source: □
destination: □ □
spec: ES cells are used because they are able to differentiate into nearly any type of adult cell , which means that if a gene is knocked out in an ES cell , the effects can be observed in any tissue in an adult mouse . Of course , all your modeling calls have to omit the data = argument and you have to be very careful to have the right search list in effect and all that . Liquid nitrogen is used because it is relatively inexpensive , but it also requires no refrigeration , thus cutting down on energy needed . The school has recently evolved a new curriculum which aims to de-emphasize lecture in favor of small group discussions . Prior-year income is used because it is a good predictor of current-year income and is verifiable . The `` recharge area '' for a well depends on how deep the well is and in what types of rock or sediment it is located . More likely , the name came from a popular local saying of the time , `` tough as a Bearkat ! Focus groups were used because they are able to elicit more precise and indepth information about the experiences and opinions of hard-to-reach populations than surveys . '' Most lawyers in big companies and big firms have very narrow jobs - - they're supposed to be an expert on this particular area or that particular area . " Therefore , an is used because it is acting as an article proceeding a word beginning with a vowel sound .