{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"7aee3203f0e3ae89a9dfc8420ebd340af60aff1ddf298ed1e5082364439f24d3","created":"2026-10-03T07:18:06Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"c5e70c2f6130147b13f98de74e75ba08d8bc99145ee5a34e0bf84fc0714d7fdf","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"med.diffusion-mri.membrane-exchange","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"Water moves in and out of brain cells while it is being measured, which blurs the distinction between inside and outside. Reported exchange times disagree by large factors.","posed_since":"","precise":"Determine the mean intra-to-extracellular water exchange time $\\tau_{ex}$ in human and rodent grey matter, which reported analyses place anywhere from about 10 ms to over 100 ms, using diffusion-time-dependent kurtosis, filter-exchange imaging or multi-dimensional relaxation-diffusion methods, while separating exchange from structural time dependence. An answer is a value with uncertainty that is consistent across methods.","problem_ref":null,"references":"","settled_by":"Agreement within 30 percent among independent exchange-sensitive methods on the same tissue, with a control of known permeability.","status_note":"","title":"Water exchange times across cell membranes in grey matter","topic_ref":"7d6543da8b95cbfe0f88251dd0987163345fc9bcbe4e99e44fdf7b56a0f8bcd0"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"20b0cccfeb2cb8b6fd0b8a006a5eeda25c959910fa6bc9c4cf138863627dbf1e","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"48e9d507ab7dc3906ed82c1ac9667f835826fcadd1abce1fec359643ff8817ef","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"6xYSltdbnaewRtFB7zPFZ7YmBzHKjhaI53-4KycNgr4RZEMP2cijoT6rQkQQvZ24f_32n8ylzHoZIAS4liwYAw"},"schema":"pubphys.envelope/1"},"record_hash":"20b0cccfeb2cb8b6fd0b8a006a5eeda25c959910fa6bc9c4cf138863627dbf1e","leaf_index":1670}