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...concept in immunology. It is necessary to distinguish between antigenicity, the ability of a molecule to be recognised as non-self by the cells of the immune system – and immunogenicity, the ability of that antigen to induce an immune response. Immunogenicity is not a fixed property: whether a particular antigen behaves as an immunogen is highly contingent on a number...

...objects float or sink at all. This relates to the object’s density. Density is a concept that sometimes confuses people, but it is simply the amount (mass) of something that is contained within a certain volume of space. For example, if you have one person in an elevator, it is not densely packed, but if you try and squeeze ten people in, things are going to get a bit tight. In this case the number of people is the ......

...concept of vector quantities. Vector quantities are different from scalar quantities because they describe direction as well as magnitude. For this reason the arrow representation is useful to visually represent vector quantities...Introducing vectors for engineering applications: 1.1 Modelling motion with perpendicular vectors - Let’s consider, where two people, Alice...

...De-oxygenated blood from the systemic tissues is carried to the lungs by the pulmonary arteries and has a PO2 of 40 and a PCO2 of 45 millimetres of mercury. As the blood enters the alveoli, the higher PO2 in the lungs drives oxygen shown in red out of the alveoli and into the blood. At the same time, the slightly higher PCO2 in the blood drives carbon dioxide, shown in...