Search Results (125)

Diopside–hedenbergite solid solution is the most common clinopyroxene end-member combination in mafic and ultramafic igneous rocks. The crystal structure variety caused by Mg-Fe isomorphous substitution can indicate geological processes such as Mg-Fe isotope fractionation. To explore the effect of Hubbard U correction and Fe content on iron-bearing clinopyroxene structures, we employed GGA and GGA + U to study the lattice constants, unit-cell volume, and average Fe-O bond length of the diopside–hedenbergite solid solution series. On the whole, the results by GGA + U are the increase in lattice constant a (from 9.910 Å to 10.030 Å) and volume (from 456.656 ų to 464.640 ų), the decrease in β angle (from 106.121°to 105.320°), and a slight variation in the lattice constant b (from 9.007 Å to 9.010 Å) with increasing Fe content, which is a better match with the experiment than those by GGA. The average Fe-O bond lengths and polyhedral volumes calculated by GGA and GGA + U both increase with increasing Fe content. The Hubbard U correction significantly affects the lattice constants and unite-cell volume at medium-high Fe content (Fe/(Ca+ Mg + Fe) > 2/8), the Fe-O bond at low Fe content (Fe/(Ca+ Mg + Fe) < 1/8), the bond angle variance, distortion index and quadratic elongation at relatively medium Fe content (1/8 ≤ Fe/(Ca+ Mg + Fe) ≤ 5/16). This study verifies the effectiveness of U-value correction on iron-bearing clinopyroxene and provides a theoretical basis for understanding its structural evolution. Full article

This study explores the hydrochemical and thermal characteristics of a fault-controlled geothermal field within the Northern Qinghai Lake Coalfield Area on the northeastern Qinghai–Tibetan Plateau (QTP). This research integrates hydrochemical analyses, isotopic tracers, and the regional geological framework to define hydrochemical signatures, identify recharge sources and flow paths, assess cold–hot water mixing, estimate reservoir temperatures, determine circulation depths and residence times, and explain the geothermal system’s formation. Systematic sampling included geothermal waters, cold springs, and surface waters, followed by laboratory analysis of major ions, stable isotopes (δ²H, δ¹⁸O), radiocarbon (¹⁴C), and tritium (³H). The geothermal water is categorized as a low-temperature, weakly acidic to near-neutral HCO₃-Ca•Mg type, exhibiting temperatures from 35.6 to 46.2 °C. Isotopic analyses indicate that cold spring and river waters align with the local meteoric water line, while geothermal waters display distinct isotopic signatures, suggesting deeper circulation. A silica–enthalpy mixing model reveals substantial cold-water mixing during upwelling, with mixing ratios between 74.5% and 85.6%. The corrected recharge elevation is estimated to be 4378–4456 amsl, implying a primary recharge zone in the branch of the Qilian mountains—the middle section of Datong Mountain to the northeast. Geothermometry, employing quartz and chalcedony temperature scales and accounting for mixing, estimates reservoir temperatures of 150–202 °C. The calculated circulation depth spans 3211–4291 amsl. Low tritium levels and carbon dating suggest a deep-cycling system predating 1952, characterized by deeply circulating “ancient water”. The geothermal system’s development is associated with regional tectonics, fault systems, and the Kesuer Formation (J_xk) acting as the reservoir. This study provides a scientific foundation for the development and sustainable use of geothermal resources in the northern Qinghai Lake region and offers insights applicable to comparable fault-controlled geothermal systems across the QTP. Full article

Sustainable soil–water management under climate and socio-economic pressures requires predictive capability that is both mechanistic and continuously corrected by observations. Data assimilation (DA) provides the formal machinery to merge models with heterogeneous measurements—from satellite evapotranspiration and soil moisture to cosmic-ray neutron sensing, proximal geophysics, lysimeters, and groundwater hydrographs—while propagating uncertainty. This review (based on 90 references) synthesizes frontiers in DA and modeling for soil–water systems across scales, emphasizing (i) multi-source observation operators and scaling; (ii) coupled crop–vadose–groundwater modeling frameworks and their structural hypotheses; (iii) modern DA methods (ensemble, variational, particle-based, and hybrid physics–ML) for joint estimation of states, parameters, and biases; and (iv) emerging digital twins that enable predict-then-verify management loops for irrigation, recharge enhancement, and drought risk reduction. We highlight how tracer-aided and isotope-informed components can improve evapotranspiration partitioning and recharge threshold detection, and how agent-based or socio-hydrological coupling can represent human decision feedback. Finally, we outline research gaps in uncertainty quantification, benchmarking, reproducibility, and governance needed to operationalize trustworthy soil–water digital twins for resilient food and water systems. Full article

Background/Objectives: Therapeutic drug monitoring (TDM) of β-lactams (BL), BL/β-lactamase inhibitor (BLI) combinations (BL/BLIc), and of fosfomycin may play a key role in optimizing antimicrobial therapy and in preventing resistance development, especially when used by continuous infusion in critically ill or immunocompromised patients. Unfortunately, analytical methods for simultaneously quantifying multiple BL/BLIc in plasma are still lacking. Methods: The aim of this study was to develop and validate two rapid, sensitive, and accurate UPLC–qTOF–MS/MS methods for the simultaneous quantification of five novel β-lactam or β-lactam/β-lactamase inhibitor combinations (ceftolozane/tazobactam, ceftazidime/avibactam, meropenem/vaborbactam, cefiderocol, and ceftobiprole) along with fosfomycin. Methods: Human plasma samples were prepared by protein precipitation using methanol containing isotopically labeled internal standards. Chromatographic separation was achieved within 10–12 min using two Agilent Poroshell columns (EC-C18 and PFP) under positive and negative electrospray ionization modes. The method was validated according to the EMA guidelines by assessing selectivity, linearity, precision, accuracy, matrix effects, extraction recovery, and stability. Results: The methods exhibited excellent linearity (R² ≥ 0.998) across the calibration ranges for all of the analytes (1.56–500 µg/mL), with limits of quantification ranging from 1.56 to 15.62 µg/mL. Intra- and inter-day precision and accuracy were always within ±15%. Extraction recovery always exceeded 92%, and the matrix effects were effectively corrected through isotopic internal standards. No carry-over or isobaric interferences were observed. All the analytes were stable for up to five days at 4 °C, but the BL and BL/BLIc stability was affected by multiple freeze–thaw cycles. Conclusions: These UPLC-qTOF-MS/MS multi-analyte methods enabled a simultaneous, reliable quantification in plasma of five novel beta-lactams and of fosfomycin. Robustness, high throughput, and sensitivity make these multi-methods feasible for real-time TDM, supporting personalized antimicrobial dosing and improved therapeutic outcomes in patients with severe or multidrug-resistant infections. Full article

Ochratoxins (OTs) pose a major food safety threat, yet analytical methodologies and regulations focus almost exclusively on ochratoxin A (OTA), overlooking the toxic analogues OTB and OTC, especially in complex coffee and spice matrices. The present study addressed this gap by first systematically confirming the high cross-reactivity (>85%) of commercial OTA immunoaffinity columns (IACs) toward OTB and OTC. It was identified that conventional alkaline methanol extraction caused OTC degradation, and subsequently a stable and unified acetonitrile-water (8/2, v/v) extraction protocol was developed. To overcome severe matrix interference endemic to these foods, a novel 0.5% Tween-20-PBS IAC load and wash procedure was optimized. The resulting method was fully validated in representative roasted coffee and pepper matrices on both HPLC-FLD and UHPLC-MS/MS platforms, demonstrating excellent linearity (r > 0.999), accuracy (mean recovery 82.00–112.51%), and precision (RSD% ≤ 8.81%) across three spiked levels (0.3, 5, 10 µg/kg). While UHPLC-MS/MS achieved higher sensitivity (LOQs 0.1 µg/kg) than that of HPLC-FLD (LOQs 0.3 µg/kg), with isotope internal standards essential for correcting significant matrix effects. Application to forty commercial coffee and spice samples (19 coffee, 21 spice) revealed OTA contamination in 47.5% of products (up to 3.46 µg/kg) and co-occurrence of OTA/OTB in 3 of 8 cumin samples. This work establishes the first comprehensively validated IAC-based method for multi-OTs in complex foods, facilitating an urgently needed, robust tool for comprehensive risk assessment. Full article

Understanding the feeding mechanisms and interspecific coexistence of sharks is crucial for effective conservation. This study conducted stable isotope analysis on muscle and liver samples from 449 individuals of eight common bycatch shark species collected via bottom trawling in the northern South China Sea (NSCS). Results revealed significant differences in δ¹³C and δ¹⁵N values among species and tissue types. Scoliodon laticaudus exhibited the highest trophic position (TP_muscle = 4.60 ± 0.33; TP_liver = 4.53 ± 0.29), while Apristurus platyrhynchus had the lowest (TP_muscle = 2.97 ± 0.44; TP_liver = 2.75 ± 0.53). Muscle and liver isotopic signals were consistent, but δ¹³C differences indicated distinct carbon sources, with Carcharhinus sorrah linked to deep-sea organic matter and S. laticaudus to coastal inputs. Significant correlations between δ¹³C/δ¹⁵N and body length in A. platyrhynchus and Cephaloscyllium fasciatum suggest ontogenetic shifts in diet and habitat toward deeper waters. Trophic niche analysis using corrected standard ellipse area (SEAc) showed Halaelurus burgeri with the widest trophic niche (SEAc > 1.7‰²), reflecting a broad diet, while C. fasciatum had the narrowest (SEAc < 0.3‰²), indicating specialized feeding. Additionally, H. burgeri and C. sarawakensis exhibited significant niche differentiation, reducing interspecific competition, whereas C. fasciatum and Squalus megalops showed high niche overlap, suggesting intense resource competition. The narrower liver niche of C. sarawakensis may reflect recent habitat constriction due to bottom trawling. This study elucidates the feeding ecology and habitat resource utilization of NSCS sharks, providing a scientific basis for effective conservation strategies for shark populations in the region. Full article

The maternal circulating proteome reflects critical physiological adaptations during pregnancy, yet standardized reference profiles for early gestation are lacking. In this prospective study, we employed targeted liquid chromatography–multiple reaction monitoring–mass spectrometry (LC-MRM-MS) with stable isotope-labeled (SIS) standards to characterize the serum proteome of 83 women with uncomplicated singleton pregnancies between 11⁺² and 13⁺⁶ weeks’ gestation. Robust analysis quantified 115 proteins (83% of targets), with 101 meeting ICH M10 standards. These included 38 FDA-approved, 19 CVD-related, and 25 CLIA-approved biomarkers. We identified 43 proteins significantly associated (p < 0.05) with gestational age, maternal factors (BMI, age, parity, and myomas), and fetal sex. Key findings included identification of 12 proteins significantly associated with trisomy risk (|R| = 0.21–0.45, p < 0.05) and extreme physiological variability in pregnancy zone protein (PZP, 123.9-fold), followed by apolipoprotein (a) (LPA; 9.9-fold) and pregnancy-associated plasma protein A (PAPP-A, 9.3-fold). In contrast, hemopexin (HPX) demonstrated remarkable stability (CV = 8.5%), suggesting its utility as a reference marker. The study successfully implemented multiples of the median (MoM) transformation for clinical standardization of protein profiles, with RobNorm proving particularly effective for batch-effect correction in our dataset. These methodological advances, combined with the establishment of comprehensive pregnancy-specific reference ranges, provide a valuable foundation for future research. The optimized analytical framework and protein signatures identified in this work not only enable the development of next-generation screening approaches but also offer new insights into the molecular adaptations occurring during early pregnancy. Full article

The widespread environmental dissemination of imidazole compounds necessitates robust analytical monitoring tools. This study developed a novel isotope-labeled surrogate-based high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) method for the simultaneous determination of 21 imidazoles in water, sediment, and soil. The optimized SPE protocol using Oasis HLB cartridges achieved high recoveries, with chromatographic separation completed in 25 min. Six isotope-labeled standards effectively corrected matrix effects (−57% to 8%), yielding MQLs < 1.0 ng·L⁻¹ (water) and <1.0 μg·kg⁻¹ (sediment/soil). Validation confirmed linearity (R² > 0.995), accuracy (60–120% recovery for 20/21 analytes), and precision (relative standard deviation, RSD < 15%). Its application in Jiulong River revealed significant contamination, detecting eight imidazoles in both water (up to 49.29 ng·L⁻¹) and sediment (up to 24.01 μg·kg⁻¹). This standardized tool enables routine monitoring of pharmaceutical residues across environmental compartments, supporting regulatory frameworks. Full article

Background: Correct assessment of resting metabolic rate (RMR) is fundamental for estimating total energy expenditure in both clinical nutrition and sports sciences research. Various methods have been proposed for RMR determination, including predictive equations, isotopic dilution techniques, and indirect calorimetry. Over the past two decades, portable gas analyzers have emerged as promising alternatives, offering more accessible and cost-effective solutions for metabolic assessment. However, evidence regarding their validity remains inconsistent, particularly across diverse populations and varying metabolic assessment protocols. Methods: This systematic review was conducted in May 2025 using the PubMed, Web of Science, and EBSCO databases, following the PRISMA-DTA guidelines, and included observational studies with the objective of examining the available evidence regarding the validity of portable gas analyzers to determine RMR in humans. The methodological quality of each study was assessed using the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Results: From an initial pool of 230 studies, 16 met the eligibility criteria. The findings revealed notable variability in measurement validity among devices, mainly influenced by device model, population characteristics, and methodological factors. While portable analyzers such as FitMate and Q-NRG exhibited high validity, MedGem exhibited systematic biases, particularly in individuals with higher adiposity, leading to RMR overestimations. Conclusions: The main results demonstrated the critical need for rigorous validation of portable gas analyzers before their implementation in clinical and research settings to ensure their applicability across diverse populations and metabolic assessments. Full article

The isotopic shift of the bound-electron g factor in highly charged ions (HCI) provides a sensitive probe for testing physics beyond the Standard Model, particularly through interactions mediated by a hypothetical scalar boson. In this study, we analyze the sensitivity of this method within the Higgs portal framework, focusing on the uncertainties introduced by quantum electrodynamics corrections, including finite nuclear size, nuclear recoil, and nuclear polarization effects. All calculations are performed for the ground-state $1s$ configuration of hydrogen-like HCI, where theoretical predictions are most accurate. Using selected isotope pairs (e.g., ${\mathrm{He}}^{4/6}$, ${\mathrm{Ne}}^{20/22}$, ${\mathrm{Ca}}^{40/48}$, ${\mathrm{Sn}}^{120/132}$, ${\mathrm{Th}}^{230/232}$), we demonstrate that the dominant source of uncertainty arises from finite nuclear size corrections, which currently limit the precision of new physics searches. Our results indicate that the sensitivity of this method decreases with increasing atomic number. These findings highlight the necessity of improved nuclear radius measurements and the development of alternative approaches, such as the special differences method, to enable virtually the detection of fifth-force interactions. Full article

Carbon isotopes, particularly ¹³C, are critical for applications in food authentication, biomedical diagnostics, and metabolic research; however, their efficient separation remains challenging due to their low natural abundance. This study investigates the adsorption behavior of ¹²CO and ¹³CO on various low-index $\mathsf{\alpha }$-Al₂O₃ surfaces as a strategy for isotope separation. Density functional theory (DFT) calculations with D3 (BJ) dispersion corrections were employed to optimize surface models for five representative $\mathsf{\alpha }$-Al₂O₃ facets. Nine adsorption configurations were systematically evaluated by optimizing geometric structures, computing adsorption enthalpies with zero-point energy corrections, and performing Bader charge and charge density difference analyses to elucidate interfacial interactions. The results reveal that CO preferentially adsorbs in a vertical configuration via its carbon end at Al sites, with the (0001) surface exhibiting the lowest surface energy and most favorable adsorption characteristics. Furthermore, we found that facets with lower surface energy not only facilitate stronger CO adsorption but also demonstrate pronounced adsorption enthalpy differences between ¹²CO and ¹³CO, driven by vibrational zero-point energy disparities. These findings highlight the potential of low adsorption enthalpy surfaces, particularly (0001), ($01\overline{1}2$), and ($11\overline{2}0$), for enhancing isotope separation efficiency, providing valuable insights for the design of advanced separation materials. Full article

This study investigates the potential of strontium isotopes as a geographical tracer for Vignola cherries. Despite several studies having employed this indicator to trace the origin of food products, the mechanisms underlying the fractionation and translocation of strontium from soil to edible parts remain poorly understood. In this study, the ⁹¹Zr/⁹⁰Zr ratio was used as a normalization pair to correct measurements of ⁸⁷Sr/⁸⁶Sr and ⁸⁸Sr/⁸⁶Sr (δ⁸⁸Sr). Soil, cherry branches, and fruit samples were collected from various producers and locations. Isotopic analyses were carried out using a double-focusing multi-collector–inductively coupled plasma/mass spectrometer (MC-ICP/MS). External correction was applied using the ⁹¹Zr/⁹⁰Zr ratio, assuming both equal and different fractionation factors for Sr and Zr isotopes. Results from both correction models showed improved accuracy by accounting for fluctuations in instrumental mass bias. Regarding the translocation of strontium, the data indicate an increase in ⁸⁸Sr of approximately 0.2‰ from soil to plant tissue. This trend was consistent across all sampled locations. Full article

Food fraud is a matter of great interest, particularly when organic productions are involved. Therefore, policymakers and institutions are asked to introduce new effective official control methods, not only based on documentary compliance to EU regulations. Lately, an integrated approach based on the use of isotopic, chemical and biological data treated by chemometrics has been suggested to authenticate organic products. The present research aims to validate the beforementioned integrated approach for the reliable classification of organically and conventionally grown fennel productions obtained by applying different treatments at diverse percentages of mineral fertilizers. Moreover, to the best of our knowledge, for the first time, an N-fixing plant (alfalfa), as an agroecological service crop in intercropping fennel, was introduced. Physicochemical parameters (fresh weight, total soluble solids, total acidity, consistency, Commission Internationale de l’Eclairage (CIE) lightness (L*), green-red (a*), blue-yellow (b*) color components), total phenolic content, in vitro antioxidant activity, total and inorganic N, and stable isotope ratios (¹⁵N/¹⁴N, ¹³C/¹²C, and ³⁴S/³²S) analyses were performed over a two-year field trial and further multivariate discriminant analysis was performed. The physicochemical parameters were not affected by the differential growing practice while antioxidant activity showed higher values in the organic treatments. The conventional treatments increased the NO₃⁻ values over 440% compared to the organic ones and the lowest values were found when alfalfa was used for intercropping. δ(¹⁵N) of fennel, δ(³⁴S) of fennel and δ(¹⁵N) of leaves showed great discriminatory potential, with respect to the applied agronomic practice. However, these parameters alone were not sufficient as biomarkers for differentiating cultivation methods. Instead, the proposed innovative tool demonstrated that only a comprehensive multivariate approach was able to achieve a correct classification of grouped cases. Furthermore, the discrimination between organic and conventional horticultural products showed feasible results, even when N-fixing plants were incorporated in organic practice, thus avoiding misinterpretations solely based on the isotopic N fingerprint. These promising findings highlight the potential of this method and suggest that further research should extend its application to other horticultural crops to confirm and expand upon the current results. Full article