Variation Of Bond Strength Research Articles

Improved one-pot protein synthesis enabled by a more precise assessment of peptide arylthioester reactivity

By investigating 17 peptide arylthioesters that were previously challenging to produce, this study reveals a clear correlation between increased ligation activity and decreased pKa values of their corresponding arylthiols. The observed differences are attributed to variations in thioester bond strength and steric hindrance. These insights have led to the development of an improved one-pot chemical protein synthesis approach that leverages the reactivity differences between peptide arylthioesters with C-terminal Ala-S-Ph(4-NO2) and Ala-S-Ph(2,6-diCH3). This approach eliminates the need for thiol-thioester exchange and additive removal steps while enabling in situ desulfurization, thereby significantly simplifying the protein synthesis process.

Comparison of the Adhesive Remnant Index and Shear Bond Strength of Different Metal Bracket Bases on Artificially Aged Human Teeth: An In vitro Study

Abstract Aim: Bond failure can compromise the clinical efficacy and duration of orthodontic treatment. A decemented bracket can lengthen the course of treatment by about 0.6 months. This study aimed to compare the adhesive remnant index (ARI) and shear bond strength of different metal bracket bases on artificially aged human teeth. Materials and Methods: In this experimental in vitro, prospective, cross-sectional study, thirty-six human premolars were cemented with three types of metal bracket base designs: Group 1 had a laser-structured base, Group 2 had a mesh base, and Group 3 had a base with retention grooves. All groups were bonded with Transbond XT light-curing resin. Shear strength testing was performed, and the ARI was evaluated. The parametric one-factor analysis of variance test and Tukey’s post hoc test were used for the comparison of shear bond strength, and the effect size was also evaluated with eta squared. In addition, the Kruskal–Wallis test was used to compare the ARI of the three groups on an ordinal scale. All statistics were set at a significance of P < 0.05. Results: The ARI scores did not exhibit any statistically significant differences (P = 0.163). Nevertheless, the three groups exhibited statistically significant differences in shear bond strength, with an effect size of 69% (P < 0.001). The mesh base bracket had the lowest average (9.9 ± 2.6 MPa) (P < 0.001), while the laser-structured base bracket had the greatest average (19.1 ± 3.0 MPa) (P = 0.006). Conclusion: The variation in shear bond strength was influenced by 69% due to the type of the metal bracket base used. Laser-structured and mesh-based brackets had the highest and lowest shear strength, respectively. All bases left a similar ARI on the tooth enamel.

Effect of Ge4+-substituted on the structure characteristics and microwave/terahertz dielectric properties of ultra-low εr, high Q·f cordierite ceramics

In this study, Ge4+-substituted cordierite, Mg2Al4(Si1–xGex)5O18 ceramics, were successfully prepared by the traditional solid-state method to broaden its application potential. Notably, the excellent dielectric properties with εr = 4.90, Q·f = 128,200 GHz, and τf = −21.01 ppm °C–1 were achieved. The increase in εr value is mainly due to the heightened content of Ge4+ with high polarizability. The Q·f value improved by 2.21 times compared to the cordierite matrix, which can be primarily attributed to enhanced lattice energy, bond covalency, and hexagonal ring symmetry. The alteration in τf value arises from the variation of bond energy, bond strength, and distortion in the [MgO6] octahedra. These conclusions provide valuable insights for the design of silicate ceramics with higher Q·f values. In addition, the dielectric properties in the microwave and terahertz bands were compared. The higher Q·f and lower εr values in the terahertz band mainly result from the withdrawal of partial polarization mechanisms and differences in measurement methods. Mg2Al4(Si0.92Ge0.08)5O18 ceramics, demonstrating an ultra-low εr value of 4.54 and an ultra-high Q·f value of 286,533 GHz in the terahertz band, emerge as formidable contenders for future terahertz communications materials. Finally, a microstrip patch antenna was fabricated, achieving a bandwidth of 150 MHz at 4.78 GHz, which confirms the application in the n79 band for wireless communication.

Exploring the Thermal and Ionic Transport of Cu+ Conducting Argyrodite Cu7PSe6

AbstractUnderstanding the origin of low thermal conductivities in ionic conductors is essential for improving their thermoelectric efficiency, although accompanying high ionic conduction may present challenges for maintaining thermoelectric device integrity. This study investigates the thermal and ionic transport in Cu7PSe6, aiming to elucidate their fundamental origins and correlation with the structural and dynamic properties. Through a comprehensive approach including various characterization techniques and computational analyses, it is demonstrated that the low thermal conductivity in Cu7PSe6 arises from structural complexity, variations in bond strengths, and high lattice anharmonicity, leading to pronounced diffuson transport of heat and fast ionic conduction. It is found that upon increasing the temperature, the ionic conductivity increases significantly in Cu7PSe6, whereas the thermal conductivity remains nearly constant, revealing no direct correlation between ionic and thermal transport. This absence of direct influence suggests innovative design strategies in thermoelectric applications to enhance stability by diminishing ionic conduction, while maintaining low thermal conductivity, thereby linking the domains of solid‐state ionics and thermoelectrics. Thus, this study attempts to clarify the fundamental principles governing thermal and ionic transport in Cu+‐superionic conductors, similar to recent findings in Ag+ argyrodites.

Effect of Chitosan Irrigant and Lubricating Gel on Bond Strength of Resin Sealer to Radicular Dentin: An In Vitro Study.

The adhesive strength of sealers to dentin is influenced by various factors, and the presence of a smear layer is among the critical variables. Chitosan, known for its dentin compatibility, has previously demonstrated a reduction in dentin change and resin sealer bond strength comparable to ethylenediaminetetraacetic acid (EDTA) when used as an irrigant and final rinse. The study investigates the impact of chitosan, used as both a lubricating gel and final rinse, on the push-out bond strength of resin sealer. Forty single-rooted premolar teeth, each with a fully formed root and a single root canal, were collected post-extraction. During canal preparation, 1 mlsodium hypochlorite (3%) was used for irrigation at every change ofinstrument, followed by applying specific chelating gel and final rinse for each experimental group. The groups included: Group 1 (17% EDTA chelating gel, final rinse with saline), Group 2 (17% EDTA chelating gel, final rinse with 17% EDTA solution), Group 3 (chitosan chelating gel, final rinse with saline solution), and Group 4 (chitosan chelating gel, final rinse with 0.2% chitosan solution), 10 specimens in each group.After obturation, specimens were sealed and incubated for a week at 37°C with 100% humidity. The universal testing machine was used for push-out tests, and specimens were examined using a scanning electron microscope (SEM) to identify various types of bond failure. Among the four groups, Group 2 exhibited the highest mean push-out bond strength (7.33 ± 0.26 MPa), followed by Group 4 (5.33 ± 0.25 MPa), Group 1 (4.61 ± 0.30 MPa), and Group 3 (2.94 ± 0.32 MPa). The variations in bond strength suggest a notable impact of the chelating agents and final rinse solutions on the resin sealer's interaction with dentin. The study concludes that the use of EDTA as both a lubricating gel and a final rinse significantly enhances push-out bond strength, outperforming chitosan in this study. Groups with saline as the final rinse (Group 1 and Group 3) exhibited the least bond strength, highlighting the importance of the final rinse in root canal therapy.

Experimental investigation of bond behavior with lap splice for CFRP-steel composite bars in coral sea-sand aggregate seawater concrete

The pull-out tests on a total of 81 lap-spliced specimens in 27 groups were conducted to investigate the lap-spliced behavior and the appropriate splice length for CFRP-steel composite bars (C-FSCB) in coral sea-sand aggregate seawater concrete (CSSC). The test variables included the C-FSCB diameter (dc), splice length, concrete cover thickness, concrete strength, lap spacing, stirrup ratio, and materials type. Then, the influence of various test variables on the lap-spliced behavior of C-FSCB in CSSC was analyzed. The results showed that when the splice length was less than 17dc, the specimens exhibited pull-out and concrete splitting failure, while C-FSCB fracture failure occurred when the splice length exceeded 17dc. Severe shear damage was observed on the C-FSCB surface in the case of pull-out and concrete splitting failure. When the splice length was less than 14dc, the bond strength of the specimens was approximately 7.2 MPa. As the splice length increased beyond 14dc, the bond strength gradually decreased. After the cover thickness was greater than 4dc or the compressive strength of CSSC was greater than 30 MPa, the variation in bond strength of the specimens can be negligible. Increasing the stirrup ratio led to an increase in bond strength and a significant reduction in crack width. Compared to specimens with steel bars, the bond strength reduction for specimens with C-FSCB exceeded 25%. Based on the test results, calculation formulas for the bond strength and splice length of C-FSCB in CSSC were established. Furthermore, referring to the approach in the Chinese code GB 50010–2010, a simplified calculation formula for splice length was proposed.

Comprehensive analysis of bond stress transfer mechanisms in glass fiber-reinforced polymer-reinforced concrete beams using acoustic emission monitoring

The present study investigates the critical bond characteristics between glass fiber-reinforced polymer (GFRP) bars, which is essential for the application bars as corrosion-resistant components in structural concrete. The interfacial bond deterioration and stress transfer mechanisms have been investigated in the present study by employing acoustic emission (AE) monitoring in hinged-type GFRP-reinforced concrete (GFRP-RC) beam specimens. The bond strength of the test specimens, governed by chemical adhesion, mechanical interlocking, and frictional resistance, has been intricately examined. Various AE signal parameters as well as historic and severity indices derived from the AE signal parameters have been meticulously evaluated and correlated with bond stress and rebar slip variations. The present study has also introduced an innovative approach of using the sentry function for the assessment of bond deterioration and associated mechanisms. The results of the present study demonstrate the reliability of AE parameters in monitoring debonding and bond strength variation, the effectiveness of the sentry function in evaluating damage progression, and the utility of historic and severity indices in capturing micro-mechanism transformations. The accurate localization of debonding and the qualitative distribution of bond stress have also been demonstrated by through correlations between cumulative AE parameters and rebar slip, Additionally, the present study also highlights the significance of peak frequency variations in AE signals, serving as a crucial tool for quantifying the mechanical interlocking and interfacial friction. The results contribute significantly to precise assessments and development of effective strategies for mitigating bond deterioration in GFRP-RC elements.

Microscopic understanding of the in-plane thermal transport properties of 2H transition metal dichalcogenides

Transition metal dichalcogenides (TMDs) are a class of layered materials that hold great promise for a wide range of applications. Their practical use can be limited by their thermal transport properties, which have proven challenging to determine accurately, both from a theoretical and experimental perspective. We have conducted a thorough theoretical investigation of the thermal conductivity of four common TMDs, MoSe2, WSe2, MoS2, and WS2, at room temperature, to determine the key factors that influence their thermal behavior. We analyze these materials using calculations performed with the program, anharmonic lattice dynamics and the Boltzmann transport equation formalism, as implemented in the temperature-dependent effective potentials method. Within this framework, we analyze the microscopic parameters influencing the thermal conductivity, such as the phonon dispersion and the phonon lifetimes. The aim is to precisely identify the origin of differences in thermal conductivity among these canonical TMD materials. We compare their in-plane thermal properties in monolayer and bulk form, and we analyze how the thickness and the chemical composition affect the thermal transport behavior. We showcase how bonding and the crystal structure influence the thermal properties by comparing the TMDs with silicon, reporting the cases of bulk silicon and monolayer silicene. We find that the interlayer bond type (covalent vs. van der Waals) involved in the structure is crucial in the heat transport. In two-dimensional silicene, we observe a reduction by a factor ∼15 compared to the Si bulk thermal conductivity due to the smaller group velocities and shorter phonon lifetimes. In the TMDs, where the group velocities and the phonon bands do not vary significantly passing from the bulk to the monolayer limit, we do not see as strong a decrease in the thermal conductivity: only a factor 2–3. Moreover, our analysis reveals that differences in the thermal conductivity arise from variations in atomic species, bond strengths, and phonon lifetimes. These factors are closely interconnected and collectively impact the overall thermal conductivity. We inspect each of them separately and explain how they influence the heat transport. We also study artificial TMDs with modified masses, in order to assess how the chemistry of the compounds modifies the microscopic quantities and thus the thermal conductivity. Published by the American Physical Society 2024

Stabilization of Diborynes versus Destabilization of Diborenes by Coordination of Lewis Bases: Unravelling the Dichotomy.

We have quantum chemically investigated the boron-boron bonds in B2 , diborynes B2 L2 , and diborenes B2 H2 L2 (L=none, OH2 , NH3 ) using dispersion-corrected relativistic density functional theory at ZORA-BLYP-D3(BJ)/TZ2P. B2 has effectively a single B-B bond provided by two half π bonds, whereas B2 H2 has effectively a double B=B bond provided by two half π bonds and one σ 2p-2p bond. This different electronic structure causes B2 and B2 H2 to react differently to the addition of ligands. Thus, in B2 L2 , electron-donating ligands shorten and strengthen the boron-boron bond whereas, in B2 H2 L2 , they lengthen and weaken the boron-boron bond. The aforementioned variations in boron-boron bond length and strength become more pronounced as the Lewis basicity of the ligands L increases.

Bond strength of alkali-activated flyash based masonry system for sustainable construction

Bond strength is a crucial factor that impacts the performance, structural reliability and stability of masonry constructions. This paper aims to examine the efficacy of various masonry unit and mortar combinations and their bond strength thereby, evaluating their adhesion performance. It experimentally analyzes two masonry unit types paired with two mortar combinations. One is the traditional clay brick and the other is an alkali activated flyash based brick. Alkali activated flyash bricks and mortars use flyash as a sole binder, activated with popular alkalis, thereby reducing carbon footprints compared to cement manufacturing. Two types of mortar used are conventional cement mortar and alkali activated flyash mortar. Bonded prisms were tested to determine the compressive, tensile, shear, and flexural bond strengths. The results revealed significant variations in bond strength across different combinations of masonry units and mortar. Notably, it was observed that alkali-activated bricks bonded with alkali-activated mortar exhibited higher bond strength, compared to conventional cement mortar. These findings provide valuable insights in assessing the compatibility between masonry units and mortar, highlighting the potential of this technology for sustainable construction practices.

Exploring the excited state multi-proton transfer path and the associated photophysical properties of P-TNS molecule by DFT and TDDFT theory

Recently, Chen et al. designed and synthesized a new multi-purpose dye probe P-TNS with bifunctional groups, which has an ultra-fast excited state intramolecular proton transfer characteristic (ESIPT) (Spectrochim Acta A Mol Biomol Spectrosc., 2021, 262: 120084.). The P-TNS molecules are very sensitive to hydrazine (N2H4) and cyanide (CN-), which makes it have a good practical application prospect in the field of probe detection. However, the corresponding optical properties and the related mechanisms have not been systematically investigated in experiments. In the present work, the proton transfer pathways as well as the photophysical properties changes in the transfer path of P-TNS with three intramolecular hydrogen bonds (HB1, HB2 and HB3) are revealed for the first time. First, the analysis of potential energy surface and potential energy curve determined the stable conformation of P-TNS molecule and its isomer structure, and clarified the reaction mechanism of ESIPT process. Subsequently, the analysis of the frontier molecular orbitals reveal that the charge difference is the driving force required for the proton transfer process from the microscopic level, which led to the determination that the HB1 structure without the charge difference could not complete the ESIPT process. Finally, the variation of hydrogen bond strength and the path of proton transfer are demonstrated from several perspectives of hydrogen bond parameters, hydrogen bond energy, infrared vibrational frequency (IR) and reduced density gradient (RDG) surface. This study essentially explains the photophysical properties and proton transfer pathways of a new multipurpose dye probes for organic luminescence with bifunctional groups, which are important for the fields of spectroscopy and measurement technology, and also provides ideas for the design and synthesis of new fluorescent probes.

Data-driven based ultrasonics analysis for evaluating the bond strength of concrete layers

In accelerated bridge constructions, the 3D printing process, and structural retrofitting, the bond condition between concrete layers considerably affects their structural safety and functionality. Nondestructive tests can effectively and efficiently monitor these structures' bond conditions. This paper used the convolutional neural network (CNN) and multilayer perceptron (MLP) to estimate the bond strength of concrete layers based on vital ultrasound parameters. In this regard, ultrasound pulse velocity, attenuation, maximum amplitude, and energy loss of the ultrasound wave were assessed as the inputs of the machine learning models. The target was the bi-surface shear strength of the specimens. Two different approaches were considered to evaluate the energy loss of the wave 1) in the whole specimen and 2) at the bond zone, and the models based on each dataset's accuracy were compared. Parameters resulting from the second approach were more reliable and had better consistency with bond strength variation than the first one. Moreover, the ultrasonic parameters were investigated to determine the most sensitive ultrasound factor to the different bond treatments. Accordingly, attenuation was the most susceptible parameter toward the change of bond strength.

Bond Strength of Orthodontic Brackets to Temporary Crowns: In vitro Effects of Surface Treatment.

To evaluate bond strength of orthodontic brackets to temporary crowns. A bis-acrylic composite was used to create a total of 25 discs, which were then divided into five groups based on how their surfaces were treated with black, blue, green, and sandblasted diamond burs, in addition to a control group. Software called SPSS was used to analyze the outcome. The average pressures measured for the green bur, black bur, and sandblasting, respectively, were 12.05 MPa, 12.87 MPa, and 19.25 MPa. Comparing the control and blue groups, a substantial variation in shear bond strength was only noticed with reference to sandblasting. The binding strength of orthodontic brackets is increased by sandblasting temporary crowns.

Motherhood and DREADD manipulation of the nucleus accumbens weaken established pair bonds in female prairie voles

Monogamous pair bonding has evolved to enhance reproductive success and ensure offspring survival. Although the behavioral and neural mechanisms regulating the formation of pair bonds have been relatively well outlined, how these relationships are regulated and maintained across the lifetime of an individual remains relatively unexplored. One way to explore this is to study the maintenance of a social bond across a major life-history transition. The transition to motherhood is among the most poignant moments in the life history of a female, and is associated with significant neural and behavioral changes and shifting priorities. The nucleus accumbens (NAc) is known to modulate social valence and is central to mammalian pair bonding. In this study, we investigated two mechanisms driving variation in bond strength in the socially monogamous prairie vole (Microtus ochrogaster). We manipulated neural activity of the NAc at two distinct stages of life-history, before and after the birth of offspring, to assess how neural activity and social contexts modulate female pair bond strength. Our results showed DREADD (Designer Receptor Exclusively Activated by Designer Drugs) inhibition of the NAc decreases affiliative behavior towards the mating partner, whereas DREADD activation of the NAc increases affiliative behavior of strangers, thereby decreasing social selectivity. We also found a robust “birth effect” on pair bond strength, such that bonds with partners were weakened after the birth of offspring, an effect not attributable to the amount of cohabitation time with a partner. Overall, our data support the hypotheses that NAc activity modulates reward/saliency within the social brain in different ways, and that motherhood comes with a cost for the bond strength between mating partners.

A new adhesion concept based on a dual surface modification for resin Ti adhesion

The objective of this resin Ti adhesion study was to compare and contrast the effect of two novel dual surface modification methods on the surface morphology, changes in surface chemistry and to evaluate their enclosed mold micro-shear bond strength variation on artificial ageing. A total amount of 168 c.p. grade 2 titanium specimens were first manually polished, then 24 of them were randomly selected as control specimens. To study the effect of dual surface modification (silicatization followed by etching), 72 polished titanium specimens were silicatized (Rocatec™ Plus, 3M ESPE, 110 μm silica-coated alumina powder) according to the manufacturer’s protocol and then 36 of the silicatized specimens were etched with a blend of HNO3–HCl at 60 °C for 2 mins. The reversed dual surface modification (etching followed by silicatization) was done for the remaining 72 titanium specimens. They were first etched with a blend of HNO3–HCl at 60 °C for 2 mins, and then 36 of the etched specimens were silicatized with the same protocol as mentioned above. As a final treatment one third of all differently modified sample groups were silanized by Monobond™ Plus (Ivoclar Vivadent), and the other third with an experimental silane primer blend, 1.0 vol% 3-acryloxypropyltrimethoxysilane + 0.3 vol% 1,2-bis-(triethoxysilyl)ethane. One third of each sample groups was left without silanization. SEM, EDX, XPS, AFM, and surface roughness profilometry were conducted to study the effects of different surface modifications. Two enclosed mold resin stubs were bonded on each surface treated titanium specimens to evaluate the enclosed mold micro-shear bond strength. The specimens were artificially aged for 1 day, 1 week, 4 weeks, and 8 weeks, followed by adhesion strength testing and failure mode analyses. SpeedCem™ (Ivoclar Vivadent) was used as resin cement. The highest surface roughness was detected on the titanium specimens, silicatized and followed by etching with and without silanization (group E), while the lowest surface roughness was observed in two groups, silanized polished titanium (group A, control) and etched polished titanium with and without silanization (group C). The surface roughness of titanium only silicatized (group B) and specimens silicatized after etching (group D) exhibited similar surface roughness, higher than groups A and C, but lower than group E. These results were supported by the SEM images and AFM analysis. The EDX and EM-μSBS analyses pointed out that specimens which had higher [Si] and [Al], exhibited higher EM-μSBS values. The highest EM-μSBS values were observed in Ti specimens which were silicatized only or those which were silicatized after etching, i.e., groups B and D. Adhesive and mixed mode of fractures were observed in the specimens after EM-μSBS tests. A novel approach of silicatized titanium surface after etching might prevent the removal of embedded SiO2 and Al2O3, allowing the formation of a durable chemical bond with a silane blend.

The fundamental nature and importance of electrostatic potential in hydrogen bond formation: a case study of heterocycles frequently observed in drugs

The study utilizes MESP topology data of CO–HC, CN–HN, CN–HC, CF–HC, and CN–OC motifs in rings in drugs to predict hydrogen bond strength with H2O, while also elucidating how even minor variations in bond strength correspond to MESP features.

Electronic spectroscopy of homo- and heterometallic binuclear coinage metal phosphine complexes in isolation.

Binuclear coinage metal phosphine complexes are examined under ion trap isolation in order to elucidate their noncovalent binding, structural properties and intrinsic electronic spectra. Our survey shows an intriguing order of electronic transitions obtained by in situ synthesis and mass-spectrometrically supported UV photodissociation spectroscopy on a series of six isolated homo- and heterobinuclear complexes of type [MM'(dcpm)2]2+ (M, M' = CuI, AgI, AuI; dcpm = bis(dicyclohexyl-phosphino)methane). This approach provides the unique opportunity to study all possible coinage metal interactions within a fixed ligand framework. A successive blue-shift (33 700-38 500 cm-1; 297-260 nm) of the lowest-energy bright electronic transition energy in gas phase was observed in the order of Cu2 < CuAu < CuAg < Au2 < AgAu < Ag2. This order was reproduced by quantum chemical calculations using a scalar-relativistic GW-Bethe-Salpeter-equation (GW-BSE) approach. Theory ascribes the electronic bands of all complexes to metal-centered 1MC(dσ*-pσ) transitions revealing a strengthening of metal-metal' (M-M') binding upon excitation, in agreement to mass spetrometric results. A test of the correlation of transition energies with M-M' distance by quantum chemical calculations of single point energies as a function of intermetallic distance indicates qualitative agreement with experimental results. However, the experimentally observed high sensitivity of spectroscopic shifts towards metal composition cannot be accounted for solely by M-M' distance variation. The differences in electronic transitions are qualitatively rationalized by the varying (n + 1)s (n = 3, 4, 5) orbital contributions (increase from Cu2via CuAu/CuAg to Au2/AgAu/Ag2) within the nd(n + 1)s/p-hybridization for the ground electronic state of the different complexes, whereas the excited state (of (n + 1)p orbital character) shows significantly less variation in energy. In particular, the observed spectroscopic and mass spectrometric sequence for the Ag/Au complexes is traced back to the interplay of Pauli repulsion and variation in metal-ligand bond strength within the orbital hybridization model.

Failure Mechanisms of Fibre Reinforced Shotcrete: Numerical Simulations Considering Local Variations in Thickness and Bond Strength

Abstract Fibre-reinforced shotcrete is the most common support method for hard rock tunnels in the Nordic countries. The design of shotcrete is often based on empirical methods or simplified analytical equations, which neglect variations in mechanical properties and shotcrete thickness. Data collected from the field shows that significant variations in shotcrete thickness and bond strength should be expected during tunnel construction. However, how this affects the structural behaviour and capacity of the shotcrete lining is unknown. Moreover, the design philosophy for shotcrete assumes that the primary failure modes of shotcrete, i.e. bond and flexural failure, can be treated separately. This was derived based on observations of experiments in a laboratory environment. Therefore, the focus of a finalized doctoral project was to develop a numerical framework to simulate the structural behaviour of fibre-reinforced shotcrete in interaction with hard rock and rock bolts. The effect of variations in shotcrete thickness and bond strength was studied through numerical simulations to increase the understanding of its effect on the failure load of the lining. The results indicate that the most important parameter is the mean value of the shotcrete thickness and bond strength around a narrow perimeter of the block.’

EXPERIMENTAL INVESTIGATION AND COMPARATIVE EVALUATION OF PUSH-OUT BOND STRENGTH FIBER POST CEMENTED WITH DIFFERENT ADHESIVE RESIN CEMENTS: AN IN-VITRO STUDY

This article present an experimental investigation of push-out bond strength of fiber post that are cemented with various adhesive resin cements. Various modes of failure are also studied and discussed herein. Three resins namely Fluorocore 2+, Rely-X U200 and G-Cem are used in this study. The study is carried out on forth five single rooted teeth randomly divided into three groups. The teeth specimens were prepared by chemo-mechanical procedure and cemented with various adhesive resin cement. These teeth are further sliced at coronal, middle and apical levels for experimental testing of bond strength. These samples further tested on universal spring testing machine until the post was dislodged. Using Chi square, Mann Whitney U and Kruskal Wallis test, the obtained results were analyzed with significance level of p = 0.05. Bond strength of Fluorocore 2+ showed highest as compared to others. Rely-X U200 and G-Cem showed insignificant variation in bond strength at coronal, middle and apical levels.

Surface roughness – the key for roll bonding aluminium

In this study, the commercially pure aluminium is roll bonded at ambient temperatures. The effect of surface roughness and roll speed on the bond strength is evaluated by using the lap shear test. It is observed that the bond strength increased considerably with increasing surface roughness. The deformation caused owing to scratch brushing changed the surface roughness profile, which is the salient reason for the bond strength variation. Continuous striations with peaks and valleys of small-scale heights are observed at lower roughness values. Increasing roughness has reformed them into discrete profile asperities with sharp tips, influencing localised junction formation. On the other hand, the roll velocity has shown hardly any effect on the roll bonding of aluminium. With thorough investigation, it was conclusively explained that the effective change in the bond strength was not appreciable with varying the roll speed, provided the roll bonding takes place at optimised surface roughness conditions.