Papers by Geraldo Magela Couto Oliveira
Astrophysics and Space Science, 2017
The strongly perturbed environment of a small body, such as an asteroid, can complicate the predi... more The strongly perturbed environment of a small body, such as an asteroid, can complicate the prediction of orbits used for close proximity operations. Inaccurate predictions may make the spacecraft collide with the asteroid or escape to the deep space. The main forces acting in the dynamics come from the solar radiation pressure and from the body's weak gravity field. This paper investigates the feasibility of using bi-impulsive maneuvers to avoid the aforementioned non-desired phenomena (collisions and escapes) by connecting orbits around the triple system asteroid 2001SN 263 , which is the target of a proposed Brazilian space mission. In terms of a mathematical formulation, a recently presented rotating dipole model is considered with oblateness in both primaries. In addition, a "two-point boundary value problem" is solved to find a proper transfer trajectory. The results presented here give support to identifying the best strategy to find orbits for close proximity operations, in terms of long orbital lifetimes and low delta-V consumptions. Numerical results have also demonstrated the significant influence of the spacecraft orbital elements (semi-major axis and eccentricity), angular position of the Sun and spacecraft area-to-mass ratio, in the performance of the bi-impulsive maneuver.
X Semana De Ciencia Tecnologia 2014, Sep 15, 2014
Os jogos eletronicos fazem parte da vida da maioria dos estudantes, criancas, jovens ou adolescen... more Os jogos eletronicos fazem parte da vida da maioria dos estudantes, criancas, jovens ou adolescentes, apresentando-se como uma ferramenta de mediacao de grande potencial para a imersao desses no aprofundamento de seus estudos e de seu conhecimento dos conteudos de informatica. Esse tipo de software apresenta a caracteristica de envolver diversas areas do ensino de informatica e, devido a sua grande atratividade, apresenta-se como um grande motivador na busca de conhecimento de sua construcao e repercussao de seu uso. Esse projeto teve como objetivo desenvolver recursos instrucionais, como tutoriais e artigos, a partir da confeccao e uso de jogos eletronicos que possam auxiliar os professores das areas tecnicas e de formacao geral no ensino das diversas areas do ensino, alem de contribuir com ferramentas para o aprimoramento dos cursos tecnicos de informatica. Como resultados do projeto realizou-se a manutencao do blog e de um mural na escola, desenvolvimento de jogos pelos alunos e realizacao de campeonatos. Com a manutencao do blog e das outras atividades do projeto, observou-se um aumento na problematizacao sobre o uso de jogos na escola, e uma maior conscientizacao de que games tambem podem funcionar como um espaco rico de aprendizado.
Computational and Applied Mathematics, 2015
The goal of the present paper is to study close approaches of a cloud of particles with an oblate... more The goal of the present paper is to study close approaches of a cloud of particles with an oblate planet, which means that there is a J 2 term in the gravitational potential of the planet. This cloud of particles is assumed to be created during the passage of a spacecraft by the periapsis of its orbit, by an explosion or any other disruptive event. The system is formed by two large bodies (Sun and planet), assumed to be in circular orbits around the center of mass of the system, and the cloud of particles. The particles that belong to the cloud make a close approach to the flat planet and then they are dispersed by the gravitational force of the planet. The motion is governed by the equations of motion given by the planar restricted circular three-body problem plus the effects of the oblateness of the planet. Jupiter is used for numerical simulations. The results show the differences between the behavior of the cloud after the passage, considering or not the effects of the oblateness of the planet. The results show that the oblateness of the planet is equivalent to an increase in the mass of the planet.
2010 Eleventh Brazilian Symposium on Neural Networks, 2010
... Amazonas, 7675, Belo Horizonte, MG, Brasil {gabriela, henrique, rogerio, magela}@lsi.cefetmg.... more ... Amazonas, 7675, Belo Horizonte, MG, Brasil {gabriela, henrique, rogerio, magela}@lsi.cefetmg. br ... STDP is a rule that can select matching conduction delays and spontaneously organize neurons into such neu-ronal groups [7]. For this study the STDP algorithm presented by ...
Memórias do Instituto Oswaldo Cruz, 2011
Memórias do Instituto Oswaldo Cruz, 2001
Positive Montenegro's skin test is a delayed type hypersensitivity reaction widely used as indica... more Positive Montenegro's skin test is a delayed type hypersensitivity reaction widely used as indicative of previous infection with Leishmania in both humans and dogs. Montenegro's antigen consists of a crude Leishmania antigen solution, usually containing thimerosal as preserving agent. In this work it is shown that a large proportion of dogs (11 out of 56) examined in an endemic area of leishmaniasis presented induration at the site of injection of a diluent containing thimerosal alone. This clearly demonstrates that thimerosal leads to a high number of false positive skin reactions in dogs and that its use in Montenegro's skin test antigenic preparations should be avoided.
Veterinary Parasitology, 2012
Veterinary Parasitology, 2006
In this study, humoral (circulating anti-Leishmania antibodies) and cellular (Montenegro's skin t... more In this study, humoral (circulating anti-Leishmania antibodies) and cellular (Montenegro's skin test) immune responses of dogs from an endemic area of visceral leishmaniosis were tested using Leishmania chagasi, Leishmania amazonensis and Leishmania braziliensis antigens. The antibody response was tested in three animal groups, selected according to their anti-L. chagasi antibody activity, as measured by ELISA in the serum: 19 negative (O.D. below 0.30), seven with undefined (O.D. between 0.40 and 0.70) and 12 positive (O.D. above 1.0) ELISA result. In the group of animals with positive ELISA, the antibody activity against L. chagasi antigens (mean O.D. = 1.31) was significantly higher (ANOVA, P < 0.01) than against L. amazonensis (mean O.D. = 0.88) or L. braziliensis (mean O.D. = 0.87) antigens. The Montenegro's skin test results obtained with L. chagasi and L. braziliensis antigens showed a fair agreement (k = 0.309). The same was observed when antigens from L. braziliensis and L. amazonensis were compared (k = 0.374), whereas a moderate agreement between the results from tests performed with L. chagasi and L. amazonensis antigens was observed (k = 0.530). The induration areas obtained with L. braziliensis antigen were smaller than those obtained with the other antigens. The data presented herein indicate that the use of antigens from different Leishmania species may interfere with the results of the immunological tests performed in dogs in an endemic area of visceral leishmaniosis.
Veterinary Parasitology, 2003
Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on ... more Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre-including this research content-immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.
Veterinary Immunology and Immunopathology, 2004
This work aims at identifying an effective protocol to raise anti-Leishmania chagasi amastigote a... more This work aims at identifying an effective protocol to raise anti-Leishmania chagasi amastigote antibodies in different animal species. Protocols of immunization by subcutaneous injections of L. chagasi promastigote and amastigote lysates or by either intravenous or subcutaneous inoculation of live metacyclic promastigotes were assessed in mice, rabbits, and dogs. The immunization with live promastigotes produced a strong humoral immune response against L. chagasi amastigotes in all three animal species. The sera from animals immunized with the promastigote lysate did not react with amastigotes and, conversely, the sera from mice immunized with the amastigote lysate did not react with promastigotes. Taken all data together, the immunization through infection with metacyclic promastigotes was considered the most satisfactory way to immunize animals for obtaining anti-amastigote and anti-promastigote antibodies, since it did not only allowed the obtention of antibody against the two forms of the parasite, but it is also cheap, less laborious than carrying out the purification of amastigotes from infected tissues and avoid the use of a large number of hamsters for obtention the amastigotes, necessary to produce the immunogenic lysates. Furthermore, this immunization protocol was comparable to the amastigote lysate immunization protocol for the obtaining of mouse monoclonal antibodies (mAbs).
Parasite Immunology, 2008
The aim of this study was to identify splenic immuno-inflammatory patterns associated with natura... more The aim of this study was to identify splenic immuno-inflammatory patterns associated with natural infection by Leishmania chagasi. Spleen samples were obtained from 72 stray dogs from an endemic area of visceral leishmaniasis. The animals were grouped into four categories as follows: (i) potentially resistant to visceral leishmaniasis, with a positive leishmanin skin test result, and negative splenic culture for Leishmania parasites (ii) potentially susceptible to visceral leishmaniasis, with a negative leishmanin skin test and positive splenic culture for Leishmania (iii) infected with undefined susceptibility status, with a positive leishmanin skin test and positive splenic culture for Leishmania , and (iv) noninfected, with a negative leishmanin skin test, negative splenic culture for Leishmania , and negative serology for anti-Leishmania antibodies. Histopathological analyses showed that there was a higher frequency of perisplenitis (18/25, P < 0•0001), granuloma (7/25, P = 0•0102), structural disorganization (14/25, P < 0•0001), and atrophy of the lymphoid follicles (20/25, P = 0•0036) and of the marginal zone (15/25, P = 0•0025) in the potentially susceptible group than in the other groups. The data presented here show changes in the white pulp of the spleen that are associated with naturally acquired visceral leishmaniasis.
Memórias do Instituto Oswaldo Cruz, 1993
Journal of Autoimmunity, 2002
The protozoan Trypanosoma cruzi causes chronic Chagas' disease myocarditis (CCDM) in infected mam... more The protozoan Trypanosoma cruzi causes chronic Chagas' disease myocarditis (CCDM) in infected mammals. The pathogenesis of CCDM, however, is still unclear. Indirect evidence for either parasite-or heart-specific immune responses playing a pathogenic role is available. In this work, the participation of autoimmunity in the development of CCDM is demonstrated in mice in which immunological tolerance to heart antigens was induced or strengthened prior to their infection by T. cruzi. Tolerance was induced by heart antigen administration in the presence of complete Freund's adjuvant and anti-CD4 antibodies. Tolerized mice developed less intense CCDM than control nontolerized animals that had received only anti-CD4 and adjuvant. This result confirms the important notion that tolerance to self, and in particular to heart antigens, may be reinforced/induced in normal animals, and raises the possibility that analogous interventions may prevent the development of CCDM in millions of T. cruzi-infected human beings.
Immunology Letters, 1994
New Zealand Black (NZB) mice spontaneousl2,. develop autoimmune haemolytic anaemia as the result ... more New Zealand Black (NZB) mice spontaneousl2,. develop autoimmune haemolytic anaemia as the result of production of autoantibodies to erythrocytes. We have recently shown that antibodies to CD4 prevent the development of erythrocyte autoantibodies in young mice (Coombs' negative). In spite of this inhibition of erythrocyte autoantibody production, the anti-CD4-treated mice show a precocious and severe anaemia. Balb, c mice treated with the same protocol do not develop anaemia. Our results suggest that er.~thropoiesis in NZB mice is particularly sensitive to depletion of CD4 + T cells.
European Journal of Immunology, 1993
Biologicals, 2007
Different individuals, when infected with the same parasite, rarely produce antibodies against th... more Different individuals, when infected with the same parasite, rarely produce antibodies against the same set of antigens. Indeed, unless a particular antigen happens to be recognized by antibodies in all individuals, the use of a single antigen in the serodiagnosis of parasitic diseases leads, invariably, to false-negative results. A straightforward method for pinpointing , in genetic libraries, the precise antigens that would increase serodiagnostic assay sensitivities is presented. The method is based on the utilization of sera that produced false-negative results against previously available antigens. Employing this false-negative serum-selection methodology for the identification of new Leishmania infantum recombinant antigens (rAgs), the sensitivity of a dipstick assay for anti-Leishmania antibodies in a panel of sera from patients with visceral leishmaniasis was increased from 83.3% to 98.1%, without affecting its specificity, by the inclusion of a fifth and a sixth L. infantum rAg.
The American Journal of Tropical Medicine and Hygiene, 2011
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Papers by Geraldo Magela Couto Oliveira