Ra Values Research Articles

INVESTIGATION OF TRIBOLOGICAL PROPERTIES OF DETONATION COATINGS BASED ON ALUMINUM OXIDE AND TUNGSTEN CARBIDE

Detonation spraying is one of the most promising variants of thermal spraying for the deposition of wear-resistant coatings. This study aims to investigate the tribological properties of coatings deposited by the detonation method using WC-12%Co and Al2O3 as examples. These are two common coating materials widely used in wear resistant applications. A computerized detonation spraying system CCDS2000 (Computer-Controlled Detonation Spraying) was used for coating deposition. The roughness parameter of the WC-Co coating has a value of Ra = 3.95 μm and that of the Al2O3 coating has a value of Ra = 2.53 μm. To investigate the detonation coatings, the coating materials were characterized and microhardness measurements were carried out. Microhardness for stainless steel 12Х18Н10Т (AISI 321, 321H) – 392.32 Hv; for WC-12Co coating – 1332.3 Hv and Al2O3 – 805.50 Hv. By results of researches the greatest resistance to all kinds of wear has coatings WC-12%Co. Al2O3 coatings can also be recommended for operation under sliding wear conditions.

Study on the Manufacturing of Composite Materials Made from Glass Fiber Reinforced Polymer (GFRP) in Indonesia for Use as Lining in Open Channels

This study explained the potential use of glass fiber-reinforced polymer (GFRP) composite materials as an alternative lined material for irrigation channels in Indonesia. Currently, only four recommended materials are used as lining in irrigation channels in Indonesia, i.e., stone masonry, concrete, soil-cement, and ferrocement. Almost all lined material's main constituents are sourced from nature/environment. The exploitation of these mined materials will impact environmental destruction. This study focused on the manufacturing process of GFRP material, GFRP surface roughness testing, and the water flow characteristics in the hydraulic model experimental testing. The manufacturing process of GFRP material used polyester resin as the polymer matrix, E-glass type with a combination of woven roving mat covered by non-woven standard mat as the glass fiber reinforcement, and manufacturing process with a combination of hand lay-up and spray-up techniques. The GFRP material product has an average surface roughness coefficient value of Ra around 5.19 to 5.97 μm. The GFRP manufacturing has a good uniform product, as the average surface roughness coefficients of GFRP material have relatively the same values. It is shown that a factory in Indonesia has sufficient capacity to manufacture GFRP material for lining in open channels. The water flow characteristics in the flume were turbulent during testing in the hydraulic laboratory. The experimental study concluded that the GFRP composite materials could be implemented as preliminary references for alternative lined material in irrigation channels in Indonesia.

Impact of vortex generator, magnetic field, and magnetic two-phase hybrid nanofluid on the performance of a dual-tube heat exchanger: Hydrodynamic and exergy analyses

In this study, a three-dimensional model of a counter-flow dual-tube heat exchanger is developed. The heat exchanger is equipped with a vortex generator, and the working fluid used is a hybrid nanofluid consisting of water and iron-copper oxide. The effects of using the hybrid nanofluid and pure water are investigated. Turbulent flow conditions are assumed within a Reynolds number (Re) range of 30,000 to 48,000, employing the realizable k-ε turbulence model. The coupled algorithm is employed to solve the velocity and pressure equations, and the equations are discretized using the least square method. The vortex generator is utilized with various pitch ratios (Ω). Furthermore, the magnetic field affects the middle section of the inner tube, with Hartmann numbers (Ha) of 35, 65, 95, and 125. The study reveals that an increase in the volume fraction (φ) positively impacts the exergy of the heat exchanger, while an enhancement in Ω negatively influences it. Furthermore, the energy efficiency improves with increasing Re. By applying the magnetic field, the maximum power of the system in producing work corresponds to Re = 36,000 because ηex is reduced when Re > 36,000. At all values of Re, the increase in Ha improves ηex.

Impact of Natural Disasters on the Value of (Re)Insurance Companies

Impact of Natural Disasters on the Value of (Re)Insurance Companies

Effect of Different Polishing Systems on Surface Roughness of IPS Empress Ceramic Materials

For evaluation and comparison of the effect of surface treatment (glazings, polishing with rubber wheel and diamond paste, and polishing with rubber wheel) on pressable porcelain (IPS Emax porcelain) surface roughness in comparison with non-treated surface. Forty-disc shaped specimens of baseplate wax with 10 mm diameter and 2 mm thickness have been prepared. They were invested and subjected to lost wax technique in fabricate the pressable ceramic. Following pressing, they have been divided randomly into four groups: Group A: no surface treatments, Group B: glazing (paste, HT, Ivoclar, Vivadent, Germany) glazing (paste, HT, Ivoclar, Vivadent, Germany), Group C: polishing with burs (DIAPRO TWIST, EVE, GmbH, Germany), and Group D: polishing with burs (DIAPRO TWIST, EVE, GmbH, Germany) and diamond paste (All in one, RENFERT, GmbH, Germany). For each specimen, examination of mean roughness profile (Ra) was performed for total surface roughness description. Specimens were stabilized with the acrylic holder used previously in the initial polishing procedure. A contact stylus profilometer was used to conduct a quantitative measurement of surface roughness in micrometers (µm) for all specimens. The highest (Ra) value was for control group (1.9520), whereas the lowest values were in group D (Polishing by rubber wheel .4670. One-way ANOVA test showed a high significant value at (P <. 000), and LSD test showed a high significant value at (P <. 000) when comparison was established among groups. From the results of the current study, we can conclude the following; polishing procedure for the surface of pressable ceramic with or without diamond paste produced better surface smoothness than glazed surface and non-treated surface and polishing with burs could be an alternative to glazing to provide smooth surface.

N-Nitro-L-Arginine Methyl Ester Hydrochloride Induced Endothelial Dysfunction and Atherosclerosis Model in Rats

Purpose: Atherosclerosis (AS) related diseases are the most common causes of mortality worldwide. N-Nitro-L-Arginine Methyl Ester Hydrochloride (L-NAME)-induced endothelial dysfunction (ED) and AS models require invasive methods for diagnosis.
 We aimed to establish noninvasive ultrasonography (USG) model for evaluating ED and AS in rats. 
 Matherial and Methods: 23 Wistar Albino rats were divided into four groups. Right CCA (rCCA), left CCA (lCCA), abdominal aorta (AA), and right iliac artery (rIA) IMT values of all rats were measured at the beginning of the experiment and before sacrification by USG. Right kidney RI values were calculated at similar times also. Histopathological and immunohistochemical analyzes were performed.
 In the sham group, rats received intraperitoneally (IP) sodium chloride. In the L-NAME groups, IP L-NAME was administered. 
 Results: In the early effect group, significant increase was found in IMT measurements compared to the sham group. 
 In the late effect group, significant increase was found in IMT measurements compared to the sham group. In addition, rRI increased significantly in the group at the end of the experiment. 
 Conclusion: In small animal experiments which ED and AS were studied, a whole-body diagnostic noninvasive model was created for the first time with ultrasonography.

Surface properties and flexural fatigue strength of an advanced lithium disilicate

The aim of this study was to evaluate the surface properties and fatigue mechanical behavior of an advanced lithium disilicate ceramic in comparison to lithium disilicate and zirconia. First, discs (n = 15, diameter = 13.5 mm and thickness = 1.2 mm) were made from the following materials: 4Y-PSZ – 4% mol yttria-stabilized zirconia (IPS e.max ZirCAD A2); LD - lithium disilicate (IPS e.max CAD); ALD - advanced lithium disilicate (CEREC Tessera). The specimens were crystalized/sintered and subsequently analyzed by a rugosimeter (Mitutoyo SJ-410) to determine surface roughness (parameters Ra and Rz). Specimens were subjected to biaxial flexural fatigue testing using the step-test method (20 Hz; 10,000 cycles per step; initial stress of 200 MPa; and step size of 25 MPa) until specimen fracture. Statistical analyses included Shapiro-Wilk, Kruskal-Wallis, and post-hoc tests for roughness data, while survival analysis (Kaplan-Meier and Mantel-Cox) and reliability analysis (Weibull modulus) were applied to flexural fatigue strength data. Hardness (Vickers) results were submitted to analysis of variance (1-way ANOVA) and Tukey's test. Zirconia (4Y-PSZ) showed higher FFS, CFF (467 MPa and 115216 cycles) and survival compared to the other materials. ALD had the lowest FFS, CFF (215 MPa and 11,908 cycles) and survival. ALD showed lower Weibull modulus (m = 6.63 for FFS; m = 1.27 for CFF) than LD for FFS (m = 17.33), and lower than LD (m = 4.64) and 4Y-PSZ (m = 6.69) for CFF. ALD showed the lowest Ra (0.07 μm) and Rz (1.05 μm) values, while 4Y-PSZ (Ra = 0.22 μm; Rz = 1.91 μm) and LD (Ra = 0.21 μm; Rz = 2.17 μm) showed higher and similar values. Zirconia (4-YPSZ) was the hardest material, while lithia-based ceramics (LD and ALD) presented the lowest and similar hardness values. Fractures originated in surface defects in the tensile stress concentration region. ALD has lower flexural fatigue strength compared to the other tested materials, along with higher variability (lower structural reliability).

Machine vision assisted fused deposition modelling process optimization using grey level co-occurrence matrix

Taguchi's Design of Experiments was applied to determine the effect of Fused Deposition Modeling (FDM) parameters such as layer thickness, infill density, and infill line thickness and deposition pattern on surface roughness. Nylon material was fused to produce samples. Conventional probe surface area measurements were performed to extract the Ra values of the samples. Subsequently, the non-contact measurement of 3D printed textures using the Gray Level Co-Occurrence Matrix (GLCM) algorithm was introduced through image processing. The FDM-printed surface image parameters such as correlation and homogeneity are Ra responsive and therefore a signal-to-noise ratio (S/N) analysis was performed to identify optimal parameters. A slight, unexplained deviation in surface image parameters was detected, and this inaccurate deviation may be due to image noise, image distortion, and different lighting associated with capturing and processing printed surface images. The result of the analysis shows that a good surface quality is achieved if a layer thickness of 0.2 mm, 100% bulk density and 1.0 mm bulk thickness are selected. When optimal parameters were reached, the FDM print was repeated and then the results were validated to ensure the accuracy of the method used. The results obtained in the present study could be proposed in the field of additive manufacturing, which improves the surface quality of the FDM sample.

Co-pyrolysis of textile dyeing sludge/litchi shell and CaO: Immobilization of heavy metals and the analysis of the mechanism

To relieve the secondary contamination of heavy metals (HMs), the synergistic effect of co-pyrolysis of textile dyeing sludge (DS)/litchi shell (LS) and CaO on the migration of HMs was demonstrated in this study. The proportions of Cu, Zn, Cr, Mn, and Ni in the F4 fraction increased to 75%, 55%, 100%, 50%, and 62% at the suitable CaO dosages. When 10% CaO was added, the RI value of DLC-10% was reduced to 7.89, indicating low environmental risk. The characterizations of the physicochemical properties of biochar provided support for the HMs immobilization mechanism. HMs combined with inorganic minerals or functional groups to form new stable HMs crystalline minerals and complexes to achieve immobilization of HMs. The pH value and pore structure also play an important role in improving the immobilization performance of HMs. In conclusion, the results provided a new direction for the subsequent harmless treatment of HMs-enriched waste.

Convective heat transfer enhancement in an inverted T-shaped porous enclosure through vertical varying circular cylinder

This research aims to enhance convective thermal transport in an inverted T-shaped porous enclosure filled with a water-based hybrid nanofluid, incorporating a circular cylinder at different vertical locations (Case C1-no cylinder, Case C1-cylinder at (0.5, 0.25), Case C2-cylinder at (0.5, 0.5), Case C3-cylinder at (0.5, 0.75)). The numerical investigation employs the penalty finite element technique to simulate the Darcy–Brinkmann–Forchheimer-based mathematical model. Moreover, the complete results of streamlines, isotherms, mean Nusselt number (Num ), and thermal enhancement percentage ( En % ) are analyzed at the broad range of flow parameters, including Rayleigh number ( Ra = ( 10 3 − 10 6 ) ), Darcy number ( Da = ( 10 − 5 − 10 − 2 ) ), and porosity value ( ϵ = ( 0.1 − 0.9 ) ). Initial comparative investigations of different configurations (C0–C3) at selected Ra values reveal that case C1 exhibits significant potential for enhancing convective heat transport phenomena. Consequently, only case C1 physical domain has been explicitly analyzed for convective heat and fluid flow characteristics at the selected range of flow parameters. Further, it is analyzed that the increasing range of Ra, Da, and ϵ enhances the convective heat and fluid flow phenomena. Furthermore, the comparative study of Num and En % for case C1 against the simple case C0 reveals substantial improvements as Ra, Da, and ϵ increase. The En % for Da and Ra reaches up to 97%, while a maximum of 25% improvement is observed with varying values of ϵ. These findings highlight the promising opportunities to optimize convective thermal transport in the investigated system, mainly through adopting case C1.

A transient numerical approach for phase change material effect on mixed convection in an open cavity

The effects of heated wall locations on mixed convection flow in a 2-D rectangular open cavity are investigated numerically using ANSYS-Fluent software. The flow is supposed to be a two-dimensional laminar and is regulated by parameters such as Reynolds, Re (100 and 200), and Richardson numbers, Ri (1, 5, 10, 15 and 20). One of the walls is heated uniformly, while the others are adiabatic. The heated wall might be vertical on the inflow and outflow sides or horizontal on the bottom of the cavity. The flow is stable at all Re and Ri values except at Ri = 20 and Re = 100 for bottom heated wall. It is found that using phase change material (PCM) reduces flow variations in the cavity. Further, the mixed convection effects are developed with increased Richardson number. This pushes the recirculating zone upstream and creates an unstable flow behavior. According to the results, the condition that minimized the fluctuations in the flow direction was the application of PCM to the bottom heated wall case. Therefore, thermal control of the flow is most efficient in this condition. The PCM melting rate is quite high for the Re = 200 condition as there is higher convective heat transfer in all cases than the Re = 100. Dimensionless wall temperature values with PCM case are lower than without PCM case for all conditions. The decrease of this parameter in bottom heated case is about 18.8% while 43.1% and 56.3% for left and right heated case, respectively. Additionally, the highest average Nusselt number is found for the bottom heated case for the same Re, with and without PCM cases.

Influence of specimen size on granite fracture characteristics and acoustic emission phenomena under mode I loading conditions

The rock mode I fracture characteristics and the size effect are of great significance in understanding the crack initiation, nucleation, propagation, and characterizing the fracture toughness of rocks which is essential for predicting the behavior of rock masses and designing underground structures. In this paper, three-point bending fracture experiments were carried out using single-edge notched beam specimens of different sizes. The fracture characteristics of the entire loading stage, including the post peak stage, were analyzed using digital image correlation (DIC) technology and acoustic emission (AE) technology. Specifically, the calculation of the b value uses the Fisher optimal split and global search algorithm (FGS) method. The results show that both the Fracture process zone (FPZ) length and fracture toughness of granite are size-dependent parameters, and the FPZ length growth rate increases with increasing load level. The failure mode of the source during fracture is mainly tensile failure, and the proportion of tensile failure tends to increase with the increase of specimen size. The temporal b value, average AF value and RA value show corresponding stage changes with time, and the minimum b value, minimum AF value and maximum RA value can characterize the maximum of macroscopic growth rate.

Remineralization Induced by Biomimetic Hydroxyapatite Toothpastes on Human Enamel.

This work aimed to compare the effect of four new toothpastes (P1-P4) based on pure and biomimetic substituted nano-hydroxyapatites (HAPs) on remineralization of human enamel. Artificially demineralized enamel slices were daily treated for ten days with different toothpastes according to the experimental design. Tooth enamel surfaces were investigated using atomic force microscope (AFM) images and surface roughness (Ra) determined before and after treatment. The surface roughness of enamel slices was statistically analyzed by one-way ANOVA and Bonferroni's multiple comparison test. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) data revealed the HAP structure with crystal sizes between 28 and 33 nm and crystallinity between 29 and 37%. The average size of HAP particles was found to be between 30 and 40 nm. The Ra values indicated that P3 (HAP-Mg-Zn-Sr-Si) toothpaste was the most effective after 10 days of treatment, leading to the lowest mean roughness. The P3 and P2 (HAP) toothpastes were found to be effective in promoting remineralization. Specifically, their effectiveness can be ranked as follows: P3 = P2 > P4 (HAP-Mg-Zn-Si) > P1 (HAP-Zn), considering both the chemical composition and the size of their constitutive nanoparticles. The proposed toothpastes might be used successfully to treat early tooth decay.

Condensation particle counters: Exploring the limits of miniaturisation

The measurement of airborne particles continues to attract increased interest for the detection and characterisation of air pollution, emissions, fire detection, occupational and climate impacts. Concerted efforts have reduced the size and cost of optical counters that have enabled widespread sensor deployment. Currently the World Health Organisation (WHO) enforces particle regulations that are mass-based which has resulted in an influx of low-cost portable optical particle counters (OPCs) calibrated to mass standards and widely utilised for research and personal monitoring. However, OPCs are incapable of measuring particles with diameters dp≲ 300 nm which misses ultrafine particles (≤ 100 nm) that often represent the majority of particles by number concentration. Condensation particle counters (CPCs) capable of measuring ultrafine particle number concentration with high instrument sensitivity, accuracy and precision have recently been targeted for miniaturisation.Herein, we explore the limitations of the miniaturisation of a CPC growth chamber (CPC-GC). Results presented in this work use water, but equivalent expressions can be obtained for other working fluids or design criteria using the same methods. Scaling analysis considers phenomenological constraints of supersaturation, heat transfer, particle penetration and droplet growth to establish limits during miniaturisation.The results showed that optimal thermal and saturation conditions are similar where the optimum device aspect ratio is L∗≥Lmin,s∗= 1.68 Re + 7.98 and L∗≥Lmin,th∗= 1.78 Re + 8.02 respectively. L∗ is the non-dimensional aspect ratio and Lmin∗ is the minimum non-dimensional device length required as a function of the flow Reynolds number Re. Higher Reynolds numbers lead to a convection-dominated regime, where the saturation and temperature profiles take a parabolic shape. As the Reynolds number approaches unity, the reduced mass and thermal Péclet numbers result in vapour and heat diffusing upstream of the condenser, creating ellipsoidal saturation and temperature profiles. To achieve a satisfactory performance, the heat and mass transport within the CPC-GC must be convection-dominated, leading to a minimum value of Re ≳2. Desired penetration P≥0.9 for particles with an initial diameter dpinit=10nm is achieved by designs with an aspect ratio, L∗≤Lmax,p∗= 2.5 Re. Together, these constraints define an allowable range of aspect ratios for a CPC-GC as a function of the Reynolds number.The final size of the grown droplets can be controlled by varying the interaction residence time τint, defined as the time a particle spends in the supersaturation profile. Having defined a target final droplet size for optical detection, and hence having fixed τint, the aspect ratio necessary to achieve the desired growth is a function of the Reynolds number and of the dimensional radius of the CPC-GC (Ricpc) according to: Lgrowth∗=γRe/(Ricpc)2 with γ= 2τintν, where ν is the kinematic viscosity of air. Selecting a value of Ricpc such that the line for Lgrowth∗ falls in the centre of the allowable operating region defined above will optimise the dimensional CPC-GC for the selected design criteria.Limits from this model were used to realising a prototype successfully tested experimentally against a reference commercial CPC within a laboratory environment. The outcome of the present work enables designers and researchers with a toolkit to optimise the next generation of high performance miniaturised CPC-GC designs.

Evaluation of heat transfer transition for nanofluids within an enclosure based on magnetic field angles

The present simulation deals with Magnetohydrodynamics (MHD) with focus on heat transfer attributes with the addition of nanoparticle volume concentration (NVC). Influences of the governing parameters, including natural convection strength of Rayleigh number (Ra), magnetic field intensity of Hartmann number (Ha), and magnetic directions with a complete period of γ = 0°–180° are studied. The results disclose that MHD heat transfer patterns can be divided into three groups, i.e., Type-1 (Increase), Type-2 (Transition), and Type-3 (Optimum). With the increasing Ha, the heat convection is suppressed, resulting in Type-1. Enhancing Ra improves the thermal convection and thus leads to the occurrence of Type-3. In between, a critical Ha (Hacr) at a specific Ra exists for heat transfer transition (Type-2). The flow structure and heat transfer patterns vary with γ stemming from the Lorentz force component. The maximum stream function and best heat transfer rate are found at γ = 45°, corresponding to a higher Hacr for Type-2. For a wide range of Ra values, the combination of Ha2/Ra is adopted to describe the relationship between the Hacr and γ for the heat transfer transition with an empirical equation as Ra ≥ 5 × 104.

The Effects of Ball-Mill Grinding Parameters on Lignite Morphology

In recent years, because of the decreasing liberation sizes of the minerals, processes such as grinding need to be evaluated in more detail. As is well known, size reduction processes are very important both in mineral processing and in many industrial applications. However, to increase the efficiency of the processes after size reduction, variations in particle morphology should also be evaluated, along with particle size. Although the effectiveness of grinding media (ball, rod, autogenous) has been shown for different materials, there are very few studies on the effect of the powder/grinding media ratio and grinding time on particle morphology in terms of shape factor and roughness values. This study aims to investigate the variations in the morphology of lignite samples under different grinding conditions such as grinding time and powder/grinding media ratio (U). The results of these analyses showed that while the d80 size of the ground lignite was 1.1 mm after 2 min grinding time, it decreased to 0.5 mm following 15 min grinding time. The roundness values of particles vary in the range of 0.746–0.790 with increasing grinding time. In addition to the grinding time, while the roundness of particles was found to be 0.739 for 0.34 U values (powder/grinding medium rate), it increased to 0.788 when the U value was adjusted to 0.67. The average roughness (Ra) values of particles increased from 60.9 nm to 107.9 nm upon increasing the grinding time from 2 min to 16 min. Due to these findings, it can be suggested that lignite samples became rounder with increasing grinding times, and roughness analyses made in a 10 × 10 μm surface area with an Atomic Force Microscope (AFM) indicated that particle roughness increased in direct proportion to grinding time.

Circular, zero waste formwork - Sustainable and reusable systems for complex concrete elements

The construction sector contributes significantly to global carbon emissions, leading to a new need and demand for sustainable and material-efficient construction technologies. Digital form-finding, simulation, and optimization methods are advancing, resulting in highly efficient, but often geometrically complex components. Concrete construction, which is currently dominant worldwide and crucial for sustainable material savings due to its large market volume, still faces challenges in implementing complex geometries. The significant requirements for formwork material and limitations in feasibility and cost at the current state of the art contribute to these challenges. This research presents a zero waste process using recyclable and reusable digitally fabricated formwork made from waste ingredients that can be immediately implemented in the construction industry. Residual sands (quartz and ceramics) were investigated as a basic moulding material in combination with biogenic binders (bentonite, eco-resin, sodium silicate, starch) for the production of stable formwork composites. The material compound were shaped into precise complex forms using 5-axis milling, and the removed material was recycled in a closed material cycle. Testing and characterization methods for evaluating mechanical properties such as compressive forces (20.1 N/mm2), surface roughness (Ra 9.1 μm), tolerances (0), and moulding processes indicate that the presented procedure conforms to common industry standards. Demonstrating feasibility, complex ultra-thin 1:1 concrete prototypes were designed and manufactured under industrial conditions using prefabricated formworks made of researched bio composite. The resulting high-resolution formwork surfaces and exposed concrete precast elements correspond to the highest fair-faced concrete class (SB04), with line roughness values of Ra 14.4 μm. The developed circulation concept allows reproducibility of different geometries and repeated concreting of formwork moulds. The formwork process is free from harmful additives, enabling recycling through grinding and reintegration into a closed material cycle. Sustainability has been continuously monitored and evaluated through a life cycle assessment. This system utilizes standard machines and offers an accessible and easily integrated approach for a holistic zero waste solution, suitable for efficient industrial applications.

Effect of polishing and denture cleansers on the surface roughness of new-generation denture base materials and their color change after cleansing.

To evaluate the effect of polishing and denture cleansers on the surface roughness (Ra) of new-generation denture base materials that are additively, subtractively, and conventionally fabricated, while also assessing their color change after cleansing. One hundred and fifty disk-shaped specimens (Ø10×2mm) were prepared from five denture base materials (one subtractively manufactured nanographene-reinforced prepolymerized polymethylmethacrylate (PMMA) (SM-GC), one subtractively manufactured prepolymerized PMMA (SM-PM), two additively manufactured denture base resins (AM-DT and AM-ND), and one heat-polymerized PMMA (CV) (n = 30). The Ra of the specimens was measured before and after conventional laboratory polishing, while color coordinates were measured after polishing. Specimens were then divided into three subgroups based on the denture cleanser: distilled water, 1% sodium hypochlorite (NaOCl), and effervescent tablet (n=10). The Ra and color coordinates were remeasured after nine cleansing cycles over a period of 20 days. The CIEDE2000 formula was used to calculate the color differences (ΔE00). Two-way analysis of variance (ANOVA) was used to analyze the Ra values before (n = 30) and after (n = 10) cleansing, while repeated measures ANOVA was used to analyze the Ra of material-time point pairs within each denture cleanser (n = 10). ΔE00 data after denture cleansing was also analyzed by using two-way ANOVA (n = 10) (α = 0.05). Before polishing, Ra varied significantly among the materials. SM-GC and SM-PM had the lowest and AM-ND the highest Ra values (P<0.001). Polishing significantly reduced Ra of all materials (P<0.001), and after polishing, Ra differences among materials were nonsignificant (P≥0.072). Regardless of the denture cleanser, the Ra of AM-DT, AM-ND, and CV was the highest before polishing when different time points were considered (P<0.001). After cleansing, AM-ND had the highest Ra of all the materials, regardless of the cleanser (P≤0.017). AM-DT had higher Ra than SM-PM when distilled water (P = 0.040) and higher Ra than SM-GC, SM-PM, and CV when NaOCl was used (P<0.001). The type of cleanser significantly influenced the Ra of AM-DT, AM-ND, and CV. For AM-DT, NaOCl led to the highest Ra and the tablet led to the lowest Ra (P≤0.042), while for AM-ND, distilled water led to the lowest Ra (P≤0.024). For CV, the tablet led to lower Ra than distilled water (P=0.009). Color change varied among the materials. When distilled water was used, SM-GC had higher ΔE00 than SM-PM and AM-DT (P≤0.034). When NaOCl was used, AM-ND had higher ΔE00 than SM-GC, SM-PM, and AM-DT, while CV and SM-GC had higher ΔE00 than SM-PM and AM-DT (P≤0.039). Finally, when the tablet was used, AM-ND and CV had the highest ΔE00, while AM-DT had lower ΔE00 than SM-GC (P≤0.015). The tested materials had unacceptable surface roughness (>0.2μm) before polishing. Roughness decreased significantly after polishing (<0.2μm). Denture cleansers did not significantly affect the surface roughness of the materials, and roughness remained clinically acceptable after cleansing (<0.2μm). Considering previously reported color thresholds, AM-ND and CV had unacceptable color change regardless of the denture cleanser, and the effervescent tablet led to perceptible, but acceptable color change for SM-GC, SM-PM, and AM-DT.

Influence of Sucrose and Arenga pinnata Solutions on Enamel Surface Demineralization: A Profilometric Study.

Background Dental caries is a multifactorial disease that has the potential to impact individuals across various life stages. The influential role of sugar as a contributing risk element in the inception and advancement of dental caries is significantly pronounced. Aim The research aim was to analyze and compare the enamel surface roughness in teeth exposed to sucrose and Arenga pinnata (palm sugar) solutions by using a stylus profilometer Materials and methods In this investigation, 34 freshly extracted anterior teeth were obtained and they were split into two groups depending on the solution in which they were immersed. Group A consists of 17 teeth immersed in 1% sucrose solution supplemented in brain heart infusion(BHI) broth solution and Group B consists of 17 teeth immersed in 1% Arenga pinnataBHIbroth. Each sample served as its own control. Streptococcus mutans was inoculated into these groups and they were immersed in their respective solution for five days. A stylus profilometer was utilized to measure the surface roughness of the teeth in this study. Data analysis involved paired t-tests for intragroup comparisons and independent t-tests for intergroup comparisons using SPSS software version 23. Results After five days of exposure to palm sugar or sucrose, it was observed that there was demineralization of the enamel surface on both samples. Although there was no statistical significance (p<0.05) when an independent t-test was conducted among these samples, there was a visible increase in the numerical values of Ra, Rq, Rz of teeth exposed to sucrose compared to palm sugar with a p-value of 0.529, 0.122 and 0.357, respectively. Conclusion From this study, it was concluded that although both sucrose and Arenga pinnata causedemineralization of enamel, it was shown that the latter caused lesser demineralization when compared to refined sugars to a certain extent. This study establishes a foundation for forthcoming investigations that could potentially explore the utilization of natural sugars as a substitute for sucrose, while also evaluating the mechanistic aspects underlying the impact of these sugars on enamel demineralization.

Experimental investigations on the mechanical properties and damage detection of carbon nanotubes modified crumb rubber concrete

This study presents a modified crumb rubber (MCR) concrete design mix reinforced with multi-walled carbon nanotubes (MWCNTs), mechanical characterization, and cracking monitoring using the acoustic emission (AE) technique. The results showed that the bridging effect of MWCNTs and MCR in the concrete mix mitigated the shortcomings of MWCNT-MCR concrete and improved the flexural and compressive strengths by 18.3% and 26.5%, respectively, at 28 days. The stress-strain behavior of the MWCNT-MCR concrete showed improved ductility (48.12%), axial strain (50.12%), and toughness (27.15%) compared to the reference specimens. The MWCNT–MCR concrete exhibited a mechanical response in three distinct loading phases. Overall, tensile failure (>4000 μs/v and >35 kHz) was observed in the tested specimens through the RA value (ratio of rise time to amplitude of AE waves) and average frequency (AF) distribution. Based on the amplitude distribution of the AE waves, the damping capacity of the MWCNT-MCR concrete was improved by 27.83%, and the fracture mechanism between micro and macro cracks was identified through a b-value approach. Finally, a regression model was established to predict the Ec of MWCNT-MCR concrete and the two-way interaction effect on the mechanical properties of the developed mix design.