Question:
Who was the chair of Brazilian Academy of Sciences in Oct, 1981?

Context:
 Aristides Azevedo Pacheco Leão is the chair of Brazilian Academy of Sciences from Jan, 1967 to Jan, 1981. 
 Maurício Peixoto is the chair of Brazilian Academy of Sciences from Jan, 1981 to Jan, 1991. 
 Cândido Firmino de Mello-Leitão is the chair of Brazilian Academy of Sciences from Jan, 1943 to Jan, 1945. 
 Inácio Manuel Azevedo do Amaral is the chair of Brazilian Academy of Sciences from Jan, 1939 to Jan, 1941. 
 Carlos Chagas Filho is the chair of Brazilian Academy of Sciences from Jan, 1965 to Jan, 1967. 
 Luiz Davidovich is the chair of Brazilian Academy of Sciences from Jan, 2016 to Dec, 2022. 
 Miguel Osório de Almeida is the chair of Brazilian Academy of Sciences from Jan, 1929 to Jan, 1931. 
 Henrique Charles Morize is the chair of Brazilian Academy of Sciences from Jan, 1916 to Jan, 1926. 
 Álvaro Alberto da Mota e Silva is the chair of Brazilian Academy of Sciences from Jan, 1935 to Jan, 1937. 
 Arthur Alexandre Moses is the chair of Brazilian Academy of Sciences from Jan, 1933 to Jan, 1935. 
 Jacob Palis is the chair of Brazilian Academy of Sciences from Jan, 2007 to Jan, 2016. 
 Eusébio Paulo de Oliveira is the chair of Brazilian Academy of Sciences from Jan, 1931 to Jan, 1933. 
 Oscar Sala is the chair of Brazilian Academy of Sciences from Jan, 1991 to Jan, 1993. 
 Eduardo Krieger is the chair of Brazilian Academy of Sciences from Jan, 1993 to Jan, 2007. 
 Juliano Moreira is the chair of Brazilian Academy of Sciences from Jan, 1926 to Jan, 1929.

Answer:
Maurício Peixoto