Papers by Benedikt Schmidt
Werden bei einem Monitoring bestimmte Regeln eingehalten, können zuverlässige Aussagen zum Zustan... more Werden bei einem Monitoring bestimmte Regeln eingehalten, können zuverlässige Aussagen zum Zustand und zur Veränderung der Bestände der untersuchten Organismen gemacht werden. Von zentraler Bedeutung sind eine saubere Auswahl der Stichprobe und die Minimierung des Messfehlers.
Ecosphere, 2021
Predation can affect prey behavior, demography, abundance, and distribution, particularly in lent... more Predation can affect prey behavior, demography, abundance, and distribution, particularly in lentic freshwater ecosystems. Fish are predators known to reduce the abundance of their prey and to restrict the distribution of species. Using time series which spanned 43 and 22 yr, respectively, we analyzed the effect of a change in the fish predator community on the dynamics of two pond-breeding amphibian populations (Rana temporaria and Rana dalmatina). Specifically, we used a state-space time series model which allows for density dependence and observation error, to ask whether the change in predation risk affects population growth rate and the return point around which the populations fluctuate. The results showed that the type of observation error assumed did not affect the biological parameters. We found evidence for density dependence in both populations. The effect of the change in fish predation on population growth rate and the return point was strong in the population where fish invaded a previously fish-free pond. The effect was weaker in the population where the change was from cyprinid fish to pike. The results showed that fish predation can have strong effects on amphibian population dynamics. The observed population dynamical pattern is phenomenologically similar to alternative stable states.
Salamandra, 2012
1) Trier University, Biogeography Department, 54286 Trier, Germany 2) Department of Biology, Cope... more 1) Trier University, Biogeography Department, 54286 Trier, Germany 2) Department of Biology, Copenhagen University, Universitetsparken 15, 2100 Copenhagen, Denmark 3) Department of Evolutionary Biology, University of Vienna, Vienna, Austria 4) KARCH, Passage Maximilien-de-Meuron 6, 2000 Neuchâtel, Switzerland 5) Herpetology Department, Zoologisches Forschungsmuseum Alexander Koenig, Adenauerallee 160, 53113 Bonn, Germany 6) Department for Molecular Biodiversity, Zoologisches Forschungsmuseum Alexander Koenig, Adenauerallee 160, 53113 Bonn, Germany 7) Institut fur Evolutionsbiologie und Umweltwissenschaften, Universitat Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
Herpetological Journal, 2004
Most data used in the study of the demography, dynamics, distributions, diversity, and declines o... more Most data used in the study of the demography, dynamics, distributions, diversity, and declines of amphibians are count data that are not adjusted for detection probabilities, which are generally variable and low. Such unadjusted count data are unreliable for understanding amphibian ecology, amphibian declines, or when developing conservation and management strategies. In the future, detection probabilities should be estimated and counts adjusted accordingly. This could be achieved by using capture-mark-recapture, distance sampling or novel Bayesian methods.
Die Grose von Amphibien-Populationen fluktuiert stark von Jahr zu Jahr. Verschiedene Studien habe... more Die Grose von Amphibien-Populationen fluktuiert stark von Jahr zu Jahr. Verschiedene Studien haben die Populationsdynamik mit mathematischen Modellen analysiert und kamen zu dem Schluss, dass das Schicksal der Juvenilen das Schicksal der Population bestimmt. Eine Veranderung bei der Uberlebenswahrscheinlichkeit der Juvenilen hat einen starkeren Einfluss auf die Populationsdynamik als eine gleich grose Veranderung bei der Uberlebenswahrscheinlichkeit der Adulten oder Larven. Diese Erkenntnis ist auch fur den Amphibienschutz von Bedeutung, denn ein verbesserter Schutz der Juvenilen (z. B. bei Amphibientunneln an Strasen) wurde sich positiv auf Amphibien-Populationen auswirken.
Based on a two-year monitoring, we analysed the distribution of dice snake populations in the Can... more Based on a two-year monitoring, we analysed the distribution of dice snake populations in the Canton of Ticino (Switzerland). Imperfect detection was taken into account in order to avoid underestimation of the distrub- tion range and hence overestimating the species threat status: we therefore used a model based on a mark-recapture- like approach to estimate detection probability, which was 61.2% (± 6.8%; standard error), and site occupancy, which was 78.0% (± 7.9%). Detection probability depended on habitat characteristics (tree cover and naturalness of the streams and lake shores) while occupancy was best predicted by the number of previous dice snake records at a site. We observed local decline or extinction of some small populations located on secondary streams, apparently because of habitat deterioration. However, populations located on lakes (Lugano, Maggiore) and main rivers (Ticino, Brenno, Maggia, Vedeggio and Tresa) showed no signs of decline and rather high densities. The...
Virtual assistant systems promise ubiquitous and straightforward access to information, applicati... more Virtual assistant systems promise ubiquitous and straightforward access to information, applications, and physical appliances. Their foundation on intent-oriented queries and support of natural language makes them an ideal tool for human-centric applications. The general approach to build such systems and the main building blocks are well-understood and offered as off-the-shelf components. While there are prominent examples in the service sector, other sectors such as the manufacturing and process industries have nothing comparable. We investigate the practical challenges of building a virtual assistant using a representative and simplified case from of knowledge retrieval domain. A qualitative study reveals two significant obstacles: Firstly, while systems can be tuned to tackle the most relevant types of question tasks, user acceptance is lower than for comparable GUI-based systems and, secondly, a disproportional amount of effort to get all details and having a robust system. Ove...
In this paper, a first step to analyse the effects of reducing the uncertainty of aircraft trajec... more In this paper, a first step to analyse the effects of reducing the uncertainty of aircraft trajectories on sector demand is presented. The source of uncertainty is wind, forecasted by Ensemble Prediction Systems, which are composed of different possible atmosphere realizations. A trajectory predictor determines the routes to be followed by the different flights to reduce the uncertainty of the arrival times. The sector demand is described in terms of entry count, that is, the number of flights entering the sector during a selected time period, which is uncertain because so are the the entry times to the sector. Results are presented for a realistic application, where the dispersion of the entry count is shown to be reduced when the dispersion of the arrival times is also reduced.
Wenn sich Fische, deren Herkunft nicht klar ist, in naturlicherweise fischfreien Amphibienlaichge... more Wenn sich Fische, deren Herkunft nicht klar ist, in naturlicherweise fischfreien Amphibienlaichgewassern befinden, wird oft der Eintrag uber Entern postuliert. In diesem Artikel wird dargestellt, welche Beweise es fur diese These gibt. Es zeigt sich, dass es fur einzelne Aspekte der Verbreitung von Fischen durch die Luft Hinweise gibt, aber keine schlussigen Studien, welche die Ausbreitung von Fischen durch Enten belegen. Andere Erklarungen fur die Ausbreitung von Fischen sind wesentlich plausibler als die Ausbreitung durch Enten.
Wenn sich Fische, deren Herkunft nicht klar ist, in naturlicherweise fischfreien Amphibienlaichge... more Wenn sich Fische, deren Herkunft nicht klar ist, in naturlicherweise fischfreien Amphibienlaichgewassern befinden, wird oft der Eintrag uber Entern postuliert. In diesem Artikel wird dargestellt, welche Beweise es fur diese These gibt. Es zeigt sich, dass es fur einzelne Aspekte der Verbreitung von Fischen durch die Luft Hinweise gibt, aber keine schlussigen Studien, welche die Ausbreitung von Fischen durch Enten belegen. Andere Erklarungen fur die Ausbreitung von Fischen sind wesentlich plausibler als die Ausbreitung durch Enten.
Si un monitoring respecte certaines regles, il permettra de formuler des enonces fiables sur l’et... more Si un monitoring respecte certaines regles, il permettra de formuler des enonces fiables sur l’etat et l’evolution des effectifs des organismes etudies. La selection scrupuleuse des echantillons et la reduction de l’erreur de mesure revetent une importance capitale.
A security protocol is a distributed program that might be executed on a network controlled by an... more A security protocol is a distributed program that might be executed on a network controlled by an adversary. Even in such a setting, the protocol should satisfy the desired security property. Since it is hard to consider all possible executions when designing a protocol, formal methods are often used to ensure the correctness of a protocol with respect to a model of the protocol and the adversary. Many such formal models use a symbolic abstraction of cryptographic operators by terms in a term algebra. The properties of these operators can then be modeled by equations. In this setting, we make the following contributions: 1. We present a general approach for the automated symbolic analysis of security protocols that use Diffie-Hellman exponentiation and bilinear pairings to achieve advanced security properties. We model protocols as multiset rewriting systems and security properties as first-order formulas. We analyze them using a novel constraint-solving algorithm that supports both...
DEUTSCH: Neue Forschungsresultate zeigen, dass die Landnutzung fernab vom Laichgewasser das Vorko... more DEUTSCH: Neue Forschungsresultate zeigen, dass die Landnutzung fernab vom Laichgewasser das Vorkommen von Amphibien im Gewasser beeinflusst. »Fernab« bedeutet hier, dass Landnutzungen wie Siedlungsflachen, Wald oder Strasen in Entfernungen von Hunderten von Metern, in vielen Fallen sogar Tausenden von Metern noch eine Wirkung haben. Der biologische Mechanismus dieser Effekte auf grose Distanz ist noch unklar. Denkbar ist, dass Amphibien in groser Zahl Landlebensraume nutzen, die sehr weit vom Gewasser entfernt sind oder dass die Landnutzung das Gewasser direkt, beispielsweise die Wasserqualitat, beeinflusst. ENGLISH: Recent research shows that land use far away from ponds affects amphibian pond occupancy. »Far away« means that land uses such as urban areas, forest or roads affect pond occupancy even at several hundreds of meters distance from the ponds. In many cases, the spatial scale is even thousands of meters. The biological mechanisms causing these effects are unclear. Either a...
Rote Listen nach den Kriterien der IUCN sind ein wichtiges Instrument im Naturschutz. Sie haben a... more Rote Listen nach den Kriterien der IUCN sind ein wichtiges Instrument im Naturschutz. Sie haben aber auch ihre Tucken, denn weit verbreitete Arten gelten kaum je als gefahrdet, und Bestandeseinbruche mussen massiv sein, ehe eine Art als gefahrdet eingestuft werden kann. Dies verhindert in vielen Fallen, dass eine Art einen Rote-Liste-Status erhalt – obwohl dies aus Sicht der Fachleute dringend notig ware. Eine Verbesserung ware es, die Ausdunnung der Bestande zu messen.
Was steckt hinter der Aussage «die Art ist bedroht und steht auf der Roten Liste»? Wie der Gefahr... more Was steckt hinter der Aussage «die Art ist bedroht und steht auf der Roten Liste»? Wie der Gefahrdungsgrad gemessen wird, soll hier am Beispiel der Roten Liste der Amphibien von 2005 erlautert werden.
The invention relates to a control element (1), comprising: a about a first pivot axis (3) operat... more The invention relates to a control element (1), comprising: a about a first pivot axis (3) operating lever pivotally mounted (2) with a respect to the first pivot axis (3) facing the operator section (2d) and an operating lever portion facing away from the operator (2e); a a Mitnehmerschwenkachse (13) along a pivoting direction (7) pivotably mounted drive lever (8); one at the driving lever (8) rigidly fixed, the first magnet (10), preferably a permanent magnet, a plurality of stationary, second magnets (9), preferably permanent magnets, which are arranged so as to cross the magnetic fields of the second magnets (9), when pivoting the drive lever (8) of the first magnet (10) to a haptic feedback on the actuating lever (2) to create; wherein a first operative engagement (2b, 8b) between the actuating lever portion (2a) and drive lever (8) is provided to effect a synchronous pivoting of operating lever (2) and drive lever (8).
Ecological Applications, 2021
Monitoring programs serve to detect trends in the distribution and abundance of species. To do so... more Monitoring programs serve to detect trends in the distribution and abundance of species. To do so, monitoring programs often use static state variables. Dynamic state variables that describe population dynamics might be more valuable because they allow for a mechanistic understanding of the processes that lead to population trends. We fit multistate occupancy models to data from a country-wide multispecies amphibian occupancy monitoring program and estimated occupancy and breeding probabilities. If breeding probabilities are determinants of occupancy dynamics, then they may serve in monitoring programs as state variables that describe dynamic processes. The results showed that breeding probabilities were low and that a large proportion of the populations had to be considered to be non-breeding populations (i.e., populations where adults are present but no breeding occurs). For some species, the majority of populations were non-breeding populations. We found that non-breeding populations have lower persistence probabilities than populations where breeding occurs. Breeding probabilities may thus explain trends in occupancy but they might also explain other ecological phenomena, such as the success of invasive species, which had high breeding probabilities. Signs of breeding, i.e., the presence of eggs and larvae, were often hard to detect. Importantly, non-breeding populations also had low detection probabilities, perhaps because they had lower abundances. We suggest that monitoring programs should invest more in the detection of life history stages indicative of breeding, and also into the detection of nonbreeding populations. We conclude that breeding probability should be used as a state variable in monitoring programs because it can lead to deeper insights into the processes driving occupancy dynamics.
International Conference on Liquid Atomization and Spray Systems (ICLASS), 2021
Spray/wall interactions and single drop impact phenomena have been extensively studied in the pas... more Spray/wall interactions and single drop impact phenomena have been extensively studied in the past to better understand the underlying hydrodynamics and thermodynamics due to their high number of applications. One of these applications is a cooling by a chain of drops. The influence of many factors, such as impact parameters, material properties, surface temperature and liquid properties have already been largely identified. Various drop impact regimes, including nucleate boiling and film boiling, have been observed and described. In this study the cooling of a hot substrate by an impacting monodispersed chain of drops is examined. The temperature distribution inside the substrate and its evolution in time are measured with a set of thermocouples. Additionally, a theoretical model is developed for the transient cooling of a semi-infinite solid target, allowing prediction of the increment of the wall temperature due to cooling at a single point. The theoretical prediction agrees well with the experimental data.
Uploads
Papers by Benedikt Schmidt