Low Humidity Atmosphere Research Articles

Wind Erodibility and Particulate Matter Emissions of Salt‐Affected Soils: The Case of Dry Soils in a Low Humidity Atmosphere

AbstractArid and semiarid ecosystems around the world are often prone to both soil salinization and accelerated soil erosion by wind. Soil salinization, the accumulation of salts in the shallow portions of the soil profile, is known for its ability to decreases soil fertility and inhibit plant growth. However, the effect of salts on soil erodibility by wind and the associated dust emissions in the early stages of soil salinization (low salinity conditions) remains poorly understood. Here we use wind tunnel tests to detect the effects of soil salinity on the threshold velocity for wind erosion and dust production in dry soils with different textures treated with salt‐enriched water at different concentrations. We find that the threshold velocity for wind erosion increases with soil salinity. We explain this finding as the result of salt‐induced (physical) aggregation and soil crust formation, and the increasing strength of surface soil crust with increasing soil salinity, depending on soil texture. Even though saline soils showed resistance to wind erosion in the absence of abraders, the salt crusts were readily ruptured by saltating sand grains resulting in comparable or sometimes even higher particulate matter emissions compared to non‐saline soils. Interestingly, the salinity of the emitted dust is found to be significantly higher (5–10 times more) than that of the parent soil, suggesting that soil salts are preferentially emitted, and airborne dust is enriched of salts.

Fabrication of Highly Luminescent Quasi Two-Dimensional CsPbBr3 Perovskite Films in High Humidity Air for Light-Emitting Diodes.

Perovskite light-emitting diodes (LEDs) have attracted extensive attention in recent years due to their outstanding performance and promise in lighting and display applications. However, the fabrication of perovskite LEDs usually requires a low-humidity atmosphere, which is unfavorable for industrial production. Herein, we report an effective strategy to fabricate highly luminescent quasi two-dimensional CsPbBr3 perovskite films in an ambient atmosphere with a humidity up to 60%. We reveal that the hole transport layer (HTL) plays a significant role in the morphology and optical properties of the perovskite films. Using hydrophobic self-assembled monolayer materials as HTLs can remarkably improve the quality of the perovskite films processed in high humidity air. The resultant perovskite LEDs show reduced leakage current and significantly enhanced performance. Furthermore, surface treatment is conducted to prevent water invasion and promote radiative recombination in perovskite films and LEDs. Eventually, the perovskite LEDs exhibit bright green emission with an external quantum efficiency of 4.87%. The present work provides a feasible pathway to overcome the humidity limitation for obtaining bright perovskite films and LEDs, which would contribute to further reducing the fabrication cost of perovskite LEDs and promoting their applications.

Screen Printed Reflective Electrochromic Displays for Paper and Other Opaque Substrates.

Paper electronics is a viable alternative to traditional electronics, leading to more sustainable electronics. Many challenges still require solutions before paper electronics become mainstream. Here, we present a solution to enable the manufacturing of reflective all-printed organic electrochromic displays (OECDs) on paper substrates; devices that are usually printed on transparent substrates, for example, plastics. In order to operate on opaque paper substrates, an architecture for reversely printed OECDs (rOECDs) is developed. In this architecture, the electrochromic layer is printed as the last functional layer and can therefore be viewed from the print side. Square shaped 1 cm2 rOECDs are successfully screen printed on paper, with a high manufacturing yield exceeding 99%, switching times <3 s and high color contrast (ΔE* > 27). Approximately 60% of the color is retained after 15 min in open-circuit mode. Compared to the conventional screen printed OECD architectures, the rOECDs recover approximately three times faster from storage in a dry environment, which is particularly important in systems where storage in low humidity atmosphere is required, for example, in many biosensing applications. Finally, a more complex rOECD with 9 individually addressable segments is successfully screen printed and demonstrated.

The ice–vapour interface during growth and sublimation

Abstract. We employed environmental scanning electron microscopy (ESEM) in low-humidity atmosphere to study the ice growth, coalescence of crystallites, polycrystalline film morphology, and sublimation, in the temperature range of −10 to −20 ∘C. First, individual ice crystals grow in the shape of micron-sized hexagonal columns with stable basal faces. Their coalescence during further growth results in substantial surface defects and forms thick polycrystalline films, consisting of large grains separated by grain boundaries. The latter are composed of 1 to 3 µm wide pores, which are attributed to the coalescence of defective crystallite surfaces. Sublimation of isolated crystals and of films is defect-driven, and grain boundaries play a decisive role. A scallop-like concave structure forms, limited by sharp ridges, which are terminated by nanoscale asperities. The motivation for this work is also to evaluate ESEM's ability to provide a clean and reproducible environment for future study of nucleation and growth on atmospherically relevant nucleators such as materials of biological origin and inorganic materials. Hence, extensive information regarding potential ESEM beam damage and effect of impurities are discussed.

Pseudocrossidium replicatum (Taylor) R.H. Zander is a fully desiccation-tolerant moss that expresses an inducible molecular mechanism in response to severe abiotic stress

Key messageThe moss Pseudocrossidium replicatum is a desiccation-tolerant species that uses an inducible system to withstand severe abiotic stress in both protonemal and gametophore tissues.Desiccation tolerance (DT) is the ability of cells to recover from an air-dried state. Here, the moss Pseudocrossidium replicatum was identified as a fully desiccation-tolerant (FDT) species. Its gametophores rapidly lost more than 90% of their water content when exposed to a low-humidity atmosphere [23% relative humidity (RH)], but abscisic acid (ABA) pretreatment diminished the final water loss after equilibrium was reached. P. replicatum gametophores maintained good maximum photosystem II (PSII) efficiency (Fv/Fm) for up to two hours during slow dehydration; however, ABA pretreatment induced a faster decrease in the Fv/Fm. ABA also induced a faster recovery of the Fv/Fm after rehydration. Protein synthesis inhibitor treatment before dehydration hampered the recovery of the Fv/Fm when the gametophores were rehydrated after desiccation, suggesting the presence of an inducible protective mechanism that is activated in response to abiotic stress. This observation was also supported by accumulation of soluble sugars in gametophores exposed to ABA or NaCl. Exogenous ABA treatment delayed the germination of P. replicatum spores and induced morphological changes in protonemal cells that resembled brachycytes. Transcriptome analyses revealed the presence of an inducible molecular mechanism in P. replicatum protonemata that was activated in response to dehydration. This study is the first RNA-Seq study of the protonemal tissues of an FDT moss. Our results suggest that P. replicatum is an FDT moss equipped with an inducible molecular response that prepares this species for severe abiotic stress and that ABA plays an important role in this response.

Research progress on analytical methods for the determination of hexachlorobutadiene

六氯丁二烯是一种持久性有机污染物,于2015年和2017年分别被列入《斯德哥尔摩公约》附件A和附件C的受控污染物名单中。六氯丁二烯的来源、环境赋存和影响等研究对控制该新增受控持久性有机污染物污染具有重要意义,而灵敏可靠的六氯丁二烯分析方法是开展相关研究的前提和基础。近年来已有不少学者将六氯丁二烯作为分析目标物之一进行了检测或方法学研究。基于这些研究成果,该文综述了六氯丁二烯分析方法的研究进展,其中重点介绍了空气、水体、土壤、污泥、生物组织等多种介质中六氯丁二烯的样品前处理方法,并比较了各方法的优缺点,以期为该领域的进一步研究提供参考。空气中六氯丁二烯主要由泵抽气通过吸附管而采集,再经热脱附后进行仪器分析,检出限在ng/m3水平。也有研究应用聚氨酯泡沫被动采样器和吸附剂填充聚氨酯泡沫被动采样器采集大气中六氯丁二烯及其他污染物。基于吸附剂填充聚氨酯泡沫被动采样器的分析方法灵敏度较高,其对六氯丁二烯的检出限低至0.03 pg/m3。然而目前被动采样体积仅根据六氯丁二烯的log KOA系数估算,未来仍需进一步实验校正。水体样品前处理通常也较简单,通过吹扫捕集、液-液萃取或固相萃取目标物后进行仪器分析。固相萃取法能够同步实现目标物的提取、净化和浓缩,在水样中六氯丁二烯分析方面具有明显优势。固相萃取柱类型以及干燥步骤中柱中残留水分去除率均会影响六氯丁二烯的回收率。灰尘、土壤、沉积物、污泥和生物组织等固体介质样品基质最为复杂,需联合多种方法进行前处理。固体样品中六氯丁二烯提取方法包括索氏提取,加速溶剂萃取和超声萃取,其中超声萃取法应用最为广泛。固体基质净化方面主要采用层析柱色谱法,多根净化柱联用或多层复合柱能够提升净化效果。仪器分析方面,六氯丁二烯主要采用气相色谱和质谱联用检测,高性能质谱检测器如串联质谱能够大大提高六氯丁二烯的检测灵敏度,具有较大的应用潜力。

Humidity‐Induced Switching between Two Magnetic and Structural Phases in a CoII‐[WV(CN)8] Molecular Magnet

The self-assembly of cobalt(II) with purine and octacyanidotungstate(V) results in the formation of the three-dimensional Co3 [W(CN)8 ]2 (purine)2 ⋅8.5H2 O (1) coordination polymer. This compound exhibits humidity-induced variation of the number of water molecules of crystallisation leading to a reversible structural phase transition and the alternation of the long-range ferromagnetic ordering temperature from TC =29 K for the pristine assembly (1) to TC =49 K for the sample stored in a low-humidity atmosphere (1-deh). This phenomenon can be attributed to a reversible change in the hydrogen-bonding network resulting in the modification of the local geometries of cobalt(II) as well as the cyanido bridges.

Fabrication of highly effective self-humidifying membrane electrode assembly for proton exchange membrane fuel cells via electrostatic spray deposition

One major challenge associated with proton exchange membrane fuel cells is to preserve higher proton conductivity under low-humidity atmosphere. Elevation of water uptake in the perfluorinated polymeric membrane is crucial for the facilitated transportation of proton, which dominates the fuel cell performance. Development of an intrinsic mechanism that controls water balance through the membrane electrode assembly (MEA), eliminates the need for external water management system and thus makes the system suitable for portable applications, where size is an important criterion to be considered. Herein, we report a nano-sized dense-structure (NSDS) layer coated onto the conventional catalyst layer, forming a dual-layered electrode architecture that is favorable in promoting the self-humidification process. This self-humidifying layer is fabricated by the electrostatic spray deposition with sufficiently low deposition rate, which allows for a creation of more uniformly distributed porous structure with diameters smaller than 80 nm, enabling recirculation of the water generated for proper humidification. When experimentally investigated, the MEA employing the dual-layered electrode reveals a 3.15 times elevated current density at 0.6 V than conventional MEA under 0% relative humidity. Mechanism for the water retention in the proposed electrode is further evaluated by X-ray computed tomography, which reveals dramatically increased tortuosity of 4.43 for the NSDS layer in comparison to 1.9 for the conventional catalyst layer.

Humidity and CO2 gas sensing properties of double-layer graphene

Graphene has interesting gas sensing properties with strong responses of the graphene resistance when exposed to gases. However, the resistance response of double-layer graphene when exposed to humidity and gasses has not yet been characterized and understood. In this paper we study the resistance response of double-layer graphene when exposed to humidity and CO2, respectively. The measured response and recovery times of the graphene resistance to humidity are on the order of several hundred milliseconds. For relative humidity levels of less than ∼3% RH, the resistance of double-layer graphene is not significantly influenced by the humidity variation. We use such a low humidity atmosphere to investigate the resistance response of double-layer graphene that is exposed to pure CO2 gas, showing a consistent response and recovery behaviour. The resistance of the double-layer graphene decreases linearly with increase of the concentration of pure CO2 gas. Density functional theory simulations indicate that double-layer graphene has a weaker gas response compared to single-layer graphene, which is in agreement with our experimental data. Our investigations contribute to improved understanding of the humidity and CO2 gas sensing properties of double-layer graphene which is important for realizing viable graphene-based gas sensors in the future.

Zinc oxide nanoparticle incorporated graphene oxide as sensing coating for interferometric optical microfiber for ammonia gas detection

A simple and reliable method by combination of sensing coating and interferometric optical microfiber to detect the concentration of ammonia is reported in this study. The sensor is fabricated by coating the tapered microfiber interferometer (MFI) with zinc oxide nanoparticle incorporated graphene oxide (GO-ZnO). GO-ZnO nanocomposites serving as an electron acceptor trap electrons after ammonia absorption and then change the surface refractive index of the optical microfiber in MFI. Subsequently, the MFI translates the tiny refractive index change into wavelength shift of the transmission spectra. As prepared sensor exhibits a good repeatability and high sensitivity to ammonia with different connections from 4ppm to 140ppm at room temperature. The gas sensor response to ammonia has been studied in different moisture level and show reliable operation in low humidity atmosphere. In addition, the gas sensor also displays an excellent selectivity to ammonia compared to several possible interfering volatile organic compounds. This may be attributed to the selective ammonia absorption at the GO-ZnO surface and the additional synergistic effects of GO-ZnO nanocomposites that are desirable and advantageous for gas sensing.

Influence of the drying step within disk-based solid-phase extraction both on the recovery and the limit of quantification of organochlorine pesticides in surface waters including suspended particulate matter

In this study, 21 organochlorine pesticides (OCPs) were determined based on sample preparation using solid-phase extraction disks (SPE disks) coupled with programmable temperature vaporizer (PTV)—large-volume injection gas–chromatography mass spectrometry (LVI-GC–MS). The work includes a comprehensive testing scheme on the suitability of the method for routine analysis of surface and drinking water including suspended particulate matter (SPM) with regard to requirements derived from the European Water Framework Directive (WFD, Directive 2000/60/EC). SPM is an important reservoir for OCPs, which contributes to the transport of these compounds in the aquatic environment. To achieve the detection limits required by the WFD, a high pre-concentration factor during sample preparation is necessary, which was achieved by disk SPE in this study. The performance of disk SPE is strongly influenced by the drying step, which could be significantly improved by effective elimination of the residual water by combination of a high vacuum pump and a low humidity atmosphere. Detection limits of the WFD in the ng/L range were achieved by large volume injection of 100μL sample extract. The recoveries ranged from 82% to 117% with an RSD smaller than 13%. The applicability of this method to natural samples was tested for instrumental qualification and system suitability evaluation. Successful participation in an interlaboratory comparison proved the suitability of the method for routine analysis.

Evaporative supercooling method for ice production

Producing ice with supercooled water is a favourable method for ice-storage. However, it undergoes the problems of often unexpected ice blockage and heavy electric power consumption. To improve, this paper proposes a new method: it evaporates water to supercooled state in an atmosphere of low humidity instead of supercooling water inside a heat exchanger; liquid dehumidification reproduces the atmosphere of low humidity to form a cycle. In theoretical analysis made about the evaporative supercooling, we ameliorate the traditional evaporation model to predict the temperature variation. To the experimental research, we adopted particle dynamics analyzer and infrared camera to examine the physical process, and it got ice with this new method. The theoretical results agree well with the experimental results. Also, it found this new method cannot only solve the ice blockage problem, but also reduce the electric power consumption and raise the efficiency. Compared with the conventional supercooled water method, the highest performance improvement can arrive at 98%. ► We present an evaporative supercooling method for ice slurry production. ► We investigate evaporative supercooling process theoretically and experimentally. ► We make analysis on the performance of the proposed systems. ► The proposed system has better performance compared to conventional methods.

Aging and thermal stability of Mg/SiC and Mg/Y_2O_3 reflection multilayers in the 25–35 nm region

Reflection measurements in the 25-35 nm region were made for Mg/SiC and Mg/Y2O3 multilayers kept in a low-humidity atmosphere for 4 or 5 years. Aged Mg/SiC multilayers keep their reflectances, and the reflectance value at 31.2 nm is 0.44 at 10 degrees of the normal angle of incidence. Aged Mg/Y2O3 multilayers change reflectance as top layer materials, and the best value at 30.1 nm is 0.40 at 10 degrees. Reflection measurements are also made for Mg-based multilayers that are annealed from room temperature to 400 degrees C at 50 degrees C intervals. Both multilayers keep their reflectance at annealing temperatures of 200 degrees C. These results suggest that both Mg-based multilayers can be applied to practical optics.

Correlations between adhesion hysteresis and friction at molecular scales

Correlations between adhesion hysteresis and local friction are theoretically and experimentally investigated. The model is based on the classical theory of adhesional friction, contact mechanics, capillary hysteresis, and nanoscale roughness. Adhesion hysteresis was found to scale with friction through the scaling factor containing a varying ratio of adhesion energy over the reduced Young's modulus. Capillary forces can offset the relationship between adhesion hysteresis and friction. Measurements on a wide range of engineering samples with varying adhesive and elastic properties confirm the model. Adhesion hysteresis is investigated under controlled, low humidity atmosphere via ultrasonic force microscopy. Friction is measured by the friction force microscopy.

The Effect of Humidity on the Removal of Fine Particles on a Solid Surface using High-speed Air Jet [Translated]&lt;sup&gt;†&lt;/sup&gt;

The effect of operating conditions on the removal efficiency of deposited particles using high- speed air jet was studied with particular attention to the humidity of surrounding air during particle deposition and air-jet removal. The experimental results showed that the removal efficiency of particles deposited in a low humidity atmosphere, decreased with increasing drying time after the deposition. In the case of a deposition under high humidity, the removal efficiency increased at the beginning of drying and decreased rapidly after reaching the maximum efficiency. For drying over 80 hrs, however, the humidity of the surrounding air during the particle deposition didn't affect the removal efficiency. The efficiency also depended on the humidity during the air-jet removal, and reached the maximum value at 67% relative humidity. Such a variation of the removal efficiency has been well explained by the change of Hamaker's constant with the adsorbed layer-thickness of water molecules and the variation of liquid surface tension with the thickness of liquid bridge.† This report was originally printed in KAGAKU KOGAKU RONBUNSHU 20(2), 205-212 (1994) in Japanese, before being translated into English by KONA Editorial Committee with the permission of the editorial committee of the Soc. Chemical Engineers, Japan.

The formaldehyde/low temperature steam sterilizing procedure

The sterilization of heat-labile equipment still remains a problem in the health services. Low temperature sub-atmospheric steam and formaldehyde has many advantages over ethylene oxide (EO), but the machines and cycles available have been rather uncertain in their reliability as sterilizers (Cripps, Deverill & Ayliffe, 1976). There have been differences of opinion on the relative roles of steam and formaldehyde in the sterilization process and also on how these chemicals should be applied. Nordgren (1939) studied the sporicidal activity of gaseous formaldehyde and found that the procedure was more effective in an atmosphere of low humidity. Alder, Brown & Gillespie (1966) described a sterilization system whereby a dry evacuation of air from an autoclave chamber was followed by an injection of heated formalin vapour and then by sub-atmospheric steam [low temperature steam (LTS)]. Alder (1968) and Mitchell & Alder (1970) also used a dry system for the evacuation of air, but modified the method of Alder et al. (1966) by injecting and evacuating small amounts of formalin vapour followed by LTS in a super-heated environment (unsaturated steam). The jacket surrounding the autoclave chamber was used to radiate the extra heat required. Weymes (1982) assumed that the latent heat of LTS and the formaldehyde monomer had a synergistic and sporicidal effect, that the steam was in its optimum state when it was dry and saturated, the latitude on either side of this phase boundary was unknown. Hurrell (1980) thought that the principal requirement for sterilization was a homogenous mixture of monomeric formaldehyde gas and saturated steam. Gibson (1977) and Marcos & Wiseman (1979) recognized the importance of a low humidity in their studies of this sterilizing process. Line & Cutts (1983) described a process in which a controlled injection of steam, sufficient to raise the pressure in the chamber to 80-100 mbar, and introduced at an early stage before the formaldehyde, was effective.

Freeze drying and residual moisture

Several factors associated with operation of freeze-drying equipment and residual moisture determinations have been discussed in relation to their influence on the residual moisture content of the product or on the determination of the residual moisture. Factors which should be achieved in the freeze-drying process are a relatively open physical structure of the mass as it is being dried, the presence of additives which improve the physical structure of the mass or provide protection to otherwise labile components, good heat transfer from the shelves to the product, and removal of moisture from rubber stoppers. Important factors which can influence the results from residual moisture determinations are the sample size which preferably should be at least 200 mg, transfer of samples which should be in a low-humidity atmosphere, isolation of samples by handling only one at a time in a low-humidity box and by use of separate desiccators, and monitoring the procedure with highly hygroscopic material as a test of its ability to yield valid results.