Timing the warm absorber in NGC 4051

We investigated, using spectral-timing analysis, the characterization of highly ionized outflows in Seyfert galaxies, the so-called warm absorbers. Here, we present our results on the extensive ~ 600 ks of XMM-Newton archival observations of the bright and highly variable Seyfert 1 galaxy NGC 4051, whose spectrum has revealed a complex multicomponent wind. Making use of both RGS and EPIC-pn data, we performed a detailed analysis through a time-dependent photoionization code in combination with spectral and Fourier spectral-timing techniques. The source light curves and the warm absorber parameters obtained from the data were used to simulate the response of the gas due to variations in the ionizing flux of the central source. The resulting time variable spectra were employed to predict the effects of the warm absorber on the time lags and coherence of the energy dependent light curves. We have found that, in the absence of any other lag mechanisms, a warm absorber with the characteristics of the one observed in NGC 4051, is able to produce soft lags, up to 100 s, on timescales of ~ hours. The time delay is associated with the response of the gas to changes in the ionizing source, either by photoionization or radiative recombination, which is dependent on its density. The range of radial distances that, under our assumptions, yield longer time delays are comparable to the existing estimates of the location of the warm absorber in NGC 4051. For this reason, we suggest that it is likely that the observed X-ray time lags may carry a signature of the warm absorber response time, to changes in the ionizing continuum. These results highlight the importance of understanding the contribution of the warm absorber to the AGN X-ray time lags, since it is also vital information for interpreting the lags associated with propagation and reverberation effects in the inner emitting regions.Comment: 13 pages, 12 figures, Accepted for publication by A&

Phase Acquisition and Formationkeeping of a New Power Consumption Monitoring Satellite Constellation

A new satellite constellation proposed for global monitoring of electrical power consumption is described in the paper. The optimal small satellite constellation structure as well as its control accuracy required for serving the mission objective throughout the designed life span is examined. The orbital dynamics is analysed for the purposes of optimal phase acquisition and formationkeeping strategy design. A low-cost strategy for spreading all satellites onto their prescribed positions under both time and fuel consumption constraints is explained. The separation errors due to control system uncertainties are analysed, and the system requirements for the constellation phase acquisition are specified. A control strategy is investigated for keeping of the relative pattern of the constellation in spite of the perturbation effects from atmospheric drag and the potential harmonics of the non-spherical Earth, and fuel expenditure is minimised. The system feasibility is demonstrated via simulation results. The control system relies upon low-cost, practical flight-proven sensing and actuating systems for small satellite missions

A Pragmatic Master List of Action Verbs for Bloom's Taxonomy

Bloom's Taxonomy is an approach to organizing learning that was first published in 1956. It is ubiquitous in UK Higher Education (HE), where Universities use it as the basis for teaching and assessment; Learning Outcomes are created using suggested verbs for each tier of the taxonomy, and these are then “constructively aligned” to assessments. We conducted an analysis to determine whether there is consensus regarding the presentation of Bloom's Taxonomy across UK HE. Forty seven publicly available verb lists were collected from 35 universities and textbooks. There was very little agreement between these lists, most of which were not supported by evidence explaining where the verbs came from. We were able to construct a pragmatic “master list” of action verbs by using a simple majority consensus method. We were also able to construct a master list of commonly recommended “verbs to avoid.” These master lists should be useful for anyone tasked with using Bloom's Taxonomy to write Learning Outcomes for assessment. However, our findings raise broader questions about the evidence base which underpins a common approach to teaching and assessment in UK HE and education generally

Extensin network formation in Vitis vinifera callus cells is an essential and causal event in rapid and H2O2-induced reduction in primary cell wall hydration

<p>Abstract</p> <p>Background</p> <p>Extensin deposition is considered important for the correct assembly and biophysical properties of primary cell walls, with consequences to plant resistance to pathogens, tissue morphology, cell adhesion and extension growth. However, evidence for a direct and causal role for the extensin network formation in changes to cell wall properties has been lacking.</p> <p>Results</p> <p>Hydrogen peroxide treatment of grapevine (<it>Vitis vinifera </it>cv. Touriga) callus cell walls was seen to induce a marked reduction in their hydration and thickness. An analysis of matrix proteins demonstrated this occurs with the insolubilisation of an abundant protein, GvP1, which displays a primary structure and post-translational modifications typical of dicotyledon extensins. The hydration of callus cell walls free from saline-soluble proteins did not change in response to H₂O₂, but fully regained this capacity after addition of extensin-rich saline extracts. To assay the specific contribution of GvP1 cross-linking and other wall matrix proteins to the reduction in hydration, GvP1 levels in cell walls were manipulated <it>in vitro </it>by binding selected fractions of extracellular proteins and their effect on wall hydration during H₂O₂incubation assayed.</p> <p>Conclusions</p> <p>This approach allowed us to conclude that a peroxidase-mediated formation of a covalently linked network of GvP1 is essential and causal in the reduction of grapevine callus wall hydration in response to H₂O₂. Importantly, this approach also indicated that extensin network effects on hydration was only partially irreversible and remained sensitive to changes in matrix charge. We discuss this mechanism and the importance of these changes to primary wall properties in the light of extensin distribution in dicotyledons.</p

Negotiating polyvocal strategies:re-reading de Certeau through the lens of urban planning in South Africa

The Practice of Everyday Life (de Certeau M (1984) The Practice of Everyday Life. Berkeley, CA: University of California Press) has become a canonical text in urban studies, with de Certeau’s idea of tactics having been widely deployed to understand and theorise the everyday. Tactics of resistance were contrasted with the strategies of the powerful, but the ways in which these strategies are operationalised were left ambiguous by de Certeau and have remained undertheorised since. We address this lacuna through an examination of the planning profession in South Africa as a lieu propre– a strategic territory with considerable power to shape urban environments. Based on a large interview data set examining practitioner attitudes toward the state of the profession in South Africa, this paper argues that the strategies of the powerful are themselves subject to negotiation. We trace connections with de Certeau’s earlier work to critique the idea that strategies are univocal. We do this by examining how the interests of different powerful actors can come into conflict, using the planning profession as an exemplar of how opposing strategies must be mediated in order to secure changes in society

Public attitudes towards pricing policies to change health-related behaviours: a UK focus group study.

BACKGROUND: Evidence supports the use of pricing interventions in achieving healthier behaviour at population level. The public acceptability of this strategy continues to be debated throughout Europe, Australasia and USA. We examined public attitudes towards, and beliefs about the acceptability of pricing policies to change health-related behaviours in the UK. The study explores what underlies ideas of acceptability, and in particular those values and beliefs that potentially compete with the evidence presented by policy-makers. METHODS: Twelve focus group discussions were held in the London area using a common protocol with visual and textual stimuli. Over 300,000 words of verbatim transcript were inductively coded and analyzed, and themes extracted using a constant comparative method. RESULTS: Attitudes towards pricing policies to change three behaviours (smoking, and excessive consumption of alcohol and food) to improve health outcomes, were unfavourable and acceptability was low. Three sets of beliefs appeared to underpin these attitudes: (i) pricing makes no difference to behaviour; (ii) government raises prices to generate income, not to achieve healthier behaviour and (iii) government is not trustworthy. These beliefs were evident in discussions of all types of health-related behaviour. CONCLUSIONS: The low acceptability of pricing interventions to achieve healthier behaviours in populations was linked among these responders to a set of beliefs indicating low trust in government. Acceptability might be increased if evidence regarding effectiveness came from trusted sources seen as independent of government and was supported by public involvement and hypothecated taxation.The study was funded by the UK Department of Health Policy Research Programme (Policy Research Unit in Behaviour and Health [PR-UN-0409-10109]). The Department of Health had no role in the study design, data collection, analysis, or interpretation. The research was conducted independently of the funders, and the views expressed in this paper are those of the authors and not necessarily those of the Department of Health in England.This is the final version of the article. It was first available from Oxford University Press at http://dx.doi.org/10.1093/eurpub/ckv07