248 research outputs found
On Nonmixed Symmetric End-Load Problems in Elastic Waveguides
This investigation deals with the response of the semi-infinite,
linear elastic, homogeneous, isotropic plate in plane strain, subject
to symmetric normal loads acting, in the absence of shear stress,
on its edge. A double Laplace transform technique is used to obtain
long-time information for two problems; a uniform load and a line-load.
Near- and far-field approximations are found, the far-field approximations
giving the integral of the Airy integral for both problems
The Origin of Nitrogen on Jupiter and Saturn from the N/N Ratio
The Texas Echelon cross Echelle Spectrograph (TEXES), mounted on NASA's
Infrared Telescope Facility (IRTF), was used to map mid-infrared ammonia
absorption features on both Jupiter and Saturn in February 2013. Ammonia is the
principle reservoir of nitrogen on the giant planets, and the ratio of
isotopologues (N/N) can reveal insights into the molecular
carrier (e.g., as N or NH) of nitrogen to the forming protoplanets, and
hence the source reservoirs from which these worlds accreted. We targeted two
spectral intervals (900 and 960 cm) that were relatively clear of
terrestrial atmospheric contamination and contained close features of
NH and NH, allowing us to derive the ratio from a single
spectrum without ambiguity due to radiometric calibration (the primary source
of uncertainty in this study). We present the first ground-based determination
of Jupiter's N/N ratio (in the range from to
), which is consistent with both previous space-based studies
and with the primordial value of the protosolar nebula. On Saturn, we present
the first upper limit on the N/N ratio of no larger than
for the 900-cm channel and a less stringent
requirement that the ratio be no larger than for the
960-cm channel ( confidence). Specifically, the data rule out
strong N-enrichments such as those observed in Titan's atmosphere and in
cometary nitrogen compounds. To the extent possible with ground-based
radiometric uncertainties, the saturnian and jovian N/N ratios
appear indistinguishable, implying that N-enriched ammonia ices could
not have been a substantial contributor to the bulk nitrogen inventory of
either planet, favouring the accretion of primordial N from the gas phase
or as low-temperature ices.Comment: 33 pages, 19 figures, manuscript accepted for publication in Icaru
Identification of a lipid-rich depot in the orbital cavity of the thirteen-lined ground squirrel
We discovered a previously undescribed orbital lipid depot in the thirteen-lined ground squirrel during the first ever magnetic resonance image (MRI) of this common experimental model of mammalian hibernation. In animals housed at constant ambient temperatures (5°C or 25°C, 12 h:12 h light:dark photoperiod), the volume of this depot increased in the autumn and decreased in the spring, suggesting an endogenous circannual pattern. Water-fat MRI revealed that throughout the year this depot is composed of ∼40% lipid, similar to brown adipose tissue (BAT). During arousal from torpor, thermal images showed higher surface temperatures near this depot before the rest of the head warmed, suggesting a thermoregulatory function. This depot, however, does not contain uncoupling protein 1, a BAT biomarker, or uncoupling protein 3. Histology shows blood vessels in close proximity to each other, suggesting it may serve as a vascular rete, perhaps to preferentially warm the eye and brain during arousals
The crystal structure of PD1, a Haemophilus surface fibril domain
The Haemophilus surface fibril (Hsf) is an unusually large trimeric autotransporter adhesin (TAA) expressed by the most virulent strains of H. influenzae. Hsf is known to mediate adhesion between pathogen and host, allowing the establishment of potentially deadly diseases such as epiglottitis, meningitis and pneumonia. While recent research has suggested that this TAA might adopt a novel `hairpin-like' architecture, the characterization of Hsf has been limited to in silico modelling and electron micrographs, with no high-resolution structural data available. Here, the crystal structure of Hsf putative domain 1 (PD1) is reported at 3.3 Å resolution. The structure corrects the previous domain annotation by revealing the presence of an unexpected N-terminal TrpRing domain. PD1 represents the first Hsf domain to be solved, and thus paves the way for further research on the `hairpin-like' hypothesis.Peer reviewe
Effects of a patellar strap on knee joint kinetics and kinematics during jump landings: an exploration using a statistical parametric mapping and Bayesian approach
Purpose
The aim of the current research was to investigate the effects of a patellar tendon strap on knee joint kinetics and kinematics during a vertical jump task using a statistical parametric mapping (SPM) and Bayesian approach.
Methods
Twenty-eight (14 male and 14 female) participants performed a vertical jump task under two conditions (patellar tendon strap/no-patellar tendon strap). Biomechanical data were captured using an eight-camera 3D motion capture system and force platform. Participants also subjectively rated the comfort/stability properties of the patellar tendon strap and their knee joint proprioception was examined with and without the strap using a weight bearing joint position sense test. Differences between patellar tendon strap/no-patellar tendon strap conditions were examined using SPM and Bayesian analyses and subjective ratings using Chi-squared tests.
Results
The results showed that neither knee joint kinetics or kinematics were affected as a function of wearing the patellar tendon strap. The findings did show that the knee brace helped to significantly increase participants perceived knee stability, but there were no improvements in weight bearing knee proprioception.
Conclusions
The current investigation indicates that the utilization of a patellar tendon strap akin to the device used in the current study does not appear to reduce the biomechanical parameters linked to the aetiology of knee pathologies, during vertical jump movements
Vertical Structure and Color of Jovian Latitudinal Cloud Bands during the Juno Era
The identity of the coloring agent(s) in Jupiter's atmosphere and the exact
structure of Jupiter's uppermost cloud deck are yet to be conclusively
understood. The Cr\`{e}me Br\^ul\'ee model of Jupiter's tropospheric clouds,
originally proposed by Baines et al. (2014) and expanded upon by Sromovsky et
al. (2017) and Baines et al. (2019), presumes that the chromophore measured by
Carlson et al. (2016) is the singular coloring agent in Jupiter's troposphere.
In this work, we test the validity of the Cr\`{e}me Br\^ul\'ee model of
Jupiter's uppermost cloud deck using spectra measured during the Juno
spacecraft's 5 perijove pass in March 2017. These data were
obtained as part of an international ground-based observing campaign in support
of the Juno mission using the NMSU Acousto-optic Imaging Camera (NAIC) at the
3.5-m telescope at Apache Point Observatory in Sunspot, NM. We find that the
Cr\`{e}me Br\^ul\'ee model cloud layering scheme can reproduce Jupiter's
visible spectrum both with the Carlson et al. (2016) chromophore and with
modifications to its imaginary index of refraction spectrum. While the
Cr\`{e}me Br\^ul\'ee model provides reasonable results for regions of Jupiter's
cloud bands such as the North Equatorial Belt and Equatorial Zone, we find that
it is not a safe assumption for unique weather events, such as the 2016-2017
Southern Equatorial Belt outbreak that was captured by our measurements.Comment: 38 pages, 21 figures; Accepted for publication in AAS Planetary
Science Journa
Identification of a lipid-rich depot in the orbital cavity of the 13-lined ground squirrel
We discovered a previously undescribed orbital lipid depot in the 13-lined ground squirrel during the first ever magnetic resonance image (MRI) of this common experimental model of mammalian hibernation. In animals housed at constant ambient temperatures (5ºC or 25ºC, 12h L:12h D photoperiod) the volume of this depot increased in the autumn and decreased in the spring, suggesting an endogenous circannual pattern. Water-fat MRI revealed that throughout the year this depot is composed of ~40% lipid, similar to brown adipose tissue (BAT). During arousal from torpor, thermal images showed higher surface temperatures near this depot before the rest of the head warmed, suggesting a thermoregulatory function. This depot, however, does not contain uncoupling protein 1, a BAT biomarker, or uncoupling protein 3. Histology shows blood vessels in close proximity to each other, suggesting it may serve as a vascular rete, perhaps to preferentially warm the eye and brain during arousals
Saturn's Seasonal Variability from Four Decades of Ground-Based Mid-Infrared Observations
A multi-decade record of ground-based mid-infrared (7-25 m) images of
Saturn is used to explore seasonal and non-seasonal variability in thermal
emission over more than a Saturnian year (1984-2022). Thermal emission measured
by 3-m and 8-m-class observatories compares favourably with synthetic images
based on both Cassini-derived temperature records and the predictions of
radiative climate models. 8-m class facilities are capable of resolving thermal
contrasts on the scale of Saturn's belts, zones, polar hexagon, and polar
cyclones, superimposed onto large-scale seasonal asymmetries. Seasonal changes
in brightness temperatures of K in the stratosphere and K in
the upper troposphere are observed, as the northern and southern polar
stratospheric vortices (NPSV and SPSV) form in spring and dissipate in autumn.
The timings of the first appearance of the warm polar vortices is successfully
reproduced by radiative climate models, confirming them to be radiative
phenomena, albeit entrained within sharp boundaries influenced by dynamics.
Axisymmetric thermal bands (4-5 per hemisphere) display temperature gradients
that are strongly correlated with Saturn's zonal winds, indicating winds that
decay in strength with altitude, and implying meridional circulation cells
forming the system of cool zones and warm belts. Saturn's thermal structure is
largely repeatable from year to year (via comparison of infrared images in 1989
and 2018), with the exception of low-latitudes. Here we find evidence of
inter-annual variations because the equatorial banding at 7.9 m is
inconsistent with a -year period for Saturn's equatorial stratospheric
oscillation, i.e., it is not strictly semi-annual. Finally, observations
between 2017-2022 extend the legacy of the Cassini mission, revealing the
continued warming of the NPSV during northern summer. [Abr.]Comment: 25 pages, 15 figures, accepted for publication in Icaru
Unexpected Long-Term Variability in Jupiter's Tropospheric Temperatures
An essential component of planetary climatology is knowledge of the
tropospheric temperature field and its variability. Previous studies of Jupiter
hinted at periodic behavior that was non-seasonal, as well as dynamical
relationships between tropospheric and stratospheric temperatures. However,
these observations were made over time frames shorter than Jupiter's orbit or
they used sparse sampling. We derived upper-tropospheric (300-mbar)
temperatures over 40 years, extending those studies to cover several orbits of
Jupiter, revealing unexpected results. Periodicities of 4, 7 8-9 and 10-14
years were discovered that involved different latitude bands and seem
disconnected from seasonal changes in solar heating. Anti-correlations of
variability in opposite hemispheres were particularly striking at 16, 22 and 30
degrees from the equator. Equatorial temperature variations are also
anticorrelated with those 60-70 km above. Such behavior suggests a top-down
control of equatorial tropospheric temperatures from stratospheric dynamics.
Realistic future global climate models must address the origins of these
variations in preparation for their extension to a wider array of gas-giant
exoplanets.Comment: Primary file: 16 pages, 5 figures. Supplemental File (attached): 12
pages, 3 figures, 1 tabl
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