Differences in prevalence of diastolic arterial hypertension in 1423 young individuals in two different interviews

International audienceTo determine prevalence of diastolic arterial hypertension (DAH) in young individuals using different criteria. Secondly, to test the possible different blood pressure reactions to mental stress and hand grip in two groups: group A, a 'low blood pressure group', and group B, diastolic blood pressure 90 mmHg or greater in one interview and below these values in a second interview. SUBJECTS: A total of 1423 volunteer medical students was recruited at La Plata School of Medicine, average age 21 +/- 3 years. DESIGN: Systolic and diastolic blood pressure were measured three times on two different occasions separated by one week. With the values obtained, prevalence of arterial hypertension was determined according to the criteria suggested by The Joint National Committee 4 (JNC-4) and the World Health Organization (WHO), and to statistical bases. INTERVENTIONS: Mental stress and hand grip tests were performed by groups A and B. MAIN RESULTS: The prevalence of DAH when only the first determination of the first interview was considered was 14.7%, 6.7% (considering the WHO criterion) or 5% (using the statistical criterion). These values are reduced if repeated measurements are averaged. The greatest reduction was obtained when the JNC-4 criterion was used (1.6%). The reactivity of stressors did not show any relationship with the initial blood pressure of the subjects. CONCLUSIONS: In epidemiological studies, the differences among the criteria should be considered when analyzing blood pressure of populations. Stress tests (mental stress and hand grip) do not help in identifying differences between the groups studied

Differences in prevalence of diastolic arterial hypertension in 1423 young individuals in two different interviews

International audienceTo determine prevalence of diastolic arterial hypertension (DAH) in young individuals using different criteria. Secondly, to test the possible different blood pressure reactions to mental stress and hand grip in two groups: group A, a 'low blood pressure group', and group B, diastolic blood pressure 90 mmHg or greater in one interview and below these values in a second interview. SUBJECTS: A total of 1423 volunteer medical students was recruited at La Plata School of Medicine, average age 21 +/- 3 years. DESIGN: Systolic and diastolic blood pressure were measured three times on two different occasions separated by one week. With the values obtained, prevalence of arterial hypertension was determined according to the criteria suggested by The Joint National Committee 4 (JNC-4) and the World Health Organization (WHO), and to statistical bases. INTERVENTIONS: Mental stress and hand grip tests were performed by groups A and B. MAIN RESULTS: The prevalence of DAH when only the first determination of the first interview was considered was 14.7%, 6.7% (considering the WHO criterion) or 5% (using the statistical criterion). These values are reduced if repeated measurements are averaged. The greatest reduction was obtained when the JNC-4 criterion was used (1.6%). The reactivity of stressors did not show any relationship with the initial blood pressure of the subjects. CONCLUSIONS: In epidemiological studies, the differences among the criteria should be considered when analyzing blood pressure of populations. Stress tests (mental stress and hand grip) do not help in identifying differences between the groups studied

Quiet and perturbed ionospheric representation according to the electron content from GPS signals

Signals from Global Positioning System (GPS) satellites received at the surface of the Earth have passed through the terrestrial atmosphere and are therefore affected by refraction in the ionosphere. A large number of permanent dual frequencies GPS tracking stations have been built up in the last years and their data have proved to be suitable to study the ionosphere. The main goal of this paper is to assess the capability of these observations to continuously and routinely monitor the ionosphere at a global scale. The interest was focused on retrieving the coefficients of a spherical harmonics expansion that describe the global distribution of the vertical total electron content (VTEC) from the GPS signal. To test our results, we compare them with other GPS-derived results, with VTEC values computed with the International Reference Ionosphere (IRI-95) model, and with direct VTEC determinations provided by Topex-Poseidon satellite. A large set of global VTEC maps with a time resolution of 2 hours was used to describe the evolution of this ionospheric variable at quiet geomagnetic periods during the year 1997. The outstanding features of the VTEC during the 15 May 1997 geomagnetic storm have also been studied. The results show that our method is able to identify large-scale features and seasonal variations of the VTEC in quiet conditions, as well as its variations during a large geomagnetic Storm. Copyright 2003 by the American Geophysical Union.Fil:Van Zele, M.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Ionospheric F-region observations over American sector during an intense space weather event using multi-instruments

The critical interaction between the magnetosphere and ionosphere during intense geomagnetic storms continues to be important to space weather studies. In this investigation, we present and discuss the ionospheric F-region observations in the equatorial, low- and mid-latitude regions in both hemispheres over American sector during the intense geomagnetic storm on 01–03 June 2013. The geomagnetic storm reached a minimum Dst of −119 nT at 0900 UT on 01 June. For this investigation, we present vertical total electron content (VTEC) and phase fluctuations (in TECU/min) from a chain of 10 GPS stations and the ionospheric parameters foF2 and h′F from a chain of 4 digital ionosonde stations, covering from equatorial to mid-latitudes regions over American sector during the entire storm-time period 31 May–03 June 2013. In addition, the plasma density observed from DMSP satellites is presented. The results obtained show that during the sudden impulse/SSC and throughout the main phase of the storm, a large positive phase was observed in mid-latitudes of the northern hemisphere, which could be due to changes in the thermospheric wind circulation. On the other hand, in the mid-latitudes of the southern hemisphere, no deviations are observed in VTEC and foF2 when compared to the quiet period. During the long recovery phase of the storm on 01–02 June, a north-south asymmetry is observed in the F-region. The study confirms the dominant role of the thermospheric winds on north-south asymmetry in the ionospheric F-region. The ionospheric irregularities are found to be confined in the equatorial region, of the bottomside spread-F type, before and during the geomagnetic storm. It shows that the geomagnetic storm did not affect the generation or suppression of ionospheric irregularities at the stations investigated.Fil: de Abreu, A.J.. Instituto Tecnológico de Aeronáutica; BrasilFil: Martin, I.M.. Instituto Tecnológico de Aeronáutica; BrasilFil: Fagundes, P.R.. Universidade do Vale do Paraíba; BrasilFil: Venkatesh, K.. Universidade do Vale do Paraíba; BrasilFil: Batista, I.S.. Instituto Nacional de Pesquisas Espaciais; NamibiaFil: de Jesus, R.. Instituto Nacional de Pesquisas Espaciais; NamibiaFil: Rockenback, M.. Instituto Nacional de Pesquisas Espaciais; NamibiaFil: Coster, A.. Massachusetts Institute of Technology; Estados UnidosFil: Gende, Mauricio Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Alves, M.A.. Instituto Tecnológico de Aeronáutica; BrasilFil: Wild, M.. Science and Technology Facilities Council; Reino Unid