1,061 research outputs found
Resilience markers for safer systems and organisations
If computer systems are to be designed to foster resilient
performance it is important to be able to identify contributors to resilience. The
emerging practice of Resilience Engineering has identified that people are still a
primary source of resilience, and that the design of distributed systems should
provide ways of helping people and organisations to cope with complexity.
Although resilience has been identified as a desired property, researchers and
practitioners do not have a clear understanding of what manifestations of
resilience look like. This paper discusses some examples of strategies that
people can adopt that improve the resilience of a system. Critically, analysis
reveals that the generation of these strategies is only possible if the system
facilitates them. As an example, this paper discusses practices, such as
reflection, that are known to encourage resilient behavior in people. Reflection
allows systems to better prepare for oncoming demands. We show that
contributors to the practice of reflection manifest themselves at different levels
of abstraction: from individual strategies to practices in, for example, control
room environments. The analysis of interaction at these levels enables resilient
properties of a system to be âseenâ, so that systems can be designed to explicitly
support them. We then present an analysis of resilience at an organisational
level within the nuclear domain. This highlights some of the challenges facing
the Resilience Engineering approach and the need for using a collective
language to articulate knowledge of resilient practices across domains
A Correlation Between Hard Gamma-ray Sources and Cosmic Voids Along the Line of Sight
We estimate the galaxy density along lines of sight to hard extragalactic
gamma-ray sources by correlating source positions on the sky with a void
catalog based on the Sloan Digital Sky Survey (SDSS). Extragalactic gamma-ray
sources that are detected at very high energy (VHE; E>100 GeV) or have been
highlighted as VHE-emitting candidates in the Fermi Large Area Telescope hard
source catalog (together referred to as "VHE-like" sources) are distributed
along underdense lines of sight at the 2.4 sigma level. There is also a less
suggestive correlation for the Fermi hard source population (1.7 sigma). A
correlation between 10-500 GeV flux and underdense fraction along the line of
sight for VHE-like and Fermi hard sources is found at 2.4 sigma and 2.6 sigma,
respectively. The preference for underdense sight lines is not displayed by
gamma-ray emitting galaxies within the second Fermi catalog, containing sources
detected above 100 MeV, or the SDSS DR7 quasar catalog. We investigate whether
this marginal correlation might be a result of lower extragalactic background
light (EBL) photon density within the underdense regions and find that, even in
the most extreme case of a entirely underdense sight line, the EBL photon
density is only 2% less than the nominal EBL density. Translating this into
gamma-ray attenuation along the line of sight for a highly attenuated source
with opacity tau(E,z) ~5, we estimate that the attentuation of gamma-rays
decreases no more than 10%. This decrease, although non-neglible, is unable to
account for the apparent hard source correlation with underdense lines of
sight.Comment: Accepted by MNRA
Observation of O+ 4P-4D0 lines in proton aurora over Svalbard
Spectra of a proton aurora event show lines of O+ 4P-4D0 multiplet (4639â4696 Ă
) enhanced relative to the N2 +1N(0,2) compared to normal electron aurora. Conjugate satellite particle measurements are used as input to electron and proton transport models, to show that p/H precipitation is the dominant source of both the O+ and N2 +1N emissions. The emission cross-section of the multiplet in p collisions with O and O2 estimated from published work does not explain the observed O+ brightness, suggesting a higher emission cross-section for low energy p impact on O
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ISO-LWS observations of IRAS16293-2422
We obtained LWS grating spectra toward IRAS 16293-2422 and the surrounding region, which covers the entire extent of the molecular outflow. The LWS spectra show that the region is relatively uncontaminated by PhotoDissociationRegion (PDR)-like emission, showing only a weak diffuse CII emission. The on-source spectrum revealed the presence of the OI(63Όm) line and several lines from CO, H2O and OH molecules. In this work we derive the macroscopic quantities associated with the UV-illuminated emitting gas which surrounds IRAS16293-2422 and compare it with previous studies. We show that the molecular lines originate in a hot (~1600 K), dense (~ 3·104cm-3) and extended (~ 8·1016cm) region, that we interprete as the shock of the wind impacting obliquely with the walls of the cavity created by the wind itself. The OI(63Όm) line observed by the Kuiper Airborne Observatory (KAO: Ceccarelli et al. 1997a) at ~ 1.2·1017cm west from the central source is hence interpreted as the head of the shock where the wind strikes the ambient gas. Finally we speculate that the OI(63Όm) line emission seen on-source originates in the collapsing envelope that surrounds the central object(s
James Huttonâs geological tours of Scotland : romanticism, literary strategies, and the scientific quest
This article explores a somewhat neglected part of the story of the emergence of geology as a science and discourse in the late eighteenth century â James Huttonâs posthumously published accounts of the geological tours of Scotland that he undertook in the years 1785 to 1788 in search of empirical evidence in support of his theory of the Earth and that he intended to include in the projected third volume of his Theory of the Earth of 1795. The article brings some of the assumptions and techniques of literary criticism to bear on Huttonâs scientific travel writing in order to open up new connections between geology, Romantic aesthetics and eighteenth-century travel writing about Scotland. Close analysis of Huttonâs accounts of his field trips to Glen Tilt, Galloway and Arran, supplemented by later accounts of the discoveries at Jedburgh and Siccar Point, reveals the interplay between desire, travel and the scientific quest and foregrounds the textual strategies that Hutton uses to persuade his readers that they share in the experience of geological discovery and interpretation as âvirtual witnessesâ. As well as allowing us to revisit the interrelation between scientific theory and discovery, this article concludes that Hutton was a much better writer than he has been given credit for and suggests that if these geological tours had been published in 1795 they would have made it impossible for critics to dismiss him as an armchair geologist
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Detection of [O I] 63 <i>Ό</i>m in absorption toward Sgr B2
A high signal-to-noise 52-90 ÎŒm spectrum is presented for the central part of the Sagittarius B2 complex. The data were obtained with the Long Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The [O I] 63 ÎŒm line is detected in absorption even at the grating spectral resolution of 0.29 ÎŒm. A lower limit for the column density of atomic oxygen of the order of 1019 cm-2 is derived. This implies that more than 40% of the interstellar oxygen must be in atomic form along the line of sight toward the Sgr B2 molecular cloud
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Resilient Health Care as the basis for teaching patient safety - A Safety-II critique of the World Health Organisation patient safety curriculum
Resilient Health Care (RHC) is predicated on the idea that health care systems constantly adjust to changing circumstances. RHC has become increasingly popular as a new way to improve patient safety, but to date there is no agreed way of using RHC as the basis for teaching patient safety. A key resource for patient safety educators is the World Health Organisation (WHO) patient safety curriculum, released ten years ago. However, it is well established that patient safety thinking in healthcare has been driven largely by Safety-I principles, and this is reflected in the WHO curriculum. The aim of this paper is to review and to provide a critique of the WHO patient safety curriculum from a Safety-II perspective, in order to assess to what extent RHC principles are already incorporated, and to identify areas where RHC might make contributions to the WHO curriculum. Based on this analysis, we argue that RHC thinking could be added in modular fashion to the WHO curriculum, but that in the future a broader curriculum should be developed that integrates RHC thinking throughout
Long Term outcomes of percutaneous atrial fibrillation ablation in patients with continuous monitoring
INTRODUCTION: There is limited data using continuous monitoring to assess outcomes of atrial fibrillation (AF) ablation. This study assessed long-term outcomes of AF ablation in patients with implantable cardiac devices. METHODS: 207 patients (mean age 68.1 ± 9.5, 50.3% men) undergoing ablation for symptomatic AF were followed up for a mean period of 924.5 ± 636.7 days. Techniques included The Pulmonary Vein Ablation Catheter (PVAC) (59.4%), cryoablation (17.4%), point by point (14.0%) and The Novel Irrigated Multipolar Radiofrequency Ablation Catheter (nMARQ) (9.2%). RESULTS: 130 (62.8%) patients had paroxysmal AF (PAF) and 77 (37.2%) persistent AF. First ablation and repeat ablation reduced AF burden significantly (relative risk 0.91, [95% CI 0.89 to 0.94]; P <0.0001 and 0.90, [95% CI, 0.86-0.94]; P <0.0001). Median AF burden in PAF patients reduced from 1.05% (interquartile range [IQR], 0.1%-8.70%) to 0.10% ([IQR], 0%-2.28%) at one year and this was maintained out to four-years. Persistent AF burden reduced from 99.9% ([IQR], 51.53%-100%) to 0.30% ([IQR], 0%-77.25%) at one year increasing to 87.3% ([IQR], 4.25%-100%) after four years. If a second ablation was required, point-by-point ablation achieved greater reduction in AF burden (relative risk, 0.77 [95% CI, 0.65-0.91]; P <0.01). CONCLUSION: Ablation reduces AF burden both acutely and in the long-term. If a second ablation was required the point-by-point technique achieved greater reductions in AF burden than "single-shot" technologies. Persistent AF burden increased to near pre ablation levels by year 4 suggesting a different mechanism from PAF patients where this increase did not occur
Shrub Communities, Spatial Patterns, and Shrub-Mediated Tree Mortality following Reintroduced Fire in Yosemite National Park, California, USA
Shrubs contribute to the forest fuel load; their distribution is important to tree mortality and regeneration, and vertebrate occupancy. We used a method new to fire ecologyâextensive continuous mapping of trees and shrub patches within a single large (25.6 ha) study siteâto identify changes in shrub area, biomass, and spatial pattern due to fire reintroduction by a backfire following a century of fire exclusion in lower montane forests of the Sierra Nevada, California, USA. We examined whether trees in close proximity to shrubs prior to fire experienced higher mortality rates than trees in areas without shrubs. We calculated shrub biomass using demography subplots and existing allometric equations, and we developed new equations for beaked hazel (Corylus cornuta ssp. californica [A. de Candolle] E. Murray) from full dissection of 50 stems. Fire decreased shrub patch area from 15.1 % to 0.9 %, reduced live shrub biomass from 3.49 Mg haâ1 to 0.27 Mg haâ1, and consumed 4.41 Mg haâ1 of living and dead shrubs. Distinct (non-overlapping) shrub patches decreased from 47 haâ1 to 6 haâ1. The mean distance between shrub patches increased 135 %. Distances between montane chaparral patches increased 285 %, compared to a 54 % increase in distances between riparian shrub patches and an increase of 267 % between generalist shrub patches. Fire-related tree mortality within shrub patches was marginally lower (67.6 % versus 71.8 %), showing a contrasting effect of shrubs on tree mortality between this forest ecosystem and chaparral-dominated ecosystems in which most trees are killed by fire
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