Damage Evolution Research Articles

CONGENITAL PULMONARY AIRWAY MALFORMATION IN A NEWBORN: A CASE REPORT

Congenital pulmonary airway malformation (CPAM) is one of the many causes of respiratory distress, generally occurring in about 7 % of infants in the early neonatal period. This article describes a clinical case of CPAM in a neonate who presented with signs of severe respiratory failure from the fi rst hours of life. The repeated occurrence of pneumothorax, development of pneumonia and hypoxicischemic damage of the central nervous system complicated the course of the disease in this child during the neonatal period. The clinical features of the course of the disease and their correlation with the results of laboratory and instrumental studies are analyzed. The results of dynamic radiography of the thoracic organs and spiral computed tomography (CT) of the lungs are presented. The presented clinical case shows that congenital lung pathology, namely malformation of the pulmonary airways, may be an unrecognized cause of respiratory distress in the neonatal period for a long time. The presented case report shows that congenital lung pathology, especially CPAM, in neonates may be an unrecognized cause of respiratory distress for a long time. In order to diagnose this disease promptly, a comprehensive evaluation of the child should include not only a chest x-ray, which is not always informative in the early stages, but also a CT scan of the lungs. Optimizing the choice of diagnostic measures contributes to increasing the eff ectiveness of treatment, including surgical treatment, and preventing the development of possible complications, improves the prognosis for life and health of children with the specifi ed pathology.

Fracture mode classification of UHPC based on deep learning and wavelet time–frequency spectrum derived from acoustic emission waveform

Fracture mode categorization is essential in identifying the failure stage, evaluating the damage characteristics, and providing references for structural maintenance. Acoustic emission (AE), as a passive nondestructive technique, presents great potential in damage characterization of cementitious materials and structures. In this study, a convolutional neural network (CNN) and gated recurrent unit (GRU) integrated model for tensile, shear, and mixed cracking mode classification of ultra-high-performance concrete (UHPC) was proposed and verified based on AE waveform features. First, four-point bending and direct shear tests for UHPC specimens were carried out, respectively, to generate AE waveform signals corresponding to different cracking modes (tensile, shear, and mixed ones). Subsequently, the collected one-dimensional AE signals were converted into two-dimensional time–frequency spectrum by continuous wavelet transform. And an AE dataset was constructed after manual labeling based on the corresponding relationships between cracking modes and wavelet time–frequency spectra. Then, an automatic CNN-GRU automatic classification model was established using wavelet time–frequency spectrum images as input variables, where the CNN extracts spatial image features, and the GRU screens time dependencies and realizes final classification. The proposed CNN-GRU model achieves an accuracy of 96.17% for cracking mode classification of UHPC, which is superior both in computational accuracy and efficiency to lightweight CNN and AlexNet. Classification outcomes for UHPC specimen under four-point bending and direct shear tests revealed the proportion of tensile cracks progressively decreased with the increase of damage, while shear cracks exhibited the opposite trend. The percentage of mixed mode cracks maintained relatively stable throughout the failure stages. The model proposed in this study presents favorable performance to reveal the underlying damage evolution mechanism during UHPC fracture, which can also provide references for the cracking mode classification of other cementitious materials and structures.

Exploring Haptoglobin as a Promising Marker for Severe Liver Diseases: A Comprehensive Review

Liver damage is a common symptom of many diseases, including metabolic disorders and cancers. Such patient condition requires effective examinations aimed at prompt diagnosis and implementation of the most appropriate treatment for a specific disease. Haptoglobin, the subject of many studies, has proven to be a protein that can be used as a biomarker of liver damage, thereby aiding not only in the diagnosis but also in the treatment, resulting in more favorable prognoses regarding patient longevity and quality of life.The aim of this study is to elucidate the role of haptoglobin as a diagnostic and prognostic biomarker in cases of liver damage.This is a review of scientific literature and analysis of clinical data regarding haptoglobin levels in liver damage were conducted to assess the reliability of haptoglobin as a biomarker.This paper primarily utilized the latest publications produced after 2015. PubMed and Google Scholar were used to find relevant publications. All cited works provided useful information to achieve the aim of our article.Analysis of the literature suggests that haptoglobin levels may be significantly associated with the development and severity of liver damage. It may serve as a suitable biomarker for diagnosing diseases that coincide with hepatocyte damage, thus improving the diagnosis of these diseases and increasing the chance of appropriate treatment, which may contribute to prolonging and improving the patient's quality of life.Haptoglobin appears to be a promising biomarker in liver damage; however, further research is necessary to confirm its diagnostic and prognostic accuracy. Haptoglobin exists in various genotypic forms, each characteristic of different disease entities. Understanding the mechanisms regulating haptoglobin levels may lead to a better understanding of liver damage pathogenesis and the development of more effective therapies, increasing the chance of patient recovery and improving their quality of life.

Abstract 4139169: Treatment with methotrexate associated with LDL-like nanoparticles prevents the development of left ventricular fibrosis in a spontaneously hypertensive rat model

Introduction: Systemic arterial hypertension (SAH) can lead to left ventricle (LV) fibrosis and ventricular dysfunction. Methotrexate (MTX) associated with lipid nanoparticles (LDE) increases the cellular uptake of MTX by ninety-fold, which leads to therapeutic efficacy and reduces drug toxicity. Previously, treatment of rats with myocardial infarction with LDE-MTX decreased LV fibrosis and prevented ventricular dysfunction. The aim was to test LDE-MTX to preclude the development of cardiac damages caused by hypertension in spontaneously hypertensive rats (SHR). Methods: Twenty-four male rats with six-week-old were allocated in 3 groups: Control (CT): Wistar-Kyoto rats injected with saline; SHR: treated with LDE only and SHR-LDE-MTX: treated with LDE-MTX (1mg/Kg/week, I.P.). After 20 weeks of treatment, echocardiography, morphometry and protein expression were performed in the LV. The data were analyzed by ANOVA with Turkey’s post-test or Kruskal-Wallis test with Dunn's post-test. Linear regression was used to evaluate potential relationships. Results: Compared to CT, the two SHR groups showed dilation (increase in systolic and diastolic diameter); hypertrophy (increased thickness of the posterior wall) and systolic dysfunction (decreased ejection and shortening fractions). Furthermore, the SHR group showed increased LV fibrosis in both the interstitial region and the papillary muscle, possibly resulting from increased of type I collagen content. Treatment of SHR with LDE-MTX had no effect on LV dilation, hypertrophy or systolic dysfunction. However, LDE-MTX decreased LV fibrosis of the interstitial region and the papillary muscle. In addition, LDE-MTX increased the expression of MMP-2, and increased the bioavailability of intracellular adenosine, via increased expression of the adenosine A3 receptor. There was a negative correlation between the expression of the adenosine A3 receptor with interstitial fibrosis (r2=-0.31, p=0.03) and papillary muscle (r2=-0.47, p=0.03), indicating that the increased bioavailability of intracellular adenosine also contributed to the decrease in LV fibrosis in SHR. Conclusion: In SHR, treatment with LDE-MTX reduced LV fibrosis, possibly by modulating MMP-2 expression and increasing the bioavailability of intracellular adenosine, via the adenosine A3 receptor. These results suggest a therapeutic role for LDE-MTX in patients with LV fibrosis and heart failure caused by SAH, to be explored in future clinical studies.

Comparison of Different Additives and Ages on Mechanical and Acoustic Behavior of Coal Gangue Cemented Composite

Cemented backfill represents a significant trend in mine filling methods; however, it often exhibits high brittleness and limited resistance to failure, which can restrict its practical application. This study investigates the mechanical properties and damage evolution of fiber-reinforced coal gangue cemented materials (CGCMs) at various curing times using uniaxial compressive tests, acoustic emission (AE) analysis, and scanning electron microscopy (SEM). Specimens were created with different fillers, including carbon fibers (CFs), steel fibers (SFs), and carbon black (CB), and subjected to uniaxial compression until failure. Control specimens without fillers were also tested for comparison. The microstructure of the specimens was examined using scanning electron microscopy (SEM). The findings indicate that (1) the compressive strength of filler-reinforced CGCMs increases between 7 and 14 days of curing but decreases thereafter, with CB significantly improving early-age strength; (2) specimens reinforced with CFs and SFs exhibit significantly enhanced toughness in their post-cracking response; (3) AE events during specific stages can effectively identify the reinforcing effects of CFs and SFs; (4) the presence of fillers improves resistance to shear cracks, with CFs and SFs being more effective than CB; and (5) adding CB results in a denser and more stable hydration product structure, while CFs and SFs lead to a more porous structure with increased cracking.

ROLE OF NF-κB ACTIVATION IN CHANGES OF NITRIC OXIDE PRODUCTION IN SKELETAL MUSCLES DURING METABOLIC SYNDROME

Nitric oxide, as a signaling molecule, plays an ambiguous role in many pathological processes. On the one hand, nitric oxide is necessary for maintaining the tone of the vascular wall of arteries and prevents the development of ischemia in various organs and skeletal muscles in particular. On the other hand, excessive production of nitric oxide in the tissue can contribute to the formation of toxic metabolites, such as peroxynitrite that leads to the development of nitrosative damage to various organs and tissues. Metabolic syndrome is also one of the diseases accompanied by disturbances in the nitric oxide production system. Currently, the sources of nitric oxide production, the predominant ways of its metabolism, and the influence of the transcription factor NF-κB on these processes in skeletal muscles under the conditions of the metabolic syndrome are insufficiently studied. The purpose of this study is to study the effect of an inhibitor of the activation of the transcription factor NF-κB on the production of nitric oxide and the concentration of its metabolites in the biceps femoris muscle of rats under the conditions of modeling the metabolic syndrome. The experimental study was carried out on male Wistar rats weighing 200-260 g. The animals were randomly divided into 4 groups of 6 animals each. Animals of group 1 (control group) received a standard vivarium diet. In group 2 (metabolic syndrome), in addition to the standard diet, the animals received a 20% fructose solution as their sole source of drinking water for 60 days. In group 3, the animals were given a standard vivarium diet and were injected intraperitoneally with ammonium pyrrolidine dithiocarbamate at a dose of 76 mg/kg, three times a week for 60 days. Group 4 received the same diet as group 2 along with the injections administered in group 3. In 10% homogenate of the biceps femoris muscle, the following were determined: total NO-synthase activity, activity of constitutive and inducible isoforms of NO-synthase, arginase activity, aitrate- and nitrite reductase activity, concentrations of nitrite, peroxynitrite, nitrosothiols, and sulfides. The administration of ammonium pyrrolidinedithiocarbamate during metabolic syndrome simulation resulted in a reduction in total NO-synthase activity and inducible NO-synthase activity by 33.85% and 34.66%, respectively, compared to the metabolic syndrome group; arginase activity decreased by 37.56%, while nitrate and nitrite reductase activities were reduced by 19.29% and 47.71%, respectively; nitrite concentration increased by 21.77%, peroxynitrite concentration decreased by 32.05%, nitrosothiol concentration increased by 29.27%, and sulfide concentration decreased by 17.39% compared to the group with metabolic syndrome. Activation of the transcription factor NF-κB under metabolic syndrome conditions leads to increased nitric oxide production through both L-arginine-dependent and L-arginine-independent pathways in the biceps femoris muscle, enhances arginase activity, and results in elevated peroxynitrite formation.

Robust seismic fragility curves for concrete gravity dams incorporating aleatory, epistemic, and fuzzy uncertainties

Concrete gravity dams are critical infrastructure assets, and their failure in seismically active regions poses significant risks. The primary problem addressed in this research is the need for a reliable assessment of the seismic fragility of these dams to ensure safety in such areas. The research aims to develop a comprehensive methodology for seismic fragility analysis that accounts for various uncertainties affecting dam performance, including uncertainties in material properties and seismic characteristics and the fuzziness of damage state thresholds through the Latin Hypercube Sampling method. The methodology involves a three-stage approach: first, a finite element model is created using Abaqus software, incorporating uncertainties in material properties and earthquake characteristics using the Latin Hypercube Sampling method (LHS). Second, incremental dynamic analysis (IDA) defines damage states based on concrete cracking severity and overall stability, utilizing four performance categories of limit states (minor, moderate, extensive, and heavy). Finally, a mathematical model is introduced to characterize the ambiguity in damage state thresholds, recognizing the gradual nature of damage evolution. The primary findings demonstrate that fuzziness substantially influences the probability of exceedance across all damage states, with varying effects on different damage indices because of their differing frequency distributions. This research enhances the reliability and accuracy of seismic fragility assessments, contributing to more robust design guidelines and effective risk mitigation strategies for concrete gravity dams.

Irradiation damage evolution dependence on misorientaton angle for ∑ 5 grain boundary of Nb: An atomistic simulation-based study

Abstract Niobium as refractory element holds ability to arrest the primary radiation damage in reactor's fissionable conditions and can withstand high temperature applications. We have inclined the investigation of irradiated Nb ∑ 5 symmetric tilt angled-grain boundary (STGB) models at two high-angled grain boundary misorientation: 53.13 ° (∑ 5(2-10)/ (120)) and 36.87 ° (∑ 5(3-10)/ (130)) respectively. A hybrid of Ziegler-Biersack-Littmark (ZBL) and embedded atom method (EAM) potentials were superimposed to simulate radiation damage. Statistical averaging of the displacement cascades were conducted to study dynamic evolution of the point defects and interstitial clusters at varying magnitudes of primary knock-on atom (PKA) energies, irradiation temperatures and PKA directions respectively. The irradiated GB models were compared with a irradiated bulk Nb specimen and the results of the study indicate that the irradiated Nb system with greater misorientation angle i.e., Nb ∑ 5 (θ = 53.13 ° ) survived with lower number Frenkel pair defects as well as the population small-sized interstitial clusters. The cluster analysis indicated the highest population of interstitial clusters survived in Nb STGB models were irradiated along <1 3 5> PKA direction and 100 keV recoil energies respectively.

The Mesoscopic Damage Mechanism of Jointed Sandstone Subjected to the Action of Dry–Wet Alternating Cycles

The effect of the dry–wet cycle, characterized by periodic water level changes in the Three Gorges Reservoir, will severely degrade the bearing performance of rock formations. In order to explore the effect of the dry–wet cycle on the mesoscopic damage mechanism of jointed sandstone, a list of meso-experiments was carried out on sandstone subjected to dry–wet cycles. The pore structure, throat features and mesoscopic damage evolution of jointed sandstone with the action of the dry–wet cycle were analyzed using a-low-field nuclear magnetic resonance (NMR) technique. Subsequently, the impact on the mineral content of dry–wet cycles was studied by small angle X-ray scattering (SAXS). Based on this, the mesoscopic damage mechanism of sandstone subjected to dry–wet cycles was revealed. The results show that the effects of the drying–wetting cycle can promote the development of porous channels within sandstone, resulting in cumulative damage. Besides, with an increase in dry–wet cycles, the proportion of small pores and pore throats decreased, while the proportion of medium and large pores and pore throats increased. The combined effects of extrusion crush, tensile fracture, chemical reaction and dissolution of minerals inside the jointed sandstone contributed to the development of mesoscopic pores, resulting in the increase of porosity and permeability of rock samples under the dry–wet cycles. The results provide an important reference value for the stability evaluation of rock mass engineering under long-term dry–wet alternation.

IMMUNE DYSREGULATION IN AUTOIMMUNE HEPATITIS: THE ROLE OF AUTOANTIBODIES, T-REG CELLS, AND NOVEL THERAPEUTIC APPROACHES

Introduction. The liver is a crucial immunological tolerogenic organ with a unique ability to generate effective immune responses against hepatotropic pathogens while maintaining both local and systemic immune tolerance to self and foreign antigens. Autoimmune hepatitis (AIH) is an immune-mediated inflammatory liver disease caused by the loss of tolerance to liver-specific antigens, leading to autoimmune liver damage.Aim – to summarize current knowledge on the immunopathogenesis of AIH based on information from open sources.Material and methods. The selection of publications was conducted using databases such as PubMed, Clinical Key Elsevier, Cochrane Library, eBook Business Collection, and Google Scholar, which covered information on the immunopathogenesis of AIH. Literature search was performed using keywords: autoimmune diseases, autoimmune hepatitis, Kupffer cells, autoantibodies to liver microsomal antibodies, and mesenchymal stem cells.Research results. Liver immune regulation is mediated by unique cell populations, including T-reg cells, Kupffer cells, and NK cells, which interact to maintain immune tolerance and regulate inflammation. Deficiency or dysfunction of T-reg cells, along with the activation of Th17 cells, contribute to the development of inflammatory processes and autoimmune liver damage. The quantitative and qualitative composition of immune cells in the liver differs significantly from that in secondary lymphoid organs, such as lymph nodes, spleen, or peripheral blood. The CD8+/CD4+ ratio (3.5:1) of liver T cells contrasts with the 1:2 ratio observed in peripheral blood, lymph nodes, and spleen.Conclusions. AIH is a complex disease with a multifaceted immunopathogenesis. T-reg and MSC-based therapies show promising results in clinical trials; however, further research is needed to optimize these methods and ensure their safe and effective application.

Evaluating Rock Brittleness Through a Novel Statistical Damage Theory-Based Index: A Case Study on Sandstones

Evaluating the brittleness of rocks or rock masses is a fundamental problem in geotechnical engineering. This study proposed a new index that expresses brittleness as the rate of damage development in rock. The brittleness index was derived from statistical damage theory. It depends on the four material parameters, i.e., the peak strain, peak strength, Poisson’s ratio and elastic modulus. The validity of the proposed brittleness index was confirmed through two case studies, including triaxial compression test results for coals subjected to varying confining pressures and for sandstones at various temperatures. Uniaxial compression experiments were then performed on rock-like materials to examine the effects of model size and joint dip angle on rock brittleness using the proposed brittleness index. Results show that the brittleness of the jointed specimens varies in a complex pattern with the model size and joint dip angle. Generally, the brittleness index initially reduces and then grows with the increasing joint dip angle, and larger specimens tend to be more brittle. Furthermore, large specimens containing horizontal or vertical joints are particularly susceptible to brittle damage. The proposed brittleness index has merits such as a clear physical meaning and simple expression, making it a valuable tool for evaluating rock brittleness.

Internal shear damage evolution of CFRP laminates ranging from −100 °C to 100 °C using in-situ X-ray computed tomography

Carbon Fiber Reinforced Polymer (CFRP) composites have been widely used in aerospace due to their high specific stiffness, strength, and fatigue properties. However, the ambient temperature significantly influences CFRP's mechanical properties and damage evolution, deriving from the temperature effect on the microstructural behavior and the mesoscopic damage evolution. In this study, the temperature-dependent in-plane shear failure behavior of CFRP composites was investigated. In-situ X-ray Computed tomography (CT) tensile experiments of laminates ([45°/-45°]2s) at RT, −100 °C, and 100 °C were carried out to study the in-plane shear failure mechanisms. The 3D fracture morphology was extracted with internal damage evolution process estimated and quantified. The in-situ 3D deformation fields of critical regions were acquired using the Digital Volume Correlation (DVC) method. The effect of temperature on strain field and the correlation between the high-strain region and the fracture location were analyzed. The results revealed the temperature correlations and failure mechanisms of CFRP's mechanical characteristics and internal damage evolution process. Compared to room temperature (RT), the delamination damage area of the sample increased by 80 % at 100 °C. Meanwhile, the shear modulus of CFRP decreases by 78.4 % from −100 °C to 100 °C, and the fracture strain increases by 95 % from RT to 100 °C. The DVC results indicated a dispersion of high-strain regions at −100 °C, reflecting the brittle damage characteristics, while an extensive ductile deformation region was captured at 100 °C. Fiber-matrix debonding is the dominant failure mode of composites under shear loading, whereas significant matrix cracking was observed at −100 °C and partial fiber pullout occurred at 100 °C.

25 years field test history and fatigue damage analysis for a scrapped ladle crane

Fatigue performances of ladle cranes will gradually decrease with the increase of service years. The service history and the fatigue damage of a scrapped ladle crane were investigated and analyzed in this paper. The test history of the ladle crane was collected and concluded, and the statistical parameters of lifting capacity and the crack condition during service were determined. The last comprehensive field test before scrapping the ladle crane was introduced in detail and the damage evolution was analyzed. The geometry measurement showed that the main girders’ stiffness had changed obviously. The stress test of the crack-prone positions of the metal structure revealed their remaining bearing capacity and the damage evolution characteristics. Further analysis proved that the static stiffness of the main girder has a closer relationship with damage deterioration. Some material property inspections were carried out for samples cut from the scrapped crane’s main girder, which were of the load-carrying part and the non-load-carrying part respectively. Results showed that the elastic modulus and hardness of the materials decreased evidently after service, while other mechanical properties did not change significantly. This study will provide useful references for further understanding of the fatigue characteristics and evolution behaviors of ladle cranes.

Analysis of shear creep damage model of slope rock mass under the influence of coupled damage effects (DBSM)

Abstract This article reveals the evolution law of shear creep damage of carbonaceous shale (weak interlayer of slope) under dynamic load from a mechanical perspective by combining indoor experiments and theoretical research. Firstly, a coupled damage variable D BSM was established for the initial damage D 0 and dynamic disturbance shear creep damage D BS of rock mass based on the theory of damage mechanics. Secondly, according to the fractional calculus operator theory and considering the influence of coupled damage variable D BSM on the viscosity coefficient of rock mass in the viscoelasticity and viscoplasticity creep stages, a shear creep damage model of rock mass was established. At the same time, combined with the shear creep test data under the influence of dynamic loads, the damage evolution law of shear creep in carbonaceous shale (weak interlayer of slope) was revealed, and the accuracy of the established shear creep damage model was verified. Finally, the damage evolution law of carbonaceous shale was quantitatively analyzed. Results show that: The shear creep damage model established in this article has unique advantages. The greater the initial damage, the more likely shear creep failure is to occur under the influence of dynamic disturbance and shear creep loads. Dynamic disturbance accelerates the damage of weak interlayers of slope. The cumulative coupling damage of carbonaceous shale (D ma ≤0.18) under dynamic disturbance and multi-stage shear creep loads exhibits an S-like evolution pattern. The shear creep damage mechanism of carbonaceous shale is characterized by obvious initial damage effect, dynamic disturbance damage effect, and stress response characteristics.

Fracture Mode and Thermal Damage Evolution of Sandstone Under the Coupling Effect of Thermal Treatment and Impact Load

The dynamic properties of high-temperature sandstone quickly deteriorate with different cooling methods, which leads to the instability of underground engineering rock structures. Therefore, it is of great significance to quantify the changes in the dynamic characteristics of high-temperature cooled sandstone under impact loads. Therefore, the sandstone is heated to different temperatures and cooled using three methods. A dynamic tensile test is performed using the Splitting Hopkinson Pressure Bar (SHPB) test set for high-temperature cooled sandstone. At the same time, the transient process of rock failure was examined using high-speed cameras. The influence of different temperatures and cooling methods on the thermal damage value of sandstone was analyzed, and the prediction equation was formed. The change in rock energy during rock failure under impact load was calculated.

Effect of Microstructure on Chemo-Mechanical Damage Evolution in Aluminum Foil Anodes for Lithium-Ion Batteries

Aluminum-based foil anodes could enable lithium-ion batteries with high energy density comparable to silicon and lithium metal. However, mechanical pulverization and lithium trapping within aluminum tend to cause capacity fading. The complex interplay between these damage modes is not well understood, as well as the role of microstructure on reaction front evolution. Here, we investigate aluminum foils with different compositions and processing conditions to understand how microstructure influences chemo-mechanical degradation. Backscattered electron imaging of ion-milled foil cross sections is used to visualize reaction front evolution and chemo-mechanical degradation. We find that the shape of the reaction front during lithiation is strongly affected by foil composition, defect distribution, and grain size, which, in turn, affects the evolution of chemo-mechanical damage within the foils. Furthermore, a key finding is that the extent of fracture upon delithiation is inversely related to lithium trapping, with foil compositions that exhibit uniform lithiation, and therefore, less fracturing showing greater lithium trapping. Nonreactive precipitate inclusions within alloy foils are also found to induce void formation. This work shows that material design strategies designed to overcome the inverse fracture-lithium trapping relationship could be useful for improving performance. Published by the American Physical Society 2024

Non-HLA Autoantibodies Against Angiotensin II Receptor 1 (AT1R) and Endothelin A Receptor (ETAR) in Pediatric Kidney Transplantation.

Antibody-mediated rejection (AMR) is the leading cause of premature kidney transplant failure. The role of alloantibodies against Human Leukocyte Antigens (HLA) has been a primary focus in AMR. More recently autoantibodies and alloantibodies against the angiotensin II receptor type 1 (AT1R) and the endothelin A receptor (ETAR) have been linked to poor allograft outcomes in kidney transplantation. Nevertheless, evidence supporting routine testing remains insufficient. ELISA testing for anti-AT1R and anti-ETAR antibodies was performed in a pediatric renal transplant cohort. We selected 12 pediatric recipients who had undergone protocol biopsies and antibody measurements at 6 and 24 months post-transplant. Immunohistochemistry was performed on biopsies for AT1R and ETAR as well as the adhesion molecules ICAM-1 and VCAM-1. The analysis showed that ICAM-1 and VCAM-1 expression was significantly increased, along with the presence of circulating antibodies, in patients at 24 months post-transplant compared to patients without circulating antibodies. The presence of anti-AT1R and anti-ETAR antibodies does not seem to influence the expression of their receptors in the transplanted organ. Instead, the increase in adhesion molecules may precede the development of histological damage. Therefore, enlarging the cohort and extending long-term observation would help to understand the impact of anti-AT1R and anti-ETAR antibodies after transplantation.

Numerical simulation of strengthening/deterioration and damage development of cementitious materials under sulfate attack environment

Cementitious materials exposed to sulfate environments often suffer from the combined effects of external sulfate attack and dry wet cycling. In order to predict the long-term performance of cement-based materials in sulfur rich environments, this paper aims to establish a numerical model that can reasonably characterize the degradation process of cementitious materials in sulfate environments. Using this model, we can address durability problems common to cementitious materials in real sulphate environments, such as determining the degree of corrosion, predicting the durability life of materials, and calculating the time to failure. The model consists of three parts: transportation, chemical reactions, and material damage. We establish the degradation model for cement-based materials in sulfate environments by considering ion diffusion, water convection, chemical reactions, accumulation of corrosion products, and the development of material strengthening/degradation. Compared with existing sulfate corrosion models, this model not only considers ettringite, but also takes into account the volume changes of gypsum formation, calcium leaching, and salt crystallization precipitation, which can more reasonably simulate the sulfate corrosion process in real environments. The model can reasonably simulate the distribution pattern of ion concentration, hydration products and corrosion products in the cementitious material, and on this basis calculate the porosity of the cementitious material. In order to make the simulation results more applicable to experimental and non-destructive testing results, the model uses easily obtainable relative dynamic elastic modulus to evaluate the degree of material strengthening/degradation and predict the durability life of the material.

Failure criterion and damage evolution of high-strength geopolymer concrete under compression-shear composite loading after high temperatures

Geopolymer concrete (GPC) holds significant potential for building fire safety design due to its green, low-carbon, and high-temperature resistant properties. In practical applications, concrete structures often face multiaxial composite loads. Therefore, investigating the composite stress performance of high-strength geopolymer concrete (HGPC) after exposure to high temperatures is crucial for assessing structural damage and enhancing fire prevention measures. This paper examines the compressive shear performance of HGPC at various temperatures T (20°C, 200°C, 400°C, 600°C) and stress ratios k (0.15, 0.3, 0.45, 0.6). The study analyzes failure patterns, shear load-displacement curves, shear strengths and their components, and peak shear deformation. Failure criteria are proposed to describe the damage patterns of HGPC under compressive shear loading after high temperatures. Additionally, the damage evolution process is evaluated using the energy method. The results show that HGPC damage surfaces penetrate the coarse aggregate at room temperature under compression-shear composite loading but shift to the aggregate-mortar interface at 600°C. Shear stiffness, peak shear strength, and residual strength increase with higher stress ratios but decrease with rising temperatures. Temperature affects peak shear strength by over 95 %, significantly more than the stress ratio. The shear strength decreases more slowly than compressive strength up to 400°C but more rapidly beyond 400°C. The cohesive strength of HGPC decreases with increasing stress ratio under different temperatures, while contact friction strength exceeds 50 % of peak shear strength. Shear dilation strength generally increases, then decreases, peaking at k = 0.45. The failure criterion based on the modified twin shear unified strength theory aligns best with experimental results. Furthermore, an increased stress ratio retarded the development of damage evolution, which was first accelerated and then slowed with rising temperature.

Structural damage and bubble evolution in SiC-ZrC composite irradiated with 500 keV He-ions at various temperatures

Ceramic composites with high temperature strengths and low neutron cross-sections are promising candidates for core materials in advanced nuclear systems. In present work, SiC-20 vol% ZrC composites were irradiated with 500 keV He-ions at 25, 500 and 800 °C to evaluate the effect of irradiation temperature on the structural damage and bubble evolution in ceramic composites. XRD and Raman spectra analysis give that the irradiation resulted in structural damages of both SiC and ZrC. TEM observations reveal the formation of helium bubbles and defect clusters after irradiation. Moreover, the occurrence of micro-cracks in ZrC grains and amorphization of SiC are observed for the samples irradiated at room temperature. Nanoindentation test showed that there is irradiation induced hardening or softening of the composites which depends on the irradiation temperature or fluence. The correlation between microstructural evolution and mechanical properties response is discussed.