Surface Penetration Research Articles

Determination of the Bardeen–Cooper–Schrieffer material parameters of the HIE-ISOLDE superconducting resonator

Superconducting material parameters of the Nb film coatings on the quarter-wave resonator for the HIE-ISOLDE project were studied by fitting experimental results with the Bardeen–Cooper–Schrieffer Mattis–Bardeen (BCS-MB) theory. We pointed out a strong correlation among fitted estimators of material parameters in the BCS-MB theory, and used a procedure to reduce the uncertainty by merging two χ2 distributions of the surface resistance and effective penetration depth. In this procedure, unlike previous studies, BCS coherence length (ξ0) and London penetration depth (λL) were not fixed at their literature values in the calculation because in our film, whose thickness is from 2 to 13 μm, they may take altered values as a consequence of microstructual defects. Since surface resistance and penetration depth have similar dependencies on coherence length and mean free path, the effects of the correlation between the estimators of these two parameters could not be mitigated by just combining surface resistance and penetration depth data. We used upper critical field measurement by SQUID magnetometry to provide a complementary constraint to these RF measurements, and this allowed all the material parameters to be obtained by fitting the experimental data. In the best performing cavity, the determined parameters are ξ0 = 29 nm, λL = 26 nm, mean free path l = 99 nm, and coupling strength Δ0/kBTc = 1.7. The coherence length is slightly shorter than for clean bulk Nb (39 nm) in the literature although the Nb film is thick and rather bulk-like. A poorly performing cavity showed weaker coupling constant Δ0/kBTc = 1.5 which may indicate film contamination during the coating process.

Exopolysaccharide-mediated surface penetration as new virulence trait in Enterococcus faecalis

ABSTRACTEnterococcus faecalis is a commensal bacterium that normally inhabits the gastrointestinal tract of humans. This non-motile microorganism can also cause lethal infections in other organs by penetrating and breaching the intestinal barrier. However, the precise molecular mechanisms enabling E. faecalis movement and translocation across epithelial barriers remain incompletely characterized. We recently reported that E. faecalis utilizes the RpiA-GlnA-EpaX metabolic axis to generate β-1,6-linked poly-N-acetylglucosamine (polyGlcNAc)-containing exopolymers that are necessary for its optimal migration into semisolid surfaces and efficient translocation through human epithelial cell monolayers. These findings provide new evidence indicating that non-motile bacterial pathogens can exploit carbohydrate metabolism to penetrate surfaces. Hence, targeting this process might represent a new strategy to more effectively control systemic infections by E. faecalis.

Coupling relationship between torch migration relative to surface weld pool and penetration morphology in asymmetrical fillet welding

Due to the asymmetry, on each side of the single-sided V-groove fillet weld of a plate steel, there is a certain gap between the heat conduction and heat dissipation. The thermal input is distributed randomly to both sides of the weld when unsuitable weld angle is applied during welding, and sidewall incomplete fusion defects of interior penetration often occurs. A new feasible methods is provided to predict the interior penetration morphology, preventing generation of incomplete fusion defects by acquiring the torch migration information of surface weld pool. The experimental results show that the torch migration relative to the surface of the weld pool occurs regularly when different welding angles are used. Meanwhile, the interior penetration morphology change. According to welding at different angles, the quantitative relation between them is established and verified by different welding current.

High‐speed photography of water drop impacts on sand and soil

SummaryThe way that water drops impact on soil is of widespread importance for soil science, particularly in the context of irrigation and erosion. With modern high‐speed photography techniques, impacts on granular materials are becoming more widely studied, but the variation in particle‐size distribution of soil presents particular challenges. Here, the impacts of individual water drops on two contrasting soil textures (pure sand and a loamy soil) have been studied with high‐speed photography, and compared at Weber numbers between 50 and 750. Granular samples with wider distributions of particle sizes produce larger variations in experimental outcomes. For the sand, which contained >98% particles between 60 μm and 2 mm in size, the typical outcome involved spreading and retraction of the drop to a circular profile with a raised rim. The loamy soil had greater surface roughness than the sand, with a wider distribution of particle sizes, so that the spread of the drop was more anisotropic, involved more movement of target particles and often involved droplet breakup into satellite drops. Overall outcomes were best described by a gravity‐dominated cratering mechanism, and the scaling exponent for the crater diameter with respect to impact energy was 0.22 ± 0.03. Dynamic penetration studies enabled visualization of granular motion below the surface, and both static and dynamic penetration results illustrated a transition between inertial and viscous regimes over time. As the water content of the soil was increased, droplet breakup was initially encouraged before capillary imbibition dominated at water contents close to 10%v/v. This research is useful for understanding how rain and irrigation, which comprise many millimetre‐scale drops, influence large‐scale hydraulic properties in soil, including surface sealing.Highlights Drop impact on to soil is important, but its systematic study is difficult because of variation in soil particle sizes. High‐speed photography was used to study drop impacts on to a pure sand and loamy soil, and analysed quantitatively. Results show how granular samples with wider distributions of particle sizes produce more variation in experimental outcomes. The maximum extent of drop spreading was best described by a scaling model developed for planetary cratering.

Design of NIRS Probe Based on Computational Model to Find Out the Optimal Location for Non-Invasive Brain Stimulation.

The paper presents a computational model to analyse the electric field distribution on the cerebral cortex during high definition transcranial direct current stimulation (HD-tDCS) technique. The current research aims to improve the focality in term of magnitude of electric field (norm [E]) and magnitude of current density (norm [J]) in the gyri and sulci of white matter. The proposed computational model is used to predict the magnitude of current density and magnitude of electric field distribution generated across the target region of cerebral cortex for specific small size 1 × 1cm2 multi-electrode HD-tDCS configurations. The current works aims at optimizing the number of electrodes and current density for multielectrode HD-tDCS configuration and weak current intensity is obtained by calculating surface area and penetration depth of target region of cerebral cortex. In terms of surface area and penetration depth 4 × 1 HD-tDCS and 2mA weak dc current configuration has been selected. The optimized 4 × 1 HD-tDCS configuration is placed on target location of the brain surface and the changes in the magnitude of current density and magnitude of electric field distribution is calculated at the different locations on brain surface including scalp surface, skull surface gray matter and white matter surface. The variation in magnitude electric field distribution is seen in the cerebrospinal fluid (CSF), gray and white matter surface of target cerebral cortex. Based on the insights received from the variation in the magnitude of current density and magnitude of electric field distribution, the design of an appropriate NIRS probe has been proposed to aid in non-invasive brain stimulation. Designed NIRS probe is based on distance of separation between source and photodetector to cover the affected area with 4 × 1 HD-tDCS technique and measurement sensitivity distribution at gray matter surface of cerebral cortex. The estimated percentage of pixel area of measurement sensitivity distribution is 17.094%, which confirm to cover the 7.9384% distributed pixel area in term of calculated magnitude of current density affected with 4 × 1 HD-tDCS configuration.

The influence of the essential oil extracted from hops on monolayers and bilayers imitating plant pathogen bacteria membranes.

Many plant-derived compounds possess antimicrobial, antioxidant and even anticancer activities. Therefore, they are considered as substances that can be used instead of synthetic compounds in various applications. In this work, the essential oil from hop cones was extracted and analyzed, and then its effects on model bacteria membranes were studied to verify whether the hop essential oils could be used as ecological pesticides. The experiments involved surface pressure-area measurements, penetration studies and Brewster angle microscopy (BAM) imaging of lipid monolayers as well as hydrodynamic diameter, zeta potential, steady-state fluorescence anisotropy and Cryo-Transmission Electron Microscopy (cryo-TEM) measurements of liposomes. Finally the bactericidal tests on plant pathogen bacteria Pseudomonas syringae pv. lachrymans PCM 1410 were performed. The obtained results showed that the components of the essential oils from hop cones incorporate into lipid monolayers and bilayers and alter their fluidity. However, the observed effect is determined by the system composition, its condensation and the oil concentration. Interestingly, at a given dose, the effect of the essential oil on membranes was found to stabilize. Moreover, BAM images proved that hop oil prevents the formation of a large fraction of a condensed phase at the interface. Both the studies on model membranes as well as the in vitro tests allow one to conclude that the hop essential oil could likely be considered as the candidate to be used in agriculture as a natural pesticide.

Thermal Stability of Structure and Properties of the Surface Layer of Instrumental Steel Alloyed with Zirconium and Silicon Atoms under the Action of Compression Plasma Flows

The phase and elemental composition and microhardness of instrumental steel U9 with zirconium and silicon coatings subjected to compression plasma flows and air thermal annealing are investigated. It is found that plasma impact leads to the formation of a surface layer with the thickness of up to ~8.5 μm alloyed with zirconium and silicon atoms and containing Fe2Zr intermetallic. Formation on the surface of the oxide γ-ZrO2 and carbonitride Zr(C, N) as a result of interaction with the residual atmosphere of the vacuum chamber is found. Change in the phase composition and dispersion of the structure leads to a twofold increase in microhardness. The alloyed layer retains the stability of the structure and phase composition (excluding polymorphic transition in ZrO2) up to 400°C. Annealing at 600°C leads to the internal oxidation accompanied by formation of a surface iron oxide scale and penetration of the oxygen atoms to the whole depth. The increase in the annealing temperature leads to the decrease in microhardness throughout the alloyed layer.

Algal and fungal diversity on various dimension stone substrata in the Saale/Unstrut region

Physical, chemical and biogenic weathering considerably threatens all historic stone monuments. Microorganisms, though inconspicuous, are key players of stone surface colonization and penetration. This study highlights eukaryotic microbial communities on dimension stone surfaces from two representative monuments of the “cultural landscape corridor” in the Saale–Unstrut area. The historical buildings were erected from local Triassic limestone and sandstone and are prone to various deteriorative mechanisms. Generally, trebouxiophyceaen algae and ascomycete fungi dominate among the latter dematiaceous fungi and lichen fungi are abundant. Inside the stone substratum, ascomycetes, mosses and even large soil organisms (tardigrades) are present. This may be taken as a hint for the formation of pores with large radii, which are “risk indicators” for progressive weathering and degradation of the rock matrix.

Single-sided NMR as a non-destructive method for quality evaluation of hydrophobic treatments on natural stones

Moisture is a main cause for weathering effects in historical façades made of natural stones. If applied correctly, hydrophobic agents can successfully protect these façades without altering the appearance. The major challenge is to ensure the required surface penetration. In-situ measurements for quality assurance on historical façades are still mainly done destructively through the extraction of core samples or superficially through the measurement of water ingress. An alternative approach has been found in nuclear magnetic resonance, which is able to visualize pore water. Applying this, single-sided NMR sensors provide a non-destructive tool for use at the building site. For this paper, four sandstones of different porosity and one limestone have been treated with two hydrophobic agents of different composition. The ingress of water in the treated samples has been measured by the single-sided sensor using three criteria for quality assessment, namely the hydrophobic depth, the hydrophobic efficiency, and the water absorption coefficient. The results are compared to those of common quality assurance measurements: the visual assessment and the gravimetrical water ingress on core samples as well as the superficial Karsten tube penetration test. It is shown that the single-sided NMR sensor provides a tool for the non-destructive quality evaluation of hydrophobic treatments, which is generally applicable to the building site using the quality criteria now found.

Hydrogen storage on LaNi5−xSnx. Experimental and phenomenological Model-based analysis

Three hydride-forming metals (LaNi5, LaNi4.73Sn0.27, and LaNi4.55Sn0.45) have been studied as solid phase hydrogen storage material in batch experiments using pure hydrogen and temperatures ranging from 300 K to 340 K. This process mainly involves: physisorption of hydrogen gas molecules; chemisorption and dissociation of hydrogen molecules; surface penetration of hydrogen atoms; hydride formation; and diffusion of hydrogen atoms through hydride-forming metal. In case the material is fully hydrided, hydride formation ceases and diffusion proceeds on the fully hydrided material.A phenomenological model was developed by aggregating the first four mechanisms in a single sorption kinetic term involving a first-order driving force, the remaining mechanism being the atomic diffusion in the hydride-forming material. The driving force is computed between external partial pressure and equilibrium pressure according to the Pressure-Composition-Temperature model (PCT). The corresponding parameters for an empirical PCT were estimated from equilibrium data. This equation is more suitable for process engineering optimization due to the smoothness in its concentration domain. Specific sorption rate and diffusion coefficients of the process were also estimated from dynamic data. From a sensitivity analysis, productivity proved to be related to particle diameter. In the frame of batch processes, the global rate is dominated by the sorption kinetic term at the beginning of the experiments with the material being free from hydride, whereas with more than 5–10% of the material being hydrided, diffusion dominates the process. LaNi5 shows higher hydrogen storage capacity than LaNi4.73Sn0.27 and LaNi4.55Sn0.45 within the investigated temperature and pressure ranges. Diffusion and sorption kinetic limited regions were identified from a sensitivity analysis of process productivity and normalized marginal values. The present work is oriented to modeling, designing, and optimizing storage and purification devices.

Periodic Contact Problem for a Surface with Two-Scale Waviness

An analytical solution of a periodic contact problem on the penetration of a rigid wavy surface represented by two cosine harmonics into an elastic half-plane without accounting for the frictional forces is obtained. It is shown that the presence of cosine harmonics of the second scale for moderate and large loads causes oscillations of the pressure distributions, which depend linearly on its amplitude and nonlinearly on its period. The presence of the oscillations of the contact characteristics—the nominal and maximal pressures—is discovered.

On the possibility of low-temperature removal of hydrogen isotopes from tungsten in conditions of thermonuclear and plasma facilities

Acceleration of hydrogen isotope trapping and desorption has been observed in the experiments with stainless steel (Activated Surface Penetration - ASP) under irradiation by hydrogen atoms and hydrogen plasma ions with oxygen impurity. ASP is considered in this paper for a method of low-temperature hydrogen isotope removal from tungsten and aluminum-coated tungsten under irradiation by hydrogen plasma ions with oxygen impurity. It is shown that periodic irradiation by hydrogen plasma ions with oxygen impurity allows preventing accumulation of implanted deuterium ions in tungsten.

A first-principle study of H adsorption and absorption under the influence of coverage

The investigations of interactions between hydrogen and transition metal surfaces are of vital importance to the comprehension of principals involved in many chemical processes. In this work, the influences of coverage on H adsorption and absorption on and in a series of transition metals have been studied. High enough hydrogen coverage is needed to make H absorption much more feasibly. The pre-adsorbed H adatoms can modify H binding energies as well as H absorption energetics and can be felt very deeply in the 2nd-subsurface. As a result, surface penetration of atomic H and further diffusion into the bulk can be facilitated, and in turn the resurfacing process of absorbed H is blocked.

Contact mechanics of high-density polyethylene: Effect of pre-stretch on the frictional response and the onset of wear

Nowadays, in many applications metal parts are replaced by light-weight polymer products. As a result of the processing history, these polymer fabricates are, more often than not, anisotropic, leading to a direction dependent mechanical performance. Recently we showed the frictional response of isotactic polypropylene is improved by pre-stretching the crystalline network. In the present work, the scratch response of isotropic high-density polyethylene (HDPE) is compared with that of several pre-stretched samples of the same material, subjected to a single-asperity contact with a rigid diamond indenter. The surface penetration and lateral force are measured in-situ for a range of applied loads and sliding velocities. In the direction perpendicular to the orientation, the observed response is comparable to that of isotactic polypropylene (iPP). Contrary, in the direction parallel to the oriented crystals abrasive wear is observed in HDPE already for relatively low applied loads. As the amount of anisotropy increases, the wear-rate also increases, leading to a decrease in global scratch resistance of these materials. The discrepancies between iPP and HDPE are explained by the intrinsic material behaviour; the lack of strain softening in HDPE prevents strain localization, hence the ever increasing local stress reaches its maximum value and brittle machining is observed.

Anticorrosion Effect of Silane Type Surface Penetrants on RC Degraded by Carbonation

We studied on the anticorrosion effect by applying silane type surface penetrants on RC degraded by carbonation. Two types of carbonation residue and two types of environmental conditions after accelerated carbonation were prepared and investigation was made on the corrosion behaviour of reinforcing bars by applying surface penetrants. As a result, by blocking water penetration by applying surface penetrants, there was a difference in anticorrosive effect in the behaviour of half-cell potential, polarization resistance, and investigation of reinforcing bar corrosion after the end of exposure. From the above, this paper reports on the possibility of realizing anticorrosion effect by suppressing invasion of moisture from concrete surface to carbonated RC.

A New Precast Concrete Deck System for Accelerated Bridge Construction

Abstract Full-depth precast concrete (PC) deck systems have several advantages over cast-in-place concrete decks in bridge construction, such as improved product quality, reduced construction labor and duration, and less dependence on weather and site conditions. This article presents he development of a new full-depth PC deck system that overcomes the drawbacks of existing systems, which include large numbers of joints and openings that need to be field cast, a requirement for tight tolerances in panel production and erection, a need for an overlay, and a complexity of post-tensioning and grouting operations. The developed deck system consists of full-depth, full-width PC deck panels that are 12 ft (3.66 m) long to minimize the number of transverse joints that need to be field cast. Panels have covered shear pockets at 4-ft (1.22 m) spacing over each girder line. These pockets are designed to minimize the number of shear connectors and deck surface penetrations to eliminate deck overlay. Deck panels are prestressed in both directions: pre-tensioned in the transverse direction and post-tensioned in the longitudinal direction using a new approach that is ductless and easy to install. These unique features are expected to enhance deck constructability, durability, and economy. The article presents the deck system design, construction sequence, and laboratory investigations conducted prior to its implementation in the construction of the Kearney East Bypass bridge in the State of Nebraska, USA.

Remote Sensing of Sub-Surface Suspended Sediment Concentration by Using the Range Bias of Green Surface Point of Airborne LiDAR Bathymetry

Suspended sediment concentrations (SSCs) have been retrieved accurately and effectively through waveform methods by using green-pulse waveforms of airborne LiDAR bathymetry (ALB). However, the waveform data are commonly difficult to analyze. Thus, this paper proposes a 3D point-cloud method for remote sensing of SSCs in calm waters by using the range biases of green surface points of ALB. The near water surface penetrations (NWSPs) of green lasers are calculated on the basis of the green and reference surface points. The range biases (ΔS) are calculated by using the corresponding NWSPs and beam-scanning angles. In situ measured SSCs (C) and range biases (ΔS) are used to establish an empirical C-ΔS model at SSC sampling stations. The SSCs in calm waters are retrieved by using the established C-ΔS model. The proposed method is applied to a practical ALB measurement performed by Optech Coastal Zone Mapping and Imaging LiDAR. The standard deviations of the SSCs retrieved by the 3D point-cloud method are less than 20 mg/L.

Prediction of degree of impregnation in thermoplastic unidirectional carbon fiber prepreg by multi-scale computational fluid dynamics

A multi-scale simulation approach was proposed to predict the degree of impregnation (DoI) in thermoplastic unidirectional carbon fiber prepreg (UD-CFP). The multi-scale approach included a two-dimensional (2D) micro-scale computational fluid dynamics (CFD) in a representative elementary volume (REV) of carbon fiber (CF) tow, a 3D macro-scale CFD of an entire impregnation die with 15 sliding CF tows, and a process-scale simulation assembling data from the micro- and macro-scale CFDs. In the macro-scale steady-state CFD, thermoplastic resin injection and CF tow insertion were considered for an impregnation die 10 cm in width. In the micro-scale transient CFD, impregnation mechanisms of resin into CF filaments 7 μm in diameter were identified in terms of surface coverage, capillary permeation, and penetration through CF filaments. The DoI as a function of pressure and time was obtained from the micro-scale CFD within a range of pressures found in the macro-scale CFD. In the process-scale simulation, the cumulative DoI of the 15 tows was predicted along the impregnation die length with the aid of the micro- and macro-scale CFD results. Combining the multi-scale models gives a potential to predict the uniformity of the transverse resin amount in the final UD-CFP product.

Imaging the 3-D Deformation of the Finger Pad When Interacting with Compliant Materials.

We need to understand the physics of how the skin of the finger pad deforms, and their tie to perception, to accurately reproduce a sense of compliance, or 'softness,' in tactile displays. Contact interactions with compliant materials are distinct from those with rigid surfaces where the skin flattens completely. To capture unique patterns in skin deformation over a range of compliances, we developed a stereo imaging technique to visualize the skin through optically clear stimuli. Accompanying algorithms serve to locate and track points marked with ink on the skin, correct for light refraction through stimuli, and estimate aspects of contact between skin and stimulus surfaces. The method achieves a 3-D spatial resolution of 60-120 microns and temporal resolution of 30 frames per second. With human subjects, we measured the skin's deformation over a range of compliances (61-266 kPa), displacements (0-4 mm), and velocities (1- 15 mm/s). The results indicate that the method can differentiate patterns of skin deformation between compliances, as defined by metrics including surface penetration depth, retention of geometric shape, and force per gross contact area. Observations of biomechanical cues of this sort are key to understanding the perceptual encoding of compliance.

The interaction between BSA and DOTAP at the air-buffer interface

In this article, the interaction between bovine serum albumin (BSA) and the cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) at the air-buffer interface was investigated at different subphase’s pH values (pH = 3, 5 and 10). Surface pressure measurements (π − A) and penetration kinetics process (π − t) were carried out to reveal the interaction mechanism and the dynamical behavior. The data showed that π − A isotherms moved towards larger mean molecular area when the concentration of BSA ([BSA]) increased, the amount of BSA adsorbed onto DOTAP monolayer reached a threshold value at a [BSA] of 5 × 10−8 M, and BSA desorbed from the lipid monolayer as time goes by. The results revealed that the association of BSA with DOTAP at the air-buffer interface was affected by the subphase’s pH value. When pH = 10, the interaction mechanism between them was a combination of hydrophobic interaction and electrostatic attraction, so BSA molecules could be well separated and purified from complex mixtures. AFM images demonstrated that pH value and [BSA] could affect the morphology feature of DOTAP monolayer and the adsorption and desorption processes of BSA. So the study provides an important experimental basis and theoretical support for learning the interaction mechanism among biomolecules in separation and purification of biomolecules and biosensor.