83,387 research outputs found
Refinement by interpretation in {\pi}-institutions
The paper discusses the role of interpretations, understood as multifunctions
that preserve and reflect logical consequence, as refinement witnesses in the
general setting of pi-institutions. This leads to a smooth generalization of
the refinement-by-interpretation approach, recently introduced by the authors
in more specific contexts. As a second, yet related contribution a basis is
provided to build up a refinement calculus of structured specifications in and
across arbitrary pi-institutions.Comment: In Proceedings Refine 2011, arXiv:1106.348
IMI – industry guidelines and ethical considerations for myopia control report
PURPOSE. To discuss guidelines and ethical considerations associated with the development and prescription of treatments intended for myopia control (MC). METHODS. Critical review of published papers and guidance documents was undertaken, with a view to carefully considering the ethical standards associated with the investigation, development, registration, marketing, prescription, and use of MC treatments. RESULTS. The roles and responsibilities of regulatory bodies, manufacturers, academics, eye care practitioners, and patients in the use of MC treatments are explored. Particular attention is given to the ethical considerations for deciding whether to implement a MC strategy and how to implement this within a clinical trial or practice setting. Finally, the responsibilities in marketing, support, and education required to transfer required knowledge and skills to eye care practitioners and academics are discussed. CONCLUSIONS. Undertaking MC treatment in minors creates an ethical challenge for a wide variety of stakeholders. Regulatory bodies, manufacturers, academics, and clinicians all share an ethical responsibility to ensure that the products used for MC are safe and efficacious and that patients understand the benefits and potential risks of such products. This International Myopia Institute report highlights these ethical challenges and provides stakeholders with recommendations and guidelines in the development, financial support, prescribing, and advertising of such treatments.</p
Two Years Later: Journals Are Not Yet Enforcing the ARRIVE Guidelines on Reporting Standards for Pre-Clinical Animal Studies
There is growing concern that poor experimental design and lack of transparent reporting contribute to the frequent failure of pre-clinical animal studies to translate into treatments for human disease. In 2010, the Animal Research: Reporting of In Vivo Experiments (ARRIVE) guidelines were introduced to help improve reporting standards. They were published in PLOS Biology and endorsed by funding agencies and publishers and their journals, including PLOS, Nature research journals, and other top-tier journals. Yet our analysis of papers published in PLOS and Nature journals indicates that there has been very little improvement in reporting standards since then. This suggests that authors, referees, and editors generally are ignoring guidelines, and the editorial endorsement is yet to be effectively implemented
Transport properties of graphene with one-dimensional charge defects
We study the effect of extended charge defects in electronic transport
properties of graphene. Extended defects are ubiquitous in chemically and
epitaxially grown graphene samples due to internal strains associated with the
lattice mismatch. We show that at low energies these defects interact quite
strongly with the 2D Dirac fermions and have an important effect in the
DC-conductivity of these materials.Comment: 6 pages, 5 figures. published version: one figure, appendix and
references adde
The role of shell crossing on the existence and stability of trapped matter shells in spherical inhomogeneous \Lambda-CDM models
We analyse the dynamics of trapped matter shells in spherically symmetric
inhomogeneous \Lambda-CDM models. The investigation uses a Generalised
Lema\^itre-Tolman-Bondi description with initial conditions subject to the
constraints of having spatially asymptotic cosmological expansion, initial
Hubble-type flow and a regular initial density distribution. We discuss the
effects of shell crossing and use a qualitative description of the local
trapped matter shells to explore global properties of the models. Once shell
crossing occurs, we find a splitting of the global shells separating expansion
from collapse into, at most, two global shells: an inner and an outer limit
trapped matter shell. In the case of expanding models, the outer limit trapped
matter shell necessarily exists. We also study the role of shear in this
process, compare our analysis with the Newtonian framework and give concrete
examples using density profile models of structure formation in cosmology.Comment: 17pp 12fig
Fault-Tolerant Aggregation: Flow-Updating Meets Mass-Distribution
Flow-Updating (FU) is a fault-tolerant technique that has proved to be
efficient in practice for the distributed computation of aggregate functions in
communication networks where individual processors do not have access to global
information. Previous distributed aggregation protocols, based on repeated
sharing of input values (or mass) among processors, sometimes called
Mass-Distribution (MD) protocols, are not resilient to communication failures
(or message loss) because such failures yield a loss of mass. In this paper, we
present a protocol which we call Mass-Distribution with Flow-Updating (MDFU).
We obtain MDFU by applying FU techniques to classic MD. We analyze the
convergence time of MDFU showing that stochastic message loss produces low
overhead. This is the first convergence proof of an FU-based algorithm. We
evaluate MDFU experimentally, comparing it with previous MD and FU protocols,
and verifying the behavior predicted by the analysis. Finally, given that MDFU
incurs a fixed deviation proportional to the message-loss rate, we adjust the
accuracy of MDFU heuristically in a new protocol called MDFU with Linear
Prediction (MDFU-LP). The evaluation shows that both MDFU and MDFU-LP behave
very well in practice, even under high rates of message loss and even changing
the input values dynamically.Comment: 18 pages, 5 figures, To appear in OPODIS 201
Obtaining a class of Type N pure radiation metrics using invariant operators
We develop further the integration procedure in the generalised invariant
formalism, and demonstrate its efficiency by obtaining a class of Petrov type N
pure radiation metrics without any explicit integration, and with comparatively
little detailed calculations. The method is similar to the one exploited by
Edgar and Vickers when deriving the general conformally flat pure radiation
metric. A major addition to the technique is the introduction of non-intrinsic
elements in generalised invariant formalism, which can be exploited to keep
calculations manageable.Comment: This work was presented in July 2004, in the Gr17 meeting held in
Dublin-Irelan
Comparison of Mixture and Classification Maximum Likelihood Approaches in Poisson Regression Models
In this work, we propose to compare two algorithms to compute maximum
likelihood estimators of the parameters of a mixture Poisson regression models.
To estimate these parameters, we may use the EM algorithm in a mixture
approach or the CEM algorithm in a classification approach. The comparison of
the two procedures was done through a simulation study of the performance of
these approaches on simulated data sets in a target number of iterations. Simulation
results show that the CEM algorithm is a good alternative to the EM algorithm
for fitting Poisson mixture regression models, having the advantage of converging
more quickly
Central Limit Theorem for a Tagged Particle in Asymmetric Simple Exclusion
We prove a Functional Central Limit Theorem for the position of a Tagged
Particle in the one-dimensional Asymmetric Simple Exclusion Process in the
hyperbolic scaling, starting from a Bernoulli product measure conditioned to
have a particle at the origin. We also prove that the position of the Tagged
Particle at time depends on the initial configuration, by the number of
empty sites in the interval divided by in the
hyperbolic and in a longer time scale, namely .Comment: 28 pages, no figure
Finite-Energy Landau Liquid Theory for the 1D Hubbard Model: Pseudoparticle Energy Bands and Degree of Localization/Delocalization
This paper is part of a broader study whose main goal is the study of the
finite-energy spectral properties of the non-perturbative one-dimensional (1D)
Hubbard model and the evaluation of finite-energy correlation-function
expressions. Here we study the deviations from the ground state values of
double occupancy which result from creation or annihilation of holons, spinons,
and pseudoparticles. The band-momentum dependence of the obtained
double-occupancy spectra provides important information on the degree of
localization/delocalization of the real-space lattice electron site
distribution configurations associated with the pseudoparticles. We also study
the band-momentum, on-site electronic repulsion, and electronic density
dependence of the pseudoparticle energy bands. The shape of these bands plays
an important role in the finite-energy spectral properties of the model. Such a
shape defines the form of the lines in the momentum-energy/frequency plane
where the peaks and edges of the one-electron and two-electron spectral weight
of physical operators are located. Our findings are useful for the study of the
one-electron and two-electron spectral weight distribution of physical
operators.Comment: 24 pages, 9 figures. Accepted for publication in Physical Review
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