Abstract
As the global climate warms, a key question is how increased leaf temperatures will affect tree physiology and the coupling between leaf and air temperatures in forests. To explore the ...impact of increasing temperatures on plant performance in open air, we warmed leaves in the canopy of two mature evergreen forests, a temperate Eucalyptus woodland and a tropical rainforest. The leaf heaters consistently maintained leaves at a target of 4 °C above ambient leaf temperatures. Ambient leaf temperatures (Tleaf) were mostly coupled to air temperatures (Tair), but at times, leaves could be 8–10 °C warmer than ambient air temperatures, especially in full sun. At both sites, Tleaf was warmer at higher air temperatures (Tair > 25 °C), but was cooler at lower Tair, contrary to the ‘leaf homeothermy hypothesis’. Warmed leaves showed significantly lower stomatal conductance (−0.05 mol m−2 s−1 or −43% across species) and net photosynthesis (−3.91 μmol m−2 s−1 or −39%), with similar rates in leaf respiration rates at a common temperature (no acclimation). Increased canopy leaf temperatures due to future warming could reduce carbon assimilation via reduced photosynthesis in these forests, potentially weakening the land carbon sink in tropical and temperate forests.
Graphical abstract
Efficient bacterial chromosome segregation typically requires the coordinated action of a three-component machinery, fueled by adenosine triphosphate, called the partition complex. We present a ...phenomenological model accounting for the dynamic activity of this system that is also relevant for the physics of catalytic particles in active environments. The model is obtained by coupling simple linear reaction-diffusion equations with a proteophoresis, or "volumetric" chemophoresis, force field that arises from protein-protein interactions and provides a physically viable mechanism for complex translocation. This minimal description captures most known experimental observations: dynamic oscillations of complex components, complex separation, and subsequent symmetrical positioning. The predictions of our model are in phenomenological agreement with and provide substantial insight into recent experiments. From a nonlinear physics view point, this system explores the active separation of matter at micrometric scales with a dynamical instability between static positioning and traveling wave regimes triggered by the dynamical spontaneous breaking of rotational symmetry.
We report pump-probe transient absorption measurements addressing the photocycle of the Germanium lone pair center (GLPC) point defect with an unprecedented time resolution. The GLPC is a model point ...defect with a simple and well-understood electronic structure, highly relevant for several applications. Therefore, a full explanation of its photocycle is fundamental to understand the relaxation mechanisms of such molecular-like systems in solid state. The experiment, carried out exciting the sample resonantly with the ultraviolet (UV) GLPC absorption band peaked at 5.1 eV, gave us the possibility to follow the defect excitation-relaxation dynamics from the femto-picosecond to the nanosecond timescale in the UV-visible range. Moreover, the transient absorption signal was studied as a function of the excitation photon energy and comparative experiments were conducted on highly- and weakly-germanium doped silica glasses. The results offer a comprehensive picture of the relaxation dynamics of GLPC and allow observing the interplay between electronic transitions localized on the defect and those related to bandgap transitions, providing a clear evidence that the role of dopant high concentration is not negligible in the earliest dynamics.
Hard X‐ray microscopy is a prominent tool suitable for nanoscale‐resolution non‐destructive imaging of various materials used in different areas of science and technology. With an ongoing effort to ...push the 2D/3D imaging resolution down to 10 nm in the hard X‐ray regime, both the fabrication of nano‐focusing optics and the stability of the microscope using those optics become extremely challenging. In this work a microscopy system designed and constructed to accommodate multilayer Laue lenses as nanofocusing optics is presented. The developed apparatus has been thoroughly characterized in terms of resolution and stability followed by imaging experiments at a synchrotron facility. Drift rates of ∼2 nm h−1 accompanied by 13 nm × 33 nm imaging resolution at 11.8 keV are reported.
The size distribution of the vertical flux of dust freshly emitted from a wind‐eroded surface was recently shown to depend on the thermal stratification of the surface boundary layer (SBL). These new ...results question the way dust emission is currently represented in the dust models and emphasize the need to identify the factors controlling the intensity and size‐resolved dust flux at emission. In this study, we re‐analyze the data of two major campaigns (JADE and WIND‐O‐V) performed on unvegetated plots and during which the characteristics of the (a) surface of the eroding fields, (b) aerodynamic conditions (wind speed, stability of the SBL), (c) saltation flux (intensity and size distribution), and (d) vertical dust flux (intensity and size distribution) determined by the gradient method were carefully documented. The magnitude and size distribution of the vertical dust flux are found to be deeply intertwined and to be controlled in the first place by the kinetic energy of the saltating sand grains, and to a lesser extent by the size‐dependent uplift of the sandblasted particles. In unstable conditions coarser sand grains are mobilized, which increases the kinetic energy of the saltation flux and leads to the production of finer particles by sandblasting. Conversely, the uplift of supermicron particles is facilitated by the increase of the wind friction velocity, which results in an enrichment of the vertical dust flux in the coarsest particles at large wind speeds. The implications of these new findings are particularly important for the modeling of the dust emission/transport/deposition cycle.
Key Points
During erosion events, vertical dust flux is not linearly proportional to saltation flux
The size of emitted dust is controlled by the kinetic energy of the saltating sand grains
The vertical dust flux is enriched in fine particles during intense events and in unstable conditions
•Retrospective study of primary and secondary general anesthesia for cesarean.•Evaluated a composite neonatal outcome (umbilical artery pH and 5-min Apgar score)•No difference in neonatal outcome ...between primary and secondary general anesthesia.•Gestational age and ‘code-red’ cesarean were risk factors for poor neonatal outcome.
The conversion of neuraxial anesthesia (NA) to general anesthesia (GA) during a cesarean section (CS) may be associated with a higher risk of neonatal morbidity by adding the undesirable effects of both these anesthesia techniques. We aimed to compare the neonatal morbidity of non-elective CS performed after conversion from NA to GA (secondary GA) vs. that after GA from the outset (primary GA).
We performed a monocentric retrospective study at the Angers University Hospital (France). All non-elective CSs performed under GA between January 2015 and December 2019 were included. The CSs were classified using a three-color coding system (green for non-urgent delivery, orange for urgent CS, and red for very urgent CS). The primary neonatal outcome was a composite of umbilical artery pH <7.10 or 5-min Apgar score <7. The crude and adjusted odds ratios (OR) for the risk of neonatal morbidity associated with secondary GA were estimated.
We included 247 patients, of whom 101 (41.3%) had a secondary GA and 146 (58.7%) had primary GA. In the secondary GA group, 86.1% (87/101) had epidural anesthesia and 13.9% (14/101) had spinal anesthesia. Multivariate analysis showed no difference in neonatal morbidity between the two groups (adjusted odds ratio 1.18, 95% CI 0.56 to 2.51).
Our study found insufficient evidence to identify a difference in neonatal outcomes between secondary compared with primary GA for CS, regardless of the level of emergency. However, our study is underpowered and additional studies are needed to confirm these data.
Hard X-ray microscopy is a prominent tool suitable for nanoscale-resolution non-destructive imaging of various materials used in different areas of science and technology. With an ongoing effort to ...push the 2D/3D imaging resolution down to 10nm in the hard X-ray regime, both the fabrication of nano-focusing optics and the stability of the microscope using those optics become extremely challenging. In this work a microscopy system designed and constructed to accommodate multilayer Laue lenses as nanofocusing optics is presented. The developed apparatus has been thoroughly characterized in terms of resolution and stability followed by imaging experiments at a synchrotron facility. Drift rates of 2nmh-1 accompanied by 13nm × 33nm imaging resolution at 11.8keV are reported.
The SopA protein plays an essential, though so far undefined, role in partition of the mini‐F plasmid but, when overproduced, it causes loss of mini‐F from growing cells. Our investigation of this ...phenomenon has revealed that excess SopA protein reduces the linking number of mini‐F. It appears to do so by disturbing the partition complex, in which SopB normally introduces local positive supercoiling upon binding to the sopC centromere, as it occurs only in plasmids carrying sopC and in the presence of SopB protein. SopA‐induced reduction in linking number is not associated with altered sop promoter activity or levels of SopB protein and occurs in the absence of changes in overall supercoil density. SopA protein mutated in the ATPase nucleotide‐binding site (K120Q) or lacking the presumed SopB interaction domain does not induce the reduction in linking number, suggesting that excess SopA disrupts the partition complex by interacting with SopB to remove positive supercoils in an ATP‐dependent manner. Destabilization of mini‐F also depends on sopC and SopB, but the K120Q mutant retains some capacity for destabilizing mini‐F. SopA‐induced destabilization thus appears to be complex and may involve more than one SopA activity. The results are interpreted in terms of a regulatory role for SopA in the oligomerization of SopB dimers bound to the centromere.
The potential health impacts of chronic exposures to uranium, as they occur in occupational settings, are not well characterized. Most epidemiological studies have been limited by small sample sizes, ...and a lack of harmonization of methods used to quantify radiation doses resulting from uranium exposure. Experimental studies have shown that uranium has biological effects, but their implications for human health are not clear. New studies that would combine the strengths of large, well-designed epidemiological datasets with those of state-of-the-art biological methods would help improve the characterization of the biological and health effects of occupational uranium exposure. The aim of the European Commission concerted action CURE (Concerted Uranium Research in Europe) was to develop protocols for such a future collaborative research project, in which dosimetry, epidemiology and biology would be integrated to better characterize the effects of occupational uranium exposure. These protocols were developed from existing European cohorts of workers exposed to uranium together with expertise in epidemiology, biology and dosimetry of CURE partner institutions. The preparatory work of CURE should allow a large scale collaborative project to be launched, in order to better characterize the effects of uranium exposure and more generally of alpha particles and low doses of ionizing radiation.
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