bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma FGF21 Concentration in Kidney Transplant Patients—Results from Prospective and Cross-Sectional Studies
Authors: Bartmańska Magdalena , Wiecek Andrzej , Adamczak Marcin
Published: July 2024

Background/Objectives: Fibroblast growth factor 21 (FGF21) is a protein hormone involved in physiological conditions in the regulation of energy expenditure and several metabolic processes. The aim of this present study was to analyze the effect of successful kidney transplantations on the plasma FGF21 concentration and to study the factors which may influence plasma FGF21 concentration in patients in long time after kidney transplantation. Methods: This study consisted of two independent parts. The first part was a prospective observation of CKD patients in stage 5 before and then on the 14th and 30th day and 6 months after kidney transplantation. The second part of this study was the cross-sectional study completed in patients at least one year after kidney transplantation and the control group. In CKD patients directly before and during the early period after KTx, plasma FGF21 concentrations were measured four times (immediately before and 14 and 30 days and 6 months after KTx). In patients long time after kidney transplantation and in healthy subjects, plasma FGF21 concentration was measured once. Results: Forty patients with chronic kidney disease (CKD) who were either directly before or within the early period after kidney transplantation (KTx), 184 patients longtime after KTx and 50 healthy subjects were enrolled into this study. In CKD patients at the stage directly before receiving a KTx, the mean plasma FGF21 concentration was significantly higher than in the healthy subjects [1013.0 pg/mL versus 239.5 pg/mL, p < 0.001]. At 14, 30 days, and 6 months after the KTx, a significant decrease of plasma FGF21 was observed, with values of 322.5 pg/mL; 355.0 pg/mL; and 344.0 pg/mL (p < 0.001), respectively]. In patients long time after KTx, a negative correlation was found between the plasma FGF21 concentration and the estimated glomerular filtration rate and a positive correlation was found between the plasma FGF21 concentration and the BMI, the serum concentration of triglycerides, insulin, interleukin-6, CRP, and cystatin C. Conclusions: The plasma FGF21 concentration in patients with end-stage renal disease is higher than in healthy subjects and significantly decreases after a successful KTx. The plasma FGF21 concentration measured by ELISA in patients long time after kidney transplantation seems to be related to the degree of kidney function impairment and their metabolic status. The kidneys appear to be one of the main organs involved in the biodegradation and/or elimination of FGF21.
Comprehensive Approaches to Urolithiasis in Renal Transplants: A Narrative Review
Authors: Solano Catalina , Corrales Mariela , Panthier Frédéric , Doizi Steeve , Traxer Olivier
Published: July 2024

This review addresses the management of urolithiasis in renal transplant recipients, a notably vulnerable group due to the unique anatomical and physiological alterations of the transplanted organ. The prevalence of nephrolithiasis in these patients varies between 0.1% and 6.3%, with a significant impact on graft longevity and function. Surgical access complications due to the renal graft’s position on the iliac vessels and the variety of urinary anastomoses complicate the treatment approaches. This study evaluates the effectiveness and outcomes of percutaneous nephrolithotomy (PCNL) and ureteroscopy (URS), two primary minimally invasive strategies for managing graft stones. Through a narrative review using the PubMed and EMBASE databases, it was found that PCNL offers high stone-free rates especially beneficial for large stones, whereas URS provides a less invasive option with a lower risk of complications for small stones. Both techniques require tailored approaches based on stone composition—mostly calcium oxalate—and specific patient anatomical factors. This review underscores the importance of early diagnosis, appropriate treatment selection, and continuous post-treatment monitoring to mitigate risks and promote long-term renal function in transplant recipients.
Short- and Long-Term Outcomes in Elderly Patients with Resectable Esophageal Cancer: Upfront Esophagectomy Compared to Surgery after Neoadjuvant Treatments
Authors: Moletta Lucia , Pierobon Elisa Sefora , Capovilla Giovanni , Zuin Irene Sole , Carrillo Lizarazo Jose Luis , Nezi Giulia , Lonardi Sara , Murgioni Sabina , Galuppo Sara , Zanchettin Gianpietro , Salvador Renato , Provenzano Luca , Valmasoni Michele
Published: July 2024

Background/Objectives: Despite the increased incidence of esophageal cancer (EC) in elderly people, there are no clear guidelines for its treatment in these patients. The aim of this study was to compare the outcomes of patients ≥ 75 years with resectable EC, receiving either upfront esophagectomy or neoadjuvant treatment. Methods: We retrospectively identified 127 patients with resectable EC ≥ 75 years who underwent esophagectomy between January 2000 and December 2022 at our Clinic in the University Hospital of Padova. The included patients were stratified into two groups: patients undergoing upfront esophagectomy (SURG group) and patients receiving neoadjuvant treatment (NAT group). Results: There were no statistically significant differences in OS (p = 0.7708), DFS (p = 0.7827) and cancer-related survival (p = 0.0827) between the SURG and the NAT group, except for the OS of EAC with stage III-IV, where the NAT group experienced a significant benefit in OS (p = 0.0263). When comparing the two groups, patients receiving neoadjuvant treatment experienced a significantly higher rate of postoperative complications (p = 0.0266). At univariate analysis, neoadjuvant therapy was the only variable strongly associated with postoperative morbidity (p = 0.026). Conclusions: Considering the unique characteristics of elderly patients, the choice of a multimodal approach should be tailored to each case in a multidisciplinary setting and balanced with a potential higher risk of postoperative complications, as well as potential toxicity related to chemoradiation and reduced life expectancy.
Early Access for Medicines in ITALY: The Case of Ruxolitinib for Patients with Graft-Versus-Host Disease
Authors: Gozzo Lucia , Leotta Salvatore , Romano Giovanni Luca , Vetro Calogero , Duminuco Andrea , Milone Giuseppe , Cupri Alessandra , Palumbo Fanny Erika , Brancati Serena , Ruscica Rosy , Longo Laura , Vitale Daniela Cristina , Fiorenza Giorgia , Lombardo Giovanni Enrico , Lazzara Antonio , Di Raimondo Francesco , Palumbo Giuseppe Alberto , Drago Filippo
Published: July 2024

After European Medicines Agency (EMA) approval, national pricing and reimbursement procedures are necessary to guarantee access to drugs, based on the willingness to pay and the recognition of therapeutic value. These can result in delays in drug availability for patients, even for those with important unfmet needs for whom it may be necessary and ethical to ensure access. The objective of this study was to evaluate the use of ruxolitinib for patients with graft-versus-host disease (GvHD) after EMA approval at the University Hospital of Catania. We analysed data about the use of ruxolitinib in patients with GvHD, describing their basic characteristics, their outcomes and the cost of the treatment. In the reference period, 24 ruxolitinib treatments were started according to the Summary of Product Characteristic. The average treatment duration was 10 months. Twenty patients showed a response, maintained over time, with no adverse reactions. The total expenditure amounts to EUR 963,424. The use of ruxolitinib in a real population confirms its role in an important therapeutic need. The quantification of costs requires a reflection on the sustainability of early access to medicines authorised by the EMA for serious diseases and in the absence of therapeutic alternatives.
Serotonin-Mediated Anti-Allodynic Effect of Yokukansan on Diabetes-Induced Neuropathic Pain
Authors: Kajikawa Yoko , Yokomi Hiroshi , Narasaki Soshi , Kamiya Satoshi , Miyoshi Hirotsugu , Kato Takahiro , Tsutsumi Yasuo M.
Published: July 2024

Background: Diabetic neuropathic pain is a known complication of diabetes mellitus (DM) and results from the complex interaction of various factors affecting the nervous system. Yokuansan (YKS) is a versatile traditional Japanese herbal medicine with a wide range of applications, especially in pain management and neurological manifestations. YKS has analgesic properties for nerve damage and is a potential treatment for DM-induced neuropathic pain, especially in patients with diabetic neuropathy. Thus, we examined the anti-allodynic effect of YKS on DM-induced neuropathic pain. Methods: All experiments were performed on 6-week-old male Sprague–Dawley rats. DM and diabetic neuropathy were induced in rats with streptozotocin. Mechanical allodynia was assessed using dynamic plantar esthesiometry. Additionally, we conducted an immunological assessment of microglia cell changes in the spinal cord and an experiment to clarify the involvement of serotonin. Results: Diabetes significantly reduced withdrawal thresholds in rats during the initial two weeks of the experiment, which stabilized thereafter. However, this effect was not investigated in the control group. We assessed, using the dynamic plantar test, the anti-allodynic effects of orally administered YKS (1 g/kg). Daily YKS administration significantly increased the withdrawal threshold in DM animals. Additionally, oral YKS reduced the expression of Ibal-1-positive microglia. To elucidate the mechanism of action of YKS, we explored the involvement of serotonin (5-hydroxytryptamine [5-HT]) receptors in mediating its effects. Intrathecal administration of 5-HT receptor antagonists (WAY-100635, ketanserin, and ondansetron) inhibited the protective effects of YKS. Conclusions: YKS exhibited an anti-allodynic effect, suggesting that YKS may activate 5-HT receptors in the spinal cord, thereby alleviating diabetic neuropathic pain.
Comparative Approaches in Treating Double-J Stent Syndrome: Monotherapy or Combination Therapy?
Authors: Pricop Cătălin , Bandac Carina Alexandra , Ivanuță Marius , Rădăvoi Daniel , Jinga Viorel , Puia Dragoş
Published: July 2024

Introduction: The application of double-J ureteral stents in urology is widespread, but their use is often accompanied by complications and bothersome symptoms, affecting patients’ quality of life (QoL). While various medications have been tested for alleviating the symptoms associated with double-J stents, consensus on their effectiveness remains elusive. This study aims to investigate the effectiveness of tamsulosin, solifenacin, mirabegron, desloratadine, and combination therapy using a Romanian-adapted version of the Ureteral Stent Symptom Questionnaire (USSQ). Materials and Methods: A prospective, observational, randomised trial was conducted at the Urology and Renal Transplant Clinic of Dr. “C.I. Parhon” Clinical Hospital in Iasi between 1 January 2022 and 1 August 2023. Three hundred twenty seven patients who underwent their first double-J stent insertion were evaluated with the Romanian-adapted USSQ at baseline and 30 days post-insertion. Patients were randomly divided into six groups based on the prescribed medications: control, tamsulosin, mirabegron, solifenacin, desloratadine, and combination therapy. Results: The data suggest a significant reduction in symptoms in patients who received medication compared with the control group. Furthermore, the combined medication of solifenacin 10 mg and tamsulosin 0.4 mg was particularly effective in reducing pain with statistical significance compared to the control group (p = 0.001). The highest mean scores for urinary symptom severity were observed in the control group (12.37 ± 6.82), and the lowest was in the mirabegron group (9.94 ± 5.82). The individuals who received a daily dose of 50 mg of mirabegron saw the most notable influence on their job. Conclusions: While no single medication emerged as a “miracle drug” for managing symptoms related to double-J stent insertion, the combination therapy of solifenacin and tamsulosin is the most promising option for improving symptoms related to double-J stent insertion and QoL. Additional extensive research is required to validate these initial results.
The Influence of Cement Thickness within the Cap on Stress Distribution for Dental Implants
Authors: Ceddia Mario , Romasco Tea , Comuzzi Luca , Cipollina Alessandro , Piattelli Adriano , Dipalma Gianna , Inchingolo Angelo Michele , Inchingolo Francesco , Di Pietro Natalia , Trentadue Bartolomeo
Published: July 2024

The purpose of this finite element analysis (FEA) was to evaluate the stress distribution within the prosthetic components and bone in relation to varying cement thicknesses (from 20 to 60 μm) utilized to attach a zirconia crown on a conometric cap. The study focused on two types of implants (Cyroth and TAC, AoN Implants, Grisignano di Zocco, Italy) featuring a Morse cone connection. Detailed three-dimensional (3D) models were developed to represent the bone structure (cortical and trabecular) and the prosthetic components, including the crown, cement, cap, abutment, and the implant. Both implants were placed 1.5 mm subcrestally and subjected to a 200 N load at a 45° inclination on the crown. The results indicated that an increase in cement thickness led to a reduction in von Mises stress on the cortical bone for both Cyroth and TAC implants, while the decrease in stress on the trabecular bone (apical zone) was relatively less pronounced. However, the TAC implant exhibited a higher stress field in the apical area compared to the Cyroth implant. In summary, this study investigated the influence of cement thickness on stress transmission across prosthetic components and peri-implant tissues through FEA analysis, emphasizing that the 60 μm cement layer demonstrated higher stress values approaching the material strength limit.
Osteoproductivity of Injectable Bone Grafts with and without Ostrich Eggshell Membrane Protein in Rabbit Femur
Authors: Cengiz Ziya Ozan , Durmus Ercan , Celik Ilhami , Aktı Ahmet
Published: July 2024

Background: The aim of this study was to evaluate the biocompatibility and effectiveness in terms of osseointegration of dental implants composed of novel injectable bone grafts with and without ostrich eggshell particles and membrane protein in rabbit femur. Methods: Sixteen adult male New Zealand rabbits were used in this study. A bone defect was created in each animal’s right and left femur, and a dental implant was placed adjacent to the defect. Two graft materials were prepared, one containing the membrane protein and the other not. In two groups, the defects were filled with these materials. In the negative control group (NC, (n:8)), the defects were left empty. A commercial product of biphasic calcium sulfate was used as a positive control material (PC, n = 8). The graft groups were defined as the group with the membrane protein (MP+, (n:8)), and without the membrane protein (MP−, n:8). The animals were euthanized at the 12th week after surgery. The samples were investigated using histology, histomorphometry, and micro-computed tomography. Data were statistically analyzed using one-way ANOVA and Tukey’s tests (p = 0.05). Results: Both the PC and MP+ groups had similar newly formed bone areas, and the mean values of these groups were significantly (p < 0.05) higher than those of the MP− and NC groups. The PC group had the highest amount of unresorbed material, while the MP− group had the lowest amount of unresorbed material. The bone–implant contact (BIC) scores of the PC and MP+ groups were significantly higher (p < 0.05) than that of the NC group. The connective tissue area of the PC group was the lowest, which was significantly lower than the other groups (p < 0.05). Conclusions: The grafts produced are highly biocompatible and also showed osteoproductivity. Their cost-effectiveness and osteoproductive activity require further investigation.
An Improved NSGA-II Algorithm for MASS Autonomous Collision Avoidance under COLREGs
Authors: Liang Zuopeng , Li Fusheng , Zhou Shibo
Published: July 2024

Autonomous collision avoidance decision making for maritime autonomous surface ships (MASS), as one of the key technologies for MASS autonomous navigation, is a research hotspot focused on by relevant scholars in the field of navigation. In order to guarantee the rationality, efficacy, and credibility of the MASS autonomous collision avoidance scheme, it is essential to design the MASS autonomous collision avoidance algorithm under the stipulations of the Convention on the International Regulations for Preventing Collisions at Sea (COLREGs). In order to enhance the autonomous collision avoidance decision-making capability of MASS in accordance with the relevant provisions of COLREGs, an improved NSGA-II autonomous collision avoidance decision-making algorithm based on the good point set method (GPS-NSGA-II) is proposed, which incorporates the collision hazard and the path cost of collision avoidance actions. The experimental results in the four simulation scenarios of head-on situation, overtaking situation, crossing situation, and multi-ship encounter situation demonstrate that the MASS autonomous collision avoidance decision making based on the GPS-NSGA-II algorithm under the constraints of COLREGs is capable of providing an effective collision avoidance scheme that meets the requirements of COLREGs in common encounter situations and multi-ship avoidance scenarios promptly, with a promising future application.
Numerical Study of the Ultra-High-Speed Aerodynamically Alleviated Marine Vehicle Motion Stability in Winds and Waves
Authors: Song Yani , Du Xiaoxu , Hu Yuli
Published: July 2024

The ultra-high-speed aerodynamically alleviated marine vehicle (AAMV) is a high-performance vessel that combines a hydrodynamic configuration and an aerodynamic wing to reduce wave-making resistance during the high-speed planing phase. The forces of the AAMV exhibit strong nonlinear and water–air coupling characteristics, resulting in particularly complex motion characteristics. This paper presents a longitudinal and lateral stability model of the AAMV, which considers the effects of aerodynamic alleviation. Additionally, a numerical model of wind and wave turbulence forces is established, which considers viscous correction based on the potential theory. Finally, the effect of wind and wave turbulence forces on the motion stability of the AAMV under regular and irregular waves is analyzed by numerical solution. The simulation results demonstrate the influence of these disturbance forces on the stability of the AAMV under different sea states. The motion parameters of the AAMV exhibit a pronounced response to changes in sea state level. The aerodynamically alleviated effect is enhanced as speed increases, and the influence of winds and waves on the AAMV is greatly weakened, reducing the possibility of instability. During the cruising phase under class V sea state, the pitch, roll, and heave response are 0.210°, 0.0229°, and 0.0734 m, respectively. This effect can effectively improve the motion stability of the AAMV in winds and waves.
Uncertainty Analysis and Maneuver Simulation of Standard Ship Model
Authors: Li Hui , Zhao Nan , Zhou Jian , Chen Xiangyu , Wang Chenxu
Published: July 2024

Maneuver simulation of a standard ship model gives indication of numerical accuracy. In the numerical calculation of ship maneuvering, uncertainty analysis is a necessary step to ensure the accuracy of the calculation. In this study, uncertainty pair analysis is carried out in the simulation of the turning circle motion of the standard ship model ONRT in waves. According to the uncertainty analysis procedure recommended by the International Towing Tank Conference (ITTC), the change of ship resistance caused by the number of grids is studied to determine the influence of grid density on the numerical prediction. The simulation of turning motion in waves is carried out based on the uncertainty analysis. It is found that the minimum number of overset grids for this simulation is 1.4 million. The numerical results are fairly accurate compared to experimental results, and this technique provides a method with low calculated cost for this simulation.
The Influence of Pre-Chamber Parameters on the Performance of a Two-Stroke Marine Dual-Fuel Low-Speed Engine
Authors: Guo Hao , Wang Zhongcheng , Zhou Song , Zhang Ming , Shreka Majed
Published: July 2024

With increasing environmental pollution from ship exhaust emissions and increasingly stringent International Maritime Organization carbon regulations, there is a growing demand for cleaner and lower-carbon fuels and near-zero-emission marine engines worldwide. Liquefied natural gas is a low-carbon fuel, and when liquefied natural gas (LNG) is used on ships, dual-fuel methods are often used. The pre-chamber plays a key role in the working process of dual-fuel engines. In this paper, an effective three-dimensional simulation model based on the actual operating conditions and structural characteristics of a marine low-pressure dual-fuel engine is established. In addition, the effects of changing the Precombustion chamber (PCC) volume ratio and the PCC orifice diameter ratio on the mixture composition, engine combustion performance, and pollutant generation were thoroughly investigated. It was found that a small PPC volume ratio resulted in a higher flame jet velocity, a shorter stagnation period, and an acceleration of the combustion process in the main combustion chamber. When the PCC volume was large, the Nitrogen oxygen (NOx) ratio emission was elevated. Moreover, the angle of the PCC orifice affected the flame propagation direction of the pilot fuel. Optimizing the angle of the PCC orifice can improve combustion efficiency and reduce the generation of NOx. Furthermore, reasonable arrangement of the PCC structure can improve the stability of ignition performance and accelerate the flame jet velocity.
Effects of Angle of Attack on Flow-Induced Vibration of a D-Section Prism
Authors: Fan Shiguang , Li Zhuang , Song Jining , Du Xietian , Wang Juan
Published: July 2024

The VIVACE device, which utilizes flow-induced vibration for harvesting ocean current energy, has been a research hotspot in the field of renewable energy. In this study, the flow-induced vibration characteristics and energy conversion efficiency of a D-section prism were investigated using the k-ω SST turbulence model and Newmark-β method. The vibration amplitude, frequency, equilibrium position offset, and energy conversion efficiency of the two-degree-of-freedom cylinder were systematically analyzed at seven angles of attack between 0 and 180 degrees. The Reynolds number ranged from 368 to 14,742, corresponding to equivalent speeds of 2 to 20. The results indicate that the angle of attack has a significant influence on the flow-induced vibration response of the D-section prism. As the angle of attack changes, the vibration amplitude of the cylinder continuously increases, and the cylinder sequentially enters the vortex-induced vibration, vortex-induced vibration-galloping, and fully galloping branches. The change in the angle of attack disrupts the symmetry of the cylinder’s vibration in the streamwise direction, leading to a shift in the equilibrium position of the cylinder’s vibration. When the angle of attack is 0°, the energy conversion efficiency of the column reaches a maximum of 11.75%. Additionally, at high Reynolds numbers, the vibration of the cylinder is not self-limiting, making it more advantageous for energy conversion devices compared to cylinders with circular cross-sections.
Estimation of Optimal Hedge Ratio: A Wild Bootstrap Approach
Authors: Nguyen Phong Minh , Henry Darren , Kim Jae H. , Colombage Sisira
Published: July 2024

This paper proposes a new approach to estimating the minimum variance hedge ratio (MVHR) based on the wild bootstrap and evaluates the approach using a spectrum of conservative to aggressive alternative hedging strategies associated with the percentiles of the MVHR’s bootstrap distribution. This approach is suggested to be more informative and effective relative to the conventional method of hedging solely based on a single-point estimate. Furthermore, the percentile-based MVHRs are robust to influential outliers, non-normality, and unknown forms of heteroskedasticity. The bootstrap percentile-based hedging strategies’ effectiveness is compared with those from the naïve method and the asymmetric DCC-GARCH model for a range of financial assets and commodities. The bootstrap percentile-based hedging technique is identified to outperform its alternatives in terms of hedging effectiveness, downside risk, and return variability, suggesting its superiority to other methods in both the literature and in practice.
Corporate Cash Holdings and Investment Efficiency: Do Women Directors and Financial Crisis Matter?
Authors: Ardianto Ardianto , Sulaiman Noor Adwa
Published: July 2024

This study investigates the relationship between corporate cash holdings and investment efficiency, with a focus on how COVID-19 and the presence of women directors may influence this relationship. Using data from Indonesian public companies during the COVID-19 period, comprising 2350 firm-year observations, we employ fixed-effect regression models with industry and year controls to test our hypotheses. Robustness and endogeneity tests are conducted to ensure the reliability of our findings. Our research reveals that companies with larger cash reserves tend to experience decreased investment efficiency during the COVID-19 crisis. Moreover, the negative impact of substantial cash reserves on investment efficiency is exacerbated by the presence of female directors on the board. However, our findings also suggest that female directors can mitigate the adverse effects of excessive cash reserves on a company’s investment efficiency, particularly during unforeseen economic challenges such as the pandemic.
Spatial-Temporal Coupling Coordination Relationship between Urban Green Infrastructure Construction and Economic Development in China
Authors: Wang Weiwei , Wen Yanping , Chen Wanxu , Qu Yiran
Published: July 2024

Urban green infrastructure construction and economic growth are necessary ways and important supports to promote sustainable development. Exploring their coupling coordination relationship is important for achieving high-quality economic development. This study uses the entropy method, coupling coordination degree, kernel density estimation, the Dagum Gini coefficient, and spatial autocorrelation to explore the spatial-temporal pattern characteristics and coupling coordination relationship between green infrastructure construction and economic development for 273 cities in Chinese mainland in 2010–2020. The results show that the level of China’s green infrastructure construction and economic development gradually increased during 2010–2020. There were significant regional differences in space, exhibiting a decreasing spatial pattern from east to west. The coupling coordination degree was constantly improving. The overall Gini coefficient shows an upward trend. Among the four regions, eastern China has the greatest intraregional variation. The uneven level of coupled coordination is mainly from interregional variation. There was a significant positive spatial autocorrelation relationship, and cities that had a higher degree of coupling coordination tended to agglomeration development. Meanwhile, it also had certain spatial heterogeneity. China’s entire level of coupling coordination degree still has much room for improvement. The study is of great significance in reducing disparities between regions and strengthening regional spatial coordination development.
Spatial–Temporal Variations in Soil Organic Carbon and Driving Factors in Guangdong, China (2009–2023)
Authors: Tian Mi , Wu Chao , Zhu Xin , Hu Qinghai , Wang Xueqiu , Sun Binbin , Zhou Jian , Wang Wei , Chi Qinghua , Liu Hanliang , Liu Yuheng , Yang Jiwu , Li Xurong
Published: July 2024

Spatial–temporal variation in soil organic carbon is an important factor for national targets to mitigate climate change and land degradation impacts. In this research, we took Guangdong Province of China as the study area, evaluated the spatial–temporal distributions of soil organic carbon using data from three China Geochemical Baseline projects (conducted in 2009, 2016, and 2023, respectively), and quantified the main driving factors of spatial–temporal variations in soil organic carbon using the random forest algorithm, further predicting the density and inventories of soil organic carbon. The results demonstrate that the mean value of SOC in Guangdong in 2009 was 0.81%; in 2016 it was 1.13%; and in 2023 it was 1.02%. The inventories of soil organic carbon (0–30 cm) in Guangdong Province were 0.61 Pg in 2009, 0.74 Pg in 2016, and 0.62 Pg in 2023. Soil in Guangdong acted as a carbon sink from 2009 to 2023 as a whole, and the most important driving force behind spatial–temporal variations in soil organic carbon was temperature, followed by precipitation and vegetation cover.
The Identification, Spatial Distribution, and Reconstruction Mode of Abandoned Mining Areas
Authors: Gligor Viorel , Nicula Emanuela-Adina , Crețan Remus
Published: July 2024

The rehabilitation of abandoned mining sites is an increasingly pressing issue in the context of sustainable development. Recent research has emphasized the need for a holistic approach to the abandoned mining sites and their environmental rehabilitation. Based on field analysis, environmental assessments, satellite imagery processing and geographic information operations, this paper pushes forward the existing knowledge by conducting a comprehensive assessment of abandoned mining sites in the Romanian Carpathians and by proposing innovative and sustainable rehabilitation solutions. Our findings highlight that abandoned mining sites and their surrounding territories in the Romanian mountains have significant ecological imbalances and complex socio-economic issues. The findings also suggest that by adopting innovative, integrated, and sustainability-oriented approaches, territories affected by mining can be transformed into valuable and sustainable spaces to meet human needs. We conclude by presenting the importance of innovation in ecological reconstruction and spatial–functional reintegration of mining sites in mountain areas as a useful tool in making fair decisions, both in the context of implementing appropriate development policies as well as for the resilience and environmental sustainability of mining-affected mountain areas.
Improved Operating Behavior of Self-Lubricating Rolling-Sliding Contacts under High Load with Oil-Impregnated Porous Sinter Material
Authors: Sprogies Nicolai , Lohner Thomas , Stahl Karsten
Published: July 2024

Resource and energy efficiency are of high importance in gearbox applications. To reduce friction and wear, an external lubricant supply like dip or injection lubrication is used to lubricate tribosystems in machine elements. This leads to the need for large lubricant volumes and elaborate sealing requirements. One potential method of minimizing the amount of lubricant and simplifying sealing in gearboxes is the self-lubrication of tribosystems using oil-impregnation of porous materials. Although well established in low-loaded journal bearings, self-lubrication of rolling-sliding contacts in gears is poorly understood. This study presents the self-lubrication method using oil-impregnated porous sinter material variants. For this, the tribosystem of gear contacts is transferred to model contacts, which are analyzed for friction and temperature behavior using a twin-disk tribometer. High-resolution surface images are used to record the surface changes. The test results show a significant increase in self-lubrication functionality of tribosystems by oil-impregnated porous sinter material and a tribo-performance comparable to injection-lubricated tribosystems of a sinter material with additionally solid lubricant added to the sinter material powder before sintering. Furthermore, the analyses highlight a significant influence of the surface finish, and in particular the surface porosity, on the overall tribosystem behavior through significantly improved friction and wear behavior transferable to gear applications.
Sheet Forming via Limiting Dome Height (LDH) Test: Influence of the Application of Lubricants, Location and Sheet Thickness on the Micro-Mechanical Properties of X8CrMnNi19-6-3
Authors: Ovsik Martin , Bednarik Martin , Reznicek Martin , Stanek Michal
Published: July 2024

This work is concerned with forming, specifically deep drawing, and its influence on the micro-mechanical properties of sheet metal. In practice, there are several applications in which fractions can occur due to weak spots in the deep-drawn sheet metal, especially after long-term use. The deep drawing process was carried out on BUP–600 machines using the LHD (Limiting Dome Height) method, which uses a forming tool with a diameter of 100 mm and bead groove. Sheet metals X8CrMnNi19-6-3 (1.4376) with thicknesses of 1, 1.5, and 3 mm were selected for this process. To study the effect of a lubricant on the formability of the sheet metal, deep drawing without and with a lubricant was compared. An FEM analysis was conducted to identify critical points in the deep drawing process, and the results were later compared with real results. The analysis was conducted using the AutoForm program. The micro-mechanical properties of these points were subsequently examined. The specified points on the formed part showed significant differences in their micro-mechanical properties, suggesting a higher strength but also less resistance to fractures. The difference in micro-mechanical properties (indentation and Vickers hardness) in points that were not deep-drawn and points located in critical areas was up to 86%. Significant changes in behavior were found in the indentation modulus and plastic/elastic deformation work as well. This study demonstrates the significant effect of the use of a lubricant in achieving the deep drawing of the sheet metal. The application of a lubricant resulted in a 33% increase in drawing range compared to drawing without lubrication. This study has a significant influence on the deep drawing of sheet metals in practice, showing the fundamental influence of the lubricant on the drawing process and also showing the problem of critical points that need to be eliminated.
Molecular Dynamics Simulation and Experimental Study of Friction and Wear Characteristics of Carbon Nanotube-Reinforced Nitrile Butadiene Rubber
Authors: Liang Ce , Shuai Changgeng , Wang Xin
Published: July 2024

Nitrile butadiene rubber (NBR) and its various composite materials are widely employed as friction materials in mechanical equipment. The use of carbon nanotube (CNT) reinforcement in NBR for improved friction and wear characteristics has become a major research focus. However, the mechanisms underlying the improvement in the friction and wear characteristics of NBR with different CNT contents remain insufficiently elucidated. Therefore, we conducted a combined analysis of NBR reinforced with varying CNT contents through molecular dynamics (MD) simulations and ring–block friction experiments. The aim is to analyze the extent to which CNTs enhance the water-lubricated friction and dry wear properties of NBR and explore the improvement mechanisms through molecular chain characteristics. The results of this study demonstrate that as the mass fraction of CNTs (0%, 1.25%, 2.5%, 5%) increases, the water-lubricated friction coefficient of NBR continuously decreases. Under water-lubricated conditions, CNTs improve the water storage capacity of the NBR surface and enhance lubrication efficiency. In the dry wear state, CNTs help reduce scratch depth and dry wear volume.
Insights into Cis-Amide-Modified Carbon Nanotubes for Selective Purification of CH4 and H2 from Gas Mixtures: A Comparative DFT Study
Authors: Rahmanzadeh Atyeh , AL-Hamdani Nasser , Favvas Evangelos P. , De Luca Giorgio
Published: July 2024

Among a plethora of mixtures, the methane (CH4) and hydrogen (H2) mixture has garnered considerable attention for multiple reasons, especially in the framework of energy production and industrial processes as well as ecological considerations. Despite the fact that the CH4/H2 mixture performs many critical tasks, the presence of other gases, such as carbon dioxide, sulfur compounds like H2S, and water vapor, leads to many undesirable consequences. Thus purification of this mixture from these gases assumes considerable relevance. In the current research, first-principle calculations in the frame of density functional theory are carried out to propose a new functional group for vertically aligned carbon nanotubes (VA-CNTs) interacting preferentially with polar molecules rather than CH4 and H2 in order to obtain a more efficient methane and hydrogen separations The binding energies associated with the interactions between several chemical groups and target gases were calculated first, and then a functional group formed by a modified ethylene glycol and acetyl amide was selected. This functional group was attached to the CNT edge with an appropriate diameter, and hence the binding energies with the target gases and steric hindrance were evaluated. The binding energy of the most polar molecule (H2O) was found to be more than six times higher than that of H2, indicating a significant enhancement of the nanotube tip’s affinity toward polar gases. Thus, this functionalization is beneficial for enhancing the capability of highly packed functionalized VA-CNT membranes to purify CH4/H2 gas mixtures.
Influence of Compression Loading on Acoustic Emission and Light Polarization Features in TeO2 Crystal
Authors: Machikhin Alexander , Chernov Dmitry , Khokhlov Demid , Marchenkov Artem , Bykov Alexey , Eliovich Yan , Petrov Ivan , Balandin Timofey , Kren Alexander , Sergeev Ilya , Pisarevsky Yuri
Published: July 2024

Monitoring the processes inside crystalline materials under their operating conditions is of great interest in optoelectronics and scientific instrumentation. Early defect detection ensures the proper functioning of multiple crystal-based devices. In this study, a combination of acoustic emission (AE) sensing and cross-polarization imaging is proposed for the fast characterization of the crystal’s structure. For the experiments, tellurium dioxide (TeO2) crystal was chosen due to its wide use in acousto-optics. Studies were performed under uniaxial compression loading with a simultaneous acquisition of AE signals and four polarized optical images. An analysis of the temporal dependencies of the AE data and two-dimensional maps of the light depolarization features was carried out in order to establish quantitative criteria for irreversible damage initiation and crack-like defect formation. The obtained results reveal the polarization image patterns and the AE pulse duration alteration specific to these processes, and they open up new possibilities for non-destructively monitoring in real-time the structure of optically transparent crystals under their operating conditions.
Effects of Tungsten Addition on the Microstructure and Properties of FeCoCrNiAl High-Entropy Alloy Coatings Fabricated via Laser Cladding
Authors: Ma Shibang , Zhang Congzheng , Li Liang , Chen Haodong , Yang Yinhai
Published: July 2024

This study examines the effects of different addition levels of tungsten (W) content on the microstructure, corrosion resistance, wear resistance, microhardness, and phase composition of coatings made from FeCoCrNiAl high-entropy alloy (HEA) using the laser cladding technique. Using a preset powder method, FeCoCrNiAlWx (where x represents the molar fraction of W, x = 0.0, 0.2, 0.4, 0.6, 0.8) HEA coatings were cladded onto the surface of 45 steel. The different cladding materials were tested for dry friction by using a reciprocating friction and wear testing machine. Subsequently, the detailed analysis of the microstructure, phase composition, corrosion resistance, wear traces, and hardness characteristics were carried out using a scanning electron microscope (SEM), X-ray diffractometer (XRD), electrochemical workstation, and microhardness tester. The results reveal that as the W content increases, the macro-morphology of the FeCoCrNiAlWx HEA cladding coating deteriorates; the microstructure of the FeCoCrNiAlWx HEA cladding coating, composed of μ phase and face-centered cubic solid solution, undergoes an evolution process from dendritic crystals to cellular crystals. Notably, with the increase in W content, the average microhardness of the cladding coating shows a significant upward trend, with FeCoCrNiAlW0.8 reaching an average hardness of 756.83 HV0.2, which is 2.97 times higher than the 45 steel substrate. At the same time, the friction coefficient of the cladding coating gradually decreases, indicating enhanced wear resistance. Specifically, the friction coefficients of FeCoCrNiAlW0.6 and FeCoCrNiAlW0.8 are similar, approximately 0.527. The friction and wear mechanisms are mainly adhesive and abrasive wear. In a 3.5 wt.% NaCl solution, the increase in W content results in a positive shift in the corrosion potential of the cladding coating. The FeCoCrNiAlW0.8 exhibits a corrosion potential approximately 403 mV higher than that of FeCoCrNiAl. The corrosion current density significantly decreases from 5.43 × 10−6 A/cm2 to 5.26 × 10−9 A/cm2, which suggests a significant enhancement in the corrosion resistance of the cladding coating.
Influence of the Plastic Deformation Process on the Residual Stresses and Hardness of an Al-5Mg Alloy
Authors: Samara Fayez , Goanta Viorel , Istrate Bogdan , Alkisswani Layth , Munteanu Corneliu , Cosau Roxana
Published: July 2024

The service behavior of ductile metallic materials, when they have previously undergone technological plastic deformation, depends on the deformation conditions. These are represented, among others, by the deformation rate, the process temperature, the applied pressures, and the introduced stresses, as well as other process variables. The investigation of the mechanical properties obtained after plastic deformation is an important means that contains two characteristics: on the one hand, to determine to what extent the parameters of the technological manufacturing process influence the main characteristics of the final component; and, on the other hand, on the basis of these characteristics, to analyze whether the component subjected to plastic deformation will be able to function reliably and safely. In the present work, an experimental study was made of the residual stresses developed and hardnesses obtained both in the immediate vicinity of a highly plastically deformed area and in an area previously obtained by rolling, without additional plastic deformation. For the determination of the residual stresses, the tensiometric rosette drilling method was used. By determining the same quantities in a non-plastically deformed area, significant changes in the values of the two quantities in the plastically deformed area were found. An increase in the maximum principal normal stresses by approx. 60 MPa and an increase in the Rockwel hardness by approx. 10 HRC was found. A sample was taken from the area under a plastic deformed circular shape, and was analyzed microscopically.
Analysis of Thermoelastic Contact of Gas-Lubricated Rough Sealing Faces
Authors: Bai Shaoxian , Chen Yangyang , Yang Jing
Published: July 2024

Friction and wear are the main failure sources of face seals. When the surfaces of sealing rings exhibit greater roughness, the level of friction might increase and lead to sealing failure. Therefore, in this paper, based on the elastic contact hypothesis of rough and wavy surfaces and the influence of temperature on the elastic modulus of materials, a thermoelastic contact lubrication model of a gas-lubricated end seal is established. The novelty and advantage of this study is that it takes the effect of surface roughness into consideration during thermoelastic analysis of gas-lubricated seals. The film pressure, temperature, contact force and deformation of a gas spiral groove-faced seal are numerically determined. The influence of surface roughness on the contact distribution, deformation and temperature of the end-face seal at different speeds and pressures is analyzed. The film thickness increases as the rotational speed increases from 1 rpm to 2000 rpm, while the contact pressure sharply decreases from 0.25 kPa to 0. The analysis shows that the roughness contact mainly happens on the inner side of the rings due to convergent distortion of the seal faces, which easily causes partial wear of the seal faces. Moreover, it can also be found that the spiral grooves on the sealing surface can produce obvious hydrodynamic pressure effect due to the function of shear speed when the speed increases to 2000 rpm, while the film temperature increases from 293.3 K to about 306 K. The greater surface roughness results in a larger temperature rise under low-rotational-speed and lower-seal-pressure conditions, which further increases the risk of severe wear or even failure of the seal faces.
Reliability Risk Mitigation in Advanced Packages by Aging-Induced Precipitation of Bi in Water-Quenched Sn–Ag–Cu–Bi Solder
Authors: Shukla Vishnu , Ahmed Omar , Su Peng , Jiang Tengfei
Published: July 2024

Bi-doped Sn–Ag–Cu (SAC) microelectronic solder is gaining attention for its utility as a material for solder joints that connect substrates to printed circuit boards (PCB) in future advanced packages, as Bi-doped SAC is reported to have a lower melting temperature, higher strength, higher wettability on conducting pads, and lower intermetallic compound (IMC) formation at the solder-pad interface. As solder joints are subjected to aging during their service life, an investigation of aging-induced changes in the microstructure and mechanical properties of the solder alloy is needed before its wider acceptance in advanced packages. This study focuses on the effects of 1 to 3 wt.% Bi doping in an Sn–3.0Ag–0.5Cu (SAC305) solder alloy on aging-induced changes in hardness and creep resistance for samples prepared by high cooling rates (>5 °C/s). The specimens were aged at ambient and elevated temperatures for up to 90 days and subjected to quasistatic nanoindentation to determine hardness and nanoscale dynamic nanoindentation to determine creep behavior. The microstructural evolution was investigated with a scanning electron microscope in tandem with energy-dispersive spectroscopy to correlate with aging-induced property changes. The hardness and creep strength of the samples were found to increase as the Bi content increased. Moreover, the hardness and creep strength of the 0–1 wt.% Bi-doped SAC305 was significantly reduced with aging, while that of the 2–3 wt.% Bi-doped SAC305 increased with aging. The changes in these properties with aging were correlated to the interplay of multiple hardening and softening mechanisms. In particular, for 2–3 wt.% Bi, the enhanced performance was attributed to the potential formation of additional Ag3Sn IMCs with aging due to non-equilibrium solidification and the more uniform distribution of Bi precipitates. The observations that 2–3 wt.% Bi enhances the hardness and creep strength of the SAC305 alloy with isothermal aging to mitigate reliability risks is relevant for solder samples prepared using high cooling rates.