Original	Revision
The existence of chlorite mineral (1 - 8%) may explain this behaviour.	The presence of chlorite mineral (1 - 8%) may explain this behaviour.

The second student is researching Medieval Islamic Philosophy. His first language is also Turkish.

Original	Revision
They argue that in the existence of all determinants, namely full power, definite will, proper time and conditions, and the disappearance of all hindrances, the act necessarily occurs.	They argue that in the presence of all determinants, namely full power, definite will, proper time and conditions, and the removal of all hindrances, the act necessarily occurs.

The central point here is that in these students' second languages of academic study (Farsi and Arabic respectively) the standard translation for both presence and existence is vujud. This helps to explain the difficulty they had in distinguishing between thee two words in English, in which existence is the general term ("Philosophers argue about the existence of God') and presence is the local term ("When he prayed he believed that he was in the presence of God"). The following sentence citations illustrate the difference between the two terms:

1. Michel Dutang, began looking for alternatives to chlorine after studies linked its presence in drinking water to cancer.
2. Looking at the question from an economic standpoint, the key justification for a continued British presence in the Middle East was access to oil.
3. Clement V (1305~14) went so far as to decree that even the presence of Muslims on Christian soil amounted to "an insult to the Creator".
4. Calculations seemed to show that it was difficult to explain how galaxies would form in the presence of large numbers of neutrinos.
5. The most striking feature of the frog retina is the presence of "bug-detectors": that is, fibres in the optic nerve which are stimulated by small dark moving objects on the retina.

6. The individual organism is something whose existence most biologists take for granted.
7. Gary Goldstein, one of Dalitz's collaborators, says he is "quite confident" that they have discovered the existence and the mass of the quark.
8. Moral pluralism asserts the existence of a multitude of incompatible but morally valuable forms of life.
9. This view holds that the cosmos has been generated and may be destroyed, and that men similarly first came into existence at a definite time.
10. Opposing pressure groups were already in existence and preparing for the campaign: in favour, the Divorce Action Group; and against, such groups as Family Solidarity, Women in the Home, and the Knights of Columbanus.

1. A few scientists had predicted the __________________ of black holes for more than 200 years, but most scientists did not take black holes seriously.

2. Some people are more likely to develop these complications and can be identified by demonstrating the __________________ of a particular tissue-type in their body make-up.

3. This difference has not so far been accounted for, but could in part be attributable to the __________________ of additional HeLa cell proteins in the complex.

4. The rules of Equity are only a sort of supplement or appendix to the Common Law; they assume its __________________ but they add something further.

5. At present, inspectors can only detect the __________________ of harmful bacteria in organic waste by taking a water sample back to the laboratory, separating out solid matter containing microorganisms, and culturing it in a Petri dish.

6. He guessed that the molecules were shaped like balls – an unusual configuration – and set about gathering evidence. Five years passed until the __________________ of these molecules, nicknamed buckyballs, was confirmed.

7. In its 18 months of __________________, Classic FM's blend of music has gained a weekly audience of 4.5 million.

8. With those he attacks he shares the premiss that all that we are directly aware of are ideas, which have no __________________ apart from a perceiving mind.

9. Just as the __________________ of salmon in Scottish rivers can be used as an indicator of a waterway's health, butterflies signal the health of Madagascar's forests.

10. Sussex police said that the __________________ of armed officers in the area was part of their normal counter-terrorist patrols.