Time verb tenses in English sentences as predicate occurs and presence of different, also different forms of expression, such different forms of the verb referred to. When writing a sentence, the sentence accurately grasp the tense is one of the key scientific papers Writing. Although the verb in English sentences of 16 tenses, but commonly used in scientific papers only five species, namely present tense, past tense, future tense general, past perfect and present perfect tense . The most frequently used only past tense and present tense in general.
(1) General present tense
For content published officially.
Optically active amines bearing the stereogenic center as the position areimportant compounds because of their broad range of applications and theirpharmacological properties.
Used to describe the general background of the Preamble.
In most cases, the pharmacological activities of these amines are relatedto the configuration of the stereogenic center.
A lead-out table or FIG.
Fig.2 representsthe binding mode of the substituents of R-amines 1~6.
The results are collected in Table 1.
For discussion of the experimental results.
Amphetamine shows a lower E value than those of its methoxy analogous,which is due to the fact that (R)-methoxyamphetamines react faster than(R)-amphetamine and that (S)-amphetamine is transformed more quickly than(S)-methoxyamphetamines. In the same way, the higher E value for mexile- tineis mainly a consequence of the slower reactivity of its (S)-enantiomer. Theseresults can be explained to a large extent on the basis of the size of thesubstituents attached to the stereocenter and size of the small pocket.
Used to describe a general truth.
Streptomycin inbibits the growth of tuberculosis.
(2) past tense
It is used to describe the experimental part of the paper used on the reagents and materials.
Lipase was from C.Antarctica , Novozym 435 was a gift Novo Nordisk Co and was employed without any further treatment.solvent were of spectrophotometric grade and they were stored with 4 A molecular sieves under nitrogen prior to use.(±)-Mexiletine waspurchased as its chlorohydree from Aldrich. The other racemic amines were obtainedby reductive amination the corresponding ketone.
Describe using a test instrument.
Melting pointswere determined on a Kofler hot-stage apparatus. Ultra-violet spectra wererecorded by using pye-unicam SP 800 and Philips PU 8720 spectrometers.Infra-red spectra were recorded on a Perkin-Elmer FE 1710 Fourier Transformspectrometer 1H NMR spectra were recorded Bruker WH 360 (360 MHz)spectrometer and tetramethylsilane was used as the internal standard. Massspectra were recorded on Kratos MS 80 or MS 25 spectrometers.
Used to describe the experimental procedure.
Imprintingmolecules were added to the combined eluates , ASTM printers were used, theracemic substrates, (R)-enantiomer of the substrate, or the (S)-enantiomer ofthe substrate The samples were mixed and kept at room temperature for 20 min,then put on ice for 5 min. The imprinted proeteins were precipitated with 30%isopropanol. After mixing for 10 min, the samples were put on ice for 60 min.After centrifugation, the precipitates were washed once with ice-coldisopropanol and after a second centrifugation step the precipitates werelyophilized.
It is used to describe experimental results and discussions.
The parameters k1 , k2 and α1 in eq.(2) weredetermined by nonlinear regression program. Values of immobilized lipases weresimilar and greater than those of free lipase. The solid curves in Figs. 1 and2 were calculated by using the parameters estimated.
It is used to describe the conclusions.
Theoctadecyl-sepabeads preparation was the most efficient among those examined.This preparation presented the highest enantioselectivity, good activity andhigh stability under the harsh reaction conditions.
The thermostability of lipase was enhanced by immobilization. Deactivation of the lipases followed a two-step series model. When incubation temperature was below 60℃. lipase immobilized in alginate gels was found to have very high thermostability compared with free and the immobilized lipases. This was because of the strong affinity between lipase and alginate. Likewise, thermostabilization was loand for the lipase immobilized in inorganic microcapsules when incubation temperature was above 60℃. This was due to thestabilization of the intermediate state of the lipase.
(3) Future Tense
The results for the intended work to be done and the expected description.
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We will nextuse the conversion values obtained after a reaction time of 7h.
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In some areas ofthe world, cancer has become or shortly will become the leading disease-relatedcause of death of the human population.
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Studies on genetherapy will be carried out in the near future.
(4) present perfect tense
For a period of time up to the time of writing paper from a results point of view associated with the current situation is described.
Though immobilization does not necessarily lead to stabilization, there have been manyreports on enzyme stabilization by immobilization In most cases, including thepresent study it has not been possible to clearly elucidate the nature of theinteraction between the enzyme and the support.
Although fewchemotherapeutic regimens have yielded lasting remissions or cures, it is clearthat new therapeutic options are necessary.
Paper used to describe the conclusion of the general summary of the full text, emphasize the results of the action to the current generated.
The effectof enzyme immobilization on the catalytic properties of different CAL-Bpreparations in the resolution of several cyclopyrrolone compounds in aqueousmedia has been studied. This work has demonstrated the strong influence of theenzyme preparation and the nature of the substrate.
(5) past tenses
Buxu for flashback or actions with respect to a time elapsed before occurred.
When the genetic information could betranslated into therapeutics that could selectively ablate tumors without the systemicside effect often associated with cancer druge , some of the first oncogenedefects had been discovered.
When the state science and technology is a key question in English grammar paper expressed in. In the various sections of the paper, although the focus of presentation is different, but the use of the verb is regular. Usually describes the author's own research work should use the simple past tense, as a summary, the research methods and processes, research results, etc. obtained because these chapters describes the author's own work done before writing papers, what happens phenomenon resulting data and results. He has published a content authors and general use of the present tense when their own results obtained are discussed in the paper, as these are to be confirmed knowledge is usually described in the preface.
Learning Source: "Scientific Writing in English Course"