function slideSwitch() {
    var $active = $('.pub a.active');

    if ( $active.length == 0 ) $active = $('.pub a:last');

    // use this to pull the images in the order they appear in the markup
   // var $next = $active.next().length ? $active.next() : $('.pub a:first');

    // uncomment the 3 lines below to pull the images in random order
    
     var $sibs  = $active.siblings();
     var rndNum = Math.floor(Math.random() * $sibs.length );
     var $next  = $( $sibs[ rndNum ] );


    $active.addClass('last-active'); 

   $next.addClass('active').children('img').css({opacity: 0.0})
        .animate({opacity: 1.0}, 0, function() {
            $active.removeClass('active last-active');
        });
}