Influence of thermal treatments on Ag Sn Cu powders in order to reduce mercury contents in dental amalgam

The mercury content of dental amalgams is a controversial subject with regard to the biological properties of these materials. The object of this study is to optimize the thermal treatments performed on an experimental powder in order to obtain a low mercury ratio (41% by weight) while preserving the desirable clinical qualities of the material. Using atomized powder, two types of thermal treatments are performed: A1, to obtain a partially annealed structure and A2, to obtain a complete homogenization. The kinetics of the amalgamation reaction is mainly evaluated by X-ray diffraction to identify the newly formed phases as a function of setting time. Mechanical properties are evaluated according to the ISO norms at 37 °C. Metallographical examination of the amalgams shows a «Ag-Hg» phase which acts as a matrix incorporating the «Cu-Sn» and «Ag-Sn» compounds. The setting kinetics of the A1 amalgams is linear and slightly more rapid than that of the A2 amalgam. The mechanical properties of the amalgams are significantly improved regarding the higher mercury content commercial amalgams. A specific thermal treatment permits us to slow down the diffusion of mercury between the different intermetallic compounds into the powder. The final amalgam composition, thus, most approaches the stoechiometric ratio calculated from a quaternary diagram.     

Validation of bibliometric indicators in the field of mathematics

Bibliometric analyses of scientific publications provide quantitative information that enables evaluators to obtain a useful picture of a team's research visibility. In combination with peer judgements and other qualitative background knowledge, these analyses can serve as a basis for discussions about research performance quality. However, many mathematicians are not convinced that citation counts do in fact provide useful information in the field of mathematics. According to these mathematicians, citation and publication habits differ completely from scholarly fields such as chemistry or physics. Therefore, it is impossible to derive valid information regarding research performance from citation counts. The aim of this study is to obtain more insight into the significance of citation-based indicators in the field of mathematics. To which extent do citation-scores mirror to the opinions of experts concerning the quality of a paper or a journal? A survey was conducted to answer this question.Top journals, as qualified by experts, receive significantly higher citation rates thangood journals. Thesegood journals, in turn, have significantly higher scores than journals with the qualificationless good. Top publications, recorded in the ISI database, receive on the average 15 times more citations than the mean score within the field of mathematics as a whole. In conclusion, the experts' views on top publications or top journals correspond very well to bibliometric indicators based on citation counts.     

Influence of Latin American journals coverage by international databases

The coverage of Latin American journals by international databases influences the visibility of these countries' scientific output, and has a direct effect in their activity index per scientific discipline. Local, regional and international character of the most visible Latin American journals in SCI expanded and restricted databases is analysed, as well as its influence in the percentage share of each country in certain disciplines. Suggestions to enhance visibility of local journals are presented.     

The visibility of Italian journals

The main purpose of this study was to analyze the Italian journals indexed in the 2000 edition of the Journal Citation Reports (JCR) published by the Institute for Scientific Information (ISI) (Philadelphia, USA). The performance and the visibility of these journals were evaluated in terms of Impact Factor (IF), mean IF from citing journals and cited journals, and self-citing and self-cited rates. Seventy-three Italian journals were indexed in the JCR, 14 of which achieved an IF equal to or higher than one. Most citing journals were European and American, thus showing a fairly good visibility of the articles published in the 14 journals analyzed. The self-citing and self-cited rates showed a wide variation. The journal that appeared to perform best was theJournal of High Energy Physics, an electronic publication whose success seemingly confirms Internet circulation as an effective means to enhance the visibility and consequently the quality, in term of citations, of a journal. Italy's low overall expenditure on research & development (R&D) and low number of researchers compared to countries with longstanding high publishing standards and traditions are no doubt partly to blame for its poor performance in scientific publishing. This revised version was published online in August 2006 with corrections to the Cover Date.     

Publication dynamics: Models and indicators

Models and indicators characterizing the dynamics of national publication productivity distributions are presented. The indicator triplet: transience, renewal, and dynamism is used to describe the «physical shape» of a national scientific community.     

The role of domestic journals in geographically-oriented disciplines: The case of Spanish journals on earth sciences

The role of domestic journals in disseminating research results in the filed of Earth Sciences in Spain is discussed. The analysis is based on bibliometric indicators of Spanish scientific production, as well as on the opinion of Spanish researchers in this field, obtained through a specially designed survey. A reasonable correspondence has been found between the results of bibliometric analysis and scientists' judgements. Results show that 69% of Spanish articles in Earth Sciences were published in Spanish journals during the period 1990–1994. Scientists use both national and international journals to communicate, their research results, although due to the nature of the discipline, geographically oriented and therefore mostly devoted to local problems, they use basically domestic journals. In terms of international visibility, although none of the Spanish journals in this field is covered by the SCI, most of them are covered by some of the most representative international databases in the field concerned. The study points out the importance of domestic journals in the field of Earth Sciences in Spain.     

Spanish scientific and technical journals. State of the art

This article analyses the current situation in the field of scientific and technical journals published in Spain, by determining the following scientific indicators for each: I: Specifications. II: Scientific production covered. III: Visibility and accessibility. The first section provides a qualitative and quantitative study of the journals, asking what subjects they cover, who publishes them, how often they are published, how up to data they are and whether the way they are presented meets international publishing standards. The second section analyses scientific production by research sectors and the percentage of articles collected in the ICYT database compared with the total number of papers published in the journals studied. It also studies the reference habits of the authors published therein to identify whether the literature referred to is of local origin or international. Finally, the third section deduces these journals' degree of visibility by analysing how they are distributed amongst the usual media, i.e. international periodicals directories and databases, and how efficiently they work as vehicles for the diffusion of research by foreign authors. The study covers 10 years (1980–1989), thus enabling to recognise past and current trends in Spanish scientific literature.     

Advantages and limitations in the use of impact factor measures for the assessment of research performance

Impact factor is a quasi-qualitative indicator, which provides a measurement of the prestige and international visibility of journals. Although the use of impact factor-based indicators for science policy purposes has increased over the last two decades, several limitations have been pointed out and should be borne in mind. The use of impact factor should be treated carefully when applied to the analysis of peripheral countries, whose national journals are hardly covered by ISI databases. Our experience in the use of impact factor based indicators for the analysis of the Spanish scientific production is shown. The usefulness of the impact factor measures in macro, meso and micro analyses is displayed. In addition, the main advantages, such as the great accessibility of impact factor and its ready-to-use nature are pointed out. Several limitations such as the need to avoid inter-field comparisons or the convenience of using a fixed journal set for international comparisons are also stressed. It is worth noting that the use of impact factor in the research evaluation process has influenced strongly the publication strategy of scientists. This revised version was published online in June 2006 with corrections to the Cover Date.     

Some aspects of citation indexes in Spain: A comparative analysis

This paper studies the main characteristics of the citation indexes currently developed in Spain. The paper compares the impact factors offered by Spanish citation indexes with the impact factor of Spanish journals also collected by the JCRs of the ISI (SCI and SSCI) over a five-year period (2001–2005). Spanish journals published in English have higher impact factor scores in the JCR databases of the ISI than in Spanish citation indexes.     

Mapping interdisciplinarity at the interfaces between the Science Citation Index and the Social Science Citation Index

The two Journal Citation Reports of the Science Citation Index 2004 and the Social Science Citation Index 2004 were combined in order to analyze and map journals and specialties at the edges and in the overlap between the two databases. For journals which belong to the overlap (e.g., Scientometrics), the merger mainly enriches our insight into the structure which can be obtained from the two databases separately; but in the case of scientific journals which are more marginal in either database, the combination can provide a new perspective on the position and function of these journals (e.g., Environment and Planning B — Planning and Design). The combined database additionally enables us to map citation environments in terms of the various specialties comprehensively. Using the vector-space model, visualizations are provided for specialties that are parts of the overlap (information science, science & technology studies). On the basis of the resulting visualizations, “betweenness” — a measure from social network analysis — is suggested as an indicator for measuring the interdisciplinarity of journals.     

The representation of nationalities on the editorial boards of international journals and the promotion of the scientific output of the same countries

This paper analyses the nationalities of the editorial board members of the top 20 journals (according to their impact factor in the ISI Journal Citation Report, Science Edition 2005) serving 15 scientific disciplines. A total of 281 journals were analysed (some journals crossed disciplinary boundaries) and 10,055 of their editorial board members were identified. Some 53% of board members were from the United States. Europe provided 32%, with the United Kingdom making the greatest contribution (9.8%). The analysis of scientific output by nationality in these journals showed a significant correlation, in all disciplines, with the representation of the corresponding nations on the editorial boards. The composition of editorial boards may therefore provide a useful indicator for measuring a country’s international scientific visibility. The present results should be taken into account in the design of national policies with the aim of enhancing the presence of a country’s most prestigious scientists on the editorial boards of the main international journals.     

Impact of studies published in the international literature by scientists at the National University of Mexico

A total of 2192 articles published in the international literature with UNAM (National University of Mexico) first author affiliation and registered by the CICH (Centro de Iformación Científica y Humanística) BIBLAT database from 1978-mid-1987 were included in our analysis. Distribution of articles according to the main subject areas of the 692 different journal titles used was as follows: Physics 24.1%, Medicine 19.7%, Biology 19.4%, Chemistry 9.7%, Engineering 8.9%, Exact Sciences 7.3%, Geosciences 4.7%, Psychology 0.96%, Agrosciences 0.27%. Thirty-seven percent of articles were published in journals with a known impact factor for 1987 of 1, 46.1% (920) in journals within the range of >1–3 average citations/article and only 16.4% (327) in those titles with a factor >3. Fifty-four percent (1082) of studies appeared in journals whose total citation count for 1987 was 5000; 7.3% (146) in journals cited >50,000 times in that same year. UNAM scientists therefore as a group tend to publish in journals whose articles are not frequently cited in subsequent publications thus limiting their impact and visibility in the international scientific literature.Paper presented at the International Conference on Science Indicators for Developing Countries, Paris, 15–19 October, 1990.     

Measuring China"s research performance using the Science Citation Index

This contribution focuses on the application of bibliometric techniques to research activities in China, based on data extracted from the Science Citation Index (SCI) and related Citation Indexes, produced by the Institute for Scientific Information (ISI). The main conclusion is that bibliometric analyses based on the ISI databases in principle provide useful and valid indicators of the international position of Chinese research activities, provided that these analyses deal properly with the relatively large number of national Chinese journals covered by the ISI indexes. It is argued that it is important to distinguish between a national and an international point of view. In order to assess the Chinese research activities from a national perspective, it is appropriate to use the scientific literature databases with a good coverage of Chinese periodicals, such as the Chinese Science Citation Database (CSCD), produced at the Chinese Academy of Sciences. Assessment of the position of Chinese research from an international perspective should be based on the ISI databases, but it is suggested to exclude national Chinese journals from this analysis. In addition it is proposed to compute an indicator of international publication activity, defined as the percentage of articles in journals processed for the ISI indexes, with the national Chinese journals being removed, relative to the total number of articles published either in national Chinese or in other journals, regardless of whether these journals are processed for the ISI indexes or not. This indicator can only be calculated by properly combining CSCD and ISI indexes. This revised version was published online in June 2006 with corrections to the Cover Date.     

A complete stress-function representation of stresses for a continuum of second grade

Summary At present, Cauchy's equations of linear momentum and of moment of momentum seem to demand a modification, advancing forward Cauchy's classical considerations in the sense of incorporating the concept of couple-stresses in those equations. This concept is well-known in the theory of Cosserat-continua, less so in the theory of point-continua. However, the theory of point-continua is widely known and has been applied with great success e.g. to such materials as steel, water or air in engineering mechanics. Incorporating the concept of couple-stresses in the theory of point-continua, however, involves many serious problems. One such problem is the type of structure of the couple-stress tensor. An-other problem is the question of the completeness of a stress-function representation of stresses. In the following paper the author presents a complete stress-function representation of stresses for his «refined theory» of the point-continuum. The main features of incorporation of the concept of couple-stresses in that theory—e.g. the reason why the couple-stress tensor must be of skew-symmetric structure—have already been presented in [1].     

China Scientific and Technical Papers and Citations (CSTPC): History,impact and outlook

This paper traces the history of China Scientific and Technical Papers and Citations database (CSTPC) since its founding in 1988. The fact that most Chinese scientists publish their research results in Chinese journals requires that China establish SCI counterparts dedicated to domestic S & T journals. The article describes the selection criteria for source journals, the approach used to adjust the structure of source journals, the criteria for selecting items to be included in the database, and the indexing method. Then it discusses the impact upon government R & D administration agencies and the science community in general by both CSTPC team and CSTPC database. Finally, the article analyzes the main factors that lead to the primary success of CSTPD. The authors encourages information workers in other non-English developing countries to build up similar databases. This revised version was published online in June 2006 with corrections to the Cover Date.     

Online determination of the journal impact factor and its international properties

The article describes the method for the online determination of the journal impact factor (JIF). The method is very simple and can be used both for the ISI defined journal impact factor and for the calculation of other generalised journal impact factors. But the direct online method fails for non-ISI journals i.e. journals not indexed by ISI to the three citation databases. For such journals only the “External Cited Impact Factor” associated with citations from ISI journals (ECIFisi) can be determined online by the common method. As an extra benefit the online method makes available the determination of the geographical distribution of citations and citable units in relation to any given JIF, i.e. the international impact for a particular journal in a given year. The method is illustrated by calculating the generalised JIF, self-citations and ECIF(isi) as well as the international impact for Journal of Documentation and Scientometrics.     

Empirical series of journal h-indices: The JCR category Horticulture as a case study

Two types of series of h-indices for journals published in the field of Horticulture during the period 1998–2007 are calculated. Type I h-indices are based on yearly data, while type II h-indices use cumulative data. These h-indices are also considered in a form normalised with respect to the number of published articles. It is observed that type I h-indices, normalised or not, decrease linearly over a period of ten years. The type II series, however, is not linear in nature: it exhibits partly a concave shape. This proves that the journals (in Horticulture) do not exhibit a linear increase in h-index as argued by Hirsch in the case of life-time achievements of scientists. In the second part of the paper, an attempt is made to study the relative visibility of a journal and its change over time, based on h-indices of journals. It is shown that:

Epitaxial Film Growth of Tl0.78Bi0.22Sr1.6Ba0.4Ca2Cu3O9 on Rolling Assisted Biaxially Textured Nickel Substrates with YSZ And CeO2 Buffer Layers

Epitaxial film growth of Tl_0.78Bi_0.22Sr_1.6Ba_0.4Ca₂Cu₃O₉ ((Tl,Bi)-1223) on rolling assisted biaxially textured substrates with YSZ and CeO₂ buffer layers (RABiTS) has been successfully demonstrated by laser ablation and post-deposition annealing in flowing argon. X-ray diffraction (XRD) -2 spectra showed that the films consisted mainly of c-axis aligned 1223 phase with some intergrown 1212 phase, while XRD -scans of (102) pole figure revealed that the films are also a- and b-axes aligned, with an epitaxy of the «100» of (Tl,Bi)-1223 film on the «110» of the top YSZ buffer layer. Four-terminal electrical transport measurements showed that the zero-resistance transition temperature (T_c) was in the range of 106 - 110 K, and the critical current density (J_c) at 77 K and zero field was about 10⁵ A/cm² for the entire film width (3 mm) of a longer film (14 mm) which was processed differently from the shorter films (7 mm). For a shorter film (7 mm) that showed better ab-in-plane alignment, the magnetization J_c, at 77 K and extrapolated to zero field, calculated from Bean's model using the full film width (3.5 mm) as the appropriate lateral dimension, was 2 × 10⁵ A/cm².