Incorporating sedimentological observations, hydrogeophysics and conceptual knowledge to constrain 3D numerical heterogeneity models of alluvial systems

Coarse, braided river deposits are highly heterogeneous in terms of hydraulic properties and make up many groundwater reservoirs worldwide and more than two-thirds of the exploited aquifers in Switzerland. The management of these resources often requires the understanding of the subsurface flow processes and therefore, of the subsurface heterogeneity. While coarse, braided river deposits were the focus of many studies, the relationship between the braided river dynamics and the resulting sedimentary structures is still poorly known. A better knowledge of this relationship is the key to geologically more realistic modelling of the subsurface heterogeneity by accounting for the former controls on the fluvial system (slope of the floodplain, terraces, lateral confinement, bedrock steps, etc.). This thesis aims to (i) investigate the link between braided river morphodynamics and subsurface heterogeneity in a hydrogeological context and (ii) develop a numerical model of subsurface heterogeneity that accounts for this link. The sedimentological knowledge on coarse, braided river deposits was mainly gained from the observation of analogue coarse deposits in Switzerland. The Tagliamento River (northeast Italy) was chosen as a field laboratory to thoroughly study the geomorphology (surface) and near-surface sedimentology of coarse, braided rivers. The Tagliamento River is considered to be one of the last large semi-natural rivers of the Alps that has retained much of its natural sediment and discharge dynamics. The observations focused on a single reach sharing similar characteristics with partly confined valleys such as in the alpine foreland. The sedimentary structures of coarse, braided river deposits can be comprehensively described by a small limited number of sedimentary structures that have specific hydraulic properties. A handful of depositional elements were identified. Among them, the cross bedded trough fills can significantly influence the flow field because their highly-permeable cross beds act as fast flow conduit. Such trough fills most probably form from confluence scour holes. The geomorphological analysis of the Cimano-Pinzano reach is based on a LiDAR-derived digital elevation model (LiDAR-derived DEM), aerial and satellite photographs, a water-stage time series and regular field observations. Complex aggradation/degradation dynamics resulted in the formation of higher-lying zones incised by a drainage gully network and surrounded by zones that are often reworked by the river. The main geomorphological elements are identified in terms of their topographic signature and genesis, setting apart the trichotomy water–vegetation–bar. Two morphologies mark the active zones: a low-discharge morphology (low-discharge incisions and channels, slip-face lobes, etc.) superimposed on a high-discharge morphology (gravel sheets, scours, etc.). Based on the observations of vertical exposure of coarse, braided river deposits, each morphological element is associated with a depositional element. The preservation potential of the depositional elements is evaluated as a function of the river-bed aggradation dynamics and the resulting subsurface heterogeneity is discussed in terms of its impact on the subsurface flow. Ground-penetrating radar (GPR) surveys performed on the active zones of the Cimano-Pinzano reach imaged many cross bedded trough fills as observed in ancient deposits. Finding a link between these structures and the evolution of the morphology is challenging. Nevertheless, some hypotheses about the formation of the trough structures are advanced. All the observations suggest the importance of the gravel sheets in the formation of cross bedded trough fills. An object-based model was developed that mimics the dominant processes of floodplain dynamics. Contrary to existing models, this object-based model possesses the following properties: (i) it is consistent with field observations (outcrops, ground-penetrating radar data, etc.), (ii) it allows different sedimentological dynamics to be modeled that result in different subsurface heterogeneity patterns, and (iii) it is light in memory and computationally fast. To demonstrate its applicability, the object-based model is conditioned to interpreted two-dimensional data and the uncertainty on the three-dimensional subsurface heterogeneity is quantified with Monte Carlo sampling. The impact of an isolated trough fill complex on subsurface flow mixing is evaluated in terms of advective mixing. The trough fill complex is modelled with the object-based model that is fitted to GPR data. Hydraulic properties are assigned to the model cells and a subsurface flow through the model is simulated. The advective mixing is quantified with particle tracking. The results indicate strong advective mixing as well as a large flow deviation induced by the asymmetry of the trough fills with regard to the main flow direction. These findings depict possible advective mixing found in natural environments and can guide the interpretation of ecological processes such as in the hyporheic zone. The geomorphological and sedimentological characterisations of the coarse, braided Cimano-Pinzano reach of the Tagliamento River contribute to a better understanding of the morphodynamics of coarse, braided river in relation to the subsurface heterogeneity. The object-based model allows the simulation of various geological settings and the methodology developed for the stereological study can be adapted to other types of data without many changes. Preliminary results of subsurface flow simulations through coarse, braided river deposits show a strong subsurface flow mixing

Fundamental accuracy-resolution trade-off for timekeeping devices

From a thermodynamic point of view, all clocks are driven by irreversible processes. Additionally, one can use oscillatory systems to temporally modulate the thermodynamic flux towards equilibrium. Focusing on the most elementary thermalization events, this modulation can be thought of as a temporal probability concentration for these events. There are two fundamental factors limiting the performance of clocks: On the one level, the inevitable drifts of the oscillatory system, which are addressed by finding stable atomic or nuclear transitions that lead to astounding precision of today's clocks. On the other level, there is the intrinsically stochastic nature of the irreversible events upon which the clock's operation is based. This becomes relevant when seeking to maximize a clock's resolution at high accuracy, which is ultimately limited by the number of such stochastic events per reference time unit. We address this essential trade-off between clock accuracy and resolution, proving a universal bound for all clocks whose elementary thermalization events are memoryless.Comment: 5 + 7 pages, 8 figures, published versio

Cyclic deformations in the Opalinus clay: a laboratory experiment

The influence of tunnel climate on deformation cycles of joint openings and closings is often observed immediately after excavation. At the EZ-B niche in the Mt. Terri rock laboratory (Switzerland), a cyclic deformation of the shaly Opalinus clay has been monitored for several years. The deformation cycles of the joints parallel to the clay bedding planes correlate with seasonal variations in relative humidity of the air in the niche. In winter, when the relative humidity is the lowest (down to 65%), the joints open as the clay volume decreases, whereas they tend to close in the summer when the relative humidity reaches up to 100%. Furthermore, in situ measurements have shown the trend of an increasingly smaller aperture of joints with time. A laboratory experiment was carried out to reproduce the observed cyclic deformation in a climate chamber using a core sample of Opalinus clay. The main goal of the experiment was to investigate the influence of the relative humidity on the deformation of the Opalinus clay while excluding the in situ effects (e.g. confining stress). The core sample of Opalinus clay was put into a closed ended PVC tube and the space between the sample and the tube was filled with resin. Then, the sample (size: 28 cm × 14 cm × 6.5 cm) was cut in half lengthways and the open end was cut, so that the half-core sample could move in one direction. The mounted sample was exposed to wetting and drying cycles in a climate chamber. Air temperature, air humidity and sample weight were continuously recorded. Photographs taken at regular time intervals by a webcam allowed the formation/deformation of cracks on the surface of the sample to be monitored. A crackmeter consisting of a double-plate capacitor attached to the core sample was developed to measure the dynamics of the crack opening and closing. Preliminary results show that: - Deformation movements during different climate cycles can be visualized with the webcam - The crackmeter signal gives a relatively precise response for relative humidity below 80% - The sample weight variations are clearly related to the climatic conditions (temperature and relative humidity) and associated with deformation of the sample (widening and narrowing of the cracks) - The control of the relative humidity in the climate chamber turned out to be difficult in a laboratory without climate conditioning, especially during summer tim

Reduction of conceptual model uncertainty using ground-penetrating radar profiles: Field-demonstration for a braided-river aquifer

Hydrogeological flow and transport strongly depend on the connectivity of subsurface properties. Uncertainty concerning the underlying geological setting, due to a lack of field data and prior knowledge, calls for an evaluation of alternative geological conceptual models. To reduce the computational costs associated with inversions (parameter estimation for a given conceptual model), it is beneficial to rank and discard unlikely conceptual models prior to inversion. Here, we demonstrate an approach based on a quantitative comparison of ground-penetrating radar (GPR) sections obtained from field data with corresponding simulation results arising from various geological scenarios. The comparison is based on three global distance measures related to wavelet decomposition, multiple-point histograms, and connectivity that capture geometrical characteristics of geophysical reflection images. Using field data from the Tagliamento braided river system, Italy, we demonstrate that seven out of nine considered geological scenarios can be discarded as they produce GPR sections that are incompatible with those observed in the field. The retained scenarios reproduce important features such as cross-stratified deposits and irregular property interfaces. The most convenient distance measure of those considered is the one based on wavelet-decomposition. Direct analysis of the distances is the most intuitive and fastest way to compare scenarios

Zeitliche und räumliche Skalen der Fluss-Grundwasser-Interaktion: Ein multidimensionaler hydrogeologischer Untersuchungsansatz

Zusammenfassung: Die Prozesse der Fluss-Grundwasser-Interaktionen sind stark skalenabhängig und im Allgemeinen stark instationär. Einen für das Prozessverständnis wichtigen Aspekt betreffen die kleinräumigen Strömungsverhältnisse an der Grenzschicht zwischen Oberflächengewässer und Grundwasser im hyporheischen Interstitial. Dies betrifft insbesondere auch Fragestellungen zu Strömungsverhältnissen in Forellenlaichgruben kiesführender Flüsse. Exemplarisch für kleinere mit Sohlschwellen verbaute und kanalisierte Fließgewässer wurden am voralpinen Schweizer Fluss Enziwigger verschiedene Methoden entwickelt, getestet und kombiniert, die es erlauben die vier Dimensionen (drei räumliche und eine zeitliche) der Interaktion Oberflächengewässer-Interstitialraum-Grundwasser für einzelne Flussabschnitte zu erfassen. Der Aufbau eines Messnetzes sowie die Durchführung von Feldmessungen lieferten Grundlagen für eine Grundwasserströmungsmodellierung. Kontinuierliche Zeitreihen der Hydraulik, Temperatur und elektrischen Leitfähigkeit im Fließgewässer, an der Gewässersohle sowie im flussnahen Grundwasser dienten zudem der Identifizierung von Zonen mit signifikantem Fluss-Grundwasser-Austausch und von zeitlich instationären bevorzugten Fließpfaden im Grundwasser bei unterschiedlichen hydrologischen Randbedingungen. Die Resultate der Feldmessungen in Kombination mit der instationären Modellierung und Szenarienentwicklung illustrieren die Bedeutung von sich dynamisch verändernden Infiltrations- und Exfiltrationsmustern im Flussbet

Exploring Lip Segmentation Techniques in Computer Vision: A Comparative Analysis

Lip segmentation is crucial in computer vision, especially for lip reading. Despite extensive face segmentation research, lip segmentation has received limited attention. The aim of this study is to compare state-of-the-art lip segmentation models using a standardized setting and a publicly available dataset. Five techniques, namely EHANet, Mask2Former, BiSeNet V2, PIDNet, and STDC1, are qualitatively selected based on their reported performance, inference time, code availability, recency, and popularity. The CelebAMask-HQ dataset, comprising manually annotated face images, is used to fairly assess the lip segmentation performance of the selected models. Inference experiments are conducted on a Raspberry Pi4 to emulate limited computational resources. The results show that Mask2Former and EHANet have the best performances in terms of mIoU score. BiSeNet V2 demonstrate competitive performance, while PIDNet excels in recall but has lower precision. Most models present inference time ranging from 1000 to around 3000 milliseconds on a Raspberry Pi4, with PIDNet having the lowest mean inference time. This study provides a comprehensive evaluation of lip segmentation models, highlighting their performance and inference times. The findings contribute to the development of lightweight techniques and establish benchmarks for future advances in lip segmentation, especially in IoT and edge computing scenarios

Machine Learning for Outcome Prediction in First-Line Surgery of Prolactinomas.

Background First-line surgery for prolactinomas has gained increasing acceptance, but the indication still remains controversial. Thus, accurate prediction of unfavorable outcomes after upfront surgery in prolactinoma patients is critical for the triage of therapy and for interdisciplinary decision-making. Objective To evaluate whether contemporary machine learning (ML) methods can facilitate this crucial prediction task in a large cohort of prolactinoma patients with first-line surgery, we investigated the performance of various classes of supervised classification algorithms. The primary endpoint was ML-applied risk prediction of long-term dopamine agonist (DA) dependency. The secondary outcome was the prediction of the early and long-term control of hyperprolactinemia. Methods By jointly examining two independent performance metrics - the area under the receiver operating characteristic (AUROC) and the Matthews correlation coefficient (MCC) - in combination with a stacked super learner, we present a novel perspective on how to assess and compare the discrimination capacity of a set of binary classifiers. Results We demonstrate that for upfront surgery in prolactinoma patients there are not a one-algorithm-fits-all solution in outcome prediction: different algorithms perform best for different time points and different outcomes parameters. In addition, ML classifiers outperform logistic regression in both performance metrics in our cohort when predicting the primary outcome at long-term follow-up and secondary outcome at early follow-up, thus provide an added benefit in risk prediction modeling. In such a setting, the stacking framework of combining the predictions of individual base learners in a so-called super learner offers great potential: the super learner exhibits very good prediction skill for the primary outcome (AUROC: mean 0.9, 95% CI: 0.92 - 1.00; MCC: 0.85, 95% CI: 0.60 - 1.00). In contrast, predicting control of hyperprolactinemia is challenging, in particular in terms of early follow-up (AUROC: 0.69, 95% CI: 0.50 - 0.83) vs. long-term follow-up (AUROC: 0.80, 95% CI: 0.58 - 0.97). It is of clinical importance that baseline prolactin levels are by far the most important outcome predictor at early follow-up, whereas remissions at 30 days dominate the ML prediction skill for DA-dependency over the long-term. Conclusions This study highlights the performance benefits of combining a diverse set of classification algorithms to predict the outcome of first-line surgery in prolactinoma patients. We demonstrate the added benefit of considering two performance metrics jointly to assess the discrimination capacity of a diverse set of classifiers

Tidal Dissipation in the Early Eocene and Implications for Ocean Mixing

The tidally driven vertical diffusivity in the abyssal ocean during the early Eocene (55 Ma) is investigated using an established tidal model. A weak tide is predicted in the Eocene ocean, except in the Pacific. Consequently, the integrated global tidal dissipation rate is a mere 1.44TW, of which 40% dissipate in the Pacific. However, due to a stronger abyssal vertical stratification the predicted Eocene vertical diffusivities are consistently larger than at present. The results support the hypothesis that altered tidal dissipation may play a role in explaining the maintenance of past climate regimes, especially the anomalously warm temperatures in the southwest Pacific in the Eocene, and the low dissipation rates may be important for lunar evolution history

Evaluation of a newly developed flipped-classroom course on interprofessional practice in health care for medical students

Interprofessional education is expected to promote collaborative practice and should therefore be included in health professionals’ curricula. Reports on interprofessional curricular development and its evaluation are rare. We therefore undertook a comprehensive quantitative and qualitative evaluation of a new, mandatory course on interprofessional collaboration for medical students during their third year of the Bachelor of Medicine study programme. The newly developed and implemented course spans over six weeks and was designed in a hybrid, flipped-classroom format. It incorporates experience- and case-based learning as well as interactions with other health professionals. Each student completes an eLearning and a clinical workshadowing individually before attending the – due to the pandemic – virtual live lectures. To assess quality and usefulness of teaching-learning formats and course structure to learn about interprofessional collaboration and to develop interprofessional competencies and identity, a quantitative and qualitative evaluation was performed with more than 280 medical students and 26 nurse educators from teaching hospitals using online surveys (open & closed-ended format). Data were analyzed descriptively and using content analysis processes. Students appreciated the flipped-classroom concept, the real-world case-based learning scenarios with interprofessional lecturer teams, and the possibility of an experience-based learning opportunity in the clinical setting including interaction with students and professionals from other health professions. Interprofessional identity did not change during the course. Evaluation data showed that the course is a promising approach for teaching-learning interprofessional competencies to medical students. The evaluation revealed three factors that determined the success of this course, namely, a flipped-classroom concept, the individual workshadowing of medical students with another health professional, mainly nurses, and live sessions with interprofessional teaching-learning teams. The course structure and teaching-learning methods showed potential and could serve as a template for interprofessional course development in other institutions and on other course topics