# Changeset c78d677 in sasmodels

Ignore:
Timestamp:
Sep 28, 2018 10:31:31 AM (3 months ago)
Branches:
master, beta_approx, cuda-test, py3, ticket-1015-gpu-mem-error, ticket-1015-quick-fix, ticket-1157, ticket-608-user-defined-weights, ticket_1156
Children:
c351383
Parents:
9235fc3
Message:

Fixed inline substitution errors & improved formatting and presentation

File:
1 edited

### Legend:

Unmodified
 r9235fc3 r""" .. note:: Please read the Validation section below. Definition ---------- $K$ is the contrast factor for the polymer which is defined differently than in other models and is given in barns where $1 barn = 10^{-24} cm^2$.  $K$ is other models and is given in barns where 1 $barn = 10^{-24}$ $cm^2$.  $K$ is defined as: a = b_p - (v_p/v_s) b_s where $b_p$ and $b_s$ are sum of the scattering lengths of the atoms constituting the monomer of the polymer and the sum of the scattering lengths of the atoms constituting the solvent molecules respectively, and $v_p$ and $v_s$ are the partial molar volume of the polymer and the solvent respectively $L_b$ is the Bjerrum length(|Ang|) - **Note:** This parameter needs to be kept constant for a given solvent and temperature! $h$ is the virial parameter (|Ang^3|) - **Note:** See [#Borue]_ for the correct interpretation of this parameter.  It incorporates second and third virial coefficients and can be Negative. $b$ is the monomer length(|Ang|), $C_s$ is the concentration of monovalent salt(1/|Ang|- converted from mol/L), $\alpha$ is the ionization degree (ionization degree : ratio of charged monomers  to total number of monomers), $C_a$ is the polymer molar concentration(1/|Ang|- converted from mol/L), and $background$ is the incoherent background. where: - $b_p$ and $b_s$ are **sum of the scattering lengths of the atoms** constituting the polymer monomer and the solvent molecules, respectively. - $v_p$ and $v_s$ are the partial molar volume of the polymer and the solvent, respectively. - $L_b$ is the Bjerrum length (|Ang|) - **Note:** This parameter needs to be kept constant for a given solvent and temperature! - $h$ is the virial parameter (|Ang^3|) - **Note:** See [#Borue]_ for the correct interpretation of this parameter.  It incorporates second and third virial coefficients and can be *negative*. - $b$ is the monomer length (|Ang|). - $C_s$ is the concentration of monovalent salt(1/|Ang| - converted from mol/L). - $\alpha$ is the degree of ionization (the ratio of charged monomers to the total number of monomers) - $C_a$ is the polymer molar concentration (1/|Ang| - converted from mol/L) - $background$ is the incoherent background. For 2D data the scattering intensity is calculated in the same way as 1D, that in that implementation, while both the polymer concentration and salt concentration were converted from experimental units of mol/L to more dimensionally useful units of 1/|Ang|^3, only the converted version of the dimensionally useful units of 1/|Ang^3|, only the converted version of the polymer concentration was actually being used in the calculation while the unconverted salt concentration (still in apparent units of mol/L) was being used.  This was carried through to sasmodels as used for sasview 4.1(though the line of code converting the salt concentration to the new units was removed somewhere along the line). Simple dimensional analysis of the calculation shows that the converted salt concentration should be used, which the original code suggests was the intention, so this has now been corrected (for sasview 4.2). Once better validation has been performed this note will be removed. unconverted salt concentration (still in apparent units of mol/L) was being used.  This was carried through to Sasmodels as used for SasView 4.1 (though the line of code converting the salt concentration to the new units was removed somewhere along the line). Simple dimensional analysis of the calculation shows that the converted salt concentration should be used, which the original code suggests was the intention, so this has now been corrected (for SasView 4.2). Once better validation has been performed this note will be removed. References