A heat engine gives greater efficiency when run with a large temperature difference. In the oceans the temperature difference between surface and deep water is greatest in the tropics, although still a modest 20 to 25 Â°C.
A blastocyst is a cellular mass that forms early in the process of embryo development in mammals. In humans, this stage of embryogenesis occurs five days after fertilization, when there are fewer than 100 cells in the mass.
The blastocyst phase is the development stage prior to implantation of the embryo in the motherâs uterus. Transferring a blastocyst on day 5+ has the following advantages: It makes a better selection of embryos possible.