520 research outputs found
The effect of age and font size on reading text on handheld computers
Though there have been many studies of computer based text reading, only a few have considered the small screens of handheld computers. This paper presents an investigation into the effect of varying font size between 2 and 16 point on reading text on a handheld computer. By using both older and younger participants the possible effects of age were examined. Reading speed and accuracy were measured and subjective views of participants recorded. Objective results showed that there was little difference in reading performance above 6 point, but subjective comments from participants showed a preference for sizes in the middle range. We therefore suggest, for reading tasks, that designers of interfaces for mobile computers provide fonts in the range of 8-12 point to maximize readability for the widest range of users
Time transfer and frequency shift to the order 1/c^4 in the field of an axisymmetric rotating body
Within the weak-field, post-Newtonian approximation of the metric theories of
gravity, we determine the one-way time transfer up to the order 1/c^4, the
unperturbed term being of order 1/c, and the frequency shift up to the order
1/c^4. We adapt the method of the world-function developed by Synge to the
Nordtvedt-Will PPN formalism. We get an integral expression for the
world-function up to the order 1/c^3 and we apply this result to the field of
an isolated, axisymmetric rotating body. We give a new procedure enabling to
calculate the influence of the mass and spin multipole moments of the body on
the time transfer and the frequency shift up to the order 1/c^4. We obtain
explicit formulas for the contributions of the mass, of the quadrupole moment
and of the intrinsic angular momentum. In the case where the only PPN
parameters different from zero are beta and gamma, we deduce from these results
the complete expression of the frequency shift up to the order 1/c^4. We
briefly discuss the influence of the quadrupole moment and of the rotation of
the Earth on the frequency shifts in the ACES mission.Comment: 17 pages, no figure. Version 2. Abstract and Section II revised. To
appear in Physical Review
Higher moments of nucleon spin structure functions in heavy baryon chiral perturbation theory and in a resonance model
The third moment of the twist-3 part of the nucleon spin structure
function is generalized to arbitrary momentum transfer and is
evaluated in heavy baryon chiral perturbation theory (HBChPT) up to order
and in a unitary isobar model (MAID). We show how to link
as well as higher moments of the nucleon spin structure functions
and to nucleon spin polarizabilities. We compare our results with the
most recent experimental data, and find a good description of these available
data within the unitary isobar model. We proceed to extract the twist-4 matrix
element which appears in the suppressed term in the twist
expansion of the spin structure function for proton and neutron.Comment: 30 pages, 7 figure
Hadronic freeze-out following a first order hadronization phase transition in ultrarelativistic heavy-ion collisions
We analyze the hadronic freeze-out in ultra-relativistic heavy ion collisions
at RHIC in a transport approach which combines hydrodynamics for the early,
dense, deconfined stage of the reaction with a microscopic non-equilibrium
model for the later hadronic stage at which the hydrodynamic equilibrium
assumptions are not valid. With this ansatz we are able to self-consistently
calculate the freeze-out of the system and determine space-time hypersurfaces
for individual hadron species. The space-time domains of the freeze-out for
several hadron species are found to be actually four-dimensional, and differ
drastically for the individual hadrons species. Freeze-out radii distributions
are similar in width for most hadron species, even though the Omega-baryon is
found to be emitted rather close to the phase boundary and shows the smallest
freeze-out radii and times among all baryon species. The total lifetime of the
system does not change by more than 10% when going from SPS to RHIC energies.Comment: 11 pages, 4 eps-figures included, revised versio
Management of Pain in the United StatesâA Brief History and Implications for the Opioid Epidemic
Pain management in the United States reflects attitudes to those in pain. Increased numbers of disabled veterans in the 1940s to 1960s led to an increased focus on pain and its treatment. The view of the person in pain has moved back and forth between a physiological construct to an individual with pain where perception may be related to social, emotional, and cultural factors. Conceptually, pain has both a medical basis and a political context, moving between, for example, objective evidence of disability due to pain and subjective concerns of malingering. In the 20th century, pain management became predominately pharmacologic. Perceptions of undertreatment led to increased use of opioids, at first for those with cancer-related pain and then later for noncancer pain without the multidimensional care that was intended. The increased use was related to exaggerated claims in the medical literature and by the pharmaceutical industry, of a lack of addiction in the setting of noncancer pain for these medicationsâa claim that was subsequently found to be false and deliberatively deceptive; an epidemic of opioid prescribing began in the 1990s. An alarming rise in deaths due to opioids has led to several efforts to decrease use, both in patients with noncancer conditions and in those with cancer and survivors of cancer
Disordered Systems and the Replica Method in AdS/CFT
We formulate a holographic description of effects of disorder in conformal
field theories based on the replica method and the AdS/CFT correspondence.
Starting with copies of conformal field theories, randomness with a
gaussian distribution is described by a deformation of double trace operators.
After computing physical quantities, we take the limit at the final
step. We compute correlation functions in the disordered systems by using the
holographic replica method as well as the formulation in the conformal field
theory. We find examples where disorder changes drastically the scaling of two
point functions. The renormalization group flow of the effective central charge
in our disordered systems is also discussed.Comment: 26 pages, references added, published versio
Reconstruction of Black Hole Metric Perturbations from Weyl Curvature
Perturbation theory of rotating black holes is usually described in terms of
Weyl scalars and , which each satisfy Teukolsky's complex
master wave equation and respectively represent outgoing and ingoing radiation.
On the other hand metric perturbations of a Kerr hole can be described in terms
of (Hertz-like) potentials in outgoing or ingoing {\it radiation
gauges}. In this paper we relate these potentials to what one actually computes
in perturbation theory, i.e and . We explicitly construct
these relations in the nonrotating limit, preparatory to devising a
corresponding approach for building up the perturbed spacetime of a rotating
black hole. We discuss the application of our procedure to second order
perturbation theory and to the study of radiation reaction effects for a
particle orbiting a massive black hole.Comment: 6 Pages, Revtex
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