NPUT:</span>
0010 <span class="comment">%    d: sediment grain size in m</span>
0011 <span class="comment">%</span>
0012 <span class="comment">% OUTPUT:</span>
0013 <span class="comment">%    phi: sediment grain size in phi scale</span>
0014 <span class="comment">%</span>
0015 <span class="comment">% EXAMPLE USAGE</span>
0016 <span class="comment">%    phi = ST_d2phi(.001)</span>
0017 <span class="comment">%</span>
0018 <span class="comment">% Author(s):</span>
0019 <span class="comment">%    Geoff Cowles (