Present perfect

Abstract Many biological activities have been envisioned for fullerenes and some of them seem to be very promising. The lack of solubility in biologically friendly environments is the major obstacle in the development of this field. The possibility of multiple fuctionalization can be exploited to get more soluble compounds but, up to now, only a few polyadducts, presenting perfectly defined geometry, can be selectively prepared avoiding long purification processes. 

The construction have been shown (in P13) is an example of a verb form known as present perfect. There are two forms of the present perfect ... 

Present perfect-active has shown, have shown... 

Present perfect-passive has been shown, have been shown... 

Present perfect is typically used to signal that the knowledge gained from work completed in the past is still believed to be true in the present. Present perfect combines has or have with a past-participle verb form, which is usually (but not always) the same as the past tense form (see table 6.2). Note that the use of the present perfect is not limited to this submove you will see it used in other sections of the journal article, as well. 

Table 6.2 Examples of active and passive constructions in present perfect.

When citing others works to establish importance or provide background information, authors often use present tense or present perfect in either active or passive voice. 

Present perfect-active Nagy etal. (/) have proposed... 

Present perfect-passive Arsenic has been recognized as...(/)... 

The following passages comprise the first several sentences of two articles from the same issue of the Journal of Agricultural and Food Chemistry. Make a list of the present tense and present perfect verb constructions used in each passage. Which construction do the authors seem to prefer ... 

Present perfect (active Many highly enantioselective approaches... 

Present perfect-passive PMj 5 has not been studied by EPR. (From Dellinger et ak, 2001)... 

Present perfect can be used to summarize the work of others, demonstrate a gap, introduce one s own work, and/or report principal Endings ... 

Verb tense The poster Introduction is written primarily in the present tense, though instances of the present perfect (to signal that knowledge gained from work completed in the past is still believed to be true in the present) are also possible. 

Present perfect Thus, countries have established recommended maximum limits for PCBs... 

Lastly, we briefly consider verb tense and voice used in move 2. As shown in table 12.5, past and present tenses and present perfect may all be used. Past tense and present perfect are used to provide background information (work done in the past), typically in passive voice. Passive voice allows the writer to focus on the science rather than the scientist ... 

Present perfect-passive (more common) Aryl nitrenes have been studied... 

Present perfect-active (less common) Scientists have studied aryl nitrenes... 

Present perfect-passive An artificial pancreas has been developed. (From Tyon, 2000)... 

We close our discussion of move 3 by analyzing common verb tense and voice combinations used in this move (table 12.6). Gaps are often stated in present tense (in active and passive voice), sometimes in combination with a present perfect-passive statement fill-the-gap statements are usually in present or future tense and active voice. Personal pronouns (I or we) are common in fill-the-gap statements. 

Present perfect-passive Present-passive Although... has been studied in depth, little is known about... 

We end this section by examining a few commonly used verb tense—voice combinations in move 1. As shown in table 13.3, prior accomplishments are typically written in active voice in either past tense or present perfect. Statements that establish expertise are typically written in present tense. 

We end this section by examining a few commonly used verb tense-voice combinations in move 2 (table 13.5). Present perfect is commonly used to describe preliminary work (done in the past) present tense is commonly used to share preliminary findings (believed to be true over time). Active voice is also common. Note that because authors want to call attention to their own promising results in this move, personal pronouns such as we or our are often used. 

To describe preliminary Present perfect- We have recently completed... 

We conclude our discussion of move 3 by considering verb tense and voice combinations commonly used in this move (summarized in table 14.5). Present tense, present perfect, and future tense are used to reiterate goals. Future tense is used most often to state broader impacts. Active voice is common throughout the move, and personal pronouns (e.g., we and our) may be used at the authors discretion. 

While perfect order is never present, perfect disorder also does not exist at surfaces. 

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