182 research outputs found
Carbendazim dissipation in the biomixture of on-farm biopurification systems and its effect on microbial communities
The impact of repeated carbendazim (CARB) applications on the extent of \CARB\ dissipation, the microbial diversity, the community level physiological profile (CLPP), and the enzymatic activity within the biomixture of an on-farm biopurification system was evaluated. After three successive \CARB\ applications, the \CARB\ dissipation efficiency was high; the efficiency of dissipation was 87%, 94% and 96% after each application, respectively. Although microbial enzymatic activity was affected significantly by \CARB\ application, it could recover after each \CARB\ pulse. Likewise, the numbers of cultivable bacteria, fungi and actinomycetes (as measured in CFUs) were slightly affected by the addition of CARB, but the inhibitory effect of the pesticide application was temporary. Denaturing gradient gel electrophoresis (DGGE) and Biolog Ecoplate assays demonstrated that the microbial populations remained relatively stable over time when compared to the control. The results obtained herein therefore demonstrate the high dissipation capacity of this biomixture and highlight the microbiological robustness of this biological system.This work was supported by FONDECYT project No 11100236
A Possible Detection of Occultation by a Proto-planetary Clump in GM Cephei
GM Cep in the young (~4 Myr) open cluster Trumpler 37 has been known to be an
abrupt variable and to have a circumstellar disk with very active accretion.
Our monitoring observations in 2009-2011 revealed the star to show sporadic
flare events, each with brightening of < 0.5 mag lasting for days. These
brightening events, associated with a color change toward the blue, should
originate from an increased accretion activity. Moreover, the star also
underwent a brightness drop of ~1 mag lasting for about a month, during which
the star became bluer when fainter. Such brightness drops seem to have a
recurrence time scale of a year, as evidenced in our data and the photometric
behavior of GM Cep over a century. Between consecutive drops, the star
brightened gradually by about 1 mag and became blue at peak luminosity. We
propose that the drop is caused by obscuration of the central star by an
orbiting dust concentration. The UX Orionis type of activity in GM Cep
therefore exemplifies the disk inhomogeneity process in transition between
grain coagulation and planetesimal formation in a young circumstellar disk.Comment: In submission to the Astrophysical Journal, 4 figure
On the implementation of a primal-dual algorithm for second order time-dependent Mean Field Games with local couplings
We study a numerical approximation of a time-dependent Mean Field Game (MFG) system with local couplings. The discretization we consider stems from a variational approach described in [14] for the stationary problem and leads to the finite difference scheme introduced by Achdou and Capuzzo-Dolcetta in [3]. In order to solve the finite dimensional variational problems, in [14] the authors implement the primal-dual algorithm introduced by Chambolle and Pock in [20], whose core consists in iteratively solving linear systems and applying a proximity operator. We apply that method to time-dependent MFG and, for large viscosity parameters, we improve the linear system solution by replacing the direct approach used in [14] by suitable preconditioned iterative algorithms
Inner disc rearrangement revealed by dramatic brightness variations in the young star PV Cep
Young Sun-like stars at the beginning of the pre-main sequence (PMS)
evolution are surrounded by accretion discs and remnant protostellar envelopes.
Photometric and spectroscopic variations of these stars are driven by
interactions of the star with the disc. Time scales and wavelength dependence
of the variability carry information on the physical mechanisms behind these
interactions. We conducted multi-epoch, multi-wavelength study of PV Cep, a
strongly variable, accreting PMS star. By combining our own observations from
2004-2010 with archival and literature data, we show that PV Cep started a
spectacular fading in 2005, reaching an I_C-band amplitude of 4 mag. Analysis
of variation of the optical and infrared fluxes, colour indices, and emission
line fluxes suggests that the photometric decline in 2005-2009 resulted from an
interplay between variable accretion and circumstellar extinction: since the
central luminosity of the system is dominated by accretion, a modest drop in
the accretion rate could induce the drastic restructuring of the inner disc.
Dust condensation in the inner disc region might have resulted in the
enhancement of the circumstellar extinction.Comment: 11 pages, 4 figures, accepted for publication by MNRAS. 3 online
tables adde
YETI observations of the young transiting planet candidate CVSO 30 b
CVSO 30 is a unique young low-mass system, because, for the first time, a
close-in transiting and a wide directly imaged planet candidates are found
around a common host star. The inner companion, CVSO 30 b, is the first
possible young transiting planet orbiting a previously known weak-lined T-Tauri
star. With five telescopes of the 'Young Exoplanet Transit Initiative' (YETI)
located in Asia, Europe and South America we monitored CVSO 30 over three years
in a total of 144 nights and detected 33 fading events. In two more seasons we
carried out follow-up observations with three telescopes. We can confirm that
there is a change in the shape of the fading event between different
observations and that the fading event even disappears and reappears. A total
of 38 fading event light curves were simultaneously modelled. We derived the
planetary, stellar, and geometrical properties of the system and found them
slightly smaller but in agreement with the values from the discovery paper. The
period of the fading event was found to be 1.36 s shorter and 100 times more
precise than the previous published value. If CVSO 30 b would be a giant planet
on a precessing orbit, which we cannot confirm, yet, the precession period may
be shorter than previously thought. But if confirmed as a planet it would be
the youngest transiting planet ever detected and will provide important
constraints on planet formation and migration time-scales.Comment: 14 pages (20 with appendix), 7 figures (16 with appendix), 6 tables
(7 with appendix
The low level of debris disk activity at the time of the Late Heavy Bombardment: a Spitzer study of Praesepe
We present 24 micron photometry of the intermediate-age open cluster
Praesepe. We assemble a catalog of 193 probable cluster members that are
detected in optical databases, the Two Micron All Sky Survey (2MASS), and at 24
micron, within an area of ~ 2.47 square degrees. Mid-IR excesses indicating
debris disks are found for one early-type and for three solar-type stars.
Corrections for sampling statistics yield a 24 micron excess fraction (debris
disk fraction) of 6.5 +- 4.1% for luminous and 1.9 +- 1.2% for solar-type
stars. The incidence of excesses is in agreement with the decay trend of debris
disks as a function of age observed for other cluster and field stars. The
values also agree with those for older stars, indicating that debris generation
in the zones that emit at 24 micron falls to the older 1-10 Gyr field star
sample value by roughly 750 Myr.
We discuss our results in the context of previous observations of excess
fractions for early- and solar-type stars. We show that solar-type stars lose
their debris disk 24 micron excesses on a shorter timescale than early-type
stars. Simplistic Monte Carlo models suggest that, during the first Gyr of
their evolution, up to 15-30% of solar-type stars might undergo an orbital
realignment of giant planets such as the one thought to have led to the Late
Heavy Bombardment, if the length of the bombardment episode is similar to the
one thought to have happened in our Solar System.
In the Appendix, we determine the cluster's parameters via boostrap Monte
Carlo isochrone fitting, yielding an age of 757 Myr (+- 36 Myr at 1 sigma
confidence) and a distance of 179 pc (+- 2 pc at 1 sigma confidence), not
allowing for systematic errors.Comment: 22 pages, 14 figures, 9 tables, emulateapj format; Accepted for
publication in The Astrophysical Journa
Niveles del factor de crecimiento derivado de plaquetas en el plasma rico en plaquetas antes y despues de antiagregantes plaquetarios
El PDGF es uno de los mitógenos más potentes para el tejido conectivo, su secreción parece ser particularmente importante cuando la fuente es el Plasma Rico en Plaquetas (PRP), de allí el rol protagónico de este último en la regeneración tisular. Se determinó mediante ELISA los niveles de PDGFBB en el PRP, Plasma Pobre en Plaquetas (PPP) y Exudado de 32 sujetos sanos antes y 24 horas después de ingerir AAS (Aspirina) y Clopidogrel. Los niveles basales de PDGFBB ueron de 10, 6 ± 1, 9 ng/ml (PPP), 12, 12 ± 2, 5 ng/ml (PRP) y 10, 84 ± 1, 68 ng/ml (Exudado). Mientras que después del tratamiento con AAS las concentraciones de PDGFBB estuvieron en 8, 96 ± 1, 4 ng/ml (PPP), 11, 36 ± 1, 48ng/ml (PRP), 11, 11 ± 1, 14ng/ml (Exudado) y para el Clopidogrel fueron de 8, 53 ± 0, 59 ng/ml (PPP), 9, 65 ± 1, 17 ng/ml (PRP) y 8, 51 ± 0, 75 ng/ml (Exudado). Se notó que luego de la administración de AAS y Clopidogrel los valores de PDGFBB disminuyeron de manera estadísticamente significativa, en especial para el grupo del Clopidogrel. El AAS pareció afectar en menor grado las concentraciones de PDGFBB, lo cual puede ser atribuible al mecanismo de acción farmacológica diferencial existente entre la AAS y Clopidogrel. No se encontró correlación entre el recuento plaquetario y los niveles basales de PDGFBB del PRP.
PDGF levels in platelet-rich plasma before and after anti platelets drugs
Abstract
PDGF is one of the most potent mitogen for connective tissue, its secretion appears to be particularly important when the source is Platelet Rich Plasma (PRP), hence the latter leading role in tissue regeneration. ELISA PDGFBB levels in PRP, Platelet Poor Plasma (PPP) and exudates, were determined in 32 healthy subjects before and 24 hours after ingestion of Aspirin (ASA) and Clopidogrel (CLO). PDGFBB baseline levels were 10.6 ± 1.9 ng / ml (PPP), 12.12 ± 2.5 ng / ml (PRP) and 10.84 ± 1.68 ng / ml (exudate). After treatment with ASA concentrations were PDGFBB in 8.96 ± 1.4 ng / ml (PPP), 11.36 ± 1.48 ng / ml (PRP), 11.11 ± 1.14 ng / ml (exudate) and the Clopidogrel were 8.53 ± 0.59 ng / ml (PPP), 9.65 ± 1.17 ng / ml (PRP) and 8.51 ± 0.75 ng / ml (exudate). It was noted that after the administration of ASA and CLO, PDGFBB values statistically significantly decreased, especially for the group of CLO. ASA lesser extent appears to affect th concentrations of PDGFBB, which may be attributable to the pharmacological mechanism of action between the ASA and Clopidogrel. No correlation was found between platelet count and baseline levels of PRP PDGFBB
UBVRI Light Curves of 44 Type Ia Supernovae
We present UBVRI photometry of 44 type-Ia supernovae (SN Ia) observed from
1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence
Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The
data set comprises 2190 observations and is the largest homogeneously observed
and reduced sample of SN Ia to date, nearly doubling the number of
well-observed, nearby SN Ia with published multicolor CCD light curves. The
large sample of U-band photometry is a unique addition, with important
connections to SN Ia observed at high redshift. The decline rate of SN Ia
U-band light curves correlates well with the decline rate in other bands, as
does the U-B color at maximum light. However, the U-band peak magnitudes show
an increased dispersion relative to other bands even after accounting for
extinction and decline rate, amounting to an additional ~40% intrinsic scatter
compared to B-band.Comment: 84 authors, 71 pages, 51 tables, 10 figures. Accepted for publication
in the Astronomical Journal. Version with high-res figures and electronic
data at http://astron.berkeley.edu/~saurabh/cfa2snIa
Métodos para la identificación del antígeno de histocompatibilidad HLA-B27: comparación de cuatro protocolos técnicos
Introducción: La asociación del HLA-B27 y las Espondiloartritis, ha hecho evidente que la tipificación del HLA-B27 sea considerada como un apoyo en el diagnóstico de estas enfermedades. Los métodos más empleados para la determinación del antígeno HLA-B27 en los laboratorios clínicos y en investigación son: la microlinfocitotoxicidad (MCTX), la citometría de flujo digital (CMFd), la citometría de flujo análoga (CMFa) y la reacción en cadena de la polimerasa con primers de secuencia específicos (PCR-SSP).Objetivo: Comparar MCTX con la CMFd, la CMFa con la CMFd, y la técnica de CMFd frente a PCR-SSP.Métodos para la identificación del antígeno de histocompatibilidad hla-b27 Métodos: Se analizaron 4109 solicitudes de HLA-B27 en población con manifestaciones sugestivas de EAS remitidas entre 2009 y 2012 al Hospital Militar Central y al Instituto de Referencia Andino. Se evaluaron las frecuencias obtenidas por Chi cuadrado (X2); para estimar la concordancia metodológica se utilizó el Coeficiente de Correlación Intraclase (CCI). Los análisis se realizaron con el paquete estadístico SPSS V18.Resultados: Al evaluar 467 datos por la técnica de CMFa frente a PCR-SSP, la CMFa mostró 239 resultados entre positivos y en rango indeterminado, de los cuales, luego de ser confirmados PCRSSP, solo 213 demostraron la expresión de HLA-B27 (p<0.05). Se obtuvieron 208 resultados realizados por CMFd y PCR-SSP simultáneamente, observándose una alta correspondencia entre estas técnicas (p<0.05). Para evaluar la concordancia entre la MCTX y CMFd se analizaron 34 datos,revelando un 100% de correspondencia entre esta dos metodologías CCI=1,p<0.05).Conclusión: La citometría de flujo digital es un método rápido que presenta un desempeño altamente confiable para la identificación de HLA-B27, resultados que se recomiendan confirmar por PCR SSP
- …