Quenching of the radio jet during the X-ray high state of GX 339-4

We have observed the black hole candidate X-ray binary GX 339-4 at radio wavelengths before, during and after the 1998 high/soft X-ray state transition. We find that the radio emission from the system is strongly correlated with the hard X-ray emission and is reduced by a factor > 25 during the high/soft state compared to the more usual low/hard state. At the points of state transition we note brief periods of unusually optically-thin radio emission which may correspond to discrete ejection events. We propose that in the low/hard state black hole X-ray binaries produce a quasi-continuous outflow, in the high/soft state this outflow is suppressed, and that state transitions often result in one or more discrete ejection events. Future models for low/hard states, such as ADAF/ADIOS solutions, need to take into account strong outflow of relativistic electrons from the system. We propose that the inferred Comptonising corona and the base of the jet-like outflow are the same thing, based upon the strong correlation between radio and hard X-ray emission in GX 339-4 and other X-ray binaries, and the similarity in inferred location and composition of these two components.Comment: Accepted for publication in ApJ Letter

VII Zw 403: H I structure in a blue compact dwarf galaxy

‘In these times, during the rise in the popularity of institutional repositories, the Society does not forbid authors from depositing their work in such repositories. However, the AAS regards the deposit of scholarly work in such repositories to be a decision of the individual scholar, as long as the individual's actions respect the diligence of the journals and their reviewers.’ Original article can be found at : http://iopscience.iop.org/ Copyright American Astronomical SocietyWe present optical (UBVJ), ultraviolet (FUV, NUV), and high-resolution atomic hydrogen (H I) observations of the nearby blue compact dwarf (BCD), VII Zw 403. We find that VII Zw 403 has a relatively high H I mass-to-light ratio for a BCD. The rotation velocity is nominally 10-15 km s(-1), but rises to similar to 20 km s(-1) after correction for the similar to 8-10 km s(-1) random motions present in the gas. The velocity field is complex, including a variation in the position angle of the major axis going from the northeast to the southwest parts of the galaxy. Our high-resolution Hi maps reveal structure in the central gas, including a large, low-density Hi depression or hole between the southern and northern halves of the galaxy, coincident with an unresolved X-ray source. Although interactions have been proposed as the triggering mechanism for the vigorous star formation occurring in BCDs, VII Zw 403 does not seem to have been tidally triggered by an external interaction, as we have found no nearby possible perturbers. It also does not appear to fall in the set of galaxies that exhibit a strong central mass density concentration, as its optical scale length is large in comparison to similar systems. However, there are some features that are compatible with an accretion event: optical/Hi axis misalignment, a change in position angle of the kinematic axis, and a complex velocity field.Peer reviewe

Bicarbonate Recycling by HIF‐1–Dependent Carbonic Anhydrase Isoforms 9 and 12 Is Critical in Maintaining Intracellular pH and Viability of Nucleus Pulposus Cells

Intervertebral disc degeneration is a ubiquitous condition closely linked to chronic low‐back pain. The health of the avascular nucleus pulposus (NP) plays a crucial role in the development of this pathology. We tested the hypothesis that a network comprising HIF‐1α, carbonic anhydrase (CA) 9 and 12 isoforms, and sodium‐coupled bicarbonate cotransporters (NBCs) buffer intracellular pH through coordinated bicarbonate recycling. Contrary to the current understanding of NP cell metabolism, analysis of metabolic‐flux data from Seahorse XF analyzer showed that CO2 hydration contributes a significant source of extracellular proton production in NP cells, with a smaller input from glycolysis. Because enzymatic hydration of CO2 is catalyzed by plasma membrane‐associated CAs we measured their expression and function in NP tissue. NP cells robustly expressed isoforms CA9/12, which were hypoxia‐inducible. In addition to increased mRNA stability under hypoxia, we observed binding of HIF‐1α to select hypoxia‐responsive elements on CA9/12 promoters using genomic chromatin immunoprecipitation. Importantly, in vitro loss of function studies and analysis of discs from NP‐specific HIF‐1α null mice confirmed the dependency of CA9/12 expression on HIF‐1α. As expected, inhibition of CA activity decreased extracellular acidification rate independent of changes in HIF activity or lactate/H+ efflux. Surprisingly, CA inhibition resulted in a concomitant decrease in intracellular pH that was mirrored by inhibition of sodium‐bicarbonate importers. These results suggested that extracellular bicarbonate generated by CA9/12 is recycled to buffer cytosolic pH fluctuations. Importantly, long‐term intracellular acidification from CA inhibition lead to compromised cell viability, suggesting that plasma‐membrane proton extrusion pathways alone are not sufficient to maintain homeostatic pH in NP cells. Taken together, our studies show for the first time that bicarbonate buffering through the HIF‐1α–CA axis is critical for NP cell survival in the hypoxic niche of the intervertebral disc. © 2017 American Society for Bone and Mineral Research.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142506/1/jbmr3293.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142506/2/jbmr3293-sup-0001-SuppData-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142506/3/jbmr3293_am.pd

An ultra-wide bandwidth (704 to 4 032 MHz) receiver for the Parkes radio telescope

We describe an ultra-wide-bandwidth, low-frequency receiver recently installed on the Parkes radio telescope. The receiver system provides continuous frequency coverage from 704 to 4032 MHz. For much of the band ( ${∼}60$ ), the system temperature is approximately 22 K and the receiver system remains in a linear regime even in the presence of strong mobile phone transmissions. We discuss the scientific and technical aspects of the new receiver, including its astronomical objectives, as well as the feed, receiver, digitiser, and signal processor design. We describe the pipeline routines that form the archive-ready data products and how those data files can be accessed from the archives. The system performance is quantified, including the system noise and linearity, beam shape, antenna efficiency, polarisation calibration, and timing stability

Challenges and opportunities for conducting a vaccine trial during the COVID-19 pandemic in the United Kingdom

The COVID-19 pandemic has resulted in unprecedented challenges for healthcare systems worldwide. It has also stimulated research in a wide range of areas including rapid diagnostics, novel therapeutics, use of technology to track patients and vaccine development. Here, we describe our experience of rapidly setting up and delivering a novel COVID-19 vaccine trial, using clinical and research staff and facilities in three National Health Service Trusts in Cambridgeshire, United Kingdom. We encountered and overcame a number of challenges including differences in organisational structures, research facilities available, staff experience and skills, information technology and communications infrastructure, and research training and assessment procedures. We overcame these by setting up a project team that included key members from all three organisations that met at least daily by teleconference. This group together worked to identify the best practices and procedures and to harmonise and cascade these to the wider trial team. This enabled us to set up the trial within 25 days and to recruit and vaccinate the participants within a further 23 days. The lessons learned from our experiences could be used to inform the conduct of clinical trials during a future infectious disease pandemic or public health emergency

UvA-DARE (Digital Academic Repository) Link to publication Citation for published version (APA): QUENCHING OF THE RADIO JET DURING THE X-RAY HIGH STATE OF GX 339Ϫ4

Quenching of the radio jet during the x-ray high state in GX 339-4 Fender, R.P.; Corbel, S.; Tzioumis, A.K.; Sood, R.; McIntyre, V.; Campbell-Wilson, D.; Durouchoux, P.; Harmon, B.A. Published in: Astrophysical Journal DOI: 10.1086/312128 Link to publication Citation for published version (APA): Fender, R. P., Corbel, S., Tzioumis, A. K., Sood, R., McIntyre, V., Campbell-Wilson, D., ... Harmon, B. A. (1999). Quenching of the radio jet during the x-ray high state in GX 339-4. Astrophysical Journal, 519, L165-L168. https://doi.org/10.1086/312128 General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Download date: 29 Jun 2019 L165 The Astrophysical Journal, 519:L165-L168, 1999 July 10 ᭧ 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A. ABSTRACT We have observed the black hole candidate X-ray binary GX 339Ϫ4 at radio wavelengths before, during, and after the 1998 high/soft X-ray state transition. We find that the radio emission from the system is strongly correlated with the hard X-ray emission and is reduced by a factor of ≥25 during the high/soft state compared with the more usual low/hard state. At the points of state transition, we note brief periods of unusually optically thin radio emission that may correspond to discrete ejection events. We propose that in the low/hard state, black hole X-ray binaries produce a quasi-continuous outflow, that in the high/soft state, this outflow is suppressed, and that state transitions often result in one or more discrete ejection events. Future models for low/hard states, such as advection-dominated solutions, need to take into account the strong outflow of relativistic electrons from the system. We propose that the inferred Comptonizing corona and the base of the jetlike outflow are the same thing, based on the strong correlation between radio and hard X-ray emission in GX 339Ϫ4 and other X-ray binaries and on the similarity in inferred location and composition of these two components. QUENCHING OF THE RADIO JET DURING THE X-RAY HIGH STATE OF GX 339Ϫ