Surface Topography Images Research Articles

Visualization and Quantification of State of Charge-Dependent Young's Modulus of LiMn2O4 Nanosized Particles by Bimodal AFM.

Mechanical damage of LiMn2O4 active material caused by volume change, phase transition, and lithium diffusion-induced stress is the main degradation mechanism in lithium-ion batteries. Young's modulus is a key parameter of mechanical property, and its variation with lithium content x or state of charge (SOC) at the nanoscale is an important issue because such variation may have influences on the stress level and lithium-ion transport. In this study, we successfully developed bimodal atomic force microscopy (bimodal AFM) and related approaches to carry out surface topography imaging and Young's modulus mapping of LixMn2O4 nanosized particles. It was validated that the size of particles decreased with decreasing SOC due to delithiation during the charging cycle. The variation in Young's modulus with SOC was quantitatively determined using the silicon material as a reference, and the trend of the variation is consistent with the reported results of molecular dynamics simulation. Furthermore, spatially nonuniform distribution of Young's modulus on the nanosized particle surface was found even upon completion of charging. This phenomenon could be attributed to the coexistence of two phases during the charging process. Our experimental study reveals the correlation between Young's modulus of LiMn2O4 and SOC at the nanosized particle level, and we believe that the bimodal AFM will be widely used in the nanocharacterization of the electrode materials because lithium content- or SOC-dependent mechanical properties are common in battery electrode materials.

Application of Sodium silicate as a halogen-free flame-retardant and evaluate its effectiveness on the flame-retardancy of Polypropylene fabric

A halogen-free flame-retardant was synthesized using Silica gel and Sodium hydroxide within the scope of the study. The Polypropylene (PP) fabric was treated with the synthesized Sodium Silicate to investigate its thermal behaviour. The limiting oxygen index (LOI) value of the Polypropylene fabrics dramatically increased after finishing with Sodium silicate and the 50.4% noteworthy LOI value was achieved. The Sodium silicate-treated PP fabrics exhibited a 30.1% LOI value even after washing, compared to the neat PP LOI value which was reported to be 16.4%. The surface modification of the Polypropylene fabric following the plasma treatment was evaluated by elemental mapping, surface topography images, and contact angle measurements and the homogeneity of the Sodium silicate coating was evaluated by Scanning electron microscopy.

Evaluating the antibacterial efficacy of a silver nanocomposite surface coating against nosocomial pathogens as an antibiofilm strategy to prevent hospital infections

Antimicrobial nanocoatings may be a means of preventing nosocomial infections, which account for significant morbidity and mortality. The role of hospital sink traps in these infections is also increasingly appreciated. We describe the preparation, material characterization and antibacterial activity of a pipe cement-based silver nanocoating applied to unplasticized polyvinyl chloride, a material widely used in wastewater plumbing. Three-dimensional surface topography imaging and scanning electron microscopy showed increased roughness in all surface finishes versus control, with grinding producing the roughest surfaces. Silver stability within nanocoatings was >99.89% in deionized water and bacteriological media seeded with bacteria. The nanocoating exhibited potent antibiofilm (99.82–100% inhibition) and antiplanktonic (99.59–99.99% killing) activity against three representative bacterial species and a microbial community recovered from hospital sink traps. Hospital sink trap microbiota were characterized by sequencing the 16S rRNA gene, revealing the presence of opportunistic pathogens from genera including Pseudomonas, Enterobacter and Clostridioides. In a benchtop model sink trap system, nanocoating antibiofilm activity against this community remained significant after 11 days but waned following 25 days. Silver nanocoated disks in real-world sink traps in two university buildings had a limited antibiofilm effect, even though in vitro experiments using microbial communities recovered from the same traps demonstrated that the nanocoating was effective, reducing biofilm formation by >99.6% and killing >98% of planktonic bacteria. We propose that conditioning films forming in the complex conditions of real-world sink traps negatively impact nanocoating performance, which may have wider relevance to development of antimicrobial nanocoatings that are not tested in the real-world.

Stochastic Assessment of Dissolution at Fluid‐Mineral Interfaces

AbstractChemical weathering associated with dissolution/precipitation at interfaces between minerals and flowing fluids is key for the evolution of geologic systems, including groundwater contamination and storage capacity. Relying on Atomic Force Microscopy (AFM) yields reaction rates at nanoscale resolutions. Challenges limiting our ability to quantify heterogeneity associated with these processes include establishing reliable platforms allowing AFM imaging of real‐time and in situ absolute material fluxes across mineral surfaces under continuous flow conditions to complement typically acquired surface topography images. We provide an experimental workflow and heterogeneous absolute rates at the nanoscale across the surface of a calcite crystal under dissolution. These high‐quality experimental observations are then interpreted through a stochastic approach. The latter is geared to embed diverse kinetic modes driving the degree of spatial heterogeneity of the reaction and corresponding to different mechanistic processes documented across the crystal surface.

How Accurate are Anatomical Surface Topography Parameters in Indicating the Presence of a Scoliosis?

Retrospective analysis of a longitudinal cohort. To identify the presence of a scoliosis from surface data. Identifying AIS can be difficult. Screening is not universal for reasons including high false positive and negative rates. These difficulties can lead to some adolescents missing out on bracing. Logistic regression analysis of ISIS2 surface topography images only was performed. The x,y positions of the shoulders (Sh), axillae (Ax), waist (Waist) and the x,y,z positions of the most prominent points over the posterior torso (Scap) were used for the thoracic, thoracolumbar / lumbar and whole spine. The models were used to identify the presence of a 20° or larger scoliosis. Differences in the position of the landmarks were analysed comparing left and right, with the suffix 'Ht' representing a difference in the y coordinate,'Off' the x coordinate and 'Depth', the z coordinate. Model accuracy was assessed as both percentages and ROC curves with the coefficients as odds ratios. There were 1283 images (1015 females and 268 males) all with a diagnosis of AIS. The models identified a scoliosis in the thoracic spine with an 83% accuracy (AUC 0.91), thoracolumbar / lumbar spine 74% accuracy (AUC 0.76) and whole spine 80% accuracy (AUC 0.88). Significant parameters were AxDiffHt, AxDiffOff, WaistDiffHt, ScapDiffOff and ScapDiffHt for the thoracic curves, AxDiffHt, AxDiffOff, WaistDiffHt for the thoracolumbar / lumbar curves and AxDiffHt, AxDiffOff, WaistDiffHt and ScapDiffHt for the whole spine. The use of fixed anatomical points around the torso, analysed using logistic regression, has a high accuracy for identifying curves in the thoracic, thoracolumbar / lumbar and whole spines. Whilst coming from surface topography images, the results raise the future use of digital photography as a tool for the identification of a small scoliosis without using other imaging techniques.

Machine learning for multi-dimensional performance optimization and predictive modelling of nanopowder-mixed electric discharge machining (EDM)

AbstractAluminium 6061 (Al6061) is a widely used material for various industrial applications due to low density and high strength. Nevertheless, the conventional machining operations are not the best choice for the machining purposes. Therefore, amongst all the non-conventional machining operations, electric discharge machining (EDM) is opted to carry out the research due to its wide ability to cut the materials. But the high electrode wear rate (EWR) and high dimensional inaccuracy or overcut (OC) of EDM limit its usage. Consequently, nanopowder is added to the dielectric medium to address the abovementioned issues. Nanopowder mixed EDM (NPMEDM) process is a complex process in terms of performance predictability for different materials. Similarly, the interactions between the process parameters such as peak current (Ip), spark voltage (Sv), pulse on time (Pon) and powder concentration (Cp) in dielectric enhance the parametric sensitivity. In addition, the cryogenic treatment (CT) of electrodes makes the process complex limiting conventional simulation approaches for modelling inter-relationships. An alternative approach requires experimental exploration and systematic investigation to model EWR and overcutting problems of EDM. Thus, artificial neural networks (ANNs) are used for predictive modelling of the process which are integrated with multi-objective genetic algorithm (MOGA) for parametric optimization. The approach uses experimental data based on response surface methodology (RSM) design of experiments. Moreover, the process physics is thoroughly discussed with parametric effect analysis supported with evidence of microscopic images, scanning electron microscopy (SEM) and 3D surface topographic images. Based on multi-dimensional optimization results, the NT brass electrode showed an improvement of 65.02% in EWR and 59.73% in OC using deionized water. However, CT brass electrode showed 78.41% reduction in EWR and 67.79% improved dimensional accuracy in deionized water. In addition to that, CT brass electrode gave 27.69% less EWR and 81.40% improved OC in deionized water compared to kerosene oil.

Fibroblasts and osteoblasts behavior after contact with different titanium surfaces used as implant abutment: An in vitro experimental study

BackgroundThe goal of this in vitro study was to compare three different surfaces: two types of implant surfaces commercially available ([a] smooth/machined and [b] acid-treated surface) versus (c) anodized surface. Discs were manufactured with commercially pure titanium (CP) grade IV, which were subsequently analyzed by scanning microscopy and fibroblastic and osteoblastic cell cultures. MethodsNinety-nine discs (5 × 2 mm) were manufactured in titanium grade IV and received different surface treatments: (i) Mach group: machined; (ii) AA group: double acid etch; and (iii) AN group: anodizing treatment. Three discs from each group were analyzed by Scanning Electron Microscopy (SEM) to obtain surface topography images and qualitatively analyzed by EDS. Balb/c 3T3 fibroblasts and pre-osteoblastic cells (MC3T3-E1 lineage) were used to investigate each group's biological response (n = 10/cellular type). The data were compared statistically using the ANOVA one-way test, considered as a statistically significant difference p < 0.05. ResultsThe AA group had numerous micropores with diameters between 5 and 10 μm, while nanopores between 1 and 5 nm were measured in the AN group. The EDX spectrum showed a high titanium concentration in all the analyzed samples. The contact angle and wetting tension were higher in the AA, whereas similar results were observed for the other groups. A lower result was observed for base width in the AA, which was higher in the other two groups. The AN showed the best values in the fibroblast cells, followed by Mach and AA; whereas, in the culture of the MC3T3 cells, the result was precisely the opposite (AA > Mach > AN). There was similar behavior for cell adhesion for the test groups (Mach and AN), with greater adhesion of Balb/c 3T3 fibroblasts compared to MC3T3 cells; in the AA group, there was greater adherence for MC3T3 cells compared to Balb/c 3T3 fibroblasts. ConclusionsThe findings suggest that different surface characteristics can produce different biological responses, possibly cell-line dependent. These findings have important implications for the design of implantable medical devices, where the surface characteristics can significantly impact its biocompatibility.

Evaluation of intelligent packaging functions of black carrot extract-infused polyvinyl alcohol nanofibers

In this study, we aimed to evaluate the characteristic changes in polyvinyl alcohol-based nanofibers after being stored with black sea salmon fillets. For this purpose, electrospun nanofibers were produced as control (PVA), black carrot extract-incorporated (PVAB), and extract+SnO2 incorporated (PVASN), and their properties were compared. Morphological results showed the formation of regular ultrafine nanostructures, and differences between nanofiber samples were evaluated by measuring fiber diameters. Nanofiber sizes increased with the addition of black carrot and SnO2. Elemental analysis was performed to obtain information about the concentration in the nanofibers. Different O and Sn concentrations indicated that important constituents of anthocyanins and SnO2 were attached to the samples. The location of C, O, Sn atoms was determined by Energy Spectrum Analysis (EDS) color mapping, which confirmed the attachment of Sn in the PVASN sample. To elucidate the relationship between spoilage and the absorption of volatiles from smoked salmon fillets, nanofibers and fillets were kept together in a petri dish at room temperature. After being stored with salmon meat, the PVASN sample showed fewer entanglements without any defects. Upon exposure to volatiles, molecular structures changed, and water contact angle values decreased. X-Ray Diffraction (XRD) results indicated the state of the polymer matrix and SnO2. Chemical bond interactions with released volatiles effected the peak parameters of nanofibers. 3D and 2D surface topographical images of PVASN were also compared before and after storage using a profilometer. This study's results showed that functionalized nanofibers with extract-SnO2 could be applied as an intelligent food packaging layer, providing valuable data about the potential usage of electrohydrodynamic processing.

Operando Nanomechanical Mapping of Silicon Thin Film Electrode during the First Lithiation and Delithiation Investigated By Bimodal Atomic Force Microscopy

Si is emerging as one of the most prospective anode materials for all-solid-state Li-ion batteries due to its extremely high theoretical capacity density of 4200 mAh g-1 and relatively negative potential for lithiation/delithiation. Towards its widespread use, controlling severe volume expansion/contraction during lithiation/delithiation is a challenge because it may cause cracking, fracture, and pulverization that negatively influence the cycle performance and rate capability of the cells [1]. Such mechanical event is induced by the change in the lattice structure due to the formation of LixSi and successive increasing/decreasing of Li content x in LixSi [2].Bimodal atomic force microscopy (AFM) offers quantitative mapping of nanoscale mechanical property, simultaneously with surface topography imaging [3]. Our group previously applied this technique to the cross-section of a composite electrode consist of active materials, binders, conductive additives, and deposited electrolyte solution and successfully demonstrated nanomechanical mapping [4]. Here, we develop an operando bimodal AFM system to track Young’s modulus changes of electrode materials in an all-solid-state battery configuration during the lithiation and delithiation reactions in real-time.A cell in a Cu/Si/LLZT/In/Li configuration was fabricated as follows; a 3 µm-thick Si thin-film and a 100 nm-thick Cu layer were sputter-deposited on one side of Li6.6La3Zr1.6Ta0.4O12 (LLZT) solid electrolyte, an In layer was sputter-deposited on the other side of LLZT, the Cu/Si/LLZT/In sample was milled with an Ar-ion beam to yield a flat and smooth cross-section suitable for AFM analysis, and then a 50 µm-thick Li metal foil was combined with the pre-coated In thin layer. Operando nanomechanical mapping was performed by mounting the cross-section-exposed cell in the custom-made sample holder coupled with a potentiostat for bias applications, in an Ar-filled glove box to prevent any atmospheric influences.Electrochemical lithiation and delithiation were carried out within a potential window of 0.01-1.20 V vs. Li/Li+. Electrochemical characterization indicated that the capacities of the Si electrode for the first lithiation and delithiation are 3300 and 1833 mAh g-1, respectively. These capacities are equal to the formation of Li3.46Si after the first lithiation of the pristine Si and Li1.54Si after the successive delithiation from Li3.46Si. Throughout the lithiation, the averaged Young’s modulus of Si electrode decreased due to the formation of LixSi and increase in the Li content x in LixSi. In the initial stage of lithiation, it drastically decreased because LixSi was formed by the lithiation of pristine Si. Then, it moderately decreased with increasing Li content x in LixSi. Unfortunately, the Young’s modulus maps were only recorded until the formation of Li1.54Si because the successive delithiation was not completed possibly due to the phase transformation of crystalline LixSi to amorphous LixSi [5], which may cause a significant mechanical strain inside the thin film. The measured Young’s modulus values were consistent with those obtained by first principle calculation [6]. Further details are given at the presentation.

Assessment of enamel surface roughness and hardness with metal and ceramic orthodontic brackets using different etching and adhesive systems: An in vitro study

BackgroundThis study aimed to evaluate enamel surface roughness and microhardness following the use of different bracket materials (metal or ceramic), etchants (total- and self-etchants), and adhesive systems (precoated or flash-free). MethodA total of 99 extracted human premolars were selected for the analysis. The surface roughness was first assessed (roughness control). One specimen from each subgroup was examined using a scanning electron microscope to illustrate the surface topography. Eighty-eight teeth were prepared using total- or self-etchants and bonded to precoated or flash-free adhesive metal or ceramic brackets. The remaining 11 specimens were not bonded to brackets (microhardness controls). The brackets were debonded after immersion in distilled water for 24 h. The specimens were again scanned for surface roughness and topography imaging. Finally, the microhardness was assessed using a micro-Vickers hardness test at a force of 200 g for 10 s. ResultAn overall statistically significant increase in surface roughness and reduced surface microhardness were observed in all experimental groups when compared with those in the control groups. The etchant type was the only variable found to contribute to the measured surface properties, with increased roughness and reduced microhardness introduced by total-etching compared to those by self-etching. ConclusionOrthodontic brackets introduced a significant increase in enamel surface roughness and reduce microhardness compared with untreated enamel, regardless of the bracket material, etchant type, and adhesive system. The etchant type was the only variable contributing to these changes, with total etching having a more pronounced effect.

A characterization method for the physical features of honed texture surface of engine cylinder liner

A machine vision method is proposed to characterize the physical features of the honed surface texture on the cylinder liner of internal combustion engines. According to the gray image information of the surface texture of the cylinder liner, the curvelet transform method is employed to extract the physical features of the multi-scale anisotropic surface topography image of the cylinder liner, and the partitioned iterated function system (PIFS) is constructed to calculate fractal dimension to describe the physical features of the surface texture of the cylinder liner. The proposed PIFS-based method is applied to the honed surface and dimple-textured surface of the cylinder liner, the effectiveness and the accuracy are verified by comparing with the other two methods.

Comparison of Continuous and Pulsating Water Jet during Piercing of Ductile Material.

More efficient ways to process materials are constantly being sought, even in the case of continuous water flow technology, which acts on materials mainly by stagnant pressure. An alternative method is an ultrasound-stimulated pulsating water jet, the basis of which is the repeated use of impact pressure, which reduces the time interval for mechanical relaxation. This article focuses on a comparative study from the point of view of water mass flow rate on material penetration and its integrity. Relatively low pressures (p = 20, 30, and 40 MPa) with varying nozzle diameters (d = 0.4 and 0.6 mm) were used to identify the effectiveness of the pulsating water jet. The time exposure of the jet at a fixed place was varied from t = 0.5 to 5 s for each experimental condition. The results showed that with an increase in the pressure and diameter values, the disintegration depth increased. In addition, the surface topography and morphology images showed signs of ductile erosion in the form of erosion pits, upheaved surfaces, and crater formation. The microhardness study showed an increase of 10% subsurface microhardness after the action of the pulsating water jet as compared to the original material.

Synchronous Phase-Shifting Interference for High Precision Phase Imaging of Objects Using Common Optics.

Quantitative phase imaging and measurement of surface topography and fluid dynamics for objects, especially for moving objects, is critical in various fields. Although effective, existing synchronous phase-shifting methods may introduce additional phase changes in the light field due to differences in optical paths or need specific optics to implement synchronous phase-shifting, such as the beamsplitter with additional anti-reflective coating and a micro-polarizer array. Therefore, we propose a synchronous phase-shifting method based on the Mach-Zehnder interferometer to tackle these issues in existing methods. The proposed method uses common optics to simultaneously acquire four phase-shifted digital holograms with equal optical paths for object and reference waves. Therefore, it can be used to reconstruct the phase distribution of static and dynamic objects with high precision and high resolution. In the experiment, the theoretical resolution of the proposed system was 1.064 µm while the actual resolution could achieve 1.381 µm, which was confirmed by measuring a phase-only resolution chart. Besides, the dynamic phase imaging of a moving standard object was completed to verify the proposed system's effectiveness. The experimental results show that our proposed method is suitable and promising in dynamic phase imaging and measurement of moving objects using phase-shifting digital holography.

Multiresponse optimization of performance indicators through Taguchi-grey relational analysis in EDM of cemented carbide

Cemented carbide is mostly used in the mold and tool industry due to their high hardness, temperature and wear resistance, and it is very difficult to shape with conventional machining methods. Because, during the machining of certain geometry from these materials, microcracks on surface and flaking at the machined edges due to their brittleness as well as rapid tool wear mostly due to their high hardness occur. In this case, EDM is considered one of the most suitable machining technologies for brittle material such as carbides, as it provides a non-contact shaping with electrical sparks between the tool and the workpiece. This study focused on the simultaneous optimization of the most important performance indicators namely material removal rate, tool wear rate and surface roughness in creating a keyway on WC-15Co material with the die-sinking EDM. As a result of experiments using copper electrode, the impacts on performance indicators of discharge current, pulse time and pulse interval were investigated with 3D surface topography images. It was determined that the peaks and craters formed on the machined surface expanded with the increase of pulse time, and the decreased with the increase in the pulse interval. As a result of the Taguchi-grey relational analysis (TGRA) application, discharge current of 6 A, pulse time of 25 µs and pulse interval of 100 µs were found as optimum parameters. ANOVA results showed that Ip, Ton and Toff affected GRG values by 44.23%, 28.77% and 5.87%, respectively. A 23.95% improvement in performance indicators was achieved thanks to the TGRA multiresponse optimization.

Research of Moisture Sorption by Laminated Composite Materials

This article focuses on the moister sorption by laminated composites. Moisture sorption was carried out on layered polymer composite materials consisting of layers of basalt fabric and fiberglass based on epoxy-diane resin. It is shown that the process of moisture absorption for glass fiber-reinforced polymers is more intense and with a higher concentration of moisture in comparison with basalt fiber-reinforced polymer. Curves of the sorption processes of moisture absorption and water absorption are obtained. The diffusion coefficients for the corresponding processes are calculated. Alteration in the surface structure of polymer composite materials were recorded using surface topography and REM images before and after exposure in the climate of Yakutsk (Russia).

The relationship between minor coronal asymmetry of the spine and measures of spinal sagittal shape in adolescents without visible scoliosis

The purpose of this work is to identify what features of overall spinal sagittal shape are associated with coronal asymmetry in those without scoliosis. Using a longitudinal analysis of Integrated Shape Imaging System 2 (ISIS2) surface topography images of those without scoliosis, measures of coronal asymmetry, along with measures of spinal sagittal shape (kyphosis, lordosis and sagittal imbalance, which is a measure of the position of the top of the thoracic spine relative to the sacrum) were analysed using linear mixed effect models (LMEM), which is a method of analysing the components of a complex model (such as that describing overall spinal shape), to ascertain the relative relationships between the parameters. Data was also analysed when subdivided for the anatomical level of coronal asymmetry (thoracic or thoracolumbar/lumbar pattern). There were 784 measures from 196 children. Kyphosis had little effect on coronal asymmetry for males and females, lordosis increased with coronal asymmetry in females only and sagittal imbalance increased with coronal asymmetry in males only. The results of the LMEM modelling were that the parameters related to coronal asymmetry were lordosis and sagittal imbalance. In thoracic coronal asymmetry, whilst lordosis was predominant, kyphosis played more of a role. In thoracolumbar/lumbar coronal asymmetry, lordosis and sagittal imbalance were the larger coefficients. Coronal asymmetry of the spine in those without scoliosis is related to features of spinal sagittal shape, particularly lordosis and sagittal imbalance. This knowledge adds to the understanding of the aetiology of adolescent idiopathic scoliosis.

Development and characterization of antioxidant composite films based on starch and gelatin incorporating resveratrol fabricated by extrusion compression moulding

Starch/gelatin (SG) films incorporated with resveratrol (RES) at various concentrations (0%–20%, w/w, on the weight of starch and gelatin) were developed via thermal extrusion followed by compression moulding. The SG based films were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, together with the determination of optical, physical, thermal, and antioxidant properties of the films. SEM images showed the SG films containing RES had a higher surface roughness than that without RES, which was also confirmed by the three-dimensional surface topography images. The FTIR analysis revealed the existence of physical interactions among starch, gelatin, and RES through hydrogen bonding. The incorporation of RES significantly increased the thickness, opacity, and tensile strength of the films, while decreasing their transmittance, water solubility, water vapor and oxygen permeability. Furthermore, the elongation at break, surface hydrophobicity and thermal stability of the films also enhanced to some extent after addition of RES. More importantly, the composite films showed excellent antioxidant activity proportional to the RES concentration, and all films showed good anti-permeate property for oil without or with RES. Consequently, the SG film containing 20% RES with the highest oxygen barrier property and antioxidant activity could effectively reduce oxidative rancidity of soybean oil stored at 50 °C for 24 days when compared to SG film without RES and control sample (without film). To sum up, the thermoplastic processed SG films incorporating RES exhibited adequate properties for food packaging such as oil products which are highly susceptible to oxidation.

Calculation of tunneling current across trapezoidal potential barrier in a scanning tunneling microscope

Accurate calculation of the tunneling currents in a scanning tunneling microscope (STM) is needed for developing image processing algorithms that convert raw data of the STM into surface topographic images. In this paper, an accurate calculation of the tunneling current for several tip–sample distances, bias voltages, and tips of a hyperboloidal shape with several radii of curvature is carried out. The main features of this calculation are the following. Non-WKB exact solutions to the trapezoidal (linear) potential in the barrier region are used to calculate the tunneling probabilities. Pauli blocking effects on both forward and reverse current densities are introduced. Finite temperature (viz. 300K) calculation in which electrons belonging to a narrow band of energy about the Fermi level contribute to tunneling is carried out. Integration over a field line method is used to obtain tunneling currents for the nonplanar hyperboloidal shaped tips, using the expressions obtained in the paper, for planar model current densities. An estimate of the lateral resolution is introduced. Earlier works do not consider all these aspects together in a single calculation. Tunneling currents are found to increase rapidly with increasing bias voltage and decrease exponentially with increasing tip–sample distances. Airy function determined currents are a more accurate function of a tip–sample distance than the WKB determined currents. Pauli effects are found to not always reduce currents from their non-Pauli values. The lateral resolution is found to be degraded for blunter tips, larger bias voltages, and larger tip–sample distances.

Effectiveness of Different Polishing Kits for Chairside CAD/CAM Provisional Restorative Materials.

To investigate the efficacy of three specially designed polishing kits for provisional restorations made from three chairside computer-aided design and computer-aided manufacturing (CAD/CAM) provisional resin blocks. Ninety-six chairside CAD/CAM provisional restorations were milled out of three chairside CAD/CAM provisional resin blocks: (1) ArtBloc Temp (Merz Dental); (2) Telio CAD (Ivoclar Vivadent); and (3) Vita CAD-Temp (VITA Zahnfabrik). The provisional restorations for each material were allocated into the following groups: (1) milled restorations (no polish); (2) polished with CADMaster CAD/CAM Adjustment & Polishing Kit (CM, Shofu); (3) polished with KUT Ultimate Bisacryl (Temporaries) Polishing Kit (KU, Dental Savings Club); and (4) polished with K0330 PMMA Adjusting, Finishing & Polishing (KP, Brasseler USA). Optical profilometry and atomic force microscopy (AFM) were used to assess the surface roughness (Ra) of each provisional restoration at the microscale and nanoscale, respectively, and obtain topographical images. In addition, the milled and polished restorations were visually evaluated by 16 dentists. There was a strong positive correlation with Ra values between optical profilometry and AFM. Only KP significantly improved the surface roughness of CAD/CAM provisional restorations compared to the milled equivalent, regardless of material type or measurement modality (ie, lateral length scale). Although surface topography imaging with AFM revealed some shallow scratches, even for KP polished specimens, all KP polished restorations were categorized as clinically acceptable for provisional restorations in visual inspections from dentists. Specially designed polishing kits for provisional restorations did not all improve the surface roughness of chairside CAD/CAM provisional restorations, regardless of the measurement method. KP was more consistently effective in polishing milled chairside CAD/CAM provisional restorations than CM and KU.

Effect of Saccharides Coating on Antibacterial Potential and Drug Loading and Releasing Capability of Plasma Treated Polylactic Acid Films.

More than half of the hospital-associated infections worldwide are related to the adhesion of bacteria cells to biomedical devices and implants. To prevent these infections, it is crucial to modify biomaterial surfaces to develop the antibacterial property. In this study, chitosan (CS) and chondroitin sulfate (ChS) were chosen as antibacterial coating materials on polylactic acid (PLA) surfaces. Plasma-treated PLA surfaces were coated with CS either direct coating method or the carbodiimide coupling method. As a next step for the combined saccharide coating, CS grafted samples were immersed in ChS solution, which resulted in the polyelectrolyte complex (PEC) formation. Also in this experiment, to test the drug loading and releasing efficiency of the thin film coatings, CS grafted samples were immersed into lomefloxacin-containing ChS solution. The successful modifications were confirmed by elemental composition analysis (XPS), surface topography images (SEM), and hydrophilicity change (contact angle measurements). The carbodiimide coupling resulted in higher CS grafting on the PLA surface. The coatings with the PEC formation between CS-ChS showed improved activity against the bacteria strains than the separate coatings. Moreover, these interactions increased the lomefloxacin amount adhered to the film coatings and extended the drug release profile. Finally, the zone of inhibition test confirmed that the CS-ChS coating showed a contact killing mechanism while drug-loaded films have a dual killing mechanism, which includes contact, and release killing.