For two variables that are frequently active, the number of mutual first activations will also be large, even if they are causally unrelated.
Killer whales are frequently active at the surface, engaging in acrobatic behaviors such as breaching, spyhopping, and tail-slapping.
When two neurons are frequently active at the same time, the connection between them becomes stronger (Hebb, 1949).
A scenario thus emerges according to which neurons expressing ORs associated with environmentally salient odors are frequently active and may increase in relative abundance over time due to enhanced longevity, while neurons expressing infrequently activated ORs have a shortened life span, mediated in part by H2BE, and become less abundant.
c-met is frequently constitutively active in human tumors [ 36- 38], and several reports have shown that Stat3 is one of the downstream effectors of HGF/c-met signaling [ 20, 39].
Fang et al. [ 23] have demonstrated the involvement of the NTPDase5 also as an important link in the PI3K/PTEN loop-signaling pathway, which promotes cell growth and survival and is frequently found active in tumor cells.
The need for collaboration and compromise in a dynamic aid system is universally recognised, and is frequently achieved through active contribution by aid workers to their organisational programmes and directives.
Blood pressure and heart rate are increased; muscle tone is increased and is frequently associated with active shivering and subsequent increase in oxygen consumption.
These studies have shown that among histone acetylation marks [ 29], H3K27Ac is frequently associated with active enhancer regulatory elements [ 30], and genes associated with these enhancers are expressed at higher levels than those lacking the H3K27Ac mark [ 31].
It often plays critical roles in the arrangement of the protein tertiary and quaternary structures, and is frequently found in active sites of enzymes and proteins containing specific binding sites for other molecules.
