16,749 research outputs found
Capacity of a Class of Deterministic Relay Channels
The capacity of a class of deterministic relay channels with the transmitter
input X, the receiver output Y, the relay output Y_1 = f(X, Y), and a separate
communication link from the relay to the receiver with capacity R_0, is shown
to be
C(R_0) = \max_{p(x)} \min \{I(X;Y)+R_0, I(X;Y, Y_1) \}.
Thus every bit from the relay is worth exactly one bit to the receiver. Two
alternative coding schemes are presented that achieve this capacity. The first
scheme, ``hash-and-forward'', is based on a simple yet novel use of random
binning on the space of relay outputs, while the second scheme uses the usual
``compress-and-forward''. In fact, these two schemes can be combined together
to give a class of optimal coding schemes. As a corollary, this relay capacity
result confirms a conjecture by Ahlswede and Han on the capacity of a channel
with rate-limited state information at the decoder in the special case when the
channel state is recoverable from the channel input and the output.Comment: 17 pages, submitted to IEEE Transactions on Information Theor
Increasing the Capacity of Primary Care Through Enabling Technology.
Primary care is the foundation of effective and high-quality health care. The role of primary care clinicians has expanded to encompass coordination of care across multiple providers and management of more patients with complex conditions. Enabling technology has the potential to expand the capacity for primary care clinicians to provide integrated, accessible care that channels expertise to the patient and brings specialty consultations into the primary care clinic. Furthermore, technology offers opportunities to engage patients in advancing their health through improved communication and enhanced self-management of chronic conditions. This paper describes enabling technologies in four domains (the body, the home, the community, and the primary care clinic) that can support the critical role primary care clinicians play in the health care system. It also identifies challenges to incorporating these technologies into primary care clinics, care processes, and workflow
State Amplification
We consider the problem of transmitting data at rate R over a state dependent
channel p(y|x,s) with the state information available at the sender and at the
same time conveying the information about the channel state itself to the
receiver. The amount of state information that can be learned at the receiver
is captured by the mutual information I(S^n; Y^n) between the state sequence
S^n and the channel output Y^n. The optimal tradeoff is characterized between
the information transmission rate R and the state uncertainty reduction rate
\Delta, when the state information is either causally or noncausally available
at the sender. This result is closely related and in a sense dual to a recent
study by Merhav and Shamai, which solves the problem of masking the state
information from the receiver rather than conveying it.Comment: 9 pages, 4 figures, submitted to IEEE Trans. Inform. Theory, revise
Leading Quenching Effects in the Proton Magnetic Moment
We present the first investigation of the extrapolation of quenched nucleon
magnetic moments in quenched chiral effective field theory. We utilize
established techniques in finite-range regularisation and compare with standard
dimensional regularisation methods. Finite-volume corrections to the relevant
loop integrals are also addressed. Finally, the contributions of dynamical sea
quarks to the proton moment are estimated using a recently discovered
phenomenological link between quenched and physical QCD.Comment: 9 pages, 11 figs; v2: revised finite volume discussio
Towards a Connection Between Nuclear Structure and QCD
As we search for an ever deeper understanding of the structure of hadronic
matter one of the most fundamental questions is whether or not one can make a
connection to the underlying theory of the strong interaction, QCD. We build on
recent advances in the chiral extrapolation problem linking lattice QCD at
relatively large ``light quark'' masses to the physical world to estimate the
scalar polarizability of the nucleon. The latter plays a key role in modern
relativistic mean-field descriptions of nuclei and nuclear matter (such as QMC)
and, in particular, leads to a very natural saturation mechanism. We
demonstrate that the value of the scalar polarizability extracted from the
lattice data is consistent with that needed for a successful description of
nuclei within the framework of QMC. In a very real sense this is the first hint
of a direct connection between QCD and the properties of finite nuclei.Comment: Lecture presented at: 18th Nishinomiya-Yukawa Memorial Symposium On
Strangeness In Nuclear Matter : 4-5 Dec 2003, Nishinomiya, Japa
Absorbing-state phase transitions on percolating lattices
We study nonequilibrium phase transitions of reaction-diffusion systems
defined on randomly diluted lattices, focusing on the transition across the
lattice percolation threshold. To develop a theory for this transition, we
combine classical percolation theory with the properties of the supercritical
nonequilibrium system on a finite-size cluster. In the case of the contact
process, the interplay between geometric criticality due to percolation and
dynamical fluctuations of the nonequilibrium system leads to a new universality
class. The critical point is characterized by ultraslow activated dynamical
scaling and accompanied by strong Griffiths singularities. To confirm the
universality of this exotic scaling scenario we also study the generalized
contact process with several (symmetric) absorbing states, and we support our
theory by extensive Monte-Carlo simulations.Comment: 11 pages, 10 eps figures included, final version as publishe
Baryon resonances and hadronic interactions in a finite volume
In a finite volume, resonances and multi-hadron states are identified by
discrete energy levels. When comparing the results of lattice QCD calculations
to scattering experiments, it is important to have a way of associating the
energy spectrum of the finite-volume lattice with the asymptotic behaviour of
the S-matrix. A new technique for comparing energy eigenvalues with scattering
phase shifts is introduced, which involves the construction of an exactly
solvable matrix Hamiltonian model. The model framework is applied to the case
of decay, but is easily generalized to include
multi-channel scattering. Extracting resonance parameters involves matching the
energy spectrum of the model to that of a lattice QCD calculation. The
resulting fit parameters are then used to generate phase shifts. Using a sample
set of pseudodata, it is found that the extraction of the resonance position is
stable with respect to volume for a variety of regularization schemes, and
compares favorably with the well-known Luescher method. The model-dependence of
the result is briefly investigated.Comment: 7 pages, 3 figures. Talk presented at the 30th International
Symposium on Lattice Field Theory (Lattice 2012), June 24-29, 2012, Cairns,
Australi
Underflight calibration of SOHO/CDS and Hinode/EIS with EUNIS-07
Flights of Goddard Space Flight Center's Extreme-Ultraviolet Normal-Incidence
Spectrograph (EUNIS) sounding rocket in 2006 and 2007 provided updated
radiometric calibrations for SOHO/CDS and Hinode/EIS. EUNIS carried two
independent imaging spectrographs covering wavebands of 300-370 A in first
order and 170-205 A in second order. After each flight, end-to-end radiometric
calibrations of the rocket payload were carried out in the same facility used
for pre-launch calibrations of CDS and EIS. During the 2007 flight, EUNIS, SOHO
CDS and Hinode EIS observed the same solar locations, allowing the EUNIS
calibrations to be directly applied to both CDS and EIS. The measured CDS NIS 1
line intensities calibrated with the standard (version 4) responsivities with
the standard long-term corrections are found to be too low by a factor of 1.5
due to the decrease in responsivity. The EIS calibration update is performed in
two ways. One is using the direct calibration transfer of the calibrated
EUNIS-07 short wavelength (SW) channel. The other is using the insensitive line
pairs, in which one member was observed by EUNIS-07 long wavelength (LW)
channel and the other by EIS in either LW or SW waveband. Measurements from
both methods are in good agreement, and confirm (within the measurement
uncertainties) the EIS responsivity measured directly before the instrument's
launch. The measurements also suggest that the EIS responsivity decreased by a
factor of about 1.2 after the first year of operation. The shape of the EIS SW
response curve obtained by EUNIS-07 is consistent with the one measured in
laboratory prior to launch. The absolute value of the quiet-Sun He II 304 A
intensity measured by EUNIS-07 is consistent with the radiance measured by CDS
NIS in quiet regions near the disk center and the solar minimum irradiance
obtained by CDS NIS and SDO/EVE recently.Comment: 16 pages, 14 figures, 5 tables, accepted by ApJ Supplement (Sep.
2011
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