Flux Ratio Research Articles

JWST NIRSpec High-resolution Spectroscopy of MACS0647–JD at z = 10.167: Resolved [O ii] Doublet and Electron Density in an Early Galaxy

We present JWST/NIRSpec high-resolution G395H/F290LP spectroscopy of MACS0647−JD, a gravitationally lensed galaxy merger at z = 10.167. The new spectroscopy, which is acquired for the two lensed images (JD1 and JD2), detects and resolves emission lines in the rest-frame ultraviolet and blue optical, including the resolved [O ii] λ λ3726, 3729 doublet, [Ne iii] λ3870, He i λ3890, Hδ, Hγ, and [O iii] λ4363. This is the first observation of the resolved [O ii] λ λ3726, 3729 doublet for a galaxy at z > 8. We measure a line flux ratio [O ii] λ3729/λ3726 = 0.9 ± 0.3, which corresponds to an estimated electron density of log(ne/cm−3)=2.9±0.5 . This is significantly higher than the electron densities of local galaxies reported in the literature. We compile measurements from the literature and further analyze the redshift evolution of n e . We find that the redshift evolution follows the power-law form of n e = A × (1 + z) p with A=54−23+31 cm−3 and p=1.2−0.4+0.4 . This power-law form may be explained by a combination of metallicity and morphological evolution of galaxies, which become, on average, more metal poor and more compact with increasing redshift.

JWST NIRSpec Spectroscopy of the Triply Lensed z = 10.17 Galaxy MACS0647–JD

We present JWST/NIRSpec prism spectroscopy of MACS0647−JD, a triply lensed z ∼ 11 candidate discovered in Hubble Space Telescope imaging and spatially resolved by JWST imaging into two components, A and B. Spectroscopy of component A yields a spectroscopic redshift z = 10.17 based on seven detected emission lines: C iii] λ λ1907, 1909, [O ii] λ3727, [Ne iii] λ3869, [Ne iii] λ3968, Hδ λ4101, Hγ λ4340, and [O iii] λ4363. These are the second-most distant detections of these emission lines to date, in a galaxy observed just 460 million years after the Big Bang. Based on observed and extrapolated line flux ratios we derive a gas-phase metallicity 12 + log(O/H) ∼ 7.5–8.0, or Z ∼ (0.06–0.2) Z ⊙, ionization parameter log(U) = −1.9 ± 0.2, and an ionizing photon production efficiency log(ξion)=25.2±0.2 erg−1 Hz. The spectrum has a softened Lyα break, evidence for a strong Lyα damping wing. The Lyα damping wing also suppresses the F150W photometry, explaining the slightly overestimated photometric redshift z = 10.6 ± 0.3. MACS0647−JD has a stellar mass log(M/M ⊙) = 8.1 ± 0.3, including ∼6 × 107 M ⊙ in component A, most of which formed recently (within ∼20 Myr) with a star formation rate ∼ 2 ± 1 M ⊙ yr−1, all within an effective radius 70 ± 24 pc. Spectroscopy of a fainter companion galaxy C separated by a distance of ∼ 3 kpc reveals a Lyman break consistent with z ∼ 10.17. MACS0647−JD is likely the most distant galaxy merger known.

Gamma-ray line emission from the Local Bubble

Deep-sea archives that include intermediate-lived radioactive 60Fe particles suggest the occurrence of several recent supernovae inside the present-day volume of the Local Bubble during the last ~10 Myr. The isotope 60Fe is mainly produced in massive stars and ejected in supernova explosions, which should always result in a sizeable yield of 26Al from the same objects. 60Fe and 26Al decay with lifetimes of 3.82 and 1.05 Myr, and emit γ rays at 1332 and 1809 keV, respectively. These γ rays have been measured as diffuse glow of the Milky Way, and would also be expected from inside the Local Bubble as foreground emission. Based on two scenarios, one employing a geometrical model and the other state-of-the-art hydrodynamics simulations, we estimated the expected fluxes of the 1332 and 1809 keV γ-ray lines, as well as the resulting 511 keV line from positron annihilation due to the 26Al β+ decay. We find fluxes in the range of 10−6–10−5 ph cm−2 s−1 for all three lines with isotropic contributions of 10–50%. We show that these fluxes are within reach for the upcoming COSI-SMEX γ-ray telescope over its nominal satellite mission duration of 2 yr. Given the Local Bubble models considered, we conclude that in the case of 10–20 Myr-old superbubbles, the distributions of 60Fe and26 Al are not co-spatial - an assumption usually made in γ-ray data analyses. In fact, this should be taken into account however when analysing individual nearby targets for their 60Fe to26 Al flux ratio as this gauges the stellar evolution models and the age of the superbubbles. A flux ratio measured for the Local Bubble could further constrain models of 60Fe deposition on Earth and its moon.

Multivariate Predictors of Lyman Continuum Escape. I. A Survival Analysis of the Low-redshift Lyman Continuum Survey* * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO-15626, GO-13744,

To understand how galaxies reionized the Universe, we must determine how the escape fraction of Lyman continuum (LyC) photons (f esc) depends on galaxy properties. Using the z ∼ 0.3 Low-redshift Lyman Continuum Survey (LzLCS), we develop and analyze new multivariate predictors of f esc. These predictions use the Cox proportional hazards model, a survival analysis technique that incorporates both detections and upper limits. Our best model predicts the LzLCS f esc detections with an rms scatter of 0.31 dex, better than single-variable correlations. According to ranking techniques, the most important predictors of f esc are the equivalent width (EW) of Lyman-series absorption lines and the UV dust attenuation, which track line-of-sight absorption due to H i and dust. The H i absorption EW is uniquely crucial for predicting f esc for the strongest LyC emitters, which show properties similar to weaker LyC emitters and whose high f esc may therefore result from favorable orientation. In the absence of H i information, star formation rate surface density (ΣSFR) and [O iii]/[O ii] ratio are the most predictive variables and highlight the connection between feedback and f esc. We generate a model suitable for z > 6, which uses only the UV slope, ΣSFR, and [O iii]/[O ii]. We find that ΣSFR is more important in predicting f esc at higher stellar masses, whereas [O iii]/[O ii] plays a greater role at lower masses. We also analyze predictions for other parameters, such as the ionizing-to-nonionizing flux ratio and Lyα escape fraction. These multivariate models represent a promising tool for predicting f esc at high redshift.

Study on the fuel/air mixing process in a compact combustor with uneven flame stabilizer wall

Close-coupled injection is an important fuel injection method for future compact design combustors, and improving the mixing of fuel and gas is an important challenge for a wide operating range of the engine. By arranging uneven flame stabilizer walls behind the injection nozzles, the fuel penetration depth and fuel/air mixing of the close-coupled injection can be effectively improved at a low thrust state. In this paper, two kinds of uneven flame stabilizer wall structures were proposed, namely, the forked tail type and the lug-shaped type. The flow characteristics of different uneven flame stabilizer wall structures were investigated by combining numerical simulation and atomization experiments, and the differences in fuel distribution, jet trajectory, and combustion performance between the strut with uneven flame stabilizer wall structures and the U-shaped strut were qualitatively assessed. The results show that both proposed strut structures had a larger low-speed flame stabilization region, a greater jet penetration depth, and better combustion performance than did the common U-shaped strut, but with a greater flow resistance loss. The strut with a forked tail caused the airflow to deflect at the trailing edge of the strut, which in turn deflected the fuel, resulting in a larger recirculation zone and greater jet penetration depth. The lug-shaped strut produced a small recirculation zone behind the lug-shaped structure, and the fuel with a low fuel/air jet momentum flux ratio collided with the lug-shaped structure, thereby increasing the fuel jet penetration depth. The gap lug-shaped structure enhanced fuel diffusion and fuel/air mixing in the radial direction. Numerical studies under real operating conditions showed that the two types of uneven flame stabilizer wall structures were promising for improving the compactness of the combustor. Overall, two types of uneven flame stabilizer wall structures can promote fuel/air mixing during low engine operating states, which is conducive to widening the engine operating range and providing design solutions for the next generation of engine combustor designs with wide operating ranges.

Interface and mixing zone between soil waters arising from upward and downward seepage - Part II: Heterogeneous total density.

Freshwater lenses in otherwise saline environments contain an important source of fresh water for natural vegetation and agricultural crops. Such lenses are regularly found in areas where both upward seeping saline groundwater and downward infiltrating fresh recharge water occur simultaneously during part of the year, resulting in shallow freshwater lenses which are highly susceptible to changes in recharge or seepage. In a series of two papers, we consider the water – and solute transport in a 2D cross-section between two parallel outflow faces. In this second part of the series, we build upon expressions presented in the first part to consider a situation where the density of seepage water exceeds that of recharge water, as typical for many deltaic areas around the world. Analytical expressions and approximations are given to obtain the steady state position of the interface between the two types of water using a sharp interface approximation, with a focus on the position midway between two outflow faces. Results show that the effect of a heterogeneous density distribution is limited when the seepage flux exceeds the density difference induced flux, but increases rapidly for ratios of the seepage flux over the density flux falling below 1. The heterogeneous density distribution then results in a decrease in freshwater lens thickness and, correspondingly, a decrease in fresh water availability. We also consider time-variant, oscillatory boundary conditions, and show that for heterogeneous density distributions the interface approaches its equilibrium position faster than for a corresponding situation with a homogeneous density distribution, indicating a higher vulnerability for changing boundary conditions. We also demonstrate that heterogeneous density distributions have limited effect on the amplitude of the interface oscillations. Analytical results obtained with the simplified model are validated using the numerical code SUTRA, which solves the full model for a numerical grid.

Hidden Companions to Intermediate-mass Stars. XXII. Inferring a 0.43M ⊙, 1.65 au Companion in the Astrometric Binary within the Triple System Lambda Muscae* *Based on observations collected at the European Southern Observatory, Chile, Program ID 111.24UP.001.

Lambda Muscae is a nearby A-type star reported as a P = 474 days astrometric binary in Gaia DR3 (and previously in Hipparcos) and which also has a 0.16M ⊙ M dwarf companion at a projected separation 6.4 au discovered by VLT/SPHERE. Based on a K band flux ratio upper limit of 1% from a VLTI/GRAVITY interferometric observation, we estimate a primary mass M Aa = 2.28M ⊙ and infer that the closer companion is a M Ab = 0.43M ⊙ star (almost certainly an M dwarf) orbiting at a = 1.65 au. The triple system might be dynamically interesting given the low hierarchy and the ratio of angular momenta of the inner and outer orbits of about one.

Molecular beam epitaxy growth of topological insulator Bi4Br4 on silicon for the infrared applications

Bi4Br4 is a material rich in intriguing topological properties. Monolayer Bi4Br4 film exhibits helical edge states characteristic of a quantum spin Hall insulator, while bulk Bi4Br4 represents a higher-order topological insulator with hinge states. However, direct exfoliation from single crystal can only obtain thin nanowires due to the weak van der Waals forces between Bi4Br4 chains, which limits its optical analysis and application, while the growth of Bi4Br4 thin films is also full of challenges due to the extremely narrow growth temperature range and the accurate control of the BiBr3 flux. Here, we reported the controlled growth of α-Bi4Br4 thin films on intrinsic silicon substrates using molecular beam epitaxy. The growth temperature, BiBr3 flux, and the flux ratio of Bi and BiBr3 were accurately controlled. Then, the morphology, composition, and bonding of the prepared films were investigated using atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The growth of large, uniform thin films provides an ideal material platform for studying the physical properties of Bi4Br4. Additionally, we utilized Fourier-transform infrared spectroscopy to explore the film’s infrared characteristics, revealing strong absorption in the low frequency range due to the high proportion of one-dimensional topological edge states and laying the groundwork for further exploration of its potential applications in the optoelectronic field.

Pressure retarded osmosis enhanced by micro-nano bubbles: Coupling effects of operation conditions and mass transfer resistance analyses

The concentration polarization is one of the bottlenecks of pressure retarded osmosis (PRO) for industrial-scale application. Micro-nano bubbles (MNBs) could form a strong repulsion and shear force on the membrane surface, thus, the degree of concentration polarization is reduced, and hence, both the water flux and power density could be increased. In this paper, the synergistic effects of MNBs with concentration, temperature, water and air flow rates, pressure, and spacers were investigated through membrane cell scale experiments. A numerical model with trans-membrane heat flux and MNBs effects is built and validated by the experiment results. The mechanism of strengthening effect of MNBs could be explained. A maximum promotion of 6.28 % was achieved for concentration combination of 0.171–1 mol/L. However, the promotion ratio of water flux was deceased significantly with higher temperature (<1 % for 45 °C) and higher pressure (nearly zero for 7 bar). The light MNBs would be pushed away from membrane under larger water flux with larger osmotic pressure difference. The variations of mass transfer resistances, and the thicknesses of boundary layers were discussed. Moreover, the key variables that have significant impacts on the metrics of PRO process were identified through partial least squares analysis.

Influence of mass flux ratio and phase difference on impingement heat transfer characteristics of coaxial synthetic jet

The aim of the present study is to introduce and investigate the performance of a novel independently controlled coaxial synthetic jet (CSJ) designed for enhancing impinging heat transfer applications. The CSJ features a unique configuration with two coaxial cavities, each featuring inner and annular orifices of the same hydraulic diameter, all aligned at 0∘ The independently controlled CSJ allows precise manipulation of jet conditions and phase differences between its inner and outer cavities, offering a versatile platform for optimizing heat transfer performance under varying operational scenarios. This capability not only enhances our understanding of the heat transfer characteristics of the CSJ but also underscores its potential as an innovative tool for advancing thermal management in engineering systems. Here, the actuators are operated at a Reynolds number (Re) of 1260 to perform the jet impingement experiment. The study explores mass flux ratios, including 0.5, 1, and 2, to understand how these ratios affect impinging heat transfer characteristics. The investigation also explores the influence of different phase differences (∅) between the inner and outer diaphragms, ranging from 0∘ to 180∘ for different mass flux ratios. It has been observed that the percentage enhancement of the peak stagnation Nusselt number (Nustag) for Mr=0.5 is approximately 30.36░% and 53.68░% compared to Mr=1 and Mr=2, respectively. The peak Nustag enhancement of CSJ operated at Mr=0.5 is approximately 63.9░% and 58.6░% compared to the inner jet and annular jet operated separately. In the far field, when a phase difference of ∅=135∘ is provided, the peak Nustag is enhanced by approximately 17.29░% compared to ∅=0∘ for Mr=0.5. Based on the present study, it is recommended to operate the CSJ at a lower mass flux ratio (Mr=0.5) and a higher phase difference between the actuators (∅=135∘) to achieve maximum cooling effect from the heated plate.

Impact of energy deposition as active flow control on scramjet inlet performance using Immersed Boundary Method

This study investigates the impact of upstream energy deposition as an active flow control method on the performance of a two-dimensional scramjet inlet through numerical simulations. An in-house inviscid finite volume solver was employed for the simulations, with boundary reconstruction of the scramjet achieved using a ghost-cell based immersed boundary method. The effects of different energy spot locations, various energy strengths, and different freestream Mach numbers on the scramjet performance were thoroughly analyzed. Four inlet parameters, namely, mass capture ratio (μ), total pressure ratio (TPR), kinetic energy efficiency (ηKE), and flow distortion index (DI), were used to assess the scramjet performance. The analysis revealed that energy deposition significantly reduced flow distortion, resulting in noticeable improvements in mass flux and total pressure ratio. However, kinetic energy efficiency exhibited minimal change. The study provides comprehensive insights into the impact of energy deposition on scramjet performance, highlighting its potential for enhancing inlet characteristics.

Effects of injector spacing and momentum flux ratio on combustion instability in a model chamber with gas-centered swirl coaxial injectors

This study investigates the effects of injector spacing and momentum flux ratio on combustion instability in a model chamber with single and two injectors, both experimentally and numerically. For the experiments, injectors similar to those used in actual rocket engines were installed in a laboratory-constructed model chamber. Numerical simulations were conducted using ANSYS Fluent, employing a detailed combustion model to complement the experimental data. Flow conditions were categorized as fuel-lean and fuel-rich based on the fuel mass flow rate. The injector spacing varied from 15 to 45 mm, and the momentum flux ratio was adjusted from 6.4 to 139.8 by manipulating the fuel and oxidizer flow rates. Both experimental and numerical results consistently revealed distinct trends in combustion instability for lean and rich conditions, influenced by injector spacing and momentum flux ratio. Combustion stabilization was consistently more effective under fuel-rich conditions. Increasing the momentum flux ratio intensified combustion instability regardless of the fuel condition. For fuel-lean conditions, a rapid transition in combustion stability was observed, with the specific transition point varying depending on the injector spacing. Considering the trade-off between instability and injector number density, a spacing of 30 mm between injectors is recommended. Additionally, for both single and two injectors with various spacings under both lean and rich conditions, combustion stability was generally better when the momentum flux ratio was less than 48.8. These findings provide valuable insights into the control and management of combustion instability, aiding in the design of rocket engine combustors.

High-Quality Single-Step Growth of GaAs on C-Plane Sapphire by Molecular Beam

We report on the growth of high-quality GaAs semiconductor materials on an AlAs/sapphire substrate by molecular beam epitaxy. The growth of GaAs on sapphire centers on a new single-step growth technique that produces higher-quality material than a previously reported multi-step growth method. Omega-2theta scans confirmed the GaAs (111) orientation. Samples grown at 700 °C displayed the highest crystal quality with minimal defects and strain, evidenced by narrow FWHM values of the rocking curve. By varying the As/Ga flux ratio and the growth temperature, we significantly improved the quality of the GaAs layer on sapphire, as compared to that obtained in multi-step studies. Photoluminescence measurements at room temperature and 77 K further support these findings. This study underscores the critical role of the As/Ga flux ratio and growth temperature in optimizing GaAs epitaxial growth on sapphire.

Interplay of Kinetic and Thermodynamic Factors in the Stationary Composition of Vapor-Liquid-Solid IIIVxV1-x Nanowires.

Compositional control over vapor-liquid-solid III-V ternary nanowires based on group V intermix (VLS IIIVxV1-x NWs) is complicated by the presence of a catalyst droplet with extremely low and hence undetectable concentrations of group V atoms. The liquid-solid and vapor-solid distributions of IIIVxV1-x NWs at a given temperature are influenced by the kinetic parameters (supersaturation and diffusion coefficients in liquid, V/III flux ratio in vapor), temperature and thermodynamic constants. We analyze the interplay of the kinetic and thermodynamic factors influencing the compositions of VLS IIIVxV1-x NWs and derive a new vapor-solid distribution that contains only one parameter of liquid, the ratio of the diffusion coefficients of dissimilar group V atoms. The unknown concentrations of group V atoms in liquid have no influence on the NW composition at high enough levels of supersaturation in liquid. The simple analytic shape of this vapor-solid distribution is regulated by the total V/III flux ratio in vapor. Calculating the temperature-dependent desorption rates, we show that the purely kinetic regime of the liquid-solid growth occurs for VLS IIIVxV1-x NWs in a wide range of conditions. The model fits the data well on the vapor-solid distributions of VLS InPxAs1-x and GaPxAs1-x NWs and can be used for understanding and controlling the compositions of any VLS IIIVxV1-x NWs, as well as modeling the compositional profiles across NW heterostructures in different material systems.

The characterisation of water ice in debris discs: implications for JWST scattered light observations

Abstract Water ice plays a crucial role throughout the different stages of planetary evolution and is abundant in the Universe. However, its presence and nature in debris discs of exoplanetary systems are not yet strongly established observationally. In this study, we quantify and discuss the impact of ice parameters such as volume fraction ${\mathcal {F}}_{\rm ice}$, blow-out grain size, size distribution, and its phase on the observational appearance of debris discs, considering the diverse nature of these systems around stellar spectral types ranging from A to M. Our findings reveal that the prominent ice features at approximately 2.7 and 3.3 μm depend on both the water ice fraction ${\mathcal {F}}_{\rm ice}$ and the scattering angle, with backscattering geometries yielding the most prominent signatures. When the phase function is considered and data are not background limited, strong forward and backward scattering (near edge-on discs) are expected to yield the strongest detections in images/spectra for A or F-type stars, while scattering angle matters less for later type stars. The Fresnel peak at 3.1 μm serves as a viable discriminant for the transitional phase (crystalline/amorphous), while simultaneously constraining the water ice temperature. For JWST imaging, we find that the F356W and F444W filter combination is most effective for constraining the grain size distribution, while the F356W and F277W filter combination provides better constraints on the ice fraction ${\mathcal {F}}_{\rm ice}$ in debris discs. However, degeneracy between the grain size distribution and ice fraction when using photometric flux ratios means that obtaining robust constraints will likely require more than two filters, or spectroscopic data.

Hidden Companions to Intermediate-mass Stars. XXI. Discovery of a 0.5 M ⊙, 1.5 au Companion to Sadachbia = Gamma Aquarii* *Based on observations collected at the European Southern Observatory, Chile, Program ID 113.26GM.001.

Sadachbia = Gamma Aquarii is a nearby A0V star that was suspected to be a spectroscopic binary. Here we report on the direct detection of a companion with a K band flux ratio of 1.2% at a projected separation of 38.2 mas based on a VLTI/GRAVITY near-infrared interferometric observation. The implied mass and separation of the companion are 0.46 M ⊙ and 1.5 au based on the Gaia DR3 distance (or 0.55 M ⊙ and 1.9 au if the discrepant Hipparcos distance is used instead). The companion explains the X-ray emission of γ Aqr and the orbital motion with a period of about one year likely explains the discrepant Gaia and Hipparcos parallaxes. Further observations are necessary to measure the binary semimajor axis but it is likely that the system will undergo common envelope evolution. The primary is partially resolved with an angular diameter of 0.52 mas.

Analysis of anthropogenic CO2 emission uncertainty and influencing factors at city scale in Yangtze River Delta region: One of the world's largest emission hotspots

Cities occupy only 3% of the earth's land area, yet they contribute over 70% of anthropogenic CO2 emissions. Accurately quantifying the corresponding uncertainty of CO2 emissions at the city scale is the first step in simulating global/regional greenhouse gas concentration and implementing effective emission reduction policies. As the world's largest emitter, China has committed to reaching its CO2 emissions peak by 2030, and cities are facing substantial pressure to reduce CO2 emissions. The Yangtze River Delta (YRD) region is treated as the largest urban agglomeration in China and globally. Despite the availability of multiple emission inventories, comprehensive assessments of city-level CO2 emissions uncertainty within this region are still lacking. This study focused on the YRD region, compared six inventories and used nighttime light intensity, GDP, population, and satellite-based xCO2 concentrations as proxy data to identify potential sources of emission bias. The findings are as follows: (1) The city-level CO2 emissions in the YRD region ranged from tens of Mt to approximately 600 Mt. From 2010 to 2019, emissions in the region increased slowly. However, emission intensity (calculated by dividing the CO2 emissions by the Gross Domestic Product) showed a declining trend. The relatively low proportion of point source emissions in EDGAR inventory is attributed to its reliance on the point source CARMA, which overlooks smaller point sources. (2) The average uncertainties for low emission (0–50 Mt), medium emission (50–100 Mt) and high emission (>100 Mt) cities were 51.1%, 34.0%, and 45.0%, respectively. The absolute errors of emissions showed strong positive correlations with proxy data. There exists a logarithmic relationship between them and uncertainty, which can assist in estimating emission uncertainty in other cities in the future. (3) The ratios of biological CO2 flux to the ten-year average of CO2 emissions varied between-6.79% and −0.02%, which are much smaller than the uncertainty of anthropogenic emissions, the comparisons indicate that recent large biases in estimating anthropogenic CO2 emissions hinder the evaluation of carbon neutrality ability.

Water fluxes and energy partitioning over a Larix principis-rupprechtii plantation forest in a dryland mountain ecosystem, Northwest China

Plantations make up a sizable component of forest ecosystems in China's drylands and play an important role controlling the energy balance and water cycle. However, there is limited knowledge regarding the exchange of water and energy in dryland plantations, particularly those located within the intricate and unique environments of dryland mountain regions. The focus of this study was the investigation of a Larix principis−rupprechtii plantation within a dryland mountain ecosystem located in Northwest China. The eddy covariance method was employed to calculate the water and energy fluxes, while the thermal dissipation probe (TDP) method was utilized to measure forest overstory transpiration (T) from 2018 to 2021. The links between energy allocation and various components in water flux were investigated, as well as the variable dynamics of water and energy flux and their relationship with environmental conditions. The findings demonstrated that the annual mean cumulative evapotranspiration (ET) was about 510 mm, accounting for over 82.8 % of the precipitation, which was mainly from soil evaporation and understory transpiration, rather than overstory transpiration (T). The average value of T/ET was 0.25 for the growing season, and surface conductance (Gs) was always higher than canopy conductance (Gc) on both daily and monthly scales. The evaporative fraction (EF) and Priestley-Taylor model coefficient (α) in the growing season were significantly higher than those in the non-growing season, and α>1 from June to September, indicating that the ecosystem in the study area had sufficient water supply. Furthermore, during the growing season, the ratio of latent heat flux (LE) to net radiation (Rn) was larger than that in the non-growing season, while the proportion of sensible heat flux (H) was opposite, and soil heat flux (G) accounted for the smallest proportion of net radiation. This study provides valuable insights into the energy fluxes and water fluxes within the ecosystem of dryland mountain plantations, and it serves as a guide for choosing afforestation tree species in the future.

Improving the performance of the photosynthetic apparatus of Citrus sinensis with the use of chitosan-selenium nanocomposite (CS + Se NPs) under salinity stress

BackgroundAbiotic stress, such as salinity, affects the photosynthetic apparatus of plants. It is reported that the use of selenium nanoparticles (Se NPs), and biochemical compounds such as chitosan (CS) increase the tolerance of plants to stress conditions. Therefore, this study aimed to elucidate the potential of Se NPs, CS, and their composite (CS + Se NPs) in improving the photosynthetic apparatus of C. sinensis under salt stress in greenhouse conditions. The grafted seedlings of C. sinensis cv. Valencia after adapting to the greenhouse condition, were imposed with 0, 50, and 100 mM NaCl. After two weeks, the plants were foliar sprayed with distilled water (control), CS (0.1% w/v), Se NPs (20 mg L− 1), and CS + Se NPs (10 and 20 mg L− 1). Three months after treatment, the levels of photosynthetic pigments, leaf gas exchange, and chlorophyll fluorescence in the treated plants were evaluated.ResultsUnder salinity stress, total chlorophyll, carotenoid, and SPAD values decreased by 31%, 48%, and 28% respectively, and Fv/Fm also decreased compared to the control, while the ratio of absorption flux (ABS), dissipated energy flux (DI0) and maximal trapping rate of PSII (TR0) to RC (a measure of PSII apparent antenna size) were increased. Under moderate (50 mM NaCl) and intense (100 mM NaCl) salinity stress, the application of CS + Se NPs significantly increased the levels of photosynthetic pigments and the Fv/Fm value compared to plants treated with distilled water.ConclusionsIt may be inferred that foliar treatment with CS + Se NPs can sustain the photosynthetic ability of C. sinensis under salinity stress and minimize its deleterious effects on photosynthesis.

Changes in holding time depending liquid filling ratio, heat transfer parameters, and shape of the tank

This study simulates the self-pressurization of liquefied hydrogen using a three-element lumped model. We analyze the effects of liquid filling ratio, heat flux distribution, interface heat transfer parameters, and tank shape on pressure build-up, which can vary due to ship transportation conditions. Key findings are: lower liquid levels correlate with faster pressure build-up; the sensitivity of pressure build-up to changes in the heat flux ratio between vapor and liquid is higher during laden voyages compared to ballast voyages; The effect of heat absorption by vapor on pressure build-up is greater than that of BOG caused by heat transfer; and horizontal tanks exhibit the longest holding time. These findings enhance the understanding and prediction of pressure dynamics in liquid hydrogen transportation, aiding the design and optimization of systems for safe and efficient operation.