965 research outputs found
Tzitzeica solitons versus relativistic CalogeroâMoser three-body clusters
We establish a connection between the hyperbolic relativistic CalogeroâMoser systems and a class of soliton solutions to the Tzitzeica equation (also called the DoddâBulloughâZhiberâShabatâMikhailov equation). In the 6N-dimensional phase space Omega of the relativistic systems with 2N particles and N antiparticles, there exists a 2N-dimensional PoincarĂ©-invariant submanifold OmegaP corresponding to N free particles and N bound particle-antiparticle pairs in their ground state. The Tzitzeica N-soliton tau functions under consideration are real valued and obtained via the dual Lax matrix evaluated in points of OmegaP. This correspondence leads to a picture of the soliton as a cluster of two particles and one antiparticle in their lowest internal energy state
Are constant loop widths an artifact of the background and the spatial resolution?
We study the effect of the coronal background in the determination of the
diameter of EUV loops, and we analyze the suitability of the procedure followed
in a previous paper (L\'opez Fuentes, Klimchuk & D\'emoulin 2006) for
characterizing their expansion properties. For the analysis we create different
synthetic loops and we place them on real backgrounds from data obtained with
the Transition Region and Coronal Explorer (\textit{TRACE}). We apply to these
loops the same procedure followed in our previous works, and we compare the
results with real loop observations. We demonstrate that the procedure allows
us to distinguish constant width loops from loops that expand appreciably with
height, as predicted by simple force-free field models. This holds even for
loops near the resolution limit. The procedure can easily determine when loops
are below resolution limit and therefore not reliably measured. We find that
small-scale variations in the measured loop width are likely due to
imperfections in the background subtraction. The greatest errors occur in
especially narrow loops and in places where the background is especially bright
relative to the loop. We stress, however, that these effects do not impact the
ability to measure large-scale variations. The result that observed loops do
not expand systematically with height is robust.Comment: Accepted for publication in Ap
Coronal Loop Expansion Properties Explained Using Separators
One puzzling observed property of coronal loops is that they are of roughly
constant thickness along their length. Various studies have found no consistent
pattern of width variation along the length of loops observed by TRACE and
SOHO. This is at odds with expectations of magnetic flux tube expansion
properties, which suggests that loops are widest at their tops, and
significantly narrower at their footpoints. Coronal loops correspond to areas
of the solar corona which have been preferentially heated by some process, so
this observed property might be connected to the mechanisms that heat the
corona. One means of energy deposition is magnetic reconnection, which occurs
along field lines called separators. These field lines begin and end on
magnetic null points, and loops forming near them can therefore be relatively
wide at their bases. Thus, coronal energization by magnetic reconnection may
replicate the puzzling expansion properties observed in coronal loops. We
present results of a Monte Carlo survey of separator field line expansion
properties, comparing them to the observed properties of coronal loops.Comment: 16 pages, 9 figures, to be submitted to Ap
French translation and validation of the Jefferson Scale of Empathy - Health Professions Student version
Background: Background: Jefferson Scale of Empathy is one of the most widely used tools worldwide to assess empathy.
The extended version for Health Professions Students (JSE HPS) has not yet been translated into French. Objective:
The aim of our study was to translate the JSE HPS into French and assess the psychometric properties of this new
version (JSE HPS Fr). Methods: The JSE HPS was translated according to international recommendations. The main
psychometric qualities (test-retest reliability, internal consistency, floor and ceiling effects and construct validity) were studied in a sample of physiotherapy students. Participants provided general information (age, gender, year of study) and completed the JSE HPS Fr and the Questionnaire of Cognitive and Affective Empathy (QCAE). Participants were also asked to complete the JSE-HPS-Fr again one week later to assess its test-retest reliability. Results: 408 students (161 males and 247 females; mean age: 21.3 years) participated. The JSE HPS Fr demonstrated good test-retest reliability for the total score (ICC=0.81) and good internal consistency (α Cronbach: 0.79). The JSE HPS also showed good convergent validity with the QCAE questionnaire (r=0.41, p<0.05). No floor or ceiling effects were observed. Conclusions: The results indicate that the JSE HPS Fr is a valid and reliable tool to assess the level of empathy of French-speaking physiotherapy students
The 3D structure of an active region filament as extrapolated from photospheric and chromospheric observations
The 3D structure of an active region (AR) filament is studied using nonlinear
force-free field (NLFFF) extrapolations based on simultaneous observations at a
photospheric and a chromospheric height. To that end, we used the Si I 10827
\AA\ line and the He I 10830 \AA\ triplet obtained with the Tenerife Infrared
Polarimeter (TIP) at the VTT (Tenerife). The two extrapolations have been
carried out independently from each other and their respective spatial domains
overlap in a considerable height range. This opens up new possibilities for
diagnostics in addition to the usual ones obtained through a single
extrapolation from, typically, a photospheric layer. Among those possibilities,
this method allows the determination of an average formation height of the He I
10830 \AA\ signal of \approx 2 Mm above the surface of the sun. It allows, as
well, to cross-check the obtained 3D magnetic structures in view of verifying a
possible deviation from the force- free condition especially at the
photosphere. The extrapolations yield a filament formed by a twisted flux rope
whose axis is located at about 1.4 Mm above the solar surface. The twisted
field lines make slightly more than one turn along the filament within our box,
which results in 0.055 turns/Mm. The convex part of the field lines (as seen
from the solar surface) constitute dips where the plasma can naturally be
supported. The obtained 3D magnetic structure of the filament depends on the
choice of the observed horizontal magnetic field as determined from the
180\circ solution of the azimuth. We derive a method to check for the
correctness of the selected 180\circ ambiguity solution.Comment: 31 pages, 13 figures, ApJ Accepte
The Construction and (Re)Construction of Mentoring Relations, Conversations, Observations and Cameras
The purpose of this study is to better understand mentoring as a relational process. Employing a constructionist form of Action Research called âAppreciative Inquiryâ (AI), twelve teachers, six pairs of Mentors and Newly Qualified Teachers explored through their joint actions with a digital camera, alternative forms of âobservationâ and âfeedbackâ practices. The study took a fresh theoretical approach to mentoring, enabling the teachers to focus on the âpositiveâ aspects of their mentoring experiences. This approach provided constructionist tools with which to analyse the teachersâ experiences. These included âjoint actionâ (Shotter, 1993); the application of âin-vivoâ and âvaluesâ coding (Saldana, 2009) and a form of discourse analysis known as âInterpretative Repertoiresâ (Wetherell and Potter, 1988). Emerging themes showed how the teachers developed an understanding of how they co-constructed their observation and feedback practices; developed their teaching identities; and how filming enabled them to see how their practices connected or disconnected them to childrenâs learning; resources; the environment; and to the wider school and beyond. Findings show how co-constructed learning with a digital camera can support the professional development of both Mentors and Newly Qualified Teachers as part of the induction process, through everyday local mentoring practices. It also shows how mentoring practices can be more effectively aligned with the GTCS (2012) Standards. This small co-study addresses issues raised in key âpolicyâ texts shaping mentoring practices in Scottish education. For these continue to highlight the need for coherence in the language of âmentoringâ; how âfeedbackâ might be more productive in supporting Newly Qualified Teachers; how training for Mentors is required and how pedagogical skills might be enhanced through the Mentoring Process (Evaluation of Teaching Scotlandâs Future, Scottish Government, March 2016)
Final Report: Theory of Advanced High Efficiency Concentrator Cells
The goal of this project was to begin -developing accurate, and ultimately predictive, device models for III-V concentrator cells. The project consisted of extending a one-dimensional numerical device model previously developed at Purdue to III-V solar cells. We also began verifying the accuracy of the code by comparing computed and measured solar cell characteristics. Gallium arsenide was selected because it is the most mature III-V technology and because GaAs solar cells have demonstrated high conversion efficiency [l,2,3]. The present device model should be useful in optimizing GaAs solar cells and forms a foundation that can be extended to other III-V homo- and heterostructure solar cells. The numerical device model developed in this work solves Poissonâs equation simultaneously with the electron and hole continuity equations without making common assumptions such as low-level injection, piece-wise uniform doping, neglect of space-charge recombination, etc. Materials models for GaAs solar cells (e. g. intrinsic carrier concentration, carrier mobilities, lifetimes, optical absorption and reflection coefficients, etc.) were compiled, evaluated, and in some cases extended. These materials models were then implemented into the numerical device model. The device model was also extended to analyze optical absorption and reflection from bare and anti-reflection (AR) coated cells. To test the GaAs cell model, we compared its predictions to measured results for an N+P cell (the shallow homojunction cell reported by Fan and co-workers) and a P+N cell (fabricated by Borrego and co-workers). In general, good agreement between theory and experiment was obtained for both concentrated and unconcentrated conditions. Although detailed comparisons of the modelâs predictions with measured results continue, the present model is a useful tool for GaAs cell design and optimization
How are Emerging Flux, Flares and CMEs Related to Magnetic Polarity Imbalance in MDI Data?
In order to understand whether major flares or coronal mass ejections (CMEs)
can be related to changes in the longitudinal photospheric magnetic field, we
study 4 young active regions during seven days of their disc passage. This time
period precludes any biases which may be introduced in studies that look at the
field evolution during the short-term flare or CME period only. Data from the
Michelson Doppler Imager (MDI) with a time cadence of 96 minutes are used.
Corrections are made to the data to account for area foreshortening and angle
between line of sight and field direction, and also the underestimation of the
flux densities. We make a systematic study of the evolution of the longitudinal
magnetic field, and analyze flare and CME occurrence in the magnetic evolution.
We find that the majority of CMEs and flares occur during or after new flux
emergence. The flux in all four active regions is observed to have deviations
from polarity balance both on the long-term (solar rotation) and on the short
term (few hours). The long-term imbalance is not due to linkage outside the
active region; it is primarily related to the east-west distance from central
meridian, with the sign of polarity closer to the limb dominating. The sequence
of short term imbalances are not closely linked to CMEs and flares and no
permanent imbalance remains after them. We propose that both kinds of imbalance
are due to the presence of a horizontal field component (parallel to the
photospheric surface) in the emerging flux.Comment: 22 pages, 8 figures, Solar Physics (in press
Liquid transport in scale space
International audienceWhen a liquid stream is injected into a gaseous atmosphere, it destabilizes and continuously passes through different states characterized by different morphologies. Throughout this process, the flow dynamics may be different depending on the region of the flow and the scales of the involved liquid structures. Exploring this multi-scale, multi-dimensional phenomenon requires some new theoretical tools, some of which need yet to be elaborated. Here, a new analytical framework is proposed on the basis of two-point statistical equations of the liquid volume fraction. This tool, which originates from single phase turbulence, allows us notably to decompose the fluxes of liquid in flowâposition space and scale space. Direct numerical simulations of liquidâgas turbulence decaying in a triply periodic domain are then used to characterize the time and scale evolution of the liquid volume fraction. It is emphasized that two-point statistics of the liquid volume fraction depend explicitly on the geometrical properties of the liquidâgas interface and in particular its surface density. The stretch rate of the liquidâgas interface is further shown to be the equivalent for the liquid volume fraction (a non-diffusive scalar) of the scalar dissipation rate. Finally, a decomposition of the transport of liquid in scale space highlights that non-local interactions between non-adjacent scales play a significant role
Translation validation of a new back pain screening questionnaire (the STarT Back Screening Tool) in French
Background: Low back pain (LBP) is a major public health problem and the identification of individuals at risk of
persistent LBP poses substantial challenges to clinical management. The STarT Back questionnaire is a validated
nine-item patient self-report questionnaire that classifies patients with LBP at low, medium or high-risk of poor
prognosis for persistent non-specific LBP. The objective of this study was to translate and cross-culturally adapt the
English version of the STarT Back questionnaire into French.
Methods: The translation was performed using best practice translation guidelines. The following phases were
performed: contact with the STarT Back questionnaire developers, initial translations (English into French), synthesis,
back translations, expert committee review, test of the pre-final version on 44 individuals with LBP, final version.
Results: The linguistic translation required minor semantic alterations. The participants interviewed indicated that
all items of the questionnaire were globally clear and comprehensible. However, 6 subjects (14%) wondered if two
questions were related to back pain or general health. After discussion within the expert committee and with the
developer of the STarT Back tool, it was decided to modify the questionnaire and to add a reference to back pain
in these two questions.
Conclusions: The French version of the STarT Back questionnaire has been shown to be comprehensible and
adapted to the French speaking general population. Investigations are now required to test the psychometric
properties (reliability, internal and external validity, responsiveness) of this translated version of the questionnaire
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