[tag=VBP] [tag=DT] [lemma=number] [lemma=of] [!word=□]
[tag=VBP] [tag=DT] [lemma=number] [lemma=of] [!word=replies]
All rely on the fact that certain elements ( particularly uranium and potassium ) contain a number of different isotopes whose half-life is exactly known and therefore the relative concentrations of these isotopes within a rock or mineral can measure the age . For example , there are a number of distance learning initiatives around the System that will require funding to implement and support in the long term , and at this time , it is not clear what those costs will be . Part of the problem is that many products contain a number of different elements , each of which may be acting on several different aspects of human physiology . As well as maintaining momentum – and not withstanding my confidence that you are able to achieve this - there remain a number of areas where more work is needed . However , microarrays also pose a number of new challenges . There are a number of courses and topics from which you can choose , and your work in these courses will help develop your abstract thinking skills , your problem solving strategies , and your ability to communicate effectively ( both in your writing and in your speaking ) .