bounds
list of parameter bounds used for
  experimental design, e.g.  bounds=list(h=c(0,1),
  d=c(0.001, 2), s=c(200L, 2000L)) where - h : bounds of
  the heterogeneity.  - d : bounds of the
  heteroscedasticity.  - a : bounds of the balancing factor
  of group assignments.  - s : bounds of the study sizes.
  - r : fixed risk in the control.