8 research outputs found
The density Turán problem for hypergraphs
Given a k-graph H a complete blow-up of H is a k-graph Hˆ formed
by replacing each v ∈ V (H) by a non-empty vertex class Av and
then inserting all edges between any k vertex classes corresponding
to an edge of H. Given a subgraph G ⊆ Hˆ and an edge e ∈ E(H)
we define the density de(G) to be the proportion of edges present
in G between the classes corresponding to e.
The density Tur´an problem for H asks: determine the minimal
value dcrit(H) such that any subgraph G ⊆ Hˆ satisfying de(G) >
dcrit(H) for every e ∈ E(H) contains a copy of H as a transversal,
i.e. a copy of H meeting each vertex class of Hˆ exactly once.
We give upper bounds for this hypergraph density Tur´an problem that generalise the known bounds for the case of graphs due
to Csikv´ari and Nagy [3], although our methods are different, employing an entropy compression argument
Gravitational Lensing in Astronomy
Deflection of light by gravity was predicted by General Relativity and
observationaly confirmed in 1919. In the following decades various aspects of
the gravitational lens effect were explored theoretically, among them the
possibility of multiple or ring-like images of background sources, the use of
lensing as a gravitational telescope on very faint and distant objects, and the
possibility to determine Hubble's constant with lensing. Only relatively
recently gravitational lensing became an observational science after the
discovery of the first doubly imaged quasar in 1979. Today lensing is a booming
part of astrophysics.
In addition to multiply-imaged quasars, a number of other aspects of lensing
have been discovered since, e.g. giant luminous arcs, quasar microlensing,
Einstein rings, galactic microlensing events, arclets, or weak gravitational
lensing. By now literally hundreds of individual gravitational lens phenomena
are known.
Although still in its childhood, lensing has established itself as a very
useful astrophysical tool with some remarkable successes. It has contributed
significant new results in areas as different as the cosmological distance
scale, the large scale matter distribution in the universe, mass and mass
distribution of galaxy clusters, physics of quasars, dark matter in galaxy
halos, or galaxy structure.Comment: Review article for "Living Reviews in Relativity", see
http://www.livingreviews.org . 41 pages, latex, 22 figures (partly in GIF
format due to size constraints). High quality postscript files can be
obtained electronically at http://www.aip.de:8080/~jkw/review_figures.htm
Imagem corporal de mulheres com câncer de mama: uma revisão sistemática da literatura
Erratum: The significance of the time interval between antecedent pregnancy and diagnosis of high-risk gestational trophoblastic tumours
Reduced loads of pre-existing Gill-associated virus (GAV) infection in juvenile Penaeus monodon injected with single or multiple GAV-specific dsRNAs
Evaluating the therapeutic effects of museum object handling with hospital patients: A review and initial trial of wellbeing measures
Arts therapy interventions within health care produce positive outcomes for patients, staff and carers, though little rigorous evaluation of these activities is conducted using clinically accepted measures. Similarly, heritage-specific therapeutic interventions offer comparable potential to increase well-being. Although museums and galleries have significant capacity to contribute to health and social care, widespread implementation is impeded by lack of robust clinical data quantifying the impact of such interventions. Measurement scales for psychological well-being, quality of life and health status were reviewed for their suitability to evaluate well-being in hospital patients before and after 30-minute museum object handling sessions. Measures were short-listed using selection criteria of internal and external validity, practicality and sensitivity. Focus on usage in health care, breadth of application, ease of administration and degree of responsiveness informed the choice of optimum measures for preliminary research with female oncology patients (n=40). Findings indicated effectiveness of selected measures (Positive Affect Negative Affect Scale; PANAS and Visual Analogue Scale; VAS) for heritage-specific interventions