Citation patterns of 400 very highly cited scientific papers are identified and the relationship of citation patterns to literature aging rates is investigated. Standardized citation counts for 1972 through 1980 are used as variables in a cluster analysis which groups papers with similar citation patterns and a discriminant analysis is used to refine the descriptions of clusters and to confirm the results. Among highly cited papers published in 1972, two basic citation patterns are identified: one group is highly cited in the first years following publication and declines in citedness thereafter; the second group reaches its citation peak in the sixth year following publication and declines in citedness in the seventh, eighth, and ninth years of the series. Both groups show general evidence of aging.Price's suggestion that less highly cited papers age more rapidly than more highly cited papers is confirmed.
In this study, the specialization profiles of eleven countries are compared along two interconnected but distinct dimensions of research, viz. publication output and citation impact in nine subfields of chemistry. The data for comparative analysis were taken from Scientometric Datafiles.1Since raw counts of publications and citations are confounded by the size of the countries and the size of subject fields, cross-national comparison is made, using relative indicators—activity index and attractivity index. The subfields of relative strength and weakness for these countries are identified from the values of these indicators. The similarity structure of specialization profiles of the eleven countries is mapped, using hierarchical cluster analysis and multidimensional scaling. This mapping leads to the representation of chemistry as it is structured by the dynamics of national science policies of these countries.
Thirty bread wheat cultivars grown in Lesotho were analysed with sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). High and low molecular weight glutenin subunits (HMW-GS and LMW-GS) and gliadins were used to determine genetic variability and relationships between the cultivars. The HMW-GS could not distinguish the cultivars, while both LMW-GS and gliadins could. The Glu-1 score showed that all the quality classes from excellent to poor were represented in the material, but 11 cultivars had the highest score of 10, indicating excellent quality. Cluster analysis performed using gliadins in combination with LMW-GS generated dendrograms which segregated cultivars according to genetic distance. However, the genetic distance between the cultivars were so close that it could be concluded that they are from the same gene-pool and have been used several times in regional breeding programmes.
Different pattern recognition techniques were applied for classification and characterization of a large number of coal, and coal fly ash samples. Cluster analysis was performed on 116 samples using the concentration data of 40 elements. The effect of the number and type of the elements on the clustering was studied in detail. It was proved that short time activation analysis enables the characterization of these types of samples if139Ba and87Sr are included, these data being obtained by increasing the irradiation and counting times. The two elements and chlorine were found to be necessary for such a classification. The combination between cluster analyses and principal component analysis gives accurate and confirmed results. The statistical analyses of the subgroups are compared.
Authors:O. Asubiojo, I. Obioh, E. Oluyemi, A. Oluwole, N. Spyrou, A. Farooqi, W. Arshed, and O. Akanle
Airborne particulate matter collected during the Harmattan season at Kano in the northern part, and Ile-Ife in the southern part of Nigeria was analyzed for about 30 elements by a combination of instrumental neutron activation analysis and X-ray fluorescence analysis. Although the total suspended particulate concentration (ng/m3) is much higher in Kano than Ife, the elemental composition at both locations is very similar and cluster analysis shows a strong correlation between the two, indicating a common origin for particulates. Particle-size distribution studies show that Kano dust is mainly coarse while Ife dust is mainly fine. The crustal-type elements are mainly concentrated in the coarse particles (3 m) at both locations while the conventional anthropogenic elements are hosted mainly by the fine particles (0.49 m and below).
The technique of co-citation cluster analysis is applied to a special three-year (1972–1974) file of theSocial Sciences Citation Index. An algorithm is devised for identifying clusters which belong to a discipline based on the percentage of source documents which appear in a disciplinary journal set. Clusters in three disciplines (economics, sociology and psychology) are identified using this algorthm. Clusters in a specialty of natural science (particle physics) obtained from the 1973Science Citation Index are compared and contrasted with the three groups of social sciences clusters. Certain common structural characteristics of the social science and natural science groups suggest that knowledge is developing in parts of the social science disciplines in a manner similar to the natural sciences.
Authors:F. De Moya Anegón, E. Contreras, and Mercedes Corrochano
Publications and author cocitations in library and information science in Spain during the period from 1985 to 1994 were analyzed
as a measure of the structure, specificity and composition of research fronts in this country. A cocitation matrix developed
from an ad hoc database was subjected to cluster analysis, multidimensional scaling and principal components analysis. The
resulting cocitation maps identified specific areas of research and their knowledge bases. We inferred the degree of consolidation
of the discipline of library and information science, and of the subdisciplines informetrics, librarianship and university
affiliation, from the research activities revealed. In this respect, the conclusions from the study show the existence of
several research fronts in Spanish literature the contents of which are in most cases difficult to compare with those in other
countries. A lesser degree of maturity of research in this field is shown.
Authors:Z. Zhang, J. Yang, H. Ouyang, Z. Li, Z. Chai, J. Zhu, J. Zhao, Z. Yu, and J. Wang
Sixty-two heroin samples were analyzed for their contents of 15 trace elements (Au, Ba, Br, Ca, Ce, Co, Cr, Fe, La, Na, Sb,
Sc, Sm, Th, and Zn) by neutron activation analysis (NAA). Large variations of elemental concentrations between samples were
found to possess statistical significance. Of all the elements calcium was the most abundant element, followed by zinc and
sodium. The concentrations of Au, Ce, Co, La, Sb, Sc, Sm, and Th in all the samples were below 1 mg·g−1. Classification of these heroin samples was achieved by the application of hierarchical cluster analysis. The results show
that NAA can provide useful information on the origin of the illicit drugs.
The analysis of polymorphism between 46 maize inbred lines with known genetic background and the classification of these lines in related groups was carried out by means of morphological, isoenzyme and genetic markers. The degree of relationship between the lines was determined using cluster analysis. Only a very limited extent of allele polymorphism could be detected in isoenzyme analyses. Nevertheless, on the basis of RAPD and SSR markers, all the lines could be distinguished from each other. Grouping lines into related groups it was found that, while the individual marker systems only partially reflected the actual relationships, a joint analysis of genetic markers and morphological data revealed a close correlation between the groups formed on the dendrogram and genetic backgrounds.
In this study, some natural Vicia L. species growing naturally in eastern Mediterranean and southern Aegean Regions have been investigated morphological and cytotaxonomic point of view. Morphology, chromosome number and morphometries of the 9 taxa belonging to the Vicia L. genus including Vicia peregrina, V. lutea var. hirta, V. anatolica, V. hybrida, V. grandiflora var. grandiflora, V. grandiflora var. dissecta, V. cuspidata, V. sativa subsp. sativa, V. sativa subsp. nigra var. segatalis have been studied by using karyological and numerical taxonomic techniques. Data obtained chromosome measurements were analysed by using cluster analysis. The chromosome number of studied Vicia species have been found as 2n = 10, 12 and 14. The member of Vicia section, related taxa were compared with respect to their chromosomal and morphological characteristics. Some karyological relationships among the studied Vicia taxa were discussed with help of taxonomic history and evolutionary data.