139 research outputs found
Relació entre la salut autopercebuda i les concentracions sanguínies de compostos tòxics persistents
No full textEls resultats d'un estudi que ha analitzat la relació entre les concentracions o nivells en sang de diversos compostos tòxics persistents (CTPs) i la salut autopercebuda (SAP) mostren que les persones amb majors concentracions de CTPs tenen una pitjor SAP. També s'ha trobat que amb l'edat, la concentració de CTPs és major i la SAP pitjor, segurament degut al fet que les persones més grans han acumulat més CTPs que no pas les joves. Els resultats també suggereixen que els CTPs podrien causar determinats trastorns crònics, els quals provoquen una pitjor SAP
Relació entre la salut autopercebuda i les concentracions sanguínies de compostos tòxics persistents
No full textEls resultats d'un estudi que ha analitzat la relació entre les concentracions o nivells en sang de diversos compostos tòxics persistents (CTPs) i la salut autopercebuda (SAP) mostren que les persones amb majors concentracions de CTPs tenen una pitjor SAP. També s'ha trobat que amb l'edat, la concentració de CTPs és major i la SAP pitjor, segurament degut al fet que les persones més grans han acumulat més CTPs que no pas les joves. Els resultats també suggereixen que els CTPs podrien causar determinats trastorns crònics, els quals provoquen una pitjor SAP.Los resultados de un estudio que ha analizado la relación entre las concentraciones o niveles en sangre de varios compuestos tóxicos persistentes (CTPs) y la salud autopercibida (SAP) muestran que las personas con mayores concentraciones de CTPs tienen una peor SAP. También se ha visto que con la edad, la concentración de CTPs es mayor y la SAP peor, seguramente debido a que las personas mayores han acumulado más CTPs que las jóvenes. Los resultados también sugieren que los CTPs podrían causar determinados trastornos crónicos, los cuales provocan una peor SAP.The results of a study which has examined the relationship between blood concentrations or levels of several persistent organic pollutants (POPs) and self-rated health (SRH) show that people with higher POP concentrations have a worse SRH. It has also been found that with age, POP concentrations are greater and SRH is worse, probably due to the fact that older people have accumulated more POPs than younger ones. The results also suggest that POPs could cause certain chronic disorders, which would then cause worse SRH
Anàlisi de la contaminació de la població general per compostos tòxics persistents i d’alguns dels seus efectes adversos per a la salut
No full textL’objectiu principal de la recerca realitzada és analitzar la contaminació de la població general per compostos tòxics persistents (CTPs) i estudiar la relació de les concentracions corporals d’aquests contaminants amb alguns dels seus possibles efectes adversos en la salut humana. La tesi aporta dades i coneixement sobre la contaminació per CTPs de la població general a Catalunya i a la ciutat de Barcelona. Es basa per una banda en una mostra de participants de l’Enquesta de Salut de Catalunya i, per l’altra, en una mostra de participants de l’Enquesta de Salut de Barcelona; són dos dels tres únics estudis sobre CTPs a nivell espanyol lligats a enquestes de salut o nutricionals i amb dades representatives de la població general. En la tesi s’apliquen noves formes de presentar i analitzar els resultats d’aquest tipus d’estudis a través de corbes de distribució poblacional i d’indicadors com el ‘nombre de compostos detectats a altes concentracions’, el qual també s’aplica en aquesta tesi a les dades disponibles de l’enquesta de salut dels Estats Units (l’anomenada NHANES). Aquesta enquesta recull periòdicament una àmplia quantitat de dades de biomonitorització ambiental representatives de la població general d’Estats Units. La tesi també analitza les relacions entre les concentracions sèriques de CTPs i la salut autopercebuda, la prevalença de diabetis tipus 2, prediabetis i de fenotips metabòlics alterats en persones amb sobrepès i obesitat i, per primer cop, en persones amb pes normal. A més, té en compte marcadors poc utilitzats en aquest context com és la proteïna C-reactiva. Les troballes plantegen noves hipòtesis que poden ser analitzades en estudis amb dissenys prospectius longitudinals, els quals poden incloure a més altres contaminants i factors rellevants. El coneixement generat pot ser utilitzat tant alhora d’avaluar l’impacte i els efectes de la contaminació de la població per CTPs, com alhora d’avaluar l’impacte de les polítiques públiques i privades que es puguin realitzar per reduir-la.The main aims of the research are to analyse the contamination of the general population by persistent toxic pollutants (PTS), as well as to study the relation between body concentrations of such compounds and some their possible adverse health effects. The thesis provides data and knowledge about the contamination by PTS of the general population of Catalonia and of the city of Barcelona. On one hand, it is based on a sample of participants of the Catalan Health Interview Survey, and in the other, on a sample of participants of the Barcelona Health Survey; these are two out of the three only studies on PTS in Spain linked to health or nutritional surveys and with representative data of the general population. New ways to present and analyse the results of this type of studies are applied in the thesis through population distribution curves and indicators such as the ‘number of compounds detected at high concentrations’, which is also computed in this thesis for the available data of the United States’ health survey (the so called NHANES). This survey periodically collets a wide quantity of environmental biomonitoring data representative of the general population of the United States. The thesis also analyses the relationships between serum concentrations of PTS and self-rated health, the prevalence of type 2 diabetes, prediabetes, and unhealthy metabolic phenotypes in overweight and obese individuals and, for the first time, in normal weight subjects. Moreover, markers not much used in this context, such as C-reactive protein, are considered. Findings suggest new hypotheses to be analysed in prospective longitudinal studies considering also other contaminants and relevant factors. The knowledge provided can be used when assessing the impact and effects of the population contamination by PTS, and also when assessing the impact of the public and private polices aimed to reduce such contamination
Study of Perturbed Lotka–Volterra Systems Via Abelian Integrals
No full textAbstractWe consider the Lotka–Volterra system as a Hamiltonian one and study a special perturbation of it. For this perturbed system we get results on the number of limit cycles. The main tools used are Abelian integrals and degenerate Hopf bifurcation
On the number of limit cycles for perturbed pendulum equations
No full textAgraïments: The second author is supported by the project J3452 "Dynamical Systems Methods in Hydrodynamics" of the Austrian Science Fund (FWF).We consider perturbed pendulum-like equations on the cylinder of the form x (x)= _=0^mQ_n, (x) x^ where Q_n, are trigonometric polynomials of degree n, and study the number of limit cycles that bifurcate from the periodic orbits of the unperturbed case =0 in terms of m and n. Our first result gives upper bounds on the number of zeros of its associated first order Melnikov function, in both the oscillatory and the rotary regions. These upper bounds are obtained expressing the corresponding Abelian integrals in terms of polynomials and the complete elliptic functions of first and second kind. Some further results give sharp bounds on the number of zeros of these integrals by identifying subfamilies which are shown to be Chebyshev systems
Distribution of blood concentrations of persistent organic pollutants in a representative sample of the population of Barcelona in 2006, and comparison with levels in 2002
No full textPOP biomonitoring programs are useful for exposure assessment, to analyze patterns, and to evaluate policies. However, population-representative surveys are scarce and heterogeneous. Reports on time trends in representative samples using the same methods are rare.Supported in part by research grants from the Department of Health, Government of Catalonia; ‘Red temática de investigación cooperativa de centros en Cáncer’ (C03/10); ‘Red temática de investigación cooperativa de centros en Epidemiología y salud pública’ (C03/09); and CIBER de Epidemiología, Instituto de Salud Carlos III, Ministry of Health, Government of Spain. The authors gratefully acknowledge technical and scientific assistance provided by Joan Guix, Montserrat Guillén, Elisa Puigdomènech, Javier Selva, Magda Bosch de Basea, Jordi Sunyer, Carolina Rebato, Vicky Turmo, Ana Linas, Xavier Llebaria, Marta Crous-Bou and Yolanda Rovira.Peer reviewe
On a family of polynomial differential equations having at most three limit cycles
No full textAgraïments/Ajudes: The first author is partially supported by by grants MTM2005-06098-C02-1. The second author is partially supported by the Spanish grant SAB-2005-0029, NSF of China (No.10571184) and SRF for ROCS, SEM. The second author also wants to express his thanks to the Departament de Matemàtiques of the Universitat Autònoma de Barcelona for the hospitality and support during the period in which this paper was started.We prove the existence of at most three limit cycles for a family of planar polynomial differential equations. Moreover we show that this upper bound in sharp. The key point in our approach is that the differential equations of this family can be transformed into Abel differential equations
On the number of limit cycles bifurcating from a non-global degenerated center
No full textAbstractWe give an upper bound for the number of zeros of an Abelian integral. This integral controls the number of limit cycles that bifurcate, by a polynomial perturbation of arbitrary degree n, from the periodic orbits of the integrable system (1+x)dH=0, where H is the quasi-homogeneous Hamiltonian H(x,y)=x2k/(2k)+y2/2. The tools used in our proofs are the Argument Principle applied to a suitable complex extension of the Abelian integral and some techniques in real analysis
Periodic points of a Landen transformation
No full textPreprintWe prove the existence of 3-periodic orbits in a dynamical system associated to a Landen transformation previously studied by Boros, Chamberland and Moll, disproving a conjecture on the dynamics of this planar map introduced by the latter author. To this end we present a systematic methodology to determine and locate analytically isolated periodic points of algebraic maps. This approach can be useful to study other discrete dynamical systems with algebraic nature. Complementary results on the dynamics of the map associated with the Landen transformation are also presented.Preprin
A new Chebyshev family with applications to Abel equations
No full textAgraïments: The second author is partially supported by NSFC-10831003 and by AGAUR grant number 2009PIV00064.We prove that a family of functions defined through some definite integrals forms an extended complete Chebyshev system. The key point of our proof consists of reducing the study of certain Wronskians to the Gram determinants of a suitable set of new functions. Our result is then applied to give upper bounds for the number of isolated periodic solutions of some perturbed Abel equations
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