Variation Of Bond Strength Research Articles

Evaluation of hydroxyapatite-based cement for geothermal well applications

The working fluid in geothermal wells often contains naturally occurring CO2. In an aqueous environment, CO2 forms carbonic acid and subsequently reacts with the binding components of cement, resulting in the loss of strength and early failure. Well cement formulations containing hydroxyapatite (HOAP) are considered resistant to the carbonic acid attack. The main goal of this work is to study the effects of hydroxyapatite on cement degradation in high-pressure, high-temperature (HPHT) acidic environments. For evaluating the carbonic acid resistance of HOAP cement, aging experiments were conducted using cement cores and shear-bond test specimens. The aging temperature, pressure, and CO2 content of the gas were varied. After aging, the cores and specimens were recovered and tested to assess the level of degradation based on variation in bond and compressive strengths, porosity, permeability, and mineralogical composition. The results showed that HOAP cement has better resistance to carbonic acid attack than the baseline cement that does not contain hydroxyapatite. Nevertheless, due to the lack of silica flour, HOAP samples were thermally degraded after aging under extremely harsh conditions and exhibited high permeability due to the formation of microcracks.

Social integration influences fitness in allied male dolphins

Understanding determinants of differential reproductive success is at the core of evolutionary biology because of its connection to fitness. Early work has linked variation in reproductive success to differences in age,1 rank,2 or size,3,4 as well as habitat characteristics.5 More recently, studies in group-living taxa have revealed that social relationships also have measurable effects on fitness.6-8 The influence of social bonds on fitness is particularly interesting in males who compete over reproductive opportunities. In Shark Bay, Western Australia, groups of 4-14 unrelated male bottlenose dolphins cooperate in second-order alliances to compete with rival alliances over access to females.9-12 Nested within second-order alliances, pairs or trios of males, which can vary in composition, form first-order alliances to herd estrus females. Using 30 years of behavioral data, we examined how individual social factors, such as first-order alliance stability, social connectivity, and variation in social bond strength within second-order alliances, affect male fitness. Analyzing the reproductive careers of 85 males belonging to 10 second-order alliances, we found that the number of paternities a male achieved was positively correlated with his cumulative social bond strength but negatively correlated with his variation in bond strength. Thus, well-integrated males with more homogeneous social bonds to second-order allies obtained most paternities. Our findings provide novel insights into the fitness benefits of polyadic cooperation among unrelated males and highlight the adaptive value of social bonds in this context.

Comparative Studies of Phonon Properties of Three-Dimensional Hybrid Organic–Inorganic Perovskites Comprising Methylhydrazinium, Methylammonium, and Formamidinium Cations

Three-dimensional hybrid organic–inorganic perovskites with halide, formate, or hypophosphite ligands are promising photovoltaic, light-emitting, and multiferroic materials. Since the properties of these compounds are strongly affected by changes in lattice dynamics, it is of great importance to understand their phonon properties. We report Raman and IR spectra for a number of perovskites to understand the effect of various metal-linker frameworks on vibrations of methylhydrazinium, formamidinium, and methylammonium cations as well as effects of these cations on lattice phonons in lead bromide analogues. Our results show that the lattice dynamics and energy of lattice phonons of lead halides depend strongly on the type of organic cation and temperature. In particular, at room temperature, the dynamics of methylhydrazinium cations is much slower compared to the dynamics of methylammonium and formamidinium cations, implying weaker electron scattering in the former case and thus significantly different optoelectronic properties compared to the formamidinium and methylammonium analogues. We also show that the size of the halide ion affects the energy of internal modes, but this effect is much more pronounced when halide ligands are replaced by formate or hypophosphite anions, especially in the case of formamidinium analogues. We attribute this behavior to strong variation of hydrogen bond strength and changes in the internal structure of organic cations.

Bond behavior and anchorage length of deformed bars in steel-polyethylene hybrid fiber engineered cementitious composites

Steel-polyethylene hybrid fiber engineered cementitious composites (HECC) featuring relatively high tensile strength and ductility, high elastic modulus, and high temperature resistance, making it an ideal alternative material under severe loading conditions. To understand the bond behavior between the HECC and rebar, direct pullout tests were conducted to systematically investigate the effects of rebar diameter d, anchorage length la, and cover thickness c on the bond performance. The experimental results indicate that the variation of bond strength with d is not apparent; la affects negatively while c influences positively on the average bond strength; and the critical c for HECC is about 4d. Additionally, the bond strength of HECC specimen is obviously higher than that of ECC and stirrups-confined concrete due to the crack-bridging effect of hybrid fibers at different scales. As noted, the ductility of HECC specimens is comparable with that of stirrups-confined concrete specimens, indicating that stirrup can be partially replaced when HECC is used which can simplify construction. Then, a calculation equation for the average bond strength of HECC is proposed, and the critical anchorage length of the rebar embedded in HECC is about 40% less than that embedded in ECC. Lastly, the design anchorage length of the rebar embedded in HECC is suggested based on a reliability analysis which is much smaller compared with the minimum embedment length of rebar in concrete predicted by the existing standards, providing a useful reference for reinforced HECC structural design.

Raman spectroscopy reveals variation in free OH groups and hydrogen bond strength in ultrahigh dilutions

Objective: To decipher the nature of water structure in two ultrahigh diluted (UHD) homeopathic drugs by Laser Raman Spectroscopy.
 Method: Two homeopathic drugs Calcarea carbonica (Calc.) and Sepia officinalis (Sep.) in 8cH, 202cH, and 1002cH and their diluent medium 90% ethanol in 8cH and 202cH were used in the present study. Laser Raman spectra of all the samples were obtained in the wave number region of 2400 – 4200 cm-1. The intensity ratio at vibration frequencies between 3200 and 3420 (R1) and that between 3620 and 3420 (R2) were calculated for each UHD of the samples. 
 Results: The spectra show a marked difference in intensities in the stretching vibrations of CH and OH groups of all the samples. R1 values for three UHDs of Calc. and Sep. show negative and positive relationships, respectively. In the case of R2 values, the relationship in three UHDs is 81002 for Calc., and 8> 202 < 1002 for Sep. In the case of control (ethanol UHDs) both R1 and R2 show a negative relationship.
 Conclusion: R1 denotes a relative number of OH groups with strong and weak hydrogen bonds. R2 indicates the relative number of OH groups with broken and weak H-bonds. Therefore, the UHDs of the two drugs and the control are different from each other with respect to hydrogen bond strength of OH groups and the number of free OH groups or non-hydrogen bonded water molecules.

Evaluation of bond strength of polyether ether ketone (PEEK) to composite resin on hypobaric and hyperbaric conditions

The aim of this study was to investigate the shear bond strength of composite resin to PEEK under hypobaric and hyperbaric pressure changes in different PEEK surface treatments. Ninety-six PEEK specimens were divided into three groups (n = 32). PEEK surfaces were sandblasted; acid-etched, and non-treated. Every group was then divided into three sub-groups (n = 10) for simulating hyperbaric pressure (2.8 atm-18 m under sea level), hypobaric pressure (0.34 atm-8,200 m high altitude), and the control group (atmospheric pressure). The specimens underwent pressure cycles for 20 days. Results were compared by using ANOVA followed by the post-hoc Tukey test. Variations in bond strength within each group were also evaluated by the Weibull modulus. Regardless of the environmental pressure changes, it was determined that the bonding strength and the Weibull modulus were the highest in the acid-etched PEEK. Bonding strengths were lower in all groups after exposure to environmental pressure changes, but this difference was not statistically different. Bond strengths between the PEEK material and composite resin can be affected by environmental pressure, while surface modification of the PEEK material plays an important role in bond strength. Dentists should take importance in choosing the appropriate material on patients who are exposed to different barometric changes, as fractures on restorations may be life-threatening.

Variations in rock support capacity due to local variations in bond strength and shotcrete thickness

Fibre reinforced shotcrete (sprayed concrete) is often used to support tunnels in hard rock. The shotcrete should be designed to carry the load from a loose block, which is assumed to be transferred to the surrounding rock mass over a narrow band. It is commonly accepted that the width of this band is constant, and independent of the shotcrete thickness. In this paper, numerical simulations are used to show that the width of this band and the load capacity is strongly correlated to the mean shotcrete thickness around the perimeter of the block. Furthermore, it is also shown that a strong linear correlation exists between the mean bond strength and the rock support capacity. Based on this, a lower bound function to estimate the structural capacity for the lining is suggested. No correlation was found between the structural capacity and the minimum or maximum shotcrete thickness or bond strength. This indicates that, under certain conditions, local areas with low thickness and bond strength can exist around the block perimeter without having any significant effect on the rock support capacity.

Drugs in ultra-high dilution induce changes in the enthalpy associated with loss of crystallization water in lactose

Drugs in ultra-high dilution (UHD) are used in homeopathy. Lactose is used as a binding medium for UHD drugs. FTIR and Raman spectroscopy revealed that although devoid of molecules of the starting substance, different UHD drugs exhibit different amounts of free water molecules and variation in hydrogen bond strength. The aim of the present study was to establish whether specific water structures in UHD could specifically modify the water structure in lactose, particularly the water of crystallization. 3 UHD’s (potencies), 30cH, 200cH and 1000cH, of 2 drugs, Natrum muriaticum and Sulphur were mixed to lactose samples separately. Differential scanning calorimetry (DSC) of the samples was measured. The thermograms of potencies mixed to lactose differed from each other with respect to temperature and enthalpy associated with the removal of water of crystallization from lactose. We believe that the tested UHD modified the water structure in lactose thereby changing the enthalpy for the removal of water of crystallization. Different levels of thermal energy are needed to remove both free water molecules and water of crystallization from lactose. UHD’s also contributed to the change in enthalpy associated with the removal of water of crystallization from lactose. The tested UHD might have modified the number and strength of hydrogen bonds in the crystal structure of lactose. Specific water structures in liquid aqueous ethanol medium are transferable to the solid medium(lactose).

Enhanced anticorrosion properties of nitrogen ions modified polyvinyl alcohol/Mg-Ag ions co-incorporated calcium phosphate coatings

Nitrogen ions (70 keV) were implanted on composite coatings containing polymer/Mg (magnesium)–Ag (silver) ions co-incorporated hydroxyapatite which was developed using microwave irradiation. Average crystallite size of modified coatings is reduced by 80% compared to the pristine. The variation of atomic bond strength of modified coatings is realized. The electrical resistance (77%), microhardness (4.3%), roughness (4.5 times) and pore size are enhanced on the nitrogen implanted coatings. Superhydrophilic surface is turned to hydrophobic on implantation. At higher fluence (1 × 1017 ions/cm2) depicted an enhanced corrosion potential compared to the other coatings. Thus, the new insight on modified coatings is elucidated by correlating phase-structure, surface and corrosion resistance.

Dielectric and thermal properties of aluminoborosilicate glasses doped with mixed rare-earth oxides

This study discusses aluminoborosilicate glasses with La2O3 and CeO2. Structural, thermal, and dielectric properties were investigated by FTIR, DSC, and impedance analyzer. Results indicate that more Q3 and Q4 would form at the sample with the same amount of La2O3 and CeO2, meaning the most compact structure, while more La2O3 would lead to a loosen network. Meanwhile, glasses obtained the best dielectric properties here, and the dips in dielectric constant and loss are ascribed to the structural changes in the glass network. The glass transition temperature, Tg ascends first and then declines, due to the variation of bond strength and non-bridge oxygen content, as well as changes in field strength. Parameters for thermal stability decrease firstly and then increase slightly, indicating small changes in thermal stability. The glass density gradually increases, which is mainly from the small field strength of La3+ ions and the larger molar mass of La2O3.

Chitosan capping of CuO nanoparticles: Facile chemical preparation, biological analysis, and applications in dentistry

This investigation is vital contribution to the healthcare system utilizing techniques of nanobiotechnology. It interestingly applies chitosan capped CuO nanoparticles in the field of medicine and restorative dentistry. The CuO nanoparticles and CuO-Chitosan nanoparticles are prepared by co-precipitation, and their characterization is performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX). The average crystallite size of these nanoparticles has been found to be in the dimensions of <40 nm and <35 nm, respectively. CuO-Chitosan nanoparticles show significant enhancement in in vitro antibacterial, antioxidant, cytotoxic, and antidiabetic activity as compared to CuO nanoparticles. In addition, the successful amalgamation of CuO nanoparticles and CuO-Chitosan nanoparticles into dentine bonding agents results in providing efficient remedy against secondary caries. CuO-Chitosan nanoparticles reinforced dental adhesive discs cause significant upsurge in reduction of Lactobacillus acidophillus and Streptococcus mutans. Also, the augmentation of mechanical properties, water sorption and solubility plus slow and sustained release profile and slight variation of shear bond strength is attained. Taken together, the chemically synthesized CuO nanoparticles and CuO-Chitosan nanoparticles have proven to be promising candidates having enormous potential to be utilized in drug delivery and nanotheranostics.

Numerical Characterization of Cohesive and Non-Cohesive ‘Sediments’ under Different Consolidation States Using 3D DEM Triaxial Experiments

The Discrete Element Method has been widely used to simulate geo-materials due to time and scale limitations met in the field and laboratories. While cohesionless geo-materials were the focus of many previous studies, the deformation of cohesive geo-materials in 3D remained poorly characterized. Here, we aimed to generate a range of numerical ‘sediments’, assess their mechanical response to stress and compare their response with laboratory tests, focusing on differences between the micro- and macro-material properties. We simulated two endmembers—clay (cohesive) and sand (cohesionless). The materials were tested in a 3D triaxial numerical setup, under different simulated burial stresses and consolidation states. Variations in particle contact or individual bond strengths generate first order influence on the stress–strain response, i.e., a different deformation style of the numerical sand or clay. Increased burial depth generates a second order influence, elevating peak shear strength. Loose and dense consolidation states generate a third order influence of the endmember level. The results replicate a range of sediment compositions, empirical behaviors and conditions. We propose a procedure to characterize sediments numerically. The numerical ‘sediments’ can be applied to simulate processes in sediments exhibiting variations in strength due to post-seismic consolidation, bioturbation or variations in sedimentation rates.

Experimental investigation on the durability of a novel lightweight prefabricated reinforced-EPS based construction system

This paper investigates the durability of a low-cost construction system named HOMEDONE developed to realize affordable and also temporary housing solutions. The system is based on the assembly of 3D-reinforced EPS panels externally topped off with a multi-layer rendering system. Similar technologies showed durability issues, especially in hot climates, due to the thermal and hygrometric stresses of the thin finishing layers when coupled to thick EPS panels and exposed to extreme events. For this reason, in this work freeze–thaw and wet/drying-UV aging tests on HOMEDONE panels with different finishing systems have been carried out, monitoring macroscopic, microscopic (ATR-FT-IR analysis) and bond strength variations due to aging. Results have pointed out good mechanical properties of the system and only small color variations of the finishing layer due to UV cycles. Then, HOMEDONE can be considered as a durable option for affordable and temporary housing solutions.

Ferrimagnetic to antiferromagnetic transition and complex impedance analysis of Cr-doped magnesium ferrite nanoparticles

The chromium-doped magnesium ferrite (MgCrxFe2−xO4, x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0) were prepared using sol–gel technique. X-ray diffraction scans confirmed the cubic spinel structure for all the nanoparticles samples. Reduction in lattice parameter and average crystallite size with increasing Cr3+ concentration was observed due to smaller ionic radii of Cr3+ (0.67 A) ions as compared to Fe3+ (0.63 A) ions. In FTIR vibrational studies, the addition of Cr3+ shows the splitting of ν1 band into two sub-bands due to variation of bond strength between same cations present at tetrahedral and octahedral lattice sites. With increasing Cr3+ concentration, the ZFC–FC magnetic curves revealed a ferrimagnetic (FiM) to antiferromagnetic (AFM) transition as compound transformed from MgFe2O4 to MgCr2O4. The M–H loops revealed decrease in saturation magnetization with increase in Cr3+ concentration which is attributed to FiM to AFM transition. The coercivity showed a non-monotonic behavior and has maximum value of 750 Oe for x = 1.2 due to overlapping of blocking and Neel transition temperatures. The dielectric properties showed a decreasing trend with increasing Cr3+ concentration. The room temperature impedance spectroscopy (Nyquist plots) was simulated using equivalent RC circuit model and an appearance of second semi-circle in the Nyquist plot with increasing Cr3+ concentration is observed which can be attributed to the contribution of grains in the hooping mechanism.

Interface bond strength of lightweight low-cement functionally layered concrete elements

Production of cement accounts for around 5% of human-made carbon emissions. When the selection of a cement-intensive mix with low porosity is driven by durability requirements, the resulting low permeability of the material is only fully exploited in peripheral regions of the element where the material acts as a physical barrier against the penetration of aggressive substances. This paper explores the potential of casting layered prismatic elements composed of an external durability layer and a lightweight core section as a means to achieve cement and weight savings. Layered elements are traditionally obtained by casting new concrete layers onto already hardened older concrete layers. A major problem with this technique is that planes of weakness are obtained at the interfaces between the layers. The bond between the layers can be improved by casting the materials at approximately the same time. However, research to date has not yet demonstrated the viability of producing elements with wet cast external layers. Furthermore, the effects of delays between successive pours on the mechanical tensile performance of the interfaces in layered elements have not been quantified. An original method is presented to form prismatic elements composed of an external durability layer and a lightweight core section by casting two concrete mixes at approximately the same time. The approach is validated by realising a proof-of-concept prototype layered element. A set of additional layered elements are cast with various pour delays and cored across the interface between their layers to characterize the interlayer bond strength by direct tension. To interpret the mechanisms affecting the bond, the variation of tensile bond strength with the location of the sample and the impact of roughness are also investigated. When the pour delay was minimal, failure did not occur at the interlayer. The relationship between pour delay and bond strength is markedly nonlinear, with bond strength reductions of more than 30% for pour delays of only three hours. It was also found that the bond strength of the interface varies significantly with the considered location and that up to 40% of the bond strength reduction due to a delay between the castings can be recovered by roughening the surface of the older concrete prior to casting the newer mix. The successful realisation of wet cast prismatic elements with an external durability layer is an important step towards the realisation of light-weight layered concrete elements with low embodied energy.

Amorphous cobalt-cerium binary metal oxides as high performance electrocatalyst for oxygen evolution reaction

The amorphous Co-Ce binary metal oxides Co1-yCeyOx prepared by the photochemical metal–organic deposition (PMOD) method is developed as high performance electrocatalysts for oxygen evolution reaction (OER). The influence of Ce content on the OER activity is investigated in terms of geometric and electronic factors. Ce can remarkably enhance the OER activity of CoOx due to the synergistic effect of surface area, Co3+ content, and metal-OH bond strength when the content of Ce is less than 60%. Co0.9Ce0.1Ox supported on fluorine-doped tin oxide (FTO) coated glass substrate shows overpotential of 320 (2) mV at 10 mA cm−2 in 1 M KOH solution. The OER mechanism exploration reveals that the rate determining step changes with the Ce content due to the variation of metal-OH bond strength. This work sheds light on the design of high-performance yet cost-effective OER catalysts.

The role of surfactant force field on the properties of liquid/liquid interfaces

Surfactant-laden liquid/liquid interfaces mediate numerous chemical processes, from commercial applications of microemulsions to chemical separations. Classical molecular dynamics simulation is a prevalent method for studying microscopic and thermodynamic properties of such interfaces. However the extent to which these features can be reliably predicted, and the variations in predicted behavior, depend upon the force field parameters employed. At present, the impact of force fields upon simulated properties is relatively understudied. Yet recent advances to sampling and analysis algorithms are increasing the interpretation of simulation data and therefore understanding force field dependence is increasingly relevant. In this study, the impact of the force field of the surfactant tri-n-butyl phosphate (TBP), as well as that of water, is investigated at a water/(n-hexane + surfactant) interface. Empirical charge scaling was employed to modulate the hydrophilicity of the surfactant. As anticipated, the relative hydrophilicity of TBP influences a number of properties, including the adsorbed concentrations of TBP at the interface, and macroscopic properties that result from hydrogen bonding interactions, such as interfacial tension and width. The dynamic properties of solvents at the interface are strongly modulated by the variation in hydrogen bond strength caused by different charge scalings of the TBP model. This includes the residence times of water at the interface, where stronger water-TBP hydrogen bonding causes long-lived residences. Interestingly, there are a number of features that are relatively insensitive to the TBP hydrophilicity. In one important case, the concentration of water-bridged TBP dimers was only impacted by the least hydrophilic model. As these dimeric species are the building block of surface protrusions that lead to water transport across the interface, this implies that collective organizational patterns and surface structures that derive from multiple driving forces (e.g., TBP hydrophilicity and organic solvent free energies of solvation) are less sensitive to individual force field parameters. Further, we note that competitive interactions can “cancel” the effects of changing TBP charge on interfacial properties. One example is the orientation and hydrogen bonding structure of interfacial water, where the direct TBP-water hydrogen bonding competes against the indirect TBP-induced interfacial roughness. In combination, these observations may assist future simulation studies in calibrating surfactant models to, or interpreting results of, a broad range of dynamic, structural and thermodynamic properties.

Experimental study on bond strength of GFRP bars

Abstract Composite materials in the form of bars is good alternative to conventional steel due to their non corrosiveness. To work out effectiveness of GFRP bars as internal reinforcement in Civil Engineering structures, it is necessary to find its bond performance with concrete. Good bonding results into effective transfer of stresses from concrete to reinforcement. Many of available FRP bars in Indian market are with plain surface texture, lacking ribs on it as that of steel. In this study experimentation is done for pull out test on plain GFRP bars and ribbed steel bars, based on IS 2770:1967. To find variation in bond strength, bars of diameter 8 , 10 and 12 mm were used. Enhancement in bond strength due to change in surface texture was also studied by roughening the surface through application of fine and coarse ennore sand on bar surface. Bond strength of plain GFRP bars was found to be lesser than that of steel. Also by roughening the surface using ennore sand and epoxy resin, no considerable rise was observed, may be due to lack of bond transfer between bar, sand and concrete

Bonobo personality predicts friendship

In bonobos, strong bonds have been documented between unrelated females and between mothers and their adult sons, which can have important fitness benefits. Often age, sex or kinship similarity have been used to explain social bond strength variation. Recent studies in other species also stress the importance of personality, but this relationship remains to be investigated in bonobos. We used behavioral observations on 39 adult and adolescent bonobos housed in 5 European zoos to study the role of personality similarity in dyadic relationship quality. Dimension reduction analyses on individual and dyadic behavioral scores revealed multidimensional personality (Sociability, Openness, Boldness, Activity) and relationship quality components (value, compatibility). We show that, aside from relatedness and sex combination of the dyad, relationship quality is also associated with personality similarity of both partners. While similarity in Sociability resulted in higher relationship values, lower relationship compatibility was found between bonobos with similar Activity scores. The results of this study expand our understanding of the mechanisms underlying social bond formation in anthropoid apes. In addition, we suggest that future studies in closely related species like chimpanzees should implement identical methods for assessing bond strength to shed further light on the evolution of this phenomenon.

Experimental research on bond anchorage performance of 1860-grade high-strength steel strands and lightweight aggregate concrete

To study the bond anchorage performance of 1860-grade high-strength prestressed steel strands and lightweight aggregate concrete, taking the cover thickness, anchorage length, stirrup spacing and matrix material as characteristic parameters, 10 groups of three specimens – a total of 30 test specimens – were designed and manufactured for pull-out tests. In these tests, the failure modes and the variation of bond strength of specimens were examined, and the influence of the variation of characteristic parameters on the bond anchorage performance of 1860-grade high-strength steel strand and lightweight aggregate concrete was studied. Optimal results were produced with a larger cover thickness and anchorage length, and smaller stirrup spacing. Based on the experimental data, we established the formula of ultimate bond strength and the formula of bond strength when the average slip is 1 mm, and a recommended formula for the anchorage length of components was devised incorporating current building design codes.