5,466 research outputs found
Coulomb plasmas in outer envelopes of neutron stars
Outer envelopes of neutron stars consist mostly of fully ionized, strongly
coupled Coulomb plasmas characterized by typical densities about 10^4-10^{11}
g/cc and temperatures about 10^4-10^9 K. Many neutron stars possess magnetic
fields about 10^{11}-10^{14} G. Here we briefly review recent theoretical
advances which allow one to calculate thermodynamic functions and electron
transport coefficients for such plasmas with an accuracy required for
theoretical interpretation of observations.Comment: 4 pages, 2 figures, latex2e using cpp2e.cls (included). Proc. PNP-10
Workshop, Greifswald, Germany, 4-9 Sept. 2000. Accepted for publication in
Contrib. Plasma Phys. 41 (2001) no. 2-
Kinetic approaches to particle acceleration at cosmic ray modified shocks
Kinetic approaches provide an effective description of the process of
particle acceleration at shock fronts and allow to take into account the
dynamical reaction of the accelerated particles as well as the amplification of
the turbulent magnetic field as due to streaming instability. The latter does
in turn affect the maximum achievable momentum and thereby the acceleration
process itself, in a chain of causality which is typical of non-linear systems.
Here we provide a technical description of two of these kinetic approaches and
show that they basically lead to the same conclusions. In particular we discuss
the effects of shock modification on the spectral shape of the accelerated
particles, on the maximum momentum, on the thermodynamic properties of the
background fluid and on the escaping and advected fluxes of accelerated
particles.Comment: 22 pages, 7 figures, accepted for publication in MNRA
Implementing WHO-Quality Rights Project in Tunisia: Results of an Intervention at Razi Hospital
Background: The aims were: 1) to measure the attitudes of learners (and future trainers) before and after a course on WHO-Quality Rights (QR); 2) to evaluate a psychiatric ward, by previously trained staff on QR, comparing it with a previous evaluation and discussing an improvement plan. Methods: 1) Training sample: 19 subjects (8 males), 41.4±10.6 years, including jurists/lawyers, health professionals, and experts. The QR team developed the 26-item tool to assess the knowledge and attitudes of participants. 2) Evaluation of quality of care and respect for human rights in the ward was carried out on 20 staff representatives, 20 family members and 20 users with QRToolkit. Results: 1) Learning in QR has partially changed the knowledge and attitudes of trained people. 2) The evaluation shows significant delays in the implementation of the rights advocated by the United Nations Convention on the Human Rights of Persons with Disabilities (CRPD). In Themes 1, 3, 4 and 5, the evaluation shows no differences compared to 2014, but in Theme 2, the level was lower than four years before. Conclusion: The scarcity of resources due to the economic crisis that Tunisia is going through, cannot be considered the only cause of the delays highlighted. However, it is likely that in a context of uncertainty for the future, scarcity of resources and a decrease in staff (i.e., professionals dedicated to psychosocial intervention) may have demotivated the team towards recovery. The improvement in knowledge and attitudes of many staff members after the training may open future positive scenarios
Unveiling the nature of the unidentified gamma-ray sources IV: the catalog of potential X-ray counterparts
A significant fraction ( %) of the high-energy gamma-ray sources
listed in the second LAT (2FGL) catalog are still of unknown
origin, being not yet associated with counterparts at lower energies. In order
to investigate the nature of these enigmatic sources, we present here an
extensive search of X-ray sources lying in the positional uncertainty region of
a selected sample of these Unidentified Gamma-ray Sources (UGSs) that makes use
of all available observations performed by the X-ray Telescope
before March 31, 2013, available for 205 UGSs. To detect the fainter sources,
we merged all the observations covering the LAT positional
uncertainty region at 95 % level of confidence of each UGSs. This yields a
catalog of 357 X-ray sources, finding {candidate} X-ray counterparts for % of the selected sample. In particular, 25 % of the UGSs feature a single
X-ray source within their positional uncertainty region while 45 % have
multiple X-ray sources. For each X-ray source we also looked in the
corresponding UVOT merged images for optical and ultraviolet
counterparts, also performing source photometry. We found ultraviolet-optical
correspondences for % of the X-ray sources. We searched several major
radio, infrared, optical and ultraviolet surveys for possible counterparts
within the positional error of the sources in the X-ray catalog to obtain
additional information on their nature. Applying the kernel density estimator
technique to infrared colors of WISE counterparts of our X-ray sources we
select 6 -ray blazar candidates. In addition, comparing our results
with previous analyses, we select 11 additional -ray blazar candidates.Comment: 19 pages, 10 figures, 6 tables. Accepted for publication on Ap
Progress in Monte Carlo design and optimization of the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) will be an instrument covering a wide
energy range in very-high-energy (VHE) gamma rays. CTA will include several
types of telescopes, in order to optimize the performance over the whole energy
range. Both large-scale Monte Carlo (MC) simulations of CTA super-sets
(including many different possible CTA layouts as sub-sets) and smaller-scale
simulations dedicated to individual aspects were carried out and are on-going.
We summarize results of the prior round of large-scale simulations, show where
the design has now evolved beyond the conservative assumptions of the prior
round and present first results from the on-going new round of MC simulations.Comment: 4 pages, 5 figures. In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at
arXiv:1307.223
The physics of spreading processes in multilayer networks
The study of networks plays a crucial role in investigating the structure,
dynamics, and function of a wide variety of complex systems in myriad
disciplines. Despite the success of traditional network analysis, standard
networks provide a limited representation of complex systems, which often
include different types of relationships (i.e., "multiplexity") among their
constituent components and/or multiple interacting subsystems. Such structural
complexity has a significant effect on both dynamics and function. Throwing
away or aggregating available structural information can generate misleading
results and be a major obstacle towards attempts to understand complex systems.
The recent "multilayer" approach for modeling networked systems explicitly
allows the incorporation of multiplexity and other features of realistic
systems. On one hand, it allows one to couple different structural
relationships by encoding them in a convenient mathematical object. On the
other hand, it also allows one to couple different dynamical processes on top
of such interconnected structures. The resulting framework plays a crucial role
in helping achieve a thorough, accurate understanding of complex systems. The
study of multilayer networks has also revealed new physical phenomena that
remain hidden when using ordinary graphs, the traditional network
representation. Here we survey progress towards attaining a deeper
understanding of spreading processes on multilayer networks, and we highlight
some of the physical phenomena related to spreading processes that emerge from
multilayer structure.Comment: 25 pages, 4 figure
New Particles Working Group Report of the Snowmass 2013 Community Summer Study
This report summarizes the work of the Energy Frontier New Physics working
group of the 2013 Community Summer Study (Snowmass)
Nucleon-Nucleon Interaction: A Typical/Concise Review
Nearly a recent century of work is divided to Nucleon-Nucleon (NN)
interaction issue. We review some overall perspectives of NN interaction with a
brief discussion about deuteron, general structure and symmetries of NN
Lagrangian as well as equations of motion and solutions. Meanwhile, the main NN
interaction models, as frameworks to build NN potentials, are reviewed
concisely. We try to include and study almost all well-known potentials in a
similar way, discuss more on various commonly used plain forms for two-nucleon
interaction with an emphasis on the phenomenological and meson-exchange
potentials as well as the constituent-quark potentials and new ones based on
chiral effective field theory and working in coordinate-space mostly. The
potentials are constructed in a way that fit NN scattering data, phase shifts,
and are also compared in this way usually. An extra goal of this study is to
start comparing various potentials forms in a unified manner. So, we also
comment on the advantages and disadvantages of the models and potentials partly
with reference to some relevant works and probable future studies.Comment: 85 pages, 5 figures, than the previous v3 edition, minor changes, and
typos fixe
Gender and line size factors modulate the deviations of the subjective visual vertical induced by head tilt
<p>Abstract</p> <p>Background</p> <p>The subjective visual vertical (SVV, the visual estimation of gravitational direction) is commonly considered as an indicator of the sense of orientation. The present study examined the impact of two methodological factors (the angle size of the stimulus and the participant's gender) on deviations of the SVV caused by head tilt. Forty healthy participants (20 men and 20 women) were asked to make visual vertical adjustments of a light bar with their head held vertically or roll-tilted by 30° to the left or to the right. Line angle sizes of 0.95° and 18.92° were presented.</p> <p>Results</p> <p>The SVV tended to move in the direction of head tilt in women but away from the direction of head tilt in men. Moreover, the head-tilt effect was also modulated by the stimulus' angle size. The large angle size led to deviations in the direction of head-tilt, whereas the small angle size had the opposite effect.</p> <p>Conclusions</p> <p>Our results showed that gender and line angle size have an impact on the evaluation of the SVV. These findings must be taken into account in the growing body of research that uses the SVV paradigm in disease settings. Moreover, this methodological issue may explain (at least in part) the discrepancies found in the literature on the head-tilt effect.</p
Unintentional high density p-type modulation doping of a GaAs/AlAs core-multi-shell nanowire
Achieving significant doping in GaAs/AlAs core/shell nanowires (NWs) is of
considerable technological importance but remains a challenge due to the
amphoteric behavior of the dopant atoms. Here we show that placing a narrow
GaAs quantum well in the AlAs shell effectively getters residual carbon
acceptors leading to an \emph{unintentional} p-type doping. Magneto-optical
studies of such a GaAs/AlAs core multi-shell NW reveal quantum confined
emission. Theoretical calculations of NW electronic structure confirm quantum
confinement of carriers at the core/shell interface due to the presence of
ionized carbon acceptors in the 1~nm GaAs layer in the shell.
Micro-photoluminescence in high magnetic field shows a clear signature of
avoided crossings of the Landau level emission line with the Landau
level TO phonon replica. The coupling is caused by the resonant hole-phonon
interaction, which points to a large 2D hole density in the structure.Comment: just published in Nano Letters
(http://pubs.acs.org/doi/full/10.1021/nl500818k
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