Dehydration In Air Research Articles

Effects of desiccation rate and inhibition of protein synthesis and the violaxanthin cycle on the rewetting recovery of Porella platyphylla

Following 5 different rates of 1-week desiccation to which Porella platyphylla (a desiccation-tolerant leafy liverwort) was subjected, physiological recovery upon rehydration (after 1 h, 24 h, 48 h) in light was monitored by cytological, photosynthetic (e-transport rate, photoprotective mechanisms), and other metabolic parameters using nuclear- and chloroplast-encoded protein synthesis inhibitors and a violaxanthin cycle inhibitor (DTT: dithiothreitol). Desiccation tolerance is mainly constitutive in P. platyphylla, allowing survival of rapid drying, and employs an active rehydration-induced repair and recovery mechanism. Following 24 hours of rehydration after the one-week dehydration in laboratory air (∼35% relative humidity /RH/), the chloroplasts had an irregular round shape. The recovery within 1 h of the thylakoid-function-related photosynthetic processes was extremely fast and independent of protein synthesis, while the overall recovery (except plants dried up at 76% RH, which depended on protein synthesis only to a limited extent) required de novo protein synthesis during rewetting. During the course of rehydration protein synthesis affects rehydrin expression, osmolite and general carbohydrate metabolism, the main repair and antioxidant mechanisms. Recovery was the best in samples dried up at 76% RH. Membrane permeability increased upon rehydration following 1-week dehydration. Normal membrane function recovered after 24 h (max. 48 h), except in plants that suffered drastic dehydration. Total protein content of plants dried under different conditions and of samples taken during recovery was generally lower than in the control plants at full turgor. The xanthophyll cycle has a great importance during the recovery in light; we confirmed the existence of a greater zeaxanthin-dependent and a smaller zeaxanthin-insensitive NPQ (nonphotochemical quenching). Plants dried under more favorable conditions had better light protection. The highest values of the osmotic potential belonged to the plants subjected to intense dehydration. Total soluble carbohydrate content was well-balanced and seemed to be unchanged following the different treatments. There was a significant increase in proline, while total fructan showed lower values at different degrees of 1-week desiccation. The cytoplasmic protein synthesis is likely to be involved in the change of the fructan content during rehydration.

Increasing the strength and water resistance of materials based on poly-vinyl alcohol with boric acid

Polyvinyl alcohol (PVA) is a promising polymer for the production of materials with desired properties, primarily water solubility and biodegradability. The main reason for limiting the use of film materials based on PVA is the lack of a mechanism for regulating the rate of their dissolution. Purpose of work: evaluation of the strength characteristics and water resistance of PVA films and PVA:MC composites when crosslinked with boric acid, depending on the amount of borate introduced into the polymer matrix. The objects of the study were 8 experimental samples: No. 1 - a film of unmodified PVA grade KurarayPoval 3-83, plasticized with glycerin, obtained by pouring from a 5% solution; No. 2-4 - PVA films modified with boric acid in various amounts, obtained similarly to sample No. 1; No. 5 - a plate of PVA:MC composite (50:50 wt.%), obtained by liquid-phase combination of PVA unmodified with boric acid and microcellulose dispersion, followed by dehydration in air; No. 6-8 - plates of the PVA:MC composite (50:50 wt.%), obtained on the basis of PVA modified with various amounts of boric acid, similarly to sample No. 5. As a result of the study, it was found that the modification ("crosslinking") of PVA grade KurarayPoval 3-83 with boric acid is accompanied by an increase in the viscosity of PVA (which manifests itself in the clouding of the films during dehydration), an increase in strength indicators in proportion to the amount of borate ion introduced into the PVA polymer matrix, but at At the same time, the water resistance of the modified PVA films increases to a certain limit of the borate content (in particular, with the introduction of 0.075 and 0.15 ml of boric acid per 1 ml of PVA, the films did not dissolve within 1 week of exposure to water at t = 20 °C, but with the introduction of 0.30 ml of boric acid per 1 ml of PVA, the film dissolved in 3 hours of exposure, for comparison, unmodified PVA of the specified brand dissolves in water at n.o. for 10 minutes).

Bioinspired Janus particles for hydrophobic modification of hydrogels with photothermal antibacterial capability

Hydrogels have received considerable attention due to their biocompatibility and desirable physical characteristics. Nonetheless, due to their open structure, hydrogels are prone to dehydration in air, resulting in a loss in their elasticity and function. Herein, we report a facile yet effective method for the modification of hydrophobic hydrogel surfaces by using bioinspired amphiphilic Janus silica particles, which are obtained by modifying hydrophilic polydopamine and hydrophobic 1H,1H,2H,2H-perfluorodecanthiol on their two sides via a templating method. With the coating of amphiphilic Janus silica particles, the water contact angles of poly(ethylene imine)-polyacrylamide and polydopamine-polyacrylamide hydrogels significantly increase to 96° and 97°, respectively. Furthermore, we demonstrate that the hydrophobic modification of the hydrogels by Janus silica particles improves the water retention capability, and the overall mechanical properties of bulk hydrogels are not compromised. In addition, we show that hydrogels coated with Janus silica particles not only exhibit hydrophobic surfaces but also have photothermal antibacterial capabilities. Consequently, this study provides a facile method for the fabrication of hydrogels with hydrophobic surfaces, which could potentially be applied to biomedical materials.

Features of high-filled composites based on various brands of polyvinyl alcohol

Composites based on polyvinyl alcohol (PVA) and polysaccharides (PS) have significant potential for use as compostable packaging materials, as well as in various fields of crop production. PVS are produced by the industry of various brands that differ in molecular weight (MM) and the residual content of vinyl acetate (BA) groups, and as a result - the degree of hydrolysis. Depending on the brand of PVA and the nature of the filler, such properties of composites based on them as water resistance, strength, degree of bioconversion, etc.will differ significantly. The purpose of the work: a comprehensive assessment of the properties of high-filled composites based on PVA of various brands, differing in the degree of hydrolysis, and polysaccharides. Objects of research: composites obtained by direct combination of a 5% solution of PVA (grades 1799, VS-05, BP-05, KurarayPoval 3-83) and PS powder (wood microcellulose - MCD, corn native starch - KK), with and without the addition of a plasticizer (P) - glycerin, followed by dehydration in air or in a vacuum drying cabinet. Based on the presence of external defects after dehydration and the strength characteristics of the material, it was found that for PVA-1799 it is possible to achieve a filling degree of 80 vol.%, for a PVA BP-05, VS-05 KurarayPoval and 3-83-no more than 50 vol.% without plasticizer and up to 70 vol.% in the presence of a plasticizer. It is noted that when filling PVA with starch up to 50 vol.% dehydrated composites are transparent or semi-transparent, which gives them additional advantages as packaging materials (including film). For composites based on PVA-1799, it was found that the maximum water absorption (250% by weight) has a PVA filled with MCD (20: 80 vol.%), and the introduction of a plasticizer (5 vol.% ) significantly reduces the degree of water absorption (up to 150% by weight), which is not typical for this brand of PVA filled with CC (water absorption was about 50% by weight with and without plasticizer). Composites based on PVA grades VS-05, BP-05, KurarayPoval 3-83 dissolve in water at room temperature for 5-10 minutes. During the preliminary assessment of the biodegradation of the studied PVA-1799 composites, it was found that micro-cracks and areas with immobilized microbiota were observed in the polymer matrix during microscopy after 6 months of composting and soil testing, however, no significant damage to the integrity of the polymer of this brand occurred during the specified composting period, which emphasizes the complex nature of the biodegradation of PVA with high MM and low content of VA groups.

Zero-Dimensional Hybrid Organic-Inorganic Lead Halides and Their Post-Synthesis Reversible Transformation into Three-Dimensional Perovskites.

Zero-dimensional (0D) mixed-halide hybrid organic-inorganic MA4PbX6·2H2O (MA = CH3NH3+; X = Br1-xIx with 0 < x < 1) has been synthesized by a solvent-free mechanochemical approach. It has been shown that this 0D phase with sharp absorption features in the near-UV is a hydrated structure, which can be reversibly transformed into the three-dimensional perovskite phase MAPbX3 by simple thermal annealing (dehydration) in air. This work reveals a new approach to hybrid organic-inorganic perovskites and related 0D structures, which have so far only been thoroughly studied for the inorganic Cs4PbX6 compounds.

Effect of the synthesis conditions of Ce0.9Gd0.1O1.95 powder on its morphology and characteristics of the oxygen ion-conducting ceramics obtained by spark plasma sintering

In this work, Ce0.9Gd0.1O1.95(10GDC) powders were synthesized by thermal decomposition of oxalate precursor crystals Ce1.8Gd0.2(C2O4)3·10H2O having a plate shape. The morphology of the oxide was found to be strongly influenced by the dehydration conditions of the precursor crystals. Dehydration in air at 125 °C led to the formation of the product in a pseudomorph form, retaining the shape of the precursor crystals and showing only slight dimensional changes. The formation of a pseudomorph was accompanied by a loss of crystallinity. When dehydration occurred at an increased water vapor pressure at the same temperature, a crystalline product formed having a significantly altered morphology. Unlike dehydration in air, after which the crystals retained their shape, an intensive shattering of the crystals occurred upon dehydration at an increased water vapor pressure. Structural transformations during dehydration were shown to determine the product morphology. The 10GDC powders with different textural characteristics were obtained by oxidative thermolysis (at 300 °C) of dehydration products. The oxide powders were sintered by spark plasma sintering at a temperature of 1100 °C and a pressure of 40 MPa. The microstructure, relative densities, and conductivities of the ceramic samples obtained from powders of two different morphologies were compared. The sintered ceramic samples had comparable grain size (<1 μm); however, the material obtained from the crystalline product of dehydration showed a higher relative density. The ionic conductivity of the ceramic material obtained using the crystalline product of dehydration was almost one order of magnitude higher than that of the sintered material obtained from the poorly crystallized product of dehydration.

Reversible Breathing Process and Associated Thermochromism of a Stacked-Layer Porous Supramolecular Material

The two-dimensional (2-D) catena-{Co(amp)3Cr(ox)3·6H2O}(amp = 2-picolylamine, ox = oxalate) compound is built by the [Co(amp)3]3+ (D) and [Cr(ox)3]3– (A) ions via multiple hydrogen bonds and hosts well-resolved R12 dodecameric discrete water cluster rings between its stacked layers. It undergoes reversible single crystal to single crystal transformation upon dehydration and rehydration in air, both processes being correlated to gradual changes from brown (hydrated phase) to green (dehydrated phase) and vice versa. The water uptake mass of this compound is 0.13 g/g of sample, and the rehydration process needs 90 min. The rate limiting step of the rehydration process is the diffusion of the water molecules into the framework of the dehydrated phase because the latter does not have voids. The 2-D catena-{Co(amp)3Cr(ox)3·6H2O} can undergo many cycles of dehydration/rehydration (breathing) processes without losing its crystallinity. During these processes, its unit cell contracts and expands by 9.39% along the...

Direct Analysis of Water Content and Movement in Single Dormant Bacterial Spores Using Confocal Raman Microspectroscopy and Raman Imaging

Heavy water (D2O) has a distinct molecular vibration spectrum, and this has been used to analyze the water content, distribution, and movement in single dormant Bacillus cereus spores using confocal Raman microspectroscopy and Raman imaging. These methods have been used to measure the kinetics of D2O release from spores suspended in H2O, the spatial distribution of D2O in spores, and the kinetics of D2O release from spores during dehydration in air at room temperature. The results obtained were as follows. (1) The Raman spectrum of single D2O-loaded dormant spores suggests that D2O in spores is in a relatively weak hydrogen-bonded mode, compared to the strong hydrogen-bonded mode in pure D2O. (2) The D2O content of individual spores in a population was somewhat heterogeneous. (3) The spatial distribution of D2O in single dormant spores is uneven, and is less dense in the central core region. Raman images of different molecular components indicate that the water distribution is somewhat different from those of proteins and Ca-dipicolinic acid. (4) Exchange of spore D2O with external H2O took place in less than 1 s. (5) However, release of spore D2O during air dehydration at room temperature was slow and heterogeneous and took 2-3 h for complete D2O release.

Partial removal of pore and loosely bound water by low-energy drying decreases cortical bone toughness in young and old donors

With an ability to quantify matrix-bound and pore water in bone, 1H nuclear magnetic resonance (NMR) relaxometry can potentially be implemented in clinical imaging to assess the fracture resistance of bone in a way that is independent of current X-ray techniques, which assess bone mineral density as a correlate of bone strength. Working towards that goal, we quantified the effect of partial dehydration in air on the mechanical and NMR properties of human cortical bone in order to understand whether NMR is sensitive to water–bone interactions at low energy and whether such interactions contribute to the age-related difference in the toughness of bone. Cadaveric femurs were collected from male and female donors falling into two age groups: 21–60 years of age (young) and 74–99 years of age (old). After extracting two samples from the medial cortex of the mid-shaft, tensile tests were conducted on Wet specimens and paired, Partially Dry (PtlD) specimens (prepared by low-energy drying in air to remove ∼3% of original mass before testing). Prior analysis by micro-computed tomography found that there were no differences in intra-cortical porosity between the Wet and PtlD specimens nor did an age-related difference in porosity exist. PtlD specimens from young and old donors had significantly less toughness than Wet specimens, primarily due to a dehydration-related decrease in post-yield strain. The low-energy drying protocol did not affect the modulus and yield strength of bone. Subsequent dehydration of the PtlD specimens in a vacuum oven at 62°C and then 103°C, with quantification of water loss at each temperature, revealed an age-related shift from more loosely bound water to more tightly bound water. NMR detected a change in both bound and pore water pools with low-energy air-drying, and both pools were effectively removed when bone was oven-dried at 62°C, irrespective of donor age. Although not strictly significant due to variability in the drying and testing conditions, the absolute difference in toughness between Wet and PtlD tended to be greater for the younger donors that had higher bone toughness and more bound water for the wet condition than did the older donors. With sensitivity to low-energy bone–water interactions, NMR, which underpins magnetic resonance imaging, has potential to assess fracture resistance of bone as it relates to bone toughness.

Cation regulation by the terrestrial isopod Armadillidium vulgare (Crustacea: Isopoda: Oniscidea) during dehydration in air

Many terrestrial arthropods display tight osmotic and ionic regulation of the hemolymph during dehydration. In this study, we sought to quantify the level of regulation of the major hemolymph cations in the terrestrial isopod Armadillidium vulgare (Isopoda, Oniscidea). Inulin space measurements showed that the hemolymph comprises 52 ± 2.2% of the hydrated water content but contributes 71 ± 9.8% of water losses during desiccation. Hemolymph concentrations of Na +, K + and Ca 2+ were measured in variably dehydrated animals using ion-selective microelectrodes and compared with predicted concentrations assuming no regulation. Na + and Ca 2+ are quite tightly regulated, showing respective concentration increases of 20.8% and 7.1% following a 50% reduction in hemolymph volume, but K + showed no measurable regulation. The excreted cation fraction during desiccation is negligible. Sites of ion sequestration were examined by injecting 22Na and 45Ca into the hemolymph of hydrated animals and assaying tissue-specific activities following dehydration. Na + is apparently sequestered non-specifically by an unknown mechanism. Ca 2+ accumulates in the dorsal somatic tissues, possibly in the calcium pool of the cuticle. How A. vulgare avoids significant disruptions of E m and neuromuscular function in the absence of K + regulation, and how it sequesters Na +, both pose intriguing challenges for future work.

Thermal behaviour and kinetics of dehydration in air of bassanite, calcium sulphate hemihydrate (CaSO40.5H2O), from X-ray powder diffraction

Thermal behaviour and kinetics of dehydration in air of bassanite (calcium sulphate hemihydrate, CaSO 4 ·0.5H 2 O) have been investigated in situ real-time using laboratory parallel-beam X-ray powder diffraction data. Thermal expansion has been analyzed between 303 and 383 K at increments of 5 K. The bassanite → γ-anhydrite conversion starts at 388 K and is completed at 408 K. Thermal expansion of hemihydrate is isotropic and not related to the expansion of CaO 8–9 polyhedra. Lattice parameters and volume dependence from T is linear within the studied temperature range. Kinetics of dehydration has been investigated from isothermal diffraction data collected at 10 temperatures between 378 and 423 K with steps of 5 K using a fresh sample at each temperature. Transformed fraction α vs. t curves were fitted with seven different kinetic models. The best fit was found for the Avrami-Erofe’ev equation that provided an empirical activation energy E a of the process of 73(5) kJ/mol. E a was found to be substantially independent from the kinetic model selected.

Precipitated calcium phosphatesilicates and their dehydration in air at room temperature

By exchange reaction in the aqueous solutions between sodium phosphatesilicates and calcium chloride is obtained a group of the crystalline and amorphous substances, which contain up to 80 wt % of water. Dehydration of amorphous calcium phosphatesilicates at room temperature is studied.

Amorphous calcium barium monophosphate and its dehydration in air at room temperature

The change in the state of chemical bonds during dehydration of amorphous calcium barium monophosphate was studied. The monophosphate was obtained by precipitation from an aqueous phosphate solution under the action of a binary solution containing simultaneously calcium and barium chlorides in the atomic ratio Ba/Ca ∼0.2.

Preparation of nano-and submicrosized aluminum oxide fibers by the dehydration of a hybrid gel

The spontaneous growth of hybrid (organoinorganic) microfibers on the surface of a gel prepared by dispersing an organoinorganic nanocomposite in water and subjected to dehydration in air, has been investigated. Aluminum oxide nano-and submicrofibers have been prepared by the thermal treatment of the microfibers.

Room, low, and high temperature dehydration and phase transitions of kernite in vacuum and in air

AbstractKernite Na2B4O6(OH)2·3H2O dehydration in air at high temperature and in vacuum at room temperature has been studied. It was found that kernite easily dehydrates forming a new phase‐I both on heating and in vacuum. The chemical formula Na2B4O6(OH)2·1.5H2O of the new phase‐I has been estimated on the basis of thermogravity analysis. It is triclinic with the unit cell parameters a = 7.047(8), b = 8.76(1), c = 13.08(2) Å, α = 93.40(9), β = 95.32(9), γ = 90.28(9)° changing slightly on pressure reduction. Due to the relatively low temperature (353 K) and reversibility of the kernite ⟷ phase‐I transition an anion of the new phase‐I likely consists of the same chains [B4O6(OH)2]2– like in kernite structure. The high anisotropy of kernite thermal expansion was explained by approaching of NaO chains due to the initial removing of water molecules from kernite crystal structure. The behaviour of the new phase‐I at low temperatures in vacuum was also investigated. A formation of an additional new phase II has been detected at the temperature of 93 K. (© 2005 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Raman spectroscopic evidence of the bronze-like recharging behavior for conducting films deposited from isopolytungstates

In situ Raman spectroscopy (spectral regions 200–1700 cm −1 and 2800–3800 cm −1) at various potentials is applied to study the oxidation states of tungsten in oxotungstate films electrodeposited on Pt support from metastable Na 2WO 4 + 0.5 M H 2SO 4 solution. Comparison of in situ and ex situ spectra confirms that the films under study consist of the hydrated tungsten bronze (H x WO 3, or H x W x v W ( 1 − x ) VI O 3) and undergo quasi-reversible dehydration in air. Cyclic voltammetry (CV) and scanning tunnelling microscopy (STM) are applied to demonstrate the difference of freshly deposited and aged films. The pronounced changes of electrochemical properties and morphology found by these means are not accompanied by the changes in potential-dependent spectral behavior. The most pronounced effects of potential on Raman intensities are observed in the region of 0.05–0.60 V (reversible hydrogen electrode, RHE) and correspond to the decrease in W V content (i.e. x decrease) with potential. The behavior of bands at 2900–3800 cm −1 confirms that this process is accompanied by deprotonation. There is no any W V in the films at E > 0.60 V, which region corresponds to the thermodynamically stable hydrated WO 3. The experimental coulometric data are considered in the framework of the regular solution model and are applied to quantitative determination of potential— x dependence. The latter corresponds to reduction of one tungsten unity in [W 10O 32] 4− isopoly anion, which predominates in the deposition solution and, according to polarographic data, gives the main contribution to tungsten bronze deposition.

Time-resolved photoluminescence analysis of distribution and migration of terbium ions in zeolites X

The photoluminescence (PL) dynamics of terbium-exchanged zeolites X was investigated upon laser excitation at 355nm. The results evidenced the presence of at least two terbium main environments with PL lifetimes varying between 391–411 and 753–770μs. The two-site nature of terbium distribution in zeolites X permitted a quantitative analysis of the migration process of terbium ions inside the pores and cavities upon dehydration in air at 200°C. Besides the increase of the PL lifetimes with about 30% and 80% compared to those of the hydrated zeolite, a fraction of almost 30% of terbium ions was estimated to migrate from the supercages to the neighboring sodalites or hexagonal prisms. Our results evidenced for the first time the capability of time-resolved luminescence spectroscopy in quantitatively tracking for the intrazeolitic migration of lanthanides.

Kinetics of thermal dehydration and decomposition of hydrated chlorides of some 3d transition metals (Mn-Cu series). Part-I. Dehydration of MnCl2.4H2O

The thermal dehydration of MnCl 2 hydrate has been studied by using simultaneous TG/DTA under the static air (or self-generated atmosphere) and also under the flowing nitrogen condition at different heating rates. In either of the above condition the salt dehydrates in three steps, with the losses of about 1.0, 1.2 and 1.1 moles of water in static air and 0.9, 2.1 and 1.1 moles of water in flowing nitrogen atmosphere. The heats of the three steps of dehydration in air have been estimate2d from area under the corresponding DTA peaks at the heating rate of 10°/min. The first step of dehydration is accompanied with the melting of the salt and therefore does not follow any kinetic model of solid state decomposition. For the other two steps of dehydration changes in the mechanism are observed and attempts have been made to identify these changes. All these have been possible by converting non-isothermal time into isothermal time which is more appropriate in the kinetic analysis. It is observed that either nucleation and growth or progress of the reactant/product interface is generally the most suitable kinetic model for the dehydration of manganese chloride hydrate.

Studies on thermal dehydration of hydrated chromic oxide

Hydrated chromic oxide was prepared by the reduction of potassium dichromate in an autoclave using sucrose. The thermal dehydration of the parent gel in different atmospheres was studied comparatively using the techniques of thermal gravimetry, differential thermal analysis, X-ray diffraction analysis, FT-IR spectroscopy, and gas adsorption. The results of thermogravimetric and differential thermal analysis show that the temperature at which the glow phenomenon occurs is dependent on the gaseous atmosphere in the heat-treatment process and increases in the following order: air, nitrogen, and carbon dioxide. When heated in CO 2, the parent gel is transformed into crystalline α-Cr 2O 3 going through the phase of amorphous Cr 2O 3. In air, however, it is decomposed directly into crystalline α-Cr 2O 3 without going through the amorphous Cr 2O 3 phase. It is also found that microcrystallites of α-Cr 2O 3 have been formed before the glow phenomenon occurs at 390 °C in air and at 590 °C in CO 2, respectively. The mechanism for thermal dehydration in air and CO 2 is discussed.

The crystal structure of synthetic autunite, Ca[(UO2)(PO4)]2(H2O)11

Autunite, Ca[(UO2)(PO4)]2(H2O)11, is amongst the most abundant and widely distributed of the uranyl phosphate minerals, yet because of its pseudo-tetragonal symmetry and rapid dehydration in air, the details of its symmetry, stoichiometry, and structure were previously uncertain. The crystal structure of synthetic autunite was solved by direct methods and refined by full-matrix least-squares techniques to agreement indices R1 = 0.041, calculated for the 1497 unique observed reflections (|F0| ≥ 4σF), and wR2 = 0.119 for all data. Autunite is orthorhombic, space group Pnma, Z = 4, a = 14.0135(6), b = 20.7121(8), c = 6.9959(3) Å, V = 2030.55(15) Å3. The structure contains the wellknown autunite type sheet with composition [(UO2)(PO-)]-, resulting from the sharing of equatorial vertices of the uranyl square bipyramids with the phosphate tetrahedra. The calcium atom in the interlayer is coordinated by seven H2O groups and two longer distances to uranyl apical O atoms. Two symmetrically independent H2O groups are held in the structure only by hydrogen bonding. Bond-length-constrained refinement provided a crystal-chemically reasonable description of the hydrogen bonding.