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Related Concept Videos

Redox Reactions01:24

Redox Reactions

Oxidation-reduction or redox reactions involve the transfer of electrons from one molecule or atom to another. When an atom gains an electron, another atom must lose an electron, meaning oxidation and reduction must occur together. Since the redox occurs in pairs, the atom that gets oxidized is also called the reducing agent or reductant, and the atom that is reduced is also called the oxidizing agent or oxidant. A straightforward way to remember the definitions of oxidation and reduction is...
The Electrical Double Layer01:30

The Electrical Double Layer

In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...
Anoxygenic Photosynthesis01:30

Anoxygenic Photosynthesis

Anoxygenic photosynthesis is a phototrophic process that captures light energy to drive carbon fixation without producing molecular oxygen. Unlike oxygenic photosynthesis, which utilizes water as an electron donor and releases oxygen, anoxygenic phototrophs use alternative electron donors such as hydrogen sulfide (H₂S), elemental sulfur (S⁰), or thiosulfate (S₂O₃²⁻). This process is carried out by diverse groups of bacteria, including purple bacteria, green sulfur bacteria, heliobacteria, and...
Metabolism of Chemolithotrophs01:15

Metabolism of Chemolithotrophs

Chemolithotrophs are microorganisms that obtain energy by oxidizing inorganic molecules such as hydrogen gas (H₂), ammonia (NH₃), reduced sulfur compounds (H₂S, S²⁻), and ferrous iron (Fe²⁺). Unlike heterotrophic organisms that rely on organic carbon, chemolithotrophs transfer electrons from these inorganic donors to the electron transport chain (ETC), generating a proton motive force (PMF) that drives ATP synthesis through oxidative phosphorylation. However, because inorganic electron donors...
Origin of Photosynthesis01:26

Origin of Photosynthesis

Photosynthesis represents a fundamental biological process that transformed Earth's atmosphere and paved the way for complex life. Emerging roughly 3.4–3.8 billion years ago, the earliest photosynthetic organisms harnessed light energy to produce organic compounds. These anoxygenic phototrophs used electron donors like hydrogen sulfide (H₂S) or ferrous iron (Fe²⁺), rather than water, and did not release molecular oxygen (O₂) as a byproduct. Various groups, including green sulfur and purple...
Microbes and Other Elemental Cycles01:24

Microbes and Other Elemental Cycles

Microbial activity plays a pivotal role in the biogeochemical cycling of iron and manganese, especially at the redox gradients characteristic of stratified aquatic environments. These cycles are driven by microbial transformations between oxidized and reduced forms of the metals, allowing organisms to exploit them for metabolic energy and structural purposes.Iron Cycling Across Redox GradientsIn neutral, oxygen-rich surface waters, iron is predominantly found in its oxidized, insoluble ferric...

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Related Experiment Video

Updated: Jun 18, 2026

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells
15:08

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

Published on: September 20, 2012

Stratospheric aluminum oxide.

D E Brownlee, G V Ferry, D Tomandl

    Science (New York, N.Y.)
    |March 26, 1976
    PubMed
    Summary
    This summary is machine-generated.

    Aluminum oxide spheres are the main stratospheric particulate matter, measuring 3-8 micrometers. These particles likely originate from solid-fuel rocket exhaust, impacting atmospheric composition.

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    Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing
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    Last Updated: Jun 18, 2026

    Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells
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    Published on: September 20, 2012

    Laboratory Simulation of an Iron(II)-rich Precambrian Marine Upwelling System to Explore the Growth of Photosynthetic Bacteria
    09:45

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    Published on: July 24, 2016

    Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing
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    Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing

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    Area of Science:

    • Atmospheric Science
    • Aerosol Science
    • Planetary Science

    Background:

    • Stratospheric aerosols play a crucial role in Earth's climate and atmospheric chemistry.
    • Understanding the composition and sources of stratospheric particulates is vital for atmospheric modeling.

    Purpose of the Study:

    • To identify the major component of micrometer-sized stratospheric aerosols.
    • To determine the origin of these identified stratospheric particulates.

    Main Methods:

    • Collection of stratospheric aerosols using high-altitude balloons and U-2 aircraft.
    • Analysis of particulate matter in the 3 to 8 micrometer size range.

    Main Results:

    • Aluminum oxide spheres identified as the predominant stratospheric particulate in the 3-8 micrometer range.
    • This composition has been consistent for at least the past six years.

    Conclusions:

    • The primary source of these aluminum oxide spheres is inferred to be the exhaust from solid-fuel rocket engines.
    • Rocket exhaust represents a significant, previously underestimated source of stratospheric aerosols.