1,221 research outputs found
Molecular orientational dynamics of the endohedral fullerene ScN@C as probed by C and Sc NMR
We measure 13C and 45Sc NMR lineshapes and spin-lattice relaxation times (T1)
to probe the orientational dynamics of the endohedral metallofullerene
Sc3N@C80. The measurements show an activated behavior for molecular
reorientations over the full temperature range with a similar behavior for the
temperature dependence of the 13C and 45Sc data. Combined with spectral data
from Magic Angle Spinning (MAS) NMR, the measurements can be interpreted to
mean the motion of the encapsulated Sc3N molecule is independent of that of the
C80 cage, although this requires the similar temperature dependence of the 13C
and 45Sc spin-lattice relaxation times to be coincidental. For the Sc3N to be
fixed to the C80 cage, one must overcome the symmetry breaking effect this has
on the Sc3N@C80 system since this would result in more than the observed two
13C lines.Comment: 6 pages, 5 figure
Magnetic field independence of the spin gap in YBa_2Cu_3O_{7-delta}
We report, for magnetic fields of 0, 8.8, and 14.8 Tesla, measurements of the
temperature dependent ^{63}Cu NMR spin lattice relaxation rate for near
optimally doped YBa_2Cu_3O_{7-delta}, near and above T_c. In sharp contrast
with previous work we find no magnetic field dependence. We discuss
experimental issues arising in measurements of this required precision, and
implications of the experiment regarding issues including the spin or pseudo
gap.Comment: 4 pages, 3 figures, as accepted for publication in Physical Review
Letter
A-STAR: The All-Sky Transient Astrophysics Reporter
The small mission A-STAR (All-Sky Transient Astrophysics Reporter) aims to
locate the X-ray counterparts to ALIGO and other gravitational wave detector
sources, to study the poorly-understood low luminosity gamma-ray bursts, and to
find a wide variety of transient high-energy source types, A-STAR will survey
the entire available sky twice per 24 hours. The payload consists of a coded
mask instrument, Owl, operating in the novel low energy band 4-150 keV, and a
sensitive wide-field focussing soft X-ray instrument, Lobster, working over
0.15-5 keV. A-STAR will trigger on ~100 GRBs/yr, rapidly distributing their
locations.Comment: Accepted for the European Astronomical Society Publications Series:
Proceedings of the Fall 2012 Gamma-Ray Burst Symposium held in Marbella,
Spain, 8-12 Oct 201
The Superconducting Condensation Energy and an Antiferromagnetic Exchange Based Pairing Mechanism
For the traditional low T_c superconductors, the superconducting condensation
energy is proportional to the change in energy of the ionic lattice between the
normal and superconducting state, providing a clear link between pairing and
the electron-ion interaction. Here, for the t-J model, we discuss an analogous
relationship between the superconducting condensation energy and the change in
the exchange energy between the normal and superconducting states. We point out
the possibility of measuring this using neutron scattering and note that such a
measurement, while certainly difficult, could provide important evidence for an
exchange interaction-based pairing mechanism.Comment: Replaced with revised versio
Incommensurate Charge and Spin Fluctuations in d-wave Superconductors
We show analytic results for the irreducible charge and spin
susceptibilities, , where is the momentum
transfer between the nodes in d-wave superconductors. Using the BCS theory and
a circular Fermi surface, we find that the singular behavior of the irreducible
charge susceptibility leads to the dynamic incommensurate charge collective
modes. The peaks in the charge structure factor occur at a set of wave vectors
which form an ellipse around and in
momentum space with momentum dependent spectral weight. It is also found that,
due to the non-singular irreducible spin susceptibility, an extremely strong
interaction via random phase approximation is required to support the magnetic
peaks near . Under certain conditions, the peaks in the magnetic
structure factor occur near and .Comment: 5 pages, 3 figure
The Value of Participating in British Exploring Society Expeditions: A Three Year Multi Cohort Study
A primary aim of many expeditions is to facilitate personal development of young people and 15 while there is much anecdotal evidence to support this aim, there is limited empirical work of 16 varied quality that explores the specific nature of such benefits. This research examined nine 17 summer BES expeditions (Norway, Namibia & Amazon in 2012; Finnmark, Ladakh and 18 Namibia in 2013 and 2014) involving 58 young people (aged between 15 and 22) who completed 19 three on-line questionnaires to collect qualitative (open ended questions) and quantitative (likert 20 scale) data. Measurement of four psychological attributes associated with effective character 21 development were used: mental toughness, coping skills, GRIT and leadership skills. Surveys 22 were completed at three stages; 1) pre expedition, 2) immediately post expedition and 3) three 23 months post expedition. Results indicated that the expeditions impacted positively on the 24 psychological attributes of young people, with short term effects (three months). 25 For the 58 participants, there were statistically significant improvements and small positive 26 effect sizes in mental toughness (P=.006; ηp 2 .167), leadership skills (P=.004; ηp 2 .18), and 27 GRIT (P=.001; ηp 2 .218). There was no significant difference (P>0.05) or effect size for the 28 application of coping strategies. Qualitative data provided insights into how the learning took 29 place and individual perspectives on the overall value of the expedition in relation to narrative 30 understandin
The Microchannel X-ray Telescope for the Gamma-Ray Burst mission SVOM
We present the Microchannel X-ray Telescope, a new light and compact
focussing telescope that will be flying on the Sino-French SVOM mission
dedicated to Gamma-Ray Burst science. The MXT design is based on the coupling
of square pore micro-channel plates with a low noise pnCCD. MXT will provide an
effective area of about 50 cmsq, and its point spread function is expected to
be better than 3.7 arc min (FWHM) on axis. The estimated sensitivity is
adequate to detect all the afterglows of the SVOM GRBs, and to localize them to
better then 60 arc sec after five minutes of observation.Comment: 12 pages, 8 figures, to be published in SPIE Astronomical Telescopes
+ Instrumentation, Montreal, June 201
The Influence of Magnetic Imperfections on the Low Temperature Properties of D-wave Superconductors
We consider the influence of planar ``magnetic" imperfections which destroy
the local magnetic order, such as Zn impurities or vacancies, on the
low temperature properties of the cuprate superconductors. In the unitary
limit, at low temperatures, for a pairing state such
imperfections produce low energy quasiparticles with an anistropic spectrum in
the vicinity of the nodes. We find that for the system, one
is in the {\em quasi-one-dimensional} regime of quasiparticle scattering,
discussed recently by Altshuler, Balatsky, and Rosengren, for impurity
concentrations in excess of whereas YBCO appears likely to be
in the true 2D scattering regime for Zn concentrations less than . We
show the neutron scattering results of Mason et al. \cite{Aeppli} on
provide strong evidence for ``dirty d-wave"
superconductivity in their samples. We obtain simple expressions for the
dynamic spin susceptibility and spin-lattice relaxation time,
, in the superconducting state.Comment: 10 pages; revtex; Los Alamos preprint LA-UR-94-53
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
Does training increase the use of more emotionally laden words by nurses when talking with cancer patients? A randomised study
The emotional content of health care professionalsâcancer patient communication is often considered as poor and has to be improved by an enhancement of health care professionals empathy. One hundred and fifteen oncology nurses participating in a communication skills training workshop were assessed at three different periods. Nurses randomly allocated to a control group arm (waiting list) were assessed a first time and then 3 and 6 months later. Nurses allocated to the training group were assessed before training workshop, just after and 3 months later. Each nurse completed a 20-min clinical and simulated interview. Each interview was analysed by three content analysis systems: two computer-supported content analysis of emotional words, the Harvard Third Psychosocial Dictionary and the Martindale Regressive Imagery Dictionary and an observer rating system of utterances emotional depth level, the Cancer Research Campaign Workshop Evaluation Manual. The results show that in clinical interviews there is an increased use of emotional words by health care professionals right after having been trained (P=0.056): training group subjects use 4.3 (std: 3.7) emotional words per 1000 used before training workshop, and 7.0 (std: 5.8) right after training workshop and 5.9 (std: 4.3) 3 months later compared to control group subjects which use 4.5 (std: 4.8) emotional words at the first assessment point, 4.3 (std: 4.1) at the second and 4.4 (std: 3.3) at the third. The same trend is noticeable for emotional words used by health care professionals in simulated interviews (P=0.000). The emotional words registry used by health care professionals however remains stable over time in clinical interviews (P=0.141) and is enlarged in simulated interviews (P=0.041). This increased use of emotional words by trained health care professionals facilitates cancer patient emotion words expressions compared to untrained health care professionals especially 3 months after training (P=0.005). This study shows that health care professionals empathy may be improved by communication skills training workshop and that this improvement facilitates cancer patients emotions expression
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