19,934 research outputs found
The habitability of the Universe through 13 billion years of cosmic time
The field of astrobiology has made tremendous progress in modelling
galactic-scale habitable zones which offer a stable environment for life to
form and evolve in complexity. Recently, this idea has been extended to
cosmological scales by studies modelling the habitability of the local Universe
in its entirety (e.g. Dayal et al. 2015; Li & Zhang 2015). However, all of
these studies have solely focused on estimating the potentially detrimental
effects of either Type II supernovae (SNII) or Gamma Ray Bursts (GRBs),
ignoring the contributions from Type Ia supernovae (SNIa) and active galactic
nuclei (AGN). In this study we follow two different approaches, based on (i)
the amplitude of deleterious radiation and (ii) the total planet-hosting volume
irradiated by deleterious radiation. We simultaneously track the contributions
from the key astrophysical sources (SNII, SNIa, AGN and GRBs) for the entire
Universe, for both scenarios, to determine its habitability through 13.8
billion years of cosmic time. We find that SNII dominate the total radiation
budget and the volume irradiated by deleterious radiation at any cosmic epoch
closely followed by SNIa (that contribute half as much as SNII), with GRBs and
AGN making up a negligible portion (<1%). Secondly, as a result of the total
mass in stars (or the total number of planets) slowly building-up with time and
the total deleterious radiation density, and volume affected, falling-off after
the first 3 billion years, we find that the Universe has steadily increased in
habitability through cosmic time. We find that, depending on the exact model
assumptions, the Universe is 2.5 to 20 times more habitable today compared to
when life first appeared on the Earth 4 billion years ago. We find that this
increase in habitability will persist until the final stars die out over the
next hundreds of billions of years.Comment: Under refereeing in Ap
Economic and Social Models in Europe and the Importance of Reform
This paper contributes to the ongoing debate on European economic and social models. It provides a comparative assessment of fiscal and regulatory policies in 17 industrialised countries (the EU15, US and Japan) and presents the records of these countries in attaining key economic and social objectives. Social and economic systems that feature efficient public sectors and flexible market structures tend to experience reasonably sustainable public finances, high economic growth, education standards and employment, and well-functioning markets. Anglo-Saxon countries broadly fit this mould, albeit, seemingly, at some cost of income equality. A more pronounced emphasis on welfare state policies and the corresponding relatively high levels of public spending bring benefit to income distribution in the Nordic countries while the resulting inefficiencies in their economies are counterbalanced by flexibility in labour and particularly product markets. Also, a number of reform-minded European countries have improved their fiscal and regulatory policies while significantly enhancing the functioning of markets, fiscal sustainability and economic performance. This was generally attained without jeopardising social objectives. On the other hand, those continental and Mediterranean countries that maintain market inefficiencies and at the same time sustain expensive and inefficient welfare states generally suffer from low growth and employment and less well-functioning markets and face serious risks to their economies’ fiscal sustainability. The findings of this note support calls for the comprehensive reform of fiscal policies, as well as of product and labour markets.fiscal policy, regulation, Nordic model, welfare state, efficiency, reform
Antonovsky Bütünlük Duygusu Ölçeği ve Hemşirelik Araştırmalarında Kullanımının Sistematik İncelemesi: Ruh Sağlığı ve Psikiyatri Hemşireliği Açısından Anlamlar
Text in English and TurkishObjectives: Antonovsky’s salugenetic model focuses on factors that
promote health and well-being. The objectives of this paper were to
review the existing research literature related to Antonovsky’s Sense
of Coherence Scale (SOC) and establish implications for psychiatric
and mental health nurses.
Methods: Electronic databases were searched with selected studies
compared for sample, sample size, study designs and basic results.
Cross-sectional studies were reviewed for correlations between personality
traits, stress, burnout, disease-scales, job satisfaction and
the SOC scale, with Intervention studies used to establish the impact
of training on the SOC.
Results: The review discovered serious methodological difficulties,
including interpretations of Antonovsky’s philosophical values and
the apparent use of the SOC scales as a measure of disease absence.
Conclusion: The review was able to draw important conclusions for
psychiatric and mental health nurses (PMHNs) related to stress, burnout,
dealing with psychiatric emergencies and the selection of new
recruits to the profession.peer-reviewe
Star Formation in the Circumnuclear Environment of NGC1068
We present near-infrared emission line images of the circumnuclear ring in
NGC1068. We have measured the Br_gamma fluxes in a number of star forming
complexes and derived extinctions for each of these by comparison with H_alpha.
We investigate the star forming histories of these regions and find that a
short burst of star formation occured co-evally throughout the ring within the
last 30-40 Myr, and perhaps as recently as 4-7 Myr ago. The 1-0 S(1) flux and
S(1)/Br_gamma ratios indicate that as well as fluorescence, shock excited H_2
emission contributes to the total flux. There is excess H_2 flux to the
North-West where the ionisation cone crosses the ring, and we have shown it is
possible that the non-stellar continuum from the Seyfert nucleus which produces
the high excitation lines could also be causing fluorescence at the edges of
molecular clouds in the ring. The nuclear 1-0 S(1) is more extended than
previously realised but only along the bar's major axis, and we consider
mechanisms for its excitation.Comment: 10 pages, 4 figures, LaTeX (mn.sty & psfig.sty). Accepted for
publication in MNRA
Galactic exploration by directed Self-Replicating Probes, and its implications for the Fermi paradox
This paper proposes a long term scheme for robotic exploration of the
galaxy,and then considers the implications in terms of the `Fermi paradox' and
our search for ETI. We discuss the parameter space of the `galactic ecology' of
civilizations in terms of the parameters T (time between ET civilizations
arising) and L, the lifetime of these civilizations. Six different regions are
described.Comment: 1 figur
Assembler to C migration using the FermaT transformation system
The FermaT transformation system, based on research carried out over the last twelve years at Durham University and Software Migrations Ltd., is an industrial-strength formal transformation engine with many applications in program comprehension and language migration. This paper describes one application of the system: the migration of IBM 370 Assembler code to equivalent, maintainable C code. We present an example of using the tool to migrate a small, but complex, assembler module to C with no manual intervention required. We briefly discuss a mass migration exercise where 1,925 assembler modules were successfully migrated to C code
A chemoenzymatic route to the (+)-form of the amaryllidaceae alkaloid narseronine
The enzymatically derived and enantiopure cis-1,2-dihydrocatechol 1 has been converted, over 14 one-pot operations, into the (+)-form of the alkaloid narseronine (2). The present study, which complements earlier work that established a route from metabolite 1 to enantiomer (–)-2, involves an N-bromosuccinimide/tri-n-butyltin hydride-mediated cyclisation reaction to construct the unsaturated B-ring lactone of the target compound.We thank the Australian Research Council and the Institute of Advanced Studies for generous financial support
Utilizing Ground-Based LIDAR Measurements to Aid Autonomous Airdrop Systems
Uncertainty in atmospheric winds represents one of the primary sources of landing error in airdrop systems. In this work, a ground-based LIDAR system samples the wind field at discrete points above the target and transmits real-time data to approaching autonomous airdrop systems. In simulation and experimentation, the inclusion of a light detection and ranging (LIDAR) system showed a maximum of 40% improvement over unaided autonomous airdrop systems. Wind information nearest ground level has the largest impact on improving accuracy
Extended Gas in Seyfert Galaxies: Near Infrared Observations of NGC 2110 and Circinus
We present results of near--IR long-slit spectroscopy in the J and K bands of
the Seyfert 2 galaxies NGC 2110 and Circinus, investigating the gaseous
distribution, excitation, reddening and kinematics. In NGC 2110, the emission
line ratio [FeII]/Pa beta increases towards the nucleus (to ~ 7). The nuclear
[Fe II]1.257 (microns) and Pa beta lines are broader (FWHM ~ 500 km/s) than the
H2 (2.121) line (FWHM ~ 300 km/s). Both these results suggest that shocks,
driven by the radio jet, are an important source of excitation of [Fe II]. The
H2 excitation appears to be dominated by X-rays from the nucleus. In Circinus,
both [FeII]/Pa beta and H2/Br gamma decrease from ~ 2 at 4 arcsec from the
nucleus to nuclear values of ~ 0.6 and ~ 1, respectively, suggesting that the
starburst dominates the nuclear excitation, while the AGN dominates the
excitation further out (r > 2 arcsec). For both galaxies, the gaseous
kinematics are consistent with circular rotation in the plane of the disk. Our
rotation curves suggest that the nucleus (identified with the peak of the IR
continuum) is displaced from the kinematic centre of the galaxies. This effect
has been observed previously in NGC 2110 based on the kinematics of optical
emission lines, but the displacement is smaller in the infrared, suggesting the
effect is related to obscuration. The continuum J-K colours of the nuclear
region indicate a red stellar population in NGC 2110 and a reddened young
stellar population in Circinus. Right at the nucleus of both galaxies, the
colours are redder, apparently a result of hot dust emission from the inner
edge of a circumnuclear torus.Comment: 11 pages, 14 figures, accepted for publication in MNRA
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