Useful LaTeX aliases
\newcommand{\ddiff}{\mathrm{d}}
\newcommand{\diff}[3][]{\frac{\ddiff^{#1} {#2}}{\ddiff #3^{#1}}}
\newcommand{\pdiff}[3][]{\frac{\partial^{#1} {#2}}{\partial #3^{#1}}}
\newcommand{\nabladiv}{\nabla \cdot}
\newcommand{\vv}[1]{\boldsymbol{#1}}