Steady-State Transitions and Polymorph Transformations in Continuous Precipitation of Calcium Carbonate

1994 ◽  
Vol 33 (9) ◽  
pp. 2187-2197 ◽  
Author(s):  
D. Chakraborty ◽  
V. K. Agarwal ◽  
S. K. Bhatia ◽  
J. Bellare
Keyword(s):  
Steady State ◽  
Calcium Carbonate ◽  
State Transitions ◽  
Continuous Precipitation

Effects of Calcium Source on Calcium-Metabolic Parameters in Healthy Women and Men

2021 ◽  
Vol 8 (2) ◽  
Author(s):  
Hitz MF ◽  
◽  
Dahl M ◽  
Jørgensen NR ◽  
◽  
...  
Keyword(s):  
Vitamin D ◽  
Steady State ◽  
Calcium Carbonate ◽  
Calcium Absorption ◽  
Menopausal Status ◽  
Daily Intake ◽  
Dietary Calcium ◽  
Calcium Excretion ◽  
Steady State Condition

Background/Objectives: Calcium and vitamin D are important for bone health. We compared 24-hour urinary calcium-excretion (Uca/24hrs), during dietary calcium steady-state condition, for different calcium-sources and effects of vitamin D, age and sex. Subjects/Methods: Fifty-two healthy pre- and postmenopausal women and men completed the regimens: placebo, calcium carbonate (400mg) +18μg vitamin D, calcium carbonate (400mg) +38μg vitamin D and 400mg calcium phosphate (milk). Uca/24hrs was measured during dietary calcium steady state as a surrogate measure of calcium-absorption. Serum-calcium, parathyroid hormone (PTH), 25-hydroxy-vitamin D, Procollagen Type 1 N-terminal Pro- Peptide (P1NP) and C-terminal Telopeptide of type 1 collagen (CTX) were measured. Results: Mean daily intake of calcium for the study group ± SD was 1105 ±396 mg. Mean-Uca ± SD: placebo 5.19 ± 2.04 mmol/24hrs, milk 5.88 ± 2.39 mmol/24hrs, (CaCO3+D) 6.19 ± 2.34 mmol/24hrs and (CaCO3 + DD) 6.26 ± 2.32 mmol/day. Uca were higher for all regimens compared to placebo (p <0.001), no difference was found between regimens. CTX was lower during all regimens compared to placebo (p <0.001): placebo 450 ± 243 μg/L, Milk 377 ± 248 μg/L, (CaCO3+D) 392 ± 266 μg/L and (CaCO3+DD) 361 ± 232 μg/L. Conclusions: Uca was higher during supplementation with calcium compared to placebo. Supplementation with calcium reduced bone resorption significantly without effecting PTH. Menopausal status, sex and supplement with vitamin d demonstrated no effect on calcium excretion.

scholarly journals Crystallization kinetics of amorphous calcium carbonate in confinement

2019 ◽  
Vol 10 (19) ◽  
pp. 5039-5043 ◽  
Author(s):  
Jack Cavanaugh ◽  
Michael L. Whittaker ◽  
Derk Joester
Keyword(s):  
Steady State ◽  
Calcium Carbonate ◽  
Crystal Nucleation ◽  
Amorphous Calcium Carbonate ◽  
Emulsion Droplets ◽  
Individual Crystal ◽  
Upper Limit ◽  
Kinetics Of

In situ observation of amorphous calcium carbonate (ACC) confined in ∼500 pL emulsion droplets allows determination of the timing of individual crystal nucleation events. Statistical analysis of events in hundreds of droplets establishes an upper limit for the steady-state nucleation rate of 1.2 cm−3 s−1 for the crystallization from ACC.

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