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from article Regolith
Diagram showing the components of residual regolith.
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from article Manganese
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from article Oscillatory reaction
Oscillatory behavior in a sulfuric acid medium containing potassium bromate, malonic acid, and cerous nitrate. The upper curve is the potential (in unspecified units) of a tungsten electrode and is related to the concentration ratio of…
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from article Oscillatory reaction
Rotating spiral bands of oxidation in a thin layer of solution containing the same reagents as in Fig. 1 except that the redox indicator ferrous phenanthroline has been substituted for cerous ion. (Courtesy of Prof. A. T. Winfree, University of…
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from article Oscillatory reaction
Layers of crystallization from an initially uniform magma in the Skaergaard Intrusion in Greenland. (From A. R. McBirney and R. M. Noyes, Crystallization and layering of the Skaergaard Intrusion, J. Petrol., 20:487–554, 1979)
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from article Sol-gel process
Flow chart showing the sol-gel methods used to prepare bulk glasses, thin films of glass or ceramics, and powders; the powders are then sintered to produce ceramics.
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from article Turnip
Purple Top turnip (Brassica rapa). (Credit: Stami Kieren Donovan; courtesy of Greenpatch Organic Seeds, Glenthorne, New South Wales, Australia)
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from article Meteor
Leonid meteor shower observed at the Modra Astronomical Observatory in Slovakia through a fisheye lens. The exposure on November 16–17, 1998, lasted 4 h. About 150 bolides brighter than magnitude −2 can be seen; the brightest fireball is about…
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from article Dill
Flowering of dill (Anethum graveolens). (Photo courtesy of Forest and Kim Starr)
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from article Surface and interfacial chemistry
Scheme for reducing bacterial adhesion at an implanted biomaterial.
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from article Surface and interfacial chemistry
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from article Surface and interfacial chemistry
Microscopic surface structures. (a) Surface atoms occupying positions other than the bulk-terminated locations. The first interlayer spacing d12 is greater than the bulk interlayer spacing d34. The second interlayer spacing d23 is smaller than the…
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from article Surface and interfacial chemistry
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from article Surface and interfacial chemistry
Processes of electron spectroscopies. (a) Auger electron spectroscopy. A core-level electron is ejected by excitation from the incident high-energy electron. A second electron fills the vacancy left by the ejected electron. The third electron, the…
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from article Surface and interfacial chemistry
Typical configuration for application of optical spectroscopies to surface analysis. (a) Transmission. (b) External or specular reflection. (c) Internal reflection. I = reflected light intensity. I0 = initial light intensity. θi = angle of incidence…
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from article Surface and interfacial chemistry
Scanning tunneling microscopy and images for (a) constant-current mode and (b) constant-height mode; shown only in x dimension for simplicity.
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from article Fiber crops
Cotton, the most important textile fiber crop grown in the world. (Photo by Gary Kramer, Natural Resources Conservation Service, U.S. Department of Agriculture)
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from article Agricultural soil and crop practices
A crop of wheat is harvested by a combine harvester, which is a key machine that helps to implement various agricultural soil and crop practices. (Credit: Orientaly/Shutterstock)
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from article Agricultural soil and crop practices
A farmer in a tractor plowing the land for sowing. (Credit: Oticki/Shutterstock)
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from article Agricultural soil and crop practices
A tractor pulls a tilling machine. Stubble remains on the cornfield after the previous harvest. The soil must be properly tilled and cultivated for spring planting. (Credit: Lynn Betts, Natural Resources Conservation Service, U.S. Department of…
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from article Agricultural soil and crop practices
A cotton stripper, which harvests a cotton crop by stripping both the cotton and bolls from the stalks. (Credit: David Hughes/Getty Images)
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from article Lignin
Chemical formula representation of lignin, in which bold lines represent linkages between individual phenylpropane lignin monomer units, and shaded area represents the structure of a typical lignin model compound.
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from article Chromium
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from article Tree diseases
White pine blister rust (Cronartium ribicola) on eastern white pine (Pinus strobus). The blisters are masses of aeciospores (rust spores). (Photo courtesy of the Minnesota Department of Natural Resources Archive)
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from article Tree diseases
Chestnut blight on an American chestnut tree (Castanea dentata). This devastating disease is caused by Cryphonectria parasitica. (Photo by Joseph O'Brien, U.S. Department of Agriculture Forest Service)
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from article Tree diseases
Sulfur shelf fungus (Laetiporus sulphureus) on a tree. This wood-rotting fungus enters through tree roots and wounds, decaying the heartwood and sapwood of both hardwoods and softwoods. (Photo by William Jacobi, Colorado State University)
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from article Tree diseases
Symptoms of Dutch elm disease, caused by Ophiostoma ulmi, on an elm (Ulmus species). Typically, the foliage of an infected tree will begin to wither and yellow in the summer months. (Photo by Joseph O'Brien, U.S. Department of Agriculture Forest…
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from article Tree diseases
An American elm (Ulmus americana) infected with bacterial wetwood. The causal agent for this disease is Enterobacter nimipressuralis. The bacterial ooze (slime flux) is coming from a wound. (Photo by Mike Schomaker, Colorado State Forest Service)
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from article Barium
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from article Soap
Soap bars. (Credit: Getty Images)
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from article Molecular structure and spectra
Diatomic molecule with nuclei at distance Re apart, built from atoms of radii r and r′.
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from article Molecular structure and spectra
Electric dipole moment p of typical diatomic molecule as function of internuclear distance R; pe is the dipole moment at the equilibrium distance Re.
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from article Molecular structure and spectra
U(R) curve of ground electronic state of H2 with vibrational levels and dissociation continuum. D indicates the dissociation energy. Maximum v here is 14. ( After G. Herzberg, Molecular Spectra and Molecular Structure, vol. 1, 2d ed., Van Nostrand,…
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from article Molecular structure and spectra
Lowest vibrational levels of H2, O2, and I2, numbered by vibrational quantum number v. Vibration level spacings decrease with increasing v. Where spacing reaches zero, the molecule dissociates; dissociation level D is indicated for I2. Energies are…
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from article Molecular structure and spectra
Lowest rotational levels of H2, O2, and I2. For H2 and I2, J is the rotational quantum number, according to Eq. (5) in the text. O2 is in a Hund's case b triplet state, and the rotational levels are designated by N, where the total angular momentum…
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from article Molecular structure and spectra
Normal vibration modes of H2O and CO2. Synchronized displacements of atoms occur in proportion to lengths of the arrows. Diagram corresponds to snapshot taken at one phase of vibration.
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from article Molecular structure and spectra
Relation of band lines (lower part) [see Eqs. (8) and (9)] to rotational levels [see Eq. (6)] for a vibration-rotation band or an electronic band. In the former case, the upper and lower sets of rotational levels belong to two vibrational levels of…
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from article Molecular structure and spectra
Intensity distribution at several temperatures for a diatomic absorption band. Line positions are based on Eq. (9) assuming B′ = B′ for simplicity; frequency increases toward the left (opposite to Fig. 7). (a) and (b) correspond respectively to B…
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from article Molecular structure and spectra
Fundamental (1,0) vibration-rotation band of DCl in absorption showing the intensity distribution of the lines. The wavenumber scale increases to the right (in contrast to Fig. 8), so the R branch is to the right of the band origin, P branch to the…
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from article Molecular structure and spectra
Diatomic U(R) curves for three cases to explain the vibrational intensity distribution according to the Franck-Condon principle. The asymptote of each curve for large R corresponds to dissociation into atoms, with one or both atoms excited in the…
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from article Molecular structure and spectra
Assignment of individual transitions in the spectrum of the S-F stretching fundamental ν3 of sulfur hexafluoride (SF6) as resolving power increases. (a) Fourier transform spectrum; resolution of 0.06 cm−1 [2 GHz]. (b) Spectrum recorded with tunable…
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from article Rutabaga
The fleshy root and leaves of a rutabaga (Brassica napobrassica). (Courtesy of Real Seed Catalogue/Wild Garden Seed)
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from article Ursa Major
Modern boundaries of the constellation Ursa Major, the Great Bear. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension…
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from article Supercritical fluid
Typical pressure-temperature diagram of a pure material. cp = critical point.
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from article Supercritical fluid
Typical supercritical-fluid extraction process.
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from article Supercritical fluid
Simplified flow diagram of a commercial hydrothermal oxidation process (supercritical-water oxidation).
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from article X-ray telescope
Wolter type I x-ray telescope, in this case the Chandra X-ray Observatory. Two surfaces of revolution (paraboloid and hyperboloid) reflect the incident x-rays to a common focus. The horizontal scale is greatly compressed. (Chandra X-ray Center)
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from article X-ray telescope
A composite image of the Sun using the Solar Dynamics Observatory (SDO). The x-rays are shown in three colors: red (21.1 nm), green (19.3 nm), and blue (17.1 nm). (Lockheed Martin Solar and Astrophysics Laboratory, Smithsonian Astrophysical…
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from article X-ray telescope
Schematic of a microcalorimeter. An absorber is kept very cold. Then when an x-ray hits, the temperature change is measured. From this, the energy of the x-ray can be computed. (NASA)
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from article Polyolefin
The repeating unit of polyethylene.
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from article Polyolefin
Polyethylene structures. (a) Conventional low-density polyethylene. (b) Linear low-density polyethylene and high-density polyethylene with alpha-olefin comonomer. (c) Linear high-density polyethylene with no comonomer [a polymethylene chain]. (d)…
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from article Polyolefin
Idealized structure of polypropylene materials. (a) Isotactic; methyl group always on same side of chain. (b) Syndiotactic; methyl group position alternating. (c) Atactic; methyl groups randomly distributed.
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from article Bismuth
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from article Wood chemicals
Chemical pathways for obtaining chemicals from wood.
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from article Combinatorial chemistry
Scheme for using optical pattern encoding for the synthesis of a combinatorial library. (Courtesy of X. Xiao)
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from article Combinatorial chemistry
Dynamic equilibrium for mixture components (A1…An), following Le Chatelier's principle. T indicates the target.
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from article Combinatorial chemistry
Equilibrium shift utilized to produce a dynamic library. (a) Reversible reaction between amines and aldehydes produces a Schiff base. (b) Addition of the enzyme carbonic anhydrase leads to the formation of the preferred sulfonamide compound.
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from article Combinatorial chemistry
Separation of equilibration and binding sites in a dynamic combinatorial experiment.
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from article Ester
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from article Fungal agribiotechnology
Demonstration of fungal biocontrol, with a healthy armyworm (right) on a leaf next to two armyworms killed and overgrown by B. bassiana. (Credit: Keith Weller/USDA)
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from article Fungal agribiotechnology
Leaves of the ulmo tree, which harmlessly hosts the fungi Gliocladium roseum as an endophyte. (Credit: Gary Strobel, Montana State University)
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from article Rocket astronomy
Launch of a NASA Black Brant XII sounding rocket. (NASA Goddard Space Flight Center)
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from article Rocket astronomy
Current NASA sounding rockets (2012). (NASA Sounding Rockets Projects Office, Wallops Flight Facility)
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from article Rocket astronomy
Lift capability of NASA sounding rockets. Apogee is shown as function of payload weight.
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from article Aluminum
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from article Aluminum
Bauxite, primary raw ore material used to produce aluminum metal. (Credit: Shutterstock/Bjoern Wylezich)
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from article Aluminum
Extruded aluminum. (Credit: Copyright © Alejandro da Silva Farias/Getty Images)
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from article Extraction
Soxhlet extractor: A flask and condenser device for the continuous extraction of solvent-soluble materials. 1. Stirrer bar or boiling (anti-bumping) chips. 2. Extraction pot. 3. Distillation path. 4. Soxhlet thimble. 5. Extraction (residue) solid .…
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from article Gadolinium
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from article Scorpius
Modern boundaries of the constellation Scorpius, the Scorpion. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension representing…
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from article Animal breeding
Specialized breeds of cattle have been developed and adapted to different environmental and economic conditions. Through breeding, the cattle have been modified with respect to one or more phenotypic traits (for example, the production of meat or…
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from article Animal breeding
Artificial insemination is a process often used by animal breeders. Through the use of this method, sperm collected from male animals can be deposited in female animal genitalia by instruments rather than by natural service. (Credit: alex-mit/Getty…
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from article Animal breeding
Dolly (the world's first cloned mammal) and her first-born lamb, Bonnie. (Credit: Roslin Institute)
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from article Ozone
Ozone
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from article Ozone
Ozone generation using a corona cell.
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from article Date
Ripening Deglet Noor dates (Phoenix dactylifera). (Photo courtesy of Stan Shebs, Agricultural Research Service, United States Department of Agriculture)
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from article Rainforest
Clouds overlying a rainforest in Costa Rica. (Credit: John J. Mosesso/U.S. Geological Survey)
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from article Rainforest
Tree ferns and profuse tropical vegetation framing a mountainside waterfall (visible in the background) in a rainforest located on the Caribbean island of Dominica. (Credit: Randolph Femmer/U.S. Geological Survey)
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from article Fused-salt phase equilibria
Diagram of typical phase equilibrium relationships in condensed binary systems of molten salts. Here ℓ is liquid and ss is solid solution.
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from article Fused-salt phase equilibria
Typical phase equilibrium relationships in condensed ternary systems of molten salts.
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from article Fused-salt phase equilibria
The system LiF-BeF2-ThF4. Temperature is in °C. °F = (°C × 1.8) + 32. (After R. E. Thoma et al., Phase equilibria in the systems BeF2-ThF4 and LiF-BeF2-ThF4, J. Phys. Chem., 64:865–870, 1960)
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from article Archeoastronomy
Angular swing of the Sun along the horizon at rising and setting from solstice to solstice. The angle is for a latitude of 36°, that of the North American Southwest.
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from article Archeoastronomy
Monthly angular swing of the Moon along the horizon at moonrise, for times of maximum angle (major standstill) and minimum angle (minor standstill). The angles are shown for a latitude of 36°.
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from article Archeoastronomy
Inner great trilithons of Stonehenge. (Courtesy of O. Gingerich)
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from article Archeoastronomy
Diagram of the major features of Stonehenge that may have been used astronomically. (After O. Gingerich, in K. Brecher and M. Feirtag, eds., Astronomy of the Ancients, MIT Press, 1979)
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from article Archeoastronomy
Fajada Butte in Chaco Canyon. (a) View of entire butte (photo by M. Zeilik). (b) Rock slabs near the top of the butte. They rest against the rock surface on which two spirals are pecked. Their upper edges cause sunlight in late morning to play upon…
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from article Archeoastronomy
Wijiji site in Chaco Canyon. (a) Painted white sun symbol above the ledge near the ruin. The emblem resembles that of the Zia pueblo sun symbol and a sun symbol on a war shield from Jemez pueblo. (b) Winter solstice sunrise observed from the ledge…
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from article Cardamon
Seeds of cardamon (Elettaria cardamomum). (Photo by Rainer Zenz)
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from article Microbial fuel cell
Model of microbial metabolism and anode reduction. Microorganisms oxidize electron donors, either organic or inorganic, and pass the electrons through the cell energy-generating machinery to an electron acceptor [oxygen, nitrate, iron, or carbon…
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from article Microbial fuel cell
Schematic of a two-chambered microbial fuel cell showing both direct and indirect reduction at the anode. In this example, acetate (CH3COO−) is oxidized to carbon dioxide (CO2) and protons (H+) with the aid of a bacterial cell. The electrons are…
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from article Microbial fuel cell
Diagram of the main mechanisms of electron transfer from bacterial cells to the anode of a microbial fuel cell. The chelation mechanism is not applicable to MFCs using a carbon electrode because the anode cannot be dissolved. Both the direct and…
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from article Hemp
Close-up view of hemp (Cannabis sativa). (Credit: Ondřej Zicha)
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from article Phytoremediation
Depiction of the various methods of phytoremediation. Heavy-metal phytoremediation involves phytoextraction of the toxic metal from the soil and subsequent transport and storage of the metal in the shoots (for removal). For some toxic metals that…
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from article Ionic liquids
Examples of (a) inorganic and high-melting salts and (b) organic and low-melting salts known as ionic liquids. (After J. D. Holbrey et al., Crystal polymorphism in 1-butyl-3 methylimidazolium halides: Supporting ionic liquid formation by inhibition…
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from article Ionic liquids
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from article Ionic liquids
X-ray crystal structure of 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) in its ortho polymorph (its most common conformation). (After J. D. Holbrey et al., Crystal polymorphism in 1-butyl-3 methylimidazolium halides: Supporting ionic liquid…
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from article Thorium
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from article Vetch
Developing seed pods of hairy vetch (Vicia villosa). (Photo by Peggy Greb, Agricultural Research Service, U.S. Department of Agriculture)
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from article Vetch
Narrow-leaf or blackpod vetch (Vicia sativa ssp. nigra). (Photo by James H. Miller, U.S. Department of Agriculture Forest Service)
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from article Vetch
Purple vetch (Vicia bengalensis). (Photo courtesy of Petrified Forest National Park, National Park Service, Arizona)
