Pc3-4 geomagnetic pulsations at very low latitude in Brazil

Made available in DSpace on 2019-09-12T16:53:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2004In order to investigate Pc3-4 geomagnetic pulsations at very low and equatorial latitudes, L = 1.0 to 1.2, we analyzed simultaneous geomagnetic data from Brazilian stations for 26 days during October November 1994. The multitaper spectral method based on Fourier transform and singular value decomposition was used to obtain pulsation power spectra, polarization parameters and phase. Eighty-one (81) simultaneous highly polarized Pc3-4 events occurring mainly during daytime were selected for the study. The diurnal events showed enhancement in the polarized power density of about 3.2 times for pulsations observed at stations close to the magnetic equator in comparison to the more distant ones. The phase of pulsation observed at stations near the magnetic equator showed a delay of 48-62degrees in relation to the most distant one. The peculiarities shown by these Pc3-4 pulsations close to the dip equator are attributed to the increase of the ionospheric conductivity and the intensification of the equatorial electrojet during daytime that regulates the propagation of compressional waves generated in the foreshock region and transmitted to the magnetosphere and ionosphere at low latitudes. The source mechanism of these compressional Pc3-4 modes may be the compressional global mode or the trapped fast mode in the plasmasphere driving forced field line oscillations at very low and equatorial latitudes. (C) 2004 Elsevier Ltd. All rights reserved.ITA, Elect Engn Div, IEE, BR-12228900 Sao Jose Dos Campos, SP, Brazil; Universidade de Taubaté (Unitau), Dept Math & Phys, BR-12020270 Taubate, SP, Brazil; INPE, Natl Inst Space Res, Div Space Geophys, DGE, BR-12201970 Sao Jose Dos Campos, Brazil; Kyushu Univ, Dept Earth & Planetary Sci, Fukuoka 812, Japa

Impact of Seasonality on the Prevalence of Dyslipidemia: A Large Population Study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Assessment of lipid profile parameters has been considered a cornerstone in classifying individuals and populations at risk for cardiovascular disease. Recently, however, preliminary data have raised the possibility of seasonal variations in these parameters, which may cause under- or overestimation. Biological rhythms and seasonal variation of lipid profile was investigated in 227 359 consecutive individuals who underwent health checkups in primary care centers between 2008 and 2010. Plasma low-density lipoprotein cholesterol (LDL-C) >130 mg/dL was 8% more prevalent during winter than summer, with a larger difference among women and middle-aged adults (p150 mg/dL were respectively 9% and 5% more prevalent during the summer (p<0.001). Variation amplitude was 3.4 +/- 0.3 mg/dL for HDL-C (p = 0.005), 7 +/- 2 mg/dL for LDL-C (p = 0.047), and 12 +/- 9 mg/dL for TG (p = 0.058). Based on a large population sample, this study confirms the existence of biological rhythms and seasonal variation in lipid profile. This finding must be particularly accounted for in cross-sectional analyses of relative risk, prevalence, or the rate of goal achievement for lipid parameters.30810111015Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq