Number of football research papers published by year.

Number of football research papers published by year.</p

Analysis of text network for football research keywords in 2010s.

Analysis of text network for football research keywords in 2010s.</p

Analysis of text network for football research keywords over all study periods.

Analysis of text network for football research keywords over all study periods.</p

Analysis of text network for football research keywords in 2020s.

Analysis of text network for football research keywords in 2020s.</p

Frequency of keywords appearing in football research papers.

Frequency of keywords appearing in football research papers.</p

Analysis of text network for football research keywords in 2000s.

Analysis of text network for football research keywords in 2000s.</p

Procedure for text network analysis adopted in this study.

Procedure for text network analysis adopted in this study.</p

Analysis of text network for football research keywords in 1990s.

Analysis of text network for football research keywords in 1990s.</p

S1 Raw data -

This study was aimed to identify football research trends in various periods. A total of 30,946 football papers were collected from a representative academic database and search engine, the ‘Web of Science’. Keyword refinement included filtering nouns, establishing synonyms and thesaurus, and excluding conjunctions, and the Cyram’s Netminer 4.0 software was used for network analysis. A centrality analysis was conducted by extracting the words corresponding to the top 2% of the main research topics to obtain the degree and eigenvector centralities. The most frequently mentioned research keywords were injury, performance, and club. Keyword performance showed the highest degree centrality (0.294) and keyword world and cup showed the highest eigenvector centrality (0.710). The keyword with the highest eigenvector degree changed from injury in the 1990s and world in the 2000s to cup since the 2010s. Although various studies on football injuries have been conducted, research on the sport itself has recently been conducted. This study provides fundamental information on football trends from research published over the past 30 years.</div

Effect of pH on Anodic Formation of Nanoporous Gold Films in Chloride Solutions: Optimization of Anodization for Ultrahigh Porous Structures

Nanoporous gold (NPG) structures have useful applications based on their unique physical and chemical properties; therefore, the development of NPG preparation methods is the subject of extensive research. Recently, the anodization of Au surfaces was suggested as an efficient method for preparing porous Au structures. In this work, the mechanistic aspects of the anodization of Au in Cl^–-containing solutions for the preparation of NPG layers were investigated. The effects of the experimental parameters of the anodization reaction on the porosity of the NPG layers in terms of the roughness factor (<i>R</i>_f) were examined. The anodic formation of NPG was more effective in buffered solutions than in unbuffered electrolytes. The <i>R</i>_f of the NPG layer was sensitive to the electrolyte pH; this was ascribed to the efficient formation of protecting layers of gold oxide on the newly formed NPG structures. In buffer solutions at pH 8, ultrahigh porous NPG layers with <i>R</i>_f values of 1300 were obtained within 15 min. The ultrahigh porous NPG layers were used for the electrochemical detection of glucose; a high sensitivity of 135 μA mM^–1 cm^–2 was achieved in the presence of 0.1 M Cl^–. This straightforward and time-saving preparation of NPG surfaces will provide new opportunities for applications of NPG structures