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Attention:The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 7:00 AM ET to 7:30 AM ET on Friday, April 24 due to maintenance. We apologize for the inconvenience.

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Do you have questions about PAR content, procedures, or policies? More information is available at NSF's Public Access page and in our Frequently Asked Questions. You may also leave feedback by clicking on this .