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  1. Free, publicly-accessible full text available August 1, 2024
  2. Abstract

    We present the results of an all-sky search for continuous gravitational waves in the public LIGO O3 data. The search covers signal frequencies 20.0 Hz ≤f≤ 800.0 Hz and a spin-down range down to −2.6 × 10−9Hz s−1, motivated by detectability studies on synthetic populations of Galactic neutron stars. This search is the most sensitive all-sky search to date in this frequency/spin-down region. The initial search was performed using the first half of the public LIGO O3 data (O3a), utilizing graphical processing units provided in equal parts by the volunteers of the Einstein@Home computing project and by the ATLAS cluster. After a hierarchical follow-up in seven stages, 12 candidates remain. Six are discarded at the eighth stage, by using the remaining O3 LIGO data (O3b). The surviving six can be ascribed to continuous-wave fake signals present in the LIGO data for validation purposes. We recover these fake signals with very high accuracy with our last stage search, which coherently combines all O3 data. Based on our results, we set upper limits on the gravitational-wave amplitudeh0and translate these into upper limits on the neutron star ellipticity and on ther-mode amplitude. The most stringent upper limits are at 203 Hz, withh0= 8.1 × 10−26at the 90% confidence level. Our results exclude isolated neutron stars rotating faster than 5 ms with ellipticities greater than5×108d100pcwithin a distancedfrom Earth andr-mode amplitudesα105d100pcfor neutron stars spinning faster than 150 Hz.

     
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  3. Slafractonia leguminicola infects red clover and other legumes, causing black patch disease. This pathogenic fungus also produces two mycotoxins, slaframine and swainsonine, that are toxic to livestock grazing on clover hay or pasture infested with S. leguminicola. Swainsonine toxicosis causes locoism, while slaframine causes slobbers syndrome. The mechanism of toxin secretion by S. leguminicola is poorly understood. The aim of this research was to investigate the role of a putative transmembrane transporter, SwnT, in mycotoxin transport. The swnT gene was silenced by RNA interference using the silencing vector Psilent1, which included inverted repeat transgenes of swnT. This resulted in a significant reduction of swnT transcript levels compared with the controls. Silencing caused a decline in the active efflux of toxins from the mycelia to the media, as shown by LC–MS analysis. Transformants in which swnT was silenced showed higher concentrations of both toxins in the mycelia compared with the concentrations in the media. These transformants exhibited a visibly distinct phenotype with much thicker and shorter mycelia than in the wild type. These transformants were also unable to infect detached clover leaves, unlike the controls, suggesting that SwnT function may play an important role in pathogenesis in addition to mycotoxin transport. This research demonstrates the importance of this transporter to the secretion of mycotoxins for this phytopathogenic fungus.

     
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  4. Interferometry is a powerful tool for estimating the incident angle of electromagnetic (EM) waves by calculating the correlation of received signals at different antennas. Motivated by very-long-baseline interfereometry (VLBI) in radio astronomy, an interferometry based sensing scheme is proposed as integrated sensing and communications (ISAC). It reuses the communication signal from base stations (BSs), similarly to passive radars, which improves the sensing precision and spectrum efficiency. Different from the almost-perfect synchronization in VLBI realized by atomic clocks, the synchronization in BSs of cellular communication networks (usually based on GPS signals) could have significant errors. Therefore, algorithms for compensating for synchronization errors in both time and frequency are proposed. Numerical simulations demonstrate that the proposed algorithms can substantially alleviate the synchronization errors. 
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  5. Abstract We present results of a search for periodic gravitational wave signals with frequencies between 20 and 400 Hz from the neutron star in the supernova remnant G347.3-0.5 using LIGO O2 public data. The search is deployed on the volunteer computing project Einstein@Home, with thousands of participants donating compute cycles to make this endeavour possible. We find no significant signal candidate and set the most constraining upper limits to date on the amplitude of gravitational wave signals from the target, corresponding to deformations below 10 −6 in a large part of the band. At the frequency of best strain sensitivity, near 166 Hz, we set 90% confidence upper limits on the gravitational wave intrinsic amplitude of h 0 90 % ≈ 7.0 × 10 − 26 . Over most of the frequency range our upper limits are a factor of 20 smaller than the indirect age-based upper limit. 
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