Answer: Ptolemaic system, also called geocentric system or geocentric model, mathematical model of the universe formulated by the Alexandrian astronomer and mathematician Ptolemy about 150 CE and recorded by him in his Almagest and Planetary Hypotheses. The Ptolemaic system is a geocentric cosmology; that is, it starts by assuming that Earth is stationary and at the centre of the universe. The “natural” expectation for ancient societies was that the heavenly bodies (Sun, Moon, planets, and stars) must travel in uniform motion along the most “perfect” path possible, a circle. However, the paths of the Sun, Moon, and planets as observed from Earth are not circular. Ptolemy’s model explained this “imperfection” by postulating that the apparently irregular movements were a combination of several regular circular motions seen in perspective from a stationary Earth.
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Answer:
Hydrogen gas has the highest calorific value of 150 KJ/g among all the fuels. So, hydrogen gas is considered to be an extremely good fuel.
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During bleeding, both formed elements (platelets, white blood cells, red blood cells) and plasma are lost from the circulatory system. They are lost proportionally, so initially there is no change in hematocrit.
Hematocrit is the percentage of the blood volume made up of elements (Hct = cell volume/blood volume). During dehydration, only water and electrolytes are lost, and the number of cells remains constant - the same number of cells in a smaller volume leads to an increase in hematocrit. When the body tries to restore blood volume, the first thing to recirculate is water from the ECF and this increases the amount of water without increasing the amount of red blood cells, so the compensatory mechanism causes the hematocrit to fall.
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DNA helicase untwists the helix at the replication origins. Then the DNA is seperated into a "Y" shape called the replication fork.
