Categories and page filtering with pre_get_posts

by

Please Consider this snippets of code.

<?php 
     $myarticles = new WP_Query( 'post_type=myarticles&orderby=date&order=DESC&cat=4' );    
         while ($myarticles->have_posts()) : $myarticles->the_post();
                $postTitle = get_the_title();
            $postid = get_the_id();
        $postContent    = get_the_content();
?>

 <li><p><?php echo $postTitle;  ?></p>
<a href="#"><?php the_post_thumbnail(array(219,143)); ?></a> 
                  <p><?php echo $postContent;  ?></p>
 </li>
    <?php endwhile; ?>