53,691 research outputs found
Supporting research and development in ambulance services: research for better healthcare in prehospital settings
Background This paper discusses recent developments in research support for ambulance trusts in England and Wales and how this could be designed to lead to better implementation, collaboration in and initiation of high-quality research to support a truly evidence-based service.
Method The National Ambulance Research Steering Group was set up in 2007 to establish the strategic direction for involvement of regional ambulance services in developing relevant and well-designed research for improving the quality of services to patients.
Results Ambulance services have been working together and with academic partners to implement research and to participate, collaborate and lead the design of research that is relevant for patients and ambulance services.
Conclusion New structures to support the strategic development of ambulance and prehospital research will help address gaps in the evidence for health interventions and service delivery in prehospital and ambulance care and ensure that ambulance services can increase their capacity and capability for high-quality research
GRB 060218/SN 2006aj: A Gamma-Ray Burst and Prompt Supernova at z=0.0335
We report the imaging and spectroscopic localization of GRB 060218 to a
low-metallicity dwarf starburst galaxy at z = 0.03345 +/- 0.00006. In addition
to making it the second nearest gamma-ray burst known, optical spectroscopy
reveals the earliest detection of weak, supernova-like Si II near 5720
Angstroms (0.1c), starting 1.95 days after the burst trigger. UBVRI photometry
obtained between 1 and 26 days post-burst confirms the early rise of supernova
light, and suggests a short time delay between the gamma-ray burst and the
onset of SN 2006aj if the early appearance of a soft component in the X-ray
spectrum is understood as a ``shock breakout''. Together, these results verify
the long-hypothesized origin of soft gamma-ray bursts in the deaths of massive
stars.Comment: 5 pages, 2 figure
Acoustically evoked potentials in two cephalopods inferred using the auditory brainstem response (ABR) approach
It is still a matter of debate whether cephalopods can detect sound frequencies above 400 Hz. So far there is no proof for the detection of underwater sound above 400 Hz via a physiological approach. The controversy of whether cephalopods have a sound detection ability above 400 Hz was tested using the auditory brainstem response (ABR) approach, which has been successfully applied in fish, crustaceans, amphibians, reptiles and birds. Using ABR we found that auditory evoked potentials can be obtained in the frequency range 400 to 1500 Hz (Sepiotheutis lessoniana) and 400 to 1000 Hz (Octopus vulgaris), respectively. The thresholds of S. lessoniana were generally lower than those of O. vulgaris
Electronic and optical properties of LiBC
LiBC, a semiconducting ternary borocarbide constituted of the lightest
elements only, has been synthesized and characterized by x-ray powder
diffraction, dielectric spectroscopy, and conductivity measurements. Utilizing
an infrared microscope the phonon spectrum has been investigated in single
crystals. The in-plane B-C stretching mode has been detected at 150 meV,
noticeably higher than in AlB2, a non-superconducting isostructural analog of
MgB2. It is this stretching mode, which reveals a strong electron-phonon
coupling in MgB2, driving it into a superconducting state below 40 K, and is
believed to mediate predicted high-temperature superconductivity in hole-doped
LiBC [H. Rosner, A. Kitaigorodsky, and W. E. Pickett, Phys. Rev. Lett. 88,
127001 (2002)].Comment: 4 pages, 4 figure
Environment-dependent dissipation in quantum Brownian motion
The dissipative dynamics of a quantum Brownian particle is studied for
different types of environment. We derive analytic results for the time
evolution of the mean energy of the system for Ohmic, sub-Ohmic and super-Ohmic
environments, without performing the Markovian approximation. Our results allow
to establish a direct link between the form of the environmental spectrum and
the thermalization dynamics. This in turn leads to a natural explanation of the
microscopic physical processes ruling the system time evolution both in the
short-time non-Markovian region and in the long-time Markovian one. Our
comparative study of thermalization for different environments sheds light on
the physical contexts in which non-Markovian dissipation effects are dominant.Comment: 10 pages, 6 figures, v2: added new references and paragraph
Who Contributes to the Knowledge Sharing Economy?
Information sharing dynamics of social networks rely on a small set of
influencers to effectively reach a large audience. Our recent results and
observations demonstrate that the shape and identity of this elite, especially
those contributing \emph{original} content, is difficult to predict.
Information acquisition is often cited as an example of a public good. However,
this emerging and powerful theory has yet to provably offer qualitative
insights on how specialization of users into active and passive participants
occurs.
This paper bridges, for the first time, the theory of public goods and the
analysis of diffusion in social media. We introduce a non-linear model of
\emph{perishable} public goods, leveraging new observations about sharing of
media sources. The primary contribution of this work is to show that
\emph{shelf time}, which characterizes the rate at which content get renewed,
is a critical factor in audience participation. Our model proves a fundamental
\emph{dichotomy} in information diffusion: While short-lived content has simple
and predictable diffusion, long-lived content has complex specialization. This
occurs even when all information seekers are \emph{ex ante} identical and could
be a contributing factor to the difficulty of predicting social network
participation and evolution.Comment: 15 pages in ACM Conference on Online Social Networks 201
Nucleon-nucleon cross sections in neutron-rich matter and isospin transport in heavy-ion reactions at intermediate energies
Nucleon-nucleon (NN) cross sections are evaluated in neutron-rich matter
using a scaling model according to nucleon effective masses. It is found that
the in-medium NN cross sections are not only reduced but also have a different
isospin dependence compared with the free-space ones. Because of the
neutron-proton effective mass splitting the difference between nn and pp
scattering cross sections increases with the increasing isospin asymmetry of
the medium. Within the transport model IBUU04, the in-medium NN cross sections
are found to influence significantly the isospin transport in heavy-ion
reactions. With the in-medium NN cross sections, a symmetry energy of
was found most acceptable
compared with both the MSU isospin diffusion data and the presently acceptable
neutron-skin thickness in Pb. The isospin dependent part of isobaric nuclear incompressibility was further narrowed down to
MeV. The possibility of determining simultaneously the in-medium
NN cross sections and the symmetry energy was also studied. The proton
transverse flow, or even better the combined transverse flow of neutrons and
protons, can be used as a probe of the in-medium NN cross sections without much
hindrance from the uncertainties of the symmetry energy.Comment: 32 pages including 14 figures. Submitted to Phys. Rev.
Interaction of hemojuvelin with neogenin results in iron accumulation in human embryonic kidney 293 cells
Type 2 hereditary hemochromatosis (HH) or juvenile hemochromatosis is an early onset, genetically heterogeneous, autosomal recessive disorder of iron overload. Type 2A HH is caused by mutations in the recently cloned hemojuvelin gene (HJV; also called HFE2) (Papanikolaou, G., Samuels, M. E., Ludwig, E. H., MacDonald, M. L., Franchini, P. L., Dube, M. P., Andres, L., MacFarlane, J., Sakellaropoulos, N., Politou, M., Nemeth, E., Thompson, J., Risler, J. K., Zaborowska, C., Babakaiff, R., Radomski, C. C., Pape, T. D., Davidas, O., Christakis, J., Brissot, P., Lockitch, G., Ganz, T., Hayden, M. R., and Goldberg, Y. P. (2004) Nat. Genet. 36, 77–82), whereas Type 2B HH is caused by mutations in hepcidin. HJV is highly expressed in both skeletal muscle and liver. Mutations in HJV are implicated in the majority of diagnosed juvenile hemochromatosis patients. In this study, we stably transfected HJV cDNA into human embryonic kidney 293 cells and characterized the processing of HJV and its effect on iron homeostasis. Our results indicate that HJV is a glycosylphosphatidylinositol-linked protein and undergoes a partial autocatalytic cleavage during its intracellular processing. HJV co-immunoprecipitated with neogenin, a receptor involved in a variety of cellular signaling processes. It did not interact with the closely related receptor DCC (deleted in Colon Cancer). In addition, the HJV G320V mutant implicated in Type 2A HH did not co-immunoprecipitate with neogenin. Immunoblot analysis of ferritin levels and transferrin-55Fe accumulation studies indicated that the HJV-induced increase in intracellular iron levels in human embryonic kidney 293 cells is dependent on the presence of neogenin in the cells, thus linking these two proteins to intracellular iron homeostasis
The Fate of the Accelerating Universe
The presently accelerating universe may keep accelerating forever, eventually
run into the event horizon problem, and thus be in conflict with the
superstring idea. In the other way around, the current accelerating phase as
well as the fate of the universe may be swayed by a negative cosmological
constant, which dictates a big crunch. Based on the current observational data,
in this paper we investigate how large the magnitude of a negative cosmological
constant is allowed to be. In addition, for distinguishing the sign of the
cosmological constant via observations, we point out that a measure of the
evolution of the dark energy equation of state may be a good discriminator.
Hopefully future observations will provide much more detailed information about
dark energy and thereby indicates the sign of the cosmological constant as well
as the fate of the presently accelerating universe.Comment: 16 pages, 5 figures, LaTe
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