Thin Water Film Research Articles

Devitrification reduces beam-induced movement in cryo-EM.

As cryo-EM approaches the physical resolution limits imposed by electron optics and radiation damage, it becomes increasingly urgent to address the issues that impede high-resolution structure determination of biological specimens. One of the persistent problems has been beam-induced movement, which occurs when the specimen is irradiated with high-energy electrons. Beam-induced movement results in image blurring and loss of high-resolution information. It is particularly severe for biological samples in unsupported thin films of vitreous water. By controlled devitrification of conventionally plunge-frozen samples, the suspended film of vitrified water was converted into cubic ice, a polycrystalline, mechanically stable solid. It is shown that compared with vitrified samples, devitrification reduces beam-induced movement in the first 5 e Å-2 of an exposure by a factor of ∼4, substantially enhancing the contribution of the initial, minimally damaged frames to a structure. A 3D apoferritin map reconstructed from the first frames of 20 000 particle images of devitrified samples resolved undamaged side chains. Devitrification of frozen-hydrated specimens helps to overcome beam-induced specimen motion in single-particle cryo-EM, as a further step towards realizing the full potential of cryo-EM for high-resolution structure determination.

Experimental Study of Boiling Heat Transfer in a Thin Film on Horizontal Tube.(Dept.M)

Boiling heat transfer process in thin film on horizontal tubes is, experimentally. investigated . The effect of the operating parameters on the boiling heat transfer coefficient is studied and accordingly the optimum operating conditions is deduced. The operating parameters such as heat flux. mass flow rate, feed water height and test tube configuration are considered. To carry out this experimental work, a suitable test rig hag been constructed such that the effect of these operating parameters can be investigated. The test tube is heated by & heating steam flowing inside it in a stratified flow pattern. A perforated distributer sprays a thin water film on a test tube forming dripping flow, The considered ranges of the investigated parameters are heat flux from 20 to 300 kw/m2 , mass flow rate from 0.02 to 0,1 kg/m.s. height to diameter ratio from 0.1 to 1 , and tube diameter from 12.2 to 38 mm. The effect of test tube configuration in case of circular , horizontal elongated oval shape and vertical elongated oval shape is studied. It is found that the heat transfer coefficient in case of circular cross sectional tube is the best one specially , compared with horizontal elongated oval shape.

Martian subsurface cryosalt expansion and collapse as trigger for landslides.

On Mars, seasonal martian flow features known as recurring slope lineae (RSL) are prevalent on sun-facing slopes and are associated with salts. On Earth, subsurface interactions of gypsum with chlorides and oxychlorine salts wreak havoc: instigating sinkholes, cave collapse, debris flows, and upheave. Here, we illustrate (i) the disruptive potential of sulfate-chloride reactions in laboratory soil crust experiments, (ii) the formation of thin films of mixed ice-liquid water "slush" at -40° to -20°C on salty Mars analog grains, (iii) how mixtures of sulfates and chlorine salts affect their solubilities in low-temperature environments, and (iv) how these salt brines could be contributing to RSL formation on Mars. Our results demonstrate that interactions of sulfates and chlorine salts in fine-grained soils on Mars could absorb water, expand, deliquesce, cause subsidence, form crusts, disrupt surfaces, and ultimately produce landslides after dust loading on these unstable surfaces.

Influence of aluminium parabolic fins as energy absorption material in the solar distillation system

Abstract This paper encompasses the experimental effect of Aluminium parabolic fins as energy absorption material in single basin double slope solar still compared with conventional still without fins. A single basin dual slope single basin solar still is made of a wooden box outside and aluminium on the inside 1 × 0.5 × 0.2 m. Still with parabolic fins of 50 mm height and 30 mm diameter. Experimentation was carried out under the same climatic conditions of Hyderabad (17.3850° N, 78.4867° E) by the varying depth of water (1 cm, 2 cm and 3 cm) experimental results depicts that parabolic finned basin still attained a maximum of 1250 ml per day and the conventional still attained maximum of 1180 ml per day, parabolic finned basin still has got 70 ml higher than conventional still. The elevated fraction of the heat was carried from the absorber plate to basin water because of the thin film of water at 1 cm depth of water which results in higher desalinated water productivity.

The controlling role of atmosphere in dawsonite versus gibbsite precipitation from tetrahedral aluminate species.

In highly alkaline solution, aluminum speciates as the tetrahedrally coordinated aluminate monomer, Al(OH)4- and/or dimer Al2O(OH)62-, yet precipitates as octahedrally coordinated gibbsite (Al(OH)3). This tetrahedral to octahedral transformation governs Al precipitation, which is crucial to worldwide aluminum (Al) production, and to the retrieval and processing of Al-containing caustic high-level radioactive wastes. Despite its significance, the transformation pathway remains unknown. Here we explore the roles of atmospheric water and carbon dioxide in mediating the transformation of the tetrahedrally coordinated potassium aluminate dimer salt (K2Al2O(OH)6) to gibbsite versus potassium dawsonite (KAl(CO3)(OH)2). A combination of in situ attenuated total reflection infrared spectroscopy, ex situ micro X-ray diffraction, and multivariate curve resolution-alternating least squares chemometrics analysis reveals that humidity plays a key role in the transformation by limiting the amount of alkalinity neutralization by dissolved CO2. Lower humidity favors higher alkalinity and incorporation of carbonate species in the final Al product to form KAl(CO3)(OH)2. Higher humidity enables more acid generation that destabilizes dawsonite and favors gibbsite as the solubility limiting phase. This indicates that the transition from tetra- to octahedrally coordinated Al does not have to occur in bulk solution, as has often been hypothesized, but may instead occur in thin water films present on mineral surfaces in humid environments. Our findings suggest that phase selection can be controlled by humidity, which could enable new pathways to Al transformations useful to the Al processing industry, as well as improved understanding of phases that appear in caustic Al-bearing solutions exposed to atmospheric conditions.

Viscous liquid-liquid wetting and dewetting of textured surfaces.

We experimentally investigate the spreading and receding behavior of small water droplets immersed in viscous oils on grid-patterned surfaces using synchronized bottom and profile views. In particular, the evolution of apparent advancing and receding contact angles of droplets fed at constant flow rate is studied as a function of grid surface coverage and height for a wide range of external phase viscosity. Detailed examination of droplet aspect ratio during inflation process provides an averaging method for characterization of quasi-static advancing angles on heterogeneous surfaces. Droplets spreading in partial Cassie state on planar microfluidic grids are also shown to capture oil patches that further evolve into trapped oil droplets depending on grid aspect ratio. The natural retraction velocity of thin water films is examined based on external phase velocity and regime maps of trapped droplets are delineated based on control parameters.

Terahertz aqueous photonics.

Developing efficient and robust terahertz (THz) sources is of incessant interest in the THz community for their wide applications. With successive effort in past decades, numerous groups have achieved THz wave generation from solids, gases, and plasmas. However, liquid, especially liquid water has never been demonstrated as a THz source. One main reason leading the impediment is that water has strong absorption characteristics in the THz frequency regime.A thin water film under intense laser excitation was introduced as the THz source to mitigate the considerable loss of THz waves from the absorption. Laser-induced plasma formation associated with a ponderomotive force-induced dipole model was proposed to explain the generation process. For the one-color excitation scheme, the water film generates a higher THz electric field than the air does under the identical experimental condition. Unlike the case of air, THz wave generation from liquid water prefers a sub-picosecond (200-800 fs) laser pulse rather than a femtosecond pulse (~50 fs). This observation results from the plasma generation process in water.For the two-color excitation scheme, the THz electric field is enhanced by one-order of magnitude in comparison with the one-color case. Meanwhile, coherent control of the THz field is achieved by adjusting the relative phase between the fundamental pulse and the second-harmonic pulse.To eliminate the total internal reflection of THz waves at the water-air interface of a water film, a water line produced by a syringe needle was used to emit THz waves. As expected, more THz radiation can be coupled out and detected. THz wave generation from other liquids were also tested.

Semi-convertible Hydrogel Enabled Photoresponsive Lubrication

Summary A semi-convertible hydrogel with reversible photoresponsive supramolecular lubricating ability is demonstrated by integrating a responsive supramolecular system of α-cyclodextrins/polyethylene glycol (α-CD/PEG) and competitive guest 1-[p-(phenylazo)benzyl]pyridinium bromide (AzoPB) within a poly(vinyl alcohol) (PVA) and polyacrylamide (PAAm) framework. The competitive host-guest interaction between α-CD/PEG supramolecular network and AzoPB after UV and visible-light irradiation enables the appearance and disappearance of the sol-state layer on the hydrogel surface while the PVA and PAAm consistently keeps the framework. This semi-convertible process realizes the reversible photoresponsive lubricating ability and variable toughness. We envision that this finding will offer a possible way for fabricating novel smart devices far beyond lubrication, leading to an emerging branch of interdisciplinary materials science that integrates supramolecular chemistry, hydrogel, and surface science.

Pore network modeling of thin water film and its influence on relative permeability curves in tight formations

The thin water film stabilized by disjoining pressure is non-negligible in tight formations which results in significant difference in multiphase flow behavior compared with that in conventional formations. In this work, a pore network model is proposed to simulate two phase flow in tight formations to highlight the contribution of thin water film on multiphase flow. The newly developed pore network model includes the influence of thin water film on fluid configuration, capillary entry pressure, fluid conductance and connectivity during multiphase flow in pore space. Our approach is first validated with the existing pore network model and then the influence of thin water film on two-phase flow is investigated extensively. The results show that the connate water saturation increases and its associated oil relative permeability decreases as the average pore radius decreases. It also suggests that in water-wet systems, the influence of thin water film on both oil and water phases becomes significant when the average pore radius is smaller than 100 nm. Existence of thin water film will increase the proportion of film water and corner water, resulting in an increasement in oil phase relative permeability and a slight decline of water phase relative permeability in tight porous media dominated by angular pores and throats; while in porous media dominated by circular shaped pores and throats, oil and water phase relative permeability are both enhanced due to better connectivity caused by thin water film; at the same time swelling of water film results in lower residue oil saturation and higher end point of water relative permeability. We also found higher water relative permeability when porous media has more irregular pores.

Activating Bubble's Escape, Coalescence, and Departure under an Electric Field Effect.

In this paper, we present the results of applying an electric field to activate bubbles' escape, coalescence, and departure. A simple electrowetting-on-dielectric device was utilized in this bubble dynamics study. When a copper electrode wire inserted into deionized water was positioned on one side of single or multiple bubbles, the bubble tended to continuously escape from its initial position as the voltage was turned on. Contact angle imbalance at different sides of the bubble was observed, which further promoted the bubble's escape. An analysis model with an electromechanical framework was developed to study the charging time difference on two sides of the bubble, which generated a wettability gradient and capillary force to propel it away from the electrode. Sine, ramp, and square alternating current waveforms with 60 V amplitude and 2 Hz frequency were tested for comparison. It was shown that all waveforms promoted the bubble's escape; the square wave shape manifested the farthest escape capability, followed by sine and ramp waves. An upper view of several bubbles aligning in triangle, square, pentagon, and hexagon shapes demonstrated that the bubbles tended to move outward when the electrode is placed at the geometric centers. Experiments with an electrode on one side and several bubbles positioned in a line were conducted. In these cases, the bubbles closer to the electrode reacted faster than those farther from the electrode, resulting in coalescence. Once the bubble size became larger, it departed either by overcoming the disjoining pressure in a thin film of water or via the buoyancy force in a thick film of water. Controlling bubble dynamics by the electric field, including escape, coalescence, and departure provides an active and reversible approach to move bubbles or increase departure frequency in many fluid mechanics and heat transfer studies.

Improving the performance of tubular solar still using rotating drum – Experimental and theoretical investigation

In the current work, we introduced, experimentally and theoretically, a modified technique of reducing the water depth as much as possible inside the tubular solar still using a rotating drum. The existence of the rotating drum inside the tubular solar still provides the lowest amount of basin water and creates a thin water film, which is evaporated quickly. So, the effect of using closed ends drum and open ends drum on the performance of tubular distiller was investigated. Besides, using the rotating drum increased the evaporative and exposure surface areas inside the tubular solar still. Moreover, the effect of different rotating speeds (0.02, 0.05, 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, and 4.0rpm) on the performance of tubular distiller was investigated. Furthermore, the system was studied with and without wick. The results revealed that the speed of 0.05 and 0.1rpm obtained superior performance of tubular drum distiller with and without wick, respectively. In addition, at 0.1rpm and without wick, the productivity of the tubular drum still was improved by 121 % and 136 % for the closed ends and open ends drums, respectively. While, at 0.05rpm and with wick, the productivity of the tubular drum still was enhanced by 140 % and 175 % for the closed ends and open ends drums, respectively. Furthermore, with wick, the thermal and exergy efficiencies of the tubular drum still were 56.4 % and 3.45 % for the closed ends drum and 61 and 3.6 % for the open ends drum, respectively.

Corrosion Behavior of Carbon Steel in Soil with Different Particle Size Distribution during Wet-to-Dry Process

Introduction Corrosion of carbon steel in soil is considered to be similar to that in a neutral solution. That is, soil corrosion is considered to be promoted by water and dissolved oxygen in soil water. In the outdoor environment, soil water content changes due to rainfall. Therefore, in order to understand the corrosion mechanism, it is important to evaluate soil corrosion with a system that reproduces the dry and wet cycle. We measured the time course of the corrosion rate in terms of soil corrosiveness in a single wet and dry cycle. So far, we have focused on the soil particle size as the dominant environmental factor, which is considered to affect the diffusion of water and oxygen in the soil, and have clarified the corrosion tendency. In this study, the relationship between the particle size distribution and corrosion behavior was evaluated using the AC impedance method. Experimental The soil was prepared from three levels of blown lowland soil (Soil A, B and C) with different particle size distribution. The particle size distribution was measured by the laser diffraction/scattering method. The soil was placed in a glass container, and the electrodes were buried in the soil. At the beginning of the experiment, enough water was supplied so that the soil was immersed. The soil water content decreased with time after the water supply had been stopped. The impedance measurements were carried out at constant time interval. The temperature in the chamber was held at 25ºC. Results and discussion Figure 1 shows Nyquist plots obtained from the impedance measurement of the carbon steel in soil A at different time. The equivalent circuit is also shown, where R s is the solution resistance, R ct the charge transfer resistance, CPE the constant phase element and Z W the Warburg impedance. Capacitive loops appeared on the Nyquist plots, and the diameter of the loops varied with the measurement time. R ct was calculated from the radius of the capacitive loops. Figure 2 shows the particle size distributions measured at three levels of soil. The maximum frequency appeared around 10 μm in all soils. Soil A contained more particles larger than 100 μm, although the peak at 10 μm was the lowest. On the other hand, Soil C showed the highest peak at 10 μm, but contained few particles larger than 300 μm. Soil B showed properties intermediate between soil A and C. Figure 3 shows the time course of 1/R ct for each soil. Soil A and B showed a 1/R ct maximum around 200 hours, and the maximum of soil A was greater than that of soil B. On the other hand, soil C did not show a clear maximum value of 1/R ct and remained constant. The difference in the corrosion behavior in each soil is considered to be due to the filling rate of the soil particle. It is known that the larger the particle size distribution is, the larger the filling rate of the particles and the smaller the gap diameter between the particles become. In soil with a wide particle size distribution, water is strongly trapped by capillary force in the narrow gaps between particles. Thus, as the soil dried, a thin water film was maintained on the steel surface, and oxygen was efficiently supplied. Therefore, it is considered that the maximum value of 1/R ct was the largest in soil A. Soil C had a high porosity, and the oxygen was efficiently supplied to the steel surface during the drying process, but at the same time, the wetted area decreased. Therefore, 1/R ct did not show a maximum value and remained constant. Conclusion The corrosion rate of steel in soil with different particle size distributions was evaluated by the AC impedance method. It was found that the corrosion behavior differed depending on the particle size distribution. The corrosion behavior is considered to be due to the diffusion of water and oxygen through gaps between particle. Figure 1

Investigation of physically transient resistive switching memory based on GeO2 thin films

Physically transient resistive switching memory has attracted much attention in recent years for potential applications in security information storage and environmental protection. Herein, we demonstrated that resistive switching memory composed of Ag/GeO2/fluorine-doped tin oxide structures exhibited remarkable electrical properties and could be rapidly dissolved by de-ionized water. The robust capabilities of the as-fabricated memory with more than 100 enduring cycles, a comparable resistance window larger than the OFF/ON ratio of 102, and a long retention time of more than 10 h was achieved. In addition, the degradable characteristics were demonstrated by the dissolution of amorphous GeO2 thin films in de-ionized water with the disappearance of resistive switching properties. Furthermore, the switching mechanism has been explained by the filament model, and the degradable mechanism of GeO2 films has been investigated by the change of chemical bonds and resistive switching properties in different humidity environments. Our results suggest that GeO2-based resistive switching memory could find opportunities for applications in physically transient electronics.

Adsorption- and Diffusion-Controlled Wettability Change in Modified Salinity Water Flooding

During the modified salinity water (MSW) flooding, the injected water must first reach and interact with the residual oil attached on the pore surfaces through a thin formation water film to mobili...

Dewetting of Co thin films in water driven by ns pulsed laser

We report on the pulsed laser-induced dewetting (LID) process of Co/sapphire(0001) thin films in water environment. In contrast to LID in a vacuum, where only Co nanoparticles (NPs) are formed, a 12 nm thick Co film was dewetted into a mixture of crystalline CoO NPs and nanowalls (NWs). The formation of the CoO NPs can be explained by the grooving model occurring concurrent with the oxidation of Co to CoO. Possible scenarios for the formation of NWs are proposed. The dissolution of Co into water occurred near the hole area. Upon subsequent laser irradiation, and O2− ions abundant in water facilitate the laser-induced hydrothermal process (LIHP) producing CoO NWs. Furthermore, we found that the combination of dissolution and LIHP is energetically more favorable over dewetting in a 4.8 nm thick sample, where only CoO NWs were observed. Finally, the reduction of sapphire substrate is revealed by the formation of Al-rich NPs.

Experimental study of the thermocapillary rupture dynamics of water and ethanol layers

Rupture dynamics of thin (500 μm) horizontal liquid films of water and ethanol was experimentally investigated during non-uniform heating from the side of smooth substrate. On the same substrate under similar heating conditions, the propagation rate of a dry spot in a horizontal water film was found to be several orders of magnitude higher than the rate of propagation of a dry spot in an ethanol layer.

Investigation into fluid-fluid interaction phenomena during low salinity waterflooding using a reservoir-on-a-chip microfluidic model

Injection of modified salinity brines (MSB), i.e. brine with seawater-like salinity (SWS) and low salinity water (LSW) in oil-wet carbonate rocks has proven to be relevant to improved oil recovery operations. Many reports in the literature related the underlying mechanisms to rock-fluid interactions such as ionic exchange and electrical double layer expansions, which caused wettability alterations at the rock surface. Little attention appears to have been paid to fluid-fluid interactions as a potential mechanism in displacement processes.In this work, we investigated the role of fluid-fluid interactions in improved oil recovery using MSBs. Interfacial tension and surface elasticity calculations were correlated to visual observations of displacement processes in order to investigate the role of crude oil snap-off. Microfluidic devices featuring pore throats 50 μm in diameter were used to observe snap-off as a function of salinity of the displacing fluid. Flow experiments suggested that, in a water-wet constricted pore throat, SWS brines suppressed crude oil snap-off as compared to formation water brine (FWS) brine. This behavior was correlated to the higher surface elasticity of oil-SWS interfaces than that of oil-FWS interfaces. Higher surface elasticity suppressed the expansion of the thin water film coating pore throat walls and hence it increased the capillary number at which snap-off of the crude oil phase was expected to occur.Moreover, water interacted with the polar components to form reverse micelles called microdispersions. These microdispersions were observed in both aged and non-aged microfluidic devices near oil-brine interfaces in the pore-network. Similarly, in a vial test performed by Tetteh and Barati (2019), microdispersion formation was only observed very close to oil-brine interfaces, caused by transport of water molecules into the oil phase due to reduced intermolecular forces at oil-LSW interfaces. This microdispersion formation was visualized using environmental scanning electron microscopy. These microdispersions remobilized, redistributed the oil, and along with a slight change in wettability in the medium, they improved the observed recovery. In the pore-network flow experiments, the use of SWS brines resulted in the formation of relatively larger oil droplets, which is attributed to the suppression of crude oil snap-off and enhanced oil coalescence resulting from changes in oil-brine interfaces. The integrated experimental study presented in this work demonstrates the importance of fluid-fluid interactions in improved oil recovery using MSBs.

Femtosecond laser ablation of thin silver films in air and water under tight focusing

In this work, microscale holes and intermediate self-organized structures were obtained on the surface of a thin 50-nm silver film in air and under a water layer using single tightly focused femtosecond laser pulses with variable energy. We study the differences in the relief of microholes using scanning electron microscopy. The comparison of the silver film ablation thresholds under irradiation in air and water is carried out. A non-monotonic change in the size of craters in a water medium at peak powers more than 1.5MW was found, which corresponds to the critical filamentation power of laser pulses in water.

Colloid retention and mobilization mechanisms under different physicochemical conditions in porous media: A micromodel study

Clear understanding of pore-scale mechanisms that control transport and retention of colloids in porous media at different physicochemical conditions is critical to improve design and efficient cleanup methodologies of filter beds. The objective of this work was to investigate the impact of hydrophobicity, solution ionic strength, and pH on colloid retention mechanisms in single-phase and two-phase flow in porous media systems. A series of experiments were conducted using a geometrically representative micromodel. Hydrophilic and hydrophobic colloids were dispersed in water at different solution ionic strength and pH conditions. Findings indicate that hydrophilic colloids exhibit high filtration efficiency as the colloids interact attractively with other colloids and solid-water-interface irrespective of the solution chemistry. However, for hydrophobic colloids, changes in solution chemistry significantly increase colloid retention where the colloid interaction become attractive with the increase in ionic strength and decrease in pH values. Colloids attached to the collector surfaces mobilized by the strong capillary forces induced by the moving gas-water interface and transported along with the interface. However, hydrophilic colloids redeposited on gas-water-solid interfaces or thin water films because of their greater capillary potential. Therefore, greater filtration efficiency is achieved with the hydrophilic colloids compared to the hydrophobic colloids for which the efficiency can be improved by changing the solution chemistry. Moreover, the removal efficiency by the moving gas-water interface was observed to be more for hydrophobic colloids compared to hydrophilic colloids for which the efficiency can be improved by lowering the ionic strength or increasing the pH value. This study indicates that the coupled effects of solution chemistry and colloid hydrophobicity should be taken into account while investigating efficient filtration and cleaning practices for the filter beds.

Physical mechanisms for soil moisture effects on microbial carbon-use efficiency in a sandy loam soil in the western United States

Microbial carbon-use efficiency (CUE) is defined as the portion of carbon (C) incorporated into biomass relative to the total carbon consumed and plays a pivotal role in regulating microbially-mediated C and nutrient transformations in soil. However, little is understood about how CUE is impacted by edaphic properties, like soil moisture. Soil moisture physically regulates microbial activity through its effects on both water potential and water content. Low water potential can result in high, compensatory intracellular solute concentrations that may inhibit biochemical functions through cytoplasmic desiccation, whereas low soil water content results in thin water films that can limit substrate diffusion, reducing microbial access to dissolved substrates. Because these two aspects of soil moisture may affect microbial respiration differently than C assimilation, they may have different effects on CUE. The purpose of this research was to evaluate the relative importance of water potential and water content in regulating CUE of soil microbial communities. Moist soil incubations of a sandy loam soil were used to determine the impact of both aspects of soil moisture on CUE, and soil slurries were used to determine the impact of water potential alone. Both 13C-acetate and 15N-ammonium were added to moist soils and slurries to quantify gross rates of C and N transformations. In moist soils, acetate assimilation and respiration rates and gross N mineralization and immobilization rates increased exponentially with increasing soil moisture (−3.0 to −0.03 MPa). In contrast, acetate assimilation and respiration and gross N transformation rates remained constant in soil slurries across a similar water potential gradient, created by modifying solute concentrations. Similarly, values of CUE in moist soils increased exponentially with increasing soil moisture, whereas slurry values of CUE remained constant across the soil water potential gradient. Because no changes in rates and CUE were observed in slurries, changes observed in moist soils were attributed to limited substrate diffusion associated with low water contents rather than to adverse physiological effects associated with low water potentials. Results of this study demonstrate that limited substrate diffusion is the primary physical mechanism through which soil moisture regulates microbially-mediated C and N transformation rates and CUE in this sandy loam soil.