
Introduction
The subject Microbiology is the field of biological science that studies the microscopic organisms, for example, bacteria, viruses, archaea, prions, algae, fungi, and protozoa. These microorganisms are together known as 'microbes' (Microbiology, n.d.). The microbes are responsible for biodegradation/bio deterioration, nutrient cycling, food spoilage, climate change, the origin and resistor of disease, and biotechnology (Microbiology Society, n.d.). Microbiology research has always been predominant area of research in India, because it is vital to consulting several contemporary global objectives and challenges, such as upholding the safety of food, water, and energy for a healthy population on the inhabitable earth (Lal, 2012).
As a subject microbiology is growing due to the vast research enduring in various facades in the world (Gillen and Oliver, 2012). Following to this, there is a radical growth of research output through numerous formats such as journal articles, conference papers, books, research reports and so on. Every arena of research has limited journals (core journals) where researchers desire to publish their research paper. Bibliometric techniques are useful in determining various scientific indicators, assessment of scientific productivity, procuring of journals to the libraries and projecting the latent of a field (Kattimani, 2012). In this paper, an effort is made to disclose the research tendencies in Microbiology and to recognize the core journals in the subject by applying the Bradford's Law of Scattering.

Objectives
The objectives of the present study are to:
* prepare the rank list of most productive journals in Microbiology research publications
* examine the relative growth rate and doubling time
* estimate the future growth
* identify the core journals by applying the Bradford's Law

Methodology
Required data for the study has been gathered from Web of Science database. The database has been searched with the keyword as 'Microbiology' in the 'Title' for the period 20022016 and 25,744 articles published in 328 journals with bibliographic details were downloaded for analysis.

Results
4.1 Growth of articles
Table 1 shows the yearwise distribution of articles. It is perceived from Table 1 that the highest number of 2,602 (10.11%) articles are published in the year 2016, followed by 2,567 (9.97%) in 2014 and 2,520 (9.79%) in 2015. Though the number of papers published each year is not steady but excluding for the few years the research output in Microbiology is dependably increasing.
4.2 Relative Growth Rate and Doubling Time
The RGR is the increase in number of articles/pages/reports/patents per unit of time. This definition is taken from study of growth analysis of individual plants and successfully applied in the field of Botany (Hunt, 1978) which in turn had its origin form the study of the rate of interest in the financial investments by Blackman (1919). The mean Relative Growth Rate (R) can be calculated form the following equation.
1  [2.sup.R]=([Log.sub.e][W.sub.2][Log.sub.e][W.sub.1])/(T2  T1)
where,
1  2R = Mean relative growth rate over the specific period of interval
LogeW1 = log of initial number of articles
LogeW2 = log of final number of articles after a specific period of interval
T2  T1 = Unit difference between the initial time and the final time
[aa.sup.1] = average number of articles
The RGR for articles is hereby calculated as below.
1  2R (aa1 year1) can represent the mean RGR per unit of articles per unit of year over a specific period of interval.
2002= [Log.sub.e](1326) [Log.sub.e] (650)/20032002 = 7.196.48/1 = 0.71/1
2003 = 0.71
2003 [Log.sub.e](2025) [Log.sub.e] (1326)/20042003 = 7.617.19/1 = 0.42/1
2004 = 0.42
Likewise, the relative growth rate for other years is also calculated (Table 2). The mean relative growth rate is 0.24.
Doubling Time (DT)
There is a correspondence between the RGR and the DT. If the total number of research articles of a scientific field twofold during the study period, then the difference between the log numbers at the beginning year and end of the study period must be log number 2. Here, if we use natural logarithm the changed value is 0.693. Thus, the doubling time can be calculated by using the formula:
Doubling time (DT) = 0.693/R
Therefore,
Doubling time for articles:
Dt (a) = 0.693/1  2R(aa1 year1)
2003= 0.693/0.71 = 0.98
2004 = 0.693/0.42 = 1.65
In the same way, doubling time for other years is also calculated. The mean doubling time is 3.23.
4.3 Time series analysis
A time series is a series of data points listed or graphed in time order. The time series is a sequence taken at consecutive equally spread out points in time. Therefore, it is a sequence of discretetime data. Time series analysis comprises methods for analyzing time series data to extract meaningful statistics and other characteristics of the data. Time series forecasting is the use of a model to predict future values based on previously observed values. In this study time series analysis is applied to forecast the growth of Microbiology literature in India.
To arrive at assessments for future growth, Straight...
Application of Bradford's law of Scattering to the Literature of Microbiology in India.
Author:  Gourikeremath, Gouri N. 
Position:  Report 
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