Search Results (34,412)

Silicon carbide (SiC) ceramics have gained significant attention in advanced engineering applications because of their superior mechanical properties, resistance to wear and corrosion, and thermal stability. However, the precision machining of these materials is extremely challenging because of their intrinsic hardness and brittleness. Wire Electrical Discharge Machining (WEDM) has become increasingly popular as a viable technique for processing SiC ceramics because of its ability to produce intricate geometries and high-quality surface finishes. In this review paper, a comprehensive overview of WEDM technology applied to SiC ceramics is presented, emphasizing the influence of process parameters, wire materials, and dielectric fluids on cutting efficiency and quality. This research explores recent experimental findings related to Wire Electrical Discharge Machining (WEDM) and highlights the challenges in reducing material damage. It also presents strategies to improve machining performance. Additionally, potential future directions are discussed, providing a roadmap for further research and the application of WEDM in processing silicon carbide (SiC) and its variants, including solid silicon carbide (SSiC) and silicon-infiltrated silicon carbide (SiSiC). Full article

Carbon dioxide is naturally present in the Earth’s atmosphere and plays a role in regulating and balancing the planet’s temperature. However, due to various human activities, the amount of carbon dioxide is increasing beyond safe limits, disrupting the Earth’s natural temperature regulation system. Today, CO₂ is the most prevalent greenhouse gas; as its concentration rises, significant climate change occurs. Therefore, there is a need to utilize anthropogenically released carbon dioxide in valuable fuels, such as formic acid (HCOOH). Single-atom catalysts are widely used, where a single metal atom is anchored on a surface to catalyze chemical reactions. In this study, we investigated the potential of Cu@Phosphorene as a single-atom catalyst (SAC) for CO₂ reduction using quantum chemical calculations. All computations for Cu@Phosphorene were performed using density functional theory (DFT). Mechanistic studies were conducted for both bimolecular and termolecular pathways. The bimolecular mechanism involves one CO₂ and one H₂ molecule adsorbing on the surface, while the termolecular mechanism involves two CO₂ molecules adsorbing first, followed by H₂. Results indicate that the termolecular mechanism is preferred for formic acid formation due to its lower activation energy. Further analysis included charge transfer assessment via NBO, and interactions between the substrate, phosphorene, and the Cu atom were confirmed using quantum theory of atoms in molecules (QTAIM) and non-covalent interactions (NCI) analysis. Ab initio molecular dynamics (AIMD) calculations examined the temperature stability of the catalytic complex. Overall, Cu@Phosphorene appears to be an effective catalyst for converting CO₂ to formic acid and remains stable at higher temperatures, supporting efforts to mitigate climate change. Full article

The use of solid products deriving from the pyrolysis of wastes as potential substitute of traditional binders in asphalt preparation is investigated with the final goal of reducing production costs, preserving non-renewable resources, and promoting an effective resource use as well as recovery and recycling procedures, thus implementing a regenerative circular economy approach. Char derived from the pyrolysis of agricultural and aquaculture wastes has been explored as a novel alternative additive for asphalt production. Different feedstocks were used for the preparation of biochar by pyrolysis. The produced char samples, after an in-depth chemical and structural characterization, have been implemented in the preparation of asphalt mixtures, with their potential use as a binder evaluated by performing conventional rheological tests. To evaluate the potential anti-aging effect of char as an additive, bituminous formulations containing 3 to 6 wt.% char were subjected to short-term simulated aging using the Rolling Thin-Film Oven Test (RTFOT) method. The resulting mechanical properties were then assessed. The results indicate that the all the tested char samples have limited modifying properties towards the gel-to-sol transition temperature. Among the samples, lemon peel-derived char (LP-char) showed superior antioxidant properties against bitumen oxidative aging. This study suggests that certain chemical characteristics can serve as predictive indicators of antioxidant activity in biochars produced from biomass pyrolysis. Full article

The structures of the developing eye may be damaged as a result of the impact of reactive oxygen species (ROS) interacting with different cellular components. The antioxidant molecules found in the eye, especially in the vitreous body—the largest component of the eye, playing a crucial role in the formation of structures and functions of the developing eye—provide protection to the eye tissues from ROS. This review considers various antioxidant molecules (ascorbic acid, lutein, bilirubin, uric acid, catecholamines, erythropoietin, albumin, and alpha-fetoprotein) that have been found in the human vitreous body during the early stages of pregnancy (10–31 weeks of gestation) and their functions in the development of the eye. The presence of some molecules is transient (lutein, AFP), whereas a temporal decrease (albumin, bilirubin) or increase (ascorbic acid, erythropoietin) in the concentrations of other antioxidants is observed. Since the actual overall content of antioxidants in the developing vitreous body is probably much higher than that found to date, further research is needed to study antioxidants there. It is especially important to study the antioxidant status of the vitreous body at the earliest stages of its development. Antioxidants found suggest their use for the prophylactic of ocular diseases during pregnancy and finding new antioxidants could create an additional opportunity in this regard. Full article

Trailers for passenger cars are often used for the transportation of goods. There are various trailer designs. Most trailers are equipped with axles, which include swinging arms and are suspended by rubber segments. Observations have revealed that empty trailers have unfavorable driving properties when they are driven on uneven roads, for example, the wheels could jump off the road. Such a situation is dangerous because it is not possible to transmit any contact forces (longitudinal, lateral, or vertical) between the wheel and the road. The goal of the present research was to measure acceleration generated in a single-axle trailer when driving over a road obstacle. Measurements were conducted in a non-public area to avoid the risk of accidents. Acceleration was recorded using two accelerometers placed on the single-axle trailer frame above the wheels’ axle of rotation. Tests were performed using a vehicle–trailer combination at the chosen driving speeds, and the results for driving speeds of 20 and 30 km/h are presented. Wood plates with a height of 25 and 50 mm were used as an artificial road obstacle. The single-axle trailer was loaded with gravel bags weighing 0 to 300 kg. The measurements revealed that heavier trailer loads and lower driving speeds are safer for trailer operation. Furthermore, the measurements also demonstrated that the wheels were significantly more likely to jump off the road with a 0 kg load and low driving speed. Full article

Background: Endometrial carcinoma is the most common gynaecological malignant tumour in developed countries. At present, no routinely used serum biomarker is available for the prediction of lymph node metastasis (LNM). This study thus evaluates the potential of tumour markers CA125 and HE4 as LNM predictors in endometrial carcinoma patients. Objectives: The aim of this study was to evaluate the potential use of CA125 and HE4 and to assess the viability of a model developed using the parameters of serum tumour marker levels for LNM risk stratification. Methods: A retrospective, single-institution study of 220 patients with biopsy-proven endometrial carcinoma was conducted from May 2020 to December 2023. Preoperative serum levels of HE4 and CA125 were determined. All patients underwent surgical lymph node staging. The study evaluated the sensitivity and specificity of tumour markers and of the developed LNM risk prediction model. Results: No LNM was observed in 167 of the 220 patients (75.9%), micrometastatic lymph node involvement was observed in 13 patients (5.9%), and macrometastatic involvement was observed in 24 patients (10.9%). Median CA125 and HE4 levels were significantly higher in patients with LNM than in those without. With a CA125 cut-off value of 35 IU/mL, a sensitivity of 70% and a specificity of 92% were obtained, while an HE4 cut-off value of 103 pmol/L yielded a sensitivity of 78% and a specificity of 80%. A prediction model combining CA125, HE4, and the extent of uterine invasion, as detected by ultrasound, yielded a sensitivity of 84% and a specificity of 98% in predicting LNM. Conclusions: CA125 and HE4, along with the prediction model, facilitate endometrial carcinoma patient subdivision into low- and high-risk LNM groups. As this method is technically simple, non-invasive, and inexpensive, it could be of undeniable benefit in the risk stratification of patients with multiple comorbidities, which limit the duration and extent of surgery. Full article

The aim of this work is to determine the production function using the method of complex-valued economics as a criterion for the management of the centralized heat supply of a city. This paper used the methodology of using stepped production functions of complex variables with real coefficients as a tool to perform dynamic analysis and forecasting of production results, allowing the performance of Manufacturing Execution System tasks of the heat supply system to be tracked. Based on this, a justified selection of a management criterion was made, objectively reflecting both the passive and active components of the administrative and economic activities of the heat supply enterprise. A comparative analysis of production functions was conducted to identify a predictive model for resource provision in the process of heat energy generation. A predictive model of resource provision was developed based on the capital/labor ratio of the enterprise, using a production function with complex variables. In other words, determining the production function allows the analysis of both the quantity and quality of resources used to produce 1 Gcal of energy, as well as the forecast of resource procurement to ensure a reliable and cost-effective heat supply. Full article

In this paper, I will discuss a topic concerning part–whole structures in the nominal and verbal domain. Specifically, I will address the question of whether there is a universal mechanism for the individuation of entities and events by exploring parallels between singulatives and semelfactives in Slavic. Singulatives are derived unit nouns, whereas semelfactives are punctual verbs that describe a brief event which culminates by returning to the initial state. Cross-linguistically, singulative morphology often alternates with collective marking, whereas semelfactives alternate with iteratives. Collectives and iteratives describe homogenous groupings of entities and events, respectively. From a conceptual perspective, both singulatives and semelfactives individuate to the effect of singular bounded unit reference and in the literature, the parallel between the mass count/distinction and aspect has often been drawn. In Slavic, singulative and semelfactive morphologies share a component; specifically, both markers involve a nasal -n and a vocalic component, e.g., compare Russian gorox ‘peas (as a mass)’ ∼goroš-in-a ‘a pea’ and prygať ‘to jump (repeatedly)’ ∼ pryg-nu-ť ‘to jump once’. I will argue that the singulative -in and semelfactive -nu are complex and both involve the very same -n, which denotes a declustering atomizer modeled in mereotopological terms. Full article

This paper investigates the oscillatory effect of a single blade on the turbulence wake downstream of a low-pressure turbine cascade. Experimental investigations were conducted at a chord-based Reynolds number of $2.3\times {10}^5$ with an excitation frequency of $73\mathrm{Hz}$. The experimental campaign encompassed two incidence angles ($-3^{\circ }$ and $+6^{\circ }$) and three blade motion conditions: stationary, bending, and torsional vibrations. Turbulence characteristics were analyzed using hot-wire anemometry. The results indicate that the bending mode notably alters the wake topology, causing a 5% decline in streamwise velocity deficit compared to other modes. Additionally, the bending motion promotes the formation of large-scale coherent vortices within the wake, increasing the integral length scale by 7.5 times. In contrast, Kolmogorov’s microscale stays mostly unaffected by blade oscillations. However, increasing the incidence angle causes the smallest eddies in the inter-blade region to grow three times larger. Moreover, the data indicate that at $-3^{\circ }$, bending-mode results in an approximate 13% reduction in the turbulence energy dissipation rate compared to the stationary configuration. Furthermore, the study emphasizes the spectral features of turbulent flow and provides a detailed assessment of the Taylor microscale under different experimental conditions. Full article

The study employed a green, template-free ball milling method to construct a series of Ni-Al mixed oxide catalysts modulated by different nickel precursors (nitrate, acetate, carbonate, sulfate, and chlorate). Through multiscale characterization techniques (XRD, TEM, XPS, H₂-TPR, etc.) and catalytic performance evaluations, we systematically elucidated the regulatory mechanism of precursor types on the structure-performance relationship. The NiAlO_x-CO₃²⁻ catalyst derived from nickel carbonate exhibited a unique structure, an optimal Ni/Al ratio, and well-tuned active oxygen species, thereby demonstrating exceptional catalytic performance in the oxidative dehydrogenation of ethane (ODHE) at 475 °C with 53.2% ethane conversion, 72.6% ethylene selectivity, and maintained stability over 40 h of continuous operation. Beyond developing high-performance ODHE catalysts, this work establishes a “precursor chemistry–material structure–catalytic performance” relationship model, offering new insights for the rational design of efficient catalysts for light alkane conversion. Full article

Dust explosion prevention and mitigation of the consequences thereof require measurement of dust explosion parameters. Testing methods are defined by European and American standards, producing results in explosion chambers of a 1 m³ standard volume and, alternatively, 20 L. However, the results are influenced by some processes that are neglected by the standards, perhaps because it is believed that their effect is small in a 1 m³ chamber. But their effect becomes significant in a smaller 20 L chamber. Preconditioning of the system caused by dust dispersion itself, as well as the ignitor flame, is one such problem. The aim of this work is to further investigate the physical and chemical processes caused by dust preheating after an ignitor’s action. Analytical methods, such as STA, GC/MS and FTIR, were used to analyse the composition of the atmosphere after exposure of lycopodium dust, a natural material, to certain temperatures up to 550 °C in air and nitrogen. In the second step, gas samples were taken from the 20 L chamber after dispersion of lycopodium and ignition by two 5 kJ pyrotechnical ignitors. Depending on the temperature and atmosphere, various concentrations of CO, CO₂, H₂O, NO_x and organic compounds were measured. It was observed that the dispersed dust decomposed into mostly CO and CO₂ in the area near the ignitors, even in an atmosphere in which the oxygen concentration was lower than 2% by volume. The concentrations of other organic compounds were very low and included mostly methane, ethylene and acetaldehyde. However, when incorporating CO, the overall concentration of flammables was high enough to generate a hybrid mixture. Full article

Calibrating the ages, masses, and radii of stars on the upper main sequence depends heavily on accurate measurements of the effective temperature ($T_{\mathrm{eff}}$) and surface gravity ($logg$). These parameters are difficult to obtain meticulously due to the nature of hot stars, which exhibit features such as rapid rotation, atomic diffusion, pulsation, and stellar winds. We compare the $T_{\mathrm{eff}}$ and $logg$ values of apparent normal B-F stars in four recent catalogues that employ different methods and pipelines to obtain these parameters. We derived various statistical parameters to compare the differences between the catalogues and discussed the astrophysical implications of these differences. Our results show that the huge differences in $T_{\mathrm{eff}}$ (up to ${10}^4$ K) and $logg$ (up to 2 dex) between the catalogues have serious implications on the determination of ages, masses, and radii of the stars in question. We conclude that there appears to be no homogeneous set of stellar parameters on the upper main sequence, and one must be cautious when interpreting results obtained from using only one of the catalogues. The homogenisation of said parameters is an essential task for the future and will have a significant impact on astrophysical research dealing with stars on the upper main sequence. Full article

Background/Objectives: Lichen simplex chronicus (LSC) of the vulva is a chronic dermatologic disorder characterized by persistent pruritus, compulsive scratching, and progressive thickening of the vulvar skin. Currently, LSC diagnosis primarily relies on clinical presentation, with histopathological examination performed when the diagnosis is unclear. However, the precise pathogenic mechanisms driving the disease remain poorly understood. This study aimed to investigate the pathogenesis of LSC and evaluate the feasibility of tape stripping as a non-invasive diagnostic technique. Methods: Skin specimens were obtained using both traditional biopsy and tape stripping methods, and the metabolites and oxidized lipids in these samples were analyzed using advanced mass spectrometry techniques. Results: Our findings suggest that 20-hydroxyeicosatetraenoic acid (20-HETE), an oxidized derivative of arachidonic acid (AA), activates the TRPV1 receptor, thereby exacerbating the itch–scratch cycle. This activation upregulates energy metabolism and promotes epidermal hyperplasia, providing new insights into the disease’s pathophysiology. Conclusions: Our study suggests that tape stripping could serve as a viable non-invasive diagnostic tool for LSC, with linoleic acid (LA) and AA potentially acting as biomarkers for the disease. Full article

Objective: This umbrella review aims to analyze the effectiveness of exercise therapy for low back pain through an analysis of systematic reviews that evaluate pain reduction, quality of life improvement, and functional outcomes. Methods: This review adhered to PRISMA guidelines and systematic review of review recommendations by searching across PubMed, Scopus, and the Cochrane Library. This study searched for systematic reviews alongside meta-analyses that evaluated exercise interventions in treating low back pain (LBP). This study included reviews that examined exercise therapy for LBP patients and presented data regarding their pain intensity, disability, and quality-of-life outcomes. Data extraction and quality assessment were performed independently by several reviewers. The methodological quality of the included systematic reviews was assessed using the AMSTAR 2 tool. Results: This research yielded 88 systematic reviews from 997 evaluated records. Reduction of pain emerged as the primary measured outcome in systematic reviews (81.8%, n = 72), and these studies showed significant improvement rates of 83.0%. The proportion of studies that concluded no change was 9.1%. The most frequently studied exercises were strengthening, aerobic, and mind–body exercises. The reviews reported quality of life improvements in 27.3% (n = 24), but most reviews (68.2%) did not assess this outcome. No studies indicated worsening outcomes. Exercise interventions demonstrated various forms that effectively contribute to LBP management, according to the study results. Conclusions: This umbrella review of 88 systematic reviews highlights that exercise therapy is a safe, effective, and commonly used strategy for managing low back pain. However, key limitations include the low methodological quality of several included reviews, risk of bias, imprecision, limited reporting of adverse effects, and confounding from multicomponent interventions. While there is limited certainty that any one type of exercise is more effective than others, individualized approaches and patient adherence appear to be critical factors in optimizing outcomes. Full article