Calcium Dissolution Research Articles

Experimental study on mix proportion optimization of anti-calcium dissolution shotcrete for tunnels based on response surface methodology

Aiming at the issue of crystallization and blockage of drainage system due to the massive calcium loss from the tunnel shotcrete, a self-designed tunnel seepage crystallization modelling system was developed. This system was produced in conjunction with the initial tunnel support shotcrete construction and drainage pipe installation, and is capable of simulating both the seepage process of groundwater in the shotcrete and the process of crystallization in the drainage pipe. Based on three different mechanisms of anti-crystallization, which include absorbing free calcium, reducing the porosity and increasing hydrophobicity, antialkali agent, nano-calcium carbonate, and silane were selected to test, respectively. Firstly, the suitable dosing ranges of these three external admixtures for resisting calcium loss in shotcrete were determined by single factor tests, which were 7%–11%, 4%–8%, and 0.3%–0.5%, respectively. Thereafter, the response surface method was employed to evaluate the interaction of antialkali agent, nano-calcium carbonate and silane on calcium loss in shotcrete, and to establish the relationship between them, and thus to determine the admixture ratio that can effectively reduce calcium loss crystallization in shotcrete, with the optimal admixture amounts of antialkali agent being 9.242%, nano-calcium carbonate 4.889% and silane 0.366%. Lastly, the reliability of the model test results was verified by the microscopic analysis, and the results showed that the total amount of calcium dissolution in the optimized group could be reduced by 75% compared with the blank control group, and was basically consistent with that derived from the response surface regression model, validating the high accuracy of the buildup response surface regression model. The present study can provide some ideas and references for reducing the seepage crystallization behavior of groundwater in the initial tunnel support shotcrete.

The pathophysiology of diabetic foot: a narrative review.

An aging population and changes in dietary habits have increased the incidence of diabetes, resulting in complications such as diabetic foot ulcers (DFUs). DFUs can lead to serious disabilities, substantial reductions in patient quality of life, and high financial costs for society. By understanding the etiology and pathophysiology of DFUs, their occurrence can be prevented and managed more effectively. The pathophysiology of DFUs involves metabolic dysfunction, diabetic immunopathy, diabetic neuropathy, and angiopathy. The processes by which hyperglycemia causes peripheral nerve damage are related to adenosine triphosphate deficiency, the polyol pathway, oxidative stress, protein kinase C activity, and proinflammatory processes. In the context of hyperglycemia, the suppression of endothelial nitric oxide production leads to microcirculation atherosclerosis, heightened inflammation, and abnormal intimal growth. Diabetic neuropathy involves sensory, motor, and autonomic neuropathies. The interaction between these neuropathies forms a callus that leads to subcutaneous hemorrhage and skin ulcers. Hyperglycemia causes peripheral vascular changes that result in endothelial cell dysfunction and decreased vasodilator secretion, leading to ischemia. The interplay among these four preceding pathophysiological factors fosters the development and progression of infections in individuals with diabetes. Charcot neuroarthropathy is a chronic and progressive degenerative arthropathy characterized by heightened blood flow, increased calcium dissolution, and repeated minor trauma to insensate joints. Directly and comprehensively addressing the pathogenesis of DFUs could pave the way for the development of innovative treatment approaches with the potential to avoid the most serious complications, including major amputations.

An approach for quantifying the calcium leaching effect on service performance of concrete cutoff wall of embankment dams

Calcium leaching is one of the essential diseases of concrete impermeable structures; therefore, an effective numerical approach to quantifying the effect of calcium leaching on concrete impermeable structures is critical for evaluating the long-term service performance of the structure. To this end, a seepage and dissolution coupling model for simulating the degradation of hydraulic concrete properties is proposed in this paper by introducing performance parameter evolutionary models based on saturated–unsaturated seepage and calcium dissolution and migration theories. The model is developed in COMSOL with a staggered solution scheme, and a detailed numerical implementation method is presented. The effectiveness of the proposed method is examined by laboratory calcium leaching tests. On this basis, the model was applied to evaluate the effect of calcium leaching on the service performance of a concrete cutoff wall (CCW) of an embankment dam in Shaanxi Province, China. The results demonstrate that the proposed method can effectively reproduce the calcium leaching process of concrete, and the variation of leaching depth based on model simulations is highly consistent with the experimental results. Calcium leaching primarily occurs at the CCW’s upstream waterfront surface, bypass seepage area and the partition of adjacent soil layers where the permeability varies greatly. Under seepage dissolution, the amount of leached calcium, average porosity, diffusion coefficient and hydraulic conductivity of the CCW increased exponentially with service duration, and solid-phase calcium leaching was the underlying cause of structural performance degradation. The length of the seepage path in the CCW decreases as the service duration increases, and the hydraulic gradient within it gradually increases. Based on the allowable hydraulic gradient of CCW, the safe service life of the CCW considering the calcium leaching effect was determined to be approximately 52a.

Study on calcium dissolution behavior of manufactured sand concrete

The accelerated calcium dissolution tests of concrete with different replacement rates of manufactured sand (ρms ) and different contents of stone powder (ρsp ) were carried out using the ammonium chloride solution. The results show that the dissolution resistance of manufactured sand concrete (MSC) is higher than that of ordinary concrete, although the ρms and ρsp influence its physical and mechanical properties. When the ρms is low, the mass loss ratio and dissolution depth of MSC after dissolution both increase with the increasing ρsp . They also increase with the increasing of ρms , but the ρsp no longer influences them when the ρms is high. The ρsp corresponding to the maximum ultrasonic velocity of MSC is different for the various ρms . The addition of manufactured sand inhibits the reduction of the compressive strength after dissolution, while stone powder has no significant impact on this. Finally, the fitting model of dissolution depth and prediction model of compressive strength of MSC after dissolution are established.

The therapeutic effects of fermented milk with lactic acid bacteria from traditional Daqu on hypertensive mice

Lactic acid bacteria (LAB), a type of microorganism widely used in functional foods, has gained notable research attention in recent years. Certain strains possess the proteolytic ability to release potentially antihypertensive peptides from dairy proteins, which prompted us to explore the LAB strains from an understudied and unique ingredient, Daqu. We screened for 67 strains of LAB strains from traditional Daqu using the calcium dissolution ring method. Sixteen strains exhibiting angiotensin-converting enzyme inhibition (ACE-I) activity exceeding 50% were chosen for 16S rDNA sequencing and safety assessment. It is noteworthy that Enterococcus faecium CP640 and Lacticaseibacillus rhamnosus CP658 exhibited significant ACE-I activity, which was the result of strain fermentation in reconstituted skim milk. These 2 strains did not exhibit hemolytic activity or antibiotic resistance. They also did not produce biogenic amines and showed high survival rates in the gastrointestinal tract. Additionally, Enterococcus faecium CP640 and Lacticaseibacillus rhamnosus CP658 fermented milk exhibited a notable reduction in blood pressure levels in spontaneously hypertensive rats (SHR) compared with negative controls in SHR. Importantly, no adverse effect was observed in normal Wistar-Kyoto rats. Through the analysis of physiological, serum, and urine-related indicators, it was observed that Enterococcus faecium CP640 and Lacticaseibacillus rhamnosus CP658 have the potential to promote weight gain in SHR, alleviate excessive heart rate, improve renal function indicators, and effectively regulate blood sugar and uric acid levels in SHR. These 2 strains showed optimal properties in lowering blood pressure and have the potential to be used in functional dairy products in the future.

The leaching-deterioration properties and leaching mechanism of cement mortar under dry-wet cycles

The dry–wet cycle in cement mortar is essential for accelerating ion transport; however, it results in an increase in severity of durability damage. Leaching damage is a primary-contributing factor that reduces durability. Studies on calcium corrosion degradation of cement-based materials and its inhibition process during dry–wet cycles are lacking. In this work, the frequency of dry–wet cycles, concentration of soaking liquid, reduction of water–cement ratio, and incorporation of silica fume on the corrosion deterioration of cement mortar were studied. Using NH4Cl solution as the corrosion medium, the variation in leaching depth, calcium-ion dissolution, compressive strength, flexural strength, phase composition, and microstructure was analyzed. The results showed that calcium dissolution occurs during dry–wet cycles, hence the mechanical properties of the cement mortar declines, and pore expansion occurs. With the shortening of the dry–wet cycles, leaching damage increased and the dissolution rate gradually deviated from Fick's law. Increasing the concentration of NH4Cl solution significantly increased the leaching depth of mortar and accelerated the reduction of the compressive flexural strength. Reducing the water–cement ratio or adding a proper amount of silica fume effectively inhibited the dissolution rate of cement mortar and the deterioration of compressive strength and flexural strength. The results of this study provide a new insight and deeper understanding of the leaching-degradation properties and mechanisms of cement-based materials during dry–wet cycles. Furthermore, the results may be used for the inhibition of cement-based material dissolution during dry–wet cycles.

Erosive potential of ice tea beverages and kombuchas

Objectives Kombuchas and other tea-based beverages are often perceived as healthy products despite the lack of knowledge on their effects on oral health. This in vitro study determined the erosive potential of commercial kombuchas, and ice teas compared to cola drinks. Materials and methods The pH and fluoride content of 7 kombuchas and 18 tea drinks were measured with ion-selective electrodes. Calcium dissolution from hydroxyapatite grains was quantified by atomic absorption spectroscopy after beverage exposure. The effect of beverages on the enamel surface was visualized by scanning electron microscopy (SEM). Distilled water, and cola drinks were used as negative and positive controls. Results The kombuchas exhibited lower pH values (2.82–3.66) than the ice teas (2.94–4.86), but still higher than the cola drinks (2.48–2.54). The fluoride concentration varied between 0.05 and 0.46 ppm and for 7 beverages the concentration was below the detection limit. The calcium release for kombuchas was 198–746 mg/l, for ice teas 16.1–507 mg/l, and for cola drinks 57.7–71.9 mg/l. Twenty-two beverages had a significantly greater calcium release than the cola drinks (p = .009–.014). The surface etching of the enamel was seen in the SEM analysis after beverage exposure. Conclusions Tea-based beverages have even higher erosive potential than cola drinks. Kombuchas especially, displayed a considerable erosive potential.

Alkaline Activation of Ferrous Foundry Sand: A Look at the Effect of Activator Concentration, Liquid-Solid Ratio and Curing Temperature

In this study, ferrous foundry slag was used as a precursor for the synthesis of a geopolymer. The effect of NaOH concentration, liquid solid ratio (L/S), and curing temperature on the unconfined compressive strength (UCS) of the synthesized geopolymer was investigated. The optimum concentration was found to be 15 M as it yielded a geopolymer brick with the highest UCS of 8.2 MPa. It was observed that as the concentration of NaOH increases the dissolution of alumina, calcium and silica increases resulting in higher UCS. The SEM results showed zeolite formation in large quantities at 15 M which shows that the geopolymerization reaction was near completion and the calcium, alumina and silicates dissolved in large quantities leading to increased gelling of C-S-H and C-A-H over time filling more pores inside the geopolymer brick. The liquid to the solid ratio that gave the highest UCS of 8.2 MPa was 0.15. The optimum temperature was found to be 80 °C. This increased temperature favoured the dissolution of reactive species and contributed to higher UCS. The results reveal that ferrous foundry sand geopolymers have the potential to be used as a building and construction material.

Enhanced phosphorus fixation in red mud-amended acidic soil subjected to periodic flooding-drying and straw incorporation

Globally, red mud is a solid waste from the aluminum industry, which is rich in iron oxides. It is an effective soil amendment in agriculture that protects connected waters from legacy diffuse phosphorus (P) soil losses. However, other management practices such as flooding and drying and/or organic carbon inputs could potentially alter P fixation in these red mud-amended soils thereby releasing P to waters. The present study was designed and conducted to monitor the mobilization of P in a red mud-amended acidic soil subjected to periodic flooding-drying, straw incorporation, and a mix of both management practices. Sequential extraction and K edge X-ray absorption near-edge structure spectroscopy (k-XANES) were employed to distinguish P fractions/species and the Langmuir model was fitted to evaluate soil P sorption capacity. The content of labile P indicated by CaCl2–P was increased significantly by 101% and 28.7% in the straw incorporation and periodic flooding-drying treatments, while it decreased significantly by 22.3% in the combined periodic flooding-drying with straw incorporation treatment, compared with Control. The inherent phosphate contained in sorghum straw, and the enhanced iron (Fe) reduction and dissolution of Calcium (Ca)-bound P induced by straw addition contributed to mobilization of P in the straw incorporation treatment. In contrast, the increased poorly crystalline Al/Fe oxides-bound P and occluded Fe-bound P fraction in the combined periodic flooding-drying with straw incorporation treatment explains the decrease in CaCl2–P. Furthermore, the increased soil P sorption capacity and the decreased P desorption rate were also responsible for the reduced P loss risk in the treatment. The results of structural equation modelling (SEM) indicated that organically complexed Fe and Fe-bound P were directly affecting P mobilization in the amended soil. Overall, the present study shows that appropriate flooding-drying events coupled with straw incorporation could be a mitigation practice for stabilizing P in red mud-amended soil. However, before it can be applied on a wide scale, multi-point and field trials should be carried out to further evaluate actual environmental implications.

Water sorption on pyrochlore – Niobium hydration and calcium susceptibility to leaching unraveled by DFT simulations

Hydration of pyrochlore is a preponderant step during its flotation well before any other surface-reagent interaction to take place. Water adsorption on low-index pyrochlore surfaces is investigated by Density Functional Theory (DFT) simulation, with a focus on the mechanisms of water interaction with surface sites and their coordination. As far as the pyrochlore (100) and (111) surfaces favor the associative physisorption of water, the dissociative chemisorption of water on the (110) surface is by far the most energetically favorable. The affinity of pyrochlore surface to water increases from −81.4 (111), −102.7 (100) to −331.6 kJ/mol (110) leading to decreasing hydrophilic surfaces: (110) ≫ (100) > (111). Water adsorption on the Nb sites located on the (100) surface is unlikely due to the full-coordination state of the exposed Nb. Moreover, the dissociative adsorption of water, driven by a lack of coordination on the (110) surface, would be at the origin of the selective (or non-congruent) dissolution of pyrochlore calcium by weakening its innate bonds. These primary results on the relationship between water and the atomic topology of pyrochlore cleavage planes will help guide the choice of aqueous chemical reagents to be used to address the challenges of this mineral's flotation.

A Novel Low Molecule Peptides-calcium Chelate from Silkworm Pupae Protein Hydrolysate: Preparation, Antioxidant Activity, and Bioavailability.

The antioxidant properties of active peptides from silkworm pupae protein hydrolysate are of interest, and it serves as a novel source of calcium supplement. Optimize the preparation parameters of silkworm pupae bioactive peptide-calcium chelate, and investigate the mechanism and bioavailability of silkworm pupae active peptide as a transport carrier to promote calcium ion absorption using simulated gastrointestinal digestion and Caco-2 monolayer cell model. The optimal process parameters for preparing peptide calcium chelate were the peptide calcium mass ratio of 3:1, pH of 6.7, a temperature of 35.6°C, and time of 32.8 min by Box-Behnken design, and the calciumchelating rate reached 84.67%. The DPPH radical scavenging activity of silkworm pupae protein hydrolysatecalcium chelate was 79.36 ± 4.31%, significantly higher than silkworm pupae protein hydrolysate (61.00 ± 9.56%). Fourier transform infrared spectroscopy shows that the COO-, N-H, C-H, and C-O groups participated in the formation of silkworm pupae protein hydrolysate-calcium chelate. The particle size of the silkworm pupae protein hydrolysate-calcium chelate was 970.75 ± 30.12 nm, which was significantly higher than that of silkworm pupae protein hydrolysate (253.14 ± 5.72 nm). The silkworm pupae protein hydrolysate-calcium chelate showed a calcium dissolution rate of 71.01 ± 1.91% in the simulated intestinal phase, significantly higher than that of CaCl2 (59.34 ± 1.24%). In the Caco-2 cell monolayers, the silkworm pupae protein hydrolysatecalcium chelate was more favorable for calcium transport. A novel silkworm pupa protein hydrolysate-calcium chelate with high antioxidant activity was successfully prepared to improve the bioavailability of calcium.

Chemical Composition, but Not Specific Surface Area, Affects Calcium Retention of Nanostructured Calcium Compounds in Growing Rats

Background: Low dietary calcium intake and bioavailability may adversely affect bone health. Reducing the size of calcium compounds increases their specific surface area (SSA, expressed as m2/g) and may increase calcium dissolution and bioavailability.Objective: We investigated the influence of SSA and chemical composition on the bioavailability of calcium and compared in vitro calcium dissolution with in vivo absorption.Methods: Calcium dissolution was measured in 0.1 M phosphoric acid, whereas color and pH changes of foods were assessed as indicators for potential sensory performance. Calcium absorption, retention, and fractional retention were measured over a 5-d balance study in growing Sprague-Dawley male rats after 21 d of feeding. Femoral and vertebral bone mineral density (BMD) and extensive tissue histology were assessed at study end. The influence of SSA on calcium bioavailability was assessed by comparing the groups fed pure calcium carbonate (CaCO3) with increasing SSAs of 3, 36, and 64 m2/g (CaCO3_3, CaCO3_36 and CaCO3_64), whereas chemical composition was assessed by comparing the smallest CaCO3_64, a 50:50 wt:wt percent solution mixture of CaCO3 and hydroxyapatite_94, and pure hydroxyapatite_100.Results: In vivo, fractional calcium retention from hydroxyapatite_100 (mean ± SEM: 54.86% ± 0.95%/5 d) was significantly greater than from CaCO3_64 (49.66% ± 1.15%/5 d) (P = 0.044). Increasing SSA of the pure CaCO3 did not significantly improve calcium retention. Across all 5 groups, there were no significant differences in BMD or tissue calcification by histology. In vitro calcium dissolution did not correlate with SSA or calcium absorption. In selected food matrixes, hydroxyapatite_100 caused less color change and/or smaller pH increase than did the other calcium compounds.Conclusions: Our findings suggest that chemical composition rather than SSA is a predictor of nanostructured calcium bioavailability and that in vitro dissolution of nanostructured calcium does not predict in vivo absorption. Although its phosphorus content may limit use in some populations, nanostructured hydroxyapatite may be a promising calcium compound for food fortification.

Fuzzy logic-based health risk assessment of fluoride in groundwater used as drinking source in Sira region, Tumkur, India.

Fluoride contamination in drinking water is a serious public health concern across the world, and more than 90 million people in India are affected by health risks associated with fluoride. Though the fatality due to fluoride chronic toxicity is uncommon, the exposure to fluoride at different concentration levels shows various adverse health effects such as dental and skeletal fluorosis, multiorgan failure, cognitive and behavioural effects. Hence, the objectives of the present study are to understand the hydrogeochemistry and drinking water suitability of groundwater of the Sira region, Karnataka, India, and to understand the occurrence of fluoride and its health risks using the United State Environmental Protection Agency (US EPA) method and fuzzy logic concepts. Forty-six samples were collected from each pre and post-monsoon season. The hydrogeochemistry studied through Chadha's diagram and Gibb's diagram indicated that the groundwater in this region is of Na-Cl type and the hydrogeochemistry is majorly controlled by rock-water interaction and followed by evaporative dominance. Water quality parameters were compared with drinking water standards guidelines, and the results showed that around 50% of the samples were contaminated with fluoride. The occurrence of high levels of fluoride in the study region is associated to the presence of granitic rocks and it is influenced by high pH and low calcium dissolution in the groundwater. Based on US EPA method, the order ofpopulation group under the risk of dental and skeletal fluorosis, is children > adolescents > adults. A fuzzy inference system model is developed to assess the health risk due to fluoride and its output gives severity levels of each type of health risk, i.e. dental caries, dental fluorosis and skeletal fluorosis. The results of the application of the fuzzy inference system model in the Sira region showed that the children (< 8Yr.) are more susceptible to the moderate risk of dental caries, dental fluorosis and skeletal fluorosis. Whereas adolescents (8-18Yr.) and adults (> 18Yr.) are less susceptible to low-very low risk. Hence, health risks associated with fluoride can be better addressed with the help of a fuzzy inference system model which can be used for more reliable and grounded results to improve the quality of decision-making.

Calcium dissolution in bridgmanite in the Earth's deep mantle.

Accurate knowledge of the mineralogy is essential for understanding the lower mantle, which represents more than half of Earth's volume. CaSiO3 perovskite is believed to be the third-most-abundant mineral throughout the lower mantle, following bridgmanite and ferropericlase1-3. Here we experimentally show that the calcium solubility in bridgmanite increases steeply at about 2,300 kelvin and above 40 gigapascals to a level sufficient for a complete dissolution of all CaSiO3 component in pyrolite into bridgmanite, resulting in the disappearance of CaSiO3 perovskite at depths greater than about 1,800 kilometres along the geotherm4,5. Hence we propose a change from a two-perovskite domain (TPD; bridgmanite plus CaSiO3 perovskite) at the shallower lower mantle to a single-perovskite domain (SPD; calcium-rich bridgmanite) at the deeper lower mantle. Iron seems to have a key role in increasing the calcium solubility in bridgmanite. The temperature-driven nature can cause large lateral variations in the depth of the TPD-to-SPD change in response to temperature variations (by more than 500 kilometres). Furthermore, the SPD should have been thicker in the past when the mantle was warmer. Our finding requires revision of the deep-mantle mineralogy models and will have animpact onour understanding of the composition, structure, dynamics and evolution of the region.

Calcium leaching from cement hydrates exposed to sodium sulfate solutions

Calcium leaching from cement hydrates to pore solution increases the porosity and reduces the bonding strength of cement hydrates, accelerating the degradation of concrete. Calcium leaching can be quantified by solid–liquid equilibrium curves, which have been studied in deionized water or ammonium nitrate. The research of solid–liquid equilibrium curve of calcium under sulfate attack is limited and its mechanism is poorly understood. Reported here provide insights into the dissolution process of calcium from cement hydrates exposed to the sodium sulfate solution. The experimental programme examines the effects of sulfate ion concentration and temperature. An external sulfate attack (ESA) model considering the influence of calcium leaching is established and validated. The results show that, compared to deionized water, sulfate ions impact strongly the leaching process. Qualitatively, the dissolution of calcium in cement hydrates is accelerated by increasing the concentration of sulfate ions and decreasing the environmental temperature. Quantitatively, the presence of sulfate ions modifies the equilibrium curve describing calcium leaching in deionized water. In addition, the prediction results of the ESA model considering the influence of calcium leaching are in good agreement with the experimental results.

Effect of Types of Calcium‐Containing Cored Wires on the Inclusion Modification by Calcium Treatment

Calcium treatment experiments with equal calcium amounts using different calcium‐containing cored wires are carried out in the laboratory to investigate the effect of calcium wire types on the modification of inclusions. Inclusions change from Al2O3(–MgO) to calcium aluminates with the feeding of calcium wires; however, the modification degrees are different. The CaO content in inclusions increases to 25.8, 34.5, and 31.0 wt%, respectively, at 1 min after the addition of pure Ca, SiCa, and AlCa. The calcium yield is the highest when using SiCa wire and is the lowest under the use of pure Ca wire. The difference in calcium yield is attributed to the increasing effect of Si or Al on the solubility of calcium in molten steel. When calcium treatment is performed using SiCa and AlCa wires, the local Si and Al content around calcium bubbles would be large, which can promote the dissolution of calcium into steel and increase the yield of calcium. From the perspective of improving calcium yield, calcium treatment with SiCa or AlCa wires is better than that with pure Ca wires. However, steel grade, ladle capacity, and calcium treatment parameters should be further considered in the actual selection of calcium‐containing cored wires.

Hydrogeochemical Survey along the Northern Coastal Region of Ramanathapuram District, Tamilnadu, India

Ramanathapuram is a drought-prone southern Indian district that was selected for conducting a hydrogeochemical study. Groundwater samples from 40 locations were collected during January 2020 (pandemic interdiction according to COVID) and January 2021. The hydrogeochemical properties of the groundwater samples were evaluated and compared with drinking water regulations to assess their water quality. The order of cation dominance was as follows: Na+ &gt; Ca2+ &gt; K+ &gt; Mg2+ in January 2020 and Na+ &gt; Ca2+ &gt; Mg2+ &gt; K+ in January 2021 with respect to the mean value. The order of anion dominance was as follows: Cl− &gt; HCO3− &gt; SO42− &gt; NO3− &gt; F− in January 2020 and Cl− &gt; SO42− &gt; HCO3− &gt; NO3− &gt; F− in January 2021 with respect to the mean value. In the study area, the southern coastal region was identified as a groundwater-polluted zone through spatial analysis based on all analysis results. The irrigation water quality was analyzed using various calculated indices, such as Na% (percent sodium), SAR (sodium absorption ratio), PI (permeability index), MgC (magnesium risk), RSC (residual sodium concentration), and KI (Kelly ratio), demonstrating the suitability of the groundwater for irrigation in most parts of the study area. This was also confirmed by the Na% vs. EC Plot, USSL, and Doneen’s Plot for PI. In addition, the WQI results for drinking water and irrigation confirmed the suitability of the groundwater in most parts of the study area, except for the coastal regions. The dominant hydrogeologic facies of Na+-Cl−, Ca2+-Mg2+-SO42−, and Ca2+-Mg2+-Cl− types illustrated by the Piper diagram indicate the mixing process of freshwater with saline water in the coastal aquifers. Rock–water interaction and evaporation were the main controllers of groundwater geochemistry in the study area, as determined using the Gibbs plot. Ion exchange, seawater intrusion, weathering of carbonates, and the dissolution of calcium and gypsum minerals from the aquifer were identified as the major geogenic processes controlling groundwater chemistry using the Chadha plot, scatter plot, and Cl−/HCO3− ratio. Further, multivariate statistical approaches also confirmed the strong mutual relationship among the parameters, several factors controlling hydrogeochemistry, and grouping of water samples based on the parameters. Appropriate artificial recharge techniques must be used in the affected regions to stop seawater intrusion and increase freshwater recharge.

Seamless route of self-assembly and 3D printing to fabricate hierarchical mesoporous bioactive glass scaffold for customized bone regeneration with enhanced efficacy

Mesoporous bioactive glass (MBG) was one of the most promising bone regenerative materials for its well-acknowledged bioactivity, biodegradability, and osteoinductivity, as well as its potential for drug delivery. However, it remained a challenge to fabricate MBG scaffold with precisely controllable macro-structure and robust mechanical strength meanwhile to maintain uncompromised composition and mesoporosity. Herein, a fabricating route incorporating self-assembly and 3D printing (SAP) via acryloylating F127 (mesoporous template) was proposed and successfully realized directly printing MBG sol into hierarchical macro-/mesoporous SAP-MBG scaffold with compact and integral structure. Compared to traditional polyurethane (PU) templated MBG scaffold, SAP-MBG scaffold exhibited significantly enhanced mechanical strength meanwhile maintained non-composite component and mesoporous structure. SAP-MBG presented improved macropore interconnectivity and faster calcium dissolution, resulting in superior cellular penetration, in vitro osteogenic performances and in vivo bone regenerative efficacy in a critical-size rat cranial defect model. The SAP fabricating route represented an available approach to overcome the drawbacks of conventional manufacturing methods and realized individualized manufacturing of MBG scaffold. The synthetic design of this study might be extended to the fabricating process improvement of other mesoporous inorganic materials and shed light on future clinical translation of MBG scaffold in bone regeneration.

POS0478 TOPICAL CALCIUM CHELATORS FOR TARGETING CUTANEOUS CALCIFICATION: PRECLINICAL EVIDENCE OF EFFICACY

BackgroundCutis calcinosis, defined as sub-epidermal deposition of calcium salts, is a painful, disabling, disfiguring, problem in 20-40% of patients with systemic sclerosis. Its pathogenesis remains poorly understood and currently there is no effective disease-modifying pharmacotherapy. One potential strategy is topical application of calcium chelating agents, able to penetrate the epidermal barrier and dissolve subcutaneous calcinotic deposits in situ. To date, the only compound reported for this application has been sodium thiosulfate (STS), with often-contradictory results.ObjectivesTo test the hypothesis, in pre-clinical studies, that polycarboxylic acids can induce calcium dissolution without skin toxicity, with the long-term aim of developing an effective topical treatment for cutis calcinosis.MethodsWe compared the metal ion-chelating agents citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) - polycarboxylic acids with well-characterised chelation profiles – to STS for their ability to chelate calcium, without inducing cytotoxicity or inflammation (pro-inflammatory cytokine expression and release), using in vitro 2D (keratinocyte [HaCaT]; fibroblast ([HCA2]) and recombinant human epidermal (RHE) models. The resultant data was subsequently used to predict therapeutic concentrations for assessment in a validated skin irritation model (SkinEthicTM; Episkin SA) and to assay maximal percutaneous absorption. At relative dermal concentrations, the dissolution performance of each chelator was further assessed using two different models of calcinosis: 1) pharmaceutical dissolution of a hydroxyapatite (HAp) tablet (1) and; 2) dissolution of a calcified extracellular matrix laid down by mineralising SaOS2 in vitro monolayer culture (2).ResultsIncubation with CA, EDTA and STS induced cytotoxicity in both in vitro cell lines studied at concentrations of &gt;10 mM; only EDTA (10 mM) resulted in inflammatory cytokine release (IL8) from cells at these higher concentrations (cf positive control, Lipopolysaccharide 10 mg/mL). When applied topically to RHE models as near-saturated solutions, none of the chelators were categorised as skin irritants. Due to differences in their relative aqueous solubility, higher concentrations of CA (1600 mM) and STS (1200 mM) could be delivered through the RHE model than EDTA (200 mM). Using a simple linear regression model, the rate of compound absorption was: CA, 0.43 ± 0.05; STS, 0.26 ± 0.03 and; EDTA, 0.05 ± 0.01 g/L/hr. At each time-point, the cumulative concentration of compound in the receptor media was CA &gt; STS &gt; EDTA. Incubation with chelators had no effect on the integrity of the RHE by standard histology. Based on the rate of percutaneous absorption, the dissolution performance of each chelator was tested at relative dermal concentrations for phosphate dissolution (nmoles) of HAp (CA, 9.61 ±0.97; EDTA, 5.38 ± 0.28; 3.78 ± 0.58) and in the calcified in vitro model (Figure 1; CA, 3285 ± 105, STS, 947 ± 95, EDTA, 1174 ± 89), showing the superiority of CA in both model systems.Figure 1.Dissolution of a calcified extracellular matrix by citric acidConclusionOverall, this study highlights the promise of polycarboxylic acids, particularly CA, to target subcutaneous calcification, which are neither toxic nor inflammatory to the skin. Specifically, we have identified CA as a potentially more efficacious alternative to STS for the topical treatment of cutis calcinosis.

Calcium dissolution behaviors of recycled coarse aggregate concrete with the initial stress damage

The accelerated calcium dissolution tests of concrete with different replacement rates of recycled coarse aggregate (RCA) and different initial damage degrees D0 were carried out by using ammonium chloride solution. The results show that the dissolution resistance of recycled aggregate concrete (RAC) is negatively correlated with the replacement rate of RCA and the D0. The mass loss, dissolution depth, the attenuation of ultrasonic wave velocity, and the degradation of mechanical properties (compressive strength and splitting tensile strength) of RAC after calcium dissolution increase with the increasing replacement rate of RCA. When the D0 is less than 0.2, the dissolution resistance of RAC is not obviously affected by the initial stress damage; however, when the D0 is greater than 0.2, the mass loss, dissolution depth, the attenuation of ultrasonic wave velocity, and the deterioration of mechanical properties of RAC increase linearly with the increasing of D0. Compared with the compressive strength, the splitting tensile strength is more sensitive to the calcium dissolution and the initial stress damage of concrete. An obvious pH gradient is formed in the concrete after dissolution, and the pH value in a certain depth of the concrete decreases with the increasing of the replacement rate of RCA and the D0. Finally, the prediction model for compressive strength and splitting tensile strength of RAC after calcium dissolution is established.