Highlights ► The fraction of exhaled nitric oxide ( F E NO ) increased during 6 h of normobaric hypoxia exposure. ► Subjects who developed acute mountain sickness had lower F E NO at baseline ...compared to subjects who did not develop the condition. ► Innate nitric oxide production could contribute to acute mountain sickness susceptibility.
ABSTRACT
Stomata respond to increasing leaf‐to‐air vapour pressure difference (LAVPD) (D) by closing. The mechanism by which this occurs is debated. A role for feedback and peristomatal transpiration ...has been proposed. In this paper, we apply a recent mechanistic model of stomatal behaviour, and compare model and experimental data for the influence of increasing D on stomatal conductance.
We manipulated cuticular conductance (gc) by three independent methods. First, we increased gc by using a solvent mixture applied to both leaf surfaces prior to determining stomatal responses to D; second, we increased gc by increasing leaf temperature at constant D; and third, we coated a small area of leaf with a light oil to decrease gc. In all three experiments, experimental data and model outputs showed very close agreement.
We conclude, from the close agreement between model and experimental data and the fact that manipulations of gc, and hence cuticular transpiration, influenced gs in ways consistent with a feedback mechanism, that feedback is central in determining stomatal responses to D.
Data on the distribution of root biomass are critical to understanding the ecophysiology of vegetation communities. This is particularly true when models are applied to describe ecohydrology and ...vegetation function. However, there is a paucity of such information across continental Australia. We quantified vertical and horizontal root biomass distribution in a woodland dominated by Angophora bakeri and Eucalyptus sclerophylla on the Cumberland Plains near Richmond, New South Wales. The site was characterised by a duplex (texture contrast) soil with the A horizon (to 70 cm) consisting of loamy sand and the B horizon (to > 10 m) consisting of sandy clay. The topsoil had a smaller bulk density, a smaller water holding capacity but a larger organic component and a larger hydraulic conductivity in comparison to the subsoil. Root biomass was sampled to 1.5 m depth and declined through the soil profile. Whilst total biomass in the B horizon was relatively small, its contribution to the function of the trees was highly significant. Coarse roots accounted for approximately 82% of the root mass recovered. Lateral distribution of fine roots was generally even but coarse roots were more likely to occur closer to tree stems. Variation in tree diameter explained 75% of the variation in total below-ground biomass. The trench method suggested the belowground biomass was 6.03 ± 1.21 kg m⁻² but this method created bias towards sampling close to tree stems. We found that approximately 68% of root material was within a 2 m radius of tree stems and this made up 54% of the total number of samples but in reality, only approximately 5 to 10% of the site is within a 2 m radius of tree stems. Based on these proportions, our recalculated belowground biomass was 2.93 ± 0.59 kg m⁻². These measurements provide valuable data for modeling of ecosystem water use and productivity.
Water availability has long been recognized as an important driver of species distribution patterns in forests. The conifer Agathis australis (D. Don) Lindl. (kauri; Araucariaceae) grows in the ...species-rich forests of northern New Zealand. It is accompanied by distinctive species assemblages, and during summer the soil beneath A. australis is often significantly drier than soils beneath surrounding broadleaved angiosperm canopy species. We used a shade house dry-down experiment to determine whether species that grow close to A. australis differed in drought tolerance physiology compared with species that rarely grow close to A. australis. Stomatal conductance (g(s)) was plotted against leaf water potential (ψ) to identify drought tolerance strategies. Seedlings of species that occur in close spatial association with A. australis (including A. australis seedlings) were most resistant to drought stress, and all displayed a drought avoidance strategy of either declining gs to maintain ψ or simultaneous declines in g(s) and ψ. The species not commonly occurring beneath A. australis, but abundant in the surrounding forest, were the most drought-sensitive species and succumbed relatively quickly to drought-induced mortality with rapidly declining gs and ψ values. These results were confirmed with diurnal measurements of g(s) and assimilation rates throughout the day, and leaf wilting analysis. We conclude that the varied abilities of the species to survive periods of drought stress as seedlings shapes the composition of the plant communities beneath A. australis trees. Furthermore, forest diversity may be impacted by climate change as the predicted intensification of droughts in northern New Zealand is likely to select for drought-tolerant species over drought-intolerant species.
The Laser Interferometer Gravitational Wave Observatory (LIGO) has been directly detecting gravitational waves from compact binary mergers since 2015. We report on the first use of squeezed vacuum ...states in the direct measurement of gravitational waves with the Advanced LIGO H1 and L1 detectors. This achievement is the culmination of decades of research to implement squeezed states in gravitational-wave detectors. During the ongoing O3 observation run, squeezed states are improving the sensitivity of the LIGO interferometers to signals above 50 Hz by up to 3 dB, thereby increasing the expected detection rate by 40% (H1) and 50% (L1).
On April 1st, 2019, the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), joined by the Advanced Virgo detector, began the third observing run, a year-long dedicated search for ...gravitational radiation. The LIGO detectors have achieved a higher duty cycle and greater sensitivity to gravitational waves than ever before, with LIGO Hanford achieving angle-averaged sensitivity to binary neutron star coalescences to a distance of 111 Mpc, and LIGO Livingston to 134 Mpc with duty factors of 74.6% and 77.0% respectively. The improvement in sensitivity and stability is a result of several upgrades to the detectors, including doubled intracavity power, the addition of an in-vacuum optical parametric oscillator for squeezed-light injection, replacement of core optics and end reaction masses, and installation of acoustic mode dampers. This paper explores the purposes behind these upgrades, and explains to the best of our knowledge the noise currently limiting the sensitivity of each detector.
Detecting de novo mutations in viral and bacterial pathogens enables researchers to reconstruct detailed networks of disease transmission and is a key technique in genomic epidemiology. However, ...these techniques have not yet been applied to the malaria parasite, Plasmodium falciparum, in which a larger genome, slower generation times, and a complex life cycle make them difficult to implement. Here, we demonstrate the viability of de novo mutation studies in P. falciparum for the first time. Using a combination of sequencing, library preparation, and genotyping methods that have been optimized for accuracy in low-complexity genomic regions, we have detected de novo mutations that distinguish nominally identical parasites from clonal lineages. Despite its slower evolutionary rate compared with bacterial or viral species, de novo mutation can be detected in P. falciparum across timescales of just 1-2 years and evolutionary rates in low-complexity regions of the genome can be up to twice that detected in the rest of the genome. The increased mutation rate allows the identification of separate clade expansions that cannot be found using previous genomic epidemiology approaches and could be a crucial tool for mapping residual transmission patterns in disease elimination campaigns and reintroduction scenarios.
The Laser Interferometer Gravitational Wave Observatory (LIGO) consists of two widely separated 4 km laser interferometers designed to detect gravitational waves from distant astrophysical sources in ...the frequency range from 10 Hz to 10 kHz. The first observation run of the Advanced LIGO detectors started in September 2015 and ended in January 2016. A strain sensitivity of better than 10 super(-23)/radicalHz was achieved around 100 Hz. Understanding both the fundamental and the technical noise sources was critical for increasing the astrophysical strain sensitivity. The average distance at which coalescing binary black hole systems with individual masses of 30Mmiddot could be detected above a signal-to-noise ratio (SNR) of 8 was 1.3 Gpc, and the range for binary neutron star inspirals was about 75 Mpc. With respect to the initial detectors, the observable volume of the Universe increased by a factor 69 and 43, respectively. These improvements helped Advanced LIGO to detect the gravitational wave signal from the binary black hole coalescence, known as GW150914.
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