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Questioned document examination is one of the most challenging tasks in the field of forensic science. Examining the document without destroying its integrity is difficult in such cases. Microscopic examination is a noble and mostly non-destructive approach in document examination. It enables the examiner to visualize the evidence in the document, which would have been otherwise difficult with unaided eyes. The purpose of the study was to establish the importance of microscopic examination in document examination. A critical review of 60 years, from 1963 to 2023, of various research papers from different journals has been conducted. Applications of various microscopes including stereo microscopes, digital microscopes, scanning electron microscopes (SEM), and atomic force microscopes (AFM) were reviewed. Compared to the basic examinations performed before the year 2000, there was a remarkable evolution involving complex examinations with more precise results after the year 2000. Microscopy helped solve almost all kinds of problems involved in document examination. Among all microscopes, the stereo microscope was found to be a prominent tool in document laboratories. Certain limitations were also listed for microscopic examination over spectroscopic methods. However, microscopes have been the tool of choice for forensic document examiners. [ABSTRACT FROM AUTHOR]

Interproximal enamel reduction is a part of the orthodontic treatment as a method of space generation in addition to other vast indications. Some studies found that different techniques might impose changes to the enamel surface that alter its topography, which in turn might influence its integrity and susceptibility to caries. Polishing, however, after this procedure is thought to be helpful to reduce these adverse effects. To evaluate the nano-topography of the enamel surfaces after interproximal reduction (IPR) and determine its influence on enamel surface roughness and examine the need for polishing to minimise these influences, when combined with topical fluoride application. A total of 60 proximal surfaces of 40 extracted maxillary premolars (10 premolars left unprepared as the control group) were reduced with different stripping instruments (discs, burs and manual strip system). The surface roughness of enamel was analysed with an atomic force microscope to determine the results quantitatively as well as qualitatively on the nanoscopic scale. One of each proximal surface was followed by polishing and fluoride varnish after the reduction. The results showed that surface roughness was increased in all groups without polishing. The greatest mean roughness was recorded for the disc group (212 ±125.7), followed by the bur group (172 ±93.1) and manual strips (153.8±106.7). The difference between the groups, however, was not significant for both mean roughness (P = 0.656) and height (P = 0.737). The parameters were decreased after polishing in all groups but the difference between methods was not significant for both parameters (P = 0.946 and P = 0.849); however, the mean height was reduced to nearly half the reading in the bur and manual strip method. The disc group only showed a statistically significant decrease in surface roughness with polishing (P < 0.05). All other results were not significant. All methods of interproximal reduction do not influence enamel surface nanotopography significantly with and without polishing. Polishing resulted in significant reduction of surface roughness only in the disc group. [ABSTRACT FROM AUTHOR]

The urgent necessity of reducing pesticides in the agricultural sector compels us to explore alternative, environmentally friendly approaches for controlling pathogenic bacteria and crop diseases. The usage of bacterial viruses or bacteriophages (phages) to control pathogenic bacteria is still limited due to the lack of understanding of the factors influencing shelf life. We examined the effects of pH and NaCl on the storage buffers on the infectivity of the RSJ2 phage. The RSJ2 phage infects Ralstonia solanacearum, causing bacterial wilt disease in tomatoes. The buffer that retained the highest phage titer (63 % after two months) was at pH 8.3 and 0.5 M NaCl. pH and NaCl concentrations directly affected the phage particles. The phage stiffness was measured with the nanoindentation technique, and a correlation between the phage remaining titers and the stiffness was revealed. The average stiffness associated with the highest remaining titer was 0.07 N/m, which falls into the intermediate stiffness range. The results agree with the previous study on the C22 phage stiffness, revealing an association between intermediate stiffness and phage infectivity. Phage stiffness can become an attribute of phage metastability and can be used to predict the phage shelf life. [ABSTRACT FROM AUTHOR]

Brain gliomas represent some of the most aggressive tumors encountered by modern medicine and, despite major efforts to optimize early diagnosis and treatment, the prognosis remains poor. Due to the complex structure of the brain and the unique mechanical properties of the extracellular matrix, gliomas invade and expand into the brain parenchyma, along white matter tracts and within perivascular spaces, usually sparing normal vessels. Different methods have been developed to study the mechanical properties of gliomas in a wide range of scales, from cells and the microscale to tissues and the macroscale. In this review, the current view on glioma mechanics is presented and the methods used to determine glioma mechanical properties are outlined. Their principles and current state of affairs are discussed. [ABSTRACT FROM AUTHOR]

The threat of multi-drug resistant bacterial pathogens evokes researchers to synthesized safe and effective chemotherapeutic agents for nano-drug delivery system. In current study, Schiff base of nicotinic hydrazide(NHD) and its silver nanoparticles(NHD-AgNPs) were synthesized and characterized. These compounds were investigated for cytotoxicity, antibacterial and AFM activity. The NHD showed LD50 at >1000μg/mL while NHD-AgNPs didn't exhibit toxicity at 1000μg/mL against 3T3 cell line. The NHD showed zone of inhibition against two strains of salmonella enteric (ATCC 14028 and 700408) 45.29±1.66 and 48.01±1.43mm respectively at 160μg/mL (p<0.01) while NHDAgNPs exhibited 55.87±2.08 and 52.88±1.42 mm respectively at 130μg/mL (p<0.001) in disc diffusion method. NHD showed more than 70% growth inhibition for both strains at 85 and 125μg/ml (p<0.01) respectively, while NHD-AgNPs inhibit 80% and 75% respectively at 75 and 125 μg/ml (p<0.01, p<0.001) against Alamar blue antibacterial assay. For morphological changes in bacterial cell wall NHD and NHD-AgNPs treated bacterial cells were observed under atomic force microscope(AFM) and treated bacterial cells were severely damaged with leaked cytoplasmic contents as compare to untreated bacterial cell. These results validate that NHD-AgNPs were highly active as compared to NHD against both strains at their MIC concentrations. In future, comparative wound healing potential will be emphasized. [ABSTRACT FROM AUTHOR]

In recent years, 3D printing technology has flourished and applied to tissue engineering regeneration. The purpose of this study is to investigate the effects of gap width between struts (GWbS) of three-dimensional-printed polylactic acid scaffolds (3DP-PLASs) on neural differentiation of human dental pulp stem cells (hDPSCs). Both the 3DP-PLASs with the GWbS of 150 μm and 200 μm were experimental groups and the 3DP-PLAS without microfilament struts was the control group. Properties of 3DP-PLASs were observed by water contact angles (WCA), atomic force microscope (AFM), and differential scanning calorimeter (DSC). The cell culture of hDPSCs on 3DP-PLASs was performed, and cytotoxicities were measured with Alamar Blue assay. The neural differentiation of hDPSCs on different 3DP-PLASs was compared after neural induction. Expressions of neural markers Nestin, MAP2, beta III tubulin, and GFAP were evaluated with immunocytochemical staining. Our results demonstrated no cytotoxicities among scaffolds, whereas they may differ in crystal sizes and directions resulting from different orders of cooling time, contact surface, and temperature distribution during the building process. In addition, hDPSCs could successfully adhere to 3DP-PLAS modified by alcohol or poly- l -Lysine and demonstrate morphological change and related protein performance. We conclude that 3DP-PLASs with 150 μm gaps can induce cellular orientations more easily than those with 200 μm gaps. In addition, 3DP-PLASs seem to improve cell adhesion after being coated with poly- l -lysine or soaked with alcohol. [ABSTRACT FROM AUTHOR]

Background/purpose: In recent years, 3D printing technology has flourished and applied to tissue engineering regeneration. The purpose of this study is to investigate the effects of gap width between struts (GWbS) of three-dimensional-printed polylactic acid scaffolds (3DP-PLASs) on neural differentiation of human dental pulp stem cells (hDPSCs).Methods: Both the 3DP-PLASs with the GWbS of 150 μm and 200 μm were experimental groups and the 3DP-PLAS without microfilament struts was the control group. Properties of 3DP-PLASs were observed by water contact angles (WCA), atomic force microscope (AFM), and differential scanning calorimeter (DSC). The cell culture of hDPSCs on 3DP-PLASs was performed, and cytotoxicities were measured with Alamar Blue assay. The neural differentiation of hDPSCs on different 3DP-PLASs was compared after neural induction. Expressions of neural markers Nestin, MAP2, beta III tubulin, and GFAP were evaluated with immunocytochemical staining.Results: Our results demonstrated no cytotoxicities among scaffolds, whereas they may differ in crystal sizes and directions resulting from different orders of cooling time, contact surface, and temperature distribution during the building process. In addition, hDPSCs could successfully adhere to 3DP-PLAS modified by alcohol or poly-l-Lysine and demonstrate morphological change and related protein performance.Conclusion: We conclude that 3DP-PLASs with 150 μm gaps can induce cellular orientations more easily than those with 200 μm gaps. In addition, 3DP-PLASs seem to improve cell adhesion after being coated with poly-l-lysine or soaked with alcohol. [ABSTRACT FROM AUTHOR]

Many techniques were developed for enamel polishing after orthodontic bracket debonding to keep the enamel surface as smooth as possible to pretreatment condition, in addition to many bracket adhesives used for orthodontic brackets bonding. This study aimed to compare the effect of two different adhesive materials and polishing protocols on enamel surface roughness after debonding of orthodontic brackets. Forty maxillary premolars were divided into four groups, orthodontic brackets were bonded using two different adhesive materials (Resilience LC Orthodontic Adhesive from Orthotechnology and Bisco Ortho bracket paste LC from Bisco). After brackets debonding adhesive remnants were removed using carbide bur followed by either Enhance Finishing tip then Prisma Gloss Polishing Cup with Prisma Gloss Polishing Paste or High Shine Enamel Polisher and Astropol green polishing cups. Then Atomic force microscope was used to evaluate surface roughness parameters among groups. The roughness data were statistically analyzed with Tukey post hoc test. Results showed significantly lower surface roughness parameters with Bisco Ortho bracket paste group compared with Resilience LC Orthodontic Adhesive group when both were polished with Enhance Finishing tip and Prisma Gloss Polishing Paste. Additionally, significantly lower Sz (Ten points height) value was seen with Bisco Ortho bracket paste group polished with Enhance Finishing tip and Prisma Gloss Polishing Paste in comparison with Resilience LC Orthodontic Adhesive polished with High Shine Enamel Polisher and Astropol green polishing cups. Pre-mounted, aluminum oxide impregnated, cured urethane dimethacrylate resin finishers tips (Enhance finishing tips) with a fine-grit aluminum-oxide polishing paste (Prisma Gloss Polishing Paste) could produce smoother enamel surface than 5 micron diamond grit suspended in resilient silicone tip (high shine enamel polisher) followed by Multipleuse polishing cups consist of silicone rubber and silicon carbide particles (Astropol green polishing cups) when Bisco Ortho bracket paste LC used. [ABSTRACT FROM AUTHOR]

Precise measurement of mechanical properties of living cells is important in understanding their mechanics-biology relations. In this study, we adopted the atomic force microscope to measure the creep deformation and stress relaxation of six different human cell lines. We examined whether the measured creep and relaxation trajectories satisfy a verification relation derived based on the linear viscoelastic theory. We compared the traditional spring-dashpot and the newly developed power-law-type constitutive relations in fitting the experimental measurements. We found that the human normal liver (L02), hepatic cancer (HepG2), hepatic stellate (LX2) and gastric cancer (NCI-N87) cell lines are linear viscoelastic materials, and human normal gastric (GES-1) and gastric cancer (SGC7901) cell lines are nonlinear due to failing in satisfying the verification relation for linear viscoelastic theory. The three-parameter power-law-type constitutive relation can fit the experimental measurements better than that of the five-parameter classical spring-dashpot. [ABSTRACT FROM AUTHOR]

The formation of clay suspensions involves complex interactions among clay particles subjected to the geochemical environment during the sedimentation process. The structural characteristics have a major influence on the physical and mechanical behavior of the suspension. A modeling framework involving a Discrete Element Method (DEM) model with customized particle mechanical interactions is proposed in this paper for the holistic prediction of the physical structure of clay suspensions. The particle interaction force model is based on the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory that accounts for electrostatic repulsion, van der Waals attraction, contact repulsion, etc. Kaolinite is used as the model clay to demonstrate the model performance. The surface charge density of kaolinite is obtained through Atomic Force Microscope (AFM) force measurement and is implemented in the particle interaction force model in the subsequent simulations. Influencing factors, such as centrifugal acceleration, ionic concentration, platy structure of particles, and particle size, on the formation of kaolinite suspensions are studied with the numerical model and compare favorably well with the experimental data. This work lays down a unique framework consisting of computational modeling and microscale characterization of clay particles to holistically predict the characteristics of clay suspensions, which paves the basis to model and predict their bulk physical and mechanical behavior. fx1 • Holistic modeling framework integrating Discrete Element Model with interaction force model for prediction of the formation of clay suspensions. • Particle interaction force model based on the Derjaguin, Landau, Verwey and Overbeek (DLVO) theory calibrated with Atomic Force Microscope (AFM) force measurement. • Simulating the effects of centrifugal acceleration, ionic concentration, platy structure of particles, and particle size on the formation of kaolinite suspensions. • Experimental validation with the general trends predicted by the computational model. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effects of instrumentation and irrigation on the initial adherence of Enterococcus faecalis to root canal dentin and to explore initial microbial adhesion to root filling materials. The following specimens were prepared: instrumented and uninstrumented dentin, dentin treated with different irrigation protocols, and root filling materials. The number of E. faecalis cells adhered on dentin was measured. The adhesion force of E. faecalis cells on different materials and the roughness of different surfaces were measured. The contact angle of the surfaces was recorded. The results were analyzed using the t test. Instrumented dentin specimens had a significantly higher amount of E. faecalis adherence than uninstrumented dentin. There were higher numbers of adhering bacteria on the dentin when EDTA was used alone (P <.05) compared with other irrigants alone. The use of chlorhexidine (CHX) as the last irrigant for a certain time resulted in a reduced number of adhering bacteria when the specimens were first exposed to sodium hypochlorite (NaOCl) followed by EDTA. EDTA used alone had the highest adhesion force followed by NaOCl alone and CHX alone (P <.05). Dentin treated with EDTA alone had the highest roughness and contact angle followed by NaOCl alone and CHX alone (P <.05). CHX added as the final irrigant after NaOCl with EDTA irrigation reduced the contact angle (P <.05). Larger amounts of adhering bacteria and higher adhesion force were detected on the surface of gutta-percha and sealer than on the dentin surface (P <.05). Instrumentation and irrigation alter the initial adherence of E. faecalis to root canal dentin and the surface properties of the dentin as well. • Instrumented dentin had more E. faecalis adherence than uninstrumented dentin. • The longer irrigation time resulted in less adhering bacteria on the dentin. • Root filling material had higher adhesion activity compared with dentin. [ABSTRACT FROM AUTHOR]

In the present study, nanochannels are fabricated on a poly (methyl methacrylate) (PMMA) surface using an atomic force microscopy (AFM) tip-based nanomilling method. Experiments are conducted using a silicon tip with a radius around 30 nm. The influence of three typical feeding directions of the relative rotational motion between the tip and the sample on the machined results is studied in detail. Results show that the processing outcomes are obviously different when machining with various feed directions. The chip formation, machined depth and the material accumulated on the sides of the groove are considered as the evaluation indicators for the machining outcomes. Finally, the optimized feed direction is selected based on these results to guarantee the machining quality of the fabricated nanochannels, which may have the potential for the nanofluidic applications. [ABSTRACT FROM AUTHOR]

We investigated the viscoelastic response of direct and indirect dental restorative composites by the novel technique of AM-FM atomic force microscopy. We selected four composites for direct restorations (Adonis, Optifil, EPH, CME) and three composites for indirect restorations (Gradia, Estenia, Signum). Scanning electron microscopy with micro-analysis was also used to support the results. The mean storage modulus of all composites was in the range of 10.2-15.2 GPa. EPH was the stiffest (p<0.05 vs. all other composites but Adonis and Estenia), while no significant difference was observed between direct and indirect group (p≥0.05). For the loss tangent, Gradia had the highest value (~0.3), different (p<0.05) from Optifil (~0.01) and EPH (~0.04) despite the large coefficient of variation (24%), and the direct composites showed higher loss tangent (p<0.01) than the indirect composites. All composites exhibited minor contrast at the edge of fillers, showing that these are pre-polymerized, as confirmed by EDS. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) indentation is the most suitable way to characterize micromechanical properties of soft materials such as bio tissues. However, the mechanical data obtained from force-indentation measurement are still not well understood due to complex geometry of the bio tissue, nonlinearity of indentation contact, and constitutive relation of hyperelastic soft material. Poly-N-isopropyl acrylamide (PNIPAM) filled with 5 wt% polystyrene (PS) sphere particles material system can be utilized as a simplified model for mimicking a whole host of soft materials. Finite element model has been constructed to simulate indentation as in AFM experiments using colloidal probes for a parametric study, with the main purpose of understanding the effect of particles on overall behavior of mechanical data and local deformation field under indentation contact. Direct comparison between finite element simulation and indentation data from AFM experiments provides a powerful method to characterize soft materials properties quantitatively, addressing the lack of analytical solutions for hard-soft composites, both biological and synthetic ones. In this framework, quantitative relations are found between the depth, at which the particle was embedded, the particle size and the elastic modulus of the overall composite. Comprehensive characterizations were established to distinguish indentation on a particle residing on top of the hydrogel from a particle embedded inside the hydrogel matrix. Finally, different assumptions of interface friction at the boundary between the particle and the hydrogel have been tested and directly compared with experimental measurements. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The progression of creep damage in heat resistant steels for boiler application has to be monitored regularly as part of an asset integrity management. The damage is normally evaluated using qualitative technique which involves in-situ replication and microscopic examination. The results are rather subjective and depend on the personnel who carry out the interpretation and evaluation of the microstructures. The assessment is based on the distribution of creep cavities present and rarely considers their quantity. This qualitative approach has been used extensively to evaluate creep damage in conventional heat resistant steel such as grade P22 due to the reason that the microstructures are relatively simple with creep cavities readily observed. However, with the wider applications of supercritical technology in power industry, more complex alloys such as grades P91 and P92 steels are gradually replacing the P22 steels in the hotter part of the boilers to accommodate higher operating stresses and temperatures. This type of steels is of tempered martensite with numerous strengthening precipitates of carbides and carbo-nitrites. For this reason, the creep cavities in these alloys tend to be masked by the presence of precipitates. The creep cavities sometimes become less readily detectable under optical microscope. This paper reports a study on a quantitative method in which the depths and areas of cavities were measured using Atomic Force Microscopy (AFM). The cavities were formed by exposing P91 samples in a creep machine at a temperature of 625°C and a constant uniaxial load corresponding to 100 MPa. The results show that the method can be used to quantify creep cavities and can potentially be used to provide information on the creep life consumption of components operating in creep regime. For samples exposed to the above test conditions for 1200 and 3100 hours, the quantification of the cavities number at threshold -250 nm yielded 12 and 131 respectively for 100 μm 2 areas of the samples examined. [ABSTRACT FROM AUTHOR]

Staphylococcus comprises of more than half of all pathogens in orthopedic implant infections and they can cause major bone infection which can result in destruction of joint and bone. In the current study, adhesion force of bacteria on the surface of various biomaterial surfaces is measured using atomic force microscope (AFM). Staphylococcus aureus was immobilized on an AFM tipless cantilever as a force probe to measure the adhesion force between bacteria and biomaterials (viz. ultra-high molecular weight poly ethylene (UHMWPE), stainless steel (SS), Ti–6Al–4V alloy, hydroxyapatite (HA)). At the contact time of 10 s, UHMWPE shows weak adhesion force (~4 nN) whereas SS showed strong adhesion force (~15 nN) due to their surface energy and surface roughness. Bacterial retention and viability experiment (3M™ petrifilm test, agar plate) dictates that hydroxyapatite shows the lowest vaibility of bacteria, whereas lowest bacterial retention is observed on UHMWPE surface. Similar results were obtained from live/dead staining test, where HA shows 65% viability, whereas on UHMWPE, SS and Ti–6Al–4V, the bacterial viability is 78%, 94% and 97%, respectively. Lower adhesion forces, constrained pull-off distance (of bacterial) and high antibacterial resistance of bioactive-HA makes it a potential biomaterial for bone-replacement arthroplasty. [ABSTRACT FROM AUTHOR]

Atomic force Microscopy (AFM) has become a versatile tool in biology due to its advantage of high-resolution imaging of biological samples close to their native condition. Apart from imaging, AFM can also measure the local mechanical properties of the surfaces. In this study, we explore the possibility of using AFM to quantify the rough eye phenotype of Drosophila melanogaster through mechanical properties. We have measured adhesion force, stiffness and elastic modulus of the corneal lens using AFM. Various parameters affecting these measurements like cantilever stiffness and tip geometry are systematically studied and the measurement procedures are standardized. Results show that the mean adhesion force of the ommatidial surface varies from 36 nN to 16 nN based on the location. The mean stiffness is 483±5 N/m, and the elastic modulus is 3.4±0.05 GPa (95% confidence level) at the center of ommatidia. These properties are found to be different in corneal lens of eye expressing human mutant tau gene (mutant). The adhesion force, stiffness and elastic modulus are decreased in the mutant. We conclude that the measurement of surface and mechanical properties of D. melanogaster using AFM can be used for quantitative evaluation of ‘rough eye’ surface. [ABSTRACT FROM AUTHOR]

Copyright of Kobunshi Ronbunshu is the property of Society of Polymer Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Staphylococci species have been isolated from removable orthodontic retainers. The aims of this study were to determine the most suitable device to analyze surface roughness of autopolymerized acrylic and thermoplastic materials and whether the surface dynamics of these materials influences the attachment of Methicillin-Resistant Staphylococcus aureus (MRSA). Clinically simulated samples of autopolymerized acrylic and thermoplastic material were first evaluated using laser non-contact, stylus mechanical profilometries and atomic force microscopy (AFM) followed by contact angle measurement to characterize their surface dynamics. Finally, an in vitro biofilm assay was carried out using a constant depth film fermentor to assess biofilm attachment. The results showed a significant difference between the roughness values obtained from the tested profilometers with the AFM exhibiting the most consistent roughness values. MRSA tended to accumulate initially within the microscopic irregularities of autopolymerized acrylic samples whereas acid-base and electron donor interactions influenced the bacterial attachment onto the thermoplastic samples. [ABSTRACT FROM AUTHOR]

By using the outcrop shale of Longmaxi-3, a series of experiments including in-situ AFM Force Map, SEM-EDS before and after water vapor saturation and uniaxial/triaxial compression tests are conducted to discover the changing pattern of shale mechanical properties from micro and macro level. The current research first measures the micro elastic modulus distribution changes of shale under water condition, also verifying the water-softening effects. Expectation Maximization algorithm programmed by C language is utilized to define Gaussian Mixture Model of micro elastic modulus under different moisture. Self-Consistent Scheme by C program and Mori-Tanaka Scheme is adopted to upscale the micro modulus based on the results of EM. In the comparison with compression test results, M-T scheme behaves better on estimating modulus of originally dry shale core than SC scheme, however, the homogenization technique cannot achieve the accurate estimation of core sample modulus based on micro modulus. The combination of AFM morphology and SEM-EDS verifies the component CaSO 4 of newborn particles when moisture is low. Due to strong heterogeneity of shale, the relationship between elastic modulus and water saturation is negative and non-linear, homogenization technique is not proper to upscale micro modulus of sample processed by water or other factors. • The relationship between elastic modulus of shale and moisture is negative and non-linear. • Mori-Tanaka scheme and Self-Consistent scheme cannot upscale the micro modulus to macro level accurately. • Water can strongly soften the contact surface from GPa level to MPa level. • All micro mechanical measurements are in-situ conducted and compared before-after wetting. [ABSTRACT FROM AUTHOR]

It is well known that wetting plays a crucial role in many processes due to its impact on the emerging adhesive forces. In general, high wetting angles between solid and liquid lead to higher adhesive forces and vice versa. For ideal systems the calculation of these adhesive forces is possible using analytical approaches for van der Waals and polar forces. But there is still a lack of knowledge how to consider impacts like roughness and irregular shape of the solids during the calculation. The present paper aims to show the correlation between wetting behaviour and adhesive forces for non-ideal systems. Therefore, a model system is created wherewith the wetting angle can be changed in a high range. Coated alumina particles are used as solids in this model system. The coating leads to a low surface energy and consequently to a high wetting angle to water of 105°. The wetting angle is reduced by adding ethanol to the aqueous phase and thus the influence of wetting on the adhesive force can be investigated. To correlate the wetting angle with the adhesive force, both of them must be measured. Using a substrate with the same surface coating as the used particles the sessile drop method for the determination of the wetting angle can be applied. Subsequently, the calculation of the interfacial energy, which should be linked up directly to the adhesive force, is possible. The adhesive forces are determined directly by using an atomic force microscope (AFM). Therefore, a coated alumina particle is glued on the end of the cantilever to measure the particle-substrate force directly. The particle and substrate are entirely submerged into the surrounding liquid. As confirmed, measurements of the wetting angle show a decrease with higher ethanol fractions. This is due to the lower surface energy of ethanol compared to water. Furthermore, the results show a selective adsorption of ethanol to the solid surface. This leads to an increased surface saturation of ethanol depending on the concentration in the liquid which can be described with a Langmuir isotherm. AFM measurements show a variation of adhesive forces caused by the high roughness of the substrate. This can be described with statistical distributions. Parameters of this distributions show a correlation to the ethanol saturation. Semi-empirical approaches using van der Waals and polar forces confirm this behaviour. [ABSTRACT FROM AUTHOR]

Biofilms formed on various plastics (vinyl chloride, silicone resin, Nylon 66, polycarbonate and polypropylene) have been investigated by atomic force microscopy (AFM) and optical microscopy (OM). A biofilm formation reactor (BFR) fabricated in our group was used for the biofilm formation on a laboratory scale. After biofilm formation for 4 days in BFR, the biofilm formed on silicone resin had a finely rugged surface, while that formed on vinyl chloride had only coarse ruggedness, suggesting that the surface texture of the biofilms depends on the kind of plastic on which they are formed. After biofilm formation for 4 weeks in BFR, both the root mean square roughness (Rq) and arithmetic mean roughness (Ra) were found to be dependent on the samples, in the order vinyl chloride>Nylon 66, polycarbonate>polypropylene. [ABSTRACT FROM AUTHOR]

The aim of the paper is to give a feasibility study on the material deposition of Nanoscale textured morphology of titanium and titanium oxide layers on titanium and glass substrates. As a recent development in nanoscale deposition, Physical Vapor Deposition (PVD) based DC magnetron sputtering has been the choice for the deposition process. The nanoscale morphology and surface roughness of the samples have been characterized using Atomic Force Microscope (AFM). The surface roughnesses obtained from AFM have been compared using surface profiler. From the results we can say that the roughness values are dependent on the surface roughness of the substrate. The glass substrate was relatively smoother than the titanium plate and hence lower layer roughness was obtained. From AFM a unique nano-pattern of a boomerang shaped titanium oxide layer on glass substrate have been obtained. The boomerang shaped nano-scale pattern was found to be smaller when the layer was deposited at higher sputtering power. This indicated that the morphology of the deposited titanium oxide layer has been influenced by the sputtering power. [ABSTRACT FROM AUTHOR]

To investigate the possibility of nanoprocessing by metal forming, the generation of super smooth surface by a simple compression test was attempted. To obtain fundamental information about the generation of a super-smooth surface during metal forming, we investigated a simple compression test of aluminum strips (A1100, 0.8 mm thick). In the present study, to examine the effect of materials, compression tests of copper strips were conducted. The tool and specimen surfaces were observed using a conventional stylus surface profilometer and an atomic force microscope. The tool and specimen surfaces were examined by the power spectrum method and the zeroset method of fractal analysis. [ABSTRACT FROM AUTHOR]

This study explored the testing technologies characterizing the interaction between asphalt and filler. An atomic force microscope (AFM) was used to describe the surface morphology and surface adhesion force of asphalt mastic and analyze their effect factors. Fourier transform infrared spectroscopy (FTIR) was used to analyze the physicochemical interaction between asphalt and filler. Adsorption tests were used to study adsorption and desorption properties of asphalt on aggregate. The results show that andesite aggregate had a smoother surface and a weaker adhesion force than granite aggregate. The greater the asphalt penetration, the stronger the surface adhesion force. A small number of filler material increased the adhesion force of the asphalt mastic, but too much filler decreased the adhesion force. FTIR tests were employed to explore the various functional groups of asphalt and fillers. No obvious new stretching vibration peak or deformation vibration peak indicated that the interaction between asphalt and filler was mainly a physical action. Net absorption test revealed that the greater the equilibrium concentration, the greater the adsorption amount. Distilled water stripped asphalt from aggregate. The type of adsorption isotherm corresponded to multi-molecular layer adsorption that further indicated that the interaction between asphalt and fillers was mainly a physical action. [ABSTRACT FROM AUTHOR]

Copyright of Revista de la Universidad del Valle de Guatemala is the property of Universidad del Valle de Guatemala and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We herein report, for the first time, the mechanical properties of ovarian cancer stem-like/tumor-initiating cells (CSC/TICs). The represented model is a spontaneously transformed murine ovarian surface epithelial (MOSE) cell line that mimics the progression of ovarian cancer from early/non-tumorigenic to late/highly aggressive cancer stages. Elastic modulus measurements via atomic force microscopy (AFM) illustrate that the enriched CSC/TICs population (0.32±0.12kPa) are 46%, 61%, and 72% softer (P<0.0001) than their aggressive late-stage, intermediate, and non-malignant early-stage cancer cells, respectively. Exposure to sphingosine, an anti-cancer agent, induced an increase in the elastic moduli of CSC/TICs by more than 46% (0.47±0.14kPa, P<0.0001). Altogether, our data demonstrate that the elastic modulus profile of CSC/TICs is unique and responsive to anti-cancer treatment strategies that impact the cytoskeleton architecture of cells. These findings increase the chance for obtaining distinctive cell biomechanical profiles with the intent of providing a means for effective cancer detection and treatment control. [ABSTRACT FROM AUTHOR]

An atomic force microscope (AFM) is an extremely versatile investigative tool in the field of nanotechnology, the performance of which is significantly influenced due to the nonlinear behavior of its scanning unit; i.e., the piezoelectric tube scanner (PTS). In order to increase the imaging speed of the AFM, a model predictive control (MPC) scheme is applied in both the X and Y -piezo axes of the PTS to reduce its nonlinearity effects and to improve in damping of the resonant mode. The proposed controller provides an AFM with the capability to achieve improved tracking and it results in the reduction of the hysteresis, creep, vibration, and cross-coupling effects in piezoactuators. The experimental results demonstrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Abstract: Dental restorative materials need to be carefully engineered and designed in order to meet many different clinical requirements. The oral biomaterials have to possess such properties which enable them to withstand the conditions present in the oral environment. The improvements in the dental materials science are the main initiators of the entire dental professional progress. In order to exploit all the improved characteristics of new commercial dental materials, dental clinicians need to be familiar with working mechanisms of dental processing methods, and to be able to choose the best therapeutic processing condition for the each material. The aim of this study was to investigate the influence of diamond paste finishing on surface topography and roughness of two dental resin-based nanohybrid composites. Results of this study showed that diamond paste polishing was useful processing method which significantly reduced surface roughness and created favorable topography of tested nanohybrid composite materials. [Copyright &y& Elsevier]

Abstract: The stiffness of tumor cells varies during cancer progression. In particular, metastatic carcinoma cells analyzed by Atomic Force Microscopy (AFM) appear softer than non-invasive and normal cells. Here we examined by AFM how the stiffness of melanoma cells varies during progression from non-invasive Radial Growth Phase (RGP) to invasive Vertical Growth Phase (VGP) and to metastatic tumors. We show that transformation of melanocytes to RGP and to VGP cells is characterized by decreased cell stiffness. However, further progression to metastatic melanoma is accompanied by increased cell stiffness and the acquisition of higher plasticity by tumor cells, which is manifested by their ability to greatly augment or reduce their stiffness in response to diverse adhesion conditions. We conclude that increased plasticity, rather than decreased stiffness as suggested for other tumor types, is a marker of melanoma malignancy. These findings advise caution about the potential use of AFM for melanoma diagnosis. From the Clinical Editor: This study investigates the changes to cellular stiffness in metastatic melanoma cells examined via atomic force microscopy. The results demonstrate that increased plasticity is a marker of melanoma malignancy, as opposed to decreased stiffness. [Copyright &y& Elsevier]

In this paper, the sensitivity of flexural and torsional vibration modes of a rectangular cantilever immersed in a fluid to surface stiffness variations has been analyzed and a closed-form expression is derived. To represent this sensitivity, we use analytical formulas for the vibrational resonant frequencies of a rectangular cantilever beam immersed in an inviscid fluid. The effect of the surface contact stiffness on both flexural and torsional sensitivities in a fluid is investigated and compared with cases in which the cantilever operates in air. The results show that in low surface stiffness, the first mode is the most sensitive. As sample surface stiffness is increased, higher resonant frequencies show a larger shift, compared with lower resonant frequencies. In addition, comparison between modal sensitivities in air and fluid shows that the resonance frequency shifts in air are greater than resonant frequency shifts in fluid. [ABSTRACT FROM AUTHOR]

Abstract: Carboxylated (4%) multi-walled carbon nanotubes were covalently functionalized with poly(ethylene glycol)1000 (PEG1000), PEG1500 and PEG4000 with a PEG loading of approximately 11% in all cases. PEG loading generated non-uniform and heterogeneous higher surface structures and increased nanotube width considerably, but all PEGylated nanotube species activated the complement system in human serum equally. Increased PEG loading, through adsorption of methoxyPEG2000(or 5000)-phospholipid conjugates, generated fewer complement activation products; however, complement activation was never completely eliminated. Our observations address the difficulty in making carbon nanotubes more compatible with innate immunity through covalent PEG functionalization as well as double PEGylation strategies. From the Clinical Editor: Complement-mediated toxicity is a major limiting factor in certain nanomedicine applications. This study clarifies that PEGylation of carbon nanotubes is unlikely to address this complication. [Copyright &y& Elsevier]

Piezoelectric microcantilevers (MCs) are types of MCs which can be used in Atomic Force Microscopy (AFM) as a micro-robot, sensor, and imaging actuator. In this paper, the vibrating motion of piezoelectric MCs in AFM application is analyzed. With respect to the geometrical discontinuities, due to the piezoelectric layer, as well as tip, a non-uniform beam model is chosen for analysis. At first, to determine the accuracy of the non-uniform beam model in simulating the vibrating motion of piezoelectric MC, the simulation results are compared with the experimental ones in the absence of the tip-sample force. Good agreement of these results indicates the ability of this model in modeling this type of MC. A numerical solution and a Multiple Time Scale (MTS) method are used to study the nonlinear response of the MC near the sample surface. Comparison of results, at the non-contact mode, shows good agreement between the two solving methods at normal equilibrium distances ( d ≥ 2 nm ). The effects of the angle of MC, the probe length, and the geometric dimensions of the piezoelectric layer on the nonlinearity of the system are studied and it then becomes clear that they can affect the frequency response curvature of the curve and the nonlinearity of the system. [ABSTRACT FROM AUTHOR]

Abstract: Scanning Probe Microscopy (SPM) define a broad group of instruments used to image and measure properties of material, chemical and biological surfaces. Despite the success of SPM, it has some limitation. Because it uses the tunneling current between a biased tip and a sample as the feedback signal, it requires that the sample must be electrically conductive. Also it is difficult to achieve high-resolution images with AFM. The solution to this limitation is to maintain cryogenic temperature for the sample. The cryogenic AFM appears to be the most promising approach, because it will work on all macromolecules. Lowering the sample temperature will increase the mechanical stability of the molecules and will decrease its thermal induced motion. Lower temperature will reduce the thermal induced motion of the cantilever and also the overall noise of the instrument. Lowering the sample temperature up to 137K will decrease RMS area and surface roughness. In2O3 thin film has been used as a sample. Low temperature has been providing by liquid nitrogen container. To avoid condensation on the tip of AFM as well as on the sample Vacuum chamber has been provided. The entire set up must be isolated from surrounding vibration that can damage the tip of AFM. RMS roughness area of In2O3 thin film decreases from 13.682nm to 1.984nm and also line roughness from 2.889nm from 1.443nm. The films exhibit a finer microstructure [Copyright &y& Elsevier]

Abstract: This article presents the application of a mathematical model with a statistical experiment in order to develop robust surface properties of zirconium nitride (ZrN) films. In this research, ZrN films, with a (Ti,Cr) interface, were prepared by an unbalanced magnetron (UBM) sputtering. An experimental array was employed in a few tests. A second-order model resulting from the experiments on film thickness in the UBM sputtering processes was explored. In this study, the desired thickness that significantly influenced the characteristics and structural performance was achieved in the ZrN films; it guided the smaller worn scar depth and yielded larger adhesive strength. Furthermore, a quadric model was constructed efficiently in regard to film thickness variations. The predicted values and experimental results are close, which shows that the quadric model can be effectively used to predict surface properties of ZrN films in a UBM sputtering system. [Copyright &y& Elsevier]

Abstract: The deformation and stacking of graphene significantly affect the overall electronic and mechanical properties. The graphene sheets are easily stacked each other due to van der Waals attraction. The folded characteristic may prevent graphene stacking and increase the d-spacing between graphenes. It can easily form dense graphene structures with high surface area and be applied on electrode materials of battery, nano-composites and so on. The traditional topographic mapping of atomic force microscope (AFM) is hard to measure the characters of surface deformation and distinguish the folding and stacking. In this study, we apply a novel quantitative nano-mechanical AFM to analyze the reduced-graphene oxide (r-GO). The results indicate that the novel AFM system could recognize the difference between folding and stacking of r-GO effectively. Nevertheless, the images including topography, deformation, adhesion, and elastic modulus show the different phenomena between measuring region, which appears that status on measuring region are folding and stacking, respectively. [Copyright &y& Elsevier]

All atomic force microscope (AFM) images suffer from distortions, which are principally produced by the interaction between the measured sample and the AFM tip. The atomic force microscope (AFM) is a very important instrument for use in nanotechnology and biology since it can be used to measure a wide variety of objects, such as nano-particles and cells, either in air or liquid. However, the images that are measured using AFM are distorted because of both the influence of the tip geometry and the dynamic response of the instrument. This influence means that the images do not accurately represent the real shape of the measured particles or cells. Therefore, it is necessary to reconstruct the AFM tip shape. This paper proposes a new approach (impulse response technique) to reconstruct the AFM tip shape from either a square or cylindrical pillar sample that is measured using AFM. Once the tip shape is known, a deconvolution process is carried out between the estimated tip shape and typical AFM 'distorted' images in order to reduce the distortion effects. The experimental results and the computer simulations validate the performance of the proposed approach, in which it is shown that the AFM image accuracy has been significantly improved. The suitability of this novel approach for restoring AFM images has been confirmed using both computer simulation and also with real experimental AFM images. The blind tip estimation approach is an industrial and research standard algorithm for the restoration of AFM images. We therefore also compare the proposed algorithms with the blind tip estimation algorithm, via the use of both computer simulations and real AFM images, and our algorithm is shown to give enhanced results when compared with the blind tip estimation approach. [ABSTRACT FROM AUTHOR]

Abstract: Microcantilevers are used in a number of applications including atomic-force microscopy (AFM). In this work, piezoresistive deflection-sensing elements are integrated onto micromachined cantilevers to increase sensitivity, and reduce complexity and cost. An array of probes with 5nm gold ultrathin film sensors on silicon substrates for high throughput scanning probe microscopy is developed. The gauge factor of the piezoresistive sensor is 3.16±0.05 and the deflection sensitivity is 0.2ppm/nm. Plots of the change in resistance of the sensing element with displacement are used to calibrate the probes and determine probe contact with the substrate. Topographical scans demonstrate high throughput and nanometer resolution. [Copyright &y& Elsevier]

Abstract: The aim of this study is to determine the nano and micro mechanical properties for uncross-linked and cross-linked chitosan films. Specifically, we looked at nanoindentation hardness, microhardness, and elastic modulus. It is important to study the nano and microscale mechanical properties of chitosan since chitosan has been widely used for biomedical applications. Using the solvent-cast method, the chitosan films were prepared at room temperature on the cleaned glass plates. The chitosan solution was prepared by dissolving chitosan in acetic acid 1% (v/v). Tripolyphosphate (TPP) was used to create the cross-links between amine groups in chitosan and phosphate groups in TPP. In this study, atomic force microscopy was used to measure the nanoindentation hardness and surface topography of the uncross-linked and cross-linked chitosan films. Elastic modulus was then calculated from the nanoindentation results. The effective elastic modulus was determined by microhardness with some modifications to previous theories. The microhardness of the chitosan films were measured using Vicker’s hardness meter under three different loads. Our results show that the microhardness and elastic modulus for cross-linked chitosan films are higher than the uncross-linked films. However, the cross-linked chitosan films show increased brittleness when compared to uncross-linked films. By increasing the load magnitude, the microhardness increases for both uncross-linked and cross-linked chitosan films. [Copyright &y& Elsevier]

Abstract: The objective of the present study was to examine the effects of phosphoric acid and polyacrylic acid used as pretreatment for orthodontic direct bonding procedures on changes in the overall mineral levels of the subsurface white-spot lesions, and to examine the effects on the surface structure using contact microradiography (CMR) and an Atomic Force Microscope (AFM). Enamel specimens with in vitro production of artificial subsurface white-spot lesions were used for these studies. The enamel acid conditions were as follows: non-etched (Group I), 10% polyacrylic acid (Group II), 2% phosphoric acid (group III), 10% phosphoric acid (Group IV). After each acid treatment, the four groups were exposed to a remineralization solution at pH 7.0 at 37°C for 2 weeks. An AFM was used to observe the surface after the acid treatment and remineralization. After 2 weeks of remineralization, the mineral profiles were assessed using CMR. AFM observation revealed different acid etching patterns on the enamel surface of subsurface white-spot lesions after the different acid treatments. From the AFM observation after remineralization, Group I and Group II demonstrated deposits of mineral-like substances on the surface. From the CMR observation, the amount of minerals present increased in Groups I and II, while, in Group IV, the surface layer was removed and the amount of minerals present decreased. It was found that polyacrylic acid produced a less roughness than low concentration phosphoric acid. Moreover, the minerals were recovered during remineralization after treatment with polyacrylic acid. The minerals were not recovered after phosphoric acid treatment. [Copyright &y& Elsevier]

Abstract: The aim of the study was to verify the influence of surface sealants on the surface roughness of resin composite restorations before and after mechanical toothbrushing, and evaluate the superficial topography using atomic force microscope. Five surface sealers were used: Single Bond, Opti Bond Solo Plus, Fortify, Fortify Plus and control, without any sealer agent. The lowest values of surface roughness were obtained for control, Single Bond and Fortify groups before toothbrushing. Fortify and Fortify Plus were the sealer agents that support the abrasive action caused by the toothbrushing although Fortify Plus group remained with high values of surface roughness. The application of specific surface sealants could be a useful clinical procedure to maintain the quality of resin-based composite restorations. [Copyright &y& Elsevier]

It has been recently found that a direct current (DC) can be generated through sliding a metal tip (or electrode) against a doped semiconductor if the two materials are of distinct work functions. However, it is also well observed that the DC current generation is degraded if the sliding is repeatedly performed over the same area. Thus, to maintain a stable DC current generation is challenging. In this paper, we present that an ultrathin silicon oxide layer is induced during sliding a platinum coated atomic force microscope tip on a clean doped silicon substrate. With increasing number of sliding over the same area, electron transfer across the tip contacted surface changes from a tribo-voltaic process to a tribo-tunneling process. Moreover, it is also observed that current degradation can be mitigated if the clean silicon substrate is annealed nitrogen. This work not only provides new understanding of electron transfer process in the dynamic Schottky junctions, but also suggests a route for further optimization of the junctions for stable current generation. [Display omitted] • Silicon oxide layer at contact interface of metal-silicon Schottky nanogenerator is demonstrated. • Silicon oxide layer induce electron transfer changed from the tribo-voltaic process to the tribo-tunneling process. • Interaction between the build-in electric field and adsorbed water molecules formed the silicon oxide layer. • The current degradation process can be mitigated after the silicon substrate is annealed and slid in nitrogen environment. [ABSTRACT FROM AUTHOR]

Abstract: The surface topography and local elastic moduli of endothelial cells exposed to shear stress were measured using atomic force microscopy. Bovine aortic endothelial cells were exposed to shear stress of 2Pa for 6, 12 or 24h. In addition, a confocal laser-scanning microscope used in conjunction with the atomic force microscope was used to observe the actin filament structure of these endothelial cells to elucidate the relationship between mechanical properties and cytoskeletal structure. The elastic modulus, calculated using the Hertz model, was measured at 50×50 points at 1μm intervals within 40min. For endothelial cells sheared for 6h and 12h, the elastic modulus at the upstream region was found to be higher than that at the downstream region. For endothelial cells sheared for 24h, the elastic modulus at both the upstream and downstream regions increased. Fluorescent images showed thick, elongated actin filaments oriented in the direction of flow at the ventral surface of the cells. In the middle plane of the cells, actin filaments developed around the nucleus, while in the upper plane, short, thick actin filaments were observed but thick stress fibers were not present. The high elastic modulus came from the stress fibers. These results indicate that the higher elastic modulus observed in the upstream and downstream regions of sheared endothelial cells is mainly due to the development of stress fibers at the ventral surface and middle plane of the cell. [Copyright &y& Elsevier]

Nanoindentation tests performed in an atomic force microscope have been utilized to directly measure the mechanical properties of single crystal metal thin films fabricated by the vacuum vapour deposition technique. Nanoindentation tests were conducted at various indentation depths to study the effect of indentation depths on the mechanical properties of thin films. The results were interpreted by using the Oliver-Pharr method with which direct observation and measurement of the contact area are not required. The elastic modulus of the single crystal copper film at various indentation depths was determined as 67.0 ± 6.9 GPa on average, which is in reasonable agreement with the results reported by others. The indentation hardness constantly increases with decreasing indentation depth, indicating a strong size effect. In addition to the experimental work, a three-dimensional nanoindentation model of molecular dynamics (MD) simulations with embedded atom method (EAM) potential is proposed to elucidate the mechanics and mechanisms of nanoindentation of thin films from the atomistic point of view. MD simulations results show that due to the size effect no distinct dislocations were observed in the plastic deformation processes of the single crystal copper thin films, which is significantly different from the plastic deformation mechanism in bulk materials. [ABSTRACT FROM AUTHOR]

The article presents a study on the changes of the structure of cuticles on violin bow hair caused by wear. The study used atomic force microscopy to observe new and worn-out bow hairs. The results of the study showed that cuticles of the new bow hair were damaged already by bleach and delipidation, while the worn-out bow hairs were much damaged and broken off by force.