function ampliar(url) {
  larg = 537;
  alt = 450;
  calcleft = (screen.width / 2) - (larg / 2);
  calctop = (screen.height / 2) - (alt / 2);
  janela = window.open(url,"nova","toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=yes, resizable=no, copyhistory=no, width="+larg+", height="+alt+", left="+calcleft+", top="+calctop);
  janela.focus();
}