Water Ice Research Articles

Signature of Proton-Hole Transfer in Hydrogen-Bonded Solids at 10 K.

Although proton transport in water ice is well understood, proton-hole transfer (PHT) involving proton abstraction by anions remains less explored. This study investigates PHT in H2S and NH3 solids at low temperatures, aiming to determine whether these solids exhibit negative charge transport similar to that in ice. In H2S and NH3 solids at 10 K, surface HS- and NH2- anions in hydrogen-bonded systems trigger negative current flow, providing a clear signature of PHT. This negative current is controlled by electron flow and 193 nm ultraviolet irradiation, which generates HS- and NH2- anions on the solid surfaces. In bilayer H2S/H2O and NH3/H2O solids, a significant negative current is observed only in the NH3/H2O solid, which is attributed to the exothermic proton abstraction by NH2- from H2O at the bilayer interface, a process not available for H2S on ice. This study is the first to demonstrate PHT-induced electrochemical behavior in hydrogen-bonded solids other than ice.

Extinction of Taurus, Orion, Perseus and California Molecular Clouds Based on the LAMOST, 2MASS, and Gaia Surveys. II. The Extinction Law

The extinction law from ultraviolet (UV) to infrared (IR; 0.2–24 μm) is determined by relying on the blue-edge method and color-excess ratios for some nearby molecular clouds, from the low-mass star-forming region to the massive star-forming region. The observational data are collected from nine photometric surveys, along with stellar parameters from the Apache Point Observatory Galaxy Evolution Experiment and LAMOST spectroscopic surveys. Within the uncertainties, the optical ratio of selective to total extinction ( RGBP ) does not vary substantially across the clouds, irrespective of the density, specifically RGBP=2.302±0.027 , where RGBP≡AGBP/EGBP,GRP . The IR extinction law is consistent with Wang & Chen. The extinction law in the UV band is compromised by the shallow depth with A V ≤ 2 mag and is hard to describe by one parameter R. In addition, the extinction in the WISE/W1 band is significantly larger than in the Spitzer/IRAC1 band in the dense regions, which is attributed to the ice water absorption.

Numerical Simulation Study on Ice–Water–Ship Interaction Based on FEM-SPH Adaptive Coupling Algorithm

To address the impact of layered ice and seawater on polar vessels navigating in icy waters, this study employs a coupled finite element method (FEM) and smoothed particle hydrodynamics (SPH) algorithm to simulate the collision dynamics between the bow and stern of a designated icebreaker and the ice layers. The foundational principles and deployment strategies of the coupling algorithm have been meticulously delineated, with a subsequent simulation conducted to model the trajectory of icebreakers navigating through stratified ice conditions. The ice load on the hull, the movement of broken ice bodies, and the temporal variation of ice resistance during collision were analyzed. The method’s applicability and precision were substantiated through a comparative analysis between the simulated ice resistance outcomes and the ice load estimations derived from the Lindqvist formula. Finally, the differences between the bow and stern icebreaking methods were compared. The research findings indicate that the coupling algorithm demonstrates high precision in simulating the navigation of icebreakers under layered ice conditions, aligning with actual scenarios. This provides a solid foundation for further exploration of the ice load on polar vessels. Furthermore, at equivalent speeds and ice thicknesses, stern icebreaking was observed to induce greater oscillations in ice load and yield a higher mean resistance compared to bow icebreaking.

The impact of cloud microphysics and ice nucleation on Southern Ocean clouds assessed with single-column modeling and instrument simulators

Abstract. Supercooled liquid clouds are common at higher latitudes (especially over the Southern Ocean) and are critical for constraining climate projections. We take advantage of the Macquarie Island Cloud and Radiation Experiment (MICRE) to perform an analysis of observed and simulated cloud processes over the Southern Ocean in a region and season dominated by supercooled liquid clouds. Using a single-column version of the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS), we compare two different cloud microphysical schemes to ground-based observations of cloud, precipitation, and radiation over a 2.5-month period (1 January–17 March 2017). Both schemes are able to reproduce aspects of the cloud and radiation observations during MICRE to within the uncertainty of the data when the thermodynamic profile is prescribed with relaxation. There are differences in water mass and representation of reflectivity between the schemes. A sensitivity study of the cloud microphysics schemes, one a bulk one-moment scheme and the other a two-moment scheme with prediction of mass and number, indicates that several key processes create differences between the schemes. Surface radiative fluxes and total water path are highly sensitive to the formation and fall speed of precipitation. The prediction of hydrometeor number with the two-moment scheme yields a better comparison with observed reflectivity and radiative fluxes, despite predicting higher liquid water contents than observed. With the two-moment scheme, we are also able to test the sensitivity of the results to the input of liquid cloud condensation nuclei (CCN) and ice nuclei (IN). The cloud properties and resulting radiative effects are found to be sensitive to the CCN and IN concentrations. More CCN and IN increase liquid and ice water paths, respectively. Thus, both the dynamic environment and aerosols, integrated through the cloud microphysics, are important for properly representing Southern Ocean cloud radiative effects.

Key processes controlling the variability of the summer marine CO2 system in Fram Strait surface waters

The aim of this study was to decouple and quantify the influence of various biological and physical processes on the structure and variability of the marine carbonate system in the surface waters of the eastern part of the Fram Strait area. This productive region is characterized by its complex hydrographic and sea ice dynamics, providing an ideal set up to study their influence on the variability of the marine carbonate system. Different variables of the marine CO2 system: Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), partial pressure of CO2 (pCO2), and pH, were analysed together with temperature, salinity, sea ice extension, and chlorophyll a distribution during three consecutive summers (2019, 2020 and 2021), each of them having a unique oceanographic setting. The data revealed that TA and DIC are mostly controlled by the mixing of Atlantic water and sea ice meltwater. The combined effects of organic matter production/remineralization, calcium carbonate precipitation/dissolution, and air/sea CO2 gas exchange cause deviations from this salinity-related mixing. The scale of these deviations and the proportion between the effects observed for TA and DIC suggest interannual shifts in net primary production and dominant phytoplankton species in the area. These shifts are correlated with the sea ice extent and the spread of the Polar Surface Waters in the region. Net primary production is the main factor controlling the temporal and spatial variability of pH and pCO2 in the study area followed by the influence of temperature and, mixing of water masses expressed with salinity (seawater freshening). Surface waters of the Fram Strait area were generally undersaturated in CO2. The lowest pCO2 values, coinciding with an increase in oxygen saturation, were observed in areas of mixing of Arctic and Atlantic-derived water masses. However, as shown for 2021, a reduction of the sea ice extent may induce a westward shift of the chlorophyll maximum, resulting in pCO2 increase and pH decrease in the eastern part. This indicates that sea ice extent and associated spread of Polar Surface Waters may be important factors shaping primary production, and thus pCO2 and pH, in the Fram Strait area.

Investigation of thunderstorm characteristics with severe lightning events over NE region of India

Abstract. The north eastern region (NER) of India is among the hotspot regions for thunderstorm events leading to substantial loss of lives and properties every year. A reliable thunderstorm early warning system can prevent these losses. As these events are highly dynamic, prediction becomes equally challenging. Diagnostic studies of such events could provide more understanding of lightning and storms over a region which could then be used as input for the prediction of such events. Improving the efficiency of the prediction of associated meteorological parameters could improve the prediction of thunderstorm. In this study, two thunderstorm events have been identified with high lightning flash counts, using observations from the INSAT-3D satellite and lightning detection sensors. These observations revealed that one of the events was caused by a cloud system that originated elsewhere and travelled over the area of impact while the other event was an isolated convective system that occurred over a small region. The characteristic features of thunderstorms, like vertical wind velocity, cloud ice water content, relative humidity, cloud fraction and radar reflectivity, etc. were simulated using the WRF model. These simulations were validated with the ERA-5 reanalysis data and observations from Radar and satellite data. Validation results suggest that the WRF model could predict these features associated with thunderstorm events quite reliably. The study helped to improve the severe weather warning over NER of India and the stakeholders are trained on effective utilization of such warning.

Shape-from-Shading Derived DEMs from ShadowCam Images in Permanently Shadowed Regions at the Lunar South Pole: A First Look

Abstract. The lunar south pole, particularly its permanently shadowed regions (PSRs), has been the focus of future lunar exploration. The solar altitude angle at the lunar south pole is less than ∼ 2°, resulting in the PSRs not being directly illuminated and the possible existence of water ice in the PSRs due to the low temperatures. High-resolution digital elevation models (DEMs) in PSRs are crucial for future exploration missions and scientific research. However, existing image datasets (e.g., LROC NAC images) cannot penetrate the PSRs. Laser altimetry (e.g., LOLA) can measure the PSRs, but the DEMs derived from LOLA suffer from noises and interpolation defects. ShadowCam is a newly deployed camera onboard the Korea Pathfinder Lunar Orbiter, with a high imaging sensitivity. ShadowCam can capture the faint secondary illumination within PSRs, revealing previously indistinguishable topographic features in persistent darkness. Based on our existing Shape-from-Shading (SfS) pipeline for generating high-resolution DEMs from monocular images, we introduce a novel SfS approach that utilizes secondary illumination and reflectance to reconstruct pixel-wise high-resolution DEMs from ShadowCam images in PSRs. The approach consists of three steps: (1) modeling the secondary illumination on the target surfaces in PSRs based on the view factor; (2) optimizing a low-resolution LOLA DEM using the secondary illumination model; (3) refining the DEM to pixel-wise resolution based on SfS using the ShadowCam images. A test area (approximately 1 km × 1 km) within the PSR in the Shackleton crater near the lunar south pole is used for experimental evaluation. The results show that the DEM generated by the proposed approach is highly consistent with the direct LOLA measurements, particularly in small-scale topographic features such as crater floors and rims that are absent from the LOLA DEM. A first look at the results indicates that the proposed approach has great potential for generating high-resolution DEMs from ShadowCam images in PSRs, which can aid future exploration missions targeting the PSRs at the lunar south pole and support related scientific research on the water ice in the PSRs.

Phase transitions of ice VIII-VII-X: A potential energy landscape perspective

Water ice, an archetypal molecular system, exhibits a complex phase diagram characterized by numerous phase transitions under varying pressure-temperature conditions. However, it remains a significant challenge to theoretical modeling of these transitions owing to the high dimensionality in representing the potential energy landscapes (PEL) of ice crystalline phases. In an attempt to deeply understand the mechanisms of phase transitions between ice VII, VIII, and X, a graph-based stationary-point network was employed to simplify the representation of the PEL and locally constructed the PEL of ice at different pressures by our developed high-index saddle dynamic scheme. The stationary-point networks at 40 and 80 GPa indicate a pronounced flattened PEL of ice over a wide range of pressure (up to at least 80 GPa), where multiple structures (i.e., local minima) are energetically degenerate with phase VIII and separated by low-energy barriers (∼10 meV/atom at 40 GPa). These features indicate the disordered VII phase is more favorable at finite temperatures, in agreement with previous experimental observations. Additionally, we demonstrated that the PEL topology undergoes a fundamental alteration at higher pressures, with a single funnel emerging at 120 GPa, facilitating the crystallization of phase X. This work serves as a proof of concept for using the stationary-point network to explicitly represent the PEL, highlighting their potential in elucidating complex phase transitions. Published by the American Physical Society 2024

A Broad Set of Solar and Cosmochemical Data Indicates High C-N-O Abundances for the Solar System

We examine the role of refractory organics as a major C carrier in the outer protosolar nebula and its implications for the compositions of large Kuiper Belt objects (KBOs) and CI chondrites. By utilizing Rosetta measurements of refractory organics in comet 67P/Churyumov–Gerasimenko, we show that they would make up a large fraction of the protosolar C inventory in the KBO-forming region based on the current widely adopted solar abundances. However, this would free up too much O to form water ice, producing solid material that is not sufficiently rock-rich to explain the uncompressed density of the Pluto–Charon system and other large KBOs; the former has been argued as the most representative value we have for the bulk composition of large KBOs. This inconsistency further highlights the solar abundances problem—an ongoing challenge in reconciling spectroscopically determined heavy-element abundances with helioseismology constraints. By employing a new data set from solar CNO neutrinos and solar wind measurements of C, N, and O, we show that the uncompressed density of the Pluto–Charon system can be reproduced over a wide range of scenarios. We show that a lack of sulfates in Ryugu and Bennu samples implies a lower amount of water ice initially accreted into CI chondrite parent bodies than previously thought. These data are found to be consistent with the solar C/O ratio implied by the new data set. Our predictions can be tested by future neutrino, helioseismology, and cosmochemical measurements.

A fluorine-free bioinspired multifunctional slippery coating for ultra-long-term anticorrosion of Mg alloy, static/dynamic anti-icing, antibacterial and antifouling

Poor corrosion resistance limits the application of Mg alloy and it is meaningful to explore a surface coating technology for ultra-long-term corrosion protection of Mg alloy. Superhydrophobic surface (SHS) and smooth liquid-injected porous surface (SLIPS) have shown important application value in the field of Mg alloy corrosion protection. However, the unstable special interface of air layer or lubricant cannot act as stable corrosion barrier for the long term. Inspired by frog skin, a bionic fluorine-free multifunctional slippery coating (MSC) is prepared by one-step spraying a mixture of epoxy resin, silicone oil, modified nano TiO2 and modified micron mica powder. MSC exhibits a microstructure similar to frog skin, excellent slippery (sliding angle ∼ 3°) and strong lubricant retention. Different from anticorrosion mechanism of SHS and SLIPS by their special interface, MSC, storing silicone oil on the surface and inside the coating, demonstrates ultra-long-term anticorrosion to Mg alloy (both neutral salt spray and 3.5 wt% NaCl solution immersion for 60 days) due to excellent barrier effect throughout coating, and the scratch defect area of MSC is not significantly eroded after 14 days of salt spray. Moreover, MSC exhibits excellent static/dynamic anti-icing ability and low ice adhesion in a −20℃ environment, outstanding adhesion (level 4B), high hardness (3H), antibacterial (>94 %), antifouling, chemical stability and resistance to boiling water, ice water and UV radiation. All these excellent properties can promote the application of Mg alloy in a wider range of fields.

Water and carbon fluxes from a supra-permafrost aquifer to a stream across hydrologic states

Supra-permafrost aquifers within the active layer are present in the Arctic during summer. Permafrost thawing due to Arctic warming can liberate previously frozen particulate organic matter (POM) in soils to leach into groundwater as dissolved organic carbon (DOC). DOC transport from groundwater to surface water is poorly understood because of the unquantified variability in subsurface properties and hydrological environments. These dynamics must be better characterized because DOC transport to surface waters is critical to predict the long-term fate of recently thawed carbon in permafrost environments. Here, we used distributed Darcy’s Law calculations to quantify groundwater and DOC fluxes into Imnavait Creek, Alaska, a representative headwater stream in a continuous permafrost watershed. We developed a statistical ensemble approach to model the parameter variability and range of potential contributions of steady-state groundwater flow to the creek. We quantified the model prediction uncertainty using statistical sampling of in-situ, active-layer soil hydro-stratigraphy (water table, ice table, and soil stratigraphy), high-resolution topography data, and DOC data. Moreover, the predicted groundwater discharge values representing all possible hydrologic conditions towards the end of the thawing season were also considered given the potential variability in saturation. The model predictions were similar to and span most of the observed range of Imnavait Creek streamflow, especially during recession periods, and also during saturation excess overland flow. As the Arctic warms and supra-permafrost aquifers deepen, groundwater flow is expected to increase. This increase is expected to impact stream, river, and lake biogeochemical processes by dissolving and mobilizing more soil constituents in continuous permafrost regions. This study highlights how quantifying the uncertainty of hydro-stratigraphical input parameters helps understand and predict supra-permafrost aquifer dynamics and connectivity to aquatic systems using a simple, but scalable, modeling approach.

Influence of starch on freeze-thaw stability of Hypophthalmichthys molitrix surimi gel observed via ice crystal distribution and gel properties

Starch has been recognized as a vital ingredient in surimi products due to its ability to absorb water, which reduces the deterioration of gels and water loss during freezing and thawing. However, it is essential to ascertain the role of starch in the formation of ice crystals and the texture of surimi gels. The impact of freeze-thaw cycles on the morphology and distribution of ice crystals, as well as the textural characteristics of gelatinized and ungelatinized starch-surimi gels was investigated. The results of light microscopy revealed that the presence of starch, irrespective of whether it was gelatinized, resulted in a reduction in the size of ice crystals within the surimi gel network during the freeze-thaw process. In addition, starch in surimi gels was subjected to freeze-thaw cycles, resulting in the emergence of two distinct states of bound water (0.1–1 ms and 1–10 ms). The higher relative content of immobile water indicated that the gelatinized starch had improved water holding properties. Furthermore, the incorporation of gelatinized starch into surimi enhanced its freeze-thaw stability and retarded the loss of gel strength, hardness, and whiteness. The addition of starch had a synergistic impact, enhancing the gel properties by affecting the formation of ice crystals and water absorption.

Estimating ice water content for winter storms from millimeter-wavelength radar measurements using a synthesis of polarimetric and dual-frequency radar observations

Abstract The potential of millimeter-wavelength radar-based Ice Water Content (IWC) estimation is demonstrated using a Ka-band Scanning Polarimetric Radar (KASPR) for the U.S northeast coast winter storms. Two IWC relations for Ka-band polarimetric radar measurements are proposed: one that uses a combination of the radar reflectivity Z and the estimated total number concentration of snow particles Nt and the other based on the joint use of Z, specific differential phase KDP, and the degree of riming frim. A key element of the algorithms is to obtain the “Rayleigh-equivalent” value of Z measured at Ka band, i.e., the corresponding Z at longer radar wavelength for which Rayleigh scattering takes place. This is achieved via polarimetric retrieval of the mean volume diameter Dm and incorporating the relationship between the dual wavelength ratio DWRS/Ka and Dm. Those techniques allow for retrievals from single millimeter-wavelength radar measurements and do not necessarily require the DWR measurements, if the DWR-Dm relation and Rayleigh assumption for Ka-band KDP are valid. Comparison between the quasi-vertical profile product obtained from KASPR and the columnar vertical profile product generated from the nearby WSR-88D S-band radar measurements demonstrates that the DWRS/Ka can be estimated from the two close radars without the need for collocated radar beams and synchronized antenna scanning and can be used for determining the “Rayleigh-equivalent” value of Z. The performance of the suggested techniques is evaluated for seven winter storms using surface disdrometer and snow accumulation measurements.

Changing disc compositions via internal photoevaporation

The chemical evolution of protoplanetary discs is a complex process that is not fully understood. Several factors influence the final spatial distribution of atoms and molecules in the disc. One such factor is the inward drift and evaporation of volatile-rich pebbles that can enrich the inner disc with vapour. In particular, the inner disc is first enriched with evaporating water-ice, resulting in a low C/O ratio, before carbon-rich gas from the outer disc – originating from the evaporation of CO, CO2, and CH4 ice – is transported viscously inwards, elevating the C/O ratio again. However, it is unclear how internal photoevaporation – which carries away gas and opens gaps in the disc that can block inward drifting pebbles – affects the chemical composition of the disc. Our goal is to study how and to what extent internal photoevaporation and the subsequent opening of gaps influence the chemical evolution of protoplanetary discs around solar-like stars (M* = 1 M⊙), where we specifically focus on the C/O ratio and the water content. To carry out our simulations, we use a semi-analytical 1D disc model. The code chemcomp includes viscous evolution and heating, pebble growth and drift, pebble evaporation and condensation, as well as a simple chemical partitioning model for the disc. We show that internal photoevaporation plays a major role in the evolution of protoplanetary discs and their chemical composition: As photoevaporation opens a gap, inward drifting pebbles are stopped and can no longer contribute to the volatile content in the gas. In addition, volatile-rich gas from the outer disc, originating from evaporated CO, CO2, or CH4 ice, is carried away by the photoevaporative winds. Consequently, the C/O ratio in the inner disc remains low. In contrast, gaps opened by giant planets still allow the gas to pass, resulting in an elevated C/O ratio in the inner disc, similar to the evolution of viscous discs without internal photoevaporation. This opens the possibility to distinguish observationally between these two scenarios when measuring the C/O ratio, implying that we can infer the root cause of deep gap structures when observing protoplanetary discs. In the case of a clear separation of the disc by photoevaporation, we additionally find an elevated water content in the inner disc, because the water vapour and ice undergo a cycle of evaporation and recondensation, preventing the inward accretion of water onto the star, in contrast to the situation for hydrogen and helium. We conclude that it is very difficult to achieve supersolar C/O ratios in the inner parts of protoplanetary discs when taking internal photoevaporation into account. This indicates the potential importance of photoevaporation for understanding the chemical evolution of these discs and the planets forming in them.

Terahertz Emission Modeling of Lunar Regolith

We investigate the terahertz (THz) scattering and emission properties of lunar regolith by modeling it as a random medium with rough top and bottom boundaries and a host medium situated beneath. The total scattering and emission arise from three sources: the rough boundaries, the volume, and the interactions between the boundaries and the volume. To account for these sources, we model their respective phase matrices and apply the matrix doubling approach to couple these phase matrices to compute the total emission. The model is then used to explore insights into lunar regolith scattering and emission processes. The simulations reveal that surface roughness is the primary contributor to total scattering, while dielectric contrasts between the volume and the boundaries dominate total emission. The THz emissivity is highly sensitive to the regolith dielectric constant, particularly its imaginary part, making it a promising alternative for identifying previously undetected water ice in the lunar polar regions. The THz emissivity model developed in this study can be readily applied to invert the surface parameters of lunar regolith using THz observations.

Evaluation of Physical Microphysical Property Retrieval Algorithms During the 2020 IMPACTS Field Campaign

Abstract The NASA Investigation of Microphysics and Precipitation for Atlantic Coast Threatening Snowstorms (IMPACTS) field campaign provides high-quality, high-altitude aircraft lidar (532 nm), radar (W-band) and in-cloud microphysical aircraft data taken during wintertime storm events impacting the United States. This study evaluates two mass-dimensional relationships (Brown and Francis (1995, BF95); Heymsfield (2014, H14) and two lidar-radar microphysical retrieval algorithms (Cloudsat and CALIPSO Ice Cloud Property Product (2C-ICE); VarPy (a variational method derived from the satellite lidar-radar data community)) to estimate aircraft-retrieved volume extinction coefficient (σ), ice water content (IWC), and effective radius (re) during the 2020 IMPACTS deployment. BF95 and H14 have a close 1:1 correlation (R2 = 0.98) with in-situ observations of σ. However, only BF95 displays a linear, consistent, and almost temperature-independent low bias for IWC and re, which likely arises from the environmental conditions used to determine each. Unlike the field-campaign-derived BF95 and H14 relationships, VarPy and 2C-ICE directly ingest the aircraft-based lidar and radar data to simulate σ, IWC, and re. For all three microphysical parameters, VarPy and 2C-ICE retrieval errors became notably more pronounced around the dendritic growth zone (−15°C to −10°C) and near freezing (≥−5°C), which suggests that both algorithms experience difficulty addressing riming and aggregation processes and with larger particles (dendrites and plates) due in part to their simplified ice particle assumptions. However, the mean-melt diameter ice-particle assumption did yield more accurate IWC estimates, which led to slightly better overall results for VarPy.

Analysis of Macro- and Microphysical Characteristics of Ice Clouds over the Tibetan Plateau Using CloudSat/CALIPSO Data

Utilizing CloudSat/CALIPSO satellite data and ERA5 reanalysis data from 2007 to 2016, this study analyzed the distributions of optical and physical characteristics and change characteristics of ice clouds over the Tibetan Plateau (TP). The results show that the frequency of ice clouds in the cold season (November to March) on the plateau is over 80%, while in the warm season (May to September) it is around 60%. The average cloud base height of ice clouds in the warm season is 3–5 km, and mostly around 2 km in the cold season. The average cloud top height in the warm season is around 5–8 km, while in the cold season it is mainly around 4.5 km. The average thickness of ice clouds in both seasons is around 2 km. The statistical results of microphysical characteristics show that the ice water content is around 10−1 to 103 mg/m3, and the effective radius of ice clouds is mainly in the range of 10–90 μm. Both have their highest frequency in the west of the TP and lowest in the northeast. A comprehensive analysis of the change in temperature, water vapor, and ice cloud occurrence frequency shows that the rate of increase in water vapor in the warm season is greater than that in the cold season, while the rates of increase in both surface temperature and ice cloud occurrence are smaller than in the cold season. The rate of increase in temperature in the warm season is around 0.038 °C/yr, and that in the cold season is around 0.095 °C/yr. The growth rate of thin ice clouds in the warm season is around 0.15% per year, while that in the cold season is as high as 1% per year. The results suggest that the surface temperature change may be related to the occurrence frequency of thin ice clouds, with the notable increase in temperature during the cold season possibly being associated with a significant increase in the occurrence frequency of thin ice clouds.

Establishment of numerical model for precooling broccoli with ice water integrated with salicylic acid and its effect on broccoli apparent quality

Postharvest precooling is crucial for delaying yellowing of broccoli efficiently removing field heat. In this experiment, a numerical model for ice water precooling broccoli was established, and based on this, the main precooling parameters were optimized. Furthermore, the appropriate concentration of salicylic acid (SA) in the process of ice water integrated with SA precooling was determined. Through numerical simulation and experimental validation, the ice water precooling treatment with a 30 % ice volume fraction and a 1:1 mass ratio of ice water to broccoli was identified as optimal for achieving the best precooling uniformity and meeting the specified temperature requirements. Application of 2 mmol L-1 SA integrated with ice water precooling treatment effectively delayed yellowing, and maintained the apparent quality of broccoli, manifested as a higher h° value (chromaticity value) and chlorophyll content, a lower yellowing index. The shelf life of the treated broccoli was extended by 3 d

Effect of heat treatment on phase transformation behavior, tensile fracture mechanism and spring application characteristics of 631 stainless steel

This study focuses on enhancing the mechanical properties of 631 stainless steel through heat treatment for spring applications. 631 stainless steel (17–7PH), can achieve increased hardness and mechanical properties, offering high strength and hardness suitable for use in aerospace, chemical, and automotive industries. Heat treatment was recommended as one of the best ways in this regard; hence, the effects of temperature and time on the microstructure, mechanical, and corrosion properties of 631 stainless steel have been studied. This research conducted a series of heat treatments on 631 stainless steel, included solid-solution treatment, CH900, RH950, and TH1050 processes to modify the temperature holding period and the degree of undercooling of phase transformations. The study explored the microstructure and mechanical properties of each heat treatment, including spring tests. The results indicate that solid-solution treatment has no significant contribution to hot-rolled 631 stainless steel, whereas two-stage aging is able to conspicuously improves material hardness and mechanical performance. Quenching in 0°C ice water (increasing the degree of undercooling) can elevate hardness to approximately HRC40. After a two-stage aging heat treatment, 631 stainless steel possesses excellent strength and corrosion resistance. Spring test results show a K value of 1.1 kg/ mm, indicating its potential application.

How external photoevaporation changes the chemical composition of the inner disc

Stars mostly form in cluster environments, where neighbouring stars can have an influence on the evolution of the newly formed protoplanetary discs. Besides gravitational interactions, external photoevaporation can also shape protoplanetary discs. Depending on the strength of external photo-evaporation, discs may be destroyed within 1–2 Myrs, or more gradually, depending on whether the external photo-evaporation field is stronger or weaker, respectively. We used the chemcomp code, which includes a viscous disc evolution model including pebble drift and evaporation to calculate the chemical composition of protoplanetary discs. We extended this code to include external photoevaporation following the FRIED grid. Before external photoevaporation becomes efficient, the disc follows a purely viscous disc evolution, where the C/O ratio in the inner disc initially decreases due to inwardly drifting and evaporating water ice pebbles. Over time, the C/O ratio increases again as water vapour is accreted onto the star and carbon-rich gas gradually migrates inwards. However, once external photo-evaporation commences, the outer disc begins to get dispersed. During this process, the inner disc’s chemical evolution still follows the evolution of a purely viscous disc because the majority of the pebbles have already drifted inwards on timescales shorter than 1 Myr. At low viscosity, the inner disc’s C/O ratio remains sub-solar until the disc is dispersed through external photoevaporation. At a high viscosity, the inner disc’s composition can reach super-solar values in C/O, because the water vapour is accreted onto the star faster and carbon rich gas from the outer disc can move inwards faster as well, as long as the disc can survive a few Myrs. In both cases, there is no visible difference in terms of the chemical composition of the inner disc compared to a purely viscous model, due to the rapid inward drift of pebbles that sets the chemical composition of the disc. Thus, our model predicts that the inner disc chemistry would be similar between discs that are subject to external photoevaporation and discs that are isolated and experience no external photo-evaporation. This finding is in line with observations of protoplanetary discs with JWST.