5,479 research outputs found
Interagency telemetry arraying for Voyager-Neptune encounter
The reception capability of the Deep Space Network (DSN) has been improved over the years by increasing both the size and number of antennas at each complex to meet spacecraft-support requirements. However, even more aperture was required for the final planetary encounters of the Voyager 2 spacecraft. This need was met by arraying one radio astronomy observatory with the DSN complex in the United States and another with the complex in Australia. Following a review of augmentation for the Uranus encounter, both the preparation at the National Radio Astronomy (NRAO) Very Large Array (VLA) and the Neptune encounter results for the Parkes-Canberra and VLA-Goldstone arrays are presented
Stellar Double Coronagraph: a multistage coronagraphic platform at Palomar observatory
We present a new instrument, the "Stellar Double Coronagraph" (SDC), a
flexible coronagraphic platform. Designed for Palomar Observatory's 200" Hale
telescope, its two focal and pupil planes allow for a number of different
observing configurations, including multiple vortex coronagraphs in series for
improved contrast at small angles. We describe the motivation, design,
observing modes, wavefront control approaches, data reduction pipeline, and
early science results. We also discuss future directions for the instrument.Comment: 25 pages, 12 figures. Correspondence welcome. The published work is
open access and differs trivially from the version posted here. The published
version may be found at
http://iopscience.iop.org/article/10.1088/1538-3873/128/965/075003/met
A Population of Short-Period Variable Quasars from PTF as Supermassive Black Hole Binary Candidates
Supermassive black hole binaries (SMBHBs) at sub-parsec separations should be
common in galactic nuclei, as a result of frequent galaxy mergers.
Hydrodynamical simulations of circumbinary discs predict strong periodic
modulation of the mass accretion rate on time-scales comparable to the orbital
period of the binary. As a result, SMBHBs may be recognized by the periodic
modulation of their brightness. We conducted a statistical search for periodic
variability in a sample of 35,383 spectroscopically confirmed quasars in the
photometric database of the Palomar Transient Factory (PTF). We analysed
Lomb-Scargle periodograms and assessed the significance of our findings by
modeling each individual quasar's variability as a damped random walk (DRW). We
identified 50 quasars with significant periodicity beyond the DRW model,
typically with short periods of a few hundred days. We find 33 of these to
remain significant after a re-analysis of their periodograms including
additional optical data from the intermediate-PTF and the Catalina Real-Time
Transient Survey (CRTS). Assuming that the observed periods correspond to the
redshifted orbital periods of SMBHBs, we conclude that our findings are
consistent with a population of unequal-mass SMBHBs, with a typical mass ratio
as low as q = M2/M1 ~ 0.01.Comment: MNRAS (accepted), new section 4.
Benefits and Success of an Interdisciplinary Wellness Interest Group (iWIG) at a Modern Jesuit University
Aim: To highlight the early achievements and discuss the benefits of forming an Interdisciplinary Wellness Interest Group (iWIG) on a modern Jesuit University campus.
Background: While wellness programs have a place in academic communities, universal perspectives on the best way to lead Wellness initiatives is lacking. An iWIG gives a common platform to share ideas, communicate across audiences, and provide important information to the campus community about health promotion and health patterns of the campus community.
Methods: After assembling the iWIG team, on-campus meetings were held with members of the interdisciplinary group. These meetings include faculty, staff, and students from various departments. The iWIG continues to meet regularly to expand and develop wellness initiatives, research opportunities and to ensure a presence on campus.
Results: The iWIG has impacted many initiatives on campus, a select few which are profiled in this manuscript. The group is involved in funded research studies, has received a Healthy Workplace designation, and continues to expand health and wellness into various departments on campus.
Conclusions: The interdisciplinary group has provided those with an interest in health and wellness with a formal platform to express ideas and implement initiatives for all individuals to better the overall well-being of the university community
Genomics goes chromosomal to explore the wheat genome
OBJECTIVES: The implant design and surface modification are independent conditions that can alter the implant bone response. The objective of this study is to compare the bone response to roughened tapered and cylindrical screw-type implants with and without hydroxyapatite (HA) surface coating in the femoral trabecular bone of rabbits. MATERIAL AND METHOD: Thirty-two implants (8 x 3.5 mm) consisting of four different types (eight implants in each group), that is, tapered implants, cylindrical implants, HA-coated tapered implants, and HA-coated cylindrical implants were installed in the femoral condyle of 16 rabbits. After 8 weeks of healing, the femoral condyles were retrieved and studied histologically. The bone-to-implant contact percentage was assessed and analyzed statistically. Results : The histomorphometric analysis revealed that the bone-to-implant contact (BIC) values seemed to be higher for HA-coated tapered implants (65.62 +/- 13.02) followed by cylindrical non-coated implants. All four types of implants showed wide distribution of BIC with no statistical significance between different types of implants. CONCLUSION: It can be concluded that under the current experimental conditions, implant design and surface composition had little effect on the bone-to-implant interface
Recurrent Neutrino Emission from Supermassive Black Hole Mergers
The recent detection of possible neutrino emission from the blazar TXS
0506+056 was the first high-energy neutrino associated with an astrophysical
source, making this special type of active galaxies promising neutrino
emitters. The fact that two distinct episodes of neutrino emission were
detected with a separation of around 3 years suggests that emission could be
periodic. Periodic emission is expected from supermassive binary black hole
systems due to jet precession close to the binary's merger. Here we show that
if TXS 0506+056 is a binary source then the next neutrino flare could occur
before the end of 2021. We derive the binary properties that would lead to the
detection of gravitational waves from this system by LISA. Our results for the
first time quantify the time scale of these correlations for the example of TXS
0506+056, providing clear predictions for both the neutrino and
gravitational-wave signatures of such sources.Comment: 6 pages, 3 figures, submitte
Impactos en las propiedades del suelo de los bosques de pinabete en terrenos agrÃcolas abandonados
Forest floor is considered a major feature distinguishing forest from agricultural soils. Forest floor develops as forest stands grow and is composed of more or less altered plant-tissue biomass accumulated on the soil surface. Our study’s aim was to find whether properties of both the organic layers and mineral soil differ according to the land-use history of the sites compared. Each site included an afforested area of immature 50-year-old spruce forest (AFF) on formerly agricultural land plus an adjacent area of old-growth 100-year-old spruce stand (FOR). The localities are situated at altitudes ranging between 600 and 850 metres above sea level. From the results of our study it can be concluded that both forest floor and mineral soil had higher pH and Ca concentration at formerly agricultural sites. C/N ratio is significantly lower in afforested soil. First-generation humus was significantly higher in phosphorus.El piso forestal es considerado una de las principales caracterÃsticas distintivas de los suelos forestales frente a los
agrÃcolas. El piso forestal se desarrolla según crecen las masas forestales y se compone de tejidos de vegetales de la
biomasa más o menos alterados acumulados en la superficie del suelo. El objetivo de nuestro estudio fue determinar
si las propiedades de las capas orgánicas y minerales del suelo difieren de acuerdo a la historia del uso del suelo de
los sitios. Cada sitio incluye un área reforestada de bosque de pinabete inmaduro de 50 años de edad (AFF) en antiguo
terreno agrÃcola, más un área adyacente madura de pinabete de 100 años de edad. Las localidades se encuentran
en altitudes que oscilan entre 600 y 850 metros sobre el nivel del mar. De los resultados de nuestro estudio se puede
concluir que tanto el suelo del bosque como el suelo mineral tenÃan un pH más alto y mayor concentración de Ca en
los sitios agrÃcolas abandonados. La relación C/N es significativamente menor en los suelos reforestados. La primera
generación de humus presentó un significativamente mayor contenido en fósforo
Supercooled Liquid Dynamics Studied via Shear-Mechanical Spectroscopy
We report dynamical shear-modulus measurements for five glass-forming liquids
(pentaphenyl trimethyl trisiloxane, diethyl phthalate, dibutyl phthalate,
1,2-propanediol, and m-touluidine). The shear-mechanical spectra are obtained
by the piezoelectric shear-modulus gauge (PSG) method. This technique allows
one to measure the shear modulus ( Pa) of the liquid within a
frequency range from 1 mHz to 10 kHz. We analyze the frequency-dependent
response functions to investigate whether time-temperature superposition (TTS)
is obeyed. We also study the shear-modulus loss-peak position and its
high-frequency part. It has been suggested that when TTS applies, the
high-frequency side of the imaginary part of the dielectric response decreases
like a power law of the frequency with an exponent -1/2. This conjecture is
analyzed on the basis of the shear mechanical data. We find that TTS is obeyed
for pentaphenyl trimethyl trisiloxane and in 1,2-propanediol while in the
remaining liquids evidence of a mechanical process is found. Although
the the high-frequency power law behavior of the shear-loss
may approach a limiting value of when lowering the temperature, we
find that the exponent lies systematically above this value (around 0.4). For
the two liquids without beta relaxation (pentaphenyl trimethyl trisiloxane and
1,2-propanediol) we also test the shoving model prediction, according to which
the the relaxation-time activation energy is proportional to the instantaneous
shear modulus. We find that the data are well described by this model.Comment: 7 pages, 6 figure
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