Changes in / [e262dd6:9f2216f] in sasmodels

Files:

• doc/guide/pd/polydispersity.rst (modified) (3 diffs)
• sasmodels/models/core_shell_sphere.py (modified) (1 diff)

doc/guide/pd/polydispersity.rst

@@ -20 +20 @@
   P(q) = \text{scale} \langle F^* F \rangle / V + \text{background}
 
-where $F$ is the scattering amplitude and $\langle\cdot\rangle$ denotes an
-average over the size distribution.
+where $F$ is the scattering amplitude and $\langle\cdot\rangle$ denotes an 
+average over the size distribution $f(x; \bar x, \sigma)$, giving
+
+.. math::
+
+  P(q) = \frac{\text{scale}}{V} \int_\mathbb{R} 
+  f(x; \bar x, \sigma) F^2(q, x)\, dx + \text{background}
 
 Each distribution is characterized by a center value $\bar x$ or
@@ -41 +46 @@
 with larger values of $N_\sigma$ required for heavier tailed distributions.
 The scattering in general falls rapidly with $qr$ so the usual assumption
-that $G(r - 3\sigma_r)$ is tiny and therefore $f(r - 3\sigma_r)G(r - 3\sigma_r)$
+that $f(r - 3\sigma_r)$ is tiny and therefore $f(r - 3\sigma_r)f(r - 3\sigma_r)$
 will not contribute much to the average may not hold when particles are large.
 This, too, will require increasing $N_\sigma$.
@@ -63 +68 @@
 
 Additional distributions are under consideration.
+
+.. note:: In 2009 IUPAC decided to introduce the new term 'dispersity' to replace 
+           the term 'polydispersity' (see `Pure Appl. Chem., (2009), 81(2), 
+           351-353 <http://media.iupac.org/publications/pac/2009/pdf/8102x0351.pdf>`_ 
+           in order to make the terminology describing distributions of properties 
+           unambiguous. Throughout the SasView documentation we continue to use the 
+           term polydispersity because one of the consequences of the IUPAC change is 
+           that orientational polydispersity would not meet their new criteria (which 
+           requires dispersity to be dimensionless).
 
 Suggested Applications

sasmodels/models/core_shell_sphere.py

@@ -21 +21 @@
 .. math::
 
-    F^2(q) = \frac{3}{V_s}\left[
+    F(q) = \frac{3}{V_s}\left[
        V_c(\rho_c-\rho_s)\frac{\sin(qr_c)-qr_c\cos(qr_c)}{(qr_c)^3} +
        V_s(\rho_s-\rho_\text{solv})\frac{\sin(qr_s)-qr_s\cos(qr_s)}{(qr_s)^3}