Direct Flux Research Articles

Pore-scale numerical studies on determination of the effective thermal conductivity of the fluid saturated porous media

Accurate prediction of the effective thermal conductivity (ETC) of a fluid saturated rock is crucial for fulfilling efficient geo-energy harvest practices. In this paper, the ETCs of a rock with 23% porosity and 2.7 W/m·K thermal conductivity when saturated with various fluids, including water, oil, hydrogen gas, and air, are numerically investigated. Advanced digital rock technique is employed to reconstruct the complex solid-pore structure in the rock, and CFD simulations are performed to assess the ETCs, focusing on the influence of fluid type and heat flux direction. The results show the maximum ETC values of 2.10 W/m·K for water-saturated rocks, in contrast to the minimum values of 1.3 W/m·K for air-saturated samples. When the internal fluid possesses a higher thermal conductivity than air, the ETCs of the fluid-saturated rock display minimal anisotropy, while significant anisotropy is observed in the air filling rock sample. The methodology is validated based on satisfactory agreements between the numerical ETC results and the Geometric Mean model predictions in the water saturated rock case. Due to the fact that the commonly used empirical correlations produce significant deviations when applying to low thermal conductivity fluids, a new ETC model that achieves less than 8% deviation for all studied fluid types is proposed based on the numerical results. This study provides pore-scale insights into fluid flow and thermal conduction behavior within fluid-saturated porous media.

Eddy covariance with slow-response greenhouse gas analysers on tall towers: bridging atmospheric and ecosystem greenhouse gas networks

Abstract. Greenhouse gas monitoring is important to ensure climate goals are being achieved. This study unveils the potential of using atmospheric tall towers in direct flux measurements, bridging the gap between atmospheric and ecosystem monitoring networks. The ICOS Cities (PAUL) project aims to monitor CO2 emissions in urban areas, where concentrated emissions make them key targets for climate change mitigation. This study explores the synergy between ICOS atmospheric and ecosystem networks by utilizing slow-response analysers (∼ 3 s) on tall atmospheric towers for ecosystem studies using the eddy covariance method. A standard setup with an ultrasonic anemometer and an infrared (IR) fast-response CO2 analyser was installed and compared with measurements from an existing cavity ring-down spectroscopy (CRDS) analyser measuring CO2, CO, and CH4. Deployed on the 100 m Saclay tower near Paris, covering a 43.9 km2 80 % footprint with heavy traffic roads, a nearby heating plant, and a forest, the setup addressed technical challenges and height-induced complexities. Corrections for flux attenuation by high-frequency losses were limited to < 20 % on average for all stabilities and around 11 % for unstable conditions. Elevated mean fluxes for CO2 (10 µmolm-2s-1) and CH4 (200 µmolm-2s-1) were observed from the heating plant wind direction during December and January. Conversely, the forest direction exhibited the strongest sink among all wind directions, with −4 µmolm-2s-1 during July and August. Storage and vertical advection were estimated using the routine three-level profile measurements done in ICOS atmospheric towers. Storage term was of the same magnitude as turbulent flux, increasing at night and de-stocking during the first half of the day. Vertical advection averaged zero on a monthly basis. These results demonstrate the feasibility and versatility of utilizing atmospheric towers for urban emission monitoring, offering valuable insights for emission monitoring strategies worldwide.

A comparative study on the lamella effect and properties of atomized iron powder and reduced iron powder in Fe-based soft magnetic composites

We prepared Fe soft magnetic composites (SMCs) with lamellar structure by using the flaky Iron powder, and studied the effects of types of iron powder on the microstructure and properties of Fe SMCs. The results show that the atomized iron powder and the reduced iron powder are deformed into flaky structure after ball milling, and these flaky iron powder have greater magnetic susceptibility and eddy current diameter perpendicular to the magnetic flux direction. In addition, compared with flaky gas atomized iron powder, the flaky reduced iron powder has large aspect ratio and lower coercivity. Therefore, the Fe SMCs with flaky reduced iron powder exhibit relatively high permeability (82) and low eddy current loss (0.033 W/kg at 50 kHz, 0.05 T), which shows the potential possibility of application at high frequency.

Kyanite-muscovite-dumortierite vein mineralization mechanisms from advanced microstructural analysis using EBSD

Abstract Dumortierite, an aluminous borosilicate mineral, is relatively rare in Earth’s crust, but it is the second most abundant aluminous borosilicate after tourmaline. Boron is an element with many uses in modern societies worldwide, from health products to wind turbine blades for clean energy, but of limited availability and at future risk of supply. Only a limited number of studies have been published on dumortierite mineralization processes and the factors that control its abundance and distribution remain poorly understood. Here we present the first comprehensive electron backscatter diffraction (EBSD) study of dumortierite mineralization mechanisms in kyanite-muscovite-dumortierite veins occurring in the metapelites of the Amgaon Gneiss Supracrustals, in the Girola hill area, Sakoli region, Central India. Advanced microstructural and chemical analyses show that mixed-mode brittle-viscous deformation in kyanite, by fracturing and easy glide on (100) [001] slip system, facilitates fluid-rock interactions with reactive hydrothermal fluids rich in B, F, and K and containing Na, Ti, Mg, Fe and Pt. These interactions cause the dissolution of kyanite along fracture and cleavage surfaces and the precipitation of muscovite (F = 0.32 wt %) and topaz (F = 16.48 wt %). The motion of ripplocation defects in muscovite facilitates fluid migration along cleavage surfaces and crystallisation of dumortierite needles within these surfaces. Fluid flux removes silica in solution from the system, so reactions may continue. The observed mineral assemblage, the microstructural signature of kyanite and muscovite, the moderate fluorine content of topaz, and low fluorine content of muscovite, together suggest that dumortierite mineralization results from hydrothermal activity, possibly in a transitional magmatic-hydrothermal environment, likely at P > 2.5 kbar and 400°<T < 550°, that could be linked with granite intrusions in the area. Using EBSD we demonstrate that dumortierite mineralization is focussed along muscovite basal cleavage surfaces and dumortierite needle elongation is likely controlled by the fluid flux direction. These new results advance our understanding of dumortierite mineralization mechanisms and conditions and have important implications for our understanding of the distribution of this aluminous borosilicate mineral in muscovite-rich rocks.

Analysis of the air gap magnetic field in cylindrical magnetic couplings based on mathematical and finite element approach

The air gap magnetic field of a magnetic coupling plays a crucial role in the examination of its static torque and eddy current losses. Precise characterization of the air gap magnetic field is essential for ensuring the accuracy of performance assessments of the magnetic coupling. This study focuses on the cylindrical magnetic coupling as the subject of investigation, employing mathematical analysis and finite element methods to evaluate and quantify the magnetic field properties. The study establishes a mathematical model of the magnetic field of a magnetic coupling based on electromagnetic field principles and the superposition theorem. An analytical formula for the magnetic flux density distribution of the air-gap magnetic field is derived. Subsequently, a three-dimensional magnetic field finite element model is created using the finite element method to numerically calculate the air gap magnetic field and validate the analytical formula. The research also explores the periodic distribution characteristics of the magnetic field in the air gap, analyzing axial differences in magnetic flux density value and direction distribution influenced by end effects.

Phase-selective fabrication of Cu-based films by magnetic field-assisted sparking process for improved photocatalytic dye degradation and CO2 reduction

Copper-based films (Cu2(OH)3NO3, Cu2O, and CuO) were successfully synthesized using a sparking process under an external magnetic field, without requiring an annealing process. We thoroughly investigate the impact of magnetic field orientation on the structural, morphological, and optical properties of the films, along with their performance in photocatalytic degradation of methylene blue (MB) and carbon dioxide (CO2) reduction. Field-emission scanning electron microscopy (FE-SEM) images reveal that the CuEB(S) sample displays secondary particles forming spherical, dense clusters, whereas the CuEB(N) sample exhibits larger, loosely packed clusters. In contrast, the cluster-like structures disperse in the CuEB(P) sample, resulting in a smoother film surface aligned with the parallel magnetic flux direction. Upon close observation, rice-shaped particles of varying sizes (26.3–60.3 nm) were found stacked together. This study presents a facile method to selectively fabricate films comprising single-phase Cu2(OH)3NO3, a CuO/Cu2O composite, or a combination of all phases by manipulating the external magnetic field orientation during the sparking process. All synthesized materials exhibit photocatalytic activity, with the heterojunction composed of CuO, Cu2O, and Cu2(OH)3NO3 demonstrating superior performance. This heterostructure achieved up to a 180 % enhancement in MB degradation and approximately doubled the CO2-to-CO conversion rate to 16.09 μmol g–¹ h–¹ compared to the sample prepared without a magnetic field.

Analytical model for CO2-water displacement with rate-dependent phase permeability for geological storage

Analytical modelling is an effective tool for predicting reservoir behaviour under high uncertainties, like CO2 storage in aquifers, where multiple simulation runs are necessary for stochastic modelling and risk assessment. This paper formulates the Buckley-Leverett problem with x-dependent fractional flow. We derive a new analytical model for displacement of brine by CO2 accounting for (i) rate-dependent phase permeability during radial flows and (ii) radial flows of Forchheimer's high-rate gas injection; this analytical model is also valid for (iii) linear flows during flooding in micro heterogeneous or composite cores and (iv) CO2-water flow upscaling in reservoirs where layering is perpendicular to flux direction. An exact solution of the flow equation is based on the observation that the flux of each phase conserves along the characteristic trajectories. We discuss S-shape fractional flow function, which is typical for reservoir rocks. The solution includes formulae for phase saturations and fluxes and trajectories of the displacement CO2-water front and of the forward and rear mixture zone boundaries. The fast analytical model can be used for multivariate sensitivity study and sweep efficiency prediction.

A new method for temperature field characterization of microsystems based on transient thermal simulation

Microsystems face challenges such as high heat flux density and localized hot spots in the temperature field, significantly impacting their thermal reliability. Accurately and comprehensively characterizing the temperature field is a challenging problem in current research. We present a general high-order finite difference (GHOFD) algorithm for the high-accuracy numerical solution of the two-dimensional transient heat conduction equations (THCEs). The 10th-order GHOFD algorithm is accurate up to 10−7 °C. Secondly, we present a viable approach for characterizing microsystems' steady-state and transient heat conduction mechanisms. We introduce two new characterization parameters: the gradient modulus and the heat flux direction factor (HFDF). The gradient modulus can more clearly characterize the magnitude of the gradient vector and quantitatively analyze the spatial position of the temperature field change in the microsystem. The HFDF can dynamically display the heat conduction process in the temperature field. Finally, using temperature field simulation and microsystem characterization, we have validated the effectiveness of the proposed method and new parameters.

Eigenmode twist by energy flux during fast-ion driven instabilities

Twisting of the spatial structure of eigenmodes by energy fluxes generated due to the spatial channeling (SC)—the fast-ion energy and momentum transfer across the magnetic field by destabilized modes—is considered. It is revealed that there is a correlation between the direction of the radial wave energy flux, orientation of the mode twist (MT), and the direction of mode rotation. The mode twist parameter is introduced and relations connecting it with the energy flux are established. It is shown the energy flux transforms zeros of the radial profile of the mode amplitude into minima (i.e., zeros disappear). It is found that the radial group velocity and phase velocity of reversed shear Alfvén eigenmodes (RSAEs) have opposite directions. These findings can be used for diagnostics of the energy fluxes during fast-ion driven instabilities and understanding whether the SC degrades or improves plasma performance. Specific calculations are carried out for fast magnetoacoustic modes, FMMs (known also as compressional Alfvén eigenmodes, CAEs), and Alfvén eigenmodes, AEs. A DIII-D experiment where RSAEs were observed is considered. It is concluded that an outward SC took place in this experiment. Peculiarities of various modes are discussed, which may explain why twisting of AEs, but not of FMMs, was observed experimentally in the DIII-D and NSTX tokamaks.

Mixing characteristics and co-flow behavior in interactive cascade ventilation: An Experimental Approach

Achieving optimal indoor air quality that is both healthy and comfortable remains a persistent pursuit. Interactive cascade ventilation (ICV) has demonstrated remarkable performance, harnessing a temperature gradient to reverse the direction of buoyancy flux. The aim of this study is to investigate the mixing characteristics and co-flow behavior of ICV. Experiments, informed by Abramovich's theory and the principles of similarity, are conducted using a scaled-down experimental setup. The research results indicate that varying the temperature difference between the upper and lower jets from 2°C to 7°C significantly influences the deflection angle. Notably, the lower jet exhibits a more pronounced decrease of 52%, suggesting that the warmer lower jets effectively uplift the cooler upper jets. It can counteract their descent, optimizing the use of cool air in occupied spaces. Additionally, analysis of different velocity ratios reveals a reduction in the deflection angle from 12.69° to 5.57° as the velocity ratio increases from 0.5 to 0.81. A modified jet equation has been derived, which delineates the central path of the jet trajectory. The insights obtained from this research serve to bolster the theoretical framework for optimizing critical supply air parameters within the ICV system, thereby significantly enhancing its ventilation performance. These findings elucidate the underlying mechanisms of ICV, leading to a more profound understanding of its operational dynamics.

Membrane potential stimulates ADP import and ATP export by the mitochondrial ADP/ATP carrier due to its positively charged binding site.

The mitochondrial adenosine 5'-diphosphate (ADP)/adenosine 5'-triphosphate (ATP) carrier imports ADP into the mitochondrion and exports ATP to the cell. Here, we demonstrate that 3.3 positive charges are translocated with the negatively charged substrate in each transport step. They can be assigned to three positively charged residues of the central substrate-binding site and two asparagine/arginine pairs. In this way, the membrane potential stimulates not only the ATP4- export step, as a net -0.7 charge is transported, but also the ADP3- import step, as a net +0.3 charge is transported with the electric field. These positive charge movements also inhibit the import of ATP and export of ADP in the presence of a membrane potential, allowing these nucleotides to be maintained at high concentrations in the cytosol and mitochondrial matrix to drive the hydrolysis and synthesis of ATP, respectively. Thus, this is the mechanism by which the membrane potential drives adenine nucleotide exchange with high directional fluxes to fuel the cellular processes.

Quantification and Flow Simulation of Ecosystem Service Supply and Demand in the Yellow River Delta High-Efficiency Eco-Economic Zone

The identification of supply and demand areas for ecosystem services (ES) and the simulation of ES flows are essential for optimizing ESs to achieve socio-economic sustainable development. However, the selection of investigation methods and simulation model remains a persistent challenge. This study selected the Yellow River Delta High-Efficiency Eco-Economic Zone in China as the case study area and assessed the habitat quality and carbon sequestration services for 2000, 2010, and 2020. The quantile regression method was employed to quantify the impacts of land use structure on balancing the supply and demand of ESs. The minimum cumulative resistance model, circuit corridor model, and wind direction model were utilized to analyze changes in flux and flow direction of ESs’ supply and demand. The results demonstrated that the following: (1) the supply of ESs generally increased, with a significant rise in demand for carbon sequestration service and a declining trend in habitat quality service demand. (2) A clear spatial mismatch existed between the supply and demand of ESs. (3) The impact of land use structure on the balance of ES supply and demand is complex. (4) Habitat quality and carbon sequestration services exhibited distinct spatial clustering patterns. (5) The flow patterns of habitat quality service were characterized by specific supply and demand areas, with corridors and pinch points indicating the flow paths and potential barriers; not all demand areas for carbon sequestration service can be satisfied due to variations in service levels and geographical distance. The innovation of this study lies in the following aspects: (1) it acknowledges the uniqueness of ecosystem services, with a focus on assessing habitat quality and carbon sequestration services; (2) it precisely quantifies the flow of ecosystem services, analyzes the spatial dynamics of service flows, and investigates the impact of changes in land-use structure on these flows; (3) it strengthens the correlation between the supply and demand of ecosystem services and socio-economic activities, uncovers the contradictions between supply and demand along with their underlying causes, and proposes effective strategies for resolution. The findings can provide theoretical and methodological references for the optimization of ES.

Enhanced ocean CO2 uptake due to near-surface temperature gradients

The ocean annually absorbs about a quarter of all anthropogenic carbon dioxide (CO2) emissions. Global estimates of air–sea CO2 fluxes are typically based on bulk measurements of CO2 in air and seawater and neglect the effects of vertical temperature gradients near the ocean surface. Theoretical and laboratory observations indicate that these gradients alter air–sea CO2 fluxes, because the air–sea CO2 concentration difference is highly temperature sensitive. However, in situ field evidence supporting their effect is so far lacking. Here we present independent direct air–sea CO2 fluxes alongside indirect bulk fluxes collected along repeat transects in the Atlantic Ocean (50° N to 50° S) in 2018 and 2019. We find that accounting for vertical temperature gradients reduces the difference between direct and indirect fluxes from 0.19 mmol m−2 d−1 to 0.08 mmol m−2 d−1 (N = 148). This implies an increase in the Atlantic CO2 sink of ~0.03 PgC yr−1 (~7% of the Atlantic Ocean sink). These field results validate theoretical, modelling and observational-based efforts, all of which predicted that accounting for near-surface temperature gradients would increase estimates of global ocean CO2 uptake. Accounting for this increased ocean uptake will probably require some revision to how global carbon budgets are quantified.

Analysis of Magnetization Dynamics in NiFe Thin Films with Growth-Induced Magnetic Anisotropies

We have used angled magnetron sputter deposition with and without sample rotation to control the magnetic anisotropy in 20 nm NiFe films. Ferromagnetic resonance spectroscopy, with data analysis using a Bayesian approach, is used to extract material parameters relating to the magnetic anisotropy. When the sample is rotated during growth, only shape anisotropy is present, but when the sample is held fixed, a strong uniaxial anisotropy emerges with in-plane easy axis along the azimuthal direction of the incident atom flux. When the film is deposited in two steps, with an in-plane rotation of 90 degrees between steps, the two orthogonal induced in-plane easy-axes effectively cancel. The analysis approach enables precise and accurate determination of material parameters from ferromagnetic resonance measurements; this demonstrates the ability to precisely control both the direction and strength of uniaxial magnetic anisotropy, which is important in magnetic thin-film device applications.

Torque dynamic performance enhancement of five‐phase permanent magnet synchronous motor with open‐circuit fault

AbstractMultiphase permanent magnet synchronous motors (PMSMs) have attracted much more attention for their high efficiency, low torque ripple and good fault tolerance. However, open‐circuit fault results in asymmetrical motor behaviour, and deteriorates torque performance, especially dynamic response. This paper proposes a novel fault‐tolerant direct torque and flux control (DTFC) strategy to restrain fluctuating torque and enhance torque dynamic performance of a five‐phase PMSM with open‐circuit fault. The novelty of the proposed strategy is the development of DTFC based on stator flux orientation under the open‐circuit fault condition and the third harmonic current suppression with carrier‐based pulse width modulation technology. Consequently, the decoupling control of torque and stator flux can be achieved under the open‐circuit fault condition, and the third harmonic current can be restrained without additional control. Combined with deadbeat control, the heavy computation burden can be reduced. Thus, the proposed strategy not only can enhance torque dynamic performance under open‐circuit fault operation, but also keep smooth torque with circular stator flux trajectory before and after open‐circuit fault. The effectiveness of the proposed strategy is verified by the simulation and experimental results.

Angular Momentum Transportation by Zonal Circulation Helps Meridional Displacements of East Asian Westerly Jet

ABSTRACTThe meridional displacements of the East Asian westerly jet (EAJ) exhibit remarkable interannual variability characteristics, significantly modulating the weather and climate over East Asia. Our study aims to refine the thermal‐driven (angular momentum transport) and dynamically driven (atmospheric eddy activities) processes that dominate the interannual meridional motion of the wintertime EAJ. We employ the recently proposed three‐pattern decomposition of global atmospheric circulation (3P‐DGAC) theory to decompose the zonal momentum equation for the purpose of diagnosing the zonal momentum budget of the EAJ from three‐dimensional (3D) horizontal, meridional and zonal circulation perspectives. Results indicate that, in addition to the widely recognised driving mechanisms of angular momentum transported by thermal direct meridional Hadley circulation and horizontal eddy momentum flux convergence, the previously neglected role of local zonal circulation in transporting angular momentum significantly impacts the meridional shift of EAJ. The uneven accumulation of angular momentum transported by asymmetric zonal circulations emerges on the northern and southern sides of EAJ axis, causing an abnormal meridional displacement of EAJ. Notably, the local zonal circulation rising from the Tibetan Plateau and descending across the North Pacific Ocean transported angular momentum to the core and downstream regions of EAJ, thereby significantly accelerating zonal winds and pushing the EAJ northward. Further investigation into the potential mechanisms suggests that anomalous snow depth on the southern Tibetan Plateau is the main factor causing abnormal local zonal circulation. Our study addresses the deficiency in traditional two‐dimensional (2D) circulation decomposition methods that neglect the significant role of zonal circulation in the thermal‐driven process of EAJ, complements the understanding of 3D angular momentum transport mechanisms and reveals potential nonlinear synergies of 3D circulations related to the interannual meridional displacement of EAJ.

Intercomparison of fast airborne ozone instruments to measure eddy covariance fluxes: spatial variability in deposition at the ocean surface and evidence for cloud processing

Abstract. The air–sea exchange of ozone (O3) is controlled by chemistry involving halogens, dissolved organic carbon, and sulfur in the sea surface microlayer. Calculations also indicate faster ozone photolysis at aqueous surfaces, but the role of clouds as an ozone sink is currently not well established. Fast-response ozone sensors offer opportunities to measure eddy covariance (EC) ozone fluxes in the marine boundary layer. However, intercomparisons of fast airborne O3 sensors and EC O3 fluxes measured on aircraft have not been conducted before. In April 2022, the Technological Innovation Into Iodine and GV Environmental Research (TI3GER) field campaign deployed three fast ozone sensors (gas chemiluminescence and a combination of UV absorption with coumarin chemiluminescence detection, CID) together with a fast water vapor sensor and anemometer to study iodine chemistry in the troposphere and stratosphere over Colorado and over the Pacific Ocean near Hawaii and Alaska. Here, we present an instrument comparison between the NCAR Fast O3 instrument (FO3, gas-phase CID) and two KIT Fast AIRborne Ozone instruments (FAIRO, UV absorption and coumarin CID). The sensors have comparable precision < 0.4 % Hz−0.5 (0.15 ppbv Hz−0.5), and ozone volume mixing ratios (VMRs) generally agreed within 2 % over a wide range of environmental conditions: 10 < O3 < 1000 ppbv, below detection < NOx < 7 ppbv, and 2 ppmv < H2O < 4 % VMR. Both instrument designs are demonstrated to be suitable for EC flux measurements and were able to detect O3 fluxes with exchange velocities (defined as positive for upward) as slow as −0.010 ± 0.004 cm s−1, which is in the lower range of previously reported measurements. Additionally, we present two case studies. In one, the direction of ozone and water vapor fluxes was reversed (vO3 = +0.134 ± 0.005 cm s−1), suggesting that overhead evaporating clouds could be a strong ozone sink. Further work is needed to better understand the role of clouds as a possibly widespread sink of ozone in the remote marine boundary layer. In the second case study, vO3 values are negative (varying by a factor of 6–10 from −0.036 ± 0.006 to −0.003 ± 0.004 cm s−1), while the water vapor fluxes are consistently positive due to evaporation from the ocean surface and spatially homogeneous. This case study demonstrates that the processes governing ozone and water vapor fluxes can become decoupled and illustrates the need to elucidate possible drivers (physical, chemical, or biological) of the variability in ozone exchange velocities on fine spatial scales (∼ 20 km) over remote oceans.

Electrocaloric effect in chemically modified barium titanate ferroelectric ceramics

Electrocaloric (EC) refrigeration offers superior energy-conversion efficiency, miniaturization, and environmental benefits compared to compression refrigeration. However, its practical application is limited by the challenge of aligning the adiabatic temperature change (ΔT) with the operational temperature range. In this study, we have tailored the EC characteristics of BaTiO3 (BT)-based Ba(Ti0.9Sn0.1)O3 (BTS) ferroelectric ceramics using Bi(Mg0.5Ti0.5)O3 (BMT). We provide a comprehensive analysis of the microstructure, electrical properties, and EC behavior of the (1–x)BTS-xBMT system. Our results indicate that the incorporation of BMT establishes a broad platform in the dielectric spectrum while maintaining high polarization. This improvement potentially increases the electrocaloric effect (ECE) and expands the operating temperature range. Direct heat flux measurements reveal that the x = 0.02 composition achieves a maximum ΔT (ΔTmax) of 0.41 K with a temperature span (Tspan) of 68 °C under an intermediate electric field of 50 kV/cm. Moreover, the x = 0.01 sample exhibits a room-temperature ΔT of 0.33 K and relatively good temperature stability within 30–130 °C. These findings indicate that chemical modification methods have the potential to optimize the cooling capacity of refrigerants.

Seasonal variability and seagrass traits affect methane fluxes in a subtropical meadow

Abstract Plant traits which vary both within and between species often drive biogeochemical cycling. Understanding the relative role of within‐ and between‐species trait variability in driving carbon cycling is essential to scaling site measurements to global carbon budgets. In seagrass meadows, carbon and nitrogen mineralization rates and associated greenhouse gas emissions are highly variable, impeding our ability to reliably predict whether meadows are net carbon sinks. Evaluating the influence of within‐ and between‐species trait variability on greenhouse gas fluxes will improve our understanding of local‐scale drivers of greenhouse gas production and consumption in seagrass meadows. To test the effects of plant traits on dissolved greenhouse gas fluxes, we performed mesocosm incubations with live, intact seagrass plants. We compared methane (CH4) and nitrous oxide (N2O) fluxes under dark and light conditions from sediments dominated by Halodule wrightii and Thalassia testudinum across dormant, early and peak growing seasons in a subtropical meadow along the west coast of peninsular Florida. We also measured oxygen (O2) fluxes to interpret greenhouse gas fluxes within the context of community metabolism. We measured several seagrass traits, such as above‐ and below‐ground biomass and leaf and root area and assessed their impact as well as the impact of species identity on dissolved gas fluxes. We found that abiotic factors linked to metabolism (i.e. light and temperature) influenced greenhouse gas fluxes across seasons. In addition to light conditions and sampling month, plant size (a composite trait variable) was a significant predictor of O2 consumption and CH4 production under dark conditions, and better predicted fluxes than individual plant traits. CH4 production was slightly higher in H. wrightii‐dominated sediments, but species identity was less important than plant size in driving CH4 production. N2O fluxes were low and not influenced by plant traits or species identity. Synthesis: Our results indicate that within‐species more so than between‐species trait variability drives the direction and magnitude of CH4 fluxes in seagrass meadows. We identified a trade‐off where seagrass biomass is often associated with enhanced sediment carbon storage, but in our study, plant size promoted CH4 production, potentially offsetting the benefits of long‐term storage.

Моделирование чувствительности литийсодержащих кристаллических сцинтилляторов к нейтронному излучению

This paper presents the results of Monte Carlo modelling of the sensitivity of the lithium containing detectors CLYC, NaIL, CLLB to thermal neutrons. The difference between the sensitivity and the neutron freepath depth of the CLYC scintillator enriched and unenriched with the 6Li isotope is shown. The analysis of the distribution of alpha particles and neutrons in the scintillator volume is performed, showing the inefficiency of the unenriched scintillator due to the fact that not all neutrons react with the crystal material. Mathematical modelling by the Monte Carlo method of the scintillator sensitivity and its comparison with respect to the irradiation direction has been carried out. It is shown that for the scintillator in the face and side geometry with the size more than 38 mm the difference in sensitivity at change of the neutron flux direction is connected only with the scintillator cross section and 6Li concentration with the same value of the specific sensitivity. The obtained model results were compared with available experimental data for NaIL and CLLB scintillators, which showed the reliability of the developed models and calculation methods.