We present two comparison principles for viscosity suband supersolutions of Monge-Ampère-type equations associated to a family of vector fields. In particular, we obtain the uniqueness of a viscosity solution to the Dirichlet problem for the equation of prescribed horizontal Gauss curvature in a Carnot group.

Faculdade de Medicina, Universidade Federal de Minas Gerais – UFMG Belo Horizonte (MG), Brasil. (2) Departamento de Engenharia de Estruturas da Escola de Engenharia, Universidade Federal de Minas Gerais – UFMG Belo Horizonte (MG), Brasil. (3) Departamento de Estatística do Instituto de Ciências Exatas da Universidade Federal de Minas Gerais – UFMG Belo Horizonte (MG), Brasil. (4) Departamento d...

Catastrophe for Central America? Jorge A. Huete-Perez,†,∥,* Jose G. Tundisi,‡ and Pedro J. J. Alvarez†,§ †Academy of Sciences of Nicaragua and University of Central America, UCA, Rotonda R. Dario 150 mts Oeste, Apartado 69, Managua, Nicaragua ‡International Institute of Ecology. Saõ Carlos, Brazil. Rua Bento Carlos 750, Saõ Carlos, Saõ Paulo, 13560-660 Brazil Department of Civil & Environmental...

In an earlier paper (Nunez & Colhoun 1986), the gradient of near-surface air temperature with altitude, commonly known as the environmental lapse rate (ELR), was obtained for Mount Wellington, Tasmania. Comparing these local lapse rates with an ELR for the entire island did not give good agreement for maximum temperatures in summer or minimum temperatures in winter. These differences are attrib...