Widely distributable and retainable in-situ gelling material for treating myocardial infarction.

Intramyocardial hydrogel injection is a promising therapy to prevent negative remodeling following myocardial infarction (MI). In this study, we report a mechanism for in-situ gel formation without external stimulation, resulting in an injectable and tissue-retainable hydrogel for MI treatment, and investigate its therapeutic outcomes. A liquid-like polymeric solution comprising poly(3-acrylamidophenylboronic acid-co-acrylamide) (BAAm), polyvinyl alcohol (PVA), and sorbitol (S) increases the viscous modulus by reducing the pre-added sorbitol concentration is developed. This solution achieves a sol-gel transition in-vitro in heart tissue by spontaneously diffusing the sorbitol. After intramyocardial injection, the BAAm/PVA/S with lower initial viscous modulus widely spreads in the myocardium and gelate compared to a viscoelastic alginate (ALG) hydrogel and is retained longer than the BAAm/S solution. Serial echocardiogram analyses prove that injecting the BAAm/PVA/S into the hearts of subacute MI rats significantly increases the fraction shortening and ejection shortening and attenuates the expansion of systolic LV diameter for up to 21 d after injection compared to the saline injection as a control, but the ALG injection does not. In addition, histological evaluation shows that only the BAAm/PVA/S decreases the infarct size and increases the wall thickness 21 d after injection. The BAAm/PVA/S intramyocardial injection is better at restraining systolic ventricular dilatation and cardiac failure in the rat MI model than in the control groups. Our findings highlight an effective injectable hydrogel therapy for MI by optimizing injectability-dependent distribution and retention of injected material. STATEMENT OF SIGNIFICANCE: In-situ gelling material is a promising strategy for intramyocardial hydrogel injection therapy for myocardial infarction (MI). Since the sol-gel transition of reported materials is driven by external stimulation such as temperature, pH, or ultraviolet, their application in vivo remains challenging. In this study, we first reported a synthetic in-situ gelling material (BAAm/PVA/S) whose gelation is stimulated by spontaneously reducing pre-added sorbitol after contacting the heart tissue. The BAAm/PVA/S solution spreads evenly, and is retained for at least 21 d in the heart tissue. Our study demonstrated that intramyocardial injection of the BAAm/PVA/S with more extensive distribution and longer retention had better effects on preventing LV dilation and improving cardiac function after MI than that of viscoelastic ALG and saline solution. We expect that these findings provide fundamental information for the optimum design of injectable biomaterials for treating MI.

Optimization of urban emergency support material distribution under major public health emergencies based on improved sparrow search algorithm.

The outbreak of major public health emergencies such as the coronavirus epidemic has put forward new requirements for urban emergency management procedures. Accuracy and effective distribution model of emergency support materials, as an effective tool to inhibit the deterioration of the public health sector, have gradually become a research hotspot. The distribution of urban emergency support devices, under the secondary supply chain structure of "material transfer center-demand point," which may involve confusing demands, is studied to determine the actual situation of fuzzy requests under the impact of an epidemic outbreak. An optimization model of urban emergency support material distribution, based on Credibility theory, is first constructed. Then an improved sparrow search algorithm, ISSA, was designed by introducing Sobol sequence, Cauchy variation and bird swarm algorithm into the structure of the classical SSA. In addition, numerical validation and standard test set validation were carried out and the experimental results showed that the introduced improved strategy effectively improved the global search capability of the algorithm. Furthermore, simulation experiments are conducted, based on Shanghai, and the comparison with existing cutting-edge algorithms shows that the designed algorithm has stronger superiority and robustness. And the simulation results show that the designed algorithm can reduce vehicle cost by 4.83%, time cost by 13.80%, etc. compared to other algorithms. Finally, the impact of preference value on the distribution of emergency support materials is analyzed to help decision-makers to develop reasonable and effective distribution strategies according to the impact of major public health emergencies. The results of the study provide a practical reference for the solution of urban emergency support materials distribution problems.

Optimization of regional emergency supplies distribution vehicle route with dynamic real-time demand.

Given the particular characteristics of a sudden outbreak of an epidemic on a regional scale and considering the possible existence of a latent period process, this paper takes the distribution of regional emergency supplies as the research object. Form the proposes a dynamic vehicle path problem from the perspective of real-time demand changes. First, when there is a sudden outbreak of a small-scale epidemic, there is uncertainty about demand in the epidemic area. The objective functions of minimizing the vehicle travel route cost of emergency vehicles, the late arrival penalty cost of emergency vehicles, and the fixed cost of emergency vehicles, as well as the objective function of minimizing the total distance traveled by vehicles, are established. Second, a mathematical model of the dynamic real-time demand vehicle route problem is built using the actual vehicle routing problem as a basis. The model is then solved using the SFSSA method. Finally, the computational results demonstrate that the SFSSA algorithm can effectively reduce transportation cost and distance when solving the constructed mathematical model problem, providing a solution to the problem of optimizing the route of emergency material distribution vehicles for a regional scale.

Optimal path planning and data simulation of emergency material distribution based on improved neural network algorithm.

Today, data storage technology is also gradually improving. Various industries can store massive amounts of data for analysis. The global climate change and the bad ecology led to frequent occurrence of natural disasters. Therefore, it is necessary to establish an effective emergency materials distribution system. The neural network model is used to calculate and the optimal emergency distribution route is analyzed according to the historical information and the data. Considering backpropagation, this paper further disposing a method to further improve the calculation of neural network algorithm. From the perspective of structural parameters of neural network algorithms, this paper uses genetic algorithms to construct predictions, and combines the actual purpose of material distribution after disasters. Considering the capacity constraints of distribution centers, time constraints, material needs of disaster relief points and different means of transportation, a dual-objective path planning with multiple distribution centers and multiple disaster relief points with the shortest overall delivery time and lowest overall delivery cost is constructed. By establishing an emergency material distribution system, it can maximize the prompt and accurate delivery after a natural disaster occurs, and solves the urgent needs of the people.

Mechanical Performance of Lightweight-Designed Honeycomb Structures Fabricated Using Multijet Fusion Additive Manufacturing Technology.

Cellular structures including three-dimensional lattices and two-dimensional honeycombs have significant benefits in achieving optimal mechanical performance with light weighting. Recently developed design techniques integrated with additive manufacturing (AM) technologies have enhanced the possibility of fabricating intricate geometries such as honeycomb structures. Generally, failure initiates from the sharp edges in honeycomb structures, which leads to a reduction in stiffness and energy absorption performance. By material quantity, these hinges account for a large amount of material in cells. Therefore, redesigning of honeycomb structures is needed, which can improve aforementioned characteristics. However, this increases the design complexity of honeycombs, such that novel manufacturing techniques such as AM has to be employed. This research attempts to investigate the optimal material distribution of three different topologies of honeycomb structures (hexagonal, triangular, and square) with nine different design configurations. To achieve this, higher amount of material was distributed at nodes in the form of fillets while keeping overall weight of the structure constant. Furthermore, these design configurations were analyzed in terms of stiffness, energy absorption, and the failure behavior by performing finite element analysis and experimental tests on the samples manufactured using Multijet fusion AM technology. It was found that adding material to the edges can improve the mechanical properties of honeycombs such as stiffness and energy absorption efficiency. Furthermore, the failure mechanism is changed due to redistribution of material in the structure. The design configurations without fillets suffer from brittle failure at the start of the plastic deformation, whereas the configurations with increased material proportion at the nodes have larger plastic deformation zones, which improves the energy absorption efficiency.

Proper Generalized Decomposition for Parametric Study and Material Distribution Design of Multi-Directional Functionally Graded Plates Based on 3D Elasticity Solution.

The use of mesh-based numerical methods for a 3D elasticity solution of thick plates involves high computational costs. This particularly limits parametric studies and material distribution design problems because they need a large number of independent simulations to evaluate the effects of material distribution and optimization. In this context, in the current work, the Proper Generalized Decomposition (PGD) technique is adopted to overcome this difficulty and solve the 3D elasticity problems in a high-dimensional parametric space. PGD is an a priori model order reduction technique that reduces the solution of 3D partial differential equations into a set of 1D ordinary differential equations, which can be solved easily. Moreover, PGD makes it possible to perform parametric solutions in a unified and efficient manner. In the present work, some examples of a parametric elasticity solution and material distribution design of multi-directional FGM composite thick plates are presented after some validation case studies to show the applicability of PGD in such problems.

Taste-masking mechanism of layer-by-layer self-assembly coating investigated by synchrotron radiation-based Fourier-transform infrared spectromicroscopy / 药学学报

Ibuprofen lipid pellets prepared by melting method could mask the bitter taste of the drug to some extent. The pellets were further coated with chitosan (cationic) and gelatin (anionic) by ionic interaction layerby- layer self-assembly (LBL) coating to improve masking effects. In this paper, the release percentage of drugs in short time (1 min) was utilized as an indicator for the taste-masking, and it had confirmed the LBL coating inhibited the release of model drug of ibuprofen. Synchrotron radiation-based Fourier-transform infrared spectromicroscopy (SR-FTIR) has been applied to investigate the material distributions on the cross section of pellets and film. Characteristic absorptions of the compositions were obtained by SR-FTIR single spectrum scanning. The distributions of the drug and materials in coated films were determined by SR-FTIR mapping. The FTIR absorptions of chitosan and gelatin on the surface of lipid pellets was examined to verify the existence of chitosan and gelatin on the surface and a film formed using SR-FTIR ratio analysis. Whilst pellets coated only by chitosan or gelatin did not show the typical absorption of chitosan or gelatin, which confirmed the effects of ionic interaction on the film forming process. In conclusion, the method of SR-FTIR established for the study of the existence and distribution of materials in coated film offers a new choice for researches on membranes/films in drug delivery systems and pharmaceutical preparations.

Stress distributions in human teeth modeled with a natural graded material distribution.

OBJECTIVE: This study aimed to investigate how the structural stress distribution in human teeth could be affected by the presence of a graded material distribution often found in nature using the finite element (FE) method. METHODS: Hydroxyapatite (HA) tablets with different densities were scanned using a Micro-CT scanner to obtain a relationship between the attenuation coefficient and the elastic modulus via the mineral density. Two maxillary premolars were scanned to provide the geometries and material distributions for constructing the FE models. Stress analyses were then performed to compare the stress distributions between the models with uniform material properties and those with a graded material layout. RESULTS: The attenuation coefficients and densities of the HA tablets measured ranged from 109.77 to 175.01cm(-1) and 0.99 to 1.54gcm(-3), respectively. A linear relationship was found between them and applied to the premolars to derive the elastic modulus via the mineral density. Stress analysis showed that, with a graded material layout, the peak maximum principal stress in the enamel was reduced by about 50% and the overall stress distribution was more uniform. Along the DEJ, two stress peaks were found near the dentin horns, but again they were much lower in magnitude in the models with a graded material distribution. SIGNIFICANCE: The results from this study support the hypothesis that the material layout in human enamel is optimized for distributing the external load evenly. They also point to the importance of taking into account the graded material distribution in nature when performing stress analysis for tooth structures.

Relationship between microstructure, material distribution, and mechanical properties of sheep tibia during fracture healing process.

The aim of this study was to investigate the relationship between microstructural parameters, material distribution, and mechanical properties of sheep tibia at the apparent and tissue levels during the fracture healing process. Eighteen sheep underwent tibial osteotomy and were sacrificed at 4, 8, and 12 weeks. Radiographs and micro-computed tomography (micro-CT) scanning were taken for microstructural assessment, material distribution evaluation, and micro-finite element analysis. A displacement of 5% compressive strain on the longitudinal direction was applied to the micro-finite element model, and apparent and tissue-level mechanical properties were calculated. Principle component analysis and linear regression were used to establish the relationship between principle components (PCs) and mechanical parameters. Visible bony callus formation was observed throughout the healing process from radiographic assessment. Apparent mechanical property increased at 8 weeks, but tissue-level mechanical property did not increase significantly until 12 weeks. Three PCs were extracted from microstructural parameters and material distribution, which accounted for 87.592% of the total variation. The regression results showed a significant relationship between PCs and mechanical parameters (R>0.8, P<0.05). Results of this study show that microstructure and material distribution based on micro-CT imaging could efficiently predict bone strength and reflect the bone remodeling process during fracture healing, which provides a basis for exploring the fracture healing mechanism and may be used as an approach for fractured bone strength assessment.

Biomechanical assessment for effects of vibration on the rehabilitation process of osteoporosis / 医用生物力学

Objective To explore biomechanical assessment for the effects on vibration against bone loss by investigating the relationship between material distribution and mechanical properties of rat femur cortical bone based on Micro CT. Methods 35 rats were randomly divided into intermittent vibration groups with the interval of 1, 3, 5, 7 days, and continuous vibration group, respectively. Tail suspended model of disuse osteoporosis was set up. All rats were loaded with mechanical vibration of 35 Hz and 0.3 g, and killed after 8 weeks. Micro CT scanning of the left femur of each rat was performed. Three-dimensional finite element model of the cortical bone was established to calculate the apparent and tissue-level mechanical parameters. Principal components (PCs) were extracted from material distribution, intermittent days and volume fraction by principal components analysis (PCA). Results The PCA revealed the three independent components that could fully explaine the variability of cortical bone characteristics under vibration. The linear regression equations were also created between the material property and the apparent and tissue-level mechanical properties, respectively. Mechanical properties of the cortical bone were influenced by material distribution mostly, and the volume fraction and intermittent days were next in importance. Conclusions The cortical bone material distribution can reflect changes in its mechanical properties, and the bone strength could be assessed by establishing the linear relationship, which could provide a theoretical basis for osteoporosis prevention and treatment as well as the assessment on its rehabilitation process.