The stress distribution around a thick-walled cylinder by a proposed constitutive model for rocks.

To simulate the nonlinear stress-strain curve of rocks under static loads and contribute to the design and construction of rock engineering structures, a constitutive model has been proposed based on the elastic modulus E decreasing with the increase in longitudinal cracks. This constitutive equation offers numerous advantages, with the most noteworthy being that the simulation of stress-strain curves for rocks necessitates only three equations (Eqs 1-3) and four parameters (A, k0, C and εs). Following this, we employ the constitutive equation to analyze the stress distribution around a thick-walled cylinder and explore the impact of its four parameters on the stress distribution surrounding the thick-walled cylinder. Parameter A primarily affects the range of the plastic zone and the magnitude of the maximum tangential stress; parameter C mainly influences the magnitude of the maximum tangential stress; parameter εs mainly affects the range of the plastic zone and the magnitude of the maximum tangential stress; parameter k0 primarily influences the magnitude of the maximum tangential stress. We got the similar results with Bray model, but distribution of stress around the tunnel are different present that the shape of stress-strain curves are different.

Aligners: review of their chemical components, recycling, mechanical properties and therapeutic needs - Part 1 / Aligneurs : mise en perspective de la composition chimique, du recyclage, des propriétés mécaniques et des besoins thérapeutiques ­ Partie 1.

Introduction: The aligner is a thermoformed plastic device composed of various chemical components: polyurethane, polyethylene terephthalate glycol, polypropylene… All these plastics must be sufficiently resistant to abrasion and translucent for aesthetic purposes, but their solubility to salivary enzymes, insertion-disinsertion fatigue and recyclability vary according to material. From an orthodontic point of view, they must facilitate tooth movement. However, their behavior differs from that of orthodontic archwires: their Young's modulus, resilience and unloading curve are distinct, resulting in mechanical properties that fall significantly below the orthodontic requirements of multi-bracket systems. Objective: The aim of this article was to review the chemical composition, recycling and mechanical properties of aligners, and to put them into perspective with therapeutic indications. Materials and Methods: Literature data were approximated to orthodontic needs. Results: Neither plastic nor direct printing can match the mechanical properties of our archwires or the procedures of a reliable vestibular multi-attachment appliance. Discussion: Aligners remain an interesting tool in targeted indications.

Introduction: L'aligneur est un dispositif en plastique thermoformé dont la composition chimique est diverse : polyuréthane, polyéthylène téréphtalate glycol, polypropylène… Tous ces plastiques doivent être suffisamment résistants à l'abrasion et translucides pour être esthétiques mais ils présentent une solubilité aux enzymes salivaires, une fatigue liée à l'insertion-désinsertion et une recyclabilité qui sont variables selon le matériau. D'un point de vue orthodontique, ils doivent permettre de déplacer les dents. Mais leur comportement ne ressemble pas à celui des arcs orthodontiques : leur module de Young, leur résilience et leur courbe de décharge en sont éloignés et confèrent des propriétés mécaniques très inférieures aux exigences orthodontiques des appareils multi-attaches. Objectif: L'objectif de l'article était de faire le point sur la composition chimique, le recyclage, les propriétés mécaniques des aligneurs et de les mettre en perspective avec les indications thérapeutiques. Matériel et méthode: Les données de la littérature sont approchées des besoins orthodontiques. Résultats: Ni le plastique, ni l'impression directe ne sont en capacité de rivaliser avec les propriétés mécaniques de nos arcs ou avec les procédures d'un appareil multi-attache vestibulaire fiables. Discussion: Les aligneurs restent un outil intéressant dans des indications ciblées.

In situ assembly of an injectable cardiac stimulator.

Without intervention, cardiac arrhythmias pose a risk of fatality. However, timely intervention can be challenging in environments where transporting a large, heavy defibrillator is impractical, or emergency surgery to implant cardiac stimulation devices is not feasible. Here, we introduce an injectable cardiac stimulator, a syringe loaded with a nanoparticle solution comprising a conductive polymer and a monomer that, upon injection, forms a conductive structure around the heart for cardiac stimulation. Following treatment, the electrode is cleared from the body, eliminating the need for surgical extraction. The mixture adheres to the beating heart in vivo without disrupting its normal rhythm. The electrofunctionalized injectable cardiac stimulator demonstrates a tissue-compatible Young's modulus of 21 kPa and a high conductivity of 55 S/cm. The injected electrode facilitates electrocardiogram measurements, regulates heartbeat in vivo, and rectifies arrhythmia. Conductive functionality is maintained for five consecutive days, and no toxicity is observed at the organism, organ, or cellular levels.

Influence of prosthetic index structures and implant materials on stress distribution in implant restorations: a three-dimensional finite element analysis.

BACKGROUND: Mechanical complications affect the stability of implant restorations and are a key concern for clinicians, especially with the frequent introduction of new implant designs featuring various structures and materials. This study evaluated the effect of different prosthetic index structure types and implant materials on the stress distribution of implant restorations using both in silico and in vitro methods. METHODS: Four finite element analysis (FEA) models of implant restorations were created, incorporating two prosthetic index structures (cross-fit (CF) and torc-fit (TF)) and two implant materials (titanium and titanium-zirconium). A static load was applied to each group. An in vitro study using digital image correlation (DIC) with a research scenario identical to that of the FEA was conducted for validation. The primary strain, sensitivity index, and equivalent von Mises stress were used to evaluate the outcomes. RESULTS: Changing the implant material from titanium to titanium-zirconium did not significantly affect the stress distribution or maximum stress value of other components, except for the implant itself. In the CF group, implants with a lower elastic modulus increased the stress on the screw. The TF group showed better stress distribution on the abutment and a lower stress value on the screw. The TF group demonstrated similar sensitivity for all components. DIC analysis revealed significant differences between TF-TiZr and CF-Ti in terms of the maximum (P < 0.001) and minimum principal strains (P < 0.05) on the implants and the minimum principal strains on the investment materials in both groups (P < 0.001). CONCLUSIONS: Changes in the implant material significantly affected the maximum stress of the implant. The TF group exhibited better structural integrity and reliability.

Quality Assurance of Point and 2D Shear Wave Elastography through the Establishment of Baseline Data Using Phantoms.

Ultrasound elastography has been available on most modern systems; however, the implementation of quality processes tends to be ad hoc. It is essential for a medical physicist to benchmark elastography measurements on each system and track them over time, especially after major software upgrades or repairs. This study aims to establish baseline data using phantoms and monitor them for quality assurance in elastography. In this paper, we utilized two phantoms: a set of cylinders, each with a composite material with varying Young's moduli, and an anthropomorphic abdominal phantom containing a liver modeled to represent early-stage fibrosis. These phantoms were imaged using three ultrasound manufacturers' elastography functions with either point or 2D elastography. The abdominal phantom was also imaged using magnetic resonance elastography (MRE) as it is recognized as the non-invasive gold standard for staging liver fibrosis. The scaling factor was determined based on the data acquired using MR and US elastography from the same vendor. The ultrasound elastography measurements showed inconsistency between different manufacturers, but within the same manufacturer, the measurements showed high repeatability. In conclusion, we have established baseline data for quality assurance procedures and specified the criteria for the acceptable range in liver fibrosis phantoms during routine testing.

Marginal integrity and physicomechanical properties of a thermoviscous and regular bulk-fill resin composites.

OBJECTIVES: To evaluate the marginal integrity (MI%) and to characterize specific properties of a thermoviscous bulk-fill resin composite, two regular bulk-fill resin composites, and a non-bulk-fill resin composite. MATERIALS AND METHODS: VisCalor bulk (VBF), Filtek One Bulk Fill (OBF), and Aura Bulk Fill (ABF) were evaluated. Filtek Z250 XT (ZXT) was used as non-bulk-fill control. MI% was evaluated in standardized cylindrical cavities restored with the composites by using a 3D laser confocal microscope. The following properties were characterized: volumetric polymerization shrinkage (VS%), polymerization shrinkage stress (Pss), degree of conversion (DC%), microhardness (KHN), flexural strength (FS), and elastic modulus (EM). Data were analyzed by one-way and two-way ANOVA, and Tukey HSD post-hoc test (α = 0.05). RESULTS: VBF presented the highest MI% and the lowest VS% and Pss (p < 0.05). DC% ranged from 59.4% (OBF) to 71.0% (ZXT). ZXT and VBF presented similar and highest KHN than OBF and ABF (p < 0.05). ABF presented the lowest FS (p < 0.05). EM ranged from 5.5 GPa to 7.7 GPa, with the values of ZXT and VBF being similar and statistically higher than those of OBF and ABF (p < 0.05). CONCLUSIONS: Thermoviscous technology employed by VisCalor bulk was able to improve its mechanical behavior comparatively to regular bulk-fill resin composites and to contribute to a better marginal integrity in restorations built up in cylindrical cavities with similar geometry to a class I cavity as well. Although presenting overall better physicomechanical properties, Z250 XT presented the worst MI%. CLINICAL RELEVANCE: The marginal integrity, which is pivotal for the success of resin composite restorations, could be improved using VisCalor bulk-fill. The worst MI% presented by Z250 XT reinforces that non-bulk-fill resin composites shall not be bulk-inserted in the cavity to be restored.

An attempt to identify brain tumour tissue in neurosurgery by mechanical indentation measurements.

BACKGROUND: The intraoperative differentiation between tumour tissue, healthy brain tissue, and any sensitive structure of the central nervous system is carried out in modern neurosurgery using various multimodal technologies such as neuronavigation, fluorescent dyes, intraoperative ultrasound or the use of intraoperative MRI, but also the haptic experience of the neurosurgeon. Supporting the surgeon by developing instruments with integrated haptics could provide a further objective dimension in the intraoperative recognition of healthy and diseased tissue. METHODS: In this study, we describe intraoperative mechanical indentation measurements of human brain tissue samples of different tumours taken during neurosurgical operation and measured directly in the operating theatre, in a time frame of maximum five minutes. We present an overview of the Young's modulus for the different brain tumour entities and potentially differentiation between them. RESULTS: We examined 238 samples of 75 tumour removals. Neither a clear distinction of tumour tissue against healthy brain tissue, nor differentiation of different tumour entities was possible on solely the Young's modulus. Correlation between the stiffness grading of the surgeon and our measurements could be found. CONCLUSION: The mechanical behaviour of brain tumours given by the measured Young's modulus corresponds well to the stiffness assessment of the neurosurgeon and can be a great tool for further information on mechanical characteristics of brain tumour tissue. Nevertheless, our findings imply that the information gained through indentation is limited.

The value of real-time shear wave elastography in spontaneous preterm birth.

This study aimed to investigate the predictive value of real-time shear wave elastography (SWE) for spontaneous preterm birth (SPB). This study prospectively selected 175 women with singleton pregnancies at 16 to 36 weeks of gestation. Cervical length (CL) and uterocervical angle (UCA) were measured using transvaginal ultrasonography. Real-time shear wave elastography was used to measure Young's modulus values, including the average Young's modulus (Emean) and the maximum Young's modulus (Emax) at 4 points: point A on the inner lip of the cervical os, point B on the outer lip of the cervical os, point C on the inner lip of the external os, and point D on the outer lip of the external os. Receiver operating characteristic (ROC) curve analysis was performed to compare the accuracy of Young's modulus values at the 4 points, CL, and UCA in predicting SPB. Significant variables were used to construct a binary logistic regression model to predict the multifactorial predictive value of SPB, which was evaluated using an ROC curve. A total 176 valid cases, including 160 full-term pregnancies and 16 SPB, were included in this study. Receiver operating characteristic curve analysis revealed that Emean at point A, as well as Emean and Emax at point D, had a relatively high accuracy in diagnosing SPB, with area under the curve values of 0.704, 0.708, and 0.706, respectively followed by CL (0.670), SWE at point C (Emean 0.615, Emax 0.565), SWE at point B (Emean 0.577, Emax 0.584), and UCA (0.476). Binary logistic regression analysis showed that comorbidities during pregnancy (including diabetes mellitus, hypertension, cholestasis and thyroid dysfunction), CL, and Emean at point A were independent predictors of preterm birth. In addition, the AUC value of the logistic regression model's ROC curve was 0.892 (95% CI: 0.804-0.981), with a sensitivity of 0.867, specificity of 0.792, and Youden's index of 0.659, indicating that the regression model has good predictive ability for SPB. Real-time shear wave elastography showed a higher predictive value for SPB than CL and UCA. The SWE combined with CL and comorbidities during pregnancy model has a good predictive ability for SPB.

Shear modulus of lower limb muscles in school-aged children with mild hypotonia.

The objective of this study is to compare shear modulus of lower limb muscles between children with hypotonia versus typical development (TD) or developmental disorders associated with altered tone. Nineteen children with mild hypotonia (mean age 9.4 ± 2.3y, 13 male) completed assessment of resting shear modulus of rectus femoris, biceps femoris (BF), tibialis anterior (TA) and gastrocnemius lateralis (GL) at short and long lengths using shear wave elastography. Data was compared with previous data from TD children and a scoping review for children with developmental disorders. Data were collated according to Net-Longitudinal Tension Angle (Net-LTA), which is the muscle length expressed as the net proximal and distal joint angles. Effects of Net-LTA (e.g., short, neutral, long) were examined according to sex, age and body mass index (BMI). In children with hypotonia, shear modulus was: higher at longer versus shorter lengths for four muscles (p < 0.01); correlated with age for BF-short (r = 0.60, p < 0.03) and GL-short (r = -0.54, p < 0.03), with BMI for BF-short (r = 0.71, p < 0.05); and not different between sexes (p > 0.05). The shear modulus values for lower limb muscles for children with mild hypotonia were lower than those for children with Duchenne Muscular Dystrophy (TA-neutral), or Cerebral Palsy (GL-neutral), but not TD children (all four muscles). In conclusion, shear modulus increases with longer muscle length (i.e. higher Net-LTA) in mildly hypotonic children. Children with mild hypotonia have lower shear modulus than children with cerebral palsy and Duchenne muscular dystrophy.

Guided wave elastography of human skins with a layered model incorporating the effect of muscle state.

In vivo mechanical characterization of skin finds broad applications in understanding skin aging, diagnosis of some skin diseases and assessing the effectiveness of diverse skin care strategies. Skin has a layered structure consisting of the epidermis, dermis and subcutaneous layers. Although much effort has been made towards mechanical characterization of skin, it remains a challenging issue to measure the mechanical properties of an individual layer in vivo. To address this issue, we here report a guided wave elastography method for layered human skin which incorporates the effect of muscle states. Both finite element simulations and phantom experiments have been performed to validate the method. For skin-mimicking phantoms with different fat layer thicknesses, the errors in the identified shear modulus of the skin layers are no more than 11 %. In vivo experiments have been carried out on 6 healthy subjects to demonstrate the potential use of the method in clinics. A statistical analysis indicates the muscle contraction contributes to the stiffening of the skin (p < 0.001). Finally, a phase diagram has been constructed to reveal the extent to which muscle sates (including both passive and active states) affect the measurement of elastic modulus of a skin layer, which may guide the application of the method in practice.

Comparison of the flexural strength of printed and milled denture base materials.

BACKGROUND: To evaluate the flexural strength of digitally milled and printed denture base materials. METHODS: The materials tested were Lucitone 199 denture base disc (Dentsply Sirona), AvaDent denture base puck (AvaDent), KeyMill denture base disc (Keystone), Lucitone digital print denture base resin (Dentsply Sirona), Formlab denture base resin (Formlabs), and Dentca base resin II (Dentca). Sixty bar-shaped specimens of each material were prepared for flexural strength testing and were divided into five groups: control, thermocycled, fatigue cycled, and repair using two different materials. The flexural strength and modulus were tested using a 3-point bend test performed on an Instron Universal Testing Machine with a 1kN load cell. The specimens were centered under a loading apparatus with a perpendicular alignment. The loading rate was a crosshead speed of 0.5 mm/min. Each specimen was loaded with a force until failure occurred. A one-way ANOVA test was used to analyze the data, followed by Tukey's HSD test (α = 0.05). RESULTS: The milled materials exhibited higher flexural strength than the printed materials. Thermocycling and fatigue reduce the flexural strengths of printed and milled materials. The repaired groups exhibited flexural strengths of 32.80% and 30.67% of the original flexural strengths of printed and milled materials, respectively. Nevertheless, the type of repair material affected the flexural strength of the printed materials; the composite resin exhibited higher flexural strength values than the acrylic resin. CONCLUSIONS: The milled denture base materials showed higher flexural strength than the printed ones.

How Static and Cyclic Loading Affect the Mechanical Properties of the Porcine Annulus Fibrosus.

This study sought to evaluate the effects of prolonged cyclic loading on the tissue-level mechanical properties of the spinal annulus fibrosus. Functional spinal units (FSUs) were obtained from porcine cervical spines at the C3-C4 and C5-C6 levels. Following a 15-min preload of 300 N of axial compression, the FSUs were split into three groups: the cyclic loading group cycled between 0.35 MPa and 0.95 MPa for 2 h (n = 8); the static loading group was compressed at 0.65 MPa for 2 h (n = 10); and a control group which only underwent the 300 N preload (n = 11). Following loading, samples of the annulus were excised to perform intralamellar tensile testing and interlamellar 180 deg peel tests. Variables analyzed from the intralamellar test were stress and strain at the end of the toe region, stress and strain at initial failure (yield point), Young's modulus, ultimate stress, and strain at ultimate stress. Variables evaluated from the interlamellar tests were lamellar adhesion strength, adhesion strength variability, and stiffness. The analysis showed no significant differences between conditions on any measured variable; however, there was a trend (p = 0.059) that cyclically loaded tissues had increased adhesion strength variability compared to the static and control conditions. The main finding of this study is that long-duration axial loading did not impact the intra- or interlamellar mechanical properties of the porcine annulus. A trend of increased adhesion strength variability in cyclically loaded samples could indicate a potential predisposition of the annulus to delamination.

Incorporation of montmorillonite into microfluidics-generated chitosan microfibers enhances neuron-like PC12 cells for application in neural tissue engineering.

The complexity in structure and function of the nervous system, as well as its slow rate of regeneration, makes it more difficult to treat it compared to other tissues. Neural tissue engineering aims to create an appropriate environment for nerve cell proliferation and differentiation. Fibrous scaffolds with suitable morphology and topography and better mimicry of the extracellular matrix have been promising for the alignment and migration of neural cells. On this premise, to improve the properties of the scaffold, we combined montmorillonite (MMT) with chitosan (CS) polymer and created microfibers with variable diameters and varied concentrations of MMT using microfluidic technology and tested its suitability for the rat pheochromocytoma cell line (PC12). According to the findings, CS/MMT 0.1 % compared to CS/MMT 0 % microfibers showed a 201 MPa increase in Young's modulus, a 68 mS/m increase in conductivity, and a 1.4-fold increase in output voltage. Analysis of cell mitochondrial activity verified the non-toxicity, resulting in good cell morphology with orientation along the microfiber. Overall, the results of this project showed that with a low concentration of MMT, the properties of microfibers can be significantly improved and a suitable scaffold can be designed for neural tissue engineering.

Cellulose Nanofibrils/Alginates Double-Network Composites: Effects of Interfibrillar Interaction and G/M Ratio of Alginates on Mechanical Performance.

Interfibrillar phases and bonding in cellulose nanofibril (CNF)-based composites are crucial for materials performances. In this study, we investigated the influence of CNF surface characteristics, the guluronic acid/mannuronic acid ratio, and the molecular weight of alginates on the structure, mechanical, and barrier properties of CNF/alginate composite films. Three types of CNFs with varying surface charges and nanofibril dimensions were prepared from wood pulp fibers. The interfacial bonding through calcium ion cross-linking between alginate and carboxylated CNFs (TCNFs) led to significantly enhanced stiffness and strength due to the formation of an interpenetrating double network, compared to composites from alginates and CNFs with native negative or cationic surface charges. Various alginates extracted from Alaria esculenta (AE) and Laminaria hyperborea (LH) were also examined. The TCNF/AE composite, prepared from alginate with a high mannuronic acid proportion and high molecular weight, exhibited a Young's modulus of 20.3 GPa and a tensile strength of 331 MPa under dry conditions and a Young's modulus of 430 MPa and a tensile strength of 9.3 MPa at the wet state. Additionally, the TCNF/AE composite demonstrated protective properties as a barrier coating for fruit, significantly reducing browning of banana peels and weight loss of bananas stored under ambient conditions.

Research on the mean maximum Young's modulus value as a new diagnostic parameter for prostate cancer.

Ultrasound-based shear wave elastography (SWE) can non-invasively assess prostate tissue stiffness for the diagnosis of prostate cancer (PCa). So far, there is no widely recognized standard for the detection process and calculation method of Young's modulus value in transrectal SWE ultrasound imaging (TSWEUI). In our study, the mean maximum Young's modulus value (m-Emax) of the maximum cross-section of prostate is obtained by calculating the mean of 12 measured Emax in the four quadrants. This retrospective study included 209 suspected malignant prostate disease patients with pathological results in our hospital. Among the 209 patients, 75 patients completed TSWEUI, and 63 of the 75 patients completed magnetic resonance imaging (MRI). The area under the receiver operating characteristic (ROC) curve (AUC) of 75 patients for m-Emax was 0.754. The prostate volume, prostate-specific antigen, and m-Emax were used to develop a nomogram (AUC = 0.868). The nomogram could effectively predict the probability of PCa, thereby reducing the needle biopsy rate for diagnosing PCa. The AUC of 63 patients was not statistically different between m-Emax (AUC = 0.717) and MRI (AUC = 0.787) (P = 0.361). These indicate that m-Emax can be used as an innovative parameter in TSWEUI to diagnosis PCa. TSWEUI is more cost-effective than MRI in diagnosing PCa.

MXene-Based Skin-Like Hydrogel Sensor and Machine Learning-Assisted Handwriting Recognition.

Conductive hydrogels are widely used in flexible sensors owing to their adjustable structure, good conductivity, and flexibility. The performance of excellent mechanical properties, high sensitivity, and elastic modulus compatible with human tissues is of great interest in the field of flexible sensors. In this paper, the functional groups of trisodium citrate dihydrate (SC) and MXene form multiple hydrogen bonds in the polymer network to prepare a hydrogel with mechanical properties (Young's modulus (23.5-92 kPa) of similar human tissue (0-100 kPa)), sensitivity (stretched GF is 4.41 and compressed S1 is 5.15 MPa-1), and durability (1000 cycles). The hydrogel is able to sensitively detect deformations caused by strain and stress and can be used in flexible sensors to detect human movement in real time such as fingers, wrists, and walking. In addition, the combination of matrix sensing and machine learning was successfully used for handwriting recognition with an accuracy of 0.9744. The combination of machine learning and flexible sensors shows great potential in areas such as healthcare, information security, and smart homes.

The feasibility and safety of biomaterials for posterior scleral reinforcement in rabbits.

To explore the feasibility and safety of biomaterials for posterior scleral reinforcement (PSR) in rabbits. Decellularization and genipin crosslink were applied to the fresh bovine pericardium and porcine endocranium, and then mechanical properties, suture retention strength, and stability were tested. PSR operation was performed on 24 rabbit eyes using treated biological materials. Ophthalmic examination was performed regularly before and after PSR operation (1 week, 1 month, 3 months, 6 months). To evaluate the effectiveness, A ultrasound, diopter, and optical coherence tomography were conducted. General condition, fundus photograph, and pathological examination were recorded to evaluate the safety. Compared with genipin crosslinked bovine pericardium (Gen-BP) (21.29 ± 13.29 Mpa), genipin crosslinked porcine endocranium (Gen-PE) (34.85 ± 3.67 Mpa,P< 0.01) showed a closer elastic modulus to that of genipin crosslinked human sclera. There were no complications or toxic reactions directly related to the materials. Capillary hyperplasia, inflammatory cell infiltration, and collagen fiber deposition were observed, and the content of type I collagen fibers increased after PSR. Overall, the choroidal thickness of treated eyes was significantly thickened at different time points after PSR, which were 96.84 ± 21.08 µm, 96.72 ± 22.00 µm, 90.90 ± 16.57 µm, 97.28 ± 14.74 µm, respectively. The Gen-PE group showed changes that were almost consistent with the overall data. Gen-BP and Gen-PE are safe biological materials for PSR. The Gen-PE group demonstrated more significant advantages over the Gen-BP group in terms of material properties.

The radial dynamics and acoustic emissions of phase-shift droplets are impacted by mechanical properties of tissue-mimicking hydrogels.

Acoustic droplet vaporization (ADV) offers a dynamic approach for generating bubbles on demand, presenting new possibilities in biomedical applications. Although ADV has been investigated in various biomedical applications, its potential in tissue characterization remains unexplored. Here, we investigated the effects of surrounding media on the radial dynamics and acoustic emissions of ADV bubbles using theoretical and experimental methodologies. For theoretical studies, bubble dynamics were combined with the Kelvin-Voigt material constitutive model, accounting for viscoelasticity of the media. The radial dynamics and acoustic emissions of the ADV-bubbles were recorded via ultra-high-speed microscopy and passive cavitation detection, respectively. Perfluoropentane phase-shift droplets were embedded in tissue-mimicking hydrogels of varying fibrin concentrations, representing different elastic moduli. Radial dynamics and the acoustic emissions, both temporal and spectral, of the ADV-bubbles depended significantly on fibrin elastic modulus. For example, an increase in fibrin elastic modulus from ≈0.2 kPa to ≈6 kPa reduced the maximum expansion radius of the ADV-bubbles by 50%. A similar increase in the elastic modulus significantly impacted both linear (e.g., fundamental) and nonlinear (e.g., subharmonic) acoustic responses of the ADV-bubbles, by up to 10 dB. The sensitivity of ADV to the surrounding media was dependent on acoustic parameters such as driving pressure and the droplets concentration. Further analysis of the acoustic emissions revealed distinct ADV signal characteristics, which were significantly influenced by the surrounding media.

Dynamic composite hydrogels of gelatin methacryloyl (GelMA) with supramolecular fibers for tissue engineering applications.

In the field of tissue engineering, there is a growing need for biomaterials with structural properties that replicate the native characteristics of the extracellular matrix (ECM). It is important to include fibrous structures into ECM mimics, especially when constructing scar models. Additionally, including a dynamic aspect to cell-laden biomaterials is particularly interesting, since native ECM is constantly reshaped by cells. Composite hydrogels are developed to bring different combinations of structures and properties to a scaffold by using different types and sources of materials. In this work, we aimed to combine gelatin methacryloyl (GelMA) with biocompatible supramolecular fibers made of a small self-assembling sugar-derived molecule (N-heptyl-D-galactonamide, GalC7). The GalC7 fibers were directly grown in the GelMA through a thermal process, and it was shown that the presence of the fibrous network increased the Young's modulus of GelMA. Due to the non-covalent interactions that govern the self-assembly, these fibers were observed to dissolve over time, leading to a dynamic softening of the composite gels. Cardiac fibroblast cells were successfully encapsulated into composite gels for 7 days, showing excellent biocompatibility and fibroblasts extending in an elongated morphology, most likely in the channels left by the fibers after their degradation. These novel composite hydrogels present unique properties and could be used as tools to study biological processes such as fibrosis, vascularization and invasion.

Effect of "fast"-crystallization and simultaneous glazing on physicochemical properties of lithium-disilicate CAD/CAM ceramic.

OBJECTIVE: Evaluate the impact of a "fast" crystallization and simultaneous-glazing on the physicochemical properties of lithium-disilicate CAD/CAM-ceramic. METHODS: Lithium-disilicate bars and crowns (IPS e.max CAD, Ivoclar-Vivadent) were divided into four groups (n = 30): WG/F (WG=with glaze/F=fast crystallization), NG/F (NG=no glaze), WG/C (C=conventional crystallization), and NG/C. A liquid/powder glaze system was used (IPS Ivocolor®, Ivoclar-Vivadent). Specimens were crystallized (Programat P310, Ivoclar-Vivadent) using the P161 program for C (approx. 20-25 min), and P165 for F (approx. 14-16 min). Bars (n = 30) underwent three-point bending tests (flexural strength-FS in MPa and modulus of elasticity-E in GPa) using a universal testing machine. Crowns were analyzed via scanning electron microscopy (SEM) after selective etching, and to Raman, FTIR-ATR, and X-ray diffraction (XRD) spectroscopies to assess chemical composition. RESULTS: For FS, both factors/interaction were statistically significant. C (427.48±42.41 MPa) showed significantly higher values than F (409.82±38.82 MPa). WG (398.32±29.80 MPa) exhibited significantly lower FS than NG (438.21±41.77 MPa). For E data, both factors/interaction were significant. NG (90.28±14.71 GPa) displayed higher E than WG (83.07±5.69 GPa), while C (90.08±12.98 GPa) exhibited higher E than F (83.46±9.40 GPa). NG/C showed the best results for both variables. F groups showed (SEM) porous surfaces and crack-like marks on crystals. FTIR, Raman and XRD spectra confirmed the typical composition of a lithium-disilicate glass ceramic, and some attenuated signals and structural variations (XRD) in WG. CONCLUSIONS: "Fast" crystallization and simultaneous-glazing produced weaker/less-rigid structures with irregular crystals and glassy phases. Simultaneous glazing may have hindered proper thermal distribution during crystallization. SIGNIFICANCE: "Fast" crystallization and simultaneous glazing with non-recommended systems, can adversely affect the final properties of lithium disilicate restorations.