Synthetic fuel the fuel, and the fuel is less dense than conventional jet fuel allowing aircraft to fly further on the same load of fuel. The "cleanness" of these FT synthetic fuels is further demonstrated by the fact that they are sufficiently non-toxic and environmentally benign as to be considered biodegradable. This owes primarily to the near-absence of sulfur and extremely low level of aromatics present in the fuel. One concern commonly raised about the development of synthetic fuels plants is sustainability. Fundamentally, transitioning from oil to coal or natural gas for transportation fuels production is a transition from one inherently depletable
Interlanguage fossilization on interlanguage fossilization are fascinating in that they contradict our basic understanding of the human capacity to learn. How is it that some learners can overcome interlanguage fossilization, even if they only constitute, according to Selinker, "a mere 5%", while the majority of second language learners cannot, "no matter what the age or amount of explanation or instruction"? Or is it perhaps not that they cannot overcome fossilization, but that they will not? Does complacency set in after second language learners begin to communicate, as far as they are concerned, effectively enough, in the target language, and as a result