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A nickel superalloy such as IN625 is widely employed in the oil, chemical processing, nuclear, and aviation industries due to its exceptional high-temperature strength, hardness, and corrosion resistance characteristics. These industries often require components with intricate and complex geometries that must adhere to close tolerances with adequate surface finish. Fiber laser beam machining (FLBM) has emerged as a significant advancement in fabrication technology, creating intricate forms and structures, especially in superalloys. This work aims to analyze the effect of laser frequency ($L_F)$, number of passes ($N_P$), laser power ($L_P)$, and scanning speed ($S_S$) in the machining of IN625 to achieve minimum surface undulation ($S_U$) and maximum erosion quantity ($E_Q$). The responsive surface methodology (RSM) was employed to model and optimize the parameters. The optimal condition was identified as $L_P$= 10.5W, $N_P$= 18, $S_S$= 283mm/min, and $L_F$= 18kHz; confirmation trials showed an improvement of 8.0% in $S_U$ and 19.75% in $E_Q.$ The influence of scanning speed on surface undulation and erosion quantity is significant. Analysis of variance (ANOVA) indicates that scanning speed contributes the most to surface undulation (70.48%) and erosion quantity (72.90%), followed by the number of passes with contributions of 13.94% to surface undulation and 14.41% to erosion quantity. Additionally, the surface topography and morphology of the machined surface are analyzed using 3D topography images and scanning electron microscopy (SEM) images.

The random deposition model must be enhanced to reflect the variety of surface roughness due to some material characteristics of the film growing by vacuum deposition or sputtering. The essence of the computer simulation in this case is to account for possible surface migration of atoms just after the deposition, in connection with the binding energy between atoms (as the mechanism provoking the diffusion) and/or diffusion energy barrier. The interplay of these two factors leads to different morphologies of the growing surfaces, from flat and smooth ones to rough and spiky ones. In this paper, we extended our earlier calculation by applying an extra diffusion barrier at the edges of terrace-like structures, known as the Ehrlich–Schwoebel barrier. It is experimentally observed that atoms avoid descending when the terrace edge is approached, and these barriers mimic this tendency. Results of our Monte Carlo computer simulations are discussed in terms of surface roughness, and compared with other model calculations and some experiments from literature. The power law of the surface roughness σ against film thickness t was confirmed. The nonzero minimum value of the growth exponent β near 0.2 was obtained which is due to the limited range of the surface diffusion and the Ehrlich–Schwoebel barrier. Observations for different diffusion ranges are also discussed. The results are also confirimed with some deterministic growth models.

In this paper we present a generalization of a simple solid-on-solid epitaxial model of thin film growth, when surface morphology anisotropy is provoked by anisotropy in the model control parameters of binding energy and/or diffusion barrier. The anisotropy is discussed in terms of the height–height correlation function. It was experimentally confirmed that the difference in diffusion barriers yields anisotropy in morphology of the surface. We obtained antisymmetric correlations in the two in-plane directions for antisymmetric binding.

The new Raster Spring Imaging Mode is developed to study soft and bad – fixed objects in AFM. The normal and lateral force between tip and sample is minimized. We discuss the principle of operation, main features and its prospect for specific applications. Experimental results revealed advantages with regard to other techniques like contact or semicontact mode. The silicon structure measurements with Raster Spring Imaging Mode allow to obtain information of elastic and adhesion properties without losing sight of good topography image.

In this paper, the mechanisms of excitation and propagation of nonlinear Rossby waves are investigated by the approach of topographic balance under the beta approximation for the first time. Using time-space elongation transformation and perturbation expansion method, a Korteweg–de Vries model equation for topographic Rossby wave amplitude is derived. The influences of topography parameters on Rossby solitary waves are discussed through qualitative and quantitative analysis.

We used multifractals to analyze the Lebanese topography focusing on Mount Lebanon. The elevation data were obtained from NASA STRM Global Digital Elevation of Earth Land, spaced at 80m in the East-West direction, and at 90m in the North-South direction. After transforming the grid to be perpendicular and parallel to the range, we found anisotropic scaling from 500m to 10,000m, and it reflected the fact that the Lebanese topography was more correlated in the direction perpendicular to the mountain range, probably due to occurrence of valleys and ridges in that direction. We estimated the parameters of the Universal Multifractal (UM) model and found $\alpha =1.45$ and $c1=0.05$, consistent with values reported for topography. The UM parameter $H$ was found to be 0.72 across the range and 0.57 along the range, the latter value agrees with prior observations. However, the larger value across the range is consistent with the higher spatial correlation in that direction. We introduced a new expression for the 2D power spectral density, and we showed that it can decently capture the anisotropic scaling. We also generated multiple realizations and we showed that the generation of anisotropic scaling did not alter the underlying parameter values $\alpha$ and $c1$ of the UM model. We also proposed an approximate method for generating conditional simulations, and we showed that through a judicious selection of values, one may reproduce approximately the observed field values at the desired locations. We believe such an approach could be used to generate realistic simulations of fields that are time-invariants, such as topography and soil properties.

The Discretized Kirchhoff Integral method has been recently tested against laboratory experiments using a model with surface curvatures and sharp edges generating wave diffraction effects. Comparisons between numerical and laboratory data have exhibited a good quantitative fit in terms of time arrivals and amplitudes, except in the vicinity of secondary shadow boundaries created by the interaction of the edges of some topographical structures. Following this work, the effect of multiple scattering and the surface curvatures on the wavefield is studied here, using the so-called diffraction attenuation coefficient, in order to define the cases where these effects may be neglected in the numerical modeling without loss of accuracy.

The electrochemical formation of single silver needles from aqueous silver sulfate was studied under both potentiostatic and galvanostatic conditions utilizing different quasi-2D cells. Under potentiostatic conditions, four (I–IV) stages of growth were distinguished. Stage III involved single needle growth under a quasi-steady-state (q-ss) regime in which, at the millimeter scale, the tip profile remained almost unchanged. Fast growing needles exhibited a truncated quasi-conical tip, and slow growing ones approached prolate hemispheroids. At stage III, the almost constant q-ss silver deposition rate was evaluated from the tip front displacement (dL_z/dt) perpendicularly to the tangential plane of the tip. For the cathode to anode potential difference in the range -1.00 ≤ E_c-a ≤ -0.22 V, values of (dL_z/dt) in the range 0.08–2.0 μm s^-1 were obtained. At the needle stem, the q-ss radial silver deposition rate (dL_x/dt) was about two orders of magnitude lower than (dL_z/dt). The transition from stage III to IV was characterized by tip thickening, i.e. a change in the tip q-conical profile to that of a prolate hemispheroid, and eventual tip splitting. Scanning electron micrographs at the micrometer scale of single silver needle tips from potentiostatic runs showed either a defined crystallography or an irregular topography covered by a large number of tiny crystals. In contrast, stems were always faceted. This difference indicated that surface relaxation processes following silver ion mass transport and discharge played a relevant role in the needle growth mode. At stage III, the growth regime is described utilizing a dual diffusion (D) and migration (M) model consisting of a DM direct contribution that becomes dominant at the needle stem, and a space charge (SC)-assisted DM contribution that operates at the tip apex. This explanation is consistent with the local cathodic current density values, the concentration ratio of silver clusters at the stem and tip apex surface, and the distinct kinetic behavior of needles produced from potentiostatic and galvanostatic runs. The complex link between mass transport phenomena of silver ions from the binary solution side, the silver ion discharge at the interface and the surface relaxation of silver adatoms and clusters at the metal lattice shed new light on the aspects of single silver needle formation.

While surface patterns are effective in improving tribological properties, nevertheless they alter the surface wettability, which will in turn affect the surface–lubricant interactions. When there is a shortage of lubricant on a patterned surface, the lubricant stored inside the cavities will be extracted to compensate the surface lubricant dissipation. Additionally, the lubricant retention effect provided by the cavities is competing with the release of the lubricant. With weak surface–lubricant interaction, the retention is limited. Therefore, the lubrication will have a sudden failure, giving a dramatic transition to abrasive wear. To improve the performance of polar lubricants on hydrophobic polymer surfaces, both topographical and selective surface modifications were incorporated on injection molded polypropylene surfaces. Distinctive lubrication improvement was observed when the surface structure density for the lubricant storage was high, and the release of the lubricant was controlled by the interaction with the selectively modified surfaces.

Hospital-acquired infections cause severe patient problems because of the augmented appearance of antibiotic-resistant bacteria, including Pseudomonas aeruginosa. Material surfaces modified with several biophysical parameters can decrease bacterial biofilm formation, which could be an advantageous alternative to treatment with antibiotics. Since stainless steel is an extensively used material for manufacturing medical implants and in healthcare settings, in this study, we used stainless steel (SS 316L and SS 304) to examine the result of the material surface topographies on bacterial biofilm establishment. This work used the electrochemical etching method to modify the stainless steel surface topography as an anode. The electrochemical etching method influenced the nanocones’ formation on stainless steel surfaces of both SS316L (Disk-6: 2682 peaks/$\mu$m${}^2)$ and SS304 (Disk-12: 1654 peaks/$\mu$m${}^2)$ estimated by atomic force microscopy and 3D Profilometer reduced the biofilm by 78% and 85%, respectively. Additionally, the higher negative potential on an average of 600mV measured by Kelvin probe atomic force microscopy reduced the biofilm formation on both SS316L and SS304 surface synergistically compared to the non-electrochemically etched surface. Biofilm growth and nanopotrusions on the stainless-steel surface examined by atomic force microscopy and scanning electron microscopy demonstrated significantly dead bacterial cells (20%) on the electrochemically etched surface than on the non-electrochemically etched surface after 2h contact time. Our observations exhibit that the nanotextured surface topographies and surface negative potential effectively inhibit bacterial adhesion and biofilm formation.

Topography and specific electrical conductivity of films of molecular complexes of zinc(II)tetra-tert-butylphthalocyanine (Zn(t-Bu)₄Pc) with electron-donating ligands and films of pure α-polymorphous modification of zinc(II)tetra-tert-butylphthalocyanine have been studied. It has been found that the specific electrical conductivity increases from 30 to 3.5 × 10⁵ times upon molecular complex formation of Zn(t-Bu)₄Pc with ligands.

A time-domain parametric study for the seismic response of a region located on the eastern bank of the Kifisos river canyon is performed to evaluate the significance of topography and soil effects on the seismic response of slopes. This region experienced unexpectedly heavy damage during the 7 September 1999 M_s 5.9 earthquake. Two-dimensional finite-element and spectral-element analyses are conducted using Ricker wavelets of various central frequencies as horizontal and vertical base excitation. The significance of a layered soil profile and the frequency content of the input motion, the emergence of "parasitic" acceleration components, and the effect of the angle of incidence on the amplification of the incoming waves are all discussed in detail. It is shown that the presence of a surface soil layer significantly affects the amplification pattern. The so-called Topographic Aggravation Factor (defined as the 2D/1D Fourier spectral ratio) achieves its maximum value very near the crest, in function of the frequency content of the excitation. For the particular soil conditions and geometry analysed, vertically propagating SV waves incite at about the critical angle, resulting in the highest topographic amplification.

A densely grown coastal vegetation belt of Pandanus odoratissimus for reducing the tsunami energy was quantitatively analyzed by an enhanced one-dimensional numerical model that included variations of topography and tsunami characteristics. The drag and inertia forces were assumed as the total resistance generated by the vegetation. It was found that a relatively small period tsunami wave was more destructive than a relatively large period tsunami wave of the same height, although densely grown vegetation effectively reduced the tsunami energy in the case of the small period tsunami wave. A very mild ground slope was also more vulnerable to thrashing by tsunami waves than a relatively steep ground slope. Moreover, densely growing coastal vegetation on very mild ground slope dissipated tsunami energy more efficiently than the same vegetation on relatively steep ground slope.

An investigated lump method based on the mixed mesh of triangle and quadrangle for simulating near-fault ground motion is presented by using finite-fault sources and a differential type of viscoelastic constitutive equations of the generalized zener body (GZB) with two mechanisms. One numerical test is performed to verify the validity and accuracy of the investigated lump method. The ground motion in Beichuan town during the Wenchuan earthquake is simulated, considering attenuation of real earth material and the effect of realistic topography. Numerical results of simulations demonstrated that the viscoelasticity of earth medium attenuates the PGAs noticeably and changes the frequency characteristics of the ground motion. The local topography influences greatly the PGAs in the area of Beichuan town.

Many beaches in Penang island were severely inundated by the 26 December 2004 Indian Ocean mega tsunami with 57 deaths recorded. It is anticipated that the next big tsunami will cause even more damages to beaches in Penang. Hence, developing community resilience against the risks of the next tsunami is essential. Resilience entails many interlinked components, beginning with a good understanding of the inundation scenarios critical to community evacuation and resilience preparation. Inundation scenarios are developed from tsunami simulations involving all three phases of tsunami generation, propagation and run-up. Accurate and high-resolution bathymetric–topographic maps are essential for simulations of tsunami wave inundation along beaches. Bathymetric maps contain information on the depths of landforms below sea level while topographic maps reveal the elevation of landforms above sea level. Bathymetric and topographic datasets for Malaysia are, however, currently not integrated and are available separately and in different formats, not suitable for inundation simulations. Bathymetric data are controlled by the National Hydrographic Centre (NHC) of the Royal Malaysian Navy while topographic data are serviced by the Department of Survey and Mapping Malaysia (JUPEM). It is highly desirable to have seamless integration of high-resolution bathymetric and topographic data for tsunami simulations and for other scientific studies. In this paper, we develop a robust method for integrating the NHC bathymetric and JUPEM topographic data into a regularly-spaced grid system essential for tsunami simulation. A primary objective of this paper is to develop the best Digital Elevation and Bathymetry Model (DEBM) for Penang based upon the most suitable and accurate interpolation method for integrating bathymetric and topographic data with minimal interpolation errors. We analyze four commonly used interpolation methods for generating gridded topographic and bathymetric surfaces, namely (i) Kriging, (ii) Multiquadric (MQ), (iii) Thin Plate Spline (TPS) and (iv) Inverse Distance to Power (IDP). The study illustrated that the Kriging interpolation method produces an integrated bathymetric and topographic surface that best approximates the admiralty nautical chart of Penang essential for tsunami run-up and inundation simulations. Tsunami inundation scenarios critical to risk analysis and mitigation could then be developed using this DEBM for various earthquake scenarios, as presented in this paper for the 2004 Indian Ocean Tsunami.

Hydroxyapatite (HA)-coated metallic prostheses, which combine the osteoconductivity of HA and high strength of metallic alloys, have been increasingly the choice of joint replacement prostheses by surgeons as the general population lives longer. Surface modification of metallic implant surfaces is one of the key focal points to implantation technology. In addition to material chemistry, surface topography has been found to positively impact cellular response and is able to enhance the life time of the implant. Recently, a new technique, template-assisted electrohydrodynamic atomization (TAEA) spraying, developed using the principles of electrohydrodynamic atomization spraying, which is an electrically driven jet-based deposition method, is of considerable interest in surface topography formation. The process offers the attractive advantages of compatibility with micro-fabrication technology and versatility in pattern specification for advanced implant designs. This technology incorporates nanosized calcium phosphate to mimic the size and chemical composition of bone mineral in a micrometer-dimension pattern configuration to guide cellular responses. In vitro studies showed that both pillar and track nano Silicon-substituted HA (SiHA) patterns were able to encourage the attachment and growth of osteoblast cells, the track patterns provided the favourite surface for the initial cell attachment while a fast cell proliferation rate was found on the pillar pattern from day 1 to day 5 in comparison with that of a SiHA-coated surface. The alignment of actin cytoskeleton of osteoblast cells matched the orientation of the entire cell. The shear peel strength of the patterned interlocking nano-HA coating was found to be at least an order of magnitude higher than the conventional HA coating. Therefore, TAEA offers great potential for producing new coatings with a tailored surface topography, on both the micro- and nano-scale in a more cost effective way to enhance the performance of medical implants.

This article demonstrates that the surface micro-topography regulates the biology of breast cancer cells, including the expression of HER-2 gene and protein. The breast tumor microenvironment is made up of heterogenous mixture of pores, ridges and collagen fibers with well defined topographical features. Although, significant progress has been achieved towards elucidating the biochemical and molecular mechanisms that underlie breast cancer progression, quantitative characterization of the associated mechanical/topographical properties and their role in breast tumor progression remains largely unexplored. Therefore, the aim of this study is to investigate the effect of topography on the adhesion and biology of breast cancer cells in in vitro cultures. Polydimethylsiloxane (PDMS) surfaces containing different topographies were coated with polyelectrolyte multilayers (PEMs) to improve cell adhesion and maintain cell culture. HER-2 expressing breast cancer cells, BT-474 and SKBr3, were cultured on these PDMS surfaces. We demonstrate that micro-topography affects the cell adhesion and distribution depending on the topography on the PDMS surfaces. We also report for the first time that surface topography down-regulates the HER-2 gene transcription and protein expression in breast cancer cells when cultured on PDMS surfaces with micro-topographies compared to the tissue culture polystyrene surface (TCPS) control. Results from this study indicate that micro-topography modulates morphology of cells, their distribution and expression of HER-2 gene and protein in breast cancer cells. This study provides a novel platform for studying the role of native topography in the progression of breast cancer and has immense potential for understanding the breast cancer biology.

Bacterial pathogens, such as Pseudomonas aeruginosa, readily form biofilms on surfaces, limiting the efficacy of antimicrobial and antibiotic treatments. To mitigate biofilm formation, surfaces are often treated with antimicrobial agents, which have limited lifetime and efficacy. Recent studies have shown that well-ordered topographic patterns can limit bacterial attachment to surfaces and limit biofilm formation. In this study, nano and microscale patterned poly(dimethylsiloxane) surfaces were evaluated for their ability to affect adhesion and biofilm formation by Pseudomonas aeruginosa. Feature size and spacing were varied from 500 nm to 2 μm and included repeating arrays of square pillars, holes, lines and biomimetc Sharklet™ patterns. Bacterial surface adhesion and biofilm formation was assessed in microfluidic flow devices and under static conditions. Attachment profiles under static and fluid flow varied within topography types, sizes and spacing. Pillar structures of all sizes yielded lower surface attachment than line-based patterns and arrays of holes. This trend was also observed for biomimetic Sharklet™ patterns, with reduced bacterial attachment to "raised" features as compared to "recessed" features. Notably, none of the topographically patterned surfaces outperformed smooth surfaces (without topography) for resisting cell adhesion. Initial surface attachment patterns were indicative of subsequent biofilm formation and coverage, suggesting a direct role of surface topography in biofilm-based biofouling.

Tissue engineering strategies for regenerating damaged cartilage using hydrogels have garnered significant attention due to the limited self-healing capacity of damaged cartilage tissue and the restrictions of current medical treatment methods. In particular, using human mesenchymal stem cells (hMSCs) as the cell source has shown the potential to differentiate along a chondrogenic lineage. Hydrogels, whether made of synthetic polymers, natural polymers, or combinations, are widely explored as scaffolding materials mimicking the natural cartilage environment. Based on the understanding of the importance of surface nanotopographies and mechanical stiffness, hydrogels have been presented in various forms and tested for the differentiation of hMSCs. The primary focus of this review is to provide a summary of recent advances in physically and chemically modified hydrogels promoting the chondrogenesis of hMSCs. Advances in micromachining have helped in forming surfaces with the required roughness or an array of micropillars of defined architecture. Hydrogels have been combined with various stimulants such as small peptides, growth factors, and many modified matrix elements. Creating anisotropic hydrogels mimicking the extracellular matrix of cartilage has also been reported. These studies show promising results and identify a niche for in-vitro differentiation of chondrocytes from hMSCs.