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  2. Biogeochemical cycle - Wikipedia

    en.wikipedia.org/wiki/Biogeochemical_cycle

    A biogeochemical cycle, or more generally a cycle of matter, [1] is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the carbon cycle, the nitrogen cycle and the water cycle. In each cycle, the chemical element or molecule is ...

  3. Carbon cycle - Wikipedia

    en.wikipedia.org/wiki/Carbon_cycle

    Other major biogeochemical cycles include the nitrogen cycle and the water cycle. Carbon is the main component of biological compounds as well as a major component of many rocks such as limestone . The carbon cycle comprises a sequence of events that are key to making Earth capable of sustaining life.

  4. Citric acid cycle - Wikipedia

    en.wikipedia.org/wiki/Citric_acid_cycle

    Overview of the citric acid cycle. The citric acid cycle—also known as the Krebs cycle, Szent–Györgyi–Krebs cycle, or TCA cycle (tricarboxylic acid cycle) [1] [2] —is a series of biochemical reactions to release the energy stored in nutrients through the oxidation of acetyl-CoA derived from carbohydrates, fats, proteins, and alcohol.

  5. Phosphorus cycle - Wikipedia

    en.wikipedia.org/wiki/Phosphorus_cycle

    The phosphorus cycle is the biogeochemical cycle that involves the movement of phosphorus through the lithosphere, hydrosphere, and biosphere.Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based materials do not enter the gaseous phase readily, [1] as the main source of gaseous phosphorus ...

  6. Thermodynamic cycle - Wikipedia

    en.wikipedia.org/wiki/Thermodynamic_cycle

    A thermodynamic cycle consists of linked sequences of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventually returns the system to its initial state. [1]

  7. Milankovitch cycles - Wikipedia

    en.wikipedia.org/wiki/Milankovitch_cycles

    Other components have 95,000-year and 124,000-year cycles [8] (with a beat period of 400,000 years). They loosely combine into a 100,000-year cycle (variation of −0.03 to +0.02). The present eccentricity is 0.0167 [8] and decreasing. Eccentricity varies primarily due to the gravitational pull of Jupiter and Saturn.

  8. Get help with your AOL billing questions

    help.aol.com/articles/account-management...

    • Communication surcharges - We answer to a higher calling - the phone company. If you connect to AOL using a long-distance number or AOLnet 800 number, you’ll see these surcharges in addition to your monthly subscription fee.

  9. Rankine cycle - Wikipedia

    en.wikipedia.org/wiki/Rankine_cycle

    The actual vapor power cycle differs from the ideal Rankine cycle because of irreversibilities in the inherent components caused by fluid friction and heat loss to the surroundings; fluid friction causes pressure drops in the boiler, the condenser, and the piping between the components, and as a result the steam leaves the boiler at a lower ...