High Vapor Pressure Research Articles

Oreate - Oxide Reduction by Electrochemical Amalgamation and Thermal Extraction

Establishing a capability for generating consistent, small-scale, and high-purity metals (i.e., transition metals, lanthanides and actinides) would have significant impact in many levels from fundamental science to national security related applications. Among the many procedures to purify transition and f-block metals (direct oxide reduction, electrolysis in molten salts, etc), there does not exist a U.S. process that can respond to the diverse needs of small- and large-scale science campaigns. Hence, there is widespread need to develop a capability that can supply a broad range of customers with “craft” metals of interest. The main goal is to consistently convert metal oxides to chemically pure metals in near quantitative yield.Traditional separation methods of actinides and lanthanides from aqueous media has been based on structure and bonding differences between these metals with various ligands. Although liquid-liquid extractions have proven to be quite efficient, they are expensive and require complex engineering. On the other hand, separation by pyro-chemistry based on the difference of their reductive extraction to metallic phase provides a good separation performance but requires the use of high temperatures, which adds technological difficulties to the process. An alternative method that has grown interest in the last few years is the utilization of the difference in the reduction potentials from ionic state to metallic state. However, this electrochemical approach has been believed difficult because of the highly negative reduction potentials of these metals (more negative than hydrogen evolution) and the challenging control of their electrolytic deposition onto solid cathodes.In this work we present a process comprising the oxide reduction by electrochemical amalgamation and thermal extraction (OREATE) that intends to be an optimized version of the traditional electrochemical amalgamation process in aqueous medium for trivalent f-elements. A mercury pool is used as cathode material to overcome most of the difficulties related to the use of solid cathodes: (i) Once reduced to the metallic state, the metal quickly dissolves into the liquid mercury to form amalgam, which ensures more stable surface condition of the cathode. (ii) Higher hydrogen over-voltage on mercury enables more effective reduction of the metals in a slightly acidic solution. (iii) Mercury's high vapor pressure allows an easy thermal extraction process to obtain a highly pure metal.As part of our study, we have maximized the yield of the Ce electrochemical amalgamation (yield > 99%) by monitoring dissolved Ce3+ concentration in solution by UV-vis, optimized the mercury recycling process during the thermal extraction (Hg recycling > 99%), as well as improved the purity of the Ce content in the product (Ce purity > 99%). The proposed OREATE method appears easier and simpler than traditional separation and purification methods and is suitable for laboratory scale preparation of high purity metals.

Diverse responses of gross primary production and leaf area index to drought on the Mongolian Plateau

Drought is a crucial factor regulating vegetation growth on the Mongolian Plateau (MP). Previous studies of drought effects on the MP have mainly concentrated on drought characterization, while the response of vegetation to drought remains unclear. To close this knowledge gap, we examined the response of MP vegetation to drought in terms of gross primary production (GPP) and leaf area index (LAI) from 1982 to 2018. Our findings show that intra-seasonally the frequency of drought occurrence in autumn had a greater impact on GPP (relative importance over 70 %), while the intensity of drought was more influential for LAI (relative importance approximately 60 %). Inter-seasonally, summer droughts had the most pronounced effect on vegetation (with median standardized anomalies of −0.72 for GPP and −0.4 for LAI, respectively). Additionally, we found that meteorological drought was more consistent with atmospheric aridity (high vapor pressure deficit) than soil drought (low soil moisture). This study advances knowledge of vegetation's susceptibility to climate extremes and improves the precision of predicting ecosystem response to climate change.

Seasonal variability of forest cooling and warming effects and response to drought in mid-to-high latitudes of the Northern Hemisphere

The cooling or warming effects of forests in mid-to-high latitudes of the Northern Hemisphere are still a highly controversial topic, while few studies link these effects to drought using large-scale in situ observation data. Here, the temperature difference between forests and non-forests (ΔT; ΔT > 0 represents the warming effect of forests, and vice versa) and its response to drought has been quantified by utilizing eddy covariance data across 31 FLUXNET paired sites, covering a large region in the mid-to-high latitudes (ranging from 40°N to 60°N) of the Northern Hemisphere. We found that high vapor pressure deficit (VPD) during summer (warm season) droughts decreased the cooling effect of forests from ΔT = -0.70 °C to −0.41 °C due to water deficit (precipitation < evapotranspiration). Conversely, winter (cold season) drought decreased the warming effect of forests, due to moderate VPD promoting forests evaporative cooling in water surpluses conditions (precipitation > evapotranspiration). The cooling effect of forests in the warm season is highly sensitive to water stress. Overall, the seasonal warming/cooling of forests responds differently to drought, which increases the difficulty of predicting climate. Our observations can help in the implementation of forestry policies for regulating climate change, especially when the frequency and intensity of drought increase in the future.

Coordination Chemistry as a Universal Strategy for a Controlled Perovskite Crystallization.

The most efficient and stable perovskite solar cells (PSCs) are made from complex mixture of precursors, which are practically always dissolved in combinations of the volatile (and toxic) N, N-Dimethylformamide (DMF), and the non-volatile (and green) dimethyl sulfoxide (DMSO) solvents. Typically, to then form a thin film, an extreme oversaturation of the perovskite precursor is initiated to trigger nucleation sites, e.g. by vacuum, an airstream or a so-called antisolvent. Unfortunately, most such oversaturation triggers do not expel the lingering (and highly coordinating) DMSO, which is highly coordinating, from the thin films; this detrimentally affects long-term stability. Here, for the first time, we introduce (the green) dimethyl sulfide (DMS) as a novel nucleation trigger for perovskite films combining, uniquely, high coordination and high vapor pressure. More precisely, DMS coordinates more strongly than all currently used solvents, hence replacing them, including DMSO, effectively during film formation. Crucially, DMS also has among the highest vapor pressures reported in literature, thus effectively leaving the thin film shortly after formation. This gives DMS a universal scope: DMS replaces other solvents by coordinating more strongly and removes itself once the film formation is finished. To demonstrate this novel coordination chemistry approach, we process MAPbI3 PSCs, typically dissolved in hard-to-remove (and green) DMSO achieving 21.6% efficiency, among the highest reported efficiencies for this system. To confirm the universality of our strategy, we tested DMS for FAPbI3 as another composition, which showed higher efficiency of 23.5% compared to 20.9% for fabricated device with CB. This work provides a universal strategy to control perovskite crystallization using coordination chemistry heralding the revival of perovskite compositions with pure DMSO, such as MAPbI3 . This article is protected by copyright. All rights reserved.

Residual hydrogen reduction and refining effect during two-step hydrogen-argon plasma arc melting of cerium

Herein, the two-step hydrogen-argon plasma arc melting technology (HPAM-APAM) namely hydrogen plasma arc melting (HPAM) followed by argon plasma arc melting (APAM), was put forward to successfully realize the application of HPAM on cerium refining. The residual hydrogen content was significantly decreased to 79 ppm with the increase of APAM time to 40 min. The contents of volatile impurities Li and Mg were greatly reduced to less than 0.1 ppm. Paradoxically, the contents of Ti and W with low vapor pressures could be reduced to 2 ppm, whereas the impurities Fe and Si with high vapor pressures were hardly removed. The analysis indicated that the reduction of W and Ti was ascribed to the formation of volatile WO3 and TiO, while the negligible reduction of Fe and Si was attributed to the strong interaction strength with cerium based on “alloy phase formation theory”. A new kinetic refining mechanism by the activated H during HPAM process was proposed. This work helps to extend HPAM to refine hydrogen absorbing metals and provides new insights into the removal mechanism of metallic impurities.

Perioperative exposure to volatile organic compounds in neonates undergoing cardiac surgery

ObjectiveVolatile organic compounds (VOCs) are used in the sterilization and manufacture of medical equipment. These compounds have high vapor pressures with low water solubility and are emitted as gases from solids or liquids. They can be mutagenic, neurotoxic, genotoxic, and/or carcinogenic. Safe limits of exposure are not known for neonates. This study examined determinants of exposure in newborns undergoing cardiac surgery. MethodsTwenty metabolites of 16 VOCs (eg, xylene, cyanide, acrolein, acrylonitrile, N, N-dimethylformamide, 1,3-butadiene, styrene, and benzene) were measured as metabolites in daily urine samples collected from 10 neonates undergoing cardiac operations (n = 150 samples). Metabolites were quantified using reversed-phase ultra-high performance liquid chromatography and electrospray ionization tandem mass spectrometry. Repeated measures analysis of covariance was performed for each metabolite to examine associations with use of medical devices. ResultsAt least 3 metabolites were detected in every sample. The median number of metabolites detected in each sample was 14 (range, 3-15). In a model controlling for other factors, the use of extracorporeal membrane oxygenation was associated with significantly (P ≤ .05) greater metabolite levels of acrolein, acrylonitrile, ethylene oxide, propylene oxide, styrene, and ethylbenzene. Patients breathing ambient air had greater levels of metabolites of acrolein, xylene, N,N-dimethylformamide, methyl isocyanate, cyanide, 1,3-butadiene (all P ≤ .05). ConclusionsExposure to volatile organic compounds is pervasive in newborns undergoing cardiac surgery. Sources of exposure likely include medical devices and inhalation from the air in the intensive care unit. The contribution of VOC exposure during cardiac surgery in newborns to adverse outcomes warrants further evaluation.

Investigating the effect of temperature, pressure, and inert gas on the flammability range of ethane/oxygen mixtures

The flammability limit is a critical parameter used to evaluate the risk of explosions from flammable gases and design appropriate explosion-proof measures. This study employs a combined approach of theoretical analysis and experimental determination to investigate the impact of temperature, pressure, and inert gas on the FL of ethane/oxygen mixtures in an environment of elevated temperatures and pressures. The findings demonstrate that the flammability range of ethane/oxygen mixtures progressively widens at elevated temperature and pressure conditions. At high pressures, the upper flammability limit (UFL) of ethane displays a quadratic-linear relationship with temperature, with a turning point at 200 °C. The impact of temperature and pressure on explosion risk is primarily achieved through their effect on the UFL. A new inerting capacity of added diluting gas, δ, is defined for inert gas, revealing that the inerting effect of diluting gas is enhanced under the influence of temperature or pressure. However, the inerting effect of nitrogen weakens as the initial pressure increases, while it strengthens as the initial temperature increases. The inerting effect of water vapor in the system of ethane/oxygen/nitrogen is superior to that of nitrogen. The combustion reaction kinetics of ethane and nitrogen near the UFL is influenced by high temperature, high pressure, and water vapor. The coupling effect of high initial temperature and pressure on the inerting effect of the two inert gases is less pronounced than that of single factors.

Microbial volatile compounds (MVCs): an eco-friendly tool to manage abiotic stress in plants.

Microbial volatile compounds (MVCs) are produced during the metabolism of microorganisms, are widely distributed in nature, and have significant applications in various fields. To date, several MVCs have been identified. Microbial groups such as bacteria and fungi release many organic and inorganic volatile compounds. They are typically small odorous compounds with low molecular masses, low boiling points, and lipophilic moieties with high vapor pressures. The physicochemical properties of MVCs help them to diffuse more readily in nature and allow dispersal to a more profound distance than other microbial non-volatile metabolites. In natural environments, plants communicate with several microorganisms and respond differently to MVCs. Here, we review the following points: (1) MVCs produced by various microbes including bacteria, fungi, viruses, yeasts, and algae; (2) How MVCs are effective, simple, efficient, and can modulate plant growth and developmental processes; and (3) how MVCs improve photosynthesis and increase plant resistance to various abiotic stressors.

Evaluation of radiative absorption effect to estimate mean radiant temperature in environments with high water vapor concentration such as in a sauna

The importance of modeling the radiative absorption in an environment with a high concentration of water vapor, such as inside a sauna, was studied through numerical analyses and fieldwork. Radiative heat transfer analysis using the discrete ordinate method (DOM) was performed using OpenFOAM software to evaluate the influence of thermal radiation inside a sauna. In a high-temperature environment, such as a sauna, the effect of radiation heat transfer in the surrounding medium gradually increases. Therefore, the effects of the medium cannot be ignored. A full-spectrum k-distribution (FSK) was adopted to model the radiative absorption of the medium, which was composed of carbon dioxide and water vapor. The mean radiant temperature (MRT) was also determined using numerical simulations to compare the results with those measured directly using a globe thermometer. The measured MRT was lower than the air temperature because of radiative cooling by the surroundings. To evaluate the quality of the radiative absorption model, the MRT obtained using the transparent gas and FSK methods were compared. When the distance from the cooling front window was approximately 4 m, the FSK method improved the prediction of MRT by approximately 1 °C when compared with the transparent gas method, which is the conventional method. The FSK method improved the MRT prediction from the conventional method by approximately 27% in terms of the Root Mean Square Error. This result indicates the importance of modeling the MRT by considering radiative absorption in the presence of high water vapor pressure.

Study of the Harmonic Analysis of the High-Intensity Discharge Lamps

The high-intensity discharge (HID) lamp, mainly the high-pressure sodium vapor lamp and the MH lamp are the most common lamps used in public lighting purposes in Indian context, despite of the fact that uses of light emitting diodes are becoming common nowadays. The aim of this paper is to study the harmonic content in these high-power lighting networks. These light sources have been chosen because of their high power and another component, known as the igniter, which is connected to the circuit and whose effect can be studied. The study presented in this paper is completely based on measurements, including the harmonic analysis. Different combinations of ballasts and lamps have been chosen to perform the experiment. The main results show that high-pressure sodium vapour (SON) lamps have a much higher harmonic content in the lamp voltage and supply current waveforms as compared to the metal halide (MH) lamps. Results also indicate that lamp voltage harmonic contains significant amount of higher order harmonics, and its waveform is much distorted than the supply current or the ballast waveform. Furthermore, the percent of total harmonic distortion (THD) content is higher. These results will guide the future designer to select a light source from the point of view of the harmonic content in the lamp voltage, ballast voltage, and the supply current.

Response of Ecosystem Productivity to High Vapor Pressure Deficit and Low Soil Moisture: Lessons Learned From the Global Eddy‐Covariance Observations

AbstractAlthough there is mounting concern about how high vapor pressure deficit (VPD) and low soil moisture (SM) affect ecosystem productivity, their relative importance is still under debate. Here, we comprehensively quantified the relative impacts of these two factors on ecosystem gross primary production (GPP) using observations from a global network of eddy‐covariance towers and two approaches (sensitivity analysis and linear regression model). Both approaches agree that a higher percentage of sites experience GPP reduction from high VPD than from low SM over the growing season. However, the constraint of high VPD and low SM on GPP reduction is tightly linked with climates and plant functional types. Humid and mesic ecosystems including forests and grasslands are dominated by VPD, while the semi‐arid and arid ecosystems including shrublands and savannas are dominated by SM. The varying dominant role of these two factors on GPP is closely related to plant stomatal behavior, as predicted by a stomatal conductance model. Additionally, we highlight the non‐linear impact of SM on GPP during droughts and the possible underestimation of the SM effects for deep‐rooted plants when only using surface‐layer SM. Our results shed light on a better understanding of the impacts of VPD and SM on vegetation productivity, with important implications for modeling the response and feedback of ecosystem dynamics to current and future climates.

Soil moisture dominates the variation of gross primary productivity during hot drought in drylands

The frequency and severity of hot drought will increase in the future due to impact of climate change and human activities, threatening the sustainability of terrestrial ecosystems and human societies. Hot drought is a typical type of drought event, high vapor pressure deficit (VPD) and low soil moisture (SM) are its main characteristics of hot drought, with increasing water stress on vegetation and exacerbating hydrological drought and ecosystem risks. However, our understanding of the effects of high VPD and low SM on vegetation productivity is limited, because these two variables are strongly coupled and influenced by other climatic drivers. The southwestern United States experienced one of the most severe hot drought events on record in 2020. In this study, we used SM and gross primary productivity (GPP) datasets from Soil Moisture Active and Passive (SMAP), as well as VPD and other meteorological datasets from gridMET. We decoupled the effects of different meteorological factors on GPP at monthly and daily scales using partial correlation analysis, partial least squares regression, and binning methods. We found that SM anomalies contribute more to GPP anomalies than VPD anomalies at monthly and daily scales. Especially at the daily scale, as the decoupled SM anomalies increased, the GPP anomalies increased. However, there is no significant change in GPP anomalies as VPD increases. For all the vegetation types and arid zones, SM dominated the variation in GPP, followed by VPD or maximum temperature. At the flux tower scale, decoupled soil water content (SWC) also dominated changes in GPP, compared to VPD. In the next century, hot drought will occur frequently in dryland regions, where GPP is one of the highest uncertainties in terrestrial ecosystems. Our study has important implications for identifying the strong coupling of meteorological factors and their impact on vegetation under climate change.

Ultrahigh frequency shear-horizontal acoustic wave humidity sensor with ternary nanocomposite sensing layer

Surface acoustic wave (SAW) technology is promising for humidity monitoring due to its digital output, small size, large-scale production and wireless passive capability, but there are major challenges to achieve ultra-high sensitivity and fast responses using the conventional SAW devices. Herein, ultrahigh frequency (4.7 GHz and 5.9 GHz) shear-horizontal (SH) SAW devices were developed and a ternary nanocomposite strategy of graphene quantum dots/polyethyleneimine/silicon dioxide nanoparticles (GQDs-PEI-SiO2 NPs) was proposed as a sensitive layer to achieve ultrahigh sensitivity and fast response. This ternary material system was constructed by modifying the surface of SiO2 NPs with the PEI through an electrostatic force, and then adsorbing the GQDs onto the PEI through hydrogen bonds. Compared with the conventional low frequency SAW devices, the ultrahigh frequency SH-SAW devices showed exceptionally ultra-high sensitivity (2.4 MHz/%RH, 1000 times as high as a 202 MHz SAW device), fast response (20 s/5 s), excellent linearity, and good repeatability in the range of 20–80% RH. These superior performances are attributed to ultrahigh frequency of SAW devices, large specific surface areas of the nanocomposite (which exposed multiple hydrophilic groups in PEI and GQDs), and high vapor pressure of convex spherical curved liquid surface (which accelerated the adsorption and desorption of water molecules).

High vapour pressure deficit enhances turgor limitation of stem growth in an Asian tropical rainforest tree.

Tropical forests are experiencing increases in vapour pressure deficit (D), with possible negative impacts on tree growth. Tree-growth reduction due to rising D is commonly attributed to carbon limitation, thus overlooking the potentially important mechanism of D-induced impairment of wood formation due to an increase in turgor limitation. Here we calibrate a mechanistic tree-growth model to simulate turgor limitation of radial stem growth in mature Toona cilitata trees in an Asian tropical forest. Hourly sap flow and dendrometer measurements were collected to simulate turgor-driven growth during the growing season. Simulated seasonal patterns of radial stem growth matched well with growth observations. Growth mainly occurred at night and its pre-dawn build-up appeared to be limited under higher D. Across seasons, the night-time turgor pressure required for growth was negatively related to previous midday D, possibly due to a relatively high canopy conductance at high D, relative to stem rehydration. These findings provide the first evidence that tropical trees grow at night and that turgor pressure limits tree growth. We suggest including turgor limitation of tree stem growth in models also for tropical forest carbon dynamics, in particular, if these models simulate effects of warming and increased frequency of droughts.

Limited-transpiration trait in response to high VPD from wild to cultivated species: Study of the Lens genus.

Lentil (Lens culinaris Medik.) is commonly grown in drought-prone areas where terminal heat and drought are frequent. The limited transpiration trait (TRlim) under high vapor pressure deficit (VPD) could be a way to conserve water and increase yield under water deficit conditions. The TRlim trait was examined in cultivated and wild lentil species and its evolution throughout the selection pipeline. 61 accessions representing the six wild lentil species (L. orientalis, L. tomentosus, L. odemensis, L. lamottei, L. ervoides, and L. nigricans), and 13 interspecific advanced lines were evaluated in their transpiration response to high VPD. A large variation in transpiration rate (TR) response to increased VPD was recorded among wild lentil accessions with 43 accessions exhibiting a breakpoint (BP) in their TR response to increasing VPD with values ranging from 0.92 to 3.38 kPa under greenhouse conditions. Ten genotypes for the interspecific advanced lines displayed a BP with an average of 1.95 kPa, much lower than previously reported for cultivated lentil. Results from field experiments suggest that the TRlim trait (BP = 0.97 kPa) positively affected yield and yield-related parameters during the years with late-season water stress. The selection of TRlim genotypes for high VPD environments could improve lentil productivity in drought-prone areas.

Optimizing the carbonic anhydrase temperature response and stomatal conductance of carbonyl sulfide leaf uptake in the Simple Biosphere model (SiB4)

Abstract. Carbonyl sulfide (COS) is a useful tracer to estimate gross primary production (GPP) because it shares part of the uptake pathway with CO2. COS is taken up in plants through hydrolysis, catalyzed by the enzyme carbonic anhydrase (CA), but is not released. The Simple Biosphere model version 4 (SiB4) simulates COS leaf uptake using a conductance approach. SiB4 applies the temperature response of the RuBisCo enzyme (used for photosynthesis) to simulate the COS leaf uptake, but the CA enzyme might respond differently to temperature. We introduce a new temperature response function for CA in SiB4, based on enzyme kinetics with an optimum temperature. Moreover, we determine Ball–Woodrow–Berry (BWB) model parameters for stomatal conductance (gs) using observation-based estimates of COS flux, GPP, and gs along with meteorological measurements in an evergreen needleleaf forest (ENF) and deciduous broadleaf forest (DBF). We find that CA has optimum temperatures of 20 ∘C (ENF) and 36 ∘C (DBF), which is lower than that of RuBisCo (45 ∘C), suggesting that canopy temperature changes can critically affect CA's catalyzation activity. Optimized values for the BWB offset parameter are similar to the original value (0.010 ± 0.003 mol m−2 s−1), and optimized values for the BWB slope parameter (ENF: 16.4, DBF: 11.4) are higher than the original value (9.0) at both sites. The optimization reduces prior errors on all parameters by more than 50 % at both stations. We apply the optimized gi and gs parameters in SiB4 site simulations, thereby improving the timing and peak of COS assimilation. In addition, we show that SiB4 underestimates the leaf humidity stress under conditions where high vapor pressure deficit (VPD) should limit gs in the afternoon, thereby overestimating gs. Furthermore, global COS biosphere sinks with optimized parameters show smaller COS uptake in regions where the air temperature is over 25 ∘C, mostly in the tropics, and larger uptake in regions where the temperature is below 25 ∘C. This change corresponds with reported deficiencies in the global COS fluxes, such as missing sinks at high latitudes and required sources in the tropics. Using our optimization and additional observations of COS uptake over various climate and plant types, we expect further improvements in global COS biosphere flux estimates.

Indoor Levels of Volatile Organic Compounds at Households in Ulaanbaatar City

Objectives: VOCs, or Volatile Organic Compounds, are a group of organic chemicals that can easily evaporate into the air at room temperature. They are called “volatile” because they have high vapor pressure and can readily form vapors or gases at normal atmospheric conditions. To address this knowledge gap, we aimed to assess VOC exposure and its associated health risks.Method: Samples were collected through the adsorbent tube, followed by detachment from the solvent by organic solvents solvent or methanol, and analyzed by gas chromatographic equipment attached with a flame ionization detector (FID). We selected 150 households from the Chingeltei and Bayangol districts in Ulaanbaatar city, specifically sections 4, 5, 6, and 12, to examine the levels of indoor VOCs in this study. We used the nonparametric Mann-Whitney U test to compare medians of VOC levels for two independent groups. Kruskal-Wallis test was carried out to determine if there was any significant difference between medians of VOC levels for more than two independent groups, including the type of paint used, wooden furniture used, and construction year.Results: We found no significant difference in benzene concentration among different types of households (p&lt;0.8112). The highest benzene concentration (0.181 µg/m3) was measured in apartments and houses. Although there was no statistically significant difference between household room types, the kitchen had a higher benzene concentration than other rooms (p&lt;0.8156). Factors such as household total volume, building construction year, and materials used for floors and walls did not significantly affect indoor benzene concentration. Most of the day, the benzene levels exceeded the standards set by the Indoor Air Quality Act of South Korea and the recommended levels by the Health Minister and Construction and Urban Development Minister of Mongolia. In 133 households in Ulaanbaatar city, indoor VOCs, specifically benzene concentration, exceeded the recommended level stated in Order No. A105/08 by the Health Minister and Construction and Urban Development Minister in 2017.Conclusion: Indoor benzene concentration did not vary significantly based on household type, room type, household volume, building construction year, construction wall material, construction floor material, whether new furniture was purchased or the dwelling was repaired and painted within the last two months, proximity to major roads, or indoor smoking status.

A gas detector planning method that considers the area and zone based on the range of influence of chemicals with high vapor pressure

AbstractIn some countries with high population densities including Korea, chemical plants are densely distributed, and strict regulations are imposed. According to the Chemical Control Act, one gas detector must be installed every 10 m indoors and 20 m outdoors around a facility. However, the diffusion of chemicals should be evaluated based on area rather than perimeter. In the US and EU, gas detector locations are selected through chemical accident modeling. Here, we evaluated the feasibility of gas detector installation standards in the Chemicals Control Act by comparing highly volatile and toxic chemicals with sulfuric acid (relatively low volatility). Consequently, we suggested an appropriate installation location and number of gas detectors for initial countermeasures. For nitric acid, hydrochloric acid, and hydrofluoric acid, there was a difference in the number of detectors recommended via modeling and the number of detectors legally required. For the mezzanine design, four gas detectors should be installed on each floor in a 5‐story building; however, the modeling results showed that installing one was sufficient. For sulfuric acid with low vapor pressure, it is equitable to install a leak detector rather than a gas detector. Overall, regulations should be continuously evaluated for the response and prevention of chemical accidents.

Decline in stability of forest productivity in the tropics as determined by canopy water content

The impacts of low soil moisture (SM) and high vapour pressure deficit (VPD) on tree's photosynthesis and productivity are ultimately realized by changing water content in the canopy leaves. In this study, variations in canopy water content (CWC) that can be detected from microwave remotely sensed vegetation optical depth (VOD) have been proposed as a promising measure of vegetation water status, and we first reported that the regulation of CWC on productivity stability is universally applicable for global forests. Results of structural equation model (SEM) also confirmed the significant negative effect of CWC on coefficient of variation (CV) of productivity, indicating that the decrease in CWC could inevitably induce the instability of forest productivity under climate change. The most significant decrease (p<0.01) of CWC is observed primarily in evergreen broadleaf forest in the tropics, implying an increasing instability of the most important carbon sink in terrestrial ecosystem.

Novel polymer optical fibers with high mass-loading g-C3N4 embedded metamaterial porous structures achieve rapid micropollutant degradation in water

The performance of conventional photocatalytic reactors suffers from low photocatalyst mass-loading densities affixed to surfaces and light scattering losses or light attenuation in slurry reactors. These limitations are overcome by fabrication of high mass-loading g-C3N4 embedded metamaterial porous structures on flexible polymeric optical fibers (g-C3N4-POFs). In this study, the fabricated g-C3N4-POFs contain g-C3N4 with mass-loading 100−1000x higher than previouly reported, enabling efficient light delivery to g-C3N4 and improved pollutant mass transport within metamaterial porous structures. The key fabrication step involved using acetone, based on its high saturated vapor pressure and low dielectric constant, making roll-to-roll mass production of high mass-loading photocatalyst-embedded metamaterial POFs possible at room-temperature within seconds. Using bundles of 150 individual g-C3N4-POFs in the reactors, we achieved 4x higher degradation rates for micropollutants under visible light irradiation at 420 nm compared with equivalent mass-to-volume ratios of photocatalysts in a slurry suspension reactor. The bundled g-C3N4-POF reactor showed no degradation in the structural integrity or loss of pollutant degradation using deionized or model drinking water under accumulated HO• exposures of ∼4.5 × 10−9 M•s after 20 cycles of treatment. It operates continuously at g-C3N4 dosages equivalent to 100−1000 g/L and a water depth over 40 cm, making it a feasible alternative to conventional photocatalytic reactors.