Problem:

1. When a sensible publication title term is given, then the query delivers some images (=> expected).
2. When a nonsensical publication title term is given, then the query delivers many more images => not expected.

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How to use the Case sensitive checkbox ?
The only way I found is to

1. Check (or uncheck) the checkbox
2. Hit Enter on the keyboard

This is not intuitive - checkbok selection is followed by confirmation by Enter.

Thanks @pwalczysko.

With Gene symbol PDX or pgam5 gives 5790 Images
http://idr-testing.openmicroscopy.org/search/?q=(((key:Gene+Symbol,value:pdx,operator:contains,resource:image),(key:Gene+Symbol,value:pgam5,operator:equals,resource:image)))

Also with AND Human we get the same 5790 Images:
http://idr-testing.openmicroscopy.org/search/?q=((key:Organism,value:homo+sapiens,operator:equals,resource:container),((key:Gene+Symbol,value:pdx,operator:contains,resource:image),(key:Gene+Symbol,value:pgam5,operator:equals,resource:image)))

Add Publication Title 'invalid', we get 5548 Images:
http://idr-testing.openmicroscopy.org/search/?q=((key:Publication+Title,value:studysdsd,operator:contains,resource:container),(key:Organism,value:homo+sapiens,operator:equals,resource:container),((key:Gene+Symbol,value:pdx,operator:contains,resource:image),(key:Gene+Symbol,value:pgam5,operator:equals,resource:image)))

Without the 'Human' AND statement, the Study Title behaves correctly (invalid keyword returns no results):
http://idr-testing.openmicroscopy.org/search/?q=((key:Publication+Title,value:study,operator:contains,resource:container),((key:Gene+Symbol,value:pdx,operator:contains,resource:image),(key:Gene+Symbol,value:pgam5,operator:equals,resource:image)))

Also, without the OR clause, the Study Title behaves correctly (invalid keyword returns no results):
http://idr-testing.openmicroscopy.org/search/?q=((key:Publication+Title,value:study,operator:contains,resource:container),(key:Organism,value:homo+sapiens,operator:equals,resource:container),(key:Gene+Symbol,value:pdx,operator:contains,resource:image))

@pwalczysko - Ah, yes I've not looked at the Case sensitive checkbox - I'll try fix now...

@pwalczysko The case_sensitive checkbox should be working now on idr-testing (needs full refresh to clear cache).
Checking/unchecking will update the URL, search results and undo/redo buttons. Undo/redo should update the checkbox as expected etc.