8,050 research outputs found
The semiclassical--Sobolev orthogonal polynomials: a general approach
We say that the polynomial sequence is a semiclassical
Sobolev polynomial sequence when it is orthogonal with respect to the inner
product where is a semiclassical linear functional,
is the differential, the difference or the --difference
operator, and is a positive constant. In this paper we get algebraic
and differential/difference properties for such polynomials as well as
algebraic relations between them and the polynomial sequence orthogonal with
respect to the semiclassical functional . The main goal of this article
is to give a general approach to the study of the polynomials orthogonal with
respect to the above nonstandard inner product regardless of the type of
operator considered. Finally, we illustrate our results by
applying them to some known families of Sobolev orthogonal polynomials as well
as to some new ones introduced in this paper for the first time.Comment: 23 pages, special issue dedicated to Professor Guillermo Lopez
lagomasino on the occasion of his 60th birthday, accepted in Journal of
Approximation Theor
Community, work and family in diverse contexts and changing times
The 8th International Community, Work and Family conference took place in Malta at the Valletta campus of the University of Malta between the 23rd to the 25th May 2019. In a pre-COVID-19 world with no traveling restrictions, the conference brought together over 100 experts, academics, and students from a broad range of countries and disciplines to focus on the theme of Community, Work and Family in Diverse Contexts and Changing Times.
The research presented during the conference highlights some of the challenges that communities, organizations and families are facing in the twenty-first century across diverse and rapidly changing contexts. The topics presented spanned from broad studies that analyze the work-life interface of well-studied groups such as fathers and mothers, to other clusters that are generally less well-researched such as the police and the military, migrants, solo entrepreneurs, the LGBTIQ community, and those who work with people with special needs.
The recurrent theme of the gendered division of labor and work-life measures was discussed by various researchers, as were the issues of flexible work, family policy, and the impact of technology. It was refreshing to note that various researchers focused on the issue of community as a source of support, whilst others explored how peer, supervisor and management support impacts work-life issues. Overall, the conference provided a diverse and rich range of scholarly material upon which to develop this special issue for Community, Work & Family. [...
The Gromov Norm of the Product of Two Surfaces
We make an estimation of the value of the Gromov norm of the Cartesian
product of two surfaces. Our method uses a connection between these norms and
the minimal size of triangulations of the products of two polygons. This allows
us to prove that the Gromov norm of this product is between 32 and 52 when both
factors have genus 2. The case of arbitrary genera is easy to deduce form this
one.Comment: The journal version contains an error that invalidates one direction
of the main theorem. The present version contains an erratum, at the end,
explaining thi
Correlations between 21 cm Radiation and the CMB from Active Sources
Neutral hydrogen is ubiquitous, absorbing and emitting 21 cm radiation
throughout much of the Universe's history. Active sources of perturbations,
such as cosmic strings, would generate simultaneous perturbations in the
distribution of neutral hydrogen and in the Cosmic Microwave Background (CMB)
radiation from recombination. Moving strings would create wakes leading to 21
cm brightness fluctuations, while also perturbing CMB light via the
Gott-Kaiser-Stebbins effect. This would lead to spatial correlations between
the 21 cm and CMB anisotropies. Passive sources, like inflationary
perturbations, predict no cross correlations prior to the onset of
reionization. Thus, observation of any cross correlation between CMB and 21 cm
radiation from dark ages would constitute evidence for new physics. We
calculate the cosmic string induced correlations between CMB and 21 cm and
evaluate their observability.Comment: 8 pages, 5 figure
Development of a Tool to Recreate the Mars Science Laboratory Aerothermal Environment
The Mars Science Laboratory will enter the Martian atmosphere in 2012 with multiple char depth sensors and in-depth thermocouples in its heatshield. The aerothermal environment experienced by MSL may be computationally recreated using the data from the sensors and a material response program, such as the Fully Implicit Ablation and Thermal (FIAT) response program, through the matching of the char depth and thermocouple predictions of the material response program to the sensor data. A tool, CHanging Inputs from the Environment of FIAT (CHIEF), was developed to iteratively change different environmental conditions such that FIAT predictions match within certain criteria applied to an external data set. The computational environment is changed by iterating on the enthalpy, pressure, or heat transfer coefficient at certain times in the trajectory. CHIEF was initially compared against arc-jet test data from the development of the MSL heatshield and then against simulated sensor data derived from design trajectories for MSL. CHIEF was able to match char depth and in-depth thermocouple temperatures within the bounds placed upon it for these cases. Further refinement of CHIEF to compare multiple time points and assign convergence criteria may improve accuracy
Probing the first galaxies with the SKA
Observations of anisotropies in the brightness temperature of the 21 cm line
of neutral hydrogen from the period before reionization would shed light on the
dawn of the first stars and galaxies. In this paper, we use large-scale
semi-numerical simulations to analyse the imprint on the 21 cm signal of
spatial fluctuations in the Lyman-alpha flux arising from the clustering of the
first galaxies. We show that an experiment such as the Square Kilometer Array
(SKA) can probe this signal at the onset of reionization, giving us important
information about the UV emission spectra of the first stars and characterizing
their host galaxies. SKA-pathfinders with ~ 10% of the full collecting area
should be capable of making a statistical detection of the 21 cm power spectrum
at redshifts z 67 MHz). We then show
that the SKA should be able to measure the three dimensional power spectrum as
a function of the angle with the line of sight and discuss the use of the
redshift space distortions as a way to separate out the different components of
the 21 cm power spectrum. We demonstrate that, at least on large scales where
the Lyman-alpha fluctuations are linear, they can be used as a model
independent way to extract the power spectra due to these Lyman-alpha
fluctuations.Comment: 13 pages, 17 figures. New version to match version accepted by A&A.
Improved discussions on the Lyman-alpha simulation, adiabatic cooling
fluctuations, the Fisher matrix approach and the Poisson term calculation.
New version of the code available at: http://www.SimFast21.or
Intensity Coding in Two-Dimensional Excitable Neural Networks
In the light of recent experimental findings that gap junctions are essential
for low level intensity detection in the sensory periphery, the
Greenberg-Hastings cellular automaton is employed to model the response of a
two-dimensional sensory network to external stimuli. We show that excitable
elements (sensory neurons) that have a small dynamical range are shown to give
rise to a collective large dynamical range. Therefore the network transfer
(gain) function (which is Hill or Stevens law-like) is an emergent property
generated from a pool of small dynamical range cells, providing a basis for a
"neural psychophysics". The growth of the dynamical range with the system size
is approximately logarithmic, suggesting a functional role for electrical
coupling. For a fixed number of neurons, the dynamical range displays a maximum
as a function of the refractory period, which suggests experimental tests for
the model. A biological application to ephaptic interactions in olfactory nerve
fascicles is proposed.Comment: 17 pages, 5 figure
Contribution of Cross-Correlations to the 21cm Angular Power Spectrum in the Epoch of Reionization
Measurement of the 21cm hyperfine transition of neutral hydrogen provides a
unique probe of the epoch of reionization and the Dark Ages. Three major
mechanisms are believed to dominate the radiation process: emission from
neutral hydrogen surrounding the ionized bubbles of first galaxies and/or
quasars, emission from neutral hydrogen inside minihalos, and absorption of
diffuse neutral hydrogen against the cosmic microwave background. In the
present work, by simply combining the existing analytic models for the three
mechanisms, we investigate the contribution of cross-correlation between these
three components to the total 21cm angular power spectrum, in the sense that
neutral hydrogen associated with different radiation processes traces the
large-scale structures of underlying density perturbations. While the overall
21cm power spectrum remains almost unchanged with the inclusion of the
cross-correlations, the cross-correlation may play a key role in the
determination of the 21cm power spectrum during the transition of 21cm
radiation from emission-dominated phase to absorption-dominated phase at
redshift z~20. A significant suppression in the 21cm angular power spectrum
during this transition is anticipated as the result of negative contribution of
the cross-correlation between the absorption of diffuse neutral hydrogen and
the emission components. Therefore, an accurate prediction of the cosmic 21cm
power spectrum should take the cross-correlation into account especially at the
transition phase.Comment: 10 pages, 4 figures, accepted for publication in MNRA
Consensus: guidelines: best practices for detection, assessment and management of suspected acute drug-induced liver injury during clinical trials in patients with nonalcoholic steatohepatitis
BACKGROUND:
The last decade has seen a rapid growth in the number of clinical trials enrolling patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis (NASH). Due to the underlying chronic liver disease, patients with NASH often require different approaches to the assessment and management of suspected drug-induced liver injury (DILI) compared to patients with healthy livers. However, currently no regulatory guidelines or position papers systematically address best practices pertaining to DILI in NASH clinical trials.
AIMS:
This publication focuses on best practices concerning the detection, monitoring, diagnosis and management of suspected acute DILI during clinical trials in patients with NASH.
METHODS:
This is one of several papers developed by the IQ DILI Initiative, comprised of members from 15 pharmaceutical companies, in collaboration with DILI experts from academia and regulatory agencies. This paper is based on extensive literature review, and discussions between industry members with expertise in drug safety and DILI experts from outside industry to achieve consensus on common questions related to this topic.
RESULTS:
Recommended best practices are outlined pertaining to hepatic inclusion and exclusion criteria, monitoring of liver tests, DILI detection, approach to a suspected DILI signal, causality assessment and hepatic discontinuation rules.
CONCLUSIONS:
This paper provides a framework for the approach to assessment and management of suspected acute DILI during clinical trials in patients with NASH
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