17 research outputs found
The binary progenitor of Tycho Brahe's 1572 supernova
The brightness of type Ia supernovae, and their homogeneity as a class, makes
them powerful tools in cosmology, yet little is known about the progenitor
systems of these explosions. They are thought to arise when a white dwarf
accretes matter from a companion star, is compressed and undergoes a
thermonuclear explosion Unless the companion star is another white dwarf (in
which case it should be destroyed by the mass-transfer process itself), it
should survive and show distinguishing properties. Tycho's supernova is one of
the only two type Ia supernovae observed in our Galaxy, and so provides an
opportunity to address observationally the identification of the surviving
companion. Here we report a survey of the central region of its remnant, around
the position of the explosion, which excludes red giants as the mass donor of
the exploding white dwarf. We found a type G0--G2 star, similar to our Sun in
surface temperature and luminosity (but lower surface gravity), moving at more
than three times the mean velocity of the stars at that distance, which appears
to be the surviving companion of the supernova.Comment: accepted by Natute (subject to embargo policy), 31 pages, 4 figure
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
Mitochondrial Complex I Activity is Conditioned by Supercomplex I–III2–IV Assembly in Brain Cells: Relevance for Parkinson’s Disease
Electrodeposition of 4,4′-di-tert-butylbiphenyl peroxide from the anodic oxidation of p-tert-butylphenol in an alkaline acetonitrile solution
Patients with stage II of the knee osteoarthritis most likely benefit from the intra-articular injections of autologous adipose tissue—from 2 years of follow-up studies
High Intensity Interval Training (HIIT) Induces Specific Changes in Respiration and Electron Leakage in the Mitochondria of Different Rat Skeletal Muscles
Earthworm Comet Assay for Assessing the Risk of Weathered Petroleum Hydrocarbon Contaminated Soils: Need to Look Further than Target Contaminants
Accessory subunits are integral for assembly and function of human mitochondrial complex I
Complex I (NADH:ubiquinone oxidoreductase) is the first enzyme of the mitochondrial respiratory chain and is composed of 45 subunits in humans, making it one of the largest known multi-subunit membrane protein complexes. Complex I exists in supercomplex forms with respiratory chain complexes III and IV, which are together required for the generation of a transmembrane proton gradient used for the synthesis of ATP. Complex I is also a major source of damaging reactive oxygen species and its dysfunction is associated with mitochondrial disease, Parkinson's disease and ageing. Bacterial and human complex I share 14 core subunits that are essential for enzymatic function; however, the role and necessity of the remaining 31 human accessory subunits is unclear. The incorporation of accessory subunits into the complex increases the cellular energetic cost and has necessitated the involvement of numerous assembly factors for complex I biogenesis. Here we use gene editing to generate human knockout cell lines for each accessory subunit. We show that 25 subunits are strictly required for assembly of a functional complex and 1 subunit is essential for cell viability. Quantitative proteomic analysis of cell lines revealed that loss of each subunit affects the stability of other subunits residing in the same structural module. Analysis of proteomic changes after the loss of specific modules revealed that ATP5SL and DMAC1 are required for assembly of the distal portion of the complex I membrane arm. Our results demonstrate the broad importance of accessory subunits in the structure and function of human complex I. Coupling gene-editing technology with proteomics represents a powerful tool for dissecting large multi-subunit complexes and enables the study of complex dysfunction at a cellular level