Thin Water Layer Research Articles

High efficiency fuel sleds for polar traverses

We describe here the evolution of lightweight, high-efficiency fuel sleds for Polar over-snow traverses. These sleds consist of flexible bladders strapped to sheets of high molecular weight polyethylene. They cost 1/6th, weigh 1/10th and triple the fuel delivered per towing tractor compared with steel sleds. An eight-tractor fleet has conducted three 3400-km roundtrips to South Pole with each traverse delivering ∼320,000kg of fuel while emitting <1% the pollutants, consuming 1/2 the fuel and saving ∼$1.6M compared with aircraft resupply. A two-tractor fleet in Greenland recently delivered ∼83,000kg of fuel in bladder sleds to Summit with similar benefits. Performance monitoring has revealed that bladder-sled towing resistance is largely governed by sliding friction, which can start high and drop in half over the first 30min of travel. Frictional heating probably produces a thin water layer that lubricates the sled–snow interface. Consequently, towing resistance depends on the thermal budget of the sled. For example, black fuel bladders increase solar gain and thus decrease sled resistance; data suggest they could double again the fuel delivered per tractor. The outstanding efficiency and low cost of these sleds has transformed fuel delivery to Polar research stations.

Bone and mucosal dosimetry in skin radiation therapy: a Monte Carlo study using kilovoltage photon and megavoltage electron beams

This study examines variations of bone and mucosal doses with variable soft tissue and bone thicknesses, mimicking the oral or nasal cavity in skin radiation therapy. Monte Carlo simulations (EGSnrc-based codes) using the clinical kilovoltage (kVp) photon and megavoltage (MeV) electron beams, and the pencil-beam algorithm (Pinnacle3 treatment planning system) using the MeV electron beams were performed in dose calculations. Phase-space files for the 105 and 220 kVp beams (Gulmay D3225 x-ray machine), and the 4 and 6 MeV electron beams (Varian 21 EX linear accelerator) with a field size of 5 cm diameter were generated using the BEAMnrc code, and verified using measurements. Inhomogeneous phantoms containing uniform water, bone and air layers were irradiated by the kVp photon and MeV electron beams. Relative depth, bone and mucosal doses were calculated for the uniform water and bone layers which were varied in thickness in the ranges of 0.5–2 cm and 0.2–1 cm. A uniform water layer of bolus with thickness equal to the depth of maximum dose (dmax) of the electron beams (0.7 cm for 4 MeV and 1.5 cm for 6 MeV) was added on top of the phantom to ensure that the maximum dose was at the phantom surface. From our Monte Carlo results, the 4 and 6 MeV electron beams were found to produce insignificant bone and mucosal dose (<1%), when the uniform water layer at the phantom surface was thicker than 1.5 cm. When considering the 0.5 cm thin uniform water and bone layers, the 4 MeV electron beam deposited less bone and mucosal dose than the 6 MeV beam. Moreover, it was found that the 105 kVp beam produced more than twice the dose to bone than the 220 kVp beam when the uniform water thickness at the phantom surface was small (0.5 cm). However, the difference in bone dose enhancement between the 105 and 220 kVp beams became smaller when the thicknesses of the uniform water and bone layers in the phantom increased. Dose in the second bone layer interfacing with air was found to be higher for the 220 kVp beam than that of the 105 kVp beam, when the bone thickness was 1 cm. In this study, dose deviations of bone and mucosal layers of 18% and 17% were found between our results from Monte Carlo simulation and the pencil-beam algorithm, which overestimated the doses. Relative depth, bone and mucosal doses were studied by varying the beam nature, beam energy and thicknesses of the bone and uniform water using an inhomogeneous phantom to model the oral or nasal cavity. While the dose distribution in the pharynx region is unavailable due to the lack of a commercial treatment planning system commissioned for kVp beam planning in skin radiation therapy, our study provided an essential insight into the radiation staff to justify and estimate bone and mucosal dose.

Layered water in crystal interfaces as source for bone viscoelasticity: arguments from a multiscale approach

Extracellular bone material can be characterised as a nanocomposite where, in a liquid environment, nanometre-sized hydroxyapatite crystals precipitate within as well as between long fibre-like collagen fibrils (with diameters in the 100 nm range), as evidenced from neutron diffraction and transmission electron microscopy. Accordingly, these crystals are referred to as ‘interfibrillar mineral’ and ‘extrafibrillar mineral’, respectively. From a topological viewpoint, it is probable that the mineralisations start on the surfaces of the collagen fibrils (‘mineral-encrusted fibrils’), from where the crystals grow both into the fibril and into the extrafibrillar space. Since the mineral concentration depends on the pore spaces within the fibrils and between the fibrils (there is more space between them), the majority of the crystals (but clearly not all of them) typically lie in the extrafibrillar space. There, larger crystal agglomerations or clusters, spanning tens to hundreds of nanometers, develop in the course of mineralisation, and the micromechanics community has identified the pivotal role, which this extrafibrillar mineral plays for tissue elasticity. In such extrafibrillar crystal agglomerates, single crystals are stuck together, their surfaces being covered with very thin water layers. Recently, the latter have caught our interest regarding strength properties (Fritsch et al. 2009 J Theor Biol. 260(2): 230–252) – we have identified these water layers as weak interfaces in the extrafibrillar mineral of bone. Rate-independent gliding effects of crystals along the aforementioned interfaces, once an elastic threshold is surpassed, can be related to overall elastoplastic material behaviour of the hierarchical material ‘bone’. Extending this idea, the present paper is devoted to viscous gliding along these interfaces, expressing itself, at the macroscale, in the well-known experimentally evidenced phenomenon of bone viscoelasticity. In this context, a multiscale homogenisation scheme is extended to viscoelasticity, mineral-cluster-specific creep parameters are identified from three-point bending tests on hydrated bone samples, and the model is validated by statistically and physically independent experiments on partially dried samples. We expect this model to be relevant when it comes to prediction of time-dependent phenomena, e.g. in the context of bone remodelling.

Modeling the hydrodynamic interactions of deep anoxic lagoons with their source basins

This study investigates the management of an extension of the anoxic water layers, from deeper to shallower environments, and aims to control the consequences in lagoon environments with great economic and ecological value. The physicochemical status in a deep anoxic lagoon (Aitoliko, Greece) was monitored and the spatial distribution of anoxic conditions in the bottom waters was the focal point. The study investigated the management of an extension of the anoxic water layers, from deeper to shallower environments, and aims to control the consequences in lagoon environments with great economic and ecological value. A three-dimensional numerical model was used in order to describe the hydrodynamic conditions in the lagoon. The model was calibrated and validated with field measurements and it was used as a tool to examine how morphological modifications in lagoon's sill and changes of the lagoon's salt/fresh water budget can affect water column hydrodynamics. The model reliably reproduced the hydrodynamic changes in the lagoon caused by morphological and/or hydraulic modification, demonstrating an ideal management plan for the control of deep anoxic hypolimnia. It is concluded that by decreasing fresh water discharges into a deep lagoon, epilimnetic density values increase while the metalimnion extends. By extending the sill's cross section, water fluxes with the source basin are increased, affecting the surface layer density. Even under these conditions fresh water discharges control the characteristics of a thin surface water layer. If the sill's cross section expansion is followed by a decrease of fresh water discharge, turbulence conditions in the water column of a deep basin are substantially affected.

DFT-GGA and DFT+USimulations of Thin Water Layers on Reduced TiO2Anatase

We investigated the effect of a reducing subsurface Ti interstitial defect on the structure and reactivity of thin water layers adsorbed on the majority anatase(101) surface of titanium oxide using ab initio molecular dynamics simulations. We find that standard DFT-GGA and the DFT+U method predict similar energetics and dissociation barrier for a single water molecule adsorbed on the reduced surface; moreover, the two approaches also lead to very similar structural features and reactivity for an adsorbed water monolayer (ML) on the same surface. This allows us to model 1, 2, and 3 water layers on the reduced surface through Car–Parrinello molecular dynamics simulations up to 20 ps long. Compared to the defect-free surface, the simulations highlight how the interstitial defect alters the stability of surface adsorption sites, substantially enhancing the surface reactivity and leading to a markedly different structure of the first water layers adsorbed on the reduced surface.

Model of cooperative character of hydrogen bonds in water

A quantitative description of hydrogen bonds in liquid water is developed using a simple model. The proposed approach is based on the notion of a hydrogen bond as mediated by proton exchange between neighboring hydroxyl groups under adiabatic conditions with respect to the electron subsystem. Application of the model is illustrated by means of the example of analysis of the IR absorption spectrum of a thin water layer. It is shown that the structure of water in layers with thicknesses on the order of 1 μm differs from the structure of bulk water.

XPS characterization of passive films formed on Type 304 stainless steel in humid atmosphere

Cr enriched passive films were hardly formed on Type 304 stainless steel under humid atmosphere. Cr fraction in passive films under relative humidities (R.H.) in the range 30–70% was similar to the alloy composition. However, slightly Cr enriched passive films were formed under R.H. 90%. This is attributed to the thin continuous water layer into which Fe ions are selectively dissolved. When chloride is in the water layer, the Cr enrichment was enhanced by accelerated dissolution of Fe as chloride complex. At lower R.H., pitting corrosion occurred because of the more concentrated chloride in the water layer.

Contact of Oil with Solid Surfaces in Aqueous Media Probed Using Sum Frequency Generation Spectroscopy

We have studied the interface between hexadecane droplets and sapphire substrates in water using infrared-visible sum frequency generation spectroscopy (SFG). At high pH and above the isoelectric point of the sapphire substrate, the hexadecane drop is repelled due to electrostatic forces. The SFG measurements are consistent with the observation that a thick layer of water is present between the oil and the sapphire substrate. Below the isoelectric point of the sapphire substrate, the hexadecane drops stick to the sapphire surface. Surprisingly, the SFG results show the presence of a thin layer of water between hexadecane drop and the sapphire substrate. At this contact interface, we observe contributions to the SFG signal from both the hexadecane/water and water/sapphire interfaces. The reasons for the presence of a thin water layer with adhesive contact can be explained due to weaker repulsive double layer and the attractive van der Waals interactions.

Performance analysis of an evacuated multi-stage solar water desalination system

In this paper, a novel multi-stage evacuated solar desalination system is developed by utilizing latent heat recovery. A transient model is proposed for the solar desalination system. The effect of various design and operating parameters on the system performance is studied to optimize the configuration. The distillate yield increases initially due to enhanced evaporation caused by the presence of a thin layer of water in the stages. The distillate yield decreases with increase in salinity of water due to an increase in ion activity and the reduction of thermodynamically spontaneous change from liquid to vapor. The optimum number of stages, gap between the stages and the supplied mass flow rate for the system were found to be 4, 100mm and 55kg/m2/day respectively throughout the year. The overall thermal efficiency of the system is found to be 53.9% and 29.6% for the months March and December respectively in India. The maximum yield of 53.2kg/m2/day is found in March at an operating pressure of 0.03bar. The multi-stage evacuated solar desalination system is a viable option to meet the needs of rural and urban communities.

C-C and C-O Coupling Reactions of Terminal Alkynes by a Water Soluble Organoiridium Electron-transfer Mediator in Thin Layer of Water on Gold Electrode

An electrochemical reduction process is described for the rapid and efficient conversion of terminal alkynes into useful products. Terminal alkynes (HC≡CR; R = C 6 H 5 , p -C 6 H 4 CH 3 , CH 2 C 6 H 5 , C 6 H 9 ) were hydrated and dimerized by cathodic reduction of catalytic amount (5 %) of [Cp * Ir(NCMe) 2 (PAr 3 )](OTf) 2 , 1 , ( E pc = −620 mV vs Ag/AgCl) through an aqueous/nonaqueous interface. Thin aqueous layer containing water-soluble compound 1 was formed on gold electrode. The cathodic reduction current height of 1 increases as increasing the concentration of terminal alkynes. The electrolysis of 1 while contacting with terminal alkynes containing organic solvent produced ketones, aldehydes and dimerized enyne products from terminal alkyne/water reaction systems. A new micro-scale electrocatalysis technique is depicted.

Growth Process of Passive Films on Austenitic Stainless Steels under Wet-dry Cyclic Condition

Passive films formed on Type 304 and 316 stainless steels under a wet-dry cyclic condition were characterized using X-ray photoelectron spectroscopy (XPS). Cr enrichment in the passive films during early stage of the wet-dry cycles occurred due to the preferential oxidation of Cr and the selective dissolution of Fe. However, the Cr fraction of hydroxide layer in passive film gradually decreased with time, because Fe(OH)aq dissolved in the thin water layer were accumulated into the outermost hydroxide layer of a passive film during the dry condition. Chloride in thin water layer facilitated selective dissolution of Fe ions. On the other hand, the Mo in Type 316 stainless steel suppressed the dissolution of Fe ions. Consequently, Cr fraction in passive film on Type 316 became smaller than that of Type 304 stainless steel.

Quantifying riverine surface currents from time sequences of thermal infrared imagery

River surface currents are quantified from thermal and visible band imagery using two methods. One method utilizes time stacks of pixel intensity to estimate the streamwise velocity at multiple locations. The other method uses particle image velocimetry to solve for optimal two‐dimensional pixel displacements between successive frames. Field validation was carried out on the Wolf River, a small coastal plain river near Landon, Mississippi, United States, on 26–27 May 2010 by collecting imagery in association with in situ velocities sampled using electromagnetic current meters deployed 0.1 m below the river surface. Comparisons are made between mean in situ velocities and image‐derived velocities from 23 thermal and 6 visible‐band image sequences (5 min length) during daylight and darkness conditions. The thermal signal was a small apparent temperature contrast induced by turbulent mixing of a thin layer of cooler water near the river surface with underlying warmer water. The visible‐band signal was foam on the water surface. For thermal imagery, streamwise velocities derived from the pixel time stack and particle image velocimetry technique were generally highly correlated to mean streamwise current meter velocities during darkness (r2 typically greater than 0.9) and early morning daylight (r2 typically greater than 0.83). Streamwise velocities from the pixel time stack technique had high correlation for visible‐band imagery during early morning daylight hours with respect to mean current meter velocities (r2 &gt; 0.86). Streamwise velocities for the particle image velocimetry technique for visible‐band imagery had weaker correlations with only three out of six correlations performed having an r2 exceeding 0.6.

Sucrose Exclusion and Inclusion in a Lipid-Water System

Sugars are known to strongly affect lipid-water phase behavior and often serve as protectants against cold, heat, and dehydration. However, a detailed picture of how sugars interact with lipids remains an active question. We have determined the phase diagram of the lipid SOPE (1-stearoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine) as a function of sucrose concentration by means of DSC and laser-light scattering. Using thermodynamic arguments, our data can be used to determine the interfacial concentration of sucrose in lipid-water-sucrose mixtures. Our preliminary results are consistent with a model of sucrose being excluded in a thin layer of water immediately in front of the lipid head groups, but partially included in the gaps between lipid head groups in the fluid lamellar phase and in the core of the inverted hexagonal phase.

Comment on “Study of dielectric relaxations of anhydrous trehalose and maltose glasses” [J. Chem. Phys. 134, 014508 (2011)

Very recently Kwon et al. [H.-J. Kwon, J.-A. Seo, H. K. Kim, and Y. H. Hwang, J. Chem. Phys. 134, 014508 (2011)] published an article on the study of dielectric relaxation in trehalose and maltose glasses. They carried out broadband dielectric measurements at very wide range of temperatures covering supercooled liquid as well as glassy state of both saccharides. It is worth to mention that authors have also applied a new method for obtaining anhydrous glasses of trehalose and maltose that enables avoiding their caramelization. Four relaxation processes were identified in dielectric spectra of both saccharides. The slower one was identified as structural relaxation process the next one, not observed by the others, was assigned as Johari-Goldstein (JG) β-relaxation, while the last two secondary modes were of the same nature as found by Kaminski et al. [K. Kaminski, E. Kaminska, P. Wlodarczyk, S. Pawlus, D. Kimla, A. Kasprzycka, M. Paluch, J. Ziolo, W. Szeja, and K. L. Ngai, J. Phys. Chem. B 112, 12816 (2008)]. In this comment we show that the authors mistakenly assigned the slowest relaxation process as structural mode of disaccharides. We have proven that this relaxation process is an effect of formation of thin layer of air or water between plate of capacitor and sample. The same effect can be observed if plates of capacitor are oxidized. Thus, we concluded that their slowest mode is connected to the dc conduction process while their β JG process is primary relaxation of trehalose and maltose.

Picosecond ultrasonic microscopy of semiconductor nanostructures

We describe a new picosecond ultrasonics method for the study of nanostructures. A sound pulse is generated when an ultra-short laser pulse is absorbed in a transducer structure. The sound then propagates across a thin layer of water and is reflected from the surface of the sample being examined. A resonant optical cavity is used to improve the efficiency of optoacoustic detection and generation of the sound. We report on experiments in which sound is reflected from patterned nanostructures. In these experiments, we are able to study the propagation of sound down channels of width as small as 35 nm.

Heterogeneous Ice Nucleation Induced by Electric Fields

Heterogeneous ice nucleation is an important phenomenon in the physical environment influencing atmospheric and biological processes. Despite this relevance, the mechanism of heterogeneous ice nucleation is not understood at the microscopic level, and what exactly constitutes a good ice nucleus is an open question. Employing molecular dynamics simulations, we demonstrate that an electric field, which acts very near a surface, can create an effective ice nucleus in models of supercooled liquid water. To serve as an ice nucleus, the field must polarize only a very thin water layer (∼10 Å), and the field strength required is realistic on the relevant length scale. Our results support the idea that local electric fields could play a major role in heterogeneous ice nucleation, particularly for the very rough particles with many surface structure variations, that serve as ice nuclei in environmentally realistic situations.

Laser Shot Peening of 304 Austenitic Stainless Steel without Protective Coating

Laser Shot Peening without protective Coating (LPPC) was performed on SS304 austenitic stainless steel using a 300 mJ, 10 ns pulse, 1064 nm wavelength Nd:YAG laser with three different pulse densities. A thin layer of water was used as a confinement layer. The peened specimen was characterised with XRD, AFM and a Profilometer. The stress evaluated at the surface of the laser peened sample shows a maximum compressive stress of 1.6 GPa. The surface roughness and depth profile of microhardness before and after LPPC were investigated.The LPPC region indicate substantial improvement in microhardness and compressive residual stress, with marginal increase of surface roughness.

Experimental observation of standing interfacial waves induced by surface waves in muddy water

A striking feature has been observed in a laboratory wave tank with a thin layer of clear water overlying a layer of mud. A piston-type wave maker is used to generate long monochromatic surface waves in a tank with a layer of kaolinite clay at the bottom. The wave action on the mud causes the clay particles to rise from the bottom into the water column, forming a lutocline. As the lutocline approaches the water surface, a set of standing interfacial waves form on the lutocline. The interfacial wave directions are oriented nearly orthogonal to the surface wave direction. The interfacial waves, which sometimes cover the entire length and width of the tank, are also temporally subharmonic as the phase of the interfacial wave alternates with each passing surface wave crest. These interfacial waves are the result of a resonant three-wave interaction involving the surface wave train and the two interfacial wave trains. The interfacial waves are only present when the lutocline is about 3 cm of the water surface and they can be sufficiently nonlinear as to exhibit superharmonics and a breaking-type of instability.

IR spectroscopy of thin water layers and the mechanism of action α-tocopherol in ultra low concentrations

IR spectroscopy of thin water layers and the mechanism of action α-tocopherol in ultra low concentrations

The point spectrum of the water-wave problem in intersecting channels

Trapped modes are examined on the water surface in two channels, which intersect each other at right angle and have the same symmetric cross-sections. These trapped modes correspond to eigenvalues embedded into the continuous spectrum of the Steklov boundary value problem, decay exponentially at infinity, i.e., they are localized near the crossing of the channels. A sufficient condition is presented for the existence of such trapped waves. The effect is discussed of the concentration of eigenvalues under a perturbation in the vicinity of the channels crossing by means of the formation of a shoal, a thin water layer. A condensed review of known results on curved, cranked, and branched waveguides is given and open questions are formulated. Bibliography: 24 titles.