Search Results (5,762)

This study investigates the influence of various parameters on the synthesis of oligosiloxanes with degrees of polymerization below 15. The work provides insights into methods for synthesizing oligosiloxanes with precisely controlled molecular weight and degrees of polymerization. Low-molecular-weight polysiloxanes with well-defined molecular characteristics have attracted attention due to their versatile functional properties and potential applications. Although some studies have explored the control of polysiloxane molecular weights, precise regulation of oligosiloxane molecular weight has been rarely investigated. This study aims to establish optimized reaction conditions for the synthesis of oligosiloxanes with precisely controlled molecular weights. The results reveal that the molecular weight of oligosiloxanes can be effectively tuned by adjusting the molar ratio between the promoter and initiator, the initiator and cyclotrisiloxane (D₃), as well as by varying the lithium type and solvent composition in the ring-opening polymerization of D₃. These findings provide valuable guidance for tailoring oligosiloxane properties and expanding their potential applications in advanced materials. Full article

With the rapid development of unmanned surface vessels (USVs), a vector thruster was designed in this paper to meet their evolving operational demands. The anti-impact capability of the vector thruster, in which the universal joint plays a critical role in attenuating impact loads, directly governs the stability and security of power transmission in USVs. A mechanical model of the vector thruster with a universal joint was established, incorporating length and stiffness ratio coefficients to characterize its key dynamics. Based on this model, numerical simulation using the Newmark method was conducted to systematically evaluate the thruster’s mechanical characteristics, particularly the dynamic variation of the inclination angle, under various working conditions and impact loads. The results indicate that an increase in stiffness ratio amplifies the angular displacement amplitude of the driven shaft but shortens the vibration stabilization time. During the operation of the vector thruster, an increase in the inclination angle leads to greater vibration amplitude. Furthermore, systems with a higher, longer ratio exhibit a more pronounced tendency for amplitude growth as the inclination angle increases. Finally, the theoretical model was validated through a test bench, and the variation pattern of dynamic thrust under impact load was revealed. These results emphasize that the stiffness and dimensional parameters must be carefully considered in the design and control optimization of vector thrusters to ensure reliable performance under demanding operational conditions. Full article

Microalgae are extremely diverse photosynthetic organisms, adapted to live in different habitat conditions, from freshwater to marine environments. This adaptability is also associated with the ability to produce several metabolites. Polyunsaturated aldehydes (PUAs), first identified in 1999 in Thalassiosira gravida and Skeletonema costatum, are known to influence the development of their predators, having teratogenic effects and blocking their development. PUAs have shown several activities, such as antitumor, antimicrobial and antiparasite. Another relevant compound is pheophorbide a (PPBa), a chlorophyll degradation product, which has previously shown properties useful to be considered as a photosensitizer in photodynamic therapy, demonstrating cytotoxic effects on various tumor cell lines. It has also been shown to have activity against some bacteria and fungi. Considering the growing problem of multi-antibiotic resistance of human pathogenic bacteria and the increasing market demand for new drugs, the aim of our work was to screen two PUAs, i. e., 2,4-octadienal and trans,trans-2,4-decadienal, and PPBa against a panel of human pathogenic bacteria and fungi: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and Aspergillus fumigatus. The antimicrobial activity was evaluated through MIC (Minimum Inhibitory Concentration) and MFC/MBC (Minimum Fungicidal/Bactericidal Concentration), demonstrating that the two PUAs had a greater antimicrobial activity than PPBa on both bacteria and fungi, except for P. aeruginosa, where the antimicrobial activity was low. The compound 2,4-Octadienal showed extremely high antifungal activity, especially against the fungus A. fumigatus, where the MIC and MFC were 0.001 µL/mL and 0.004 µL/mL, respectively. These results are shedding light on the antimicrobial activity of microalgal compounds and their possible applications for different human infection diseases. Full article

Against the backdrop of growing climatic variability, the identification of genotypes combining high yield with stability and resilience to stress factors has become a central objective of contemporary wheat breeding. Therefore, the objective of this work was to assess the stability and adaptability of a collection of 13 wheat–wheatgrass hybrids (WWHs, lines) (Triticum aestivum L. (2n = 42)) in comparison with 10 commercial spring bread wheat (Tr. aestivum L.) cultivars under various meteorological conditions. This study was conducted in one location (Moscow region, Russia) over three growing seasons (2020, 2021, and 2022), which included a highly stressful year (2021) characterized by a severe combination of drought and heat during critical growth stages. Statistical analysis employed analysis of variance (ANOVA), clustering, and modern models for assessing the genotype-by-environment interaction (GEI)—AMMI (Additive Main Effects and Multiplicative Interaction). The results showed a significant effect of year conditions on all yield components. Under the stressful conditions of 2021, most genotypes exhibited a 30–70% decrease in productivity. Cluster analysis revealed a dynamic regrouping of genotypes depending on the conditions of the growing season. The AMMI model identified genotypes with high stability, such as Sudarinya (ASV = 9.3) and WWH 200 (ASV = 11.2), as well as genotypes specifically adapted to certain conditions: KWS Akvilon (ASV = 52.1) to stressful conditions and WWH 127 (ASV = 55.9) to favorable conditions. Under stress, lines WWH 107, WWH 127, and WWH 2430 exhibited the most adaptive strategies, including compensatory mechanisms, making these hybrids promising for further breeding. In conclusion, although wheat–wheatgrass hybrids demonstrate high productive potential under favorable conditions, their successful use in breeding requires the selection of genotypes that combine productivity and stress resistance. The identified stable and adaptive genotypes are valuable for developing new competitive cultivars under changing climatic conditions. Full article

Over the past few years, the misuse of medications has progressively increased, posing a significant public health concern. This study proposed the development and validation of an alternative and greener analytical method for the determination of dextromethorphan (DXM) and its major metabolite, dextrorphan (DXO), in urine matrices using bar adsorptive microextraction (BAμE), followed by gas chromatography–mass spectrometry (GC-MS) analysis. Under optimized experimental conditions, average recoveries of 96.3% and 80.4% were achieved for DXM and DXO, respectively. The analytical limits obtained were 0.016 μg/mL for the limit of detection and 0.054 μg/mL for the limit of quantification. The working range was from 0.06 μg/mL to 2.0 μg/mL, with linearity for both compounds by determination coefficients (r² > 0.99) and the goodness-of-fit and lack-of-fit tests. Intra-day precision and trueness yielded values below 8.77% and 16.28%, respectively, for both compounds. Inter-day precision and trueness values were below 7.67% and 9.73%, respectively. The application to 26 urine samples allowed the quantification of both compounds, with concentrations ranging from 0.06 to 3.21 μg/mL for DXM and 0.06 to 8.88 μg/mL for DXO. The method proved to be effective, selective, sensitive, simple, and cost-effective in the detection and quantification of DXM and DXO, reinforcing its applicability and feasibility in various laboratory contexts. Full article

Chrysanthemum, a traditional medicinal and edible plant, possesses diverse health-promoting properties attributed to its rich profile of bioactive compounds. However, the intrinsic quality, influenced by the composition of fundamental components like starch and lignin, varies significantly across different cultivars and origins. This study establishes a comprehensive phytochemical profile of 12 representative Chinese chrysanthemum cultivars by systematically quantifying their starch and lignin contents. Furthermore, it develops and validates a novel, low-cost rapid detection method for starch utilizing smartphone-based colorimetry. The starch content, determined by a colorimetric anthrone-sulfuric acid assay, ranged from 2.68 to 18.69 g/100 g, while the lignin content, measured via the acetyl bromide digestion followed by UV spectrophotometry at 280 nm, varied from 4.21 to 13.63 g/100 g, revealing substantial inter-cultivar differences. For starch analysis, a low-cost, immediate, general-purpose, and high-throughput (LIGHt) smartphone-based colorimetry was implemented. Standard curves constructed from both absorbance and the LIGHt assay demonstrated excellent linearity (R² > 0.99). The method’s performance was evaluated under different lighting conditions and across various smartphone models. The UV spectrophotometry condenses lignin quantification to a single 30-min digestion–reading cycle, bypassing the two-day Klason protocol and increases efficiency greatly. The work successfully provides a foundational component analysis and validates a portable, high-throughput framework for on-site quality control of plant-based products, demonstrating the strong potential of smartphone-based colorimetry for rapid starch detection and a complementary laboratory-scale lignin assay. Full article

The present research examines how employees perceive their firms’ CSR initiatives that ultimately translate into desired attitudes and behaviors, i.e., employee environmental commitment (EEC) and knowledge sharing (KS) at the workplace, by underpinning social identity theory. However, when do undesired working conditions, i.e., Perception of Politics (POP), adversely influence these desired outcomes? We deliberately selected 45 firms in the services and manufacturing sectors of Pakistan operating in larger metropolitan cities and prevalent tourist destinations, and actively participating in CSR activities. Thereafter, three self-administered surveys were conducted by employing a time-lagged design with two temporal breaks. A total of 655 surveys were distributed among middle managers across selected firms. Accordingly, it is found that employees who strongly identify with their organizations tend to align their personal values with organizational sustainability efforts and actively participate in environmentally responsible practices. They also demonstrate a greater willingness to share knowledge and enhance the organization’s collective intelligence. However, when employees perceive a high level of political behavior within the organization, their trust in its ethical standards diminishes, leading to various negative attitudes and behaviors in the workplace. This research contributed in two ways to the existing literature: (a) by examining the employees’ understandings of firms’ CSR engagements and their trickle-down effect on EEC and KS, (b) and studying when POP adversely effects the above relationship. Full article

Terahertz Synthetic Aperture Radar (THz-SAR) is highly sensitive to platform vibrations and trajectory deviations, which introduce severe phase errors and limited resolution. Typically, platform vibrations and trajectory deviations are investigated individually, and vibrations are modeled as a stationary sine term. In this work, a hybrid motion compensation (MOCO) scheme is proposed to address both platform vibrations and trajectory deviations simultaneously, achieving improved imaging quality. The scheme initiates with a parameter self-adaptive quadratic Kalman filter designed to resolve severe phase wrapping. Then, platform vibration is modeled as a non-stationary multi-sine term, whose components are accurately extracted using an improved signal decomposition algorithm enhanced by a dynamic noise adjustment mechanism. Subsequently, the trajectory deviation is parameterized following subaperture division, estimated using a hybrid optimizer that combines particle swarm optimization and gradient descent. Additionally, a composite modulated waveform application ensures low sidelobes and a low probability of intercept (LPI). Extensive simulations on point targets and complex scenes under various signal-to-noise-ratio (SNR) conditions are applied for SAR image reconstruction, demonstrating robust suppression of motion errors. Under identical simulated error conditions, the proposed method achieves an azimuth resolution of 4.28 cm, which demonstrates superior performance compared to the reported MOCO techniques. Full article

Wide-area damping controls, like the wide-synchronization control (WSC), are crucial for power system stability but are vulnerable to communication latencies. This article presents a comprehensive theoretical characterization of the impact of time delays on the WSC. The formal analysis derives mathematical models for both differential and common modes. Two distinct scenarios are investigated: a symmetric condition, where the WSC is applied to both coupled areas, and an asymmetric condition, where it is applied to only one area. A formal stability assessment is conducted to determine stability boundaries and critical delay-induced crossings into unstable regions. Key findings show that under symmetric conditions, the system remains stable for all delays, as latencies only affect the common mode. Conversely, the asymmetric condition introduces a coupling between modes, making the system susceptible to delay-induced instability, especially at high control gains. The work validates the theoretical findings through numerical experiments and evaluates the accuracy of various linear Padé approximant models for representing delays, highlighting how low-order models can fail to predict instabilities, requiring high-order approximants to guarantee adequate accuracy in the analysis. Full article

The progress in metal additive manufacturing (AM) technology has enabled the printing of parts with intricate geometries. Predicting and reducing geometrical deviations (i.e., the difference between the printed part and the design) in metal AM parts remains a challenge. This work explores how changes in laser speed, laser power, and hatch spacing affect geometrical deviations in parts made using laser powder bed fusion (L-PBF) and emphasizes predicting geometrical defects in AM parts. Sliced images obtained from CAD designs and printed parts are utilized to capture the effects of various L-PBF process parameters and to generate a comprehensive data set. Conditional Generative Adversarial Networks (cGANs) are trained to predict images that accurately reflect actual geometrical deviations. In this study, the influence of L-PBF process parameters on geometric deviation is quantified, and the prediction results demonstrate the effectiveness of the proposed cGAN-based method in improving the predictability of geometric deviations in parts fabricated via L-PBF. This approach is expected to facilitate early correction of geometrical deviations during the L-PBF process. Full article

Power semiconductor devices are fundamental components in modern electronic power conversion. In applications demanding high power density and efficiency, the choice between silicon (Si) IGBTs and Silicon Carbide (SiC) MOSFETs is critical. SiC MOSFETs, owing to their high critical electric field, superior thermal conductivity, wide band gap, and low power loss, realize significant performance improvements and compact design. This work presents a comprehensive, simulation-driven comparative investigation under identical setups, evaluating both technologies across various parameters. The effects of temperature variations on gate-source threshold voltage drift, current slew rate, device stress, and energy dissipation during switching transitions are evaluated. Furthermore, the characteristic switching behavior when the DC-bus voltage, gate resistance, and load current are varied is investigated. This study addresses a current scarcity of systematic investigation by presenting a comprehensive comparative evaluation of switching losses and efficiency across varied operating conditions, providing validated conclusions for the design of advanced WBG converters. The results demonstrate that SiC exhibits lower losses and faster switching speeds than Si IGBTs, with minimal temperature-dependent loss variations, unlike Si devices, whose losses rise significantly with temperature. Si shows distinct tail currents during turn-off, absent in SiC devices. A conclusive comparative evaluation of switching energy losses under varied operating conditions demonstrates that SiC devices can effectively retrofit Si counterparts for fast, low-loss, high-efficiency applications. Full article

Oily wastewater treatment is crucial for protecting the environment and ensuring sustainable water use. The current study examines the effectiveness of electrocoagulation in treating oily wastewater by conducting several batch experiments designed to determine the best operating conditions. Various factors affecting the performance of electrocoagulation, such as applied current density, electrode type, and pH, were studied. The results indicate that, under ideal conditions, electrocoagulation worked very well. The best results were obtained by involving an applied current density of 6 mA/cm², a mild steel anode, and a pH of 6.7. Under these conditions, the process removed 94% of the chemical oxygen demand (COD) from the oily wastewater. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDAX) were used to characterize the residual sludge left in the reactor. The characterization results show that the oily pollutants were successfully removed through electroflotation. Additionally, oil precipitate particles were easily coated during the electrocoagulation operation. The findings show that electrocoagulation is an effective method for treating oil-contaminated wastewater. Full article

There is a critical gap in the preclinical research of recombinant human interferons (rhIFNα-2b and rhIFN-γ), as most studies focus on modified variants, which complicates the understanding of the native molecules’ properties. This study addresses this limitation by comprehensively evaluating the structural stability and intrinsic toxicity of purified IFNs. Our findings confirm that both interferons retain their bioactivity (antiviral, antiproliferative, and immunomodulatory) and exhibit remarkable stability under controlled conditions. Accelerated stability assays showed that neither protein lost biological potency after 18 days at various temperatures, supporting their potential as liquid formulations. Acute and sub-chronic toxicity studies in rodent, non-rodent, and higher-organism animal models showed no signs of toxicity, even at doses 100 to 300 times higher than therapeutic levels. These assays, combined with the absence of pyrogens, support a favorable safety profile for clinical use, with no evidence of systemic or structural damage. This work establishes a reproducible experimental model and lays the groundwork for future preclinical evaluations. We underscore the importance of characterizing the safety profile of active pharmaceutical ingredients from the earliest stages of biopharmaceutical development to ensure a safe and well-founded transition to human clinical trials. Furthermore, these results open the door for the development of advanced formulations and alternative routes of administration, such as the intranasal route, an area with significant potential. Full article

In this work, we propose a simple analytical/semi-analytical approach to solve various φ,ψ-fractional partial differential equations (φ,ψ-FPDEs) using initial and boundary conditions (ICs, BCs) depending on the φ,ψ-Double Elzaki transform (φ,ψ-DET) method. The suggested approach takes advantage of a DPET modification that works well with φ,ψ-fractional operators. The proposed method not only solves the φ,ψ-FPDEs but also reduces them to a more straightforward algebraic recurrence issue. This simple yet powerful idea can be used to solve φ,ψ-FPDEs in science and engineering. We contrast the outcomes of the stated computational examples with exact solutions in order to verify the exactness and efficacy of this methodology. Full article

Ethyl butyrate is a typical flavor ester with pineapple-banana scents, but the poor yield from natural fruits limits its feasibility in food and fragrance industries. In this study, dendritic fibrous nano-silica (DFNS) was hydrophobically modified with octyl groups (DFNS-C₈) to immobilize Candida antarctica lipase B (CALB) for solvent-free esterification of ethyl butyrate. The immobilized lipase CALB@DFNS-C₈, with the enzyme loading of 354.6 mg/g and the enzyme activity of 0.064 U/mg protein, achieved 96.0% ethyl butyrate conversion under the optimum reaction conditions where the molar ratio of butyric acid to ethanol was 1:3, with a reaction temperature and time of 40 °C and 4 h. Under the solvent-free catalytic reactions, CALB@DFNS-C₈ presented the maximum catalytic efficiency of 35.1 mmol/g/h and retained 89% initial activity after ten reuse cycles. In addition, the immobilized lipase can efficiently catalyze the synthesis of various flavor esters (such as butyl acetate, hexyl acetate, butyl butyrate, etc.) and exhibits excellent thermostability and solvent tolerance. A molecular docking simulation reveals that the hydrophobic cavity around the catalytic triad stabilizes the acyl intermediate and ensures the precise orientation of both acid and alcohol substrates. This work provides new insights into the sustainable production of flavor esters using highly active and recyclable immobilized lipases through rational carrier hydrophobization and structural confinement design. Full article