Search Results (299)

Deuteration provides a controlled perturbation for probing isotope and symmetry effects in organometallic vibrational spectra. Here, density functional theory (DFT) is used to systematically examine the evolution of far-infrared (400–600 cm⁻¹) Fe–Cp vibrational modes in fully protonated, partially deuterated, and fully deuterated ferrocene. All three characteristic modes—the a₂″ torsional mode and the two e₁′ bending modes—exhibit monotonic red-shifts with increasing deuteration. The a₂″ mode shows the largest isotope sensitivity, shifting by ~28 cm⁻¹ across the DFT series, whereas the e₁′ modes shift by ~11–12 cm⁻¹ and undergo symmetry-dependent splitting of up to ~2 cm⁻¹ under partial deuteration. These results establish the a₂″ band as a sensitive probe of the degree of deuteration and the e₁′ splitting as a diagnostic of symmetry reduction. A physics-based AI surrogate model reproduces the overall red-shift trends but deviates at high deuteration, with maximum errors of ~16.6 cm⁻¹, highlighting the limits of reduced-mass scaling. Full article

The Chutuan and Jiashan fluorite deposits are situated in the Donghai–Linshu area within the southwestern segment of the Sulu ultrahigh–pressure metamorphic belt. Both deposits share similar mineralization characteristics, with fluorite veins strictly controlled by fault structures and associated with mineral assemblages comprising fluorite, barite, quartz, and calcite. Two mineralization stages have been identified in both deposits: Stage I (quartz–fluorite–barite stage), representing the main ore–forming event, and Stage II (quartz–barite–calcite stage). This study focuses on integrated geochemical and geochronological analyses of fluorite from Stage I, providing new constraints on the genesis and metallogenic processes of these deposits. Direct Sm–Nd isotopic dating of fluorite yields an isochron age of 104 ± 16 Ma, indicating that mineralization occurred during the late Early Cretaceous. Fluid inclusion and stable isotope studies reveal that the ore–forming fluids constitute a complex hydrothermal system characterized by a wide temperature range (112–324 °C) and variable salinities (0.18–21.87 wt% NaCl eq.). The H–O isotopic compositions exhibit a distinct latitudinal trend, supporting a dominant meteoric water component. However, the presence of high–temperature, high–salinity fluid inclusions, along with a shift in some δD values towards the magmatic water field, suggests episodic mixing between meteoric water and deep–seated magmatic–hydrothermal fluids. Sr–Nd isotopic data (⁸⁷Sr/⁸⁶Sr = 0.711785–0.713424; εNd(t)= −27.7 to −27.5) potentially demonstrate that the ore–forming materials (Ca and REEs) were not derived from coeval magmatic rocks. Instead, they were primarily leached from the Precambrian Donghai Group metamorphic complex through extensive water–rock interaction. Based on these findings, the Chutuan and Jiashan deposits are classified as hydrothermal vein–type systems. Fluorite precipitation was governed by a combination of fluid cooling, water–rock interaction, and fluid mixing. Finally, a metallogenic model is established, offering important insights into the genesis of fluorite mineralization in the Sulu Orogenic Belt and analogous geological settings in eastern China. Full article

The Sichuan–Yunnan–Guizhou (SYG) metallogenic belt hosts numerous carbonate-hosted Pb-Zn deposits, yet the genesis of lead-dominated deposits remains poorly understood. This study investigates the Wuyi Pb deposit, a representative lead-dominated deposit in the SYG belt, through an integrated approach including field geology, fluid inclusion microthermometry, and C-H-O-S-Pb isotope geochemistry. The ore bodies occur as stratoid and lenticular lenses within the dolomitic limestone of the Ordovician Dajing Formation, controlled by both lithology and the Wuyi composite fold structure. Mineralization is divided into two stages: (I) pyrite–sphalerite–dolomite–calcite, and (II) galena–calcite–quartz–anhydrite. Fluid inclusion studies reveal that the ore-forming fluids are of the NaCl-H₂O system, characterized by moderate-low temperatures (Stage II, average 201 °C) and moderate-low salinities (Stage II, average 5.35 wt% NaCl eq.). Hydrogen and oxygen isotopes (δD = −100.97 to −76.33‰; δ¹⁸O_fluid = 7.09 to 12.10‰) indicate that the ore-forming fluids were predominantly meteoric in origin. Carbon isotopes (δ¹³C = −4.45 to 0.75‰) suggest that carbon was derived mainly from dissolution of the host carbonate rocks. Sulfur isotopes show a significant shift from Stage I (δ³⁴S = −12.40 to −3.00‰) to Stage II (δ³⁴S = −8.20 to −0.10‰ for sulfides; 25.00–29.40‰ for sulfates), indicating a transition from bacterial sulfate reduction (BSR) to thermochemical sulfate reduction (TSR) as the dominant sulfur reduction mechanism, with sulfur derived from Ordovician seawater sulfate. Lead isotopes (²⁰⁶Pb/²⁰⁴Pb = 18.10–25.37, ²⁰⁷Pb/²⁰⁴Pb = 15.50–21.72, ²⁰⁸Pb/²⁰⁴Pb = 38.29–53.90; μ = 9.30–21.05) demonstrate that metals were sourced predominantly from the Proterozoic basement rocks (Kunyang and Huili groups). Integration of geological, geochemical, and isotopic evidence indicates that the Wuyi Pb deposit formed during the Indosinian post-collisional intracontinental orogeny (ca. 230–200 Ma), when topography-driven meteoric water circulation extracted metals from the Precambrian basement and sulfur from Ordovician strata. Metal precipitation under the reduced sulfur model is caused by decreases in temperature and pressure and the water–rock reaction. This study establishes the Wuyi deposit as an MVT Pb deposit and provides a genetic model for lead-dominated mineralization in the SYG belt. Full article

Newly constructed regulation reservoirs experience dramatic seasonal environmental shifts, yet the temporal dynamics of their aquatic food webs remain poorly understood. In this study, we investigated the seasonal variations in fish community structure and trophic niches in Xianlin Reservoir (Zhejiang, China) using catch surveys and stable isotope analysis (δ¹³C and δ¹⁵N). Our results revealed that the fish assemblage was persistently dominated by the non-native fish Lepomis macrochirus and the native Xenocypris argentea. Community-wide isotopic metrics, calculated via SIBER, demonstrated pronounced seasonal plasticity in the trophic architecture. During winter, driven by limited basal resources, the community exhibited a “dietary expansion” strategy, resulting in the longest vertical food chain, the broadest core isotopic niche area (SEAc = 16.33), and the lowest trophic redundancy (indicated by the highest mean nearest neighbor distance). Conversely, the spring community displayed a highly compressed trophic structure characterized by dense species packing and maximum redundancy. These findings highlight that the reservoir food web exhibits a reduced functional buffering capacity during winter due to weak functional substitutability among high-trophic-level species. Given the ongoing community assembly in this newly constructed reservoir, the system is potentially more susceptible to seasonal environmental perturbations. Full article

Despite a plethora of studies in recent years focusing on the impact of nitrogen source addition on plant responses, there remains a lack of clarity regarding the differential utilization and distribution patterns of various nitrogen sources by Larix olgensis A. Henry seedlings. Specifically, the mechanisms by which ammonium nitrogen, nitrate nitrogen, and urea are differentially absorbed and distributed among different organs within the plant, as well as how these processes couple with rhizosphere soil microbial processes, still await elucidation. This study, conducted under field experimental conditions, employed a combination of ¹⁵N isotopic tracing, soil physicochemical property measurements, enzyme activity analysis, and microbial community functional analysis to investigate the effects of three nitrogen sources (NH₄⁺, NO₃⁻, and urea) and their varying addition levels on nitrogen absorption and distribution in Larix olgensis A. Henry seedlings. The results indicate that nitrogen source type significantly influences the nitrogen absorption rate and internal distribution patterns of plants. Within 24 h, seedlings preferentially absorb ammonium nitrogen and retain a higher proportion of newly absorbed nitrogen in their roots. The high ammonium chloride (GN) treatment group exhibited the highest ¹⁵N abundance in the root region, suggesting rapid root assimilation and short-term underground retention. By 48 h, the ¹⁵N abundance and AT% values in most organs across different treatment groups were significantly higher than those at 24 h, facilitating the transport of nitrate nitrogen and urea to stems and leaves, indicating a gradual shift in nitrogen distribution towards the aboveground parts. Moderate nitrogen addition improved soil nutrient conditions, altered pH and conductivity, enhanced nitrogen transformation processes related to urease and nitrate reductase, and increased microbial diversity and metabolic functions related to carbon metabolism, nitrogen metabolism, and energy metabolism. Soil pH, total nitrogen (TN), ammonium nitrogen (NH₄⁺-N), and organic carbon (OC) are core environmental factors driving the differentiation of soil microbial community structure, with distinct specificity in the response of microbial groups across different taxonomic levels to soil physicochemical properties. Full article

Revitalisation of contaminated brownfield sites is essential for sustainable development, particularly near sensitive ecological areas like Natura 2000 sites. The lagoon in Slovenia’s Regional Park Šturmovci, an artificial wastewater convergence point created during hydroelectric construction, is a highly relevant example. This study integrates geochemical, mineralogical and isotopic analyses to identify sources and controlling mechanisms of contaminant distribution in lagoon sediments and assess their transfer to nearby agricultural soils during flooding events. Results indicate anaerobic conditions, with depth-related shifts in phosphorus, sulphur and redox-sensitive elements, such as rare earth elements (REE), arsenic (As), barium (Ba), cobalt (Co), chromium (Cr), lead (Pb) and vanadium (V), as well as fluctuations in pyrite-rich laminated layers, suggesting potential flood-driven remobilisation of trace elements. Lagoon sediments are highly contaminated with As (73 mg kg⁻¹), Ba (247 mg kg⁻¹), Pb (97 mg kg⁻¹) and Zn (1118 mg kg⁻¹), with elevated concentrations also observed in agricultural soil, all exceeding respective limit values of 20, 160, 85 and 200 mg kg⁻¹. Pollutant concentrations were highest near wastewater inflows and decreased with distance, with nitrogen isotopic patterns indicating partial nitrification and surface ammonium accumulation, reflecting intensive agricultural inputs in the area. High enrichment factor (EF > 20) and geoaccumulation index (I_geo > 3) values, in particular for As, Cd and Zn, indicated severe contamination and highlighted the urgent need for effective remediation strategies, including immobilisation using biochar or cement-based binders, as well as phytoremediation approaches. Full article

The Huoyanshan Cu-Zn volcanogenic massive sulfide (VMS) deposit, located in the North Qilian Orogenic Belt, China, is of significant economic importance. This study provides new constraints on the ore-forming processes through high-resolution in situ trace element and sulfur isotope analyses of pyrite and sphalerite using LA-(MC)-ICP-MS. Petrographic and geochemical investigations identified three distinct generations of pyrite (Py l to Py III). Early-stage Py I and Py II are characterized by high trace element contents (Au, As, Bi, Cu, Pb), elevated Co/Ni ratios (>1–10), and enriched δ³⁴S values (+4.98‰ to +7.47‰). These signatures indicate precipitation from high-temperature, reduced magmatic–hydrothermal fluids influenced by thermochemical sulfate reduction (TSR). Late-stage Py IIl exhibits markedly lower Co/Ni ratios (<0.1) and lighter δ³⁴S values (+3.72‰ to 3.89‰). This geochemical shift reflects a transition toward a cooler, more oxidized environment driven by the incursion and mixing of ambient seawater as the hydrothermal system waned. Trace element geochemistry of sphalerite reveals an average crystallization temperature of 265.8 °C (derived from the “GGIMFis” geothermometer), consistent with fluid inclusion data and representing a thermal “snapshot” of the waning hydrothermal stage. Systematic discriminant analysis using Ga/In, Ge/In, and Co-Ni-As systematics further confirms a strong magmatic–hydrothermal affiliation. Full article

Against the backdrop of global coral reef degradation, benthic resource structure is shifting from coral dominance to turf algae and detritus-dominated epilithic algal matrix (EAM). As a typical detritivorous reef fish, Ctenochaetus striatus (Quoy & Gaimard, 1825) plays an important ecological role in regulating the functioning of degraded coral reef ecosystems. Using stable isotope analysis (δ¹³C and δ¹⁵N), this study systematically compared the trophic niche characteristics of different size classes of C. striatus across four reef habitats in the Xisha Islands, South China Sea, representing a gradient of disturbance (Qilianyu Island > Lingyang Reef > North Reef > Langhua Reef), in order to elucidate habitat-specific ontogenetic shifts and their adaptive features. The results showed that C. striatus from Qilianyu Island and Lingyang Reef exhibited overall higher δ¹⁵N values, suggesting an overall pattern consistent with stronger nitrogen enrichment at the more disturbed reefs, whereas individuals from Langhua Reef had significantly lower δ¹³C values, indicating a stronger reliance on offshore-derived carbon pathways. Across size classes, the trophic niche area (SEAc) and intraspecific trophic heterogeneity, measured as mean nearest neighbor distance and standard deviation of nearest neighbor distance, of populations from Qilianyu Island, Lingyang Reef, and North Reef generally decreased with increasing body size, revealing a pattern of trophic convergence toward core resources. In contrast, the Langhua Reef population exhibited a distinct expansion–contraction pattern, suggesting flexible resource use across developmental stages under conditions of low human disturbance and high resource heterogeneity. Although smaller size classes generally showed high probabilities of niche overlap among reefs, overlap declined markedly in the largest size class, with most values falling below 50%, indicating that resource assimilation strategies increasingly reflected reef-specific resource backgrounds. These findings demonstrate that ontogenetic trophic niche shifts in C. striatus are not fixed, but are highly dependent on local resource context and habitat conditions. In degraded reefs with simplified resource structure, individuals tend to converge on core resource spectra to maintain survival, whereas in healthier reefs with greater habitat heterogeneity, they tend to show greater variation in major food sources and resource use. This study provides a theoretical basis for coral reef ecological restoration. Full article

Bird migration is an awe-inspiring phenomenon that causes massive global shifts in bird distributions twice a year. To understand the evolution of this phenomenon, it is crucial to know the mortality costs of these journeys. Extreme weather-related events can lead to abnormally high mortality rates among migratory birds, while high mercury concentration may reduce the survival of songbirds in the field, especially for the long-distance migrant insectivores. Yet the specific vulnerability factors remain largely unknown. We collected the opportunistic dead Eastern Red-rumped Swallows (Cecropis daurica) in a mass-mortality event caused by a cold wave in autumn migration in Southern China. Mercury concentration in their tail feathers is 0.57 ± 0.37 µg g⁻¹, lower than the established toxicity threshold for birds. The claws’ hydrogen stable isotopic (δD) values ranged from −116 to −78 ‰, with a mean of (−88.00 ± 8.22) ‰. Stable hydrogen isotopes indicated broad origins for the Eastern Red-rumped Swallows, ranging from ~30° N to ~62° N and ~10° E to ~150° E. Considering subspecies ranges, most of the dead swallows likely came from their almost furthest breeding sites. Our results indicated the primary cause of the mass-mortality event was likely fatigue or starvation resulting from long-distance flight during an extreme cold wave. Mercury exposure may not be the main direct cause of death. Full article

Ionizing radiation therapy has undergone a clear paradigm shift in veterinary oncology and inflammatory disease management, moving from mainly palliative use toward structured, curative treatment programs. This review synthesizes current evidence on key modalities used in veterinary practice, including external beam radiotherapy, brachytherapy, systemic targeted radionuclide therapy, stereotactic radiosurgery, stereotactic body radiotherapy, radiosynoviorthesis, and low-dose radiotherapy. Each modality is discussed in relation to its physical and biological basis, major isotopes or beam types, routes of delivery, target species such as dogs, cats, and horses, clinical indications, and global availability. Comparative analysis highlights differences in clinical acceptance, evidence strength, access, and cost. External beam radiotherapy and stereotactic techniques support curative tumor management, whereas radiosynoviorthesis and low-dose radiotherapy are effective for inflammatory and degenerative disorders. Despite ongoing progress, challenges remain in access, dosimetry standardization, and prospective evidence. Companion animals are also emphasized as valuable translational models, guiding future innovation and collaboration internationally. Full article

Variscan two-mica granites are widespread in the Trás-os-Montes region (NE Portugal), yet their emplacement ages, petrogenesis, and relationship with Variscan deformation phases remain poorly constrained. This study integrates U–Pb zircon geochronology, whole-rock geochemistry, and oxygen isotope data to characterise four peraluminous two-mica granites in the Trás-os-Montes area (Fornos, Carviçais, Fonte Santa, and Bruçó) and to refine their tectonomagmatic context within the Central Iberian Zone. All granites are S-type, ilmenite-series, and derived from reduced magmas, as indicated by their strongly peraluminous compositions, mineral assemblages (muscovite ± biotite), absence of magnetite and presence of ilmenite, and high δ¹⁸O values (>11‰), consistent with partial melting of metasedimentary crust. U–Pb ages reveal two distinct magmatic pulses: an older event at ~340 Ma (Fornos and Fonte Santa granites), predating the onset of C3 deformation and likely associated with late C1 crustal thickening to early C2 tectonics, and a younger pulse at ~320–318 Ma (Carviçais and Bruçó granites). These magmatic pulses are linked to contrasting structural controls, with the older granites emplaced within regional-scale antiforms and the younger intrusions localised along structures related to C3 deformation. Together, these results document two discrete crustal melting events separated by ~20 Ma and record a progressive shift from fold-controlled to strike-slip-dominated granite emplacement during Variscan orogenic evolution. Moreover, the study highlights that tungsten mineralisation is preferentially associated with reduced, crust-derived granites emplaced during specific tectonic regimes, providing new constraints for metallogenic models in NW Iberia. Full article

The dry period is a critical window of susceptibility to intramammary infection in dairy cows, yet the metabolic environment of the mammary gland during this phase remains largely uncharacterized. The objective of this study was to profile the metabolome of bovine dry secretion fluid from quarters with subclinical mastitis (SCM; SCC ≥ 200,000 cells/mL) and healthy quarters (H; SCC < 200,000 cells/mL) on day 2 (D2) and day 21 (D21) of the dry period (n = 10 per group quarters per group, drawn from a cohort of 41 enrolled Holstein dairy cows) using high-performance chemical isotope labeling liquid chromatography–mass spectrometry (CIL-LC–MS). A total of 474 metabolites were positively identified. At D2, 186 metabolites differed significantly between SCM and H quarters, with dipeptides dominating the upregulated metabolites, indicating active proteolysis in infected quarters. Norepinephrine was the most significantly depleted metabolite (FC = 0.27, p = 3.37 × 10⁻⁷), pointing to local catecholamine exhaustion. By D21, only 36 metabolites remained altered, representing an 80.6% attenuation of the SCM signature. Interestingly, temporal changes from D2 to D21 far exceeded disease-related differences, with 316 metabolites shifting in both SCM and healthy quarters, establishing mammary involution as the dominant metabolic event during the dry period. Principal component and PLS-DA analyses confirmed that time, not disease status, was the primary driver of metabolic variation. Pathway analysis revealed significant perturbations in amino acid metabolism, glyoxylate and dicarboxylate metabolism, and tryptophan metabolism. These findings provide the first comprehensive metabolomic map of bovine dry secretion, reveal that subclinical mastitis superimposes a proteolytic and neuroimmune disruption onto the involution process, and identify candidate biomarkers for early detection of intramammary infection during the dry period. Full article

Total body water (TBW) undergoes substantial physiological expansion during pregnancy, reflecting coordinated cardiovascular, renal, and endocrine adaptations required to support maternal metabolism, uteroplacental perfusion, and fetal growth. These changes involve not only an overall increase in body water but also shifts in the distribution of extracellular water (ECW) and intracellular water (ICW), which influence maternal body composition, the interpretation of biochemical biomarkers affected by hemodilution, and pregnancy-related clinical outcomes. Despite its physiological and clinical relevance, the regulation and assessment of body-water compartments during pregnancy remain insufficiently integrated within nutritional and clinical research. This narrative review synthesizes current knowledge on the physiological regulation of TBW and its compartments across gestation and provides a critical analysis of the methodological approaches used to assess body-water distribution in pregnant populations. We review the mechanisms underlying plasma volume expansion, interstitial fluid accumulation, and tissue hydration, and discuss their implications for fetal growth, hypertensive disorders of pregnancy, and gestational diabetes mellitus. We also examine the principles, strengths, and limitations of the main techniques used to assess TBW and body-water compartments during pregnancy. Isotope dilution using stable isotopes (²H₂O and H₂¹⁸O) remains the reference method for TBW assessment, whereas bioelectrical impedance-based approaches, including bioelectrical impedance analysis (BIA), bioelectrical impedance spectroscopy (BIS), and bioelectrical impedance vector analysis (BIVA), offer practical alternatives for longitudinal monitoring of fluid redistribution during gestation. By integrating physiological and methodological perspectives, this review provides a framework for understanding body-water dynamics during pregnancy and for selecting appropriate approaches to assess maternal body composition and hydration. Full article

In this study, the growth of high-quality graphite single crystals from a molten metal flux at atmospheric pressure was optimized. The crystals were precipitated from a saturated iron–carbon solution by slowly cooling (4 °C/h) from a maximum temperature to reduce the carbon solubility. The graphite flakes were >25 square millimeters in area and >10 microns thick, with individual crystal grains as large as 1.2 mm². The crystals were (0002) oriented, as determined by X-ray diffraction. The high structural quality of the graphite crystals was verified by Raman spectroscopy. For graphite with the natural distribution of carbon isotopes, the G-peak at 1580 cm⁻¹ was narrow (~12 cm⁻¹) and the defect peak (D-peak) was absent. To demonstrate the process versatility, graphite crystals enriched in the ¹³C isotope were grown at 5 degrees of enrichment. The Raman G-peak linearly shifted from 1580 cm⁻¹ to 1520 cm⁻¹ for graphite crystals enriched from 1 to 99% ¹³C. The etch pit densities from defect-sensitive etching ranged from 0 to 1.6 × 10⁸ per cm². The process was refined by examining the grain size and quality as functions of the carbon concentration in the starting sources, the carrier gas composition, and maximum temperature. The simplicity of this process suggests it can be scaled to produce very large graphite crystals that would be suitable for a wide range of technologies. Full article

Kelp transplantation is a nature-based strategy aimed at restoring coastal habitat integrity and marine biodiversity. However, its functional consequences for trophic integration within benthic food webs remain poorly understood. Using δ¹³C and δ¹⁵N stable isotope analyses, we evaluated how Undaria pinnatifida transplantation alters consumer trophic structures and isotopic niche characteristics in Oeyeondo, South Korea. While basal source remained isotopically uniform across sites, the introduction of U. pinnatifida triggered significant isotopic shifts in consumers, reflecting a reorganization of carbon assimilation pathways. At the transplanted site, herbivores exhibited significantly enriched δ¹³C values (−14.7 ± 2.0‰ to −13.2 ± 0.3‰) compared to the control site (−19.3 ± 1.2‰), indicating direct assimilation of kelp-derived carbon. Conversely, grazers showed depleted δ¹³C values (−20.6 ± 0.6‰) reflecting a shift toward alternative benthic resources. Isotopic niche metrics revealed a broader community-level niche width at the transplanted site, driven by increased resource diversity and niche partitioning. These findings demonstrate that kelp transplantation effectively restructures benthic food web dynamics by providing new energy pathways, offering a robust functional framework for evaluating marine forest restoration success. Full article