Spontaneous emission of an atom near an oscillating mirror

We investigate the spontaneous emission of one atom placed near an oscillating reflecting plate. We consider the atom modeled as a two-level system, interacting with the quantum electromagnetic field in the vacuum state, in the presence of the oscillating mirror. We suppose that the plate oscillates adiabatically, so that the time-dependence of the interaction Hamiltonian is entirely enclosed in the time-dependent mode functions, satisfying the boundary conditions at the plate surface, at any given time. Using time-dependent perturbation theory, we evaluate the transition rate to the ground-state of the atom, and show that it depends on the time-dependent atom-plate distance. We also show that the presence of the oscillating mirror significantly affects the physical features of the spontaneous emission of the atom, in particular the spectrum of the emitted radiation. Specifically, we find the appearance of two symmetric lateral peaks in the spectrum, not present in the case of a static mirror, due to the modulated environment. The two lateral peaks are separated from the central peak by the modulation frequency, and we discuss the possibility to observe them with actual experimental techniques of dynamical mirrors and atomic trapping. Our results indicate that a dynamical (i.e., time-modulated) environment can give new possibilities to control and manipulate also other radiative processes of two or more atoms or molecules nearby, for example their cooperative decay or the resonant energy transfer

‘Where’s the trick?’: Practices of commoning across a reclaimed shop front

Occupation-based urban practices such as squatted social centres have long been associated with political processes of resistance to capitalist dynamics and with the constitution of prefigurative alternative urban relations (Vasudevan, 2011; 2015). The spatial appropriation of disused buildings and their transformation into spaces of public and collective use have been studied in the context of the radical political landscape of ‘autonomous geographies’ in cities across Europe (Montagna, 2006; Ruggiero, 2000; Squatting Europe Kollective, 2013) and in the UK (Hodkinson and Chatterton, 2006). While autonomous urban spaces are at times imagined and represented as ‘liberated enclaves surrounded by a hostile capitalist environment’ (Stavrides, 2014, p. 547), equating autonomy to distinct spaces ‘defined by their exteriority to the rest of the city-society’ (ibid.), authors concerned with the transformative power of reclaimed urban spaces as ‘urban commons’ (Eizenberg, 2012; Newman, 2013) have increasingly paid attention to the politics of interaction of those spaces and practices with the wider city (Stavrides, 2014)

Public-cooperative policy mechanisms for housing commons

Cooperative housing is experiencing a resurgence of interest worldwide. As a more democratic and affordable alternative to dominant housing provision, it is often heralded as a blueprint for ‘housing commons’. Despite its long history, however, cooperative housing has rarely gone beyond a ‘niche’ in the housing market. Recent critical housing scholarship is beginning to address this marginalisation and understand how a more widespread development of the sector can be supported. In times and places where cooperative housing has expanded beyond a ‘niche’ solution, the role of the state, through policy making at national, regional and municipal scale, stands out as an important enabling factor. Drawing on ten international cases, this study presents a framework for a rigorous and politically meaningful comparative approach to public-cooperative policy mechanisms for ‘housing commons’. Three key phases in the housing process (production, access and management, and maintenance of the model in time) are identified and discussed through concrete examples of policy areas and mechanisms. The article contributes to scholarship on cooperative housing policy making and ‘housing commons’ and argues for a shift in attention to questions of accessibility over time, and the thorny issue of permanent decommodification

Passion without Objects. Young Graduates and the Politics of Temporary Art Spaces

This paper addresses the position of young arts graduates seeking to respond to the unequal access and precarity of jobs in the cultural sector by establishing artist-led temporary spaces. With the increasing dissemination of the discourse of pop-up urban uses in the United Kingdom since 2008, former genealogies of autonomous self-organised spaces intersect with the urban agendas of public commissioners and private actors. Following a long-established critique of the “creative industries” and recent studies of working conditions in the sector, this paper brings together critical textual analysis of specialized press and policy documents and a series of in-depth interviews with a young arts graduate collective involved in setting up a pop-up space in London. Our research shows how in the context of low-budget public commissions in affluent areas of central London artists are encouraged to translate their passion for autonomous, self-organised practice into dominant discourses of artistic “community provision” and place marketing

Phylogenetic networks: A tool to display character conflict and demographic history

Evolutionary trees have the assumption that evolution and phylogeny can be represented in a strictly bifurcating manner. Firmly speaking, from one ancestral taxon, two descendant taxa emerge. Nevertheless, hybridization, recombination and horizontal gene transfer is in conflict with this straightforward concept. In such cases, evolutionary lines do not only separate from each other, but have the possibility of melting again and are called reticulations. Consequently, networks can represent evolutionary events more realistically than phylogenetic trees. Networks can display alternative topologies and co-existence of ancestors and descendants, which are otherwise not obvious when a comparison is done on several single trees or a consensus tree. Therefore, networks have the ability to visualize the conflicting information in a given data set. Moreover, the distribution, frequencies and arrangement of haplotypes in populations can reveal the phylogenetic histories of the taxa, regarding predictions from the coalescent theory. This review aims to: (1) give a brief comparison between phylogenetic trees and networks, (2) provide the overall concept of the coalescent theory, (3) clarify how phylogenetic networks can be used to display conflict data and evaluate phylogenetic histories, and (4) offer a useful starting point and guide for sequence analysis, with the aim to discover population dynamics.Key words: Phylogenetic networks, reticulation, coalescent theory, population history, character conflict

Confronto fra valutazioni del run-up fatte con un modello matematico e una formula empirica con misure di campo

La posizione planimetrica della linea di riva, soli tamente, viene determinata attraverso l\u2019uso di immagini aeree ed utilizzata pe r la ricostruzione dell\u2019evoluzione storica dei litorali. Tuttavia, le informazioni est ratte da tali immagini, descrivendo il confine istantaneo acqua-terra, consentono l\u2019indivi duazione della linea di riva esclusivamente come limite asciutto-bagnato proprio nel momento della ripresa. Per una pi\uf9 corretta localizzazione della linea di riva , \ue8 quindi necessario quantificare, oltre agli effetti di marea e di trasporto solido, gli effetti prodotti dal moto ondoso su tale posizione e in particolare il cosiddetto ru n-up. Nel presente lavoro si studia il run-up in una spia ggia naturale a debole pendenza ricadente nella Sicilia occidentale. Lo studio geom orfologico del sito precede lo studio idraulico, che partendo dalle misure di onde al largo, attraverso la loro trasposizione e la propagazione simulata con un mod ello matematico, porta alla stima delle onde sotto costa. Queste ultime sono ut ilizzate per valutare il run-up sia mediante una nota formula empirica sia utilizzando un modello numerico alla Boussinesq con una nuova condizione al contorno per la linea di riva. Il confronto dei risultati con le misure di campo mostra che i r isultati migliori si ottengono con la formula empirica, nella quale \ue8 tuttavia necessa rio calibrare i coefficienti con misure in situ

Aerobic growth of Rhodococcus aetherivorans BCP1 using selected naphthenic acids as the sole carbon and energy sources

Naphthenic acids (NAs) are an important group of toxic organic compounds naturally occurring in hydrocarbon deposits. This work shows that Rhodococcus aetherivorans BCP1 cells not only utilize a mixture of eight different NAs (8XNAs) for growth but they are also capable of marked degradation of two model NAs, cyclohexanecarboxylic acid (CHCA) and cyclopentanecarboxylic acid (CPCA) when supplied at concentrations from 50 to 500 mgL-1. The growth curves of BCP1 on 8XNAs, CHCA, and CPCA showed an initial lag phase not present in growth on glucose, which presumably was related to the toxic effects of NAs on the cell membrane permeability. BCP1 cell adaptation responses that allowed survival on NAs included changes in cell morphology, production of intracellular bodies and changes in fatty acid composition. Transmission electron microscopy (TEM) analysis of BCP1 cells grown on CHCA or CPCA showed a slight reduction in the cell size, the production of EPS-like material and intracellular electron-transparent and electron-dense inclusion bodies. The electron-transparent inclusions increased in the amount and size in NA-grown BCP1 cells under nitrogen limiting conditions and contained storage lipids as suggested by cell staining with the lipophilic Nile Blue A dye. Lipidomic analyses revealed significant changes with increases of methyl-branched (MBFA) and polyunsaturated fatty acids (PUFA) examining the fatty acid composition of NAs-growing BCP1 cells. PUFA biosynthesis is not usual in bacteria and, together with MBFA, can influence structural and functional processes with resulting effects on cell vitality. Finally, through the use of RT (Reverse Transcription)-qPCR, a gene cluster (chcpca) was found to be transcriptionally induced during the growth on CHCA and CPCA. Based on the expression and bioinformatics results, the predicted products of the chcpca gene cluster are proposed to be involved in aerobic NA degradation in R. aetherivorans BCP1. This study provides first insights into the genetic and metabolic mechanisms allowing a Rhodococcus strain to aerobically degrade NAs

Toward a feminist housing commons? Conceptualising care - (as) - work in collaborative housing

This article conceptualizes care-(as)-work in collaborative housing and addresses current debates on the potential of cohousing to embody a feminist commons. A focus on purpose-built cohousing projects in the UK enables us to focus on the values present in the initial phases of collective design and on the ongoing negotiations and mediation that take place through social interactions, resident-led self-management, and formal and informal mutual support. Our analysis is based on in-depth interviews and focus group discussions with two communities in England. Our contribution focuses on two aspects of care-(as)-work: how difficult emotions related to cohousing maintenance work are minimized for the good of the common and how such work is differentially embodied. Returning to cohousing’s transformational capacities as a feminist commons, we show that while boundaries of care in commoning are critical to residents, they are inherently blurry, performative and gendered