20518 research outputs found
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Star formation scales and efficiency in Galactic spiral arms
No full textWe positionally match a sample of infrared-selected young stellar objects, identified by combining the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire, Wide-field Infrared Survey Explorer and Herschel Space Observatory Herschel infrared Galactic Plane Survey, to the dense clumps identified in the millimetre continuum by the Bolocam Galactic Plane Survey in two Galactic lines of sight centred towards l = 30° and 40°. We calculate the ratio of infrared luminosity, LIR, to the mass of the clump, Mclump, in a variety of Galactic environments and find it to be somewhat enhanced in spiral arms compared to the interarm regions when averaged over kiloparsec scales. We find no compelling evidence that these changes are due to the mechanical influence of the spiral arm on the star formation efficiency rather than, e.g. different gradients in the star formation rate due to patchy or intermittent star formation, or local variations that are not averaged out due to small source samples. The largest variation in LIR/Mclump is found in individual clump values, which follow a lognormal distribution and have a range of over three orders of magnitude. This spread is intrinsic as no dependence of LIR/Mclump with Mclump was found. No difference was found in the luminosity distribution of sources in the arm and interarm samples and a strong linear correlation was found between LIR and Mclump
Minimum Density Hyperplanes
No full textAssociating distinct groups of objects (clusters) with contiguous regions of high probability density (high-density clusters), is central to many statistical and machine learning approaches to the classification of unlabelled data. We propose a novel hyperplane classifier for clustering and semi-supervised classification which is motivated by this objective. The proposed minimum density hyperplane minimises the integral of the empirical probability density function along it, thereby avoiding intersection with high density clusters. We show that the minimum density and the maximum margin hyperplanes are asymptotically equivalent, thus linking this approach to maximum margin clustering and semi-supervised support vector classifiers. We propose a projection pursuit formulation of the associated optimisation problem which allows us to find minimum density hyperplanes efficiently in practice, and evaluate its performance on a range of benchmark datasets. The proposed approach is found to be very competitive with state of the art methods for clustering and semi-supervised classification
How do teachers’ articulate ‘effective’ with regard to leadership? An exploration of how contextual factors function and shape leadership within a primary school
No full textThis paper centres on exploring how do contextual factors function and shape leadership of Primary Schools. Methodologically the research is best described as ‘involved’ research and is informed by interpretavist principles, seeking to gain a deeper professional understanding. Social reality for the author is meaningfully understood by perceiving individuals as social actors, actors who are not always fully aware of the impact of the social stage on their actions. The social stage consists of the often implicit expectations of ‘communities of practice’. This research is interested in how individual actors’ interpretations of their actions are situated in such communities and where is their understanding about processes at play in the leadership they are experiencing
Cold-Water Mediates Greater Reductions in Limb Blood Flow than Whole Body Cryotherapy.
Get PDFPURPOSE: Cold-water immersion (CWI) and whole body cryotherapy (WBC) are widely used recovery methods in an attempt to limit exercise-induced muscle damage, soreness and functional deficits after strenuous exercise. The aim of this study was to compare the effects of ecologically-valid CWI and WBC protocols on post-exercise lower limb thermoregulatory, femoral artery and cutaneous blood flow responses. METHODS: Ten males completed a continuous cycle exercise protocol at 70% maximal oxygen uptake until a rectal temperature of 38°C was attained. Participants were then exposed to lower-body CWI (8°C) for 10 min, or WBC (-110°C) for 2 min, in a randomized cross-over design. Rectal and thigh skin, deep and superficial muscle temperatures, thigh and calf skin blood flow (laser Doppler flowmetry), superficial femoral artery blood flow (duplex ultrasound) and arterial blood pressure were measured prior to, and for 40 min post, cooling interventions. RESULTS: Greater reductions in thigh skin (CWI, -5.9±1.8°C; WBC, 0.2±0.5°C; P < 0.001) and superficial (CWI, -4.4±1.3°C; WBC, -1.8±1.1°C; P < 0.001) and deep (CWI, -2.9±0.8°C; WBC, -1.3±0.6°C; P < 0.001) muscle temperatures occurred immediately after CWI. Decreases in femoral artery conductance were greater after CWI (CWI, -84±11%; WBC, -59±21%, P < 0.02) and thigh (CWI, -80±5%; WBC, -59±14%, P < 0.001) and calf (CWI, -73±13%; WBC, -45±17%, P < 0.001) cutaneous vasoconstriction was greater following CWI. Reductions in rectal temperature were similar between conditions after cooling (CWI, -0.6±0.4°C; WBC, -0.6±0.3°C; P = 0.98). CONCLUSION: Greater reductions in blood flow and tissue temperature were observed after CWI in comparison to WBC. These novel findings have practical and clinical implications for the use of cooling in the recovery from exercise and injury
SDN-Based Channel Assignment Algorithm for Interference Management in Dense Wi-Fi Networks
No full textThe popularity of Wi-Fi-enabled devices alongside the growing demand for non-licensed spectrum, has made the Wi-Fi networks exceedingly congested. This endangers the efficiency of Wi-Fi and negatively affect the users' experience. The problem is especially pressing in dense areas (e.g. shopping centers) where Wi-Fi channel assignment is more likely to be uncoordinated and the working environment of Wi-Fi Access Points (APs) has become increasingly time-variant. As a result, the availability of Software-Defined Networking (SDN) and network virtualization technologies has motivated the use of centralized resource management as a solution. This paper provides an algorithm for channel assignment functionality in the context of SDN-based centralized resource management, which captures the live status of a Wi-Fi network and is capable of optimising the Radio Frequency (RF) channel assignment process. The APs' network arrangement, the current assignment of the channels and the characteristics of the RF channels in IEEE 802.11 have all been taken into account in the proposed model. The performance of the proposed model in terms of the level of the interference, the spectral efficiency at each AP and the Signal to Interference plus Noise Ratio (SINR) at the user-side is evaluated through simulation and compared against state of the art solutions
Developing a model for the application of post-occupancy evaluation (POE) as a facilities performance enhancement tool in the higher education sector
No full textPost-occupancy evaluation provides a mechanism for systematically evaluating facilities performance. However, the effectiveness of existing models within HE is subject to question with few institutions fully embracing its application. The research sought to establish the extent to which POE models are utilised and the degree to which they satisfy the needs of HE in England and Wales. The outcome of the work was to propose a POE model that addresses the needs of Higher Education institutions. The research found that development of POE models has been driven by numerous factors resulting in creation of sophisticated POE frame-works. However the extent to which they are considered effective is limited. Earlier work focuses on the identification of factors that influence user satisfaction and development of complex quantitative models. Users of such models seek to learn lessons from projects to improve the design and delivery of facilities and enhance their performance in use. However, the extent to which existing POE models facilitate this is subject to question. The study adopted a mixed methods approach to establish whether existing models reflected the factors influencing user satisfaction in the specific context of HE. It revealed that physical and internal environmental factors influenced user satisfaction in varying patterns with varying results in differing situations. The perception of quality consistently correlated with users' overall perceptions of satisfaction with buildings. The term 'quality' is a made up of several discrete factors; further work could be developed to allow these to be fully defined. The research concluded that a single POE model would be inappropriate and a frame-work is proposed based on a balanced scorecard, reflecting four performance dimensions tailored to the context of HE and allowing linkage of POE to strategic institutional plans. The project liberated contribution to theoretical knowledge and professional practice. It established that within HE the concept of a consistent set of factors correlating with overall satisfaction is flawed. It went further to identify the construct of 'quality' as a key factor influencing satisfaction and established user satisfaction is a construct that is time related. It also found that application of POE is inconsistent across the HE sector in terms of purpose and extent of connectivity to institutional objectives. These findings indicated that adoption of a standardised POE model within HE is unlikely to liberate consistent, useful data to enhance building and facilities performance. The adoption of the proposed approach offers a vehicle cost effective development of tailored POE solutions
A phenomenological investigation into the psychological transformation interpreted as 'Spiritual Awakening' : possible causes, characteristics, and after-effects
No full textRED SUPERGIANTS AS COSMIC ABUNDANCE PROBES: THE SCULPTOR GALAXY NGC 300
No full textWe present a quantitative spectroscopic study of 27 red supergiants (RSGs) in the Sculptor Galaxy NGC 300. J-band spectra were obtained using KMOS on the Very Large Telescope and studied with state of the art synthetic spectra including NLTE corrections for the strongest diagnostic lines. We report a central metallicity of [Z] = −0.03 ± 0.05 with a gradient of −0.083 ± 0.014 [dex/kpc], in agreement with previous studies of blue supergiants and H ii-region auroral line measurements. This result marks the first application of the J-band spectroscopic method to a population of individual RSG stars beyond the Local Group of galaxies and reveals the great potential of this technique
SUPERLUMINOUS SUPERNOVA SN 2015bn in the NEBULAR PHASE: EVIDENCE for the ENGINE-POWERED EXPLOSION of A STRIPPED MASSIVE STAR
No full text© 2016. The American Astronomical Society. All rights reserved.We present nebular-phase imaging and spectroscopy for the hydrogen-poor superluminous supernova (SLSN) SN 2015bn, at redshift z = 0.1136, spanning +250-400 days after maximum light. The light curve exhibits a steepening in the decline rate from 1.4 mag (100 days)-1 to 1.7 mag (100 days)-1, suggestive of a significant decrease in the opacity. This change is accompanied by a transition from a blue continuum superposed with photospheric absorption lines to a nebular spectrum dominated by emission lines of oxygen, calcium, and magnesium. There are no obvious signatures of circumstellar interaction or large 56Ni mass. We show that the spectrum at +400 days is virtually identical to a number of energetic SNe Ic such as SN 1997dq, SN 2012au, and SN 1998bw, indicating similar core conditions and strengthening the link between "hypernovae"/long gamma-ray bursts and SLSNe. A single explosion mechanism may unify these events that span absolute magnitudes of -22 < M B < -17. Both the light curve and spectrum of SN 2015bn are consistent with an engine-driven explosion ejecting 7-30 M o of oxygen-dominated ejecta (for reasonable choices in temperature and opacity). A strong and relatively narrow O i λ7774 line, seen in a number of these energetic events but not in normal supernovae, may point to an inner shell that is the signature of a central engine
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