45 research outputs found
New approaches for the standardization and validation of a real-time qPCR assay using TaqMan probes for quantification of yellow fever virus on clinical samples with high quality parameters
No full textFundação Oswaldo Cruz. Biomanguinhos. Instituto deTecnologia em Imunobiológicos. Laboratório de Tecnologia Virológica (LATEV). Rio de Janeiro, RJ, Brasil / Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular e Doenças Endêmicas (LABIMDOE). Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Biomanguinhos. Instituto deTecnologia em Imunobiológicos. Laboratório de Tecnologia Virológica (LATEV). Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Biomanguinhos. Instituto deTecnologia em Imunobiológicos. Laboratório de Tecnologia Virológica (LATEV). Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular e Doenças Endêmicas (LABIMDOE). Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Desenvolvimento Tecnológico em Virologia (LADTV). Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Biomanguinhos. Instituto deTecnologia em Imunobiológicos. Laboratório de Tecnologia Virológica (LATEV). Rio de Janeiro, RJ, Brasil.Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Laboratório de Biologia Molecular e Doenças Endêmicas (LABIMDOE). Rio de Janeiro, RJ, BrasilFundação Oswaldo Cruz. Biomanguinhos. Instituto deTecnologia em Imunobiológicos. Laboratório de Tecnologia Virológica (LATEV). Rio de Janeiro, RJ, Brasil.The development and production of viral vaccines, in general, involve several steps that need the monitoring of viral
load throughout the entire process. Applying a 2-step quantitative reverse transcription real time PCR assay (RT-qPCR),
viral load can be measured and monitored in a few hours. In this context, the development, standardization and
validation of a RT-qPCR test to quickly and efficiently quantify yellow fever virus (YFV) in all stages of vaccine
production are extremely important. To serve this purpose we used a plasmid construction containing the NS5 region
from 17DD YFV to generate the standard curve and to evaluate parameters such as linearity, precision and specificity
against other flavivirus. Furthermore, we defined the limits of detection as 25 copies/reaction, and quantification as 100
copies/reaction for the test. To ensure the quality of the method, reference controls were established in order to avoid
false negative results. The qRT-PCR technique based on the use of TaqMan probes herein standardized proved to be
effective for determining yellow fever viral load both in vivo and in vitro, thus becoming a very important tool to assure
the quality control for vaccine production and evaluation of viremia after vaccination or YF disease
Optical spectroscopy and X-ray observations of the D-type symbiotic star EF Aql
No full textWe performed high-resolution optical spectroscopy and X-ray observations of the recently identified Mira-type symbiotic star EF Aql. Based on high-resolution optical spectroscopy obtained with the Southern African Large Telescope (SALT), we determine the temperature (∼55 000 K) and the luminosity (∼5.3 L⊙) of the hot component in the system. The heliocentric radial velocities of the emission lines in the spectra reveal possible stratification of the chemical elements.We also estimate the mass-loss rate of the Mira donor star. Our Swift observation did not detect EF Aql in X-rays. The upper limit of the X-ray observations is 10-12 erg cm-2 s-1, whichmeans that EF Aql is consistent with the faintestX-ray systems detected so far. Otherwise we detected it with the UltraViolet and Optical Telescope (UVOT) instrument with an average UVM2 magnitude of 14.05. During the exposure, EF Aql became approximately 0.2 UVM2 magnitudes fainter. The periodogram analysis of the V-band data reveals an improved period of 320.4 ± 0.3 d caused by the pulsations of the Mira-type donor star.Fil: Stoyanov, K. A.. Bulgarian Academy of Sciences; BulgariaFil: Ilkiewicz, K.. Polish Academy of Sciences; PoloniaFil: Luna, Gerardo Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Universidad Nacional de Hurlingham; ArgentinaFil: Mikołajewska, J.. Polish Academy of Sciences; PoloniaFil: Mukai, K.. National Aeronautics and Space Administration; Estados Unidos. University of Maryland; Estados UnidosFil: Martí, J.. Universidad de Jaén; EspañaFil: Latev, G.. Bulgarian Academy of Sciences; BulgariaFil: Boeva, S.. Bulgarian Academy of Sciences; BulgariaFil: Zamanov, R. K.. Bulgarian Academy of Sciences; Bulgari
Pre-outburst signal in the light curves of the recurrent novae RS Oph and T CrB
No full textPre-outburst signal (a decrease of the optical brightness) just before the outburst is clearly detected in the observations of the T CrB obtained before and during the 1946 outburst. A similar decrease is also visible in the light curve of RS Oph during the 2021 outburst. We suppose that this is due to formation of a thick, dense envelope around the white dwarf, and we estimate its size (1000 - 2000 km), mass (5.10 - 6.10 M) and average density (5 - 16 g cm)
Simultaneous UBVRI Observations of the AE Aquarii Blobs
No full textWe summarize the results of our study of the cataclysmic variable AE Aqr on the basis of simultaneous UBV RI observations. For the flares, we estimated the average risetime of about 300 sec, and colours (U−B)0~1.1 and (B−V )0~0.1. We also calculated temperatures, sizes, masses and expansion velocities of a few individual fireballs. In a single night (16.08.2012), we detected ~ 8 min quasi-periodic modulation
Simultaneous UBVRI Observations of the AE Aquarii Blobs
No full textWe summarize the results of our study of the cataclysmic variable AE Aqr on the basis of simultaneous UBV RI observations. For the flares, we estimated the average risetime of about 300 sec, and colours (U−B)0~1.1 and (B−V )0~0.1. We also calculated temperatures, sizes, masses and expansion velocities of a few individual fireballs. In a single night (16.08.2012), we detected ~ 8 min quasi-periodic modulation
H
No full textWe report 138 spectral observations of the Hα emission line of the radio- and γ-ray-emitting Be/X-ray binary LSI+61°303 obtained during the period of September 1998 – January 2013. From measuring various Hα parameters, we found that the orbital modulation of the Hα is best visible in the equivalent width ratio EW(B)/EW(R), the equivalent width of the blue hump, and in the radial velocity of the central dip. The periodogram analysis confirmed that the Hα emission is modulated with the orbital and superorbital periods. For the past 20 years the radius of the circumstellar disk is similar to the Roche lobe size at the periastron. It is probably truncated by a 6:1 resonance. The orbital maximum of the equivalent width of Hα emission peaks after the periastron and coincides on average with the X-ray and γ-ray maxima. All the spectra are available upon request from the authors and through the CDS
Accretion in the recurrent nova T CrB: Linking the superactive state to the predicted outburst
No full textContext: T CrB (NOVA CrB 1946) is a famous recurrent nova with a recurrence
timescale of 80 years.
Aims: We aim to estimate the colours, luminosity, and mass-accretion rate for
T CrB (NOVA CrB 1946) during and after the superactive state.
Methods and Results: We performed and analysed photometry of the
recurrent nova T~CrB. For the hot component of T~CrB, we find average
dereddened colours of and ,
which correspond to an effective temperature of ~K and an optical
luminosity of during the superactive state (2016-2022). After
the end of the superactive state, the hot component became significantly
redder, and in August 2023, and
its luminosity decreased markedly to ~ in April-May 2023, and
to in August 2023. The total mass accreted during the superactive
state from 2014 to 2023 is ~M. This is a
significant fraction of the mass required to cause a thermonuclear runaway
(TNR). Overall our results support a model in which a large accretion disc acts
as a reservoir with increased accretion rate onto the central white dwarf
during disc high states, ultimately leading to a TNR explosion, which now seems
to be imminent.Comment: Astronomy & Astrophysics (accepted
Accretion in the recurrent nova T CrB: Linking the superactive state to the predicted outburst
No full textContext. T CrB (NOVA CrB 1946) is a famous recurrent nova with a recurrence timescale of 80 years.
Aims. We aim to estimate the colours, luminosity, and mass-accretion rate for T CrB (NOVA CrB 1946) during and after the superactive state.
Methods. We performed and analysed UBV photometry of the recurrent nova T CrB.
Results. For the hot component of T CrB, we find average dereddened colours of (U − B)0 = −0.70 ± 0.08 and (B − V)0 = 0.23 ± 0.06, which correspond to an effective temperature of 9400 ± 500 K and an optical luminosity of 40 − 110 L⊙ during the superactive state (2016–2022). After the end of the superactive state, the hot component became significantly redder, (U − B)0 ≈ −0.3 and (B − V)0 ≈ 0.6 in August 2023, and its luminosity decreased markedly to 20 − 25 L⊙ in April–May 2023, and to 8 − 9 L⊙ in August 2023. The total mass accreted during the superactive state from 2014 to 2023 is ∼2 × 10−7 M⊙.
Conclusions. This is a significant fraction of the mass required to cause a thermonuclear runaway (TNR). Overall our results support a model in which a large accretion disc acts as a reservoir with increased accretion rate onto the central white dwarf during disc high states, ultimately leading to a TNR explosion, which now seems to be imminent
