{"id":2536,"date":"2017-10-30T10:17:15","date_gmt":"2017-10-30T09:17:15","guid":{"rendered":"http:\/\/www.lookingatnothing.com\/?p=2536"},"modified":"2017-10-30T10:17:15","modified_gmt":"2017-10-30T09:17:15","slug":"bad-saxs-under-the-microscope-tbt-method-further-discredited","status":"publish","type":"post","link":"https:\/\/lookingatnothing.com\/index.php\/archives\/2536","title":{"rendered":"Bad SAXS under the microscope: TBT method further discredited"},"content":{"rendered":"

It has been a while since I last vented about the continued use of the so-called “Tangent-by-tangent” (TBT) method. This method ostensibly is able to determine accurate size distributions using nothing but a superposition of Guinier functions. The last time that I talked about this (probably) was in the pitfalls-section of the Everything SAXS review paper<\/a>. But now there’s good news!
\n<\/p>\n

\"From<\/a>
From “Le Voyage dans la lune” (A Trip to the Moon) (1902). out of copyright.<\/figcaption><\/figure>\n

A little bit of background. The TBT method first appeared in 1946 in a paper by Jellinek<\/a> et al.. They indicated that it was a distinct approximation that looked useful, upon which it was correctly noted: “At this stage of development it would be premature to take too seriously these computations of particle size distribution.”<\/p>\n

If you take a look at what happens to the Guinier method for polydisperse systems, you see that it assumes the volume-squared weighted mean radius of gyration, as re-demonstrated here<\/a> and here<\/a>. The idea that you can pick apart a scattering curve originating from a monomodal size distribution of objects, by using a superposition of Guinier functions alone is, therefore, farfetched.<\/p>\n

Despite these demonstrations, the TBT method is still in use today. Currently, it is still being used by a group in China, who also wrote some software based on it (and whom I personally confronted at SAS2012). There is a steady drip of seemingly interesting papers culminating from their efforts which casually mention the TBT method. One of the latest papers claiming its successful application is this one<\/a>.<\/p>\n

In order to prevent other researchers from wasting their time on this (risking discrediting the field in the process), it is useful to let people know that it doesn’t work. I do so from time to time, but I was happy to see an actual paper<\/a> a few weeks ago which does just that. The paper appeared in a Russian institute journal which is not so well known and may not have a large readership, however, with some amplification it may turn out to be a useful tool in the battle against bad SAXS.<\/p>\n

Have a read, let me know what you think below!<\/p>\n","protected":false},"excerpt":{"rendered":"

It has been a while since I last vented about the continued use of the so-called “Tangent-by-tangent” (TBT) method. This method ostensibly is able to […]<\/a><\/p>\n<\/div>","protected":false},"author":2,"featured_media":2538,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":4,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[1],"tags":[],"class_list":["post-2536","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/lookingatnothing.com\/wp-content\/uploads\/2017\/10\/Le_Voyage_dans_la_lune.png","jetpack_shortlink":"https:\/\/wp.me\/p1gZ2v-EU","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/posts\/2536","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/comments?post=2536"}],"version-history":[{"count":2,"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/posts\/2536\/revisions"}],"predecessor-version":[{"id":2539,"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/posts\/2536\/revisions\/2539"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/media\/2538"}],"wp:attachment":[{"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/media?parent=2536"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/categories?post=2536"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/lookingatnothing.com\/index.php\/wp-json\/wp\/v2\/tags?post=2536"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}