1) How does a "floating lien" help a secured party's protection against debtor default?

2) Creditor (C) lends money to a debtor (D) to buy inventory and equipment for D's business and attaches and perfects a security interest in all of D's present equipment and inventory PLUS any "after acquired" equipment and inventory. Subsequently D wants to purchase more inventory and equipment from E on credit. Is there any way for E to have priority over ANY of D's equipment or inventory?