In the absence of the selective availability, which was turned off on May 1, 2000, the ionosphere can be the largest source of error in GPS positioning and navigation. Its effects on GPS observable cause a code delays and phase advances. The magnitude of this error is affected by the local time of the day, season, solar cycle, geographical location of the receiver and Earth’s magnetic field. As it is well known, the ionosphere is the main drawback for high accuracy positioning, when using single frequency receivers, either for point positioning or relative positioning of medium and long baselines. The ionosphere effects were investigated in the determination of point positioning and relative positioning using single frequency data. A model represented by a Fourier series type was implemented and the parameters were estimated from data collected at the active stations of RBMC (Brazilian Network for Continuous Monitoring of GPS satellites). The data input were the pseudorange observables filtered by the carrier phase. Quality control was implemented in order to analyse the adjustment and to validate the significance of the estimated parameters. Experiments were carried out in the equatorialregion, using data collected from dual frequency receivers. In order to validate the model, the estimated values were compared with “ground truth”. For point and relative positioning of baselines of approximately 100 km, the values of the discrepancies indicated an error reduction better than 80% and 50% respectively, compared to the processing without the ionospheric model. These results give an indication that more research has to be done in order to provide support to the L1 GPS users in the Equatorialregion.
Influenza viruses are well recognised for their viral properties such as sialic-acid receptor specificity, gly- cosylation, virulence, pathogenicity and development of resistance to drug therapy as well as for their high mutation rates, with the ability to generate antigenically distinct variants (Kilander et al. 2010, Ghedin et al. 2011, Sun et al. 2011). The haemagglutinin (HA) gene pres- ents the highest mutation rates in the influenza genome and its encoded glycoprotein is responsible for the ini- tial steps of successful infection (Wagner et al. 2002). In April 2009, the World Health Organization (WHO) iden- tified the occurrence of novel human influenza cases in Mexico and the United States of America (USA), which were caused by influenza A(H1N1) of swine origin (Gar- ten et al. 2009), thereafter referred to as A(H1N1)pdm09. Within months, the virus had spread worldwide, provok- ing the first pandemic of the XXI century, accounting for more than 18,000 deaths (WHO 2010). In Brazil, the first cases were confirmed by sequencing and real- time reverse transcription-polymerase chain reaction (RT-PCR) on 7 May 2009 in the Southeast Region from
Low-income populations are expected to display more severe disease that can be related to less access to medical treatment  as well as to an increased prevalence of the polyarticular category . More than 90 % of our patients have a family (mean 6 people/family) monthly income of <U$ 900.00 (data not shown). Although we have no limi- tations concerning prescription of high-cost medications in our reference services, difficulties of patients to attend the outcare clinic, irregular adherence to prescriptions, and very limited access to non-pharmacological therapy may adversely impact disease severity [31, 32]. We cannot rule out that underdiagnosis of less severe oligoarticular presen- tations accounts for our low numbers of this JIA category . However, despite the economic burden, our patients had an apparently less than expected joint damage in the long term. Coupled to a greater prevalence of polyarticular patients, the low CHAQ, vis-à-vis other series from devel- oped countries, lead us to speculate that normal or near- normal 25OHD levels increased prevalence in our region could positively influence the evolution of JIA.
Abstract - Despite uncertainties as to the real causes, there is a large amount of evidence of climatic change on Earth. With the objective of investigating changes in extreme air temperatures, as well as the local effects of these changes, eight data sets, collected throughout the State of Ceará in Brazil, were analyzed. Four series of data were obtained from the semi-arid region, three from the coastal zone, and one from a mountainous region. To quantify the changes that occurred during the study period, variations in maximum and minimum temperatures were calculated in relation to the mean of each data series. The annual rates of temperature increase were estimated from the angular coefficients of the best-fit lines. The results showed that although there are differences in trends between stations, there was a systematic increase in the maximum and minimum temperature in the nineties, which was especially evident in the following decade. The highest rates of increase were recorded for the minimum temperatures (from 9.0 to 8.3 °C per century) for the stations at Guaramiranga and Crateús respectively. These data provide evidence for a greater retention of energy in the form of sensible heat during the night, possibly due to a more difficult energy exchange between the surface and the atmosphere.
. For performance variables, except egg weight, there was interaction effect (light program x posture cycle period), however, this effect was not observed for egg quality variables. The birds submitted to the natural light program in the growth phase showed lower ration intake until the second period (71 to 92 days old), lower egg production during all periods, lower egg mass and worse feed conversion until the third period (93 to 114 days old). These variables did not differ between the continuous and the intermittent program from the second period (71 to 92 days old). Light programs in growth stage didn’t influence the quality characteristics of the eggs, however, as the age of the birds increased, there was egg yolk reduction and egg shell ad albumen increase, from the first (49 to 71 days old) for the remaining periods of the cycle, and worsening of albumen and shell quality, from the first (49 to 71 days old) to the third period (93 to 114 days old). It is concluded that in equatorialregion, the natural light program in the growth phase (7 to 49 days of age) increases the age of sexual maturity and worsens the performance of the birds during the production cycle (49 to 136 days of age); In turn, the flashing light program maintains the sexual maturity, performance and quality of the eggs during the production cycle.
ABSTRACT. This paper presents results from a new model of field-line-integrated ionospheric conductivity for the Brazilian equatorialregion. It was developed aiming to calculate zonal electric fields at E-region heights in the equatorialregion. The present model is based on a constant neutral atmosphere model and on an empirical electron densities model (which also gives the ion composition) adjusted by E-region electron density measured by digisonde. It is also based on a geomagnetic field model that we approximate with a dipole which is not located at the centre of the Earth due to the large magnetic declination angle in the Brazilian sector. We have also considered the eccentric dipole having an inclination of 20 ◦ with respect to the Earth rotation axis. The conductivities are calculated for the year 2002 and the results from the present model are compared to those obtained from the conductivity model of the Kyoto University.
Perturbações atmosféricas geradas por ondas de gravidade e com características quase periódicas têm sido intensamente estudadas nas últimas décadas. No entanto, poucos desses estudos se referem a atmosfera equatorial sobre o setor sul americano de latitudes. No presente trabalho se discute resultados relativos a detecção de assinaturas de ondas de gravidade no perfil de temperatura da estratosfera equatorial, em uma faixa de altura compreendida entre 16 – 25 km, a partir de dados de radiossondas instaladas em balões meteorológicos lançados, rotineiramente, do Centro de
À semelhança do que ocorre em outras doenças consideradas autoimunes, a AIJ tem etiopatogenia multifatorial, com componentes genéticos e ambientais. Esse primeiro, embora tenha participação, não explica o quadro clínico nem evolução, haja vista a discordância entre gêmeos monozigóticos. Com relação a aspectos ambientais, infecções, aspectos socioeconômicos, geográficos e possíveis comorbidades têm recebido atenção ultimamente. Dentre esses, exposição ao fumo, doença periodontal, amamentação e escolaridade dos pais parecem influenciar a prevalência e/ou evolução da AIJ. Um aspecto em particular, na situação geográfica, diz respeito a um possível papel da vitamina D (ELLIS; MUNRO; PONSONBY, 2010). Entretanto, não é do nosso conhecimento que exista estudo sobre os níveis séricos de vitamina D e uma possível associação com quadro clínico e evolução da AIJ em pacientes de uma região equatorial. Recentemente, relatamos que nossos pacientes tiveram uma aparentemente surpreendente resposta positiva ao tratamento com DMARD não biológicos, quando comparados a pacientes de comunidades do hemisfério norte, vivendo em maiores latitudes (ALCANTARA et al., 2014).
As nuvens exercem um papel fundamental na dinâmica da Circulação de Walker através de uma influência direta sobre a quantidade de radiação que atinge a superfície do mar. Existe uma clara transição das nuvens no Pacífico Equatorial, no sentido de leste para oeste. No leste, nas águas mais frias, temos a formação de estratocúmulos (região 1 da figura 2.3). À medida que o ar advecta em direção às águas mais quentes, ocorre desacoplamento, aprofundamento da camada de mistura e redução da cobertura de nuvens (figura 2.4). A subsidência é mais fraca nesta região e a presença de cúmulos é comum (centro da figura 2.3). Finalmente nas águas mais quentes da célula de Walker temos o regime de convecção profunda caracterizado por ascendência de larga escala. Esta imagem descrita aqui é, no entanto, um perfil médio com uma grande variação sazonal. Na subseção seguinte temos uma descrição mais detalhada deste perfil médio.
Para o presente estudo, foram realizadas duas campanhas oceanográficas, sendo a primeira, em outubro de 2012, a bordo do Navio Corenav III, e a segunda, em setembro de 2014, a bordo do NHo. Cruzeiro do Sul (H-38), navio-hidroceanográfico da Marinha do Brasil. Além dessas campanhas, foram ainda trabalhados dados, de 2008 a 2012, de regiões próximas aos dois Cruzeiros oceanográficos, obtidos por Navios Mercantes (MS Monte Olivia, MS Rio Blanco e MS Santa Cruz) e em regiões do Atlântico Equatorial mais afastadas no oceano aberto a fim de compará-los com os dados das regiões mais próximas da costa.
Área de estudo A região Equatorial Ocidental do Oceano Atlântico compreende a plataforma continental e planície abissal do Norte do Ceará ao Sul de Pernam- buco. Nesta área localiza-se a cadeia norte do Brasil e a cadeia de Fernando de Noronha, da qual também faz parte o Atol das Rocas (Schobbernhaus et al. 1984). Esta região é dominada pela Zona de Convergência Intertropical (ZCIT), que é caracterizada por baixa pressão atmosférica, ventos fracos e alta precipitação, devido à influência dos dois sistemas de alta pressão localizados nas regiões subtropicais dos dois hemisfé- rios, os anticiclones dos Açores ao Norte e o de Santa Helena no Sul (Nimer 1989).
The post-sunset ionosphere at low magnetic latitudes is in- herently unstable, allowing plasma density irregularities to develop. The irregularities initially form in the bottom side of the F layer through the generalized Rayleigh-Taylor (R-T) instability (Ott, 1978). Severe radio signal disruptions oc- cur when the irregularities propagate into the topside iono- sphere as density depletions called equatorial plasma bub- bles (EPBs). Because of their appearance in altitude-versus- time radar displays and ionograms, EPBs are also referred to as plasma plumes (Woodman and La Hoz, 1976) and range spread F (Aarons, 1993). Strong seasonal-versus- longitudinal (S/L) variability characterizes the frequency of EPB occurrence (Aarons, 1993; Huang et al., 2001).
Multiple aspects are still under debate about the evolution of transform margins. The first aspect relates to how major oceanic transform faults/fracture zones in the Equatorial Atlantic evolved through time ( Bonatti et al., 1991 ). The Kane, Saint Paul, Romanche, and Chain transform faults show deep transform valleys that are sub-parallel to transverse ridges. However, systematic changes in movement and regional stresses have occurred throughout their evolution to induce important transpression and uplift between crustal blocks generated between the transform faults ( Bonatti et al., 1978; Tucholke and Schouten, 1988 ; Klitgord and Schouten, 1986 ). These fracture zones in the Equatorial Atlantic seem to be characterized by broad zones of mixed strike-slip and extensional faulting ( Azevedo, 1991; Davison
Instabilidades do plasma da região-F da ionosfera equatorial são geralmente agrupados sob um nome genérico que vem do Inglês, “Equatorial Spread-F” (ESF). Isto decorre das primeiras observações utilizando ionossondas, que mostrou na ocasião, que o eco refletido não exibia um padrão bem-comportado, mas foi "espalhado" nos ionogramas. Um nome baseado literatura da física para este fenômeno é tempestade ionosférica equatorial convectiva (CEIS, do Inglês “convective equatorial ionospheric storm”). O fenômeno ocorre principalmente à noite, apesar de ocorrerem eventos isolados durante o dia (Woodman et al., 1985). A era moderna das pesquisas do ESF (CEIS) começou com uma nota teórica em 1970 com a publicação da primeira compilação de medições feita pelo Observatório de Radar Jicamarca no Peru (Farley et al., 1970; Kelley, 2009).
In addition to the importance of the PNMA region, this study appears to show another important, though much smaller area, in RNRC and the region just to the east of the reserve. It is difficult to determine if this is indeed the case, as the transect in that region fell outside of the country and was not surveyed as a result, and we hence cannot rule out the extent of modelling error. On the other side of the border lies the Campo Ma’an National Park (CMNP) in Cameroon, however, which extends down to Rı´o Muni. Although the gorilla population is low in CMNP, the chimpanzee density was found to be high compared to other parts of the country and the rest of West and Central Africa in earlier studies [71–73]. Furthermore, it is understood that the current elephant population to the east of RNRC crossed over from CMNP . Although a transboundary complex, the ‘Rı´o Campo Ma’an’ initiative, has been launched, shortage of funding has prevented further developments beyond its initial stages. Financial security is a priority and there is additionally the need to expand the Rı´o Campo Ma’an complex to include the regions to the east of RNRC.