Role Of Strontium Research Articles

The Role of Strontium as an Economic Promoter Over WO3 + ZrO2 Supported Ni Catalyst for H2 Production Through Dry Reforming of Methane

The Role of Strontium as an Economic Promoter Over WO3 + ZrO2 Supported Ni Catalyst for H2 Production Through Dry Reforming of Methane

Role of Strontium on Sensitization and Unusual Passivation Behavior of a 5xxx Series Aluminum Alloy Containing a Trace Amount of Chromium

This paper reports the beneficial effects of strontium (Sr) on the sensitization kinetics and an unusually high passivation behavior in Al-5.7 wt% Mg alloy. The presence of strontium has aided not only in retarding the sensitization kinetics of Al-5.7 wt% Mg alloy but also significantly enhanced the intergranular corrosion resistance. The surface enrichment of Cr and Sr as oxides and hydroxides has caused an unusual increase in the passivity and pitting potential of Al-5.7 wt% Mg alloy. The presence of both Cr and Sr helped in retaining the passivity of the alloy even in the sensitized condition.

The role of strontium on the enhancement of photocatalytic response of TiO2 nanotubes – application in methylene blue and formic acid photodegradation under visible light and UV-A

The influence of ferroelectric strontium nanoparticles on the photocatalytic performance of 1 D TiO2 nanotubes (NT) was herein highlighted. The effect of adding various amounts of Sr nanoparticles onto NTs was therefore deeply characterized by means of Raman, UV-vis diffuse reflectance, photoluminescence (PL) and X-ray photoelectron spectroscopies, X-ray diffraction, N2 adsorption-desorption measurements and scanning electron microscopy coupled with energy-dispersive X-ray analysis as well as determining dielectric properties. The different xwt%Sr-NTs with x =(0.2, 0.4, 0.6, 0.8 and 1 wt%) were investigated for the photodegradation of Methylene Blue (MB) under visible light and formic acid under UV-A. Results emphasize that the kinetic study fits well with Langmuir-Hinshelwood (LH) model; for the same surface coverage (θ =0.99), the rate constant kLH increases versus Sr loading with an optimum at 0.8 wt% Sr. Under UV-A light, photodegradation increases versus Sr loading. As evidenced by PL, impedance and XPS measurements, the presence of ferroelectric strontium generates structural defects (Ti3+ and Ov) with strong opportunity to monitor the separation the photogenerated (electron- hole) pairs regardless of the synthesis limitations. Herein, the molar ratio O2-/Ti4+ increases vs strontium loading. Hence, Sr-NTs opens new route for “assisted” photocatalysts.

3D-bulk to nanoforms of modified hydroxyapatite: Characterization and osteogenic potency in an in vitro 3D bone model system.

Synthetic bioceramics are replacing conventional methods of treating bone defects with autografts owing to the high demand of bone substitutes, with their Surface topography and size contributing to favor cytocompatibility in tissue regeneration. This experimental study deals with the comparative evaluation of the physical characterizations of four different in-house synthesized bioceramics from 3D-bulk to nanoforms of hydroxyapatite (HA), Biphasic calcium phosphate (BCP), Strontium doped hydroxyapatite (SrHA) and Silica coated hydroxyapatite (HASi) and also simultaneously evaluates adhesion, proliferation and osteogenic differentiation of rabbit adipose derived mesenchymal stem cells (RADMSCs) on these biomimetic ceramic niches. The osteogenic induced cells grown on 3D scaffolds for a period of 7, 14, 21, and 28 days were analyzed for their viability (MTT, LDH, live-dead assays), morphology (SEM), proliferation (Cytox-Red) and osteogenic differentiation (ALP, osteocalcin expression). Cellular activities and differentiation of RADMSCs were significantly higher on SrHA indicating the role of strontium in the differentiation of mesenchymal stem cells on this ceramic platform to the bone lineage. In order to reinforce the materials for hard tissue implantation and drug delivery, nano-SrHA (nSrHA) became the nanoparticle of choice based on its non-toxicity, cytocompatibility and osteogenic properties (nSrHA > nHASi > nBCP > nHA).

A Facile Approach for the Synthesis of SrTiO3/g‐C3N4 Photo‐catalyst and its Efficacy in Biodiesel Production

AbstractVisible light active photocatalysts have attracted a lot of interest due to their simple chemical workup and recyclability. In this study, the role of Strontium Titanate/graphitic Carbon Nitride composite (SrTiO3/g‐C3N4) was investigated for the pretreatment of waste frying oil (WFO) to reduce high free fatty acids (FFAs) for biodiesel production. SrTiO3/g‐C3N4 photo‐catalyst was synthesized through the facile refluxing method and its activity was also compared with simple graphitic carbon nitride (g‐C3N4). Experimental results revealed that SrTiO3/g‐C3N4 possesses higher efficiency as compared to g‐C3N4. Photo‐catalyst was characterized through SEM‐EDX, XRD and FT‐IR. Maximum conversion of FFAs (85 %) was achieved at 1 % catalyst dose, 800 rpm stirring speed, 3 : 1 methanol to oil ratio, and 4 hours of reaction time. Esterified WFO was converted to waste frying oil methyl esters (WFOME) by using CaO‐KOH heterogeneous catalyst. The maximum yield of WFOME was obtained at 1.25 % catalyst dose, 65 °C, 600 rpm, 2 h of reaction time, and 12 : 1 methanol to oil ratio. Physicochemical analysis of WFOME revealed that it is in accord with ASTM standards.

The Influence of Strontium on Bone Tissue Metabolism and Its Application in Osteoporosis Treatment.

Osteoporosis is a chronic disease characterized by low bone mass caused by increased bone turnover and impaired bone microarchitecture. In treatment, we use antiresorptive or anabolic drugs, which usually have a unidirectional effect, i.e., they inhibit the activity of osteoclasts or stimulate the effect of osteoblasts. Strontium ranelate is an anti-osteoporosis drug with a unique mechanism of action (used primarily in postmenopausal women). Unlike other medicines, it has a multidirectional effect on bone tissue, intensifying osteoblastogenesis while inhibiting osteoclastogenesis. It turns out that this effect is demonstrated by strontium ions, an element showing physical and chemical similarity to calcium, the basic element that builds the mineral fraction of bone. As a result, strontium acts through the calcium-sensing receptor (CaSR) receptor in bone tissue cells. In recent years, there has been a significant increase in interest in the introduction of strontium ions in place of calcium ions in ceramics used as bone replacement materials for the treatment of bone fractures and defects caused by osteoporosis. The aim of this study was to summarize current knowledge about the role of strontium in the treatment of osteoporosis, its effects (in various forms), and the ways in which it is administered.

Role of strontium as doping agent in LaMn0.5Ni0.5O3 for oxygen electro-catalysis

Doping is an effective way to trigger various behaviors in ceramics. LaMn0.5Ni0.5O3 perovskites with or without strontium (Sr) doping were prepared using a sol-gel process and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) gas adsorption techniques. A structural transition in the LaMn0.5Ni0.5O3 perovskite was observed upon doping, suggesting its pinning effect on the crystal structure. The SEM and BET results showed that the incorporation of Sr2+ into this oxide material markedly decreased the particle size into the nanoscale range and increased the active surface area. The oxide electrocatalytic properties toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in an alkaline medium were measured using a rotating disk electrode. The results revealed that La0.8Sr0.2Ni0.5Mn0.5O3 is a more active catalyst than LaNi0.5Mn0.5O3 for the ORR and OER. The improved electrocatalytic performance of the Sr-doped oxide is related to the increase in ORR/OER current density and the positive shift in the ORR onset potential compared with that of the LaNi0.5Mn0.5O3 catalyst. The overall electron transfer number was measured as approximately 4. The basis of this enhanced performance is discussed in terms of the material electronic structure and morphology.

Plasma Strontium and Interactions between Calcium and Strontium for Type 2 Diabetes—A Hospital-Based Case-Control Study

Objective: Strontium and calcium play an essential role in bone metabolism but a paucity of epidemiological or experimental studies referring the role of strontium in the development type 2 diabetes (T2D). Prior studies have reported conflicting results for the relationships between plasma strontium and T2D. We therefore investigated the association between plasma strontium as well as the ratio of calcium to strontium (Ca/Sr) and newly diagnosed T2D. Methods: After propensity score matching for age and sex, 2,5newly-diagnosed T2D patients and 2,5controls with normal glucose tolerance were recruited in the case-control study. Plasma strontium and calcium levels were determined by inductively coupled plasma mass spectrometry (ICP-MS). Multivariate logistic regression analysis was used to evaluate the independent association of plasma strontium levels and Ca/Sr values with the likelihood of T2D. Results: Compared with the middle quintile, the multivariate-adjusted odds ratios (ORs) and 95% confidence intervals of T2D associated with the lowest quintile and the highest quintile of plasma strontium were 2.01 (1.66, 2.44) and 2.01 (1.65, 2.44), of plasma Ca/Sr were 2.11 (1.75, 2.54) and 2.01 (1.66, 2.43), respectively. In spline analysis, the U-shaped associations were consistently indicated, with the lowest odds of T2D at the plasma strontium concentration of 42.52 μg/L, and Ca/Sr value of 1500 approximately. We also discovered the pattern of high plasma calcium and low strontium level was associated with the highest odds of T2D, while the pattern of high plasma calcium and moderate to high strontium level was associated with the lowest odds of T2D. Conclusions: Our results suggested U-shaped associations between plasma strontium, Ca/Sr and T2D; both low and high levels of plasma strontium and Ca/Sr were associated with higher odds of newly diagnosed T2D. We should not only pay attention to calcium, but also to strontium and the homeostasis of the both. Disclosure L. Chen: None. Q. Wang: None. X. Hu: None. X. Wang: None. T. Sun: None. W. Bao: None. L. Liu: None.

Strontium, a new marker of the origin of gypsum in cultural heritage?

A new possible methodology for recognizing the nature of gypsum in artworks, in particular for wall paintings, was developed. Calcium sulfate can be an alteration product of the calcium carbonate, or a component used by the Artist himself; the problem of identification of the presence and the nature of gypsum could be found detecting the presence of strontium. This element could be used as a marker since, differently from the alteration form, in mineral gypsum simultaneous presence of calcium and strontium occurs. The correlation between these two elements may be recognized using non-invasive in situ X-ray fluorescence measurements. In the present work, we tested this occurrence in various mineral samples of gypsum and alabaster as well in tempera, fresco and Egyptian paintings. Considering the new possible role of strontium indicating the presence of natural gypsum, we expect to provide a valuable tool for conservation scientists, restorers and art historians.

Strontium and caries: a long and complicated relationship

Investigations into the role of strontium (Sr) in caries prevention have attracted great interest in the research community in the past, with their peak in the 1970-80s. To this date, no clear indication of the relative importance of Sr in caries prevention has been provided. A vast number of animal caries, epidemiological and mechanistic studies have been conducted. Although there is much discrepancy, the majority of studies suggest that Sr exhibits some cariostatic properties, predominantly in the presence of fluoride. An optimum Sr concentration of 5-10 ppm in drinking water has been proposed as a direct result of several epidemiological caries studies. Despite these results, no direct link can be established between Sr and caries prevention as, to date, no relevant, randomized controlled trials have been reported. The extrapolation of potential cariostatic properties of Sr from epidemiological studies is difficult due to the co-presence of several other trace elements in the water of the study areas, with many of these elements being attributed cariostatic properties in their own right. Furthermore, the role of caries risk factors was not taken into consideration. There is a clear need for further research, especially on the mineral phases in the dental hard tissues, plaque and plaque fluid associated with Sr as these may give rise to a better understanding of this subject matter. Based on the current data, the cariostatic properties of Sr, or at least those proposed by some authors, cannot be supported.

The role of strontium and potassium on crystallization and bioactivity of Na 2O–CaO–P 2O 5–SiO 2 glasses

The effect of SrO/CaO and K 2O/Na 2O replacements on the crystallization process of glasses based on Na 2O–CaO–P 2O 5–SiO 2 system was investigated. The glasses were thermally treated through controlled heat treatment regimes to obtain glass ceramic materials. Combeite Na 2Ca 2Si 3O 9, sodium calcium silicate Na 2Ca 3Si 6O 16, wollastonite solid solution, and whitlockite Ca 3(PO 4) 2 were identified as major crystalline phases in the prepared thermally treated glasses. No potassium and strontium-containing phases could be detected in the glass–ceramics; potassium seems to be accommodated in the wollastonite structure, while strontium might be incorporated in the sodium calcium silicate structure. The surface reactivity of the prepared glass–ceramic specimens was also studied in vitro in Kokobo's simulated body fluid (SBF). EDAX, SEM, inductively coupled plasma ICP, and FTIR were used to examine the formation of apatite layer's surface and characterize the glass ceramic surface and SBF compositional changes. A decrease in the bioactivity of the glass ceramic was observed as Na 2O was replaced by K 2O. Strontium together with calcium ions in the apatite layer formed was detected with SrO/CaO replacement. The role played by the glass oxide constituents in determining the crystallization and bioactivity behaviour of the prepared thermally treated glasses was discussed.

Role of Strontium on the Crystallization of Calcium Hydrogen Phosphate Dihydrate (CHPD)

Calcium hydrogen phosphate dihydrate (CHPD, CaHPO 4· 2H2O) or brushite is found quite frequently in urinary calculi (stones) . Crystallization of brushite has been carried out in sodium metasilicate (SMS) gel with and without adding ‘Sr’ as additive. In pure system, dicalcium phosphate anhydrous (DCPA, CaHPO 4) or monetite and hydroxyapatite (HA, Ca 5(PO 4)3(OH)) grew along with brushite. The presence of Sr suppressed the formation of HA and enhanced the number and size of monetite crystals and changed the morphology of brushite crystals from needle shape to octopus-like shape. The samples were characterized by powder & single crystal X-ray diffraction (XRD), scanning electron microscopy (SEM), Xray fluorescence spectroscopy (XRF), Fourier transform infrared spectroscopy (FTIR) and thermal analyses (TG-DTA) .

Phase transition of Sr on Si (0 0 1): First principles prediction and experiment

The ability to understand and predict the phase diagrams of surface phases from first principles can be valuable for developing processes for growth of epitaxial structures. In the growth of epitaxial oxides on Si (0 0 1), a submonolayer phase of Sr plays a key role. The physical structure for this phase, which has 2 × 3 symmetry and occurs at 1/6 monolayer Sr coverage, was recently elucidated using both first principles theory and diffraction experiments [J.W. Reiner, K.F. Garrity, F.J. Walker, S. Ismail-Beigi, C.H. Ahn, Role of strontium in oxide epitaxy on silicon (0 0 1), Phys. Rev. Lett. 101 (10) (2008) 105503.]. Our approach to understanding the broader Sr/Si phase diagram combines density functional theory with a thermodynamic analysis of the phase equilibrium between a Sr lattice gas and the 2 × 3 structure. We use reflection high energy electron diffraction (RHEED) to experimentally determine the phase diagram, finding good agreement with theoretical predictions.

The role of strontium in the formation of unoccupied electronic states in SrTiO3 investigated by electron energy loss spectroscopy

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The Effect of Strontium on Embryonic Calcification of Aplysia californica.

During embryogenesis of the marine opisthobranch gastropod Aplysia californica Cooper, 1863, there is a brief critical time (window) during which strontium is essential for the onset of calcification. The present study was undertaken to elucidate the role of this element in mineralization. Strontium performed no structural function; deformed shells of strontium-deprived animals had normal atomic crystal structure and the element was excluded during calcification. Calcium deposition and fixation was reduced by approximately 80% in the absence of strontium but was not significantly altered in the presence of sub-optimal concentrations of this metal ion despite dramatic deficits in shell and statolith morphology. This suggests that calcium deficiency per se is not responsible for deficits induced by strontium deprivation. The reduced total calcium may be a secondary effect resulting from the complete inhibition of precipitation. Strontium did not modulate total alkaline phosphatase activity or total sulfated mucopolysaccharide synthesis during embryogenesis, and no morphological abnormalities of the organic shell were observed. Although the role of strontium in embryonic calcification of Aplysia californica remains enigmatic, these data suggest that strontium affects a highly discrete regulatory component because these more general indicators of calcification and differentiation are unaffected by its absence.

The role of strontium in the densification of Sr-zeolite-A to the low dielectric ceramic, anorthite

Analysis, using x-ray diffraction and Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS), of the reconstructive transition from strontium exchanged zeolite type-A through amorphous intermediates to Sr-anorthite has shown that, although long range order is lost, the environment around strontium remains essentially intact. EXAFS allows us to follow the mechanism of the solid state reaction which is dictated by the coordination requirements of strontium.

Strontium is required for statolith development and thus normal swimming behaviour of hatchling cephalopods.

When cephalopod eggs were incubated in artificial sea water it was found that they sometimes resulted in hatchlings with defects of the statocyst suprastructure, leading to the severe behavioural defect of uncontrolled swimming. Experiments in defined media (seven basic salts mixed in deionized water) with seven species of cephalopods demonstrated clearly that there is 100% normal development of the aragonite statoliths when strontium levels were 8 mg l-1. Conversely, statoliths did not develop when strontium was absent. In cuttlefish, the growth of the cuttlebone was also affected adversely when strontium was absent. In mariculture production tanks, supplementing commercial artificial sea water with strontium to normal levels of 8 mg l-1 almost eliminated the occurrence of abnormal hatchlings. Circumstantial evidence indicates that there is a critical window in development during which strontium is required for normal development. The role of strontium in biomineralization during embryogenesis is unknown, but it appears to be important in the Mollusca.