5,224 research outputs found
Spherical harmonic decomposition applied to spatial-temporal analysis of human high-density EEG
We demonstrate an application of spherical harmonic decomposition to analysis
of the human electroencephalogram (EEG). We implement two methods and discuss
issues specific to analysis of hemispherical, irregularly sampled data.
Performance of the methods and spatial sampling requirements are quantified
using simulated data. The analysis is applied to experimental EEG data,
confirming earlier reports of an approximate frequency-wavenumber relationship
in some bands.Comment: 12 pages, 8 figures, submitted to Phys. Rev. E, uses APS RevTeX
style
Swift observations of the 2015 outburst of AG Peg -- from slow nova to classical symbiotic outburst
Symbiotic stars often contain white dwarfs with quasi-steady shell burning on
their surfaces. However, in most symbiotics, the origin of this burning is
unclear. In symbiotic slow novae, however, it is linked to a past thermonuclear
runaway. In June 2015, the symbiotic slow nova AG Peg was seen in only its
second optical outburst since 1850. This recent outburst was of much shorter
duration and lower amplitude than the earlier eruption, and it contained
multiple peaks -- like outbursts in classical symbiotic stars such as Z And. We
report Swift X-ray and UV observations of AG Peg made between June 2015 and
January 2016. The X-ray flux was markedly variable on a time scale of days,
particularly during four days near optical maximum, when the X-rays became
bright and soft. This strong X-ray variability continued for another month,
after which the X-rays hardened as the optical flux declined. The UV flux was
high throughout the outburst, consistent with quasi-steady shell burning on the
white dwarf. Given that accretion disks around white dwarfs with shell burning
do not generally produce detectable X-rays (due to Compton-cooling of the
boundary layer), the X-rays probably originated via shocks in the ejecta. As
the X-ray photo-electric absorption did not vary significantly, the X-ray
variability may directly link to the properties of the shocked material. AG
Peg's transition from a slow symbiotic nova (which drove the 1850 outburst) to
a classical symbiotic star suggests that shell burning in at least some
symbiotic stars is residual burning from prior novae.Comment: Accepted by MNRAS 23 June 2016. Manuscript submitted in original form
5 April 201
Local cohomology and Lyubeznik numbers of F-pure rings
In this article, we study certain local cohomology modules over F-pure rings. We give sufficient conditions for the vanishing of some Lyubeznik numbers, derive a formula for computing these invariants when the F-pure ring is standard graded and, by its means, we provide some new examples of Lyubeznik tables. We study associated primes of certain Ext-modules, showing that they are all compatible ideals. Finally, we focus on properties that Lyubeznik numbers detect over a globally F-split projective variety
Early copper metallurgy in Northern Chile
The Central Andean region of South America has a long tradition of mining and metallurgy. Such activities were fundamental to the economic, socio-political and ideological dynamics of the pre-Columbian cultures that inhabited this area. In spite of their importance, few archaeological investigations of metallurgy have been carried out in the Central Andes in general, and in current Chilean territory in particular. The present project investigates archaeometallurgical sites in northern Chile using scientific analysis, as a first step towards a large-scale map of prehistoric copper production and exchange across South America. This research involves documentation and sampling of already excavated archaeological materials from a number of copper-producing sites located in the Atacama District. Preliminary results of XRF analysis of artefacts from the collection of the R. P. Gustavo Le Paige Archaeological Museum, San Pedro de Atacama, have been obtained and enabled us to characterise the different elements present in the metal objects. These results might provide information on the nature of the raw materials used
Prevalencia de factores de riesgo cardiovascular clásicos en población adulta de Talca, Chile, 2005
Departamento de Bioquímica Clínica e Inmunohematología, Facultad de Ciencias de la Salud, Universidad de Talca, Talca, Chile.
Instituto de Matemática y Física, Universidad de Talca, Talca, Chile.
Departamento de Salud Pública, Facultad de Ciencias de la Salud, Universidad de Talca, Talca, Chile. Escuela
de Psicología, Universidad de Talca, Talca, Chile.Background: Cardiovascular disease (CVD) has several traditional risk factors (RF), and some of them are potentially modifiable. Aim: To determine the prevalence of most common risk factors in adult population in Talca in Central Chile. Subjects and methods: We studied 1007 subjects aged 18 to 74 years (66% women), living in Talca, selected by a probability sampling. They answered a questionnaire and anthropometry, blood pressure, lipid profile and blood glucose were measured. Results: Thirty seven percent of subjects smoked, 70.1% had a body mass index over 25 kg/m2 and 41% had an abnormally high circumference. High blood pressure was found in 37% (36% of these subjects were unaware of this condition), 44.5% had hypercholesterolemia, 21.5% had low HDL cholesterol, 40.1% had hypertriglyceridemia and 26.3% had high blood glucose levels. Conclusions: There is a high prevalence of risk factors for CVD in adult population from Talca. The prevalence of risk factors is higher than that reported by the 2003 National Health Survery
Extended Recurrence Plot Analysis and its Application to ERP Data
We present new measures of complexity and their application to event related
potential data. The new measures base on structures of recurrence plots and
makes the identification of chaos-chaos transitions possible. The application
of these measures to data from single-trials of the Oddball experiment can
identify laminar states therein. This offers a new way of analyzing
event-related activity on a single-trial basis.Comment: 21 pages, 8 figures; article for the workshop ''Analyzing and
Modelling Event-Related Brain Potentials: Cognitive and Neural Approaches``
at November 29 - December 01, 2001 in Potsdam, German
Patrón de comportamiento tipo A, ira y enfermedades cardiovasculares (ECV) en población urbana chilena
Diaz, EM (Moyano Diaz, Emilio)1; Icaza, G (Icaza, Gloria); Mujica, V (Mujica, Veronica); Nunez, L (Nunez, Loreto); Leiva, E (Leiva, Elba); Vasquez, M (Vasquez, Marcela); Palomo, I (Palomo, Ivan)A worldwide raise in the number of cardiovascular disease (CVD) and the existence of a higher percentage in Maule (Chile) than the national media, and increased attention in the analysis of psychological factors motivate to analyze the Type A Behavior Pattern (TABP) and anger in relation to CVD. The sample was 1007 adults between 18 and 74 years old (citizens of Talca, Chile), mostly women. They provided information about their demographic details, eating habits and lifestyle, answered the Novaco's Anger inventory and the Retiro Scale of Type A Behavior (RSTAB), and also were taken measurements like weight, body mass index and blood pressure and blood tests related to risk factors to traditional cardiovascular diseases. The results show Overall, that the participants appear highly sedentary (79.9%) with relatively high levels of tabaquism (53.6%), and hypercholesterolemia (44.5%), overweight (40.7%) and obesity (32.6%). A quarter of the sample also presents hyperglycemic indexes, hypertension and TABP unequally distributed by sex. The absence of PCTA (or PCTB presence) appeared mostly associated with traditional cardiovascular risk factors (CRF). Regarding anger, women present more high than men (2.1% against 0.3%; c(2)(3) = 27.99,p<.0001), decreasing for both sexes with age, while also befall stroke by sex
Chemistry of Chern-Simons Supergravity: reduction to a BPS kink, oxidation to M-theory and thermodynamical aspects
We construct a supersymmetric extension of the two dimensional
Kaluza-Klein-reduced gravitational Chern-Simons term, and globally study its
solutions, labelled by mass and U(1) charge c. The kink solution is BPS, and in
an appropriate conformal frame all solutions asymptotically approach AdS. The
thermodynamics of the Hawking effect yields interesting behavior for the
specific heat and hints at a Hawking-Page-like transition at T_{critical} \sim
c^{3/2}. We address implications for higher dimensions ("oxidation"), in
particular D=3,4 and 11, and comment briefly on AdS/CFT aspects of the kink.Comment: 39 pages, 2 figures. v2: reference added, minor changes, typo
Gesture analysis for physics education researchers
Systematic observations of student gestures can not only fill in gaps in
students' verbal expressions, but can also offer valuable information about
student ideas, including their source, their novelty to the speaker, and their
construction in real time. This paper provides a review of the research in
gesture analysis that is most relevant to physics education researchers and
illustrates gesture analysis for the purpose of better understanding student
thinking about physics.Comment: 14 page
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