FIRST-based survey of Compact Steep Spectrum sources, IV. Multifrequency VLBA observations of very compact objects

Evidence has been mounting recently that activity in some radio-loud AGNs (RLAGNs) can cease shortly after ignition and that perhaps even a majority of very compact sources may be short-lived phenomena because of a lack of stable fuelling from the black hole. Thus, they can fade out before having evolved to large, extended objects. Re-ignition of the activity in such objects is not ruled out. With the aim of finding more examples of these objects and to investigate if they could be RLAGNs switched off at very early stages of their evolution, multifrequency VLBA observations of six sources with angular sizes significantly less than an arcsecond, yet having steep spectra, have been made. Observations were initially made at 1.65 GHz using the VLBA with the inclusion of Effelsberg telescope. The sources were then re-observed with the VLBA at 5, 8.4 and 15.4 GHz. All the observations were carried out in a snapshot mode with phase referencing. One of the sources studied, 0809+404, is dominated by a compact component but also has diffuse, arcsecond-scale emission visible in VLA images. The VLBI observations of the "core" structure have revealed that this is also diffuse and fading away at higher frequencies. Thus, the inner component of 0809+404 could be a compact fading object. The remaining five sources presented here show either core-jet or edge-brightened double-lobed structures indicating that they are in an active phase. The above result is an indication that the activity of the host galaxy of 0809+404 may be intermittent. Previous observations obtained from the literature and those presented here indicate that activity had ceased once in the past, then restarted, and has recently switched off again.Comment: 15 pages, 7 figures, matches the version printed in Astronomy & Astrophysic

The Emission Structure of Formaldehyde MegaMasers

The formaldehyde MegaMaser emission has been mapped for the three host galaxies IC\,860. IRAS\,15107$+$0724, and Arp\,220. Elongated emission components are found at the nuclear centres of all galaxies with an extent ranging between 30 to 100 pc. These components are superposed on the peaks of the nuclear continuum. Additional isolated emission components are found superposed in the outskirts of the radio continuum structure. The brightness temperatures of the detected features ranges from 0.6 to 13.4 $\times 10^{4}$ K, which confirms their masering nature. The masering scenario is interpreted as amplification of the radio continuum by foreground molecular gas that is pumped by far-infrared radiation fields in these starburst environments of the host galaxies.Comment: Accepted MNRA

Conversion of New Zealand's 30m Telecommunication Antenna into a Radio Telescope

We describe our approach to the conversion of a former 100-foot (30-m) telecommunication antenna in New Zealand into a radio telescope. We provide the specifications of the Earth Station and identify the priorities for the conversion. We describe implementation of this plan with regards to mechanical and electrical components, as well as design of the telescope control system, telescope networking for VLBI, and telescope maintenance. Plans for RF, front-end and back-end developments based on radio astronomical priorities are outlined.Comment: Accepted for PASA with small modifications, 11 pages, 13 Figure

Deuterated molecules in regions of high-mass star formation

We present the results of our studies of deuterated molecules (DCN, DNC, DCO$^+$, N$_2$D$^+$ and NH$_2$D) in regions of high-mass star formation, which include a survey of such regions with the 20-m Onsala radio telescope and mapping of several objects in various lines with the 30-m IRAM and 100-m MPIfR radio telescopes. The deuteration degree reaches $\sim$10$^{-2}$ in these objects. We discuss its dependencies on the gas temperature and velocity dispersion, as well as spatial distributions of deuterated molecules. We show that the H$^{13}$CN/HN$^{13}$C intensity ratio may be a good indicator of the gas kinetic temperature and estimate densities of the investigated objects.Comment: 8 pages, 4 figures, to be published in Proceedings of Science (Proceedings of the conference "The Multifaceted Universe: Theory and Observations - 2022", 23-27 May 2022, SAO RAS, Nizhny Arkhyz, Russia

Ring-Like Structure in the Radio Lobe of MG0248+0641

We present radio and optical observations of MG0248+0641, which contains a kiloparsec-scale ring-like structure in one of its radio lobes. The radio observations show a typical core-double morphology: a central core between two lobes, each of which has a hotspot. The western radio lobe appears as a nearly continuous ring, with linear polarization electric field vectors which are oriented in a radial direction from the ring center. We consider several different interpretations for the nature of this ring, including gravitational lensing of a normal jet by a foreground galaxy. Even though simple lensing models can describe the ring morphology reasonably well, the high linear polarization seen around the ring cannot be easily explained. The chance interposition of a galactic supernova remnant, nova, planetary nebula, or H II region, has been ruled out. The highly polarized ring of MG0248+0641 is much like the prominent ring seen in 3C219, and the multiple ones in 3C310 and Hercules A, suggesting that similar physical processes are producing shell structures in these radio galaxies. The ring in MG0248+0641 may be caused by the formation of ``bubbles'', as a result of instabilities in the energy flow down the western radio jet. It may also be possible that the required instabilities are triggered by the infall of gas, via tidal interaction of the central source with a nearby galaxy. This scenario may be indicated by our marginal detection of an optical source close to the western hotspot.Comment: 21 pages. Submitted to AJ Aug 15, 1997; Accepted Sep 30, 1997. Minor changes in conten

Inflammatory breast cancer: dynamic contrast-enhanced MR in patients receiving bevacizumab. Initial experience

To retrospectively compare three dynamic contrast material-enhanced magnetic resonance (MR) imaging (dynamic MR imaging) analytic methods to determine the parameter or combination of parameters most strongly associated with changes in tumor microvasculature during treatment with bevacizumab alone and bevacizumab plus chemotherapy in patients with inflammatory or locally advanced breast cancer. MATERIALS AND METHODS: This study was conducted in accordance with the institutional review board of the National Cancer Institute and was compliant with the Privacy Act of 1974. Informed consent was obtained from all patients. Patients with inflammatory or locally advanced breast cancer were treated with one cycle of bevacizumab alone (cycle 1) followed by six cycles of combination bevacizumab and chemotherapy (cycles 2-7). Serial dynamic MR images were obtained, and the kinetic parameters measured by using three dynamic analytic MR methods (heuristic, Brix, and general kinetic models) and two region-of-interest strategies were compared by using two-sided statistical tests. A P value of .01 was required for significance. RESULTS: In 19 patients, with use of a whole-tumor region of interest, the authors observed a significant decrease in the median values of three parameters measured from baseline to cycle 1: forward transfer rate constant (Ktrans) (-34% relative change, P=.003), backflow compartmental rate constant extravascular and extracellular to plasma (Kep) (-15% relative change, P<.001), and integrated area under the gadolinium concentration curve (IAUGC) at 180 seconds (-23% relative change, P=.009). A trend toward differences in the heuristic slope of the washout curve between responders and nonresponders to therapy was observed after cycle 1 (bevacizumab alone, P=.02). The median relative change in slope of the wash-in curve from baseline to cycle 4 was significantly different between responders and nonresponders (P=.009). CONCLUSION: The dynamic contrast-enhanced MR parameters Ktrans, Kep, and IAUGC at 180 seconds appear to have the strongest association with early physiologic response to bevacizumab. Clinical trial registration no. NCT0001654

If an ontologist could speak we couldn't understand him

It is common for contemporary ontologists to claim that they are not concerned with what exists simpliciter, but rather with what exists ’fundamentally’, or what ’really’ exists. I argue that positions of this sort cannot satisfy reasonable constraints concerning the acquisition of language. I assess and dismiss possible responses to this complaint before commenting on the prospects for a metaphysics without bespoke existence claims

What Is a Thing?

‘Thing’ in the titular question should be construed as having the utmost generality. In the relevant sense, a thing just is an entity, an existent, a being. The present task is to say what a thing of any category is. This task is, I believe, the primary one of any comprehensive and systematic metaphysics. Indeed, an answer provides the means for resolving perennial disputes concerning the integrity of the structure in reality—whether some of the relations among things are necessary merely given those relata themselves—and the intricacy of this structure—whether some things are more or less fundamental than others. After considering some reasons for thinking the generality of the titular question makes it unanswerable, I propound the methodology, original inquiry, required to answer it. The key to this methodology is adopting a singular perspective; confronting the world as merely the impetus to inquiry, one can attain an account of what a thing must be. Radical ontology is a systematic metaphysics—broadly Aristotelian, essentialist and nonhierarchical—that develops the consequences of this account. With it, it is possible to move past stalemate in metaphysics by revealing the grounds of a principled choice between seemingly incommensurable worldviews