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What is the role of companion cells?

Companion cells, sieve-tube elements, fibers and parenchyma are all parts of the phloem, which is a vascular tissue necessary for the transport of sugars, proteins and mRNAs from source to sink in plants. The sieve-tube elements are responsible for conducting the sugars, but are not able to keep themselves alive without the help of companion cells. Companion cells are the "life support" for the sieve-tube element, which allows the phloem to function properly.

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What is an extraneous solution?

In the equation (2/x-4) + (2/x+4) = [8/(x-4)(x+4), the possible solutions for "x" cannot be 4 or -4 because those would end up resulting in division by zero. Transforming the equation by multiplying all terms by (x-4)(x+4) leads to this equation: (x+4) + (x-4) = 8, or 2x = 8, or x = 4. This is an extraneous solution because it is not in the original domain; as a result, the equation does not have a solution.

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What is a Julian date code?

At noon Greenwich Mean Time, the standard time of London, England, the Julian day begins. The Gregorian calendar, the standard modern calendar system as of 2015, was introduced by Pope Gregory XIII in 1582. Prior to this time, the Julian calendar, as established by Julius Caesar about 50 B.C., was the standard. The units the Gregorian calendar system uses are not constant, for example the 366-day leap year, while the Julian Calendar is constant.\nA Julian Period is an interval of 7980 chronological years from 4713 B.C. The next Julian Period begins in 3268 A.D. Previously limited to four digit..

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What are the properties of argon gas?

Argon is approximately as soluble as oxygen and 2.5 times more soluble in water than nitrogen. The Earth’s atmosphere is approximately 0.94 percent argon, and fractionating liquid air produces argon gas. Industrial uses for argon gas include cutting and welding, creating a protective atmosphere for growing germanium and silicon crystals and blanketing reactive elements. Manufacturers also use it in manufacturing lasers, glow tubes and electric lights.

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What evidence is there of the continental drift theory?

Continental drift is a theory originally proposed by Alfred Wegener, who believed the continents were once one large continent known as Pangaea that later separated into several continents. One indication of this possibility is the appearance of the western African and eastern South American coasts, which look like two interlocking jigsaw puzzle pieces. Finding fossils of the Mesosaurus on the southern hemispheres of both continents is a further indication that the two continents were once together and later drifted apart.\nAnother indication of continental drift is tectonic activity and seafl..

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What is the average temperature of a freshwater biome?

On the other hand, Practical Fishkeeping advises that freshwater Taiwanese biotopes have an average temperature of 64-75 degrees Fahrenheit. No two fish species are exactly alike, and no single range of temperatures works for every freshwater biome or biotope. Instead, it is vital to research and match the aquarium temperature with the species that inhabit the ecological environment emulated by the biome.

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What is the difference between an empirical formula and a molecular formula?

The ratio is given by dividing the actual molar mass of the compound to its empirical mass. The subscripts in the empirical formula are multiplied by the ratio in order to determine the molecular formula. The molecular formula for glucose, for example, is six carbon and oxygen atoms for 12 hydrogen atoms, while the empirical formula is one carbon and oxygen atom for every two hydrogen atoms. The ratio between them is six, and if the amount of each atom in the empirical formula is multiplied by six, the molecular formula is found.\nThe empirical formula is also found by using a compound's ..

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Where does it rain the most in the United States?

The mountain lies in the center of the northernmost main Hawaiian island and peaks at 5,148 feet. Its round, conical shape exposes all sides of its summit to moisture-heavy winds, and the mountain's steep cliffs cause the humid air to rise more than 3,000 feet in less than one-half mile, dropping a large portion of rain in the same area between 330 and 360 days each year.

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How long does it take Mercury to go around the sun?

Due to its relative proximity to the sun, a person standing on Mercury would perceive the sun as three times larger than a person on Earth. The planet is considered a terrestrial planet due to its rocky composition. Its surface appearance features multiple craters, making it visually similar to the Earth's moon.

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How do mercury barometers work?

A classic mercury barometer is constructed from a 3-foot glass tube that is open at one end and sealed at the opposite end. The glass tube is filled with liquid mercury and rests upside-down in a reservoir of mercury. As the mercury moves down the glass tube, a vacuum is created. When the atmospheric pressure above the reservoir increases, the mercury inside the tube rises. As atmospheric pressure decreases the mercury moves down the tube, into the reservoir. This type of barometer was first constructed in 1643 by Evangelista Torricelli.\nThe change in the mercury level in the glass tube is eq..

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