Intrinsic Water Content Research Articles

Bidirectional Actuation of Silk Fibroin Films: Role of Water and Alcohol Vapors

Three-dimensional (3D) shape morphism observed in nature inspires the development of stimuli-responsive soft actuators. Vapor-responsive actuators are promising among the different stimuli-responsive materials due to their capability to produce macroscale movements in response to a minuscule amount of specific chemical vapor. Here, we report unusual multiple vapor-responsive bidirectional macroscale actuation behaviors of single-layer regenerated silk fibroin films. The vapor-responsive silk fibroin actuator exhibits antagonistic actuation characteristics in a reversible manner to both water and ethanol vapors. For instance, it produces an upward bending in the presence of water vapor and downward bending in ethanol vapor, which demonstrates the chemical vapor-specific actuation. However, the actuation characteristics remain largely invariant upon changing the polarity of alcohol molecules. The silk fibroin actuators effectively utilize the vapor-induced minuscule expansion and contraction of the film surface to produce large-scale actuation, which is fully reversible. The intrinsic water content of the films and the vapor pressure of the stimulants are exploited to control the actuation performance. Further, we demonstrated the 3D shape morphing ability of the actuator by generating an undulating wavelike motion via preprogrammed water and ethanol vapor exposure conditions. The change in the actuation direction is instantaneous, which ensures the sensitivity and rapid response of the fabricated actuators.

A systematic comparison of obsidian hydration measurements: The first application of micro-image with secondary ion mass spectrometry to the prehistoric obsidian

Archaeologists have long used obsidian hydration dating method to give chronometric dates for obsidian artifacts. Models using these equations independently employ different measurement systems, which are based on rim thicknesses determined by optical microscope and hydrogen depths measured by secondary ion mass spectrometry (SIMS), respectively, although the inconsistency of both measurements has been reported. Firstly, this paper describes a systematic comparison that was done on optical rim thicknesses and hydrogen depths by means of an isotope microscope, which provides micro-imaging with SIMS. Depth profiles of hydrogen were precisely obtained from the spots where optical measurements were taken on the archaeological obsidian flakes from two distinctive cultural horizons (older: Upper Paleolithic, younger: Initial Jomon) in the stratified open-air site of Jozuka in southern Kyushu (Japan). Secondarily, using the measurements of hydrogen depths that are the most consistent to the measurements of optical thicknesses, the estimated hydration rate of the Holocene (Initial Jomon) is slower than that of the Late Pleistocene (Upper Paleolithic), implying that the difference in hydration rates was due to the difference of intrinsic water content of obsidian and/or obsidian geochemistry. An application of micro-imaging with SIMS to measure hydrogen depths on obsidian shows promise as a tool for improving the practice of hydration dating and evaluating local climatic condition.

TDR-Based Measurements of Water Content in Construction Materials for In-the-Field Use and Calibration

In this paper, a time domain reflectometry (TDR)-based system for measuring water content of raw construction materials is presented. The proposed system relies on the fact that the presence of water leads to an increase of the dielectric permittivity of materials; therefore, from TDR-based permittivity measurements, it is possible to infer the water content value. In practical applications, the proposed system could be used for assessing the intrinsic water content of construction materials before they are poured into the concrete mixture. Knowing the intrinsic water content of the raw materials, in fact, would allow to evaluate the optimal amount of water that should be added to the mixture in order to achieve the desired water-to-cement ratio. This, in turn, would permit to fine-tune and control the mechanical properties of the final concrete structures. For assessing the feasibility of using the proposed system for the intended purpose, water content measurements were carried out on three construction materials, namely, sand, gray cement, and white portland cement. For each of these materials, a calibration curve relating water content to the apparent dielectric permittivity was derived; additionally, through repeated measurements, also a confidence interval was associated with the calibration curves.

A Review on Radiation Damage in Concrete for Nuclear Facilities: From Experiments to Modeling

Concrete is a relatively cheap material and easy to be cast into variously shaped structures. Its good shielding properties against neutrons and gamma-rays, due to its intrinsic water content and relatively high-density, respectively, make it the most widely used material for radiation shielding also. Concrete is so chosen as biological barrier in nuclear reactors and other nuclear facilities where neutron sources are hosted. Theoretical formulas are available in nuclear engineering manuals for the optimum thickness of shielding for radioprotection purposes; however they are restricted to one-dimensional problems; besides the basic empirical constants do not consider radiation damage effects, while its long-term performance is crucial for the safe operation of such facilities. To understand the behaviour of concrete properties, it is necessary to examine concrete strength and stiffness, water behavior, volume change of cement paste, and aggregate under irradiated conditions. Radiation damage process is not well understood yet and there is not a unified approach to the practical and predictive assessment of irradiated concrete, which combines both physics and structural mechanics issues. This paper provides a collection of the most distinguished contributions on this topic in the past 50 years. At present a remarkable renewed interest in the subject is shown.

Biomolecular damage induced by ionizing radiation: the direct and indirect effects of low-energy electrons on DNA.

Many experimental and theoretical advances have recently allowed the study of direct and indirect effects of low-energy electrons (LEEs) on DNA damage. In an effort to explain how LEEs damage the human genome, researchers have focused efforts on LEE interactions with bacterial plasmids, DNA bases, sugar analogs, phosphate groups, and longer DNA moieties. Here, we summarize the current understanding of the fundamental mechanisms involved in LEE-induced damage of DNA and complex biomolecule films. Results obtained by several laboratories on films prepared and analyzed by different methods and irradiated with different electron-beam current densities and fluencies are presented. Despite varied conditions (e.g., film thicknesses and morphologies, intrinsic water content, substrate interactions, and extrinsic atmospheric compositions), comparisons show a striking resemblance in the types of damage produced and their yield functions. The potential of controlling this damage using molecular and nanoparticle targets with high LEE yields in targeted radiation-based cancer therapies is also discussed.

Subcritical Water as Reaction Environment: Fundamentals of Hydrothermal Biomass Transformation

Subcritical water, that is, water above the boiling and below critical point, is a unique and sustainable reaction medium. Based on its solvent properties, in combination with the often considerable intrinsic water content of natural biomass, it is often considered as a potential solvent for biomass processing. Current knowledge on biomass transformation in subcritical water is, however, still rather scattered without providing a consistent picture. Concentrating on fundamental physical and chemical aspects, this review summarizes the current state of knowledge of hydrothermal biomass conversion in subcritical water. After briefly introducing subcritical water as a reaction medium, its advantages for biomass processing compared to other thermal processes are highlighted. Subsequently, the physical-chemical properties of subcritical water are discussed in the light of their impact on the occurring chemical reactions. The influence of major operational parameters, including temperature, pressure, and reactant concentration on hydrothermal biomass transformation processes are illustrated for selected carbohydrates. Major emphasis is put on the nature of the carbohydrate monomers, since the conversion of the respective polymers is analogous with the additional prior step of hydrolytic depolymerization.

Polymerization contraction stress in resin–tooth bonds under hydrated and dehydrated conditions

Objective This study hypothesizes that, with enamel or dentin as a bonding substrate, intrinsic water affects the development of polymerization contraction stress in the bonds of self-etching adhesives during bonding. Materials and methods The influence of the water content in dentin and enamel (wetness with water as control and acetone-dried specimens) on the stress development in self-etching adhesives was determined with a tensilometer. Thin layers of self-etching primer and/or adhesive resins were created between a glass plate and a flat enamel or dentin surface. Results After an initial maximum shortly after light curing for 30 min, the contraction stress was decreased in the dentin (30–70%) and enamel (approximately 20%). In the acetone-dried specimens, the stress was continuously increased for 20–50%. Significance The intrinsic water content of tooth tissue influences the initial polymerization of polymers. This effect is favorable for stress relief in resin restoration but causes unwanted nanoleakage channel formation in resin–tooth bonds.

Analysis of Er:YAG Lased Dentin Using Attenuated Total Reflectance Fourier Transform Infrared and X-ray Diffraction Techniques

The purpose of this study was to investigate the chemical characteristics of dentin after Er:YAG laser irradiation using various output energies with or without water irrigation. Analysis was carried out by means of attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR/ATR) and X-ray diffraction (XRD). Furthermore, the relative infrared peak intensities of dentin specimens were compared statistically. Results showed that Er:YAG laser with an output energy of 100 mJ/pulse with water irrigation did not cause any detectable change in dentin. However, a higher energy output or the absence of water irrigation affected the organic portion of dentin. With XRD, no obvious phase changes were observed between the XRD pattern of the control (non-irradiated) dentin powder and those after Er:YAG irradiation - regardless of Er:YAG laser output energy or dehydration condition. It was suggested that the intrinsic water content of dentin - together with extrinsic water irrigation - were important factors to achieving the desired outcome of dentin ablation by Er:YAG laser.

Poisson’s ratio of eclogite: Implications for lower crustal delamination of orogens

Laboratory measurements of combined P- and S-wave-velocities of eclogite from the Dabie-Sulu ultrahigh pressure metamorphic belt and from literature data show a significant increase of Poisson’s ratio of eclogite with its intrinsic water content H2O+ and thus the degree of hydration. Unaltered eclogites with H2O+ 0.26. This, together with their normal upper mantle P-wave velocities, implies that eclogites are no longer an important component of the present-day lower crust and upper mantle of these subduction-collision belts. Combined with age constraints on eclogite-facies metamorphism and subsequent exhumation, this in turn suggests that the interval from formation to delamination of eclogites is confined to a very short period of <15 Ma.

Poisson’s ratio of eclogite: the role of retrogression

Available laboratory measurements of combined P- and S-wave velocities of eclogites from the Dabie–Sulu ultrahigh-pressure metamorphic belt and data from Manghnani et al. [J. Geophys. Res. 79 (1974) 5427–5446] show clear positive correlations between Poisson’s ratio and the intrinsic water content H 2O + for samples with SiO 2<56% with the correlation coefficient r of 0.63–0.72. There are no significant correlations (| r|≤0.43) between Poisson’s ratio and other major oxides. The positive correlations are interpreted to result from hydration of eclogites during their exhumation and exposure at the surface. Our best estimates of the average Poisson’s ratios for unaltered quartz-bearing eclogites with H 2O +<1.0% are 0.24–0.25 (±0.01), which is identical to that calculated from single crystal elastic properties, but lower than the averages (0.27±0.02) of measurements compiled by Rudnick and Fountain [Rev. Geophys. 33 (1995) 267–309] and Christensen [J. Geophys. Res. 101 (1996) 3139–3156]. Accordingly, unaltered quartz-bearing eclogites have Poisson’s ratios distinct from mafic granulites (0.28±0.01) and marginally different from ultramafic rocks (0.26±0.02).

Homogeneity of water content in obsidian from the coso volcanic field: Implications for obsidian hydration dating

AbstractUsers of the obsidian hydration dating method have routinely assumed that artifacts which originate from the same geological flow will be of the same chemical composition and thus hydrate at the same rate under equivalent conditions of temperature and relative humidity. Recent laboratory experimentation into the hydration process has shown that the intrinsic water content of the glass is the dominant factor in establishing the rate of hydration. Water content determinations on a large suite of samples from numerous prehistoric quarries within the Coso volcanic field, California, indicated that water content values, and thus hydration rate, varied significantly on a within flow basis. It is recommended that water determinations be made on individual artifacts prior to obsidian hydration dating. © 1993 John Wiley &amp; Sons, Inc.

The segregation and emplacement of granitic magmas

The segregation of granitic magma from residual crystals at low melt-fraction is strongly dependent on the viscosity of the melt. Theoretical considerations imply that for the typical range of granitic melt viscosities (10 4 Pas to 10 11 Pas) only very limited separation will be possible by a compaction mechanism over the typical duration of a crustal melting event ( c . 10 6 years). Small-scale segregations (millimetre to metre) of the type observed in migmatite terranes may be generated by compaction (possibly assisted by continuous deformation), or by flow of melt into extensional fractures, but low melt-fraction liquids are unlikely to be extracted to form large (kilometre-size) granitic plutons because of the limited separation efficiency. At higher melt-fractions (&gt;30%) the rapid decrease in strength and effective viscosity during partial melting allows other segregation processes to operate. Calculations and experiments indicate that in granitic systems the effective viscosity of partially melted rocks, having a very narrow melt fraction range of 30–50% will fall rapidly to levels at which convective overturn of kilometre-thick zones can occur. Convective motion within anatectic regions is capable of generating large (kilometre-size) homogeneous, high crystal-fraction, crustally-derived magma bodies, which are orders of magnitude greater in size than low melt-fraction segregates. Before convective instability is reached, small (centimetre- to metre-sized) pods of granitic liquid may rise buoyantly through, and pond at the top of such partly molten zones; such a process is consistent with the observation that some granulites appear to be residue rocks, chemically depleted in a minimum melt component. The effective viscosity (and hence the susceptibility to convection) of a partially melted zone within the crust, is strongly dependent on the water content of the system at a given pressure and temperature, because this controls both the quantity of melt generated and also the viscosity of the melt. The intrinsic water content of most crustal lithologies is incapable of promoting the high percentages of partial melting, or the low liquid viscosities, required to form large kilometre-sized granitic plutons by convective homogenization, at typical crustal temperatures. This suggests that the anatexis involved in the generation of large crustally-derived magma bodies has in many cases been promoted by an influx of externally derived aqueous fluid. These magma segregation processes are illustrated with respect to the petrogenesis of three different types of granitoid pluton from a Hercynian low-pressure, metamorphic-anatectic terrane in the Pyrenees.

Deformation and fracture of synthetic ?-quartz

The deformation and fracture properties of synthetic α-quartz crystals were measured using hardness, pre-cracked bend and Hertzian tests over the range 20 to 545° C in air and dry nitrogen. The resistance to fracture decreases significantly with increase in temperature and is orientation-dependent (becoming very small as the inversion temperature is approached), while the microhardness remains relatively insensitive to temperature and environment. These effects are interpreted in terms of the moisture content of the environment and the intrinsic water content of the crystals.