Search results for "spring"
showing 10 items of 600 documents
A GALTON-WATSON BRANCHING PROCESS IN VARYING ENVIRONMENTS WITH ESSENTIALLY CONSTANT OFFSPRING MEANS AND TWO RATES OF GROWTH1
1983
Summary A Galton-Watson process in varying environments (Zn), with essentially constant offspring means, i.e. E(Zn)/mnα∈(0, ∞), and exactly two rates of growth is constructed. The underlying sample space Ω can be decomposed into parts A and B such that (Zn)n grows like 2non A and like mnon B (m > 4).
Physical simulation for real-time image/video retargeting
2012
Retargeting methods present content on arbitrary aspect ratio me- dia displays limiting distortions in relevant objects. This is done by means of applying non-homogeneous resizing operators across the whole media, constraining it to fit into the required size. Several succesful systems have been proposed to achieve image retargeting, while video retargeting is still challenging due to time consistency and computational complexity requirements. Two important con- tributes were proposed: non-homogeneous retargeting [Wolf et al. 2007] and improved seam-carving [Rubinstein et al. 2008]. The first one claims to achieve real-time performance but considers spa- tial coordinates separately. The lat…
Queen loss increases worker survival in leaf-cutting ants under paraquat-induced oxidative stress
2021
Longevity is traded off with fecundity in most solitary species, but the two traits are positively linked in social insects. In ants, the most fecund individuals (queens and kings) live longer than the non-reproductive individuals, the workers. In many species, workers may become fertile following queen loss, and recent evidence suggests that worker fecundity extends worker lifespan. We postulated that this effect is in part owing to improved resilience to oxidative stress, and tested this hypothesis in three Myrmicine ants: Temnothorax rugatulus, and the leaf-cutting ants Atta colombica and Acromyrmex echinatior . We removed the queen from colonies to induce worker reproduction and subjec…
Der Völkerfrühling von 1848/1849 – revolutionäre Gefahr oder republikanischer Durchbruch? Ästhetisch-historische Bilder
2022
The aim of this article is to present the revolutionary events of 1848/1849 in German states from the point of view of Joseph von Eichendorff and Theodor Opitz, which are based on their refl ections, experiences and reactions to this political and breakthrough coup. Eichendorff and Opitz present two different views on the events of the Spring of Nations. These two intellectuals and writers are linked by the last letter from Eichendorff to Theodor Opitz as well as the ideal of freedom, which became their life motto.
A new displacement-based framework for non-local Timoshenko beams
2015
In this paper, a new theoretical framework is presented for modeling non-locality in shear deformable beams. The driving idea is to represent non-local effects as long-range volume forces and moments, exchanged by non-adjacent beam segments as a result of their relative motion described in terms of pure deformation modes of the beam. The use of these generalized measures of relative motion allows constructing an equivalent mechanical model of non-local effects. Specifically, long-range volume forces and moments are associated with three spring-like connections acting in parallel between couples of non-adjacent beam segments, and separately accounting for pure axial, pure bending and pure sh…
Banned: A History of Pesticides and the Science of Toxicology.
2018
Many academic and popular works reviewing Rachel Carson's book Silent Spring (1962) have been published during the last years, particularly after the fiftieth anniversary of its release. Some of th...
Aberrant gene expression profiles in Mediterranean sea urchin reproductive tissues after metal exposures
2019
Abstract Marine organisms are simultaneously exposed to numerous pollutants, among which metals probably represent the most abundant in marine environments. In order to evaluate the effects of metal exposure at molecular level in reproductive tissues, we profiled the sea urchin transcriptional response after non-lethal exposures using pathway-focused mRNA expression analyses. Herein, we show that exposures to relatively high concentrations of both essential and toxic metals hugely affected the gonadic expression of several genes involved in stress-response, detoxification, transcriptional and post-transcriptional regulation, without significant changes in gonadosomatic indices. Even though …
Regional variations in the chemical and helium–carbon isotope composition of geothermal fluids across Tunisia
2011
Abstract Tunisia has numerous thermo-mineral springs. Previous studies have shown that their chemical composition and occurrence are strongly influenced by the regional geology. However little work has been done so far to study the isotopic composition of volatiles associated with these geothermal manifestations. Here, we report on the results of an extensive survey of both natural hot springs and production wells across Tunisia, aimed at investigating the spatial distribution of thermal fluids' geochemical characteristics and He–C isotopic composition. The chemistry of the analyzed samples highlights the heterogeneity of the water mineralization processes in Tunisia, as a consequence of th…
Anthropogenic travertine between History, Archaeology and Environment: a geoarchaeological study of the Roman site of Jebel Oust, Tunisia.
2013
Travertine, known as lapis tiburtinus during Roman times, are continental limestones precipitated in calcareous environments from thermal waters of hot springs (travertine) or cool waters of karstic springs (calcareous tufa). This phenomenon is well-known during Classical Antiquity and had been described by several ancient authors (Strabo, Pliny the Elder, Vitruvius) who depicted a stone that forms extremely rapidly, a stone that outlines the landscape and which is largely used for construction (e.g. The Colosseum in Roma, the Greek temple at Segesta in Sicily). These deposits are widespread on Earth’s surface showing various morphologies and are great sedimentary records of climatic and hy…
Development of lumped-parameter mathematical models for a vehicle localized impact
2011
Published version of an article in the journal:Journal of Mechanical Science and Technology. Also available from the publisher on SpringerLink: http://dx.doi.org/10.1007/s12206-011-0505-x In this paper, we propose a method of modeling for vehicle crash systems based on viscous and elastic properties of the materials. This paper covers an influence of different arrangement of spring and damper on the models’ response. Differences in simulating vehicle-torigid barrier collision and vehicle-to-pole collision are explained. Comparison of the models obtained from wideband (unfiltered) acceleration and filtered acceleration is done. At the end we propose a model which is suitable for localized co…