Abstract We investigate nuclear reactions and feedback in hyperaccreting neutron star environments, considering accretion rates in the range 0.3–3 × 10 4 M ⊙ yr −1 , typical of short-period compact-object binaries in common envelopes. Our models account for weak reactions, neutrino energy loss, nuclear energy release, pair production, degenerate equations of state, and general relativistic hydrodynamics. Depending on the accretion rates, these systems can develop both proton- and neutron-rich atmospheres with strong convective instabilities linking the neutrino sphere to the outgoing accretion shock inside the radiation trapping zone. Convection drives nucleons through multiple heating and cooling cycles, with photodisintegration dominating during the heating phase and heavy element synthesis during the cooling phase, ejecting material with abundances that depend on the accretion rate and depth of the final decompression trajectory. The turbulent nature of convective currents is conducive to creating a wide range of nuclear products through a variety of effects, including nuclear statistical equilibrium freeze-out and the r -, p -, and γ -processes. We also observe a novel multistep process in reheated trajectories, consisting of proton-capture and photodissociation reactions operating on r -process seeds, producing overall neutron-deficient isotopes. A significant amount of infalling gas experiences high entropy and short (millisecond) freeze-out timescales capable of making r -process elements with high overabundances through a disequilibrium effect between neutrons and α -particles that does not require an excess of neutrons.

ABSTRACT Aim Polar and alpine plants live at the edge of their physiological limits. Thus, relatively small changes in climate can have disproportionate effects on biological and ecological processes. Antarctic mosses display highly variable micro‐topography (canopy architecture) over centimetre scales that correspond with spatial patterns in moss health. We aimed to assess the influence of centimetre‐scale micro‐topography on biologically relevant canopy microclimates across Antarctic moss beds. Location Trans‐Antarctic. Time Period 2018–2023. Major Taxa Studied Moss communities (bryophytes). Methods Spatially explicit microclimate data were measured (canopy temperature and water content) at different micro‐topographic positions (micro‐ridges and valleys, and various micro‐slopes and aspects) within 1 m 2 plots of continuous moss cover in Maritime and East Antarctica. Solar radiation was modelled at 1 cm 2 resolution. Results (1) Moss canopies varied by up to 2.24°C in mean and 15°C in maximum temperature within plots, with centimetre‐scale micro‐topography consistently shaping microclimate conditions. (2) Micro‐topographic position, seasonal solar dynamics and processes such as radiative trapping jointly influence the spatial structure of moss temperatures over centimetre scales. (3) East Antarctic mosses show a greater ability to warm above ambient air temperature compared to Maritime Antarctic mosses and may be especially at risk of exceeding upper temperature thresholds. Main Conclusions This study considers the effect of centimetre‐scale moss micro‐topography on moss canopy microclimates and more broadly offers novel insights into the spatial structure and variation of ground‐level climate over scales typically overlooked by in situ measurements. We discuss centimetre‐scale microclimate variation in terms of moss physiology and observed declines in the health of East Antarctic mosses which visibly map to the micro‐topography. These findings are especially relevant for regions across the globe with short‐stature vegetation, like bio‐crusts, and alpine and polar fellfields. Recognising climate variation at micro‐topographic scales is crucial for understanding ecophysiology and plant–climate interactions.

The anthropogenic rise in greenhouse gas emissions intensifies the trapping of longwave radiation emitted from the Earth's surface, leading to increased global temperatures. High temperatures (HT) adversely affect the critical developmental stages in chilli, such as root initiation, flowering and fruit set. In response, chilli plant employs a range of strategies including escape, acclimation and adaptation mediated by the expression of stress responsive proteins, genes and metabolites. The key components of this response include heat shock proteins (HSPs), reactive oxygen species (ROS) scavenging enzymes, aquaporins, osmoprotectants and other stress inducible genes that collectively enhance thermotolerance. Conventional breeding efforts have improved HT adaptability by selection for traits such as increased biomass, normalized difference vegetation index (NDVI) and reduced canopy temperature. In addition, landraces represent valuable genetic resources for identifying heat tolerant genotypes, and can be evaluated by advanced phenotyping platforms. Moreover, the integration of next generation sequencing (NGS) technologies with physiological data allows for the rapid and high-throughput discovery of candidate genes associated with heat stress tolerance. Molecular breeding approaches such as marker assisted selection (MAS), genomic selection and genome wide association studies (GWAS) enable the development of heat tolerant chilli cultivars in shortest time duration. This review offers an in-depth analysis of the physiological, biochemical and genetic mechanisms underlying heat tolerance (HT) in chilli, recent omics advancements and the challenges of breeding heat resilient cultivars. A deeper understanding of these mechanisms is crucial for creating robust chilli varieties capable of withstanding HT, ensuring sustainable yields and food security under changing global climatic conditions.

University campuses feature spatially diverse environments where thermal performance varies seasonally and spatially. In this study, we integrate field measurements with ENVI-met simulations to evaluate how sky view factor (SVF) influences microclimate and outdoor thermal comfort-quantified via air temperature (Ta), mean radiant temperature (Tmrt), wind speed (WS), relative humidity (RH), physiologically equivalent temperature (PET), and the Universal Thermal Climate Index (UTCI)-within urban street and urban building spaces on a temperate Chinese campus. The results reveal contrasting thermal responses: in summer, low-SVF urban street spaces (SVF_avg 0.075) exhibit moderate heat stress (PET_avg 34.5–39.5 °C) due to radiative trapping and limited ventilation, whereas high-SVF urban building spaces (SVF_avg 0.159) face greater heat load and stronger thermal stress, with peak PET exceeding 49.9 °C. In winter, high-SVF urban building spaces benefit from solar gain, improving thermal comfort. Statistical analyses indicate non-linear threshold effects of SVF on comfort indices, with summer comfort positively correlated at SVF > 0.2, and winter comfort negatively associated at SVF ≤ 0.4. These findings identify SVF as a key geometric predictor of seasonal thermal comfort in distinct campus spatial types, provide quantitative thresholds to guide climate-resilient campus planning in warm temperate zone.

Abstract Improving our understanding of thermal interactions between urban buildings is a major challenge regarding future climate projections. In this paper, we quantify the influence of radiative trapping on indoor thermal comfort into dwellings located in an urban canyon during a summer heatwave. A numerical urban model based on the finite element method (FEM) coupled to a radiosity method is used to simulate a Mediterranean city building. The complete thermal problem, including conduction, convection, and radiation, is solved in a transient regime using meteorological data representative of heatwave conditions. Physiological Equivalent Temperature (PET) indicator is used to assess indoor comfort, accounting for radiation exposure. The results show that longwave radiative trapping leads to a sustained increase in indoor PET of approximately 4K, whereas the influence of shortwave varies by ±1K.

Abstract When operated at sufficiently high pressures, inductively coupled plasmas (ICPs) can produce intense gas heating which is useful for a range of applications including materials processing, gas conversion, and analytical chemistry. However, the use of physical measurement probes can be challenging inside ICPs because of the high-temperature plasma-gas environment and diagnostic access may often be limited or perturb the system. Non-invasive diagnostics, such as optical emission spectroscopy (OES), are therefore attractive alternatives but often require an associated mathematical model for complete analysis and interpretation. In this work, we present a collisional-radiative model (CRM) of a radio-frequency (RF) ICP operating with argon gas and terminated with a supersonic nozzle. The two-temperature model considers 20 different charged and neutral particle species, and accounts for important collisional (such as excitation and de-excitation), radiative (including radiation trapping), and diffusive processes. The CRM is coupled to a global plasma discharge model that enables the temperatures and species population densities to be self-consistently determined as a function of ICP operating conditions (such as mass flow rate, RF power, and nozzle size). The coupled model is compared with both a simplified analytical theory and experimental measurements obtained with several non-invasive diagnostics (including OES and electrical circuit probes) showing good agreement. The system is found to be non-equilibrium even near atmospheric pressure conditions, although the model electron temperature is close to the measured argon excitation temperature indicating at least partial local thermodynamic equilibrium between electrons and excited neutral states.

We present a statistical study of the transmission and dwell-time matrices in disordered media composed of resonators, focusing on how frequency detuning influences their eigenvalue distributions. Our analysis reveals that the distribution of transmission eigenvalues undergoes a transition from a monomodal to a bimodal profile, and back to monomodal, as the frequency approaches the resonant frequency of the particles. Moreover, the distribution of dwell-time eigenvalues broadens significantly near resonance, with the longest lifetimes exceeding the median by several orders of magnitude. These results are explained by examining how frequency ω affects the transport mean free path of light ℓ(ω) and the energy transport velocity vE(ω), which in turn shape the observed distributions. We demonstrate the strong potential of wavefront shaping to synthesize wavefronts associated with eigenstates that enhance transmission and energy storage (or radiation trapping) in resonant disordered media. In the diffusive regime, where the system thickness L exceeds the mean free path, both transmission and dwell time can be enhanced by a factor ∝L/ℓ(ω)≫1 when using wavefronts associated with the largest eigenvalues instead of plane waves. In the localized regime, the enhancements become ∝Ne2L/ξ for transmission and ∝Nξ/L for dwell time, where ξ is the localization length and N is the number of controlled scattering channels. Finally, we show that employing high-Q resonators instead of low-Q ones increases energy storage within the medium by a factor of ∝Q/kℓ(ω) in both the diffusive and localized regimes.

Urban Heat Islands (UHIs) significantly influence local climate, energy consumption, and public health, yet the role of atmospheric electromagnetic (EM) radiation in UHI dynamics remains underexplored. This study presents a physics-based modeling approach to quantify the impact of EM radiation—including solar, terrestrial, and anthropogenic sources—on UHI intensity. By integrating radiative transfer equations (RTEs) with urban microclimate models, we simulate the absorption, scattering, and thermal effects of EM waves across different urban geometries and materials. High-resolution remote sensing data and ground-based measurements validate the model, revealing that microwave and infrared bands contribute disproportionately to localized heating. Our results demonstrate that electromagnetic interactions amplify UHI effects by 10–15% in dense urban areas, particularly near high-reflectivity surfaces and RF-emitting infrastructure. Furthermore, the model identifies mitigation strategies, such as spectrally selective coatings and vegetation-based shielding, to reduce radiative heat trapping. This work advances the understanding of EM-driven thermal dynamics in cities and provides a predictive framework for sustainable urban planning in a warming climate.

The effusive Holuhraun eruption in Iceland emitted large quantities of sulfur into the troposphere during the fall and winter of 2014–15. Previous studies have shown that the resulting volcanic aerosols led to reduced insolation, and thus surface cooling, through increased cloud shortwave reflectance, mostly over the North Atlantic and Europe. Less attention has been paid to the Arctic, which at the time of the eruption received limited sunlight. Based on evidence from observations and model simulations, here we argue that increased cloud liquid water path and cloud cover following the 2014–15 Holuhraun eruption led to surface warming in the Arctic through trapping of longwave radiation. Our results show that sulfur emissions from the eruption led to extended lifetime of low and middle level clouds, reducing the longwave radiative cooling of the surface. This is the first time, to our knowledge, that an effusive volcanic eruption is shown to have this effect. Given the high level of volcanic activity in Iceland, these findings demonstrate the need to further investigate the climate impacts of high-latitude effusive volcanic eruptions. Moreover, marine cloud brightening through cloud seeding has been suggested as one way to combat anthropogenic climate change but, as our results suggest, such actions might have counteractive regional consequences.

Abstract This study systematically investigates the spin relaxation characteristics of alkali‐metal atoms in spin‐exchange relaxation‐free (SERF) co‐magnetometers, focusing on mitigating the radiation trapping to reduce the alkali‐metal spin relaxation rate. Radiation trapping is one of the dominant mechanisms exacerbating spin relaxation in alkali‐metal atoms and is conventionally suppressed by introducing nitrogen () as a quenching agent. However, experiments reveal that the typical concentration in current SERF co‐magnetometers is insufficient to effectively suppress radiation trapping. By increasing the quenching gas concentration, additional attenuation of the radiation trapping effect is achieved. Meanwhile, to address the enhanced spin‐exchange collision relaxation arising from higher concentration, the operating temperature is adjusted to increase the alkali‐metal atom number density, thereby effectively curtailing this adverse effect. Experimental results demonstrate that the synergistic optimization of concentration and temperature reduces alkali‐metal spin relaxation by approximately 55% and decreases the noise power spectral density of the co‐magnetometer by 48.5% at 1 Hz. These findings confirm the effectiveness of this approach in improving the accuracy and sensitivity of SERF co‐magnetometers.

Shortwave cloud warming effect observed over highly reflective Greenland.

Urban heat intensification and its implications for environmental health due to solar radiation absorption is a key driver of the Urban Heat Island (UHI) effect, particularly in Mediterranean climates. In dense urban fabrics, shortwave radiation is repeatedly reflected within street canyons, affecting pedestrian-level radiative exposure. This study introduces the Urban Canyon Shortwave Trapping Index (STIc), a dimensionless parameter quantifying geometry-induced shortwave accumulation near the ground. Shortwave fluxes were simulated using the SOLWEIG model over the centre of Nicosia, Cyprus, under typical summer conditions. Wall albedo was systematically varied (0.2–0.8) to represent a range of common building materials and cooling strategies, including Nature-Based Solution (NBS). Results show that STIc increases with both wall reflectivity and canyon depth, reaching values above 2 in high-albedo, high aspect ratio configurations. Maximum thermal trapping occurs between 11:00 and 14:00 local time, coinciding with peak in solar altitude. Spatial variability of STIc also increases with wall albedo, indicating greater sensitivity to morphological differences under more reflective conditions. These findings support the integration of both morphological and material-based strategies in UHI mitigation and thermal comfort improvement and sustainable urban development.

Abstract The work is aimed at revealing the influence of volume recombination on the formation of plasma parameters on the example of a diffuse and constricted positive column of a DC discharge in argon depending on the discharge current at pressures of 100–300 Torr·cm. At a qualitative level, the limiting transitions from the diffusion mode to the recombination mode of discharge maintenance are analyzed, which lead either to a rectangle-shaped radial profile of charged particles (arc discharge) or to a compressed profile (constricted discharge). Valuable information about the processes occurring in the plasma volume can be obtained from the ion current flowing toward the wall of the discharge tube since it is determined as a difference between the volume ionization and recombination. Based on a collision-radiative model, the ion current towards the tube wall was calculated and compared with the experimental results of probe measurements. In a diffuse discharge (low discharge current) a satisfactory agreement between the theory and experiment is observed. After the abrupt transition to the constricted regime (high discharge current), the theoretical values become strongly underestimated, and not able to describe the experimental data. The reasons for these discrepancies are analyzed. It is shown that the photoemission from the surface of the probe under the action of resonance photons gives an additional ion probe current which allows eliminating the discrepancies between the theory and experiment. Based on the Holstein–Biberman equation, the influence of the resonance radiation trapping on the discharge properties is revealed. The account of radiation trapping improves the agreement between the theory and experiment, including the values of the critical discharge currents at which the constriction occurs.

The radiation force of a partially coherent self-focusing vortex beam on Rayleigh particles is studied in this paper. According to the generalized Huygens-Fresnel principle and Rayleigh scattering theory, the effects of two main parameters of the beam, namely relative coherence length and non-trivial phase factor, on the self-focusing characteristics and radiation force are respectively researched. We have also conducted a brief analysis of the stability of particle capture using this self-focusing vortex beam. It has been found that changing the values of such parameters can flexibly regulate the self-focusing effect of the beam on propagation so as to effectively adjust the magnitude of the radiation force and trapping range. The results show that such beams can be used to trap and manipulate particles without using a focusing lens. In addition, this beam is able to capture two different refractive index particles, that is, high refractive index particles are captured near the focus, and low refractive index particles are captured on the z-axis. The research results establish a theoretical basis for the application of this novel partially coherent self-focusing vortex beams in optical tweezers technology.

This study reports light narrowing in paraffin-coated vapor cells from room temperature 27 to 59 °C, where spin-exchange relaxation is suppressed. By means of a coating lock and eliminating the reservoir effect, an ultra-narrow magnetic resonance linewidth of 0.36 Hz and an atomic coherence lifetime of T2=0.9 s are achieved. In cells free of buffer gas, the narrow linewidth over this broad temperature range is a result of enhanced spin polarization, which is facilitated by the effective suppression of radiation trapping benefiting from the stability of the vapor density. Using such cells in atomic magnetometers, the photon shot noise limit is estimated as 0.2 fT/Hz1/2 and the spin-projection noise limit is estimated as 1.1 fT/Hz1/2. Also, a magnetometer system with the stable coated cell is identified, which demonstrates the potential for achieving relatively stable magnetometer sensitivity without precisely controlling the cell temperature. The long coherence lifetime and the broad operating temperature range expand the potential applications of quantum memory and other quantum sensors such as atomic clocks.

Misty plasmas have recently emerged as a promising tool for nanocomposite thin films deposition. However, aerosol-plasma interactions remain poorly documented, especially at low working pressure. In this work, optical emission spectroscopy is used to probe the temporal evolution of three fundamental plasma parameters during pulsed liquid injection in an inductively coupled argon plasma at low-pressure. Time-resolved values of metastable argon density, electron temperature, and electron density are determined from radiation trapping analysis and particle balance equations of selected argon 1s and 2p levels. Pulsed liquid injection is found to induce a sudden drop in metastable density and electron temperature, and an increase in electron density. These results are attributed to the lower ionization thresholds of the injected molecular species compared to the one of argon. In addition, upstream liquid temperature is found to affect the transitory kinetics for non-volatile solvents more than volatile ones, in accordance with a previously reported flash boiling atomization mechanism.

We report the development of a computational framework for the calculation of the optical emission spectrum of a low-pressure argon capacitively coupled plasma (CCP), which is based on the coupling of a particle-in-cell/Monte Carlo collision simulation code with a diffusion-reaction-radiation code for Ar I excited levels. In this framework, the particle simulation provides the rates of the direct and stepwise electron-impact excitation and electron-impact de-excitation for 30 excited levels, as well as the rates of electron-impact direct and stepwise ionization. These rates are used in the solutions of the diffusion equations of the excited species in the second code, along with the radiative rates for a high number of Ar-I transitions. The calculations also consider pooling ionization, quenching reactions, and radial diffusion losses. The electron energy distribution function and the population densities of the 30 excited atomic levels are computed self-consistently. The calculations then provide the emission intensities that reproduce reasonably well the experimentally measured optical emission spectrum of a symmetric CCP source operated at 13.56 MHz with 300 V peak-to-peak voltage, in the 2–100 Pa pressure range. The accuracy of the approach appears to be limited by the one-dimensional nature of the model, the treatment of the radiation trapping through the use of escape factors, and the effects of radiative cascades from higher excited levels not taken into account in the model.

Graded metal pushered single shells (PSS) are a viable alternative to low-Z capsules (Z is the atomic number) for indirect drive inertial confinement fusion implosions due to enhanced core tamping and radiation trapping, but they can be compromised by the pusher mixing with the fuel. We compare 2-shock and 3-shock laser pulses for Be/Cr PSS capsules filled with deuterium–tritium gas fuel at 6 mg/cc density. 1D radiation-hydrodynamic simulations predict higher core compression and, hence, ∼2× higher fusion yield for the 3-shock drive than for 2-shock. Nevertheless, we observe similar core ion temperatures and fusion yields for both drives. The implosion burn duration is 25% shorter and the core volume is ∼2.5× smaller for the 3-shock drive than for 2-shock, consistent with a higher compression. 1D LASNEX mix simulations using a buoyancy-drag model matching the measured yields also agree with the observed core sizes and burn durations and suggest ∼40% and ∼70% yield degradations for 2-shock and 3-shock drives due to hydrodynamic instabilities and atomic mix at the pusher–fuel interface. At the same time, 2D HYDRA simulations show that mid-mode (2–250) instability degradations are negligible for the 2-shock implosion (9%) and significant (45%) for 3-shock. Subtracting these from the 1D mix simulations, we infer similar degradations from high-mode instabilities and atomic mix for both drives. Due to its robustness to mid-mode instabilities, future pusher–gas mix studies will use the 2-shock drive.

We propose the application of helium line intensity ratio spectroscopy in a low-pressure (0.3 mTorr) xenon E × B discharge with an electron temperature of ∼2 eV and a density of 1010−1011cm−3 . We successfully identified the helium atom line emissions at 388.9, 447.1, 501.6, 504.8, and 706.5 nm with helium pressures of up to ∼20 mTorr. The measured electron temperature, density, and I−V characteristics of the discharge remained almost constant in all helium pressures in the present experiment, indicating the suitability of the helium gas as a diagnostic gas. The results of helium line intensity ratio spectroscopy using the line emissions at 388.9, 447.1, and 504.8 nm showed fair agreement with the Langmuir probe measurement. Considering the trade-off relationship between the disturbance introduced by the helium gas and the signal-to-noise ratio, we conclude that a helium pressure of approximately 4 mTorr (approximately 13 times the partial pressure of xenon) represents the optimal pressure range for the application of the helium line emission intensity ratio method to this xenon plasma. It is found that the use of the line emissions at 501.6 and 706.5 nm result in a significant disturbance in the helium line intensity ratio method due to the radiation trapping effect.

Laser-direct-drive fusion target designs with solid deuterium-tritium (DT) fuel, a high-Z gradient-density pusher shell (GDPS), and a Au-coated foam layer have been investigated through both 1D and 2D radiation-hydrodynamic simulations. Compared with conventional low-Z ablators and DT-push-on-DT targets, these GDPS targets possess certain advantages of being instability-resistant implosions that can be high adiabat (α≥8) and low hot-spot and pusher-shell convergence (CR_{hs}≈22 and CR_{PS}≈17), and have a low implosion velocity (v_{imp}<3×10^{7}cm/s). Using symmetric drive with laser energies of 1.9 to 2.5MJ, 1D lilac simulations of these GDPS implosions can result in neutron yields corresponding to ≳50-MJ energy, even with reduced laser absorption due to the cross-beam energy transfer (CBET) effect. Two-dimensional draco simulations show that these GDPS targets can still ignite and deliver neutron yields from 4 to ∼10MJ even if CBET is present, while traditional DT-push-on-DT targets normally fail due to the CBET-induced reduction of ablation pressure. If CBET is mitigated, these GDPS targets are expected to produce neutron yields of >20MJ at a driven laser energy of ∼2MJ. The key factors behind the robust ignition and moderate energy gain of such GDPS implosions are as follows: (1) The high initial density of the high-Z pusher shell can be placed at a very high adiabat while the DT fuel is maintained at a relatively low-entropy state; therefore, such implosions can still provide enough compression ρR>1g/cm^{2} for sufficient confinement; (2) the high-Z layer significantly reduces heat-conduction loss from the hot spot since thermal conductivity scales as ∼1/Z; and (3) possible radiation trapping may offer an additional advantage for reducing energy loss from such high-Z targets.