The genus
We hypothesized that both larvae and adults of the heat and hypoxia‐adapted Tabasco‐line of the Nile tilapia
The hydration of the two most reactive phases of ordinary Portland cement (OPC), tricalcium silicate (C3S), and tricalcium aluminate (C3A) is successfully halted when the activity of water (
- NSF-PAR ID:
- 10454483
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 104
- Issue:
- 4
- ISSN:
- 0002-7820
- Page Range / eLocation ID:
- p. 1831-1840
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Oreochromis is among the most popular of the tilapiine cichlid tribe for aquaculture. However, their temperature and hypoxia tolerance, if tested at all, is usually tested at temperatures of 20–25°C, rather than at the considerably higher temperatures of 30–35°C typical of tropical aquaculture.Oreochromis niloticus would be relatively hypoxia‐tolerant. Oxygen consumption rate (), Q10and aquatic surface respiration (ASR) was measured using closed respirometry at 2 ( c . 0.2 g), 30 (c . 2–5 g), 105c . (10–15 g) and 240 (c . 250 g) days of development, at 25°C, 30°C and 35°C.at 30°C was inversely related to body mass: c . 90 μM O2g−1/h in larvae down toc . 1 μM O2g−1/h in young adults. Q10forwas typical for fish over the range 25–35°C of 1.5–2.0. ASR was exhibited by 50% of the fish at pO2of 15–50 mmHg in a temperature‐dependent fashion. However, the largest adults showed notable ASR only when pO2fell to below 10 mmHg. Remarkably, pcritfor was 12–17 mmHg at 25–30°C and still only 20–25 mmHg across development at 35°C. These values are among the lowest measured for teleost fishes. Noteworthy is that all fish maintain equilibrium, ventilated their gills and showed routine locomotor action for 10–20 min after ceased at near anoxia and when then returned to oxygenated waters, all fish survived, further indicating a remarkable hypoxic tolerance. Remarkably, data assembled for from >30 studies showed a > x2000 difference, which we attribute to calculation or conversion errors. Nonetheless, pcritwas very low for all Oreochromis sp. and lowest in the heat and hypoxia‐adapted Tabasco line. -
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Key points Extreme aviation is accompanied by ever‐present risks of hypobaric hypoxia and decompression sickness. Neuroprotection against those hazards is conferred through fractional inspired oxygen (
) concentrations of 60–100% (hyperoxia). Hyperoxia reduces global cerebral perfusion (gCBF), increases reactive oxygen species within the brain and leads to cell death within the hippocampus. However, an understanding of hyperoxia's effect on cortical activity and concomitant levels of cognitive performance is lacking. This limits our understanding of whether hyperoxia could lower the brain's threshold of tolerance to physiological stressors inherent to extreme aviation, such as high gravitational forces.
This study aimed to quantify the impact of hyperoxia upon global cerebral perfusion (gCBF), cognitive performance and cortical electroencephalography (EEG).
Hyperoxia evoked a rapid reduction in gCBF, yet cognitive performance and vigilance were enhanced. EEG measurements revealed enhanced alpha power, suggesting less desynchrony, within the cortical temporal regions.
Collectively, this work suggests hyperoxia‐induced brain hypoperfusion is accompanied by enhanced cognitive processing and cortical arousal.
Abstract Extreme aviators continually inspire hyperoxic gas to mitigate risk of hypoxia and decompression injury. This neuroprotection carries a physiological cost: reduced cerebral perfusion (CBF). As reduced CBF may increase vulnerability to ever‐present physiological challenges during extreme aviation, we defined the magnitude and duration of hyperoxia‐induced changes in CBF, cortical electrical activity and cognition in 30 healthy males and females. Magnetic resonance imaging with pulsed arterial spin labelling provided serial measurements of global CBF (gCBF), first during exposure to 21% inspired oxygen (
) followed by a 30‐min exposure to 100% . High‐density EEG facilitated characterization of cortical activity during assessment of cognitive performance, also measured during exposure to 21% and 100% . Acid‐base physiology was measured with arterial blood gases. We found that exposure to 100% reduced gCBF to 63% of baseline values across all participants. Cognitive performance testing at 21% was accompanied by increased theta and beta power with decreased alpha power across multiple cortical areas. During cognitive testing at 100% , alpha activity was less desynchronized within the temporal regions than at 21% . The collective hyperoxia‐induced changes in gCBF, cognitive performance and EEG were similar across observed partial pressures of arterial oxygen ( ), which ranged between 276–548 mmHg, and partial pressures of arterial carbon dioxide ( ), which ranged between 34–50 mmHg. Sex did not influence gCBF response to 100% . Our findings suggest hyperoxia‐induced reductions in gCBF evoke enhanced levels of cortical arousal and cognitive processing, similar to those occurring during a perceived threat. -
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Abstract The air‐sea exchange of oxygen (O2) is driven by changes in solubility, biological activity, and circulation. The total air‐sea exchange of O2has been shown to be closely related to the air‐sea exchange of heat on seasonal timescales, with the ratio of the seasonal flux of O2to heat varying with latitude, being higher in the extratropics and lower in the subtropics. This O2/heat ratio is both a fundamental biogeochemical property of air‐sea exchange and a convenient metric for testing earth system models. Current estimates of the O2/heat flux ratio rely on sparse observations of dissolved O2, leaving it fairly unconstrained. From a model ensemble we show that the ratio of the seasonal amplitude of two atmospheric tracers, atmospheric potential oxygen (APO) and the argon‐to‐nitrogen ratio (Ar/O2), exhibits a close relationship to the O2/heat ratio of the extratropics (40–
). The amplitude ratio, / , is relatively constant within the extratropics of each hemisphere due to the zonal mixing of the atmosphere. / is not sensitive to atmospheric transport, as most of the observed spatial variability in the seasonal amplitude of APO is compensated by similar variations in (Ar/ ). From the relationship between /heat and / in the model ensemble, we determine that the atmospheric observations suggest hemispherically distinct /heat flux ratios of 3.3 0.3 and 4.7 0.8 nmol between 40 and in the Northern and Southern Hemispheres respectively, providing a useful constraint for and heat air‐sea fluxes in earth system models and observation‐based data products. -
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Abstract Motivated by its potential use as a starting point for solving various cosmological constant problems, we study F‐theory compactified on the warped product
where Y 8is amanifold, and the S 3factor is the target space of anWess–Zumino–Witten (WZW) model at level N . Reduction to M‐theory exploits the abelian duality of this WZW model to anorbifold. In the large N limit, the untwisted sector is captured by 11D supergravity. The local dynamics of intersecting 7‐branes in thegeometry is controlled by a Donaldson–Witten twisted gauge theory coupled to defects. At late times, the system is governed by a 1D quantum mechanics system with a ground state annihilated by two real supercharges, which in four dimensions would appear as “ supersymmetry” on a curved background. This leads to a cancellation of zero point energies in the 4D field theory but a split mass spectrum for superpartners of order specified by the IR and UV cutoffs of the model. This is suggestively close to the TeV scale in some scenarios. The classical 4D geometry has an intrinsic instability which can produce either a collapsing or expanding Universe, the latter providing a promising starting point for a number of cosmological scenarios. The resulting 1D quantum mechanics in the time direction also provides an appealing starting point for a more detailed study of quantum cosmology. -
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Abstract A graph
G is said to be 2‐divisible if for all (nonempty) induced subgraphsH ofG ,can be partitioned into two sets such that and . (Here denotes the clique number of G , the number of vertices in a largest clique ofG ). A graphG is said to be perfectly divisible if for all induced subgraphsH ofG ,can be partitioned into two sets such that is perfect and . We prove that if a graph is ‐free, then it is 2‐divisible. We also prove that if a graph is bull‐free and either odd‐hole‐free or P 5‐free, then it is perfectly divisible.
