Microscopic Damage Research Articles

Mechanical properties and the mechanism of microscopic thermal damage of basalt subjected to high-temperature treatment

Mechanical properties and the mechanism of microscopic thermal damage of basalt subjected to high-temperature treatment

Study on mechanical properties and microscopic damage mechanism of tight sandstone reservoir under uniaxial compression

Due to the characteristics of low porosity, low permeability and serious anisotropy in tight reservoirs, it is difficult for conventional hydraulic fracturing theory to accurately guide the efficient exploitation of tight reservoirs. It has been shown that the reservoir rock mechanical properties are the key factor impacting the fracturing effect, but the current research on the damage properties of tight reservoir rocks is not comprehensive enough. Therefore, in order to improve the fracturing theory of tight reservoirs, this paper first explores the evolution mechanism of rock fractures through uniaxial compression experiments. Secondly, based on the particle discrete element method, the damage and failure process of tight sandstone under uniaxial compression is simulated from the microscopic scale. The test results show that the rock failure mainly includes tensile failure, shear failure, and tensile-shear failure; Internal micro-fractures will interconnect during rock destruction to form primary fractures through the rock mass, while secondary micro-fractures will also be generated. The numerical simulation results show that when the rock is subjected to tensile-shear failure, with the increase of load, tensile micro-fractures are mainly produced in the specimen, accompanied by a few shear fractures. Under the joint action of shear failure and tensile failure, V-shaped cracks are easily formed in rock. The tensile strength of rock is mainly affected by the microscopic tensile strength, and the cohesive force, modulus, stiffness ratio, friction coefficient and friction angle have significant effects on the compressive strength of rock. Therefore, a reasonable choice of microscopic parameters can realistically simulate the compression-tensile strength ratio of the rock. The research results of this paper can provide the theoretical basis of rock mechanics for the efficient exploitation of tight reservoirs.

Polymer shape effect on damage evolution, internal defects and crack propagation of 3D-printed polymer-based cementitious backfill

The strength property and damage mode of cementitious tailings backfill (CTB) are governed by its structural characteristics in the presence of the microstructure/internal defect effects. However, this correlation is still unclear for 3D-printed polymer (3D-PPL) based CTB materials. Hence, the mechanical properties of microscopic damage and fracture evolution of 3D-PPL reinforced CTB were studied in this study. The fracture of CTBs with three shapes of polymer (cross, quarter, and EEP) were visualized and digitally characterized by the Brazilian splitting test, scanning electron microscopy (SEM) and industrial computed tomography. Experimental results indicate that CTB’s failure mode mainly starts from the low-density pore area, gradually evolves to a crack, and finally expands to the main crack by the center of the specimen. 3D-PPL has a certain interface bonding and supporting effect on CTB specimens, and the 3D-PPL specimen’s porosity is significantly below that of ordinary backfill. Incorporating 3D-PPL into CTBs effectively decrease the penetrated pore number, while enhancing the density of CTB’s microstructure, which dominates the strength and integrity of specimens. 3D-PPL-based backfill specimens also indicate a complex and diverse damage pattern, with a negative link between crack volume and tensile strength. The 3D fractal dimension of cracks in 3D-PPL-based fills is greater than that of ordinary fills. Combined with SEM-EDS tests, CTB’s hydration materials were mostly CSH gels, which interleaved as nucleating agents to inhibit crack growth. The findings of the present work will be beneficial for manufacturing and operational usage of 3P-PPL-based backfills.

Swelling damage evolution of argillaceous slate in a water-rich environment

The swelling of rock is a key issue in engineering. With large infrastructure construction trending towards complex geological conditions, an increasing number of projects could suffer from soft-rock swelling. To solve this problem, an understanding of the evolution of damage occurring during the swelling process is essential. Argillaceous slate is a typical metamorphic rock and shows strong swelling characteristics in a water-rich environment due to its abundance of hydrophilic minerals. In this paper, argillaceous slate was selected as the research object. The evolution of damage in argillaceous slate during swelling was explored via laboratory tests that included swelling characteristic tests, soft-rock needle penetration tests and scanning electron microscope tests, and damage theory. The research findings reveal that the slate swelling process in a water-rich environment can be divided into three stages, with the swelling rate being highest in the early stage of the tests, then slowing over time and finally stabilizing. However, the strength of the argillaceous slate decreased rapidly in the early stage, and the degradation rate was generally slow in the later stage. After water absorption, the clay mineral particles begin to expand and the microscopic structure of the argillaceous slate becomes complicated, with the pore area increasing and the pore diameter decreasing. A low degree of microscopic damage was found to induce a high degree of macroscopic mechanical degradation. In addition, the damage mechanism that occurs during argillaceous slate swelling is discussed in this paper from both a microscopic and a macroscopic perspective. Indeed, a relationship between macroscopic mechanical degradation and microscopic damage to argillaceous slate was established that can provide theoretical support for further research on soft-rock swelling characteristics: the microscopic damage drives the macroscopic mechanical degradation.

Low-intensity open-field blast exposure effects on neurovascular unit ultrastructure in mice

Mild traumatic brain injury (mTBI) induced by low-intensity blast (LIB) is a serious health problem affecting military service members and veterans. Our previous reports using a single open-field LIB mouse model showed the absence of gross microscopic damage or necrosis in the brain, while transmission electron microscopy (TEM) identified ultrastructural abnormalities of myelin sheaths, mitochondria, and synapses. The neurovascular unit (NVU), an anatomical and functional system with multiple components, is vital for the regulation of cerebral blood flow and cellular interactions. In this study, we delineated ultrastructural abnormalities affecting the NVU in mice with LIB exposure quantitatively and qualitatively. Luminal constrictive irregularities were identified at 7 days post-injury (DPI) followed by dilation at 30 DPI along with degeneration of pericytes. Quantitative proteomic analysis identified significantly altered vasomotor-related proteins at 24 h post-injury. Endothelial cell, basement membrane and astrocyte end-foot swellings, as well as vacuole formations, occurred in LIB-exposed mice, indicating cellular edema. Structural abnormalities of tight junctions and astrocyte end-foot detachment from basement membranes were also noted. These ultrastructural findings demonstrate that LIB induces multiple-component NVU damage. Prevention of NVU damage may aid in identifying therapeutic targets to mitigate the effects of primary brain blast injury.

U-fiber diffusion kurtosis and susceptibility characteristics in relapsing-remitting multiple sclerosis may be related to cognitive deficits and neurodegeneration.

To evaluate the diffusion kurtosis and susceptibility change in the U-fiber region of patients with relapsing-remitting multiple sclerosis (pwRRMS) and their correlations with cognitive status and degeneration. Mean kurtosis (MK), axial kurtosis (AK), radial kurtosis (RK), kurtosis fractional anisotropy (KFA), and the mean relative quantitative susceptibility mapping (mrQSM) values in the U-fiber region were compared between 49 pwRRMS and 48 healthy controls (HCs). The U-fiber were divided into upper and deeper groups based on the location. The whole brain volume, gray and white matter volume, and cortical thickness were obtained. The correlations between the mrQSM values, DKI-derived metrics in the U-fiber region and clinical scale scores, brain morphologic parameters were further investigated. The decreased MK, AK, RK, KFA, and increased mrQSM values in U-fiber lesions (p < 0.001, FDR corrected), decreased RK, KFA, and increased mrQSM values in U-fiber non-lesions (p = 0.034, p < 0.001, p < 0.001, FDR corrected) were found in pwRRMS. There were differences in DKI-derived metrics and susceptibility values between the upper U-fiber region and the deeper one for U-fiber non-lesion areas of pwRRMS and HCs (p < 0.05), but not for U-fiber lesions in DKI-derived metrics. The DKI-derived metrics and susceptibility values were widely related with cognitive tests and brain atrophy. RRMS patients show abnormal diffusion kurtosis and susceptibility characteristics in the U-fiber region, and these underlying tissue abnormalities are correlated with cognitive deficits and degeneration. The macroscopic and microscopic tissue damages of U-fiber help to identify cognitive impairment and brain atrophy in multiple sclerosis and provide underlying pathophysiological mechanism. • Diffusion kurtosis and susceptibility changes are present in the U-fiber region of multiple sclerosis. • There are gradients in diffusion kurtosis and susceptibility characteristics in the U-fiber region. • Tissue damages in the U-fiber region are correlated with cognitive impairment and brain atrophy.

Macroscopic and mesoscopic comparative study of frozen loess under loading and unloading

This paper utilizes computed tomography (CT) real–time observation technology to investigate the damage mechanism of frozen loess under loading and unloading. The intrinsic connections between macroscopic mechanical degradation and mesoscopic damage in frozen loess were established through a comparative analysis of macroscopic mechanical parameters (such as dissipation energy and elastic strain energy) and mesoscopic structural parameters (such as porosity increment and mesoscopic structural damage increment) of frozen loess under loading and unloading. Furthermore, the relationships between damage variables at different scales under the effects of loading and unloading were explored. The experimental results demonstrate that during the elastic strain stage, the dissipated energy, porosity increment, and microscopic damage increment of frozen soil exhibit a linear increase with strain. Following loading and unloading, the porosity is unable to be fully restored to its original state due to the development of new cracks. At this stage, the deformation is not entirely elastic and includes some plastic deformation. During the plastic deformation stage, the dissipated energy tends to stabilize, while the porosity increment and microscopic damage increment continue to increase substantially. The pore structure of a specimen undergoes significant alterations, with increased displacement and rearrangement of soil particles and ongoing expansion of cracks. The damage evolution trends at both the macroscale and mesoscale remain consistent during this stage. This study offers insights into the construction of a cross–scale macroscale/mesoscale ontological damage model, serving as a valuable reference for future research.

Microscopic damage evolution of anisotropic rocks under indirect tensile conditions: Insights from acoustic emission and digital image correlation techniques

Microscopic damage evolution of anisotropic rocks under indirect tensile conditions: Insights from acoustic emission and digital image correlation techniques

Copper and Zinc Metal-Organic Frameworks with Bipyrazole Linkers Display Strong Antibacterial Activity against Both Gram+ and Gram- Bacterial Strains.

Here, we report a new synthetic protocol based on microwave-assisted synthesis (MAS) for the preparation of higher yields of zinc and copper in MOFs based on different bis(pyrazolyl)-tagged ligands ([M(BPZ)]n where M = Zn(II), Cu(II), H2BPZ = 4,4'-bipyrazole, [M(BPZ-NH2)]n where M = Zn(II), Cu(II); H2BPZ-NH2 = 3-amino-4,4'-bipyrazole, and [Mx(Me4BPZPh)] where M = Zn(II), x = 1; Cu(II), x = 2; H2Me4BPZPh = bis-4'-(3',5'-dimethyl)-pyrazolylbenzene) and, for the first time, a detailed study of their antibacterial activity, tested against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria, as representative agents of infections. The results show that all MOFs exert a broad-spectrum activity and strong efficiency in bacterial growth inhibition, with a mechanism of action based on the surface contact of MOF particles with bacterial cells through the so-called "chelation effect" and reactive oxygen species (ROS) generation, without a significant release of Zn(II) and Cu(II) ions. In addition, morphological changes were elucidated by using a scanning electron microscope (SEM) and bacterial cell damage was further confirmed by a confocal laser scanning microscopy (CLSM) test.

Experimental investigation of single and butt-welded GFRP filament winding tubes bending behavior based on conventional and Digital Image Correlation method

Composite joints have become increasingly popular in pipeline assembly, replacing conventional fasteners. However, butt-welded joint composite techniques still need further structural study. This paper aims to study the flexural mechanical performance of the above mentioned composite joint method. Four-point bending tests were conducted on both unassembled (single) and two butt-welded tube types (based on NFT and DIN standard methods). In this context, the 2D digital image correlation (DIC) technique was applied during these tests to analyze the damage scenario based on full-field strain mapping. To further visualize the microscopic damage modes, X-ray tomography observations were conducted on both single and butt-welded specimens. The experimental results show that single tubes have the highest mechanical properties, with quasi-elastic behavior until the occurrence of fracture. The NFT butt-welded composite tubes present the maximum flexural stiffness and strength compared with the DIN tubes. It has also been shown that the strain distribution depends on the specimen configuration. The DIC analysis results show that the damage scenario is divided into two events: the onset of fracture and then the fracture propagation. These results were confirmed through microscopic inspections.

Experimental study on damage mechanism of blood vessel by cavitation bubbles

Ultrasound-induced cavitation in blood vessels is a common scenario in medical procedures. This paper focuses on understanding the mechanism of microscopic damage to vessel walls caused by the evolution of cavitation bubbles within the vessels. In this study, cavitation bubbles were generated using the low-voltage discharge method in 0.9% sodium chloride saline, and vessel models with wall thicknesses ranging from 0.7 mm to 2 mm were made using a 3D laminating process. The interaction between cavitation bubbles and vessel models with different wall thicknesses was observed using a combination of high-speed photography. Results show that cavitation bubble morphology and collapse time increased and then stabilized as the vessel wall thickness increased. When the cavitation bubble was located in vessel axial line, pair of opposing micro-jets were formed along the axis of the vessel, and the peak of micro-jet velocity decreased with increasing wall thickness. However, when the cavitation bubble deviated from the vessel model center, no micro-jet towards the vessel model wall was observed. Further analysis of the vessel wall deformation under varying distances from the cavitation bubble to the vessel wall revealed that the magnitude of vessel wall stretch due to the cavitation bubble expansion was greater than that of the contraction. A comparative analysis of the interaction of between the cavitation bubble and different forms of elastic membranes showed that the oscillation period of the cavitation bubble under the influence of elastic vessel model was lower than the elastic membrane. Furthermore, the degree of deformation of elastic vessel models under the expansion of the cavitation bubble was smaller than that of elastic membranes, whereas the degree of deformation of elastic vessel models in the contraction phase of the cavitation bubble was larger than that of elastic membranes. These new findings provide important theoretical insights into the microscopic mechanisms of blood vessel potential damage caused by ultrasound-induced cavitation bubble, as well as cavitation in pipelines in hydrodynamic systems.

Experimental and Numerical Investigation of the Tensile and Failure Response of Multiple-Hole-Fiber-Reinforced Magnesium Alloy Laminates under Various Temperature Environments.

In this paper, the tensile mechanical behavior and progressive damage morphology of glass-fiber-reinforced magnesium alloy laminate for different numbers of holes in a temperature range of 25-180 °C were investigated. In addition, based on extensive tensile tests, the tensile mechanical behavior and microscopic damage morphology of porous-glass-fiber-reinforced magnesium alloy laminates at different temperatures were observed by finite element simulation and scanning electron microscopy (SEM). Finally, the numerical simulation and experimental results were in good accordance with the prediction of mechanical properties and fracture damage patterns of the laminates, the average difference between the residual strength values of the specimens at ambient temperature was 5.57%, and the stress-strain curves were in good agreement. The experimental and finite element analysis results showed that the damaged area of the bonded layer tended to expand with the increase in the number of holes, which has a lesser effect on the ultimate tensile strength. As the temperature increased, the specimens changed from obvious fiber breakage (pull-out) and the resin matrix damage mode to matrix softening damage and interfacial delamination fracture damage. As the testing temperature of the specimens increased from 25 °C to 180 °C, the tensile strength of the specimens decreased by an average of 51.59%, while the tensile strength of the specimens showed a nonlinear decreasing trend. The damage mechanism of porous-glass-fiber-reinforced magnesium alloy laminates at different temperatures is discussed in this paper, which can provide a reference for engineering applications and design.

A Coupled Tensor–DEM–FEM Model for the Whole Process of Internal Fine-Scale Damage to Surface Damage in Red-Bed Soft Rocks in the Coastal Area of South China

Calculation and characterization of the whole process of internal microscopic damage to surface damage in red-bed soft rock is a theoretical research difficulty and an urgent need for engineering safety protection. However, the current study cannot accurately and directly correlate internal and external damage. Therefore, in this paper, a coupled tensor–DEM–FEM model is proposed to deal with surface damage by indoor triaxial test digital image processing (DIC), internal damage by FJM acoustic emission study, and internal and external damage by moment tensor correlation. The study demonstrates that the whole process damage process of the red-bed soft rock peak front can be divided into six distinct phases, with early damage beginning with the elastic phase; the local strain divergence value begins to spiral out of control during the period of crack acceleration development; the overall acoustic emission intensity distribution is in the range of [−8.5, −6.3] in two dimensions and in the range of [−11, −9] in three dimensions; the R were between −40 and 40, which corresponded to the results of the indoor tests. A model has been developed that allows a direct reflection of the whole damage process. The method can be used to better understand the disaster mechanism and guide engineering practice.

Dynamic evaluation of microscopic damage and fluid flow behavior in reservoir shale under deviatoric stress

This study presented a three-dimensional reconstruction method for digital shale cores in detail and examined the impact of deviatoric stress on the microscopic damage and fluid flow behavior in reservoir shale under deviatoric stress. In particular, this paper investigated the distribution of damage, deformation, and stress in shale under different deviatoric stresses. In addition, the characteristics of fluid velocity and pressure distribution under deviatoric stress and permeability evolution were discussed. The results showed that: (1) The deformation and damage in digital cores increased with the deviatoric stress, and the pore area will be more affected by deviatoric stress than the matrix area. (2) The fluid velocity distribution varies significantly between the matrix and the pore area, and the flaky connected fracture will aggravate this difference. (3) The fluid velocities of digital cores D1 and D2 decreased first and then increased with the increase of the deviatoric stress. (4) The permeability of digital cores D1 and D2, as the deviatoric stress increased, initially decreased due to rock deformation but subsequently increased due to the increasing damage.

Damage Assessment of Glass-Fibre-Reinforced Plastic Structures under Quasi-Static Indentation with Acoustic Emission.

The use of fibre-reinforced plastics (FRPs) in various industrial applications continues to increase thanks to their good strength-to-weight ratio and impact resistance, as well as the high strength that provides engineers with advanced options for the design of modern structures subjected to a variety of out-of-plane impacts. An assessment of the damage morphology under such conditions using non-destructive techniques could provide useful data for material design and optimisation. This study investigated the damage mechanism and energy-absorption characteristics of E-glass laminates and sandwich structures with GFRP face sheets with PVC cores under quasi-static indentation with conical, square, and hemispherical indenters. An acoustic emission (AE) technique, coupled with a k-means++ pattern-recognition algorithm, was employed to identify the dominant microscopic and macroscopic damage mechanisms. Additionally, a post-mortem damage assessment was performed with X-ray micro computed tomography and scanning electron microscopy to validate the identified clusters. It was found that the specific energy absorption after impact with the square and hemispherical indenters of the GFRP sandwich and the plain laminate differed significantly, by 19.29% and 43.33%, respectively, while a minimal difference of 3.5% was recorded for the conical indenter. Additionally, the results obtained with the clustering technique applied to the acoustic emission signals detected the main damaged modes, such as matrix cracking, fibre/matrix debonding, delamination, the debonding of face sheets/core, and core failure. The results therefore could provide a methodology for the optimisation and prediction of damage for the health monitoring of composites.

Interfacial bonding property and microscopic damage mechanism of bitumen-aggregate in salt-freeze-thawing environment

Deicing salt or snow-melting agent has a corrosive effect on the pavement, which reduces the durability of asphalt pavement. The interfacial bonding properties of bitumen-aggregate is one of the main factors affecting the durability of asphalt mixture. To evaluate the interfacial bonding properties of bitumen-aggregate and reveal the damage mechanism under salt-freeze-thaw coupling effect, the bitumen-aggregate samples with the same film thickness were formed by controlling the applied load. The corrosion of deicing salt on bitumen-aggregate and bitumen film samples was simulated by freeze-thaw cycles in 1 %, 3 % and 5 % NaCl solution. The pull-off test of SBS modified bitumen-aggregate after salt-freeze-thaw cycles was conducted. The Fourier transform infrared spectrometer (FTIR) test was carried out to qualitatively and quantitatively analyze the impact of salt-freeze-thaw coupling effect on bitumen functional groups. The surface morphology of bitumen samples treated in salt-freeze-thawing environment was also scanned by atomic force microscopy (AFM) in tapping mode. The results illustrate that the pull-off strength of bitumen-aggregate decreases sharply first and then the decrease rate slows down with the rise of salt-freeze-thaw coupling cycles. The carbonyl index and sulfoxide index of SBS modified bitumen increases, and the butadiene index decreases after freeze-thaw cycles in NaCl solution. The environment of salt erosion and freeze-thaw cycle accelerates the deterioration of SBS modifier and reduces the distinction of various phases in bitumen binder. Then the Ra and Rq of SBS modified bitumen decreases significantly in salt-freeze-thawing environment. The decrease of butadiene index and root mean square roughness leads to the weakening of adsorption between SBS modified bitumen and aggregate, which is the main reason for the damage of interfacial bonding performance of bitumen-aggregate. In summary, the salt-freeze-thawing environment damages the bonding performance of bitumen-aggregate. The damage law and deterioration mechanism of bonding properties of bitumen-aggregate presented in this paper provides some references for the optimal design of asphalt mixture in salt-freeze-thawing environment.

A new surgical tape with a mesh designed to prevent skin tears and reduce pain during tape removal.

We devised a surgical tape that prevents skin tears while maintaining adhesive strength. Under the assumption that microscopic damage to the skin is reflected in pain felt on the skin, we statistically analyzed skin pain when the tape was peeled off to show the skin protection effect of the mesh on the new tape. This tape has a three-layer structure consisting of a tape substrate, adhesive, and mesh. When the tape is applied to the skin, a mesh is located between the adhesive and the skin. The adhesive contacts the skin through the mesh holes and fixes the substrate to the skin; it does not come into contact with the skin at the mesh body; therefore, the adhesive-skin contact area is reduced. In this experiment, we used surgical tape with and without mesh. At 8 hours after the application of each tape to the forearm of five adult males, it was removed. All tapes were peeled off while maintaining an angle of approximately 120° between the skin and tape substrate. For the tape with mesh, the tape substrate was peeled off in two ways: peeling off the substrate together with the mesh and peeling off the substrate, leaving the mesh on the skin. A perception and pain quantification analyzer (Pain Vision™) was used to quantify pain. The data were compared and examined statistically (Friedman's test and Wilcoxon's coded rank test). The least pain was experienced while peeling off the tape substrate, leaving the mesh on the skin. There was a significant difference in pain levels among the three tape removal methods. There was also a significant difference between the two peeling methods in the experimental group. The skin protection effect of the mesh reduced pain when the surgical tape was removed.

Fracture toughness and microstructure damage behavior of thin Al–Cu alloy fabricated by wire-arc directed energy deposition

This study aimed to investigate the factors influencing the fracture toughness of thin Al–Cu alloy fabricated using Arc-Direct Energy Deposition (Arc-DED). By adjusting process parameters, samples with different microstructure characteristics were obtained, including an air-cooled (AC) deposit with a high proportion of equiaxed grains, a water-cooled (WC) deposit with a high proportion of columnar grains, and a post-heat-treated air-cooled deposit (T6) with numerous nano-sized precipitates. The conditional fracture toughness (KQ)/crack tip opening displacement (CTOD) values for the AC, WC, and T6 samples were 11.7 MPa m1/2/23.27 μm,11.4 MPa m1/2/22.70 μm, and 17.6 MPa m1/2/22.39 μm, respectively. The fracture toughness of the T6 sample was 50.4% and 54.4% higher than that of the AC and WC samples, respectively. The heterogeneity of the equiaxed/columnar microstructure affected the distribution of brittle θ-Al2Cu phases and pores, thereby influencing crack behavior. While columnar grains exhibited a stronger capacity for accumulating geometrically necessary dislocations (GNDs) and coordinating deformation compared to equiaxed grains, cracks were more likely to propagate along grain boundaries when the loading direction was parallel to the growth direction of columnar grains. Consequently, flat crack paths were observed in columnar grains, while equiaxed grains displayed tortuous paths. Furthermore, the precipitation of nano-sized θ'-Al2Cu phases contributed to improved fracture toughness. By integrating microstructure characterization, fractographic observation, analysis of uneven grain deformation behavior, and examination of GNDs distribution near crack paths, the study revealed microscopic damage characteristics, fracture behavior, and toughening mechanisms.

Development of trans-Chalcone loaded pectin/casein biodegradable microcapsules: Efficacy improvement in the management of experimental colitis

Improved therapies for inflammatory bowel diseases are sorely needed. Novel therapeutic agents and the development of controlled release systems for targeted tissue delivery are interesting approaches to overcome these barriers. We investigated the activity of trans-chalcone (T) in acetic acid-induced colitis in mice and developed, characterized, and determined the therapeutic effect of pectin/casein polymer microcapsules containing T (MT) in a colitis mouse model. In vitro, compound release was achieved in simulated intestinal fluid but not in the simulated gastric fluid. In vivo, since T at the dose of 3 mg/kg but not 0.3 mg/kg ameliorated colitis, we next tested the effects of MT at 0.3 mg/kg (non-effective dose). MT, but not free T at 0.3 mg/kg, significantly improved colitis outcomes such as neutrophil recruitment, antioxidant capacity, cytokine production, and NF-kB activation. This translated into reduced macro and microscopic damage in the colon. T release from the microcapsules is mediated by a pH-dependent and pectinase-regulated mechanism that provide controlled and prolonged release of T. Moreover, MT lowered the required dose for T therapeutic effect, indicating that could be a suitable pharmaceutical approach to colitis treatment. This is the first demonstration that T or MT is effective at reducing the signs of colitis.

Experimental and numerical analysis of low-velocity impact behavior of wound products using multi-filament winding technique

The wound products are subjected to various impact loads during their service life, which caused invisible damage to the composite layers. In this paper, we investigated the failure behavior of composite layers fabricated using an innovative multi-filament winding (MFW) process under impact load. Firstly, the principle of the MFW technique was introduced. Finite element models were constructed for both novel and conventional techniques, and subsequent low-velocity impact (LVI) tests were performed to acquire the time-force and time-energy data for the CFRP (Carbon Fiber Reinforced Polymer) laminates. The test results were in good agreement with the LVI responses of the composites obtained from the simulations. The failure modes and microscopic damage of the composite layers of the two techniques were analyzed by scanning electron microscopy (SEM). The results showed that under the same impact velocity, three damage modes of fiber fracture, matrix cracking, and delamination were observed for both techniques. However, the composite layers of the MFW technique exhibited more excellent impact resistance properties in terms of maximum contact force, absorbed energy, as well as inter-laminar and intra-laminar damage. The MFW technique exhibits a notable level of winding efficiency and demonstrates exceptional performance of manufactured products, which can meet the increasing demand of winding products over the years.