4,407 research outputs found
Attitudes and impressions of participants in a study of the causes of childhood cancer
Researchers and ethics committees are increasingly concerned about the perceived emotional impact on individuals following participation in epidemiologic studies. This attitudinal survey was designed to investigate this issue among 751 of the parents who had already given an interview in the UK Childhood Cancer Study (UKCCS), one of the largest case-control studies ever undertaken to investigate the aetiology of cancer in children. Information was collected by postal questionnaire on their reasons for agreeing to take part in the UKCCS, on whether questions had caused distress or difficulty and what their feelings were immediately after the interview and at the time of this survey. Parents were asked if they felt they had benefited in any way by taking part and control parents were asked if they would have taken part without prior consent of their doctor. 90% of both cases and controls felt glad to have taken part immediately after the interview and few reported any anxiety at having done so; 95% of both cases and controls felt satisfied that they had made a worthwhile contribution. Although 18% of cases felt tense and 14% felt unhappy after the interview, over 90% of them felt glad that they had taken part a few weeks later. Of particular interest is that 38% of cases and 24% of controls said they had positively benefited from taking part in the UKCCS and 96% of control mothers did not mind their family doctor giving permission for them to be contacted. © 2001 Cancer Research Campaign http://www.bjcancer.co
Bathymetry and Sediment Geochemistry of Lake Hazen (Quttinirpaaq National Park, Ellesmere Island, Nunavut)
Arctic lakes can provide a long-term perspective on environmental change, including trends in long-range atmospheric transport and deposition of contaminants, inferred from studies of sediment cores. In this study, we conducted the first detailed bathymetric survey of Lake Hazen (Quttinirpaaq National Park, Ellesmere Island, Nunavut), the worldâs largest lake north of 74Ë latitude. With these data we were able to determine optimal locations for sediment coring and to collect and analyze profundal sediment cores. A bathymetric map of Lake Hazen was developed on the basis of 362 spot soundings obtained with GPS-coupled sounding equipment placed directly on the ice combined with additional soundings from a small boat. The deepest point in the lake (81Ë49.5Êč N; 70Ë42.8Êč W) was found to be 267 m deep. The lake volume was estimated to be 5.14 Ă 1010 m3, about 10% larger than previous estimates. Using estimates of the discharge of Lake Hazen from the Water Survey of Canada, we estimated the water retention time to be 89 years. Sediment cores were dated using 210Pb and 137Cs. Sedimentation rates at the deep point, estimated using the Constant Rate of Supply model for excess 210Pb, were relatively high (1260 g m-2yr-1) in the period 2005 â 1963 and lower (650 ± 100 g m-2yr-1) in horizons dated to 1950 â 1880. The majority of elements measured in sediment (24 of 29 consistently above detection limits), as well as organic carbon, showed less than 20% variation in concentrations in the top 10 cm (compacted depth), which represent deposition over approximately 140 years. Geochemical characteristics of the sediment suggest that erosional inputs from annual glacial melting are the major source of essentially all elements and that anthropogenic inputs from long-range transport of toxic metals such as mercury and lead are very low.Les lacs de lâArctique peuvent fournir une perspective Ă long terme en matiĂšre de changement environnemental, notamment en ce qui a trait aux tendances relatives au transport atmosphĂ©rique et au dĂ©pĂŽt de contaminants sur de longues pĂ©riodes, tendances infĂ©rĂ©es Ă partir dâĂ©tudes de carottes de sĂ©diments. Dans le cadre de la prĂ©sente Ă©tude, nous avons effectuĂ© le premier levĂ© bathymĂ©trique dĂ©taillĂ© du lac Hazen (parc national Quttinirpaaq, Ăźle dâEllesmere, Nunavut), le plus grand lac de la planĂšte situĂ© au nord de 74Ë de latitude. GrĂące aux donnĂ©es prĂ©levĂ©es, nous avons rĂ©ussi Ă dĂ©terminer les meilleurs emplacements pour le prĂ©lĂšvement de carottes de sĂ©diments de mĂȘme que pour la collecte et lâanalyse de carottes de sĂ©diments profonds. Une carte bathymĂ©trique du lac Hazen a Ă©tĂ© dressĂ©e en fonction de 362 sondages obtenus au moyen de matĂ©riel dâappareils phoniques dotĂ©s de GPS placĂ©s directement sur la glace et supplĂ©mentĂ©s par des sondages recueillis Ă partir dâun petit bateau. Le point le plus profond du lac (81Ë49,5Êč N; 70Ë42,8Êč O) a Ă©tĂ© trouvĂ© Ă 267 m de profondeur. Le volume du lac a Ă©tĂ© Ă©valuĂ© Ă 5,14 Ă 1010 m3, soit 10 % de plus que les Ă©valuations prĂ©cĂ©dentes. Ă lâaide dâestimations du dĂ©versement du lac Hazen obtenues auprĂšs de la Division des relevĂ©s hydrologiques du Canada, nous avons Ă©valuĂ© que la durĂ©e de rĂ©tention de lâeau Ă©tait de 89 ans. La datation des carottes de sĂ©diments a Ă©tĂ© faite Ă lâaide de 210Pb et de 137Cs. Les taux de sĂ©dimentation au point profond, estimĂ©s en sâappuyant sur le modĂšle CRS (Constant Rate of Supply) pour lâexcĂ©dent 210Pb, Ă©taient relativement Ă©levĂ©s (1260 g m-2an-1) pour la pĂ©riode allant de 2005 Ă 1963, et moins Ă©levĂ©s (650 ± 100 g m-2an-1) pour la pĂ©riode de 1950 Ă 1880. La majoritĂ© des Ă©lĂ©ments mesurĂ©s dans les sĂ©diments (24 sur 29 Ă©taient uniformĂ©ment au-dessus des seuils de dĂ©tection) ainsi que dans le carbone organique ont produit une variation de concentrations de moins de 20 % dans les 10 cm supĂ©rieurs (profondeur compactĂ©e), ce qui reprĂ©sente des dĂ©pĂŽts sâĂ©chelonnant sur environ 140 ans. Les caractĂ©ristiques gĂ©ochimiques des sĂ©diments laissent prĂ©sumer que les matiĂšres dâĂ©rosion dĂ©coulant de la fonte glaciaire annuelle constituent la source principale de sensiblement tous les Ă©lĂ©ments, et que les matiĂšres anthropiques provenant du transport Ă grande distance de mĂ©taux toxiques, tels que le mercure et le plomb, sont trĂšs faibles
Micromechanics of seismic wave propagation in granular materials
In this study experimental data on a model soil in a cubical cell are compared with both discrete element (DEM) simulations and continuum analyses. The experiments and simulations used point source transmitters and receivers to evaluate the shear and compression wave velocities of the samples, from which some of the elastic moduli can be deduced. Complex responses to perturbations generated by the bender/extender piezoceramic elements in the experiments were compared to those found by the controlled movement of the particles in the DEM simulations. The generally satisfactory agreement between experimental observations and DEM simulations can be seen as a validation and support the use of DEM to investigate the influence of grain interaction on wave propagation. Frequency domain analyses that considered filtering of the higher frequency components of the inserted signal, the ratio of the input and received signals in the frequency domain and sample resonance provided useful insight into the system response. Frequency domain analysis and analytical continuum solutions for cube vibration show that the testing configuration excited some, but not all, of the systemâs resonant frequencies. The particle scale data available from DEM enabled analysis of the energy dissipation during propagation of the wave. Frequency domain analysis at the particle scale revealed that the higher frequency content reduces with increasing distance from the point of excitation
Blaming Bill Gates AGAIN! Misuse, overuse and misunderstanding of performance data in sport
Recently in Sport, Education and Society, Williams and Manley (2014) argued against the heavy reliance on technology in professional Rugby Union and elite sport in general. In summary, technology is presented as an elitist, âgold standardâ villain that management and coaches use to exert control and by which players lose autonomy, identity, motivation, social interactions and expertise. In this article we suggest that the sociological interpretations and implications offered by Williams and Manley may be somewhat limited when viewed in isolation. In doing so, we identify some core methodological issues in Williams and Manleyâs study and critically consider important arguments for utilising technology; notably, to inform coach decision making and generate player empowerment. Secondly, we present a different, yet perhaps equally concerning, practice-oriented interpretation of the same results but from alternative coaching and expertise literature. Accordingly, we suggest that Williams and Manley have perhaps raised their alarm prematurely, inappropriately and on somewhat shaky foundations. We also hope to stimulate others to consider contrary positions, or at least to think about this topic in greater detail. More specifically, we encourage coaches and academics to think carefully about what technology is employed, how and why, and then the means by which these decisions are discussed with and, preferably, sold to players. Certainly, technology can significantly enhance coach decision making and practice, while also helping players to optimise their focus, empowerment and independence in knowing how to achieve their personal and collective goals
Tunneling and Quantum Noise in 1-D Luttinger Liquids
We study non-equilibrium noise in the transmission current through barriers
in 1-D Luttinger liquids and in the tunneling current between edges of
fractional quantum Hall liquids. The distribution of tunneling events through
narrow barriers can be described by a Coulomb gas lying in the time axis along
a Keldysh (or non-equilibrium) contour. The charges tend to reorganize as a
dipole gas, which we use to describe the tunneling statistics. Intra-dipole
correlations contribute to the high-frequency ``Josephson'' noise, which has an
algebraic singularity at , whereas inter-dipole correlations
are responsible for the low-frequency noise. Inter-dipole interactions give a
correlation between the tunneling events that results in a
singularity in the noise spectrum. We present a diagrammatic technique to
calculate the correlations in perturbation theory, and show that contributions
from terms of order higher than the dipole-dipole interaction should only
affect the strength of the singularity, but its form should remain
to all orders in perturbation theory.Comment: RevTex, 9 figures available upon request, cond-mat/yymmnn
Enhancement of the Deuteron-Fusion Reactions in Metals and its Experimental Implications
Recent measurements of the reaction d(d,p)t in metallic environments at very
low energies performed by different experimental groups point to an enhanced
electron screening effect. However, the resulting screening energies differ
strongly for divers host metals and different experiments. Here, we present new
experimental results and investigations of interfering processes in the
irradiated targets. These measurements inside metals set special challenges and
pitfalls which make them and the data analysis particularly error-prone. There
are multi-parameter collateral effects which are crucial for the correct
interpretation of the observed experimental yields. They mainly originate from
target surface contaminations due to residual gases in the vacuum as well as
from inhomogeneities and instabilities in the deuteron density distribution in
the targets. In order to address these problems an improved differential
analysis method beyond the standard procedures has been implemented. Profound
scrutiny of the other experiments demonstrates that the observed unusual
changes in the reaction yields are mainly due to deuteron density dynamics
simulating the alleged screening energy values. The experimental results are
compared with different theoretical models of the electron screening in metals.
The Debye-H\"{u}ckel model that has been previously proposed to explain the
influence of the electron screening on both nuclear reactions and radioactive
decays could be clearly excluded.Comment: 22 pages, 12 figures, REVTeX4, 2-column format. Submitted to Phys.
Rev. C; accepte
Integration of professional judgement and decision-making in high-level adventure sports coaching practice
This study examined the integration of professional judgement and decision-making processes in adventure sports coaching. The study utilised a thematic analysis approach to investigate the decision-making practices of a sample of high-level adventure sports coaches over a series of sessions. Results revealed that, in order to make judgements and decisions in practice, expert coaches employ a range of practical and pedagogic management strategies to create and opportunistically use time for decision-making. These approaches include span of control and time management strategies to facilitate the decision-making process regarding risk management, venue selection, aims, objectives, session content, and differentiation of the coaching process. The implication for coaches, coach education, and accreditation is the recognition and training of the approaches thatâcreate timeâ for the judgements in practice, namelyâcreating space to thinkâ. The paper concludes by offering a template for a more expertise-focused progression in adventure sports coachin
Higher analogues of the discrete-time Toda equation and the quotient-difference algorithm
The discrete-time Toda equation arises as a universal equation for the
relevant Hankel determinants associated with one-variable orthogonal
polynomials through the mechanism of adjacency, which amounts to the inclusion
of shifted weight functions in the orthogonality condition. In this paper we
extend this mechanism to a new class of two-variable orthogonal polynomials
where the variables are related via an elliptic curve. This leads to a `Higher
order Analogue of the Discrete-time Toda' (HADT) equation for the associated
Hankel determinants, together with its Lax pair, which is derived from the
relevant recurrence relations for the orthogonal polynomials. In a similar way
as the quotient-difference (QD) algorithm is related to the discrete-time Toda
equation, a novel quotient-quotient-difference (QQD) scheme is presented for
the HADT equation. We show that for both the HADT equation and the QQD scheme,
there exists well-posed -periodic initial value problems, for almost all
\s\in\Z^2. From the Lax-pairs we furthermore derive invariants for
corresponding reductions to dynamical mappings for some explicit examples.Comment: 38 page
Influence of dissipation on the extraction of quantum states via repeated measurements
A quantum system put in interaction with another one that is repeatedly
measured is subject to a non-unitary dynamics, through which it is possible to
extract subspaces. This key idea has been exploited to propose schemes aimed at
the generation of pure quantum states (purification). All such schemes have so
far been considered in the ideal situations of isolated systems. In this paper,
we analyze the influence of non-negligible interactions with environment during
the extraction process, with the scope of investigating the possibility of
purifying the state of a system in spite of the sources of dissipation. A
general framework is presented and a paradigmatic example consisting of two
interacting spins immersed in a bosonic bath is studied. The effectiveness of
the purification scheme is discussed in terms of purity for different values of
the relevant parameters and in connection with the bath temperature.Comment: 10 pages, 3 figure
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