713 research outputs found
Power-law weighted networks from local attachments
This letter introduces a mechanism for constructing, through a process of
distributed decision-making, substrates for the study of collective dynamics on
extended power-law weighted networks with both a desired scaling exponent and a
fixed clustering coefficient. The analytical results show that the connectivity
distribution converges to the scaling behavior often found in social and
engineering systems. To illustrate the approach of the proposed framework we
generate network substrates that resemble steady state properties of the
empirical citation distributions of (i) publications indexed by the Institute
for Scientific Information from 1981 to 1997; (ii) patents granted by the U.S.
Patent and Trademark Office from 1975 to 1999; and (iii) opinions written by
the Supreme Court and the cases they cite from 1754 to 2002.Comment: 18 pages, 3 figures; Proceedings of the IEEE Conference on Decision
and Control and the European Control Conference, Orlando, FL, Dec. 2011;
Added references; We modified the model in order to take into account
extended power-law distributions which better fit to the citations data sets;
Added proofs of theorems; Shorten version; Updated plo
Construction and application of a questionnaire for the social scientific investigation of environmental noise effects
A social psychological questionnair has been developed to study the effects of environmental noise and was applied to 636 people living in 19 different areas of Hamburg. The theoretical foundations and the statistical means employed in its development are described. Four main reactions to noise are isolated statistically, and it is determined that these are moderated by several intervening variables, chief of which are coping capacity for noise, the perceived dangerousness of the noise souce, other daily loads and the individual's liability
Long-lasting XUV activation of helium nanodroplets for avalanche ionization
We study the dynamics of avalanche ionization of pure helium nanodroplets
activated by a weak extreme-ultraviolet (XUV) pulse and driven by an intense
near-infrared (NIR) pulse. In addition to a transient enhancement of ignition
of a nanoplasma at short delay times ~fs, long-term activation of the
nanodroplets lasting up to a few nanoseconds is observed. Molecular dynamics
simulations suggest that the short-term activation is caused by the injection
of seed electrons into the droplets by XUV photoemission. Long-term activation
appears due to electrons remaining loosely bound to photoions which form stable
`snowball' structures in the droplets. Thus, we show that XUV irradiation can
induce long-lasting changes of the strong-field optical properties of
nanoparticles, potentially opening new routes to controlling
avalanche-ionization phenomena in nanostructures and condensed-phase systems
Key features of palliative care service delivery to Indigenous peoples in Australia, New Zealand, Canada and the United States: A comprehensive review
Background: Indigenous peoples in developed countries have reduced life expectancies, particularly from chronic diseases. The lack of access to and take up of palliative care services of Indigenous peoples is an ongoing concern.
Objectives: To examine and learn from published studies on provision of culturally safe palliative care service delivery to Indigenous people in Australia, New Zealand (NZ), Canada and the United States of America (USA); and to compare Indigenous peoplesâ preferences, needs, opportunities and barriers to palliative care.
Methods: A comprehensive search of multiple databases was undertaken. Articles were included if they were published in English from 2000 onwards and related to palliative care service delivery for Indigenous populations; papers could use quantitative or qualitative approaches. Common themes were identified using thematic synthesis. Studies were evaluated using Dalyâs hierarchy of evidence-for-practice in qualitative research.
Results: Of 522 articles screened, 39 were eligible for inclusion. Despite diversity in Indigenous peoplesâ experiences across countries, some commonalities were noted in the preferences for palliative care of Indigenous people: to die close to or at home; involvement of family; and the integration of cultural practices. Barriers identified included inaccessibility, affordability, lack of awareness of services, perceptions of palliative care, and inappropriate services. Identified models attempted to address these gaps by adopting the following strategies: community engagement and ownership; flexibility in approach; continuing education and training; a whole-of-service approach; and local partnerships among multiple agencies. Better engagement with Indigenous clients, an increase in number of palliative care patients, improved outcomes, and understanding about palliative care by patients and their families were identified as positive achievements.
Conclusions: The results provide a comprehensive overview of identified effective practices with regards to palliative care delivered to Indigenous populations to guide future program developments in this field. Further research is required to explore the palliative care needs and experiences of Indigenous people living in urban areas
Galaxy Clusters as Reservoirs of Heavy Dark Matter and High-Energy Cosmic Rays: Constraints from Neutrino Observations
Galaxy Clusters (GCs) are the largest reservoirs of both dark matter and
cosmic rays (CRs). Dark matter self-annihilation can lead to a high luminosity
in gamma rays and neutrinos, enhanced by a strong degree of clustering in dark
matter substructures. Hadronic CR interactions can also lead to a high
luminosity in gamma rays and neutrinos, enhanced by the confinement of CRs from
cluster accretion/merger shocks and active galactic nuclei. We show that
IceCube/KM3Net observations of high-energy neutrinos can probe the nature of
GCs and the separate dark matter and CR emission processes, taking into account
how the results depend on the still-substantial uncertainties. Neutrino
observations are relevant at high energies, especially at >10 TeV. Our results
should be useful for improving experimental searches for high-energy neutrino
emission. Neutrino telescopes are sensitive to extended sources formed by dark
matter substructures and CRs distributed over large scales. Recent observations
by Fermi and imaging atmospheric Cherenkov telescopes have placed interesting
constraints on the gamma-ray emission from GCs. We also provide calculations of
the gamma-ray fluxes, taking into account electromagnetic cascades inside GCs,
which can be important for injections at sufficiently high energies. This also
allows us to extend previous gamma-ray constraints to very high dark matter
masses and significant CR injections at very high energies. Using both
neutrinos and gamma rays, which can lead to comparable constraints, will allow
more complete understandings of GCs. Neutrinos are essential for some dark
matter annihilation channels, and for hadronic instead of electronic CRs. Our
results suggest that the multi-messenger observations of GCs will be able to
give useful constraints on specific models of dark matter and CRs. [Abstract
abridged.]Comment: 31 pages, 20 figures, 1 table, accepted for publication in JCAP,
references and discussions adde
Association of Serum Ferritin Levels Before Start of Conditioning With Mortality After alloSCT - A Prospective, Non-interventional Study of the EBMT Transplant Complications Working Party
Elevated serum ferritin levels occur due to iron overload or during inflammation and macrophage activation. A correlation of high serum ferritin levels with increased mortality after alloSCT has been suggested by several retrospective analyses as well as by two smaller prospective studies. This prospective multicentric study aimed to study the association of ferritin serum levels before start of conditioning with alloSCT outcome. Patients with acute leukemia, lymphoma or MDS receiving a matched sibling alloSCT for the first time were considered for inclusion, regardless of conditioning. A comparison of outcomes between patients with high and low ferritin level was performed using univariate analysis and multivariate analysis using cause-specific Cox model. Twenty centers reported data on 298 alloSCT recipients. The ferritin cut off point was determined at 1500 mu g/l (median of measured ferritin levels). In alloSCT recipients with ferritin levels above cut off measured before the start of conditioning, overall survival (HR = 2.5, CI = 1.5-4.1, p = 0.0005) and progression-free survival (HR = 2.4, CI = 1.6-3.8, p <0.0001) were inferior. Excess mortality in the high ferritin group was due to both higher relapse incidence (HR = 2.2, CI = 1.2-3.8, p = 0.007) and increased non-relapse mortality (NRM) (HR = 3.1, CI = 1.5-6.4, p = 0.002). NRM was driven by significantly higher infection-related mortality in the high ferritin group (HR = 3.9, CI = 1.6-9.7, p = 0.003). Acute and chronic GVHD incidence or severity were not associated to serum ferritin levels. We conclude that ferritin levels can serve as routine laboratory biomarker for mortality risk assessment before alloSCT.Peer reviewe
Fermi Discovery of Gamma-Ray Emission from NGC 1275
We report the discovery of high-energy (E>100 MeV) gamma-ray emission from
NGC 1275, a giant elliptical galaxy lying at the center of the Perseus cluster
of galaxies, based on observations made with the Large Area Telescope (LAT) of
the Fermi Gamma ray Space Telescope. The positional center of the gamma-ray
source is only ~3' away from the NGC 1275 nucleus, well within the 95% LAT
error circle of ~5'.The spatial distribution of gamma-ray photons is consistent
with a point source. The average flux and power-law photon index measured with
the LAT from 2008 August 4 to 2008 December 5 are F_gamma = (2.10+-0.23)x
10^{-7} ph (>100 MeV) cm^{-2} s^{-1} and Gamma = 2.17+-0.05, respectively. The
measurements are statistically consistent with constant flux during the
four-month LAT observing period.Previous EGRET observations gave an upper limit
of F_gamma 100 MeV) cm^{-2} s^{-1} to the gamma-ray flux
from NGC 1275. This indicates that the source is variable on timescales of
years to decades, and therefore restricts the fraction of emission that can be
produced in extended regions of the galaxy cluster. Contemporaneous and
historical radio observations are also reported. The broadband spectrum of NGC
1275 is modeled with a simple one-zone synchrotron/synchrotron self-Compton
model and a model with a decelerating jet flow.Comment: 27 pages, 7 figures, Accepted for publication in the Astrophysical
Journa
Fermi Gamma-ray Space Telescope Observations of Recent Gamma-ray Outbursts from 3C 454.3
The flat spectrum radio quasar 3C~454.3 underwent an extraordinary outburst
in December 2009 when it became the brightest gamma-ray source in the sky for
over one week. Its daily flux measured with the Fermi Large Area Telescope at
photon energies E>100 MeV reached F = 22+/-1 x 10^-6 ph cm^-2 s^-1,
representing the highest daily flux of any blazar ever recorded in high-energy
gamma-rays. It again became the brightest source in the sky in 2010 April,
triggering a pointed-mode observation by Fermi. The correlated gamma-ray
temporal and spectral properties during these exceptional events are presented
and discussed. The main results show flux variability over time scales less
than 3 h and very mild spectral variability with an indication of gradual
hardening preceding major flares. No consistent loop pattern emerged in the
gamma-ray spectral index vs flux plane. A minimum Doppler factor of ~ 15 is
derived, and the maximum energy of a photon from 3C 454.3 is ~ 20 GeV. The
spectral break at a few GeV is inconsistent with Klein-Nishina softening from
power-law electrons scattering Ly_alpha line radiation, and a break in the
underlying electron spectrum in blazar leptonic models is implied.Comment: submitted to the Astrophysical Journa
Fermi Large Area Telescope Gamma-Ray Detection of the Radio Galaxy M87
We report the Fermi-LAT discovery of high-energy (MeV/GeV) gamma-ray emission
positionally consistent with the center of the radio galaxy M87, at a source
significance of over 10 sigma in ten-months of all-sky survey data. Following
the detections of Cen A and Per A, this makes M87 the third radio galaxy seen
with the LAT. The faint point-like gamma-ray source has a >100 MeV flux of 2.45
(+/- 0.63) x 10^-8 ph cm^-2 s^-1 (photon index = 2.26 +/- 0.13) with no
significant variability detected within the LAT observation. This flux is
comparable with the previous EGRET upper limit (< 2.18 x 10^-8 ph cm^-2 s^-1, 2
sigma), thus there is no evidence for a significant MeV/GeV flare on decade
timescales. Contemporaneous Chandra and VLBA data indicate low activity in the
unresolved X-ray and radio core relative to previous observations, suggesting
M87 is in a quiescent overall level over the first year of Fermi-LAT
observations. The LAT gamma-ray spectrum is modeled as synchrotron self-Compton
(SSC) emission from the electron population producing the radio-to-X-ray
emission in the core. The resultant SSC spectrum extrapolates smoothly from the
LAT band to the historical-minimum TeV emission. Alternative models for the
core and possible contributions from the kiloparsec-scale jet in M87 are
considered, and can not be excluded.Comment: ApJ, accepted, 6 pages, 4 figures. Corresponding authors: C.C.
Cheung, W. McConvill
Misperceptions in the Trajectories of Objects undergoing Curvilinear Motion
Trajectory perception is crucial in scene understanding and action. A variety of trajectory misperceptions have been reported in the literature. In this study, we quantify earlier observations that reported distortions in the perceived shape of bilinear trajectories and in the perceived positions of their deviation. Our results show that bilinear trajectories with deviation angles smaller than 90 deg are perceived smoothed while those with deviation angles larger than 90 degrees are perceived sharpened. The sharpening effect is weaker in magnitude than the smoothing effect. We also found a correlation between the distortion of perceived trajectories and the perceived shift of their deviation point. Finally, using a dual-task paradigm, we found that reducing attentional resources allocated to the moving target causes an increase in the perceived shift of the deviation point of the trajectory. We interpret these results in the context of interactions between motion and position systems
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