Although the nematode worm Caenorhabditis elegans reproduces primarily as a self-fertilizing hermaphrodite, males are maintained in natural populations at low frequency. In this commentary, I discuss the evolutionary forces that maintain males and the role males might play in this mating system.

Current approaches to topdressing and weeding operations for rice cultivation present several disadvantages, such as poor precision, low efficiency, serious environmental pollution, so on. This paper presents a row-controlled fertilizing–weeding machine improve the precision of fertilizing reduce heavy pollution associated with cultivation. A proportional–integral–derivative algorithm was adopt...

ÐChanges in land use and management of tropical systems are considered to be major factors in the recent upsurge in increases in atmospheric nitrous oxide (N2O) and methane (CH4). Studies were initiated in western Puerto Rico grasslands to determine the e€ect of plowing, or liming and fertilizing an acid Oxisol on the soil±atmosphere exchanges of N2O and CH4. Weekly ®eld ̄ux measurements and ®el...