In the eastern United States, the use of prescribed fire as a silvicultural technique to manage for desirable upland tree species is increasing in popularity. Bark physical properties such as ...thickness, density, and porosity have known associations with fire tolerance among species. These physical properties simultaneously influence rainfall interception and canopy storage and thus are of interest across a range of disciplines. Furthermore, while these characteristics are innate to a species, it is unknown whether repeated exposure to fire facilitates physical change in bark structure and whether these changes are consistent among species. To answer these questions, bark samples were collected from mature pine (Pinus taeda L.) and oak (Quercus montana Willd.) trees from sites across the Bankhead National Forest in Alabama, USA under three different burn regimes: 3‐year cycle, 9‐year cycle, and no fire. Samples were analysed in the laboratory for bulk density, porosity, water storage capacity, and hygroscopicity (the amount of atmospheric water vapour absorbed by bark during non‐rainfall conditions). Drying rates of saturated samples under simulated wetting conditions were also assessed. Oak bark had higher bulk density, lower porosity, and dried slower than pine bark. Interestingly, bark from both species had lower bulk density, higher porosity, greater water storage capacity, and dried faster in stands that were burned every 3 years compared to other fire regimes (p < 0.001). In summary, this study demonstrates that prescribed fire regimes in an eastern US forest alter bark structure and thus influence individual tree control on hydrological processes. The increase in bark water storage capacity, coupled with faster bark evaporation times may lead to less water inputs to the forest floor and drier overall conditions. Further investigation of this fire‐bark‐water feedback loop is necessary to understand the extent of these mechanisms controlling landscape‐scale conditions.
Across both loblolly pine and Chestnut oak, frequent prescribed fire decreases bark density and decreases porosity. Frequent prescribed fire also decreases hygroscopicity and increases the rate at which water is evaporated from bark. The ability of bark to absorb, retain, and evaporate moisture is a key trait that changes with increasing fire frequency and needs further consideration from perspectives of both fire ecology and forest hydrology.
This review discusses the currently available 3D printing approaches, design concepts, and materials that are used to obtain programmable hydrogel actuators. These polymer materials can undergo ...complex, predetermined types of motion and thereby imitate adaptive natural actuators with anisotropic, hierarchical substructures. 3D printing techniques allow replicating these complex shapes with immense design flexibility. While 3D printing of thermoplastic polymers has become a mainstream technique in rapid prototyping, additive manufacturing of softer polymers including polymer hydrogels is still challenging. To avoid deliquescence of printed hydrogel structures, the polymer inks used for hydrogel manufacture need to be sheer‐thinning and thixotropic, with fast recovery rates of the high viscosity state. This is achieved by adding polymer or particle‐based viscosity modifiers. Further stabilization of the interfaces of the printed voxels, e.g., by UV cross‐linking, is often also required to obtain materials with useful mechanical properties. Here state‐of‐the‐art techniques used to 3D print stimulus responsive, programmable polymer hydrogels, and hydrogel actuators, as well as ink formulation and post‐printing strategies used to obtain materials with structural integrity are reviewed.
This review discusses the currently available 3D printing approaches, design concepts, and materials that are used to obtain programmable hydrogel actuators. These polymer materials can undergo complex, predetermined types of motion and thereby imitate adaptive natural actuators with anisotropic, hierarchical substructures.
•The hydrophobic polyester shellac and WPI were used to encapsulate LGG.•The two-side effect of shellac on the probiotic microcapsules was revealed.•The lower drying rate and Tg of shellac were ...detrimental to viability during drying.•The addition of shellac improved storage stability by reducing hygroscopicity.•It's positive effect was more conducive to the long-term storage of probiotics.
Heat shock and hygroscopicity are two main factors that resulted in low viability of probiotics in spray-dried microcapsules during storage. Hydrophobic polyester shellac was combined with whey protein isolate (WPI) to solve this problem. The results suggested that although the survival rate after drying decreased from 20.63% to 0.01% with increased shellac to WPI ratio, the 1:1 shellac-WPI provided the best protection among all samples during storage. The consistence between moisture-adsorption-isotherm and bacterial inactivation constants confirmed the moisture barrier effect of shellac under moderate humidity. Single-droplet drying and differential scanning calorimeter revealed that shellac addition reduced the drying rate and glass transition temperature of microcapsules, which in turn decreased the membrane integrity and growth capability of the probiotics after drying. This study revealed the dual effect of hydrophobic material on instant and long-term survival of spray-dried probiotic microcapsules, which provided new sight to the design of composite wall materials.
•The thermal performance of OHP with LiCl solution was investigated.•Multiple behaviors in LiCl solution have a positive effect on OHP.•LiCl solution of various concentrations behave differently.•The ...optimum performance was achieved with a 10wt% LiCl at a filling ratio of 62%.
The heat transfer performance of oscillating heat pipes (OHPs) with LiCl solution was investigated experimentally at the concentration of 5wt%, 10wt% and 15wt% with the heat input ranging from 10 to 100 W and the filling ratio (FR) of 45%, 55%, 62%, 70%, 80%, and 90%. OHP with different concentrations of LiCl solution can improve the heat transfer performance compared with deionized water (DW) in most conditions, because of the combined positive effects of bubble characteristics, absorption and generation mechanism, two-phase flow, mass transfer, and other behaviors caused by hygroscopicity of LiCl solution. At an appropriate filling ratio (62% and 70%), the addition of LiCl in DW reduces the thermal resistance of OHP. The thermal resistance of a 62% volume of 10wt% LiCl solution reduces up to 61% compared with DW. At low filling ratio (45% and 55%), LiCl solution can reduce the temperature of the evaporation section and improve the anti-dry-out ability; simultaneously, the higher the concentration, the better the effect. It is due to the low water activity and the characteristics of bubble generation and growth in LiCl solution. At increased filling ratio (80% and 90%), the reduction of the gas phase space inside the OHP and the slowing down of the working fluid make the effect of adding LiCl less on the heat transfer performance, 5wt% LiCl solution performs better than the other concentrations.
•Designing and synthesizing three pharmaceutical salts of enoxacin (EX).•Cocrystallization of enoxacin with hydroxybenzoic acids by CAHBs interactions.•Improving the solubility of enoxacin by forming ...pharmaceutical salts.•Avoiding hygroscopicity of enoxacin by forming pharmaceutical salts.•Antibacterial activities of pharmaceutical salts are higher than that of enoxacin.
With our ongoing purpose to improve the solubility of enoxacin (EX) and avoid its hygroscopicity by forming pharmaceutical salts, three unreported pharmaceutical salts of EX with m-hydroxybenzoic acid ((HEX)·C7H5O3·H2O, EX-MHBA) (1), protocatechuic acid ((HEX)·C7H5O4·2H2O, EX-PCA) (2) and gallic acid ((HEX)·C7H5O5, EX-GLA) (3) have been designed and synthesized by using solution evaporation approach and the description of their structures has been provided. Crystal structure and theoretical calculation analysis show that all three pharmaceutical salts undergo proton transfer and held stable crystal structure via charge assisted hydrogen bond. The solubility analysis of EX-MHBA, EX-PCA and EX-GLA showed that their solubilities were significantly higher than those of pure EX. The reason may be that both EX and the three hydroxybenzoic acids depend on charge assisted hydrogen bond to form EX-MHBA, EX-PCA and EX-GLA pharmaceutical salts, which increase the solubility of EX by ionizing it from the neutral molecule to the ionic state. Meanwhile, the hygroscopicity of EX-MHBA, EX-PCA and EX-GLA pharmaceutical salts was markedly improved compared to pure EX. This may be due to the near saturation of hydrogen bonds between the carboxylic acid group of hydroxybenzoic acid and its neighboring groups, resulting in the carboxylic acid group of hydroxybenzoic acid may have difficulty binding to external water molecules. The success of this work suggests that it may provide an encouraging approach to improve the solubility of insoluble active pharmaceutical ingredients while avoiding their hygroscopicity. Further to this, it is surprising that the antibacterial activities in vitro of three pharmaceutical salts of EX are better than that of the EX.
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Amino acids are important water-soluble nitrogen-containing compounds in atmospheric aerosols. They can be involved in cloud formation due to their hygroscopicity and have significant influences on ...the hygroscopicity of inorganic compounds, which have not yet been well characterized. In this work, the hygroscopic properties of three amino acids, including aspartic acid, glutamine, and serine, as well as their mixtures with ammonium sulfate (AS) were investigated using a hygroscopicity tandem differential mobility analyzer (HTDMA) system. The gradual water uptake of aspartic acid, glutamine and serine particles indicates that they exist as liquid phase at low RH. When mixing either aspartic acid or glutamine with AS by mass ratio of 1:3, we observed a clear phase transition but with a lower deliquescence relative humidity (DRH) with respect to that of pure AS. This suggests the crystallization of AS in the presence of each of these two amino acids. However, as the mass fractions of these two amino acids increased in the mixed particles, the deliquescence transition process was not obvious. In contrast, the crystallization of AS was efficiently hampered even at low content (i.e., 25% by mass) of serine in the mixed particles. The Zdanovskii-Stokes-Robinson (ZSR) method in general underestimated the hygroscopic growth of any mixtures at RH below 79% (prior to AS deliquescence), suggesting both amino acid and the partially dissolved AS contributed the overall hygroscopicity at RH in this range. Relatively good agreements were reached between the measurements and model predictions using the Extended Aerosol Inorganic Model (E-AIM) assuming solid state AS in the mixed particles for 1:3 aspartic acid-AS and glutamine-AS systems. However, the model failed to simulate the water uptake behaviors of any other systems. It demonstrates that the interactions between components within the aerosols have a significant effect on the phase state of the mixed particles.
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•The hygroscopicity of three amino acids and their mixtures with ammonium sulfate (AS) has been investigated.•Our results indicate that the hygroscopicity of studied amino acids is strongly dependent on their water solubility.•The interactions between amino acids and AS are found to affect the hygroscopicity and phase state of AS in the mixtures.
Soft materials that can reversibly transform shape in response to moisture have applications in diverse areas such as soft robotics and biomedicine. However, the design of a structurally ...transformable or mechanically self‐healing version of such a humidity‐responsive material, which can arbitrarily change shape and reconfigure its 3D structures remains challenging. Here, by drawing inspiration from a covalent–noncovalent network, an elaborately designed biopolyester is developed that features a simple hygroscopic actuation mechanism, straightforward manufacturability at low ambient temperature (≤35 °C), fast and stable response, robust mechanical properties, and excellent self‐healing ability. Diverse functions derived from various 3D shapes that can grasp, swing, close–open, lift, or transport an object are further demonstrated. This strategy of easy‐to‐process 3D structured self‐healing actuators is expected to combine with other actuation mechanisms to extend new possibilities in diverse practical applications.
An elaborately designed hygroscopic actuator is synthesized with hydrogen bonding and a covalently bonded interpenetrating network. It features straightforward shaping processability at low ambient temperature (≤35 °C), fast and stable response, robust mechanical properties, and excellent self‐healing ability. Therefore, diverse functions derived from various 3D shapes are demonstrated, including grasping, swinging, closing–opening, lifting, or transporting an object.
A fast-growing area of research is the development of low-cost sensors for
measuring air pollutants. The affordability and size of low-cost particle
sensors makes them an attractive option for use in ...experiments requiring a
number of instruments such as high-density spatial mapping. However, for
these low-cost sensors to be useful for these types of studies their accuracy
and precision need to be quantified. We evaluated the Alphasense OPC-N2, a
promising low-cost miniature optical particle counter, for monitoring ambient
airborne particles at typical urban background sites in the UK. The precision
of the OPC-N2 was assessed by co-locating 14 instruments at a site to
investigate the variation in measured concentrations. Comparison to two
different reference optical particle counters as well as a TEOM-FDMS enabled
the accuracy of the OPC-N2 to be evaluated. Comparison of the OPC-N2 to the
reference optical instruments shows some limitations for measuring mass
concentrations of PM1, PM2.5 and PM10. The OPC-N2 demonstrated
a significant positive artefact in measured particle mass during times of
high ambient RH (> 85 %) and a calibration factor was
developed based upon κ-Köhler theory, using average bulk particle
aerosol hygroscopicity. Application of this RH correction factor resulted in
the OPC-N2 measurements being within 33 % of the TEOM-FDMS, comparable to
the agreement between a reference optical particle counter and the TEOM-FDMS
(20 %). Inter-unit precision for the 14 OPC-N2 sensors of
22 ± 13 % for PM10 mass concentrations was observed. Overall,
the OPC-N2 was found to accurately measure ambient airborne particle mass
concentration provided they are (i) correctly calibrated and (ii) corrected
for ambient RH. The level of precision demonstrated between multiple
OPC-N2s suggests that they would be
suitable devices for applications
where the spatial variability in particle concentration was to be determined.
Personal cooling technology using functional clothing that could provide localized thermal regulation instead of cooling the entire space is regarded as a highly anticipated strategy to not only ...facilitate thermal comfort and human health but also be energy-saving and low-cost. The challenge is how to endow textiles with prominent cooling effect whenever the wearer is motionless or sportive. In this study, high content of edge-selective hydroxylated boron nitride nanosheets (BNNSs) up to 60 wt % was added into a biodegradable cellulose/alkaline/urea aqueous solution, and then regenerated cellulose (RCF)/BNNS multifilaments were successfully spun in a simple, low-cost, and environmentally friendly process, which was demonstrated to serve as both static and dynamic personal cooling textile. Typically, excellent axial thermal conductivity of RCF/BNNS filament rendered that body-generated heat could directly escape from skin to the outside surface of the textile by means of thermal conduction, achieving a much better static personal cooling result through continuous thermal radiation. Besides, synergistic effect between excellent heat dissipation capability and good hygroscopicity also resulted in much better dynamic cooling effect once the wearer is doing some sports, whose efficiency was even better than commercial hygroscopic textiles such as cotton and RCF.
Huyou fruit is mainly consumed in fresh form. The saturation of the fresh food market and the lack of deep processing research have caused a huge quantity of Huyou fruits to be wasted due to ...spoilage. In this study, microwave vacuum drying (MVD) was combined with freeze-drying (FD) to study the effect of drying processing on Huyou quality. MVD was used as pre-drying (MVD-FD), post-drying (FD-MVD) or pre-drying as well as post-drying (MVD-FD-MVD) of FD to process Huyou fruit. The drying characteristic, phytochemicals content, antioxidant activity, color, absorption behavior and hygroscopicity were evaluated as affected by drying conditions. The results showed that the combined drying in all cases significantly shortened the drying time of FD. FD samples had the highest content of reducing sugar and carotenoids. FD-MVD gave significant advantages in increasing the total phenol content and flavonoid content of Huyou extracts, which presented the highest antioxidant activity (based on the evaluation of DPPH scavenging activity and ferric reducing antioxidant potential). In terms of color, MVD-FD samples had good color as the FD samples. All dried samples exhibited similar moisture adsorption behavior. MVD-FD was the best in terms of the overall effect of maintaining product quality and reducing hygroscopicity when compared with FD and MVD.
•Combined drying of freeze-drying (FD) and microwave vacuum drying (MVD) for Huyou was evaluated.•Application of microwave in post-drying stage improved the content of phenolic compounds.•FD-MVD produced dried Huyou with highest antioxidant capacity.•Huyou samples dried by MVD-FD showed the lowest hygroscopicity.
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