126 research outputs found
Contributions of Astronauts Aerobic Exercise Intensity and Time on Change in VO2peak during Spaceflight
There is considerable variability among astronauts with respect to changes in maximal aerobic capacity (VO2peak) during International Space Station (ISS) missions, ranging from a 5% increase to 30% decline. Individual differences may be due to in-flight aerobic exercise time and intensity. PURPOSE: To evaluate the effects of in-flight aerobic exercise time and intensity on change in VO2peak during ISS missions. METHODS: Astronauts (N=11) performed peak cycle tests approx 60 days before flight (L-60), on flight day (FD) approx 14, and every approx 30 days thereafter. Metabolic gas analysis and heart rate (HR) were measured continuously during the test using the portable pulmonary function system. HR and duration of each in-flight cycle ergometer and treadmill (TM) session were recorded and averaged in time segments corresponding to each peak test. Mixed effects linear regression with exercise mode (TM or cycle) as a categorical variable was used to assess the contributions of exercise intensity (%time >70% peak HR or %time >90% peak HR) and time (min/wk), adjusted for body weight, on %change in VO2peak during the mission, and incorporating the repeated-measures experimental design. RESULTS: 110 observations were included in the model (4-6 peak cycle tests per astronaut, 2 exercise devices). VO2peak was reduced from preflight throughout the mission (FD14: 13+/-13% and FD 105: 8+/-10%). Exercise intensity (%peak HR: FD14=66+/-14; FD105=75+/-8) and time (min/wk: FD14=82+/-46; FD105=158+/-40) increased during flight. The models showed main effects for exercise time and intensity with no interactions between time, intensity, and device (70% peak HR: time [z-score=2.39; P=0.017], intensity [z-score=3.51; P=0.000]; 90% peak HR: time [zscore= 3.31; P=0.001], intensity [z-score=2.24; P=0.025]). CONCLUSION: Exercise time and intensity independently contribute to %change in VO2peak during ISS missions, indicating that there are minimal values for exercise time and intensity required to maintain VO2peak. As the FD105 average exercise intensity and time did not prevent a decline in VO2peak from preflight, astronauts' exercise prescriptions should target at least 160 min of weekly aerobic exercise at an average above 75% peak HR with increased time at intensities above 90% of peak HR starting early in the mission
Evaluation of the Danish Aerospace Corporation Portable Pulmonary Function System
A research project designed to investigate changes in maximal oxygen consumption (VO2max) during and following long duration flight on the International Space Station (ISS) has recently been completed. The device used to measure VO2 on board ISS, the Portable Pulmonary Function System (PPFS) manufactured by the Danish Aerospace Corporation (DAC), is based on previous-generation devices manufactured by DAC, but the PPFS has not been validated for analyzing metabolic gases or measuring cardiac output (Qc). The purpose of the present evaluation is to compare PPFS metabolic gas analysis measurements to measurements obtained using a clinically-validated system (ParvoMedics TrueOne(c) 2400 system; Parvo). In addition, Qc data collected with the PPFS were compared to Qc measurements from echocardiography. METHODS: Ten subjects completed three cycle exercise tests to maximal exertion. The first test was conducted to determine each subject's VO2max and set the work rates for the second and third (comparison) tests. The protocol for the two comparison tests consisted of three 5-minute stages designed to elicit 25%, 50%, and 75% VO2max (based upon results from the initial test), followed by 1-minute stages of increasing work rate (25 watt/minute) until the subject reached maximal effort. During one of the two comparison tests, metabolic gases and Qc were assessed with the PPFS; metabolic gases and Qc were assessed with the Parvo and by echocardiography, respectively, during the other test. The order of the comparison tests was counterbalanced. VO2max and maximal work rate during the comparison tests were compared using t tests. Mixed-effects regression modeling was used to analyze submaximal data. RESULTS: All of the data were within normal physiological ranges. The PPFS-measured values for VO2max were 6% lower than values obtained with the Parvo (PPFS: 3.11 +/- 0.75 L/min; Parvo: 3.32 +/- 0.87 L/min; mean +/- standard deviation; P = 0.02); this difference is probably due to flow restriction imposed by the PPFS Qc accessories. Submaximal VO2 values were slightly lower when measured with the PPFS, although differences were not physiologically relevant. The PPFS-measured values of submaximal carbon dioxide production (VCO2) were lower than the data obtained from Parvo, which could be attributed to lower fractions of expired carbon dioxide measured by the PPFS. The PPFS Qc values tended to be lower than echocardiography-derived values. CONCLUSIONS: The results of the present study indicate a need to further examine the PPFS and to better quantify its reproducibility; however, none of the findings of the current evaluation indicate that the PPFS needs to be replaced or modified
Reliability of the Danish Aerospace Corporation Portable Pulmonary Function System
Metabolic gas analysis is a critical component of investigations that measure cardio-pulmonary exercise responses during and after long-duration spaceflight. The primary purpose of the current study was to determine the reliability and intra-subject repeatability of a metabolic gas analysis device, the Portable Pulmonary Function System (PPFS), designed for use on the International Space Station (ISS). The second objective of this study was to directly compare PPFS measurements of expired oxygen and carbon dioxide (FEO2 and FECO2) to values obtained from a well-validated clinical metabolic gas analysis system (ParvoMedics TrueOne (c) [PM]). Eight subjects performed four peak cycle tests to maximal exertion. The first test was used to prescribe work rates for the subsequent test sessions. Metabolic gas analysis for this test was performed by the PM, but samples of FEO2 and FECO2 also were simultaneously collected for analysis by the PPFS. Subjects then performed three additional peak cycle tests, consisting of three 5-min stages designed to elicit 25%, 50%, and 75% maximal oxygen consumption (VO2max) followed by stepwise increases of 25 W/min until subjects reached volitional exhaustion. Metabolic gas analysis was performed using the PPFS for these tests. Intraclass correlation coefficients (ICC), within-subject standard deviations (WS SD), and coefficients of variation (CV%) were calculated for the repeated exercise tests. Mixed model regression analysis was used to compare paired FEO2 and FECO2 values obtained from the PPFS and the PM during the initial test. The ICC values for oxygen consumption (VO2), carbon dioxide production (VCO2), and ventilation (VE) indicate that the PPFS is highly reliable (0.79 to 0.99) for all exercise levels tested; however, ICCs for respiratory exchange ratio (RER) were low ( 0.11 - 0.51), indicating poor agreement between trials during submaximal and maximal exercise. Overall, CVs ranged from 1.6% to 6.7% for all measurements, a finding consistent with reported values that were obtained using other metabolic gas analysis techniques. The PPFS and PM produced comparable FEO2 data; however, there was less agreement between measures of FECO2 obtained from the two devices, particularly at lower CO2 concentrations. The PPFS appears, in practically all respects, to yield highly reliable metabolic gas analysis data. Lower reliability of RER measurements reported in the literature and likely is not a function of the PPFS device. Further examination of PPFS CO2 data is warranted to better understand the limitations of these PPFS measurements. Overall, the PPFS when used for repeated measures of cardio-pulmonary exercise should provide accurate and reliable data for studies of human adaptation to spaceflight
Peak Oxygen Uptake during and after Long-duration Space Flight
Aerobic capacity (VO2peak) previously has not been measured during or after long-duration spaceflight. PURPOSE: To measure VO2peak and submaximal exercise responses during and after International Space Station (ISS) missions. METHODS: Astronauts (9 M, 5 F: 49 +/- 5 yr, 175 +/- 7 cm, 77.2 +/- 15.1 kg, 40.6 +/- 6.4 mL/kg/min [mean +/-SD]) performed graded peak cycle tests ~90 days before spaceflight, 15 d (FD15) after launch and every ~30 d thereafter during flight, and 1 (R+1), 10 (R+10), and 30 d (R+30) after landing. Oxygen consumption (VO2) and heart rate (HR) were measured from rest to peak exercise, while cardiac output (Q), stroke volume (SV), and arterial-venous oxygen difference (a-vO2diff) were measured only during rest and submaximal exercise. Data were analyzed using mixed-model linear regression. Body mass contributed significantly to statistical models, and thus results are reported as modeled estimates for an average subject. RESULTS: Early inflight (FD15) VO2peak was 17% lower (95% CI = - 22%, -13%) than preflight. VO2peak increased during spaceflight (0.001 L/min/d, P = 0.02) but did not return to preflight levels. On R+1 VO2peak was 15% (95% CI = -19%, -10%) lower than preflight but recovered to within 2% of preflight by R+30 (95% CI = -6%, +3%). Peak HR was not significantly different from preflight at any time. Inflight submaximal VO2 and a-vO2diff were generally lower than preflight, but the Q vs. VO2 slope was unchanged. In contrast, the SV vs. VO2 slope was lower (P < 0.001), primarily due to elevated SV at rest, and the HR vs. VO2 slope was greater (P < 0.001), largely due to elevated HR during more intense exercise. On R+1 although the relationships between VO2 and Q, SV, and HR were not statistically different than preflight, resting and submaximal exercise SV was lower (P < 0.001), resting and submaximal exercise HR was higher (P < 0.002), and a-vO2diff was unchanged. HR and SV returned to preflight levels by R+30. CONCLUSION: In the average astronaut VO2peak was reduced during spaceflight and immediately after landing but factors contributing to lower VO2peak may be different during spaceflight and recovery. Maintaining Q while VO2 is reduced inflight may be suggestive of an elevated blood flow to vascular beds other than exercising muscles, but decreased SV after flight likely reduces Q at peak exertion
Discrimination between bycatch and other causes of cetacean and pinniped stranding
© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Diseases of Aquatic Organisms 127 (2018): 83-95, doi:10.3354/dao03189.The challenge of identifying cause of death in discarded bycaught marine mammals stems from a combination of the non-specific nature of the lesions of drowning, the complex physiologic adaptations unique to breath-holding marine mammals, lack of case histories, and the diverse nature of fishing gear. While no pathognomonic lesions are recognized, signs of acute external entanglement, bulging or reddened eyes, recently ingested gastric contents, pulmonary changes, and decompression-associated gas bubbles have been identified in the condition of peracute underwater entrapment (PUE) syndrome in previous studies of marine mammals. We reviewed the gross necropsy and histopathology reports of 36 cetaceans and pinnipeds including 20 directly observed bycaught and 16 live stranded animals that were euthanized between 2005 and 2011 for lesions consistent with PUE. We identified 5 criteria which present at significantly higher rates in bycaught marine mammals: external signs of acute entanglement, red or bulging eyes, recently ingested gastric contents, multi-organ congestion, and disseminated gas bubbles detected grossly during the necropsy and histologically. In contrast, froth in the trachea or primary bronchi, and lung changes (i.e. wet, heavy, froth, edema, congestion, and hemorrhage) were poor indicators of PUE. This is the first study that provides insight into the different published parameters for PUE in bycatch. For regions frequently confronted by stranded marine mammals with non-specific lesions, this could potentially aid in the investigation and quantification of marine fisheries interactions.This work was supported by the Nat -
ional Oceanic and Atmospheric Administration (NOAA)
John H. Prescott Program NA12NMF4390144. The WHOI
Marine Mammal Center, Wick and Sloan Simmons, and the
University of Las Palmas de Gran Canaria provided postdoctoral
funding for Y.B.Q
The environmental dependence of the structure of outer galactic discs in STAGES spiral galaxies
We present an analysis of V-band radial surface brightness profiles for
spiral galaxies from the field and cluster environments using Hubble Space
Telescope/Advanced Camera for Surveys imaging and data from the Space Telescope
A901/2 Galaxy Evolution Survey (STAGES). We use a large sample of ~330 face-on
to intermediately inclined spiral galaxies and assess the effect of the galaxy
environment on the azimuthally averaged radial surface brightness mu profiles
for each galaxy in the outer stellar disc (24 < mu < 26.5 mag per sq arcsec).
For galaxies with a purely exponential outer disc (~50 per cent), we determine
the significance of an environmental dependence on the outer disc scalelength
h_out. For galaxies with a broken exponential in their outer disc, either
down-bending (truncation, ~10 per cent) or up-bending (anti-truncation, ~40 per
cent), we measure the strength T (outer-to-inner scalelength ratio,
log_10(h_out/h_in) of the mu breaks and determine the significance of an
environmental dependence on break strength T. Surprisingly, we find no evidence
to suggest any such environmental dependence on either outer disc scalelength
h_out or break strength T, implying that the galaxy environment is not
affecting the stellar distribution in the outer stellar disc. We also find that
for galaxies with small effective radii (r_e < 3 kpc) there is a lack of outer
disc truncations in both the field and cluster environments. Our results
suggest that the stellar distribution in the outer disc of spiral galaxies is
not significantly affected by the galaxy environment.Comment: Accepted to MNRAS. Appendix A available at
http://www.nottingham.ac.uk/~ppxdtm/STAGES_profiles_appendix.pd
Interacting Galaxies in the A901/902 Supercluster with STAGES
We present a study of galaxy mergers and the influence of environment in the
Abell 901/902 supercluster at z~0.165. We use HST ACS F606W data from the
STAGES survey, COMBO-17, Spitzer 24um, and XMM-Newton X-ray data. Our analysis
utilizes both a visual classification system, and quantitative CAS parameters
to identify systems which show evidence of a recent or ongoing merger of mass
ratio >1/10. Our results are: (1) After visual classification and minimizing
the contamination from false projection pairs, we find that the merger fraction
f_merge is 0.023+/-0.007. The estimated fractions of likely major mergers,
likely minor mergers, and ambiguous cases are 0.01+/-0.004, 0.006+/-0.003, and
0.007+/-0.003, respectively. (2) The mergers lie outside the cluster core of
radius R < 0.25 Mpc: the lack of mergers in the core is likely due to the large
galaxy velocity dispersion in the core. Mergers populate the region (0.25 Mpc <
R <= 2 Mpc) between the core and outskirt. In this region, the estimated
frequency of mergers is similar to those seen at typical group overdensities.
This suggests ongoing growth of the clusters via accretion of group and field
galaxies. (3) We compare our observed merger fraction with those reported in
other clusters and groups out to z~0.4. Existing data points on the merger
fraction for L<= L* galaxies in clusters allow for a range of evolutionary
scenarios. (4) The fraction of mergers, which lie on the blue cloud is
80%+/-18% versus 34%+/-7% for non-interacting galaxies, implying that
interacting galaxies are preferentially blue. (5) The average SFR, based on UV
or UV+IR data, is enhanced by a factor of ~1.5 to 2 in mergers compared to
non-interacting galaxies. However, mergers in the clusters contribute only a
small fraction (between 10% and 15%) of the total SFR density.(Abridged)Comment: Accepted for publication in ApJ. 34 pages, 16 figures. Version with
full resolution figures available at: http://www.as.utexas.edu/~alh/apj/int/
; updated abridged abstrac
Generalisability of vaccine effectiveness estimates: an analysis of cases included in a postlicensure evaluation of 13-valent pneumococcal conjugate vaccine in the USA
External validity, or generalisability, is the measure of how well results from a study pertain to individuals in the target population. We assessed generalisability, with respect to socioeconomic status, of estimates from a matched case–control study of 13-valent pneumococcal conjugate vaccine effectiveness for the prevention of invasive pneumococcal disease in children in the USA
The STAGES view of red spirals and dusty red galaxies: Mass-dependent quenching of star-formation in cluster infall
We investigate the properties of optically passive spirals and dusty red
galaxies in the A901/2 cluster complex at redshift ~0.17 using restframe
near-UV-optical SEDs, 24 micron IR data and HST morphologies from the STAGES
dataset. The cluster sample is based on COMBO-17 redshifts with an rms
precision of sigma_cz~2000 km/sec. We find that 'dusty red galaxies' and
'optically passive spirals' in A901/2 are largely the same phenomenon, and that
they form stars at a substantial rate, which is only 4x lower than that in blue
spirals at fixed mass. This star formation is more obscured than in blue
galaxies and its optical signatures are weak. They appear predominantly in the
stellar mass range of log M*/Msol=[10,11] where they constitute over half of
the star-forming galaxies in the cluster; they are thus a vital ingredient for
understanding the overall picture of star formation quenching in clusters. We
find that the mean specific SFR of star-forming galaxies in the cluster is
clearly lower than in the field, in contrast to the specific SFR properties of
blue galaxies alone, which appear similar in cluster and field. Such a rich red
spiral population is best explained if quenching is a slow process and
morphological transformation is delayed even more. At log M*/Msol<10, such
galaxies are rare, suggesting that their quenching is fast and accompanied by
morphological change. We note, that edge-on spirals play a minor role; despite
being dust-reddened they form only a small fraction of spirals independent of
environment.Comment: Accepted for publication in MNRA
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