Surface Topography Parameters Research Articles

Inter-observer reproducibility of back surface topography parameters allowing assessment of scoliotic thoracic gibbosity and comparison with two standard postures

The objective of this work was to analyze the inter-observer reproducibility of an upright posture designed to bring out the thoracic humps by folding the upper limbs. The effect of this posture on back surface parameters was also compared with two standard radiological postures. A back surface topography was performed on 46 patients (40 girls and 6 boys) with a minimum of 15° Cobb angle on coronal spinal radiographs. Inter-observer reliability was evaluated using the typical error measurement (TEM) and Intraclass Correlation Coefficient (ICC). Variations between postures were assessed using a Student's t test. The inter-observer reproducibility is good enough for the three postures. The proposed posture leads to significant changes in the sagittal plane as well as in the identification of thoracic humps. This study shows the reproducibility of the proposed posture in order to explore the thoracic humps and highlights its relevance to explore scoliosis with back surface topography systems.

Does Optic Nerve Head Surface Topography Change Prior to Loss of Retinal Nerve Fiber Layer Thickness: A Test of the Site of Injury Hypothesis in Experimental Glaucoma

PurposeTo test the hypothesis that optic nerve head (ONH) deformation manifesting as changes in its mean surface height precedes thinning of the peripapillary retinal nerve fiber layer (RNFL) in experimental glaucoma (EG).Methods68 rhesus macaque monkeys each had three or more baseline imaging sessions under manometric intraocular pressure (IOP) control to obtain average RNFL thickness (RNFLT) and the ONH surface topography parameter mean position of the disc (MPD). Laser photocoagulation was then applied to the trabecular meshwork of one eye to induce chronic, mild-to-moderate IOP elevation and bi-weekly imaging continued. Event analysis was applied to determine for each parameter when an ‘endpoint’ occurred (signficant change from baseline) for eight different endpoint criteria. Specificity was assessed in the group of 68 fellow control eyes. Classical signal detection theory and survival analysis were used to compare MPD with RNFLT.ResultsRegardless of the endpoint criterion, endpoints were always more frequent for MPD than for RNFLT. The discriminability index (d’) was 2.7 ± 0.2 for MPD and 1.9 ± 0.2 for RNFLT (p<0.0001). Endpoints were reached by MPD an average of 1-2 months earlier than by RNFLT (p<0.01). At the onset of the first specific, detectable MPD change in EG eyes, there was still no significant change in RNFLT on average (p=0.29) and only 25% of individual eyes exhibited signficant reduction. In contrast, at onset of signficant RNFLT change, MPD had already changed an average of 101 µm from baseline (p<0.0001) and 71% of the individual eyes had exhibited significant change. The magnitude of MPD change was more than could be explained on the basis of axon loss alone.ConclusionsThis study demonstrates that the average surface height of the ONH changes prior to any detectable loss of average peripapillary RNFL thickness in non-human primate eyes with experimental glaucoma.

Wetting on Physically Patterned Solid Surfaces: The Relevance of Molecular Dynamics Simulations to Macroscopic Systems

We used molecular dynamics (MD) simulations to study the wetting of Lennard-Jones cylindrical droplets on surfaces patterned with grooves. By scaling the surface topography parameters with the droplet size, we find that the preferred wetting modes and contact angles become independent of the droplet size. This result is in agreement with a mathematical model for the droplet free energy at small Bond numbers for which the effects of gravity are negligible. The MD contact angles for various wetting modes are in good agreement with those predicted by the mathematical model. We construct phase diagrams of the dependence of the wetting modes observed in the MD simulations on the topography of the surface. Depending on the topographical parameters characterizing the surface, multiple wetting modes can be observed, as is also seen experimentally. Thus, our studies indicate that MD simulations can yield insight into the large-length-scale behavior of droplets on patterned surfaces.

A Dynamic Contact Model of Rough Surfaces Based on the Microscopic Contact Analysis of Asperities

Dynamic contact model of rough surfaces can provide the theoretical basis for analyzing the microscopic damage of surfaces in wear process and constructing the analytical wear model to predict wear. A dynamic contact model of sliding rough surfaces is innovatively constructed based on the characterization of the contact asperities on rough surfaces in this paper. Firstly, an asperity model of rough surface is set up according to the surface topography parameters and the static contact parameters is evaluated in the light of statistics contact theory; Then the contact characteristic of surface topography in sliding is analyzed and a series of equivalent contact models are proposed; Finally, the dynamic contact model of rough surfaces is established and from which the dynamic contact parameter of rough surfaces is formulated. The dynamic contact model can be further improved to analyze the friction fatigue wear of sliding pairs and provide reference for tribology design of mechanical surfaces.

Surface Integrity of Ti6Al4V Alloy under Dry Sliding Conditions

The present paper is aimed to investigate the evolution of the surface integrity of Ti6Al4V alloy under reciprocating sliding in contact with bearing steel and ceramic balls (Al2O3). The evolution of the surface integrity states is characterized by the evolution of the surface topography and 3D roughness parameters with the applied normal load. The tribological characteristics (coefficient of friction and weight loss) are also presented for the two contact pairs used in this study. This study has proved that Ti6Al4V/Al2O3 contact pair can be used in applications were the applied load is variable.

Variability of areal surface topography parameters due to the change in surface orientation to measurement direction

Several random surface topographies were analyzed. They were measured by optical (Talysurf CCI Lite) method. They represent one- and two-process anisotropic and isotropic surfaces. These surfaces were rotated of ± 1° and ± 2° by two methods: on the plane table (before measurement) and virtually (after measurement) using the software TalyMap Gold. After each measurement or surface rotation, each surface was levelled. Then, the forms were removed using polynomial of the 3rd degree. Areal surface topography parameters from standard ISO 25178 were calculated. The relative deviations of parameters were determined. The tendency of surface topography changes characteristic to various surface types were analyzed. It was found that change in orientation to the measurement direction of both isotropic and anisotropic surfaces could be substantial source of the measurement uncertainty. Functional parameter Smr and also feature parameters Sda, Sha, Sdv, Shv, and Spd are the mostly sensitive on measurement orientation. Statistical amplitude parameters Sa and Sq are more stable than parameters describing maximum surface height, like Sz, Sp, and Sv. The effect of surface orientation to measurement direction on values of functional parameters from V group was small. It was shown that changes of Sdq, Sdr, and Spc parameters describing hybrid properties due to surface rotation before measurement were smaller than those caused by change in surface orientation after measurement.

Mechanics of axisymmetric adhesive contact of rough surfaces involving power-law graded materials

In the present paper, the mechanics of axisymmetric adhesive contact of rough surfaces involving power-law graded materials is investigated analytically. A series of general analytical solutions have been obtained with use of the cumulative superposition and equivalent energy release rate approaches. These solutions provide closed-form expressions of equilibrium relations among applied load, indentation depth and contact radius. Based on these solutions, an effective macroscopic description of the contact evolution is obtained for a general punch profile with surface roughness. Our analysis results reveal that the simultaneous presence of surface roughness and graded material properties can influence the pull-off force and energy dissipation due to adhesion hysteresis significantly. Moreover, it is found that both the adhesion strength and toughness can be optimized by adjusting the surface topography and material parameters of power-law graded solids appropriately. The analytical results obtained in this paper include the corresponding solutions for homogeneous isotropic materials as special cases and therefore can also serve as the benchmarks for checking the validity of numerical solution results.

Surface topography characterization of automotive cylinder liner surfaces using fractal methods

This paper explores the use of fractal approaches for the possible characterization of automotive cylinder bore surface topography by employing methods such as differential box counting method, power spectral method and structure function method. Three stage plateau honing experiments were conducted to manufacture sixteen cylinder liner surfaces with different surface topographies, for the study. The three fractal methods are applied on the image data obtained using a computer vision system and 3-D profile data obtained using vertical scanning white light interferometer from the cylinder liner surfaces. The computed fractal parameters (fractal dimension and topothesy) are compared and correlated with the measured 3-D Abbott-Firestone curve parameters (Sk, Spk, Svk, Sr1 and Sr2) that are currently used for the surface topography characterization cylinder liner surfaces. The analyses of the results indicated that the fractal dimension (D) computed using the vision data as well as 3-D profile data by employing three different fractal methods consistantly showed a negative correlation with the functional surface topographical parameters that represents roughness at peak (Spk),core (Sk) and valley (Svk) regions and positive correlation with the upper bearing area (Sr1) and lower bearing area (Sr2) of the automotive of cylinder bore surface.

Predicting residual and flow stresses from surface topography created by laser cutting technology

The paper deals with the engineering method for laser cutting technology that utilizes stress equations derived from surface topography for determining residual stresses. It presents an original method for residual stress assessment in a non-contact and non-destructive manner. The high temperature around cut edges results in the development of residual stresses during the cutting process, which decreases the quality of the end product. Surface topographical parameters themselves carry information on a concrete state of technological process in the concrete moment of its usage. This method for the assessment of residual stress in materials being cut by a laser beam provides sufficient information on the residual stress state evaluation with sufficient accuracy by applying an analytical and experimental approach. Experiments were conducted on three different materials, namely steel, aluminium alloy and titanium. It was necessary to check calculation by measuring the residual stress distribution in the vicinity of cut edge using the ultrasonic method. The novelty of the method for the determination of residual stresses in a workpiece lies in the physics-based approach focusing on the mechanical and stress-deformation parameters of the material being cut and on the mechanical equilibrium of the system: material properties—tool properties—deformation properties.

A comparative study of fine polished stainless steel, TiN and TiN/Ag surfaces: Adhesion and attachment strength of Listeria monocytogenes as well as anti-listerial effect

Magnetron sputtering was used to produce nanocomposite TiN and TiN/Ag coatings on stainless steel surfaces. The surface chemistry (EDX), physicochemical properties (contact angles), topography and roughness parameters (WLP and AFM) of the fine polished stainless steel (FPSS), TiN and TiN/8.6at.% Ag surfaces were examined. Real-time initial adhesion of two Listeria monocytogenes strains (EGDe and 64) to the three surfaces was determined under flow conditions, and their attachment strength after adhesion was measured using atomic force microscopy (AFM). The anti-listerial properties of the surfaces were determined using LIVE/DEAD staining.Our results demonstrate that FPSS, TiN and TiN/8.6at.% Ag possessed different surface properties, which may influence both attachment strength and anti-listerial properties. There were no significant (p>0.05) differences in the initial adhesion of the two L. monocytogenes strains to the three different surfaces. Attachment studies showed that the two L. monocytogenes strains did not attach to FPSS under wetted conditions. However, both strains attached to TiN and TiN/8.6at.% Ag surfaces, although with less strength to TiN/8.6at.% Ag than to TiN surfaces. The TiN/8.6at.% Ag surface showed marked anti-listerial properties as compared with FPSS and TiN. Initial adhesion, attachment strength and anti-listerial properties were found to be strain dependent.

Efficacy, Safety, and Patient Satisfaction of a Monophasic Cohesive Polydensified Matrix Versus a Biphasic Nonanimal Stabilized Hyaluronic Acid Filler After Single Injection in Nasolabial Folds

Intradermal injection of hyaluronic acid (HA) is currently the criterion standard to reduce the appearance of nasolabial folds (NLF). Effects of a monophasic HA filler using cohesive polydensified matrix (CPM) technology were compared with those of nonanimal stabilized HA (NASHA). In a double-blind, half-side comparison, 20 subjects (ages 35-65, mean 52±5.6) with symmetric NLF grade 3 to 4 were randomized to contralateral treatment with a monophasic polydensified filler (CPM) and a biphasic HA filler (NASHA). Efficacy was assessed at baseline and after 2, 24, and 48weeks using a wrinkle severity rating scale (WSRS) for NLF, subject questionnaire, and biophysical in vivo methods. All subjects showed significant improvements with both fillers up to day 365. Subject questionnaires confirmed significantly less injection pain for the CPMHA, significantly greater patient satisfaction after 2weeks with both fillers, and after 24 and 48weeks significantly greater improvement with the CPMHA compared to baseline. WSRS and skin surface topography parameters improved significantly up to 48weeks with both fillers. A single intradermal injection of a monophasic CPMHA and a biphasic NASHA filler showed significant improvements in WSRS and measured wrinkle depth up to 48weeks for both fillers and significant differences in injection comfort and patient satisfaction in favor of CPMHA.

Surface topography effect on strength of lap adhesive joints after mechanical pre-treatment

This paper presents the analysis of the effect of surface topography on shear strength of lap adhesive joints from steel S235JR. Steel surfaces were prepared to bond with various methods of mechanical treatment. It was found after using the linear correlation method that strengthening properties of tested joints are strongly correlated with hybrid surface topography parameters. Shear strength of milled adherends can be increased as a result of subsequent grit blasting.

Principal Components Based Analysis of Surface Quality of Horizontal Turned Samples

Tool vibration and surface quality are closely related in turning processes. In this article, a more precise method of analysis has been developed in order to achieve a better understanding of the complex relationship between machine tool, machining processes, machining parameters and manufactured piece. This new methodology allows identifying diverse aspects in the process, as tool geometry or cutting parameters (cutting speed, feed, cutting depth) and their relationship with surface topography parameters determined from a set of profiles acquired in different zones of the workpiece, all that with a low computational cost. The final result is a characterization of the final surface beyond the statistical parameters defined by standard ISO 4287:1997. In this work, the proposed methodology has been applied to a horizontal turning process developed on aeronautical Aluminum workpieces. This procedure allows distinguishing between the roughness generated by the tool geometry from that generated by the vibration or by other cutting associated phenomena. © 2013 American Scientific Publishers All rights reserved.

The Effect of Determining Topography Parameters on Analyzing Elastic Contact Between Isotropic Rough Surfaces

The elastic contact between two computer generated isotropic rough surfaces is studied. First the surface topography parameters including the asperity density, mean summit radius, and standard deviation of asperity heights of the equivalent rough surface are determined using an 8-nearest neighbor summit identification scheme. Second, many cross sections of the equivalent rough surface are traced and their individual topography parameters are determined from their corresponding spectral moments. The topography parameters are also obtained from the average spectral moments of all cross sections. The asperity density is found to be the main difference between the summit identification scheme and the spectral moments method. The contact parameters such as the number of contacting asperities, real area of contact, and contact load for any given separation between the equivalent rough surface and a rigid flat are calculated by summing the contributions of all the contacting asperities using the summit identification model. These contact parameters are also obtained with the Greenwood-Williamson (GW) model using the topography parameters from each individual cross section and from the average spectral moments of all cross sections. Three different surfaces and three different sampling intervals were used to study how the method to determine topography parameters affects the resulting contact parameters. The contact parameters are found to vary significantly based on the method used to determine the topography parameters, and as a function of the autocorrelation length of the surface, as well as the sampling interval. Using a summit identification model or the GW model based on topography parameters obtained from a summit identification scheme is perhaps the most reliable approach.

A discrete dislocation plasticity analysis of a single-crystal semi-infinite medium indented by a rigid surface exhibiting multi-scale roughness

Discrete dislocation plasticity was used to analyse plane-strain indentation of a single-crystal elastic–plastic semi-infinite medium by a rigid surface exhibiting multi-scale roughness, characterised by self-affine (fractal) behaviour. Constitutive rules of dislocation emission, glide and annihilation were used to model short-range dislocation interactions. Dislocation multiplication and the development of subsurface shear stresses due to asperity microcontacts forming between a single-crystal medium and a rough surface were examined in terms of surface roughness and topography (fractal) parameters, slip-plane direction and spacing, dislocation source density, and contact load (surface interference). The effect of multi-scale interactions between asperity microcontacts on plasticity is elucidated in light of results showing the evolution of dislocation structures. Numerical solutions yield insight into plastic flow of crystalline materials in normal contact with surfaces exhibiting multi-scale roughness.

3D surface topography study of the biofunctionalized nanocrystalline Ti–6Zr–4Nb/Ca–P

In this work surface of the sintered Ti-6Zr-4Nb nanocrystalline alloy was electrochemically biofunctionalized. The porous surface was produced by anodic oxidation in 1 M H{sub 3}PO{sub 4} + 2%HF electrolyte at 10 V for 30 min. Next the calcium-phosphate (Ca-P) layer was deposited, onto the formed porous surface, using cathodic potential - 5 V kept for 60 min in 0.042 M Ca(NO{sub 3}){sub 2} + 0.025 M (NH{sub 4}){sub 2}HPO{sub 4} + 0.1 M HCl electrolyte. The deposited Ca-P layer anchored in the pores. The biofunctionalized surface was studied by XRD, SEM and EDS. In vitro tests culture of normal human osteoblast (NHOst) cells showed very good cells proliferation, colonization and multilayering. Using optical profiler, roughness and hybrid 3D surface topography parameters were estimated. Correlation between surface composition, morphology, roughness and biocompatibility results was done. It has been shown by us that surface with appropriate chemical composition and topography, after combined electrochemical anodic and cathodic surface treatment, supports osteoblast adhesion and proliferation. 3D topography measurements using optical profiler play a key role in the biomaterials surface analysis. - Highlights: Black-Right-Pointing-Pointer Nanocrystalline Ti-6Zr-4Nb/Ca-P material was produced for hard tissue implant applications. Black-Right-Pointing-Pointer Calcium-phosphate results in surface biofunctionalization. Black-Right-Pointing-Pointer The biofunctionalized surfacemore » shows good in-vitro behavior.« less

School screening for scoliosis: can surface topography replace examination with scoliometer?

BackgroundClinical examination with the use of scoliometer is a basic method for scoliosis detection in school screening programs. Surface topography (ST) enables three-dimensional back assessment, however it has not been adopted for the purpose of scoliosis screening yet. The purpose of this study was to assess the usefulness of ST for scoliosis screening.Methods996 girls aged 9 to 13 years were examined, with both scoliometer and surface topography. The Surface Trunk Rotation (STR) was introduced and defined as a parameter allowing comparison with scoliometer Angle of Trunk Rotation taken as reference.ResultsIntra-observer error for STR parameter was 1.9°, inter-observer error was 0.8°. Sensitivity and specificity of ST were not satisfactory, the screening cut-off value of the surface topography parameter could not be established.ConclusionsThe study did not reveal advantage of ST as a scoliosis screening method in comparison to clinical examination with the use of the scoliometer.

The influence of body mass index (BMI) on the reproducibility of surface topography measurements

Background Surface Topography can be used to evaluate patients with spinal deformity, especially adolescents with scoliosis in whom a reduced number of radiographic evaluations is desired. The Formetric 4D (Diers International GmbH, Schlangenbad, Germany) is a surface topography system that is able to identify anatomical landmarks and construct a 3-dimentional model of the spine using only surface features. One would guess that a slender patient with easily identifiable bony landmarks would be an ideal patient for this system, and that a patient with a higher Body Mass Index (BMI) would be more difficult to measure [1-5]. Materials and methods In this study, fourteen female patients were measured 30 times each to evaluate the reproducibility of the Formetric measurements. The patients ranged in BMI from 16.9 to 29.0, and the reproducibility of each of the Formetric parameters was correlated to BMI. Results Results showed that there was not a strong correlation between any of the individual surface topography parameters and the BMI. The reproducibility of the calculated scoliosis curve did correlate with BMI, however, (r = 0.65) and this correlation was significant (p = 0.012), showing that the higher the patient’ sB MI, the more variability was present in scoliosis angle calculations. Conclusions Overall, the reproducibility of the Formetric 4D was very good even in patients with higher BMI. The patient with the highest BMI (29) still had Formetric measurements that were +/- only 4.6 degrees for scoliosis curve calculations.

A comparison of static vs dynamic surface topography measurements in the evaluation of scoliosis

The Formetric 4D System (Diers International GmbH, Schlangenbad, Germany) is a surface topography system used to evaluate trunk deformity in patients with scoliosis. The original system took a single static scan of the patient which was subject to variability due to the natural sway of the body during standing. A 4D system was developed that takes multiple scans over 6 seconds and averages them to take into account patient movement during imaging. Averaged scans such as this should show less variability over time than single images do [1-4]. The purpose of this study was to compare surface topography measurements taken as a single scan with those taken as averaged scans over 6 and 15 seconds to see whether the averaged scans have less variability. Six volunteer patients without scoliosis were used to measure the position of normal spines in the standing position. Each patient was scanned ten times for each time interval. For each group of scans, a standard error of measurement was calculated. The patients were then compared based on the standard errors for each topography parameter. Data included 6 patients x30 measurements each x10 topography parameters totaling 1800 data points. Data analysis was done using ANOVA to compare the three groups. There were not significant differences between the groups in any of the surface topography parameters that were studied. Our conclusion was that in this population of 6 normal patients, we were not able to demonstrate smaller standard errors of measurement with averaged 4D scans than with single scans.

Screening the attachment and spreading of bone marrow-derived and adipose-derived mesenchymal stem cells on porous silicon gradients

Nanoscale surface topography exerts profound effects on stem cell behaviour. Detailed knowledge of these effects is of key relevance to the development of advanced materials for tissue engineering. In order to gain such knowledge, high-throughput platforms for characterising cell-surface interactions are required. One suitable platform technology involves the use of lateral gradients where a continuous variation in a chemical or physical surface parameter of choice is investigated. Here, we fabricate porous silicon (pSi) gradients displaying pore sizes ranging from approximately 2 μm down to a few nm in diameter, and changing in solid surface fraction from 15% to 95% along the 12 mm length of the gradient. Cell attachment and spreading of primary rat bone marrow-derived mesenchymal stem cells (rBMSCs), human BMSCs (hBMSCs) and primary human adipose-derived mesenchymal stem cells (hASCs) were studied on these gradients. For all three MSC types, spreading was suppressed on the large pore size region of the gradient and spreading increased towards the other end of the gradient. MSC attachment density, on the other hand, was pore size- and cell type-dependent. In contrast to hASCs, the attachment density of rBMSCs and hBMSCs was low on the pSi gradient compared with flat Si. For hASCs, we observed a peak attachment density on the pore size region of 329 ±112 nm. F-actin staining showed clearly that cytoskeleton development was related to both cell spreading and cell type. The result hence showed that the pore size gradient format allows the screening of suitable surface topography parameters for the control of MSC behaviour. We also observed that MSCs derived from different sources respond differently to pore size at the nanoscale, suggesting that intrinsic differences between MSCs affect cell-surface interactions and justifying the need for high-throughput platforms, such as the one developed here.