1,007 research outputs found
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
Long-term calorie restriction in humans is not associated with indices of delayed immunologic aging: A descriptive study.
BACKGROUND: Delayed immunologic aging is purported to be a major mechanism through which calorie restriction (CR) exerts its anti-aging effects in non-human species. However, in non-obese humans, the effect of CR on the immune system has been understudied relative to its effects on the cardiometabolic system. OBJECTIVE: To examine whether CR is associated with delayed immunologic aging in non-obese humans. METHODS: We tested whether long-term CR practitioners (average 10.03 years of CR) evidenced decreased expression of T cell immunosenescence markers and longer immune cell telomeres compared to gender-, race/ethnicity-, age-, and education-matched "healthy" Body Mass Index (BMI) and "overweight"/"obese" BMI groups. RESULTS: Long-term human CR practitioners had lower BMI (p < 0.001) and fasting glucose (p < 0.001), as expected. They showed similar frequencies of pre-senescent cells (CD8+CD28- T cells and CD57 and PD-1 expressing T cells) to the comparison groups. Even after adjusting for covariates, including cytomegalovirus status, we observed shorter peripheral blood mononuclear cell telomeres in the CR group (p = 0.012) and no difference in granulocyte telomeres between groups (p = 0.42). CONCLUSIONS: We observed no clear evidence that CR as it is currently practiced in humans delays immune aging related to telomere length or T cell immunosenescent markers
Primarily neutral effects of river restoration on macroinvertebrates, macrophytes, and fishes after a decade of monitoring
Restoring river habitat heterogeneity is expensive and time consuming, yet often has little effect on aquatic biota. Such poor restoration outcomes could be partly caused by the predominance of short‐term studies, which do not account for natural temporal fluctuations nor changes in the effects of restoration through time. Consequently, research that examines the longer‐term dynamics of river restoration is crucial for providing a temporal perspective of restoration outcomes and for informing the effectiveness of restoration methods. We used the Nidda River in Germany as a case study of the temporal effects of river hydromorphological restoration on different aquatic taxa. We surveyed macroinvertebrate, macrophyte, and fish communities across three sites prerestoration (2008) and then monitored changes in one control versus two restored sites across 10 years (2010–2019). Overall, we found few effects of restoration on the macroinvertebrate and macrophyte communities, with no effects whatsoever on fishes. Restoration improved some components of the macroinvertebrate and macrophyte communities; however, these positive effects were temporally inconsistent and did not translate to improvements in river ecosystem health (based on an index of ecological quality). Our findings illustrate how allowing for more time for community development will not necessarily alter the fact that local‐scale river habitat restoration can elicit little to no change in aquatic communities. Combining local‐ with broad‐scale restoration efforts that address the primary drivers of hydroecological decline, in addition to long‐term monitoring, may therefore be required to ensure that river restorations successfully meet their ecological goals
First Operation of a Resistive Shell Liquid Argon Time Projection Chamber -- A new Approach to Electric-Field Shaping
We present a new technology for the shaping of the electric field in Time
Projection Chambers (TPCs) using a carbon-loaded polyimide foil. This
technology allows for the minimisation of passive material near the active
volume of the TPC and thus is capable to reduce background events originating
from radioactive decays or scattering on the material itself. Furthermore, the
high and continuous electric resistivity of the foil limits the power
dissipation per unit area and minimizes the risks of damages in the case of an
electric field breakdown. Replacing the conventional field cage with a
resistive plastic film structure called 'shell' decreases the number of
components within the TPC and therefore reduces the potential points of failure
when operating the detector. A prototype liquid argon (LAr) TPC with such a
resistive shell and with a cathode made of the same material was successfully
tested for long term operation with electric field values up to about 1.5
kV/cm. The experiment shows that it is feasible to successfully produce and
shape the electric field in liquefied noble-gas detectors with this new
technology.Comment: 13 page
The influence of barefoot and barefoot inspired footwear on the kinetics and kinematics of running in comparison to conventional running shoes.
Barefoot running has experienced a resurgence in footwear biomechanics literature, based on the supposition that it serves to reduce the occurrence of overuse injuries in comparison to conventional shoe models. This consensus has lead footwear manufacturers to develop shoes which aim to mimic the mechanics of barefoot locomotion.
This study compared the impact kinetics and 3-D joint angular kinematics observed whilst running: barefoot, in conventional cushioned running shoes and in shoes designed to integrate the perceived benefits of barefoot locomotion. The aim of the current investigation was therefore to determine whether differences in impact kinetics exist between the footwear conditions and whether shoes which aim to simulate barefoot movement patterns can closely mimic the 3-D kinematics of barefoot running.
Twelve participants ran at 4.0 m.s-1±5% in each footwear condition. Angular joint kinematics from the hip, knee and ankle in the sagittal, coronal and transverse planes were measured using an eight camera motion analysis system. In addition simultaneous tibial acceleration and ground reaction forces were obtained. Impact parameters and joint kinematics were subsequently compared using repeated measures ANOVAs.
The kinematic analysis indicates that in comparison to the conventional and barefoot inspired shoes that running barefoot was associated significantly greater plantar-flexion at footstrike and range of motion to peak dorsiflexion. Furthermore, the kinetic analysis revealed that compared to the conventional footwear impact parameters were significantly greater in the barefoot condition.
Therefore this study suggests that barefoot running is associated with impact kinetics linked to an increased risk of overuse injury, when compared to conventional shod running. Furthermore, the mechanics of the shoes which aim to simulate barefoot movement patterns do not appear to closely mimic the kinematics of barefoot locomotion
The impact of submaximal exercise during heat and/or hypoxia on the cardiovascular and monocyte HSP72 responses to subsequent (post 24 h) exercise in hypoxia
Background: The aims of this study were to describe the cellular stress response to prolonged endurance exercise in acute heat, hypoxia and the combination of heat and hypoxia and to determine whether prior acute exposure to these stressors improved cellular tolerance to a subsequent exercise bout in hypoxia 24 h later. Methods: Twelve males (age 22 ± 4 years, height 1.77 ± 0.05 m, mass 79 ± 12.9 kg, VO2 max 3.57 ± 0.7 L · min-1) completed four trials (30-min rest, 90-min cycling at 50% normoxic VO2 max) in normothermic normoxia (NORM; 18°C, FIO2 = 0.21), heat (HEAT; 40°C, 20% RH), hypoxia (HYP; FIO2 = 0.14) or a combination of heat and hypoxia (COM; 40°C, 20% RH, FIO2 = 0.14) separated by at least 7 days. Twenty-four hours after each trial, participants completed a hypoxic stress test (HST; 15-min rest, 60-min cycling at 50% normoxic VO2 max, FIO2 = 0.14). Monocyte heat shock protein 72 (mHSP72) was assessed immediately before and after each exercise bout. Results: mHSP72 increased post exercise in NORM (107% ± 5.5%, p > 0.05), HYP (126% ± 16%, p
An enhanced functional ability questionnaire (faVIQ) to measure the impact of rehabilitation services on the visually impaired
AIM To develop a short, enhanced functional ability Quality of Vision (faVIQ) instrument based on previous questionnaires employing comprehensive modern statistical techniques to ensure the use of an appropriate response scale, items and scoring of the visual related difficulties experienced by patients with visual impairment. METHODS Items in current quality-of-life questionnaires for the visually impaired were refined by a multi-professional group and visually impaired focus groups. The resulting 76 items were completed by 293 visually impaired patients with stable vision on two occasions separated by a month. The faVIQ scores of 75 patients with no ocular pathology were compared to 75 age and gender matched patients with visual im pairm ent. RESULTS Rasch analysis reduced the faVIQ items to 27. Correlation to standard visual metrics was moderate (r=0.32-0.46) and to the NEI-VFQ was 0.48. The faVIQ was able to clearly discriminate between age and gender matched populations with no ocular pathology and visual impairment with an index of 0.983 and 95% sensitivity and 95% specificity using a cut off of 29. CONCLUSION The faVIQ allows sensitive assessm ent of quality-of-life in the visually im paired and should support studies which evaluate the effectiveness of low vision rehabilitation services. © Copyright International Journal of Ophthalmology Press
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
Demonstration of a switchable damping system to allow low-noise operation of high-Q low-mass suspension systems
Low mass suspension systems with high-Q pendulum stages are used to enable
quantum radiation pressure noise limited experiments. Utilising multiple
pendulum stages with vertical blade springs and materials with high quality
factors provides attenuation of seismic and thermal noise, however damping of
these high-Q pendulum systems in multiple degrees of freedom is essential for
practical implementation. Viscous damping such as eddy-current damping can be
employed but introduces displacement noise from force noise due to thermal
fluctuations in the damping system. In this paper we demonstrate a passive
damping system with adjustable damping strength as a solution for this problem
that can be used for low mass suspension systems without adding additional
displacement noise in science mode. We show a reduction of the damping factor
by a factor of 8 on a test suspension and provide a general optimisation for
this system.Comment: 5 pages, 5 figure
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