25 research outputs found
The balance of power: accretion and feedback in stellar mass black holes
In this review we discuss the population of stellar-mass black holes in our
galaxy and beyond, which are the extreme endpoints of massive star evolution.
In particular we focus on how we can attempt to balance the available accretion
energy with feedback to the environment via radiation, jets and winds,
considering also possible contributions to the energy balance from black hole
spin and advection. We review quantitatively the methods which are used to
estimate these quantities, regardless of the details of the astrophysics close
to the black hole. Once these methods have been outlined, we work through an
outburst of a black hole X-ray binary system, estimating the flow of mass and
energy through the different accretion rates and states. While we focus on
feedback from stellar mass black holes in X-ray binary systems, we also
consider the applicability of what we have learned to supermassive black holes
in active galactic nuclei. As an important control sample we also review the
coupling between accretion and feedback in neutron stars, and show that it is
very similar to that observed in black holes, which strongly constrains how
much of the astrophysics of feedback can be unique to black holes.Comment: To be published in Haardt et al. Astrophysical Black Holes. Lecture
Notes in Physics. Springer 201
An overview of jets and outflows in stellar mass black holes
In this book chapter, we will briefly review the current empirical
understanding of the relation between accretion state and and outflows in
accreting stellar mass black holes. The focus will be on the empirical
connections between X-ray states and relativistic (`radio') jets, although we
are now also able to draw accretion disc winds into the picture in a systematic
way. We will furthermore consider the latest attempts to measure/order jet
power, and to compare it to other (potentially) measurable quantities, most
importantly black hole spin.Comment: Accepted for publication in Space Science Reviews. Also to appear in
the Space Sciences Series of ISSI - The Physics of Accretion on to Black
Holes (Springer Publisher
Avanços recentes em nutrição de larvas de peixes
Os requisitos nutricionais de larvas de peixes são ainda mal compreendidos, o que leva a altas mortalidades
e problemas de qualidade no seu cultivo. Este trabalho pretende fazer uma revisão de novas metodologias de investigação, tais
como estudos com marcadores, genómica populacional, programação nutricional, génomica e proteómica funcionais, e
fornecer ainda alguns exemplos das utilizações presentes e perspectivas futuras em estudos de nutrição de larvas de peixes
LOFAR 144-MHz follow-up observations of GW170817
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 494, Issue 4, June 2020, Pages 5110–5117, ©: 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present low-radio-frequency follow-up observations of AT 2017gfo, the electromagnetic counterpart of GW170817, which was the first binary neutron star merger to be detected by Advanced LIGO-Virgo. These data, with a central frequency of 144 MHz, were obtained with LOFAR, the Low-Frequency Array. The maximum elevation of the target is just 13.7 degrees when observed with LOFAR, making our observations particularly challenging to calibrate and significantly limiting the achievable sensitivity. On time-scales of 130-138 and 371-374 days after the merger event, we obtain 3 upper limits for the afterglow component of 6.6 and 19.5 mJy beam, respectively. Using our best upper limit and previously published, contemporaneous higher-frequency radio data, we place a limit on any potential steepening of the radio spectrum between 610 and 144 MHz: the two-point spectral index . We also show that LOFAR can detect the afterglows of future binary neutron star merger events occurring at more favourable elevations.Peer reviewe
Overview of vitamin D and C requirements in fish and their influence on the skeletal system
International audienc
Organogenesis of the digestive tract in the white seabream, Diplodus sargus. Histological and histochemical approaches
The ontogeny of the digestive tract of the
white seabream, Diplodus sargus during the larval
development up to day 45 post-hatching (dph) has been
studied using histological and histochemical techniques.
The oesophageal goblet cells appeared around 6 dph and
contained neutral and acid mucosubstances
(PAS/diastase-PAS and Alcian Blue pH 2.5 positive
reactions). An incipient stomach can be distinguished
from 2 dph but the first sign of gastric gland
development was detected around 13-15 dph, increasing
in number and size by 22-23 dph. Gastric glands were
concentrated in the cardiac stomach region and they had
a high content of protein rich in tyrosine, arginine and
tryptophan. Acidophilic supranuclear inclusions related
to pynocitosis of proteins, were already observed in the
intestinal cells of the posterior intestine around 4-6 dph
(exogenous feeding) and they were present until 25 dph.
The intestinal mucous cells appeared between 15-18 dph
and contained a mixture of neutral and acid
mucosubstances/glycoconjugates, carboxylated ones
being more abundant than the sulphated ones. The
stomach and gastric glands were fully developed by the
first month of life marking the beginning of digestive
features characteristic of the juvenile stage. Around 4-6
dph, glycogen, proteins and neutral lipids were observed
in the granular cytoplasm of hepatocytes. Strongly
acidophilic zymogen granules were also present, at this
time, in the basophilic cytoplasm of the exocrine
pancreatic acinar cells and contained abundant proteins,
especially rich in arginine, tyrosine and tryptophan
Gene expression patterns during the larval development of European sea bass (Dicentrarchus labrax) by microarray analysis
International audienceDuring the larval period, marine teleosts undergo very fast growth and dramatic changes in morphology, metabolism, and behavior to accomplish their metamorphosis into juvenile fish. Regulation of gene expression is widely thought to be a key mechanism underlying the management of the biological processes required for harmonious development over this phase of life. To provide an overall analysis of gene expression in the whole body during sea bass larval development, we monitored the expression of 6,626 distinct genes at 10 different points in time between 7 and 43 days post-hatching (dph) by using heterologous hybridization of a rainbow trout cDNA microarray. The differentially expressed genes (n = 485) could be grouped into two categories: genes that were generally up-expressed early, between 7 and 23 dph, and genes up-expressed between 25 and 43 dph. Interestingly, among the genes regulated during the larval period, those related to organogenesis, energy pathways, biosynthesis, and digestion were over-represented compared with total set of analyzed genes. We discuss the quantitative regulation of whole-body contents of these specific transcripts with regard to the ontogenesis and maturation of essential functions that take place over larval development. Our study is the first utilization of a transcriptomic approach in sea bass and reveals dynamic changes in gene expression patterns in relation to marine finfish larval development