years surface runoff has increasingly occurred from higher elevations, thereby expanding the area of mass loss: between 1985 and 2020, the maximum runoff limit rose by on average 194 metres, expanding the visible runoff area by around 29%.The observed rise in the runoff limit might be related to intensive meltwater refreezing within the firn which leads to the formation of thick ice layers, also called ice slabs. Our field experiments, carried out at around 1750 m a.s.l. on the K-Transect, have shown that meltwater generated over ice slabs is generally forced to flow laterally: initially through a near-surface slush matrix and then forming streams and rivers. It remains unclear, however, how much of the meltwater contributes to runoff, and which percentage refreezes and contributes to ice slab formation or expansion.Here we present a conceptual quasi 2D-model of runoff, that simulates lateral meltwater flow on top of an ice slab using firn hydrological properties measured on the southwest Greenland ice sheet. We adapted a gridded linear-reservoir runoff routing model to calculate (i) the distance meltwater can travel within one melt season, and (ii) when meltwater breakthrough at the snow surface (i.e. slush formation) occurs. First results provide insight into the evolution of the water table height over time that matches observations made during our summer field campaign. We are exploring ways to incorporate meltwater refreezing, to better understand ice slab evolution and their impact on the fate of meltwater between vertical percolation, refreezing and lateral runoff.

Teaching Social Skills to Children and Adolescents With Visual Impairments: A Systematic Review

Abstract: Introduction: Social skills are acquired primarily through imitation using the visual system. As a result, people with visual impairments may experience difficulties in this area at any age, which can have a major effect on their social participation and on their quality of life. The objective of this study was to systematically review the effects of targeted interventions on social skills in children and adolescents with visual impairments. Methods: A systematic literature search was performed using databases Web of Science, OvidSP, EBSCOhost, Sage Journals. The scientific quality of the studies was assessed using two scales dedicated to single case studies and group studies, respectively. Results: Out of 1866 hits, 32 studies were included in the review. A total of 397 children and adolescents with visual impairments (aged 3–20 years) received different types of social skills interventions. “Peer relation” interventions were most often studied ( n = 21) and effects were mainly analyzed using observational tools. The scientific quality rating scales indicated moderate (for group studies) to high general quality (for single case studies). Overall, most studies reported improvements in targeted social skills. Discussion: Given the heterogeneity of the studies considered, both in content and in the measures used to document effects, these results should be interpreted with caution. Consequently, it is not clear which interventions should be recommended for use in practice such as in special education. Implications for Practitioners: Given the high rate of social skills difficulties reported in this population and the effect of these difficulties on all stages of development, it seems particularly relevant for practitioners to integrate social skills assessment and explicit teaching into intervention programs. In the future, researchers, stakeholders, and practitioners should work together to develop, implement, and evaluate evidence-based interventions for children and adolescents with visual impairments.

Medienpolitik

Abstract: Mit Übungen und Lösungen Digitalisierung, Transnationalisierung und Kommerzialisierung stellen die Medienpolitik vor große Herausforderungen. Wie kann sichergestellt werden, dass Medien und Plattformen ihre wichtige Funktion in einer demokratischen Gesellschaft erfüllen? In diese Thematik führt Manuel Puppis systematisch und umfassend ein. Er vermittelt die Grundlagen für eine kritische Auseinandersetzung mit Medienpolitik, Medienregulierung und Media Governance. Problemorientiert und international vergleichend diskutiert er die verschiedenen Themenbereiche der Medienpolitik in Europa – von Medienkonzentration über den öffentlichen Rundfunk, Medienförderung, Plattformen und Algorithmen bis hin zu Medienkompetenz und Datenschutz.

Elevation bias due to penetration of spaceborne radar signal on Grosser Aletschgletscher, Switzerland

Abstract: Digital elevation models (DEMs) from the spaceborne interferometric radar mission TanDEM-X hold a large potential for glacier elevation change assessments and monitoring. However, a bias is potentially introduced through the penetration of the X-band signal into snow and firn that can be substantial. The magnitude of this bias has been analysed in some glaciarized regions of the world; still, the knowledge about X-band penetration of TanDEM-X in the European Alps is limited.In this study, we investigated the unique situation of almost synchronous acquisition of TanDEM-X and Pl&#233;iades DEMs over the Grosser Aletschgletscher, complemented with in-situ observations (ground penetrating radar, snow cores, snow pits), all within a four-day period in late winter 2021. The comparison of the TanDEM-X and Pl&#233;iades DEM revealed an elevation bias due to radar penetration of up to 8 m above 3400 m. Further, the concurrent in-situ measurements reveal that the signal is not obstructed by the last summer horizon but reaches into perennial firn.Our study improves our understanding about the magnitude of X-band penetration of TanDEM-X in the Alps and the underlying process with a relevance for glaciology, snow science, remote sensing and the wider geoscience community.