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Defining user perception of distributed multimedia quality
This article presents the results of a study that explored the human side of the multimedia experience. We propose a model that assesses quality variation from three distinct levels: the network, the media and the content levels; and from two views: the technical and the user perspective. By facilitating parameter variation at each of the quality levels and from each of the perspectives, we were able to examine their impact on user quality perception. Results show that a significant reduction in frame rate does not proportionally reduce the user's understanding of the presentation independent of technical parameters, that multimedia content type significantly impacts user information assimilation, user level of enjoyment, and user perception of quality, and that the device display type impacts user information assimilation and user perception of quality. Finally, to ensure the transfer of information, low-level abstraction (network-level) parameters, such as delay and jitter, should be adapted; to maintain the user's level of enjoyment, high-level abstraction quality parameters (content-level), such as the appropriate use of display screens, should be adapted
Elastic energy of proteins and the stages of protein folding
We propose a universal elastic energy for proteins, which depends only on the
radius of gyration and the residue number . It is constructed using
physical arguments based on the hydrophobic effect and hydrogen bonding.
Adjustable parameters are fitted to data from the computer simulation of the
folding of a set of proteins using the CSAW (conditioned self-avoiding walk)
model. The elastic energy gives rise to scaling relations of the form
in different regions. It shows three folding stages
characterized by the progression with exponents , which we
identify as the unfolded stage, pre-globule, and molten globule, respectively.
The pre-globule goes over to the molten globule via a break in behavior akin to
a first-order phase transition, which is initiated by a sudden acceleration of
hydrogen bonding
A systematically coarse-grained model for DNA, and its predictions for persistence length, stacking, twist, and chirality
We introduce a coarse-grained model of DNA with bases modeled as rigid-body
ellipsoids to capture their anisotropic stereochemistry. Interaction potentials
are all physicochemical and generated from all-atom simulation/parameterization
with minimal phenomenology. Persistence length, degree of stacking, and twist
are studied by molecular dynamics simulation as functions of temperature, salt
concentration, sequence, interaction potential strength, and local position
along the chain, for both single- and double-stranded DNA where appropriate.
The model of DNA shows several phase transitions and crossover regimes in
addition to dehybridization, including unstacking, untwisting, and collapse
which affect mechanical properties such as rigidity and persistence length. The
model also exhibits chirality with a stable right-handed and metastable
left-handed helix.Comment: 30 pages, 20 figures, Supplementary Material available at
http://www.physics.ubc.ca/~steve/publications.htm
Mean-field methods in evolutionary duplication-innovation-loss models for the genome-level repertoire of protein domains
We present a combined mean-field and simulation approach to different models
describing the dynamics of classes formed by elements that can appear,
disappear or copy themselves. These models, related to a paradigm
duplication-innovation model known as Chinese Restaurant Process, are devised
to reproduce the scaling behavior observed in the genome-wide repertoire of
protein domains of all known species. In view of these data, we discuss the
qualitative and quantitative differences of the alternative model formulations,
focusing in particular on the roles of element loss and of the specificity of
empirical domain classes.Comment: 10 Figures, 2 Table
Energy Storage in a Hamiltonian System in Partial Contact with a Heat Bath
To understand the mechanism allowing for the long-term storage of excess
energy in proteins, we study a Hamiltonian system consisting of several coupled
pendula in partial contact with a heat bath. It is found that energy storage is
possible when the motion of each pendulum switches between oscillatory
(vibrational) and rotational (phase-slip) modes. The storage time increases
almost exponentially to the square root of the injected energy. The relevance
of our mechanism to protein motors is discussed.Comment: 8 pages, 4 figures, to appear in J.Phys.Soc.Jp
Radiative lifetime measurements of rubidium Rydberg states
We have measured the radiative lifetimes of ns, np and nd Rydberg states of
rubidium in the range 28 < n < 45. To enable long-lived states to be measured,
our experiment uses slow-moving Rb atoms in a magneto-optical trap (MOT). Two
experimental techniques have been adopted to reduce random and systematic
errors. First, a narrow-bandwidth pulsed laser is used to excite the target
Rydberg state, resulting in minimal shot-to-shot variation in the initial state
population. Second, we monitor the target state population as a function of
time delay from the laser pulse using a short-duration, millimetre-wave pulse
that is resonant with a one- or two-photon transition. We then selectively
field ionize the monitor state, and detect the resulting electrons with a
micro-channel plate. This signal is an accurate mirror of the target state
population, and is uncontaminated by contributions from other states which are
populated by black body radiation. Our results are generally consistent with
other recent experimental results obtained using a less sensitive method, and
are also in excellent agreement with theory.Comment: 27 pages,6 figure
Essential facts of the monitoring of the sand extraction and its impact on the Flemish banks on the Belgian Continental Shelf from 2003 to 2012
The monitoring of sand extraction on the Flemish sandbanks of the Belgian continental shelf is based on multiple types of data: statistics derived from the extraction registers, data from the Electronic Monitoring System (EMS = “black-boxes”) on board the dredging vessels (complete records are available since 2003), and regular bathymetric surveys with the multibeam echosounders MBES) EM1002 and EM3002D (installed on the R/V Belgica) across the sandbanks along parallel lines and on specific areas. The analysis of the various types of data provides a 4D (space and time) view of the evolution of the extraction and admits robust and pragmatic conclusions about the real impact of the sand extraction on the marine environment. From 2003 to 2012, the global bathymetric evolution, based on MBES EM1002 and EM3002D measurements along lines across the control zones, confirms thestraightforward relation between the extraction and the bathymetrical evolution. On a larger scale, virtually all ofthe bathymetric variation can be explained by the extraction itself. In areas without any extraction, no significanttrend of the bathymetry is observed
ProtoEXIST: Advanced Prototype CZT Coded Aperture Telescopes for EXIST
{\it ProtoEXIST1} is a pathfinder for the {\it EXIST-HET}, a coded aperture
hard X-ray telescope with a 4.5 m CZT detector plane a 9070 degree
field of view to be flown as the primary instrument on the {\it EXIST} mission
and is intended to monitor the full sky every 3 h in an effort to locate GRBs
and other high energy transients. {\it ProtoEXIST1} consists of a 256 cm
tiled CZT detector plane containing 4096 pixels composed of an 88 array
of individual 1.95 cm 1.95 cm 0.5 cm CZT detector modules
each with a 8 8 pixilated anode configured as a coded aperture
telescope with a fully coded field of view employing
passive side shielding and an active CsI anti-coincidence rear shield, recently
completed its maiden flight out of Ft. Sumner, NM on the 9th of October 2009.
During the duration of its 6 hour flight on-board calibration of the detector
plane was carried out utilizing a single tagged 198.8 nCi Am-241 source along
with the simultaneous measurement of the background spectrum and an observation
of Cygnus X-1. Here we recount the events of the flight and report on the
detector performance in a near space environment. We also briefly discuss {\it
ProtoEXIST2}: the next stage of detector development which employs the {\it
NuSTAR} ASIC enabling finer (3232) anode pixilation. When completed
{\it ProtoEXIST2} will consist of a 256 cm tiled array and be flown
simultaneously with the ProtoEXIST1 telescope
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