Homogeneous Material Research Articles

A new insight to investigate the strain distribution, evolution, and crack development of cement-stabilized coral aggregate

Cement-stabilized coral aggregate (CSCA) can be used as a base material for roads and airports in island engineering. In this study, four-point bending (FPB) tests were conducted on CSCA with different prefabricated crack depths, and distributed fiber optic sensor (DFOS) was used. The testing process of the CSCA beams was simulated using an improved bond-based peridynamic (BBPD) model that combines the bilinear damage principle and fracture parameters random field. The results indicate that DFOS has the potential to monitor strain evolution and detect crack in CSCA. The strain distribution in the spanwise direction of the beam during the plastic phase presents a single peak, which can be described by a Pearson-VII function. The fracture location can be predicted from the positions of the tensile strain peaks. The neutral axis begins to move gradually toward the compressed part of the specimen after the external load greater than 0.6 Pmax. The compression modulus of the CSCA material peaks is 4500 MPa, that is three times larger than its tensile modulus and can satisfy the requirement of semi-rigid base layer construction of island roads. The improved BBPD model is able to effectively simulate the strain-softening behavior of CSCA materials with consideration of the effect of material inhomogeneity on the actual fracture path. The peak load prediction error was less than 7 %. The R2 between the numerically predicted load-displacement curves and the test results were bigger than 0.95. The improved BBPD method can predict the actual fracture location of the specimen with a horizontal position deviation of less than 2 cm. The bending fracture process of CSCA are further explored from both experimental and numerical simulations by this study.

Structural evolution study by solid-state NMR of photopolymerizable aluminophosphosilicate hybrid materials

Aluminophosphosilicate materials of composition (mol.%) xSiO2[(Al2O3)50–(P2O5)50]100-x were prepared through sol-gel method and heat-treated yielding non-crystalline materials. The structural evolution from the hybrid to heat-treated material as a function of the SiO2 content was studied by 13C, 29Si, 31P and 27Al solid-state NMR, infrared spectroscopies, X-ray diffraction and differential scanning calorimetry (DSC). NMR analyses showed the AlPO4 formation in the matrix and heterocondensation, forming Al-O-P and P-O-Si linkages. The heat treatment promoted the formation of a more interconnected SiO2 tetrahedra network as the SiO2 content increased. Similar to the hybrid materials, the increase of SiO2 content induces the replacement of P-O-Al(IV) bonds by Si-O-Al(IV) bonds in the heat-treated materials as confirmed by 27Al NMR and 27Al{31P} REDOR data, which was also supported by Raman analysis. This sol-gel route provides a novel way to fabricate new homogeneous materials, which can be doped with rare earths and applied to new optical devices.

Experimental and Theoretical Predictors for Redox Potentials of Bispyridinylidene Electron Donors.

Bispyridinylidenes are neutral organic molecules capable of two-electron oxidation at a range of redox potentials that are widely tunable by choice of substituent, making them attractive as homogeneous organic reductants and active materials in redox flow batteries. In an effort to readily predict the redox potentials of this important class of compounds, we have developed correlations between the experimental redox potentials and both experimental and theoretical predictors. On the experimental side, we show that multinuclear NMR chemical shifts of related pyridinium ions correlate well with the redox potentials of bispyridinylidenes, with R2 and standard errors (S) reaching 0.9810 and 0.048 V, respectively, when the 13C (N-CH3) and 1H (ortho) chemical shifts are used together. Theoretical studies of the bispyridinylidenes and their doubly oxidized bipyridinium ions gave a range of predictively valuable equations at various levels of computational cost. This ranged from a simple model using only the EHOMO of the bispyridinylidenes (R2=0.9689; S=0.060 V), to a more computationally intensive model which include solvation effects for both redox states which gave the highest predictive value for all methods (R2=0.9958; S=0.022 V). This work will guide further studies of this important class of molecules.

Local and quantitative measurement of mechanical properties by electrical-nanoindentation in situ SEM: Application to a multi-phase AgCuPd alloy

Nanoindentation has now become the key technique for measuring the mechanical properties of materials at small scales. However, the quantitative and accurate processing of nanoindentation data relies on a physical quantity that is not directly available: the contact area (Ac) between the indenter tip and the sample under test. In complex systems, determining Ac is challenging due to the limitations of standard methods: analytical models have restricted validity domains (sample homogeneity and rheology), and post-mortem observations of residual imprints are time-consuming, do not appraise property gradients and cannot be applied to materials with significant elastic recovery.In this paper, a comprehensive methodology is proposed to continuously measure contact area during indentation. The proposed methodology, referred to as electrical-nanoindentation (ENI), is based on real-time monitoring of the electrical contact resistance (ECR). The protocol only requires mechanical and electrical calibrations of the indenter tip on reference materials, leading to one-to-one relationship between ECR and contact area. An original approach is also proposed to deal with the presence of surface passivating layers that generally disturb ECR measurements. As an illustration, the methodology is applied to the characterization of a multi-phase alloy (MPA) composed of silver, copper and palladium. This alloy raises the same challenges as those usually faced by nanoindentation in advanced metallurgy: heterogenous distribution of individual phases at the micro-scale, composite response of a complex mixture of hard/stiff and ductile/soft phases, … In addition, the ohmicity of contact is disturbed by surface passivating layers. Despite these numerous hindrances, the proposed methodology is successfully applied to this material. The evolution of contact area is compared with standard methods: an impressive accuracy of <2% standard-deviation is achieved when compared to post-mortem observations. The elastic moduli and hardnesses of individual phases are then accurately extracted. In addition, in order to gain in spatial definition, the ENI set-up is integrated into a scanning electron microscope (SEM), enabling indent positioning with a precision close to 100 nm.Two challenges are successfully met with the ENI methodology. On a mechanical point of view, the response of individual phases can be identified despite the complex rheology of heterogeneous materials, proving the approach applies to all mechanical behaviors (sink-in or pile-up rheologies, homogeneous or heterogeneous materials, with or without elastic recovery, …). On an electrical point of view, even if contact ohmicity is the only requirement of the methodology, it is possible to identify and overcome deviations from contact ohmicity induced by surface passivation. In particular, the non-linear resistive contribution of insulating layers fades during indentation thanks to its dependence as the reciprocal of the square of contact radius. The present work provides the keys to monitoring the contact area on any metallic sample, whether oxide-free or oxidized, making this methodology a promising alternative to standard methods.

Free and forced vibrations of beams under distributed load

Introduction. Many years of experience in design and operation of structures prove that the reliability of structures cannot be ensured by strength calculations alone. In addition to strength and stiffness of structures, their vibrations are often required to be considered. These types of calculations appear highly comprehensive, involving a large number of different factors to be taken into account. At present, as structures are becoming more and more complex, great attention is paid to seismic design, which is especially relevant for buildings subjected to high seismic loads. Engineering structures experience increased loads associated with the above-mentioned and other reasons. Free and forced vibrations of various elastic structures obtain a significant relevance among researchers as manifested by numerous publications on this issue.Aim. To present a complete mathematical problem for the two most common methods of end restraint, to determine natural frequency spectrum and eigenforms of beam vibrations.Materials and methods. The present study involves a beam of variable cross-section made of homogeneous material, subjected to transverse distributed load, which makes bending vibrations. Free and forced vibrations are described by differential equations. The homogeneous equation is solved first, then – the nonhomogeneous equation. The study involves application of D’Alembert’s principle, variable separation method, and test checks.Results. The authors obtained a fourth-order partial differential equation with constant coefficients and determined a natural frequency spectrum and eigenforms of vibrations. A high accuracy of the obtained results enables the characteristics of free and forced vibrations of beams to be determined in a shorter way with fewer calculations. Notably, the amplitude and eigenform of forced vibrations of beams appear dependent on the proximity of the disturbing frequency to the eigenvalues and the phase change of components in vector disturbance process.Conclusions. The authors advanced hypotheses about a dependence between the damping and linear viscous friction coefficients as well as about the constancy of damping coefficient for all eigenvalues.

Clinical boundary conditions for propagation-based X-ray phase contrast imaging: from bio-sample models targeting to clinical applications.

Typical propagation-based X-ray phase contrast imaging (PB-PCI) experiments using polyenergetic sources are tested in very ideal conditions: low-energy spectrum (mainly characteristic X-rays), small thickness and homogeneous materials considered weakly absorbing objects, large object-to-detector distance, long exposure times and non-clinical detector. Explore PB-PCI features using boundary conditions imposed by a low power polychromatic X-ray source (X-ray spectrum without characteristic X-rays), thick and heterogenous materials and a small area imaging detector with high low-detection radiation threshold, elements commonly found in a clinical scenario. A PB-PCI setup implemented using a microfocus X-ray source and a dental imaging detector was characterized in terms of different spectra and geometric parameters on the acquired images. Test phantoms containing fibers and homogeneous materials with close attenuation characteristics and animal bone and mixed soft tissues (bio-sample models) were analyzed. Contrast to Noise Ratio (CNR), system spatial resolution and Kerma values were obtained for all images. Phase contrast images showed CNR up to 15% higher than conventional contact images. Moreover, it is better seen when large magnifications (>3) and object-to-detector distances (>13 cm) were used. The influence of the spectrum was not appreciable due to the low efficiency of the detector (thin scintillator screen) at high energies. Despite the clinical boundary condition used in this work, regarding the X-ray spectrum, thick samples, and detection system, it was possible to acquire phase contrast images of biological samples.

2D numerical modeling of crack propagation using SFEMD method of a LEHI material

Numerical methods today play a useful and important role in solving various problems related to fracture mechanics including modeling crack propagation, fretting fatigue and cohesion... Furthermore, these methods have been widely used to solve problems in linear and nonlinear fracture mechanics in cases of elastic, plastic fracture problems. The evaluation of stress intensity factor in 2D and 3D geometries, thus these techniques widely used for non-standard crack configurations. The objective of this work is study the effects of the crack length and the number of structural elements on the two crack parameters such as the stress intensity factor KI and KII and the contour integral (J). As well as presenting a numerical modeling of crack propagation, for a LEHIM (Linear Elastic Homogeneous Isotopic Material) with mechanical characteristics by the method SFEMD (Stretching Finite Element Method Developed), the model chosen with quadratic elements with 4 nodes (CPE4). However, this method is based on the effect of the number of contours and the number of elements around the crack tip on the variation of the stress intensity factors. In addition, the crack propagation criterion (MCSC) was used, a computer program was created in FORTRAN language to develop and evaluate the stress intensity factors and the contour integral (J). Several examples of crack lengths a = 0.7, 1.4, 2.1, 2.8 and 3.5 mm were used. Additionally, the number of items has been changed several times. The stress intensity factors of modes I and II and direction angles (α) are calculated to solve the problem using the ABAQUS finite element code. The results obtained by the SFEMD method and the results of the analytical method are very close.

Bioengineered self-assembled nanofibrils for high-affinity SARS-CoV-2 capture and neutralization

The recent coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spurred intense research efforts to develop new materials with antiviral activity. In this study, we genetically engineered amyloid-based nanofibrils for capturing and neutralizing SARS-CoV-2. Building upon the amyloid properties of a short Sup35 yeast prion sequence, we fused it to SARS-CoV-2 receptor-binding domain (RBD) capturing proteins, LCB1 and LCB3. By tuning the reaction conditions, we achieved the spontaneous self-assembly of the Sup35-LCB1 fusion protein into a highly homogeneous and well-dispersed amyloid-like fibrillar material. These nanofibrils exhibited high affinity for the SARS-CoV-2 RBD, effectively inhibiting its interaction with the angiotensin-converting enzyme 2 (ACE2) receptor, the primary entry point for the virus into host cells. We further demonstrate that this functional nanomaterial entraps and neutralizes SARS-CoV-2 virus-like particles (VLPs), with a potency comparable to that of therapeutic antibodies. As a proof of concept, we successfully fabricated patterned surfaces that selectively capture SARS-CoV-2 RBD protein on wet environments. Collectively, these findings suggest that these protein-only nanofibrils hold promise as disinfecting coatings endowed with selective SARS-CoV-2 neutralizing properties to combat viral spread or in the development of sensitive viral sampling and diagnostic tools.

Dynamic stress response in reservoirs stimulated by fluctuating fluid pressure during pulsating hydraulic fracturing

Determining the most effective scheme for fracturing operations depends on accurate calculations of reservoir stress. Traditional fracturing theories usually focus on stable fluid injection modes, which employ static assumptions in modelling and analysis. However, pulsating hydraulic fracturing (PHF) introduces fluctuating fluid pressure to stimulate reservoirs, which requires considering dynamic factors and exploring the dynamic stress response within the reservoir. Furthermore, reservoirs are often classified as homogeneous continuous or porous media materials, but the boundaries between these classifications are sometimes apparent. This paper investigated the development of both an elastodynamics model and a poroelastodynamics model for calculating dynamic stress responses during PHF. The staggered grid finite difference method addressed these models, with the outer boundary employing the perfectly matched layer (PML) method to simulate an infinite reservoir. The numerical simulation results were extensively verified and compared with analytical solutions, and the differences between various models and their relevant conditions were thoroughly analyzed. Analyzing fluid pressure fluctuation parameters revealed noteworthy insights into reservoir stress response characteristics. Results indicate that as the Biot coefficient and permeability increase, the disparities between the elastodynamics and poroelastodynamics models become prominent. In practical terms, high Biot coefficient or high permeability reservoirs necessitate using the poroelastodynamics model for accurate reservoir stress analysis. As the frequency of fluid pressure fluctuation increases, the amplitude of response of reservoir circumferential stress also increases, while the response amplitude of radial stress and fluid pressure decreases. These findings offer valuable theoretical guidance for parameter design in engineering applications during PHF.

Fe3O4@CNTs/WPU@CNF aerogel/Ag foam composites with a double-layer structure for absorption-dominated electromagnetic shielding performance

With the popularity of electronic devices, absorption-dominated multilayered electromagnetic shielding materials are increasingly attractive due to the effective decrease of second pollution compared to the traditional homogeneous electromagnetic shielding materials. However, the design of multilayered structure and strong interface adhesion of functional composite while keeping light weight and practical use is not readily to realize. Therefore, we propose herein a double-layer aerogel/foam composite electromagnetic shielding composite. The absorption layer is made by a nanocellulose (CNF)@waterborne polyurethane (WPU) aerogel, in which magnetic nano iron tetraoxide (Fe3O4) joined with carbon nanotubes (CNTs) to optimize the impedance matching. The reflection layer is a chemically silver-plated foam (AF) used to reflect the transmitted electromagnetic waves through its strong electrical conductivity, improving the overall ability of electromagnetic waves shielding and achieving enhanced electromagnetic shielding performance. The two layers are strongly combined by the adhesion of WPU without the use of adhesives. When the mass ratio of CNTs to Fe3O4 of 2:1 and the total mass fraction of 5 wt%, the EMI shielding efficiency of the composites reaches 62.81 dB in the X-band (8.2–12.4 GHz) at the thickness of 4 mm and the maximum value reaches a remarkable 76.63 dB at 1.17 GHz. The specific SE value of SSE/t reaches 1744.72 dB cm2 g−1. Thanks to the effect of AF layer, the average reflectivity is only 0.141, demonstrating an absorption-dominated shielding mechanism. In addition, the as-prepared composite material is remarkably flexible and deformation-resistant, with a density of only 0.0913 g cm−3 and can withstand approximately 85,000 times its own weight.

Global existence of nonlinear elastic waves: Non-hyperelastic case

For the Cauchy problem of nonlinear elastic wave equations for three-dimensional isotropic, homogeneous and hyperelastic materials with null condition, global existence of classical solutions with small initial data was proved in Agemi (2000) [1] and Sideris (2000) [17] independently. How to treat the more general non-hyperelastic case is suggested as an open problem in Agemi (2005) [2]. The aim of this paper is to resolve this problem.

Active-compensation of systematic error for the 1000 mm aperture flat interferometer

Large-aperture elements would induce unnegligible systematic errors due to material inhomogeneity, manufacturing or gravity, that are difficult to correct in an extreme large aperture flat interferometer and result in reference wavefront distortion. We propose an active-compensation method for systematic errors by employing a deformable mirror into the interferometer to modulate reference wavefront. A mapping relationship between sag of the deformable mirror and reference wavefront error is derived by theory of matrix optics, and two interferometer optical paths are designed for whether the deformable mirror is located at the pupil or not. The algorithm for calculating and controlling the sag of a deformable mirror can eliminate the need for the deformable mirror to be positioned at the pupil in order to achieve controllable modulation of the wavefront. This algorithm has been validated through the intentional introduction of systematic errors into the 1000 mm aperture flat interferometer for effective compensation. Moreover, the optimization algorithm in Ansys Zemax is utilized to calculate the optimal solution for surface shape of the deformable mirror, treating it as a nominal value. The algorithm error is on the order of 10−6 mm, falling within the acceptable tolerance range for the deformable mirror's surface shape.

Response properties of lattice metamaterials under periodically distributed boundary loads

We discuss response properties of lattice metamaterials to sinusoidal distributed static loads applied on a material edge. Analytical displacement solutions are obtained using a Fourier domain transfer matrix for both essential and natural boundary conditions, which are valid for a state of plane strain in orthorhombic lattices, as well as for planar metasurfaces. These solutions give sinusoidal displacement profiles in the material interior of the same wavenumber (spatial frequency) as the boundary load. Their amplitudes decay in the material interior in one of two possible ways, exponential or oscillatory exponential, depending on the lattice design and on the spatial frequency of the load. There is a tendency for the oscillatory exponential behavior to occur at lower wavenumbers representing smoother boundary loads. As explained on a specific example, comparing the metamaterial’s response amplitudes with those of a homogenous material also allows studying an effective, wavenumber-dependent shear modulus of the lattice, which can take both positive and negative values.

Vat Photopolymerization of Sepiolite Fiber and 316L Stainless Steel-Reinforced Alumina with Functionally Graded Structures.

Alumina (Al2O3) ceramics are widely used in electronics, machinery, healthcare, and other fields due to their excellent hardness and high temperature stability. However, their high brittleness limits further applications, such as artificial ceramic implants and highly flexible protective gear. To address the limitations of single-phase toughening in Al2O3 ceramics, some researchers have introduced a second phase to enhance these ceramics. However, introducing a single phase still limits the range of performance improvement. Therefore, this study explores the printing of Al2O3 ceramics by adding two different phases. Additionally, a new gradient printing technique is proposed to overcome the limitations of single material homogeneity, such as uniform performance and the presence of large residual stresses. Unlike traditional vat photopolymerization printing technology, this study stands out by generating green bodies with varying second-phase particle ratios across different layers. This study investigated the effects of different contents of sepiolite fiber (SF) and 316L stainless steel (SS) on various aspects of microstructure, phase composition, physical properties, and mechanical properties of gradient-printed Al2O3. The experimental results demonstrate that compared to Al2O3 parts without added SF and 316L SS, the inclusion of these materials can significantly reduce porosity and water absorption, resulting in a denser structure. In addition, the substantial improvements, with an increase of 394.4% in flexural strength and an increase of 316.7% in toughness, of the Al2O3 components enhanced by incorporating SF and 316L SS have been obtained.

Development of bone surrogates by material extrusion-based additive manufacturing to mimic flexural mechanical behaviour and fracture prediction via phase-field approach

Background and objectiveThe limited availability of human bone samples for investigation leads to the demand for alternatives. Bone surrogates are crucial in promoting research on the intricate mechanics of osseous tissue. However, solutions are restricted to commercial brands, which frequently fail to faithfully replicate the mechanical response of bone, or oversimplified customised simulants designed for a specific application. The manufacturing and assessment of reliable bone surrogates made of polylactic acid via material extrusion-based additive manufacturing are presented in this work. MethodsAn experimental and numerical study with 3D-printed dog-bone and prismatic specimens was carried out to characterise the polymeric feedstock and analyse the influence of process parameters under three-point bending and quasi-static conditions. Besides, three porcine rib samples were considered as a reference for the development of the artificial bones. Bone surrogates were manufactured from the 3D-scanned real bone geometries. In order to reproduce the trabecular and cortical bone, a lattice structure for the infill and a compact shell surrounding the core were employed. Infill density and shell thickness were evaluated through different printing configurations. Additionally, a computational analysis based on the phase-field approach was conducted to simulate the experimental tests and predict fracture. The modelling considered homogenisation of the infill material. ResultsOutcomes demonstrated the potential of the presented methodology. Maximum force and flexural stiffness were compared to real bone properties to find the optimal printing configuration, replicating the flexural mechanical behaviour of bone tissue. Certain configurations accurately reproduce the studied properties. Regarding the numerical model, strength and stiffness prediction was validated with experimental results. ConclusionsThe presented methodology enables the manufacturing of artificial bones with accurate geometries and tailored mechanical properties. Furthermore, the described modelling strategy offers a powerful tool for designing bone surrogates.

A fully coupled system of generalized thermoelastic theory for semiconductor medium

This study presents a new mathematical framework for analyzing the behavior of semiconductor elastic materials subjected to an external magnetic field. The framework encompasses the interaction between plasma, thermal, and elastic waves. A novel, fully coupled mathematical model that describes the plasma thermoelastic behavior of semiconductor materials is derived. Our new model is applied to obtain the solution to Danilovskaya’s problem, which is formed from an isotropic homogeneous semiconductor material. The Laplace transform is utilized to get the solution in the frequency domain using a direct approach. Numerical methods are employed to calculate the inverse Laplace transform, enabling the determination of the solution in the physical domain. Graphical representations are utilized to depict the numerical outcomes of many physical fields, including temperature, stress, displacement, chemical potential, carrier density, and current carrier distributions. These representations are generated for different values of time and depth of the semiconductor material. Ultimately, we receive a comparison between our model and several earlier fundamental models, which is then graphically represented.

Multi-approach study, digitization and dissemination of a Bronze-Age engraved cup found in Filo Braccio, Filicudi (Aeolian Islands, Italy)

This paper presents a multidisciplinary study combining photogrammetry, near-infrared (NIR) imaging and archaeological analysis to analyse a 1900-1800 BC engraved cup, found at the Bronze Age site of Filo Braccio in Filicudi, Aeolian Islands, Italy. The artefact is unique within the contemporary ‘Capo Graziano’ culture, featuring a rare complex figural scene engraved along the exterior walls; the “scene” provides insights into the prehistoric culture of Filicudi and the Aeolian Islands. The study focused on generating an accurate three-dimensional (3D) model to i) support archaeological research on the artefact's engravings and ii) create engaging digital media for remote and on-site visitors. Photogrammetry used high-resolution photographs taken around the object and control points for metric accuracy assessment. This study also utilises NIR and visible light imaging to examine the engraved cup. The photogrammetric workflow provided a realistic 3D model textured with both visible and NIR data: the 3D model enabled to improve the reading of the engraved scene, revealing horizontal registers of figures, while NIR imaging highlighted material inhomogeneity. The resulting 3D model achieved a high level of detail, with 4381407 faces and a root mean square (RMS) reprojection error of approximately 3.9 µm. The NIR imaging revealed additional surface details not visible in the standard photographs. For dissemination, the optimised 3D model was uploaded to Sketchfab with informative annotations, enabling remote study and cultural promotion of the artefact. This multi-approach methodology offers a valuable tool for comprehensive artefact documentation and analysis, providing new insights into the artefact's complex figural scene.

Heterogeneous Integration of Memristive and Piezoresistive MDMO-PPV-Based Copolymers in Nociceptive Transmission with Fast and Slow Pain for an Artificial Pain-Perceptual System.

Nociceptive pain perception is a remarkable capability of organisms to be aware of environmental changes and avoid injury, which can be accomplished by specialized pain receptors known as nociceptors with 4 vital properties including threshold, no adaptation, relaxation, and sensitization. Bioinspired systems designed using artificial devices are investigated to imitate the efficacy and functionality of nociceptive transmission. Here, an artificial pain-perceptual system (APPS) with a homogeneous material and heterogeneous integration is proposed to emulate the behavior of fast and slow pain in nociceptive transmission. Retention-differentiated poly[2-methoxy-5-(3,7-dimethyoctyoxyl)-1,4-phenylenevinylene] (MDMO-PPV) memristors with film thicknesses of 160 and 80nm are manufactured and adopted as A-δ and C nerve fibers of nociceptor conduits, respectively. Additionally, a nociceptor mimic, the ruthenium nanoparticles (Ru-NPs)-doped MDMO-PPV piezoresistive pressure sensor, is fabricated with a noxiously stimulated threshold of 150kPa. Under the application of pricking and dull noxious stimuli, the current flows predominantly through the memristor to mimic the behavior of fast and slow pain, respectively, in nociceptive transmission with postsynaptic potentiation properties, which is analogous to biological pain perception. The proposed APPS can provide potential advancements in establishing the nervous system, thus enabling the successful development of next-generation neurorobotics, neuroprosthetics, and precision medicine.

Foramen magnum stenosis in patients with mucopolysaccharidoses: diagnosis and surgical treatment. Review of literature

Cervico-medullary compression and atlantoaxial dislocation syndromes are the dominant clinical manifestations of mucopolysaccharidoses at the craniovertebral level. The review provides an analysis of international literary sources concerning modern aspects of diagnosis and neurosurgical correction of the foramen magnum stenosis in patients with different types of mucopolysaccharidoses. The existing surgical approaches to determining the indications and choosing the method of surgical treatment and some aspects of the use of enzyme replacement therapy and hematopoietic stem cell transplantation are presented. A variety of options for surgical correction of pathology at the craniovertebral level have been demonstrated in patients with different types of mucopolysaccharidosis, however the described recommendations can be considered from the point of view of traditions of the hospitals or personal experience of surgeons, but not as recognized standards of treatment this pathology. Further accumulation of individual observations or clinical series is required to conduct a comparative analysis of the effectiveness of various approaches on a sufficiently large and homogeneous material to determine standards for the diagnosis and treatment of craniovertebral junction pathology in patients with mucopolysaccharidoses.

A hybrid thermo-mechanical phase-field model for anisotropic brittle fracture

The phase-field modeling approach is integrated with the isogeometric-meshfree approach to investigate the coupled thermo-mechanical fracture behaviors of composite materials, accounting for material anisotropy. The present approach is formulated within a thermodynamic framework, exploring the effects of both thermal and mechanical factors on crack evolution. The crack driving force in composites is determined by the collective contributions from both fibers and the matrix. Moreover, a hybrid computational framework, enhanced with an adaptive mesh refinement technique, is proposed for the efficient implementation of thermo-mechanical fracture. Finally, simulations of the thermal deformation and fracture processes in both homogeneous and composite materials are implemented to verify the present approach. The impact of the weak material anisotropy, such as anisotropic thermal conductivity and material strength, along with the strong anisotropy coefficient on fracture patterns in orthotropic composites is also investigated. The simulation results demonstrate that the developed approach can predict complex failure patterns in composites under thermo-mechanical loading, thus offering insights for the design of composites.