Tolerancia térmica de dos cíclidos neotropicales sudamericanos Rocio octofasciata (Regan, 1903) y Australoheros facetus (Jenyns, 1842)

La temperatura es una de las condiciones ambientales clave para los peces, ya que permite ampliar o restringir el uso de un área determinada. Cambios repentinos de temperatura ambiental pueden provocar considerables mortalidades, o alterar a las comunidades acuáticas. En este trabajo se evalúa la capacidad de aclimatación y el máximo térmico crítico de una especie tropical Rocio octofasciata y otra especie subtropical Australoheros facetus. Se realizaron 18 experimentos con un total de 87 ejemplares (n= 54 de R. octofasciata y n= 33 de A. facetus) mediante técnicas de máximo térmico crítico. Se identificaron los valores de temperatura de muerte y temperatura de pérdida de equilibrio para ambas especies. Los resultados sugieren que R. octofasciata podría aclimatarse a temperaturas entre 10 a 35 °C, mientras que A. facetus a temperaturas entre 9,5 a 35 °C. La temperatura de pérdida del equilibrio de R. octofasciata es 33,80°C - 43,03 °C y para A. facetus entre 35,55 °C - 38,06 °C mientras que la temperatura de muerte se determinó entre 36,62 y 43,80 ° C para el R. octofasciata y entre 37,70 y 39,98 °C para A. facetus.Temperature is one of the key environmental conditions for fish distributional range, since it can restricts or expand fish habitat. Sudden environmental temperature change could be the cause of important fish mortalities and could modify aquatic community’s structure. This work studied ability for temperature acclimation and the critical thermal maximum of a tropical fish species Rocio octofasciata and the subtropical fish species Australoheros facetus. A total of eighteen experiments with 87 specimens (n: 54 for R. octofasciata and n:33 for A. facetus ) has been performed using critical thermal maximum technique. The lethal temperature values and loss of equilibrium temperatures were identified for both species. Results suggested that R. octofasciata could acclimated at temperature between 10 and 35°C, while A. facetus at temperatures between 9,5 and 35°C. Loss of equilibrium temperature was established for R. octofasciata between 33,80 and 43,03°C and for A. facetus between 35,55 and 38,06°C, while lethal temperature was determined between 36,62 and 43,80°C for R. octofasciata and between 37,70 and 39.98°C for A. facetus

Tolerancia térmica de dos cíclidos neotropicales sudamericanos Rocio octofasciata (Regan, 1903) y Australoheros facetus (Jenyns, 1842)

Temperature is one of the key environmental conditions for fish distributional range, since it can restricts or expand fish habitat. Sudden environmental temperature change could be the cause of important fish mortalities and could modify aquatic community’s structure. This work studied ability for temperature acclimation and the critical thermal maximum of a tropical fish species Rocio octofasciata and the subtropical fish species Australoheros facetus. A total of eighteen experiments with 87 specimens (n: 54 for R. octofasciata and n:33 for A. facetus ) has been performed using critical thermal maximum technique. The lethal temperature values and loss of equilibrium temperatures were identified for both species. Results suggested that R. octofasciata could acclimated at temperature between 10 and 35°C, while A. facetus at temperatures between 9,5 and 35°C. Loss of equilibrium temperature was established for R. octofasciata between 33,80 and 43,03°C and for A. facetus between 35,55 and 38,06°C, while lethal temperature was determined between 36,62 and 43,80°C for R. octofasciata and between 37,70 and 39.98°C for A. facetus.La temperatura es una de las condiciones ambientales clave para los peces, ya que permite ampliar o restringir el uso de un área determinada. Cambios repentinos de temperatura ambiental pueden provocar considerables mortalidades, o alterar a las comunidades acuáticas. En este trabajo se evalúa la capacidad de aclimatación y el máximo térmico crítico de una especie tropical Rocio octofasciata y otra especie subtropical Australoheros facetus. Se realizaron 18 experimentos con un total de 87 ejemplares (n= 54 de R. octofasciata y n= 33 de A. facetus) mediante técnicas de máximo térmico crítico. Se identificaron los valores de temperatura de muerte y temperatura de pérdida de equilibrio para ambas especies. Los resultados sugieren que R. octofasciata podría aclimatarse a temperaturas entre 10 a 35 °C, mientras que A. facetus a temperaturas entre 9,5 a 35 °C. La temperatura de pérdida del equilibrio de R. octofasciata es 33,80°C - 43,03 °C y para A. facetus entre 35,55 °C - 38,06 °C mientras que la temperatura de muerte se determinó entre 36,62 y 43,80 ° C para el R. octofasciata y entre 37,70 y 39,98 °C para A. facetus.Facultad de Ciencias Naturales y Muse

Cold Accretion Disks and Lineless Quasars

The optical-UV continuum of quasars is broadly consistent with the emission from a geometrically thin optically thick accretion disk (AD). The AD produces the ionizing continuum which powers the broad and narrow emission lines. The maximum AD effective temperature is given by Teff=fmax(Mdot/M^2)^1/4, where M is the black hole mass, Mdot the accretion rate, and fmax is set by the black hole spin a_*. For a low enough value of Mdot/M^2 the AD may become too cold to produce ionizing photons. Such an object will form a lineless quasar. This occurs for a local blackbody (BB) AD with a luminosity Lopt=10^46 erg/s for M>3.6E9 Msun, when a_*=0, and for M>1.4E10 Msun, when a_*=0.998. Using the AD based Mdot, derived from M and Lopt, and the reverberation based M, derived from Lopt and the Hbeta FWHM, v, gives Teff \propto Lopt^-0.13v^-1.45. Thus, Teff is mostly set by v. Quasars with a local BB AD become lineless for v> 8,000 km/s, when a_*=0, and for v> 16,000 km/s, when a_*=0.998. Higher values of v are required if the AD is hotter than a local BB. The AD becoming non-ionizing may explain why line emitting quasars with v>10,000 km/s are rare. Weak low ionization lines may still be present if the X-ray continuum is luminous enough, and such objects may form a population of weak emission line quasars (WLQ). If correct, such WLQ should show a steeply falling SED at lambda<1000A. Such an SED was observed by Hryniewicz et al. in SDSS J094533.99+100950.1, a WLQ observed down to 570A, which is well modeled by a rather cold AD SED. UV spectroscopy of z~1-2 quasars is required to eliminate potential intervening Lyman limit absorption by the intergalactic medium (IGM), and to explore if the SEDs of lineless quasars and some additional WLQ are also well fit by a cold AD SED.Comment: Accepted for publication in MNRA

Stationary relativistic jets

In this paper we describe a simple numerical approach which allows to study the structure of steady-state axisymmetric relativistic jets using one-dimensional time-dependent simulations. It is based on the fact that for narrow jets with vz≈cvz≈c the steady-state equations of relativistic magnetohydrodynamics can be accurately approximated by the one-dimensional time-dependent equations after the substitution z=ctz=ct. Since only the time-dependent codes are now publicly available this is a valuable and efficient alternative to the development of a high-specialised code for the time-independent equations. The approach is also much cheaper and more robust compared to the relaxation method. We tested this technique against numerical and analytical solutions found in literature as well as solutions we obtained using the relaxation method and found it sufficiently accurate. In the process, we discovered the reason for the failure of the self-similar analytical model of the jet reconfinement in relatively flat atmospheres and elucidated the nature of radial oscillations of steady-state jets

Observational evidence for the accretion-disk origin for a radio jet in an active galaxy

Accretion of gas onto black holes is thought to power the relativistic jets of material ejected from active galactic nuclei (AGN) and the 'microquasars' located in our Galaxy(1-3). In microquasars, superluminal radio-emitting features appear and propagate along the jet shortly after sudden decreases in the Xray fluxes(1). This establishes a direct observational link between the black hole and the jet: the X-ray dip is probably caused by the disappearance of a section of the inner accretion disk(4) as it falls past the event horizon, while the remainder of the disk section is ejected into the jet, creating the appearance of a superluminal bright spot(5). No such connection has hitherto been established for AGN, because of insufficient multi-frequency data. Here we report the results of three years of monitoring the X-ray and radio emission of the galaxy 3C120. As has been observed for microquasars, we find that dips in the X-ray emission are followed by ejections of bright superluminal knots in the radio jet. The mean time between X-ray dips appears to scale roughly with the mass of the black hole, although there are at present only a few data points.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62888/1/nature00772.pd

Charged particle-like branes in ABJM

We study the effect of adding lower dimensional brane charges to the 't Hooft monopole, di-baryon and baryon vertex configurations in $AdS_4 \times \mathbb{P}^3$. We show that these configurations capture the background fluxes in a way that depends on the induced charges, and therefore, require additional fundamental strings in order to cancel the worldvolume tadpoles. The study of the dynamics reveals that the charges must lie inside some interval in order to find well defined configurations, a situation familiar from the baryon vertex in $AdS_5 \times S^5$ with charges. For the baryon vertex and the di-baryon the number of fundamental strings must also lie inside an allowed interval. Our configurations are sensitive to the flat $B$-field recently suggested in the literature. We make some comments on its possible role. We also discuss how these configurations are modified in the presence of a non-zero Romans mass.Comment: 31 pages, 14 figures, discussion of charges improved, published versio

Universal de Sitter solutions at tree-level

Type IIA string theory compactified on SU(3)-structure manifolds with orientifolds allows for classical de Sitter solutions in four dimensions. In this paper we investigate these solutions from a ten-dimensional point of view. In particular, we demonstrate that there exists an attractive class of de Sitter solutions, whose geometry, fluxes and source terms can be entirely written in terms of the universal forms that are defined on all SU(3)-structure manifolds. These are the forms J and Omega, defining the SU(3)-structure itself, and the torsion classes. The existence of such universal de Sitter solutions is governed by easy-to-verify conditions on the SU(3)-structure, rendering the problem of finding dS solutions purely geometrical. We point out that the known (unstable) solution coming from the compactification on SU(2)x SU(2) is of this kind.Comment: 20 pages, 3 figures, v2: added reference

Malaria mortality in Africa and Asia: evidence from INDEPTH health and demographic surveillance system sites.

BACKGROUND: Malaria continues to be a major cause of infectious disease mortality in tropical regions. However, deaths from malaria are most often not individually documented, and as a result overall understanding of malaria epidemiology is inadequate. INDEPTH Network members maintain population surveillance in Health and Demographic Surveillance System sites across Africa and Asia, in which individual deaths are followed up with verbal autopsies. OBJECTIVE: To present patterns of malaria mortality determined by verbal autopsy from INDEPTH sites across Africa and Asia, comparing these findings with other relevant information on malaria in the same regions. DESIGN: From a database covering 111,910 deaths over 12,204,043 person-years in 22 sites, in which verbal autopsy data were handled according to the WHO 2012 standard and processed using the InterVA-4 model, over 6,000 deaths were attributed to malaria. The overall period covered was 1992-2012, but two-thirds of the observations related to 2006-2012. These deaths were analysed by site, time period, age group and sex to investigate epidemiological differences in malaria mortality. RESULTS: Rates of malaria mortality varied by 1:10,000 across the sites, with generally low rates in Asia (one site recording no malaria deaths over 0.5 million person-years) and some of the highest rates in West Africa (Nouna, Burkina Faso: 2.47 per 1,000 person-years). Childhood malaria mortality rates were strongly correlated with Malaria Atlas Project estimates of Plasmodium falciparum parasite rates for the same locations. Adult malaria mortality rates, while lower than corresponding childhood rates, were strongly correlated with childhood rates at the site level. CONCLUSIONS: The wide variations observed in malaria mortality, which were nevertheless consistent with various other estimates, suggest that population-based registration of deaths using verbal autopsy is a useful approach to understanding the details of malaria epidemiology

Baryonic symmetries and M5 branes in the AdS_4/CFT_3 correspondence

We study U(1) symmetries dual to Betti multiplets in the AdS_4/CFT_3 correspondence for M2 branes at Calabi-Yau four-fold singularities. Analysis of the boundary conditions for vector fields in AdS_4 allows for a choice where wrapped M5 brane states carrying non-zero charge under such symmetries can be considered. We begin by focusing on isolated toric singularities without vanishing six-cycles, and study in detail the cone over Q^{111}. The boundary conditions considered are dual to a CFT where the gauge group is U(1)^2 x SU(N)^4. We find agreement between the spectrum of gauge-invariant baryonic-type operators in this theory and wrapped M5 brane states. Moreover, the physics of vacua in which these symmetries are spontaneously broken precisely matches a dual gravity analysis involving resolutions of the singularity, where we are able to match condensates of the baryonic operators, Goldstone bosons and global strings. We also argue more generally that theories where the resolutions have six-cycles are expected to receive non-perturbative corrections from M5 brane instantons. We give a general formula relating the instanton action to normalizable harmonic two-forms, and compute it explicitly for the Q^{222} example. The holographic interpretation of such instantons is currently unclear.Comment: 92 pages, 10 figure