The consequences of spatial environmental variability on dispersal and on the spatial distribution of species

A central goal in ecology is to identify and understand causal factors that lead to the expansion or contraction of species ranges. Spatio - temporal population dynamics depend on biotic and abiotic environmental conditions, local demography, dispersal behaviour, and phenotypic variation. In particular understanding dispersal behaviour turns out to be a tough problem, because complex feedback loops between dispersal, local demography, and individual variations can arise. Furthermore, previous attempts to understand dispersal by reducing the complexity either in space or time have often resulted in a disregard of these feedbacks. The aim of this thesis was to investigate the influence of dispersal on spatio-temporal population dynamics with models and experiments that explicitly consider the multi causality of dispersal. The thesis is composed of three different studies: Firstly, for an active dispersing species, a plausible factor affecting dispersal behaviour could be personal information. Birds, for example, might gather information on future nest sites and, as a result, individuals differ in the amount and quality of information they possess for use in reaching a dispersal decision. We manipulated the information available to flycatchers (Ficedula hypoleuca) in a field experiment and we found that individuals which were longer exposed to the information altered dispersal behaviour to a greater extent, but only at a local spatial extent. Secondly, models of sex-biased dispersal rarely take space into account. With a computer simulation model, we showed that acknowledging the spatial distribution of the sexes has consequences for the evolutionary outcome of the model leading to selection of more similar dispersal behaviour among the two sexes. Thirdly, models of invasion spread rate often ignore the dependency of dispersal on environmental heterogeneity. We expanded on a reaction-diffusion model to improve this deficit and show that the invasion dynamics of an ecto-parasite (deer ked, Lipoptena cervi) is dependent on the local density of its main host, moose (Alces alces), across its Finnish range. In conclusion, these studies point at the necessity to consider interactions between dispersal and environmental variability, feedbacks between causal factor of dispersal, and realistic assumptions about space and time in order to solve the conundrum of factors determining the spatio-temporal distribution of species.Ei saatavill

Asymptomatic Periprosthetic Joint Infection of the Hip with High-Virulence Pathogens: Report of Two Cases

Periprosthetic joint infection (PJI) may be a life-threatening condition, particularly when caused by pathogens with high virulence, capable of developing secondary bloodstream infection. We report two cases of chronic PJI of the hip, one with Staphylococcus aureus in a 27-year-old female with severe anorexia, the other one with Staphylococcus lugdunensis in a 74-year-old female suffering from morbid obesity. Both infections did not cause relevant symptoms over time despite the absence of suppressive antibiotic treatment. To our knowledge, there are no similar cases described in the literature. While it remains difficult to recommend postponing treatment in such cases, this option may be an alternative to suppressive antibiotic therapy

GENGA. II. GPU Planetary N-body Simulations with Non-Newtonian Forces and High Number of Particles

We present recent updates and improvements of the graphical processing unit (GPU) N-body code GENGA. Modern state-of-the-art simulations of planet formation require the use of a very high number of particles to accurately resolve planetary growth and to quantify the effect of dynamical friction. At present the practical upper limit is in the range of 30,000–60,000 fully interactive particles; possibly a little more on the latest GPU devices. While the original hybrid symplectic integration method has difficulties to scale up to these numbers, we have improved the integration method by (i) introducing higher level changeover functions and (ii) code improvements to better use the most recent GPU hardware efficiently for such large simulations. We added treatments of non-Newtonian forces such as general relativity, tidal interaction, rotational deformation, the Yarkovsky effect, and Poynting–Robertson drag, as well as a new model to treat virtual collisions of small bodies in the solar system. We added new tools to GENGA, such as semi-active test particles that feel more massive bodies but not each other, a more accurate collision handling and a real-time openGL visualization. We present example simulations, including a 1.5 billion year terrestrial planet formation simulation that initially started with 65,536 particles, a 3.5 billion year simulation without gas giants starting with 32,768 particles, the evolution of asteroid fragments in the solar system, and the planetesimal accretion of a growing Jupiter simulation. GENGA runs on modern NVIDIA and AMD GPUs

Novel Simulation-Inspired Roller Spreading Strategies for Fine and Highly Cohesive Metal Powders

When fine powders are to be used in powder bed metal additive manufacturing (AM), a roller is typically utilized for spreading. However, the cohesive nature of fine metal powder still presents challenges, resulting in low density and/or inconsistent layers under sub-standard spreading conditions. Here, through computational parameter studies with an integrated discrete element-finite element (DEM-FEM) framework, we explore roller-based strategies that are predicted to achieve highly cohesive powder layers. The exemplary feedstock is a Ti-6Al-4V 0-20 um powder, that is emulated using a self-similarity approach based on experimental calibration. The computational studies explore novel roller kinematics including counter-rotation as well as angular and transverse oscillation applied to standard rigid rollers as well as coated rollers with compliant or non-adhesive surfaces. The results indicate that most of these approaches allow to successfully spread highly cohesive powders with high packing fraction (between 50%-60% in a single layer) and layer uniformity provided that the angular/oscillatory, relative to the transverse velocity, as well as the surface friction of the roller are sufficiently high. Critically, these spreading approaches are shown to be very robust with respect to varying substrate conditions (simulated by means of a decrease in surface energy), which are likely to occur in LBPF or BJ, where substrate characteristics are the result of a complex multi-physics (i.e., powder melting or binder infiltration) process. In particular, the combination of the identified roller kinematics with compliant surface coatings, which are known to reduce the risk of tool damage and particle streaking in the layers, is recommended for future experimental investigation

Microangiopathic Anemia without Thrombocytopenia and Kidney Disease in a Child with Diarrhea Caused by Shiga Toxin-Producing Escherichia coli

A child with a history of diarrhea presented with transient anemia, reticolucytosis, and red blood cell fragmentation. Blood pressure and levels of blood platelets, creatinine, and urea were normal, as were results of urinalysis. Escherichia coli harboring genes for Shiga toxin were detected in stool specimens. It is concluded that extraintestinal diseases caused by Shiga toxin-producing bacteria sometimes present without any renal involvemen

Dispensed drugs during pregnancy in outpatient care between 2015 and 2021 in Switzerland: a retrospective analysis of Swiss healthcare claims data.

AIM OF THE STUDY We aimed to evaluate the utilisation of all prescribed drugs during pregnancy dispensed in outpatient care in Switzerland between 2015 and 2021. METHODS We conducted a descriptive study using the Swiss Helsana claims database (2015-2021). We established a cohort of pregnancies by identifying deliveries and estimating the date of the last menstrual period. We analysed the drug burden during a 270-day pre-pregnancy period, during pregnancy (overall and by trimester), and during a 270-day postpartum period. Subsequently, we quantified 1) the median number of drug dispensations (total vs. unique drug claims); and 2) the prevalence of exposure to at least one dispensed drug and the number of dispensed drugs (0, 1, 2, 3, 4, and ≥5); and 3) the 15 most frequently dispensed drugs were identified during each period, overall and stratified by maternal age. RESULTS Among 34,584 pregnant women (5.6% of all successful pregnancies in Switzerland), 87.5% claimed at least one drug (not including vitamins, supplements, and vaccines), and 33.3% claimed at least five drugs during pregnancy. During trimester 1 alone, 8.2% of women claimed at least five distinct drugs. The proportion of women who claimed prescribed drugs was lower pre-pregnancy (69.1%) and similar postpartum (85.6%) when compared to during pregnancy (87.5%). The most frequently claimed drugs during pregnancy were meaningfully different during pregnancy than before and after. CONCLUSIONS This study suggests that 8 of 10 women in Switzerland are exposed to prescribed drugs during pregnancy. Most drugs dispensed during pregnancy are comparatively well investigated and are considered safe. However, the high drug burden in this vulnerable patient population underlines the importance of evidence on the benefit-risk profile of individual drugs taken during pregnancy

Towards Additively Manufactured Metamaterials with Powder Inclusions for Controllable Dissipation: The Critical Influence of Packing Density

Particle dampers represent a simple yet effective means to reduce unwanted oscillations when attached to structural components. Powder bed fusion additive manufacturing of metals allows to integrate particle inclusions of arbitrary shape, size and spatial distribution directly into bulk material, giving rise to novel metamaterials with controllable dissipation without the need for additional external damping devices. At present, however, it is not well understood how the degree of dissipation is influenced by the properties of the enclosed powder packing. In the present work, a two-way coupled discrete element - finite element model is proposed allowing for the first time to consistently describe the interaction between oscillating deformable structures and enclosed powder packings. As fundamental test case, the free oscillations of a hollow cantilever beam filled with various powder packings differing in packing density, particle size, and surface properties are considered to systematically study these factors of influence. Critically, it is found that the damping characteristics strongly depend on the packing density of the enclosed powder and that an optimal packing density exists at which the dissipation is maximized. Moreover, it is found that the influence of (absolute) particle size on dissipation is rather small. First-order analytical models for different deformation modes of such powder cavities are derived to shed light on this observation

Spatial Mapping of Powder Layer Density for Metal Additive Manufacturing via X-ray Microscopy

Uniform powder spreading is a requisite for creating consistent, high-quality components via powder bed additive manufacturing (AM), wherein layer density and uniformity are complex functions of powder characteristics, spreading kinematics, and mechanical boundary conditions. High spatial variation in particle packing density, driven by the stochastic nature of the spreading process, impedes optical interrogation of these layer attributes. Thus, we present transmission X-ray imaging as a method for directly mapping the effective depth of powder layers at process-relevant scale and resolution. Specifically, we study layers of nominal 50-250 micrometer thickness, created by spreading a selection of commercially obtained Ti-6Al-4V, 316 SS, and Al-10Si-Mg powders into precision-depth templates. We find that powder layer packing fraction may be predicted from a combination of the relative thickness of the layer as compared to mean particle size, and flowability assessed by macroscale powder angle of repose. Power spectral density analysis is introduced as a tool for quantification of defect severity as a function of morphology, and enables separate consideration of layer uniformity and sparsity. Finally, spreading is studied using multi-layer templates, providing insight into how particles interact with both previously deposited material and abrupt changes in boundary condition. Experimental results are additionally compared to a purpose-built discrete element method (DEM) powder spreading simulation framework, clarifying the competing role of adhesive and gravitational forces in layer uniformity and density, as well as particle motion within the powder bed during spreading