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Dear Fatemeh,</div>
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Thank you for your report.</div>
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I just tried your steps to reproduce with one of our example datasets using SasView 6.1.0, and 6.1.1 we released last week.</div>
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I don't see any behaviour that immediately leaps out at me as 'unrealistic'. So I'd like to understand exactly what you mean by this.</div>
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Could you post a few slides with annotated screenshots illustrating what you have done/see, please?</div>
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By the way, you posted to users@sasview.org which goes to a wider audience than just the developers. If you are comfortable with that, that's cool. Otherwise reply to help@sasview.org.</div>
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Kind regards,</div>
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Steve King</div>
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On behalf of the SasView Developer Community</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> users <users-bounces@lists.sasview.org> on behalf of Abdoltajedini, Fatemeh via users <users@lists.sasview.org><br>
<b>Sent:</b> 08 October 2025 21:21<br>
<b>To:</b> users@sasview.org <users@sasview.org><br>
<b>Subject:</b> [SasView Users] Bug Report – Unexpected Behavior of Polydispersity in SASview v6</font>
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Dear SASview Team,</div>
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I would like to report a possible bug I encountered in SASview v6 related to polydispersity.</div>
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<b>Description of the issue:</b><br>
When I add polydispersity to a model, the scattering curve changes far more dramatically than expected. Even small values (e.g., 0.05 on radius) cause the intensity and curve shape to shift disproportionately, which does not seem physically reasonable.</div>
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<b>Steps to reproduce:</b></div>
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<div role="presentation" style="margin:1em 0px">Open SASview v6.</div>
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<div role="presentation" style="margin:1em 0px">Load the [Core-Shell Cylinder].</div>
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<div role="presentation" style="margin:1em 0px">Fit the model without polydispersity – the curve looks reasonable.</div>
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<div role="presentation" style="margin:1em 0px">Add a small polydispersity (e.g., 0.05 on radius).</div>
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<div role="presentation" style="margin:1em 0px">The curve changes strongly in both shape and magnitude.</div>
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<b>Expected behavior:</b><br>
Polydispersity should broaden or smooth features of the scattering curve, but not cause large intensity changes or unrealistic distortions.</div>
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<b>Observed behavior:</b><br>
Even small polydispersity values produce a strong, unrealistic effect.</div>
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<b>Environment:</b></div>
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<div role="presentation" style="margin:1em 0px">SASview version: 6.x</div>
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<div role="presentation" style="margin:1em 0px">Operating system: Windows</div>
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<div role="presentation" style="margin:1em 0px">Data used: experimental data</div>
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Thank you for your help and for maintaining this valuable software.</div>
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Best regards,<br>
Fatemeh</div>
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