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Prelimiary investigation desalting of geothermal brines in the Imperial Valley of California
The Imperial Valley Project is an applied research program to provide geologic, hydrologic, engineering, and economic information necessary for development of the geothermal resources of the delta of the lower Colorado River. It is suggested that a desalting pilot plant be associated with the project to develop an economic desalting process if 2 to 3% geothermal brine is produced. The process will be unconventional in that waste heat must be rejected to atmosphere in wet or dry cooling towers. The presence of large amounts of CO/sub 2/, H/sub 2/S, and silica will require gas removal and silicascale control equipment. The plant would process up to 75,000 gallons of brine per day. (MCW
Burkholderia cenocepacia utilizes a type VI secretion system for bacterial competition.
Burkholderia cenocepacia is an opportunistic bacterial pathogen that poses a significant threat to individuals with cystic fibrosis by provoking a strong inflammatory response within the lung. It possesses a type VI secretion system (T6SS), a secretory apparatus that can perforate the cellular membrane of other bacterial species and/or eukaryotic targets, to deliver an arsenal of effector proteins. The B. cenocepacia T6SS (T6SS-1) has been shown to be implicated in virulence in rats and contributes toward actin rearrangements and inflammasome activation in B. cenocepacia-infected macrophages. Here, we present bioinformatics evidence to suggest that T6SS-1 is the archetype T6SS in the Burkholderia genus. We show that B. cenocepacia T6SS-1 is active under normal laboratory growth conditions and displays antibacterial activity against other Gram-negative bacterial species. Moreover, B. cenocepacia T6SS-1 is not required for virulence in three eukaryotic infection models. Bioinformatics analysis identified several candidate T6SS-dependent effectors that may play a role in the antibacterial activity of B. cenocepacia T6SS-1. We conclude that B. cenocepacia T6SS-1 plays an important role in bacterial competition for this organism, and probably in all Burkholderia species that possess this system, thereby broadening the range of species that utilize the T6SS for this purpose
The SUrvey for Pulsars and Extragalactic Radio Bursts V:Recent Discoveries and Full Timing Solutions
The SUrvey for Pulsars and Extragalactic Radio Bursts ran from 2014 April to
2019 August, covering a large fraction of the southern hemisphere at mid- to
high-galactic latitudes, and consisting of 9-minute pointings taken with the
20-cm multibeam receiver on the Parkes Radio Telescope. Data up to 2017
September 21 have been searched using standard Fourier techniques, single-pulse
searches, and Fast Folding Algorithm searches. We present 19 new discoveries,
bringing the total to 27 discoveries in the programme, and we report the
results of follow-up timing observations at Parkes for 26 of these pulsars,
including the millisecond pulsar PSR J1421-4409; the faint, highly-modulated,
slow pulsar PSR J1646-1910; and the nulling pulsar PSR J1337-4441. We present
new timing solutions for 23 pulsars, and we report flux densities, modulation
indices, and polarization properties.Comment: Accepted to MNRAS; data available at
https://doi.org/10.5281/zenodo.390098
The Thousand Pulsar Array program on MeerKAT – IX. The time-averaged properties of the observed pulsar population
We present the largest single survey to date of average profiles of radio pulsars, observed and processed using the same telescope and data reduction software. Specifically, we present measurements for 1170 pulsars, observed by the Thousand Pulsar Array programme at the 64-dish SARAO MeerKAT radio telescope, in a frequency band from 856 to 1712 MHz. We provide rotation measures (RM), dispersion measures, flux densities, and polarization properties. The catalogue includes 254 new RMs that substantially increase the total number of known pulsar RMs. Our integration times typically span over 1000 individual rotations per source. We show that the radio (pseudo-) luminosity has a strong, shallow dependence on the spin-down energy, proportional to Ė0.15±0.04, that contradicts some previous proposals of population synthesis studies. In addition, we find a significant correlation between the steepness of the observed flux density spectra and Ė, and correlations of the fractional linear polarization with Ė, the spectral index, and the pulse width, which we discuss in the context of what is known about pulsar radio emission and how pulsars evolve with time. On the whole, we do not see significant correlations with the estimated surface magnetic field strength, and the correlations with Ė are much stronger than those with the characteristic age. This finding lends support to the suggestion that magnetic dipole braking may not be the dominant factor for the evolution of pulsar rotation over the lifetimes of pulsars. A public data release of the high-fidelity time-averaged pulse profiles in full polarization accompanies our catalogue
Searching for gravitational wave bursts from cosmic string cusps with the Parkes Pulsar Timing Array
Cosmic strings are potential gravitational wave (GW) sources that can be
probed by pulsar timing arrays (PTAs). In this work we develop a detection
algorithm for a GW burst from a cusp on a cosmic string, and apply it to Parkes
PTA data. We find four events with a false alarm probability less than 1%.
However further investigation shows that all of these are likely to be
spurious. As there are no convincing detections we place upper limits on the GW
amplitude for different event durations. From these bounds we place limits on
the cosmic string tension of G mu ~ 10^{-5}, and highlight that this bound is
independent from those obtained using other techniques. We discuss the physical
implications of our results and the prospect of probing cosmic strings in the
era of Square Kilometre Array (SKA).Comment: Accepted for publication by MNRA
The Green Bank Northern Celestial Cap Pulsar Survey II: The Discovery and Timing of Ten Pulsars
We present timing solutions for ten pulsars discovered in 350 MHz searches
with the Green Bank Telescope. Nine of these were discovered in the Green Bank
Northern Celestial Cap survey and one was discovered by students in the Pulsar
Search Collaboratory program in analysis of drift-scan data. Following
discovery and confirmation with the Green Bank Telescope, timing has yielded
phase-connected solutions with high precision measurements of rotational and
astrometric parameters. Eight of the pulsars are slow and isolated, including
PSR J09302301, a pulsar with nulling fraction lower limit of 30\% and
nulling timescale of seconds to minutes. This pulsar also shows evidence of
mode changing. The remaining two pulsars have undergone recycling, accreting
material from binary companions, resulting in higher spin frequencies. PSR
J05572948 is an isolated, 44 \rm{ms} pulsar that has been partially recycled
and is likely a former member of a binary system which was disrupted by a
second supernova. The paucity of such so-called `disrupted binary pulsars'
(DRPs) compared to double neutron star (DNS) binaries can be used to test
current evolutionary scenarios, especially the kicks imparted on the neutron
stars in the second supernova. There is some evidence that DRPs have larger
space velocities, which could explain their small numbers. PSR J1806+2819 is a
15 \rm{ms} pulsar in a 44 day orbit with a low mass white dwarf companion. We
did not detect the companion in archival optical data, indicating that it must
be older than 1200 Myr.Comment: 9 pages, 5 figure
The Thousand-Pulsar-Array program on MeerKAT -- IX. The time-averaged properties of the observed pulsar population
We present the largest single survey to date of average profiles of radio
pulsars, observed and processed using the same telescope and data reduction
software. Specifically, we present measurements for 1170 pulsars, observed by
the Thousand Pulsar Array (TPA) programme at the 64-dish SARAO MeerKAT radio
telescope, in a frequency band from 856 to 1712 MHz. We provide rotation
measures (RM), dispersion measures, flux densities and polarization properties.
The catalogue includes 254 new RMs that substantially increase the total number
of known pulsar RMs. Our integration times typically span over 1000 individual
rotations per source. We show that the radio (pseudo)luminosity has a strong,
shallow dependence on the spin-down energy, proportional to
, that contradicts some previous proposals of population
synthesis studies. In addition, we find a significant correlation between the
steepness of the observed flux density spectra and , and correlations
of the fractional linear polarization with , the spectral index, and
the pulse width, which we discuss in the context of what is known about pulsar
radio emission and how pulsars evolve with time. On the whole, we do not see
significant correlations with the estimated surface magnetic field strength,
and the correlations with are much stronger than those with the
characteristic age. This finding lends support to the suggestion that magnetic
dipole braking may not be the dominant factor for the evolution of pulsar
rotation over the lifetimes of pulsars. A public data release of the
high-fidelity time-averaged pulse profiles in full polarization accompanies our
catalogue.Comment: Accepted for publication in MNRAS. 21 pages, 25 figures, 6 Table
The Green Bank North Celestial Cap Pulsar Survey. IV: Four New Timing Solutions
We present timing solutions for four pulsars discovered in the Green Bank
Northern Celestial Cap (GBNCC) survey. All four pulsars are isolated with spin
periods between 0.26s and 1.84s. PSR J00382501 has a 0.26s
period and a period derivative of ,
which is unusually low for isolated pulsars with similar periods. This low
period derivative may be simply an extreme value for an isolated pulsar or it
could indicate an unusual evolution path for PSR J00382501, such as a
disrupted recycled pulsar (DRP) from a binary system or an orphaned central
compact object (CCO). Correcting the observed spin-down rate for the Shklovskii
effect suggests that this pulsar may have an unusually low space velocity,
which is consistent with expectations for DRPs. There is no X-ray emission
detected from PSR J00382501 in an archival swift observation, which suggests
that it is not a young orphaned CCO. The high dispersion measure of PSR
J1949+3426 suggests a distance of 12.3kpc. This distance indicates that PSR
J1949+3426 is among the most distant 7% of Galactic field pulsars, and is one
of the most luminous pulsars.Comment: 7 pages, 5 figure
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