"" class="an ">&ensp;</span>Surprisingly <span  title="" class="an ">&ensp;</span>a <span  title="" class="an ">&ensp;</span>significant <span  title="" class="an ">&ensp;</span>proportion <span  title="" class="an ">&ensp;</span>of <span  title="" class="an ">&ensp;</span>low <span  title="" class="an ">&ensp;</span>threshold <span  title="" class="an ">&ensp;</span>slowly <span  title="" class="an ">&ensp;</span>and <span  title="" class="an ">&ensp;</span>rapidly <span  title="" class="an ">&ensp;</span>