Water-containing Materials Research Articles

Dehydration regulates structural reorganization of dynamic hydrogels

The dehydration process is widely recognized as a significant phenomenon in nature. Hydrogels, which are important functional materials with high water content and crosslinked networks, encounter the issue of dehydration in their practical applications. Here, we report the distinctive anisotropic dehydration modality of dynamic hydrogels, which is fundamentally different from the more commonly observed isotropic dehydration of covalent hydrogels. Xerogels derived from dynamic hydrogel dehydration will fully cover a curved substrate surface and exhibit hollow structures with internal knots, in contrast to the bulk xerogels produced by covalent hydrogel dehydration. Depending on the competing cohesion of polymer chains and the adhesion at the hydrogel-substrate interface, the previously overlooked reorganization of polymer networks within dynamic hydrogels, triggered by dehydration-induced stress, has been discovered to regulate such macroscopic structural reconstruction for dynamic hydrogel dehydration. With the attached hydrogel-substrate interface, the surface microstructures of substrates can also be engraved onto xerogels with high resolution and on a large scale. This work will greatly enhance our understanding of the soft matter dehydration process and broaden the applications of dehydration technologies using water-containing materials.

Surface DBD degradation in humid air, and a hybrid surface-volume DBD for robust plasma operation at high humidity

Surface dielectric barrier discharge performance deteriorates in humid air, with permanent and/or reversible degradation of its components. Plasma operation in a humid environment is unavoidable when humid air or water-containing materials are treated. Experimental and numerical results indicate that an electrically conductive thin film of water is responsible for ohmic dissipation and inhibited plasma ignition at high relative humidity. An alternative hybrid surface-volume dielectric barrier discharge design provides more stable and uniform plasma operation in high-humidity atmospheres.

Evaluation of alternative methods to derive particle density from compression data

The determination of particle density is a critical part of material characterization regarding compression analyses. Helium pycnometry as the most commonly used method is criticized for different aspects. Most prominent is the susceptibility to errors when measuring water-containing powders. Alternative methods for determining particle density using compression data have already been described. However, a systematic investigation and evaluation is still missing. In this study, the methods by Sun and Krumme were investigated in detail regarding their robustness against variations in tableting settings. Twelve pharmaceutical excipients were tableted at five different settings to verify the applicability and sensitivity to changes in the experimental set-up. Both methods were found to be robust against influencing parameters from the experiments. A sufficiently high compression pressure to approach a constant density value of the corresponding material during tableting was considered to be an essential requirement for the performance of the methods. Brittle materials with high yield pressure were found to be unsuitable for the application of both methods. The method of Krumme gave small deviations to measurements of helium pycnometry for water-free materials. By using the tablet density after in-die elastic recovery, Krumme's method could be used for water-containing materials as well. The method of Sun was found to give significantly smaller values for particle density due to inclusion of slow elastic recovery.

STORAGE: A Source Term Model for Intermediate-Level Radioactive Waste

The French Alternative Energies and Atomic Energy Commission and Orano have developed a modeling tool named the Simulation TOol Of RAdiolysis Gas Emission (STORAGE) for assessing gas generation of intermediate-level waste (ILW). The first version of this model was designed to estimate gas (more specifically hydrogen) production by radiolysis of organic and water-containing materials. The code deals with different types of waste packages: metal drums, concrete drums, bitumen packages, and compacted waste containers. Diverse radioactive waste can be handled: spent fuel cladding, reprocessing sludge, contaminated technological waste (gloves, bags, bottles, etc.), ion exchange resin, etc. The validity of the model was evaluated using a series of measurements performed on U,Pu–contaminated solid waste from the Orano plutonium laboratories at the MELOX facility. A benchmark study for compacted waste containers was also implemented; the results of STORAGE were compared with reference calculations performed by Orano Projets. Future improvements of the STORAGE model are also presented.

Correlation between the Dynamics of Nanoconfined Water and the Local Chemical Environment in Calcium Silicate Hydrate Nanominerals.

Calcium silicate hydrates are members of a large family of minerals with layered structures containing pendant CaOH and SiOH groups that interact with confined water molecules. To rationalize the impact of the local chemical environment on the dynamics of water, SiOH- and CaOH-rich model nanocrystals were synthesized by using the continuous supercritical hydrothermal method and then systematically studied by a combination of spectroscopic techniques. In our comprehensive analysis, the ultrafast relaxation dynamics of hanging hydroxy groups can be univocally assigned to CaOH or SiOH environments, and the local chemical environment largely affects the H-bond network of the solvation water. Interestingly, the ordered "ice-like" solvation water found in the SiOH-rich environments is converted to a disordered "liquid-like" distribution in the CaOH-rich environment. This refined picture of the dynamics of confined water and hydroxy groups in calcium silicate hydrates can also be applied to other water-containing materials, with a significant impact in many fields of materials science.

Multiple methane hydrate formation in powder poly(vinyl alcohol) cryogel for natural gas storage and transportation

The aim of this work is to investigate the possibility of using a new water-containing material for multicycle gas hydrate formation with a high rate and water-to-hydrate conversion ratio in relation to natural gas storage and transportation. Recently, we developed a powdered water-containing material formed by grinding a frozen poly(vinyl alcohol) (PVA) water solution in the presence of silica nanoparticles and further thawing the prepared system. The obtained material is called powder PVA cryogel (PPVACG). In this work multiple methane hydrate formation/dissociation cycles in PPVACG were investigated for the first time. It was found that the equilibrium conditions for methane hydrate formation in PPVACG (7 wt% PVA and 5 wt% nanoparticles) were the same as those for pure bulk water. The methane hydrate formation rate as well as the water-to-hydrate conversion for PPVACGs were no less than those for the known dispersed “dry water” and “gelatinous dry solution” systems. However, PPVACGs showed a higher stability and higher methane uptake capacity in comparison with “dry water” and “gelatinous dry solution” in repeated gas hydrate formation/dissociation cycles starting from the third cycle. The results may be useful for the development of hydrate-based technologies for the storage, transportation, and utilization of natural and anthropogenic gases.

Molecular Species Generated by Surface Dielectric Barrier Discharge Micro-plasma in Small Chambers Enclosing Atmospheric Air and Water Samples

In many applications of the atmospheric pressure plasmas, the plasma is generated in chambers that enclose samples to be treated. In the case of plasma treatments of water or water-containing materials, the humidity in gaseous medium rises during the treatment, and this affects considerably the plasma generation of reactive oxygen and nitrogen species (RONS). In this study, Fourier transform infrared absorption spectroscopy is used to investigate the kinetics of reactive species generated by surface dielectric barrier (SDBD) micro-plasma in a small volume of atmospheric air (0.5 L) enclosed in a discharge chamber. The investigations were made for dry air (in absence of liquid water) and for humid air in presence of liquid water. The SDBD plasma contributes to desorption of water from the inner wall of the discharge chamber and enhances evaporation of liquid water, which increases air humidity and decreases the generation rates of reactive species. Kinetics of RONS generated in small samples of liquid water in contact with discharge medium is investigated by ex situ UV absorption spectroscopy measurements of plasma treated water.

Slide-Ring Cross-Links Mediated Tough Metallosupramolecular Hydrogels with Superior Self-Recoverability

Stiff yet recoverable water-containing materials can be found in many biological tissues including tendons, cartilages, and skins. However, it remains a challenge to develop hydrogels as load-beari...

Calculation of Radiation Loads in a Space Station Compartment with Additional Protection of High-Pressure Polyethylene

The paper presents the results of the calculation of cosmic ionizing radiation doses for conditions that simulate ISS crew quarters outfitted with additional protection in the form of a “protective shutter” kit used in the Matryoshka-R experiment; the kit is filled with high-pressure polyethylene instead of regular means of cosmonaut personal hygiene (wet wipes and towels). The calculation was performed using the ray tracing method, which was previously verified using the experimental data on the dose loads in the space station sections. The protective shutter kit has a thickness of 10 cm and covers the exterior wall of the crew quarters; its volume is filled with high-pressure polyethylene. The calculation is performed for the locations of experimental dosimetric assemblies for typical ISS orbits in the phase of minimum and maximum solar activity. The effect from the use of the additional protection (AP) in the ISS crew quarters in terms of the equivalent dose varies between 22 and 60% depending on the orbital altitude, phase of solar activity cycle, and initial conditions of protection. The results indicate a higher efficiency of the additional protection of polyethylene in comparison with water-containing materials. This AP from cosmic radiation has the potential to be used in long-term and long-range spaceflights.

Correction to "Supramolecular Nucleoside-Based Gel: Molecular Dynamics Simulation and Characterization of Its Nanoarchitecture and Self-Assembly Mechanism".

Among the diversity of existing supramolecular hydrogels, nucleic acid-based hydrogels are of particular interest for potential drug delivery and tissue engineering applications because of their inherent biocompatibility. Hydrogel performance is directly related to the nanostructure and the self-assembly mechanism of the material, an aspect that is not well-understood for nucleic acid-based hydrogels in general and has not yet been explored for cytosine-based hydrogels in particular. Herein, we use a broad range of experimental characterization techniques along with molecular dynamics (MD) simulation to demonstrate the complementarity and applicability of both approaches for nucleic acid-based gelators in general and propose the self-assembly mechanism for a novel supramolecular gelator, N4-octanoyl-2′-deoxycytidine. The experimental data and the MD simulation are in complete agreement with each other and demonstrate the formation of a hydrophobic core within the fibrillar structures of these mainly water-containing materials. The characterization of the distinct duality of environments in this cytidine-based gel will form the basis for further encapsulation of both small hydrophobic drugs and biopharmaceuticals (proteins and nucleic acids) for drug delivery and tissue engineering applications.

Electron microscopic observation of photoreceptor cells in directly inserted anesthetized Drosophila into a high-pressure freezing unit.

The high-pressure freezing (HPF) technique is known to cryofix water-containing materials with little ice-crystal formation in deep depths compared with other freezing techniques. In this study, HPF for anesthetized living Drosophila was performed by placing them directly on the carrier of the HPF unit and exposing them to light. Frozen Drosophila were freeze substituted, and their compound eyes were examined by transmission electron microscopy. The ultrastructures of ommatidia composed of photoreceptor cells were well preserved. The location of the cytoplasmic organelles inside the photoreceptor cells was observed. In some photoreceptor cells in ommatidia of the light-exposed Drosphila, the cytoplasmic small granules were localized nearer the base of rhabdomeres, compared with those of the nonlight-exposed Drosophila. Thus, HPF with the direct insertion of living Drosophila under light exposure into the HPF machine enabled us to examine changes to functional structures of photoreceptor cells that occur within seconds.

Supramolecular Nucleoside-Based Gel: Molecular Dynamics Simulation and Characterization of Its Nanoarchitecture and Self-Assembly Mechanism.

Among the diversity of existing supramolecular hydrogels, nucleic acid-based hydrogels are of particular interest for potential drug delivery and tissue engineering applications because of their inherent biocompatibility. Hydrogel performance is directly related to the nanostructure and the self-assembly mechanism of the material, an aspect that is not well-understood for nucleic acid-based hydrogels in general and has not yet been explored for cytosine-based hydrogels in particular. Herein, we use a broad range of experimental characterization techniques along with molecular dynamics (MD) simulation to demonstrate the complementarity and applicability of both approaches for nucleic acid-based gelators in general and propose the self-assembly mechanism for a novel supramolecular gelator, N4-octanoyl-2′-deoxycytidine. The experimental data and the MD simulation are in complete agreement with each other and demonstrate the formation of a hydrophobic core within the fibrillar structures of these mainly water-containing materials. The characterization of the distinct duality of environments in this cytidine-based gel will form the basis for further encapsulation of both small hydrophobic drugs and biopharmaceuticals (proteins and nucleic acids) for drug delivery and tissue engineering applications.

Calcium silicate and calcium hydroxide materials for pulp capping: biointeractivity, porosity, solubility and bioactivity of current formulations.

The chemical-physical properties of novel and long-standing calcium silicate cements versus conventional pulp capping calcium hydroxide biomaterials were compared. Calcium hydroxide-based (Calxyl, Dycal, Life, Lime-Lite) and calcium silicate-based (ProRoot MTA, MTA Angelus, MTA Plus, Biodentine, Tech Biosealer capping, TheraCal) biomaterials were examined. Calcium and hydroxyl ion release, water sorption, interconnected open pores, apparent porosity, solubility and apatite-forming ability in simulated body fluid were evaluated. All calcium silicate materials released more calcium. Tech Biosealer capping, MTA Plus gel and Biodentine showed the highest values of calcium release, while Lime-Lite the lowest. All the materials showed alkalizing activity except for Life and Lime-Lite. Calcium silicate materials showed high porosity values: Tech Biosealer capping, MTA Plus gel and MTA Angelus showed the highest values of porosity, water sorption and solubility, while TheraCal the lowest. The solubility of water-containing materials was higher and correlated with the liquid-to-powder ratio. Calcium phosphate (CaP) deposits were noted on materials surfaces after short aging times. Scant deposits were detected on Lime-Lite. A CaP coating composed of spherulites was detected on all calcium silicate materials and Dycal after 28 days. The thickness, continuity and Ca/P ratio differed markedly among the materials. MTA Plus showed the thickest coating, ProRoot MTA showed large spherulitic deposits, while TheraCal presented very small dense spherulites. calcium silicate-based cements are biointeractive (ion-releasing) bioactive (apatite-forming) functional biomaterials. The high rate of calcium release and the fast formation of apatite may well explain the role of calcium silicate biomaterials as scaffold to induce new dentin bridge formation and clinical healing.

美国黄石公园间歇泉成因机制探讨<br>Study on the Genesis of Geysers in American Yellowstone National Park

美国黄石公园内的间歇泉是一个奇特的地质景观，它们是如何形成的？目前关于黄石公园的间歇泉成因是用海底扩张和板块构造的模式解释的，但这种模式在其他地区存在自相矛盾的地方。本文结合作者提出的大陆漂移的源动力——板块自驱动模式，给出了另外一个全新的成因模式，该模式说明当大陆板块漂移时，会在板块运动的前方产生刮蹭堆积及挤压形成山脉高原，同时也可能刮起一些深海含水物质形成深部含水圈闭，该含水圈闭还会与深部岩浆连通，在板块运动中，不断接受应力变化，产生间歇泉。同时也会在板块后方形成深海沉积。通过对美国西部落基山脉的对比发现，该模型与实际情况吻合很好。该成因模型为我们重新认识北美洲地理环境成因提供了一个新的思路。 Yellowstone geyser is a unique geological landscape, how it was formed? Current explanation about Yellowstone geysers is that it was formed by seafloor spreading and plate tectonics model, but these models cannot explain in many cases and even have contradictory. Combined with the model “source power for continental drifting-plate self- driven mode” by the author, a new genetic model was given in this paper, that is when the continental plates drift, mountains and plateaus were formed in front of the plate motion by Scratching accumulation and extrusion force. It may also whip up some deep-sea water-containing material to the formation of the deep aquifer traps, and the aqueous traps also communicate with the deep magma, it will receive continuous stress changes in the movement of tectonic plates, thus produces geysers. At the same time, deep-sea sediment was formed in its rear. This model fits very well with the Rocky Mountains of North America. The genetic model provides us a new way to rethink the origin model of the North America geographical environment.

Synthesis and structural transformations of the “glaserite” type zirconosilicate Na3−xH1+xZrSi2O8·yH2O

A hydrous sodium zirconosilicate material with “glaserite” type structure and generalized formula Na3−xH1+xZrSi2O8·yH2O, 0<x<3, 0<y<1 is synthesized in the system Na2O:ZrO2:SiO2:H2O at 200°C. Its crystal structure is composed of zirconium and silicon polyhedra connected to build layers additionally stacked to form 3D zipper-like network. Within the network there are cavities interconnected to channels with irregular shapes where the sodium atoms and water molecules reside. It is found that with synthesis duration the crystal structure gradually transforms from higher symmetrical into triclinic one. The structure of the triclinic form – Na3HZrSi2O8·0.4H2O was refined from powder diffraction data. It crystallizes in the space group P-1 with lattice parameters a=9.05234, b=5.56121, c=6.96219Å, α=92.178, β=90.839, γ=90.288°. To the best of our knowledge the studied compound is the only water-containing material with “glaserite” type structure.

Determining the orientations of ice crystals using electron backscatter patterns.

Knowing the orientations of the ice crystals in a polycrystalline aggregate is essential for understanding and modeling the flow of naturally occurring ice. Here we show, for the first time, that the orientation of crystals in polycrystalline ice can be determined with a higher angular and spatial resolution and more rapidly than any currently used method by using electron backscatter patterns (EBSPs) in a cold-stage equipped scanning electron microscope. We also present an orientation image map constructed from EBSPs, and discuss possible applications of the technique for ice. The results indicate that obtaining EBSPs and orientation images from other frozen water-containing materials, such as clathrate hydrates, may also be possible.

Investigation of Plant Surfaces with Environmental Scanning Electron Microscopy (ESEM®) - A Comparison with Conventional SEM

Environmental scanning electron microscopy (ESEM) enables the investigation of untreated and watercontaining material without preparation with the benefit of SEM (depth of focus and three dimensional imaging of surfaces with a high resolution). Conventional SEM (CSEM) usually requires time consuming fixation, drying and coating of samples. Their surface structures may be altered by this procedure. For comparison a large number of plant samples was observed with both methods. Using CSEM, secretion products or mucilagineous coatings may be removed and dynamic processes cannot be observed. However, the samples can be investigated several times. In contrast, ESEM allows the observation of watercontaining, native surfaces and this method is the only possibility to watch dynamic processes in the SEM. However, using ESEM the plant material is very sensitive to beam damages because of the lack of the protecting metall layer - necessary for non-conducting surfaces in CSEM and dehydration cannot be prevented completely. In summary, ESEM will not compete with CSEM but it will establish oneself as a valuable and essential supplement in studying plant surfaces.

The Proton and Oxygen Ion Conduction in a NaCl Based Composite Electrolyte

Proton conducting and oxygen-ion conducting materials are widely studied for their applications in fuel cells, electrolysis cells, electrochemical reactors, and sensors [1±3]. Proton electrolyte materials, include water-containing materials (HUP, etc.), oxo acids and their salts (CsHSO4, etc.), and complex oxides (MCeO3, MZrO3, etc., where M ˆ Ca, Sr, Ba) [2]. The transportation of proton is based on the hydrogen-bond defects incorporated into the oxides or the rotation of tetrahedral XO4 [1±3]. In a word, most proton and=or oxygen-conducting materials are oxygen-containing materials. Furthermore, the well-known proton-conducting materials (MCeO3, MZrO3, etc.) and oxygen-conducting materials (YSZ, etc.) all operate at high temperatures (800± 1100 8C). Recently, in our experiments we found that a NaCl-based composite electrolyte showed distinct proton and oxygen ion conduction at intermediate temperatures. Moreover, pure NaCl belongs to the non-oxygen material systems, which are obviously different from the usual H‡ and O2y conductors. Compared with the reported proton and oxygen conductors, this material is very cheap and easily available, which will lower the operational cost of electrochemical devices using it as electrolyte. Sodium chloride was sintered at 850 8C for 2 h, pressed into tablets, coated with platinum paste on both sides, and calcined at 600 8C for 3 h to form porous electrodes before electrochemistry measurements. In this work, the H2=O2 fuel cell with pure NaCl as electrolyte (Fig. 1a) resulted in a current density of 70 mA cmy2 at a 100 mV terminal voltage, indicating that pure NaCl, which is a nonoxygen material, exhibits proton and=or oxygen ion conduction. To improve the structural strength and performance of the cells, a-Al2O3 was mixed with NaCl and this material was given the same experimental process as described previously. Of course, the NaCl-Al2O3 composite cannot be classi®ed as non-oxygen material system. The experimental results for both hydrogen and oxygen concentration cells indicate that the composite materials have both proton and oxygen conductivity between 650± 750 8C. In NaCl-Al2O3, composite solid electrolytes with a composition of 30 mol % Al2O3 have the highest conductivity in air [4, 5]. However, to our knowledge, no report on the proton or oxygen ion conduction of that material appears. The sintered tablets of pure inorganic salts usually have poor construction strength. The addition of a second phase (such as Al2O3, CeO2, SiO2) not only greatly improves the mechanical strength but it enhances the conductivity of the materials [6±8]. Therefore, in our experiments, we have mainly studied the properties of the hydrogen concentration cell (HCC), oxygen concentration cell (OCC), and the H2=O2 fuel cell of NaCl-Al2O3 composite electrolytes containing 30 mol % a-Al2O3. High-purity NaCl and a-Al2O3, with molar ratio of 7:3 were mixed

Use of tap water samples for monitoring the geographical variation of stable isotopes used in authenticity studies

Analysis of tap water samples is the best and most easily obtained information for estimating the pattern of stable isotope ratios in water across large areas. Usually such samples are not supplied continuously, but have to be collected and therefore stored. Storage of such water samples of about 20 ml volume in high-density polyethylene (HDPE) vials for 15 years affected the 18O/16O ratio, depending on the tightness of closure, thus resulting in enrichments of up to about +2‰. Initially a set of 900 samples across the old federal states (i. e. the former West Germany1) was collected and measured, first in 1979 and then a selected number were measured again in 1990 and in 1995. The selected set of water samples was also used to determine the D/H ratio (i. e. ratio of 2H content to 1H content) in 1995. The D/H ratio did not change in those stored samples, which maintained an only slightly altered 18O/16O ratio. Therefore, the D/H ratio is more suitable for characterizing the origin of stored water samples. Additional fresh samples from identical or comparable sites were supplied after 15 years, confirming the overall constancy of the isotopic pattern in the water supply of the old federal states. Since the geographical pattern of the water intake has changed, about half of the samples were not of identical, but only of comparable, origin. Nevertheless they showed a similar pattern to samples of identical origins collected 15 years previously. Thus, a set of limited tap water samples will be sufficient to represent the isotopic variation of water across a large area if influences of the origin (e. g. river bank filtrate) and treatment (blending) can be checked. Since tap water is commonly used by the local food industry, its isotope composition can be used to trace water-containing material to its origin in order to check its authenticity.

Microcavity dynamics during laser-induced spallation of liquids and gels

Photomechanical fracture induced by thermoelastic stress waves is an important mechanism of tissue ablation by short laser pulses. In this study, we present experimental investigations of the fracture process in ductile, water-containing materials and compare the results with a theoretical calculation. The model describes cavitation caused by the negative part of a bipolar thermoelastic stress wave. Pulses from aQ-switched, frequency-doubled Nd:YAG laser with 8 ns duration were used to irradiate dyed water and gelatine with variable absorption coefficient. Cavitation and ablation were observed with various time-resolved methods such as stress detection, video imaging and an optical pump-probe technique for the detection of individual cavities. Quantitative agreement between experiment and simulation could be achieved in the case of cavity lifetimes, especially at low laser fluence where the bubble density is low and no coalescence takes place. An increase of the threshold energy density for ablation with rising absorption coefficient and a distortion of the thermoelastic wave in the presence of cavitation were experimentally observed and could be qualitatively explained by use of the simulation. The results obtained in this study should facilitate the choice of the optimal laser parameters for photomechanical tissue ablation.