Calcium

Calcium has at least six stable natural occurring isotopes, and three radioactive ones: Ca-41, 45, 47.

The stable ones are (mass)numbered: 40, 42, 44, 46 and 48, plus the only odd one 43.

You might want to check the spelling of Sir Humphrey Davy...
Calcium was prepared as lime by the Romans under the name calyx in the 1st century A.D., but the metal was not discovered until 1808 in England.
Calcium is found throughout the body, but is primarily found in the bone, and in the blood.

It is important for neurotransmission in that its influx in neural boutons results in the triggering of exocytosis of neurotransmitter vesicles, which allows neurotransmitters to enter the synaptic gap.
calcium was discovered in England

Ductility is the characteristic of a metal or another material that allows it to be drawn or rolled to be made longer without the material breaking. To get a little more technical, it is the ability of a material to undergo plastic deformation without failure. It is one of the physical properties of a material. Some nice, soft taffy can be pulled and will "string out" without breaking. But if that taffy is cold and not completely processed, pulling on it will result in a little stretching and a quick break. The metals copper, which is drawn into wire for use as an electrical conductor, and aluminium, which is rolled repeatedly until it is turned into foil which we use in the kitchen, are both metals with high ductility. Their ductility and some other physical characteristics make them ideal choices for the common applications mentioned. A link can be found below.
The ductility of steel for concrete reinforcement can be defined as an ability to achieve significant deformations without marked increase of stresses beyond the yield strength of steel. This term applies to the behavior of a construction in the conditions of nonlinear deformations, in which ductility plays an important role.

For many years there have been observed large differences between the actual durability of statically indeterminable elements of a construction and the values determined according to the principles of linear - elastic theory. The next phenomenon observed was the behavior of a construction at the load close to the destructive load, when there followed a considerable increase of deformations in the presence of a small increase of stresses. More recently, it has become more and more popular to apply the plasticity theory to the construction calculation. It is related to the developed knowledge in this area, the greater power of computer calculations as well as to the introduction of the simplified computational method, taking the plasticity condition under consideration, which relies on the assumption of redistribution of bending moments in a calculation carried out with the linear elastic method. The need for ductility Yield strength is a property of steel used for calculation of reinforced concrete constructions. Regarding the stretch of steel, the standards (e.g. PN-B-03264:2002) determine two parameters of reinforcing steel: the yield strength for a given grade of steel and the tensile strength. WHAT CHARACTERIZES GOOD REINFORCING STEEL? '''1. GOOD RESISTANCE PROPERTIES''' ''''''2. GOOD PLASTICITY'''''' High resistance of reinforcing steel is very desirable, but is not sufficient to ensure the proper behaviour of reinforced concrete constructions, for ductility is another important parameter. Concrete, as it is widely known, is a brittle material and without reinforcement cannot be used in the parts of construction exposed to stretch. The need for ductility in construction, which cannot be ensured by concrete, is met entirely by steel. For this reason, steel should have appropriate ductility, in order to ensure the possibility of a turn of a bending cross-section and enable redistribution of bending moments in constructions statically indeterminable. '''Concrete has always been considered the only factor lowering plasticity of a construction due to its brittleness. Reinforcing steel however has ductility at such level that it doesn't disturb the process of plastification in a construction.''' This way of thinking is understandable seeing that in the past steel had lower resistance/durability and thus higher ductility (e.g. steel A-I or A-0). The development of reinforcing steel led to the growth of resistance/durability. It was achieved by increasing carbon content in steel or by squeeze in cold rolling. This happened at the cost of ductility of steel. '''Tens of research studies on the behaviour of reinforced concrete structures proved the impact of the level of ductility of steel on the possibility of a turn of a bending cross-section in places of formation of plastic joins in the construction. As a result of comparative researches of elements of constructions, it turned out that the limitation of lenghtening of steel suggested by the standards - EUK > 2.5% - is insufficient, because the steel close to this upper limit of lenghtening of steel considerably lowers the plasticity of the construction. ''' '''Talking about the plastification of a construction it is worth to mention that one of the important factors of the plastification process of a construction is the appropriate adhesion of steel to concrete, which enables a certain/specified glide, so that scratches and cracking take place in the way set up during the design.''' '''Ductility of steel is its ability to achieve significant deformations at stresses beyond the yield strength of steel.''' '''Ductility of steel is essential in the case of constructions exposed to specific kinds of influences (seismic, dynamic etc.) as well as in the case of the design method assuming strong redistribution of moments. ''' In the case of reinforced concrete constructions raised in mining or seismic areas, ductility of steel has large influence on the behaviour of a construction. Similarly, in the case of indefinable influences it is desirable to provide a safety margin, which a plastic construction has, being able to reach larger deformations before it is damaged.Ductility of steel = Safety '''

'''A PLASTIC CONSTRUCTION IN A STATE CLOSE TO THE DAMAGE UNDERGOES SIGNIFICANT DEFORMATIONS AND CRACKS.'''''' ''''''A BRITTLE CONSTRUCTION IS DAMAGED SUDDENLY WITHOUT PREVIOUS WARNINGS, HAVING UNDERGONE INSIGNIFICANT DEFORMATIONS AND CRACKS. '''''' ''' ''' The ductility of steel for concrete reinforcement can be defined as an ability to achieve significant deformations without marked increase of stresses beyond the yield strength of steel. This term applies to the behavior of a construction in the conditions of nonlinear deformations, in which ductility plays an important role.

For many years there have been observed large differences between the actual durability of statically indeterminable elements of a construction and the values determined according to the principles of linear - elastic theory. The next phenomenon observed was the behavior of a construction at the load close to the destructive load, when there followed a considerable increase of deformations in the presence of a small increase of stresses. More recently, it has become more and more popular to apply the plasticity theory to the construction calculation. It is related to the developed knowledge in this area, the greater power of computer calculations as well as to the introduction of the simplified computational method, taking the plasticity condition under consideration, which relies on the assumption of redistribution of bending moments in a calculation carried out with the linear elastic method. The need for ductility Yield strength is a property of steel used for calculation of reinforced concrete constructions. Regarding the stretch of steel, the standards (e.g. PN-B-03264:2002) determine two parameters of reinforcing steel: the yield strength for a given grade of steel and the tensile strength. WHAT CHARACTERIZES GOOD REINFORCING STEEL? '''1. GOOD RESISTANCE PROPERTIES''' ''''''2. GOOD PLASTICITY'''''' High resistance of reinforcing steel is very desirable, but is not sufficient to ensure the proper behaviour of reinforced concrete constructions, for ductility is another important parameter. Concrete, as it is widely known, is a brittle material and without reinforcement cannot be used in the parts of construction exposed to stretch. The need for ductility in construction, which cannot be ensured by concrete, is met entirely by steel. For this reason, steel should have appropriate ductility, in order to ensure the possibility of a turn of a bending cross-section and enable redistribution of bending moments in constructions statically indeterminable. '''Concrete has always been considered the only factor lowering plasticity of a construction due to its brittleness. Reinforcing steel however has ductility at such level that it doesn't disturb the process of plastification in a construction.''' This way of thinking is understandable seeing that in the past steel had lower resistance/durability and thus higher ductility (e.g. steel A-I or A-0). The development of reinforcing steel led to the growth of resistance/durability. It was achieved by increasing carbon content in steel or by squeeze in cold rolling. This happened at the cost of ductility of steel. '''Tens of research studies on the behaviour of reinforced concrete structures proved the impact of the level of ductility of steel on the possibility of a turn of a bending cross-section in places of formation of plastic joins in the construction. As a result of comparative researches of elements of constructions, it turned out that the limitation of lenghtening of steel suggested by the standards - EUK > 2.5% - is insufficient, because the steel close to this upper limit of lenghtening of steel considerably lowers the plasticity of the construction. ''' '''Talking about the plastification of a construction it is worth to mention that one of the important factors of the plastification process of a construction is the appropriate adhesion of steel to concrete, which enables a certain/specified glide, so that scratches and cracking take place in the way set up during the design.''' '''Ductility of steel is its ability to achieve significant deformations at stresses beyond the yield strength of steel.''' '''Ductility of steel is essential in the case of constructions exposed to specific kinds of influences (seismic, dynamic etc.) as well as in the case of the design method assuming strong redistribution of moments. ''' In the case of reinforced concrete constructions raised in mining or seismic areas, ductility of steel has large influence on the behaviour of a construction. Similarly, in the case of indefinable influences it is desirable to provide a safety margin, which a plastic construction has, being able to reach larger deformations before it is damaged.Ductility of steel = Safety '''

'''A PLASTIC CONSTRUCTION IN A STATE CLOSE TO THE DAMAGE UNDERGOES SIGNIFICANT DEFORMATIONS AND CRACKS.'''''' ''''''A BRITTLE CONSTRUCTION IS DAMAGED SUDDENLY WITHOUT PREVIOUS WARNINGS, HAVING UNDERGONE INSIGNIFICANT DEFORMATIONS AND CRACKS. '''''' ''' '''