Surrogate Material Research Articles

LC-MS Characterization and Quantification of Known and Unknown (Poly)phenol Metabolites-Possible Pitfalls and Their Avoidance.

This review focuses on the LC-MS characterization and quantification of dietary (poly)phenols and their metabolites. It draws attention to errors, omissions, and misunderstandings that appear frequently in published papers, and suggests strategies for their avoidance. Aspects covered include the use of authentic standards and surrogate reference materials, the importance of collecting and archiving Total Ion Current MS data, the limitations of using on-line compilations of accurate mass MS data to assign unknown components when multiple isomers are possible, and the often understated magnitude of person-to-person variation that may significantly impact at population level any potential health benefit.

Monitoring Noble Gases (Xe and Kr) and Aerosols (Cs and Rb) in a Molten Salt Reactor Surrogate Off-Gas Stream Using Laser-Induced Breakdown Spectroscopy (LIBS).

This study with surrogate materials shows that laser-induced breakdown spectroscopy (LIBS) is a robust tool with promising capability toward monitoring gaseous (Xe and Kr) and aerosol (Cs and Rb) species in an off-gas stream from a molten salt reactor (MSR). MSRs will continually evolve fission products into the cover gas flowing across the reactor headspace. The cover gas entrains Xe and Kr gases, along with aerosol particles, before passing into an off-gas treatment system. Univariate models of Xe and Kr peaks showed a strong correlation to concentration indicated by their coefficients of determination of 0.983 and 0.997, respectively. Multivariate models were built for all four analytes using partial least squares regression coupled with preprocessing steps including normalization, trimming, and/or genetic algorithm derived filters. The models were evaluated by predicting the concentrations of the analytes in four validation samples, in which all calibration models were successfully validated at a confidence interval of 99.9%. Lastly, pressure controllers were used to regulate the mass flow rate of Kr flowing into the measurement cell in sinusoidal and stepwise waveforms to test the real-time monitoring capabilities of the regression models. Both univariate and partial least squares Kr models were able to successfully quantify the gas concentration in the real-time evaluation. The root mean squared error of prediction (RMSEP) values for these real-time tests were calculated to be 0.051, 0.060, and 0.121 mol% demonstrating the measurement systems' capability to perform online monitoring with acceptable accuracy.

Mobility of Phosphine-Susceptible and -Resistant Rhyzopertha dominica (Coleoptera: Bostrichidae) and Tribolium castaneum (Coleoptera: Tenebrionidae) After Exposure to Controlled Release Materials With Existing and Novel Active Ingredients.

There is interest in developing controlled release materials (CRMs) with novel modes of action to improve resistance management. Long-lasting insecticide-incorporated netting (LLIN) with deltamethrin has been effectively used against stored-product pests. Here, we evaluated the efficacy of different CRMs (LLIN or packaging) with each of four active ingredients (AI) (deltamethrin, permethrin, indoxacarb, and dinotefuran) and compared them to control CRMs in reducing movement and increasing mortality of phosphine-susceptible and -resistant Rhyzopertha dominica and Tribolium castaneum. Adults were exposed for 0.5, 2, or 60min, and movement was assessed immediately or after 24, or 168h using video-tracking and Ethovision software. We recorded total distance and velocity traveled by adults. Finally, we tested higher rates of each AI on surrogate netting material (e.g., standardized-sized cheesecloth) and varied exposure time to obtain median lethal time (LT50) for each compound and susceptibility. Exposure to LLIN with deltamethrin significantly reduced the movement of both species compared to the other CRMs regardless of their susceptibility to phosphine. Deltamethrin was the most effective AI for both species, while dinotefuran and indoxacarb were the least effective for R. dominica and T. castaneum adults, respectively. Most AIs resulted in appreciable and approximately equivalent mortality at higher concentrations among phosphine-susceptible and -resistant strains. Our results demonstrate that CRMs can be an additional approach to combat phosphine-resistant populations of stored product insects around food facilities. Other compounds such as permethrin, dinotefuran, and indoxacarb are also effective against phosphine-resistant populations of these key stored product insects except indoxacarb for T. castaneum.

Skeletal muscle surrogates for the acquisition of muscle repair skills in upper limb surgery

IntroductionThe required fidelity of synthetic materials in surgical simulators to teach tissue handling and repair requirements should be as accurate as possible. There is a poor understanding of the relationship between choice of muscle surrogates and training outcome for trainee surgeons. To address this, the mechanical characteristics of several candidate synthetic muscle surrogates were measured, and their subjective biofidelity was qualitatively assessed by surgeons. MethodsSilicone was selected after assessing several material options and 16 silicone-based surrogates were evaluated. Three of the closest samples to muscle (Samples 1.1, 1.2, 1.3) and one with inserted longitudinal fibres (1.2F) were mechanically tested in the following: compression and tension, needle puncture force and suture pull-out in comparison with real muscle. The four samples were evaluated by 17 Plastic and Orthopaedic surgeons to determine their views of the fidelity with regard to the handling properties, needle insertion and ease of suture pull-out. ResultsThe mechanical testing showed the surrogates exhibited varying characteristics that matched some of the properties of muscle, though none recreated all the mechanical characteristics of native muscle. Good biofidelity was generally achieved for compression stiffness and needle puncture force, but it was evident that tensile stiff was too low for all samples. The pull-out forces were variable and too low, except for the sample with longitudinal fibres. In the qualitative assessment, the overall median scores for the four surrogate samples were all between 30 and 32 (possible range 9–45), indicating limited differentiation of the samples tested by the surgeons. ConclusionsThe surrogate materials showed a range of mechanical properties bracketing those of real muscle, thus presenting a suitable combination of candidates for use in simulators to attain the requirements as set out in the learning outcomes of muscle repair. However, despite significant mechanical differences between the samples, all surgeons found the samples to be similar to each other.

Promotion Mechanism of CaSO4 and Au in the Plasma-Assisted Catalytic Oxidation of Diesel Particulate Matter.

Plasma-assisted catalysis has been demonstrated to be an innovative technology for eliminating diesel particulate matter (DPM) efficiently at low temperature (≤200 °C). Moreover, past studies have demonstrated that CaSO4, which exists in small concentrations (<2%) in DPM and is toxic in thermal catalytic oxidation processes, actually enhances DPM oxidation during plasma-assisted catalytic processes. However, the role CaSO4 plays in this promotion of DPM oxidation still remains unclear. The present study addresses this issue by investigating the underlying mechanisms of DPM oxidation during plasma-assisted catalytic processes using graphitic carbon as a surrogate DPM material in conjunction with CaSO4- and Au-impregnated γ-Al2O3 catalysts. The results of mass spectrometry and in situ diffuse reflectance infrared Fourier transform spectroscopy, which employs an in situ cell with a small dielectric barrier discharge space over the catalyst bed, demonstrate that CaSO4 can save and release O atoms contributing to graphite oxidation via the −S=O units of CaSO4 through a reversible surface reaction (−S=O + O → −S(−O)2). The results are employed to propose a formal mechanism of graphite oxidation catalyzed by CaSO4 and Au. These findings both improve our understanding of the plasma-assisted catalytic oxidation mechanisms of DPM and support the development of efficient plasma-assisted catalysts.

Projection-capacitor discharge resistance welding of 430 stainless steel and 14YWT

Efforts to advance structural materials with improved properties and service life in support of next generation designs for nuclear reactor components have recently led to development of nano-ferritic alloys (NFAs) containing nano-oxides such as 14YWT. A key enabling technology to realizing the useful properties of NFAs during service involves preservation of the oxide dispersions during joining. Solid-state welding processes, such as projection-capacitor discharge resistance welding (P-CDRW) used here, are well suited for joining NFAs while retaining the oxides. Due to limitations in the supply of 14YWT NFA material, initial experiments were conducted using 430 stainless steel as an inexpensive surrogate material. The goal of the surrogate experiments was to scale suitable parameters from 430 welds to 14YWT using ratios of key properties for the two materials including flow stress at temperatures and strain rates relevant to hot working. Results indicated that weld displacement increased with increasing weld force and increasing weld energy for all other variables held constant. Weld energy appeared to have a larger effect on displacement than weld force for the sample geometry used here. Appropriate process parameters (no melting) were established for the two materials. The process window for the 430 material extended from 350 J to 600 J of energy for weld forces of 2.2 kN and 3.1 kN. Suitable parameters for 14YWT were similar in terms of energy but for force levels of 3.1 kN and 4.0 kN. Displacement for both materials ranged from 150 μm to 300 μm for welds that did not experience melting. Simple heat flow analysis confirmed that the extent of displacement was limited by the characteristic thermal distance determined from thermo-physical properties and the weld current rise time. The higher flow stresses of 14YWT relative to 430 were apparently offset by greater heating due to higher electrical resistivity near the projection tip and lesser heat conduction from the projection tip owing to lower thermal conductivity. Based on the results presented here and in our companion paper. The P-CDRW process appears capable of successfully joining the 14YWT NFA while retaining the microstructures and properties of the original material.

Diagnostic Utility of the PD-L1 Immunostaining in Biopsy Specimens of Patients with Biliary Tract Neoplasms

BackgroundAnti-programmed death 1/programmed death ligand 1 (PD1/PD-L1) antibodies have been successfully used as treatment agents for several solid tumors; however, it is difficult to predict their effectiveness. We evaluated whether biopsy specimens could predict the positive status of PD-L1 in surgically resected tissue. MethodsAmong 91 patients who underwent tissue sampling with endoscopic or liver biopsy before surgery for biliary tract neoplasms in an academic center, 45 (49%) patients were selected for retrospective analysis because the quality and quantity of their biopsy specimens were adequate for histologic evaluation. We performed immunohistochemical staining to investigate the PD-L1 expression in both resected and biopsy specimens. The percentage of the positively stained cells was calculated for subsequent use in the correlation investigation. ResultsThe biopsy methods were endoscopic retrograde cholangiopancreatography (ERCP) in 28 cases, percutaneous liver biopsy in 10 cases, and endoscopic ultrasound fine-needle aspiration in 7 cases. Among the 45 patients, when patients with > 10% positive tumor cells in surgically resected tissues were regarded as truly positive PD-L1, the positive and negative concordance rates between surgically resected tissues and biopsy samples were 56% (5/9) and 100% (36/36), respectively. With regard to the use of preoperative biopsy as a diagnostic tool, all (5/5) PD-L1-positive patients had a positive resected specimen. The accuracy of each biopsy method was as follows: ERCP, 89% (25/28); fine-needle aspiration, 86% (6/7); and liver biopsy, 100% (10/10). ConclusionsBiopsy samples could be a surrogate material for the assessment of the PD-L1 expression with substantial positive and high negative concordance rates.

Simulation of particle size distribution and source term for uranium aerosols based on zinc generated under fire conditions

Fire is a typical scenario for nuclear accidents, in which uranium-containing materials will release uranium aerosols. Limited by many aspects, uranium aerosols cannot be used directly to carry out nuclear emergency training and equipment development research under real conditions. Therefore, it is necessary to filter and evaluate available surrogate materials through experiments. In this paper, metallic zinc is used to study the source term and particle size distribution of zinc aerosols under fire conditions, and the feasibility of zinc as a surrogate material for uranium aerosol research is evaluated based on the data of uranium aerosols in the literature. The experimental results show that the mass median aerodynamic diameter obtained by fitting with lognormal distribution is between 0.36 and 0.59 µm. The cumulative mass fraction distribution data are consistent with those given in the literature, indicating that the zinc aerosols generated under fire have a nice simulation effect on uranium aerosols in terms of particle size distribution. As for air release fraction (ARF) and respirable fraction (RF), the experiment of zinc aerosols is greater than that of uranium aerosols, which means the simulation in ARF and RF is not so good.

A novel approach for the consideration of plastic material behavior in thermodynamic topology optimization

AbstractIn order to find optimal structures for realistic applications, it is essential to include the real material behavior in the optimization process. For this purpose, this research focuses on thermodynamic topology optimization accounting for plasticity for which a surrogate material model is developed. Characteristically, the stress/strain diagram resulting from physical loading and unloading shows a hysteresis for classical plasticity models. Our material model takes only the physical loading during the optimization process into account. To this end, during a virtual unloading in the optimization process, the dissipation of energy is suppressed which yields the same elasto/plastic deformation state as for physical loading. By using this novel material model, optimized structures can be computed without resourceful classical path‐dependent plasticity computation.

Microstructural effects of high dose helium implantation in ErD2

Metal hydrides can store hydrogen isotopes with high volumetric density. In metal tritides, tritium beta decay can result in accumulation of helium within the solid, in some cases exceeding 10 at.% helium after only 4 years of aging. Helium is insoluble in most materials, but often does not readily escape, and instead coalesces to form nanoscale bubbles when helium concentrations are near 1 at.%. Blistering or spallation often occurs at higher concentrations. Radioactive particles shed during this process present a potential safety hazard. This study investigates the effects of high helium concentrations on erbium deuteride (ErD2), a non-radioactive surrogate material for erbium tritide (ErT2). To simulate tritium decay in the surrogate, high doses of 120 keV helium ions were implanted into ErD2 films at room temperature. Scanning and transmission electron microscopy indicated spherical helium bubble formation at a critical concentration of 1.5 at.% and bubble linkage leading to nanoscale crack formation at a concentration of 7.5 at.%. Crack propagation occurred through the nanocrack region, resulting in spallation extending from the implantation peak to the surface. Electron energy loss spectroscopy was utilized to confirm the presence of high-pressure helium in the nanocracks, suggesting that helium gas plays a predominant role in deformation. This work improves the overall understanding of helium behavior in ErD2 by using modern characterization techniques to determine: the critical helium concentration required for bubble formation, the material failure mechanism at high concentration, and the nanoscale mechanisms responsible for material failure in helium implanted ErD2.

On the importance of self-consistency in recurrent neural network models representing elasto-plastic solids

Recurrent neural networks could serve as surrogate material models, removing the gap between component-level finite element simulations and numerically costly microscale models. Recent efforts relied on gated recurrent neural networks. We show the limits of that approach: these networks are not self-consistent, i.e. their response depends on the increment size. We propose a recurrent neural network architecture that integrates self-consistency in its definition: the Linearized Minimal State Cell (LMSC). While LMSCs can be trained on short sequences, they perform best when applied to long sequences of small increments. We consider an elastoplastic example and train small models with fewer than 5000 parameters that precisely replicate the deviatoric elastoplastic behavior, with an optimal number of state-variables. We integrate these models into an explicit finite element framework and demonstrate their performance on component-level simulations with tens of thousands of elements and millions of increments.

Initial Assessments of a Handheld Indentation Probe's Correlation With Cancellous Bone Density, Stiffness, and Strength: An Objective Alternative to “Thumb Testing”

Abstract Objective: During shoulder arthroplasty, surgeons must select the optimal implant for each patient. The metaphyseal bone properties affect this decision; however, the typical resection “thumb test” lacks objectivity. This investigation's purposes were to determine the correlation strength between the indentation depth of a handheld mechanism and the density, compressive strength, and modulus of a bone surrogate; as well as to assess how changing the indenter tip shape and impact energy may affect the correlation strengths. Methods: A spring-loaded indenter was developed. Four tip shapes (needle, tapered, flat, and radiused cylinders) and four spring energies (0.13 J–0.76J) were assessed by indenting five cellular foam bone surrogates of varying density, every five times. After each indentation, the indentation depth was measured with a separate probe and correlated with manufacturer specifications of the apparent density, compressive strength, and modulus. Results: indentation depth plateaued as the bone surrogate's material properties increased, particularly for indentation tips with larger footprints and the 0.13 J spring. All tip shapes produced strong (R2≥0.7) power-law relationships between the indentation depth metric and the bone surrogate's material properties (density: 0.70 ≤ R2 ≤ 0.95, strength: 0.75 ≤ R2 ≤ 0.97, modulus: 0.70 ≤ R2 ≤ 0.93); though the use of the needle tip yielded the widest indentation depth scale. Interpretation: these strong correlations suggest that a handheld indenter may provide objective intra-operative evidence of cancellous material properties. Further investigations are warranted to study indenter tip shape and spring energy in human tissue; though the needle tip with spring energy between 0.30 J and 0.76 J seems the most promising.

Halogenation of used aluminum matrix test reactor fuel – a bench-scale demonstration with surrogate materials

ABSTRACT Experiments with surrogate materials were performed at bench scale to demonstrate a halogenation technique applicable to treatment of used aluminum matrix test reactor fuel. The technique involves dissolution and separation of aluminum from used aluminum matrix test reactor fuel in molten-halide salt systems prior to treatment and disposition of the fuel’s uranium and fission products. Demonstration of the halogenation technique was performed with neodymium metal as a non-radiological surrogate for uranium metal. Experiments involved blending forms of aluminum and neodymium metal with ammonium and lithium chloride or ammonium and lithium bromide, which upon heating decomposed into ammonia gas and the respective hydrogen chloride or bromide gas. The latter reacted with the metals to form the respective aluminum and neodymium halides. At elevated temperatures, aluminum halides gasified away from the respective neodymium halides, which fused with their respective lithium halides. Samples of fused and distillate salts were collected and analyzed, yielding extents of aluminum removal that ranged from 94.5–98.2% for chlorination runs and 91.4–97.8% for bromination runs. No neodymium was detected in the distillate fractions. Some experiments were repeated with excess reactants, and a portion of aluminum chloride distillate was processed into a consolidated waste form.

Evaluation of ceria as a surrogate material for UO2 in experiments on fuel cracking driven by resistive heating

A variety of normal operation and accident scenarios can generate thermal stresses large enough to cause cracking in light-water reactor (LWR) fuel pellets. Cracking of fuel pellets can lead to reduced heat removal, larger centerline temperatures, and localized stress in cladding all of which impact fuel performance. Pellet cracking also contributes to a temperature reduction in the pellet since the pellet fragments tend to move towards the heat sink (cladding), and the heat flow remains predominantly radial despite the presence of cracks. It is important to understand the temperature profile on the pellet before and after cracking to improve cracking models in fuel performance codes However, in-reactor observation and measurement of cracking is very challenging owing to the harsh environment and design of fuel rods. Recently, an experimental pellet cracking test stand was developed for separate effects testing of normal operations and accident temperature conditions, using thermal imaging to capture the pellet surface temperature for evaluation of thermal stresses and optical imaging to capture the evolution of cracking in real time. Cracking experiments were initially performed using ceria (CeO2) as a surrogate fuel material, which is useful for developing and demonstrating the experimental approaches but is also valuable in its own right for cracking model development and validation. A combination of induction and resistance heating was used for volumetric heat generation in the pellet creating a thermal gradient. The material properties of CeO2 and UO2 are reviewed and compared for use in model development. Simulations of the experiment were performed to evaluate the behavior of the surrogate (CeO2) fuel in BISON. The measured temperature profiles from BISON models match reasonably well with the observed experiments for the ceria pellets before cracking. The findings from this work will help improve confidence in fracture models used for fuel pellets under similar in-reactor conditions.

Degradation of powder activated carbon by laccase-mediator system: Model experiments for the improvement of gold recovery from carbonaceous gold ore

Several efforts are made to find various green alternatives for carbonaceous matter (CM) degradation in carbonaceous gold ores. The deleterious effect of CM is observed during cyanidation, where CM adsorbs Au(CN)2- behaving like activated carbon, an effect called pre-robbing. Thus, biotechnological approaches like enzyme degradation of CM to reduce Au(CN)2- adsorption are currently being studied. In the present work, the potential of CM degradation and gold preg-robbing reduction by laccase-mediator system (LMS) oxidation was evaluated using powder activated carbon (PAC) as CM surrogate material through model experiments. Based upon gas chromatography-mass spectrometry (GC-MS) analysis of extracted by-products from bio-treated PAC, LMS treatment after seven days physically and chemically altered the surface of PAC by the reduction of specific surface area and pore volume, the disruption of aromatic moieties into aliphatic compounds, and the formation of oxygen-containing functional groups. Subsequently, under the studied condition, the adsorption capacity of Au(CN)2- on the surface-degraded PAC was dramatically decreased from 46 μmol/g to 7.36 μmol/g. The present findings provide a new outlook of an alternative pre-treatment process of carbonaceous gold ore in mineral processing.

Brazilian disk compression testing of plastic-bonded idoxuridine mock explosive

ABSTRACT Recently, there has been increased interest in developing new inert surrogate materials, or “mocks,” for plastic-bonded explosives (PBX). Idoxuridine (IDOX) has similar density and mechanical behavior to the explosive HMX, and formulated plastic-bonded IDOX showed promise for emulating the HMX-based PBX 9501 in preliminary mechanical experiments. Several improvements to the manufacture of plastic-bonded IDOX have been made and are characterized here by Brazilian Disk testing. Compression tests were performed on these disk specimens under quasi-static loading conditions and at three different temperatures, , , and . The full-field deformation over the sample surface during the compression was obtained using the optical digital image correlation (DIC) technique. In this article, we summarize the Brazilian disk compression test results of the 2020 batch of IDOX mock specimens. We present the overall response, as well as the local deformation measurement. We discuss in detail, the sequence of deformation events occurring in the disk specimen during the compression process. Elastic constants, including shear modulus, Young’s modulus, and Poisson’s ratio, of the IDOX mock material, are extracted from the Brazilian disk compression test data. Finally, we compare the Brazilian disk compression test results with the data obtained from the baseline PBX 9501, tested in 2007, as well as the data from a previous batch of IDOX mock material tested in 2017. We hope that such comparisons would point out the path of improvement for the formulation and pressing of the new IDOX mock.

An exploration into the utilization of recycled waste glass as a surrogate powder to crushed stone dust in asphalt pavement construction

Growing attempts aimed at decreasing the consumption of huge amounts of natural materials as means of saving global limited financial resources have led to investigations into the feasibility of utilizing surrogate and sustainable materials in asphalt pavements. Enormous amounts of discarded glass and its derivatives are ending up in global landfills. This massive increase in such stockpiles is now outpacing the world’s ability to degrade such post-consumer glass. It is this issue that provoked this investigation into the potential incorporation of such abundant waste glass as an alternative powder in the production of asphaltic concrete, hoping that such utilizations will not only decrease global dependency on quarry-based scarce resources, but will also serve to facilitate effective solid waste management. As a means of validating this conjecture, we conducted laboratory tests on asphalt mortars that included recycled waste glass (RWG) and reference crushed stone dust (CSD) at three filler bitumen ratios (0.1, 0.2 and 0.4). We next carried out widespread performance tests on asphalt mixtures with RWG and control asphalt mixtures with CSD. We used both conventional (penetration, softening point, penetration index, and ductility) and rheological (rotational viscosity and dynamic shear rheometer) tests to evaluate the properties of the RWG and CSD mastics. The mechanical properties of asphalt RWG and CSD mixtures were examined by using the Marshall test, indirect tensile stiffness modulus, indirect tensile fatigue test, and dynamic creep test. We also inspected the morphological impact of RWG on the bitumen phase by analyzing the images captured with a Scanning Electron Microscope. Our findings indicate that green sustainable roads augmented by RWG comply with the relevant specifications, and that RWG utilizations provide significant improvements in the thermal susceptibility and fatigue performance of these roads, thus confirming the feasibility of RWG under certain practical applications.

Production of donor-derived offsprings by allogeneic transplantation of oogonia in the adult Japanese flounder (Paralichthys olivaceus)

Germ cell transplantation (GCT) is a promising reproductive technology in animals, including teleost fish. Here, we established a GCT procedure in Japanese flounder (Paralichthys olivaceus). Two-year-old male Japanese flounder were treated with temperature (28 °C) and busulfan (two doses, 18 mg/kg) to deplete endogenous germ cells and were then used as recipients. The discontinuous Percoll gradient purified oogonia were used as donor germ cells and transplanted into the recipients' testes through the genital pore. Histological and fluorescent observations showed the colonization, proliferation, and differentiation of transplanted oogonia in the testes of recipient fish. Ten months after GCT, 16 of 17 recipients produced sperm, and among them, two recipients produced donor-derived sperm, which was confirmed by microsatellite genotyping. The sperm of these two recipients were used to fertilize the eggs of wild-type females, and the donor-derived germline transmission rates were 45.5% and 43.0%, respectively, based on the microsatellite paternity analysis of the hatched larvae. Our established protocol can be applied to accelerate the reproduction cycle and be used for generating valuable surrogate breeding material and conserving the germplasm resources of Japanese flounder.

Design of Sand‐Based, 3‐D‐Printed Analog Faults With Controlled Frictional Properties

AbstractLaboratory experiments with surrogate materials play an important role in fault mechanics. They can improve the current state of knowledge by testing various scientific hypotheses in a repeatable and controlled way. Central in these experiments is the selection of appropriate analog, rock‐like materials. Here, we investigated the frictional properties of sand‐based, 3‐D‐printed materials. We performed uniaxial compression tests, direct shear, and inclined plane tests in order to determine a) the main bulk mechanical parameters of this new analog material, b) its viscous behavior, c) its frictional properties, and d) the influence of some printing parameters. Complete stress‐strain/apparent friction‐displacement curves were presented including the post‐peak, softening behavior, which is a key factor in earthquake instability. Going a step further, we printed rock‐like interfaces of custom frictional properties. Based on a simple analytical model, we designed the a) maximum, minimum, and residual apparent frictional properties, b) characteristic slip distance, c) evolution of the friction coefficient with slip, and d) dilatancy of the printed interfaces. This model was experimentally validated using interfaces following a sinusoidal pattern, which led to an oscillating evolution of the apparent friction coefficient with slip. Our approach could be used for simulating earthquake‐like instabilities in the laboratory and mimic the periodical rupture and healing of fault sections. Additionally, our tests showed the creation of a gouge‐like layer due to granular debonding during sliding, whose properties were quantified. The experimental results and the presented methodology make it possible to design new surrogate laboratory experiments for fault mechanics and geomechanics.

Probing the mineralized tissue-adhesive interface for tensile nature and bond strength

The mechanical performance of the dentin-adhesive interface contributes significantly to the failure of dental composite restorations. Rational material design can lead to enhanced mechanical performance, but this requires accurate characterization of the mechanical behavior at the dentin-adhesive interface. The mechanical performance of the interface is typically characterized using bond strength tests, such as the micro-tensile test. These tests are plagued by multiple limitations including large variations in the test results. The challenges associated with conventional tensile tests limit our ability to unravel the complex relationships that affect mechanical behavior at the dentin-adhesive interface. This study used the diametral compression test to overcome the challenges inherent in conventional bond strength tests. The bovine femur cortical bone tissue was considered as a surrogate material (the mineralized tissue) for human dentin. Two different adhesive formulations, which differed by means of their self-strengthening properties, were studied. The tensile behavior of the mineralized tissue, the adhesive polymer, and the bond strength of the mineralized tissue – adhesive interface was determined using the diametral compression test. The diametral compression test improved the repeatability for both the tensile and bond strength tests. The rate dependent mechanical behavior was observed for both single material and interfacial material systems. The tensile strength and bond strength of the mineralized tissue-adhesive interface was greater for the self-strengthening formulation as compared to the control.