Surface Penetration Research Articles

Functionalized Surface Layer on Poplar Wood Fabricated by Fire Retardant and Thermal Densification. Part 2: Dynamic Wettability and Bonding Strength

In continuation of our former study on a novel combined treatment of nitrogen–phosphorus fire retardant and thermomechanical densification on wood, this study focuses on the dynamic wettability and the bonding strength. The contact angle was measured using the sessile drop method and the surface energy was calculated according to the van Oss method. Water surface penetrating and spreading is analyzed by both the Shi and Gardner model and the droplet volume changing model. The results reveal that the combined treatment increased the surface energy, especially the acid–base component. The contact angle declined and the water droplet spread more easily on the surface. Meanwhile, the rate of relative droplet volume decreased by 32.6% because the surface layer was densified and stabilized by the combined process. Additionally, the surface possesses the lowest roughness and highest abrasion resistance on the tangential section. Thus, the bonding strength of the combined treated poplar decreased by 29.7% compared to that of untreated poplar; however, it is still 53.3% higher than that of 220 °C heat-treated wood.

Improvement of the surface quality and aesthetics of ultra-high-performance concrete

The low moisture content of ultra-high-performance concrete (UHPC) combined with its minimal bleeding leads to quick drying of its exposed surfaces by way of moisture evaporation and self-desiccation. The result is the formation of a rough texture and occasional cracks on the exposed surfaces of UHPC within hours after its placement and finishing. This phenomenon is referred to as ‘elephant skin’ formation. Different strategies were devised and experimentally evaluated for the control of elephant skin formation on exposed UHPC surfaces. These strategies emphasised reduction of the moisture loss from the surface, enhancement of early-age dimensional stability and increase in plastic shrinkage crack resistance. The potential for elephant skin formation was assessed through monitoring of the surface aesthetics, crack area, penetration resistance and temperature under exposure to air flow and radiation. The results indicated that measures that effectively reduce moisture loss from the surface are most effective in controlling elephant skin formation on the exposed surfaces of UHPC.

Direct Nanoscopic Measurement of Laminar Slip Flow Penetration of Deformable Polymer Brush Surfaces: Synergistic Effect of Grafting Density and Solvent Quality.

A detailed quantitative nanoscopic description of soft surfaces under dynamic flow is lacking, despite its importance. To better understand the role of surface texture in nanoscopic mass transport in complex media, we used Förster resonance energy transfer in combination with total internal reflectance fluorescence microscopy (FRET-TIRFM) to directly measure laminar slip flow penetration depth (slip length) on poly(N-isopropylacrylamide) (pNIPAM) thin films (50-110 nm) of different grafting densities (0.60, 0.38, and 0.27 chain/nm2) in solvents of different qualities created via cononsolvency in situ. Nontrivial synergistic interplay of grafting density and solvent quality on slip length was observed. Slip lengths are typically tens of nm (40-100 nm), increasing and then reaching a plateau with applied linear flow velocity (192-2,952 μm/s) regardless of experimental system. Slip length was systematically larger for lower density films, but the effect of grafting density was more significant in a good solvent than a poor solvent. Interestingly, however, the stagnant film thickness (polymer swollen thickness minus the slip length) collapsed to almost a singular value for a given grafting density regardless of solvent quality, likely suggesting a large gradient of segmental mobility at nonequilibrium. Moreover, we found that slip flow penetrates into soft pNIPAM surfaces more deeply in a good solvent than in a poor solvent and that this behavior was general and independent of grafting density. This behavior is counter to the notion that less interaction between a fluid (probe) and a solid surface promotes slip.

Strength Characteristics of Mortar when Applying Silane Type Surface Penetrants at Early Age

Strength Characteristics of Mortar when Applying Silane Type Surface Penetrants at Early Age

Hybrid Soft Soil Tire Model (HSSTM). Part II: Tire-terrain interaction

This is the second of three papers on the HSSTM. Part I introduced the tire structure model. Part III presents the tire model parameterization and validation. Part II describes the computational contact models for evaluating the tire/terrain interaction. Its main objective is to characterize the terrain in the normal and tangential directions during tire-terrain interaction. A contact search algorithm examines tire nodal points close to the ground and detects the penetration of the contact surfaces. Next, the contact interface algorithm applies the contact constraints to minimize or eliminate penetration. For deformable terrain, the algorithms are based on semi-empirical formulations and are implemented using a numerical approach in a 3D scheme. The normal and shear stress distribution simulation results for rigid wheel-soil contact are validated against experimental data. The contact interface algorithm for non-deformable terrains is implemented using a distributed 3D brush model enhanced with a transient module for dynamic manoeuvres.

Surface Penetration without Enrichment: Simulations Show Ion Surface Propensities Consistent with Both Elevated Surface Tension and Surface Sensitive Spectroscopy.

Molecular dynamics was used to investigate ion surface propensities in NaCl, KBr, and CsI solutions with an MP2-based force field. Although NaCl is found to be strongly repelled from the liquid-vapor interface, softer ions, such as I-, penetrate closely to the interface. Despite the surface penetration, the concentration of CsI near the interface is still lower than that in the bulk, thus leading to no surface enrichment. The salt concentration is found to affect relative surface propensities of the ions. More significant surface penetration is observed at higher salt concentrations. Softer ions at higher concentrations form a complex multilayer arrangement that can not be characterized as a simple surface bilayer. The simulated ion distributions explain the spectroscopic evidence of surface perturbation by soft ions with a negative surface excess consistent with an increased surface tension of salt solutions.

Posterior wall acetabular fracture fixation: A mechanical analysis of fixation methods.

Stable, anatomical fixation of acetabular fractures gives the best chance of successful outcome, while penetration of the acetabular articular surface with screws is associated with poor outcomes. Spring plates are an alternative to interfragmentary lag screws when penetration is a concern. A mechanical study comparing fracture stability and construct stiffness of three fixation methods for posterior wall acetabular fractures with transverse comminutions was performed. The three fixation methods tested were a posterior wall rim plate, a posterior wall buttress plate with separate lag screws and a posterior wall plate with two spring plates. Nine samples were tested, three for each fixation method. Two-dimensional motion analysis was used to measure fracture fragment displacement and construct stiffness. After two 6000 cycle-loading protocols, to a maximum 1.5 kN, the mean fracture displacement was 0.154 mm for the rim plate model, 0.326 mm for the buttress plate and 0.254 mm for the spring plate model. Mean maximum displacement was significantly less for the rim plate fixation than the buttress plate (p = 0.015) and spring plate fixation (p = 0.02). The rim plate was the stiffest construct 10,962 N/mm, followed by the spring plate model 5637 N/mm and the buttress plate model 4882 N/mm. Based on data obtained in this study, where possible a rim plate with interfragmentary lag screws should be used for isolated posterior wall fractures as this is the stiffest and most stable construct. When this method is not possible, spring plate fixation is a safe and a superior alternative to a posterior buttress plate method.

Acetabular Subchondral and Cortical Breach During Labral Repair with Suture Anchors: Influence of Portal Location, Curved vs Straight Drill Guides, and Drill Starting Point

Objectives: Acetabular labral tears are commonly treated with arthroscopic repair using suture anchors. Iatrogenic chondral injury has been cited as one of the more common complications during hip arthroscopy, and can occur while pre-drilling for suture anchors. Proposed factors contributing to penetration of the articular subchondral bone or the far cortex of the acetabulum include the portal utilized for drilling; the position of the drill guide relative to the acetabular rim (on rim, ON; off rim, OFF); and the use of straight (ST) versus curved (CU) drill guides. The purpose of this study was to evaluate the relative impact of these variables on drill penetration of the acetabular subchondral bone or the far cortex of the acetabulum. Methods: Sixty sawbone acetabula models were marked at the 3, 2, 1, 12, and 11 o’clock position. A Simulated anterior (AP), anterolateral (AL), and distal anterolateral accessory (DALA) portals were created. Twelve groups of five acetabula were drilled at each clock face position: ST/AP/ON; ST/AL/ON; CU/AP/ON; CU/AL/ON; ST/AP/OFF; ST/AL/OFF; CU/AP/OFF; CU/AL/OFF; ST/DALA/ON; ST/DALA/OFF; CU/DALA/ON; CU DALA/OFF. Perforations of the articular subchondral bone and far cortex of the acetabulum were recorded. Results were tabulated and analyzed to assess the relative impact of each variable both in aggregate and at each position on the clock face. Results: A total of 300 acetabular suture anchor drill holes were created on 60 acetabula 12 combinations of portal utilized (anterior, anterolateral, distal anterolateral accessory), drill guide type (curved or straight), and rim position (on rim, off rim). A total of 38/300(12.7%) drillings perforated the subchondral bone, and 45/300(15%) breach the far cortex. Drilling from the AP, AL, and DALA portal breached the articular subchondral bone 21/100 (21%), 17/100(17%), and 0/100(0%) respectively; and breached the far acetabular cortex 36/100(36%), 1/100(1%), and 8/100(8%) respectively. Drillings using a curved drill guide penetrated the subchondral bone on 14/150(9.3%) attempts and drillings using a straight drill guide penetrated the subchondral bone 33/150(22%) attempts (p=0.0025). Drillings with an “On Rim” start point breached the articular subchondral bone 29/150(19.3%) versus 9/150(6%) for drillings with an “Off Rim” start point; and breached the far acetabular cortex 21/150(14%) times versus 24/150(16%) times. Articular surface penetrations were most frequent at the 2 and 3 o’clock positons, and far cortex perforations were most frequent at the 11 and 12 o’clock positions. Conclusion: This study quantifies the relative impact of portal location, drill guide, and starting point on the acetabular rim on acetabular subchondral bone and far cortex penetration. Portal location had the highest impact, with the DALA portal noted to be the safest. Curved drill guides also reduced the number of acetabular subchondral bone penetrations. These findings can be used to influence arthroscopic technique during acetabular labral repair.

Toxicity of perfluorinated compounds to soil microbial activity: Effect of carbon chain length, functional group and soil properties

Perfluorinated compounds (PFCs) have been detected at various concentrations in different environment compartments due to their widespread usage. Nowadays, soil environment has become a prominent sink of PFCs from surface runoff and penetration, but few researches have been conducted in the toxicity of PFCs to soil microorganisms. To address the issue, microcalorimetry was applied to investigate the toxicity of six PFCs with different carbon chain length (4, 8, and 10) and functional group (carboxylic and sulfonic) to microbial activities in three Chinese soils varying widely in soil properties. Adsorption of PFCs by soil matrix was a key factor in controlling the toxicity of PFCs to soil microorganisms. The differences of carbon chain length and functional groups of PFCs have different impacts on soil microbial activity while affecting adsorption progress. Particularly, the sulfonic PFCs expressed higher toxicity than the carboxylic. It is also identified that the longer the chain length, the greater the toxicity of PFCs. Soil pH was another relevant factor of soil adsorption, and with the increase of pH, adsorption capability increased. Soil available P, N and K were essential nutrients in soil, and suggested to improve microbial activity under PFCs stress.

Prediction of damage due to impact for composites on the basis of possible impact threats

This paper proposes an analytical model capable of relating damage found on a composite plate to a given impactor characteristic (size and energy). The model addresses a gap in knowledge regarding the types of damages to be expected over the lifetime of a new generation of composite aircraft. The damage type and dimensions are estimated using a superposition of local indentation and global plate deflection. The analytical approach, validated by drop-weight experiments, uniquely uses the impact characteristics predicted from metal aircraft damages as inputs to model the impact event response for composite plates under the same impact event conditions. The case study demonstrates that impact data from metal aircraft can be used to anticipate damage for a composite aircraft. The results from the model indicate that of the impactors that previously damaged metal aircraft, 75% will cause surface dent damage, fibre breakage, or penetration. As an extension of the analytical model application, a risk assessment is conducted on the predicted impactors, incorporating maintenance cost as the primary indicator for event consequences. This assessment shows the risks the similar events pose on metal vs. a comparable composite structure and allows aircraft operators to anticipate and plan maintenance actions.

Ethosomes: Transdermal Drug Delivery System

The skin is one of the most extensive and readily accessible organs of the human Body. One of the greatest disadvantages to transdermal drug delivery is the skin's low permeability that limits the number of drugs that can be delivered in this manner. Ethosomes as novel vesicles in transdermal drug delivery show significant effects on drug penetration through the biological membrane. Now-a-days we better know vesicles have importance in cellular communication. Ethosomes, Although ethosomes are conceptually sophisticated, they are simple inpreparation and safe for use. Transdermal route is promising alternative to drug delivery for systemic effect. An attempt was made to formulate the highly efficient ethosomal drug delivery system and enalapril meleate is used as model drug. Ethosomes have higher penetration rate through the skin as compared to liposomes hence these can be used widely in place of liposomes. Ethosomes enhanced skin permeation, improved drug delivery, increased drug entrapment efficiency etc Ethosomes have become an area of research interest, because of its enhanced skin permeation, improved drug delivery, increased drug entrapment efficiency etc. The purpose of writing this review on ethosomes drug delivery was to compile the focus on the various aspects of ethosomes including their mechanism of penetration, preparation, advantages, composition, characterization, application and marketed product of ethosomes. Characterizations of ethosomes include Particle size, Zeta potential, Differential Scanning Calorimertry, Entrapment efficiency, Surface tension activity measurement, Vesicle stability and Penetration Studies etc. Keywords: Transdermal Drug Delivery System, Ethosomes, Drug absorption

Tillage effect on hydrophobicity and hydrological properties of oil-contaminated sediments in a hyper-arid region

A crude oil spill in 2014 led to the contamination of an extensive area in the Evrona Nature Reserve at the hyper-arid Arava Valley of Israel. In 2015, as a part of the restoration efforts, the oil-polluted braided ephemeral stream channels underwent a single session of tillage, to a depth of 10 cm. The rationale of this treatment was to break the hard, impermeable crust of the residual oil, aiming to reduce soil hardness and water repellency, and to improve the hydrological properties of the soil. In 2017, a study was conducted to assess the effect of chiseling tillage on the soil's hydrophobicity, mechanical strength, and infiltration capacity. Water drop penetration time, critical surface tension, penetration resistance, and near-saturated hydraulic conductivity were measured on-site, at depths of 0, 5, and 10 cm in contaminated-tilled, contaminated-non-tilled, and clean plots. We found that at the ground surface, tillage had a slight and non-significantly positive effect on the nearly-saturated hydraulic conductivity and a negative effect on the penetration resistance, while no improvement was recorded for the other properties. Further, some of these properties were inferior in the contaminated-tilled sediments compared to those in the contaminated-non-tilled sediments, an effect that could be attributed to the: (1) tillage-induced inversion of the most polluted surface layer into the sub-soil, (2) absence of a clayey sublayer, and (3) limited oil degradation due to the extremely dry conditions. Therefore, the results indicate that tillage is not an effective practice for restoring oil-polluted soils and sediments in hyper-arid regions.

Reanalysis Validates Soil Health Indicator Sensitivity and Correlation with Long‐term Crop Yields

Core Ideas Soil health metrics were sensitive in North Carolina soils. Tillage intensity and fertility practices were especially differentiated by biological soil health metrics. Soil health metrics associated with labile organic matter correlated well with crop yields. Soil health (SH) refers to the ability of a soil to function and provide ecosystem services. This study reanalyzes data from long‐term agronomic management experiments in North Carolina and addresses previous conclusions regarding the utility of SH test metrics. Data for 15 SH indicators in the Comprehensive Assessment of Soil Health (CASH) framework from three long‐term trials in North Carolina were analyzed to assess effects of tillage intensity and organic vs. conventional management. This included four soil biological indicators—organic matter (OM), active carbon (ActC), respiration (Resp), and protein (Prot); four soil physical indicators—available water capacity (AWC), water‐stable aggregation (Agstab), surface and subsurface penetration resistance (SurfHard, SubHard); and seven soil chemical (fertility) indicators (P, K, Mg, Fe, Mn, Zn, pH). Corn (Zea mays L.) and soybean (Glycine max L. Merr.) yield data and SH indicator values were correlated using site‐specific and multi‐site datasets. Long‐term management practices most commonly showed significant impacts with AgStab (up to 2.2′), ActC (2.1′), Prot (2.3′), and most chemical indicators. Tillage intensity had a greater impact than organic vs. conventional management and linear regression of multi‐year mean corn and soybean yield response to tillage showed significant correlations with eight SH indicators, highest among them ActC, Protein, Resp, and Mn (R2 = 0.85–0.93). Contrary to previous conclusions, CASH indicators, especially those related to labile C and N, responded well to management practices and showed utility for SH assessment in agronomic trials.

Surface modification on MoO2+x/Mo(110) induced by a local electric potential

Oxygen adatoms on the MoO2+x/Mo(110) surface are observed to be removed when a sufficiently large bias is applied between the scanning tunneling microscope tip and the surface. Experimental observations, such as the bias polarity dependence of adatom removal and the observation of an intermediate state, indicate that the adatom penetrates the surface oxide layer. Through the comparison of finite element method simulations with various experimental relationships, the electric field is concluded to be the sole contributor to adatom penetration into the surface oxide layer. The energetic barrier to this process is estimated to be approximately 0.45 eV in magnitude. Furthermore, the resolution of this phenomenon is on the atomic scale: individual adatoms can undergo surface penetration whilst their nearest neighbour adatoms, separated by 5 Å, are unaffected. The mechanism reported here has the advantages of not strongly influencing the substrate and is exceptionally localised, which can be beneficial for the synthesis of single atom devices.

Nonlinear vibration of crowned gear pairs considering the effect of Hertzian contact stiffness

This study aims to analyze the influence of lead crowning modification of teeth on the vibration behavior of a spur gear pair. Two dynamic rotational models including an uncrowned and crowned gear are examined. Hertzian mesh stiffness is computed using tooth contact analysis in quasi-static state along a complete mesh cycle of teeth mesh. The dynamic orbits of the system are observed using some useful attractors which expand our understanding about the influence of crown modification on the vibration behavior of the gear pair. Nonlinear impact damper consists of non-integer compliance exponents identify energy dissipation of the system beneath the surface layer. By augmenting tooth crown modification, the surface penetration increases and consequently normal pressure of the contact area becomes noticeable. Finally, the results show modification prevents gear pair to experience period doubling bifurcation as the numerical results proved. Using this new method in dynamic analysis of contact, broaden the new horizon in analyzing of the surface of bodies in contact.

The influence of terpinen-4-ol and eucalyptol – The essential oil components - on fungi and plant sterol monolayers

Antifungal and herbicidal activity of terpenes, being the components of the essential oils, is directly related to the incorporation of these compounds into cellular membranes. Thus, the differences in the lipid composition of various pathogenic membranes may be the factor determining the activity of these molecules. One of the class of lipids, which form the membrane environment are sterols. The aim of this work was to compare the effect of two terpenes: terpinen-4-ol and eucalyptol on the monolayers formed by ergosterol and β – sitosterol, which are the components of fungi and plant membranes, respectively. The modifications in the sterol monolayer properties were investigated in the surface pressure-area measurements and penetration studies as well as in a micrometer scale (Brewster angle microscopy experiments) and in nanoscale (GIXD technique). It was evidenced that although at higher surface pressure the terpene molecules are in part removed from the interface, they are able to substantially modify the condensation, morphology and molecular organization of the sterol film. It was also found that the incorporation of terpenes into sterol films is comparable for both sterols, however, β – sitosterol monolayers properties are affected more strongly than ergosterol films. Finally, the analysis of the results of the studies performed on model membrane systems and the results of antimicrobial studies reported in literature, enabled us to suggest that the activity of terpenes depends on the membrane composition and that the sterol concentration may be important from the point of view of antifungal effect of terpinen-4-ol and eucalyptol.

Laboratory and Greenhouse Evaluation of a Granular Formulation of Beauveria bassiana for Control of Western Flower Thrips, Frankliniella occidentalis.

Western flower thrips (WFT) is one of the most important pests of horticultural crops worldwide because it can damage many different crops and transmit various plant viruses. Given these significant impacts on plant production, novel methodologies are required to maximize regulation of WFT to minimize crop losses. One particular approach is to develop control strategies for the non-feeding, soil-dwelling stages of WFT. Control of these stages could be enhanced through the use of granules impregnated with entomopathogenic fungi mixed in the soil. The use of soil-applied fungi contrasts with existing approaches in which entomopathogenic fungi are formulated as oil-based suspensions or water-based wettable powders for foliar applications against the feeding stages of WFT. To examine the efficacy of this approach, we evaluated the effects of a granular formulation of Beauveria bassiana on the soil-dwelling, pupal phases of Frankliniella occidentalis in laboratory bioassays and greenhouse experiments. Based on micromorphological observations of fungal conidia during the infection process after treatment of WFT with a B. bassiana suspension, fungal conidia complete the process of surface attachment, germination, and penetration of the body wall of the WFT pupa and enter the host within 60 h of treatment. Given these results, we undertook a controlled greenhouse experiment and applied B. bassiana granules to soil used to cultivate eggplants. Populations of F. occidentalis on eggplants grown in treated soil were 70% lower than those on plants grown in the untreated soil after 8 weeks. Furthermore, when measuring the survival and growth of B. bassiana on granules under different soil moisture conditions, survival was greatest when the soil moisture content was kept at 20%. These results indicate that the application of B. bassiana-impregnated granules could prove to be an effective biological control strategy for use against F. occidentalis under greenhouse conditions.

PolyGlcNAc-containing exopolymers enable surface penetration by non-motile Enterococcus faecalis.

Bacterial pathogens have evolved strategies that enable them to invade tissues and spread within the host. Enterococcus faecalis is a leading cause of local and disseminated multidrug-resistant hospital infections, but the molecular mechanisms used by this non-motile bacterium to penetrate surfaces and translocate through tissues remain largely unexplored. Here we present experimental evidence indicating that E. faecalis generates exopolysaccharides containing β-1,6-linked poly-N-acetylglucosamine (polyGlcNAc) as a mechanism to successfully penetrate semisolid surfaces and translocate through human epithelial cell monolayers. Genetic screening and molecular analyses of mutant strains identified glnA, rpiA and epaX as genes critically required for optimal E. faecalis penetration and translocation. Mechanistically, GlnA and RpiA cooperated to generate uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) that was utilized by EpaX to synthesize polyGlcNAc-containing polymers. Notably, exogenous supplementation with polymeric N-acetylglucosamine (PNAG) restored surface penetration by E. faecalis mutants devoid of EpaX. Our study uncovers an unexpected mechanism whereby the RpiA-GlnA-EpaX metabolic axis enables production of polyGlcNAc-containing polysaccharides that endow E. faecalis with the ability to penetrate surfaces. Hence, targeting carbohydrate metabolism or inhibiting biosynthesis of polyGlcNAc-containing exopolymers may represent a new strategy to more effectively confront enterococcal infections in the clinic.

Nondestructive Testing of Nonmetallic Pipelines Using Microwave Reflectometry on an In-Line Inspection Robot

Microwave and millimeter-wave reflectometry, a form of continuous-wave surface penetrating radar, is an emerging nondestructive inspection technique that is suitable for nonmetallic pipelines. This paper shows a $K$ -band microwave reflectometry instrument implemented onto an in-line pipe-crawling robot, which raster-scanned cracks and external wall loss on a high-density polyethylene (HDPE) pipe of diameter 150 mm and wall thickness 9.8 mm. The pipe was scanned with three environments surrounding the pipe that approximated the use cases of overground HDPE pipelines, plastic-lined metal pipes, and undersea HDPE pipelines. The instrument was most sensitive when cracks were oriented parallel to its magnetic (H) plane. Any small variation in the standoff distance between the instrument’s probe antenna and the pipe wall, which was not easy to avoid, was found to obscure the image. To mitigate this problem, a sensitivity analysis showed that an optimal frequency can be chosen at which standoff distance can vary by up to ±0.75 mm within a certain range without distorting the indications of defects on the image.

Increasing keyhole stability of fiber laser welding under reduced ambient pressure

Bead-on-plate laser welding was performed, and the inner keyhole behavior was observed through a transparent glass using a high-speed camera at various ambient pressures. The keyhole stability was investigated with respect to the keyhole profile area and keyhole depth using image processing. The keyhole states at atmospheric pressure and vacuum were compared according to the pressure balance at the keyhole wall. The weld surface quality and penetration depth improved with decreasing ambient pressure. The keyhole stability was also sensitive to the ambient pressure. The keyhole oscillated and collapsed periodically at atmospheric pressure (101 kPa), whereas it was stable under vacuum.