<span>She is at an increased risk of osteoporosis. Girls who first experience menarche at later ages are more disposed to having a lowered bone density and osteoporosis later in life. This is due to having a reduced peak bone mass, which can increase the risks of fracture.</span>
Fuel cells can make an electricity from a simple electrochemical
reaction in which oxygen and hydrogen combine to form water. There are several
different types of fuel cell but they are all based around a central design
which consists of two electrodes, a negative anode and a positive cathode.
These are separated by a solid or liquid electrolyte that carries electrically
charged particles between the two electrodes. A catalyst, such as platinum, is
often used to speed up the reactions at the electrodes. Fuel cells are
classified according to the nature of the electrolyte. Every type needs
particular materials and fuels and is suitable for any applications. The
article below uses the proton exchange membrane fuel cell to illustrate the
science and technology behind the fuel cell concept but the characteristics and
applications of the other main designs are also discussed. Proton Exchange Membrane Fuel Cells (PEMFC)
The hydrogen ions permeate across the electrolyte to the
cathode, while the electrons flow through an external circuit and provide
power. Oxygen, in the form of air, is supplied to the cathode and this combines
with the electrons and the hydrogen ions to produce water. These reactions at
the electrodes are as follows:
Anode: 2H24H+ + 4e-
Cathode: O2 + 4H+ + 4e- 2H2O
Overall: 2H2 + O22H2O + energy
PEM cells operate at a temperature of around 80°C. At this
low temperature the electrochemical reactions would normally occur very slowly
so they are catalysed by a thin layer of platinum on each electrode.
The correct answer is B) Treaties expanding International Trade
After the second world war, the world has gradually opened up to one another for trade and opportunities.
We see that in the development of the World Trade Organization, as well as the NAFTA (North American Free Trade Agreement) between Canada, US, and Mexico and probably the most successful example in the European Economic Zone.
<span>Continental plates pushing towards each other cause mountains to form on our planet Earth, true. </span>
Answer: 1). A and B are both dominant (because A and B are codominant to one another)
2). E. All of the above
Explanation:
1). From the image above, A and B are both dominant because they are equally expressed when they occur in a pair (when they occur as blood type AB), also they are dominant because each of them expressed itself when it occurs in a pair with a recessive allele (IAi and IBi).
2). The children of a father with A blood and a mother with B blood will have all the four blood types: A, B, AB, and O. If each parent has a recessive allele, that is if each parent is heterozygous for his/her blood type (IAi for the father and IBi for the mother), the cross between them will produce all the four possible blood types.
See the attached punnet square for more information.
