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Actinolite is an intermediate member in a solid-solution series between magnesium-rich tremolite, Ca 2 (Mg 5.0-4.5 Fe 2+ 0.0-0.5)Si 8 O 22 (OH) 2, and iron-rich ferro-actinolite, ☐Ca 2 (Mg 2.5-0.0 Fe 2+ 2.5-5.0)Si 8 O 22 (OH) 2. Mg and Fe ions can be freely exchanged in the crystal structure. Like tremolite, asbestiform actinolite is ...
Ca 2+ binding to these regulatory domains activates the transport of Ca 2+ across the plasma membrane. The structure of CBD1 shows four Ca 2+ ions arranged in a tight planar cluster. The structure of CBD2 in the Ca 2+ -bound (1.7 Å resolution) and Ca 2+ -free (1.4 Å resolution) conformations shows (like CBD1) a classical Ig fold but ...
The sodium-calcium exchanger (often denoted Na + /Ca 2+ exchanger, exchange protein, or NCX) is an antiporter membrane protein that removes calcium from cells. It uses the energy that is stored in the electrochemical gradient of sodium (Na +) by allowing Na + to flow down its gradient across the plasma membrane in exchange for the countertransport of calcium ions (Ca 2+).
Calcium batteries are one of many candidates to replace lithium-ion battery technology. It is a multivalent battery.Key advantages are lower cost, earth abundance (41,500 ppm), higher energy density, high capacity and high cell voltage, [12] and potentially higher power density.
Ca 2+ centres are eight-coordinate, being centred in a cube of eight F − centres. Each F − centre is coordinated to four Ca 2+ centres in the shape of a tetrahedron. [ 5 ] Although perfectly packed crystalline samples are colorless, the mineral is often deeply colored due to the presence of F-centers .
Due to the large size of the calcium ion (Ca 2+), high coordination numbers are common, up to 24 in some intermetallic compounds such as CaZn 13. [21] Calcium is readily complexed by oxygen chelates such as EDTA and polyphosphates , which are useful in analytic chemistry and removing calcium ions from hard water .
The structure is related to that of zirconium orthosilicate (zircon): Ca 2+ is 8-coordinate, SO 2− 4 is tetrahedral, O is 3-coordinate. CaSO 4 ·2H 2 O (gypsum and selenite (mineral)): dihydrate. [7] CaSO 4 · 1 / 2 H 2 O : hemihydrate, also known as plaster of Paris. Specific hemihydrates are sometimes distinguished: α-hemihydrate ...
The US Institute of Medicine (IOM) established Recommended Dietary Allowances (RDAs) for calcium in 1997 and updated those values in 2011. [6] See table. The European Food Safety Authority (EFSA) uses the term Population Reference Intake (PRIs) instead of RDAs and sets slightly different numbers: ages 4–10 800 mg, ages 11–17 1150 mg, ages 18–24 1000 mg, and >25 years 950 mg. [10]