How to write a scientific paper
How To Write a Scientific Paper
By Susan Cordova for the New Mexico Junior Academy of Science
In all sections of the paper, present tense should be used to report background that is already established. Forexample, "The cell membrane is the barrier which separates the inside of the cell from the outside." Usefuture tense for work that you will do. For example, "We will test the hypothesis that some anti-microbialagents can permeate the cell membrane during division to inhibit growth." Always use past tense to describeresults of a specific experiment, especially your own. For example, "Application of the antibioticChloramphenicol restricted growth of E. coli
.". Number the pages of the body of the paper beginning with theIntroduction as page 1. For a short paper a "Table of Contents" is generally not necessary.
Captioning is a method of separating the body of a paper into sections. Headings show organization and identify the topic for a section or a block of information. Capital letters, underlining, point size, and position on the page help to differentiate rank or level.
The person reading, grading or judging a scientific paper can be most objective if the author remains anonymous while the paper is read. Your name, date, and title of the paper should be on a cover page, and noton any other part of the paper. See the "Rules for the Paper Competition" for additional information neededon the title page if you are entering the NMJAS Paper Competition. Your title should be specific in describingthe experiment you performed. For example, "Effects of a Variety of Anti-microbial Agents on Four BacterialCultures" is much more interesting than just "Anti-microbial Agents".
The Abstract is a summary of the study, with the primary emphasis on results and conclusions. Very briefly present the question(s) asked, the experimental design, a summary of observations, and list conclusions. Bevery succinct - the abstract should be a single paragraph, no more than one page. It should stand on its own;therefore, do not refer to any other part of the report, such as a figure or table. Avoid long sections ofintroductory or explanatory material. As a summary of work done, it is written in past tense. Start yourintroduction on new page.
"This study was done to look at the effect of a variety of antimicrobial agents on several microorganisms.
This response is usually determined by the agent's mode of action and the structure of the microbe. Theexperiment involved applying antimicrobial disks onto agar inoculated with the test microbe. Zones ofinhibition were measured after 18 hours to determine each reaction as sensitive, resistant, or intermediate. Staph. Aureus
, a gram positive organism with a thick cell wall, was very sensitive to all agents except Nalidixic acid. P. Aeruginosa
showed resistance to all but Streptomycin which had an intermediate effect. E.
was resistant to all but Chloramphenicol and Nalidixic acid. These results were consistent with the factthat E. coli
and P. Aeruginosa
are gram negative organisms which exhibit a thin cell wall of peptidoglycan with an outer membrane acting as a barrier against some antibiotics. Further experiments should investigatethe sensitivity or resistance of strains from different sources, such as hospitals and schools."
Keep the introduction brief, but do indicate the purpose of the experiments performed as well as present appropriate background. Make sure that the reader knows enough to appreciate the relevance of the work andwhy it is appropriate to ask the question that you will address with your study. Always state the hypothesisand/or objectives in your introduction.
"This investigation involved exposing several microorganisms to a variety of anti-microbial agents to test whether the microbe was sensitive, resistant or intermediate to the particular agents. This kind of testing isvery important in the medical field because physicians need to know what antibiotics to prescribe for certain microbial infections. Anti-microbial agents, because of their mode of action, inhibit the growth of only somemicroorganisms, and some work better than others. The Kirby-Bauer method employed in this study involves applying paper disks impregnated with different anti-microbial agents onto an agar surface inoculated with the test organism. The zones of inhibition which appear after incubation can be measured to determine theclassification of sensitivity. It is hypothesized that two of the four organisms used, P. aeruginosa
and E. coli
,will show resistance to most of the anti-microbial agents due to their extra LPS (lipopolysaccharide) layer, characteristic of all gram negative organisms, which hinders growth inhibition."
You must document all methods performed in your study. Do not, under any circumstances, report methodsword-for-word from any of the written sources you used. You need to summarize, in your own words, whatyou did. Also, do not give unneeded detail. For example, instead of "I took up 1 ml of bacterial broth from a 5ml tube with a 2 ml plastic pipet and expelled it onto the surface of one agar plate", write "One agar plate wasinoculated with 1 ml of bacterial broth". We can also see that in this latter sentence passive voice was used toreport methods, a standard for most scientific publications. To give another example, one would write "Cellswere grown at 37oC." instead of "We grew the cells at 37oC.".
While it is tempting to report methods in chronological order in a narrative form, it is usually more effective to present them under headings devoted to specific procedures or groups of procedures. Some examples ofseparate headings are "Sources of Materials," "Inoculation Procedures", "Analytical Procedures", "MeasuringZones of Inhibition," and "Statistical Methods."
Don't report information that would be irrelevant to an independent investigator. For example, not everyoneuses the computer software you have in the lab. The programs you used to organize or plot data are notimportant. Most important, do not report any results of the experiment in the methods section. These, ofcourse, go in the "Results" section.
Raw data include all observations or data that you get from your experiment. Raw data are never included inyour scientific paper unless they are needed to give evidence for specific conclusions which cannot be obtained by looking at an analysis, or summation, of the data. Analyze your data, then present them in the
form of figures (graphs), tables, and/or descriptions of observations. Data in this form are called converteddata. Figures are preferable to tables, and tables are preferable to straight text. By presenting converted data,you make your point succinctly and clearly.
To give your results continuity, describe the relationship of each section of converted data to the overallstudy. For example, rather than just putting a table in the paper and going on to the discussion section, write,"Table 2 shows the means and standard deviations for each interaction of anti-microbial agent and microbe.
The results of those interactions with both 0 inhibitions and large positive inhibitions were questionable and were subsequently marked with a question mark (?)." The same goes for figures.
The table or figure should then be presented, complete with title. The title should explain what the table orfigure is showing. For example, "Table 2. Means (M) and Standard Deviations (SD) of Inhibition ZoneDiameters (mm)"
All converted data go into the body of the report, after the methods and before the discussion. Do not stickgraphs or other data onto the back of the report just because you printed or prepared them separately. Place raw data at the back of the report as an appendix, if needed. The appendix is also appropriate for any samplecalculations that are needed, such as hand-worked statistical analyses or raw calculations that show how you arrived at reported values. A published research report will seldom have such an appendix, but it may beappropriate in the case of a paper competition.
Do not draw conclusions in the results section. Reserve data interpretation for the discussion.
Interpret your data in the discussion. Decide if each hypothesis is supported, rejected, or if you cannot make adecision with confidence. Do not simply dismiss a study or part of a study as "inconclusive". Make whatconclusions you can, then suggest how the experiment must be modified in order to properly test the hypothesis(es).
Explain all of your observations as much as possible, focusing on mechanisms.
displayed an array of reactions to the antimicrobial agents. It was resistant to Bacitracinand Vancomycin, both involved in inhibiting peptidoglycan synthesis. The types of penicillins involved ininhibiting transpeptidization in the cell wall, Ampicillin and Methicillin, were more effective in inhibiting growth. The differences in these results may involve the different specific stages at which the antibiotics havetheir effect on protein synthesis."
When you refer to information, distinguish data generated by your own studies from published information orfrom information obtained from other students. Refer to work done by specific individuals (includingyourself) in past tense. Refer to generally accepted facts and principles in present tense.
"John Doe (1964) found that Chloramphenicol prevents the formation of peptide bonds during protein synthesis while Erythromycin inhibits translocation."
Most studies will require a critique of the experiment. Determine if you asked the right question in the firstplace. Decide if the experimental design adequately addressed the hypothesis, and whether or not it wasproperly controlled. For example:
"There were a few problems with the data. A few of the interactions between antibiotic and microbe showed a
great amount of inhibition along with absolutely no inhibition. Many of the antibiotic disks were out of date(some as long as 15 years) which may have caused some of the disks to lose their potency. A loss of potencywould cause a decrease in inhibition. Although it could be assumed from this fact that the positive inhibitiondata is the more accurate, it cannot be said with certainty."
Finally, where do you go next? The best studies open up new avenues of research. What questions remain?Did the study lead you to any new questions? Try to think up a new hypothesis and briefly suggest newexperiments to further address the main question. Be creative, and don't be afraid to speculate. "Future experiments might include using cultures of microbes from different sources, such as hospitals, day care centers, and schools to look for signs of lowered resistance."
Literature citations in the body of your paper should be in parentheses and contain only the author's last nameand the date; for multiple authors include the last name of the first author, et al., and the date. If the author'sname is used in the text then just the date in parentheses is sufficient. For example: (Monod, 1949)(Neidhardt et al., 1990) or Monod (1949) compared the reaction…. List all literature cited in your report inalphabetical order by the last name of the first author in a separate section. Use the proper form for citations.
If the citation is to a specific page add the page number.
Monod, J. 1949. The growth of bacterial cultures. Annu. Rev. Microbiol.
Neidhardt, F.C, Ingraham, J.L. and. Schaechter, M. 1990. Physiology of the Bacterial Cell
McKay, D. 2000. Arsenic: how much is safe? Albuquerque Journal.
July 30, 2000, p. A1.
National Research Council. 1999. Arsenic in drinking water. Subcommittee on Arsenic in Drinking
Sanchez, R. 1993. City of Socorro, Water Utilities Division, Socorro, NM. Personal communication.
Some information used in this brochure was taken from the web pages of David R. Caprette.
Written with funds from a grant from Intel Foundation
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