Cylindrical Block Research Articles

Can flowable short-fiber-reinforced resins achieve a strong adhesion to bioceramics?

This study compared the microshear bond strength (μSBS) of four calcium silicate-based cements (CSCs), TheraCal PT (TPT), TheraCal LC (TLC), Biodentine (BD), and Dia-Root Bio MTA (DR), with a short fiber-reinforced composite resin (SFRC). Forty cylindrical acrylic blocks were used, each with a center hole (diameter 5 mm, depth 2 mm). CSCs were placed in the holes (n = 10/group), and the blocks were incubated for 48 h. G-Premio BOND, a self-etching adhesive, was applied to the CSCs surfaces using a micro-applicator for 10 s and then air-dried for 5 s, followed by light curing for 20 s. SFRC materials placed in cylindrical polyethylene capsules (diameter 2 mm, height 2 mm) were polymerized for 20 s and placed over the CSCs. The samples were then incubated at 37°C and 100% humidity for 24 h, and their μSBSs were tested using an "Instron Universal Testing Machine." Data were statistically analyzed using chi-square and Kruskal-Wallis tests. Statistically significant differences were observed between the tested CSCs. The μSBS of TPT (45.17 ± 4.56 MPa) was significantly higher (p < .05) than that of the other materials: BD, TLC, and DR had μSBSs of 29.18 ± 2.86 MPa (p < .05), 23.86 ± 2.84 MPa (p > .05), and 18.08 ± 2.69 MPa (p < .05), respectively. Considering the importance of bond strength for CSC sealing with restorative material, using SFRC over CSC was promising for improving the μSBS, adhesion, and sealing of the material. RESEARCH HIGHLIGHTS: Adhesion is critical to the success of vital pulp restorations. To achieve strong adhesion, the bioceramic material and the resin composite to which it is bonded are very important. In our study, short fiber-reinforced composite resin, which is gaining popularity, was used and found to be a promising material for improved adhesion.

Experimental Analysis of Mechanical Property Enhancement of Paper-Pulp-Based Packaging Materials Using Biodegradable Additives

Generally, paper-pulp-based materials are emerging in the packaging industry due to their high degree of biodegradability. Along with agricultural byproducts as an alternative, using additive or secondary materials in various processes and products has been a solution for implementing sustainability in material utilization. However, biodegradable materials still need to be improved due to the lack of properties which are essential for their use as packaging material. Currently, a number of research attempts have focused on enhancing the mechanical and thermal properties to increase the effectivity of those biodegradable materials for use as packaging material. The objective of this study is to analyze the effectivity of using sugarcane bagasse ash (SCBA) and wheat flour (starch) as a strengthening and thermal resistive additive. Due to its proven nano range particle size and fibrous nature, this material could positively affect the material properties. A total of twelve samples were prepared by varying the weight fraction of SCBA, white flour, and paper pulp. A compression molding method was used to prepare cylindrical samples with a diameter of 50 mm and a height of 55 mm under a compression load of 2 tonnes. Wet molded cylindrical blocks were oven-dried at 105∘C for 48 h to remove excessive moisture from the samples. Subsequently, all the samples were dried further until no significant weight loss was observed after the drying process to ensure their uniform moisture conditions. The prepared samples were tested for compressive strength using a Universal Testing Machine (UTM). Both load and compressive stress acting on each sample were plotted against the deflection of the sample. For the analysis, the deflection of each sample was measured at 8.6 kN load and the sample with 10% SCBA and 12.5% starch exhibited the least displacement among all additives. The results show that the samples with 10% SCBA and 12.5% starch also had the highest compressive strength compared to the other samples. Further, samples with the same amount of SCBA were analyzed for thermal resistivity and to obtain the thermal behavior of samples which is crucial in food packaging.Overall, most of the SCBA and starch mixed samples showed superior compressive strength compared to the pure paper-pulp-based sample.

Experience of Surgical Treatment of Tuberculous and Nonspecific Spondylitis with a Barrier Collagen Membrane to Stimulate Osteogenesis in the Site of Bone Block Formation

The objective: to increase effectiveness of surgical treatment of infectious spondylitis with impaired support function of the spinal column through the combined use of a titanium cylindrical block mesh, a resorbable double-sided collagen membrane and an osteoconductor to achieve successful spinal fusion.Subjects and Methods. A prospective monocenter cohort study included 17 patients with infectious spondylitis who were operated with anterior spinal fusion with a titanium mesh graft filled with an osteoconductor and delimited by a barrier double-sided collagen membrane. In the postoperative period, antibacterial treatment was administered based according to the results of bacteriological tests of biological specimensl. Formation of the bone block (spondylodesis) was evaluated by the scale for assessing the fusion of the graft with the bed of the cranial and caudal vertebrae.Results. 6 months after surgery, the fusion of the graft with the bed of the supporting vertebra according to the Baulin scale was 4.5 ± 0.4 scores on the average. In 5 (29%) patients, a clear, homogeneous bone block with a transition of bone beams was achieved after surgery which amounted to 5 scores by the Baulin scale.

Experiment and modeling investigation of irregular block descent into water

The underwater motion of freely falling irregular blocks is a critical factor in various applications, including damming large rivers, sealing levee breaches, and embankment construction. This study first investigates the motion patterns of blocks with various shapes sinking in water through a series of experimental tests. To quantitatively describe the underwater motion characteristics of irregular blocks, a new motion model based on the concept of equivalent spheres is proposed. The coupled particle flow code – computational fluid dynamics (PFC-CFD) method is employed to simulate the movement of cubic, pyramidal, and cylindrical blocks at various flow speeds and dropping heights. The parameters of the proposed model are calibrated and validated through numerical simulations. The predicted trajectories of the model show good agreement with the coupled PFC-CFD simulation data and the indoor drop test results, demonstrating the reliability and accuracy of the model. This proposed model, being computationally simple and utilizing readily available parameters, provides valuable insights for designing underwater dumping construction plans and related projects.

Which Whitening Mouthwash With Different Ingredients Is More Effective on Color and Bond Strength of Enamel?

To examine the effects of six whitening mouthwashes on tooth color and immediate bond strength to the enamel. Human incisors were divided into seven groups (n = 10) according to mouthwashes (R.O.C.S Black Edition White, Splat White Plus, Colgate Plax White Charcoal, Signal White Now, Listerine Advanced White, Colgate Optic White, and distilled water). After the initial color measurements, the teeth were exposed to mouthwash for 4 weeks. Then, the color measurements were repeated. Then, cylindrical composite resin blocks were immediately applied to the enamel surfaces and subjected to shear bond strength tests. Data were analyzed using Kruskal-Wallis and Bonferroni tests (α = 0.05). Δ𝑏, Δ𝐿, and ΔE00 values did not present significant differences among the groups. Significant differences among the groups were determined for Δ𝑎 and ΔWID values (p < 0.05). R.O.C.S Black Edition White and Splat White Plus produced clinically acceptable color changes. Signal White Now, Splat White Plus, and Listerine Advanced White created acceptable whiteness changes. The mouthwashes did not statistically affect the bond strength compared to the distilled water (p > 0.05). Whitening mouthwash containing blue covarine revealed more acceptable color and whitening changes. Mouthwash containing charcoal led to the lowest enamel bond strength values. The content of whitening mouthwashes affected the degree of tooth whitening and shear bond strength to enamel.

Effects of radiotherapy dose and application time on the load-to-failure values of teeth filled with different sealers

BackgroundThe materials used in root canal filling and radiotherapy (RT) application can affect the load-to-failure of the teeth. This study aimed to compare the load-to-failure of the teeth filled with AH Plus (AHP) or AH Plus bioceramic (AHPB) before or after 60 Gy- and 70 Gy-dose radiotherapy.Materials and methodsOne hundred and ten maxillary incisors were endodontically prepared up to ProTaper Next X4 instruments. The teeth were randomly divided into 5 main groups as: non-irradiated, root canal treatment (RCT) before 60 Gy radiotherapy, RCT before 70 Gy radiotherapy, RCT after 60 Gy radiotherapy, RCT after 70 Gy radiotherapy. These groups were divided into 2 subgroups for filling material: AHP ve AHPB. After filling and radiotherapy procedures, the teeth were fixed on the thermoplastic mask plane. The plane were placed in the middle of a rectangular prism shaped glass phantom, and irradiated via a linear accelerator device. The teeth were then embedded in cylindrical acrylic blocks and the force (N) that caused the fracture was recorded under the Universal testing device. Student t-test was used for statistical comparisons. Statistical significance level was determined as p < 0.05.ResultsAfter 70 Gy dose radiotherapy, the group filled with AHPB showed statistically significantly lower fracture strength than the group filled with AHP (p < 0.05). In the control group, before 60 Gy RT group, after 60 Gy RT group, and before 70 Gy RT group, the sealers had statistically significantly similar load-to-failure. (p > 0.05).ConclusionThe group filled with AHPB caused a lower fracture strength than the group filled with AHP following a 70 Gy dose of RT. The sealers in the control group, before 60 Gy RT group, after 60 Gy RT group, and before 70 Gy RT group exhibited comparable load-to-failure values.

Numerical analysis of transient MHD natural convection in a channel with four heat-generating cylindrical solids filled with in a non-Newtonian Fe3O4 ferrofluid

This article presents a numerical investigation and analysis of the cooling effectiveness of thermomagnetic transient natural convection in a long channel, equipped with four cylindrical heat-generating blocks. A non-Newtonian power-law ferrofluid was employed for the present investigation to achieve optimum cooling. The governing equations are the continuity equation, the momentum equation and the energy equation. The finite volume method was used to solve the resulting algebraic system. From an energy-saving point of view, this configuration can provide a good approximation for selecting effective physical and geometrical parameters to design a reliable thermal system. For this purpose, the study was carried out for various geometric and thermophysical parameters. Different values of thermal conductivity, power law index, Rayleigh number, Hartmann number and ferrofluid volume fraction, were considered. The results are illustrated in the form of streamlines, isotherms, average Nusselt and a spatio-temporal characterization of the mean ferrofluid velocity. From the results presented, we can conclude that the choice of non-Newtonian, pseudoplastic ferrofluid with a low thermal conductivity ratio subjected to a uniform magnetic field proves to be a crucial solution for efficient and stable cooling of heat-generating cylindrical blocks, which will have to be close to the cold walls of the channel.

Quantitative Analysis of the Hsu-Nielsen Source through Advanced Measurement and Simulation Techniques

Abstract This paper presents the results from conducting a series of experiments with a Hsu-Nielsen Source, accompanied by corresponding numerical simulations on a solid block. The aim being to illustrate a Finite Element Analysis (FEA) approach for simulating Acoustic Emission (AE) wave propagation in a Hsu-Nielsen Source, by employing virtual sensors to enhance existing AE research methodologies. The objective was to examine and establish the actual unload rate derived from Pencil Lead Breaks (PLBs) by comparing results from simulations and experimental trials. These experiments and simulations were conducted using a solid cylindrical steel block, capturing the propagating Acoustic AE waves from both sources over a two-second span. When comparing the experimental data with the simulation results, it is evident that replicating the structure of an impulsive AE source is feasible for brief durations. Furthermore, both the experimental and simulated signals on the steel cylinder displayed comparable patterns in the initial 25-30 µs. The methodology presented in this study demonstrates the effectiveness of Finite Element Analysis (FEA) in precisely identifying the specific modes present in AE wave propagation, including the actual unload rates affecting the AE signals recorded.

A simple, rapid and entertaining method to measure specific heat of metals using liquid nitrogen and Leidenfrost effect

Taking advantage of the fascination of ‘playing’ with liquid nitrogen, this article proposes a didactical experiment involving the use of this liquid to measure the heat capacity of cylindrical metallic blocks (copper, aluminum, brass, and stainless steel; volume ≈ 20 cm3). It also permits to demonstrate qualitatively and quantitatively the Leidenfrost effect. The experimental setup consists of a low-cost recipient adequate for liquid N2 storage, a multimeter and a weighing scale. The experience starts by a rapid immersion of metallic block in liquid N2 and by measuring simultaneously the block’s temperature and the mass of the evaporated liquid along the cooling process. Knowing the latent heat of the liquid L , the evaporated mass Δm during a temperature variation ΔT , the heat capacity is obtained by Cp=L Δm/ΔT . This method allowed to measure the specific heat in the 100–270 K temperature range in less than 3 min and the results are in quite good agreement with the literature data. On the other hand, the cooling rate, measured by temperature and liquid N2 change, clearly shows two regimes as expected by the Leidenfrost effect and the critical heat flux calculated is in good agreement with previous experiments. Such an experiment can be adapted to various student levels and present a didactical approach to important thermodynamical concepts in parallel with appealing phenomena.

Comparative evaluations of shear bond strength of mineral trioxide aggregate, Biodentine, and calcium-enriched mixture to bulk-fill flowable composite using three different adhesive systems: An in vitro study.

The objective of the study was to assess the shear bond strength of bulk-fill flowable composite resin smart dentin replacement plus when bonded to mineral trioxide aggregate (MTA)-angelus, biodentine, and calcium-enriched mixture (CEM) at two different aging periods (15 min and 72 h) using three distinct adhesive systems. In addition, the study identified the specific modes of failure (adhesive, cohesive, or mixed) using a stereomicroscope and scanning electron microscope. One hundred and twenty-six cylindrical acrylic blocks used in the study were sorted into three groups based on the bioactive substance used to fill the 3-mm diameter and 3-mm high hole in the center of each block. The groups were MTA, Biodentine, and CEM. The specimens were then divided into subgroups based on the aging interval (15 min and 72 h) of the bioactive material and the adhesive system used (two-step total-etch, two-step self-etch [SE], and one-step SE) while bonding to the restorative bulk-fill flowable composite. The shear bond strength values were measured with a universal testing machine, and the data were analyzed using two-way and one-way analysis of variance, followed by a post hoc test. The specimens were assessed under stereomicroscope and scanning electron microscope to characterize the mode of bond failure (cohesive, adhesive, or mixed). The study showed that the type of adhesive system and the time of bonding affected the shear bond strength of bulk-fill composite to the pulp capping agents (P < 0.05). For MTA, the highest bond strength was observed with two-step SE group at 15 min (18.16 ± 2.97 MPa) (P < 0.05). CEM exhibited the highest bond strength with two-step SE group at 72 h intervals (8.77 ± 1.76) (P < 0.05). The highest bond strength for biodentine group was observed with total-etch group (8.54 ± 1.35 Mpa) and two-step SE (8.19 ± 1.94 Mpa) bonded at 72 h interval (P < 0.05). The majority of the samples in the MTA group (29/42) and CEM group (20/42) showed a cohesive fracture, whereas Biodentine group (22/42) had an adhesive fracture in most of its samples. MTA demonstrated the highest bond strength with two-step SE group at 15 min, and CEM exhibited the highest bond strength with two-step SE groups at 72 h interval. For biodentine group, the type of adhesive used did not impact the bond strength values.

Numerical analysis and experimental study of membrane-type acoustic metamaterial plate with X-shaped pendulum arm and cylindrical mass blocks

Membrane-type acoustic metamaterials have a favorable noise suppression effect. Hence, a membrane-type acoustic metamaterial plate (MAML) with an X-shaped pendulum arm and cylindrical mass blocks (CMB) was proposed in this paper. The theoretical model based on spring–mass systems and numerical simulation models of the membrane-type acoustic metamaterial cell (MAMC) were established under fixed and periodic boundary conditions to reveal the noise attenuation mechanism quantitatively, and the necessity of the CMB is discussed. Based on the results, it can be observed that the normal displacement of the membrane is nearly zero when the noise frequency is at the peak of the sound transmission loss (STL) curve. However, when the frequency is at the valley of the STL curve, the displacement is nonzero and fluctuates significantly. Meanwhile, by comparing the STL curves with and without the CMB, it was found that the MAMC performance is improved effectively by the CMB at low frequencies. The effective mass density of MAMC was found to be negative. To verify the accuracy of numerical calculations, an impedance tube experiment was conducted. Finally, orthogonal experiments were designed to describe the effects of the structural parameters a, l, and t on the effective bandwidth [Formula: see text], peak frequency [Formula: see text], and comprehensive index [Formula: see text] and to obtain the optimal structural parameter combinations for different indexes. This work further contributes to applying and developing the membrane-type acoustic metamaterial.

Two-dimensional counter-current capillary imbibition of a wetting phase into a partially submerged porous cylindrical matrix block

The purpose of this study is to address the two-dimensional counter-current capillary dominant imbibition of a wetting phase into a water-wet porous cylindrical matrix block partially submerged in the wetting phase. A two-dimensional unsteady-state diffusion equation is used to model the process. The governing equation is solved using a combination of the Laplace and the finite Fourier sine transforms to find and analyze the solutions for the normalized water saturation and the volume of the imbibed wetting phase. The results reveal that the volume of the imbibed wetting phase and the capillary diffusion shape factor for a partially submerged matrix block are significantly lower compared to those of a fully submerged matrix block, highlighting the overestimation of imbibed volume using available models based on full immersion in the wetting phase. It has been observed that the volume of the imbibed wetting phase increases over time until reaching a state of equilibrium. In the case of a partially submerged matrix block, the shape factor is inversely proportional to the square root of time (σ ∼ 1/t) during the early time and decreases sharply as the imbibed wetting phase reaches an equilibrium. In the case of a fully submerged matrix block, the shape factor is inversely proportional to the square root of time (σ ∼ 1/t) during the early time and later reaches a pseudo-steady-state value. The proposed model, along with the findings obtained, advances our understanding of capillary imbibition in porous media.

Ultrasound Assisted Aqueous Two‐Phase Extraction of Polysaccharides from Ophiopogon japonicus: Process Optimization, Structure Characterization, and Antioxidant Activity

AbstractUltrasound assisted aqueous two‐phase extraction (UATPE) is used to extract polysaccharides from Ophiopogon japonicus (OJPs). Experimental factors in UATPE process are optimized by response surface methodology. The optimal extraction conditions are obtained as follows: the ethanol concentration of 34%, ammonium sulfate concentration of 23%, solid‐to‐liquid ratio of 1:17 g/mL, and ultrasound power of 480 W, and the yield of OJPs is 9.41% ± 0.12%, and then the crude OJPs are further purified by different column chromatography to obtain a homogenous fraction (OJPs‐2‐SG), and identified its structure via different methods. OJPs‐2‐SG with a molecular weight of 1.25 × 105 Da is comprised of mannose (Man), galactose (Gal), glucose (Glc), and rhamnose (Rha) with a molar ratio of 5.15: 26.39: 68.72:8.41. Moreover, OJPs‐2‐SG contained α and β glycosidic bonds, and didn't showed a triple helix structure. Furthermore, OJPs‐2‐SG described irregular structures, and cylindrical and conical block like features. The IC50 values of scavenging 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), hydroxyl (OH), and superoxide (O2‐) radicals for OJPs‐2‐SG achieved 3.72 mg/mL, 3.89 mg/mL, and 8.71 mg/mL, respectively. These results provide important references for the extraction and application of polysaccharides.

Review on Factors Affecting Efficiency of Shell and Tube Heat Exchanger

Heat exchanger is one amongst promising thermal device in which heat transfer takes place between hot fluid and cold fluid. Among various classifications of warmth exchangers, the main focus was shown by researchers on indirect contact type compact heat exchangers. Among them the shell and tube device belongs to fluid to fluid type heat transfer device. Main applications of shell and tube device feed device in process industries, refineries, chemical plants and power plants. Usually the analysis of shell and tube heat exchangers are divided into two parts namely shell side and tube side analysis. Shell side analysis is easy and doesn't involve much modification. Whereas the tube side analysis is complex and it's done by varying baffle design and elevation with regard to arrangements of tubes. The most disadvantage of shell and tube device is pressure drop which occur at the end of tubes. To overcome this problem, drilled cylindrical copper block has been introduced to switch the tube part through which the new fluid flows and therefore the cold fluid is circulated through the shell. With this design modification, the effectiveness, mass rate, overall heat transfer co efficient are simulated and analysed.

Fracture strength of fiber post with polyetheretherketone post: An In vitro comparative study

Abstract Aim: To assess and compare the fracture strength of polyetheretherketone (PEEK) post materials with fiber posts on endodontically treated maxillary central incisors. Materials and Methods: In this in vitro comparative study, two dental post materials were evaluated: fiber-reinforced post and PEEK post. Simple random sampling was done and 30 specimens were fabricated using extracted, decoronated, and endodontically treated maxillary central incisors (n = 15 for each group). Post-space preparation was done 5 mm short of the apex and restored with prefabricated fiber post (n = 15) and customized PEEK post (n = 15). Samples were mounted in a cold cure acrylic cylindrical block, at 45° angulation for testing the fracture strength using a universal testing machine. The data were analyzed and compared statistically, using an independent t test. Results: Mean fracture strength of the PEEK post was 65.79 kg and the fiber post was 59.32 kg with no statistically significant difference in the fracture strength between the two groups. Conclusion: Within the limitations of the study, it can be concluded that the PEEK post has similar mechanical properties to the fiber post and could be considered as an alternative to the fiber post having the advantages of being custom-made requiring conservative canal preparation with minimal dentin removal.

Comparative Evaluation of Shear Bond Strength of Resin-modified Glass Ionomer Cement with ProRoot MTA and MTA Angelus.

The aim of the present study was to evaluate the shear bond strength of resin-modified glass ionomer cement with two different types of mineral trioxide aggregate at different time intervals. A total of 80 cylindrical blocks were prepared using a self-cure acrylic resin with a central cavity of 4 mm internal diameter and 2 mm height. The prepared samples were randomly divided into two groups (n = 40 each) according to the type of MTA cements used (ProRoot MTA and MTA Angelus). Two groups were further sub-divided into four sub-groups of 10 samples each according to the different time intervals. ProRoot MTA and MTA Angelus were placed in the prepared cavity and a wet cotton pellet was placed over the filled cavity. A hollow plastic tube was placed over the MTA surface and resin-modified glass ionomer cement (RMGIC) was placed into the hollow plastic tube and light-cured (Spectrum 800, Dentsply Caulk Milford, DE, USA) according to the time intervals decided. After light curing the plastic tubes were removed carefully and the specimens were stored at 37°C and 100% humidity for 24 hours to encourage setting of MTA. The specimens were mounted in a universal testing machine (ADMET) and a crosshead speed of 0.5 mm/min was applied to each specimen by using a knife-edge blade until the bond between the MTA and RMGIC failed. The data were statistically analyzed using ANOVA, post hoc Tukey's t-test and Fisher's t-test and p-value ≤ 0.5 was considered significant. For both ProRoot MTA and MTA Angelus there was no statistically significant difference between 45 minutes and 24 hours (p-value ≥ 0.8). For ProRoot MTA, shear bond strength value at 10 minutes were significantly lower than 45 minutes and 24 hours group. However, for MTA Angelus, shear bond strength value at 10 minute was not significantly different from 45 minutes group (p-value ≥ 0.3). For both ProRoot MTA and MTA Angelus shear bond strength value at 0 minute were the least and were significantly lower than 10 minutes, 45 minutes, and 24 hours, respectively (p-value ≥ 0.000). Resin-modified glass ionomer cement can be layered over MTA Angelus after it is allowed to set for 10 minutes. However, ProRoot MTA should be allowed to set for at least 45 minutes before the placement of RMGIC to achieve better shear bond strength. Due to the variety of types of mineral trioxide aggregate cements available in dentistry, it is justifiable to emphasize on different time intervals as it may affect the shear bond strength of restorative cements. Such information is pivotal for the clinicians while using mineral aggregate-based cements that receive forces from the condensation of restorative materials or occlusion, as the compressive strength may be affected due to different time intervals. How to cite this article: Tyagi N, Chaman C, Anand S, et al. Comparative Evaluation of Shear Bond Strength of Resin-modified Glass Ionomer Cement with ProRoot MTA and MTA Angelus. J Contemp Dent Pract 2024;25(1):35-40.

Comparative Evaluation of Bond Strengths Between Dual Cure Resin Cement and Light Cure Resin Cement in Root Surface Indirect Restorations: An In Vitro Analysis Study.

Aim The aim of this study was to evaluate the shear bond strength betweendual cure and light cure resin cements in root surface indirect restorations. Materials and methods Ten recently extracted human teeth were selected. Cylindrical blocks of resin were prepared and bonded nearthe Cemento-Enamel Junction (CEJ) of the prepared teeth to mimic the restoration at the root surface.The samples were randomly luted to the root surface using the light cure (Calibra Veneer, Dentsply Sirona, India) and dual cure (Fusion Ultra D/C, DenPro, USA) formingtwo groups. The bond strength was checked using the INSTRON 3000 device (INSTRON, MA, USA). The point of fracture of the prepared sample from the tooth surface was noted. All readings were tabulated and further statistically analyzed. Results On comparing the two groups, it was found that the light cured resin had a greater mean shear bond strength (57 N) than the dual cure resin cement (41 N).The difference in the mean value of the shear bond strength between two resin cements was found to be statistically not significant according to independent T-test analysis using Levene's Test (P>0.05). Conclusion From the results obtained and within the limits of the study conducted, we can infer that Calibra Veneer is a more viable option for luting to the root surface area. On the other hand, Fusion Ultra Dual cure resin cement seems to have similar results but has a lower bond strength than the other.

Dynamics of High Molecular Weight Cylindrical and Lamellar Block Copolymers with X‐ray Photon Correlation Spectroscopy

AbstractThe structure and dynamics of polystyrene (PS)‐b‐poly(ethylene oxide) block copolymers (BCPs) are studied. The BCPs exhibit microphase‐separated cylindrical and lamellar morphologies. Structural dynamics are measured with X‐ray photon correlation spectroscopy in the small‐angle regime. Morphologies and domain sizes are evaluated using small‐angle X‐ray scattering (SAXS), scanning electron microscopy, and atomic force microscopy. Different solvent processing conditions are investigated. Grain sizes evaluated using SAXS are found to depend on processing only for the rubbery majority BCP. The structural relaxation times are examined as a function of PS volume fraction, temperature, morphology, and structural sizes. Well above the glass transition temperature (Tg) of PS, all samples exhibit stretched autocorrelation decays and diffusive dynamics. Near Tg of PS, the dynamics of all samples are anomalous with compressed autocorrelation decays and hyperdiffusive dynamics. This transition occurs at 153 °C or 1.13 Tg of PS. In the diffusive regime (at high temperature), structural relaxation times are dependent on the processing method. Near PS Tg (at low temperature), structural relaxation times scale with the PS volume fraction. Structural relaxation times do not correlate with grain size, indicating that the out‐of‐equilibrium state of PS dominates the structural dynamics of these strongly phase‐segregated BCPs.

Stability analysis of a vertical excavation reinforced with horizontal nails using three-dimensional finite elements limit analysis

Three-dimensional stability analysis of a vertical excavation, reinforced with grouted horizontal nails, has been carried out by using the three dimensional lower and upper bounds based finite elements limit analysis (FELA) using Optum G3. The nail along with the surrounding grouted cementitious material is assumed to behave as a single monolithic cylindrical block which was assumed to be either rigid or an elasto-plastic material following the Von-Mises yield criterion. The excavation is assumed to fail on account of either an interface shear slippage between nails and surrounding soil mass or on an account of axial tensile rupture of the composite nail material for a few typical cases as well. The soil unit weight has been varied to induce the ultimate shear failure of the soil nailed excavation. The unit weight of the soil mass at which the failure of the nailed wall occurs is termed as γcr. Two different types of boundary conditions along the base of the excavation have been considered. In the first case, the in-situ soil mass behind the excavation is extended below the base as well (Case 1) and in the second case, the excavation is assumed to simply lie on a hard stratum (Case 2). The results have been provided in the form of a non-dimensional stability number N=γcrHc as a function of soil friction angle φ, Sv/H, SH/H, d/H, L/H and m; where H refers to height of the wall, d is diameter of the grouted nail, Sv and SH imply centre to centre vertical and horizontal spacing of the nails, and m is the mobilization factor between grouted nails and adjoining soil mass. The results from the analysis have been found to compare well with the data reported in literature. All the results have been presented in the form of non-dimensional stability charts, which will be useful for design for any given values of height H and cohesion c. From the observed failure mechanisms, an analysis has also been carried out to determine the optimized lengths of nails. The optimized lengths of nails for both Cases 1 and 2 have been also provided. The type of failure mechanism, base or face failure, dictates the optimized lengths of the nails.

THE SYNTHESIS, STUDY OF PHYSICOCHEMICAL PROPERTIES, AND EVALUATION OF CATALYTIC ACTIVITY OF A THREE-WAY CATALYST MODIFIER CONTAINING EUROPIUM (III) OXIDE

Modification of the applied Pt-containing catalysts with rare-earth metals is one of effective ways to increase their activity and resistance to thermal deactivation, which is associated with both an increase in thermal stability of the texture and structure of the carrier material and an increase in the degree of dispersion and resistance to sintering of the applied platinum metals (PM) when exposed to high temperatures. Conflicting data make it difficult to select a suitable modifier for the use as part of a three-way catalyst in the exhaust treatment system of gasoline-powered cars, whose function is to simultaneously convert CO, CxHy and NOx. In this work, the effect of europium-modified Pt-containing γ-Al2O3 -based catalyst on its physicochemical properties and activity in the oxidation of CO, CxHy, and NOx reduction processes was evaluated. The catalytic activity was evaluated by passing a gas mixture simulating the exhaust of a gasoline-powered car through the catalyst applied onto the surface of a cylindrical honeycomb block with simultaneous measurement of the degree of conversion of toxic components into relatively non-toxic CO2, N2 and H2O in the temperature range from 1000C to 4000C. The modification of the Pt/γ-Al2O3 catalytic system with europium was shown to enhance the activity in all three reactions studied, indicating a great potential for the use as a modifier of a three-way catalyst