Thin Water Layer Research Articles

Geant4 Simulation of Precipitated Activity-to-γ-Dose Rate Conversion Factors for Radon and Thoron Decay Products

The results of modeling the conversion factor from rainfall-deposited unit activity of gamma-emitting radon and thoron daughter decay products to their created gamma-radiation dose rate as a function of height above the Earth’s surface using the Geant4 toolkit are presented in this paper. Thin layers of water, soil, and air, with the height of 0.1–10 mm, are considered as the source in order to examine whether the composition of the radiation source environment affects the simulation result. Cases with different absorber-atmosphere densities are simulated. The contribution of each radionuclide 212Bi, 214Bi, 212Pb, 214Pb and 208Tl to the total gamma background was determined. The dependence of dose rate growth during the precipitation period on the detector position in relation to the area covered by precipitation was investigated numerically. The obtained conversion factors are universal values, because do not depend on soil type (material) on which radionuclides are deposited by precipitation. These coefficients can be used for solving both direct tasks of radiation background recovery during precipitation and inverse tasks of determining the intensity and amount of precipitation by the known gamma background, as well as tasks to decipher the gamma background by the shape of the response to various phenomena. Also in this work, it is shown how thoron decay products can affect the response shape of gamma background on atmospheric precipitation.

Laser shock wave loading of the vanadium and titanium

Measurements of the plastic wave attenuation in the material is very important for understanding Laser Shock Peening (LSP) surface treatment (Seddik et al. (2022)) mechanisms. We have tested thin disk-shaped specimens from titanium VT6 and vanadium VnP-1. Specimens were loaded by Beamtech SGR-Extra-10 Nd:YAG pulse laser. To increase the wave amplitude the front surface was covered by a thin water layer. The water layer should be thin because of the absorption of the IR radiation in the water. At provided laser energy density we did not observe any spallation. We did not observe grain fragmentation and other signs of severe plastic deformation.

Study of scattering characteristic of thin ice‐water layers covered dielectric material utilizing hybrid implicit‐explicit finite difference time‐domain method

AbstractIn the paper, a hybrid implicit‐explicit finite difference time‐domain (HIE‐FDTD) method is applied, and the related calculation formula of the HIE algorithm is derived in detail. Using the HIE‐FDTD method, the scattering characteristics of dielectric objects covered with very thin ice water layers are studied. The dispersive medium model of the mixture of water and ice is expressed in Debye form and can be calculated by the auxiliary difference equation technique. It is found that the change of the scattering characteristics of the water ice mixing layer mainly depends on the proportion of water in the ice water mixture, and describes the process of ice melting into water, which leads to the corresponding changes of reflectivity, transmittance, and absorptivity. Finally, the simulation results show that the HIE‐FDTD method has higher efficiency than the conventional FDTD without losing accuracy.

The influence of relative humidity upon Cu(In,Ga)Se2 thin-film surface chemistry: An X-ray photoelectron spectroscopy study

We performed a comprehensive study of Cu(In,Ga)Se2 (CIGS) surface reactivity in air, focusing on the evolution of the surface chemistry via X-ray photoemission spectroscopy (XPS). By using the different transitions (photopeaks and X-ray Auger electron spectroscopy transitions) available on XPS spectra, in order to probe different surface thicknesses, complementary chemical information is provided to investigate the surface reactivity mechanism of CIGS surface and especially highlight the importance of the relative humidity rate of the atmosphere. Indeed, by maintaining a relative humidity of 20%, we demonstrate that this degradation can be limited, even almost stopped, showing that the degradation mechanism is not only related to O2 interaction but more importantly, to the thin water layer, inherent to relative humidity, formed upon surfaces.

Thermal Emission from a Foam-covered Sea Surface Modelled as a Stratified Layer at Microwave Frequencies

In this paper, a physical based model of foam-covered sea surface was modelled as layers of randomly distributed air-bubbles coated with thin layer of sea water which evaluates thermal emission was investigated.

Controllable superlubricity achieved with mixtures of green ionic liquid and glycerol aqueous solution via humidity

In this work, superlubricity between steel surfaces lubricated by mixtures of [Choline][Proline] ([Cho][Pro]) ionic liquid and glycerol aqueous solution has been reached by using a rotating tribometer. Stable superlubricity could be obtained even under the humidity between 7 and 9% RH. The lowest friction is observed when the lubricant contains 3 wt% ionic liquid. It is found that adding 3 wt% [Cho][Pro] is helpful to maintain enough water in the steady period to retain a low viscosity. According to the calculation, the superlubricity achieved in thin film lubrication region, which is attributed to the stern layer formed by [Cho][Pro] and hydrogen-bond network that enabled a thin water layer at the interface. Interestingly, it is observed that humidity can be used to control lubrication state between superlubricity and non-superlubricity. This study provides a new method to accomplish switchable superlubricity under low humidity.

Predicting Stress Corrosion Crack Tip Electrochemical Conditions and the Influence of Exposure Environment

Metallic structures are commonly exposed to marine atmospheric conditions in real world conditions, characterized by thin water layers (WL) allowing for corrosion to occur. For austenitic stainless steels in such atmospheric environments, pitting and stress corrosion cracking (SCC) are potential degradation mechanisms. The rate and extent of corrosion and SCC on the alloy surface is dictated by the combination of environmental, physicochemical, and geometric variables, which include relative humidity, temperature, electrolyte conductivity, electrolyte film thickness, in addition to the electrochemical kinetics on the alloy surface. Due to the large potential variation in environmental conditions, modeling can serve as an important tool to evaluate environmental effects on the corrosion and SCC of alloys and galvanic couples.In this study, Finite Element Modeling approaches are used to evaluate chemical and electrochemical conditions present in a crack exposed to marine, thin film environments. A full reactive transport model, incorporating metal hydrolysis and salt formation, is built to evaluate SCC crack tip conditions. The influence of WL thickness, stress intensity level, crack length, and specimen geometry are evaluated. Specifically, crack tip pH and equilibrium potential among other variables will be compared between the various atmospheric factors both spatially and temporally. The modeling results will be compared to atmospheric SCC experiments and help give insight into critical experimental and testing phenomena. Acknowledgements Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This document is SAND2021-5051 A.

Laser interaction in a water tank configuration: Higher confinement breakdown threshold and greater generated pressures for laser shock peening

The authors present a new configuration for laser-induced plasmas in confined regimes for a 10 ns-range laser pulse in the green wavelength (532 nm) that repulses the breakdown threshold above 20 GW/cm2 compared to 8 GW/cm2 as generally indicated in previous works. Using this new configuration, pressures above 12 GPa have been reached for the first time in confined regimes. This can enlarge the range of applications of laser shock such as the range of treatable materials (very high strength materials) or facilities’ costs since neither vacuum nor heavy laser systems will be needed to reach these levels of pressure. The proposed configuration mainly consists of the usage of a water tank. Hence, a great thickness of water is used instead of the extensively used thin water layer. Therefore, the water breakdown plasma will not initiate at the surface of the water, as the laser beam is still not focused there. Instead, it will occur in the depth of the water. In that case, the breakdown threshold value is increased as either the avalanche breakdown or the multiphoton ionization may start at higher laser intensities than at the air/water interface. The authors experimentally demonstrated this new breakdown threshold with the measurement of transmitted intensity, transmitted pulse duration, and the indirect measurement of the plasma pressure. Multiple shots (laser shock treatment) were also performed, and the specimen surface deformation was measured, leading to the same conclusion.

Comparative analysis of corrosion of borosilicate glasses in water vapor

A comparative analysis of interaction of various borosilicate glasses with water vapor is carried out in the work. The fundamental dependence of the observed processes on the concentration of alkali metal oxides as well as glass formers B2O3 and Al2O3 in glass is shown. The relative content of alkali oxides determines which processes dominates. The absence of alkali metal oxides leads to the fact that no hydrated or hydrogenated layers are formed on the surface of the glass. At a concentration of alkali metal oxides above ~15% by weight, hydration of the glass surface is observed as a result of the ion exchange reaction of water protons and alkali ions; the hydrated layer grows with time of hydration according to a parabolic law. However, at a concentration of alkali metal oxides below about 8% weight, the ion exchange reaction stops after formation of a 20 nm thick hydrated layer due to a sharp decrease in the “solubility” of alkalis in a thin water layer adsorbed on the surface due to an increase of pH factor, and due to a radical decrease concentration gradients for Na and H in the glass and in the solution. And then the formation of a hydrogenated layer with the formation of silicon hydroxides in the NaBSixOy molecular complexes is observed. The top surface hydrated layer acts as a source of protons for this reaction. The growth of the hydrogenated layer occurs with time according to a linear-parabolic law.

Subtropical Freshwater Cyanobacterial Blooms as Hydrogen Peroxide Hot Spots

In aquatic environments, chemical and biological processes represent major sources of reactive oxygen species (ROS) such as hydrogen peroxide. Diurnal patterns of hydrogen peroxide in surface water may suggest photochemical processes affect ROS dynamics. We hypothesized that thin surface hydrogen peroxide maxima could be detected through millimeter-scale depth profiling. These maxima were previously overlooked because they cannot be detected using standard surface water sampling techniques. Combined field and laboratory experiments demonstrated that cyanobacterial blooms could create extremely high concentrations of hydrogen peroxide in a thin layer of surface water (5–60 mm). Hydrogen peroxide concentrations were higher within surface scums of Microcystis aeruginosa than in areas without scum. The cyanobacterial scum increased the temperature of the ambient water, and hydrogen peroxide concentrations were higher at locations exposed to sunlight that at locations in the shade. We found that scum samples directly collected from the field could release hydrogen peroxide to the surrounding water when the biomass was exposed by the light, while 20 laboratory cultures tested did not. The production of hydrogen peroxide from cyanobacteria may depend on the physiological condition of cells. Overall, we identified thin surface water layers during subtropical freshwater cyanobacterial blooms as hydrogen peroxide hot spots.

RGO wrapped tungsten trioxide hydrate on CNT-modified carbon Cloth as self-supported high-rate lithium-ion battery electrode

In this study, tungsten trioxide hydrate (WO3⋅0.33H2O) was partially wrapped by reduced graphene oxide (rGO) sheets to form flower-like structures, which was then directly loaded as a whole on carbon nanotube-modified carbon cloth (CNT-CC) to obtain a self-supported electrode with hierarchical structures. The orthorhombic WO3⋅0.33H2O contains a thin water layer in its crystal structure to offer abundant internal and surface channels for lithium ions. Also, the synthesized WO3⋅0.33H2O is proved to be partially reduced with mixed W5+/W6+ valence, which induces inter-valence charge transfer to bring increased conductivity. Additionally, by forming WO3⋅0.33H2O@rGO combining flowers, interpenetrating conductive network and interior mesoporosity are created, which shortens the electronic/ionic diffusion length and promotes charge transfer for WO3⋅0.33H2O. Specially, the rGO sheets are partially wrapped on WO3⋅0.33H2O, which ensures high Coulombic efficiency values by enabling active lithium-ion exchange between electrolyte and the electrode. Moreover, the thin CNT coating on the surface of the CNT-CC substrate helps to regulate the loading of WO3⋅0.33H2O@rGO by offering rich surface defects and regular attaching points, leading to the anchoring of WO3⋅0.33H2O@rGO layer with uniform morphology and thickness. Direct charge transfer is also demonstrated between WO3⋅0.33H2O@rGO and the flexible current collector of CNT-CC, thus inhibiting the use of binders causing side reactions during cycling. Moreover, the three-dimensional self-assembly structure can effectively alleviate the huge volume change of WO3⋅0.33H2O upon Li+ intercalation/extraction and ensures high structural stability. As an anode for lithium-ion batteries, the WG/CNT-CC electrode delivered high initial Coulomb efficiency of 81%, a high capacity of 1260.8 mAh g−1 after 200 cycles at 200 mA g−1, and a high capacity of 1087 mAh g−1 after 400 cycles at 1000 mA g−1, showing great potential as anode material for lithium-ion batteries.

Nanoscale Wetting of Single Viruses.

The epidemic spread of many viral infections is mediated by the environmental conditions and influenced by the ambient humidity. Single virus particles have been mainly visualized by atomic force microscopy (AFM) in liquid conditions, where the effect of the relative humidity on virus topography and surface cannot be systematically assessed. In this work, we employed multi-frequency AFM, simultaneously with standard topography imaging, to study the nanoscale wetting of individual Tobacco Mosaic virions (TMV) from ambient relative humidity to water condensation (RH > 100%). We recorded amplitude and phase vs. distance curves (APD curves) on top of single virions at various RH and converted them into force vs. distance curves. The high sensitivity of multifrequency AFM to visualize condensed water and sub-micrometer droplets, filling gaps between individual TMV particles at RH > 100%, is demonstrated. Dynamic force spectroscopy allows detecting a thin water layer of thickness ~1 nm, adsorbed on the outer surface of single TMV particles at RH < 60%.

Archaeological prospection in ultra‐shallow aquatic environments: the case of the prehistoric submerged site of Lambayanna, Greece

ABSTRACTOver the last three decades, multicomponent geophysical prospection has given a new perspective in the domain of inland archaeological prospection. However, the complexity and constantly evolving environmental regime encountered in the transition zones has so far limited the implementation of these technological advancements towards the understanding of the past dynamics in littoral and ultra‐shallow offshore environments. The main objective of this work is to appropriately adapt, test and validate the efficiency of diverse geophysical mapping and imaging methods for reconstructing the ancient built environment below a relatively thin water layer. The submerged prehistoric site of Lambayanna in Greece was used as an ‘open laboratory’ to explore in situ the resolving capabilities and limitations of marine three‐dimensional electrical resistivity tomography and multisensor magnetic gradiometry, as well as terrestrial ground‐penetrating radar. The geophysical mapping covered more than 4.4 hectares of the shallow marine and coastal part of the site with high spatial resolution. The data processing followed a specific flowchart to enhance the signal and the subsequent integrated analysis showed a number of candidate targets buried below the seabed, providing strong indications to support the hypothesis for the existence of an ancient submerged man‐made environment in the bay. The results demonstrate the complementary nature of applying multiple geophysical methods to under‐explored shallow offshore archaeological contexts in order to provide useful information for understanding the complex archaeological sites around the Mediterranean. The successful transfer of established geophysical methods into the ultra‐shallow aquatic environment comprises the major innovative aspect of this work. Thus, in view of climate change and the risks related to future sea‐level rise and erosion of low‐level coastal areas, the proposed research model can be integrated into a wider strategic framework for the sustainable management of coastal cultural resources.

Nanoscale Wear and Mechanical Properties of Calcite: Effects of Stearic Acid Modification and Water Vapor.

Understanding the wear of mineral fillers is crucial for controlling industrial processes, and in the present work, we examine the wear resistance and nanomechanical properties of bare calcite and stearic acid-modified calcite surfaces under dry and humid conditions at the nanoscale. Measurements under different loads allow us to probe the situation in the absence and presence of abrasive wear. The sliding motion is in general characterized by irregular stick-slip events that at higher loads lead to abrasion of the brittle calcite surface. Bare calcite is hydrophilic, and under humid conditions, a thin water layer is present on the surface. This water layer does not affect the friction force. However, it slightly decreases the wear depth and strongly influences the distribution of wear particles. In contrast, stearic acid-modified surfaces are hydrophobic. Nevertheless, humidity affects the wear characteristics by decreasing the binding strength of stearic acid at higher humidity. A complete monolayer coverage of calcite by stearic acid results in a significant reduction in wear but only a moderate reduction in friction forces at low humidity and no reduction at 75% relative humidity (RH). Thus, our data suggest that the wear reduction does not result from a lowering of the friction force but rather from an increased ductility of the surface region as offered by the stearic acid layer. An incomplete monolayer of stearic acid on the calcite surface provides no reduction in wear regardless of the RH investigated. Clearly, the wear properties of modified calcite surfaces depend crucially on the packing density of the surface modifier and also on the air humidity.

Oogenesis in the tardigrade Hypsibius exemplaris Gąsiorek, Stec, Morek & Michalczyk, 2018 (Eutardigrada, Hypsibiidae)

Tardigrades are small, globally widespred invertebrates that need at least a thin layer of water to be active. There are gonochoric, hermaphroditic, and parthenogenetic species among them. The main aim of this study was to analyze the structure of the ovary, the structure of female germ cell clusters, and the course of oogenesis in the parthenogenetic species Hypsibius exemplaris, which in 2007 was recognized as a model organism. The material was analyzed using light and confocal microscopy as well as transmission and scanning electron microscopy. Histochemical and immunohistochemical methods were used. Our study showed that in the meroistic-polytrophic ovary of the examined species, branched germ cell clusters are formed in which one cell differentiates into an oocyte while the remaining cells become trophocytes. Vitellogenesis is of the mixed type: the first part of the yolk is synthesized by the oocyte (autosynthesis); the second part is synthesized by trophocytes and transported to the oocyte by cytoplasmic bridges; and the third part is synthesized outside the ovary (in storage cells) and transported to the oocyte by endocytosis. At the end of oogenesis, the trophocytes die by apoptosis. Parthenogenetic female of H. exemplaris lays from one to a dozen smooth eggs into exuviae.

Efficient desalination by layered heating of saline water

Thin layer heating technology for desalination is one of the topics that is catching eye of many researchers recently. The sun is a very good renewable energy source that can solve many human being’s problems such as water scarcity. Solar energy can be utilized for water desalination. Nowadays, parabolic trough collector and dish reflector and other optical concentrators are used to concentrate the solar radiation to get more power. They are complex and costly. Efficiency of basin type solar still and other conventional solar still is decreases as we increase water quantity, due to the heat loss to water. Due to this reason need of solar desalination devices that use localized heating of a thin layer of water. In the past few years, significant research is done for the developing thin layer heating desalination. In this paper, basin type solar still is discussed, properties of wood and titanium dioxide materials for substrate and absorber have been discussed and results carried out by experimental performance is discussed. This paper is concerned with effects of change in radiation, effects of change in water depth in basin and effects of change in salinity of water.

Exploring Nanoscale Lubrication Mechanisms of Multilayer MoS2 During Sliding: The Effect of Humidity.

Solid lubricants have received substantial attention due to their excellent frictional properties. Among others, molybdenum disulfide (MoS2) is one of the most studied lubricants. Humidity results in a deterioration of the frictional properties of MoS2. The actual mechanism at the nanoscale is still under debate, although there are indications that chemical reactions are not likely to occur in defect-free structures. In this study, we performed nonequilibrium molecular dynamics simulations to study the frictional properties of multilayer MoS2 during sliding in the presence of water. Moreover, we also investigated the effect of sliding speed and normal load. We confirmed earlier results that a thin layer of water organizes as a solidified, ice-like network of hydrogen bonds as a result of being confined in a two-dimensional fashion between MoS2. Moreover, we found that there exists an energy-driven, rotational dependence of the water network atop/beneath MoS2. This orientational anisotropy is directly related to the dissipative character of MoS2 during sliding. Finally, three distinct frictional regimes were identified, two for a thin layer of water and one for bulk water. In the case of a thin layer and low coverage, water represents a solid-like contaminant, causing high energy dissipation. For a thin layer and high coverage, water starts to act as a solid-like lubricant, reducing dissipation during sliding. Finally, a regime where water acts as a liquid lubricant, characterized by a clear velocity dependence was found.

Formation of a large ice depression on Dålk Glacier (Larsemann Hills, East Antarctica) caused by the rapid drainage of an englacial cavity

AbstractIn the afternoon of 30 January 2017, a catastrophic outburst flood occurred in the Larsemann Hills (Princess Elizabeth Land, East Antarctica). The rapid drainage of both a thin supraglacial layer of water (near Boulder Lake) and Lake Ledyanoe into the englacial Lake Dålk provoked its overfill and outburst. As a result, a depression of 183 m × 220 m was formed in the place where Lake Dålk was located. This study summarises and clarifies the current state of knowledge on the flood that occurred in 2017. We present a phenomenological model of depression formation. We specify the reasons for the outburst of the system of lakes Boulder, Ledyanoe and Dålk. In addition, we carry out mathematical modelling of the outburst of each of the three lakes and estimate the flood severity. Outburst hydrographs, channel diameters, volume and duration of floods were calculated. Particular simulation results were validated with field data. In conclusion, we give an overview of the new outburst cycle of the lake system, which began in 2020 with the drainage of the lakes Boulder and Ledyanoe, and the new formation of Lake Dålk. Further research is required to improve our understanding of the lake system responses to changing external factors.

Ice speed skating: Onset of lubrication by frictional heating

In ice speed skating, the friction between the steel skate blade and the ice stems from boundary friction where the temperature of the interface is below zero and ice surface molecules exhibit unconventional mobility, and hydrodynamic friction where the ice melts and a thin water layer between the blade and the ice forms. An analytical solution of the steady-state lubrication equation shows that the boundary friction only plays a role at the tip of the skate blade over an extremely short contact length between the skate blade and the ice. Albeit its negligible contribution to total friction, boundary friction generates enough heat to melt the ice which allows the skater to slide smoothly on a thin layer of melt water. It is also shown that the precise value of the boundary friction coefficient is not important for speed skate friction because it works only over an extremely short contact length.

Fiber-Concentration Distributions of Papermaking Pulp Suspension Flowing in a Channel with a Sudden Expansion

In this study, we analyze the flow characteristics of pulp suspensions in a sudden expansion channel, which is used as a tube bank in papermaking machines. Flow visualization using a light section method and measurements of time averaged and fluctuating fiber concentrations, C<SUB>a</SUB> and C’, and pressure were performed. The experiments were carried out on pulp suspensions with a bulk fiber concentration (C<SUB>s</SUB>) of 0 2.0 wt% in a channel with an expansion ratio of β = 2 at varied average velocities (U<SUB>a</SUB>) of 0.04-6.6 m/s. We examined the effect of flow velocity on the changes in concentration and pressure distributions along the channel axis The distribution of the pulp fiber concentration behind the sudden expansion significantly changes depending on the flow state in the upstream channel before the expansion. In particular, for low and moderate velocities, the flow field is characterized in the main flow region consisting of flocculated plug fibers and a recirculation region with a low concentration near the expansion corner by a type of streamline originated from the thin water layer in the upstream channel. The distribution of C<SUB>a</SUB> shows a tongue shaped structure in the central part of the cross section and C’ is large near the annulus streamline As the velocity is further increased, the flocculated fibers gradually disperse and the distributions of C<SUB>a</SUB> and C’ become almost uniform. In addition, the uniformity of fiber concentration does not change much in the section downstream from a distance 10 times the step height from the sudden expansion plane.