Search Results (98)

Objective: Monosodium urate (MSU) crystallization in human joints is poorly understood. This study aimed to investigate whether the length of MSU crystals varies in relation to organized ultrasound deposits, which may lead to longer crystals. Methods: Observational, cross-sectional study analyzing MSU crystals from synovial fluid samples of patients with crystal-proven gout. Using light microscopy, we measured crystal lengths (in µm) and noted the presence of long crystals, defined by cutoffs at the 66th, 75th, and 90th percentiles. We evaluated their association with two ultrasound-defined crystal deposition models: (1) grade 2–3 double-contour (DC) sign, tophi, and/or aggregates; and (2) grade 2–3 DC sign and/or tophi. Results: In a total of 1076 MSU crystals from 28 joints, median length was 23.3 µm (95% confidence interval 22.1–24.5). MSU crystal length was similar regardless of ultrasound deposition: in model 1 (20 joints, 71.4%), 22.5 µm in joints with deposits vs. 21.7 µm without; p = 0.42; in model 2 (15 joints, 53.6%), 22.8 µm vs. 21.2 µm, respectively; p = 0.12. Joints fulfilling model 2 criteria had more long crystals (>66th percentile), both in absolute and relative terms. Long crystals mildly correlated with serum urate levels and were numerically more frequent in patients with tophaceous gout. Conclusions: Most MSU crystals in synovial fluid gathered around a common length, regardless of ultrasound deposition. Long crystals were more common in joints with DC signs or tophi. Our finding is in keeping with two different mechanisms of MSU crystallization in humans. Full article

High penetration of Inverter-Based Resources (IBRs) into the power grid could diminish the rotational inertia offered by a traditional power system and thus impact frequency stability. Several techniques are adopted to provide virtual inertial support to the grid for a short duration in the presence of IBRs. This paper uses the combined inertia support of a Dual Active Bridge (DAB) and a Voltage Source Converter (VSC)-fed Electric Vehicle Fast Charging System (EVFCS) is used to provide virtual inertia support to the grid. The Voltage Source Converter is designed to provide DC bus voltage regulation. Coordinated control of DAB converters and VSCs for mitigating frequency oscillations using cascaded droop-integrated Proportional Integral (PI) controllers is proposed. An aggregated low-frequency model of a DAB converter is considered in this work. The inertia of the DC link capacitor of the VSCs and battery is sequentially extracted to offer grid frequency support. In this work, the single droop control, dual droop control, grid-forming and Augmented Frequency Support (AFS) modes are explored to provide virtual inertia support to the grid. Full article

The large-scale integration of new power loads, such as electric vehicles and energy storage devices, has led to challenges including insufficient regulation capacity and low resource coordination efficiency in low-voltage distribution transformer areas. To address these issues, this paper proposes an optimal configuration model for flexible interconnected distribution transformer areas based on load aggregation. First, a flexible interconnection architecture is constructed using multi-port power electronic conversion devices, enabling mutual power support and voltage stabilization between adjacent areas. Second, a load aggregator scheduling model is established to quantitatively assess the dispatchable potential of electric vehicle charging loads. On this basis, a multi-objective optimization configuration model is formulated with the objectives of minimizing the comprehensive cost of the system and minimizing the average peak-valley difference of substation transformer loads. Case study results demonstrate that the proposed model significantly improves both economic efficiency and operational reliability. Compared to the traditional independent operation mode, the coordinated optimization scheme reduces the comprehensive system cost by 29.6% and narrows the average load peak-valley difference by 50.8%. These findings verify the synergistic effectiveness of flexible interconnection and load aggregation technologies in enhancing equipment utilization, reducing distribution losses, and improving power supply resilience. Full article

This paper focuses on the Input-Independent Output-Series (IIOS) DC converters within fully DC aggregation systems, which enable independent submodule control and high voltage gain. DC aggregation systems experience output voltage imbalance among submodules due to offshore wind power fluctuations. The proposed isolated DC/DC converter topology incorporates power-balancing capacitors, leveraging intrinsic characteristics to achieve self-power balancing within the system. In addition, this paper proposes an innovative PFMT-PSMN hybrid control strategy that is well-suited for the proposed topology. Firstly, this study performs a time-domain analysis of the intrinsically power-balanced DC series-connected aggregation topology and elucidates the corresponding power-balancing principle. Secondly, based on soft-switching boundary conditions, a hybrid control strategy, PFMT-PSMN, adjusts phase-shift duty cycles to maintain soft-switching conditions while minimizing the system operating frequency. Finally, MATLAB/Simulink simulations validate the power-balancing capability of the intrinsically balanced DC series-connected aggregation system and the effectiveness of the proposed PFMT-PSMN control strategy. Full article

Driven by climate change and human activities, the expansion of highly invasive moso bamboo (Phyllostachys edulis) into coniferous forests induces a serious ecological imbalance. Its rapidly spreading underground roots significantly alter soil structure, yet the mechanisms by which this expansion affects soil detachment capacity (Dc), a key soil erosion parameter, remain unclear. While bamboo expansion modifies soil physicochemical properties and root characteristics, influencing Dc and, consequently, soil erosion resistance, the underlying mechanisms, particularly stage-specific variations, are not thoroughly understood. In this study, we examined Japanese white pine (Pinus parviflora Siebold & Zucc.) forest (CF), moso bamboo–Japanese white pine mixed forest (MF), and moso bamboo forest (BF) as representative stages of bamboo expansion. By integrating laboratory-controlled measurements of soil physicochemical properties and root traits with field-based flume experiments, we comprehensively investigate the effects of moso bamboo expansion into CF on soil detachment capacity. The results of the study can be summarized as follows: (1) Expansion of moso bamboo significantly changed soil physicochemical properties and root characteristics. Soil bulk density was the highest in the MF (1.13 g·cm⁻³), followed by the CF (1.08 g·cm⁻³) and BF (1.03 g·cm⁻³); non-capillary porosity increased significantly with expansion (CF 0.03% to MF 0.10%); and although the stability of aggregates (MWD) increased by 24.5% from the CF to MF, root mass density (RMD) in the MF (0.0048 g·cm⁻³) was much higher than that in the CF (0.0009 g·cm⁻³). This intense root competition between forest types, combined with increased macroporosity development, compromised overall soil structural integrity. This weakening may lead to a looser soil structure during the transition phase, thereby increasing erosion risk. (2) There were significant stage differences in Dc: it was significantly higher in the MF (0.034 kg·m⁻²·s⁻¹) than in the CF (0.023 kg·m⁻²·s⁻¹) and BF (0.018 kg·m⁻²·s⁻¹), which revealed that the MF was an erosion-sensitive stage. (3) Our Partial Least Squares Structural Equation Modeling (PLS-SEM) results revealed that soil physicochemical properties (soil moisture content and soil total nitrogen) dominated Dc changes through direct effects (total effect −0.547); in comparison, root properties indirectly affected Dc by modulating soil structure (indirect effect: −0.339). The results of this study reveal the dynamics and mechanisms of Dc changes during bamboo expansion, and for the first time, we identify a distinct Dc peak during the mixed forest transition phase. These findings provide a scientific basis for moso bamboo forest management, soil erosion risk assessment, and optimization of soil and water conservation strategies. Full article

Wildfires, whether natural or human-caused, significantly alter soil properties and increase soil erosion susceptibility, particularly through changes in rill detachment capacity (Dc). This study aimed to evaluate the influence of fire intensity on key soil properties and to recognize their relationships with Dc under controlled laboratory conditions. The research was conducted in the Darestan Forest, Guilan Province, northern Iran, a region characterized by a Mediterranean semi-arid climate. Soil samples were collected from three fire-affected conditions: unburned (NF), low-intensity fire (LF), and high-intensity fire (HF) zones. A total of 225 soil samples were analyzed using flume experiments at five slope gradients and five flow discharges, simulating rill erosion. Soil physical and chemical characteristics were measured, including hydraulic conductivity, organic carbon, sodium content, bulk density, and water repellency. The results showed that HF soils significantly exhibited higher rill detachment capacity (1.43 and 2.26 times the values compared to the LF and NF soils, respectively) and sodium content and lower organic carbon, hydraulic conductivity, and aggregate stability (p < 0.01). Strong correlations were found between Dc and various soil properties, particularly a negative relationship with organic carbon. The multiple linear equation had good accuracy (R² > 0.78) in predicting rill detachment capacity. The findings of the current study show the significant impact of fire on soil degradation and rill erosion potential. The study advocates an urgent need for effective post-fire land management, erosion control, and the development of sustainable soil restoration strategies. Full article

Recycled concrete aggregates (RCAs) have the potential to be used as a sustainable, cost-effective, and environmentally friendly material in pavement base construction. However, there is a lack of information on the durability, strength, and hydraulic properties of RCA. The primary purpose of this study was to evaluate the properties and performances of commonly available RCAs in Oklahoma as pavement bases through laboratory testing and AASHTOWare Pavement ME simulations. For this purpose, three RCAs (RCA-1, RCA-2, and RCA-3) and a virgin limestone aggregate (VLA-1) were collected from local sources. RCA-1 and RCA-3 were produced in the field by crushing the existing concrete pavement of Interstate 40 and US 69 sections, respectively. RCA-2 was produced by crushing concrete and rubble collected in a local recycling plant. Laboratory testing for this study included particle size distribution, wash loss, optimum moisture content and maximum dry density (OMC-MDD), Los Angeles (LA) abrasion, durability indices (D_c and D_f), permeability (k), and resilient modulus (M_r). The properties of aggregates were compared and the service life (performance) of aggregate bases was studied through mechanistic analysis using the AASHTOWare Pavement ME design software (version 2.6, AASHTO, USA). The results indicated that the properties of RCAs can differ greatly based on the origin of the source materials and the methods used in their processing. Recycled aggregates from concrete pavements of interstate and state highways exhibited similar or improved performance as virgin aggregates. RCA produced in a recycling plant was found to show durability and strength issues due to the presence of inferior quality materials and contaminants. Also, the results indicated that the fine aggregate durability test is a useful tool for screening recycled aggregates to ensure quality during production and construction. Bottom-up fatigue cracking was identified as the most affected performance criterion for flexible pavements when using RCA as the base layer. The findings will help increase the use of RCA as pavement base to promote environmental sustainability. Full article

Cotton, commonly used in wound care, has limitations such as quick saturation and wound adhesion, prompting surface modifications. In our studies, iron, which promotes platelet aggregation and coagulation, was deposited onto cotton via direct current (DC) magnetron sputtering. Thus, the biochemical properties of cotton fabrics were enhanced. Microscopic analyses revealed uniform iron coating on the fibers, and biochemical tests, such as activated partial thromboplastin time (aPTT) and prothrombin time (PT), showed that the modification did not affect the material’s coagulation activity. Measurements with the thiobarbituric acid (TBA) method (TBARS) showed that iron-modified cotton had antioxidant activity by lowering lipid peroxidation, which can be beneficial for better wound healing and lower infection risk. Moreover, our analysis showed the absence of cyto- and genotoxic properties against normal peripheral blood mononuclear cells (PBM cells). It was found that tested fabrics did not directly interact with DNA. Full article

The study of the compression characteristics of loess in seasonal regions involves analyzing the mechanical properties and mesoscale damage evolution of intact loess subjected to dry–wet freeze–thaw cycles. This study meticulously examines the evolution of the stress–strain curve at the macroscale and the pore structure at the mesoscale of loess by consolidation and drainage triaxial shear tests, as well as nuclear magnetic resonance (NMR), under varying numbers of dry–wet freeze–thaw cycles. Then, utilizing the Duncan–Chang model (D-C), the damage model for intact loess is derived based on the principles of equivalent strain and Weibull distribution, with testing to verify its applicability. The results indicate that the stress–strain curve of undisturbed loess exhibits significant strain softening during the initial stage of the freeze–thaw dry–wet cycle. As the number of cycles increases, the degree of strain softening weakens and gradually exhibits a strain-hardening morphology; the volume strain also changes from dilatancy to shear contraction. According to the internal pore test data analysis, the undisturbed loess contributes two components to shear strength: cementation and friction during the shear process. The cementation component of the aggregate is destroyed after stress application, resulting in a gradual enlargement of the pore area, evidenced by the change from tiny pores into larger- and medium-sized pores. After 10 cycles, the internal pore area of the sample expands by nearly 35%, indicating that the localized damage caused by the dry–wet freeze–thaw cycle controls the macroscopic mechanical properties. Finally, a damage constitutive model is developed based on the experimental phenomena and mechanism analysis, and the model’s validity is verified by comparing the experimental data with theoretical predictions. Full article

Background: Next-generation sequencing has revealed TP53 alterations in localized prostate cancer (PCa), suggesting growing clinical potential for p53 immunohistochemistry (IHC). Prior research supports the use of IHC for the detection of p53 overexpression to predict the presence of TP53 alterations known to be associated with adverse outcomes. However, to reach a consensus definition of p53 overexpression in PCa, further insights are needed. This study aimed to compare two fundamental approaches of evaluating p53 expression across a variety of specimens regarding PCa progression. Methods: This study included 84 patients (75% self-identified as African American) diagnosed with PCa between 1996 and 2021 at the DC VA Medical Center. Representative sections of core biopsies, radical prostatectomies, transurethral prostate resections, and metastatic deposits were examined. p53 nuclear expression was scored according to the highest intensity observed (0, 1+, 2+, 3+) and the percentage (0%, <1%, 1–5%, >5%) of tumor cells expressing any level of intensity in the aggregate tumor area. All slides were reviewed by two independent pathologists. Pertinent clinical data were collected. Results: A total of 34 patients (40%) exhibited p53 nuclear expression, of which 18 (21%) showed the maximum (3+) intensity. The presence of maximum intensity, regardless of percentage, was found to be associated with Grade Group (p < 0.001), higher PSA at biopsy (p < 0.001), BCR (p < 0.001) and metastasis (p < 0.001). Importantly, maximum p53 intensity was identified only in patients who developed metastatic disease. Conclusions: Maximum (3+) p53 nuclear intensity of any percentage is highly associated with disease progression in PCa, suggesting that optimal determination of p53 overexpression should incorporate intensity. Full article

The relationships between soil aggregates, aggregate-associated carbon (C), and soil compaction indices in pomegranate orchards of varying ages (0–30 years) in Assiut, Egypt, were investigated. Soil bulk density (Bd) and organic carbon (OC) content increased with orchard age in both the surface (0.00–0.20 m) and subsurface (0.20–0.40 m) layers 0.20–0.40 m). The percentage of macroaggregates (R_0.25) and their OC content in the aggregate fraction > 0.250 mm increased as the pomegranate orchard ages increased in the surface layer (0.00–0.20 m). Older pomegranate orchards show improved soil structure, indicated by higher mean weight diameter (MWD) and geometric mean diameter (GMD), alongside reduced fractal dimension (D) and erodibility (K). As orchard ages increased, maximum bulk density (B_Max) decreased due to an increase in OC, while the degree of compactness (DC) increased, reaching a maximum at both soil layers for the 30 Y orchards. Soil organic carbon and aggregate-associated C significantly influenced B_Max, which led to reducing the soil compaction risk. Multivariate analyses identified the >2 mm aggregate fraction as the most critical factor influencing the DC, soil compaction, and K indices in pomegranate orchards. The OC content in the >2 mm aggregates negatively correlated with B_Max, DC, and K but was positively associated with MWD and GMD. Moreover, DC and Bd decreased with higher proportions of >2 mm aggregates, whereas DC increased with a higher fraction of 2–0.250 mm aggregation. These findings highlight the role of aggregate size fractions and their associated C in enhancing soil structure stability, mitigating compaction, and reducing erosion risks in pomegranate orchards. Full article

With the increasing proportion of renewable energy in power grids, the inertia level and frequency regulation capability of modern power systems have declined. In response, this paper proposes a coordinated frequency regulation strategy integrating power generation, energy storage, and DC transmission for offshore wind power MMC-HVDC transmission systems, aimed at improving the frequency stability of onshore power grids. First, considering the inability of the receiving-end MMC-HVDC converter station under constant DC voltage control to directly respond to AC system frequency variations, a frequency regulation method is developed based on constant DC voltage control. The approach employs DC voltage as a transmission signal to coordinate the responses of wind turbines and energy storage systems. Subsequently, based on the energy storage configuration of the onshore renewable energy aggregation station, a secondary frequency regulation strategy is proposed. This strategy integrates offshore wind power, MMC-HVDC transmission system, and energy storage systems, balancing AC frequency regulation and the recovery of the state of charge (SOC) of the energy storage system. Finally, the proposed method is tested on a modified IEEE 39-bus system, the results demonstrate that the minimum frequency value can be in-creased by 37.5%, the system frequency can be restored to the initial state after secondary FM, and the results demonstrate its effectiveness. Full article

With the construction of the UHV (Ultra High Voltage) AC/DC hybrid power grid and the large-scale access to renewable energy such as wind power, frequency dynamic fluctuation has become a prominent problem affecting the safe and stable operation of large power grids. The expansion of the scale of the power system makes it impossible to use traditional fine modeling to analyze the power system. In order to reduce the calculation scale and storage capacity of power system frequency dynamic simulation, it is necessary to make appropriate equivalent simplification of the external system, so the appropriate dynamic equivalent method is of great significance. This paper mainly studies the equivalent model suitable for frequency dynamic analysis of large power grids. Firstly, the typical models of generator set and load are simplified, and the parameters that have a great influence on frequency in the simplified model are obtained through characteristic analysis. Then, a dynamic aggregation method of generator governor and prime mover parameters and load parameters based on regulation performance weighting (the parameters of the generator or load are weighted and summed according to its regulation ability on the system) is proposed. This method is applied to the simulation example of the East China Power Grid. The simulation proves that the frequency of the East China Power Grid before and after equivalence can be consistent under four different faults, which verifies the effectiveness of the equivalent method proposed in this paper in the frequency dynamic analysis of large power grids. Full article

Rill erosion, mostly affecting steep and long hillslopes, is one of the most severe effects of deforestation and wildfires in natural ecosystems. Specific monitoring and accurate but simple models are needed to assess the impacts of these forest disturbances on the rill detachment process. To address this need, this study has simulated the rill detachment capacity (D_c) through flume experiments on samples of soils collected in hillslopes after deforestation and severe burning. The associations between D_c and organic matter (OM) and the aggregate stability of soil (WSA), two key parameters influencing the rill detachment process, have also been explored under the two soil conditions (deforested and burned soils) using multivariate statistical techniques. Finally, linear regression models to predict D_c from these soil parameters or the hydraulic and morphological variables (water flow rate, WFR, and soil slope, S), set in the flume experiments, have been proposed for both soil conditions. Higher D_c in samples from deforested sites compared to the burned soils (+35%) was measured. This D_c increase was associated with parallel decreases in OM (−15%) and WSA (−34%) after deforestation compared to the wildfire-affected sites. However, the discrimination in those soil properties between the two soil conditions was not sharp. Accurate linear equations (r² > 0.76) interpolating D_c and the shear stress (τ) have been set to estimate the rill erodibility (K_r) to evaluate soil resistance in erosion models to be applied in deforested or burned sites. Full article

This study offers a modular isolated grid-connected DC/DC medium-voltage DC aggregation converter to support offshore full DC wind farms’ need for lightweight and highly efficient power aggregation and transmission. The converter can simultaneously have a smaller transformer size and lower switching frequency during operation through the dual-voltage stabilization three-loop control strategy and phase-shift modulation strategy, which greatly reduces the space occupied by the converter and lowers the switching loss, Additionally, the use of a two-level structure at a lower switching frequency has lower loss, which effectively reduces the cost of the power device compared with the commonly used three-level converter. The input series output series connection between the converter sub-modules effectively lowers the voltage stress on each power switching device and facilitates expansion into a multi-module structure, expanding its application in high-voltage and large-capacity environments. This study analyzes the two working modes of the DC/DC converter and its control approach, in addition to providing a detailed introduction to the application scenarios of this converter. Ultimately, the efficacy and practicability of the suggested topology and control scheme are confirmed by simulations and experiments. Full article