1,538 research outputs found
Beyond the Standard Model with effective lagrangians
We discuss some applications of the effective quantum field theory to the description of the physics beyond the Standard Model. We consider two different examples. In the first one we derive, at the one-loop level, an effective lagrangian for an extension of the Standard Model with a charged scalar singlet by "integrating out" the heavy scalar. In the second example we illustrate the use of general effective theories at the loop level
Optimal methods for fitting probability distributions to propagule retention time in studies of zoochorous dispersal
Background: Propagule retention time is a key factor in determining propagule dispersal distance and the shape of
“seed shadows”. Propagules dispersed by animal vectors are either ingested and retained in the gut until defecation or
attached externally to the body until detachment. Retention time is a continuous variable, but it is commonly measured
at discrete time points, according to pre-established sampling time-intervals. Although parametric continuous
distributions have been widely fitted to these interval-censored data, the performance of different fitting methods
has not been evaluated. To investigate the performance of five different fitting methods, we fitted parametric probability
distributions to typical discretized retention-time data with known distribution using as data-points either the
lower, mid or upper bounds of sampling intervals, as well as the cumulative distribution of observed values (using
either maximum likelihood or non-linear least squares for parameter estimation); then compared the estimated and
original distributions to assess the accuracy of each method. We also assessed the robustness of these methods to
variations in the sampling procedure (sample size and length of sampling time-intervals).
Results: Fittings to the cumulative distribution performed better for all types of parametric distributions (lognormal,
gamma and Weibull distributions) and were more robust to variations in sample size and sampling time-intervals.
These estimated distributions had negligible deviations of up to 0.045 in cumulative probability of retention times
(according to the Kolmogorov–Smirnov statistic) in relation to original distributions from which propagule retention
time was simulated, supporting the overall accuracy of this fitting method. In contrast, fitting the sampling-interval
bounds resulted in greater deviations that ranged from 0.058 to 0.273 in cumulative probability of retention times,
which may introduce considerable biases in parameter estimates.
Conclusions: We recommend the use of cumulative probability to fit parametric probability distributions to propagule
retention time, specifically using maximum likelihood for parameter estimation. Furthermore, the experimental
design for an optimal characterization of unimodal propagule retention time should contemplate at least 500 recovered
propagules and sampling time-intervals not larger than the time peak of propagule retrieval, except in the tail of
the distribution where broader sampling time-intervals may also produce accurate fitsPeer reviewe
Migratory Birds as Global Dispersal Vectors
Propagule dispersal beyond local scales has been considered rare and unpredictable. However, for many plants, invertebrates, and microbes dispersed by birds, long-distance dispersal (LDD) might be regularly achieved when mediated by migratory movements. Because LDD operates over spatial extents spanning hundreds to thousands of kilometers, it can promote rapid range shifts and determine species distributions. We review evidence supporting this widespread LDD service and propose a conceptual framework for estimating LDD by migratory birds. Although further research and validation efforts are still needed, we show that current knowledge can be used to make more realistic estimations of LDD mediated by regular bird migrations, thus refining current predictions of its ecological and evolutionary consequences.Peer reviewe
Implementing quantum gates on oriented optical isomers
Optical enantiomers are proposed to encode molecular two-qubit information processing. Using sequences of pairs of nonresonant optimally polarized pulses, different schemes to implement quantum gates, and to prepare entangled states, are described. We discuss the role of the entanglement phase and the robustness of the pulse sequences which depend on the area theorem. Finally, possible scenarios to generalize the schemes to n-qubit systems are suggested. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70017/2/JCPSA6-120-23-10955-1.pd
Potenciando el aprendizaje proactivo con ILIAS&WebQuest: aprendiendo a paralelizar algoritmos con GPUs
Arquitectura de Computadores es una asignatura
troncal de segundo ciclo de la titulaciĂłn de IngenierĂa
de TelecomunicaciĂłn (P.E. 2004) de la Universidad
de Jaén, que desde el curso académico 2009/10
cuenta con una metodologĂa de aprendizaje proactivo
para motivar al alumno en la realizaciĂłn de las
prácticas. En concreto, se ha abordado la enseñanza
de la materia de paralelizaciĂłn de algoritmos haciendo
uso de GPUs de tarjetas gráficas convencionales.
Además, se ha dado soporte telemático al profesorado
y alumnado de la asignatura mediante el uso de
plataformas web de e-learning como ILIAS y otras
como WebQuest. Por Ăşltimo, en este trabajo se presentan
algunos de los resultados alcanzados con esta
experiencia.Peer Reviewe
The transition to irreversibility in sheared suspensions: An analysis based on a mesoscopic entropy production
We study the shear-induced diffusion effect and the transition to
irreversibility in suspensions under oscillatory shear flow by performing an
analysis of the entropy production associated to the motion of the particles.
We show that the Onsager coupling between different contributions to the
entropy production is responsible for the scaling of the mean square
displacement on particle diameter and applied strain. We also show that the
shear-induced effective diffusion coefficient depends on the volume fraction
and use Lattice-Boltzmann simulations to characterize the effect through the
power spectrum of particle positions for different Reynolds numbers and volume
fractions. Our study gives a thermodynamic explanation of the the transition to
irreversibility through a pertinent analysis of the second law of
thermodynamics.Comment: 17 pages, 3 figures, paper submitted tp phys rev
BioingenierĂa cutánea: aplicaciones preclĂnicas y clĂnicas
Regenerative Medicine is an emerging field that combines basic research and clinical observations in order to identify the elements required to replace damaged tissues and organs in vivo and to stimulate the body's intrinsic regenerative capacity. Great benefits are expected in this field as researchers take advantage of the potential regenerative properties of both embryonic and adult stem cells, and more recently, of induced pluripotent stem cells. Bioengineered skin emerged mainly in response to a critical need for early permanent coverage of extensive burns. Later this technology was also applied to the treatment of chronic ulcers. Our group has established a humanized mouse model of skin grafting that involves the use of bioengineered human skin in immunodeficient mice. This model is suitable for the study of physiologic and pathologic cutaneous processes and the evaluation of treatment strategies for skin diseases, including protocols for gene and cell therapy and tissue engineering.Our work has been funded by the Spanish Department of Science and Innovation (SAF2007-61019 and SAF 2010-16976), by the Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), and by the Ministry of Health (Advanced Therapies Plan, TRA 0160)
Dynamic simulations in SixTrack
The DYNK module allows element settings in SixTrack to be changed on a
turn-by-turn basis. This document contains a technical description of the DYNK
module in SixTrack. It is mainly intended for a developer or advanced user who
wants to modify the DYNK module, for example by adding more functions that can
be used to calculate new element settings, or to add support for new elements
that can be used with DYNK.Comment: Submission to CERN yellow report / conference proceeding, the 2015
collimation tracking code worksho
Zircon to monazite phase transition in CeVO4
X-ray diffraction and Raman-scattering measurements on cerium vanadate have
been performed up to 12 and 16 GPa, respectively. Experiments reveal that at
5.3 GPa the onset of a pressure-induced irreversible phase transition from the
zircon to the monazite structure. Beyond this pressure, diffraction peaks and
Raman-active modes of the monazite phase are measured. The zircon to monazite
transition in CeVO4 is distinctive among the other rare-earth orthovanadates.
We also observed softening of external translational Eg and internal B2g
bending modes. We attributed it to mechanical instabilities of zircon phase
against the pressure-induced distortion. We additionally report
lattice-dynamical and total-energy calculations which are in agreement with the
experimental results. Finally, the effect of non-hydrostatic stresses on the
structural sequence is studied and the equations of state of different phases
are reported.Comment: 45 pages, 8 figures, 8 table
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