scholarly journals New Radio Science Facilities for Compact Objects

2004 ◽  
Vol 218 ◽  
pp. 113-120
Author(s):  
J. M. Cordes
Keyword(s):  
Radio Astronomy ◽  
Low Frequency ◽  
Compact Objects ◽  
Telescope Array ◽  
Radio Science ◽  
New Concepts ◽  
Pulsar Timing ◽  
New Radio ◽  
Square Kilometer Array

In a throwback to the early days in radio astronomy, new concepts for radio telescopes are being considered as next-generation facilities. The Low-Frequency Array (LOFAR) and the Square-Kilometer Array (SKA) are two particular projects that will incorporate innovations in hardware and software. Along the way to these projects, major surveys for pulsars and transients and/or follow-up pulsar timing observations will be conducted with the ALFA multibeam system at Arecibo, the Allen Telescope Array (ATA), the Extended VLA (EVLA) and with SKA prototype systems that include the European MBRACE project (Multibeam Radio Astronomy Concept Experiment) and China's FAST (500m Aperture Spherical Telescope). These projects are discussed here in the context of anticipated science drivers.

Optimizing Processing Time of Radio-Astronomy Antenna Simulations Using FEKO

2020 ◽  
Vol 35 (10) ◽  
pp. 1153-1160
Author(s):  
Rowanne Steiner ◽  
Daniel Ung ◽  
Anouk Hubrechsen ◽  
Robert Jones ◽  
Randall Wayth ◽  
...  
Keyword(s):  
Radio Astronomy ◽  
Low Frequency ◽  
Computation Time ◽  
Field Pattern ◽  
Mean Deviation ◽  
Antenna Element ◽  
Single Antenna ◽  
Operational Frequency ◽  
Square Kilometer Array ◽  
Far Field Pattern

The far-field pattern of a geometrically large and complex antenna used in low-frequency radio astronomy is computationally expensive to simulate on electromagnetic simulators, such as FEKO. For example, one station of the Square Kilometer Array, which consists of 256 log-periodic antenna elements, will take years to simulate using the full CAD model for the full operational frequency band. This paper focuses on reducing the simulation time for a single antenna element by simplifying the simulation model, thus decreasing the number of unknowns that have to be solved in a simulation. An iterative process for optimizing the simplification of such an element is described, while keeping the reflection coefficient within 1 dB absolute mean deviation of the measured data. After four iterations, the amount of unknowns to be solved, which includes the number of triangles and segments, was reduced from 29,307 to 11,991. This decreased the computation time by 86.5%, making array simulations feasible. Using the techniques described in the paper, other antenna constructions can benefit from it and be simulated more efficiently.

scholarly journals Principles of Gravitational-Wave Detection with Pulsar Timing Arrays

Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2418
Author(s):  
Michele Maiorano ◽  
Francesco De Paolis ◽  
Achille A. Nucita
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Low Frequency ◽  
Black Hole Binaries ◽  
Pulsar Timing ◽  
Time Correlations ◽  
Array Detection ◽  
Square Kilometer Array ◽  
Gravitational Wave Background ◽  
Pulsar Timing Array

Pulsar timing uses the highly stable pulsar spin period to investigate many astrophysical topics. In particular, pulsar timing arrays make use of a set of extremely well-timed pulsars and their time correlations as a challenging detector of gravitational waves. It turns out that pulsar timing arrays are particularly sensitive to ultra-low-frequency gravitational waves, which makes them complementary to other gravitational-wave detectors. Here, we summarize the basics, focusing especially on supermassive black-hole binaries and cosmic strings, which have the potential to form a stochastic gravitational-wave background in the pulsar timing array detection band, and the scientific goals on this challenging topic. We also briefly outline the recent interesting results of the main pulsar timing array collaborations, which have found strong evidence of a common-spectrum process compatible with a stochastic gravitational-wave background and mention some new perspectives that are particularly interesting in view of the forthcoming radio observatories such as the Five hundred-meter Aperture Spherical Telescope, the MeerKAT telescope, and the Square Kilometer Array.

scholarly journals Pulsar Observations at the Ghana Radio Astronomy Observatory

2017 ◽  
Vol 13 (S337) ◽  
pp. 410-411
Author(s):  
T. W. Scragg ◽  
B. W. Stappers ◽  
R. P. Breton ◽  
J. N. Smith ◽  
D. Adomako ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Radio Astronomy ◽  
Astronomy Observatory ◽  
Earth Station ◽  
Radio Astronomy Observatory ◽  
Pulsar Timing ◽  
New Radio ◽  
Timing System

AbstractIn August 2017 a new radio telescope, the Ghana Radio Astronomy Observatory (GRAO), was officially inaugurated at Kuntunse, Ghana. The GRAO is a former satellite Earth station and now the first operational station in the African VLBI Network (AVN). The Jodrell Bank Centre for Astrophysics (JBCA), supported by the UK’s STFC/Newton Fund, has developed a new pulsar timing system (Hebe) for the GRAO. We present some aspects of the design of Hebe and an outline of the first pulsar detection at GRAO.

scholarly journals The gravitational wave signal from close galaxy pairs

2014 ◽  
Vol 10 (S312) ◽  
pp. 296-297
Author(s):  
Jinzhong Liu ◽  
Yu Zhang
Keyword(s):  
Gravitational Wave ◽  
Low Frequency ◽  
Sloan Digital Sky Survey ◽  
Population Synthesis ◽  
Host Galaxies ◽  
Black Hole Binaries ◽  
Pulsar Timing ◽  
Sky Survey ◽  
Square Kilometer Array ◽  
Pulsar Timing Array

AbstractThe early phase of coalescence of supermassive black hole binaries (SMBHBs) from their host galaxies provides a guaranteed source of low-frequency gravitational wave (GW) radiation by pulsar timing observations. Nowadays, SMBHBs are ubiquitous in the nuclei of galaxies. A latest sample of close galaxy pairs has been released from the Sloan Digital Sky Survey (SDSS) Data. A binary population synthesis (BPS) approach has been applied to study the characteristics of clusters and galaxies. Here we report how BPS, using SDSS results, can be used to determine the GW radiation from SMBHBs. In this study we show numerical results under the assumption that SMBHBs formed through the merger of two galaxies and give the waveform evolution using post-Newtonian approximation methods. Based on the sensitivity of the International Pulsar Timing Array (IPTA) and Square Kilometer Array (SKA) detectors, we show that the value of strain amplitude h can be changed from about 10−14 to 10−15 during the observation of 20 years, which can be considered as a precise evolution.

Ultra-Wideband Aperture Array Element Design for Low Frequency Radio Astronomy

2011 ◽  
Vol 59 (6) ◽  
pp. 1808-1816 ◽  
Author(s):  
Eloy de Lera Acedo ◽  
Nima Razavi-Ghods ◽  
Luis Enrique Garcia ◽  
Peter Duffett-Smith ◽  
P. Alexander
Keyword(s):  
Radio Astronomy ◽  
Low Frequency ◽  
Array Element ◽  
Ultra Wideband ◽  
Aperture Array

Prognostic relevance of anamnestic and diagnostic parameters in low-frequency hearing impairment

2006 ◽  
Vol 120 (8) ◽  
pp. 613-618 ◽  
Author(s):  
W Maier ◽  
J Schipper
Keyword(s):  
Prognostic Factor ◽  
Hearing Impairment ◽  
Hearing Threshold ◽  
Low Frequency ◽  
Prognostic Indicators ◽  
Infusion Therapy ◽  
Prognostic Relevance ◽  
Long Time ◽  
Dehydration Therapy

Low-frequency hearing impairment (LFHI) is mainly attributed to endolymphatic hydrops and has a great variety of possible outcomes. At present, no conservative therapeutic regimen has proven to be ‘gold-standard’, and information about the prognostic indicators of LFHI is scarce.In a retrospective investigation, we evaluated the records of 90 patients who had been treated with infusions improving blood perfusion. In patients lacking complete remission, dehydration infusion therapy was added. We also undertook audiometric follow up. We calculated the outcomes after infusion therapy, dehydration therapy and after long-time hearing follow up, and we determined the prognostic relevance of several parameters of anamnesis and clinical examination to outcomes, for both therapeutic interventions and long-time hearing.The prognosis of LFHI was significantly correlated to certain anamnestic and clinical parameters; a short duration of the disease, lack of vertigo and female gender implied a better outcome. The pretherapeutic hearing threshold was an important prognostic factor; the outcome was significantly worse in patients with distinct hearing impairment in low or high frequencies, compared with that in patients with little hearing loss. Whereas vertigo was a negative prognostic factor, the results of quantitative vestibular testing were irrelevant to the outcome. The glycerol test failed to predict the effectiveness of dehydration therapy and lacked any value in predicting prognosis.These results allow the clinician to focus the anamnesis and diagnostic examination on prognostically relevant parameters, thus enabling a better estimation of the long-term disease course and improved counselling of patients. Furthermore, these results help to distinguish valuable from irrelevant diagnostic procedures.

scholarly journals Precision Pulsar Timing with NASA's Deep Space Network

2015 ◽  
Vol 11 (A29B) ◽  
pp. 367-369
Author(s):  
Lawrence Teitelbaum ◽  
Walid Majid ◽  
Manuel M. Franco ◽  
Daniel J. Hoppe ◽  
Shinji Horiuchi ◽  
...  
Keyword(s):  
Low Frequency ◽  
Radio Waves ◽  
Deep Space ◽  
Radio Pulsars ◽  
Deep Space Network ◽  
Space Network ◽  
The Earth ◽  
Pulsar Timing ◽  
Initial Results ◽  
Stable Rotation

AbstractMillisecond pulsars (MSPs) are a class of radio pulsars with extremely stable rotation. Their excellent timing stability can be used to study a wide variety of astrophysical phenomena. In particular, a large sample of these pulsars can be used to detect low-frequency gravitational waves. We have developed a precision pulsar timing backend for the NASA Deep Space Network (DSN), which will allow the use of short gaps in tracking schedules to time pulses from an ensemble of MSPs. The DSN operates clusters of large dish antennas (up to 70-m in diameter), located roughly equidistant around the Earth, for communication and tracking of deep-space spacecraft. The backend system will be capable of removing entirely the dispersive effects of propagation of radio waves through the interstellar medium in real-time. We will describe our development work, initial results, and prospects for future observations over the next few years.

scholarly journals II BRAZILIAN CONSENSUS ON GASTRIC CANCER BY THE BRAZILIAN GASTRIC CANCER ASSOCIATION

2020 ◽  
Vol 33 (2) ◽  
Author(s):  
Leandro Cardoso BARCHI ◽  
Marcus Fernando Kodama Pertille RAMOS ◽  
André Roncon DIAS ◽  
Nelson Adami ANDREOLLO ◽  
Antônio Carlos WESTON ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Literature Review ◽  
Cancer Treatment ◽  
New Concepts ◽  
New Knowledge ◽  
Gastric Cancer Treatment

ABSTRACT Background: Since the publication of the first Brazilian Consensus on Gastric Cancer (GC) in 2012 carried out by the Brazilian Gastric Cancer Association, new concepts on diagnosis, staging, treatment and follow-up have been incorporated. Aim: This new consensus is to promote an update to professionals working in the fight against GC and to provide guidelines for the management of patients with this condition. Methods: Fifty-nine experts answered 67 statements regarding the diagnosis, staging, treatment and prognosis of GC with five possible alternatives: 1) fully agree; 2) partially agree; 3) undecided; 4) disagree and 5) strongly disagree A consensus was adopted when at least 80% of the sum of the answers “fully agree” and “partially agree” was reached. This article presents only the responses of the participating experts. Comments on each statement, as well as a literature review, will be presented in future publications. Results: Of the 67 statements, there was consensus in 50 (74%). In 10 declarations, there was 100% agreement. Conclusion: The gastric cancer treatment has evolved considerably in recent years. This consensus gathers consolidated principles in the last decades, new knowledge acquired recently, as well as promising perspectives on the management of this disease.

scholarly journals INTERSTELLAR MEDIUM AND DECAMETER RADIO SPECTROSCOPY

2021 ◽  
Vol 26 (4) ◽  
pp. 314-325
Author(s):  
S. V. Stepkin ◽  
◽  
O. O. Konovalenko ◽  
Y. V. Vasylkivskyi ◽  
D. V. Mukha ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Low Frequency ◽  
Spectral Lines ◽  
Physical Parameters ◽  
Recombination Mechanism ◽  
Radio Recombination Lines ◽  
Radio Spectroscopy ◽  
Correlation Spectrum

Purpose: The analytical review of the main results of research in the new direction of the low-frequency radio astronomy, the interstellar medium radio spectroscopy at decameter waves, which had led to astrophysical discovery, recording of the radio recombination lines in absorption for highly excited states of interstellar carbon atoms (more than 600). Design/methodology/approach: The UTR-2 world-largest broadband radio telescope of decameter waves optimally connected with the digital correlation spectrum analyzers has been used. Continuous modernization of antenna system and devices allowed increasing the analysis band from 100 kHzto 24 MHz and a number of channels from 32 to 8192. The radio telescope and receiving equipment with appropriate software allowed to have a long efficient integration time enough for a large line series simultaneously with high resolution, noise immunity and relative sensitivity. Findings: A new type of interstellar spectral lines has been discovered and studied, the interstellar carbon radio recombination lines in absorption for the record high excited atoms with principal quantum numbers greater than 1000. The line parameters (intensity, shape, width, radial velocity) and their relation ship with the interstellar medium physical parameters have been determined. The temperature of line forming regions is about 100 K, the electron concentration up to 0.1 cm–3 and the size of a line forming region is about 10 pc. For the first time, radio recombination lines were observed in absorption. They have significant broadening and are amplified by the dielectronic-like recombination mechanism and are also the lowest frequency lines in atomic spectroscopy. Conclusions: The detected low-frequency carbon radio recombination lines and their observations have become a new highly effective tool for the cold partially ionized interstellar plasma diagnostics. Using them allows obtaining the information which is not available with the other astrophysical methods. For almost half a century of their research, a large amount of hardware-methodical and astrophysical results have been obtained including a record number of Galaxy objects, where there levant lines have been recorded. The domestic achievements have stimulated many theoretical and experimental studies in other countries, but the scientific achievements of Ukrainian scientists prove the best prospects for further development of this very important area of astronomical science. Key words: low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer

Sign in / Sign up

Export Citation Format

Share Document