Search Results (58)

The spatiotemporal heterogeneity of moisture distribution causes the coal pillar dams in underground water reservoirs to undergo long-term dry–wet cycles (DWCs) under varying moisture content increments (MCIs). Accurately measuring the pore damage and fractal dimensions (D_f) of coal rock by different MCIs under DWCs is a prerequisite for in-depth disclosure of the strength deterioration mechanism of underground reservoir coal pillar dams. This study employed low-field nuclear magnetic resonance (LF-NMR) to quantitatively characterize the pore structural evolution and fractal dimension with different MCI variations (Δw = 4%, 6%, 8%) after one to five DWCs. The results indicate that increasing MCIs at constant DWC numbers (N_DWC) induces significant increases in pore spectrum area, adsorption pore area, and seepage pore area. MRI visualization demonstrates a progressive migration of NMR signals from sample peripheries to internal regions, reflecting enhanced moisture infiltration with higher MCIs. Total porosity increases monotonically with MCIs across all tested cycles. Permeability, T₂ cutoff (T_2C), and D_f of free pores exhibit distinct response patterns. A porosity-based damage model further reveals that the promoting effect of cycle numbers on pore development and expansion outweighs that of MCIs at N_DWC = 5. This pore-scale analysis provides essential insights into the strength degradation mechanisms of coal pillar dams under hydro-mechanical coupling conditions. Full article

To investigate the pore structure evolution characteristics and damage mechanism of sandstone subjected to treatment with freeze–thaw cycles, quantitative analyses were conducted on the longitudinal wave velocity (LWV) and T₂ spectrum of sandstone before and after 10, 20, 30, and 40 freeze–thaw cycles, using longitudinal wave velocity testing, low-field nuclear magnetic resonance (NMR) testing, and fractal theory. The results show that, with the increase in the number of freeze–thaw cycles, the LWV of sandstone gradually decreases, the amplitude of the saturated T₂ spectrum gradually increases, the amplitude of the centrifugal T₂ spectrum gradually decreases, the total porosity and effective porosity increase, and the residual porosity decreases. After undergoing freeze–thaw cycles, sandstone exhibits obvious fractal characteristics in both the total porosity NMR fractal dimension and the effective porosity NMR fractal dimension, and the growth rates of both decrease exponentially with the increase in the number of freeze–thaw cycles. The magnitude of the fractal dimensions reflects the complexity of the pore structure, with smaller fractal dimensions indicating better pore connectivity. In summary, the damage evolution mechanism of sandstone under freeze–thaw cycles is characterized by the gradual expansion and interconnection of internal closed micro-pores (cracks), along with increased total porosity and effective porosity, leading to enhanced freeze–thaw damage. Full article

Climate-change-induced extreme environments exacerbate pavement degradation in arid regions, where traditional concrete incurs 23~40% higher life-cycle costs due to premature cracking. Particularly in the Gobi Desert, concrete pavements suffer from conflicting performance requirements—high flexural-to-compressive strength ratio (R_f/R_c), low shrinkage, and controlled porosity—with traditional design methods failing to address multi-objective trade-offs. Existing optimization methods have proven insufficient for such complex environments, with conventional approaches addressing only individual parameters or employing subjective weighting techniques that fail to capture the interrelated nature of critical performance indicators. This study develops an integrated optimization framework combining Response Surface Methodology (RSM), Non-dominated Sorting Genetic Algorithm III (NSGA-III), Criteria Importance Through Intercriteria Correlation (CRITIC) weighting, and VIšekriterijumsko KOmpromisno Rangiranje (VIKOR) decision-making to optimize the mix proportions water–cement ratio (W/C), sand ratio, and an air-entraining agent (AEA) for sustainable pavement concrete. Response Surface Methodology (RSM) analysis via Box–Behnken design revealed distinct parameter dominance: AEA exhibited the strongest non-linear effects on R_f/R_c and porosity, while W/C primarily governed shrinkage. NSGA-III generated 73 Pareto-optimal solutions, with CRITIC selecting an optimal mix (W/C = 0.35), sand ratio = 36%, AEA = 0.200%) validated experimentally (R_f/R_c = 0.141), shrinkage = 0.0446%, porosity = 2.82%. Microstructural characterization using scanning electron microscopy and low-field nuclear magnetic resonance (SEM/LF-NMR) demonstrated refined pore distribution and enhanced compactness. This framework effectively resolves trade-offs between performance indicators, providing a scientifically robust method for designing durable pavement concrete that reduces shrinkage by 13.0% and porosity by 13.5% compared to conventional mixes, lowering maintenance costs in arid regions. Full article

Agricultural land abandonment is a widespread phenomenon found in many regions of the world. There are many studies on post-agricultural changes in temperate, arid, semi-arid regions, etc., but studies of such soils in boreal or Arctic conditions are rare. Our study aims to fill the gaps in research on the processes of post-agricultural soil transformation, with a focus on the harsh climatic conditions of the Arctic and Subarctic regions. Parameters of soil organic matter (SOM) are largely reflected in the quality of soil, and this study investigates the dynamics of SOM properties in Subarctic agricultural soils in process of post-agrogenic transformation and long-term fertilization. Using a chronosequence approach (0–25 years of abandonment) and a reference site with over 90 years of fertilization, we performed elemental (CHN-O) analysis, solid-state ¹³C NMR spectroscopy of SOM, PXRD of soil and parent material, and multivariate statistical analysis to identify the connections between SOM composition and other soil properties. The results revealed transient increases in soil organic carbon (SOC) during early abandonment (5–10 years; 3.75–4.03%), followed by significant declines after 25 years (2.15–2.27%), driven by mineralization in quartz-dominated soils lacking reactive minerals for organo-mineral stabilization. The reference site (the Yamal Agricultural Station) maintained stable SOC (3.58–3.83%) through long-term organic inputs, compensating for poor mineralogical protection. ¹³C NMR spectroscopy highlighted shifts from labile alkyl-C (40.88% in active fields) to oxidized O-alkyl-C (21.6% in late abandonment) and lignin-derived aryl-C (15.88% at middle abandonment), reflecting microbial processing and humification. Freeze–thaw cycles and quartz dominance mineralogy exacerbated SOM vulnerability, while fertilization sustained alkyl-C (39.61%) and balanced C:N (19–20) ratios. Principal Component Analysis linked SOC loss to declining nutrient retention and showed SOM to be reliant on physical occlusion and biochemical recalcitrance, both vulnerable to Subarctic freeze–thaw cycles that disrupt aggregates. These findings underscore the fragility of SOM in Subarctic agroecosystems, emphasizing the necessity of organic amendments to counteract limitations of poor mineralogical composition and climatic stress. Full article

In order to explore a model for the deterioration rate law and mechanism of concrete performance in salt lake water or sea water, the mixed sand concrete test of different forms of chloride ion erosion under a dry–wet cycle was simulated in the laboratory. The compressive strength and penetration depth were used to characterize the structural degradation degree of mixed sand concrete. The performance degradation of mixed sand concrete was analyzed through field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermogravimetry (TG), and nuclear magnetic resonance (NMR) testing. Experimental investigations have revealed that, at an age of 140 days and under alternating wet–dry conditions, liquid chloride ion erosion results in a 17.47% reduction in the compressive strength of blended sand concrete, accompanied by an erosion depth of 28.077 mm. This erosion progresses from the exterior towards the interior of the material. Conversely, gaseous chloride ion erosion exhibits a bidirectional penetration pattern. When subjected to gaseous chloride ion erosion, the compressive strength of blended sand concrete decreases by 31.36%, with an associated erosion depth of 38.008 mm. This exposure subjects the structure to heightened crystalline pressures, leading to severe deterioration of both the micro-porous structure within the concrete and the dense structure of hydration products. Consequently, the overall extent of structural damage is more pronounced, and the rate of degradation progression is accelerated. Under the action of liquid chloride ion erosion, the degradation of mixed sand concrete structure is caused by dry–wet fatigue, crystallization pressure, chloride salt erosion and calcium ion dissolution. Under the action of spray-born chloride erosion, the degradation of the mixed sand concrete structure is caused by dry–wet fatigue, crystallization pressure, chloride salt erosion, and calcium ion dissolution, among which crystallization degradation plays a major role. In line with the engineering standards for the utilization of vast desert resources in Inner Mongolia and the long-term service of concrete in the Hetao Irrigation District, our approach contributes to the achievement of sustainable development. Full article

Hydrogels have emerged as promising biomaterials due to their excellent performance; however, their biocompatibility, biodegradability, and absorbability still require improvement to support a broader range of medical applications. This paper presents a new biofunctionalized hydrogel based on in situ crosslinking between maleimide-terminated four-arm-poly(ethylene glycol) (4–arm–PEG–Mal) and poly(ε-lysine) (ε–PL). The PEG/ε–PL hydrogels, named LG–n, were rapidly formed via amine/maleimide reaction by mixing 4–arm–PEG–Mal and ε–PL under physiological conditions. The corresponding dry gels (DLG–n) were obtained through a freeze-drying technique. ¹H NMR, FT–IR, and SEM were utilized to confirm the structures of 4–arm–PEG–Mal and LG–n (or DLG–n), and the effects of solid content on the physicochemical properties of the hydrogels were investigated. Although high solid content could increase the swelling ratio, all LG–n samples exhibited a low equilibrium swelling ratio of less than 30%. LG–7, which contained moderate solid content, exhibited optimal compression properties characterized by a compressive fracture strength of 45.2 kPa and a deformation of 69.5%. Compression cycle tests revealed that LG–n demonstrated good anti-fatigue performance. In vitro degradation studies confirmed the biodegradability of LG–n, with the degradation rate primarily governing the drug (ceftibuten) release efficiency, leading to a sustained release duration of four weeks. Cytotoxicity tests, cell survival morphology observation, live/dead assays, and hemolysis tests indicated that LG–n exhibited excellent cytocompatibility and low hemolysis rates (<5%). Furthermore, the broad-spectrum antibacterial activity of LG–n was verified by an inhibition zone method. In conclusion, the developed LG–n hydrogels hold promising applications in the medical field, particularly as drug sustained-release carriers and wound dressings. Full article

The effect of the dry–wet cycle, characterized by periodic water level changes in the Three Gorges Reservoir, will severely degrade the bearing performance of rock formations. In order to explore the effect of the dry–wet cycle on the mesoscopic damage mechanism of jointed sandstone, a list of meso-experiments was carried out on sandstone subjected to dry–wet cycles. The pore structure, throat features and mesoscopic damage evolution of jointed sandstone with the action of the dry–wet cycle were analyzed using a-low-field nuclear magnetic resonance (NMR) technique. Subsequently, the impact on the mineral content of dry–wet cycles was studied by small angle X-ray scattering (SAXS). Based on this, the mesoscopic damage mechanism of sandstone subjected to dry–wet cycles was revealed. The results show that the effects of the drying–wetting cycle can promote the development of porous channels within sandstone, resulting in cumulative damage. Besides, with an increase in dry–wet cycles, the proportion of small pores and pore throats decreased, while the proportion of medium and large pores and pore throats increased. The combined effects of extrusion crush, tensile fracture, chemical reaction and dissolution of minerals inside the jointed sandstone contributed to the development of mesoscopic pores, resulting in the increase of porosity and permeability of rock samples under the dry–wet cycles. The results provide an important reference value for the stability evaluation of rock mass engineering under long-term dry–wet alternation. Full article

Using liquid crystals in near-infrared applications suffers from effects related to processes like parasitic absorption and high sensitivity to UV-light exposure. One way of managing these disadvantages is to use deuterated systems. The combined ¹H and ²H nuclear magnetic resonance relaxometry method (FFC NMR), dielectric spectroscopy (DS), optical microscopy (POM), and differential scanning calorimetry (DSC) approach was applied to investigate the influence of selective deuteration on the molecular dynamics, thermal properties, self-organization, and electric-field responsiveness to a 4′-pentyl-4-biphenylcarbonitrile (5CB) liquid crystal. The NMR relaxation dispersion (NMRD) profiles were analyzed using theoretical models for the description of dynamics processes in different mesophases. Obtained optical textures of selectively deuterated 5CB showed the occurrence of the domain structure close to the I/N phase transition. The dielectric measurements showed a substantial difference in switching fields between fully protonated/deuterated 5CB and selectively deuterated molecules. The DSC thermograms showed a more complex phase transition sequence for partially deuterated 5CB with respect to fully protonated/deuterated molecules. Full article

In order to investigate the influence of the CaO and fly ash (FA) dosage and proportion on the mechanical properties, durability, and microstructure of solidified sludge, freeze–thaw (F-T) cycles and dry–wet (D-W) cycles are conducted to study the change in appearance and the strength attenuation of CaO-FA solidified sludge. Low-field nuclear magnetic resonance (LF-NMR) is used to analyze the microstructure of the solidified sludge with various dosages and ratios of CaO-FA. The results demonstrate that the unconfined compressive strength (UCS) and direct shear strength of solidified sludge increase with the prolongation of the curing age. Furthermore, the mechanical properties of solidified sludge are improved as the ratio of CaO-FA increases. As the curing age increases, the distribution of transverse relaxation time (T₂) becomes narrow, the spectral area decreases, and the amplitude of the LF-NMR signal shows a downward and leftward tendency. Additionally, with the increase in the number of F-T cycles and D-W cycles, the UCS of solidified sludge declines and the degree of pore deterioration increased gradually. This study offers a theoretical foundation and empirical data for the dredging and treatment of sludge in cold regions. Full article

The synthesis of biodiesel can be achieved using either homogeneous or heterogeneous catalysts. Given the non-renewable nature of homogeneous catalysts, heterogeneous catalysts are increasingly preferred for biodiesel production. Agricultural wastes serve as a viable source for these heterogeneous catalysts, contributing to environmental sustainability. This study introduces a novel, eco-friendly, cost-effective, and efficient heterogeneous catalyst that was developed and derived from Citrus limetta peels for biodiesel production. The catalyst was thoroughly characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffractograms (XRD), Field Emission Scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX). Coconut oil, a rich and renewable resource, was used as the feedstock for the biodiesel synthesis. The conversion process was confirmed by ¹H NMR, IR spectra, mass spectra, and ¹³C NMR of the biodiesel. The developed method using the Citrus limetta peel-derived catalyst demonstrated a 100% yield. The results show the optimum conditions for biodiesel synthesis are 1 w/v (for the catalytical dose), with a 6:1 methanol/oil ratio at 60 °C for 3 h. The synthesized biodiesel exhibited a high cetane value of 54, contributing to improved ignition and reduced engine noise. Its sulfur-free composition, boiling point of 294 °C, high viscosity of 2.5 mm²/s, acid value of 0.09 mgKOH/g, and flash point of 142 °C enhance its environmental profile. The catalyst can be used for up to five cycles, underscoring its potential as a cost-effective and sustainable approach for biodiesel production. Full article

Litter’s chemical complexity influences carbon (C) cycling during its decomposition. However, the chemical and microbial mechanisms underlying the divergence or convergence of chemical complexity under UV radiation remain poorly understood. Here, we conducted a 397-day field experiment using ¹³C cross-polarization magic-angle spinning nuclear magnetic resonance (¹³C-CPMAS NMR) to investigate the interactions among the initial chemistry, microbial communities, and UV radiation during decomposition. Our study found that the initial concentrations of O-substituted aromatic C, di-O-alkyl C, and O-alkyl C in Deschampsia caespitosa were higher than those in Kobresia tibetica. Litter’s chemical composition exhibited divergent patterns based on the initial chemistry, UV radiation, and decay time. Specifically, D. caespitosa consistently displayed higher concentrations of di-O-alkyl C and O-alkyl C compared to K. tibetica, regardless of the UV exposure and decay time. Additionally, litter’s chemical complexity was positively correlated with changes in the extracellular enzyme activities, particularly those involved in lignin, cellulose, and hemicellulose degradation, which accounted for 9%, 20%, and 4% of the variation in litter’s chemical complexity, respectively. These findings highlighted the role of distinct microbial communities in decomposing different C components through catabolism, leading to chemical divergence in litter. During the early decomposition stages, oligotrophic Planctomycetes and Acidobacteria metabolized O-alkyl C and di-O-alkyl C under UV-blocking conditions. In contrast, copiotrophic Actinobacteria and Chytridiomycota utilized these components under UV radiation exposure, reflecting their ability to thrive under UV stress conditions due to their rapid growth strategies in environments rich in labile C. Our study revealed that the inherent differences in the initial O-alkyl C and di-O-alkyl C contributed to the chemical divergence, while UV radiation further influenced this divergence by shifting the microbial community composition from oligotrophic to copiotrophic species. Thus, differences in the initial litter chemistry, microbial community, and UV radiation affected the quantity and quality of plant-derived C during decomposition. Full article

Cancer is one of the deadliest diseases to humanity. There is significant progress in treating this disease, but developing some drugs that can fight this disease remains a challenge in the field of medical research. Thirteen new 1,2,3-triazole linked tetrahydrocurcumin derivatives were synthesized by click reaction, including a 1,3-dipolar cycloaddition reaction of tetrahydrocurcumin baring mono-alkyne with azides in good yields, and their in vitro anticancer activity against four cancer cell lines, including human cervical carcinoma (HeLa), human lung adenocarcinoma (A549), human hepatoma carcinoma (HepG2), and human colon carcinoma (HCT-116) were investigated using MTT(3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetraz-olium bromide) assay. The newly synthesized compounds had their structures identified using NMR HRMS and IR techniques. Some of prepared compounds, including compounds 4g and 4k, showed potent cytotoxic activity against four cancer cell lines compared to the positive control of cisplatin and tetrahydrocurcumin. Compound 4g exhibited anticancer activity with a IC₅₀ value of 1.09 ± 0.17 μM against human colon carcinoma HCT-116 and 45.16 ± 0.92 μM against A549 cell lines compared to the positive controls of tetrahydrocurcumin and cisplatin. Moreover, further biological examination in HCT-116 cells showed that compound 4g can arrest the cell cycle at the G1 phase. A docking study revealed that the potential mechanism by which 4g exerts its anti-colon cancer effect may be through inhabiting the binding of APC–Asef. Compound 4g can be used as a promising lead for further exploration of potential anticancer agents. Full article

The spin-lattice relaxation rates (R₁) of fluorine nuclei in perfluorosulfonic acid (PFSA) ionomer membranes and their precursor solid perfluorosulfonyl fluoride (PFSF) were measured by fast field-cycling (FFC) NMR relaxometry. The XRD profiles of PFSA and PFSF are similar and show a characteristic peak, indicating the alignment of main chains. While the SAXS profiles of the PFSA membranes show two peaks, those of the solid PFSF lack the ionomer peak which is characteristic of hydrophilic side chains in the PFSA ionomer membranes. The Larmor frequency dependence of R₁ obeys power law and the indices are dependent on the sample and temperature. The indices of the PFSA membranes change from −1/2 to −1 along with the Larmor frequency and temperature dependence decrease, which is consistent with the generalized defect diffusion model. Estimated activation energies are in good agreement with those obtained from dynamical mechanical analysis and dielectric spectroscopy, indicating the segmental motion of the backbones as the common origin of these observations. On the other hand, the index changes to −3/4 in the case of the PFSFs, which has been predicted by the reptation model. Full article

Fast-Field-Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry is a powerful, non-destructive magnetic resonance technique that enables, among other things, the investigation of slow molecular dynamics at low magnetic field intensities. FFC-NMR relaxometry measurements provide insight into molecular motion across various timescales within a single experiment. This study focuses on a model-free approach, representing the NMRD profile $R_1$ as a linear combination of Lorentzian functions, thereby addressing the challenges of fitting data within an ill-conditioned linear least-squares framework. Tackling this problem, we present a comprehensive review and experimental validation of three regularization approaches to implement the model-free approach to analyzing NMRD profiles. These include (1) MF-UPen, utilizing locally adapted $L_2$ regularization; (2) MF-L1, based on $L_1$ penalties; and (3) a hybrid approach combining locally adapted $L_2$ and global $L_1$ penalties. Each method’s regularization parameters are determined automatically according to the Balancing and Uniform Penalty principles. Our contributions include the implementation and experimental validation of the MF-UPen and MF-MUPen algorithms, and the development of a “dispersion analysis” technique to assess the existence range of the estimated parameters. The objective of this work is to delineate the variance in fit quality and correlation time distribution yielded by each algorithm, thus broadening the set of software tools for the analysis of sample structures in FFC-NMR studies. The findings underline the efficacy and applicability of these algorithms in the analysis of NMRD profiles from samples representing different potential scenarios. Full article

Phenothiazine derivatives are widely studied in various fields such as biology, chemistry, and medicine research because of their pharmaceutical effects. The first compound used successfully in the treatment of psychosis was a phenthiazine derivative, chlorpromazine. Apart from its activity in neurons, chlorpromazine has also been reported to display anticancer and antibacterial properties. In this study, we present the synthesis and research on the activity of A549, MDA, MiaPaCa, PC3, and HCT116 cancer cell lines and of S. aureus, S. epidermidis, E. coli, and P. aeruginosa bacterial strains against a series of new tetracyclic chlorpromazine analogues containing a quinoline scaffold in their structure instead of the benzene ring and various substituents at the thiazine nitrogen. The structure of these novel molecules has been determined by ¹H NMR, ¹³C NMR, and HRMS spectral techniques. The seven most active of the twenty-four new chlorpromazine analogues tested were selected to study the mechanism of cytotoxic action. Their ability to induce apoptosis or necrosis in cancer cells was assessed by flow cytometry analysis. The results obtained confirmed the proapoptotic activity of selected compounds, especially in terms of inducing late apoptosis or necrosis in cancer cell lines A549, MiaPaCa-2, and HCT-116. Furthermore, studies on the induction of cell cycle arrest suggest that the new chlorpromazine analogues exert antiproliferative effects by inducing cell cycle arrest in the S phase and, consequently, apoptosis. Full article