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We present a unified formulation of the interaction of electrons with the electromagnetic field in heavy ion collisions, based on quantized interacting fields. This reduces the effort in treating many-electron systems substantially, as compared with the usual S-matrix theory. Both formalisms are shown to be equivalent. The simplification achieved by our new approach is demonstrated in detail for the example of quasi-molecular radiation.
Kein anderer seiner Romane bereitete Hermann Broch größere Mühe als die niemals abgeschlossene, in drei Fassungen vorliegende "Verzauberung". Zu Beginn der dreißiger Jahre konzipiert, war dieser "Bergroman" (so Brochs inoffizielle Bezeichnung) als literarische Analyse der Massenwirkung Hitlers geplant, die zugleich eine Vielzahl mythen- und religionsgeschichtlicher Bezugnahmen integrieren sollte. [...] Was bis zum Ende im Status "unentschiedener Entscheidung" verblieb, spaltet auch die Leserschaft seit je. Allerdings betreffen die Probleme weniger das Unzugängliche dieser sicherlich sperrigen literarischen Hinterlassenschaft des 20. Jahrhunderts. Der wichtigste Streitpunkt ist vielmehr eine häufig gespürte, unheimliche Nähe der Broch'schen Faschismusanalyse zu ihrem Sujet selbst. [...] Auf der anderen Seite hat man schon früh versucht, den "Bergroman" als Vorläufer der Anti-Heimatliteratur zu retten; auch jüngst sind bedenkenswerte Aufsätze erschienen, die ihn als Versuch würdigen, 'gefährliche' Diskurse umzuschreiben: zeitübliche Tiefensemantiken etwa oder eben Tendenzen der Remythisierung. Auch der vorliegende Essay steht nicht auf der Seite derer, die Brochs Romanversuch als Rückzug in "extreme geistige Provinz" abtun. Stattdessen lässt er sich von den Fragen leiten, woran Broch hier eigentlich arbeitete und was von seiner unabgeschlossenen, vielleicht sogar unabschließbaren Auseinandersetzung mit dem Massenphänomen Hitler noch oder gerade heute zu lernen wäre. Speziell drei zusammenhängende Motive Brochs sollen in diesem Sinn neu beleuchtet werden: Erstens seine spezifische Arbeit am Thema des Opfers, zweitens sein Rekurs auf die (Vor-)Geschichte der griechischen Tragödie; und drittens soll ein bestimmter technikphilosophischer Einsatz Brochs betrachtet werden, der sich von heute aus als Reaktion auf den epochalen Aufstieg einer "environmentalen Macht" erweist. In allen drei Punkten wird sich zeigen, dass Broch durchaus wegweisend Fragen aufwarf, die Theoriebildung und philosophische Diskurse auch der jüngeren und jüngsten Zeit bewegt haben, wie zeitgebunden auch immer manche seiner Instrumentarien waren.
Pflanzengesellschaften der Felsspalten und Mauerfugen werden anhand von 21 Vegetationsaufnahmen beschrieben, die bei „Pflanzensoziologischen Sonntagsexkursionen“ in den Jahren 1988 bis 1995 erstellt wurden. Die in Hessen vorkommenden Pflanzengesellschaften der Klasse Asplenietea werden im Hinblick auf pflanzensoziologisch-syntaxonomische Aspekte, Ökologie, Gefährdung und Naturschutz charakterisiert.
he family of cubic noncentrosymmetric 3-4-3 compounds has become a fertile ground for the discovery of novel correlated metallic and insulating phases. Here, we report the synthesis of a new heavy fermion compound, Ce3Bi4Ni3. It is an isoelectronic analog of the prototypical Kondo insulator Ce3Bi4Pt3 and of the recently discovered Weyl-Kondo semimetal Ce3Bi4Pd3. In contrast to the volume-preserving Pt-Pd substitution, structural and chemical analyses reveal a positive chemical pressure effect in Ce3Bi4Ni3 relative to its heavier counterparts. Based on the results of electrical resistivity, Hall effect, magnetic susceptibility, and specific heat measurements, we identify an energy gap of 65–70 meV, about eight times larger than that in Ce3Bi4Pt3 and about 45 times larger than that of the Kondo-insulating background hosting the Weyl nodes in Ce3Bi4Pd3. We show that this gap as well as other physical properties do not evolve monotonically with increasing atomic number, i.e., in the sequence Ce3Bi4Ni3−Ce3Bi4Pd3−Ce3Bi4Pt3, but instead with increasing partial electronic density of states of the 𝑑 orbitals at the Fermi energy. This work opens the possibility to investigate the conditions under which topological states develop in this series of strongly correlated 3-4-3 materials.
The infrastructure for parking and parked cars themselves (e.g., parked cars blocking bike lanes and sidewalks or the visibility range) can lead to conflicts for pedestrians and cyclists. The perception of conflicts could discourage walking and cycling in neighborhoods and undermine municipalities’ efforts to provide more sustainable urban mobility. The aim of this study was therefore to analyze the effect of on-street car parking in urban neighborhoods on perceived parking and traffic-related conflicts. In addition, it examines in what way the intention to reduce one’s car use influences the perception of the conflicts (Stage Model of Self-Regulated Behavior Change (SSBC)). A household survey was conducted in the inner-city neighborhood of Frankfurt-Bornheim, Germany (N=1027). The residents most often observed the conflicts in which parked cars impeded walking and cycling as well as situations in which pedestrians felt threatened by cyclists biking on the sidewalk. Results from multiple linear regression models revealed that the influencing factors for the perception of conflicts were the use of different means of transportation and the intention to change one’s behavior (SSBC model) to reduce car use rather than car ownership. In addition, a resident’s age and household structure seemed to affect awareness of conflicts in which pedestrians and cyclists were involved. The results suggest a group-serving bias, meaning that the residents mostly observed those conflicts that they did not cause. A separate infrastructure for pedestrians and cyclists could help prevent most of the conflicts described in this study.
The organisation of parking is a key challenge to more sustainable mobility in urban areas, as its pricing and availability affect the rates of private car ownership and use. However, changing parking policies is a challenging issue for local politicians and planners because residents frequently oppose changes or restrictions to conditions they have taken for granted such as on-street parking in a public space. The aim of this paper is firstly to assess how the parking policy of an urban neighbourhood can be structured to contribute to more sustainable mobility and to increase liveability in the neighbourhood. The second aim is to apply the policies reviewed to an example neighbourhood. For this purpose, we systematically reviewed academic literature and identified five types of relevant parking policies: (i) maximum parking requirements, (ii) physical detachment of residence and parking space, (iii) residential parking permits and the limitation of available parking space, (iv) performance-based pricing and (v) parking as a demand management strategy. We discovered that most research focuses on econometric models about parking and that studies rarely address the effects of parking on the quality of life in neighbourhoods. Therefore, we need further research regarding the relationship of parking and liveability. We conclude that for the implementation of such parking policies in an example neighbourhood, the municipality needs to develop a mobility vision for its city. It has to understand parking as a tool for transportation demand management to increase the acceptance of parking policy concepts and to avoid spillover problems. Finally, in the German case, as in most other countries, states and municipalities need to redesign their legal frameworks to be able to manage parking supply better and to react to changes related to digital developments and parking. The findings have implications for other European neighbourhoods regarding the transfer from research to local circumstances and applications for the whole city.
Support for innovative on-street parking policies: empirical evidence from an urban neighborhood
(2020)
Municipalities and planners often hesitate to implement restrictive parking policies because residents regularly oppose any changes to on-street parking space. Residential parking is one key factor of parking management because its location and availability influence a household's car ownership and use. Moreover, as more residents regularly use other means of transportation that need space and infrastructure in the urban realm, and as parking takes up a vast amount of land, municipalities are considering the reuse of on-street parking space for other purposes. As public acceptability is a precondition for the successful implementation of a proposed policy, our empirical analysis investigates to what extent residents support restrictive and demand-oriented on-street parking policies in the dense, highly urbanized neighborhood of Frankfurt-Bornheim, Germany (N = 1027). Surprisingly, despite some variations, the majority of the residents in our survey are in favor of the policy options suggested. Support for the demand-oriented policies (extension of bicycle infrastructure, improved sharing supply and mobility hubs, neighborhood garages, and improved public transit supply) is higher than the acceptance of the restrictive policies, and of policies that are a combination of restrictive and demand-oriented policies. However, surprisingly, a majority is still in favor of many of these (extension of parking fees and parking restrictions, and reuse of parking space for better livability). Furthermore, we classify residents who live in a household with private cars into the stage model of self-regulated behavior change to analyze their intention towards a reduction in private car use. Results from linear regression analyses indicate that residents who have intentions to change their behavior towards car use reduction assess the policy options more similarly to car-free households and regular bike users, and not like the other car-owning households. The findings suggest that while the residents support financial-related policies the least, they are more receptive towards parking policies than policy makers and planners assume if the reuse of parking lots creates space for other users or if it increases the quality of life, for instance, by adding bike lanes, wider sidewalks or greenery. Hence, a combination of restrictive and demand-oriented on-street parking policies results in high acceptance among residents, and the communication from municipalities regarding the implementation of the different policies needs to vary depending on the kind of household.
Three fungi associated with living leaves of plants are new records for Panama: Annellophora phoenicis causing leaf spots of Cocos nucifera (Arecaceae), Cercospora corniculatae (C. apii s. lat.) on living leaves of Oxalis barrelieri (Oxalidaceae) with and without discoloration, and Sclerotium coffeicola on zonate leaf spots of Annona montana (Annonaceae) and Dioscorea alata (Dioscoreaceae). Some records of A. phoenicis and S. coffeicola relevant for known geographical distribution and available by literature are critically revised.
The paper presents two case studies from Nigeria and Burkina Faso, that differ in many respects, but show also some significant similarities. In both cases, previously existing claims on land were not recognised by the national authorities who implemented development projects. But as a contrast, in the Nigerian case people had to move out of the territories that were now claimed by the state, whereas in the Burkina case people were brought into an area that was declared state property. As a result in both cases, this had specific implications for the inter-ethnic relations in the respective regions. In Nigeria, Kanuri farmers moved to new fertile areas that incidentally emerged parallel to the development efforts of the state.