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Bone tissue engineering is a field to manufacture scaffolds for bone defects that cannot repair without medical interventions. Ceramic nanoparticles such as bredigite have importance roles in bone regeneration. We synthesized a novel strontium (Sr) doped bredigite (Bre) nanoparticles (BreSr) and then developed new nanocomposite scaffolds using polycaprolactone (PCL), poly lactic acid (PLA) by the 3D-printing technique. Novel functional nanoparticles were synthesized and characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS: map). The nanoparticles were uniformly distributed in the polymer matrix composites. The 3D- printed scaffolds were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), attenuated total reflection-fourier transform infrared (ATR-FTIR), degradation rate porosity, mechanical tests, apatite formation and cell culture. Degradation rate and mechanical strength were increased in the PLA/PCL/Bre-5%Sr nanocopmposite scaffolds. Hydroxyapatite crystals were also created on the scaffold surface in the bioactivity test. The scaffolds supported viability and proliferation of human osteoblasts. Gene expression and calcium deposition in the samples containing nanoparticles indicated statistical different than the scaffolds without nanoparticles. The nanocomposite scaffolds were implanted into the critical-sized calvarial defects in rat for 3 months. The scaffolds containing Bre-Sr ceramic nanoparticles exhibited the best potential to regenerate bone tissue.

Statement of problem Strontium has been validated for potent bone-seeking and antiosteoporotic properties and elicits a potentially beneficial impact on implant osseointegration in patients with osteoporosis. However, the efficacy of strontium supplementation on improving new bone formation and implant osseointegration in the presence of osteoporotic bone is still unclear. Purpose The purpose of this systematic review was to comprehensively assess the efficacy of strontium supplementation, encompassing oral intake and local delivery of strontium, on implant osseointegration in patients with osteoporosis. Material and methods Searches on electronic databases (MEDLINE or PubMed, Web of Science, EBSCO, Embase, and Clinicaltrials.gov ) and manual searches were conducted to identify relevant preclinical animal trials up to June 2020. The primary outcomes were the percentage of bone-implant contact and bone area; the secondary outcomes were quantitative parameters of biomechanical tests and microcomputed tomography (μCT). Results Fourteen preclinical trials (1 rabbit, 1 sheep, and 12 rat), with a total of 404 ovariectomized animals and 798 implants, were eligible for analysis. The results revealed a significant 17.1% increase in bone-implant contact and 13.5% increase in bone area, favoring strontium supplementation despite considerable heterogeneity. Subgroup analyses of both bone-implant contact and bone area exhibited similar outcomes with low to moderate heterogeneity. Results of biomechanical and μCT tests showed that strontium-enriched implantation tended to optimize the mechanical strength and microarchitecture of newly formed bone despite moderate to generally high heterogeneity. Conclusions Based on the available preclinical evidence, strontium supplementation, including local and systemic delivery, showed promising results for enhancing implant osseointegration in the presence of osteoporosis during 4 to 12 weeks of healing. Future well-designed standardized studies are necessary to validate the efficacy and safety of strontium supplementation and to establish a standard methodology for incorporating Sr into implant surfaces in a clinical setting.

Three dimensional (3D) substrates based on natural and synthetic polymers enhance the osteogenic and mechanical properties of the bone tissue engineering scaffolds. Here, a novel bioactive composite scaffolds from polycaprolactone /kappa-carrageenan were developed for bone regeneration applications. 3D PCL scaffolds were fabricated by 3D printing method followed by coating with carboxymethyl kappa-carrageenan. This organic film was used to create calcium and strontium phosphate layers via a modified alternate soaking process in CaCl

The immune microenvironment induced by biomaterials played vital roles in bone regeneration. Hydroxyapatite (HA) and its ion-substituted derivates represent a large class of core inorganic materials for bone tissue engineering. Although ion substitution was proved to be a potent way to grant HA more biological functions, few studies focused on the immunomodulatory properties of ion-doped HA. Herein, to explore the potential osteoimmunomodulatory effects of ion-doped HA, zinc and strontium co-assembled into HA through a collagen template biomimetic way (ZnSr-Col-HA) was successfully achieved. It was found that ZnSr-Col-HA could induce a favorable osteo-immune microenvironment by stimulating macrophages. Furthermore, ZnSr-Col-HA demonstrated a procedural promoting effect on osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in vitro. Specifically, the osteo-immune microenvironment acted as a dominant factor in promoting osteogenic gene expressions at the early stage through OSM signal pathway. Whereas the direct stimulating effects on BMSCs by Zn2+/Sr2+ were more effectively at the later stage with Nfatc1/Maf and Wnt signals activated. In vivo study confirmed strong promoting effects of ZnSr-Col-HA on critical-sized cranial defect repair. The current study indicated that such a combined biomaterial design philosophy of dual ion-doping and biomimetic molecular co-assembly to endow HA applicable osteoimmunomodulatory characteristics might bring up a new cutting-edge concept for bone regeneration study., Graphical abstract Image 1, Highlights • Zn/Sr dual ions-collagen co-assembly hydroxyapatite (ZnSr-Col-HA) was achieved via a molecular template biomimetic way. • A procedural promoting effect of ZnSr-Col-HA on osteogenic differentiation of BMSCs was firstly found. • A novel material design philosophy was proposed for dual ions-doped biomimetic HA with osteoimmunomodulatory properties.

The strontium (Sr) concentration and 87Sr/86Sr ratios in leachates extracted from Upper Permian (Wuchiapingian) coals from the Tianjia Mine, Chongqing, southwestern China, were investigated using a selective leaching sequential extraction technique including deionized water, dilute HCl, and a mixture of HF and HNO3. The results show that the Sr concentrations in water-leachates (mean value of 12.9 ppm) and HCl-leachates (78.4 ppm) are lower than HF/HNO3-leachates (131 ppm). The water-leachates had more radiogenic (0.707182–0.707642) 87Sr/86Sr ratios than HCl-leachates (0.707111–0.707609), while the 87Sr/86Sr ratios in the HF/HNO3-leachates had a wide range (0.706972–0.707807), and the highest 87Sr/86Sr ratios. These variations in Sr concentration and 87Sr/86Sr ratios are most likely related to the differential solubility of the different Sr-bearing minerals in the coals, in addition to the Sr associated directly with the organic components of the coals. While the Sr/Ca ratios of the HCl-leachates (median=11.3 mmole/mole) were similar to the ratio of marine carbonate dissolution, the 87Sr/86Sr values in the HCl-leachates were higher than the expected 87Sr/86Sr range of the contemporaneous seawater (0.70700–0.70725) recorded in the Wuchiapingian marine carbonate rocks. This indicates that the carbonate minerals in the coals are not of a syngenetic marine origin, despite the indications that the coal seams were influenced by seawater. The textural properties of the cell and fracture-filling carbonate minerals provide evidence that the carbonate minerals in the Tianjia coals are of late diagenetic or epigenetic origin. The combination of isotopic evolution trends of the coal seam, the petrological characteristics (high vitrinite reflectance and bireflectance) and mineralogical assemblage of NH4-illite-paragonite and kaolinite-paragonite as well as authigenic minerals such as calcite, ferroan dolomite, chamosite, quartz, anatase, and florencite suggests that the Tianjia coals was likely affected by diagenetic processes such as sediment dewatering with increasing burial depth (i.e., upward migration of pore fluids from the mudstones interbedded with the coal seams). These conclusions agree with the regional geological history marked by large-scale uplift and denudation of the crust following regional tectonic evolution (i.e., Dongwu Movement, 258–260.5 Ma).

A type of strontium and amorphous calcium phosphate dipped premixed injectable tricalcium silicate-based dental root canal sealer was developed as the following protocols. A powder mixture containing tricalcium silicate, strontium carbonate (6, 8, 10, and 12 wt%), zirconia (20 wt%), calcium chloride (6 wt%), and amorphous calcium phosphate (ACP) (5 wt%) was mixed with liquid polyethylene glycol 400 (PEG 400) at a liquid-to-powder ratio of 0.5 mL/g and mechanically ground using a planetary ball to obtain the premixed injectable calcium silicate-based sealer. The sealer’s physicochemical property and cytocompatibility were evaluated in vitro. Quantitative data were expressed as mean ± standard deviation, and Student's t-test or a one-way analysis of variance (ANOVA) test were carried out at significant differences with P

In the present investigation, we fabricated strontium (Sr2+) incorporated CsPbI2Br-based inorganic perovskite solar cells in ambient conditions. The morphology, crystallinity, absorption, elemental composition and photoluminescence analysis of the bare CsPbI2Br and CsPb1-xSrxI2Br perovskite thin films were studied systematically to investigate the role of Sr2+ incorporation. It is observed that the surface morphology of the CsPbI2Br perovskite thin film has been improved by partial substitution of Pb2+ by Sr2+ which facilitates photoactive black phase-stabilization and defect passivation. The champion device having CsPb0.98Sr0.02I2Br composition exhibited a power conversion efficiency (PCE) of 16.61% which is much higher than the bare device (13.65%). Furthermore, our CsPb0.98Sr0.02I2Br-based devices maintain > 85% of its initial efficiency over 100 h in ambient conditions.

In this work, Nb-substituted barium strontium cobaltites Ba0.5Sr0.5Co1-xNbxO3-δ (x = 0 – 0.4) have been fabricated and studied. The structural analysis showed that the Nb content influences the lattice constant as well as the distance between the (Co, Nb) and oxygen atoms. The study of morphology of samples showed that the Nb content does not change the porosity, grain size and morphology of the ceramics. The total electrical conductivity was studied as a function of temperature and pO2/pH2O. It was shown, that total conductivity is influenced by the cobalt to niobium ratio while the conduction mechanism was similar in all analyzed samples. Transport properties and the presence of protonic conductivity were studied in a dry and humidified atmosphere. A non-negligible difference between total conductivities in dry and wet atmospheres below 500 °C was observed what indicates the presence of protonic defects in these structures. Hydrogenation as a predominant protons formation mechanism was proposed.

This study investigated the influence of Sr2+ ions incorporation in calcium phosphates formation on the surface of Al2O3/ZrO2 (5 vol%) nanocomposites. For this, Al2O3/ZrO2 samples were shaped, calcined (400 °C for 1 h), and sintered (1500 °C for 2 h). After surface treatment with aqueous phosphoric acid solution (H3PO4), the nanocomposite was biomimetically coated with Simulated Body Fluid (SBF) solutions 5x enriched with different concentrations of Sr2+ ions for 14 days. The samples were then characterized by confocal microscopy, scanning electron microscopy (SEM), contact angle and X-ray diffraction. In general, the formation of phases attributed to both calcium phosphates and strontium on the surfaces of nanocomposites was observed, evidencing the partial replacement of calcium ion (Ca2+) by strontium ion (Sr2+) in the structure of phosphates. Thus, the following phases were identified: tricalcium α-phosphate (α-TCP), tricalcium β-phosphate (β-TCP), tetracalcium phosphate (TTCP), hydroxyapatite (HAp), strontium phosphate (SrP) and Sr-incorporated HAp (Sr-HAp). Moreover, Sr2+ ions incorporation in the structure of phosphates also influenced their morphology. Therefore, Sr2+ ions increase adsorption, bioactivity and osteoconduction of calcium phosphates.

Perovskite oxides with cobalt and strontium element exhibit severe degradation during the operation for the solid oxide fuel cells (SOFC). Here, we report stable non-cobalt and non-strontium La1-xNi0.6Fe0.4O3 perovskite cathodes with improved oxygen reduction reaction (ORR) activity. A-site deficient La1-xNi0.6Fe0.4O3 cathodes within 8 at.% all exhibit the invariable phase structure with LaNi0.6Fe0.4O3 (LNF), and the matched thermal expansion coefficient with that of the (Ce0.90Gd0.10)O1.95 (GDC) electrolyte. The polarization resistance of the La0.94Ni0.6Fe0.4O3 (LNF94) cathode is 0.61 Ω cm2 at 750 °C in air, which is 1/5 of the LaNi0.6Fe0.4O3 (2.78 Ω cm2). The peak power density of the corresponding single cell with LNF94 cathode is 0.37 W cm−2 at 750 °C, which is 2.36 times higher than that of the single cell with LNF cathode (0.11 W cm−2). We further study the long-term stability of LNF and LNF94 cathodes, the polarization resistance of the LNF94 electrode slightly fluctuates around 0.18 Ω cm2 during 50 h operation at 800 °C, while the polarization resistance of the LNF increases by about 15%. This work highlights the A-site deficient LNF as an effective and stable non-cobalt and non-strontium cathode for the intermediate temperature solid oxide fuel cells.

Aiming at selective adsorption and separation of Y(III) from the Y(III)-Sr(II) group in acid solution, a silica-based TODGA impregnated adsorbent [(TODGA+1-dodecanol)/SiO2-P-F600] has been prepared. Batch adsorption experiments were conducted under the effect of contact time, acid concentration, solution temperature, and adsorption capacity etc. Chromatography recovery of more than 90% Y(III) was successfully achieved under elution with 0.01 M DTPA solution in nitric acid adsorption system, and 0.1 M HCl solution in hydrochloride adsorption system, respectively.

Y3+- and Co2+-substituted Sr1-xYxFe12-xCoxO19 (0 ≤ x ≤ 0.50) M-type hexaferrites were synthesized using a traditional oxide ceramic process to study their structural and static magnetic properties. The well-defined M-type phase structures of the pure and Y–Co co-substituted strontium ferrites were verified via XRD analysis. When the Y–Co substitution amount (x) exceeded 0.20, the Fe2O3, Y3Fe5O12, SrFe2O4, and CoFe2O4 impurity phases coexisted in the M-type strontium hexaferrite structure. The lattice parameters a and c increased when x ≤ 0.20; however, a further increase in the Y–Co substitution caused them to decrease. The X-ray density dx initially decreased when x ≤ 0.20, and subsequently increased with a further increase in Y–Co substitution. The density of the sintered samples ds exhibited a decreasing trend with the increasing Y–Co substitution, inducing the porosity to increase. The saturation magnetization Ms monotonously decreased with the increasing Y–Co substitution amount. The in-plane and out-of-plane coercivities, Hc(ip) and Hc(op), initially increased as x increased from 0 to 0.20. When x > 0.20, however, Hc(ip) exhibited a decreasing trend; particularly, a linear decrease was observed as x increased from 0.30 to 0.50. The squareness ratio S reached its maximum (79.6%) at x = 0.20.

The ability of strontium ion to inhibit the abnormally high bone resorption, which occurs in pathologies characterized by loss of bone substance, has stimulated a number of research on strontium substituted/doped calcium phosphates. However, no information was available up to now on strontium substitution to calcium in the structure of α-CaHPO4, monetite, in spite of the involvement of this phosphate in the composition of biomaterials for hard tissue substitution/repair and although it is isomorphous with α-SrHPO4. Herein, we investigated the substitution of strontium to calcium in the structure of α-CaHPO4, as well as the replacement of calcium for strontium in the structure of a further polymorph of SrHPO4, namely β-SrHPO4. To this purpose, monetite at increasing degree of strontium substitution for calcium was synthesized by means of direct synthesis in aqueous solution, as well as through thermal treatment of strontium-substituted brushite; whereas the synthesis of β-SrHPO4 was carried out at low temperature. The results of structural refinements, spectroscopic analysis and electron microscopy investigation indicate that the method of synthesis has a great influence on the range of strontium incorporation into α-CaHPO4, which can reach 100 at%. The morphology of the synthesized materials is also remarkably dependent on composition. The analysis of the products synthesized at low temperature shows that the upper limit of possible substitution of calcium to strontium in the structure of β-SrHPO4 is much more limited, just up to about 20 at%. Moreover, powder X-ray analysis of β-SrHPO4 states that it crystallizes with a monoclinic cell in the space group P21/c.

In the present study, structure of zirconium-containing bioactive glass (58S-BG (Zr-BG)) with optimal fixed Zr content (5 mol.%) was modified by incorporation of strontium (Sr). These Zr and Sr-containing BGs (ZS-BGs) were synthesized by sol-gel method and substitution of Ca with modifier ions (Sr content = 0, 3, 6, 9, and 12 mol.%). The results obtained from characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and energy-dispersive X-ray spectroscopy (EDS) techniques from surface of all the ZS-BGs revealed formation of hydroxyapatite (HA) after 7 days of immersion in the simulated body fluid (SBF) solution. Evaluation of changes in the SBF solution, by monitoring pH variations and ions concentration, was in agreement with the results of morphological and structural investigations. The in-vitro biological function of synthesized BGs was studied through (MTT) assay and alkaline phosphatase (ALP) activity analysis. The results showed that all the specimens significantly stimulated proliferation and viability of MC3T3 osteoblast-like cells. Furthermore, antibacterial studies confirmed less resistance of methicillin-resistant Staphylococcus aureus (MRSA) bacteria against ZS-BGs. Eventually, the results of in-vitro bio-analysis were clarified and confirmed by two cell staining techniques of Live/Dead and Dapi/Actin. This confirmation was achieved by observing the increased quantity of live cells and their nuclei as well as the decreased number of dead cells after co-culturing with all ZS-BGs.

Calcium and strontium tantalates with general formula A2Ta2O7 (A = Ca, Sr) were prepared by the solid-state synthesis and evaluated in the photocatalytic water splitting and CO2 reduction. A predominance in the water splitting processes is observed in both materials obtaining competitive yields for H2 and O2 compared to the results reported in the literature. A better performance was observed in the Sr2Ta2O7 sample associated with its crystalline structure and morphology (H2 = 807 μmol g−1, O2 = 296 μmol g−1, CO = 5 μmol g−1 for 6 h). Besides, both materials were decorated with Co3O4 and CuO particles acting as cocatalysts. The presence of these oxides enhanced the evolution of the products considerably due to the efficient charges transport avoiding their recombination, being the Co3O4 loaded sample the most efficient in both cases. The presence of CuO favored the formation of CO in both tantalate materials; however, their rates are not comparable with the obtained for H2 and O2, being the water-splitting process also predominant with the use of both cocatalysts.

Pure and carbonate- or silicate-substituted strontium apatites (i.e., SrHAP, SrCAP and SrSiP) were synthesized via alkaline hydrolysis of strontium hydrogen phosphate using sodium hydroxide, carbonate, and metasilicate, respectively. Zinc substitution in SrSiP was performed by an ion exchange reaction to yield SrZnSiP. Characterization of these strontium apatites was carried out by powder XRD, Fourier-transform infrared (FTIR) spectroscopy, Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), SEM- Energy dispersive X-ray spectroscopy (EDS), FE-SEM and TEM- Selected Area Electron Diffraction (SAED). From elemental analyses, the Sr/P ratios of all samples were found to be around 1.5, suggesting that these are strontium-deficient apatites. From FTIR analysis, presence of both the structural OH group and the HPO4 group could not be confirmed. Crystal morphology strongly depends on the pH during sample preparation. At high pH, bundles of spindle-like nanocrystalline SrHAP, SrSiP and SrZnSiP were produced, whereas at lower pH, cubical crystallite of SrCAP with increased crystallinity was formed. Powder XRD analysis revealed the effects of these substituents on the hexagonal lattice parameters which agreed well with the known dependence for the corresponding substituted hydroxyapatite. The relationship between the lattice parameters a and c for calcium to barium hydroxyapatite groups collected from various studies together with our data, showed a universal linear relationship represented by the following equation, c = 1.1348a −3.8043 with a coefficient of determination (R2) of 0.9982. Dissolution behavior of SrZnSiP in pure water was investigated by the surface coating on β-TCP disc. For over 24 days, Sr, Si and Zn ions were released constantly within moderate concentration ranges.

Lead-free (Bi0.5Na0.5)1-xSrxBi4Ti4O15 ceramics (x = 0–0.9) are fabricated by solid state reaction process. XRD analysis shows the symmetry divergence from tetragonal to orthorhombic phase accompanied by morphotropic phase boundary with increasing strontium content. Raman spectra confirm the incorporation of strontium into (Bi2.5Na0.5Ti4O13)2- layers. SEM graphs exhibit the typical plate-like morphology with regular variation of grain size and crystallization as strontium increases. Multistage ferroelectric transition is observed with x = 0.2–0.4. Piezoelectric performance measurements present the well thermal stability at x = 0.4. The dielectric properties display a shifting of Curie temperature towards low temperature with increasing strontium ions. It can be due to the crystal lattice distortion by larger radius of strontium and the increasing tolerance factor. ac conductivity and impedance measurements suggest that electron hopping mainly contributes to the low temperature region. Ionization conductivity by oxygen vacancy migration including first-ionization and double-ionization plays the dominating role in the middle and high temperature region. The controllable properties indicate the potential applications for electric devices of (Bi0.5Na0.5)1-xSrxBi4Ti4O15 ceramic.

Strontium (Sr) can be introduced into hydroxyapatite (HA) crystals and stimulate new bone formation. In this study, the single-crystalline Sr-substituted HA microtubes with hexagonal cross-sections are synthesized under the regulation of Sr2+ via the oleic acid-assisted solvothermal method. The morphology of the as-prepared products changes from ultralong flexible nanofibers to hexagonal microtubes with the increasing Sr/(Sr + Ca) ratio. Microtubes can be formed when a small amount of Sr is doped into HA, with the optimal substitution ratio of Sr2+ being ~6%. The inner and outer diameters of the synthetic Sr-substituted HA microtubes are about 1.6 and 2.3 μm, respectively. Moreover, the effects of Sr2+ dopping on the formation process and mechanism of microtubes were discussed.

With the exception of beryllium, divalent cations of every alkaline earth metal are characterized by their calcimimetic behavior. Thus, in vivo biodistribution of these cations mostly occurs in form of a massive accumulation in bone tissues, consisting of hydroxyapatite to a major extent. Apart from the lightest elements beryllium and magnesium, animal studies and human studies regarding the overall in vivo behavior were carried out by using radioisotopes of the elements calcium, strontium, barium and radium. To date, only strontium with its radioisotopes and radium gained importance for applications in nuclear medicine, mainly for pain-reducing and palliative treatment of bone metastases. In contrast, barium radioisotopes can be ascertained as useful imaging agents and possible diagnostic analogues for theranostic approaches. This review focuses on the characteristic and chemical behavior of barium compounds, possible radioactive barium isotopes for future applications in nuclear medicine and radiopharmacy as well as recent results regarding barium-131 as diagnostic match for radium isotopes used in targeted alpha therapy.

Hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) are widely used in bone graft materials, because they have excellent biocompatibility. However, the degradation rates of HAp and β-TCP do not match the rate of osteogenesis, which limits their clinical applications. Therefore, forming biphasic calcium phosphate (BCP) is a promising method to control the biodegradation rate of the material. In addition, strontium (Sr) is an important element that promotes osteogenesis and inhibits bone absorption. Therefore, this study focused on the effects of Sr in the as-synthesized BCP with varied Sr concentrations of 1, 5, and 15 mol%, which are synthesized by chemical precipitation and a high-temperature calcination method. In this study, we assume that Sr is doped into Ca(5) of β-TCP and Ca(1) & Ca(2) of HAp during the Rietveld refinement. On the basis of the Rietveld refinement results obtained from X-ray diffraction (XRD) patterns, with increasing Sr concentration, the mass percentage of HAp decreases first, which is due to the distortion of the HAp structure, resulting in a decrease in HAp stability and phase variation from HAp to β-TCP. However, when the concentration of Sr reaches 15 mol%, the mass percentage of HAp increases, which may be because of the phase transformation from β-TCP to calcium-deficient apatite by the diffusion of Ca. In addition, the increase in the lattice constants and volumes indicates that Sr has been successfully doped into the crystal lattices of both β-TCP and HAp, since the ion radius of Sr2+ (0.113 nm) is larger than the ion radius of Ca2+ (0.099 nm). As shown in the X-ray photoelectron spectroscopy (XPS) results, the intensities of Sr3d and Sr3p increase with increasing Sr concentrations, which indicates that Sr is not only on the surface of the sample but also in the crystalline structures of both β-TCP and HAp.

The development of high-efficiency adsorbents for heavy metal ion removal from wastewater is highly desirable and challenging due to their synthesis complexity and low adsorption capacities. Herein, we reported the synthesis of strontium (Sr) doped hydroxyapatite (HAp) for the increased Cr (VI) adsorption. The effects of pH, temperature, and time on adsorption performances were studied. As a result, the Sr-HAp nanorods can achieve a Cr (VI) adsorption capacity of 443 mg/g, which is significantly higher than that of HAp nanorods (318 mg/g). To better understand the adsorption mechanism, the Langmuir isotherm model was established. The modeling results indicated that Langmuir monolayer chemical adsorption contributed to the efficient Cr (VI) ion removal for Sr-HAp nanorods adsorbents. The surface area and surface functional groups (O–H) contributed to the different Cr (VI) adsorption capacities between HAp and Sr-HAp.

Cremated human remains are commonly found in the archaeological records, especially in Europe during the Metal Ages and the Roman period. Due to the high temperatures reached during cremation (up to 1000°C), most biological information locked in the isotopic composition of different tissues is heavily altered or even destroyed. The recent demonstration that strontium isotope ratio (87Sr/86Sr) remained unaltered during cremation and was even very resistant to post-burial alterations (which is not the case of unburned bone), opened new possibility for palaeomobility studies of ancient populations that practices cremations as a funerary ritual. This paper summarizes the strontium isotopic data produced over the last decade which is then deposited on the open-access platform IsoArcH (https://isoarch.eu/) for any interested parties to use. It is the first time isotopic data on cremated remains is introduced in this database, significantly extending its impact on the scientific community.

The present research describes the results of Raman spectroscopic study of undoped and Y-doped SrZrO3 having a great potential for application in proton-conducting fuel cells. Effects of yttrium doping and strontium nonstoichiometry on the local environment of cations and vibrational properties of strontium zirconate were investigated. Ceramic samples SryZr1-xYxO3-δ (x = 0, 0.02, 0.05; y = 0.94, 0.98, 1.00) were synthesized via a chemical solution method and sintered at 1650 °C. Microstructure, phase and chemical composition of the samples were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Analysis of Raman spectra peculiarities upon changes in Sr- and Y- concentrations has shown that yttrium ions can be partitioned over both A- and B-sites in the strontium-deficient zirconates with the dopant concentrations more than 2 at%.

Investigation of thermostability will lead the groundbreaking of unraveling the mechanism of influence of ion-doping on the properties of calcium phosphates. In this work, octacalcium phosphate (OCP), a metastable precursor of biological apatite, was used as a stability model for doping ions (Fe3+ and Sr2+) with different ionic charges and radii. After treated under hot air at different temperatures (110–200 °C), the phase, morphology, structure, physicochemical properties, protein affinity, ions release, and cytological responses of the ion-doped OCPs were investigated comparatively. The results showed that the collapse of OCP crystals gradually occurred, accompanying with the dehydration of hydrated layers and the disintegration of plate-like crystals as the temperature increased. The collapsed crystals still retained the typical properties of OCP and the potential of conversion into hydroxyapatite. Compared to the undoped OCP, Fe-OCP, and Sr-OCP had lower and higher thermostability respectively, leading to different material surface properties and ions release. The adjusted thermostability of Fe-OCP and Sr-OCP significantly enhanced the adsorption of proteins (BSA and LSZ) and the cytological behavior (adhesion, spreading, proliferation, and osteogenic differentiation) of bone marrow mesenchymal stem cells to a varying extent under the synergistic effects of corresponding surface characteristics and early active ions release. This work paves the way for understanding the modification mechanism of calcium phosphates utilizing ion doping strategy and developing bioactive OCP-based materials for tissue repair., Graphical abstract Image 1, Highlights • OCP was used as a stability model for doping ions with different charges and radii. • Collapse of OCP crystals occurred with structural dehydration after heat treatment. • Fe and Sr doping altered the thermostability of OCP crystals in an opposite way. • The thermostable difference affected the surface properties and ion release of OCP. • Active surface and ion release of OCP synergistically mediated its biocompatibility.

1 mol% Re2O3/MnO – 99 mol% MAl2O4 (Re = Eu, Sm, Dy, Er and M = Ca and Sr) powder samples were prepared by solid state sintering in the temperature range of 1386–1450 °C and their structural, thermal and photoluminescence properties were compared. X-ray diffraction and Rietveld refinement studies of calcium aluminate samples confirm the formation of monoclinic CaAl2O4 along with a small concentration (1.9–4.6 wt %) of monoclinic CaAl4O7 while the strontium aluminate samples contain monoclinic SrAl2O4 and a small amount (0.7–3.5 wt %) of cubic Sr3Al2O6. The short-range structure of CaAl2O4 consists of CaO6, CaO9 and AlO4 structural units while that of SrAl2O4 contains SrO9 and AlO4 units. The Sr–O bond-lengths (2.32–3.58 A) are longer than Ca–O bond-lengths (2.04–3.18 A) and Al–O bond-lengths are of the range 1.35–2.12 A. Differential scanning calorimetry studies reveal high thermal stability of calcium aluminates, while strontium aluminate samples show reversible monoclinic to - hexagonal structural phase transition at 688 °C during heating cycle. Raman spectra exhibit Al–O vibrational modes. Photoluminescence studies show reddish-orange emission in Eu, Sm and Mn-doped samples, Er doped samples show green emission and Dy-doped samples emit yellow-white light. Calcium aluminate samples show significantly higher luminescence intensity and quantum yield than strontium aluminates.

Implant loosening remains a major clinical challenge for osteoporotic patients. This is because osteoclastic bone resorption rate is higher than osteoblastic bone formation rate in the case of osteoporosis, which results in poor bone repair. Strontium (Sr) has been widely accepted as an anti-osteoporosis element. In this study, we fabricated a series of apatite and Sr-substituted apatite coatings via electrochemical deposition under different acidic conditions. The results showed that Ca and Sr exhibited different mineralization behaviors. The main mineralization products for Ca were CaHPO4·2H2O and Ca3(PO4)2 with the structure changed from porous to spherical as the pH values increased. The main mineralization products for Sr were SrHPO4 and Sr5(PO4)3OH with the structure changed from flake to needle as the pH values increased. The in vitro experiment demonstrated that coatings fabricated at high pH condition with the presence of Sr were favorable to MSCs adhesion, spreading, proliferation, and osteogenic differentiation. In addition, Sr-substituted apatite coatings could evidently inhibit osteoclast differentiation and fusion. Moreover, the in vivo study indicated that nano-needle like Sr-substituted apatite coating could suppress osteoclastic activity, improve new bone formation, and enhance bone-implant integration. This study provided a new theoretical guidance for implant coating design and the fabricated Sr-substituted coating might have potential applications for osteoporotic patients., Graphical abstract Image 1, Highlights ∙ Ca2+ and Sr2+ showed different mineralization behaviors in acidic environments. • Apatites fabricated at high pH conditions were beneficial to MSCs growth. • Sr-substituted apatite exhibited superior anti-osteoclast activity ability. • Sr-substituted apatite facilitated osteogenesis, bone growth, and osseointegration.

Mono-mineral and ultramafic geochemical reference materials (GRMs) were analyzed using a 2.5 MeV broad-beam proton-induced X-ray emission (PIXE) system designed to emulate the PIXE branch of the Mars Science Laboratory alpha-particle X-ray spectrometer (APXS). These samples supplement the heterogeneous rocks of our earlier emulation work. The results confirm that PIXE provides high-accuracy concentrations for major and minor elements in homogeneous samples, and the results agree well with those from mono-minerals in the original APXS calibration. A second X-ray detector was added to the system to extend the emulation to the X-ray fluorescence branch of the APXS. The GRMs analyzed using this detector have relatively high concentrations of the trace elements copper, zinc, rubidium, strontium or zirconium. Our PIXE concentrations were compared to values provided by both the GRM suppliers and an independent corporation. Agreement was good in most cases, with individual deviations attributed mainly to inaccuracies in these reference concentrations.

In this study, the formation mechanism of strontium hexaaluminate (SrAl12O19) in Al2O3–SrO and Al2O3–SrO–ZrO2 composites was investigated. Strontium oxide (SrO) powder was added to initial suspensions in various quantities. High-purity submicron powders were used during the experiments. Powder compositions were thermally treated in the temperature range of 900°С–1500°С for 5 h. The stepwise character of SrAl12O19 formation was established by X-ray phase analysis. The SrAl2O4 intermediate compound formed in the temperature range of 900°С–1200°С. The onset of SrAl12O19 formation corresponded to 1200 °C. Formation of SrAl12O19 was completed in the temperature range of 1400°C-1500°С. After sintering at 1300°С–1500°С for 1 h, the samples were analysed. The density of materials indicated a decreasing trend with an increase in the amount of SrO. The density of alumina ceramics sintered at 1500 °C was 3.65 ± 0.2 g/cm3. However, alumina ceramics comprised 15 wt% SrAl12O19 and their density was 3.35 ± 0.4 g/cm3. A decrease in the density level is explained by the platelet shape of SrAl12O19 grains, which prevented additional contact points from generating between the matrix grains and led to porosity formation in the materials. The effect of a reduction in the alumina grain size was established with an increase in the content of the initial SrO and SrAl12O19 powders. Scanning electron microscopy found that the SrAl12O19 platelets comprised one to three layers fused together along the basal planes. Zirconia grains inhibited the lateral growth of the SrAl12O19 platelets.

A technical approach to design and carry out an experiment to determine the uptake of selected radionuclides in site-specific conditions in Kuwait was developed and successfully executed for developing a radioecological decision support system. The radionuclides from soil-to-plant transfer factors have been obtained for leafy and non-leafy vegetables, and root crops cultivated in Kuwait. Two types of vegetated soils were selected and spiked with high concentrations of three relatively short-lived selected radionuclides (85Sr, 134Cs, and 133Ba). The highest strontium and barium transfer factors were found in the order: leafy vegetables > root crops > non-leafy vegetables. The approximate range of radiocesium transfer factor was found to be low in all plant groups and was comparable to those reported elsewhere in different soil types of temperate and tropical environments. A strong negative correlation between the obtained transfer factors and the distribution coefficient of the radionuclide in soil was found. It is recommended to adopt the newly derived parameters for the sensitive areas in Kuwait and other Gulf countries instead of using the generic parameters, whenever dose calculation codes are used. This will help to more accurately assess and predict the end results of the committed effective dose equivalent through ingestion pathway.

The chitosan chains were integrated with MCM-48 mesoporous silica in an eco-friendly composite (CH/MCM-48) of enhanced adsorption capacity. The prepared CH/MCM-48 composite was applied in systematic retention of U (VI) as well as Sr (II) ions from water as the commonly detected radioactive pollutants. It displayed promising retention capacities of 261.3 mg/g and 328.6 mg/g for U (VI) and Sr (II) considering the equilibrium time interval that was identified after 420 min. The composite showed the kinetic behavior of the Pseudo-First order model and the isotherm properties of the Langmuir assumption. The thermodynamic assessment of the reactions validated the retention of both U (VI) and Sr (II) ions by spontaneous, favorable, and exothermic reactions. Based on the theoretical values of entropy (−5.94 kJ mol−1 (U (VI)) and −2.93 kJ mol−1 (Sr (II))), Gibbs free energy (less than 20 kJ mol−1), and Gaussian energy (5.77 kJ mol−1 (U (VI)) and 4.56 kJ mol−1 (Sr (II))) the uptake processes are related to physical adsorption reactions. The CH/MCM-48 composite is of significant recyclability and showed considerable affinities for the studied radioactive ions even in the presence of other metal ions (Cd (II), Pb (II), Zn (II), and Co (II)).

Sr segregation is one of the key issues affecting the performance and durability of lanthanum strontium cobalt ferrite electrode (LSCF) for solid oxide cells (SOCs). In this study, we investigated the Sr segregation behavior in LSCF under compression with purpose of simulating the operating condition of LSCF electrode in an assembled SOC stack. The electrochemical performance of LSCF electrode in a symmetric cell was evaluated by impedance spectrometry. The Sr segregation behavior on the surface of LSCF electrodes was investigated by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). It was confirmed that the compression load would suppress the formation of SrO on the surface of LSCF during long-term holding in air at 800 °C, resulting in significantly improved durability compared with the LSCF electrode without compression. Furthermore, it was revealed that the type of materials (YSZ, GDC and Pt) in contact with LSCF would also affect the Sr segregation in LSCF. In particular, contacting with YSZ under compression would induce more SrO formation on the surface of LSCF than GDC and Pt.

The detailed investigation of the influence of strontium on the methane activation over the state-of-the-art proton-conducting oxide catalyst La1−xSrxScO3−α was carried out using a combination of the novel H/D isotopic exchange method, Raman Spectroscopy, 1H NMR and DFT studies in the temperature range 673 – 973 K, at 10 mbar of CH4 + H2 (95%+5%) mixture. It was found that methane activation occurs via the four parallel channels of the hydrogen adsorption and incorporation mechanism, followed by the formation of methane intermediates with different hydrogen content (CHx species). The dominant type of adsorbed intermediate is governed by the temperature and the surface defect structure, which is in close correlation with the strontium content. The increase of strontium content in La1−xSrxScO3−α drastically increases the catalytic activity due to the surface modification with oxygen deficiencies in the ScO6 octahedron, and stabilisation of the CHx species with a low amount of hydrogen.

Strontium-substituted hydroxyapatite (SrHAp) materials are known to actively promote bone formation. However, the optimum level of Sr inclusion needed to elicit a physiologically relevant response from bone cells is unclear and can vary dependent on the fabrication process employed. In this work hydroxyapatite (HAp), SrHAp powders (2, 5 and 10 wt% (i.e., 1, 2 and 5 at%) with respect to [Sr/(Sr + Ca) ∙100]), were synthesized with the purity and Sr-substitution was confined in the range of 1–8 wt% (1–4 at%). All SrHAp samples contained rod-like crystals ( 300 nm in length). TEM-EDX confirmed the presence of Sr and maintenance of the HAp lattice structure for both types of crystals. Qualitative in vitro evaluation using primary human ostesoblast cells (HOBC) cultured in contact with the SrHAp over 28 days showed that the presence of Sr (in particular with the highest Sr content) directly promotes the maturation of osteoblasts into osteocytes as compared to the response observed for HAp. As these materials contain no additives other than Sr, the effects observed here can only be attributed to the physiologically important levels of Sr in the samples.

The applicability of barium for oil drilling purposes cannot but be emphasized. This research investigated the purification of Kiana barite ore using indirect flotation at varied conditions. Five kilograms (5 Kg) of the sourced sample was crushed, ground to about 1 mm, homogenized, and then randomly sampled for chemical, and mineralogical analysis by ED-XRF, SEM-EDS and XRD. The crushed sample was ground further and reduced to five particle sizes; 90, 125, 180, 250, and 300 µm, the size fractions were then charged successively into the flotation cell, mix with water at a ratio of 1:5 to form slurry, and conditioned by adding the necessary flotation reagents (corn starch, corn oil, Oleic Acid) while varying the pH values 5, 7 and 9. The resulting products were dewatered, chemically analysed, and their specific gravities were evaluated using the relative density method. From the results obtained, that Kiana barite contains predominantly 71.86% BaO, 19.3% SO3 and 4.9% SiO2 alongside other constituents. SEM-EDS and XRD results show that Kiana deposit is rich in Barium strontium sulphate and silica. It was observed that floating the ore at feed size of 300 µm and pH 7 gave the optimum concentrate assay (72.96% BaO), also the specific gravity was evaluated as 5.0. This concentrate shows high promise for oil drilling purposes, though further beneficiation using other techniques is proposed.

Strontium hexaferrite (M−type) nanoceramic is synthesized using citrate precursor sol–gel process. The Intensity of the X-ray diffraction pattern confirms that the prepared nanomaterial i.e. SrFe12O19 is in pure phase along with the presence of some impurity at annealing temperature 850 °C, which got eliminated by enhancement of 950 °C annealing temperature. The XRD measurement shows SrFe12O19 possesses a hexagonal crystal structure having space group P6/MMC. For estimating crystallite size, we used the W-H plot and found it to be 56.825 nm and 67.366 nm for 850 °Cand 950 °C, temperature respectively. Increasing annealing temperature results in an increment in grain size and lattice parameters due to induced strain, a gradual decrease in broadening of XRD peak is observed. SEM measurement supports the XRD results and indicates that the sample possesses some agglomeration, which may be due to enhancement in annealing temperature and interparticle interaction. FTIR was used for estimating force constant, bond length, and functional group present in the prepared materials. Force constant increases while bond length decreases with the increased annealing temperature. The elastic property evaluated seems to reduce by enhancement of the increasing value of annealing temperature for strontium hexaferrite sample. The Increasing Value of annealing temperature leads to a reduction in polarization value with the broadening of multiferroic loops suggesting a noticeable reduction in electrical leakage.

Dual-functional regulation for angiogenesis and osteogenesis is crucial for desired bone regeneration especially in large-sized bone defects. Exosomes have been demonstrated to facilitate bone regeneration through enhanced osteogenesis and angiogenesis. Moreover, functional stimulation to mesenchymal stromal cells (MSCs) was reported to further boost the pro-angiogenic ability of exosomes secreted. However, whether the stimulation by bioactive trace elements of biomaterials could enhance pro-angiogenic capability of bone marrow stromal cells (BMSCs)-derived exosomes and consequently promote in vivo vascularized bone regeneration has not been investigated. In this study, strontium-substituted calcium silicate (Sr-CS) was chosen and the biological function of BMSCs-derived exosomes after Sr-CS stimulation (Sr-CS-Exo) was systemically investigated. The results showed that Sr-CS-Exo could significantly promote in vitro angiogenesis of human umbilical vein endothelial cells (HUVECs), which might be attributed to elevated pro-angiogenic miR-146a cargos and inhibition of Smad4 and NF2 proteins. Moreover, the in vivo study confirmed that Sr-CS-Exo possessed superior pro-angiogenic ability, which contributed to the accelerated developmental vascularization in zebrafish along with the neovascularization and bone regeneration in rat distal femur defects. Our findings may provide new insights into the mechanisms underlying Sr-containing biomaterials-induced angiogenesis, and for the first time, proposed that Sr-CS-Exo may serve as the candidate engineered-exosomes with dual-functional regulation for angiogenesis and osteogenesis in vascularized bone regeneration.

Preservation of tooth structure by remineralisation of affected dentin can contribute greatly to the concept of minimal invasive dentistry. Remineralisation of dentin is a challenge due to the absence of seeding crystals. Biomimetic remineralising approach aids in restoring demineralised dentin close to that of normal dentin with the use of non-collagenous protein (NCP) analogues that stabilize the mineral phase of dentin resulting in intrafibrillar remineralisation. This study was done to assess the effect of a remineralising paste containing strontium doped nanohydroxyapatite (Sr-nHAp) with non-collagenous protein (NCP) analogue chitosan on the characteristics of partially demineralised dentin. Experimental pastes were formulated using 10 & 20% Strontium doped nano-hydroxyapatite (nHAp) with or without NCP analogue-chitosan. After characterization by x-ray diffraction, its remineralising efficacy on partially demineralised dentin was assessed through SEM-EDS analysis and nanoindentation and compared to that of demineralised and normal dentin. It was observed that 20% Sr-nHAp paste and the experimental formulations with Sr-nHAp and NCP analogue chitosan had the potential to remineralise the partially demineralised dentin specimens as observed by both increase in the mineral content noted in the SEM-EDS analysis and increased mechanical properties analysed by nanoindentation. Within the limitations of the study it was observed that Chitosan enhanced remineralisation potential of 10 & 20% Sr-nHAP and improved mechanical properties of partially demineralised dentin and hence has potential application as a remineralising agent and in vital pulp therapy procedures.

Strontium(Sr2+) and zinc(Zn2+) co-substituted nanobiphasic fluorohydroxyapatite (Ca10-x-ySrxZny(PO4)6F0.5OH1.5), [x = 5–40 mol% of Sr2+ and y = 5–20 mol% of Zn2+] improved osteoblastic cell response and is investigated in the present study. The structure, phase, thermal studies, morphology and composition were analysed by XRD, TG/DTA/DSC, FESEM and EDAX. The osteoblast cell response was analysed using MG-63 human osteosarcoma cells. The XRD pattern confirmed the presence of the β-TCP phase in nano-Sr/Zn-FHA which induces dissolution of Sr2+, Zn2+ and Ca2+ ions. The β-phase has influence on the osteoblasts for steady and sustained bone formation. The samples 40Sr/10Zn-FHA and 40Sr/5Zn-FHA exhibited sustained cell viability and alkaline phosphatase activity.

Strontium, a popular osteogenic component, has been incorporated into various types of orthopaedic biomaterials to enhance bone regeneration. Strontium performs dual effects in promoting bone formation and inhibiting bone resorption. Previous studies have focused on the effects of strontium ions (Sr2+) in regulating stem cell behavior to initiate regenerative capacity. However, its mechanisms for regulating the fate and homeostasis of stem cells have not been fully elucidated. In this study, the promotive effect of Sr2+ on the osteogenic differentiation of mesenchymal stem cells was confirmed both in vitro and in vivo. Interestingly, in response to Sr2+ treatment, stem cells performed asymmetric cell division to balance stemness maintenance and osteogenic differentiation. In initiating osteogenic differentiation, Sr2+ maintained more cells in the cell cycle by upregulating the population of S and G2/M phase cells, and this increase in the cell population contributed to enhanced osteogenic differentiation. The divided cells with different cell fates were observed, with one daughter cell maintained stemness, while the other committed to osteogenic lineage. Further investigation revealed that Sr2+ activated noncanonical Wnt signaling to regulate the expression and distribution of the Par complex, thus regulating cell division. As a result, the daughter cells committed to different cell fates due to the discriminately activation of osteogenic transcription factors caused by asymmetrically distributed Par3 and aPKC. The results of this study could facilitate the design of biomaterials for bone regeneration by providing a better understanding of cell fate determination regulated by strontium.

Employing the standard reaction method, partially strontium substituted lanthanum nickelate Bulk La2−xSrxNiO4 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) materials have been prepared by solid-state reaction method. The gross structure and phase purity of La2−xSrxNiO4 materials were examined by powder X-ray diffraction (XRD) technique. The X-ray diffraction patterns indicate that the structure phase of La2−xSrxNiO4 does not change by the addition of strontium up to x = 0.5. The XRD results show the formation of single tetragonal phase. The average crystallite/grain sizes of the La2−xSrxNiO4 samples were calculated by using Debye-Scherer formula. The magnetic measurement was observed by (M−H) curve, the surface morphology/topography of as-synthesized materials (pellets) was determined by Atomic Force Microscope (AFM) Field Emission Scanning Electron Microscope (FESEM) and Transmission Electron Microscopic analysis (TEM). The AFM and FESEM micrographs show many porous which closely packed themselves. These micrographs also reveal that the increase the strontium concentration in the materials, the grain size of La2−xSrxNiO4 also increases.

Functional and morphological characterization of wood charcoal/periwinkle shell (WC/PWS) particles hybrid reinforced polyester matrix composites was successfully developed. Characterization tools such as energy dispersive x-ray spectrophotometer (EDXRF), Fourier transform infrared spectrometer (FTIR) and scanning electron microscope (SEM) coupled with EDS elemental detector were used to examine the composites developed. The EDXRF identified iron, copper, zinc, calcium and CaO, Fe2O3, CuO, ZnO as primary elements and oxide constituents of WC. Also, calcium, strontium, iron and CaO, SrO, Fe2O3 and Al2O3 as the basic elements and oxides contents of PWS. It is evident that these elements and oxides constituents influenced significantly the mechanical properties of reinforced polymer composites. The EDS mapping also confirmed the major elements identified by EDXRF analysis. Hybrid composites reinforced with 75/25 and 50/50 WC/PWS ratio show stronger interfacial bonding and interlocking due to even dispersion of the filler particles revealed by SEM images. The functional assessment revealed minor shifts in the frequency bands of functional groups present in the unreinforced polyester matrix largely due to interactions of the hybrid fillers with the matrix.

Previously, complex perovskites barium strontium tantalate, i.e., Ba3Sr1.4T1.6O8.4 (BST40), has exhibited excellent proton conductivity due to its high basicity and oxygen vacancy concentration. Herein, we report proton conduction mechanism of BST40 using brick-layer model and defect equilibria model. Briefly, BST40 is prepared by solid-state synthesis method, resulting in hexagonal perovskite structure with space group of P63/m. Interestingly, grain interior and grain boundary thickness of BST40 are almost equal and the grain boundary conduction mainly dominates the conductivity at T > 500 °C. Total standard molar hydration enthalpy of BST40 and grain interior is found to be −79.6 kJ/mol and −101.3 kJ/mol, respectively. Activation energy for BST40, protons, oxygen-ions, and holes in oxygen-containing humid atmosphere is found to be 0.63 eV, 0.51 eV, 0.92 eV, and 1.08 eV, respectively. These values are higher than corresponding values for the grain interior. At 700 °C, proton transport number of BST40 and grain interior is found to be 0.7 and 0.72, respectively, which is significantly higher than other congeneric complex perovskite-type proton conductors. Overall, these results confirm that BST40 possesses excellent proton conductivity.

A series of M-type lanthanum substituted strontium cobalt hexaferrites, Sr0.5Co0.5LaxFe12-xO19 (x = 0.0, 0.05, 0.15 and 0.2) was synthesized using the simple heat treatment method. The synthesized hexagonal ferrites were calcinated at 950 °C and 1050 °C for 3 hrs in a muffle furnace and then slowly cooled to room temperature. X-ray diffraction (XRD) technique and magnetic hysteresis loops were used to investigate the structural and magnetic properties of prepared samples respectively. The X-ray diffraction analysis of all the samples shows the presence of M- type hexagonal ferrite and hematite phases. Room temperature magnetic hysteresis loops analysis shows the increase in saturation magnetization with the increase in lanthanum substitution.

Magnesium rare earth element (Mg-REE) alloys are actively used as bone implants in orthopedic applications due to their biocompatibility, strengthening ability and degradation rate. Pure Mg when casted has low strength and high rate of degradation. Properties of magnesium alloys can be strengthened and improved by using suitable alloying elements and processing conditions. When Magnesium, alloyed with elements like Al, Ca, Zn, Sr and rare earth elements (REE) used as reinforcing elements, gains high strength, better mechanical, metallurgical, and tribological property due to grain refinement and strong solution reinforcing mechanisms of the alloyed elements. This helps in developing Mg-REE alloy, which is a promising substitute for permanent bone implants due to biodegradability in the physiological environment i.e. inside the human body. In this research work using gravity casting process, by varying the elemental composition of Gadolinium (Gd) in Mg-2Sr, Mg-REE alloy of Mg-2Sr, Mg-2Sr-2Gd, Mg-2Sr-4Gd, Mg-2Sr-8Gd, Magnesium – Strontium – Gadolinium REE alloy is casted using gravity casting method and the tribological properties like wear rate, wear resistance, and coefficient of friction of Mg-REE alloy are investigated.

Quantitative profiles of stable isotopes and trace elements in biogenic carbonates have received considerable attention for the purpose of reconstructing past temperatures. The relationships between temperature and the geochemical parameters of carbonates are often subject to both inter- and intraspecific variations, which critically impair the accuracy of temperature estimation. One of the issues that must be addressed to improve temperature estimation is enhancing our understanding of the influence of the kinetic effect. This effect matters because the purely thermodynamic effect to geochemical profiles cannot be effectively separated from the effect of temperature-driven calcification rate. Cowries (Mollusca, Gastropoda, Cypraeidae) may provide a good model system for quantitatively investigating these two effects, because they undergo a callus-building stage in which aragonitic shell formation exclusively occurs to monotonically increase the thickness outward. We reared a total of 230 juvenile individuals of Monetaria annulus under six constant thermal regimes, ranging from the minimum growing temperature (21 °C) to the maximum tolerated long-term temperature (34 °C). The portions of the shells built in the callus-building stage were analyzed to quantify isotopic and elemental compositions. Shell growth rate positively depended on temperature from 21 °C to 33 °C, but dramatically decreased at 34 °C, presumably because of high temperature stress. Nevertheless, the heat stress did not make any impact on the thermal dependences (and among-individual variabilities within the same temperature) of either δ18Oc or Sr/Ca. A linear relationship exists between temperature and the stable oxygen isotope value of the shells (δ18Oc) across the entire thermal range (n = 103), whereas the shell Sr/Ca ratio increased exponentially with increasing temperature (n = 227). These results strongly suggest that any chemical processes responsible for quantitative incorporation of 18O and Sr into aragonite crystals were not impacted by heat stress at temperatures up to 34 °C. Within-temperature residual correlations between shell growth rates and δ18Oc were weakly positive, which is compatible with a widely accepted hypothesis that carbonic anhydrase suppresses the kinetic effect in molluscs. Likewise, we found no association between shell growth rates and Sr/Ca, which rejected the possibility that faster CaCO3 precipitation caused the positive relationship between temperature and Sr/Ca. A large proportion of among-individual variability in shell Sr/Ca was caused by unspecified factors other than temperature. This makes it difficult to accurately estimate the past temperature by measuring the Sr/Ca value of a single shell specimen.

The equilibrium partition coefficient of strontium ( K Sr eq ) between aqueous solutions and calcite is still poorly known, even though it is a valuable parameter for studies involving the use of calcite trace element geochemistry for reconstructing paleoenvironments and fluid chemistry. In this paper we use pore fluid data from deep sea carbonate sediments to constrain K Sr eq at low temperature (5–17 °C) and show that the derived values are consistent with laboratory calcite precipitation experiments at 25 °C when the latter are corrected for kinetic effects. Using these low-temperature values, and experimental data available at higher temperature based on replacement reactions, we show that all of the data can be accounted for by a single formulation based on the thermodynamics of the relevant components of seawater-like fluids and the SrCO3–CaCO3 solid solution. The value of pore fluid data is that the fluids and carbonate sediment have been in contact for millions of years so local equilibrium is approached, the overall system can be treated with one-dimensional models, and the temperature is constrained. These natural systems provide an opportunity to investigate low-temperature equilibrium in the carbonate system that is difficult to probe in the laboratory because of sluggish exchange kinetics. We estimate values of K Sr eq using measured Sr and Ca concentrations in pore fluid and sediment solid calcite and a numerical model of sediment deposition, reaction and transport. The model is used to fit the Sr, Ca, and sulfate concentrations observed in pore fluids of several calcite-dominated sites that we believe are optimal for understanding Sr partitioning. Combining the pore fluid results with experimental measurements at higher temperature results in the following expression which applies for the temperature range 0–200 °C: K S r eq T = 0.025 exp Δ G r , 0 R 1 298.15 - 1 T where ΔGr,0 is the free energy change associated with the exchange reaction and temperature is in Kelvin. The uncertainty is approximately ±20%. Recently summarized thermodynamic data yield ΔGr,0 = 1.2 kcal/mol (5.0 kJ/mol) which fits well the lower limit of the high temperature data. The corresponding activity coefficient for the SrCO3 component in the calcite crystal structure is 5.4 for the lower value of ΔGr,0, and 3.17 for the higher value. The derived low-temperature values of K Sr eq of 0.020 to 0.025 (for 0 °C to 25 °C) have implications for models of marine carbonate diagenesis, and the interpretation of vein carbonate Sr/Ca in oceanic crust. Published data showing much higher KSr values in Mg-bearing solutions are not representative of equilibrium values for either Mg or Sr.

Among hybrid energy storage devices, supercapattery gained profound research interest due to its ability to give high energy density while maintaining the power density and cyclic stability. Herein, novel low-cost strontium based materials are synthesized by controlled sonochemical method and subsequently calcined at various temperatures. The multiple phases of the material synergistically contributed in the electrochemical charge storage process and give high specific capacity of 220 C g−1 (as-prepared material) and 213 C g−1 (calcined at 200 °C) at 0.5 A g−1. A thorough electrochemical performance of optimized material is investigated as an electrode in asymmetric device. The supercapattery (SP2//AC) exhibits a specific capacity of 103.4 C g−1 at 0.5 A g−1 in the voltage range of 0–1.7 V. Furthermore, supercapattery offers a considerably high specific energy of 24.4 Wh kg−1 at a specific power of 425 W kg−1 and an excellent specific power of 1870 W kg−1 by maintaining specific energy at 14.5 Wh kg−1. In addition, the device retained its specific capacity to 90% after 3000 charging/discharging cycles at 1 A g−1. Strontium based materials could be proposed as an appropriate electrode material for energy storage systems.

This study was conducted to evaluate the bone regeneration effects of collagen/strontium-doped Bioglass (BG-Sr) scaffolds. The present study comprised four parts including designing and fabricating scaffolds, characterization tests such as biodegradation, water uptake, porosity, FTIR (Fourier transform infrared spectroscopy), and SEM (Scanning electron microscope), in vitro tests such as MTT ((3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)), alkaline phosphatase, calcium assay, Alizarin Red staining, and real-time PCR (Polymerase chain reaction), and ultimately in vivo and histopathological tests such as evaluating bone regeneration, mineralization with Hematoxylin-Eosin, Masson's trichrome and Alizarin Red staining, and histomorphometric studies 4, 8 and 12 weeks after implanting the scaffolds in the skull and femur of 36 rabbits. Significant reductions were observed in degradability, water absorption, and porosity in the BG-Sr samples. In vitro results showed that the synthetic scaffolds were less toxic, stimulated, and induced cell growth. The ALP (Alkaline phosphatase) activity was higher on day 14 than on day 7, and the highest calcium content was observed in the BG-Sr samples on day 14. In line with the SEM and MTT results, the DAPI (Diamidino-2-phenylindole) results confirmed cell proliferation. Moreover, osteocalcin and ALP gene expression were high in the BG-Sr group. The results of the histopathological tests showed high levels of bone formation in the BG-Sr scaffolds. As a scaffold in regenerative medicine, the BG-Sr composite can be an effective product for bone regeneration.