Surface Rugosity Research Articles

Cathode Surface Morphology Effects on Field Emission: Vacuum Breakdown Creation of Field Emitters

The effect of stainless steel cathode surface morphology on field electronic emission in high vacuum (~10 -5 Pa) is studied. The surface rugosity is shown to affect the emission intensity; high-aspect ratio surface features lead to locally enhanced electric field, thereby increasing the field electronic emission. A breakdown in the vacuum, caused either by impact of charged dust particles or other impurities, or by overheating and vaporization of field emitters, can lead to cratering on the cathode surface. This cratering drastically changes the local surface rugosity, enhancing the local field and leads to greater emission intensity. Treatment of the cathode surface by glow discharge at higher pressure is known to reduce field emission by ionic bombardment and sputtering of emission sites; an image of such a glow-type discharge in the same apparatus used to study field emission is presented.

Effects of different factors on stickiness of apple leathers

Apple leathers (ALs) are restructured food products made by dehydration of a thin layer of apple puree, resulting in a thin and flexible sheet. AL are composed mainly by low-weight carbohydrates which are highly hygroscopic, so AL become sticky when stored at ambient relative humidity (RH). Stickiness in food could be considered as a negative or positive aspect. In this work, four factors affecting stickiness of AL were studied (ingredients, RH, surface rugosity and compression time), both to decrease and to increase it. Surface rugosity of AL had the greatest impact on stickiness, being the smoothest side stickier than the roughest side. The RH at which AL were conditioned and the ingredients used in this work also had a great influence on the adhesion force. In this manner, stickiness can be modified (increasing or decreasing) according to the specific requirements for using AL in different applications.

Spontaneous Inertial Imbibition in Porous Media Using a Fractal Representation of Pore Wall Rugosity

Considering the separable phenomena of imbibition in complex fine porous media as a function of timescale, it is noted that there are two discrete imbibition rate regimes when expressed in the Lucas–Washburn (L–W) equation. Commonly, to account for this deviation from the single equivalent hydraulic capillary, experimentalists propose an effective contact angle change. In this work, we consider rather the general term of the Wilhelmy wetting force regarding the wetting line length, and apply a proposed increase in the liquid–solid contact line and wetting force provided by the introduction of surface meso/nanoscale structure to the pore wall roughness. An experimental surface pore wall feature size regarding the rugosity area is determined by means of capillary condensation during nitrogen gas sorption in a ground calcium carbonate tablet compact. On this nano size scale, a fractal structure of pore wall is proposed to characterize for the internal rugosity of the porous medium. Comparative models based on the Lucas–Washburn and Bosanquet inertial absorption equations, respectively, for the short timescale imbibition are constructed by applying the extended wetting line length and wetting force to the equivalent hydraulic capillary observed at the long timescale imbibition. The results comparing the models adopting the fractal structure with experimental imbibition rate suggest that the L–W equation at the short timescale cannot match experiment, but that the inertial plug flow in the Bosanquet equation matches the experimental results very well. If the fractal structure can be supported in nature, then this stresses the role of the inertial term in the initial stage of imbibition. Relaxation to a smooth-walled capillary then takes place over the longer timescale as the surface rugosity wetting is overwhelmed by the pore condensation and film flow of the liquid ahead of the bulk wetting front, and thus to a smooth walled capillary undergoing permeation viscosity-controlled flow.

Pore wall rugosity: The role of extended wetting contact line length during spontaneous liquid imbibition in porous media

Considering the separable phenomena of imbibition in complex fine porous media as a function of timescale, it is noted that there are two discrete imbibition rate regimes when expressed as a function of the square root of time using the traditional Lucas–Washburn equation. Commonly, to account for this deviation from uniform absorption into a single equivalent hydraulic capillary, many experimentalists propose an effective contact angle change. Such an assumption, however, challenges the consistency of constant surface energy and is difficult to justify physically. In this work, we consider rather the general term of the Wilhelmy wetting force in respect to the Washburn wetting line length, and apply a proposed increase in the liquid–solid contact line length provided by the introduction of surface meso and nanoscale rugosity in respect to the pore wall roughness. The experimental characteristic wetting line length is here defined via a relation between capillary condensation area, as measured independently using nitrogen gas (BET surface area determination plus BJH hysteresis analysis), and an equivalent capillary length containing the known saturation absorbed liquid volume. This model, constructed by applying the extended wetting contact line length to the equivalent hydraulic capillary observed at the longer timescale II imbibition, is applied for the initial timescale I imbibition rate whilst keeping the imbibition volume of the equivalent capillary tube constant. The longer timescale II imbibition is then subsequently defined traditionally by the smooth-walled equivalent hydrodynamic capillary, in which the surface rugosity is prefilled via a precursor liquid film supported further by liquid vapour condensation within the pore wall surface meso/nano-roughness. This two-stage model is compared with experimental liquid absorption data from a ground calcium carbonate porous compact and shown to provide good agreement. Using this concept, it is possible to unite the process of imbibition in complex porous media with a single equivalent hydraulic radius and an experimentally justified extended wetting line length to predict the imbibition rate of porous media on both the initial and longer timescales in cases where the imbibed liquid mass is low and the nano and microcapillary pressure of fine pore media far exceeds the effect of gravity.

Surface charges of oxides and wettability: Application to TiO2–SiO2 composite films

The super-hydrophilicity which can exist at the interface between oxides and aqueous solutions is able to sustain industrial and domestic applications. Several experimental results obtained on TiO2–SiO2 composite thin films via a sol–gel route have confirmed a natural and persistent super hydrophilicity under standard atmosphere. This property can be easily photo-regenerated after a long aging period in ambient atmosphere using a short UV illumination. The electrochemical double layer which classically exists between oxide surfaces and aqueous solution is unfavorable to high wettability properties of ideal flat surfaces. The present study indicates how the surface rugosity and the disjoining pressure caused by surface charges are able to explain the stability of a prewetting film. This film can withstand to vaporization in a weakly under saturated atmosphere, having a protective action despite a carbon contamination brought by standard atmosphere.

Classification of blocker and non-blocker of hERG potassium ion channel using a support vector machine

The human ether-a-go-go related gene (hERG) channel is responsible for the repolarization during the action potential, and blockage of that may result in severe cardiotoxicity and sudden death. In this study, a dataset containing 1969 compounds was compiled from literature and FDA-approved drugs. Using a support vector machine (SVM), two groups of computational models were built to distinguish whether a compound is a blocker or non-blocker of hERG potassium ion channel. These models fit generally satisfactory. The 100 models built with MACCS fingerprints (Model Group A) showed an average accuracy of 90% and an average matthews correlation coefficient (MCC) value of 0.77 on the test sets. The 100 models built with selected MOE descriptors (Model Group B) showed an average accuracy of 89% and an average MCC value of 0.74 on the test sets. Molecular hydrophobicity and lipophilicity were found to be very important factors which lead to block the hERG potassium ion channel. Some other molecular properties such as electrostatic properties, features based on van der Waals surface area, the number of rigid bonds and molecular surface rugosity also played important roles in blocking hERG potassium ion channel.

Methodology for the evaluation of 3D surface topography in multiple indentation processes

Elementary indentation processes are relatively simple compression processes and they are quite extended in many fields of the industry. Nevertheless, the concatenation of these processes is a new approach and has interest from a technological point of view. Incremental forming processes can be carried out in CNC machines with more flexibility, lower force requirements and simpler tools than in conventional forging processes. The purpose of this work is the analysis of the three-dimensional geometry resulting from the multiple indentation process. Based on the surface rugosity parameters defined in the specification standard ISO 4287, the state of the 3D-formed surface by several types of tools is studied and a predictive evaluation model has been developed in order to quantify, by means of shape parameters Sa and SM, the topography of the expected surface and the amount of material displaced depending on the technological and geometrical characteristics of the process.

Benefits of oxygen and nitrogen plasma treatment in Vero cell affinity to poly(lactide-co-glycolide acid)

Cell adhesion on materials surface is critical because this phenomenon occurs before other events, as cell spreading, cell migration and cell differentiation. it is commonly accepted that the adhesion of cells on solid substrate is influenced by several substratum surface properties, such as wettability, surface charge, roughness and topography. plasma technique is a convenient method for modifying surface properties of materials without affecting physical properties. in this study, poly(lactide-co-glycolide), plga, membranes were modified by oxygen and nitrogen plasma to improve polymer hydrophilicity and verify their effect on vero cells culture. the plga membranes, which were characterized by sem and contact angle, showed increased surface rugosity and narrower contact angles. cell adhesion, cytotoxicity assay, sem and cytochemistry analysis showed that plasma treatment was beneficial to cell growth by improving cell-polymer interaction. Cell adhesion on materials surface is critical because this phenomenon occurs before other events, as cell spreading, cell migration and cell differentiation. It is commonly accepted that the adhesion of cells on solid substrate is influenced by several substratum surface properties, such as wettability, surface charge, roughness and topography. Plasma technique is a convenient method for modifying surface properties of materials without affecting physical properties. In this study, poly(lactide-co-glycolide), PLGA, membranes were modified by oxygen and nitrogen plasma to improve polymer hydrophilicity and verify their effect on Vero cells culture. The PLGA membranes, which were characterized by SEM and contact angle, showed increased surface rugosity and narrower contact angles. Cell adhesion, cytotoxicity assay, SEM and cytochemistry analysis showed that plasma treatment was beneficial to cell growth by improving cell-polymer interaction.

Phenotypic plasticity of primary thallus in selected Cladonia species (lichenized Ascomycota: Cladoniaceae)

The paper presents the results of comprehensive analyses concerning the phenotypic variability of the primary thallus in five chosen Cladonia species in relation to habitat conditions. Morphology and anatomy, as well as the cortex ultrasculpture, of primary squamules were examined in individual specimens from sunny and shady populations of each species. The Mann-Whitney U test and Principal Component Analysis (PCA) revealed several clear correlations between the type of habitat and the organisation of squamules. Significant differences refer mainly to anatomical features, especially to epinecral layer frequency and cortex thickness. On the contrary, examination of the surface ultrasculpture of squamules under SEM did not show any important differences between populations. Regardless of the habitat factors, a full range of cortical surface rugosity in samples from both habitats was noticed, and a high variability often refers to a singular squamule. The results indicate that some features are largely modified by environmental factors and/or depend on the development stage of individual specimens, and examination of these relationships should be the first step towards the evaluation of the taxonomic usefulness of the considered features.

XPS Analysis of AlGaN/GaN Surface after Chemical and N-Containing Plasma Treatments

The effects of chemical treatment and nitride based plasma on an AlGaN/GaN heterostructure surface are investigated by XPS analyses. Different chemical treatments were evaluated in order to reduce the surface oxide, while N-based plasma treatments such as in-situ N2 and NH3, as well as decoupled forming gas plasmas were tested for nitridation effect on the surface. A 10% NH4OH solution proved to be the most efficient in removing surface oxides, with residual Ga oxides as low as 3% and Al oxides below the XPS detection limit. In terms of nitridation, a 500W decoupled forming gas plasma at 150{degree sign}C and a 50W N2 in-situ plasma at 350{degree sign}C increased drastically the N-presence at the surface, up to three times its original level. The nitride plasma also proved to be efficient in removing overall carbon contamination, as well as diminishing the surface rugosity.

Quantum excitation spectrum of hydrogen adsorbed in nanoporous carbons observed by inelastic neutron scattering

Inelastic neutron scattering spectra have been collected over a wide range of momentum transfer from H2 adsorbed in several high-porosity carbon substrates. We show theoretical spectra which consider the relationship between rotational and translational transitions in the highly anisotropic adsorption environment, proving that different rotational excitations contain different amount of recoil broadening and motivating a new analysis method which considers both types of transitions at once. Spectra for most of the samples, including two activated carbons, are very similar to one another, supporting models of nanoporous carbons which are quite similar on the sub-nanometer scale. The exception is the low-energy side of the rotational peak, indicating important differences in the initial distribution of motion. We also find more subtle differences in the spectra which may be linked to differences in sample heterogeneity and surface rugosity. One sample does have a very different spectrum, which is not explained by standard models of this system. We also observe a significantly reduced effective mass in the spectrum of recoil transitions and evidence of coupling of rotational and translational motion resulting from periodic variations in orientation of the rotational states.

Determination of Important Topographic Factors for Landslide Mapping Analysis Using MLP Network

Landslide is one of the natural disasters that occur in Malaysia. Topographic factors such as elevation, slope angle, slope aspect, general curvature, plan curvature, and profile curvature are considered as the main causes of landslides. In order to determine the dominant topographic factors in landslide mapping analysis, a study was conducted and presented in this paper. There are three main stages involved in this study. The first stage is the extraction of extra topographic factors. Previous landslide studies had identified mainly six topographic factors. Seven new additional factors have been proposed in this study. They are longitude curvature, tangential curvature, cross section curvature, surface area, diagonal line length, surface roughness, and rugosity. The second stage is the specification of the weight of each factor using two methods. The methods are multilayer perceptron (MLP) network classification accuracy and Zhou's algorithm. At the third stage, the factors with higher weights were used to improve the MLP performance. Out of the thirteen factors, eight factors were considered as important factors, which are surface area, longitude curvature, diagonal length, slope angle, elevation, slope aspect, rugosity, and profile curvature. The classification accuracy of multilayer perceptron neural network has increased by 3% after the elimination of five less important factors.

Strength improvement of mortar composites reinforced with newly hybrid-blended fibres: Influence of fibres geometry and morphology

Acrylic and recently developed polypropylene/polyethylene (PP/PE) blended fibres were investigated as reinforcement on mechanical properties of cementitious mortar. The influences of structural and morphological properties of fibres have been studied by evaluating several parameters (for example, FIER- fibre intrinsic efficiency ratio, aspect ratio, cross-section area and shape). The PP/PE blended fibre reinforced composites (HyFRCs) evidenced the most promising mechanical performances. Enhancements of 38±2% on compressive and 40±1% flexural strengths were achieved for HyFRC systems reinforced with a fibre volume as high as 2.9%. Morphological observations evidenced strong mechanical interactions between fibres and the cement matrix, similar to the chemical/mechanical interactions observed for polyacrylonitrile reinforced composites (PANFRCs). These strong fibre/cement interface interactions were attributed to a combined effect of different factors: fibres’ surface rugosity, unusually high cross-section area, lower aspect ratio (50times lower than a similar PAN length fibre), higher FIER and their self-fibrillation ability during mortar mixing. These factors promoted better fibre/cement anchoring, and led to more effective fibre-reinforcement effects, such as, a higher post-cracking fibre effect of composites subjected to mechanical stresses.

Vortex state in a mesoscopic flat disk with rough surface

In this paper we study some superconducting properties of a flat disk by taking into account the roughness of the surface. Also, the sample is surrounded by a thin layer of a metallic material and submitted to and external magnetic field applied perpendicular to its plane. The boundary condition is taking into account via the de Gennes extrapolation length b. We evaluate the Gibbs free energy, magnetization, vorticity, the first and second critical thermodynamical fields as a function of the external magnetic field and b parameter. We also evaluate the first critical field as a function of the surface rugosity.

Effect of surface coating and finish upon the cleanability of bed rails and the spread of Staphylococcus aureus

Bacterial reservoirs in the near-patient environment are likely vectors of healthcare-acquired infection. To conduct a laboratory-based study to confirm a previous clinical finding of higher numbers of bacteria on plastic than on painted steel bed rails. Six different surfaces were inoculated with Staphylococcus aureus suspended in a range of synthetic soils. Aerobic colony counts and ATP bioluminescence were used to assess the efficacy of cleaning with microfibre cloths and antibacterial wipes. The ease with which S.aureus was transferred between fingertips and each bed rail was also investigated. Antibacterial wipes reduced bacterial numbers to below detectable levels on all rails but were less effective than microfibre cloths in removing organic debris. Surfaces that were comparatively easy to clean were more likely to transfer S.aureus on contact. If inadequately disinfected these rails could pose the greatest risk in terms of cross-transmission. In the absence of contaminating soil, bacterial transfer from fingertips to rail ranged from 38% to 64%. Transfer from rail to fingertip ranged from 22% to 38%. Surface material and rugosity were important factors in determining cleanability and transfer rate. However, the presence of organic soils affected bacterial transfer from all bed rails regardless of material or finish. Bed rails can become heavily contaminated. Regular wiping with antibacterial wipes could be a cost-effective means of maintaining low numbers of bacteria near to the patient. To minimize the risk of cross-transmission, cleaning protocols should be validated to ensure effective removal of microbial and non-microbial surface contamination.

Rafting on abiotic substrata: properties of floating items and their influence on community succession

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 439:1-17 (2011) - DOI: https://doi.org/10.3354/meps09344 FEATURE ARTICLERafting on abiotic substrata: properties of floating items and their influence on community succession Macarena Bravo1, Juan Carlos Astudillo1, Domingo Lancellotti1, Guillermo Luna-Jorquera1,2, Nelson Valdivia2,3, Martin Thiel1,2,* 1Facultad de Ciencias de Mar, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile 2Centro de Estudios Avanzados en Zonas Aridas (CEAZA), Coquimbo, Chile 3Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, Chile *Email: thiel@ucn.cl ABSTRACT: A wide diversity of organisms is dispersed on abiotic floating substrata, but little is known about the succession of fouling communities on these items. The main abiotic floating items found in the oceans (volcanic pumice, plastics, and Styrofoam) differ in 3 principal characteristics, namely surface rugosity, buoyancy, and floating behaviour, confirmed herein by light and electron microscopy (SEM), measurements of buoyancy, and laboratory tests to determine floating stability. In order to examine how these properties affect colonization and community succession on these substrata, 3 experiments were conducted in the field for 14 wk: (1) substrata were permanently submerged to determine if colonization depends on substratum surface (‘Rings’ experiment); (2) substrata were tethered at the sea surface to examine the importance of buoyancy (‘Lines’ experiment); and (3) substrata were caged to test the role of their floating behaviour (‘Cages’ experiment). The most common colonizers in all 3 experiments were diatoms, Ulvales, and clonal ascidians from the genus Diplosoma. Surface rugosity of the substrata had only minor effects on the taxonomic richness of the developing communities. Buoyancy caused some differences in taxon cover, but taxon richness was similar on all 3 substrata. Finally, the floating behaviour at the sea surface had a strong influence on the communities developing on the floating substrata. Plastics (fewest changes in position) presented a higher richness and cover of taxa, while Styrofoam (most positional changes) harboured very few taxa. We conclude that colonization and succession on floating substrata is strongly influenced by positional changes, while surface rugosity and buoyancy appear important only during initial stages of community succession. KEY WORDS: Rafting · Abiotic substrata · Surface rugosity · Buoyancy · Floating behaviour · Fouling Full text in pdf format Information about this Feature Article Supplementary material NextCite this article as: Bravo M, Astudillo JC, Lancellotti D, Luna-Jorquera G, Valdivia N, Thiel M (2011) Rafting on abiotic substrata: properties of floating items and their influence on community succession. Mar Ecol Prog Ser 439:1-17. https://doi.org/10.3354/meps09344Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 439. Online publication date: October 20, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

About the Cover.

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCoverThe cover image shows a large Antarctic isopod (Glyptonotus antarcticus) crawling on an ice-encrusted sponge (Homaxinella balfourensis) in the shallow water adjacent to McMurdo Station in the Ross Sea, Antarctica. Sea ice typically forms at the ocean's surface, but given a source of exceptionally cold water, an unusual form of ice—anchor ice—can grow on benthic objects such as this sponge. For several decades, ecologists have considered anchor ice to be an important agent of disturbance in the shallow-water benthic communities in McMurdo Sound and potentially elsewhere in polar seas. The presence of anchor ice coincides with reduced abundance of sponges, which provide habitat for a diverse assemblage of benthic organisms. However, the mechanism of the presumed preferential disturbance of sponges by anchor ice has not been explored.At a typical salinity of 33 psu, it is thermodynamically favorable for seawater at its freezing point (–1.81 °C) to transition from its liquid phase to ice, its solid phase. However, just because it is thermodynamically favorable for seawater to freeze does not ensure that the transition from seawater to ice takes place spontaneously. Under circumstances that occur periodically in McMurdo Sound, water can be cooled below its freezing point (supercooled), priming it to solidify as anchor ice on the first organism it encounters.In this issue, Denny et al. (pages 155 to 163) report differences in how various species of Antarctic benthic organisms form and propagate anchor ice. The sponges H. balfourensis and Suberites caminatus are more likely than urchins and sea stars to form ice crystals, and the spread of the crystals occurs more quickly. These differences may explain the disturbance patterns observed in shallow polar benthic communities. Interspecific differences in ice formation raise questions about how surface tissue characteristics such as surface area, rugosity, and mucus coating affect ice formation on invertebrates.Credits: Cover photo: Stephen Wing, University of Otago, Department of Marine Science; cover design, Beth Liles, Marine Biological Laboratory. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 221, Number 2October 2011 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/BBLv221n2cover © 2011 by Marine Biological Laboratory. All rights reserved.PDF download Crossref reports no articles citing this article.

Anchor Ice and Benthic Disturbance in Shallow Antarctic Waters: Interspecific Variation in Initiation and Propagation of Ice Crystals

Sea ice typically forms at the ocean's surface, but given a source of supercooled water, an unusual form of ice--anchor ice--can grow on objects in the water column or at the seafloor. For several decades, ecologists have considered anchor ice to be an important agent of disturbance in the shallow-water benthic communities of McMurdo Sound, Antarctica, and potentially elsewhere in polar seas. Divers have documented anchor ice in the McMurdo communities, and its presence coincides with reduced abundance of the sponge Homaxinella balfourensis, which provides habitat for a diverse assemblage of benthic organisms. However, the mechanism of this disturbance has not been explored. Here we show interspecific differences in anchor-ice formation and propagation characteristics for Antarctic benthic organisms. The sponges H. balfourensis and Suberites caminatus show increased incidence of formation and accelerated spread of ice crystals compared to urchins and sea stars. Anchor ice also forms readily on sediments, from which it can grow and adhere to organisms. Our results are consistent with, and provide a potential first step toward, an explanation for disturbance patterns observed in shallow polar benthic communities. Interspecific differences in ice formation raise questions about how surface tissue characteristics such as surface area, rugosity, and mucus coating affect ice formation on invertebrates.

Study on bisphenol-A polycarbonates samples crystallized by acetone vapor induction

Bisphenol-A polycarbonate (PC) is an important amorphous engineering polymer, which can have its crystallinity induced by special environmental conditions. Such crystallization can alter PC properties leading to flaws during its use or to new applications. Cast film samples of PC, prepared from chloroform solutions, were submitted to acetone vapor and characterized by polarized light microscopy (PLM), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). PLM showed that the PC crystalline structure was presented as spherulites of different sizes. DSC analysis exhibited a multiple melting behavior for the crystalline structure. FTIR has presented bands shifting and intensity decrease, compared to the samples before treatment. Compression molded samples were characterized by scanning electron microscopy (SEM), DSC and mechanical properties tests. For those samples, DSC also showed the presence of a crystalline phase, with a little increase on surface rugosity observed through SEM. Stress–strain tests presented a decrease on samples performance after acetone exposure.

Magnesium Fluoride Whispering Gallery Mode Disk-Resonators for Microwave Photonics Applications

We have manufactured a high-Q whispering gallery mode resonator with magnesium fluoride for microwave photonics applications in the gigahertz frequency range. This crystal is scarcely used for resonator fabrication despite its numerous advantages, that are mainly high mechanical hardness, low sensitivity to water vapor pollution, and low sensitivity to photo- and thermo-refractive fluctuations at optimal temperatures. Using a customized machining procedure, we have successfully fabricated and characterized a 5-mm resonator with a surface rugosity of the order of 1 nm (from 3 to 12 atoms). Cavity ring-down measurements enabled us to determine that the resonator has a quality factor Q = 3.4 × 108 at 1550 nm.