Action to annul an arbitral award. Dismissed. Allegation of an arbitrator's lack of impartiality due to failure to comply with the duty of disclosure (Article 14, § 1º, of the Brazilian Arbitration Act). Facts that are public and easily ascertainable. The party bears the duty to investigate any potential ground for disqualification or lack of impartiality. Inadmissibility of invoking nullity after the rendering of an unfavorable arbitral award: