Adhesion Values Research Articles

Foodborne and waterborne Arcobacter species exhibit a high virulent activity in Caco-2

Infection mechanisms of Arcobacter remain uncertain. This study aimed to determine whether 65 food and waterborne isolates of at least six species were able to adhere and invade Caco-2 cells; and whether this ability could be related to cadF, cj1349, ciaB, and/or hecA, specific genetic markers related to host cell adhesion and invasion. All adhered and invaded the cells, and harboured at least two virulence markers. The mean virulent activity shown by A. butzleri was superior to that of A. cryaerophilus (p < 0.05); but the mean adhesion and invasion values of A. lanthieri, A. skirrowii, and A. vitoriensis were even higher. Sewage isolates were significantly (p < 0.05) more adherent and invasive than the rest, and their associated gene content was higher (p < 0.05). For the first time, an association between cadF and hecA and a high adhesion capability was identified (p < 0.05). The results provide new data on the pathogenic potential of Arcobacter species present in food and water by highlighting the superiority of A. butzleri over A. cryarophilus; providing evidence on the virulence of minority species as A. lanthieri and A. vitoriensis; and confirming sewage as an important source of potentially more virulent arcobacters.

The Role of Red Blood Cell Vascular Adhesion Biomarkers in Understanding Sickle Cell Disease Associated Chronic Pain

Background: Sickle cell disease (SCD) is characterized by repeated episodes of vaso-occlusion (VOC) that can lead to a host of complications including acute and chronic pain. Prior studies have demonstrated acute changes in RBC health biomarker flow adhesion of whole blood to VCAM-1 (FA-WB-VCAM) and P-Selectin (FA-WB-Psel). Adhesive indices are significantly elevated during a proadhesive VOC. We examined whether individuals with SCD with and without chronic pain will exhibit differences in RBC health biomarkers between steady state and acute VOC pain. Methods: This was a 6-month, longitudinal, case-control cohort pilot study of FA-WB-VCAM and FA-WB-Psel indices collected in youth with SCD at Children's National Hospital in Washington, DC. SCD chronic pain patients (as defined per AAPT diagnostic criteria) were classified as “cases,” and SCD patients without chronic pain were “controls.” Controls were age (± 2 years), and genotype matched to cases. Both FA-WB-VCAM and FA-WB-Psel were collected at baseline and during acute VOC with assays performed by Functional Fluidics Inc. in Detroit, MI. Patient-reported outcomes were captured as pain scores and through completion of the centralized pain index survey to assess for centralized pain features of chronic pain. Statistical analysis included descriptive statistics and categorical analysis by t-test (GraphPad, v9, 2021). P value &amp;lt;0.05 was statistically significant. Results: We identified 10 pediatric patients, 4 with chronic pain “cases” and 6 without chronic pain “controls” with FA-WB-VCAM and FA-WB-Psel assays performed at baseline and during an acute VOC episode. The average age of the cohort was 17.5 years with 70% females (n=7) and 30% males (n=3). Eighty percent (n=8) of the cohort were HgbSS and 20% (n=2) HgbSC genotype. Twenty-five percent (n=1) of the chronic pain patients were on disease-modifying therapy (DMT) with hydroxyurea (HU) at study initiation [all patients had been offered ≥ 1 FDA-approved DMT and previously discontinued DMT use due to intolerable side effects or personal choice], whereas 83% (n=5) of the control patients were on DMT with 50% (n=3) being on dual DMT therapy (HU + voxelotor or HU + crizanlizumab). The chronic pain cohort had a higher average number of ED visits/year than the control cohort (14 ± 7 vs. 4 ± 2 ED visits/year, p=0.11). The average baseline pain score for the chronic pain cohort was 7.25 versus 1.16 in the control cohort (p= 0.069). Centralized pain index survey responses were similar between both groups [median (IQR): 11.5 (7.25 - 15) vs. 9 (7-16), p=0.72)]. Figures 1A and 1B show a comparison of FA-WB-VCAM and FA-WB-Psel at baseline versus acute VOC for each chronic pain (P) “case” with their respective “controls (C).” The average baseline FA-WB-VCAM (P: 555.8 ± 605.3 vs. C: 435.3 ± 217 cells/mm2, p=0.905) and the average baseline FA-WB-PSel (P: 83.5 ± 64.5 vs. C: 57.33 ± 45.4, p=0.833) were similar between the cohort of chronic pain versus control subjects. Acute VOC FA-WB-VCAM (P: 722 ± 366.6 vs. C: 553.5 ± 309.6 cells/mm2, p=0.667) and FA-WB-PSel (P: 116.3 ± 66.6 vs. C: 98.7 ±96 cells/mm2, p=0.777) adhesion values were similar between cases and controls although adhesion values trended higher than baseline for both groups. All the cases had acute VOC adhesion indices above clinically established critical thresholds [Figure 1A and 1B]. The FA-WB-VCAM adhesion values increased from baseline in 75% (n=3) of the chronic pain patients (#3, #14, #16) during acute VOC. All the chronic pain patients (#3, #7, #14, #16) showed increased FA-WB-Psel adhesion from baseline during acute VOC [Figure 1A and 1B]. Fifty percent (n=3) of the control patients (#10, #12, #28) exhibited increased FA-WB-VCAM adhesion during acute VOC, and 60% (n=4) of the controls (#4, #5, #10, #28) exhibited increased FA-WB-Psel adhesion during acute VOC. Conclusions: We showed changes in RBC health vascular adhesion markers from baseline to acute VOC in patients with and without chronic pain. FA-WB-VCAM and FA-WB-Psel trended higher in the chronic pain cohort and all acute VOC values for the chronic pain cohort were above established critical thresholds. FA-WB-Psel adhesion increased from baseline with the onset of acute VOC episodes for most of the chronic pain cohort. Mechanistically, there is a need to understand differences in acute versus chronic pain, which may provide further insight into pro-adhesive versus non-vascular pain mechanisms.

Radchip: A Laminin-Lined Red Blood Cell (RBC) Adhesion Device for Functional Characterization and Clinical Evaluation of Sickle RBCs at Steady-State

Sickle cell disease (SCD) is a genetic disorder caused by a point mutation in the beta-globin gene producing an abnormal hemoglobin (HbS) which, under deoxygenation, polymerizes and causes severe distortion of the red blood cell (RBC). RBCs may be dehydrated, poorly deformable and highly adhesive to the endothelium, with abnormal adhesion being of primary interest to this study. Recently, several new disease modifying drugs have been FDA approved, with more in development. These novel agents target specific aspects of SCD pathophysiology, including adhesion. Changes induced by such therapies are not always detectable by common conventional lab instruments. LORRCA (oxygen-gradient ektacytometry) is the gold-standard for deformability measurement; it has been well described both analytically and clinically in SCD. Adhesion and deformability have a dynamic, yet complementary relationship that we explore here. While these may behave in an interdependent manner, each determinant must be considered independently. There is a growing demand for innovative tools to evaluate rheological properties under physiological conditions, particularly microfluidic devices. However, many current devices are limited in their clinical utility due to, choice of ligand, complexity of design, or reliance on endothelial cell culture (typically HUVEC cells) which are difficult to use, vary with passage number, and do not represent adult SCD endothelium. We developed a Red blood cell Adhesion Chip (RAdChip) to model RBC to endothelial adhesion using laminin, a physiologically relevant ligand, to easily, effectively, and reproducibly measure RBC adhesion. Here, we describe our analytic and clinical validation of our device. Peripheral blood samples were collected in EDTA from individuals with SCD and healthy controls under an IRB approved protocol. RBCs were extracted via centrifugation, washed and resuspended in PBS to a 0.5% HCT. Microfluidic devices were fabricated using polydimethylsiloxane (PDMS). A 5ug/ml solution of recombinant laminin was applied to each channel, then blocked with 1% bovine serum albumin (BSA). Resuspended RBCs were introduced to the device through tubing connected to the inlet port. Harvard Apparatus syringe pumps were used to perfuse samples and wash channels at ~1dyne/cm 2. Adhesion was visualized with a Keyence inverted bright-field microscope at 20x (Itasca, IL). Adhered cells were counted within a 1.8mm 2 region of interest (Roi) using the iCLOTS automated cell quantification software (Fay et al, Nat comm accepted 7/2023). We measured adhesion index via RAdChip for common SCD genotypes: HbSS/SB0: (median (x͂) =756; range (r): 154-1889; n=26) HbSC/SB+ : (x͂ =299; r=: 114-731; n=11 ) HbAA: (x͂) =13; r= 5-90; n=7). RBC adhesion values were independent of age (p=0.65) and gender (p=0.63). An increase of 0.1 unit in EImin and EImax decreases RBC adhesion by 214 and 268 cells/mm 2, respectively. A 1mmHg increase in PoS increased adhesion by 19.5 cells/mm 2. sRBC adhesion had a significant positive association with vaso-occlusive events (VOE) (p=0.005), absolute neutrophil count (ANC) (p=0.005), and EImax (p&amp;lt;0.001). Notably, analytical validation of RAdChip produced a mean CV of 0.13 ± 0.94. RAdChip adds a key component of functional RBC evaluation that conventional lab equipment does not measure. We have analytically validated our device, demonstrating an excellent coefficient of variability. 44 patient samples, each examined in triplicate produced a mean CV of 0.13. We have demonstrated clinical validity of our device by establishing correlations with known markers of severity and pain event frequency. RBC adhesion values increase as the number of VOE events increase, reaffirming the belief that adhesion is a principal element in the multistep VOE cascade. In like manner, improvements in deformability are associated with decreased RBC adhesion, strengthening the interdependent nature of VOE molecular events. Recognizing the dynamic nature of SCD, it is necessary to explore sickle erythrocyte adhesion longitudinally to investigate changes before, during, and after VOE occurrences. Continued and increased integration of adhesion measurements with RAdChip and other rheology devices into routine SCD care may be helpful in assessing disease severity, identifying need for additional disease modifying agents, and assist with second line agent selection and monitoring.

Corrosion and Tribological Performance of Diamond-like Carbon-Coated ZK 60 Magnesium Alloy

In this work, hydrogenated and hydrogen-free Diamond-Like Carbon (DLC) coatings were deposited into ZK60 magnesium alloy using the promising coating method High-Power Impulse Magnetron Sputtering (HiPIMS). CrC and WC were used as interlayers of the thin films, and their influence was studied. The structure and composition of the coatings were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. Tribological tests, scratch tests, and nanoindentation were performed to obtain information about the mechanical and tribological properties of the coatings. Finally, immersion and electrochemical tests were performed to evaluate the corrosion behavior of the samples. The results showed a homogeneous layer with improved wear resistance, toughness, and hardness in addition to good adhesion to the substrate of the ZK60 magnesium alloy. The hydrogenated DLC coating showed better results that the hydrogen-free thin layer, and relevant differences were observed depending on the interlayer. In this work, the improvement in the tribological and corrosive properties of Mg alloys was studied by using thin layers of DLC and different intermediate layers, achieving similar or even better wear and adhesion values than with thicker layers.

The Effect of Variations in HPMC and Carbopol Bases on The Physical Stability of Okra (Abelmoschus esculentus L.) Fruit Gel Formulations

Okra fruit (Abelmoschus esculentus L.) is a vegetable that is often used as medicine. Okra fruit contains flavonoids which are antioxidants. Gel formulation with a concentration of 5%, and various combinations of HPMC and carbopol bases. This research aims to determine the physical stability of gel preparations and the effect of variations in the concentration of gelling ingredients in the preparations. The gel formulation consists of 4 formulas, namely F0, F1, F2, and F3. Physical stability tests include organoleptic tests (odor, color and texture), homogeneity, pH, spreadability, stickiness, viscosity and synergy. Tests were carried out for 14 days of storage, namely on days 1, 3, 5, 7, and 14 at room temperature (25℃). The observation results showed that in the organoleptic test there was no change in color, odor and texture in the gel preparation during 14 days of storage. The four gel formulas are homogeneous and there is no synergy. Variations in the combination of HPMC and carbopol bases affect the physical properties of the gel, including pH, viscosity, spreadability and adhesion. HPMC and Carbopol affect the pH of the preparation, the higher the Carbopol content and the lower the HPMC content, the more acidic it is. Carbopol and HPMC affect the values of spreadability, viscosity and adhesion because the higher the concentration of carbopol and HPMC produces a thick gel preparation so that the spreadability decreases, viscosity increases and adhesion also increases.

Adhesion of WTi to polyimide measured by complementary methods

Quantification of thin film adhesion to their substrates is crucial to ascertain reliable multi-material components, which are typically encountered in technologically relevant structures such as microelectronic devices. Metal-polymer interfaces have gained increased attention in the past since they open a new research field towards developing flexible electronic devices, yet their quantification is often experimentally challenging since standard routes to assess adhesion such as nanoindentation-based techniques or four-point bending may not be applicable due to lack of rigidity. In the present study interface adhesion of nominally 150 nm thin WTi films sputtered onto polyimide, part of a multi-material stack consisting of brittle and compliant materials, was determined experimentally. Upon contactless removal of the bilayer by etching a sacrificial layer, originally part of the multilayer stack, the WTi film showed cracks and buckles, which could be characterized by atomic force and confocal laser scanning microscopy. Hence, two models to quantify adhesion were compared: the model of tensile induced delamination – typically employed for metal films on compliant substrates – and the model of Hutchinson and Suo, which is usually applied on spontaneously formed, straight buckles. The first model reveals adhesion values for the native WTi-polyimide interface of 2.4 ± 0.8 J/m2 and the latter model 4.7 ± 2.3 J/m2. The slight difference in adhesion results, which are both rooted in the same theory, could be rationalized by the fact that the model for tensile induced delamination gives a measure of the lower bound of the adhesion energy. The overall rather lower adhesion values could be explained by additional transmission electron microscopy investigations conducted on the cross section of the interface, which reveals no interlinking morphology and a flat interface.

Evaluation of the shear bond strength of various adhesives on the surface of enamel irradiated with various doses of radiotherapy

We aimed to compare the shear bond strength (SBS) forces on the enamel surface with 2 adhesives after treatment with various radiation doses. A total of 120 premolars were included in the study. The teeth were randomly divided into 5 main groups (n= 24): negative control (without aging), positive control (with aging), 40 Gy, 60 Gy, and 70 Gy radiation. The 40 Gy, 60 Gy, and 70 Gy groups underwent conventional radiotherapy 5 days a week with a dose of 2 Gy each day. After the radiotherapy, all samples except the negative control group were subjected to thermal cycle aging. In all 5 groups, the specimens were divided into 2 subgroups, and half were bonded using 2 adhesives. After bonding, the universal Shimadzu test device was used to analyze the SBS. After the test, the tooth surfaces were examined under a stereomicroscope to determine the adhesive remnant index. When adhesives were compared, Biofix adhesive's bond strength value was statistically higher in the 40 Gy group than in the Transbond XT group (P= 0.001). The SBS value was higher in all irradiated groups than in nonirradiated groups (P= 0.001). When the adhesive remnant index score was analyzed, no significant difference was found among the groups. The SBS increased in irradiated teeth compared with unirradiated teeth, and the SBS values of both adhesives were within the acceptable limits in all radiation groups.

The Effect of Various Lasers on the Bond Strength Between Orthodontic Brackets and Dental Ceramics: A Systematic Review and Meta-Analysis.

Background/objective: This systematic review and meta-analysis aimed to assess how laser conditioning affected brackets bonded to dental ceramics' shear bond strength (SBS). Materials and methods: The study was conducted by searching Pubmed/Medline, Scopus, Embase, Web of Science, the Cochrane Library, and Google Scholar up to September 14, 2022. In addition, the reference lists of the relevant articles were checked manually. Articles that compared SBS of laser-treated feldspathic, lithium disilicate, or zirconia surfaces with other standard techniques for bonding metal or ceramic orthodontic brackets were considered. Using a random-effects model, data pooling was carried out as the weighted mean difference (WMD). Results: This study initially contained 1717 reports, and following review, 32 articles were deemed suitable for our meta-analysis. The pooling results showed that the treatments with lasers such as "Er:YAG" [WMD = -1.12 MPa; 95% confidence interval (CI): -1.93 to -0.31], "Er:YAG + Silane" (WMD = -3.08 MPa; 95% CI: -4.77 to -1.40), and "Nd: YAG + Silane" (WMD = -2.58 MPa; 95% CI: -3.76 to -1.40) had statistically significant lower adhesion values compared with controls. Contrarily, "Ti:Sapphire femtosecond" demonstrated significantly higher bonding values (WMD = 0.94 MPa; 95% CI: 0.29-1.60). In contrast, other interventions obtained no statistically significant difference in SBS. Conclusions: Most of the laser groups showed results comparable with those of conventional approaches. Although more research is necessary for definitive conclusions, laser treatment may be an effective option for treating the surfaces of ceramic materials.

Method of evaluation of pavement bitumen adhesion

The durability of an asphalt concrete pavement largely depends on the quality of the bitumen binder and the strength (or degree) of its interaction with the surface of aggregates (adhesion). The method is based on the finding of bitumen adhesion with a reference substrate, which is taken to be glass. The article presents the results of obtaining the adhesion to the glass surface: bitumen of different grades; bitumen modified with various additives; bitumen modified with adhesive additives and hardened by various methods. The results of comparing the adhesion of bitumen to the glass surface with the results of the Rolling Bottle Test are presented. It has been proved that, with a certain assumption, the value of adhesion to the glass surface can be taken as indicative value for the adhesion of unmodified bitumen to the surface of granite stone materials, obtained after 6 h of testing by the Rolling Bottle Test.

Bacterial adhesion to composite resins produced by additive and subtractive manufacturing.

The aim of this study was to evaluate the surface roughness and contact angle of composite resins produced by CAD/CAM milling and three-dimensional (3D) printing for permanent restorations as well as the adhesion of S. mutans and S. sanguinis bacteria to these composites. Three CAD/CAM milling composite resins (Vita Enamic-VE, Cerasmart-CE, Lava Ultimate-LU) and three 3D printing resins (Varseo Smile Crown plus-VSC, Saremco print Crowntech-SPC, Formlabs 3B Permanent crown-FLP) were selected. Twenty samples were prepared for each group. Using a contact profilometer, the surface roughness was determined, and an optical goniometer was used to quantify the contact angle. To evaluate the bacterial adhesion, composite specimens were immersed in mucin containing artificial saliva. All samples were incubated for 24h at 37°C in 5% CO2. CFUs were determined by counting colonies after the incubation period. Surface roughness values of test samples were the highest in the Group VSC [0.46 (0.14)µm], whereas the lowest values were found in the Group LU [0.23 (0.05)µm]. There was no statistically significant difference between the groups in contact angle values (p > 0.05). The S. mutans adhesion extent on the Group SPC was statistically higher compared to all other materials with p < 0.05. For S. sanguinis, the lowest bacterial adhesion value was recorded in Group CE (3.00 × 104CFU/ml) and statistically significant differences were found with Group VE and VSC (p < 0.05). Different digital manufacturing techniques and material compositions can affect the surface roughnesses of composite resins. All composite resin samples have hydrophobic characteristics. Microbial adhesion of the tested composite resins may be varied depending on the bacterial species. S. mutans showed much more adhesion to these materials than S. sanguinis.

Design of metal-cutting tool coatings at the atomic level

The research aims to lower tooling costs by reducing the time allotted to designing coatings on domestic cemented carbide metal-cutting tools by using the atomic force approach. The object of the study is coatings on cemented carbides of the tungsten carbide group such as titanium carbide (TiC), titanium nitride (TiN), and titanium (Ti) coatings or a nitride-based titanium, chromium and aluminum (Ti,Cr,Al)N composite coating. To select the most rational coatings, the article employed the method of calculating the functionals of interatomic systems using the density functional description of single atoms. The simplest measure to reduce the cost of designing metal-cutting instruments for manufacturing parts made of difficult-to-machine materials is to develop coatings for this tool type. The article considers various atomic arrangements in the coating material in relation to the WCo8 cemented carbide (VK8, tungsten carbide-cobalt alloy containing 8% cobalt). The calculated values of the interaction energy of the coating material atoms with one another and with the cemented carbide material ranged from 3.04 to 3.5 J/m2. Moreover, the research has established a correlation between the calculation results and the performance parameter of metal-cutting tools considering fracture toughness K1c (MPa ∙ √m). The main result of the study is that the employed computational method made it possible to determine the adhesion value for the atoms of the above-mentioned coating materials with tungsten carbide and cobalt atoms packed in different scale configurations. This enables the classification of coatings from the perspective of ensuring maximum performance properties of the tooling material. The present article assumes that the higher the adhesion value, the better the performance properties. The hypothesis has been confirmed experimentally as well as by the values of fracture toughness K1c. Thus, the most rational coating options have been selected for specified operating conditions of a metal-cutting tool, which permits reduction of tool design costs and makes it possible to predict the performance properties of tools at the design stage.

Blends of Conjugated and Adhesive Polymers for Sticky Organic Thin‐Film Transistors

AbstractHere, a polymer blend active layer that exhibits both electronic and adhesive properties is introduced. Various conjugated polymers are blended with a catechol‐based polymer that shows high adhesion, such that blends serve as the active layer of multifunctional sticky organic thin‐film transistors (OTFTs). Blend films maintain relatively constant field‐effect charge carrier mobility in OTFTs regardless of composition. Lap shear adhesion strength tests show that all blend films exhibit adhesive properties with adhesion values ranging from 0.05 to 4.30 MPa. With relatively consistent mobility and the presence of adhesive properties at different compositions, blends of conjugated and adhesive polymers can lead to next‐generation organic transistors for stable 3D stacking and waterproof adhesive sensors.

Improvement and Evaluation of a Device That Determines the Interfacial Shear Strength of Carbon Fiber/Polyphenylene Sulfide Composites.

This study improved homemade apparatus for characterizing the interfacial shear strength (IFSS) of carbon-fiber-reinforced polyphenylene sulfide (PPS/CF) composites. The upgraded generation II experimental device includes a newly developed experimental clamp for samples, as well as testing systems. Compared with the initial generation I apparatus and the commercial Toei instrument, the generation II device is easier and more efficient to operate. The average interfacial adhesion values obtained using these devices were consistently approximately 40 MPa, with relatively low data scatter, showing excellent repeatability and applicability during microbond tests. Notably, the generation II experimental device was equipped with an additional high-frequency data-capturing tool to identify the debonding peak force more precisely, which demonstrated a higher interfacial shear strength of 42.81 MPa during testing. Therefore, the new instrument was able to reflect the change in the interfacial stress state during the interface debonding process more accurately and reliably.

Influence of magnetic field on the physicochemical properties of water molecule under growing of cucumber plant in an arid region

This study highlights the potential impact of magnetic fields on water quality, which could have implications for plant growth and development. Theoretical estimates of changes in surface tension, pH, and some other properties due to passing water through a magnetic field for a certain period were experimentally validated in this study. Overall, the results revealed changes in the physicochemical properties of water after magnetic field application. In accordance, pH significantly (p < 0.05) increased from 2 to 2.25, from 4 to 4.5, from 6 to 6.45, from 7.3 to 7.8, and from 8 to 8.7 and except at pH10, which decreased from 10 to 9.7. In addition, the model developed in this study indicated that the change of electrical conductivity (EC) decreased from 9 to 6.11 dS m−1 with an increasing number of run flow through the magnetic field. The decline in EC can be described as follows: magnetically treated water contains fine colloidal molecules and electrolytic chemicals that respond to a magnetic field by enhancing their ability for precipitation, resulting in a fall in EC. Moreover, the Hardness values of recirculated water were decreased after magnetic field application. This corroborates the decline of calcium carbonate adhesion and surface tension values as increases in hydrogen bonding between protons and water molecules and changes in the distribution of molecules in magnetized water. As the internal electrical field grew and the hydration shells surrounding the constituent ions weakened, EC decreased. Lastly, by using an electronic microscope, observing the water in regular, such as regular hexagonal tree shape instead of random irregular shapes after magnetic field application, confirming that the magnetic field had a significant effect on the physical properties of water molecules. In conclusion, magnetic behavior may improve water quality, resulting in increased development and plant growth.

Relative Compatibility Analysis of Aggregate-Binder Systems in Arkansas against Stripping

Compatibility holds great importance because it can predict the overall performance of asphalt mixtures. Incompatible aggregate-binder duos can result in a weak and friable mix as well as increase mixtures’ stripping potential. Being unaware, local agencies and contractors often struggle with premature pavement failure, which consequently places unexpected strain on the budget. Thus, this study assessed the compatibility among 18 asphalt binders with a performance grade (PG) of PG 64-22, PG 70-22, and PG 76-22, each collected from six different refineries; and eight different types of aggregates (sandstone, novaculite, limestone, and dolomite, each collected from two different quarries). Viscosity, penetration, pH, and work of cohesion values of binders were used to develop a binder ranking system. Similarly, the aggregates were ranked based on physical (specific gravity and absorption), durability (abrasion resistance and soundness), and chemical (pH and surface free energy) properties. Overall relative rankings of aggregates and binders were also provided by assigning weight factors to different tested parameters. A total of 144 aggregate-binder mixture systems were ranked based on their dry and wet work of adhesion values as well as Texas boiling test results. The compatibility ratio (CR) was also computed, and each of the systems was designated A, B, C, or D based on their relative CR values. Upon analysis, three binders (S2B2, S3B1, and S4B1) and three aggregates (DM2, LS2, and DM1) were designated as the most preferable construction materials. CR values predicted LS2, DM1, and DM2 mixtures as the most compatible mixtures. SS2, LS1, and DM2 mixtures showed the highest stripping resistance in the Texas boiling test. These databases are expected to help the agency and asphalt producers to select compatible binders and aggregates for producing durable asphalt concrete.Practical ApplicationsThis study covered a wide variety of aggregates and asphalt binders prevalent in but not limited to Arkansas. A database developed under this project was based on observed individual aggregates’ and binders’ performances as well as their combined performances. The information provided in this study will help contractors and agencies to choose the most appropriate aggregate-binder system within their reach for producing quality asphalt mixtures. By knowing the rankings, state agencies can adjust project budgets and assign timely rehabilitation due to the usage of less compatible aggregate-binder systems. Contractors can tweak the existing mix design if they must use local but inferior materials. This ranking will also help them to select project-specific materials depending on the project’s significance. The refineries as well will have the opportunity to improve their products to be more compatible with local materials.

In vitro comparative study between adhesion forces obtained on zirconia ceramic micromechanically treated with femtosecond laser (1027nm), carbon dioxide laser (10,600nm), and aluminum-oxide particles.

Conventional surface roughening treatments used for silica-based ceramics in order to improve subsequent adhesion become unreliable for zirconia ceramics. Laser conditioning can be a good alternative. The purpose of this in vitro study was to compare conventional (macro) shear bond strength (SBS) values obtained between resin composite and zirconium oxide ceramic samples grouped according to different micromechanical treatments received, and examine differences in surface roughness. One-hundred and fifty disks of sintered zirconia were randomly divided into 5 groups and roughened as follows: (1) Group NOT, no surface treatment; (2) Group APA, abraded with 50-μm aluminum-oxide (Al2O3) particles; (3) Group TBS, abraded with 30-μm aluminum-oxide particles covered with silica; (4) Group CO2, irradiated with a CO2 laser which emitted in continuous wave mode at 3 W of power; and (5) Group FEM, irradiated with a pulsed femtosecond laser, with an incident energy of 10μJ, a frequency of 1000Hz, and a fluence of 1.3kJ/cm2. All surfaces were treated with a MDP-containing adhesive/silane coupling agent mixture upon which were prepared and light polymerized composite resin cylinders. Shear bond strength was measured and samples were observed by scanning electron microscopy (SEM). Statistically significant differences (p < 0.05) were found among all groups, except between CO2 and FEM, which showed the highest adhesion values (15.12 ± 2.35MPa and 16.03 ± 2.73MPa). SEM revealed differences in surface patterns. CO2 laser irradiation can be an alternative to sandblasting, although it could also weaken the ceramic. Suitable surface patterns on zirconia ceramics can be obtained with ultrashort pulsed radiation emitted by a pulsed femtosecond laser.

Investigation of pull-out characteristics of connections for post-installed rebar utilizing mortar-based binders and chemical adhesives

ABSTRACT In this study, various types of adhesives were tested for their ability to adhere steel reinforcement bars to old concrete during a pull-out test when they were used in connection to a post-installed re-bar. The cylinder samples were 150 mm in diameter and had anchors made of rebar that varied in diameter (8 mm, 10 mm, 12 mm, 16 mm, and 20 mm) and embedded depth (10, 12.5, 15, and 20 times the rebar diameter). In contrast to the control group of (60 Nos.) cast-in-situ rebar concrete specimens, the other samples (240 samples) were post-installed-rebar concrete specimens with various bonding agents, epoxy-based chemical adhesive, vinyl-ester-based chemical adhesive, and cement-based binders (geopolymer mortar, conventional mortar). The results showed that while they all performed better than cement-based mortar-bonded specimens, the use of the epoxy-based chemical adhesive and vinyl-ester-based chemical adhesive pull-out load values were closely related. The anchorage depth and rebar diameter both improve the bond strength which reflects in terms of pull-out load. The anchorage depth and the region of contact with the adhesives or binder determine the failure mechanism of post-installed rebar connections. Due to the higher strength at the interface between the binder and the rebar in comparison to the binder-concrete, larger rebar diameters favour splitting or failure of concrete.

The Effect of Finishing and Polishing Systems on Surface Roughness and Microbial Adhesion of Bulk Fill Composites: A Systematic Review and Meta-Analysis.

Objectives: This paper presents a systematic review and meta-analysis of the effect of different finishing and polishing (F/P) systems on surface roughness (SR) and microbial adhesion to bulk fill (BF) composites. Materials and Methods: An electronic search of 3 databases (the National Library of Medicine [MEDLINE/PubMed], Scopus, and ScienceDirect) was conducted. Only in vitro studies that evaluated SR and microbial adhesion to BF composites were included. The included studies were individually evaluated for the risk of bias following predetermined criteria. A meta-analysis of the reviewed studies was conducted to compare the SR values of both Filtek Bulk Fill and Tetric EvoCeram Bulk Fill with and without F/P using the Comprehensive Meta-Analysis software. Results: A total of 12 studies fulfilled the inclusion criteria. The meta-analysis showed no significant difference between Filtek Bulk Fill and Tetric EvoCeram Bulk Fill without F/P or after F/P using multi-step systems. Different F/P systems affected the SR values, on the other hand, did not affect microbial adhesion values. Conclusion: Both Filtek Bulk Fill and Tetric EvoCeram Bulk Fill had comparable roughness results. Multi-step systems may be preferable for F/P of BF composites.

Effects of interface microstructure on adhesion of polyetheretherketone metallized by titanium cold spray

Titanium powders were cold sprayed onto polyetheretherketone (PEEK) to investigate the effects of interface microstructure on bonding. Process guidelines to achieve adherent metallic deposits via cold spray onto thermoplastics are scarce, and mechanisms for metal adhesion onto thermoplastic substrates are unclear. The formation of a transition layer where deposition changes from metal-on-polymer to metal-on-metal deposition can promote adhesion but requires a clearer understanding. The microstructural features of such transition layers provide insights into mechanisms that promote coating adhesion. Select features, including developed interfacial area ratio and gradation of thermal residual stress, correlated to adhesive strength values. The understanding of interlocking mesoscale features formed during cold spray informs the parameter selection for depositing metals onto thermoplastics with strong adhesion.

Mechanical and Tribological Properties of the CrAl/CrAlN and CrAl/CrAlN-(a-CNx) Multilayers Deposited by HIPIMS

In this study, two CrAl/CrAlN multilayer coatings of 1.5 µm and 1.2 µm thicknesses were deposited from a (50:50) CrAl sectioned target by high-power impulse magnetron sputtering (HIPIMS) onto A11 tool steel to evaluate the effect over mechanical and tribological properties by the addition of an (a-CNx) top layer. XRD analysis showed a CrAlN FCC structure (111) and a Cr phase (110). A glass-like morphology was observed in the CrAl layer and in the (a-CNx) top layer, while the CrAlN layers exhibited a columnar morphology according to the FE-SEM analysis. Raman analysis results confirmed characteristic peaks G and D for the carbon amorphous structure of the (a-CNx) top layer. Nanoindentation results showed comparable hardnesses (23.08 GPa ± 2.8 and 20.58 GPa ± 1.8) in both multilayer coatings. The CrAl/CrAlN multilayer with an (a-CNx) top layer increased the absorption energy capacity and the mechanical potential energy stored. The nano scratch test showed the strongest crack resistance and highest adhesive energy values for the CrAl/CrAlN multilayer. The addition of an (a-CNx) top layer improved the tribological behavior when higher normal loads were applied during the fretting test. Raman analysis showed an increase in the I(D)/I(G) ratio and a formation of a carbon sp2 structure (i.e., graphite-like structure) over the worn surfaces, as well as dissipated energy (J/m) during the fretting test.