21 research outputs found
The Evolution of Compact Binary Star Systems
We review the formation and evolution of compact binary stars consisting of
white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and
BHs are thought to be the primary astrophysical sources of gravitational waves
(GWs) within the frequency band of ground-based detectors, while compact
binaries of WDs are important sources of GWs at lower frequencies to be covered
by space interferometers (LISA). Major uncertainties in the current
understanding of properties of NSs and BHs most relevant to the GW studies are
discussed, including the treatment of the natal kicks which compact stellar
remnants acquire during the core collapse of massive stars and the common
envelope phase of binary evolution. We discuss the coalescence rates of binary
NSs and BHs and prospects for their detections, the formation and evolution of
binary WDs and their observational manifestations. Special attention is given
to AM CVn-stars -- compact binaries in which the Roche lobe is filled by
another WD or a low-mass partially degenerate helium-star, as these stars are
thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure
Liverpool telescope 2: a new robotic facility for rapid transient follow-up
The Liverpool Telescope is one of the world's premier facilities for time domain astronomy. The time domain landscape is set to radically change in the coming decade, with surveys such as LSST providing huge numbers of transient detections on a nightly basis; transient detections across the electromagnetic spectrum from other facilities such as SVOM, SKA and CTA; and the era of `multi-messenger astronomy', wherein events are detected via non-electromagnetic means, such as gravitational wave emission. We describe here our plans for Liverpool Telescope 2: a new robotic telescope designed to capitalise on this new era of time domain astronomy. LT2 will be a 4-metre class facility co-located with the LT at the Observatorio del Roque de Los Muchachos on the Canary island of La Palma. The telescope will be designed for extremely rapid response: the aim is that the telescope will take data within 30 seconds of the receipt of a trigger from another facility. The motivation for this is twofold: firstly it will make it a world-leading facility for the study of fast fading transients and explosive phenomena discovered at early times. Secondly, it will enable large-scale programmes of low-to-intermediate resolution spectral classification of transients to be performed with great efficiency. In the target-rich environment of the LSST era, minimising acquisition overheads will be key to maximising the science gains from any follow-up programme. The telescope will have a diverse instrument suite which is simultaneously mounted for automatic changes, but it is envisaged that the primary instrument will be an intermediate resolution, optical/infrared spectrograph for scientific exploitation of transients discovered with the next generation of synoptic survey facilities. In this paper we outline the core science drivers for the telescope, and the requirements for the optical and mechanical design
Granzyme B-induced mitochondrial ROS are required for apoptosis
Caspases and the cytotoxic lymphocyte protease granzyme B (GB) induce reactive oxygen species (ROS) formation, loss of transmembrane potential and mitochondrial outer membrane permeabilization (MOMP). Whether ROS are required for GB-mediated apoptosis and how GB induces ROS is unclear. Here, we found that GB induces cell death in an ROS-dependent manner, independently of caspases and MOMP. GB triggers ROS increase in target cell by directly attacking the mitochondria to cleave NDUFV1, NDUFS1 and NDUFS2 subunits of the NADH: ubiquinone oxidoreductase complex I inside mitochondria. This leads to mitocentric ROS production, loss of complex I and III activity, disorganization of the respiratory chain, impaired mitochondrial respiration and loss of the mitochondrial cristae junctions. Furthermore, we have also found that GB-induced mitocentric ROS are necessary for optimal apoptogenic factor release, rapid DNA fragmentation and lysosomal rupture. Interestingly, scavenging the ROS delays and reduces many of the features of GB-induced death. Consequently, GB-induced ROS significantly promote apoptosis
The Significance of “White Macael” Marble Since Ancient Times: Characteristics of a Candidate as Global Heritage Stone Resource
Assessment of the physico-mechanical behaviour of gypsum-lime repair mortars as a function of curing time
Marbles and carbonate rocks from central Morocco: a petrographic, mineralogical and geochemical study
Petrographic, mineralogical, and stable isotopes (delta C-13, delta O-18
values) compositions were used to characterise marbles and sedimentary
carbonate rocks from central Morocco, which are considered to be a
likely source of ornamental and building material from Roman time to the
present day. This new data set was used in the frame of an archaeometric
provenance study on Roman artefacts from the town of Thamusida (Kenitra,
north Morocco), to assess the potential employment of these rocks for
the manufacture of the archaeological materials. A representative set of
samples from marbles and other carbonate rocks (limestone, dolostone)
were collected in several quarries and outcrops in the Moroccan Meseta,
in a region extending from the Meknes-Khenifra alignment to the Atlantic
Ocean. All the samples were studied using a petrographic, mineralogical
and geochemical methods. The petrographic and minerological
investigations (optical microscopy, electron microscopy, X-ray
diffraction) allowed to group the carbonate rocks in limestones,
foliated limestone, diagenetic breccias and dolostone. The limestones
could be further grouped as mudstones, wackestones-packstones, crinoid
grainstones, oolitic grainstone and floatstones. Textural differences
allowed to define marbles varieties. The stable carbon and oxygen
isotope composition proved to be quite useful in the discrimination of
marble sources, with apparently less discriminatory potential for
carbonate rocks