deletions | additions       diff --git a/Swimmers.tex b/Swimmers.tex  index 39ad070..82c32ec 100644  --- a/Swimmers.tex  +++ b/Swimmers.tex 
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\begin{enumerate}  \item Understand why it moves (diffusiophoresis): how fast and in what direction (on average)?  \begin{itemize}  \item See e.g. \citet{http://adsabs.harvard.edu/abs/2010PhRvL.104m8302P}, \citet{http://adsabs.harvard.edu/abs/1982JFM...117..107A} \citet{2010PhRvL.104m8302P}, \citet{1982JFM...117..107A}  \item Depends on whether the particle is charged or not.  \end{itemize} 
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\item Then consider a single active swimmer in a concentration gradient. Get superposition of two behaviours?  \begin{itemize}  \item Re-read \citet{http://adsabs.harvard.edu/abs/2005PhRvL..94v0801G}. \citet{2005PhRvL..94v0801G}.  Read \citet{http://adsabs.harvard.edu/abs/2009JPCM...21t4104G}. \citet{2009JPCM...21t4104G}.  \end{itemize}  \end{enumerate}  %%==============================================  \subsection{Answers \& More Details}  DIFFUSIOPHORESIS For {\it charged} interactions, the mobility $\mu\propto 1/c$. This leads to diffusio-phoretic velocity $V = D\nabla\log c$. This arises from the balance of osmotic and viscous forces in the Debye layer. The diffusion coefficient $D \sim T/\eta\ell_{\rm B}$, where $\ell_{\rm B}$ is the Bjerrum length (ratio of electrostatic to thermal energy). Derivation of fluid velocity done in \citet{http://adsabs.harvard.edu/abs/1989AnRFM..21...61A}, \citet{1989AnRFM..21...61A},  page 14ish.