345 research outputs found
A new method for finding and characterizing galaxy groups via low-frequency radio surveys
We describe a new method for identifying and characterizing the thermodynamic state of large samples of evolved galaxy groups at high redshifts using high-resolution, low-frequency radio surveys, such as those that will be carried out with LOFAR and the Square Kilometre Array (SKA). We identify a sub-population of morphologically regular powerful (FRII) radio galaxies and demonstrate that, for this sub-population, the internal pressure of the radio lobes is a reliable tracer of the external intragroup/intracluster medium (ICM) pressure, and that the assumption of a universal pressure profile for relaxed groups enables the total mass and X-ray luminosity to be estimated. Using a sample of well-studied FRII radio galaxies, we demonstrate that our method enables the estimation of group/cluster X-ray luminosities over three orders of magnitude in luminosity to within a factor of âŒ2 from low-frequency radio properties alone. Our method could provide a powerful new tool for building samples of thousands of evolved galaxy groups at z > 1 and characterizing their ICM
A representative survey of the dynamics and energetics of FRII radio galaxies
We report the first large, systematic study of the dynamics and energetics of a representative sample of FanaroffâRiley type II (FR II) radio galaxies with well-characterized group/cluster environments. We used X-ray inverse-Compton and radio synchrotron measurements to determine the internal radio-lobe conditions, and these were compared with external pressures acting on the lobes, determined from measurements of the thermal X-ray emission of the group/cluster. Consistent with previous work, we found that FR II radio lobes are typically electron dominated by a small factor relative to equipartition, and are overpressured relative to the external medium in their outer parts. These results suggest that there is typically no energetically significant proton population in the lobes of FR II radio galaxies (unlike for FR Is), and so for this population, inverse-Compton modelling provides an accurate way of measuring total energy content and estimating jet power. We estimated the distribution of Mach numbers for the population of expanding radio lobes, finding that at least half of the radio galaxies are currently driving strong shocks into their group/cluster environments. Finally, we determined a jet powerâradio luminosity relation for FR II radio galaxies based on our estimates of lobe internal energy and Mach number. The slope and normalization of this relation are consistent with theoretical expectations, given the departure from equipartition and environmental distribution for our sample
Pre service primary teachersâ approaches to mathematical generalisation
In our teaching with primary pre-service teachers (PSTs), each of us includes generalising tasks in the context of mathematical reasoning. We set out to explore the value of such activity from the perspective of PSTs and their approaches to generalisation. In this paper, we focus on one PSTâs mathematical reasoning when working on the âflower bedsâ problem. We analyse the ways in which this PST attends to: looking for a relationship; seeing structure within a single figure in a sequence; and seeing sameness and difference between figures in a sequence. We consider what motivates shifts in attention, we reflect on the significance of studentsâ prior experience, and of student collaboration in our teaching sessions
Personality and hospitality management development
Ovaj rad istraĆŸuje i analizira doprinos osobnosti mjerama koje poduzima management prilikom funkcije u hotelijerstvu, i demonstrira zakljuÄak da se profili korisnika mogu objektivnije sagledati koriĆĄtenjem za to specifiÄnih instrumenata. Na temelju studija provedenih u MaÄarskoj i ÄeĆĄkoj Republici, profili studenata zadnje godine studija hotelijerstva, identificirani su usporeÄeni sa sadaĆĄnjim izvrĆĄiteljima takvih poslova. Analiza rezultata istraĆŸivanja pokazuje nerazumijevanje izmeÄu studenata / sadaĆĄnjeg managementa. ZakljuÄak predlaĆŸe da se obrazovni programi trebaju
modificirati kako bi studenti bili spremni za realne i relevantne potrebe u hotelijerstvu. Implementacija ovog istraĆŸivanja trebala bi rezultirati veÄim
zadovoljstvom studenata i njihovim aspiracijama prema odreÄenim smjernicama njihove karijere na viĆĄoj razini, a time bi se pravilno usmjerilo i
djelovanje managementa u hotelijerstvu.The research analyses the contribution of personality to the exercise of the management function within the hospitality industry, and demonstrates that the profiles of incumbents can be measured more objectively by the use of self-assessment instruments. On the basis of pilot studies in Hungary and the Czech Republic a the profiles of final year hospitality students were identified and were compared with current job incumbents. Analysis of the findings indicate a mis-match between student and management traits. The conclusions suggest that educational programmes should be modified if the student experience is to be made more realistic and relevant to the needs o f industry. Implementation of the research should result in improved satisfaction of students\u27 career aspirations and on a wider level, it could contribute significantly to management performance across the industry
The Paleocene of Antarctica: dinoflagellate cyst biostratigraphy, chronostratigraphy and implications for the palaeo-Pacific margin of Gondwana
The Paleocene (66â56 Ma) was a critical time interval for understanding recovery from mass extinction in high palaeolatitudes when global climate was warmer than today. A unique sedimentary succession from Seymour Island (Antarctic Peninsula) provides key reference material from this important phase of the early Cenozoic. Dinoflagellate cyst data from a 376 m thick stratigraphical section, including the CretaceousâPaleogene boundary, is correlated with biozones from New Zealand, the East Tasman Plateau and southeastern Australia. A detailed age model is suggested for the LĂłpez de Bertodano (LDBF) and Sobral (SF) formations based on dinoflagellate cyst biostratigraphy and U-Pb dating of zircons, supported by correlated magnetostratigraphy and strontium isotope values from macrofossils. The top of the LDBF is confirmed as latest Maastrichtian to earliest Danian (~ 66.2â65.65 Ma) in age. The overlying SF is mostly Danian in age, with an inferred hiatus near the top overlain by sediments dated as? late Thanetian. Rare Apectodinium homomorphum first appear in the uppermost SF; the first in situ record from Antarctica. The distribution of marine and terrestrial fossils from uppermost Cretaceous to Eocene sediments in Patagonia, Antarctica, New Zealand and Australia required both sea and land connections between these fragments of Gondwana. Fossil evidence and reconstructions of Antarctic palaeogeography and palaeotopography reveals evidence for persistent embayments in the proto-Weddell and Ross Sea regions at this time. We conclude that a coastal dispersal route along the palaeo-Pacific margin of Gondwana could explain the fossil distribution without requiring a transAntarctic strait or closely spaced archipelago. A region in the West to East Antarctic boundary zone, elevated until the early Paleogene, perhaps acted as a site for high elevation ice caps. This supports fossil, geochemical and sedimentological evidence for cold climate intervals and significant sea level falls during the Maastrichtian and Paleocene
Personal attributes associated with successful management in the hospitality industry - a pilot study in licensed retail operations
The research sought to identify key qualities associated with successful licensed retail managers, defined as effective, efficient and profitable operators. Through semi-structured in-depth interviews, managersâ views on success criteria, and problems associated with this type of employment, were elicited. The greatest assets were considered to be personal stability, mobility, good health and support from relatives/family. Physical and mental stamina, well-developed interpersonal skills, anticipation, vigilance and attention to detail were also cited. Prior academic attainment was not considered to be crucial to success; hard biodata from application forms did not allow successful managers to be identified.. The greatest problems in the job centred on people management. Reasons for choosing the job included variety, challenge, the need to be with, enjoyment from
talking to, entertaining, pleasing and developing others and delivering a service. Elements of emotional intelligence, including commitment and hardiness, were identified as primary success indicators
The early origin of the Antarctic Marine Fauna and its evolutionary implications
The extensive Late Cretaceous â Early Paleogene sedimentary succession of Seymour Island, N.E. Antarctic Peninsula offers an unparalleled opportunity to examine the evolutionary origins of a modern polar marine fauna. Some 38 modern Southern Ocean molluscan genera (26 gastropods and 12 bivalves), representing approximately 18% of the total modern benthic molluscan fauna, can now be traced back through at least part of this sequence. As noted elsewhere in the world, the balance of the molluscan fauna changes sharply across the Cretaceous â Paleogene (K/Pg) boundary, with gastropods subsequently becoming more diverse than bivalves. A major reason for this is a significant radiation of the Neogastropoda, which today forms one of the most diverse clades in the sea. Buccinoidea is the dominant neogastropod superfamily in both the Paleocene Sobral Formation (SF) (56% of neogastropod genera) and Early - Middle Eocene La Meseta Formation (LMF) (47%), with the Conoidea (25%) being prominent for the first time in the latter. This radiation of Neogastropoda is linked to a significant pulse of global warming that reached at least 65°S, and terminates abruptly in the upper LMF in an extinction event that most likely heralds the onset of global cooling. It is also possible that the marked Early Paleogene expansion of neogastropods in Antarctica is in part due to a global increase in rates of origination following the K/Pg mass extinction event. The radiation of this and other clades at ~65°S indicates that Antarctica was not necessarily an evolutionary refugium, or sink, in the Early â Middle Eocene. Evolutionary source â sink dynamics may have been significantly different between the Paleogene greenhouse and Neogene icehouse worlds
The role of stakeholder collaboration in culture-led urban regeneration: A case study of the Gwangju project, Korea
The preliminary stages of a large scale culture-led urban regeneration project initiated by the Korean government in Gwangju were studied. Stakeholdersâ perceptions of cultureâs contribution to urban regeneration and their views on collaborative partnerships were explored. Qualitative data were gathered via semi-structured interviews from 19 purposively selected stakeholders. This case study determined publicâprivate cooperation in regenerating Gwangju could, simultaneously, generate positive socio-cultural and economic impacts in society. However, stakeholders lacked opportunities for active participation. Hence, closer working relationships between centralâmunicipal government and publicâprivate/voluntary sectors were recommended. The case confirmed that long-term implementation of such projects needs to be anticipated and based on longitudinal and structured strategic planning to promote successful partnership collaborations amongst central/municipal governments, local communities and residents. This paper contributed to the knowledge gap in the area of stakeholder collaboration in building tourism/cultural systems by examining the micro-level interactions amongst stakeholders
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Regional climate impacts of a possible future grand solar minimum.
This is the final published version. It first appeared at http://www.nature.com/ncomms/2015/150623/ncomms8535/full/ncomms8535.html.Any reduction in global mean near-surface temperature due to a future decline in solar activity is likely to be a small fraction of projected anthropogenic warming. However, variability in ultraviolet solar irradiance is linked to modulation of the Arctic and North Atlantic Oscillations, suggesting the potential for larger regional surface climate effects. Here, we explore possible impacts through two experiments designed to bracket uncertainty in ultraviolet irradiance in a scenario in which future solar activity decreases to Maunder Minimum-like conditions by 2050. Both experiments show regional structure in the wintertime response, resembling the North Atlantic Oscillation, with enhanced relative cooling over northern Eurasia and the eastern United States. For a high-end decline in solar ultraviolet irradiance, the impact on winter northern European surface temperatures over the late twenty-first century could be a significant fraction of the difference in climate change between plausible AR5 scenarios of greenhouse gas concentrations.This work was supported by the Joint DECC/Defra Met Office Hadley Centre Climate
Programme (GA01101) and also by the EU project SPECS funded by the European
Commissionâs Seventh Framework Research Programme under the grant agreement
308378 (Met Office Hadley Centre authors), by the NERC National Centre for
Atmospheric Science (NCAS) Climate directorate (L.J.G. and A.C.M.), an ERC ACCI
grant (A.C.M) and an AXA Postdoctoral Fellowship (A.C.M.)
Predicting El Niño in 2014 and 2015.
Early in 2014 several forecast systems were suggesting a strong 1997/98-like El Niño event for the following northern hemisphere winter 2014/15. However the eventual outcome was a modest warming. In contrast, winter 2015/16 saw one of the strongest El Niño events on record. Here we assess the ability of two operational seasonal prediction systems to forecast these events, using the forecast ensembles to try to understand the reasons underlying the very different development and outcomes for these two years. We test three hypotheses. First we find that the continuation of neutral ENSO conditions in 2014 is associated with the maintenance of the observed cold southeast Pacific sea surface temperature anomaly; secondly that, in our forecasts at least, warm west equatorial Pacific sea surface temperature anomalies do not appear to hinder El Niño development; and finally that stronger westerly wind burst activity in 2015 compared to 2014 is a key difference between the two years. Interestingly, in these years at least, this interannual variability in wind burst activity is predictable. ECMWF System 4 tends to produce more westerly wind bursts than Met Office GloSea5 and this likely contributes to the larger SST anomalies predicted in this model in both years
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