165 research outputs found

    Shell sources as a probe of relativistic effects in neutron star models

    Get PDF
    A perturbing shell is introduced as a device for studying the excitation of fluid motions in relativistic stellar models. We show that this approach allows a reasonably clean separation of radiation from the shell and from fluid motions in the star, and provides broad flexibility in the location and timescale of perturbations driving the fluid motions. With this model we compare the relativistic and Newtonian results for the generation of even parity gravitational waves from constant density models. Our results suggest that relativistic effects will not be important in computations of the gravitational emission except possibly in the case of excitation of the neutron star on very short time scales.Comment: 16 pages LaTeX with 6 eps figures; submitted to Phys. Rev.

    Mecanismo de Verificação de Integridade de Software Baseado em BIOS UEFI

    Get PDF
    This paper describes the proposal for a verification mechanism that takes advantage of UEFI BIOS resources to attest the integrity of the software of embedded systems used in IoT. This mechanism is composed by an integrity verification application called AVIS UEFI, which is executed in the Pre-Boot Applications phase and uses digital signature and keys stored in cryptographic devices to verify if the software has been tampered with. According to the result of the verification, the system is initialized or shut down. The next steps of this work will be to finalize the implementation of the prototype, present and evaluate the test results to show its applicability in a real scenario

    Excitation of the odd-parity quasi-normal modes of compact objects

    Get PDF
    The gravitational radiation generated by a particle in a close unbounded orbit around a neutron star is computed as a means to study the importance of the ww modes of the neutron star. For simplicity, attention is restricted to odd parity (``axial'') modes which do not couple to the neutron star's fluid modes. We find that for realistic neutron star models, particles in unbounded orbits only weakly excite the ww modes; we conjecture that this is also the case for astrophysically interesting sources of neutron star perturbations. We also find that for cases in which there is significant excitation of quadrupole ww modes, there is comparable excitation of higher multipole modes.Comment: 18 pages, 21 figures, submitted to Phys. Rev.

    Head-on collision of unequal mass black holes: close-limit predictions

    Full text link
    The close-limit method has given approximations in excellent agreement with those of numerical relativity for collisions of equal mass black holes. We consider here colliding holes with unequal mass, for which numerical relativity results are not available. We try to ask two questions: (i) Can we get approximate answers to astrophysical questions (ideal mass ratio for energy production, maximum recoil velocity, etc.), and (ii) can we better understand the limitations of approximation methods. There is some success in answering the first type of question, but more with the second, especially in connection with the issue of measures of the intrinsic mass of the colliding holes, and of the range of validity of the method.Comment: 19 pages, RevTeX + 9 postscript figure

    Transição agroecológica em sistema de produção familiar: a experiência da Família Zeferino em Brasil Novo, Pará.

    Get PDF
    Este trabalho tem como objetivo relatar a experiência de transição agroecológica vivenciada pela família Zeferino no município do Brasil Novo no Estado do Pará, caracterizando os princípios agroecológicos utilizados nos sistemas de produção e a história de vida da família. A família Zeferino composta pela Sra. Dercília e o Sr. José, conhecido como ?Cido?, e dois filhos foram pioneiros e inovadores no desenvolvimento de experiências agroecológica na região da Transamazônica, no entanto faleceram precocemente em 2014 e 2016 respectivamente. As atividades desenvolvidas pela família tinha como base a produção orgânica em sistema agroflorestais. Além de desenvolver experiências de produção sustentáveis, a família compartilhava o seu ?saber agroecológico?, com todos os segmentos da sociedade, sendo considerados como Referência no respeito no uso dos recursos naturais de nossa região.Edição dos anais do VI Congresso Latino-Americano (CLAA), X Congresso Brasileiro (CBA), V Seminário do DF e Entorno (SEMDF), 12-15 setembro de 2017, a Brasília, DF, Brasil

    Trapped and excited w modes of stars with a phase transition and R>=5M

    Get PDF
    The trapped ww-modes of stars with a first order phase transition (a density discontinuity) are computed and the excitation of some of the modes of these stars by a perturbing shell is investigated. Attention is restricted to odd parity (``axial'') ww-modes. With RR the radius of the star, MM its mass, RiR_{i} the radius of the inner core and MiM_{i} the mass of such core, it is shown that stars with R/M5R/M\geq 5 can have several trapped ww-modes, as long as Ri/Mi<2.6R_{i}/M_{i}<2.6. Excitation of the least damped ww-mode is confirmed for a few models. All of these stars can only exist however, for values of the ratio between the densities of the two phases, greater than 46\sim 46. We also show that stars with a phase transition and a given value of R/MR/M can have far more trapped modes than a homogeneous single density star with the same value of R/MR/M, provided both R/MR/M and Ri/MiR_{i}/M_{i} are smaller than 3. If the phase transition is very fast, most of the stars with trapped modes are unstable to radial oscillations. We compute the time of instability, and find it to be comparable to the damping of the ww-mode excited in most cases where ww-mode excitation is likely. If on the other hand the phase transition is slow, all the stars are stable to radial oscillations.Comment: To appear in Physical Review

    Historical analysis of the Brazilian cervical cancer screening program from 2006 to 2013: a time for reflection

    Get PDF
    BACKGROUND: The Cervical Cancer Database of the Brazilian National Health Service (SISCOLO) contains information regarding all cervical cytological tests and, if properly explored, can be used as a tool for monitoring and managing the cervical cancer screening program. The aim of this study was to perform a historical analysis of the cervical cancer screening program in Brazil from 2006 to 2013. MATERIAL AND METHODS: The data necessary to calculate quality indicators were obtained from the SISCOLO, a Brazilian health system tool. Joinpoint analysis was used to calculate the annual percentage change. RESULTS: We observed important trends showing decreased rates of low-grade squamous intraepithelial lesions (LSIL) and high-grade squamous intraepithelial lesions (HSIL) and an increased rate of rejected exams from 2009 to 2013. The index of positivity was maintained at levels below those indicated by international standards; very low frequencies of unsatisfactory cases were observed over the study period, which partially contradicts the low rate of positive cases. The number of positive cytological diagnoses was below that expected, considering that developed countries with low frequencies of cervical cancer detect more lesions annually. CONCLUSIONS: The evolution of indicators from 2006 to 2013 suggests that actions must be taken to improve the effectiveness of cervical cancer control in Brazil

    MMP-9/RECK imbalance: a mechanism associated with high-grade cervical lesions and genital infection by Human Papillomavirus (HPV) and Chlamydia trachomatis

    Get PDF
    "Manuscript"BACKGROUND: Matrix metalloproteinases (MMP) are important enzymes in the tumor microenvironment associated with progression of cervical intraepithelial neoplasia (CIN) toward squamous cell carcinoma (SCC) of the cervix. However, the role of MMPs in the inflammatory process associated with Chlamydia trachomatis infection concomitant with the carcinogenic process driven by HPV has not yet been addressed. In the present study, we analyzed the state of the MMP-9-RECK axis in cervical carcinogenesis. METHODS: The levels of MMP-9 and RECK expression were analyzed by immunocytochemistry in liquid-based cytology samples from 136 women with high-grade cervical lesions (CIN2/CIN3) and cervical SCC diagnosed by LLETZ, and in 196 women without cervical neoplasia or CIN1. Real-time qPCR was performed to analyze expression of MMP-9 and RECK in 15 cervical samples. The presence of HPV-DNA and other genital pathogens was evaluated by PCR. RESULTS: We found a higher expression of MMP-9 [OR, 4.2; 95% confidence interval (CI), 2.2-7.8] and lower expression of RECK (OR, 0.4; 95% CI, 0.2-0.7) in women with CIN2/CIN3/SCC when compared with women from the control group (no neoplasia/CIN1). A statistically significant association was also found between MMP-9/RECK imbalance and infection by alpha-9 HPV and C. trachomatis. The prevalence of C. trachomatis infection was significantly higher in women with high-grade cervical disease (OR, 3.7; 95% CI, 1.3-11.3). CONCLUSIONS: MMP-9/RECK imbalance in cervical smears is significantly associated with high-grade cervical diseases and infection by alpha-9 HPV and C. trachomatis. IMPACT: MMP-9/RECK imbalance during cervical inflammation induced by C. trachomatis might play a role in HPV-mediated cervical carcinogenesis.This work was supported by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), numbers 2008/03232-1 (to L.L. Villa) and 2012/09746-2 (to M.G. Discacciati and S.S. Maria-Engler) and National Counsel of Technological and Scientific Development pharmaceutical innovation (CNPQ-INCT-if; to S.S. Maria-Engler)
    corecore