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Hydrogen Sulfide: A flammable, poisonous gas with a characteristic odor of rotten eggs. It is used in the manufacture of chemicals, in metallurgy, and as an analytical reagent. (From Merck Index, 11th ed)

The Sulfur Cycle

JoVE 10936

Sulfur, an important element in the chemical makeup of proteins, is recycled through the atmosphere and aquatic and terrestrial environments. Found in the atmosphere as sulfur dioxide (SO2), sulfur is released by decaying organisms, weathered rocks, geothermal vents, volcanos, and burning fossil fuels. It is deposited into the ecosystem, cycled through the biotic community, and either released back into the atmosphere as gas or deposited in marine sediment for long-term storage and eventual release back into the soil and atmosphere. Sulfur is essential to biological systems and is a component of certain amino acids, such as cysteine, which plays an important role in the structure of proteins. Sulfur is distributed to terrestrial (i.e., land) ecosystems by the precipitation of weak sulfuric acid, direct fallout from the atmosphere, weathering of sulfur-containing rocks, and geothermal vents. From the soil, it is taken up by microorganisms and plants and converted into organic forms that can be used by consumers in the ecosystem. When organisms die, decomposers break the organic sulfur compounds down into gases, such as hydrogen sulfide, which is oxidized in the atmosphere to form sulfur dioxide. Additionally, some chemoautotrophs use sulfur as a biological energy source and recycle sulfur molecules directly through ecosystems. Sulfur

 Core: Biology

Primary Production

JoVE 10928

The total amount of energy acquired by primary producers in an ecosystem is called gross primary production (GPP). However, of this energy, producers use some for metabolic processes, and some is lost as heat, decreasing the amount of energy available to the next trophic level. The remaining usable amount of energy is called the net primary productivity (NPP). In terrestrial ecosystems, NPP is driven by climate, while light penetration and nutrient availability drive NPP in aquatic ecosystems. Energy can be acquired by organisms in three ways: photosynthesis, chemosynthesis and by the consumption of other organisms. Autotrophs, or producers, synthesize their food. Chemoautotrophs occur in ecosystems where sunlight is unavailable and use chemicals as an energy source—like hydrogen sulfide, H2S, from deep ocean hydrothermal vents—while photoautotrophs transform energy from sunlight into usable energy for the rest of the organisms in an ecosystem. The rate at which these producers obtain and transform this energy is known as the ecosystem’s gross primary production (GPP), which is also a measure of the total amount of energy accumulated by primary producers in an ecosystem. However, not all of the energy obtained by producers is available for use by other organisms in the ecosystem. During both chemosynthesis and photosynthesis,

 Core: Biology

Determining the Solubility Rules of Ionic Compounds

JoVE 10197

Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry

An ionic compound's solubility can be determined via qualitative analysis. Qualitative analysis is a branch of analytical chemistry that uses chemical properties and reactions to identify the cation or anion present in a chemical compound.…

 General Chemistry

Ozonolysis of Alkenes

JoVE 10339

Source: Vy M. Dong and Zhiwei Chen, Department of Chemistry, University of California, Irvine, CA

This experiment will demonstrate an example of an ozonolysis reaction to synthesize vanillin from isoeugenol (Figure 1). Ozonolysis of alkenes, an oxidation reaction between ozone and an alkene, is a common method to prepare…

 Organic Chemistry II

Making Record-efficiency SnS Solar Cells by Thermal Evaporation and Atomic Layer Deposition

1Department of Mechanical Engineering, Massachusetts Institute of Technology, 2Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, 3School of Engineering and Applied Sciences, Harvard University, 4Department of Materials Science and Engineering, Massachusetts Institute of Technology, 5Department of Chemistry & Chemical Biology, Harvard University

JoVE 52705

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