Tropical hydroelectric reservoirs are recognized hotspots for greenhouse gas emissions, yet the role of submerged forests in these emissions remains poorly understood. In this study, we investigated the contribution of standing dead trees and their associated epixylic biofilms to methane (CH4) and carbon dioxide (CO2) emissions in the permanently stratified Petit Saut reservoir, French Guiana. We conducted in situ measurements of greenhouse gas fluxes from submerged trunks at multiple depths using static chambers. To unravel the microbial mechanisms underlying CH4 dynamics, we characterized the active microbial communities and quantified methane production and oxidation rates in both wood and biofilm samples collected above and below the oxycline, using 16S rRNA sequencing and laboratory incubations. Our findings revealed that submerged wood serves as an unrecognized source of in situ CH4 production, primarily via acetoclastic methanogenesis dominated by Methanosaeta. In contrast, epixylic biofilms acted as effective CH4 sinks, with methane oxidation largely driven by Methylocystis. Microbial composition and activity showed strong vertical stratification, closely linked to oxygen availability. In situ fluxes mirrored these microbial patterns, with net CH4 and CO2 efflux observed below the oxycline and net influx above it. This study highlights the dual role of submerged wood and its surface biofilms in CH4 cycling, emphasizing the importance of microbial interactions in regulating greenhouse gas emissions from flooded tropical forests. These findings underscore the need to include wood-mediated processes in greenhouse gas budgets of tropical reservoirs, especially as dam construction continues to expand in forested tropical regions.
The applicability of short continuous artificial UV treatments has been studied to reduce the luminescence background in Raman spectra of plastics. Our method applies to two groups of polyethylene plastics, in which luminescence arises either from pigments or from surface contaminations such as biofilm or from a combination of both. Increasing the duration of continuous UV exposure resulted in decreased luminescence due to photobleaching. The evolution of surface morphology and chemical composition was monitored using optical spectromicroscopy. With progressive photobleaching, the signal-to-noise ratio of first-order Raman signatures improved, facilitating spectral analysis. In particular, we achieved a correlation rate exceeding 90% in the identification of polymers and their additives after treatment, which is mainly limited by the availability of reference databases. While the procedure allows for the rapid and non-destructive identification of polymeric species, it induces only minor chemical modifications at the surface, including the oxidation of functional groups.
Unrefreshing and non-restorative sleep is a hallmark complaint in people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). However, little is known about their habitual sleep and night-to-night fluctuations under real-life conditions. This study aimed to characterize sleep, and the intraindividual variability (IIV) of sleep in people living with ME/CFS compared with matched controls. In this case-control study, 38 ME/CFS and 38 controls wore a wrist accelerometer continuously for 7 days and completed concurrent sleep diaries, the Pittsburgh Sleep Quality Index (PSQI), and Epworth Sleepiness Scale (ESS). Within the ME/CFS group, participants were also stratified by symptom severity using the Bell Disability Scale. Sleep IIV was quantified using the coefficient of variation, the root mean square of successive differences, and the Bayesian variability model, respectively. Compared with controls, individuals with ME/CFS spent significantly more time in bed and exhibited poorer sleep efficiency (SE) (all p < 0.05). Despite a longer time in bed, total sleep time did not differ between groups. ME/CFS participants also displayed significantly greater IIV in SE. By contrast, sleep timing (bedtime) was more regular among ME/CFS. Exploratory analyses did not detect clear differences across ME/CFS severity subgroups for mean sleep variables or variability indices. Under real-life conditions, people with ME/CFS exhibit poor sleep quality and unstable SE. These findings highlight sleep IIV as a clinically relevant dimension of sleep health in ME/CFS. Unrefreshing sleep is a core symptom of ME/CFS, yet most evidence relies on single- or two-night laboratory assessments that may not reflect habitual sleep under real-life conditions. Moreover, night-to-night sleep variability, a potentially critical dimension of sleep health, has not been systematically examined in ME/CFS. Using week-long wrist accelerometry, this study shows that under free-living conditions sleep in ME/CFS is characterized not only by impaired sleep efficiency but also by pronounced night-to-night variability, despite relatively stable bedtime compared to controls. These findings highlight sleep efficiency variability as a clinically relevant feature of ME/CFS and underscore the need for multi-night assessment and targeted strategies addressing sleep variability.
Contemporary markets are increasingly structured around fragile and contested value categories, e.g, localness, sustainability, or authenticity. Yet marketing scholarship has paid limited attention to how such categories become operational and durable in decentralised contexts without dominant orchestrators. Drawing on a Market System Dynamics perspective, this study examines how the boundary of localness becomes operational. We investigate the 100% Valposchiavo initiative in a Swiss Alpine Valley, where the distinction between local and non-local is negotiated among several actors. Based on interviews, field observations, and online reviews, we identify three recursive dynamics (boundary work, boundary operationalisation, and boundary materialisation) through which symbolic distinctions are translated into practices. We conceptualise the mechanism sustaining these dynamics as boundary intermediation, a distributed process of market stabilisation under institutional ambiguity.
An experimental study in a basin of the scattering of a gravity wave by an array of regularly spaced vertical cylinders evidenced a strong reflection of the wave in the opposite direction to the incident wave under Bragg resonance conditions, i.e., for a spacing between cylinders that is a multiple of the half-wavelength of the wave. Strong reflections in oblique directions, with amplitudes greater than that of the incident wave, were also observed when the distance between two cylinders is an odd multiple of a quarter of the wavelength, i.e., under phase quadrature conditions between two successive cylinders. Finally, due to the excitation of transverse modes, strong amplitudes are observed in the central part of the array in such resonant conditions, however, of less amplitude than predicted by a linear model based on integral matching method. It is probably due to incomplete stationary conditions and dissipation, particularly in the case of large trapped mode oscillations. Finally, regarding the wave separation technique, a minimisation method is used here to determine the amplitudes and the angles of the oblique waves in addition to the incident and reflected waves along the basin.
