Advancing Open Science

Large amounts of binder system waste are produced upon the recovery of energetic components in scrapped hydroxyl-terminated polybutadiene (HTPB) propellant. This study investigated the biodegradability of the binder system waste using a microbial enrichment solution as the biodegradation medium. We measured the binder system weight loss and performed Fourier-transform infrared (FT-IR), thermogravimetric (TG), and scanning electron microscopy (SEM) analyses of the binder system after 60 days of biodegradation. The results show the binder system film weight decreased by approximately 43% and stabilized after 50 days. The FT-IR analysis shows a reduction in C=O and C-O bond signals, whereas N-H, C-N, and C=C bond signals remain nearly unchanged. The TG analysis shows that the difference between the DOA weight in the initial film and that of the thermal decomposition was almost equal to the weight loss of the binder system film after biodegradation. The SEM analysis shows irregular pits on the film. The binder system has a certain biodegradability, which is mainly caused by its plasticizer component, i.e., DOA. HTPB-based polyurethane, the other major component, is difficult to degrade by microorganisms. As such, the binder system was pretreated with sodium methoxide-methanol solution as a depolymerization reagent, and the pretreated product yielded higher biodegradability.

Enhancer of Zeste Homolog 2 (EZH2), the catalytic subunit of Polycomb Repressive Complex 2 (PRC2), mediates histone H3 lysine 27 trimethylation (H3K27me3), an epigenetic modification associated with transcriptional repression. EZH2 inhibitors (EZH2is) gained attention after the first-in-class drug Tazemetostat received FDA approval for treating epithelioid sarcoma. Preclinical studies suggest that EZH2is could be effective against melanoma, but their general inability to cross the blood–brain barrier (BBB), among others, limits the treatment of secondary brain metastases. Based on these limitations, we designed SG-8, a novel compound derived from TDI-6118 (a known brain-penetrant EZH2i). In silico docking predicted that SG-8 may exhibit high affinity for EZH2 as well as for another PRC2 subunit, Embryonic Ectoderm Development (EED). In addition, in vitro PAMPA assays suggested passive BBB permeability of SG-8. In cell-based assays, SG-8 and the structurally related EZH2i PF-06726304 displayed lower cytotoxicity than Tazemetostat in both primary (A375) and metastatic (Colo-679) human melanoma cells. Western blot analysis showed that SG-8 and PF-06726304 markedly reduced EED protein levels and, to a lesser extent, EZH2 levels, without affecting total H3K27me3, consistent with preserved canonical PRC2 activity. Instead, treatment with both compounds—most prominently SG-8—was associated with reduced phosphorylation levels of EZH2 (Ser21) and its upstream regulator Akt (Ser473), suggesting that modulation of the Akt–EZH2 signaling axis may at least partially contribute to their anti-melanoma activity.

This study addresses the dual challenges of low copper recovery and persistent arsenic pollution in the bioleaching of low-grade, high-arsenic copper ores containing enargite (Cu₃AsS₄). Through integrated electrochemical, chemical, and biological investigations, a selective and environmentally sustainable two-stage hybrid leaching process was developed. Electrochemical analysis identified a critical oxidation threshold of ~750 mV governing enargite dissolution. Chemical leaching and X-ray Photoelectron Spectroscopy (XPS) analysis revealed a temperature-dependent sulfur transformation pathway, enabling a staged thermal strategy: flotation below 40 °C to maximize hydrophobic elemental sulfur (S⁰) formation, and bioleaching at 40–55 °C to promote complete sulfur oxidation to sulfate. Optimization produced a two-stage process comprising 10-day chemical pre-leaching with FeSO₄ (10.0 g/L Fe²⁺) followed by bioleaching, achieving 78.3% copper extraction while suppressing arsenic dissolution to approximately 10%. The use of FeSO₄ instead of Fe₂(SO₄)₃ reduces reagent costs by ~70%, saving an estimated CNY 47,250 daily at 1000 t/d scale. Leaching toxicity tests confirm residue As < 0.10 mg/L, meeting non-hazardous waste standards (GB5085.3-2007). This work provides the first integrated demonstration of electrochemical threshold control combined with temperature-dependent sulfur speciation for selective copper extraction from arsenic-bearing enargite ores, offering a scalable, reagent-economical, and environmentally sustainable metallurgical route.

To facilitate the next generation of renewable energy devices, it is important to engineer oxygen reduction reaction (ORR) catalysts that balance efficiency and production costs. This work examines oxygen adsorption on the WC (0001) surface as a function of electrode potential, utilizing DFT simulations with an implicit solvent environment. The results demonstrate that electrode potential significantly influences oxygen adsorption energy and electronic structure. Among the adsorption sites examined, the top site exhibits the highest stability across the entire potential range. The observed reduction in adsorption energy at lower potentials is attributed to the d-band center moving further from the Fermi energy, which weakens C–O orbital interactions, as revealed by DOS and COHP analyses. Our results demonstrate the crucial role of electrochemical conditions in modulating catalytic behavior and provide valuable insights for optimizing tungsten carbide (WC)-based electrocatalysts for ORR applications.

Sustainable tourism is essential for preserving natural habitats and represents a vital component of sustainable development. This study addresses a business decision-making problem related to natural resource conservation and habitat protection through waste management and IT applications in the Serbian hotel sector. Tourism in Serbia and the Western Balkans represents a sensitive issue concerning the balance between economic development and environmental protection. Therefore, the multi-criteria optimization methods Analytic Hierarchy Process (AHP) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) are applied to address this problem. To achieve this goal, a hierarchical model was developed that considers nine criteria and four alternatives. The alternatives considered are: service user satisfaction, service cost, waste minimization, and service quality. The developed model was analyzed using a hybrid AHP–TOPSIS approach to identify the optimal alternative. The results indicate that environmental waste prevention ranks highest among all considered alternatives and plays a significant role in the development of sustainable tourism in Serbia.

High-dimensional mixed data often lack a unified semantic representation for continuous and discrete attributes, which hinders mixed-attribute similarity modeling and can result in unstable reducts and overfitting in existing neighborhood rough set (NRS) methods. To address this issue, we propose IF-EMD-SPA, an attribute reduction method for NRS grounded in Information Flow theory. Unlike conventional NRS methods that rely on discretization or a single reduction criterion, IF-EMD-SPA first establishes a unified representation framework for heterogeneous attributes based on classifications and an Information Channel Core. It then integrates Earth Mover’s Distance (EMD) and Set Pair Analysis (SPA) to define a similarity metric for mixed attributes. In addition, a three-stage greedy reduction strategy is designed under the dual constraints of dependency preservation and structural error, consisting of dependency-driven forward selection, similarity-driven structure completion, and backward redundancy removal. Experiments on five UCI benchmark datasets and two high-dimensional gene expression datasets show that IF-EMD-SPA achieves average accuracies of 93.5% (k-Nearest Neighbors, KNN), 93.9% (Support Vector Machine, SVM), and 90.8% (Classification and Regression Trees, CART), with SVM achieving the best results on all seven datasets. Under CART, it reaches 100% accuracy on Wine and WPBC, improving performance by up to 37.5 percentage points over comparison methods.

This study investigates the breakdown of thermal symmetry in finned square cavities under natural convection, focusing on how the fin-to-fluid conductivity ratio governs heat-transfer redistribution and localization. A band-resolved statistical framework is employed to analyze hot- and cold-wall Nusselt number responses across conductivity ratios ($k_r$) ranging from symmetric to highly contrasting conditions. At $k_r=1$, the cavity exhibits a fully symmetric conduction–convection regime with complete wall-to-wall coupling and a unified thermal response. Increasing the conductivity ratio to $k_r=10$ introduces a transitional regime marked by mild but systematic asymmetry, with convective activity beginning to favor the cold wall. At $k_r=100$, the system undergoes a structural transition to a strongly asymmetric state, characterized by attenuation of hot-wall convection and sustained cold-wall dominance. Under extreme ratio ($k_r=1000$), convective heat transfer becomes highly localized at the cold wall, forming a directional thermal pathway. Joint Gaussian envelopes, regression scaling, principal component analysis, and Hotelling separation collectively demonstrate that symmetry breakdown proceeds through distinct, statistically separable stages, rather than emerging as a gradual shift in mean heat-transfer intensity. The results establish cold-wall localization as the governing physical mechanism and provide a unified framework for controlling convective heat transfer in fin-assisted natural-convection systems.

COVID-19 not only affects the respiratory system but also increases the risk of cerebrovascular complications, including ischemic stroke. Experimental and clinical data suggest that cytokine dysregulation and polymorphisms of thrombophilia-related genes (MTHFR, MTR, and MTRR) may jointly promote hypercoagulation, endothelial dysfunction, and thromboinflammation, thereby contributing to post-COVID ischemic stroke. This study included 160 patients treated at Zangiota Infectious Diseases Hospitals (2021–2023): 60 patients with ischemic stroke in the acute or post-COVID period (experiment group), 50 COVID-19 patients without ischemic stroke (comparison group), and 50 ischemic stroke patients without COVID-19 (control group). Clinical–neurological and immunological parameters were assessed, and polymorphisms in thrombophilia/folate cycle genes (MTHFR C677T, MTR, and MTRR) were genotyped by PCR/real-time PCR. Statistical analysis included χ² tests, t-tests, logistic regression with odds ratios (OR) and 95% confidence intervals (CI); Hardy–Weinberg equilibrium was verified. A strong association was identified between the MTHFR C677T polymorphism and ischemic stroke on the background of COVID-19 (OR = 5.4; 95% CI: 2.1–13.8; p < 0.001). The TNF-α rs1800629 polymorphism was also significantly associated with COVID-19-related cerebrovascular events (OR = 3.27; 95% CI: 1.4–7.6; p = 0.006). Carriage of two or more minor alleles produced a synergistic effect, markedly increasing the risk of post-COVID ischemic stroke (OR = 5.59; 95% CI: 2.3–13.6; p < 0.001). These polymorphisms were linked to hyperhomocysteinemia, endothelial dysfunction, and mechanisms contributing to multifactorial arterial ischemic events. The combined assessment of thrombophilia and folate cycle-related genotypes and clinical indicators may provide a potential framework for improved risk stratification. Polymorphisms in MTHFR may appear to represent important genetic determinants of ischemic stroke following COVID-19, particularly in the context of arterial ischemic mechanisms.