Low RH Research Articles

Time-efficient atmospheric water harvesting using Fluorophenyl oligomer incorporated MOFs.

Adsorption-based atmospheric water harvesting (AWH) has the potential to address water scarcity in arid regions. However, developing adsorbents that effectively capture water at a low relative humidity (RH < 30%) and release it with minimal energy consumption remains a challenge. Herein, we report a fluorophenyl oligomer (FO)-incorporated metal-organic framework (MOF), HKUST-1 (FO@HK), which exhibits fast adsorption kinetics at low RH levels and facile desorption by sunlight. The incorporated fluorophenyl undergoes vapor-phase polymerization at the metal center to generate fluorophenyl oligomers that enhance the hydrolytic stability of FO@HK while preserving its characteristic water sorption behavior. The FO@HK exhibited vapor sorption rates of 8.04 and 11.76 L kg-1MOF h-1 at 20 and 30% RH, respectively, which are better than the state-of-the-art AWH sorbents. Outdoor tests using a solar-driven large-scale AWH device demonstrate that the sorbent can harvest 264.8 mL of water at a rate of 2.62 L kg-1MOF per day. This study provides a ubiquitous strategy for transforming water-sensitive MOFs into AWH sorbents.

Factors affecting the different growth rates of PM2.5：Evidence from composition variation, formation mechanisms, and importance analysis of water-soluble inorganic ions with case study in northern China

PM2.5 affects air quality, therefore, understanding the mechanism of PM2.5 growth is essential to figure out mitigation measures. Hourly real-time concentrations of water-soluble inorganic ions (WSIIs), including anions and cations, in fine particulate matter (PM2.5) were measured in Baoji, northwest China. During the winter monitoring period, the concentrations of PM2.5 and most WSIIs exhibited similar trends. Mass proportions of SNA [i.e., sulfate (SO42-), nitrate (NO3-), ammonium (NH4+)] in PM2.5 gradually increased with air deterioration, while equivalent ratios of anions to cations also increased. The heterogeneous aqueous reactions and/or gas-phase homogeneous reactions promoted the formation of secondary inorganics, especially during the haze events. Rapid transformations of primary gaseous precursors to secondary pollutants could lead to the substantial formation of SO42- and NO3-. In terms of particle growth rate, the mass proportions of SNA in PM2.5 decreased from General Growth (GG) to Explosive Growth (EG) events. Furthermore, the particle growth rates did not coincide with the pollution levels, while it occurred most frequently during the Transition Period, instead of the Polluted Period. The diurnal variation of SNA at different PM2.5 growth rates has been discussed. The results of the Random Forest (RF) model showed that RH was an important factor for EG of PM2.5, while low RH was a reliable reason for the relatively low mass proportion of SNA. The results of this study could advance our understanding of particle growth and provide scientific evidence to support the establishment of unique air quality control measures under different pollution scenarios in Fenwei Plain, China.

NaCl aerosol filtration over filter media with intrafiber porosity: can filtrate capacity be increased by wicking into this pore volume?

This paper investigates a novel fiber-based filter media wherein a NaCl filtrate is collected and reservoired not only onto the surfaces of the fibers and within their inter-fiber voidage but also within the internal porosity of high pore volume nanoporous fibers or vapor grown carbon nanofibers (VGCF) floc used to fabricate the media. This transport process is shown to occur through a NaCl dissolution into the water-filled nanopores of the fiber and a subsequent intra-fiber wicking phenomenon. The study further elucidates two distinct NaCl accommodation mechanisms which are uniquely available to filter media containing nanoporous intrafiber porosity: (1) wicking and capillary condensation of liquid NaCl aerosols directly into the intrafiber pores at high RH, and (2) dissolution of otherwise solid NaCl aerosols deposited onto fiber surfaces (at low RH) into the interior nanopores of the fiber because these pores (when hydrophilic) are saturated with water (even at low RH). To investigate these two mechanistic regimes, various media were fabricated possessing multiscale porosity in the form of: (i) embedded flocs of VGCFs (4.108 cm3gm-1pore volume), (ii) hydrophilic and high pore volume activated carbon fibers (ACFs, 0.950 cm3gm-1) and (iii) solid graphite fibers. These media were then comparatively evaluated toward NaCl aerosol filtration at different relative humidities. Pressure drop measurements versus filtrate accumulation and SEM-EDAX VGCF demonstrated the location and transport of NaCl into the intrafiber voidage. Media containing both VGCF floc and ACF accumulated 1200% more NaCl at low RH (and a specified pressure drop) than similar media prepared from non-porous graphite fibers, with an additional 315% increase from low to high RH. A Gibbs free energy driving force model is provided to illustrate the driving forces favoring water condensation into the nanopores and solid NaCl aerosol dissolution into the water phase. Filtration efficiency and quality factor assessments for the various media are also systematically evaluated to demonstrate the observed mechanistics.

Oxygen isotope fractionation during amorphous to crystalline calcium carbonate transformation at varying relative humidity and temperature

Crystalline calcium carbonate isotope compositions have been widely used to reconstruct past environments. However, if their isotopic compositions are modified because of crystallization from an amorphous precursor, their reliability as paleo-geochemical proxies can be compromised. This study explored the changes in the oxygen isotope compositions during the transformation of amorphous calcium carbonate (ACC) into crystalline carbonate under different conditions of relative humidity (RH of 33–95 %), temperature (T of 5 °C and 20 °C) and in the presence/absence of atmospheric CO2. The data showed that at low RH and T (e.g., RH ≤ 45 % and 5 °C) when a complete ACC-crystalline carbonate transformation did not take place then the original ACC δ18O values (δ18OCaCO3 = −15.9 ± 1.0 ‰, VPDB) were preserved throughout the experimental runtime (up to 144 days). In contrast, in fully crystallized CaCO3 (e.g., at RH ≥ 60 %) the δ18OCaCO3 values increased rapidly over the first few days, followed by a slower and gradual increase. By the end of the experiments (i.e., after 103–144 days) the crystalline δ18OCaCO3 values ranged from −10.4 ‰ to −8.1 ‰ in the presence of atmospheric CO2 and from −12.6 ‰ to −9.5 ‰ in the CO2-free experiments. These changes in oxygen isotope compositions of the CaCO3 reaction products (calcite and/or vaterite) were mainly driven by exchange with H2O from the hydrated ACC i.e. the synthesis fluid. In CO2-present experiments, oxygen isotope fractionation factors between the CaCO3 reaction products and the synthesis fluid (18αc–w) approached or exceeded oxygen isotope equilibrium values. This could be explained by a decrease in the initially high pH of the aqueous fluid released from ACC dissolution during CO2 hydration/hydroxylation, which would have increased the oxygen isotope exchange kinetics between H2O and dissolved inorganic carbon (DIC). In some experiments, the hydration/hydroxylation of 18O-enriched CO2, due to isotopic salt-effects, might have also resulted in 18O-enriched calcium carbonates and calculated fractionation factors that exceeded equilibrium values. In the CO2-free experiments, isotopic equilibrium between the crystalline phase and the synthesis fluid was not reached. This oxygen isotope disequilibrium suggests that without the pH lowering effect of the hydroxylation/hydration of CO2, the CO32− released during ACC/calcite dissolution-reprecipitation may have not isotopically equilibrated with the high pH synthesis fluid due to the long equilibration times required to reach isotope equilibrium at high pH values, leading to the self-buffering of δ18OCaCO3 values. The results suggest that the oxygen isotopic compositions of natural carbonates formed from ACC transformation in air and at low water/solid ratio (e.g., biominerals or carbonates formed in caves) are complex and cannot be used as simple proxies if the reaction kinetics (RH/CO2/T) and H2O sources are not known and quantified.

Effect of Rh loading on the selectivity to methanol and ethanol in the hydrogenation of CO2 over the Rh/CeO2 catalyst

The capture and hydrogenation of CO2 into high-value chemicals such as alcohols is one of the important ways to reduce CO2 emission and achieve carbon resource recycling. In this work, the catalytic performance of Rh/CeO2 catalyst in the CO2 hydrogenation was investigated; with the help of various characterization methods including XRD, Raman, H2-TPR, CO2-TPD, CO-DRIFTS and XPS, the influence of Rh loading (0.1%–2.0%) on the catalytic activity of Rh/CeO2 and product selectivity in the CO2 hydrogenation was revealed. The results indicate that for the hydrogenation of CO2 at 250 °C and 3.0 MPa over the Rh/CeO2 catalysts, ethanol is the major product at a low Rh loading of 0.1%. With the increase of Rh loading, the conversion of CO2 increases, but accompanied by a decrease in the selectivity to ethanol; when the Rh loading reaches 2.0%, the main product turns to be methanol. It seems that the difference of various Rh/CeO2 catalysts with different Rh loadings in the product selectivity for the CO2 hydrogenation is ascribed to their difference in the structural and electronic properties of Rh; atomically dispersed Rh+ species favor the stabilization of CO* and its subsequent C–C coupling with CH3* to form ethanol, whereas metallic Rh clusters facilitate the hydrogenation of CO* to produce methanol.

Stereoselective Synthesis of anti-2,4-Disubstituted Tetrahydrofurans via a Pd-Catalyzed Hayashi-Heck Arylation and Rh-Catalyzed Hydroformylation Sequence.

A catalytic, two-step protocol for the expedient synthesis of anti-2,4-disubstituted tetrahydrofurans is described. In the first step, an enantioselective and regioselective Pd-catalyzed Hayashi-Heck arylation was developed using (R)-hexaMeOBiphep to generate 5-aryl-2,3-dihydrofurans. A subsequent Rh-catalyzed hydroformylation step proceeds at low Rh loading with high regio- and diastereoselectivity for the anti-2,4-disubstituted tetrahydrofuran isomer. Key to the development of the hydroformylation reaction was the utilization of either (R)-Me-i-Pr-INDOLphos or (R,R)-Ph-BPE to control the regioselectivity and provide the kinetic product isomer.

MOF-801 enabled rapid-cycling atmospheric water harvester with vertically aligned photothermal channel

Sorption-based atmospheric water harvesting (SAWH) with metal–organic frameworks (MOFs) offer a promising solution to freshwater scarcity in arid regions. However, given the powder nature of MOFs, scaling-up such a concept with industrially favorable monolithic MOFs in bulky sizes remains challenging. In this study, a pore vertically aligned nanocomposite sorbent where MOF-801 is anchored at the polymeric structure surface was prepared via Fe3+-induced crosslinking and directional freezing methods. The continuous vertically aligned hierarchical pores not only offer sufficient sites for MOF-801 loading but also provide rapid moisture transport channels, as well as high solar-thermal conversion efficiency, resulting in a rapid ab/desorption duration of 2 h (including an absorption process for 1 h and a desorption process for 1 h under 1 sun irradiation) and multicycle daily water production of 1.40 L kg−1 at low RH of 20 % and 5.57 L kg−1 at higher RH of 80 %, respectively, which is outperformed most of the state-of-the-art MOFs based SAWH materials. This work provides a simple and effective way to shorten MOF-801 ab/desorption duration, which has great means for designing of high-performance solar-driven water harvesting materials.

Grain-refined metastable β titanium alloy with suppressed ω-assisted nucleation and enhanced mechanical properties

The mechanical characteristics of metastable β titanium alloys are related to the α precipitates that form during aging. Although precipitation behavior can be modulated by ω-assisted nucleation, the influence of grain size (GS) on this process has not been fully considered. In this study, the effects of grain refinement on mechanical properties and ω-assisted nucleation were investigated by aging the Ti-5.3Cr-4.9Mo-4.9 V-4.3Al-0.9 Nb-0.3Fe (TB18) alloy with coarse grains (87 μm) or fine grains (25 μm) at different heating rates (RH). It was found that ω-assisted nucleation depends on the RH, with a lower RH promoting the processes of ω-assisted nucleation and the precipitation of finer secondary α (αs) plates. The vacancy concentration after annealing reduced with decreasing GS, indicating that ω-assisted nucleation is suppressed by grain refinement. Additionally, grain refinement significantly improved the ductility of the TB18 alloy. This effect was attributed to enhanced homogeneous plastic deformation and an increase in slip systems, such as pyramidal <c+a> slip on αs plates. At ultimate tensile strengths of 1300–1550 MPa, the elongation of the fine-grained specimens was typically 2–3 times greater than that of the coarse-grained specimens. Furthermore, the corresponding mixed fracture mode involved a greater extent of ductile fracture. Therefore, the mechanical properties of metastable β titanium alloys are primarily limited by coarse β grains.

The impact of urban dry island on building energy consumption is overlooked compared to urban heat island in cold climate

A large number of literature reveals the impact of urban heat island on building energy consumption, however, the urban dry island impact on the energy demand is very limited. This study aimed to determine the urban–rural disparities in temperature (ΔT) and relative humidity (ΔRH) on sensible and latent heat loads (SHL, LHL) in a large city belonging to the cold climate zone of China. The results showed that apparent ΔT and ΔRH existed between the urban and rural areas, with higher T and lower RH in the urban area compared with those in the rural counterpart. The ΔT of the heating period (1.37 ℃) is far higher than that of the cooling period (0.45 ℃), whereas the ΔRH is almost same in the heating and cooling periods (−9 % vs −8 %). Due to the effect of ΔT, the urban SHL of office building was averagely lower 15.1 % than that in the rural area during the heating period, but only higher 4.6 % in the urban area compared with the rural area in the cooling period. By contrast, the decrease extent of LHL of office building between urban and rural areas in the cooling period (58.7 %) extremely exceeds the increase of LHL in the heating period (6.7 %) due to the ΔRH impact. Negative significant relationships between ΔT and the change of SHL from urban to rural areas, as well as between ΔRH and the change of LHL were found during the heating period, but being positive significant relationships during the cooling period. This study reveals that, in the cold climate zone, the LHL has large contribution to the total energy consumption of buildings, especially the LHL during the cooling period in urban area is much lower than that of the surrounding rural area, highlighting the need to fully consider the LHL in the design and operation of air-conditioning system. In addition, this study shows the potential for improving energy efficiency of other building types or other cities in the cold climate zone by considering the UDI effect.

Low Rh doping accelerated HER/OER bifunctional catalytic activities of nanoflower-like Ni-Co sulfide for greatly boosting overall water splitting

Facile synthesis of high-efficiency and stable bifunctional electrocatalyst is essential for producing clean hydrogen in energy storage systems. Herein, low Rh-doped flower-like Ni3S2/Co3S4 heterostructures were facilely prepared on porous nickel foam (labeled Rh-Ni3S2/Co3S4/NF) by a hydrothermal method. The correlation of the precursors types with the morphological structures and catalytic properties were rigorously investigated for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the control groups. The low Rh doping within the catalyst played important role in boosting the catalytic characteristics. The resulting catalyst showed the smaller overpotentials of 197 and 78 mV to drive a current density of 10 mA cm−2 for the OER and HER in alkaline electrolyte, respectively. And the potential only required 1.71 V to drive a current density of 100 mA cm-2 in a water splitting device. It reflects excellent overall water splitting of the home-made Rh-Ni3S2/Co3S4/NF. This strategy shed some constructive light for preparing transition metal sulfide-based electrocatalysts in water splitting devices.

The Effect of Humidity on the Mass and Unit Cell Volume of Montmorillonite near Room Temperature

Phase equilibria between montmorillonite (Swy-2 from Wyoming, USA) and H2O vapor phase were established by using the humidity buffer technique at 0.1 MPa and room temperature (23 ± 0.5°C). The Relative Humidity (RH; equivalent to the activity of H2O) levels of the system were defined between 6.5% and 97.4% by using six different salt-saturated aqueous solutions. There was no direct physical contact between Swy-2 sample and the buffer solution to prevent any metal ion exchanges between them. The reaction time at each humidity buffer was 10 days, after which the mass of the sample was determined and X-ray powder diffraction spectrum was collected. The experiments were carried out in two directions: one is adsorption (i.e., from low to high RH), and the other is desorption (i.e., from high to low RH), and the equilibrium of the system was demonstrated by the adsorption-desorption reversal experiments in terms of both mass change and crystal parameters (d-001 spacing and unit cell volume). When compared our data with those from previous study for Na-saturated montmorillonite, either synthetic or natural, the Na replacement in the crystal structure favored the retention of water, but only under RH higher than about 62%.

The Combined Effects of Long Term Mixture Exposure to Temperature and Relative Humidity on Asthma in China

Background: Few previous stud ies ha ve examined the joint effect of long term exposure to temperature and relative humidity ( RH on ast hma This study endeavors t o explore the combined association between long term co exposure to temperature and R H and asthma in China. Methods: The individual data of asthma were collected from the wave 1 to wave 3 (2007 2019) of the Study on global AGEing and adult health in China. M eteorological factors data were obtained from the European Center for Medium range Weather Forecasts Reanalysis 5 (ERA5) and extracted from the corresponding interpolated grid according to individual residential latitude, longi tude and survey time. Individual and joint association of long term exposure to annual mean temperature and RH with asthma were estimated using Cox regression model and Quantile Based g Computation model Q gcomp)gcomp), respectively Then , the joint effects of different temperature RH compound events w ere further estimated Results: We observed negative association between both temperature and RH with asthma. In individual effect analysis, for 1 °C or 1% decrease in 3 year average temperature and RH , asthma increased 4 44 (95% 1 76 7 0 5) and 6 45 (95% 2 79 9 98 respectively. The joint effect of long term exposure to temperature and RH on asthma was also negative . F or each percentile decreasing of both temperature and RH asthma decreased 1.50% (95%CI: 0.85% 2.15%) in total population . People 60 years old and female were more susceptible to mixture exposure to low temperature and low RH. W e also observed a higher risk of asthma in dry cold event ( 2.44 , 95%CI: 1 67 3 55 than wet cold, wet hot and dry hot events Conclusion: Long term exposure to t emperature and RH may jointly associate with asthma , and low RH and cold may have higher risk on asthma onset .

Effect of Heat Treatment on Hygroscopicity of Chinese Fir (Cunninghamia lanceolata [Lamb.] Hook.) Wood

Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) is a widely planted species of plantation forest in China, and heat treatment can improve its dimensional stability defects and improve its performance. The wood samples were heat-treated at various temperatures (160, 180, 200, and 220 °C) for 2 h. To clarify the effect of heat treatment on wood hygroscopicity, the equilibrium moisture content (EMC) was measured, the moisture adsorption and desorption rates were determined, the hygroscopic hysteresis was examined, and the Guggenheim, Anderson, and de Boer (GAB) model was fitted to the experimental data. The moisture absorption isotherms of all samples belonged to the Type II adsorption isotherm, but the shape of the desorption isotherm was more linear for heat-treated wood samples, especially when the heat treatment temperature was higher. According to the results analyzed with ANOVA, there were significant differences in equilibrium moisture content between the control samples and the heat-treated samples under the conditions of 30%, 60%, and 95% relative humidity (RH, p &lt; 0.05), and the results of multiple comparisons were similar. The decrease in hygroscopicity was more pronounced in wood treated at higher temperatures. The EMC of the 160–220 °C heat-treated samples of the control samples was 14.00%, 22.37%, 28.95%, and 39.63% lower than that of the control sample at 95% RH. Under low RH conditions (30%), water is taken up mainly via monolayer sorption, and multilayer sorption gradually predominates over monolayer sorption with the increase in RH. The dynamic vapor sorption (DVS) analysis indicated that the heat-treated wood revealed an increase in isotherm hysteresis, which was due to the change in cell wall chemical components and microstructure caused by heat treatment. In addition, the effective specific surface area of wood samples decreased significantly after heat treatment, and the change trend was similar to that of equilibrium moisture content.

Implementation of the ISORROPIA-lite aerosol thermodynamics model into the EMAC chemistry climate model (based on MESSy v2.55): implications for aerosol composition and acidity

Abstract. This study explores the differences in performance and results by various versions of the ISORROPIA thermodynamic module implemented within the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. Three different versions of the module were used, ISORROPIA II v1, ISORROPIA II v2.3, and ISORROPIA-lite. First, ISORROPIA II v2.3 replaced ISORROPIA II v1 in EMAC to improve pH predictions close to neutral conditions. The newly developed ISORROPIA-lite has been added to EMAC alongside ISORROPIA II v2.3. ISORROPIA-lite is more computationally efficient and assumes that atmospheric aerosols exist always as supersaturated aqueous (metastable) solutions, while ISORROPIA II includes the option to allow for the formation of solid salts at low RH conditions (stable state). The predictions of EMAC by employing all three aerosol thermodynamic models were compared to each other and evaluated against surface measurements from three regional observational networks in the polluted Northern Hemisphere (Interagency Monitoring of Protected Visual Environments (IMPROVE), European Monitoring and Evaluation Programme (EMEP), and Acid Deposition Monitoring Network of East Asia (EANET)). The differences between ISORROPIA II v2.3 and ISORROPIA-lite were minimal in all comparisons with the normalized mean absolute difference for the concentrations of all major aerosol components being less than 11 % even when different phase state assumptions were used. The most notable differences were lower aerosol concentrations predicted by ISORROPIA-lite in regions with relative humidity in the range of 20 % to 60 % compared to the predictions of ISORROPIA II v2.3 in stable mode. The comparison against observations yielded satisfactory agreement especially over the USA and Europe but higher deviations over East Asia, where the overprediction of EMAC for nitrate was as high as 4 µg m−3 (∼20 %). The mean annual aerosol pH predicted by ISORROPIA-lite was on average less than a unit lower than ISORROPIA II v2.3 in stable mode, mainly for coarse-mode aerosols over the Middle East. The use of ISORROPIA-lite accelerated EMAC by nearly 5 % compared to the use of ISORROPIA II v2.3 even if the aerosol thermodynamic calculations consume a relatively small fraction of the EMAC computational time. ISORROPIA-lite can therefore be a reliable and computationally efficient alternative to the previous thermodynamic module in EMAC.

Unveiling the Role of Carbonate Radical Anions in Dust‐Driven SO2 Oxidation

AbstractCarbonate radical anion () is generally overlooked in atmospheric chemistry. Our recent work emphasizes the important role of carbonate radicals produced on mineral dust surfaces in fast sulfate production under solar irradiation in the presence of CO2 at specifically low RH and light intensity. Yet so far how involves and affects secondary sulfate production under diverse RH, light intensity, and complex constituent matrix remains unknown, which essentially limits our comprehensive knowledge of initiated SO2 oxidation scheme in the atmosphere. Herein, we explored the heterogeneous SO2 oxidation over both model and authentic dust and clays in the presence of CO2 at atmospheric relevant RHs and light intensities. Interestingly, we observe that CO2 promotes sulfate yield over authentic dust and clays at atmospheric‐relevant RH and light intensity. This observation relates to the favorable kinetic between SO2 oxidation and while auto‐quenching of these radical ions is largely minimized due to the sufficient sites of crustal constituents. Furthermore, employing a suite of authentic dust and machine learning strategies, we evaluated the relative importance of each constituent within airborne minerals or clays as well as environmental conditions including relative humidity, light intensity, and CO2 concentration in affecting SO2 uptake capability. On this basis, sulfate formation mediated by dust‐driven pathway, accounting for nearly ∼20.9% of overall contribution by the end of this century during some pollution episodes, even higher than gas‐phase (∼16.9%), will be increased by 163% if CO2‐initiated SO2 oxidation scheme is incorporated.

Natural carbonation process in cement paste particles in different relative humidities

Finely ground hardened cement pastes (hcp) under 75 μm were carbonated at varying relative humidities (23–95 % RH) to determine the carbonation rate that minimized CO2 diffusion in the bulk paste. The amounts of portlandite (CH) and calcium carbonate (CC) polymorphs were quantified, and the decalcification and decomposition of C-A-S-H were analyzed using TGA, XRD, mass balance calculation, FTIR, and 29Si MAS NMR spectroscopy. A higher RH accelerated the reaction rate, and CH dissolution stopped midway at 58 % RH or below because of the loss of connectivity with the pore solution in the CC shell around CH. The precipitated CC phase included calcite at high RH, whereas all three polymorphs formed at 58 % or lower RH; amorphous CC were detected at low RH. The decalcification and decomposition of C-A-S-H were observed at 45 % or higher RH; it was rarely carbonated at 33 % or lower RH.

A new compact micro‐XRF spectrometer with polychromatic x‐ray sample excitation

AbstractA new compact micro‐x‐ray fluorescence (μ‐XRF) spectrometer covering wide range of elements was developed and fabricated. The working capabilities of this new compact custom‐made μ‐XRF spectrometer are presented. The spectrometer uses a low power Rh target x‐ray tube for sample excitation. Polycapillary optics focuses the polychromatic beam down to 40 μm. The emitted radiation is measured by a peltier cooled silicon drift detector of 30 mm2 crystal size. It was observed that the polychromatic excitation provides sufficient photons for an efficient excitation of the sample to achieve good detection limit and area resolution. The detection limits are comparable with that one obtained by TXRF for a thin film sample. The advantage of the present setup, is the fact that it is suitable for specific applications for example, for radioactive and toxic samples requiring instrument adoption in glove boxes or fume hoods because of its good analytical features accompanied by simple and compact instrumentation.

Clinical study to determine the predictability of significant rebound hyperbilirubinemia in neonates after phototherapy and conditions likely to be associated with it: Prospective observational study in a teaching hospital in Eastern India.

Neonatal hyperbilirubinemia is defined as yellowish discoloration of the skin, conjunctive, and sclera from the elevated serum or plasma bilirubin in the newborn. The standard of care for the management of neonatal hyperbilirubinemia is phototherapy to prevent long-term neurological sequelae. The aim of this study was to ascertain the predictability of significant rebound hyperbilirubinemia (SRH) in neonates after phototherapy and the factors associated with it. Neonates ≥ 35 weeks of gestation, who received treatment for hyperbilirubinemia and admitted in our hospital from 15th of March 2019 to 15th of September 2020 were enrolled after taking parental consent. SRH was defined as bilirubin levels crossing the treatment threshold within 72 hours of phototherapy termination. Logistic regression analysis was used to identify the predictability of SRH. Out of 400 neonates treated with phototherapy, 10% developed SRH. Prematurity (Gestational age < 37 weeks), low birth weight (Birth weight < 2000 gram), ABO and Rh incompatibility, Glucose-6-phophate dehydrogenase deficiency (G6PD) deficiency, sepsis, and longer duration of primary phototherapy were found to be significantly associated with rebound hyperbilirubinemia. The probability of SRH increases for all American Academy of Paediatrics (AAP) risk categories as the gestational age decreases and total serum bilirubin at the stoppage of phototherapy increases. The presence of risk factors should be taken into account while planning discharge and follow-up of neonates admitted for neonatal hyperbilirubinemia to prevent long-term complication of bilirubin neurotoxicity.

Study on Self-Humidification in PEMFC with Crossed Flow Channels and an Ultra-Thin Membrane.

In this study, a 3D model of a proton exchange membrane fuel cell (PEMFC) with crossed channels and an ultra-thin membrane is developed to investigate the feasibility of self-humidification; experiments utilizing a PEMFC stack with identical configurations are conducted to validate the simulation results and further investigate the effects of various operating conditions (OCs) on self-humidification. The results indicate that the crossed flow channel leads to enhanced uniformity of water distribution, resulting in improved cell performance under low/no humidification conditions. External humidifiers for the anode can be removed since the performance difference is negligible (≤3%) between RHa = 0% and 100%. Self-humidification can be achieved in the stack at 90 °C or below with an appropriate back pressure among 100-200 kPa. As the current density increases, there is a gradual convergence and crossing of the voltage at low RH with that at high RH, and the crossover points are observed at 60-80 °C with suitable pressure when successful self-humidification is achieved. Below the current density of the point, the stack's performance is inferior at lower RH due to membrane unsaturation, and conversely, the performance is inferior at higher RH due to flooding; this current density decreases with higher pressure and lower temperature.

Enhanced Nitrate Fraction: Enabling Urban Aerosol Particles to Remain in a Liquid State at Reduced Relative Humidity

AbstractNitrate has become the primary inorganic compound in urban aerosol particles, but its effects on particle phase state, which is crucial in multiphase chemistry, remains largely unknown. Herein, particle rebound measurements were conducted to explore the relationship between the liquid–phase–transition threshold relative humidity (RHthreshold) and the inorganic compounds mass fraction in dry particles (Finorg). Results revealed negative correlations between RHthreshold and Finorg, with more nitrate leading to lower RHthreshold. Even with RH &lt; 20%, particles with ∼50% nitrate mass fraction remained in non‐solid state. Taking Beijing as an example, decreases were observed in RHthreshold from 64% in 2015 to below 53% nowadays during the moderate‐pollution periods (PM2.5 = 35–75 μg/m3) due to an enhanced nitrate fraction. This allowed urban aerosol particles to exist in liquid state at lower RH, and consequently, kinetic limitation by bulk diffusion in nitrate‐dominated particles might be negligible, making them key seeds for secondary aerosol formation through multiphase reactions.