27 research outputs found
Kovalevski exponents and integrability properties in class A homogeneous cosmological models
Qualitative approach to homogeneous anisotropic Bianchi class A models in
terms of dynamical systems reveals a hierarchy of invariant manifolds. By
calculating the Kovalevski Exponents according to Adler - van Moerbecke method
we discuss how algebraic integrability property is distributed in this class of
models. In particular we find that algebraic nonintegrability of vacuum Bianchi
VII_0 model is inherited by more general Bianchi VIII and Bianchi IX vacuum
types. Matter terms (cosmological constant, dust and radiation) in the Einstein
equations typically generate irrational or complex Kovalevski exponents in
class A homogeneous models thus introducing an element of nonintegrability even
though the respective vacuum models are integrable.Comment: arxiv version is already officia
Self-healing during electrical treeing: A feature of the two-phase liquid-solid nature of silicone gels
We report the results of electrical treeing tests carried out on a range of silicone dielectric gel samples made by varying the ratio of the same two components used for cross-linking a commercial silicone gel. These samples range from liquids to elastomers via two-phase gels. The extent of the curing is followed by means of FTIR spectroscopy and the samples are characterized through their dynamical mechanical properties. It is shown that the gel samples exhibit treeing behavior that includes features typical of both liquids and solids. A filamentary structure is produced that has permanence together with attached bubbles that self-heal locally during treeing, although differences in detail were found depending on the degree of curing. Removal of the treeing voltage allows a more substantial self-healing to occur. This behavior is discussed in terms of the two-phase liquid-solid nature of the silicone gels.Instituto de Investigaciones FisicoquĂmicas TeĂłricas y Aplicada
A Multifaceted Analysis of Immune-Endocrine-Metabolic Alterations in Patients with Pulmonary Tuberculosis
Our study investigated the circulating levels of factors involved in immune-inflammatory-endocrine-metabolic responses in patients with tuberculosis with the aim of uncovering a relation between certain immune and hormonal patterns, their clinical status and in vitro immune response. The concentration of leptin, adiponectin, IL-6, IL-1β, ghrelin, C-reactive protein (CRP), cortisol and dehydroepiandrosterone (DHEA), and the in vitro immune response (lymphoproliferation and IFN-γ production) was evaluated in 53 patients with active untreated tuberculosis, 27 household contacts and 25 healthy controls, without significant age- or sex-related differences. Patients had a lower body mass index (BMI), reduced levels of leptin and DHEA, and increased concentrations of CRP, IL-6, cortisol, IL-1β and nearly significant adiponectin values than household contacts and controls. Within tuberculosis patients the BMI and leptin levels were positively correlated and decreased with increasing disease severity, whereas higher concentrations of IL-6, CRP, IL-1β, cortisol, and ghrelin were seen in cases with moderate to severe tuberculosis. Household contacts had lower DHEA and higher IL-6 levels than controls. Group classification by means of discriminant analysis and the k-nearest neighbor method showed that tuberculosis patients were clearly different from the other groups, having higher levels of CRP and lower DHEA concentration and BMI. Furthermore, plasma leptin levels were positively associated with the basal in vitro IFN-γ production and the ConA-driven proliferation of cells from tuberculosis patients. Present alterations in the communication between the neuro-endocrine and immune systems in tuberculosis may contribute to disease worsening
From Clock Synchronization to Dark Matter as a Relativistic Inertial Effect
Lecture at BOSS2011 on relativistic metrology, on clock synchronization,
relativistic dynamics and non-inertial frames in Minkowski spacetime, on
relativistic atomic physics, on ADM canonical tetrad gravity in asymptotically
Minkowskian spacetimes, on the York canonical basis identifying the inertial
(gauge) and tidal degrees of freedom of the gravitational field, on the
Post-Minkowskian linearization in 3-orthogonal gauges, on the Post-Newtonian
limit of matter Hamilton equations, on the possibility to interpret dark matter
as a relativistic inertial effect connected with relativistic metrology (i.e.
clock synchronization) in Einstein GR.Comment: 90 pages. Lecture at BOSS201