Adhesion Conditions Research Articles

Effect of Adhesion Conditions on the Shear Bond Strength of 3D Printing Resins after Thermocycling Used for Definitive Prosthesis.

Three-dimensional (3D) printing polymers such as urethane dimethacrylate (UDMA) and ethoxylated bisphenol A dimethacrylate (Bis-EMA) are typically used in definitive prosthesis and require surface treatments before bonding. However, surface treatment and adhesion conditions often affect long-term use. Herein, polymers were divided into Groups 1 and 2 for the UDMA and Bis-EMA components, respectively. The shear bond strength (SBS) between two types of 3D printing resins and resin cements was measured using Rely X Ultimate Cement and Rely X U200, according to adhesion conditions such as single bond universal (SBU) and airborne-particle abrasion (APA) treatments. Thermocycling was performed to evaluate the long-term stability. Sample surface changes were observed using a scanning electron microscope and surface roughness measuring instrument. The effect of interaction between the resin material and adhesion conditions on the SBS was analyzed via a two-way analysis of variance. The optimal adhesion condition for Group 1 was achieved when U200 was used after APA and SBU, whereas Group 2 was not significantly affected by the adhesion conditions. After thermocycling, the SBS significantly decreased in Group 1 without APA treatment and in the entire Group 2. Additionally, porosity, along with increased roughness, was observed on both material surfaces after APA.

A degraded adhesion model for creep force calculation based on the CONTACT algorithm

Degraded adhesion is observed extensively during the braking or traction process. An accurate degraded adhesion law, on the other hand, is difficult to acquire since it is characterized by a complicated non-linear behaviour involving various surface phenomena. This work provides a new local degraded adhesion model, its implementation in a wheel-rail contact model, and its application in a multibody railway vehicle model. The present degraded adhesion model takes into account large sliding and adhesion recovery phenomena, which are strictly related to the power dissipated at the contact interface. Implementation of the current local degraded adhesion model enhances Kalker’s CONTACT algorithm. The application into multibody dynamics simulation demonstrates the high accuracy of computations. The model is validated by comparing it to experimental findings obtained from on-field tests. Simulated results regarding the tangential pressures, the slip velocity, and the dissipated power under degraded adhesion and partial adherence conditions are reported.

HIL testing of wheel slide protection systems: criteria for continuous updating and validation

Assessment of railway wheel slide protection (WSP) systems involves the execution of complex experimental activities that are quite expensive and time-consuming, since they involve the physical reproduction of degraded adhesion conditions on a real railway line. WSP is devoted to regulating applied braking forces to avoid excessive wheel sliding in case of degraded adhesion conditions between wheel and rail. WSP must be also compliant to safety specifications related to assured braking performances and consumed air. Hardware in the loop (HIL) testing offers an affordable and sustainable way to accelerate these activities optimizing cost, duration and safety of experimental activities performed online. HIL test rigs are subjected to continuous updates, customization and natural ageing of their components. This work investigates the criteria that can be adopted to assure a continuous monitoring and validation of a real WSP test rig, the Italian test rig of Firenze Osmannoro.

Ga-containing Ti alloy with improved osseointegration for bone regeneration: In vitro and in vivo studies

Ti and Ti alloys are widely used implant materials in clinical orthopedics because of their excellent mechanical properties, wear resistance, and biocompatibility. However, the therapeutic effect of Ti alloys is limited by their poor osseointegration. Thus, this study aimed to improve the poor osteointegration of Ti by fabricating Ti alloys containing different amounts of Ga. The properties, including element distribution, hardness, and calcium salt deposition of the Ti–Ga alloys were evaluated. Results showed that Ga, as a bioactive metal, promoted apatite formation. The osteogenic performance of the Ti–Ga alloys was evaluated in vitro and in vivo using rat bone marrow mesenchymal stem cells (BMSCs) and a rat intramedullary nail model, respectively. Biological results demonstrated that the Ti–Ga alloys provided suitable conditions for cell adhesion and spreading, promoted the osteogenic differentiation of BMSCs, and enhanced osseointegration in vivo better than pure Ti. Transcriptomic results further indicated that Ga enhanced osseointegration by downregulating gremlin expression. This study introduced Ti–Ga alloys as promising implant materials with better osseointegration than pure Ti and elucidated the possible mechanism by which Ga promotes osteogenesis.

Combined single-pedal and low adhesion control systems for enhanced energy regeneration in electric vehicles: Modeling, simulation, and on-field test

In this paper, a single-pedal control algorithm was proposed, modeled, and theoretically analyzed to improve the driving range of electric vehicles and increase the intensity and frequency of energy regeneration. Specific analysis and strategy improvement were also conducted for the control problem under low adhesion conditions. The driving control function, economy, and control logic of the proposed single-pedal system were investigated using both simulations and real vehicle verifications under the New European Driving Cycle (NEDC). Based on simulations and real car testing, optimization of the single-pedal system under the traditional low adhesion control strategy was conducted, and then comprehensive comparisons were investigated. Results demonstrated that the proposed single-pedal control and its low adhesion condition control strategy are in line with the design requirements and effectively improved the vehicle economy, achieving a 24.9% energy regeneration rate. The optimized single-pedal low adhesion control strategy, according to the results, can effectively satisfy driving smoothness, economy, and stability under low adhesion conditions.

3D Spheroids — a Cellular Model for Studying the Effects of Hypoxia on the Epicardial Microenvironment

Fundamental research in recent years has allowed us to reassess the molecular and cellular mechanisms of cardiac ontogenesis and its repair after damage. The epicardium, the outer, tightly adjoining layer of the cardiac wall formed by epicardial mesothelial cells, collagen and elastic fibers, has gained special relevance as an important participant of reparative processes. Better insight into poorly understood epicardial function is challenged due to anatomical issues and lack of relevant cellular models.The aim of this study was to develop a spheroid 3D model of the epicardial microenvironment and determine responses of spheroids to hypoxia.Materials and methods. Spheroids were harvested in V-shaped culture dishes with a low adhesion coating. Immunofluorescent staining of cryosections, histological methods and real-time PCR were used for characterization of cultured spheroids.Results. We demonstrated that cultivation of cells under low adhesion conditions in V-shaped culture dishes resulted in the formation of spheroids with an average size of 136+21 µm and cell viability rates of over 98%. The cells in the spheroids cultured under normoxic conditions formed tight junctions and were characterized by a low level of proliferation and the ability to synthesize extracellular matrix proteins. Under hypoxia cells in the spheroids showed partial loss of intercellular contacts, acquired a spindle shape, started to express HIF1a, SNAIL, COL1Al and accumulate collagen. All these features demonstrated the activation of mesothelial(endothelial)-mesenchymal transition strongly resembling epicardial cellular responses to ischemia in vivo.Conclusion. An epicardial spheroid cell culture model suitable for study cellular responses to hypoxic environment was developed. This model can be used to clarify mechanisms regulating epicardial microenvironment and test new targeted candidate drugs.

Quartz Crystal Microbalance Technology Coupled with Impedance for the Dynamic Monitoring of the Cardiomyocyte Beating Function and Drug Screening

The main sensing techniques used to study myocardial pulsation are electrical impedance sensing (EIS) and by quartz crystal microbalance (QCM). While electrical impedance technology is the gold standard for the study of myocardial pulsation, the clinical application of drugs is being followed up in real time additionally, thus, QCM technology needs to be further developed as a very important class of quality sensor technology. Moreover, the application of EIS, in combination with the QCM, for monitoring myocardial pulsation, has been rarely reported. In this paper, a series of cell growth and adhesion conditions were optimized using rat primary cardiomyocytes, and QCM was used in combination with EIS to monitor the adhesion and the myocardial pulsation ability of the cells in real time. Furthermore, cardiomyocytes that adhered to the QCM and EIS were treated with isoprenaline (ISO), a positive inotropic drug, and verapamil (VRP), a negative inotropic drug. Next, the cell index (CI)-time (T) plots, beating amplitude (BA) and beating rate (BR) of the cardiomyocytes were calculated and changes in these parameters, before and after, dosing were evaluated. The results showed that the QCM technique results were not only consistent with the results obtained with EIS, but also that the QCM technique had a certain degree of sensitivity for the calculation of cardiomyocyte beating. Thus, our findings validate the reliability and validity of the QCM technique for measuring cardiomyocyte beating and drug testing. We hope that further studies would evaluate the application of the QCM technology for clinical use.

Mechanical properties characterization of 2D materials via pressure bulge testing

Pressure bulge testing is one of the standard techniques for characterizing the mechanical properties of thin films, whereas it is far less often used to characterize the mechanical properties of 2D materials. In the present work, the effectiveness of bulge testing on determining the mechanical properties of 2D materials is systematically investigated using numerical analysis. After assuming 2D materials as continuum thin films, we start by simulating the relationship between the pressure difference across the suspended film and the film deflection, and then fit the results with analytical models to extract the elastic modulus of the film. It should be noted that the clamped, pre-stretched film widely assumed in the existing analytical model is not appropriate for atomically thin materials; instead, freestanding 2D materials are actually slack in bulge testing due to the delamination of their adhesive boundary condition. Therefore, the initially unstressed flat films, pre-stretched films and slack films are investigated in the present work, and the Poisson’s ratio effect is considered to investigate the effectiveness of bulge testing for most 2D materials. It is found that bulge testing can be an effective approach to characterize the mechanical properties of 2D materials.

Critical role of extracellular DNA in the establishment and maintenance of anammox biofilms

Anaerobic ammonium oxidation (anammox) has been widely used for the sustainable removal of nitrogen from wastewater. Extracellular DNA (exDNA), as one of the main components of biofilms, not only determines the initial formation process, but also allows the three-dimensional structure to be maintained. Since the effects of exDNA on anammox biofilm formation are still poorly understood, this study elucidated the effects of exDNA on different stages of anammox biofilm establishment and maintenance under static conditions and its mechanism. The results revealed that exDNA mainly affected the maintenance stage of anammox biofilm formation. Compared with the absence of exDNA, nitrogen removal efficiency in the presence of exDNA was 6.17 % higher; the number of bacteria cells attached to the carrier was 2.23 times that in the absence of exDNA. The spatiotemporal distribution of bacteria was revealed by fluorescence in situ hybridization. After 30 days, the relative abundances of anammox in biofilms were 6.19 % and 0.4 % in the presence and absence of exDNA, respectively, indicating its positive role in anammox bacteria (AnAOB) adhesion and biofilm formation. The presence of exDNA in extracellular polymeric substances (EPS) promotes the synthesis of proteins and soluble microbial products. According to the extended Derjaguin−Landau−Verwey−Overbeek (X − DLVO) theory, the presence of exDNA also reduced the Lewis acid–base interaction energy and created favorable thermodynamic conditions for AnAOB adhesion. These findings advance our understanding of the role of exDNA in anammox-mediated biofilm formation and offer insights into the mechanism of exDNA in the establishment and maintenance stages.

Practical active traction control for independent‐wheel‐drive electric vehicle based on slip‐ratio threshold determination

AbstractThe traditional traction control system (TCS) based on hydraulic braking only works when the wheels are slipping, which will cause the problem of slow response to extreme slip. In addition, the TCS of four‐wheel‐independent‐drive electric vehicle (4WIDEV) is often based on road adhesion characteristics identification or optimal slip ratio identification to implement active control, which is difficult to achieve in engineering. Aiming at this problem, a practical active TCS is proposed in this paper. Firstly, according to the wheel slip state of the front and rear axles, the dynamic transfer of torque between axles is realized to maintain the vehicle propulsion power. Second, the adhesion conditions between road and tire are classified, and two sets of target slip ratio thresholds are formulated for high and low adhesion pavement, respectively. Then the current road adhesion coefficient is estimated by using the advantage that the in‐wheel motor torque can be obtained in real‐time. Thirdly, the overall framework of the control strategy is established, the logic threshold control algorithm is adopted for tracking the wheel target slip ratio. Finally, the simulation results show that the proposed active TCS can improve the vehicle power and avoid excessive wheel slipping.

Sanded Wheel–Rail Contacts: Experiments on Sand Crushing Behaviour

In railway operation, the sanding process is used to overcome low adhesion conditions in the wheel–rail contact. In the literature, previously conducted research has been experimental, e.g., measuring adhesion coefficients (ACs) under different contact conditions (dry, wet, …) or applying different sands. Under dry conditions, sanding can reduce measured ACs, while under wet conditions different types of rail sand can leave ACs unchanged or increase adhesion. Despite active research, the physical mechanisms causing the change in ACs under sanded conditions are still poorly understood. A possible remedy is the development of advanced models of sanding including local effects. As a basis for such a model, this study presents experimental results concerning single grain crushing behaviour of two types of rail sand under dry and wet contact conditions. Firstly, initial breakage behaviour is investigated with focus on the particle fragments’ size and spread as only fragments within the running band are available to influence the AC during roll-over. Secondly, single grain crushing tests are conducted under realistic wheel–rail load showing the formation of solidified clusters of sand fragments, as well as their size and thickness. This information is important for understanding mechanisms and for future physics-based modelling of the sanding process in wheel–rail contacts.

Mitochondrial plasticity supports proliferative outgrowth and invasion of ovarian cancer spheroids during adhesion.

Ovarian cancer cells aggregate during or after exfoliation from the primary tumor to form threedimensional spheroids. Spheroid formation provides a survival advantage during peritoneal dissemination in nutrient and oxygen-depleted conditions which is accompanied by a suppressed metabolic phenotype and fragmented mitochondria. Upon arrival to their metastatic sites, spheroids adhere to peritoneal organs and transition to a more epithelial phenotype to support outgrowth and invasion. In this study, we investigated the plasticity of mitochondrial morphology, dynamics, and function upon adhesion. Using our slow-developing (MOSE-L) and fast-developing (MOSE-LTICv) ovarian cancer models, we mimicked adhesion and reoxygenation conditions by plating the spheroids onto tissue culture dishes and changing culture conditions from hypoxia and low glucose to normoxia with high glucose levels after adhesion. We used Western Blot, microscopy and Seahorse analyses to determine the plasticity of mitochondrial morphology and functions upon adhesion, and the impact on proliferation and invasion capacities. Independent of culture conditions, all spheroids adhered to and began to grow onto the culture plates. While the bulk of the spheroid was unresponsive, the mitochondrial morphology in the outgrowing cells was indistinguishable from cells growing in monolayers, indicating that mitochondrial fragmentation in spheroids was indeed reversible. This was accompanied by an increase in regulators of mitobiogenesis, PGC1a, mitochondrial mass, and respiration. Reoxygenation increased migration and invasion in both cell types but only the MOSE-L responded with increased proliferation to reoxygenation. The highly aggressive phenotype of the MOSE-LTICv was characterized by a relative independence of oxygen and the preservation of higher levels of proliferation, migration and invasion even in limiting culture conditions but a higher reliance on mitophagy. Further, the outgrowth in these aggressive cells relies mostly on proliferation while the MOSE-L cells both utilize proliferation and migration to achieve outgrowth. Suppression of proliferation with cycloheximide impeded aggregation, reduced outgrowth and invasion via repression of MMP2 expression and the flattening of the spheroids. Our studies indicate that the fragmentation of the mitochondria is reversible upon adhesion. The identification of regulatory signaling molecules and pathways of these key phenotypic alterations that occur during primary adhesion and invasion is critical for the identification of druggable targets for therapeutic intervention to prevent aggressive metastatic disease.

Viability variation of T-cells under ultrasound exposure according to adhesion condition with bubbles.

Although cellular immunotherapyis expected as a newcancer treatment, its therapeutic efficiency is limited in solid tumors,because most cells return to the bloodstream rather than adhere to the target site. Therefore, we are motivated to develop a technique to concentrate the cells in the blood flowusing active control of bubble-surrounded cells under ultrasound exposure considering both aspects of cell controllability and viability. We prepared a lipid bubble conjugating ligand to adhere to the surface ofthe T-cells. First, we evaluated the cellcontrollability by retaining the cells on a wall of an artificial blood vesselthrough continuous ultrasound exposure.Next, we investigated the cell viability under ultrasound exposure in a suspension with various bubble concentrations. We estimatedthe concentration of bubbles when the adhesion to the cell surface was saturated.Then,we evaluated the cell viability with various conditions of ultrasound exposure and bubble concentrations.However, it was confirmed that cell damage occurred under conditions that achieved proper control of the cells. Therefore, we exposed the cells to burst waves to reducethe applied ultrasound intensity. Consequently, the significant increase in cell viability wasconfirmed to be inversely proportional to the duty ratio. To retain cellson a vessel wall, determining the appropriate ultrasound condition including sound pressure and waveform is importantto maintain cellviability.

Development of Microphysiological Systems (MPSs) Based on Microfluidic Technology for Drug Discovery in Japan

Microphysiological systems (MPSs) based on microfluidic devices are attracting attention as an alternative cell assay platform to animal experiments in drug discovery. When we use microfluidic devices for cell culture, it is possible to experiment with various culture conditions that are difficult with conventional cell culture methods, such as fabrication of microstructures for cell placement, temporal and spatial control of liquid factors and adhesive conditions, and physical stimulation by flow and expansion/contraction. MPSs, which use microfluidic technology to construct the structure and function of physiological biological tissues and organs, are being commercialized and put to practical use worldwide with the entry of venture companies and pharmaceutical companies. Although research on the practical application of MPS in Japan has lagged far behind the efforts of Western countries, the Japan Agency for Medical Research and Development (AMED) launched the MPS Development and Research Project in FY2017 and established a system for MPS commercialization through industry-government-academia collaboration. The project is characterized by the formation of a consortium involving many researchers not only from academia but also from manufacturing and pharmaceutical companies with the aim of commercializing MPS devices. By FY2021, the final year of this project, several MPSs were successfully positioned in various stages of commercialization. This paper introduces two MPSs that the author was involved in commercializing in collaboration with domestic companies within the project.

Microfluidic device combining hydrodynamic and dielectrophoretic trapping for the controlled contact between single micro-sized objects and application to adhesion assays.

The understanding of cell-cell and cell-matrix interactions via receptor and ligand binding relies on our ability to study the very first events of their contact. Of particular interest is the interaction between a T cell receptor and its cognate peptide-major histocompatibility complex. Indeed, analyzing their binding kinetics and cellular avidity in large-scale low-cost and fast cell sorting would largely facilitate the access to cell-based cancer immunotherapies. We thus propose a microfluidic tool able to independently control two types of micro-sized objects, put them in contact for a defined time and probe their adhesion state. The device consists of hydrodynamic traps holding the first type of cell from below against the fluid flow, and a dielectrophoretic system to force the second type of object to remain in contact with the first one. First, the device is validated by performing an adhesion frequency assay between fibroblasts and fibronectin coated beads. Then, a study is conducted on the modification of the cellular environment to match the dielectrophoretic technology requirements without modifying the cell viability and interaction functionalities. Finally, we demonstrate the capability of the developed device to put cancer cells and a population of T cells in contact and show the discrimination between specific and non-specific interactions based on the pair lifetime. This proof-of-concept device lays the foundations for the development of next generation fast cell-cell interaction technologies.

Numerical analysis of axial compressed multifaceted concrete-filled tube elements

The object of study is multifaceted steel concrete- filled poles. The subject of research is the bearing capacity and parameters of the stress-strain state of multifaceted steel concrete- filled poles. The purpose of the research is to numerically study the features of the operation of multifaceted concrete-filled structures under axial compression. Are discussed the features of creating a computational finite element model of such structures in ANSYS APDL. Analytical methods are described for determining the parameters of the nonlinearity of the materials used, as well as the physical and mechanical characteristics of concrete operating under compression conditions. On specific examples the change in the bearing capacity for the object of study under various conditions of materials adhesion (friction coefficient μ varied within 0.1...0.6 with step 0.1). Is analyzed the "unified" analytical method for determining the bearing capacity of steel multifaceted concrete-filled structures, indicating the degree of variability of ultimate compressive load depending on the variation in the number of faces and thickness of the metal wall of the multifaceted model. The considered features of creating a computational model in the ANSYS APDL finite element analysis system, using various laws of deformation of steel and concrete, made it possible to determine the qualitative and quantitative levels of variability of their bearing capacity, which in combination will allow designers of such structures to reach a qualitatively new level when creating structures based on pipe concrete elements.

AN INDENTATION METHOD FOR ADHESIVE STRENGTH EVALUATION OF POLYMER COATINGS

An indentation method was developed for adhesive strength evaluation of a polymer coating using the example of an epoxy composition with titanium alkoxide deposited on the surface of low-carbon steel. The method is based on the numerical implementation of the fracture mechanics approach in experimental data processing. It was found that the penetration of a Rockwell indenter perpendicular to the coating surface causes annular delamination buckling of the coating around the indentation, which is due to adhesive bond breaking as a result of radial shear when the coating material is forced out from under the indenter. A controlled parameter in finite element modeling was the experimentally determined width of the coating delamination zone at a fixed indentation depth at which delamination occurred. The adhesive contact conditions were set using the bilinear law of the cohesive zone model, which describes the relationship between the adhesive shear stress and adhesive bond stretching during shear of interacting surfaces in the contact plane. The limiting specific surface energy of adhesive failure was used as a quantitative evaluation criterion for adhesive strength. The optimal value of the limiting specific surface energy of adhesive coating failure was determined for the cohesive zone model parameters that provide the best convergence of the numerical and experimental data.

Fatigue Characterisation of Adhesives Used in Fibre-Reinforced Composites

A review of past investigations into the fatigue behaviour of structural adhesives and bonded joints in fibre-reinforced polymer composites is given. An overview of the structural adhesives used in general bonded joint applications is first provided, followed by an experimental fatigue testing of these bonded components. The aspects that influence fatigue strength and fatigue life for adhesively bonded joints in fibre-reinforced polymer composites are then discussed in terms of the adhesive composition, geometry configuration, surface condition and preparation, and loading conditions. The aspects that relate to fatigue crack initiation and crack propagation in these bonded composite components are discussed in terms of damage modelling, monitoring, and detecting of crack initiation, crack growth rates and crack propagation modelling. The impact of environmental factors such as temperature and humidity on the fatigue performance of these bonded composite joints is also discussed. The paper then concludes by providing guidelines for characterising the fatigue behaviour of adhesively bonded joints and adhesives used in fibre-reinforced polymer composite applications.

ПРИМЕНЕНИЕ АГРЕГАТНЫХ ТЯГОВЫХ ПРИВОДОВ ДЛЯ ЛОКОМОТИВОВ С ПОВЫШЕННЫМИ ТЯГОВЫМИ СВОЙСТВАМИ

In order to implement the increased traction power of locomotives, rational solutions of traction drives with an aggregate layout are considered as a more technologically advanced alternative to integrated traction drives of foreign companies. As a result of the know-why analysis, the following was established: the use of an integrated circuit is induced by the objective of developing a drive for locomotives with different track gauge; the transition to an aggregate layout requires an increase in the axial dimension of a traction drive, the creation of an elastic-compensating coupling, operable at a rotational speed of up to 4000 min-1, and an increase in the number of bearings in the drive. It is grounded that it is possible to increase the dimensions of the locomotive’s 1520 mm gauge drive to equip it with a coupling joint of a maximum diameter of 570 mm and an axial dimension of 200 mm, as well as the technical possibility of creating a workable elastic-compensating coupling joint with rubber elastic elements in these dimensions according to the conditions of adhesion of rubber with metal. The structural layouts of an aggregate traction drive are proposed, allowing to reduce the number of bearings in it, as well as an aggregate traction drive with elastic support on the axle, which makes it possible to use such a drive for passenger locomotives with the wheels of 1220-1250 mm diameter.

Soy-Flour Adhesive Bonding of Low-Moisture Hickory and Red Oak Veneer

Abstract The goal of this research was to test the effect of low-moisture-content veneer on the strength and durability of plywood test specimens constructed with a soy-flour adhesive. Soy-flour adhesive systems offer certain environmental and health advantages but research studies and performance data are lacking currently for a variety of wood types and end uses. Soyad adhesive was used in this study due to its natural, renewable soy flour, a novel cross-linking resin, and lack of added formaldehyde. Test specimens were prepared using heartwood of hickory and red oak and sapwood of hickory. These wood types were used to represent some of the most challenging wood adhesion conditions. Analytical tests included determination of select chemical properties of the adhesive and wood veneer, measurement of strength properties of the adhesive bond, and assessment of delamination tendencies of bonded panels following water soaking.