Tube worms form an important part of the community around a hydrothermal vent. They absorb nutrients directly into their tissues. There are approximately 285 billion bacteria per ounce of tubeworm tissue.
Tubeworms have red plumes which contain haemoglobin. Haemoglobin combines hydrogen sulfide and transfers it to the bacteria living inside the worm. In return the bacteria nourish the worm with carbon compounds.
Other examples of the unique fauna who inhabit this ecosystem are the gastropod "Crysomallon squamiferum", a species of snail with a foot reinforced by scales made of iron and organic materials, and the 'Pompeii Worm' "Alvinella pompejana", which is capable of withstanding temperatures up to 80°C (176°F).
Over 300 new species have been discovered at hydrothermal vents, many of them "sister species" to others in geographically separated vent areas. It has been proposed that before the North American plate overrode the Mid-Atlantic Ridge, there was a single biogeographic vent region found in the eastern Pacific. The subsequent barrier to travel began the evolutionary divergence of species in different locations. The examples of convergent evolution seen between distinct hydrothermal vents is seen as major support for the theory of natural selection and evolution as a whole.
A species of phototrophic bacterium has been found living near a black smoker off the coast of Mexico at a depth of . No sunlight penetrates that far into the waters. Instead, the bacteria, part of the Chlorobiaceae family, use the faint glow from the black smoker for photosynthesis. This is the first organism discovered in nature to exclusively use a light other than sunlight for photosynthesis.
Guava
Guavas are plants in the genus "Psidium" of the family Myrtaceae. There are about 100 species of tropical shrubs and small trees in the genus.
They are native to Mexico, the Caribbean, Central America and the northern part of South America. Now they are found in all the tropical, and in some subtropical, regions because they are edible fruits.
Guava are also a kind of berry fruit on those plants. There are many kinds of guavas. The most common guava is the apple guava ("Psidium guajava"): it is so common that the word 'guava' usually refers to this species. Red guavas are called maroonguava. In 100 g of guava are 200 mg of vitamin C, which means that guavas have five times more vitamin C than oranges.
Resting potential
The resting potential of a cell is the membrane potential that would be maintained if there were no action potentials, synaptic potentials, or other active changes in the membrane potential. In most cells the resting potential has a negative value, which by convention means that there is excess negative charge inside compared to outside. The resting potential is mostly determined by the concentrations of the ions in the fluids on both sides of the cell membrane and the ion transport proteins that are in the cell membrane. How the concentrations of ions and the membrane transport proteins influence the value of the resting potential is outlined below.
Thrust
Thrust is a force or a push. When a system pushes or accelerates mass in one direction, there is a thrust (force) just as large in the opposite direction. In math and physics, this is described by Isaac Newton’s second and third laws. Thrust is used to describe how strongly an engine pushes. It can be used for many kinds of vehicles and engines such as rockets, motorboats, propellers, and jet engines.
Thrust is measured in “pounds of thrust” in the U.S. and in newtons in the metric system. 4.45 newtons of thrust equals 1 pound of thrust. A pound of thrust is how much thrust it would take to keep a one-pound object unmoving against the force of gravity on earth.
A very common question is how to compare the thrust number of an airplane engine with the mechanical power of a piston engine (the kind of engine in cars and in many airplanes with propellers). It is hard to compare these two. This is because they are not measuring the same exact thing. A piston engine does not move the plane. It just turns the propeller, which moves the plane. Because of this, piston engines are rated by how much power they give to the propeller.
However, a jet engine has no propeller – it pushes the aircraft by moving hot air behind it. A useful way to measure the power of a jet engine is to how much power the jet engine gives to the aircraft through its thrust force. This is called the “propulsive power of the jet engine." Power is how much force it takes to move something over a distance, divided by the time it takes to move that distance:
Where P is power, F is force, d is distance, and t is time. For a rocket or jet engine, the force is the same as thrust produced by the engine. Distance divided by time is also called speed. So power is the same as thrust times speed
Where T is thrust and "v" is speed. This is the power being delivered by the engine at a certain thrust or velocity. The propulsive power of a jet engine increases with its speed.
When the thrust of a rocket or an engine is compared to the weight, it is called the Thrust-to-weight ratio. The number that comes from this comparison does not have any units, because it is a ratio. A ratio in this case means that the thrust of the engine (in Newtons) is divided by the weight (in Newtons). The purpose of this comparison is to show how well the engine or vehicle performs, for example how much acceleration. It is a number that can be used to compare various types of motors like airplane motors, jet engines, rocket engines, or car engines.
This comparison number can change while the engine is running. This is because the weight of the engine gets lighter as fuel is used. The thrust-to-weight ratio is used to actually compare engines is the number found when the engine is first running.
Thrust is measured in “pounds of thrust” in the U.S. and in Newtons in the metric system. 4.45 Newtons of thrust equals 1 pound of thrust. A pound of thrust is how much thrust it would take to keep a one-pound object unmoving against the force of gravity on earth.
An airplane makes forward thrust when air is pushed in the direction opposite to flight. The thrust is made by the spinning blades of a propeller. Thrust can also be made by a rotating fan pushing air out from the back of a jet engine. Another way is by ejecting hot gases from a rocket engine.
Reverse thrust is the opposite of forward thrust. In this way air is pushed in the same way as the motion of the body. Reverse thrust can be used to help braking after landing. This can be done by redirecting the thrust in a turbofan or jet engine or by changing the blade angle of a propeller driven aircraft.
Birds normally achieve thrust during flight by flapping their wings.
A boat with a motor makes thrust or reverse thrust when the propellers are turned to push water backwards (or forwards). The thrust that this makes pushes the boat in the opposite direction than the water is being pushed.
A rocket is pushed forward by a thrust force as large as the force the exhaust gas makes when going out of the rocket nozzle. The force the exhaust gas makes is called the exhaust velocity. The velocity is measured compared to the rocket. For vertical launch of a rocket to work, the starting thrust must be more force than the weight of the rocket.
Thrust (disambiguation)
Thrust is a reaction force described by Newton's Second and Third Law. For this meaning, see Thrust.
This word has other uses:
Robert A. Heinlein