Explore the vast range of titles available.

The aim of this study is to develop a combined in vitro and in vivo assay for the comprehensive efficacy evaluation of strontium-chelating compounds. The complexation and removal of harmful radioactive strontium ( 90 Sr) from the living organism may be necessary in the event of an accidental nuclear disaster or nearby nuclear war event, to prevent its incorporation into bones and thus avoid its long-term harmful health effects. To validate the model, we used a strontium-selective chelator macrocyclic substance (Decorporol) in our measurements, which potentially could be approved as a drug without significant toxic side effects. It has been proven to effectively remove strontium before it is incorporated into bones without significantly affecting calcium homeostasis in the body, and without relevant toxicity or side effects. In this study, we established an extremely sensitive test system that allows for the examination of chelator molecules in preventing the incorporation of non-radioactive SrCl 2 into mineralized extracellular matrix in cell culture. We also optimized an in vivo mouse model suitable to investigate strontium incorporation and the effect of chelators. These assays also provide an opportunity for the safe evaluation of similar compounds.

Radiogenic strontium (87Sr/86Sr) isotope analysis is a well-established method for reconstructing the mobility of human populations in the past and present. Baseline 87Sr/86Sr data are fundamental to the method, as Sr varies across the landscape according to local geology and geoenvironmental factors. The method's application within studies of ancient Mesoamerican paleomobility, however, has concentrated on two key regions-Teotihuacan and the Maya region-despite its potential broader relevance across greater Mesoamerica. This is due in part to a lack of available baseline 87Sr/86Sr data for the region at large. Using the Valley of Oaxaca as a case study, we use Bayesian Additive Regression Trees (BART) to generate a locally calibrated predictive 87Sr/86Sr isoscape model of Mesoamerica in general and the Valley of Oaxaca in particular. We integrate (1) observed 87Sr/86Sr data from modern plant samples (n = 95) from 17 sites across the Valley, (2) a compiled database of continental North and South American 87Sr/86Sr data, (3) geological bedrock maps, and (4) high resolution spatial data on geoenvironmental Sr covariates to iteratively develop and test a high performing predictive model for Mesoamerica, highlighting the importance of regional calibration in developing predictive 87Sr/86Sr isoscapes. Our results indicate that though overlap exists, 87Sr/86Sr can be used to detect migration within the Valley of Oaxaca as well as between the Valley and greater Mesoamerica. We then apply our isoscape to previously published human 87Sr/86Sr data from Monte Albán, Oaxaca to demonstrate how our model's explicit quantification of uncertainty in local 87Sr/86Sr ranges allows for more nuanced interpretation of paleomobility in archaeological samples.

Strontium isotope ratios (87Sr/86Sr) are gaining considerable interest as a geolocation tool and are now widely applied in archaeology, ecology, and forensic research. However, their application for provenance requires the development of baseline models predicting surficial 87Sr/86Sr variations (\"isoscapes\"). A variety of empirically-based and process-based models have been proposed to build terrestrial 87Sr/86Sr isoscapes but, in their current forms, those models are not mature enough to be integrated with continuous-probability surface models used in geographic assignment. In this study, we aim to overcome those limitations and to predict 87Sr/86Sr variations across Western Europe by combining process-based models and a series of remote-sensing geospatial products into a regression framework. We find that random forest regression significantly outperforms other commonly used regression and interpolation methods, and efficiently predicts the multi-scale patterning of 87Sr/86Sr variations by accounting for geological, geomorphological and atmospheric controls. Random forest regression also provides an easily interpretable and flexible framework to integrate different types of environmental auxiliary variables required to model the multi-scale patterning of 87Sr/86Sr variability. The method is transferable to different scales and resolutions and can be applied to the large collection of geospatial data available at local and global levels. The isoscape generated in this study provides the most accurate 87Sr/86Sr predictions in bioavailable strontium for Western Europe (R2 = 0.58 and RMSE = 0.0023) to date, as well as a conservative estimate of spatial uncertainty by applying quantile regression forest. We anticipate that the method presented in this study combined with the growing numbers of bioavailable 87Sr/86Sr data and satellite geospatial products will extend the applicability of the 87Sr/86Sr geo-profiling tool in provenance applications.

Complex topological configurations are fertile ground for exploring emergent phenomena and exotic phases in condensed-matter physics. For example, the recent discovery of polarization vortices and their associated complex-phase coexistence and response under applied electric fields in superlattices of (PbTiO 3 ) n /(SrTiO 3 ) n suggests the presence of a complex, multi-dimensional system capable of interesting physical responses, such as chirality, negative capacitance and large piezo-electric responses 1 – 3 . Here, by varying epitaxial constraints, we discover room-temperature polar-skyrmion bubbles in a lead titanate layer confined by strontium titanate layers, which are imaged by atomic-resolution scanning transmission electron microscopy. Phase-field modelling and second-principles calculations reveal that the polar-skyrmion bubbles have a skyrmion number of +1, and resonant soft-X-ray diffraction experiments show circular dichroism, confirming chirality. Such nanometre-scale polar-skyrmion bubbles are the electric analogues of magnetic skyrmions, and could contribute to the advancement of ferroelectrics towards functionalities incorporating emergent chirality and electrically controllable negative capacitance. Chiral polar-skyrmion bubbles are observed in superlattices of titanium-based perovskite oxides at room temperature.

Bioavailable strontium (Sr) isoscapes are essential tools in studies on environmental processes, animal and human mobility and provenance. The success of these studies relies on the comparison between the measured 87 Sr/ 86 Sr isotope ratios of specimens and the spatial distribution of environmental bioavailable Sr isotopic signatures across geographical regions. A critical step of this process is the construction of reference maps that integrate environmental Sr isotopic data with geographical information. Here, we present a new bioavailable Sr dataset of 113 environmental samples, including plants and malacological samples collected from center-east Argentina (Paraná Delta, Pampa and Entre Ríos plains) as well as adjacent Uruguay, covering an area of approximately 122,500 km 2 . This dataset is further integrated with archaeological bioapatite data from the literature to construct the first random forest-based Sr isoscape of the region. Notably this area is on recent Quaternary (fluvial, marine and aeolian) sediments derived from the erosion of magmatic and metamorphic terrains with different Sr isotope composition from low 87 Sr/ 86 Sr ratios (about 0.706) to highly radiogenic signatures (>0.71), and heterogeneously transported in the Delta area by the rivers and in the high plains by wind and rivers. This isoscape offers a unique perspective on the Sr isotope distribution in a lithologically homogeneous region characterized by relatively young sedimentary sequences. This work represents a significant advancement in the development of Sr isoscapes, providing a fundamental tool for environmental and archaeological applications in South America.

Interfaces in heterostructures have been a key point of interest in condensed-matter physics for decades owing to a plethora of distinctive phenomena—such as rectification 1 , the photovoltaic effect 2 , the quantum Hall effect 3 and high-temperature superconductivity 4 —and their critical roles in present-day technical devices. However, the symmetry modulation at interfaces and the resultant effects have been largely overlooked. Here we show that a built-in electric field that originates from band bending at heterostructure interfaces induces polar symmetry therein that results in emergent functionalities, including piezoelectricity and pyroelectricity, even though the component materials are centrosymmetric. We study classic interfaces—namely, Schottky junctions—formed by noble metal and centrosymmetric semiconductors, including niobium-doped strontium titanium oxide crystals, niobium-doped titanium dioxide crystals, niobium-doped barium strontium titanium oxide ceramics, and silicon. The built-in electric field in the depletion region induces polar structures in the semiconductors and generates substantial piezoelectric and pyroelectric effects. In particular, the pyroelectric coefficient and figure of merit of the interface are over one order of magnitude larger than those of conventional bulk polar materials. Our study enriches the functionalities of heterostructure interfaces, offering a distinctive approach to realizing energy transduction beyond the conventional limitation imposed by intrinsic symmetry. A built-in electric field at the interface of metals and centrosymmetric semiconductors is shown to induce polar structures in the semiconductors and generate substantial piezoelectric and pyroelectric effects.

Osteoporosis stands out as a prevalent skeletal ailment, prompting exploration into potential treatments, including dietary strontium ion supplements. This study assessed the efficacy of supplementation of three strontium forms—strontium citrate (SrC), strontium ranelate (SrR), and strontium chloride (SrCl)—for enhancing bone structure in 50 female SWISS mice, aged seven weeks. In total, 40 mice underwent ovariectomy, while 10 underwent sham ovariectomy. Ovariectomized (OVX) mice were randomly assigned to the following groups: OVX (no supplementation), OVX + SrR, OVX + SrC, and OVX + SrCl, at concentrations equivalent to the molar amount of strontium. After 16 weeks, micro-CT examined trabeculae and cortical bones, and whole-bone strontium content was determined. Results confirm strontium administration increased bone tissue mineral density (TMD) and Sr content, with SrC exhibiting the weakest effect. Femur morphometry showed limited Sr impact, especially in the OVX + SrC group. This research highlights strontium’s potential in bone health, emphasizing variations in efficacy among its forms.