private function getLastArticle(TwitterEntity $twitterStream)
 {
     $result = $this->db->execute('SELECT * FROM article WHERE stream_id = ? AND streamType = ? ORDER BY articleDate DESC LIMIT 1', array($twitterStream->getId(), ArticleModel::TWITTER));
     $result->setFetchMode(PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE, 'ArticleEntity');
     if ($articleEntity = $result->fetch()) {
         return $articleEntity;
     }
     $articleEntity = new ArticleEntity();
     $articleEntity->setArticleDate(time());
     return $articleEntity;
 }