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Search Results: 1 - 10 of 32524 matches for " John Stott "
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Orientation and disorientation in aviation
John Richard Rollin Stott
Extreme Physiology & Medicine , 2013, DOI: 10.1186/2046-7648-2-2
Abstract: A sense of orientation is a fundamental requirement for all free-living creatures. The fact that it is a largely unconscious activity, like breathing, is some evidence of its physiological importance to everyday activities and even survival. The term orientation implies an awareness of self in relation to objects in one’s surroundings, either in the immediate environment or more remotely as a sense of geographic location. There is also an important sense of orientation within the body, namely proprioception. In flight, orientation refers more specifically to an awareness of the attitude and spatial position of the aircraft relative to the external frame of reference provided by the flat surface of the earth and the gravitational vertical. A pilot's sense of orientation cannot afford to be the unconscious activity that it is on the ground; he/she needs at all times to maintain an awareness of what the aircraft is doing.The flight environment generates a number of hazards that relate to human physiology. For example, hypoxia at altitude and loss of consciousness during high G manoeuvres may have fatal consequences. The disorientating environment of flight may be less physiologically stressful, but the psychological stress of task saturation and the distraction of an in-flight emergency are important causes of accidents attributable to disorientation, a disproportionate number of which are fatal.Why do pilots become disorientated? Many authors, in attempting to give a concise answer to this question, have fallen back on the statement that humans did not evolve to fly and that their sensory systems, in particular the vestibular system, are not adapted to the flight environment. The implication is that if only this system were a more perfect inertial navigation system, then flight without external visual reference would be less prone to orientation error. The problem with this explanation is that creatures that did evolve to fly share the same sensory systems, and in all
Neither Genius nor Fudge: Edgar Allan Poe and Eureka
Stott, G. St. John
452o F : Revista de Teoría de la Literatura y Literatura Comparada , 2009,
Abstract: "Eureka" (1848) has been taken at face value as an expanded version of a lecture on cosmology that Poe gave earlier the same year. However, its seriousness as a work of science should be questioned. Its treatment of themes found in other works by Poe shows the author’s unconcern for consistency, and the text unlikely to have resulted from a serious engagement with scientific argument. Instead it should be approached as a hoax: an attempt to reveal the gullibility of its readers. Poe’s hoaxes relied for their effect on the trust created in readers by their recognition of generic conventions, and Eureka exploited and ridiculed public trust in cosmological lecturers such as John Bovee Dods.
Crowdedness Mediates the Effect of Social Identification on Positive Emotion in a Crowd: A Survey of Two Crowd Events
David Novelli, John Drury, Stephen Reicher, Clifford Stott
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0078983
Abstract: Exposure to crowding is said to be aversive, yet people also seek out and enjoy crowded situations. We surveyed participants at two crowd events to test the prediction of self-categorization theory that variable emotional responses to crowding are a function of social identification with the crowd. In data collected from participants who attended a crowded outdoor music event (n = 48), identification with the crowd predicted feeling less crowded; and there was an indirect effect of identification with the crowd on positive emotion through feeling less crowded. Identification with the crowd also moderated the relation between feeling less crowded and positive emotion. In data collected at a demonstration march (n = 112), identification with the crowd predicted central (most dense) location in the crowd; and there was an indirect effect of identification with the crowd on positive emotion through central location in the crowd. Positive emotion in the crowd also increased over the duration of the crowd event. These findings are in line with the predictions of self-categorization theory. They are inconsistent with approaches that suggest that crowding is inherently aversive; and they cannot easily be explained through the concept of ‘personal space’.
The Ratio of Luminous to Faint Red Sequence Galaxies in X-Ray and Optically Selected Low-Redshift Clusters
Diego Capozzi,Chris A. Collins,John P. Stott
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.16220.x
Abstract: We study the ratio of luminous-to-faint red sequence galaxies in both optically and X-ray selected galaxy clusters in the poorly studied redshift range 0.05< z<0.19. The X-ray selected sample consists of 112 clusters based on the ROSAT All-Sky Survey, while the optical sample consists of 266 clusters from the Sloan Digital Sky Survey. Our results are consistent with the presence of a trend in luminous-to-faint ratio with redshift, confirming that downsizing is continuous from high to low redshift. After correcting for the variations with redshift using a partial Spearman analysis, we find no significant relationship between luminous-to-faint ratio and X-ray luminosity of the host cluster sample, in contrast to recent suggestions. Finally, we investigate the stacked colour-magnitude relations of these samples finding no significant differences between the slopes for optically and X-ray selected clusters. The colour-magnitude slopes are consistent with the values obtained in similar studies, but not with predictions of theoretical models.
The Evolution of K* and the Halo Occupation Distribution since z=1.5: Observations vs. Simulations
Diego Capozzi,Chris A. Collins,John P. Stott,Matt Hilton
Physics , 2011, DOI: 10.1111/j.1365-2966.2011.19895.x
Abstract: We study the evolution of the K-band luminosity function (LF) and the Halo Occupation Distribution (HOD) using Subaru observations of 15 X-ray clusters at z=0.8-1.5 and compare the results with mock clusters (01 rich clusters. However, we cannot distinguish between this model and a simple stellar population synthesis model invoking passive evolution with a formation redshift z~5 - consistent with the presence of an old red galaxy population ubiquitous in rich clusters at z=1.5. We also see a small difference (\Delta K*~0.5) between our clusters and studies of the field population at similar redshifts, suggesting only a weak dependence of the luminous (L>L*) part of the LF on environment. Turning to our HOD study, we find that within R_{500}, high-z clusters tend to host smaller numbers of galaxies to a magnitude K*+2 compared to their low-z counterparts. This behavior is also seen in the mock samples and is relatively insensitive to the average mass of the cluster haloes. In particular, we find significant correlations of the observed number of member cluster galaxies (N) with both z and cluster mass: $N(M,z)=(53\pm1)(1+z)^{-0.61^{+0.18}_{-0.20}}(M/10^{14.3})^{0.86\pm0.05}$. Finally, we examine the spatial distribution of galaxies and provide a new estimate of the concentration parameter for clusters at high z ($c_{g}=2.8^{+1.0}_{-0.8}$). Our result is consistent with predictions from both our SAM mock clusters and literature's predictions for dark matter haloes. The mock sample predictions rise slowly with decreasing redshift reaching $c_{g}=6.3^{+0.39}_{-0.36}$ at z=0.
Measurement of the intracluster light at z ~ 1
Claire Burke,Chris A. Collins,John P. Stott,Matt Hilton
Physics , 2012, DOI: 10.1111/j.1365-2966.2012.21555.x
Abstract: A significant fraction of the total photospheric light in nearby galaxy clusters is thought to be contained within the diffuse intracluster light (ICL), which extends 100s of kpc from cluster cores. The study of the ICL can reveal details of the evolutionary histories and processes occurring within galaxy clusters, however since it has a very low surface brightness it is often difficult to detect. We present here the first measurements of the ICL as a fraction of total cluster light at z \sim 1 using deep J-band (1.2 {\mu}m) imaging from HAWK-I on the VLT. We investigate the ICL in 6 X-ray selected galaxy clusters at 0.8< z <1.2 and find that the ICL below isophotes {\mu}(J) = 22 mag/arcsec2 constitutes 1-4% of the total cluster light within a radius R500. This is broadly consistent with simulations of the ICL at a similar redshift and when compared to nearby observations suggests that the fraction of the total cluster light that is in the ICL has increased by a factor 2 - 4 since z\sim1. We also find the fraction of the total cluster light contained within the Brightest Cluster Galaxy (BCG) to be 2.0-6.3% at these redshifts, which in 5 out of 6 cases is larger than the fraction of the ICL component, in contrast to results from nearby clusters. This suggests that the evolution in cluster cores involves substantial stripping activity at late times, in addition to the early build up of the BCG stellar mass through merging. The presence of significant amounts of stellar light at large radii from these BCGs may help towards solving the recent disagreement between the semi-analytic model predictions of BCG mass growth (e.g. De Lucia & Blaziot, 2007) and the observed large masses and scale sizes reported for BCGs at high redshift.
Evolution in cluster cores since z~1
Claire Burke,Chris Collins,John Stott,Matt Hilton
Physics , 2012, DOI: 10.1017/S1743921313004602
Abstract: A large fraction of the stellar mass in galaxy clusters is thought to be contained in the diffuse low surface brightness intracluster light (ICL). Being bound to the gravitational potential of the cluster rather than any individual galaxy, the ICL contains much information about the evolution of its host cluster and the interactions between the galaxies within. However due its low surface brightness it is notoriously difficult to study. We present the first detection and measurement of the flux contained in the ICL at z~1. We find that the fraction of the total cluster light contained in the ICL may have increased by factors of 2-4 since z~1, in contrast to recent findings for the lack of mass and scale size evolution found for brightest cluster galaxies. Our results suggest that late time buildup in cluster cores may occur more through stripping than merging and we discuss the implications of our results for hierarchical simulations.
Mitosis Gives a Brief Window of Opportunity for a Change in Gene Transcription
Richard P. Halley-Stott,Jerome Jullien,Vincent Pasque,John Gurdon
PLOS Biology , 2014, DOI: 10.1371/journal.pbio.1001914
Abstract: Cell differentiation is remarkably stable but can be reversed by somatic cell nuclear transfer, cell fusion, and iPS. Nuclear transfer to amphibian oocytes provides a special opportunity to test transcriptional reprogramming without cell division. We show here that, after nuclear transfer to amphibian oocytes, mitotic chromatin is reprogrammed up to 100 times faster than interphase nuclei. We find that, as cells traverse mitosis, their genes pass through a temporary phase of unusually high responsiveness to oocyte reprogramming factors (mitotic advantage). Mitotic advantage is not explained by nuclear penetration, DNA modifications, histone acetylation, phosphorylation, methylation, nor by salt soluble chromosomal proteins. Our results suggest that histone H2A deubiquitination may account, at least in part, for the acquisition of mitotic advantage. They support the general principle that a temporary access of cytoplasmic factors to genes during mitosis may facilitate somatic cell nuclear reprogramming and the acquisition of new cell fates in normal development.
Environments and Morphologies of Red Sequence Galaxies with Residual Star Formation in Massive Clusters
Jacob P. Crossett,Kevin A. Pimbblet,John P. Stott,D. Heath Jones
Physics , 2013, DOI: 10.1093/mnras/stt2065
Abstract: We present a photometric investigation into recent star formation in galaxy clusters at z ~ 0.1. We use spectral energy distribution templates to quantify recent star formation in large X-ray selected clusters from the LARCS survey using matched GALEX NUV photometry. These clusters all have signs of red sequence galaxy recent star formation (as indicated by blue NUV-R colour), regardless of cluster morphology and size. A trend in environment is found for these galaxies, such that they prefer to occupy low density, high cluster radius environments. The morphology of these UV bright galaxies suggests that they are in fact red spirals, which we confirm with light curves and Galaxy Zoo voting percentages as morphological proxies. These UV bright galaxies are therefore seen to be either truncated spiral galaxies, caught by ram pressure in falling into the cluster, or high mass spirals, with the photometry dominated by the older stellar population.
The merger rates and sizes of galaxies across the peak epoch of star formation from the HiZELS survey
John P. Stott,David Sobral,Ian Smail,Richard Bower,Philip N. Best,James E. Geach
Physics , 2012, DOI: 10.1093/mnras/sts684
Abstract: We use the HiZELS narrow-band H-alpha survey in combination with CANDELS, UKIDSS and WIRDS near-infrared imaging, to investigate the morphologies, merger rates and sizes of a sample of H-alpha emitting galaxies in the redshift range z=0.40 - 2.23, an epoch encompassing the rise to the peak of the star formation rate density. Merger rates are estimated from space- and ground-based imaging using the M20 coefficient. To account for the increase in the specific star-formation rate (sSFR) of the star forming `main-sequence' with redshift, we normalise the star-formation rate of galaxies at each epoch to the typical value derived from the H-alpha luminosity function. Once this trend in sSFR is removed we see no evidence for an increase in the number density of star-forming galaxies or the merger rate with redshift. We thus conclude that neither is the main driver of the enhanced star-formation rate density at z=1-2, with secular processes such as instabilities within efficiently fuelled, gas-rich discs or multiple minor mergers the most likely alternatives. However, we find that 40-50% of starburst galaxies, those with enhanced specific star formation at their epoch, are major mergers and this fraction is redshift independent. Finally, we find the surprising result that the typical size of a star-forming galaxy of a given mass does not evolve across the redshift range considered, suggesting a universal size-mass relation. Taken in combination, these results indicate a star-forming galaxy population that is statistically similar in physical size, merger rate and mass over the 6 Gyr covered in this study, despite the increase in typical sSFR.
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