456 research outputs found
Reversing conditional orderings
We analyze some specific aspects concerning conditional orderings and relations among them. To this purpose we define a suitable concept of reversed conditional ordering and prove some related results. In particular we aim to compare the univariate stochastic orderings ≤ st, ≤ hr, and ≤ lr in terms of differences among different notions of conditional orderings. Some applications of our result to the analysis of positive dependence will be detailed. We concentrate attention to the case of a pair of scalar random variables X, Y ​. Suitable extensions to multivariate cases are possible
Exploring Health Insurance Status and Emergency Department Utilization
Emergency department (ED) use, by both insured and uninsured, leads to significant health care costs in the United States. While frequent ED use is often attributed to the uninsured, there is some evidence that insured populations also report utilizing the ED when otherwise preventable or nonurgent. We conducted in-person surveys of patients visiting the ED at a large research hospital and examined the differences in their characteristics based on the health insurance status. While less than the uninsured, insured individuals still report barriers to access to care outside the ED that include lack of access to another health care facility and unavailability of a doctor’s office or clinic
On the Bergman representative coordinates
We study the set where the so-called Bergman representative coordinates (or
Bergman functions) form an immersion. We provide an estimate of the size of a
maximal geodesic ball with respect to the Bergman metric, contained in this
set. By concrete examples we show that these estimates are the best possible.Comment: 20 page
Some integrability conditions for almost K\"ahler manifolds
Among other results, a compact almost K\"ahler manifold is proved to be
K\"ahler if the Ricci tensor is semi-negative and its length coincides with
that of the star Ricci tensor or if the Ricci tensor is semi-positive and its
first order covariant derivatives are Hermitian. Moreover, it is shown that
there are no compact almost K\"ahler manifolds with harmonic Weyl tensor and
non-parallel semi-positive Ricci tensor. Stronger results are obtained in
dimension 4.Comment: Latex2e, 13 page
Parametrization of the octupole degrees of freedom
A simple parametrization for the octupole collective variables is proposed
and the symmetries of the wave functions are discussed in terms of the
solutions corresponding to the vibrational limit. [PACS: 21.60Ev, 21.60.Fw,
21.10.Re]Comment: 14 page
A spinor approach to Walker geometry
A four-dimensional Walker geometry is a four-dimensional manifold M with a
neutral metric g and a parallel distribution of totally null two-planes. This
distribution has a natural characterization as a projective spinor field
subject to a certain constraint. Spinors therefore provide a natural tool for
studying Walker geometry, which we exploit to draw together several themes in
recent explicit studies of Walker geometry and in other work of Dunajski (2002)
and Plebanski (1975) in which Walker geometry is implicit. In addition to
studying local Walker geometry, we address a global question raised by the use
of spinors.Comment: 41 pages. Typos which persisted into published version corrected,
notably at (2.15
Quality assurance and assessment frameworks of biosystems engineering studies
Regulatory instruments at the national level to ensure high quality are crucial to
achieve and maintain a regional hub of higher education in Malta. While The Malta
Qualifications Council and the National Commission for Higher Education are
established and operational, the legal framework to set up a quality assurance
agency and a quality assurance and licensing framework is in place, but the
legislations is still awaiting approval. The University of Malta has set up internal
quality assurance structures, The Programme Validation Committee monitors,
reviews and recommends programmes for approval by Senate, The formation of the
INSTITUTE OF EARTH SYSTEMS will facilitate the means through which a Bio
Systems Engineering course could be offered, Furthermore the recent establishment
of a Maltese Chamber of Agrologists could in theory eventually take up the role to
grant professional accreditation,peer-reviewe
Measurement invariance in the social sciences:Historical development, methodological challenges, state of the art, and future perspectives
This review summarizes the current state of the art of statistical and (survey) methodological research on measurement (non)invariance, which is considered a core challenge for the comparative social sciences. After outlining the historical roots, conceptual details, and standard procedures for measurement invariance testing, the paper focuses in particular on the statistical developments that have been achieved in the last 10 years. These include Bayesian approximate measurement invariance, the alignment method, measurement invariance testing within the multilevel modeling framework, mixture multigroup factor analysis, the measurement invariance explorer, and the response shift-true change decomposition approach. Furthermore, the contribution of survey methodological research to the construction of invariant measurement instruments is explicitly addressed and highlighted, including the issues of design decisions, pretesting, scale adoption, and translation. The paper ends with an outlook on future research perspectives.</p
Maximum Covering Subtrees for Phylogenetic Networks
Tree-based phylogenetic networks, which may be roughly defined as
leaf-labeled networks built by adding arcs only between the original tree
edges, have elegant properties for modeling evolutionary histories. We answer
an open question of Francis, Semple, and Steel about the complexity of
determining how far a phylogenetic network is from being tree-based, including
non-binary phylogenetic networks. We show that finding a phylogenetic tree
covering the maximum number of nodes in a phylogenetic network can be be
computed in polynomial time via an encoding into a minimum-cost maximum flow
problem
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