6 Science Research Writing You probably learned the diff erence between (a) and (b) years ago: that one of the diff erences between Past Simple and Present Perfect is the 'time' of the verb, i.e. when it happened. Th e diff erence between (c) and (d) is harder to understand and more important for you as a writer of science research. In (c) and (d), 'time', i.e. when the verb happened, isn't really what separates the two sentences; it's possible that both (c) and (d) happened last month, this morning, or one nanosecond ago. What is important is that the event in (d) is considered more relevant to the situation now than the event in (c), which is why it is given in the Present Perfect. Why is this idea of relevance useful when you write an Introduction? Look at these sentences from the Introduction in Section 1.1: For example, Penney et al. showed that PLA composites could be prepared using blending techniques6 and more recently, Hillier established the toughness of such composites.7 However, although the eff ect of the rubber particles on the mechanical properties of copolymer systems was demonstrated over two years ago,8 little* attention has been paid to the selection of an appropriate rubber component. * Note: a little means 'a small amount', but little means 'virtually none'. Where does the tense change? Why do you think the writer changes from the Past Simple to the Present Perfect? Could it be because this research article is NOW paying attention to the selection of an appropriate rubber component? Now look at what happens if the writer forgets to change tense and continues in the Past Simple: However, although the eff ect of the rubber particles on the mechanical properties of copolymer systems was demonstrated over two years ago,8 little attention was paid to the selection of an appropriate rubber component.
Introduction — Grammar and Writing Skills 7 Suddenly, the sentence means that little attention was paid THEN, i.e. two years ago. Perhaps attention has been paid to this problem since then; perhaps the problem has even been solved! Tense changes are always meaningful, and they always signal a change in the function of the information — so don't change tense randomly and make sure you remember to change tense when you should. Now check what you have learned about tenses by looking carefully at the way the Past Simple and Present Perfect are used in the Introductions of your target articles. Look in particular at the way the Past Simple tense and the Present Perfect tense are used to refer to previous research. 1.2.2 Signalling language Sentence connection One of the most common errors in writing is failing to connect one sentence or idea to the next. Every time you end a sentence, your reader has no idea what the next sentence is going to do or say. As a result, the space between a full stop and the next capital letter is a dangerous space for you and your reader. Perhaps you stopped for ten minutes aft er a sentence, and during that time you thought about your work and your ideas developed. Perhaps you turned off your computer and went home. When you start typing again, if you don't share the link between those sentences with your reader, you create a gap in the text which will cause problems. One of your tasks as a writer is to make sure that gap is closed, so that your reader is carried carefully from one piece of information to the next. Connecting sentences and concepts is good for you too, as it forces you to develop your ideas logically. One way to connect sentences is to overlap, meaning to repeat something from the previous sentence: Th e pattern of infl ammation during an asthma attack is diff erent from that seen in stable asthma. In stable asthma the total number of infl ammatory cells does not increase. One way to toughen polymers is to incorporate a layer of rubber particles. As a result, there has been extensive research regarding the rubber modifi cation of PLA.