Academic literature on the topic 'Calcium concentration'
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Journal articles on the topic "Calcium concentration"
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Zhu, Zhiming, Martin Tepel, Marcus Neusser, and Walter Zidek. "Low Concentrations of Ouabain Increase Cytosolic Free Calcium Concentration in Rat Vascular Smooth Muscle Cells." Clinical Science 90, no. 1 (1996): 9–12. http://dx.doi.org/10.1042/cs0900009.
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1. Low ouabain concentrations in the nanomolar range significantly increased cytosolic free calcium concentration. 2. The ouabain-induced cytosolic free calcium concentration increase was due to transplasmamembrane calcium influx, which could be prevented in the absence of extracellular calcium or by addition of the calcium channel blocker nifedipine. 3. The amount of stored cellular Ca2+, as determined by the thapsigargin-induced cytosolic free calcium concentration increase, was also enhanced by 1 nmol/l ouabain. 4. It is concluded that low ouabain concentrations affect intracellular cytosolic free calcium concentration homoeostasis.
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Cho, Hyunji, Jisoo Lee, Seoyoung Jang, et al. "CaSR-Mediated hBMSCs Activity Modulation: Additional Coupling Mechanism in Bone Remodeling Compartment." International Journal of Molecular Sciences 22, no. 1 (2020): 325. http://dx.doi.org/10.3390/ijms22010325.
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Near the bone remodeling compartments (BRC), extracellular calcium concentration (Ca2+o) is locally elevated and bone marrow stromal cells (BMSCs) close to the BRC can be exposed to high calcium concentration. The calcium-sensing receptor (CaSR) is known to play a key role in maintaining extracellular calcium homeostasis by sensing fluctuations in the levels of extracellular calcium (Ca2+o). When human BMSCs (hBMSCs) were exposed to various calcium concentrations (1.8, 3, 5, 10, 30 mM), moderate-high extracellular calcium concentrations (3–5 mM) stimulated proliferation, while a high calcium concentration (30 mM) inhibited the proliferation. Exposure to various calcium concentrations did not induce significant differences in the apoptotic cell fraction. Evaluation of multi-lineage differentiation potential showed no significant difference among various calcium concentration groups, except for the high calcium concentration (30 mM) treated group, which resulted in increased calcification after in vitro osteogenic differentiation. Treatment of NPS2143, a CaSR inhibitor, abolished the stimulatory effect on hBMSCs proliferation and migration indicating that CaSR is involved. These results suggest that the calcium concentration gradient near the BRC may play an important role in bone remodeling by acting as an osteoblast–osteoclast coupling mechanism through CaSR.
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Weinreich, Thomas, A. Colombi, H. H. Echterhoff, et al. "Transperitoneal Calcium Mass Transfer using Dialv Sate with a Low Calcium Concentration (1.0 mM)." Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 13, no. 2_suppl (1993): 467–70. http://dx.doi.org/10.1177/089686089301302s117.
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Lower dialysate calcium concentrations were recently proposed to overcome the risk of hypercalcemia In continuous ambulatory peritoneal dialysis (CAPD) patients on calcium containing phosphate binders and/or vitamin D metabolites using the standard dialysate calcium concentration (sCa) of 1.75 mM. To assess transperitoneal calcium mass transfer (CaMT) in CAPD patients using a dialysate with a low calcium concentration (LCa, 1.00 mM), 18 stable patients were randomly allocated to receive either LCa or SCa. CaMT was assessed over 4 hours using 2L dialysate bags with three different dialysate glucose concentrations (1.5%, 2.3%, 4.25%). Total serum calcium (tCa), Ionized calcium (iCa), and the exact dialysate volume were measured before and after the 4-hour dwell. A sample of the drained dialysate was obtained to measure the dialysate calcium concentration. The tCa and iCa levels were not significantly different In both groups prior to and did not change throughout the test. CaMT (median/range) was .0.64 mmol/exchange (0.35 –1.29 mmol/exchange) using LCa with 1.5% glucose compared to 0.23 mmol (.0.18 -0.87 mmol) with SCa (p<0.0001). CaMT was negatively correlated to ICa and ultrafiltration volume [4.25%: LCa -1.22 (.0.84 -1.9); SCa .0.43 (-1.35 -0.13); p<0.001]. In summary, LCa results in a loss of calcium into the dialysate even at low ultrafiltration volumes and serum ICa levels. This might facilitate the prevention and therapy of renal osteodystrophy with calclum-containing phosphate binders and calcitriol. However, patients using LCa must be carefully monitored for calcium homeostasis and bone turnover.
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Patel, Prerna, M. Zulf Mughal, Pinal Patel, et al. "Dietary calcium intake influences the relationship between serum 25-hydroxyvitamin D3 (25OHD) concentration and parathyroid hormone (PTH) concentration." Archives of Disease in Childhood 101, no. 4 (2015): 316–19. http://dx.doi.org/10.1136/archdischild-2015-308985.
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ObjectivesTo investigate whether dietary calcium intake will modify the relationship between serum 25-hydroxyvitamin D3 (25OHD) with intact serum parathyroid hormone (PTH) concentrations in apparently healthy Indian adolescents.Study designCross-sectional study.Setting and participantsApparently healthy adolescents aged 10–14 years (n=181), from Gujarat, western India. Study conducted from January 2012 to March 2014.MethodsSerum 25OHD concentrations and intact serum PTH concentrations (both using chemiluminescent microparticle immunoassay) were measured. Diet was recorded through 24 h diet recall and calcium intake was computed (C-diet V.2.1). To assess relationship between 25OHD and PTH, data were dichotomised according to median calcium intakes (520 mg/day) and relationship between serum 25OHD and PTH in the two subgroups was plotted.ResultsSubjects with calcium intakes above median (>520 mg/day) had lower intact serum PTH values for given serum 25OHD concentration while those with calcium intakes below median (<520 mg/day) had higher intact serum PTH values for given serum 25OHD concentration. Serum 25OHD concentration was negatively correlated with intact serum PTH concentration at lower as well as higher calcium intakes (r=− 0.606 and −0.483, respectively, p<0.01 for both). Using a regression analysis, predicted values for intact serum PTH concentration for the given serum 25OHD concentrations were plotted. The plot revealed a negative shift with increasing calcium intake.ConclusionsDietary calcium intake modifies the relationship between serum 25OHD concentrations and intact serum PTH concentrations. Thus, dietary calcium intake should be taken into account when assessing an individual's vitamin D status.
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Weber, Lynn P., Wing L. Chow, Janice Moshenko, Slavica Belsher, and Kathleen M. MacLeod. "Pharmacological investigation of signaling mechanisms contributing to phasic and tonic components of the contractile response of rat arteries to noradrenaline." Canadian Journal of Physiology and Pharmacology 73, no. 5 (1995): 594–601. http://dx.doi.org/10.1139/y95-075.
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The mechanisms contributing to the contractile responses to two different concentrations of noradrenaline (NA) in rat aorta and mesenteric artery were compared using nifedipine, which inhibits calcium influx through dihydropyridine-sensitive channels, ryanodine, which depletes intracellular calcium stores, and calphostin C, which inhibits protein kinase C (PKC). Both submaximal and maximal concentrations of NA induced a biphasic response in aorta and mesenteric artery, with an early fast phase and a later sustained tonic component. Calcium release from intracellular stores contributed to the phasic component of contraction to both concentrations of NA in aorta, although to a greater extent to the submaximal concentration. In aorta, inhibiting both intracellular calcium release and calcium influx through dihydropyridine-sensitive channels simultaneously or inhibiting PKC activity alone significantly reduced the tonic response to a maximal concentration of NA. However, the tonic response to a submaximal concentration of NA in aorta was significantly inhibited only when intracellular calcium stores were depleted with ryanodine. In mesenteric artery, the phasic response to a maximal concentration of NA was significantly depressed only when both calcium influx and intracellular calcium release were inhibited simultaneously. However, the phasic response to a submaximal concentration of NA was significantly inhibited by blocking calcium influx alone, but not by blocking intracellular calcium release alone. The tonic component of the contractile response to both concentrations of NA in mesenteric artery appeared to be mediated in part by calcium from both intracellular and extracellular sources. However, the submaximal concentration relied on calcium influx to a greater extent than the maximal concentration, while PKC contributed to a greater extent to the response to the maximal concentration of NA in this artery. These results indicate that the relative contributions of the signaling mechanisms activated by NA differ between maximal and submaximal concentrations of the agonist as well as between different arteries.Key words: noradrenaline, vasoconstriction, ryanodine, nifedipine, calphostin C.
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Li, Hui, Yaoyao Zhao, Xiaohang Weng, et al. "The Most Suitable Calcium Concentration for Growth Varies among Different Tree Species—Taking Pinus tabuliformis, Pinus sylvestris var. mongolica, Populus, and Morus alba as Examples." Forests 14, no. 7 (2023): 1437. http://dx.doi.org/10.3390/f14071437.
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Ca2+ is a crucial second messenger in plant cells that plays a vital role in various physiological and biochemical processes, including plant growth and development, photosynthesis, and enzyme regulation. Exogenous calcium concentrations can have different effects on plant growth. The purpose of this study was to determine the appropriate calcium concentration for the growth of four tree seedlings, namely Pinus tabuliformis, Pinus sylvestris var. mongolica, Populus, and Morus alba seedlings, and whether this optimal calcium concentration varies among different tree species. This study utilized five calcium concentration gradients (0, 100, 200, 400, 800 mg·kg−1) for each species with three repeated treatments. To determine each species’ calcium concentration needs, several growth indices, photosynthetic metrics, chlorophyll fluorescence parameters, water usage efficiency, and antioxidant enzyme activities were analyzed. The results showed that exogenous calcium significantly affected the growth and development of each seedling. The growth, biomass, photosynthetic parameters, photosynthetic products, photosynthetic pigments, water use efficiency, and antioxidant enzyme activity all increased initially and then decreased with the increasing calcium concentration. The exogenous calcium supply increased the concentration of calcium in the leaves. Thus, there was an optimal calcium concentration for plant growth, and a high or low calcium concentration was not conducive to plant growth. Furthermore, this study found that the optimum calcium concentration of different tree species was different. The optimal calcium concentration for Pinus tabuliformis, Pinus sylvestris var. mongolica, Populus, and Morus alba seedlings was 100, 100, 200, and 400 mg·kg−1, respectively, with broadleaf seedlings requiring higher calcium concentrations than coniferous seedlings.
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Chew, Dennis J., Mark Leonard, and William Muir. "Effect of sodium bicarbonate infusions on ionized calcium and total calcium concentrations in serum of clinically normal cats." American Journal of Veterinary Research 50, no. 1 (1989): 145–50. https://doi.org/10.2460/ajvr.1989.50.01.145.
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SUMMARY The effects of sodium bicarbonate (0.5 mEq/kg of body weight, 1.0 mEq/kg, 2.0 mEq/kg, and 4.0 mEq//kg) on ionized and total calcium concentrations were determined in clinically normal cats. Also, serum pH, whole blood pH, and serum albumin, serum total protein, and serum phosrus concentrations were measured. Intravenous administration of sodium bicarbonate to awake cats decreased serum ionized calcium and serum total calcium concentrations. All dosages of sodium bicarbonate were associated with significant decreases of serum ionized calcium concentration. This effect lasted for > 180 minutes when cats were given 2.0 mEq/kg or 4.0 mEq/kg. When cats were given 4 mEq of sodium bicarbonate/kg, serum ionized calcium concentration was significantly decreased, compared with that when cats were given lower doses, but only at 10 minutes after infusion. After sodium bicarbonate infusion, serum total calcium concentration, measured by ion-specific electrode and colorimetry, was lower than baseline values at most of the times evaluated. Decreases in serum ionized calcium and serum total calcium concentrations can be attributed only in part to an increase in serum or whole blood pH and to a decrease in serum protein concentration. Serum total calcium concentrations measured by ionspecific electrode and by colorimetry were positively correlated, but the variability was high. Only 44 % of the variability in serum ionized calcium concentration could be predicted when serum total calcium, albumin, total protein, phosphorus, and bicarbonate concentrations and pH were considered.
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Zhu, Wen Kun, Xue Gang Luo, Xiao Yan Lin, and Pan He. "Effects of Ca2+ Concentration on Calcium Carbonate Crystallization in Lignin Solution System." Materials Science Forum 695 (July 2011): 521–24. http://dx.doi.org/10.4028/www.scientific.net/msf.695.521.
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The calcium carbonate crystallization was controlled by Ca2+concentrations, under the system of lignin solution with concentration of 10 g / L. Its morphology, structure and thermal decomposition were characterized by FT-IR, SEM, XRD and TG. Results showed that in lignin solution system, concentration of Ca2+had significant effects on the crystallized morphology, orientation and crystallinity of calcium carbonate. Calcium carbonate crystal under low Ca2+concentration had more uniform size while under high Ca2+concentration which tended to form various sizes with more complete crystallization. The calcium carbonate crystals were all calcite calcium carbonate, which formed under different Ca2+concentrations.
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Flanders, J. A., S. Neth, H. N. Erb, and F. A. Kallfelz. "Functional analysis of ectopic parathyroid activity in cats." American Journal of Veterinary Research 52, no. 8 (1991): 1336–40. http://dx.doi.org/10.2460/ajvr.1991.52.08.1336.
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Summary The ability of ectopic parathyroid tissue to support calcium homeostasis was evaluated by measuring serum concentrations of calcium, phosphorus, albumin, magnesium, and parathyroid hormone before and for 12 weeks after bilateral thyroparathyroidectomy in 14 cats. During the immediate postoperative period, significant decrease was observed in serum calcium, magnesium, and parathyroid hormone (pth) concentrations. Serum pth concentration remained subnormal and did not significantly increase during the 12-week observation period. Despite persistent hypoparathyroidism, serum calcium and magnesium concentrations gradually increased. Ectopic parathyroid tissue is not capable of maintaining normal serum calcium concentration immediately after thyroparathyroidectomy. Serum calcium concentration gradually normalizes after thyroparathyroidectomy, apparently by means of a pth-independent mechanism.
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Fluck, R. J., A. C. McMahon, F. M. Alameddine, A. B. S. Dawnay, L. R. I. Baker, and A. E. G. Raine. "Platelet cytosolic free calcium concentration and parathyroid hormone: changing relationships with haemodialysis in end-stage renal disease." Clinical Science 82, no. 6 (1992): 651–58. http://dx.doi.org/10.1042/cs0820651.
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1. Twelve patients receiving haemodialysis for end-stage renal failure were studied at a single dialysis session. Platelet cytosolic calcium concentration, plasma ionized calcium concentration and serum parathyroid hormone concentration were measured before dialysis, mid-dialysis and 30 min after dialysis. 2. Plasma ionized calcium concentration increased towards dialysate calcium concentrations, falling insignificantly after cessation of dialysis. Serum parathyroid hormone concentration fell by 39% during dialysis, with incomplete recovery afterwards. There was no overall change in platelet cytosolic calcium concentration. 3. Patients were divided into two subgroups: low parathyroid hormone (serum parathyroid hormone concentration < 10 pmol/l) and high parathyroid hormone (serum parathyroid hormone concentration > 10 pmol/l). Before dialysis, values of platelet cytosolic calcium concentration or plasma ionized calcium concentration were not statistically different between the subgroups, but the platelet cytosolic calcium concentration was higher in the high-parathyroid hormone subgroup during and after dialysis. 4. Before haemodialysis there was a linear correlation between plasma ionized calcium concentration and platelet cytosolic calcium concentration, which disappeared during dialysis. In contrast, there was no relationship between serum parathyroid hormone concentration and platelet cytosolic calcium concentration before dialysis, but after dialysis a hyperbolic relationship was evident. 5. These results suggest that uraemic toxins may interfere with cytosolic calcium homoeostasis, allowing passive diffusion of extracellular calcium to influence the resting concentration, and that this effect is reversible by haemodialysis.
Dissertations / Theses on the topic "Calcium concentration"
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He, Fenjin. "Substrate Concentration, Calcium Concentration and κ-Casein Hydrolysis in Milk Coagulation". DigitalCommons@USU, 1990. https://digitalcommons.usu.edu/etd/5364.
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Milk coagulation consists of four overlapping phases: enzymic hydrolysis, micelle aggregation, gelation and syneresis. The objectives of this study were to determine the effects of added CaCl2 on milk coagulation and the relationship between enzymic hydrolysis and micelle aggregation with substrate at different concentrations.
Addition of CaCl2 to milk is widely practiced in industry and in laboratories. This changes calcium concentration, pH and ionic strength. It is impossible to separate these three variables and investigate each one independently.
Addition of low levels of CaCl2 shortens coagulation time and increases curd firming rate. Low levels of CaCl2 also accelerate the enzymic hydrolysis process. Calcium ions increase hydrolysis rate, but this effect is much smaller than that of lowered pH. Increase of ionic strength due to addition of CaCl2 has an adverse effect on enzymic hydrolysis. This dominates at high CaCl2 concentration, and the overall coagulation process slows down. Adding CaCl2 also promotes micelle aggregation. However, aggregation is retarded by high levels of added CaCl2.
Results of this study show that about 90% of the κ-casein is hydrolyzed for diluted milk (1/3) to coagulate. Samples at normal concentration (12 g NDM/100 ml solution) require only 60% conversion of κ-casein to para-κ-casein. Addition of CaCl2 significantly decreases this percentage. This suggests a different aggregation and gelation process in samples containing added CaCl2
When pepstatin A is used to stop enzymic hydrolysis at different times, different degrees of κ-casein conversion are obtained. Micelles aggregate even at very low percentages of hydrolysis. Previous reports have stated that a micelle cannot participate in aggregation until almost all of its κ-caseins have been hydrolyzed.
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Vatansever, Aysun. "Bioflocculation Of Activated Sludge In Relation To Calcium Ion Concentration." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606304/index.pdf.
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Bioflocculation, which can be defined as aggregation of bacterial flocs, has important implications on the physical characteristics of sludge. It is especially critical to settling and dewatering systems which impacts the overall economy of the process greatly. One of the most common problems in activated sludge systems to negatively influence the settleability is sludge bulking which can be defined as non-settling situation of microbial mass.
The first objective of this research is to investigate the effect of calcium ion on sludge bulking in a phosphorus deficient medium and the second objective is to improve the settling, dewatering, and pumping of activated sludge by adjusting the calcium (Ca) ion concentration of the feed. For this purpose, 7 semi-continuous laboratory scale activated sludge reactors were operated with a mixed aerobic culture. The reactors had 8 days of sludge residence time and aerated with air pumps to provide a dissolved oxygen concentration of at least 3 mg/L. All the analyses were conducted after the reactors reached steady state condition.
In the first part of the research, the effect of strictly phosphorus-limited medium on bulking of activated sludge was studied at different calcium ion concentration. Three reactors were set up having 5, 10 and 20 meq/L calcium concentrations. From the results it was observed that, phosphorus deficiency caused viscous bulking independent from the calcium ion concentration. It was found out that bulking of activated sludges due to phosphorus deficiency could be cured by the addition of phosphorus. Furhermore, microorganisms starved for phosphorus, seemed to accumulate polyphosphate granules when they were exposed to a phosphorus source.
In the second part of the study, the effect of calcium ion on physical, chemical and surface chemical properties of activated sludge was investigated at 4 different concentrations (0.27, 5, 10 and 20 meq/L) under sufficient phosphorus concentration. Calcium addition resulted in significant changes in the quantity and quality of extracellular polymeric substances (EPS). Total EPS increased depending on the calcium concentration. Carbohydrate content of EPS dominated over the protein content for calcium concentration of 5 meq/L and above. The amount of calcium ions incorporated into the sludge floc matrix also increased with the dose of calcium added. Settleability and dewaterability of sludge improved significantly at 5 meq/L dose of calcium. However, settleability did not change any further with increasing calcium dose, whereas dewaterability increased for all increasing calcium concentrations. Sludge viscosity also decreased considerably at 5 meq/L concentration indicating better pumpability but it did not change further above 10 meq/L calcium addition.
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MacMillan, Debbi. "Role of the sarcoplasmic reticulum in nitric oxide induced modulation of cytoplasmic calcium in rabbit aortic smooth muscle cells." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248585.
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Price, Edmund E. 1954. "Response of Freshwater and Saltwater Toxicity Test Species to Calcium and Salinity Concentrations Encountered in Toxicity Tests." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc331168/.
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The responses of freshwater (Daphnia magna. Pimephales promelas) and saltwater (Mysidopsis bahia. Cyprinodon variegatus) toxicity test species to elevated calcium concentrations and changing salinity conditions were investigated. The use of salinity as a criterion for selection between saltwater and freshwater test species was investigated by conducting both calcium and salinity toxicity tests.
Salinity was determined to be an inappropriate criterion under conditions encountered in this study.
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Clarke, Sonia Dawn. "Design and synthesis of novel spectroscopic indicators of cystosolic free calcium concentration." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335750.
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Wilsdorf, Robert Ernst. "Evaluating the seasonal changes in calcium concentration and distribution in apple fruit after application of different calcium fertilisation strategies." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17790.
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Thesis (MScAgric)--Stellenbosch University, 2011.<br>ENGLISH ABSTRACT: Localized calcium (Ca) deficiencies frequently develop independent from total Ca supply and total fruit Ca concentration. Bulk mineral analyses is therefore not completely suitable for determination of the susceptibility of fruit in developing Ca-linked fruit physiological disorders like bitter pit, as it supplies insufficient information regarding the spatial accumulation of Ca within the fruit. Additional Ca is applied either as soil or foliar applications, where soil applications are applied either after fruit set (pre-harvest) or in the period after harvest. The contribution of these different methods of Ca application to the total Ca concentration in "Braeburn" fruit was quantified over three consecutive growing seasons. Foliar applications have been proven to be successful in suppressing bitter pit development and improving the Ca status of the fruit. The effectiveness of different formulations of foliar Ca products in influencing these parameters was also determined. Furthermore, the distribution pattern of fruit Ca resulting from different application strategies was mapped using particle induced X-ray emission technology.
In the "Braeburn" trial, mineral analyses indicated no significant differences between treatments in terms of Ca concentration at 80 days after full bloom (dafb). However, when soil applications occurred with active root growth (visually monitored), treatments differed significantly 80 dafb. Weekly foliar Ca applications from 28 dafb resulted in higher fruit Ca concentrations 80 dafb than a pre-harvest soil Ca application (January, 2010). A possible explanation for the inefficiency of pre-harvest soil Ca is the disintegration of xylem vessels from 40 dafb (before root uptake) for sensitive cultivars such as Braeburn. Bitter pit initiation has been shown to occur in the earlier part of the season. This, together with a reduced Ca supply to the fruit early in the season due to xylem disintegration (for sensitive cultivars), indicates the importance of early season foliar Ca applications. PIXE analyses were used to establish the radial Ca distribution in apples. Ca was concentrated in the skin and core, with very low values in the outer cortex. PIXE results indicated fruit Ca concentrations to be the lowest in the pre-harvest soil application treatment. This was in agreement with mineral analyses results. Ca enriched areas resulting from effective Ca delivery via the vascular bundles, had a profound effect on fruit Ca concentrations in the immediate core and cortex. At harvest, this effect was much more subtle and emphasizes the importance of untimely xylem rupturing on eventual fruit Ca concentration. At 80 dafb, treatments where foliar Ca was applied showed higher Ca concentrations in the outer cortex (where symptoms of bitter pit typically occur).
Calflo™ fruit had significantly higher Ca concentrations in "Braeburn" compared to fruits from Foliar GS™ and GG™ treatments. Calflo™ and Calcimax™ had a higher active Ca percentage (12%) compared to Foliar GSTM and GGTM (10%). Adding the Lecithin™ (surfactant) to Calcimax™ is not recommended as it did not improve its uptake.
In "Golden Delicious", the commercial spray program of seven, weekly foliar applications (Calcinit™) resulted in fruit with significantly higher Ca concentrations compared to other treatments.<br>AFRIKAANSE OPSOMMING: Kalsium (Ca) tekorte ontstaan gewoonlik in gelokaliseerde areas in die appelvrug en ontwikkel dikwels ten spyte van voldoende totale vrug Ca. Minerale analises van heel vrugte verskaf dus nie genoeg inligting aangaande die verspreiding van Ca in die vrug wanneer die ontwikkelling van fisiologiese defekte soos bitterpit ter sprake is nie. Addisionele Ca word gewoonlik aangewend as blaar- of grondtoedienings, waar grondtoedienings tipies voor-oes (net na set) of in die na-oes periode, toegedien word. Die bydraes van die verskillende toedieningsmetodes tot die totale Ca konsentrasie van "Braeburn" appels is geëvalueer oor drie agtereenvolgende seisoene. Blaartoedienings van Ca word algemeen gebruik om die voorkoms van bitterpit te beheer en die Ca konsentrasie van die vrug te verhoog. Die effektiwiteit van `n reeks blaartoedienings-produkte om hierdie faktore te verbeter, is ook ondersoek. Die spesifieke verspreiding van die Ca in die vrug is gekarteer na gelang van elke toediening deur middel van PIXE-analises (Particle induced X-ray emission).
In die "Braeburn" proef was daar geen beduidende verskille in terme van vrug Ca konsentrasie op 80 dnvb (dae na volblom) nie. Daarteenoor, was daar wel beduidende verskille by 80 dnvb toe grond toedienings saam met aktiewe wortelgroei geskied het (visuele inspeksie). Weeklikse blaartoedienings vanaf 21 dnvb het gelei tot vrugte met betekenisvol hoër Ca konsentrasies as die behandeling waar grondtoedienings slegs voor-oes geskied het (Januarie 2010). `n Moontlike oorsaak vir die oneffektiwiteit van voor-oes grondtoedings is die vroeë disintigrasie van xileem vesels in die vrug (soms voor 40 dnvb en voor die aanvang van wortelopname) in sensitiewe kultivars soos "Braeburn". Hierdie vroeë inhibering van Ca voorsiening, tesame met die vroeë inisiasie van bitterpit, beklemtoon die belangrikheid van blaarbespuitings vroeg in die seisoen. Die PIXE-analises wat aangewend is om die radiale verspreiding van Ca in die vrug te bepaal het getoon dat Ca meestal in die skil en kern van die vrug gekonsentreer was, met baie lae konsentrasies in die buitenste korteks. Die laagste Ca konsentrasies is waargeneem in vrugte van die behandeling waar voor-oes Ca slegs as `n grondtoediening geskied het. Hierdie waarneming is in ooreenstemming met die mineraalanalise resultate. Ca verykte areas, afkomstig van die naby geleë vaatbundels (xileem vesels), het egter die grootste effek op vrug Ca konsentrasie gehad. Hierdie effek was nie so groot by oes nie en beklemtoon dus die belangrikheid van die funksionaliteit van die vaatbundels. Blaartoedienings kon die Ca konsentrasie in die buitenste korteks suksesvol verhoog - waar simptome van bitterpit tipies voorkom.
Die Calflo™ behandeling het beduidende hoër Ca konsentrasies gehad as die Foliar GS™ en GG™ behandelings. Die Calflo™ en Calcimax™ behandelings het `n hoër aktiewe Ca persentasie (12%) relatief tot die Foliar GS™ en GG™ (10%) behandelings bevat. Die byvoeging van Lecithin™ by Calcimax™ word nie aanbeveel nie, omdat dit geensins Ca opname vermeerder het nie.
In die "Golden Delicious" proef het die kommersiële behandeling (Sewe weeklikse spuite van Calcinit™) gelei tot vrugte met die hoogste Ca konsentrasie van al die behandelings.
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Efanov, Alexander. "Stimulation of insulin secretion independently from changes in cytosolic free Ca²⁺-concentration : studies with imidazolines and inositol polyphosphates /." Stockholm, 1999. http://diss.kib.ki.se/1999/91-628-3876-8/.
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Guérineau, Nathalie. "Diversité des modes de régulation de la concentration de calcium cytosolique dans les cellules endocrines de l'hypophyse antérieure." Bordeaux 2, 1992. http://www.theses.fr/1992BOR28211.
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Trafford, Andrew William. "Local and global measurements of intracellular calcium concentration during spontaneous and triggered propagating calcium waves in single rat ventricular myocytes." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307663.
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Huang, Alice. "Calcium-sensing Receptor Mediated Control of CYP27B1 Promoter-dependent Gene & Protein Expression: Complex Extracellular Ca2+ Concentration Dependence." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20127.
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Changes in extracellular Ca2+ (Ca2+o) differentially modulate 25-hydroxyvitamin D3 1α-hydroxylase (1αOHase; encoded by CYP27B1) mRNA and protein levels in cell types including the renal proximal tubule (inhibitory), parathyroid, and skeletal osteoblasts (stimulatory) to control 1,25-dihydroxyvitamin D3 synthesis. We hypothesised that the calcium-sensing receptor (CaSR) mediated Ca2+o concentration-dependent control of 1αOHase, either directly through Ca2+o, or through the local production of parathyroid hormone related peptide (PTHrP). To investigate promoter activity, I transfected a firefly luciferase reporter gene under the control of the 1501 bp human CYP27B1 promoter into HEK-293 cells that stably expressed the CaSR (HEK-CaSR cells) and measured luciferase activities from cells exposed to various Ca2+o concentrations. CYP27B1 promoter-controlled luciferase expression exhibited a biphasic Ca2+o-dependent response in luciferase activity and protein that peaked with a 2-fold increase from basal levels at around 3.0 mM Ca2+o in HEK-CaSR cells. This response was absent in HEK-293 cells and was shifted to the left or right in the presence of the CaSR positive allosteric modulator, cinacalcet, or negative allosteric modulator, NPS-2143, respectively, indicating that both the stimulatory and inhibitory phases were CaSR-mediated. Firefly luciferase and 1αOHase mRNA levels obtained from quantitative RT-PCR exhibited a monophasic Ca2+o-dependent increase and suggests that the stimulatory phase arises from increased mRNA expression, whereas the inhibitory phase arises from reduced protein levels. Inhibitor and mutational studies suggested that the stimulatory phase was dependent on Gq/11 signalling, whereas the inhibitory phase requires MEK and PKC-dependent phosphorylation of the crucial T888 site of the CaSR's C-terminal tail.
Books on the topic "Calcium concentration"
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Silvestri, Livia. The regulation of intracellular calcium ion concentration and mitochondrial function by cyclosporin A: a putative mechanism for the pathogenesis of gingival overgrowth. Faculty of Dentistry, University of Toronto], 2000.
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Sikora, Lindsey. The effects of the L-type calcium channel antagonist nimodipine on learning and memory following low and high concentrations of ethanol consumption. Laurentian University, 2005.
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Chakera, Aron, William G. Herrington, and Christopher A. O’Callaghant. Disorders of plasma calcium. Edited by Patrick Davey and David Sprigings. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199568741.003.0175.
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The extracellular calcium ion concentration is tightly regulated through the actions of parathyroid hormone (PTH) and vitamin D (1,25-dihydroxyvitamin D) on bone, kidney, and intestines. Abnormalities in these homeostatic mechanisms may lead to increased or decreased serum calcium concentrations, resulting in hypercalcaemia or hypocalcaemia, respectively. Hypercalcaemic disorders may be further divided into those associated with a high/high-normal serum PTH level, and those associated with a low serum PTH concentration. Hypocalcaemia occurs when abnormalities in the physiological regulation of PTH and vitamin D results in calcium levels lower than the desired normal range. Failure of release of calcium from bone, and increased binding of calcium in the circulation, are other factors causing hypocalcaemia. This chapter discusses hypercalcaemia and hypocalcaemia, exploring definitions of the diseases, their etiologies, typical and uncommon symptoms, demographics, natural history, complications, diagnostic approaches, other diagnoses that should be considered, prognosis, and treatment.
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Turney, Ben, and John Reynard. Prevention of idiopathic calcium stones. Edited by John Reynard. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199659579.003.0015.
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The main principles of idiopathic calcium oxalate stone prevention are to maintain dilute urine through increasing fluid intake and to reduce calcium and oxalate excretion. The influence of various urinary factors on the risk of stone formation has been quantified mathematically. Urine volume and urinary oxalate concentration are most influential on the risk of stone formation, while magnesium concentration contributes a small amount to risk. It is estimated that around 50% of stone formers will form another stone within five years. Some stone formers have frequent recurrences. Most stone formers ask how they can prevent future episodes. Advice can be generic or personalized, and treatment may include changes to diet, fluid intake, and addition of drugs to alter urine biochemistry.
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Rosengart, Matthew R. Disorders of calcium in the critically ill. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0253.
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Calcium is vitally important for normal cellular signalling and function. However, its toxicity necessitates that intracellular calcium concentration [Ca2+] be tightly regulated and compartmentalized. Evolutionary pressures have yielded several regulatory mechanisms to maintain intracellular and extracellular ionized calcium concentrations compatible with life. During periods of critical illness these process are commonly overwhelmed, and disorders of calcium homeostasis are highly prevalent among intensive care unit (ICU) patients. Indeed, hypocalcaemia occurs in up to 88% of critically-ill ICU patients suffering from trauma, sepsis, and burns. Contemporary evidence suggests that although hypocalcaemia may be associated with ICU mortality, it is not in the causal pathway. A systematic review concluded there are no data to support the routine parenteral administration of calcium in the management of asymptomatic critical illness-related hypocalcaemia. Asymptomatic hypocalcaemia of critical illness does not necessitate replacement. However, acute, symptomatic hypocalcaemia necessitates parenteral supplementation to prevent tetany, seizures, and cardiac arrhythmias
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Abhishek, Abhishek, and Michael Doherty. Pathophysiology of calcium pyrophosphate deposition. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199668847.003.0049.
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Calcium pyrophosphate (CPP) dihydrate crystals form extracellularly. Their formation requires sufficient extracellular inorganic pyrophosphate (ePPi), calcium, and pro-nucleating factors. As inorganic pyrophosphate (PPi) cannot cross cell membranes passively due to its large size, ePPi results either from hydrolysis of extracellular ATP by the enzyme ectonucleotide pyrophosphatase/phosphodiesterase 1 (also known as plasma cell membrane glycoprotein 1) or from the transcellular transport of PPi by ANKH. ePPi is hydrolyzed to phosphate (Pi) by tissue non-specific alkaline phosphatase. The level of extracellular PPi and Pi is tightly regulated by several interlinked feedback mechanisms and growth factors. The relative concentration of Pi and PPi determines whether CPP or hydroxyapatite crystal is formed, with low Pi/PPi ratio resulting in CPP crystal formation, while a high Pi/PPi ratio promotes basic calcium phosphate crystal formation. CPP crystals are deposited in the cartilage matrix (preferentially in the middle layer) or in areas of chondroid metaplasia. Hypertrophic chondrocytes and specific cartilage matrix changes (e.g. high levels of dermatan sulfate and S-100 protein) are related to CPP crystal deposition and growth. CPP crystals cause inflammation by engaging with the NALP3 inflammasome, and with other components of the innate immune system, and is marked with a prolonged neutrophilic inflitrate. The pathogenesis of resolution of CPP crystal-induced inflammation is not well understood.
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Clements, Howard Eugene. Effect of Varying the Concentration of Calcium and Potassium on the Line Intensity of Phosphorus in Spectro-Analysis. Creative Media Partners, LLC, 2021.
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Houillier, Pascal. Magnesium homeostasis. Edited by Robert Unwin. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199592548.003.0027.
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Magnesium is critically important in the process of energy release. Although most magnesium is stored outside the extracellular fluid compartment, the regulated concentration appears in blood. Urinary magnesium excretion can decrease rapidly to low values when magnesium entry rate into the extracellular fluid volume is low, which has several important implications: cell and bone magnesium do not play a major role in the defence of blood magnesium concentration; while a major role is played by the kidney and especially the renal tubule, which adapts to match the urinary magnesium excretion and net entry of magnesium into extracellular fluid. In the kidney, magnesium is reabsorbed in the proximal tubule, the thick ascending limb of the loop of Henle (TALH), and the distal convoluted tubule (DCT). Magnesium absorption is mainly paracellular in the proximal tubule and TALH, whereas it is transcellular in the DCT. The hormone(s) regulating renal magnesium transport and blood magnesium concentration are not fully understood. Renal tubular magnesium transport is altered by a number of hormones, mainly in the TALH and DCT. Parathyroid hormone, calcitonin, arginine vasopressin, ß-adrenergic agonists, and epidermal growth factor, all increase renal tubular magnesium reabsorption; in contrast, prostaglandin E2 decreases magnesium reabsorption. Non-hormonal factors also influence magnesium reabsorption: it is decreased by high blood concentrations of calcium and magnesium, probably via the action of divalent cations on the calcium-sensing receptor; metabolic acidosis decreases, and metabolic alkalosis increases, renal magnesium reabsorption.
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Chau, Anthony T. Magnesium Toxicity. Edited by Matthew D. McEvoy and Cory M. Furse. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190226459.003.0058.
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Magnesium sulfate is currently the drug of choice for prophylaxis against eclampsia in women with preeclampsia and first-line treatment for eclampsia. In this population, medication administration error is a frequent cause of magnesium toxicity. Symptoms of toxicity are linked to increasing serum concentrations, but routine monitoring is not recommended. Instead, deep tendon reflexes and respiratory rate are the most commonly monitored parameters. However, magnesium serum concentration should be monitored when magnesium toxicity is suspected or in patients at high risk of toxicity. The gastrointestinal and central nervous systems are usually affected first. As the serum concentration becomes extremely high, neuromuscular and cardiovascular effects may occur, leading to respiratory failure and cardiac arrest. In addition to standard advanced life support measures, calcium is the mainstay of treatment and in some cases forced diuresis and dialysis may also be considered.
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Herrington, William G., Aron Chakera, and Christopher A. O’Callaghan. Renal calculi. Edited by Patrick Davey and David Sprigings. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199568741.003.0166.
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Nephrolithiasis is the presence of kidney stones, which are also known as ‘renal calculi’. Renal calculi arise when urine becomes supersaturated with insoluble components. This may occur when there is excessive production of these components, a decrease in factors maintaining their solubility (e.g. citrate), or a reduction in urine volume (leading to increased concentration). Infection may play a significant role in the initiation of renal calculus formation, by creating a nidus for further crystal growth. Renal calculi are usually classified into two categories: those containing calcium (80%), and non-calcareous calculi (20%).
Book chapters on the topic "Calcium concentration"
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Llinás, Rodolfo, Mutsuyuki Sugimori, and Robert Silver. "Calcium Concentration Microdomains." In Calcium and Cellular Metabolism. Springer US, 1997. http://dx.doi.org/10.1007/978-1-4757-9555-4_2.
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Zanin, Sofia, Elisa Lidron, Rosario Rizzuto, and Giorgia Pallafacchina. "Methods to Measure Intracellular Ca2+ Concentration Using Ca2+-Sensitive Dyes." In Calcium Signalling. Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9018-4_4.
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Agarwal, Ritu, Sunil Dutt Purohit, and Kritika. "Effects of Buffers Over the Cytosolic Calcium Concentration." In Modeling Calcium Signaling. Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-1651-7_3.
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Meyer, Tobias, Nancy L. Allbritton, and Elena Oancea. "Regulation of Nuclear Calcium Concentration." In Ciba Foundation Symposium 188 - Calcium Waves, Gradients and Oscillations. John Wiley & Sons, Ltd., 2007. http://dx.doi.org/10.1002/9780470514696.ch14.
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Crook, Martin. "Disorders of plasma calcium concentration." In Acute Medicine - A Practical Guide to the Management of Medical Emergencies, 5th Edition. John Wiley & Sons, Ltd, 2017. http://dx.doi.org/10.1002/9781119389613.ch87.
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Isogai, Y., T. Yokose, S. Ikemoto, et al. "Ionized Free Calcium Concentration and Deformability in Platelets." In Cerebral Ischemia and Calcium. Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-85863-5_33.
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Frifelt, J. J., and F. Bangsgaard Pedersen. "CAPD Using a High Calcium Concentration." In Frontiers in Peritoneal Dialysis. Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-662-11784-2_48.
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Reuter, Harald. "Voltage-Dependent Mechanisms for Raising Intracellular Free Calcium Concentration: Calcium Channels." In Novartis Foundation Symposia. John Wiley & Sons, Ltd., 2007. http://dx.doi.org/10.1002/9780470513347.ch2.
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Rüegg, Johann Caspar. "The Dependence of Muscle Contraction and Relaxation on the Intracellular Concentration of Free Calcium Ions." In Calcium in Muscle Contraction. Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-77560-4_4.
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Neher, E. "Concentration Profiles of Intracellular Calcium in the Presence of a Diffusible Chelator." In Calcium Electrogenesis and Neuronal Functioning. Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-70744-5_8.
Full textConference papers on the topic "Calcium concentration"
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Natsi, P. D., S. G. Rokidi, and P. G. Koutsoukos. "Calcium Carbonate Scale Formation in Water- Mono Ethylene Glycol (MEG)." In CORROSION 2019. NACE International, 2019. https://doi.org/10.5006/c2019-12817.
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Abstract The influence of mono ethylene glycol (MEG) on the precipitation of calcium carbonate was investigated at constant supersaturation, 25°C, pH 8.5. Seeded and unseeded experiments were done in aqueous supersaturated calcium carbonate solutions containing MEG over the concentration range 0-80 % v/v. The induction times and the subsequent rates of precipitation in unseeded, spontaneous precipitation of calcium carbonate were affected by the presence of MEG. At low values of the supersaturation ratio (SRcalcite=19.95-60.26) and for MEG concentrations in the range 30-80% v/v, the solutions were stable for four days. Values lower than 30% v/v of MEG concentrations, gave induction periods for calcium carbonate precipitation between 160-500min. The precipitates were examined for their morphological characteristics and showed that, in the presence of low MEG concentrations (10-20 % v/v), the precursor phase, vaterite, was stabilized. The homogeneous nucleation and growth of calcium carbonate in the absence and in the presence of MEG was also investigated, by the inoculation of substrates, like quartz calcite seed crystals, in stable supersaturated solutions. Both cases had as a result the significantly reduction of nucleation and growth of calcium carbonate, by increasing MEG concentration in the solutions.
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Xyla, Aglaia, Pavlos Klepetsanis, and Petros G. Koutsoukos. "Calcium Carbonate-Calcium Sulfate Scale Formation at Elevated Temperatures." In CORROSION 1989. NACE International, 1989. https://doi.org/10.5006/c1989-89177.
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Abstract Scale formation is a commonly occuring problem in processes employing primary waters in which ions of sparingly soluble salts are in relatively high concentrations, depending on their origin. The problem is intensified at elevated temperatures and may be associated with corrosion phenomena when scale is deposited on metallic parts of equipment. Since a number of sparingly soluble salts may precipitate, the relationship between such salts is interesting. In this work the relationship between calcium carbonate and calcium sulfate dihydrate was investigated. Calcium carbonate solutions, saturated with respect to calcium sulfate dihydrate at 120°C and at 140°C,were seeded with synthetic calcium sulfate dihydrate seed crystals and the precipitation process was monitored by following calcium concentration in solution. The deposition of calcium carbonate was induced by the introduced gypsum crystals following the lapse of induction periods proportional to the solution supersaturation. The phase initially forming was found to be vaterite, converting subsequently into aragonite and calcite. The apparent rate order was found to be 5, a value very close to that found in spontaneous precipitation studies of the calcium carbonate system. It appeared that the phase forming is stabilized by temperature mainly, since the same phases were found in the absence of calcium sulfate dihydrate and at conditions of spontaneous precipitation at 140°C. At this temperature, it was found that the precipitation of calcium carbonate was retarded by the presence of the gypsum seed crystals.
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Gates, Emily, Barbara Padgett, Bill Harper, Brett Tossey, and John Shingledecker. "Corrosion Resistance of Alloys in Calcium Bromide and Calcium Chloride Solutions." In CORROSION 2017. NACE International, 2017. https://doi.org/10.5006/c2017-09749.
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Abstract Calcium bromide is used in the coal fire power plant industry to help control mercury emissions. Adding bromide ions to the flue gas can cause the total halide ion content of the downstream Wet Flue Gas Desulfurization (WFGD) slurry to increase. The objective of this study was to determine the effect of bromide additions in chloride-rich WFDG slurries on the crevice corrosion resistance of commercially-available corrosion resistant alloys. Cyclic potentiodynamic polarization (CPP) was used to collect voltage-current traces for each alloy. The traces were analyzed to estimate the performance of three alloys in model solutions with varying concentrations of calcium chloride, calcium bromide, and a mixture of calcium chloride and calcium bromide. The alloys had pitting resistance equivalent numbers of 35, 44, and 66. Three factors from the CPP tests were assessed: the open circuit potential, the breakdown potential, and the repassivation potential. The following conclusions were drawn from the CPP study: Alloys with increasing PREn values require increasing total halide ion concentrations to shift breakdown or protection potentials.Chlorides are more aggressive than bromides to the alloys tested using model electrolytes. A multi-variable regression analysis was performed to help reveal the statistically significant relationship(s) between open circuit potential, the breakdown potential, the repassivation potential, and the total halide ion concentration. A conservative ratio of bromides to chlorides can be used to estimate total effective chloride concentrations in slurry solutions containing mixtures of chlorides and bromides.
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Flaten, Ellen Marie, Marion Seiersten, Ralf Beck, Charlotte Aanonsen, and Jens-Petter Andreassen. "Precipitation of Calcium Carbonate in Monoethylene Glycol and Water." In CORROSION 2014. NACE International, 2014. https://doi.org/10.5006/c2014-4047.
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Abstract Calcium carbonate is one of the most abundant minerals precipitating during gas production. This work is focused on precipitation of CaCO3 in presence of Monoethylene glycol (MEG), used as hydrate inhibitor. MEG is known to affect the thermodynamics of calcium carbonate and the results show that it also has a large impact on the precipitation kinetics. The whole precipitation process has been investigated including polymorphism, induction times, nucleation rates and growth rates. Emphasize has been on growth rate as it is most important and has a large impact on both induction time and transformation rate from metastable polymorphs to stable calcite. The experiments were performed at 25-80°C with MEG concentration up to 90 wt%. The growth rates of all the polymorphs are reduced in presence of MEG, but calcite is most inhibited. The slow growth of calcite at high MEG concentrations result in a very slow transformation from initially mixed metastable polymorphs. It prolongs the induction periods and makes it difficult to determine nucleation rates, too. However, it is possible to give a rough estimate of nucleation rates when the impact of the growth rate is taken account. Nucleation rates decrease with increasing MEG concentrations.
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Koutsoukos, Petros G., and Evangelia Kapetanaki. "Mixed Calcium Carbonate and Calcium Sulfate Scale." In CORROSION 2016. NACE International, 2016. https://doi.org/10.5006/c2016-07457.
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Abstract Crystallization fouling is one of the major problems in process industries using water. In the present work the precipitation of calcium carbonate (CaCO3), and of mixed calcium carbonate - calcium sulfate (CaSO4) deposits on the walls of a heated metal surface of stainless steel was investigated. All experiments were done at constant flow (2.3 ± 0.1 l/min), pressure and wall temperature (51± 1°C) using solutions either supersaturated with respect to calcium carbonate or both with respect to calcium carbonate and calcium sulfate. The kinetics of mineral deposition was monitored by the solution specific conductance change and from measurements of the calcium concentration as a function of time. The crystal growth of calcium carbonate followed a surface diffusion controlled mechanism. The dominant mineral formed was calcite, although aragonite and vaterite were found at lower proportions. Crystal growth kinetics as a function of supersaturation with respect to gypsum in solutions supersaturated with respect to both salts, suggested bulk diffusion control of the process. The solids deposited on the walls of the heated specimen, consisted of gypsum and aragonite. The morphology of the deposits suggested that gypsum crystals grow on the crystals of aragonite, which preceded in the sequence of deposition events.
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Ciolkowski, Michal, and Neil Bretherton. "Elucidating the Influence of Calcium Ion Concentration on Corrosion Inhibitor Performance." In CORROSION 2021. AMPP, 2021. https://doi.org/10.5006/c2021-16692.
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ABSTRACT CO2 corrosion is one of the most common problems faced during oil and gas production, although steel pipes offer a long-term economical use in CO2 corrosive environments with the application of carefully selected corrosion inhibitors. Inhibitor efficiency is affected by many variables, including temperature, pressure, flow velocity, pH, and composition of produced water. The impact of brine composition on corrosion inhibitor performance is elucidated in this work; more specifically, the question of whether high salinity or high Ca2+ concentration has a greater impact on corrosion inhibitor performance is answered. Corrosion inhibition performance of various inhibitors, including quaternary amines and alkyl pyridine quat, were evaluated with brines of varying Ca2+ concentration (0 to 20,000 mg/L) and salinity [57,000 to 250,000 total dissolve solids (TDS)]. The corrosion inhibition was studied in situ by linear polarization resistance (LPR), using a UNS G10180(1) (carbon steel). The goal of this study is to help improve corrosion inhibitor design for high calcium containing brines.
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Cognetti, Ann, Jennifer Parsons, Mike Geraghty, and Dan Vanderpool. "Operation of Cooling Towers at High Cycles of Concentration: Corrosion and Scale Control." In CORROSION 1996. NACE International, 1996. https://doi.org/10.5006/c1996-96575.
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Abstract Unique chemistry is developed which allows conservation of water through increased cycles. This chemistry permits control of calcium carbonate up to and exceeding 300 times saturation. This paper will discuss the superior corrosion inhibition properties under these conditions and the properties that afford good protection. Corrosion inhibition studies using weight loss, electrochemical tests and surface analysis show that PAPEMP allows a very effective invisible cathodic barrier to form which incorporates calcium carbonate. The significant property of the inhibitor that differentiates performance and allows it to work under these conditions is its extreme calcium tolerance.
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Flaten, Ellen Marie, Xiaoguang Ma, Marion Seiersten, Charlotte Aanonsen, Ralf Beck, and Jens-Petter Andreassen. "Impact of Monoethylene Glycol and Fe2+ on Crystal Growth of CaCO3." In CORROSION 2015. NACE International, 2015. https://doi.org/10.5006/c2015-05770.
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Abstract Calcium carbonate is one of the most abundant minerals precipitating during gas production. This work is focused on precipitation of CaCO3 in presence of Monoethylene glycol (MEG), used as hydrate inhibitor. MEG is known to affect the thermodynamics of calcium carbonate and this study shows that it has a large impact on the precipitation kinetics. The whole precipitation process has been investigated including polymorphism, induction times, nucleation rates and growth rates. Growth rate is emphasized as it has a large impact on both induction time and transformation rate from metastable polymorphs to stable calcite. The experiments were performed at 25-80°C with MEG concentration up to 90 wt%. MEG prolongs the induction period for precipitation as its presence decreases both nucleation rates and growth rates. The growth rates of all three polymorphs are reduced in presence of MEG, but calcite is most inhibited. The slow growth of calcite at high MEG concentrations result in a very slow transformation from initially mixed metastable polymorphs. Ferrous ions (Fe2+) affect the polymorphism of CaCO3. The growth of vaterite and aragonite is retarded to different extent. Vaterite growth is most inhibited resulting in aragonite being the most abundant polymorph in a larger MEG and temperature range. The effect depends strongly on Fe2+ concentration relative to solid surface area.
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Koutsoukos, Petros G., P. Klepetsanis, N. Spanos, and D. G. Kanellopoulou. "Calcium Carbonate Crystal Growth and Dissolution Inhibitors." In CORROSION 2007. NACE International, 2007. https://doi.org/10.5006/c2007-07052.
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Abstract Calcium carbonate scale formation was simulated by the development in situ of supersaturation in the vicinity of a stainless steel electrode immersed in a stable calcium carbonate solution. The initiation of the growth of the supercritical crystals was accompanied by a decrease of the absolute value of the cathodic current, which at the end of crystallization was constant. The absolute final value of the cathodic current was the measure of the extent of crystallization. In the absence of any additive the only phase identified on the electrode was calcite. In the presence however of additives (organic compounds) vaterite was stabilized for long periods and was identified. The compounds tested included a commercial organophosphorous inhibitor (B206G), poly-acrylate copolymers: Poly acrylic acid (MW 2000, PAA), Poly (acrylic acid 2-acrylamido-2-methyl propane sulfonic acid) (PAS), Poly (acrylic acid: 2-acrylamido-2-methyl propane sulfonic acid: sulfonated styrene) (PSS) and Humic acid (HA). The order of inhibition efficiency was: B206G&gt; PAA, PAS&gt; PSS &gt;&gt; HA. In all cases inhibition was almost complete with inhibitors concentration up to 10 ppm, with the exception of HA which was effective for concentrations of 80 ppm. The additives acted by adsorption onto the active growth sites of the growing crystals of calcium carbonate. The supersaturation developed at the electrode was sufficiently high to develop vaterite which was converted into calcite, in the absence of the additives. The presence of all additives, with the exception of HA, stabilized the formation of vaterite. The dissolution of calcium carbonate at alkaline pH, 8.25, in undersaturated solutions, close to equilibrium showed that the mechanism was a surface diffusion controlled process. The presence of (1-hydroxyethylidene) - 1,1 diphosphonic acid (HEDP) inhibited drastically the rates of dissolution, even at 1μM concentrations. The inhibition was caused because of the adsorption of the HEDP ions onto the active growth sites by electrostatic interactions as demonstrated by surface charge measurements. Additional interactions including hydrogen bonding and lateral interactions between adsorbed molecules is also a possibility according to the analysis of a surface complexation model.
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Kirboga, Semra, and Mualla Öner. "Removal of Cu(II) from Aqueous Solution with Precipitated Calcium Carbonate." In CORROSION 2016. NACE International, 2016. https://doi.org/10.5006/c2016-07445.
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Abstract Calcium carbonate (CaCO3) was synthesized in the presence of the water-soluble biopolymer carboxymethyl inulin (CMI) by a precipitation method. The obtained CaCO3 crystals were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The results showed that the polymorph of the synthesized calcium carbonate crystals changed from pure calcite to the mixture of vaterite and calcite in the presence of biopolymer at a concentration of 0.5 g/L. The sorption behavior of Cu(II) on synthesized calcium carbonate crystals was investigated. The results showed that Cu(II) sorption rate was fast and most of Cu(II) was adsorbed within 5 minute. The experimental results were fitted to the modified Freundlich, pseudo-first-order, and pseudo-second-order equations to find out sorption capacities. The results indicate that the sorption data fits well in the modified Freundlich isotherm model. This indicates the existence of multiple sites available for adsorption.
Reports on the topic "Calcium concentration"
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Slack, William, Anthony Bednar, and K. Killgore. Development of a trace element signature library across a large watershed for assessing large-scale fish movement patterns : supplemental data. Engineer Research and Development Center (U.S.), 2025. https://doi.org/10.21079/11681/49787.
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Utilizing trace element or stable isotope analysis has proven to be an effective means to characterize early life history and large-scale movement patterns in fishes. Target species are assessed for analyte concentrations occurring in calcified hard structures and compared to signatures noted from associated watersheds. Our objective was to establish a trace element signature profile for major tributaries occurring within the Mississippi River Valley (MRV). Unfiltered water samples were obtained from 49 stations from Dubuque, IA downstream to Gramercy, LA (1387 river miles) from July through December 2023 during seasonally normal water conditions with three water samples (left descending bank, mid-channel, right descending bank) obtained from each sample station. Whole water samples were evaluated for the presence and relative concentration of Barium, Strontium, Calcium, Iron and Lithium, and were acidified with ultrapure nitric acid (Fisher Optima grade) prior to determination of total metal concentrations using ICP-AES and ICP-MS following modifications of USEPA methods 6010 and 6020, respectively. A Perkin Elmer Optima 8300DV ICP-AES was used to quantify Calcium, Iron, and Lithium whereas a Perkin Elmer NexION 350D ICP-MS was used for Barium and Strontium. Analytes were assessed for total concentrations and expressed as mg/L. In addition, Barium and Strontium concentrations were also normalized to Calcium as a pseudo-internal standard and reported as element/Ca ratios (mmol/mol).
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Pulgarín Díaz, John Alexander, Lucas Esteban Cano Gallego, and Angela Maria Arcila Cardona. Influence of liming on Cedrela odorata L. seedlings growth and attack by Hypsipyla grandella Zeller (Lepidoptera: Pyralidae). Corporación colombiana de investigación agropecuaria - AGROSAVIA, 2019. http://dx.doi.org/10.21930/agrosavia.poster.2019.25.
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Cedrela odorata is one of the most important commercial Neotropical forestry species, harvested mainly from natural forest, what have taken the species to danger of extinction. Its commercial plantation is limited by Hypsipyla grandella attacks, which could reach 100% of individuals in a forest plantation (Figure 1). Inverse relation of available calcium concentration in the soil for C. odorata and attacks of H. grandella had been reported (da Silva et al., 2009). Some studies indicate that calcium and boron addition to the soil has a positive e ect in height growth of Swietenia macrophylla (da Silva Junior et al., 2014); nevertheless, some studies suggest that when growth is high there is an increase in attack probability (Newton et al., 1993). Then some clarity on this subject is required.
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Vermeul, Vincent R., Brad G. Fritz, Jonathan S. Fruchter, James E. Szecsody, and Mark D. Williams. 100-NR-2 Apatite Treatability Test: High-Concentration Calcium-Citrate-Phosphate Solution Injection for In Situ Strontium-90 Immobilization. Office of Scientific and Technical Information (OSTI), 2010. http://dx.doi.org/10.2172/1010480.
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Williams, Mark D., Brad G. Fritz, Donaldo P. Mendoza, et al. Interim Report: 100-NR-2 Apatite Treatability Test: Low Concentration Calcium Citrate-Phosphate Solution Injection for In Situ Strontium-90 Immobilization. Office of Scientific and Technical Information (OSTI), 2008. http://dx.doi.org/10.2172/969183.
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Vermeul, Vincent R., Brad G. Fritz, Jonathan S. Fruchter, James E. Szecsody, and Mark D. Williams. 100-NR-2 Apatite Treatability Test FY09 Status: High Concentration Calcium-Citrate-Phosphate Solution Injection for In Situ Strontium-90 Immobilization. Office of Scientific and Technical Information (OSTI), 2009. http://dx.doi.org/10.2172/969621.
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Stevens and Olsen. PR-179-12214-R01 CO Sensor Experimental Evaluation for Catalyst Health Monitoring. Pipeline Research Council International, Inc. (PRCI), 2014. http://dx.doi.org/10.55274/r0010827.
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Oxidation catalysts and three-way catalysts can be used to reduce the amount of CO present in engine exhaust. For 2-stroke lean-burn engines, the oxidation catalyst degrades over time be-cause of the buildup of poisons such as sulfur, zinc, phosphorous, and calcium. Three-way cata-lysts used with stoichiometric engines also degrade over time. Emissions analyzers are often used to evaluate the degradation of oxidation catalysts and three-way catalysts, but it can be very time consuming and expensive. Ideally, a simple sensor system would be beneficial for operating companies to determine if the catalyst were out of compliance according to normal operating standards. An ECM CO sensor and recording device was acquired for testing. The CO sensor system was evaluated for its ability to monitor post-catalyst CO concentration. The results show that this CO sensor system is ineffective at monitoring post-catalyst CO concentration.
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Baird, Kaitlin, Anne Cohen, and Samantha de Putron. Ocean Acidification: Building a Skeleton in a Changing Ocean. American Museum of Natural History, 2015. http://dx.doi.org/10.5531/cbc.ncep.0168.
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Coral reefs are particularly vulnerable to ocean acidification due to their calcium carbonate “skeletons,” yet little is known about how ocean acidification will affect coral recruitment. In this exercise, students will examine a species of stony or hard coral belonging to the Order Scleractinia, Favia fragum, and examine how ocean acidification and changes in seawater saturation state (carbonate ion concentration) can affect the calcification process of new recruits of this coral species in Bermuda. After a brief introduction to coral reproduction and recruitment, as well as the chemistry behind calcification and acidification, students will go on to understand the experimental design, obtain and manipulate real data, and analyze the dataset.
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Tengamnuay, Parkpoom. Efficacy and mechanistic studies of chitosan as nasal absorption enhancer of peptide drugs : research report. Chulalongkorn University, 1999. https://doi.org/10.58837/chula.res.1999.27.
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Objective. To evaluation the in vivo efficacy of chitosan as nasal absorption enhancers of peptides in rats and compare the results with that of hydroxypropyl- and dimethyl-Beta-cyclodextrins (HPBetaCD and DMBetaCD). Methods. Two types of chitosan. i.e., the free base (CSJ) and the glutamate salt form (CSG) were evaluated for their nasal absorption enhancing effect on salmon calcitonin (sCT) using an in vibo rat absorption technique. Solutions containing sCT and chitosan (0 to 1.25 % w/v) in isotonic phosphate buffers (pH 3.0 to 6.0) were nasally administered at the dose of 10 IU/kg. The plasma calcium lowering effect in each sCT-treated rat was determined by calculating the total percent decrease in plasma calcium (%D). Results. CSJ showed an increase in %D as the solution pH was decreased in accordance with the increased ionization and hydration of the free base chitosan at the more acidic pH. However, CSG showed an increase in %D with increasing pH, with maximum calcium lowereing effect observed at pH 6.0. At their optimal pH (4.0 for CSJ and 6.0 for CSG), the absorption enhancing effect of both chitosans was concentration dependent from 0.25 to 1.0 % w/v and leveled off at 1.25% w/v. Using specific RIA, the absolute bioavailability of plasma sCT was determined to be 2.45, 1.91, and 1.22 % for 1% CSJ, 5% DMBetaCD, and control group (intranasal sCt alone). Respectively. All the enhancers showed significant absorption enhancement with the highest effect observed with CSJ and DMBetaCD wheras the effect of HPBetaCD was the smallest. Also, the two chitosan did not possess any inhibitory effect on the in vitro activities of trypsin and leucine aminopeptidase, two major nasal proteolytic enzymes responsible for the degradation of sCT in the nasal cavity. Thus, the nasal absorption enhancement of chitosans may not involve protection of the peptide against proteolytic degradation in the nasal cavity. In conclusion, cationic polymer chitosans may have promising potential as an effective nasal absorption enhancer ofsCT.
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Wicker, Louise, Ilan Shomer, and Uzi Merin. Membrane Processing of Citrus Extracts: Effects on Pectinesterase Activity and Cloud Stability. United States Department of Agriculture, 1993. http://dx.doi.org/10.32747/1993.7568754.bard.
Full textAbstract:
The U.S. team studied the role of cations and pH on thermolabile (TL-PE) and thermostable (TS-PE), permeation in ultrafiltration (UF) membranes, affinity to ion exchange membranes, mechanism of cation and pH activation, and effect on PE stability. An optimum pH and cation concentration exists for activity and UF permeation, which is specific for each cation type. Incomplete release of PE from a pectin complex resulted in low PE binding to cationic and anionic membranes. Incubation of PE at low pH increases the surface hydrophobicity, especially TL-PE, but the secondary structure of TL-PE is not greatly affected. The Israeli team showed that stable cloud colloidal constituents flocculate following the conversion of soluble to insoluble biopolymers. First, formation of pectic acid by pectinesterase activity is followed by the formation of calcium pectate gel. This process initiates a myriad of poorly defined reactions that result in juice clarification. Second, protein coagulation by heat resulted in flocculation of proteinacous bound cloud constituents, particularly after enzymatic pectin degradation. Pectinesterase activity is proposed to be an indirect cause for clarification; whereas binding of cloud constituents is the primary event in clarification by pectate gel and coagulated proteins. Understanding the mechanism of interaction of protein and pectic polymers is key to understanding cloud instability. Based on the above, it was hypothesized that the structure of pectin-protein coagulates plays a key role in cloud instability.
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Desbarats, A. J., and J. B. Percival. Hydrogeochemistry of mine tailings from a carbonatite-hosted Nb-REE deposit, Oka, Quebec, Canada. Natural Resources Canada/CMSS/Information Management, 2023. http://dx.doi.org/10.4095/331256.
Full textAbstract:
Environmental impacts associated with the mining of carbonatite deposits are an emerging concern due to the demand for critical metals. This study investigates the chemistry of tailings seepage at the former Saint Lawrence Columbium mine near Oka, Québec, Canada, which produced pyrochlore concentrate and ferroniobium from a carbonatite-hosted Nb-REE deposit. Its objectives are to characterize the mineralogy of the tailings and their pore water and effluent chemistries. Geochemical mass balance modeling, constrained by aqueous speciation modeling and mineralogy, is then used to identify reactions controlling the chemical evolution of pore water along its flow path through the tailings impoundment. The tailings are composed mainly of REE-enriched calcite (82 wt. %), biotite (12 wt. %) and fluorapatite (4 wt. %). Minor minerals include chlorite, pyrite, sphalerite, molybdenite and unrecovered pyrochlore. Secondary minerals include gypsum, barite and strontianite. Within the unsaturated zone, pore water chemistry is controlled by sulfide oxidation and calcite dissolution with acid neutralization. With increasing depth below the water table, pore water composition reflects gypsum dissolution followed by sulfate reduction and FeS precipitation driven by the oxidation of organic carbon in the tailings. Concomitantly, incongruent dissolution of biotite and chlorite releases K, Mg, Fe, Mn, Ba and F, forming kaolinite and Ca-smectite. Cation exchange reactions further remove Ca from solution, increasing concentrations of Na and K. Fluoride concentrations reach 23 mg/L and 8 mg/L in tailings pore water and effluent, respectively. At a pH of 8.3, Mo is highly mobile and reaches an average concentration of 83 µg/L in tailings effluent. Although U also forms mobile complexes, concentrations do not exceed 16 µg/L due to the low solubility of its pyrochlore host. Adsorption and the low solubility of pyrochlore limit concentrations of Nb to less than 49 µg/L. Cerium, from calcite dissolution, is strongly adsorbed although it reaches concentrations (unfiltered) in excess of 1 mg/L and 100 µg/L in pore water and effluent, respectively. Mine tailings from carbonatite deposits are enriched in a variety of incompatible elements with mineral hosts of varying reactivity. Some of these elements, such as F and Mo, may represent contaminants of concern because of their mobility in alkaline tailings waters.