Search Results (1,358)

The interaction between salt solutions and expansive soils is critical for engineering in chemically aggressive environments. However, the effect of iodide salts on pore water distribution in expansive soils remains poorly understood. This study investigated the transverse relaxation time (T₂) characteristics of pore water in expansive soils under varying KI concentrations (0–20%), moisture content (8.7–26.0%), and dry density (1.26–1.79 g/cm³) using nuclear magnetic resonance (NMR). All T₂ curves exhibited a single peak. Increasing moisture content from 8.7% to 26.0% resulted in increases of approximately 63% in T₂ at peak and 408–439% in peak area. Increasing KI concentration decreased both T₂ at peak by up to 33.3% and peak area by up to 44.0% within the tested range, attributed to diffuse double-layer compression and signal loss. Increasing moisture content broadened the T₂ distribution and linearly increased T₂ at peak and peak area, indicating water gradually occupied larger pore spaces as moisture content rose. T₂ at peak was independent of dry density, while the peak area showed a linear relationship with dry density, consistent with mass balance. The observed systematic linear relationships among T₂ at peak, peak area, and the three experimental variables suggest that NMR is a promising tool for the quantitative assessment of salt solution effects on pore water in expansive soils. These findings provide a theoretical basis for evaluating salt-affected expansive soils in coastal and arid regions. Full article

Background/Objectives: Leishmaniases are a group of neglected tropical diseases that have been overlooked, and new treatments are needed. This is because the parasites that cause it, from the Leishmania genus, have become drug-resistant, and current medications can be toxic. In this regard, arylidenehydrazinyl thiazoles emerge as a potential scaffold for creating new, effective drug candidates to combat this disease. Methods: Here, we report the synthesis of a series of arylidenehydrazinyl thiazole carboxylates (3a–m, 13 examples, 66–78%) using a simple cost-effective strategy via cyclization of aryl-substituted thiosemicarbazones and ethyl-2-chloro-3-oxobutanoate in an equimolar mixture. These compounds were investigated for their promising bioactive properties. Results: All compounds were fully characterized using spectroscopic techniques (¹H-, ¹³C-NMR, FTIR spectroscopy, and HRMS) to confirm their purity and identity. These arylidenehydrazinyl thiazole carboxylates have been tested for their cytotoxicity against promastigote and intracellular amastigote forms of Leishmania amazonensis (IFLA/BR/1967/PH8) and the NIH/3T3 mouse fibroblast cell lines and their potential interaction with Leishmania trypanothione synthetase was explored through in silico molecular docking studies. Conclusions: The compounds showed little or no cytotoxicity against NIH/3T3 fibroblasts, compounds 3a, 3d and 3m showed low cytotoxicity to promastigote forms, but compounds 3b, 3c, 3h and 3m showed activity against amastigotes (IC₅₀ = 15.92 µM for 3m) at the tested concentrations. In silico molecular docking studies have been deployed to investigate the structural dynamics and the stability of the complex. These findings suggested that the newly developed compounds represent promising preliminary hits for further optimization toward the treatment of diseases associated with Leishmania parasites. Full article

The laminin-derived nonapeptide CDPGYIGSR contains the bioactive YIGSR motif, historically associated with inhibition of tumor cell adhesion, invasion, angiogenesis, and laminin-receptor-mediated cell responses. Although these activities have often been attributed to the 37/67 kDa laminin receptor/RPSA axis, the molecular identity and organization of the laminin-binding receptor system remain debated. This uncertainty makes it essential to define the intrinsic conformational preferences of CDPGYIGSR in solution before assigning a unique receptor-bound structure. In this study, temperature replica-exchange molecular dynamics (T-REMD) simulations in explicit solvent are employed to characterize the solution conformational ensemble of CDPGYIGSR. Free energy landscape analysis, clustering, and structural descriptors reveal a predominant compact bend-like backbone arrangement, together with alternative low-lying conformational states within a heterogeneous ensemble. Rather than assuming a single bioactive conformation, the conformational ensemble is analyzed in terms of structural features that are consistent with available NMR observations and reported structure–activity relationships. Importantly, the most populated conformations in solution do not necessarily correspond to the bioactive state upon receptor binding. Instead, a subset of conformations sharing common structural motifs, including a central backbone bend and specific residue exposure patterns, may represent states compatible with receptor recognition. These results provide an ensemble-based structural framework that connects simulation-derived conformational motifs with available NMR observations and structure–activity data, supporting a recognition-compatible ensemble model in which compact preorganized states may contribute to receptor binding. Full article

The growing amounts of agricultural residues require sustainable solutions for their use. Here, wheat, rice, barley, and oat straw were evaluated as renewable feedstocks for the enzymatic production of xylooligosaccharides (XOS). Hydrolysis used recombinant xylanase from Bacillus sonorensis T6 under optimized conditions (40 °C, pH 7.0), with stepwise enzyme addition. Subsequently, hydrolysis efficiency was found to vary by substrate, with wheat straw producing the highest reducing sugar yield (up to 40.1 g kg⁻¹), followed by barley, oat, and rice straw. As hydrolysis progressed, the influence of enzyme concentration became less pronounced, suggesting that substrate accessibility and the accumulation of hydrolysis products may increasingly affect the overall hydrolysis efficiency. FTIR, NMR, SEM, and TLC analyses confirmed substantial structural changes in the biomass and the formation of carbohydrate-rich hydrolysis products. TLC analysis indicated the presence of low-degree polymerization oligosaccharides with migration behavior similar to X2 and X3 standards, while FTIR and NMR spectra were consistent with β-(1→4)-linked carbohydrate structures. The xylanase from Bacillus sonorensis T6 hydrolyzed all substrates, revealing broad specificity and suitability for diverse lignocellulosic feedstocks, despite differences in biomass structure. Overall, the results highlight the importance of substrate-dependent factors in enzymatic hydrolysis and demonstrate that xylanase from Bacillus sonorensis T6 converts cereal straw into value-added oligosaccharide-rich products, thereby supporting the development of cost-effective, region-specific biorefinery strategies. Full article

Spontaneous imbibition modified by surfactants is a key technology for enhancing shale oil recovery. Currently, relevant studies mainly concentrate on marine shale worldwide, while the pore–fluid coupling characteristics of widely distributed medium-TOC terrestrial shale remain poorly understood. Against this background, this paper takes typical Paleogene terrestrial shale as the research object and integrates N₂/CO₂ adsorption and NMR T₂ spectroscopy to jointly characterize multiscale pore structures and dynamic fluid evolution during imbibition. The results show that the shale is dominated by mesopores in terms of pore volume, while micropores provide most of the specific surface area. The zwitterionic surfactant HPSB can greatly reduce oil–water interfacial tension and alter rock wettability, thereby breaking the high capillary resistance of micropores. During imbibition, water invades macropores first, followed by mesopores and micropores, and the entire process exhibits remarkable nonlinear dynamics controlled by multiscale pores. The 0.15% HPSB solution shows the best effect on activating micropores. This study innovatively quantifies the influence of surfactant concentration on fluid migration across different pore scales and reveals the internal mechanism of staged imbibition and micropore lag activation in terrestrial shale. It not only complements the global research system of shale imbibition theory but also offers practical guidance for the optimization of fracturing fluid systems in mesopore-dominated shale oil reservoirs. Full article

Reservoir effectiveness in marine shales is controlled not only by pore volume but also by pore-fluid occurrence, pore–throat connectivity, and mineral–organic matter coupling. In this study, the Permian Gufeng Formation shales from the Enshi area, western Hubei, South China, were investigated through an integrated analysis of total organic carbon (TOC), X-ray diffraction (XRD)-based mineral composition and lithofacies, low-field nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), micro-computed tomography (Micro-CT), and entropy-weighted technique for order preference by similarity to an ideal solution (TOPSIS) evaluation. The TOC content ranges from 1.60% to 21.38% and shows clear vertical differentiation, with moderate but variable enrichment in the lower interval, reduced organic matter abundance in the middle interval, and pronounced organic enrichment in the upper interval. Mineral compositions demonstrate an upward transition from a mixed siliceous–carbonate system to a dominantly siliceous shale system. NMR results reveal strong heterogeneity in porosity, NMR-derived permeability, T2cutoff, bound-fluid saturation, and free-fluid saturation. Based on saturated and centrifuged T2 spectra, four descriptive reservoir response types were identified: short-T2-dominated micropore-bound response, intermediate-T2-dominated movable-fluid response, long-T2-enriched but low-efficiency response, and NMR-inferred enhanced mobility composite response. SEM observations show diverse pore types, including organic-matter-related pores, dissolution pores, interparticle pores, mineral-edge pores, pyrite intercrystalline pores, and local microfracture-like pores. Micro-CT results indicate that micrometer-scale pore bodies are commonly isolated, demonstrating that pore abundance or pore size alone cannot determine reservoir effectiveness. TOC mainly controls pore generation potential, whereas siliceous minerals, pore–throat connectivity, movable fluid proportion, and local fractures exert stronger controls on effective reservoir development. The most favorable reservoir responses are concentrated in the upper high-organic siliceous shale interval from A33 to A42, with local enhanced responses in A16 and A21. These results provide an integrated framework for evaluating reservoir heterogeneity and favorable intervals in complex marine shale systems. Full article

Transitional marine–continental shale reservoirs are typified by intricate pore architectures and pronounced heterogeneity; accurate characterization of their pore network and fluid mobility underpins reservoir appraisal and sweet-spot forecasting. Focusing on the Longtan Formation transitional shales in the Sichuan Basin, this study integrates NMR T₂ spectrometry, geochemical–mineralogical assays and multifractal analysis to elucidate multi-scale heterogeneity of the pore framework and its governing mechanisms. Results reveal that the investigated shales are characterized by low porosity (0.46–7.43%) and high bound fluid saturation (66.77–97.28%). Multifractal spectral width (Δα) and degree of multifractality (ΔD) serve as robust metrics of pore heterogeneity, correlating closely with rock composition (e.g., TOC and clay content). By combining multifractal indices, mineralogical assemblage and fluid movability, the samples are classified into three reservoir archetypes, with Type I (weakly heterogeneous—high quality) identified as the prospective developmental sweet spot. This work provides a theoretical and methodological backbone for quality assessment and play-ranking of transitional marine–continental shale reservoirs. Full article

Background/Objectives: Ketogenic diets induce profound metabolic reprogramming; however, their impact on systemic metabolism in patients with hepatic fibrosis remains insufficiently characterized. This study aimed to investigate serum metabolic changes induced by Very Low Energy Ketogenic Therapy (VLEKT) and to assess the influence of hepatic fibrosis development on these metabolic adaptations. Methods: Fifty serum samples from 25 obese patients were analyzed using 1D 1H CPMG NMR spectroscopy at baseline (T0) and after 8 weeks of VLEKT (T1). Patients were stratified according to the FIB-E fibrosis index into a low-risk group (LR; FIB-E < 8) and an intermediate-high-risk group (IHR; FIB-E ≥ 8) for hepatic fibrosis onset. Results: An integrated approach combining NMR-based metabolomics and pathway enrichment analysis revealed a marked metabolic shift following VLEKT, characterized by increased ketone bodies (including β-hydroxybutyric acid and acetone), together with changes in amino acids and lipid-related signals. Among these, acetone provided a robust and quantifiable NMR signal, consistent with enhanced ketogenesis. Stratified analysis indicated differential metabolic flexibility: LR patients exhibited enhanced modulation of tricarboxylic acid (TCA) cycle-related metabolites, whereas IHR patients showed persistent alterations in aromatic amino acids and lipid signals. Significant correlations between tyrosine and β-alanine with clinical biochemical markers further supported the presence of a fibrosis-dependent metabolic signature. Conclusions: These findings highlight the potential of circulating metabolites as sensitive and non-invasive indicators of hepatic vulnerability and determinants of metabolic adaptability to VLEKT. Moreover, the study underscores the value of NMR-based metabolomics as an innovative tool for improving the non-invasive assessment of metabolic and hepatic health. Full article

This article describes the development of a compact and affordable variable-temperature NMR instrument designed primarily to measure dynamic molecular motion in solids and liquids. The instrument consists of Lab-Tools’ Mk4 palm-top time-domain NMR spectrometer fitted with a Peltier-cooled variable-temperature probe inside a shimmed Halbach magnet. Measurement of NMR relaxation times T₁, T₂, and ${\mathrm{T}}_1\rho$ is possible over the temperature range −20 °C to 70 °C with cooling and heating rates, and data acquisition is controlled from an integrated mini-PC. The overall footprint of the instrument is roughly that of a shoe box, making both in-the-field and bench-top measurements possible. Applications of this instrument include measuring pore-size distribution in porous rocks, the viscosity of oils and tars trapped in porous rock, the properties of polymers, and the viscosity of the liquid components of foods (e.g. fruits, vegetables and seeds). Results of test measurements for calibrated oils and olive oil are presented together with measurements of molecular mobility in a solid polymer. Full article

Understanding the proton relaxation mechanism of hydrogen gas in porous media is critical for underground hydrogen storage. This study investigates the proton relaxation mechanisms of hydrogen gas using variable-pressure NMR experiments on idealized glass bead pack models (6.8–65.9 μm). Results indicate: (1) The proton spin–spin relaxation time (T₂) of bulk H₂ gas is linearly proportional to pressure, confirming the dominance of the spin–rotation (SR) interaction. (2) In pores larger than 16.4 μm, bulk relaxation prevails, rendering the T₂ distribution single-peaked and pore-size independent. (3) Conversely, in 6.8 μm pores, a distinct bimodal T₂ distribution emerges, separating free-gas and surface-dominated components. A theoretical critical pore size (≈11.5 μm) was estimated based on a two-phase exchange model. This work elucidates the fundamental regime transition from bulk- to surface-dominated proton relaxation in micron-scale pores. Full article

An efficient catalyst for the reaction of ethanol–acetaldehyde into 1,3-butadiene (EATB) is prepared through the grafting of zirconia into a zeolite Beta lattice. The grafting is achieved through the dealumination of a zeolite framework by acid treatment followed by zirconia impregnation, leading to the substitution of aluminum in the zeolite framework by zirconia. The catalyst with zirconia grafted into the zeolite framework promotes desirable catalyst properties like high zirconium dispersion, stability, and the close proximity of Lewis acid, Bronsted acid, and medium basic sites. The phase, the coordination of zirconia, the location of the active center and the cooperative synergism were elucidated through various characterization techniques, including X-ray diffraction, Raman spectroscopy, N₂ adsorption, UV–vis spectroscopy, XPS, ²⁹Si MAS NMR, NH₃-TPD, Py-IR, CO-IR and CO₂-TPD. The catalytic results show that a suitable phase and content of zirconia were needed to improve the ethanol–acetaldehyde conversion, butadiene selectivity and catalyst stability. Among the catalysts, m+t-ZrO_x-Beta-H₂O-9020 (m = monoclinic, t = tetragonal ZrO₂ phase) achieved the best butadiene selectivity of 82–73% at the conversion of 100–66%, run over 200 h. The results allow us to propose a Lewis acid–medium basic pairing for the Si–O–Zr–O–Si group, where the adjacent Si-OH is the active center for reactions. Full article

We report a compact benchtop solid-state NMR platform that achieves 50 kHz magic-angle spinning (MAS) in a 1.4 T permanent magnet with an 18 mm bore, enabling high-speed MAS under extremely space-constrained conditions. The probe architecture leverages field–bore orthogonality for convenient magic-angle alignment and is demonstrated with miniaturized 1.8 mm rotors (≈5 mm length) at stable high-speed operation. As a demanding test case, we measure ⁷Li MAS NMR of the paramagnetic layered cathode oxide LiNi_0.5Mn_0.5O₂, where hyperfine interactions produce very large paramagnetic shifts spanning the several-thousand-ppm regime. Overall, the results establish a path toward portable, cost-effective high-MAS NMR in compact permanent-magnet geometries. Full article

Understanding the spatiotemporal variability of nanoplastics (NPs) in porous media is vital for environmental risk assessment, yet quantitative in-media analysis of NP distributions during transport remains limited. To address this, we innovatively applied low-field nuclear magnetic resonance (LF-NMR) as a non-invasive approach to dynamically monitor magnetic polystyrene nanoplastic (MPSNP) transport in saturated quartz sand. By establishing the relationship between LF-NMR transverse relaxation rate [1/T_2,I − 1/T_2,0] and MPSNP concentrations, we reconstructed spatiotemporal concentration profiles via T₂ inversion. This methodology enabled systematic evaluation of the effects of ionic strength (IS), flow velocity, initial concentration, and flow direction. Three mathematical models were further applied to analyze MPSNP transport behavior. Results revealed IS as the dominant factor; increasing IS (0.001 to 1 mM) dropped mass recovery from 85.7% to 0%, the migration front no longer advanced at IS > 5 mM. Lower flow rates, higher initial concentrations, and horizontal flow also enhanced retention. The two types of two-site kinetic models provide a better fit for the features of the breakthrough curves. This novel use of LF-NMR demonstrates its robust capability to resolve spatial transport heterogeneity, underscoring that flow velocity, flow direction, and ionic strength are critical regulatory parameters that should be carefully accounted for when evaluating nanoplastic transport in porous media. Full article

Six novel pyrazole-based carbohydrazone derivatives (3a–3f) bearing structurally diverse heteroaromatic substituents were synthesized and characterized by ATR-FTIR, ¹H NMR, APT-¹³C NMR, and HRMS analyses. Their multifunctional bioactivity was evaluated using antioxidant, photoprotective, CT-DNA-associated spectroscopic response, cytotoxicity, and scratch wound closure assays. Antioxidant activity was assessed by DPPH radical scavenging, Fe²⁺ chelation, and ferric thiocyanate (FTC) assays against appropriate reference standards, while photoprotective potential was determined by spectrophotometric SPF analysis using carrot seed oil as a reference. The benzothiazole-containing derivative (3f) showed the strongest DPPH scavenging activity, FTC antioxidant capacity, and photoprotective activity, while also producing one of the most pronounced CT-DNA-associated spectroscopic responses under the experimental conditions employed. In contrast, the benzimidazole derivative (3e) displayed the highest Fe²⁺ chelating activity among the synthesized compounds. In cell-based assays, the imidazole- and thiazole-containing derivatives (3b and 3c) showed the most favorable balance between growth-inhibitory potency and selectivity toward A431 epidermoid carcinoma cells relative to HaCaT keratinocytes. Scratch assay results did not support direct anti-migratory activity under the tested conditions but indicated compound-dependent modulation of wound-closure-associated cellular responses. Overall, these findings demonstrate that heteroaromatic substitution strongly modulates redox behavior, CT-DNA-associated spectroscopic behavior, photophysical properties, and cytotoxic selectivity in pyrazole-based carbohydrazones, identifying this scaffold as a structurally tunable platform for further bioactivity optimization. Full article

The glycosidic composition of Psolus phantapus was studied for the first time. Two new glycosides, phantapusosides A (1) and B (2), and the known psolusoside P (3) were isolated and their structures were established by analysis of ¹H, ¹³C NMR, 1D TOCSY, and 2D NMR (¹H,¹H COSY, HMBC, HSQC, ROESY), and HR-ESI mass spectra. These compounds are structurally close to those isolated from other representatives of the genus Psolus: P. fabricii, P. peronii and P. chitonoides. These data confirm the chemotaxonomic significance of triterpene glycosides of sea cucumbers, demonstrating that closely related species biosynthesize structurally similar metabolites. The cytotoxic activity of compounds 1 and 2 was studied against four human breast cancer cell lines (MCF-7, T-47D, MDA-MB-231, MDA-MB-468), as well as the non-tumorigenic mammary epithelial cell line MCF-10A and the pancreatic epithelioid carcinoma cell line PANC-1. The glycosides were selectively active against the TNBC cell lines MDA-MB-231 and MDA-MB-468. Notably, both glycosides inhibited the clonogenic potential of TNBC cell lines more significantly than their metabolic activity (MTT assay) and demonstrated a more pronounced colony-inhibiting effect toward the basal-like cell line MDA-MB-468, making this cell line a promising model for future investigation of the antitumor effects of glycosides. Full article