343 research outputs found

    A new method for finding and characterizing galaxy groups via low-frequency radio surveys

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    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 ∌2 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

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    We report the first large, systematic study of the dynamics and energetics of a representative sample of Fanaroff–Riley 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 power–radio 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 teachers’ approaches to mathematical generalisation

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    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 PST’s mathematical reasoning when working on the ‘flower beds’ 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 students’ prior experience, and of student collaboration in our teaching sessions

    Personality and hospitality management development

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    Ovaj rad istraĆŸuje i analizira doprinos osobnosti mjerama koje poduzima management prilikom funkcije u hotelijerstvu, i demonstrira zaključak da se profili korisnika mogu objektivnije sagledati koriĆĄtenjem za to specifičnih instrumenata. Na temelju studija provedenih u Mađarskoj i ČeĆĄkoj Republici, profili studenata zadnje godine studija hotelijerstva, identificirani su uspoređeni sa sadaĆĄnjim izvrĆĄiteljima takvih poslova. Analiza rezultata istraĆŸivanja pokazuje nerazumijevanje između studenata / sadaĆĄnjeg managementa. Zaključak 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 većim zadovoljstvom studenata i njihovim aspiracijama prema određenim 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

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    The Paleocene (66–56 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 Cretaceous–Paleogene boundary, is correlated with biozones from New Zealand, the East Tasman Plateau and southeastern Australia. A detailed age model is suggested for the López 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 (~ 66.2–65.65 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

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    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, managers’ 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

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    The extensive Late Cretaceous – 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 – 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 – Middle Eocene. Evolutionary source – 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

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    The preliminary stages of a large scale culture-led urban regeneration project initiated by the Korean government in Gwangju were studied. Stakeholders’ perceptions of culture’s 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 public–private 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 central–municipal government and public–private/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

    Predicting El Niño in 2014 and 2015.

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    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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