Reversible Strain Research Articles

Liquid Crystal Polycaprolactone Copolymer Elastomer With Low Autonomous Driving Temperature

ABSTRACTLiquid crystal elastomers (LCEs) are liquid crystal polymers with moderate crosslinking that exhibit elasticity in both their isotropic and liquid crystal states. These materials can be programmed through chemical design and geometric configuration to achieve autonomous actuation at specific temperatures. Typically, the autonomous actuation temperature of LCEs exceeds the phase transition temperature of their isotropic states, with most reported LCEs requiring temperatures above 100°C. Such high temperatures pose challenges for use in soft robotics due to increased energy consumption and limited operational flexibility. In this study, we introduce a small amount of polycaprolactone (PCL) into the main chain of LCEs, effectively lowering their phase transition temperature while maintaining over 90% of the reversible shrinkage strain characteristic of pure LCEs. By adjusting the PCL content, the number of twists, and the helix density, we successfully obtained an LCE‐PCL actuator with improved autonomous actuation performance at temperatures ranging from 45°C to 105°C. Moreover, by modulating the degree of torsion and the operating temperature, the LCE‐PCL autonomous actuator demonstrates the ability to perform complex motions, such as reversing and parking. This work offers new insights into the design and application of LCEs with reduced phase transition temperatures and enhanced self‐driving capabilities.

Strain-Controlled Thermal–Mechanical Fatigue Behavior and Microstructural Evolution Mechanism of the Novel Cr-Mo-V Hot-Work Die Steel

In response to the intensifying competition in the mold market and the increasingly stringent specifications of die forgings, the existing 55NiCrMoV7 (MES 1 steel) material can no longer meet the elevated demands of customers. Consequently, this study systematically optimizes the alloy composition of MES 1 steel by precisely adjusting the molybdenum (Mo) and vanadium (V) contents. The primary objective is to significantly enhance the microstructure and thermal–mechanical fatigue performance of the steel, thereby developing a high-performance, long-life hot working die steel designated as MES 2 steel. The thermal–mechanical fatigue (TMF) tests of two test steels were conducted in reverse mechanical strain control at 0.6% and 1.0% strain levels by a TMF servo-hydraulic testing system (MTS). The microstructures of the two steels were characterized using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The results indicate that throughout the entire thermomechanical fatigue cycle, both steels exhibit initial hardening during the low-temperature half-cycle (tension half-cycle) and subsequent continuous softening during the high-temperature half-cycle (compression half-cycle). Furthermore, under the same strain condition, the cumulative cyclic softening damage of MES 1 steel is more pronounced than that of the newly developed MES 2 steel. The number, width, and length of cracks in MES 2 steel are smaller than those in MES 1 steel, and the thermomechanical fatigue life of MES 2 steel is significantly longer than that of MES 1 steel. The microstructures show that the main precipitate phase in MES 1 steel is Cr-dominated rod-shaped carbide. It presents obvious coarsening and is prone to inducing stress concentration, thus facilitating crack initiation and propagation. The precipitate phase in MES 2 steel is mainly MC carbide containing Mo and V. It has a high thermal activation energy and is dispersed in the matrix in the form of particles, pinning dislocations and grain boundaries. This effectively delays the reduction in dislocation density and grain growth, thus contributing positively to the improvement in thermomechanical fatigue performance.

The Effects of Reverse Nordic Exercise Training on Measures of Physical Fitness in Youth Karate Athletes.

Background: In karate, the ability to execute high-velocity movements, particularly kicks and punches, is heavily dependent on the strength and power of the lower limb muscles, especially the knee extensors. As such, this study aimed to evaluate the effects of an 8-week eccentric training program utilizing the reverse Nordic exercise (RNE) integrated into karate training compared with regular karate training only on measures of physical fitness in youth karate athletes. Methods: Twenty-seven youth karatekas were recruited and allocated to either RNE group (n = 13; age = 15.35 ± 1.66 years; 7 males and 6 females) or an active control group ([CG]; n = 14; 7 males and 7 females; age = 15.30 ± 1.06 years). To track the changes in measures of physical fitness before and after training, tests to assess linear sprint speed (i.e., 10 m), change of direction (CoD) speed (i.e., modified 505 CoD), vertical jumping (i.e., countermovement jump [CMJ] height) and horizontal jumping distance (i.e., standing long jump [SLJ]), and lower-limb asymmetry score (i.e., the difference between SLJ-dominant and non-dominant legs) were carried out. Results: The results indicated significant group-by-time interactions in all measures of physical fitness (effect size [ES] = 1.03 to 2.89). Post-hoc analyses revealed significant changes in the RNE group across all performance measures (effect size [ES] = 0.33 to 1.63). Additionally, the asymmetry score exhibited a moderate decrease from pre to posttest (∆46.96%, ES = 0.64). In contrast, no significant changes were observed in the CG across all fitness measures. Moreover, the individual response analysis indicated that more karatekas from the RNE group consistently achieved improvements beyond the smallest worthwhile change threshold across all fitness measures. Conclusions: In summary, RNE training is an effective approach to enhance various physical fitness measures besides lower-limb asymmetry scores in youth karatekas and is easy to incorporate into regular karate training. Practitioners are therefore encouraged to consistently integrate RNE training to enhance essential physical fitness components in young karatekas.

Effect of Shear Strain Reversal on Shear Texture in Accumulative Roll Bonding (ARB) Processed Aluminium

Effect of Shear Strain Reversal on Shear Texture in Accumulative Roll Bonding (ARB) Processed Aluminium

Using Brief Habit Reversal to Decrease Speech Disfluencies in Public Speaking. A Systematic Replication

Purpose: Many social workers are concerned about public speaking because of their use of speech disfluencies. Perrin et al. (2021) used brief habit reversal to reduce public-speaking speech disfluencies. The study was systematically replicated to evaluate the benefit of brief habit reversal training for social workers in decreasing speech disfluencies. Method: Nine students of social work, divided into three groups, participated in this study. After baseline, they received brief habit reversal, consisting of awareness training and instruction on a competing response. Results: The results showed that compared to baseline, all participants reduced speech disfluencies during brief habit reversal. The low rates of speech disfluencies were maintained during postsessions. At follow-up 2.5 to 6 weeks after training, six of nine participants achieved a reduction of at least 80 percent from baseline. Discussion: To further adapt the training to the field of social workers, further research would be necessary.

Body-Focused Repetitive Behavior Disorders: Classification, Diagnosis and Treatment

Body-focused repetitive behaviors (BFRBs) such as trichotillomania and skin picking are disorders at the interface of psychiatry/psychology, dermatology and dentistry. The disorders can be both either a consequence or a cause of severe somatic disorders. If BFRBs remain undetected and untreated, they tend to become chronic with at times serious somatic complications. There is currently no approved medication for BFRBs. Cognitive-behavioral therapy, especially habit reversal training, is the method of choice. The self-help technique decoupling is also effective for a subgroup of patients. In addition to behavioral change, therapy should also address precipitating factors such as poor stress and emotion regulation strategies and sensory triggers.

A Comparison Study of High-Temperature Low-Cycle Fatigue Behaviour and Deformation Mechanisms Between Incoloy 800H and Its Weldments

The high-temperature low-cycle fatigue (LCF) behaviour of Incoloy 800H and its weldments with Haynes 230 and Inconel 82 filler metals, which were fabricated with the gas tungsten arc welding (GTAW) technique, was investigated and compared at 760 °C. The results revealed that the Incoloy 800H weldments showed lower fatigue lifetimes compared to the base metal. However, the weldments with the Haynes 230 filler metal demonstrated an improved fatigue life at the low strain amplitude compared to both Incoloy 800H and the weldment with the Inconel 82 filler metal. The Incoloy 800H base metal showed pronounced initial cyclic hardening with hardening factors increasing with strain amplitudes. In contrast, the weldments with Haynes 230 and Inconel 82 filler metals displayed short initial cyclic hardening and saturation stages, followed by long continuous cyclic softening. The fractography and microstructure after LCF the tests were characterized with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Transgranular fracture with multiple crack initiations was the predominant failure mode on the fracture surfaces of both Incoloy 800 base metal and the weldments. TEM examination revealed that planar dislocation slips at the low strain amplitude evolved to wavy slips, eventually forming a cell structure at high strain amplitudes in the Incoloy 800H material as the strain amplitudes increased. However, the weld metal exhibited a planar slip mode deformation mechanism regardless of cyclic strain amplitude in the weldment specimens. The differing cyclic hardening and softening behaviours between Incoloy 800H and its weldments are attributed to the higher strength of the weldment specimens compared to the base metal. In the Incoloy 800H base material specimens, the reverse strains during LCF created wavy dislocation structures, which could not fully recover due to the non-reversible nature of the microstructure. As a result, cells or subgrains formed within the microstructure once created. In contrast, the higher strength of the weld metal in the weldment specimens significantly suppressed the formation of wavy dislocation structures, and deformation primarily manifested as planar arrays of dislocations.

The NLRP3-inflammasome inhibitor MCC950 improves cardiac function in a HFpEF mouse model

Heart failure with preserved ejection fraction (HFpEF) is posing a significant medical challenge due to its growing prevalence, high hospitalization rates and limited response to current treatment options. Accumulating evidence suggests that a comorbidity-driven systemic pro-inflammatory state, including activation of the NLRP3 inflammasome, contributes to the pathogenesis of HFpEF. This study aimed to investigate the potential cardiac protective effects of the selective NLRP3 inhibitor MCC950, in a mouse model of HFpEF. HFpEF was obtained in 18–22 months old female mice using high-fat diet (HFD) and angiotensin II (AngII) infusion. Mice developed HFpEF and comorbidities such as obesity, type 2 diabetes, and hypertension. MCC950 was added to HFD and groups were treated for four weeks until the study endpoint. MCC950 treatment resulted in lower plasma IL-18 levels (-47.3 %), illustrating target engagement. First, we observed that MCC950 treatment improved left ventricular function, demonstrated by enhanced global longitudinal strain (GLS, 3.9 %, P<0.01) and reverse peak longitudinal strain (RPLSR, +46.8 %, P<0.05). Second, MCC950 reduced cardiac hypertrophy (cardiomyocyte size -19.5 %, P<0.001) and fibrosis (-32.5 %, P<0.05), accompanied by lower expression of pro-fibrotic genes. Finally, MCC950 treatment reduced macrophage infiltration in left ventricular tissue and attenuated macrophage accumulation in visceral adipose tissue, even more as compared to caloric restriction. Overall, this suggests that NLRP3 inhibition could be a promising treatment for HFpEF patients with a pro-inflammatory profile, potentially improving heart function, systemic inflammation, and metabolic parameters.

Ketamine differentially affects implicit and explicit memory processes in rats.

Ketamine, a non-competitive NMDA receptor antagonist, produces antidepressant effects at subanesthetic doses. The therapeutic effect, however, is often accompanied by cognitive side effects, including memory impairments. Yet, the specific effects of ketamine on different processes of implicit and explicit memory remain to be elucidated. We examined the effect of an antidepressant dose of ketamine (10mg/kg, IP) on the encoding, retrieval, and modulation processes of fear memory and spatial memory in adult Wistar rats. Ketamine was administered before the fear acquisition, retrieval, or extinction procedures in a Pavlovian fear conditioning task. In another set of experiments, it was administered before the training, probe trial, or reversal training phases of the Morris Water Maze (MWM). The antidepressant dose of ketamine partially impaired fear extinction when administered before the acquisition or retrieval. In contrast, it facilitated memory modulation and decreased the escape latency in the first day of reversal training in the MWM when administered before the training or reversal training sessions. Encoding or retrieval performance in either type of memory was not affected. These findings show that ketamine does not impair the acquisition or retrieval processes of cued fear or spatial memory; but exerts differential effects on memory modulation of these implicit and explicit memory paradigms, by disrupting fear extinction and facilitating reversal spatial learning.

Multifunctional Roles of Iron Oxide Nanoparticles in a Reversible Shape‐Memory Composite

AbstractThe utilization of functional fillers in the development of composite materials has come a long way since its advent to improve physical, chemical, or mechanical properties of the base material. However, the heterogenous roles contributed by a single type of filler remain uncommon in this field. Here the endowment of various modifications to a 1,8‐octanediol/1,12‐dodecanedioic acid/citric acid (OD/DDA/CA) matrix through the incorporation of iron oxide nanoparticles (IONPs) is reported. Owing to the relaxation and hysteresis loss behaviors of IONPs when exposed to an alternating magnetic field (AMF), the composites demonstrate a magnetothermal response. Similarly, the excitation and relaxation of electrons in IONPs under near‐infrared light (NIR) enable photothermic‐responsiveness. In combination, two findings nurtured an observed shape‐memory effect when the samples are under actuation by these indirect stimuli, where a shape recovery ratio (≥98%) and reversible strain (≤7%) are recorded. Moreover, the catalytic role of IONPs aided transesterification in the covalent network, demonstrated by successful repeated cycles of shape reconfiguration of the samples. This work highlights the prospectives of multifunctional composite fillers in the exploration of bio‐derived composite smart materials.

Thermo‐mechanical Study on Auxetic Shape Memory Periodic Open Cellular Structures—Part II: Mechanical and Shape Memory Properties

This study explores the potential of periodic open cellular structures (POCS) that combine the auxetic and the shape memory effect (SME) with the aim of enhancing heat transfer in catalytic tubular reactors. On the one hand, these structures exhibit a negative Poisson's ratio, contracting perpendicular to the load axis under compression, driven by the rotation of nodes generating complex stress fields. On the other hand, the shape memory alloy (SMA) Nitinol (NiTi) with a reversible strain of up to 8% produced via electron beam powder bed fusion (PBF‐EB) shows extraordinary material properties with a high degree of freedom in structure design. The study conducts finite element method simulations and experiments to design POCS with tailored properties. Compression tests on less expensive Ti‐6Al‐4V POCS compared to NiTi POCS validate the simulative parameter study applied to fabricate novel auxetic hexagonal reentrant structures from NiTi with a unique stacking order and curved struts. The aim of this part of the study is to offer a pathway to design a NiTi auxetic POCS based on validated simulations. Further, it explains the interactions between geometrical parameters and mechanical properties of cellular reentrant NiTi structures. An optimized auxetic NiTi POCS achieved a Poisson's ratio of −1.

Torsional behavior of Ni-rich NiTi alloys obtained by powder metallurgy and hot deformation

The effects of severe plastic deformation on NiTi alloys’ structure and properties have been extensively studied over the past decades. However, there is a notable lack of systematic data regarding the impact of industrial hot deformation techniques on these alloys. This gap arises from challenges in manufacturing processes related to the unevenness of ingots produced by casting technologies. This study investigates the effects of hot rotary swaging, extrusion, and radial shear rolling on the martensitic transformation, shape memory effect, superelasticity, and damping capacity of NiTi Ni-rich alloys fabricated through powder metallurgy. The properties were investigated under torsional load on wires prepared by spark eroding from deformed rods. Our findings indicate that samples after rolling and extrusion exhibit a superelastic strain of 14 ± 0.5% attributed to a high yield stress of approximately 600–800 MPa and torsional testing providing the material to be fully involved in recovery process. Samples after rolling and swaging demonstrate a high level of reversible strain with a one-way shape memory effect ranging from 5 to 7%. Conversely, extrusion, due to the inhomogeneity of resulting workpieces, induces a complex, multi-stage martensitic transformation that undermines the shape memory effect. Furthermore, all deformation methods except extrusion contribute to increased alloy homogeneity, resulting in a narrower temperature range for martensitic transformations. Rotary swaging notably increases the height of an internal friction peak from 0.015 to 0.045 compared to the undeformed material, whereas rolling gives the lowest value of 0.012 among others. This study provides valuable insights into how hot thermomechanical processing influences the properties of NiTi alloys and shows that powder metallurgy combined with hot deformation can be considered an alternative approach for achieving high functional properties of these alloys.

Surface chemo-mechanics coupling of MnO2/Au layered composites under electrochemical environment

The intersection of surface mechanics and electrochemistry has gradually become a prominent topic in the realm of new energy research. To explore the influence of the electrochemical process on the stress of energy storage electrode composite, supercapacitor material manganese dioxide (MnO2) was selected as the coating and the MnO2/Au composites were prepared by the electrochemical deposition. The surface stress of MnO2/Au composites under different electrochemical modes and the stress variation law of MnO2 with varying thicknesses were determined. The addition of MnO2 could alter the stress response and the strain magnitude of the gold electrode with varied electrochemical potential. The reversible tensile strain within the Au surface during 0.3 ∼ 0.8 V charging was induced by the absorption of SO42−, while the compressive strain of the MnO2/Au composites was related to the extraction of Na+ ions resulting from the redox pseudocapacitance of MnO2. Notably, the produced stress exhibited a linear correlation with the capacitance. And the long-cycle tests revealed that as the specific capacitance of electrodes decreased, the induced tensile stress progressively diminished. This study emphasized the surface chemo-mechanics coupling of both the Au layer and MnO2/Au composites, which would provide a new approach to regulating surface strain in the solid–liquid interface.

Afterslip and Creep in the Rate‐Dependent Framework: Joint Inversion of Borehole Strain and GNSS Displacements for the Mw 7.1 Ridgecrest Earthquake

AbstractThe elusive transition toward afterslip following an earthquake is challenging to capture with typical data resolution limits. A dense geodetic network recorded the Mw 7.1 Ridgecrest earthquake, including 16 Global Navigation Satellite System (GNSS) stations and 3 borehole strainmeters (BSM). The sub‐nanostrain precision and sub‐second sampling rate of BSMs bridges a gap between conventional seismologic and geodetic methods, exemplified by atypical postseismic shear strain reversals observed at nearfield (&lt;2 km) station B921 that remain unexplained. We jointly invert GNSS displacements and BSM strains for coseismic and postseismic slip spanning hours to months over 7 independent periods. Cosiesmically, our model resolves the largest slip magnitudes of up to 6.6 m on the mainshock rupture plane, with similar patterns to other inferred slip distributions. The foreshock fault appears to slip coincidently with mainshock, revealing potential asperities activated during the preceding Mw 6.4 event. Postseismically, the best‐fitting models adhere to mechanical rate‐and‐state expectations of logarithmically decaying slip adjacent to the coseismic rupture terminus, and where deep rheologic conditions favor creep. Most spatial variation occurs in the early postseismic timeframe (&lt;1–2 weeks), with evidence for regional rheologic control and static stress dependence. Triggered creep on the neighboring Garlock Fault unexpectedly persists for &gt;178 days—further highlighting the importance of fault networks in postseismic stress redistribution, critical to assessing future hazard.

Regularities of Martensitic Transformations in New Medium-Entropy Single Crystals of CoNiAlFe Alloys

This paper deals with the martensitic transformation and functional properties in the quenched single crystals of the Co35Ni35Al28Fe2 medium-entropy alloy, oriented along the [001]B2-direction. The microstructure and chemical composition of the single crystals have been studied in detail using transmission and scanning electron microscopy. The {111}L10 martensite twins up to 10-20 nm width and γ/γ′-phase precipitations larger than 100 μm are detected. The thermoelastic B2-L10 martensitic transformation upon stress-free cooling/heating in single crystals of Co35Ni35Al28Fe2 alloy is characterized by the accumulation of elastic energy, which is the driving force of the reverse martensitic transformation, and the low dissipation energy. The reverse transformation starts at lower temperatures than the forward transformation Ms&gt;As. The regularities of the stress-induced B2-L10 martensitic transformation change due to an increase in the contribution of the dissipated energy and Msσ&lt;Asσ. There is shape memory effect with the reversible strain (3.2±0.3)% and high temperature superelasticity with the reversible strain (3.3±0.3)% in the temperature range from 323 K to ≥548 K in the [001]B2-oriented single crystals. These crystals withstand stress up to 1200 MPa in compression without destruction.

Pregnancy history and estradiol influence spatial memory, hippocampal plasticity, and inflammation in middle-aged rats

Pregnancy and motherhood can have long-term effects on cognition and brain aging in both humans and rodents. Estrogens are related to cognitive function and neuroplasticity. Estrogens can improve cognition in postmenopausal women, but the evidence is mixed, partly due to differences in age of initiation, type of menopause, dose, formulation and route of administration. Additionally, past pregnancy influences brain aging and cognition as a younger age of first pregnancy in humans is associated with poorer aging outcomes. However, few animal studies have examined specific features of pregnancy history or the possible mechanisms underlying these changes. We examined whether maternal age at first pregnancy and estradiol differentially affected hippocampal neuroplasticity, inflammation, spatial reference cognition, and immediate early gene activation in response to spatial memory retrieval in middle-age. Thirteen-month-old rats (who were nulliparous (never mothered) or previously primiparous (had a litter) at three or seven months) received daily injections of estradiol (or vehicle) for sixteen days and were tested on the Morris Water Maze. An older age of first pregnancy was associated with impaired spatial memory but improved performance on reversal training, and increased number of new neurons in the ventral hippocampus. Estradiol decreased activation of new neurons in the dorsal hippocampus, regardless of parity history. Estradiol also decreased the production of anti-inflammatory cytokines based on age of first pregnancy. This work suggests that estradiol affects neuroplasticity and neuroinflammation in middle age, and that age of first pregnancy can have long lasting effects on hippocampus structure and function.

Efficacy of cognitive-behavioral therapy combined with habit reversal training on anxiety disorders in children with Tourette's syndrome.

Cognitive-behavioral therapy (CBT) and habit reversal training (HRT) have shown application potential in addressing tic symptoms and comorbid psychiatric conditions. Despite their theoretical potential, empirical evidence on their combined efficacy remains limited. To evaluate the efficacy of CBT combined with HRT on anxiety disorders in children with Tourette's syndrome (TS). Clinical data of children with TS admitted to our hospital from January 2022 to June 2023 were collected, and the patients were grouped into the conventional therapy (control) group and the CBT combined with HRT group. Baseline characteristics, anxiety scores, tic severity scores, treatment adherence, and parental satisfaction were assessed. Statistical analysis was performed using t-tests, chi-square tests, and correlation analysis. A total of 136 patients, including 65 patients in the control group and 71 patients in the CBT combined with HRT group, were included. The CBT combined with HRT group showed remarkable improvements compared with the control group. Post-intervention assessment revealed a decrease in anxiety scores from 63.52 ± 1.81 to 40.53 ± 1.64 (t = 2.022, P = 0.045), and the Yale Global Tic Severity Scale total score decreased from 22.14 ± 5.67 to 16.28 ± 4.91 (t = 2.288, P = 0.024). Treatment adherence was significantly higher in the CBT combined with HRT group (85.47 ± 7.62%) compared with the control group (82.32 ± 6.54%; t = 2.596, P = 0.010). Parental satisfaction scores were also higher in the CBT combined with HRT group (8.69 ± 1.77) compared with the control group (7.87 ± 1.92; t = 2.592, P = 0.011). This study demonstrates that CBT combined with HRT significantly reduces anxiety symptoms and tic severity in children with TS, with higher treatment adherence and parental satisfaction. These findings support the potential application of this comprehensive therapeutic approach for TS treatment.

A preliminary analysis of computer‐based asynchronous awareness training for public speaking disfluencies

AbstractSimple habit reversal training is effective at reducing public speaking disfluencies; however, the time and resources necessary to implement this intervention may reduce practicality for widespread adoption. The purpose of the present study was to evaluate the effectiveness of asynchronous awareness training. Four participants completed a computer‐based training consisting of response description and practice detecting recorded disfluencies prior to taking a quiz in which they scored the frequency of disfluencies in a recorded speech. Relative to baseline, all participants' rates of disfluencies decreased following training. In addition, acceptability ratings were high and all participants indicated greater willingness to participate in asynchronous training than in‐person training.

Gelatin-Based Scaffolds with Carrageenan and Chitosan for Soft Tissue Regeneration.

Motivated by the enormous potential of hydrogels in regenerative medicine, new biocompatible gelatin-based hybrid hydrogels were developed through a green process using poly(ethylene glycol) diglycidyl ether as a cross-linking agent, adding carrageenan and chitosan polysaccharides to the network to better mimic the hybrid composition of native extracellular matrix. Overall, the hydrogels show suitable structural stability, high porosity and pore interconnectivity, good swellability, and finally, biocompatibility. Their mechanical behavior, investigated by tensile and compression tests, appears to be characterized by nonlinear elasticity with high compliance values, fast stress-relaxation, and good strain reversibility with no sign of mechanical failure for compressive loading-unloading cycles at relatively high deformation levels of 50%. Degradation tests confirm the hydrogel bioresorbability by gradual hydrolysis, during which the structural integrity of both materials is maintained, while their mechanical behavior becomes more and more compliant. Human Umbilical Cord-derived Mesenchymal Stem Cells (hUC-MSCs) were used to test the hydrogels as potential carriers for cell delivery in tissue engineering. hUC-MSCs cultured inside the hydrogels show a homogenous distribution and maintain their growth and viability for at least 21 days of culture, with an increasing proliferation trend. Hence, this study contributes to a further understanding of the potential use of hybrid hydrogels and hUC-MSCs for a wide range of biomedical applications, particularly in soft tissue engineering.

Complementary In Situ Characterization of Superelasticity in Fe–Mn–Al–Ni–Ti Shape Memory Alloys by Acoustic Emission, Digital Image Correlation and Infrared Thermography

AbstractCoupled in situ investigations were conducted on a Fe–Mn–Al–Ni–Ti single crystal deformed in compression and two Fe–Mn–Al–Ni–Ti oligo-crystals deformed in tension. Acoustic emission measurements were employed to monitor the degradation of superelasticity and the stabilization of martensite due to dislocation processes. These observations were corroborated by the application of digital image correlation and infrared thermography measurements. A poor strain reversibility and a premature plastification of the parent phase were observed in case of the single crystal due to an unfavourable crystal orientation. A contradictory transformation behaviour of the two oligo-crystals was observed, with one specimen showing a promising strain reversibility and characterisitic signs of degradation, and the other specimen exhibiting a limited strain reversibility due to an unusual confinement of the martensitic phase transformation to an unfavourably oriented grain. In the former case, an increase in the dislocation density within five cycles was detected through a shift of the acoustic signals’ median frequencies. In the latter case, a strong coupling between martensite nucleation and dislocation generation led to a pronounced martensite stabilization after one loading cycle. For all specimens, temporal sequence effects related to the coupling of martensite nucleation and dislocation generation were detected by means of acoustic emission.