Photon Flux Research Articles

In a Different Light: Irradiation-Induced Cuticular Wax Accumulation Fails to Reduce Cuticular Transpiration.

The cuticle, an extracellular hydrophobic layer impregnated with waxy lipids, serves as the primary interface between plant leaves and their environment and is thus subject to external cues. A previous study on poplar leaves revealed that environmental conditions outdoors promoted the deposition of about 10-fold more cuticular wax compared to the highly artificial climate of a growth chamber. Given that light was the most significant variable distinguishing the two locations, we hypothesized that the quantity of light might serve as a key driver of foliar wax accumulation. Thus, this study aimed to isolate the factor of light quantity (photosynthetic photon flux density [PPFD]) from other environmental stimuli (such as relative humidity and ambient temperature) and explore its impact on cuticular wax deposition and subsequent rates of residual foliar transpiration in different species. Analytical investigations revealed a significant increase in cuticular wax amount with increasing PPFD (between 50 and 1200 µmol m-2 s-1) in both monocotyledonous (maize and barley) and dicotyledonous (tomato and bean) crop species, without altering the relative lipid composition. Despite the increased wax coverages, rates of foliar water loss did not decrease, further confirming that the residual (cuticular) transpiration is independent of the cuticular wax amount.

A unifying principle for global greenness patterns and trends

Vegetation cover regulates the exchanges of energy, water and carbon between land and atmosphere. Remotely-sensed fractional absorbed photosynthetically active radiation (fAPAR), a land-surface greenness measure, depends on carbon allocation to foliage while also controlling photon flux for photosynthesis. Here we use an equation with just two globally fitted parameters to describe annual maximum fAPAR as the smaller of a water-limited value transpiring a constant fraction of annual precipitation, and an energy-limited value maximizing annual plant growth. This minimalist description reproduces global greenness patterns and temporal trends in remote-sensing data, comparable to the best-performing dynamic global vegetation models. Widely observed greening is attributed principally to the influence of rising carbon dioxide on the light- and water-use efficiencies of photosynthesis; limited browning regions are attributed to drying. This research provides one key component of ecosystem function as a step towards more robust foundations for new-generation land ecosystem models.

Intermittent Supplementation with Far-Red Light Accelerates Leaf and Bud Development and Increases Yield in Lettuce.

Supplementation with far-red light in controlled environment agriculture production can enhance yield by triggering the shade avoidance syndrome. However, the effectiveness of this yield enhancement can be further improved through intermittent far-red light supplementation. In this study, the effects are explored of varying far-red light photon intensities and intermittent exposure durations-specifically at 5, 15, 30, and 45 min intervals-on the growth and development of lettuce (Lactuca sativa) in plant factories, while maintaining a constant red light photon flux and daily light integral. The results showed that compared to constant far-red light, 30 min intermittent far-red light increased yield by 11.7% and the number of leaves and buds by 2.66. Furthermore, the various metrics demonstrated that intermittent far-red light supplementation enhanced the overall effectiveness of the far-red light treatment. This was validated by analyzing phytohormone content and the expression of genes related to hormone metabolism and transport at the tip of the lettuce stems. Transcriptome analysis revealed that the differences in gene expression between treatments were primarily concentrated in genes related to signaling, hormone metabolism, and transport. Weighted Gene Co-expression Network Analysis identified the co-expression modules associated with yield and quality. Additionally, dynamic expression analysis showed genes involved to far-red photoreception, response, and hormone metabolism and transport exhibited optimal rhythmic responses only under 30 min intermittent far-red light supplementation. This suggests that intermittent far-red light irradiation at 30 min intervals is the most effective for activating far-red light signaling influencing hormone metabolism and transport, thereby accelerating the growth of lettuce leaves and buds and ultimately increasing yield.

Optimize the preparation process of m-TiO2@CdS by response surface methodology to enhance the light intensity adaptability of photocatalytic degradation of tetracycline

Catalyst performance is traditionally evaluated under high light intensity, where variations in e--h+ pair recombination rates at different light intensities may limit the applicability of the selected catalyst to diverse light sources. Response surface methodology (RSM) was employed to compare catalyst performance under two optimization processes, using tetracycline degradation rate and photon flux as response variables. The m-TiO2@CdS catalyst was characterized by XRD, SEM, TEM, XPS, and UV-Vis-DRS, and its preparation process was optimized using RSM, with precursor ratio, hydrothermal time, and temperature as variables. The proposed optimization model for tetracycline degradation rate and photon flux exhibited a strong correlation between predicted and experimental results. The tetracycline degradation rates for the two optimized preparation processes were nearly identical, at 61.87% and 61.18%, respectively. A comparison of tetracycline degradation kinetics under different light conditions (light saturation and non-saturation) for the two optimized m-TiO2@CdS samples demonstrated that the photon flux-based optimization model offered greater adaptability across a wider range of light intensities. Additionally, the repeatability of m-TiO2@CdS prepared under the optimal conditions was assessed, and a plausible mechanism for its photocatalytic degradation of tetracycline was proposed.

Shedding light on biochemical changes in single neuron-like pheochromocytoma cells following exposure to synchrotron sourced terahertz radiation using synchrotron source Fourier transform infrared microspectroscopy.

Synchrotron sourced Fourier transform infrared (SS FTIR) microspectroscopy was employed to investigate the biological effects on the neuron-like pheochromocytoma (PC 12) cells after exposure to synchrotron sourced terahertz (SS THz) radiation. Over 10 min of exposure, the PC 12 cells received a total energy of 600 J m2, with a total incident power density of ∼1.0 W m-2 (0.10 mW cm-2) at the beam extraction port (BEP) of the THz beamline at the Australian Synchrotron. To investigate the metabolic response of PC 12 cells after synchrotron THz radiation exposure, we utilized the FTIR microscope at the Infrared Microspectroscopy IRM beamline, which offers high photon flux and diffraction-limited spatial resolution enabling the detection of functional group variations in biological molecules at a single-cell level. Principal component analysis (PCA) based on the SS FTIR spectral data revealed a distinct separation of SS THz-exposed and control (non-exposed) cells. According to the PCA loadings, the key changes in the exposed cells involved lipid and protein compositions as indicated by the stretching vibrations of CH2/CH3 groups and amide I/II bands, respectively. An increase in lipids, such as cholesterol, or notable changes in their compositions and in some protein secondary structures were observed in the SS THz-exposed cells. The PCA analysis further suggests that PC 12 cells might maintain cell membrane stability after SS THz irradiation through higher volumes of cholesterol and cell morphology via regulation of the synthesis of cytoskeleton proteins such as actin-related proteins. The outcome of this study re-emphasized the exceptional SS FTIR capability to perform single-cell analysis directly, providing (i) unique biological information on cell variability within the population as well as between different groups, and (ii) evidence of molecular changes in the exposed cells that could lead to a deeper understanding of the effect of THz exposure at a single-cell level.

Development of a low-dose strategy for propagation-based imaging helical computed tomography (PBI-HCT): high image quality and reduced radiation dose

Background. Propagation-based imaging computed tomography (PBI-CT) has been recently emerging for visualizing low-density materials due to its excellent image contrast and high resolution. Based on this, PBI-CT with a helical acquisition mode (PBI-HCT) offers superior imaging quality (e.g., fewer ring artifacts) and dose uniformity, making it ideal for biomedical imaging applications. However, the excessive radiation dose associated with high-resolution PBI-HCT may potentially harm objects or hosts being imaged, especially in live animal imaging, raising a great need to reduce radiation dose.Methods. In this study, we strategically integrated Sparse2Noise (a deep learning approach) with PBI-HCT imaging to reduce radiation dose without compromising image quality. Sparse2Noise uses paired low-dose noisy images with different photon fluxes and projection numbers for high-quality reconstruction via a convolutional neural network (CNN). Then, we examined the imaging quality and radiation dose of PBI-HCT imaging using Sparse2Noise, as compared to when Sparse2Noise was used in low-dose PBI-CT imaging (circular scanning mode). Furthermore, we conducted a comparison study on the use of Sparse2Noise versus two other state-of-the-art low-dose imaging algorithms (i.e., Noise2Noise and Noise2Inverse) for imaging low-density materials using PBI-HCT at equivalent dose levels.Results. Sparse2Noise allowed for a 90% dose reduction in PBI-HCT imaging while maintaining high image quality. As compared to PBI-CT imaging, the use of Sparse2Noise in PBI-HCT imaging shows more effective by reducing additional radiation dose (30%-36%). Furthermore, helical scanning mode also enhances the performance of existing low-dose algorithms (Noise2Noise and Noise2Inverse); nevertheless, Sparse2Noise shows significantly higher signal-to-noise ratio (SNR) value compared to Noise2Noise and Noise2Inverse at the same radiation dose level.Conclusions and significance. Our proposed low-dose imaging strategy Sparse2Noise can be effectively applied to PBI-HCT imaging technique and requires lower dose for acceptable quality imaging. This would represent a significant advance imaging for low-density materials imaging and for future live animals imaging applications.

The ALPINE-ALMA [CII] Survey: Modelling ALMA and JWST lines to constrain the interstellar medium of z∼ 5 galaxies

Aims. We have devised a model for estimating the ultraviolet (UV) and optical line emission (i.e. CIII] 1909 Å, Hβ, [OIII] 5007 Å, Hα, and [NII] 6583 Å) that traces HII regions in the interstellar medium (ISM) of a subset of galaxies at z ~ 4-6 from the ALMA large programme ALPINE. The aim is to investigate the combined impact of binary stars in the stellar population and an abrupt quenching in the star formation history (SFH) on the line emission. This is crucial for understanding the ISM’s physical properties in the Universe’s earliest galaxies and identifying new star formation tracers in high-z galaxies. Methods. The model simulates HII plus PhotoDissociation Region (PDR) complexes by performing radiative transfer through 1D slabs characterised by gas density (n), ionisation parameter (U), and metallicity (Z). The model also takes into account (a) the heating from star formation, whose spectrum has been simulated with Starburst99 and Binary Population and Spectral Synthesis (BPASS) to quantify the impact of binary stars; and (b) a constant, exponentially declining, and quenched SFH. For each galaxy, we selected from our CLOUDY models the theoretical ratios between the [CII] line emission that trace PDRs and nebular lines from HII regions. These ratios were then used to derive the expected optical/UV lines from the observed [CII]. Results. We find that binary stars have a strong impact on the line emission after quenching, by keeping the UV photon flux higher for a longer time. This is relevant in maintaining the free electron temperature and ionised column density in HII regions unaltered up to 5 Myr after quenching. Furthermore, we constrained the ISM properties of our subsample, finding a low ionisation parameter of log U≈ − 3.8 ± 0.2 and high densities of log(n/cm−3)≈2.9 ± 0.6. Finally, we derive UV/optical line luminosity-star formation rate relations (log(Lline/erg s−1) = α log(SFR/M⊙ yr−1) + β) for different burstiness parameter (ks) values. We find that in the fiducial BPASS model, the relations have a negligible SFH dependence but depend strongly on the ks value, while in the SB99 case, the dominant dependence is on the SFH. We propose their potential use for characterising the burstiness of galaxies at high z.

Inherent stochasticity, noise and limits of detection in continuous and time-gated fluorescence systems

We present a model for the noise and inherent stochasticity of fluorescence signals in both continuous wave (CW) and time-gated (TG) conditions. When the fluorophores are subjected to an arbitrary excitation photon flux, we apply the model and compute the evolution of the probability mass function (pmf) for each quantum state comprising a fluorophore’s electronic structure, and hence the dynamics of the resulting emission photon flux. Both the ensemble and stochastic models presented in this work have been verified using Monte Carlo molecular dynamic simulations that utilize the Gillespie algorithm. The implications of the model on the design of biomolecular fluorescence detection systems are explored in three relevant numerical examples. For a given system, the quantum-limited signal-to-noise ratio (QSNR) and limits of detection are computed to demonstrate how key design tradeoffs are quantified. We find that as systems scale down to micro- and nano- dimensions, the interplay between the fluorophore’s photophysical qualities and use of CW or TG has ramifications on optimal design strategies when considering optical component selection, measurement speed, and system energy requirements. While CW systems remain a gold standard, TG systems can be leveraged to overcome cost and system complexity hurdles when paired with the appropriate fluorophore.

Combined Fit of Spectrum and Composition for FR0 Radio-galaxy-emitted Ultra–high energy Cosmic Rays with Resulting Secondary Photons and Neutrinos

This study comprehensively investigates the gamma-ray dim population of Fanaroff–Riley Type 0 (FR0) radio galaxies as potentially significant sources of ultra–high energy cosmic rays (UHECRs, E > 1018 eV) detected on Earth. While individual FR0 luminosities are relatively low compared to the more powerful Fanaroff–Riley Type 1 and Type 2 galaxies, FR0s are substantially more prevalent in the local universe, outnumbering the more energetic galaxies by a factor of ∼5 within a redshift of z ≤ 0.05. Employing CRPropa3 simulations, we estimate the mass composition and energy spectra of UHECRs originating from FR0 galaxies for energies above 1018.6 eV. This estimation fits data from the Pierre Auger Observatory (Auger) using three extensive air shower models; both constant and energy-dependent observed elemental fractions are considered. The simulation integrates an approximately isotropic distribution of FR0 galaxies, extrapolated from observed characteristics, with UHECR propagation in the intergalactic medium, incorporating various plausible configurations of extragalactic magnetic fields, both random and structured. We then compare the resulting emission spectral indices, rigidity cutoffs, and elemental fractions with recent Auger results. In total, 25 combined energy-spectrum and mass-composition fits are considered. Beyond the cosmic-ray fluxes emitted by FR0 galaxies, this study predicts the secondary photon and neutrino fluxes from UHECR interactions with intergalactic cosmic photon backgrounds. The multimessenger approach, encompassing observational data and theoretical models, helps elucidate the contribution of low-luminosity FR0 radio galaxies to the total cosmic-ray energy density.

Adaptive significance of age- and light-related variation in needle structure, photochemistry, and pigments in evergreen coniferous trees

Evergreen conifers thrive in challenging environments by maintaining multiple sets of needles, optimizing photosynthesis even under harsh conditions. This study aimed to investigate the relationships between needle structure, photosynthetic parameters, and age along the light gradient in the crowns of Abies alba, Taxus baccata, and Picea abies. We hypothesized that: (1) Needle structure, photochemical parameters, and photosynthetic pigment content correlate with needle age and light levels in tree crowns. (2) The photosynthetic capacity of ageing needles would decline and adjust to the increasing self-shading of branches. Our results revealed a non-linear increase in the leaf mass-to-area ratio. The maximum quantum yield of photosystem II photochemistry decreased linearly with needle age without reaching levels indicative of photoinhibition. Decreased maximum electron transport rates (ETRmax) were linked to declining values of saturating photosynthetic photon flux density and increasing non-photochemical quenching of fluorescence (NPQ), indicating energy losses as heat. The chlorophyll a to chlorophyll b ratio linearly decreased, suggesting older needles sustain high light capture efficiency. These findings offer new insights into the combined effects of needle ageing and self-shading on photochemistry and pigment content. This functional needle balance highlights the trade-off between the costs of long-term needle retention and the benefits of efficient resource utilization. In environments where air temperature is less of a constraint on photosynthesis due to climate warming, evergreen coniferous trees could sustain or enhance their photosynthetic capacity. They can achieve this by shortening needle lifespan and retaining fewer cohorts of needles with higher ETRmax and lower NPQ compared to older needles.

3D Ordered Macroporous Mn, Zr-Doped CaCO3 Nanomaterials for Stable Thermochemical Energy Storage.

Developing high-performance Ca-based materials that can work for long-term heat transfer and storage in concentrated solar power plants is crucial to achieve the large-scale conversion of solar photon fluxes to dispatchable electricity. This work demonstrates that a series of Mn, Zr co-doped CaCO3 nanomaterials with the 3D ordered macroporous (3DOM) skeletons are successfully prepared by a novel strategy of templated metal salt co-precipitation. The characterization results indicate that a majority of Zr and Mn are atomically dispersed into the highly-crystallized CaCO3 framework, whereas a minor amount of Mn is present in the form of CaMnO3 nanoparticles (NPs). The optimal 3DOM material made by templating with PS microspheres with a diameter of ≈350nm, 3DOM-Ca80Mn10Zr10, shows a solar light absorptance of ≈74.1% and an initial energy storage density of 1706.4 kJkg-1. Importantly, it gives an impressive energy storage density loss of <6.0% and maintains above 1600kJ kg-1 after 125 cycles. The density functional theory calculations reveal that the co-doping of Mn and Zr into the CaO crystal lattice offers a strong affinity to [Ca4O4] clusters, as a result, the anti-sintering of CaO NPs is significantly enhanced under high temperature.

Morpho-Physiological Responses of Shade-Loving Fern Polystichum spp. to Single and Combined Lead and Light Stress

The effects of lead (Pb) stress on plant growth and physiological processes may depend on other environmental stresses coinciding. Knowledge of the response of shade-loving plants to stresses, particularly the relationship between Pb stress and light stress, is lacking. The effects of single and combined Pb and light stress on the growth and physiological parameters of Polystichum setiferum and Polystichum setiferum ‘Proliferum’ ferns were evaluated under glasshouse conditions. Treatments comprised control (80% shade, ~111 μmol m−2 s−1 photosynthetic photon flux density, PPFD), light stress (100% full sunlight, ~525 μmol m−2 s−1 PPFD), 1000 mg dm−3 Pb solution applied to plants under shade and light stress conditions. Under full sunlight, plants had damaged leaves and reduced leaf biomass, and underground parts of the plants had levels of photosynthetic pigments, reducing sugars and total flavonoids. The Pb stress decreased plant growth, reducing sugars, and free amino acids content, and at the same time increased chlorophyll content in P. setiferum and total polyphenols and flavonoid content in P. setiferum ‘Proliferum’. The combined stress of Pb and full sunlight reduced plant growth and the accumulation of pigments, reducing sugars, and free amino acids without affecting the levels of secondary metabolites. P. setiferum plants accumulated more Pb than P. setiferum ‘Proliferum.’ The fern P. setiferum ‘Proliferum’ was more tolerant to abiotic stresses than the fern P. setiferum. This study provided new insights into the response of shade-loving ornamental plants to single and combined Pb and light stress.

Evaluating the effect of supplementary lighting on the growth and physiological activity of roses during winter by plant-induced electrical signal

ABSTRACT Limited light intensity and low temperature in winter lead to various challenges such as reduction in growth, yield and quality of cultivated roses, which can be complemented by artificial supplementary lights. This study aims to evaluate the effect of different supplementary lights, including metal-halide (MH), metal-halide+high-pressure sodium lamp (MH + HPS) and high-pressure sodium lamp (HPS) on the growth characteristics of cultivated roses in winter. Compared to individual light, the results demonstrated that combined supplementary lights (MH + HPS) increased stem diameter, number of leaves and flower diameter of cultivated roses. The height, leaf length, leaf width, number of petals, chlorophyll content and chlorophyll fluorescence (Fv/Fm) of roses grown in different supplementary lights were not significantly affected. In all the three treatment areas, photosynthetic photon flux density (PPFD) and temperature at night were higher in the MH + HPS area, followed by the HPS and MH areas. The plant-induced electrical signal (PIES) of roses cultivated under MH + HPS light indicated higher water and nutrient uptake than other treatments, which was positively associated with rose growth, but the difference was insignificant. Principal component analysis (PCA) revealed that the growth parameters of roses were mainly associated with MH + HPS supplementary light. Therefore, combined supplementary light was beneficial to improve the growth and quality of cultivated roses.

Oxime ether photobromination in a photomicroreactor: Process parameters and kinetic modeling

AbstractPhotobromination reaction of oxime ether (OE) to brominated oxime ether (BOE) is an important process for the synthesis of trifloxystrobin in the fungicide industry. Herein, continuous synthesis of BOE in photomicroreactors was performed. Initially, an investigation was carried out to study the effects of various parameters, including mixing performance, molar ratios, solvents, incident photon flux, and temperature, on the photobromination process. Moreover, a kinetic model was established, and the activation energies for the main and side reactions were determined. The relationship between the reaction rate constant and light flux was illuminated. Transition states and energy changes in the bromination process were analyzed using density functional theory calculation. Remarkably, an 83.1% yield of BOE was achieved in the photomicroreactor and the required reaction time was reduced to approximately 1/10 of the batch reactor. This work was of crucial theoretical significance and practical value for better understanding of photobromination processes and parameter optimization.

The effect of radiation pressure on the dispersal of photoevaporating discs

Abstract Observed IR excesses indicate that protoplanetary discs evolve slowly for the majority of their lifetime before losing their near- and mid-IR excesses on short timescales. Photoevaporation models can explain this ‘two-timescale’ nature of disc evolution through the removal of inner regions of discs after a few million years. However, they also predict the existence of a population of non-accreting discs with large cavities. Such discs are scarce within the observed population, suggesting the models are incomplete. We explore whether radiation-pressure-driven outflows are able to remove enough dust to fit observations. We simulate these outflows using cuDisc, including dust dynamics, growth/fragmentation, radiative transfer and a parameterisation of internal photoevaporation. We find that, in most cases, dust mass-loss rates are around 5-10 times too small to meet observational constraints. Particles are launched from the disc inner rim, however grains larger than around a micron do not escape in the outflow, meaning mass-loss rates are too low for the initial dust masses at gap-opening. Only systems that have smooth photoevaporation profiles with gas mass-loss rates &amp;gt;∼5 × 10−9 M⊙ yr−1 and disc dust masses &amp;lt;∼1 M⊕at the time of gap opening can meet observational constraints; in the current models these manifest as EUV winds driven by atypically large high-energy photon fluxes. We also find that the height of the disc’s photosphere is controlled by small grains in the outflow as opposed to shadowing from a hot inner rim; the effect of this can be seen in synthetic scattered light observations.

Response of Morphological Plasticity of Quercus variabilis Seedlings to Different Light Quality

This experiment explores the regulatory mechanisms of various light qualities on the phenotypic plasticity of Quercus variabilis seedlings during their growth. The light conditions included blue light (BL), red light (RL), far-red light (FrL), a blend of RL and FrL with a ratio of 1:1 (RFr1:1L), and a blend of RL and FrL with a ratio of 1:2 (RFr1:2L), alongside a broad-spectrum white light (WL) as the control. Each treatment was maintained at a consistent photosynthetic photon flux density of 400 µmol·m−2·s−1. Results indicate significant morphological variations in Q. variabilis seedlings under different light qualities. Compared to white light treatment, all light quality treatments enhance seedling height, with the FrL treatment exhibiting the most pronounced effect. Seedling ground diameter elongation is stimulated by all light quality treatments, except for the BL treatment. Although the BL treatment promotes leaf morphology in Q. variabilis seedlings, it inhibits root growth, leading to reduced biomass accumulation and a lower root-to-shoot ratio. FrL can mitigate the effects of RL. Under the FrL treatment, Q. variabilis seedlings exhibit a greater increase in plant height and a higher height-to-diameter ratio. While the leaf morphology of RFr1:1L treatment does not show significant advantages, it demonstrates substantial root growth, resulting in the highest biomass accumulation. Quercus variabilis displays the strongest morphological plasticity in its root system, showing greater sensitivity to variations in light quality compared to leaf morphology and biomass accumulation. Strategically optimizing light spectrum and wavelength can significantly boost economic yields and improve the quality of forestry products.

Development of a highly sensitive detection module incorporating a charge-sensitive infrared phototransistor and a Ge hemispherical mirror

Abstract Charge-sensitive infrared phototransistors (CSIPs) based on GaAs/AlGaAs quantum well structures permit highly sensitive detection of radiation in the wavelength range of 10–50 μm. Despite this excellent sensitivity, their quantum efficiency remains limited to approximately 20%. In this study, we first developed a cryogenic measurement system for evaluating the quantum efficiency of CSIPs using a calibrated thermal radiation source (a heated chip resistor) in a liquid-helium-free refrigerator. Using this measurement system, which sufficiently suppresses background infrared radiation, we next attempted to enhance the quantum efficiency by combining the CSIP with a hemispherical mirror composed of a germanium hemispherical lens with a metal-coated convex surface. Mounting the hemispherical mirror on the CSIP surface improved the quantum efficiency to 35%. Moreover, by covering the frontside of the CSIP, the mirror further suppressed the infrared background radiation from the surrounding environment, reducing the detectable photon flux limit to 2×10^6 s^(-1), corresponding to a power of 35 fW. The proposed optical detection module with the dielectric hemispherical mirror is anticipated to prove valuable for developing highly sensitive mid- and far-infrared detectors.

The interactive effects between far-red light and temperature on lettuce growth and morphology diminish at high light intensity.

Phytochromes (PHYs) play a dual role in sensing light spectral quality and temperature. PHYs can interconvert between the active Pfr form and inactive Pr form upon absorption of red (R) and far-red (FR) light (Photoconversion). In addition, active Pfr can be converted to inactive Pr in a temperature-dependent manner (Thermal Reversion). Recent studies have shown that FR light and temperature can interactively affect plant growth and morphology through co-regulating phytochrome activities. These studies were primarily conducted under relatively low light intensities. As light intensity increases, the impact of thermal reversion on phytochrome dynamics decreases. However, the light intensity dependency of the interactive effects between FR light and temperature on plant growth and morphology has not been characterized. In this study, lettuce (Lactuca sativa L.) 'Rex' was grown under two total photon flux densities (TPFD; 400-800 nm) (150 and 300 μmol m-2 s-1) x three temperatures (20, 24, and 28°C) x two light spectra (0 and 20% of FR light in TPFD). Our results showed that the effects of FR light on leaf, stem, and root elongation, leaf number, and leaf expansion were dependent on temperature at lower TPFD. However, the magnitude of the interactive effects between FR light and temperature on plant morphology decreased at higher TPFD. Particularly, at a lower TPFD, FR light stimulated leaf expansion and canopy photon capture only under a cooler temperature of 20°C. However, at a higher TPFD, FR light consistently increased total leaf area across all three temperatures. Plant biomass was more strongly correlated with the total number of photons intercepted by the leaves than with the photosynthetic activities of individual leaves. FR light decreased the contents of chlorophylls, carotenoids, flavonoids, and phenolics, as well as the total antioxidant capacity. In contrast, warmer temperatures and high light intensity increased the values of these parameters. We concluded that the interactive effects between FR light and temperature on plant growth and morphology diminished as total light intensity increased. Additionally, the combination of high light intensity, warm temperature, and FR light resulted in the highest crop yield and antioxidant capacity in lettuce.

High Frequency Gravitational Wave bounds from galactic neutron stars

High-Frequency Gravitational Waves (HFGWs) constitute a unique window on the early Universe as well as exotic astrophysical objects. While the current gravitational wave experiments are more dedicated to the low frequency regime, the graviton conversion into photons in a strong magnetic field constitutes a powerful tool to probe HFGWs. In this paper, we show that neutron stars, due to their extreme magnetic field, are a perfect laboratory to study the conversion of HFGWs into photons. Using realistic models for the galactic neutron star population, we calculate for the first time the expected photon flux induced by the conversion of an isotropic stochastic gravitational wave background in the magnetosphere of the ensemble of neutron stars present in the Milky Way. We compare this photon flux to the observed one from several telescopes and derive upper limits on the stochastic gravitational wave background in the frequency range 108 Hz–1025 Hz. We find our limits to be competitive in the frequency range 108 Hz–1012 Hz.

Temporal and Spectral Analysis of the Unique and Second-brightest Gamma-Ray Burst GRB 230307A: Insights from GECAM and Fermi/GBM Observations

In this study, we present the pulse profile of the unique and the second-brightest gamma-ray burst GRB 230307A, and analyze its temporal behavior using a joint GECAM–Fermi Gamma-ray Burst Monitor (GBM) time-resolved spectral analysis. The utilization of GECAM data is advantageous as it successfully captured significant data during the pileup period of the Fermi/GBM. We investigate the evolution of its flux, photon fluence, photon flux, peak energy, and the corresponding hardness–intensity and hardness–flux correlations. The findings within the first 27 s exhibit consistent patterns reported previously, providing valuable insights for comparing observations with predictions from the synchrotron radiation model invoking an expanding shell. Beyond the initial 27 s, we observe a notable transition in the emitted radiation, attributed to high-latitude emission, influenced by the geometric properties of the shells and the relativistic Doppler effects. By modeling the data within the framework of the large-radius internal shock model, we discuss the required parameters as well as the limitations of the model. We conclude that a more complicated synchrotron emission model is needed to fully describe the observational data of GRB 230307A.