Hermann Schier

What factors determine citation counts of publications in chemistry besides their quality

A number of bibliometric studies point out that citation counts are a function of many variables besides scientific quality. In this paper our aim is to investigate these factors that usually impact the number of citation counts, using an extensive data set from the field of chemistry. The data set contains roughly 2000 manuscripts that were submitted to the journal Angewandte Chemie International Edition (AC-IE) as short communications, reviewed by external reviewers, and either published in AC-IE or, if not accepted for publication by AC-IE, published elsewhere. As the reviewers’ ratings of the importance of the manuscripts’ results are also available to us, we can examine the extent to which certain factors that previous studies demonstrated to be generally correlated with citation counts increase the impact of papers, controlling for the quality of the manuscripts (as measured by reviewers’ ratings of the importance of the findings) in the statistical analysis. As the results show, besides being associated with quality, citation counts are correlated with the citation performance of the cited references, the language of the publishing journal, the chemical subfield, and the reputation of the authors. In this study no statistically significant correlation was found between citation counts and number of authors.

Citation analysis using online databases: Feasibilities and shortcomings

Extensive citation analysis with the Science Citation Index (SCI) has become possible through expanded search capabilities introduced by STN International a few years ago. STN enhanced its retrieval language with some important features, originally developed for statistical analysis of patents. Most important are an expanded select command and several functions to list the search results. The publications to be evaluated may be selected either in the SCI, or in a number of other bibliographic databases offered by the host. With the help of these features, the basic methods to appropriately measure the impact of scientific activities are demonstrated. Furthermore, possible shortcomings as well as the risks when interpreting the results of such studies are discussed.

Convergent validity of bibliometric Google Scholar data in the field of chemistry—Citation counts for papers that were accepted by Angewandte Chemie International Edition or rejected but published elsewhere, using Google Scholar, Science Citation Index, Scopus, and Chemical Abstracts

Examining a comprehensive set of papers (n=1837) that were accepted for publication by the journal Angewandte Chemie International Edition (one of the prime chemistry journals in the world) or rejected by the journal but then published elsewhere, this study tested the extent to which the use of the freely available database Google Scholar (GS) can be expected to yield valid citation counts in the field of chemistry. Analyses of citations for the set of papers returned by three fee-based databases – Science Citation Index, Scopus, and Chemical Abstracts – were compared to the analysis of citations found using GS data. Whereas the analyses using citations returned by the three fee-based databases show very similar results, the results of the analysis using GS citation data differed greatly from the findings using citations from the fee-based databases. Our study therefore supports, on the one hand, the convergent validity of citation analyses based on data from the fee-based databases and, on the other hand, the lack of convergent validity of the citation analysis based on the GS data.

The application of bibliometrics to research evaluation in the humanities and social sciences: An exploratory study using normalized Google Scholar data for the publications of a research institute

In the humanities and social sciences, bibliometric methods for the assessment of research performance are (so far) less common. This study uses a concrete example in an attempt to evaluate a research institute from the area of social sciences and humanities with the help of data from Google Scholar (GS). In order to use GS for a bibliometric study, we developed procedures for the normalization of citation impact, building on the procedures of classical bibliometrics. In order to test the convergent validity of the normalized citation impact scores, we calculated normalized scores for a subset of the publications based on data from the Web of Science (WoS) and Scopus. Even if scores calculated with the help of GS and the WoS/Scopus are not identical for the different publication types (considered here), they are so similar that they result in the same assessment of the institute investigated in this study: For example, the institutes papers whose journals are covered in the WoS are cited at about an average rate (compared with the other papers in the journals).

HREELS-studies of selectively deuterated cadmium-stearate Langmuir-Blodgett films

Monolayers of octadecanoic-18,18,18-d3 acid prepared by the Langmuir-Blodgett (LB) technique were used as model systems for studying the interaction mechanisms between slow electrons and organic thin films in high-resolution electron-energy-loss spectroscopy (HREELS). Due to their amphiphilic character these molecules are oriented with their deuterated methyl-group towards the air and with their carboxylate group towards the substrate. From the intensity ratio between the C-D- and C-H-stretching vibrations in HREEL spectra we derive a value the information depth in the order of three C-units of the aliphatic chain at a primary energy of 5 eV. The strong dependence of this intensity ratio upon the primary energy of the electrons between 2 and 7 eV is mainly attributed to a varying information depth. The energy dependence of the cross sections and the underlying interaction mechanisms are also discussed.

Interaction of metals with cadmium arachidate Langmuir-Blodgett films studied by X-ray photoelectron spectroscopy

Abstract The interaction of different metals with prototype Langmuir-Blodgett (LB) films was studied by means of X-ray photoelectron spectroscopy (XPS). Results on LB multilayers of the cadmium salt of arachidic acid on gold substrates revealed a mean free path λ of 60A at 1 keV. The attenuation of the substrate signal was used to characterize the quality of the films. Sandwich structures with monolayers of copper and aluminium evaporated onto the LB films on gold and silicon substrates under ultrahigh vacuum conditions were also investigated. The angular dependence of the XPS spectra indicates that the copper atoms migrate through the LB film. In contrast with copper, most of the evaporated aluminium atoms remain at the surface of the film. From changes in the Al 2p and C 1s binding energies and intensities, we deduce a strong interaction of aluminium with the hydrophilic car☐yl group of the fatty acids.

Interaction of slow electrons with organic films: theoretical and experimental HREELS studies on selectively deuterated molecules

Abstract The scattering processes of slow electrons in high-resolution electron-energy-loss spectroscopy (HREELS) at the surface of organic solids have been studied, both theoretically and experimentally. We used selectively deuterated molecules which were prepared in highly ordered films by the Langmuir-Blodgett (LB) technique. In the framework of a microscopic approach the intensity ratios for CD- and CH-stretching vibrations in the dipolar and impact limit were estimated. The broad angular distribution of elastically reflected electrons scattered at organic surfaces as well as the anisotropy of the films were taken into account. In a first set of experiments the influence of the substitution of hydrogen by deuterium on the intensity of the corresponding methyl and methylene stretching vibrations was measured. Comparison of the results with the theoretical considerations supports a dipolar-dominated scattering at around 5 eV with an increase of the impact contribution at lower energies. Second, the information depth and its dependence on the impact energy of the electrons was studied. The strong increase in the information depth towards lower electron energies can be correlated with a decrease of the dipolar scattering intensity and an enhancement of short-range interaction.

Does the h index for assessing single publications really work? A case study on papers published in chemistry

Schubert (Scientometrics, 78:559–565, 2009) showed that “a Hirsch-type index can be used for assessing single highly cited publications by calculating the h index of the set of papers citing the work in question” (p. 559). To demonstrate that this single publication h index is a useful yardstick to compare the quality of different publications; the index should be strongly related to the assessment by peers. In a comprehensive research project we investigated the peer review process of the Angewandte Chemie International Edition. The data set contains manuscripts reviewed in the year 2000 and accepted by the journal or rejected but published elsewhere. Single publication h index values were calculated for a total of 1,814 manuscripts. The results show a correlation in the expected direction between peer assessments and single publication h index values: After publication, manuscripts with positive ratings by the journal’s reviewers show on average higher h index values than manuscripts with negative ratings by reviewers (and later published elsewhere). However, our findings do not support Schubert’s (2009) assumption that the additional dimension of indirect citation influence contributes to a more refined picture of the most cited papers.

Proposal of a minimum constraint for indicators based on means or averages

Many field-normalized scientometric indicators are based on comparing the number of citations of a focal paper ith the average (or median) number of citations in the scientific field of the focal paper. One of the most prominent xamples is the mean normalized citation score (MNCS) (Waltman, van Eck, van Leeuwen, Visser, & van Raan, 2011). he scientometric community has been made aware of various problems of the MNCS (e.g. its dependence on single ighly cited papers) (Bornmann & Mutz, 2011; Gingras & Lariviere, 2011; Leydesdorff & Opthof, 2011). In this letter, we ould like to present another problem of the MNCS and similar field-normalized indicators which rely on averages or edians for the estimation of the expected number of citations in a scientific field. In order to exemplify the problem n this Letter, we use the algorithmically constructed classification system (ACCS) proposed by Waltman and van Eck 2012) for the definition of scientific fields. However, any other classification system could also be used. We obtained he ACCS from http://www.leidenranking.com/methodology/fields which was also used for the current Leiden Ranking http://www.leidenranking.com/ranking/2015). If the average (or median) value of citations in a scientific field is very small (i.e. close to 0), the ratio of a focal paper’s imes cited value and the “expected value of citations” is very large as long as the focal paper has at least one citation. This an lead to an enormous field-normalized impact score for a paper with very few citations. Table 1 shows a few illustrative xamples of ACCS clusters with very low average citations. For example, a paper with a single citation which is assigned to cluster 3766 has already an MNCS of 33.3 which is xtraordinarily high–more than 30 times than the average paper. Here, the concept of comparing the citations of a focal aper with papers published in the same field breaks down. A single citation is the minimum number of citations a paper an obtain: The focal paper has been cited in only one other paper. It is questionable if papers with only one citation obtain eld-normalized citation scores which can be obtained by papers in other fields only by a considerable citation impact (e.g. ore than 50 or 100 citations). This concept to normalize the impact of papers in comparison with papers published in the ame field is only meaningful if these papers have a reasonable number of average citations (e.g., 5, 10, 20, or more citations). The solution to this problem which we would like to propose here is as follows: any method to calculate a field-normalized ndicator which relies on the ratio I = c/e in some way (where I is the field-normalized citation score, c is the times cited of he focal paper, and e is the expected number of citations in the field) must ensure that e is larger than the resolution of I if > 0. In other words, for the case of the MNCS and similar field-normalized indicators, we propose that e must be larger than if a focal paper has at least one citation. Focal papers with at least one citation and e less or equal to 1 can’t be assigned a eaningful MNCS value.

Organized metal/organic film/metal heterostructures: a way towards molecular electronic devices?

Abstract This report discusses efforts to build up ordered metal/organic film/metal structures with a view towards molecular electronics. A brief background of molecular electronics is given. Organic films are prepared with the Langmuir-Blodgett (LB) technique. The thiophene-based molecules which are presented in this paper show the required order on the molecular level within the LB films. The formation of the contacting electrodes is illustrated. Aluminium and copper are evaporated onto a LB film, resulting in different behaviour with respect to reacting with and diffusing through the film: whereas the aluminium stays on top of the film, the copper completely diffuses into the LB film.