361 research outputs found
3G networks in emergency telemedicine - An in-depth evaluation & analysis
The evolution of telecommunications technologies in connection with the robustness and the fidelity these new systems provide, have opened up many new horizons as regards the provision of healthcare and the quality of service from the side of the experts to that of the patients. The purpose of this paper is to evaluate the third generation telecommunications systems that are only recently being deployed in Europe, as well as argue on why a transition from 2G and 2.5G to 3G telecommunications systems could prove to be crucial, especially in relation to emergency telemedicine. The experimental results of the use of these systems are analyzed, the implementation of a tele-consultation unit is presented and their exploitation capabilities are explored
Non--Heisenberg Spin Dynamics of Double-Exchange Ferromagnets with Coulomb Repulsion
With a variational three--body calculation we study the role of the interplay
between the onsite Coulomb, Hund's rule, and superexchange interactions on the
spinwave excitation spectrum of itinerant ferromagnets. We show that
correlations between a Fermi sea electron--hole pair and a magnon result in a
very pronounced zone boundary softening and strong deviations from the
Heisenberg spinwave dispersion. We show that this spin dynamics depends
sensitively on the Coulomb and exchange interactions and discuss its possible
relevance to experiments in the manganites.Comment: 4 pages, 4 figures, published in Physical Review B as rapid
communication
Use of 3G mobile phone links for teleconsultation between a moving ambulance and a hospital base station
The importance of this paper lays in its suggestion: minimise the time for the initial treatment of a patient. As soon as an ambulance receives a patient, a videoconferencing session can be initiated between the moving vehicle and a base station in a hospital where a medical consultant resides. The communication link is implemented using 3G networks. Effectively, the use of such a system can decrease fatality on patients being transferred to A&E, as expert opinion can be obtained straight away. This paper was repeatedly cited in IEEE papers and formed the basis for an EPSRC proposal that was recently submitted
Three--body Correlation Effects on the Spin Dynamics of Double--Exchange Ferromagnets
We present a variational calculation of the spin wave excitation spectrum of
double--exchange ferromagnets in different dimensions. Our theory recovers the
Random Phase approximation and 1/S expansion results as limiting cases and can
be used to study the intermediate exchange coupling and electron concentration
regime relevant to the manganites. In particular, we treat exactly the long
range three--body correlations between a Fermi sea electron--hole pair and a
magnon excitation and show that they strongly affect the spin dynamics in the
parameter range relevant to experiments in the manganites. The manifestations
of these correlations are many-fold. We demonstrate that they significantly
change the ferromagnetic phase boundary. In addition to a decrease in the
magnon stiffness, we obtain an instability of the ferromagnetic state against
spin wave excitations close to the Brillouin zone boundary.Within a range of
intermediate concentrations, we find a strong softening of the spin wave
dispersion as compared to the Heisenberg ferromagnet with the same stiffness,
which changes into hardening for other concentrations. We discuss the relevance
of these results to experiments in colossal magnetoresistance ferromagnets.Comment: 14 pages, 11 figures, published in Phys. Rev. B (1 figure added,
references added
Ambulance 3G
Minimising the time required for a patient to receive primary care has always been the concern of the Accidents and Emergency units. Ambulances are usually the first to arrive on the scene and to administer first aid.
However, as the time that it takes to transfer the patient to the hospital increases, so does the fatality rate.
In this paper, a mobile teleconsultation system is presented, based primarily on third generation mobile links and on Wi-Fi hotspots around a city. This system can be installed inside an ambulance and will permit high-resolution videoconferencing between the moving vehicle and a doctor or a consultant within a base station (usually a hospital). In addition to video and voice, high quality still images and screenshots from medical equipment can also be sent.
The test was carried out in Athens, Greece where a 3G system was recently deployed by Vodafone. The results show that the system can perform satisfactory in most conditions and can effectively increase the patient’s quality of service, while having a modest cost
Femtosecond Coherent Control of Spin with Light in (Ga,Mn)As ferromagnets
Using density matrix equations of motion, we predict a femtosecond collective
spin tilt triggered by nonlinear, near--ultraviolet (3eV), coherent
photoexcitation of (Ga,Mn)As ferromagnetic semiconductors with linearly
polarized light. This dynamics results from carrier coherences and nonthermal
populations excited in the \{111\} equivalent directions of the Brillouin zone
and triggers a subsequent uniform precession. We predict nonthermal
magnetization control by tuning the laser frequency and polarization direction.
Our mechanism explains recent ultrafast pump--probe experiments.Comment: 4 pages, 3 figures, published in Physical Review Letter
Magnetization Relaxation and Collective Spin Excitations in Correlated Double--Exchange Ferromagnets
We study spin relaxation and dynamics of collective spin excitations in
correlated double--exchange ferromagnets. For this, we introduce an expansion
of the Green's functions equations of motion that treats non--perturbativerly
all correlations between a given number of spin and charge excitations and
becomes exact within a sub--space of states. Our method treats relaxation
beyond Fermi's Golden Rule while recovering previous variational results for
the spin--wave dispersion. We find that the momentum dependence of the
spin--wave dephasing rate changes qualitatively due to the on--site Coulomb
interaction, in a way that resembles experiment, and depends on its interplay
with the magnetic exchange interaction and itinerant spin lifetime. We show
that the collective spin relaxation and its dependence on the carrier
concentration depends sensitively on three--body correlations between a spin
excitation and a Fermi sea electron and hole. The above spin dynamics can be
controlled via the itinerant carrier population.Comment: 13 pages, 10 figures, published in Phys. Rev.
Spin dynamics in (III,Mn)V ferromagnetic semiconductors: the role of correlations
We address the role of correlations between spin and charge degrees of
freedom on the dynamical properties of ferromagnetic systems governed by the
magnetic exchange interaction between itinerant and localized spins. For this
we introduce a general theory that treats quantum fluctuations beyond the
Random Phase Approximation based on a correlation expansion of the Green's
function equations of motion. We calculate the spin susceptibility, spin--wave
excitation spectrum, and magnetization precession damping. We find that
correlations strongly affect the magnitude and carrier concentration dependence
of the spin stiffness and magnetization Gilbert damping.Comment: 4 pages, 3 figures, content and figures changed, published in Phys.
Rev. Let
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