Aim

The Microchimerism Literature Atlas (MCLA) aims to support scientists in their search for microchimerism literature. Currently, the MCLA contains the metadata of more than 16,000 scientific articles and reviews, covering the period from 1970 to the present. The publicly available metadata was downloaded from PubMed® by applying multiple MeSH term searches.
The MCLA is structured modularly, consiststing of the 5 dashboards 'Data Table', 'Filter Settings', 'Chart View', 'Network View' and 'Info'. The currently displayed dashboard can be changed, e.g., to the filter settings, by clicking the -tab in the header or by clicking the -tab in the sidebar.

Data Table

In the -tab, the paper titles, the authors, the publication years, the publishing journals, the publishing types and the DOIs are shown in the form of a data table. The displayed columns can be changed through marking the checkboxes in the sidebar. Additionally, the abstract can be viewed by clicking the -symbol after the selection of a table row. The papers in the table occur in a random order and can be sorted ascendingly or descendingly by clicking the - or the -buttons placed in the column header, respectively.

Searching

In the -tab, the MCLA can be searched for keywords, either across all columns and in the abstracts by using the -search box, or witin columns by using the -search boxes at the top of the table columns. The search is performed after pressing the enter key. Further, the search offers the possibility to search for whole words, word parts, consecutive words and to combine them by operators.

• Search for word parts:  wordpart, e.g., microchim or  alloantibo
• Search for whole words using double quotes:  "wholeword", e.g., "chimerism" or  "bodies"
• Search for consecutive words:  word1 word2, e.g., bone marrow or  stem cell
• Use of AND-operator:  word1 AND word2, e.g., maternal AND microchimerism or  disease AND 2022
• Use of OR-operator:,  word1 OR word2, e.g., fetomaternal OR pregnancy or  stem cell OR blood cell
• Use of NOT-operator:  word1 NOT word2, e.g., NOT cancer or  "chimerism" NOT microchimerism
• Combination of the rules:  e.g., cell AND microchimerism NOT transplantation OR "chimerism" OR stem cell

If the search is not performed after pressing the 'Enter'-key, the assemblence of the search terms is incorrect - check for open double quotes. The search results received with the -search box also affect the charts in the -tab.

Filtering and Export

Pre-selected keywords in the -tab can be used to search the titles and abstracts, the article types and the publishing dates. The search terms within the categories can either be combined by OR (any article whose metadata scontains at least one of the selected search terms) or by AND (any abstract that contains all selected search terms) through toggling the radio button . The chosen filter settings are applied while switching back to the data table view, by clicking the -tab. Furthermore, the filtered papers can then be downloaded as text file, as Excel file or printed by clicking on the -, - or -buttons in the sidebar, respectively.

Chart View

Depending on the selected filter settings in the -tab, some insightful charts are shown in the -tab regarding the number of published papers over time, the most active authors, the most publishing journals, and the most frequently used title words and keywords. The styles of most charts can be changed by clicking on the plots. Additionally, heat map charts show the time development of the techniques and the top ranked publishing journals, in which the cells are colored from lowest to highest value by the following color scheme .

Network View

The literature network in the -tab is build based on the PubMed-IDs listed in the references of the downloaded papers. In the network, the PubMed-IDs are shown as number under each node . The shape of the nodes highlight articles and reviews listed in the table and further literature that does not appear in it. Moreover, arrows indicate citations. The network is created around a paper which is selected by clicking a table row in the -tab and then switching to the -tab. The construction of large citation networks may take several seconds. The selected node is indicated by a colored outer border as , or . In the -tab, the selected node can either be changed by clicking on another node or by using the drop-down list . Additionally to the selected nodes, also the direct neighbors are highlighted. To gain a better overview of the whole network, no node can be selected by clicking in the empty area between the nodes or by selecting no node in drop-down list .

Zooming can be achieved either by simultaneously holding the Ctrl-key and turning the mouse wheel or through - and -button. The original view is restored by the -button. Navigation is possible either by simultaneously clicking the left mouse button and panning or by using the navigation buttons , , and .

Access to Full Text Articles

The full text articles can be accessed, as long as the necessary access rights of the journal exist, by clicking a DOI in the -tab.

Acknowledgments
The MCLA is part of the 'We All Are Multitudes: The Microchimerism, Human Health and Evolution Project' that is funded by the John Templeton foundation (Grant-ID 62214).
The MCLA was implemented by using the Shiny package:
Chang W, Cheng J, Allaire J, Sievert C, Schloerke B, Xie Y, Allen J, McPherson J, Dipert A, Borges B (2024). shiny: Web Application Framework for R.
R package version 1.8.0.9000, https://github.com/rstudio/shiny, https://shiny.posit.co/.