In human history to date, only a few species of large animal have been domesticated. In approximate order of their earliest domestication these are: dog, sheep, goat, pig, ox, yak, reindeer, water buffalo, horse, donkey, llama, alpaca, Bactrian camel and Arabian camel.
For instance at sea level and standard weather (29.9 Hg) a gauge vacuum of -25.9 Hg is equivalent to an absolute pressure of 4 Hg. In other words, the vacuum gauges that read, for example, -25.9 Hg at full vacuum is actually reporting 4 Hg, or 136 mbar. That is still in the low vacuum range.
While pressures are, in general, positive, there are several situations in which negative pressures may be encountered: 1  When dealing in relative (gauge) pressures. For instance, an absolute pressure of 80 kPa may be described as a gauge pressure of â21 kPa (i.e., 21 kPa below an atmospheric pressure of 101 kPa).