Future carbon sequestration potential in a widespread transcontinental boreal tree species: Standing genetic variation matters!

Climate change (CC) necessitates reforestation/afforestation programs to mitigate its impacts and maximize carbon sequestration. But comprehending how tree growth, a proxy for fitness and resilience, responds to CC is critical to maximize these programs' effectiveness. Variability in tree response to CC across populations can notably be influenced by the standing genetic variation encompassing both neutral and adaptive genetic diversity. Here, a framework is proposed to assess tree growth potential at the population scale while accounting for standing genetic variation. We applied this framework to black spruce (BS, Picea mariana [Mill] B.S.P.), with the objectives to (1) determine the key climate variables having impacted BS growth response from 1974 to 2019, (2) examine the relative roles of local adaptation and the phylogeographic structure in this response, and (3) project BS growth under two Shared Socioeconomic Pathways while taking standing genetic variation into account. We modeled growth using a machine learning algorithm trained with dendroecological and genetic data obtained from over 2600 trees (62 populations divided in three genetic clusters) in four 48-year-old common gardens, and simulated growth until year 2100 at the common garden locations. Our study revealed that high summer and autumn temperatures negatively impacted BS growth. As a consequence of warming, this species is projected to experience a decline in growth by the end of the century, suggesting maladaptation to anticipated CC and a potential threat to its carbon sequestration capacity. This being said, we observed a clear difference in response to CC within and among genetic clusters, with the western cluster being more impacted than the central and eastern clusters. Our results show that intraspecific genetic variation, notably associated with the phylogeographic structure, must be considered when estimating the response of widespread species to CC.

Quantifying the chemical activity of cavitation bubbles in a cluster.

Acoustic cavitation bubbles drive chemical processes through their dynamic lifecycle in liquids. These bubbles are abundant within sonoreactors, where their behavior becomes complex within clusters. This study quantifies their chemical effects within well-defined clusters using a new laser-based method. We focus a laser beam into water, inducing a breakdown that generates a single cavitation bubble. This bubble undergoes multiple collapses, releasing several shockwaves. These shockwaves propagate into the surrounding medium, leading to the formation of secondary bubbles near a reflector, separated from the input laser beam. We evaluate the chemical activity of these bubble clusters of various sizes by KI dosimetry, and to gain insights into their dynamics, we employ high-speed imaging. Hydrophone measurements show that conversion from focused shockwave energy to chemical reactions increases to a maximum of 16.5%. Additional increases in shockwave energy result in denser bubble clusters and a slightly decreased conversion rate, falling to 14.9%, highlighting the key role of bubble dynamics in the transformation of mechanical to chemical energy and as a result in the efficiency of the sonoreactors. The size and frequency of bubble collapses influence the cluster's chemical reactivity. We introduce a correlation for predicting the conversion rate of cluster energy to chemical energy, based on the cluster's energy density. The maximum conversion rate occurs at a cluster energy density of 2500 J/L, linked to a cluster with an average bubble diameter of 91 µ m, a bubble density of 3500 bubbles/ml, and a bubble-to-bubble distance ratio of 8.

Quantifying Simulated Contamination Deposition on Healthcare Providers Using Image Analysis.

INTRODUCTION: Simulation-based research has played an important role in improving care for communicable diseases. Unfortunately, few studies have attempted to quantify the level of contamination in these simulation activities. We aim to assess the feasibility and provide validity evidence for using integrated density values and area of contamination (AOC) to differentiate various levels of simulated contamination. METHODS: An increasing number of simulated contamination spots using fluorescent marker were applied on a manikin chest to simulate a contaminated healthcare provider. An ultraviolet light was used to illuminate the manikin to highlight the simulated contamination. Images of increasing contamination levels were captured using a camera with different exposure settings. Image processing software was used to measure 2 outcomes: (1) natural logarithm of integrated density; and (2) AOC. Mixed-effects linear regression models were used to assess the effect of contamination levels and exposure settings on both outcome measures. A standardized "proof-of-concept" exercise was set up to calibrate and formalize the process for human subjects. RESULTS: A total of 140 images were included in the analyses. Dose-response relationships were observed between contamination levels and both outcome measures. For each increment in the number of contaminated simulation spots (ie, simulated contaminated area increased by 38.5 mm 2 ), on average, log-integrated density increased by 0.009 (95% confidence interval, 0.006-0.012; P < 0.001) and measured AOC increased by 37.8 mm 2 (95% confidence interval, 36.7-38.8 mm 2 ; P < 0.001), which is very close to actual value (38.5 mm 2 ). The "proof-of-concept" demonstration further verified results. CONCLUSIONS: Integrated density and AOC measured by image processing can differentiate various levels of simulated, fluorescent contamination. The AOC measured highly agrees with the actual value. This method should be optimized and used in the future research to detect simulated contamination deposited on healthcare providers.

Characterization of the aerosol produced from an aerated jet.

Faucet aerators that form aerated water jets generate aerosols, which can constitute a risk of infection if the water is contaminated, particularly for vulnerable individuals near the sink. In this study, we characterize the size and trajectory of water droplets produced from an aerated jet. The detected particle diameter ranged from 3 to 150µm. The concentration of droplets in the air varied from near-zero to a maximum of 2×1011particles/m3, depending on the location relative to the jet. We found four relevant categories of droplets based on their trajectories following their emission at the jet's free surface: particles with inertia high enough to escape the immediate vicinity of the jet (category 1), particles moving towards the jet (category 2), particles drawn into the aerator, which only included particles with a diameter smaller than 50µm (category 3), and particles with a near-vertical trajectory (category 4). Tracing category 1 particles to their generation location on the water interface shows a higher emission rate near the aerator. Finally, we employ a numerical model to compute the subsequent trajectories of droplets detected at the limits of the sampled domain. We find that particles whose diameter is smaller than 55µm completely dry and become airborne. Larger droplets deposit within a radius of 7cm around the jet, assuming a surface is located 20cm below the aerator tip. These results increase the fundamental understanding of the emission mechanisms of droplets in aerated jets and their fate in the sink environment.

Prevention of submicron aerosolized particle dispersion: evaluation of an aerosol box using a pediatric simulation model.

Background and Aim: The SplashGuard CG (SG) is a barrier enclosure developed to protect healthcare workers from SARS-CoV-2 transmission during aerosol-generating procedures. Our objective was to evaluate the protection provided by the SG against aerosolized particles (AP), using a pediatric simulation model of spontaneous ventilation (SV) and noninvasive ventilation (NIV). Methods: An aerosol generator was connected to the airways of a pediatric high-fidelity manikin with a breathing simulator. AP concentrations were measured both in SV and NIV in the following conditions: with and without SG, inside and outside the SG, with and without suction applied to the device. Results: In the SV simulated setting, AP peaks were lower with SG: 0.1 × 105 particles/L compared to without: 1.6 × 105, only when the ports were closed and suction applied. In the NIV simulated setting, AP peaks outside the SG were lower than without SG (20.5 × 105 particles/L), whatever the situation, without suction (14.4 × 105particles/L), with suction and ports open or closed: 10.3 and 0.7 × 105 particles/L. In SV and NIV simulated settings, the AP peaks measured within the SG were much higher than the AP peaks measured without SG, even when suction was applied to the device. Conclusions: The SG seems to decrease peak AP exposure in the 2 ventilation contexts, but only with closed port and suction in SV. However, high concentrations of AP remain inside even with suction and SG should be used cautiously.

Quantification and visualization of aerosols in ear, nose, and throat exam and flexible laryngoscopy.

Objective: To measure and visualize aerosol generation during ear, nose, and throat (ENT) exam and flexible laryngoscopy, as safety recommendations are currently to defer routine and low-priority examinations. Methods: Aerosols generated during ENT examination and flexible laryngoscopy were quantified by laser aerosol spectrometry and visualized live by high-speed imaging during those procedures for three participants who were tested three times for each test. Results: Routine ENT examination and flexible laryngoscopy produce aerosols at levels comparable to normal breathing and speech. Conclusion: During ENT examination and flexible laryngoscopy, the practitioner should wear a surgical mask and potentially contaminated surfaces should be cleaned after the procedure. For flexible laryngoscopy, it is recommended in addition that the patient wear a mask over the mouth in case the procedure induces a sneeze. The time during which the patient is unmasked should be minimized. In these settings, the risk to the practitioner is minimal unless the patient is sneezing or symptomatic. Level of Evidence: 1.

Dataset of temperature, heat flux and infrared emission from flat premixed laminar methane-air flames.

To enable the use of flat flame burners in the context of fire resistance testing, we present a data set covering temperature, infrared emission and heat 15 mm above the burner. A laminar premixed methane-air flame is characterized for eleven different fuel/air ratios, ranging from lean (0.9) to rich (1.45), extending an existing a widely used reference [1]. We provide complementing flame temperature readings from thermocouple measurements that can be used for calibration. In addition, broadband flame optical emissions are acquired in the visual (VIS) and the infrared (IR) spectral region. Chemiluminescence measurements reveal the spatial distribution of the OH* radicals. Heat flux density measurements with a water-cooled gauge are also provided. Finally, the expected species concentration, velocity, temperature are obtained from chemical kinetics calculations. Ambient conditions and burner control parameters are presented as supplementary data.

Metal-organic frameworks as hypergolic additives for hybrid rockets.

Hybrid rocket propulsion can contribute to reduce launch costs by simplifying engine design and operation. Hypergolic propellants, i.e. igniting spontaneously and immediately upon contact between fuel and oxidizer, further simplify system integration by removing the need for an ignition system. Such hybrid engines could also replace currently popular hypergolic propulsion approaches based on extremely toxic and carcinogenic hydrazines. Here we present the first demonstration for the use of hypergolic metal-organic frameworks (HMOFs) as additives to trigger hypergolic ignition in conventional paraffin-based hybrid engine fuels. HMOFS are a recently introduced class of stable and safe hypergolic materials, used here as a platform to bring readily tunable ignition and combustion properties to hydrocarbon fuels. We present an experimental investigation of the ignition delay (ID, the time from first contact with an oxidizer to ignition) of blends of HMOFs with paraffin, using White Fuming Nitric Acid (WFNA) as the oxidizer. The majority of measured IDs are under 10 ms, significantly below the upper limit of 50 ms required for functional hypergolic propellant, and within the ultrafast ignition range. A theoretical analysis of the performance of HMOFs-containing fuels in a hybrid launcher engine scenario also reveals the effect of the HMOF mass fraction on the specific impulse (I sp) and density impulse (ρI sp). The use of HMOFs to produce paraffin-based hypergolic fuels results in a slight decrease of the I sp and ρI sp compared to that of pure paraffin, similar to the effect observed with Ammonia Borane (AB), a popular hypergolic additive. HMOFs however have a much higher thermal stability, allowing for convenient mixing with hot liquid paraffin, making the manufacturing processes simpler and safer compared to other hypergolic additives such as AB.

Experimental and Numerical Investigation of Flow Field and Soot Particle Size Distribution of Methane-Containing Gas Mixtures in a Swirling Burner.

The formation of soot in a swirling flow is investigated experimentally and numerically in the context of biogas combustion using a CO2-diluted methane/oxygen flame. Visualization of the swirling flow field and characterization of the burner geometry is obtained through PIV measurements. The soot particle size distributions under different fuel concentrations and swirling conditions are measured, revealing an overall reduction of soot concentration and smaller particle sizes with increasing swirling intensities and leaner flames. An axisymmetric two-dimensional CFD model, including a detailed combustion reaction mechanism and soot formation submodel, was implemented using a commercial computational fluid dynamics (CFD) code (Ansys Fluent). The results are compared with the experiments, with similar trends observed for the soot size distribution under fuel-lean conditions. However, the model is not accurate enough to capture soot formation in fuel-rich combustion cases. In general, soot particle sizes from the model are much smaller than those observed in the experiments, with possible reasons being the inappropriate modeling in Fluent of governing mechanisms for soot agglomeration, growth, and oxidation for CH4-CO2 mixtures.

Faucet aerator design influences aerosol size distribution and microbial contamination level.

Faucet aerators have been linked to multiple opportunistic pathogen outbreaks in hospital, especially Pseudomonas aeruginosa, their complex structure promoting biofilm development. The importance of bacteria aerosolization by faucet aerators and their incidence on the risk of infection remain to be established. In this study, ten different types of aerators varying in complexity, flow rates and type of flow were evaluated in a controlled experimental setup to determine the production of aerosols and the level of contamination. The aerosol particle number density and size distribution were assessed using a particle spectrometer. The bacterial load was quantified with a 14-stage cascade impactor, where aerosol particles were captured and separated by size, then analysed by culture and flow cytometry. The water was seeded with Pseudomonas fluorescens as a bacterial indicator. Aerosol particle size and mean mass distribution varied depending on the aerator model. Devices without aeration or with laminar flow produced the lowest number and mass of aerosol particles when measured with spectrometry. Models with aeration displayed wide differences in their potential production of aerosol particles. A new aerator with a low flow, no air inlet in its structure, and a spray stream produced 12 to 395 times fewer aerosol particles containing bacteria. However, the impact of low flow on biofilm development and incorporation of pathogens should be further investigated. Repeated use of aerators resulted in fouling which increased the quantity of bacteria released through aerosol particles. An in-depth mechanical cleaning including complete dismantling of the aerator was required to recover initial performances. Aerators should be selected to minimize aerosol production, considering the ease of maintenance and the main water usage at each sink. Low flow aerators produced a lower number of contaminated aerosol particles when new but may be more susceptible to fouling and quickly lose their initial advantage.

Corner's rules pass the test of time: little effect of phenology on leaf-shoot and other scaling relationships.

BACKGROUND AND AIMS: Twig cross-sectional area and the surface area of leaves borne on it are expected to be isometrically correlated across species (Corner's rules). However, how stable this relationship remains in time is not known. We studied inter- and intraspecific twig leaf area-cross-sectional area (la-cs) and other scaling relationships, including the leaf-shoot mass (lm-sm) scaling relationship, across a complete growing season. We also examined the influence of plant height, deciduousness and the inclusion of reproductive buds on the stability of the scaling relationships, and we discuss results from a functional perspective. METHODS: We collected weekly current-year twigs of six Patagonian woody species that differed in growth form and foliar habit. We also used prominent inflorescences from Embothrium coccineum (Proteaceae) to assess whether reproductive buds alter the la-cs isometric relationship. Mixed effects models were fitted to obtain parameter estimates and to test whether interaction terms were non-significant (invariant) for the scaling relationships. KEY RESULTS: The slope of the la-cs scaling relationship remained invariant across the growing season. Two species showed contrasting and disproportional (allometric) la-cs scaling relationships (slope ≠ 1). Scaling relationships varied significantly across growth form and foliar habit. The lm-sm scaling relationship differed between reproductive- and vegetative-origin twigs in E. coccineum, which was explained by a significantly lower leaf mass per area in the former. CONCLUSIONS: Although phenology during the growing season appeared not to change leaf-shoot scaling relationships across species, we show that scaling relationships departed from the general trend of isometry as a result of within-species variation, growth form, foliar habit and the type of twig. The identification of these functional factors helps to understand variation in the general trend of Corner's rules.

Acoustic separation of submicron solid particles in air.

The use of ultrasound to continuously separate submicron particles suspended in air is investigated in a rectangular channel with adjustable height. An electrostatic transducer is used to generate a standing wave in the 50-80 kHz frequency range and the particles experience forces within the acoustic field causing them to concentrate at the pressure nodes. To assess the effect of several key design parameters on the separation efficiency, a simple method based on light scattering is implemented to provide information on the particle concentrations as a function of position in the channel. The images acquired are processed to yield a separation efficiency metric that is used to evaluate the effect of acoustic, flow and geometrical parameters. The results show that, in qualitative agreement with theoretical models, the maximum separation efficiency increases with the pressure amplitude of the sound wave. The separation efficiency is also linearly proportional to the standing wave frequency, when it is varied between 50-80 kHz. On the other hand, the effect of the average fluid velocity is less pronounced than expected, suggesting that in our channel separation is not limited by the interaction length between the acoustic field and the suspended particles. The effect of the parallelism of the reflector relative to the transducer is also investigated.