Impaired Mechanisms Research Articles

Physio-Metabolic Mechanisms Behind Postharvest Quality Deterioration in Broccoli (Brassica oleracea var. Italica) and Swiss Chard (Beta vulgaris L. var. Cicla): A Review

Leafy vegetables are among the potential foods that can combat food insecurity in developing countries. Their major drawback is a short shelf life, which limits their supply chain and is commonly associated with their high metabolic activities. Leafy vegetables have a high water content, which determines their freshness. Moisture loss through respiration and transpiration at postharvest storage is one quality attribute that leads to rapid quality deterioration. Little has been carried out in studying the mechanisms associated with the quality deterioration of leafy vegetables; however, understanding these mechanisms may aid in developing effective preservation measures. Furthermore, recent literature reviews that focus on discussing the mechanisms that lead to quality loss in leafy vegetables are scarce. The current paper aims to review the physiological and biochemical processes associated with quality deterioration in leafy vegetables. The respiration, ethylene production, moisture loss, colour, and texture are highly associated with the quality deterioration of fresh produce and, thus will be discussed critically in selected leafy vegetables, namely: broccoli and Swiss chard. The findings from this review indicate that the quality deterioration in leafy vegetables is primarily enzymatic. Understanding the mechanisms of quality deterioration involves identifying the specific enzymes responsible for each metabolic process and examining the internal and external factors that influence enzyme activities.

Formulation and Implicit Numerical Integration of a Kinematic Hardening Model for Unsaturated Soils

ABSTRACTCurrently, our understanding of material‐scale deterioration resulting from meteorologically induced variations in pore water pressure and its significant impact on infrastructure slopes is limited. To bridge this knowledge gap, we have developed an extended kinematic hardening constitutive model for unsaturated soils that refines our understanding of weather‐driven deterioration mechanisms in heterogeneous clay soils. This model has the capability of predicting the irrecoverable degradation of strength and stiffness that has been shown to occur when soils undergo wetting and drying cycles. The model is equipped with a fully coupled and hysteretic water retention curve and a hysteretic loading–collapse curve and has the capability to predict the irrecoverable degradation of strength and stiffness that occurs during cyclic loading of soils. Here, we employ a fully implicit stress integration technique and give particular emphasis to deriving a consistent tangent operator, which includes the linearisation of the retention curve. The proposed algorithm is evaluated for efficiency and performance by simulating various stress and strain‐driven triaxial paths, and the accuracy of the integration technique is evaluated through the use of convergence curves.

The association between metabolite profiles and impaired bone microstructure in adult growth hormone deficient rats

BackgroundAdult growth hormone deficiency (AGHD) is associated with an increased risk of fractures and impaired bone microstructure. Understanding the metabolic changes accompanying bone deterioration in AGHD might provide insights into mechanisms behind molecular changes and develop new biomarkers or nutritional strategies for bone destruction. Our study aimed to investigate the association between altered metabolite patterns and impaired bone microstructure in adult rats with growth hormone deficiency.MethodsThirty seven-week-aged adult Lewis dwarf homozygous (dw/dw) rats (five females and five males), and adult Lewis dwarf heterozygous (dw/ +) rats (five females and five males) rats were compared. Micro-computed tomography (Micro-CT) was used to examine the bone's microstructure. Hematoxylin and eosin (H&E) staining were used to quantify the histological characteristics. Liquid chromatography-mass spectrometry untargeted serum metabolomic analysis was applied in the study. ELISA was used to measure serum bone turnover markers and IGF-1 levels.ResultsAdult dw/dw rats exhibited great reductions in trabecular volume bone density (Tb.vBMD), bone volume/total volume (BV/TV), and cortical thickness (Ct. Th) compared with adult dw/ + rats (all p values < 0.05), indicating significant impairment in bone microstructure. The serum metabolite profiles revealed substantial differences between the dw/dw rats and dw/ + rats. A total of 134 differential metabolites in positive ion mode and 49 differential metabolites in negative mode were identified. Five metabolites, including Lysophosphatidylcholine(LPC) 20:3, LPC22:6, LPC22:4, cortisol and histamine levels were upregulated in dw/dw rats. The steroid hormone biosynthesis and bile secretion pathways were the main perturbed metabolic pathways. There were significant associations between differential metabolites and the impaired bone microstructure parameters, indicating that the selected metabolites might serve as potential biomarkers for deteriorated bone microstructure in AGHD.ConclusionAdult dw/dw rats exhibit impaired bone microstructure and distinct serum metabolic profiles, and the altered metabolites were significantly associated with bone microstructure destruction. This provides a new insight into understanding the mechanism of bone deterioration in AGHD patients from a metabolic perspective.

Crack Development and Electrical Degradation in Chromium Thin Films Under Tensile Stress on PET Substrates

The mechanical and electrical deterioration of chromium (Cr) thin films sputtered onto polyethylene terephthalate (PET) substrates under tensile strain was studied. Understanding mechanical and electrical stability due to imposed strain is particularly important for device reliability, as the demand for flexible electronic devices increases. Cr thin films, widely spread across the field of electronic and sensor applications, face crack propagation with electrical degradation with tensile stress that can seriously compromise the performance. Accordingly, this study offers new findings on how Cr film thickness might influence crack formation and electrical resistance differently and also the general guidelines for flexible electronic component design with respect to long-term durability. Electrical resistances were measured while mechanically stretching 100- and 200 nm thin sheets. The study focused on crack development and propagation mechanisms in both film thicknesses and their effects on percentage change in electrical resistance (PCER). Scanning electronic microscopy (SEM) was used to characterize surface morphology and observe cracks as the strain rose. Early crack formation in 100 nm Cr films led to rapid PCER increases due to quick crack propagation and fast electrical degradation. Thicker 200 nm films, however, showed a more gradual PCER rise with fewer but deeper cracks, indicating a regulated strain response. Unlike the sharp PCER spike in 100 nm films, 200 nm samples were more variable, with three out of four showing a slight PCER decrease at the end, hinting at partial crack repair or conductive realignment before full failure. These results underscore the role of layer thickness in managing crack propagation and electrical stability, relevant for flexible electronics and strain sensors. This paper is aligned with the ninth goal of the United Nations Sustainable Development Goals, specifically Target 9.5: Enhance Research and Upgrade Industrial Technologies.

Study of microstructural evolution during operation of electrically connected components and analysis of failure mechanism

Abstract As a key current-carrying structure of high-voltage bushings, the reliability of electrical connection components is crucial to the safe and stable operation of power equipment. To obtain the microstructural evolution of electrical connection components with different deterioration states, CUD strap contactors were deteriorated in different ways, and electron backscatter diffraction (EBSD) technique was used to test the microstructure of strap contactors with different deterioration states. The results showed that compared to the unused contactors, the contact resistance of the contactors under the combined effect of friction and high temperature increased 203.12 times and was in a failed state. During the process from unused state to wear deterioration, high temperature deterioration, and then to eventual failure of the contactors, the average grain size gradually grows from 8.15 μm to 25 μm, the dislocation density gradually decreases from 2.38×1014 m-2 to 1.04×1014 m-2, and there are a significant proportion of the recrystallized organization. These changes are detrimental to the mechanical properties of the contactors. In addition, the distribution of grain boundaries in the contact area proves the occurrence of over-temperature phenomenon in this area, which will accelerate the deterioration of the contactors and eventually lead to the failure of the component. The relevant conclusions can provide a theoretical basis for the design of electrical connection structure of strap contacts as well as the study of deterioration mechanism.

Study on the decay laws and deterioration mechanism of mechanical properties of cement-stabilized gravel under water-heat-salt coupled conditions

A new type of asphalt pavement disease, known as arch expansion, has appeared in the saline soil regions of Northwest China. The emergence, as well as the evolution of the disease, is strongly related to the distribution of sulfate. However, the decay of Cement-stabilized gravel (CSG) mechanical properties is closely related to the onset and development of arch expansion. The relationship between CSG mechanical strength and salinity in the arch expansion area is analyzed based on field investigations to systematically study the mechanical property degradation law and mechanism of CSG. The mechanical strength and deterioration patterns of CSG with different coupling conditions were investigated. The mineral composition and micromorphology of the erosion products were analyzed. The results show that the mechanical properties of CSG in the area of the arch deteriorate more than those in the regular section. The mechanical strength of the specimens initially containing salt and partially immersed in salt solution decayed most severely. In terms of the deterioration mechanism of mechanical strength of CSG, the water-heat-salt erosion process is also divided into two parts, including the formation stage of gypsum and ettringite, the stage of C-S-H decomposition and thaumasite formation, respectively. The degradation mechanism of CSG is a combination of physical and chemical erosion.

Freeze-thaw resistance and deterioration mechanism of alkali-activated filling grouts prepared from full industrial solid wastes for tunnels

Freeze-thaw resistance and deterioration mechanism of alkali-activated filling grouts prepared from full industrial solid wastes for tunnels

Constitutive model and deterioration mechanisms of uniaxial compressive behavior for calcium aluminate cement-based UHPC under simulated fire temperatures

Constitutive model and deterioration mechanisms of uniaxial compressive behavior for calcium aluminate cement-based UHPC under simulated fire temperatures

Microstructure evolution process and multi-scale deterioration mechanism model of graphite tailings cement-based materials subjected to high temperature

This manuscript investigated the thermal stability, crystal reconstruction and microstructure evolution of graphite tailing cement mortar subjected to high temperature. Simultaneously, a computational model for heat transfer and degradation considering chemical transformations had been developed by combining multiscale mechanics with the laws of thermodynamics. The results show that 20% graphite tailings can increase the tobermorite crystal content under high temperature and inhibit its transformation into disordered form. Furthermore, the dormant active SiOx in graphite tailing is gradually activated under the action of high temperature, which catalyzes and induces the formation of more belite crystal in graphite tailing cement mortar. Additionally, 40% graphite tailing can promote the generation of anorthite by the induction of high temperature. Finally, a new multi-scale model considering the chemical transformation is established to calculate the high-temperature degradation process of graphite tailing cement mortar.

Exploring the impacts of liquid accelerators on sulfate resistance and calcium leaching behavior of wet-mixed shotcrete

The performance of shotcrete used in underground tunnel construction is often compromised by the challenging service environment, causing severe deterioration and structural integrity concerns. Developing high-quality accelerating agents can be a viable approach to mitigate this effect. This study formulates alkali-free fluorine-free (AF-I); alkali-free fluorine-containing (AF-II); and low-alkaline (AC) liquid accelerators and explores their impacts on sulfate resistance and calcium leaching behavior of shotcrete, utilizing semi-immersion and short-term tank water testing protocols on a time-resolved basis. Microstructural analysis of eroded shotcrete was conducted employing XRD, TGA and SEM to reveal underlying mechanisms. Additionally, ionic analyses of simulated leaching systems, including groundwater and 5% sodium sulfate solution were performed using ICP-OES to monitor calcium activity and assess leaching behaviors. Results indicate that shotcrete accelerated with AF-II exhibits the strongest resistance, whereas shotcrete with AC suffers the severest deterioration. The primary deterioration mechanism of shotcrete with AC was majorly due to high ettringite and gypsum corrosion, whereas AF-I and AF-II induces little ettringite corrosion. In terms of leaching behavior, AF-II demonstrates superior calcium leaching mitigation, with leachability indices in groundwater and sodium sulfate solution measuring 0.06 and 0.19, and 0.02 and 0.16 higher values, respectively, compared to AF-I and AC. Findings of this study provide valuable insights into the application and performance of shotcrete in sulfate-prone environments, aiming to mitigate potential deterioration through optimal accelerator selection.

Mechanical property deterioration and a full-stage constitutive model of shale subject to water-softening effect

Mechanical property deterioration and a full-stage constitutive model of shale subject to water-softening effect

A Comprehensive Review of the Key Deterioration Factors of Concrete Bridge Decks

Bridges are generally acknowledged as one of the vital structures of transportation systems. Meanwhile, they are prone to time-variant damage and deterioration mechanisms over their life span. With that in mind, this research study aims to explore state-of-the-art work in relation to deterioration models and related critical factors of reinforced concrete bridges. Particularly, this study presents a mixed review methodology (scientometric and systematic) that reviews over 300 publications in Scopus and Web of Science databases over the period 1985–2023. The study scrutinized and categorized the wide spectrum of deterioration factors in reinforced concrete bridges with the help of deterioration models. Results manifested that implicating deterioration factors can be grouped into seven main clusters, namely chemical, material properties, design &amp; construction, physical, operational, environmental, and force majeure. In addition, it is noted that hitherto, there has been a lack of sufficient research efforts on non-destructive evaluation-based deterioration models.

Probing the dual mechanism of load damage and flowing solution on sulfate attack resistance of alkali-activated slag concrete

Alkali-activated slag concrete (AASC) is a representative low-carbon green building material. To effectively characterize the sulfate attack resistance of AASC in complex environments, a self-designed simulation device for complex corrosion environments was used to study the sulfate attack mechanism and property deterioration law of AASC under the loads and flowing corrosion solutions. The results indicated that both load-induced damage and dissolution accelerated the transport of sulfate ions into the AASC. On the one hand, the load-induced damage and dissolution resulted in a decrease in the proportion of gel pores, reducing the electrostatic interaction between ions and the gel pore wall as well as the gel pore wall thinning effect. On the other hand, the load-induced damage and dissolution decreased the pH of the pore solutions in AASC, causing easier decalcification or dealumination of C-A-S-H gel under sulfate ion attack. This further accelerated the sulfate ion attack and deterioration of AASC.

Analysis of active impedance characteristics and harmonic deterioration of multiple grid connected inverters considering nonlinear factors

AbstractThe harmonic problems caused by non‐linear factors of the grid connected inverter (GCI) system are more complicated, including both non‐characteristic harmonics emitted by the dead‐time and the changes in harmonic impedance characteristics. Harmonics interact with the changing impedance, and even cause harmonic amplification and resonance. The harmonic deterioration of the multiple GCIs system is serious. To analyse the mechanism and way of harmonic deterioration in grid‐connected system caused by nonlinear factors, the active impedance models of single inverter and multiple GCIs system including dead‐time effect and digital control delay are established first. In view of this, the influence mechanism of non‐linear factors on system stability is explored. The improved modal analysis method is used to traverse the network series parallel resonance caused by nonlinear factors. The results show that both the dead‐time effect and digital control delay reduce phase margin of the system, resulting in the resonant frequency shift and the resonant peak increase. When the harmonic excitation source interacts with the complex network under the influence of nonlinear factors, it will lead to further deterioration of harmonics. Finally, based on the MATLAB and RT‐LAB hardware‐in‐the‐loop simulation platforms, a multiple GCIs system model is built to verify the correctness of the established active impedance model and harmonic deterioration analysis.

Long-Term Mechanical Deterioration Trends and Mechanisms of SBS-Modified Asphalt Mixtures

Understanding the long-term performance deterioration trends and mechanisms of asphalt pavement is crucial for effective maintenance strategies. This study characterizes and correlates the multi-scale performance deterioration of a 14-year asphalt pavement. Air void measurements, indirect tensile (IDT) fatigue testing, Fourier transform infrared spectroscopy (FTIR), and dynamic shear rheometer (DSR) testing were conducted on pavement cores and recovered binder. Multiple regression analysis was then performed on various performance indicators. Laboratory results indicate that the chemical composition and viscoelastic properties of SBS-modified binders evolve rapidly in the first few years, followed by a relatively stable aging rate. After 14 years, the mechanical and rheological properties of lower-layer mixtures deteriorate to a similar degree as the surface layer. Correlation analysis revealed that the residual strength of the mixture is more influenced by air voids, while reductions in fatigue life are primarily driven by binder aging. These findings highlight the necessity of applying preventive maintenance within the first 3–5 years to rejuvenate the surface asphalt and rehabilitate both the surface and underlying layers after long-term service.

Time-varying deterioration of bamboo mechanical properties

Bamboo is a type of fast-growing and renewable natural resource that is an ideal building material. In this study, the longitudinal tensile, longitudinal compressive, flexural, longitudinal shear, transverse tensile, and transverse compressive stress-strain and strength properties of bamboo with a period of 240 days were conducted to study the time-varying deterioration performance of bamboo. The results showed that the mechanical properties of bamboo decreased gradually with the passage of time. The transverse compressive strength deteriorated the most, and the longitudinal tensile strength deteriorated the least. After 240 days of tests, bamboo CCS decreased by 52.5% and UTS decreased by 25.4%. Formulas to predict deterioration of mechanical properties were put forward and validated. It was found that the nodes of bamboo influenced its mechanical properties. The deterioration degree of the test specimens with nodes was slightly higher than that of the test specimens without nodes. These findings provide evidence about the deterioration mechanism of bamboo and are significant for promoting the development of bamboo architecture.

Macro-meso physical and mechanical deterioration properties and damage prediction model of rock under Freeze–thaw cycles

Macro-meso physical and mechanical deterioration properties and damage prediction model of rock under Freeze–thaw cycles

Experimental study evaluating the performance of thermal conductivity prediction models for air–water saturated weathered sandstone heritage

As a critical parameter, thermal conductivity directly determines the heat transfer and temperature variation within rocks, which can lead to mechanical damage and chemical corrosion. Consequently, understanding the thermal conductivity of stone heritage is vital for assessing their deterioration mechanisms and developing effective conservation strategies. This study obtained sandstone samples from the Yungang Grottoes and subjected them to freeze–thaw cycle experiments to generate weathered sandstone samples. Subsequently, the thermal conductivity of these samples was measured under both dry and water-saturated state using the transient plane source method. To analyze the relationship between air–water saturation, porosity, and thermal conductivity, a saturation influence coefficient was introduced. Thereafter, the effectiveness and applicability of 13 commonly used thermal conductivity mixing law prediction models were evaluated based on experimental data. The results suggested that the influence of water saturation on the thermal conductivity of rocks varies with porosity, and water saturation significantly enhances the thermal conductivity of weathered sandstone. Among the 13 common models, the Geometric mean model was found to be more accurate than other models, with superior performance in both dry (MAE, RMSE, MAPE are 0.148, 0.214, 5.59% respectively) and water-saturated (MAE, RMSE, MAPE are 0.244, 0.170, 8.4% respectively) state. The Albert model demonstrates a good fit in the dry state, whereas the Walsh model (with maximum effect), Ribaud model, and Huang model also exhibit good fitting efficacy in the water-saturated state. This study provides a solid foundation for better predicting the thermal conductivity of weathered stone heritage and developing effective preventive conservation strategies.

Quantum Geometry and Stabilization of Fractional Chern Insulators Far from the Ideal Limit.

In the presence of strong electronic interactions, a partially filled Chern band may stabilize a fractional Chern insulator (FCI) state, the zero-field analog of the fractional quantum Hall phase. While FCIs have long been hypothesized, feasible solid-state realizations only recently emerged, largely due to the rise of moiré materials. In these systems, the quantum geometry of the electronic bands plays a critical role in stabilizing the FCI in the presence of competing correlated phases. In the limit of "ideal" quantum geometry, where the quantum geometry is identical to that of Landau levels, this role is well understood. However, in more realistic scenarios only empiric numerical evidence exists, accentuating the need for a clear understanding of the mechanism by which the FCI deteriorates, moving further away from these ideal conditions. We introduce and analyze an anisotropic model of a |C|=1 Chern insulator, whereupon partial filling of its bands, an FCI phase is stabilized over a certain parameter regime. We incorporate strong electronic interaction analytically by employing a coupled-wires approach, studying the FCI stability and its relation to the quantum metric. We identify an unusual anti-FCI phase benefiting from nonideal geometry, generically subdominant to the FCI. However, its presence hinders the formation of FCI in favor of other competitive phases at fractional fillings, such as the charge density wave. Though quite peculiar, this anti-FCI phase may have already been observed in experiments at high magnetic fields. This establishes a direct link between quantum geometry and FCI stability in a tractable model far from any ideal band conditions, and illuminates a unique mechanism of FCI deterioration.

Insights into the Deterioration Mechanism of Charging Ability during Calendar Aging and Cycling Aging of High-Voltage Co-Poor NCM Cathode-Graphite Full Battery.

Lithium-ion battery (LIB) has gained significant recognition for the power cell market owing to its impressive energy density and appealing cost benefit. Among various cathodes, a high-voltage cobalt-poor lithium nickel manganese cobalt oxide cathode (Co-poor NCM cathode) has been considered as a promising strategy to enhance its energy density. Despite these advantages, high-voltage Co-poor NCM cathode-graphite full battery usually suffers from poor rate performance. However, fast charging has been a key indicator for widespread application of power batteries. Although many efforts have been made to improve the charging performance of fresh batteries, few works investigate the charging ability during calendar aging and cycling aging of high-voltage Co-poor NCM cathode-graphite full battery. In this work, we found that the charging ability becomes worse during calendar aging and cycling aging. Results showed that the increasing charge transfer resistance from the cathode is the major obstacle to achieving fast charging during the aging process. To address the problem, high-voltage Al2O3-coated Co-poor NCM cathode successfully prepared via a simple atomic layer deposition (ALD) method has been developed to reduce the decay of charging performance during calendar aging and cycling aging. Al2O3-coated NCM cathode can effectively reduce the growth rate of the resistance of cathode, which is benefiting from the conversion of Al2O3 into LiAlO2 with high ionic conductivity and the restriction formation of rock salt phase. Benefiting from the decreased charge transfer resistance of the NCM cathode, the mismatch of the lithium-ion reaction kinetics is well alleviated, thus effectively reducing the polarization under fast charging. As a result, Al2O3-coated NCM cathode-graphite full battery shows the slow deterioration of charging performance during the aging process. This work provides a promising strategy for constructing fast-charging batteries during calendar aging and cycling aging.