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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 Climate history
Plot of the average temperature for the contiguous United States during the month of August from 1895 to 2016. (Credit: NOAA)
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from article Climate history
Global temperature relative to peak Holocene temperature, based on ocean cores. (Credit: NASA)
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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 Heterodonta
Common heterodont bivalves. (Credit: Ronald V. Dimock, Jr.)
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from article Heterodonta
Common heterodont bivalves. (Credit: Ronald V. Dimock, Jr.)
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from article Restoration ecology
Restored sand dune habitat at Cape Canaveral, Florida. To help prevent erosion, 180,000 shrubs, including grasses, sunflowers, vines, sea grapes, and saw palmettos, were planted. (Credit: Dan Casper/National Aeronautics and Space Administration)
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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 Weathering processes
Exchange-energy relationships between a rootlet and three minerals. (a) A potassium-bearing, primary silicate mineral. (b) A clay mineral well stocked with exchangeable metal cations. (c) A clay mineral scantily stocked with metal cations. The…
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from article Weathering processes
Comparison of binding energy (calories per gram-equivalent weight) on nutrient metal cation (indicated by M) by rocks and soil minerals with exchange binding energy on cation by plant roots. The relation of plant nutrition to weathering and…
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from article Prehnite
Prehnite in reniform aggregates, Paterson, New Jersey. (Specimen from Department of Geology, Bryn Mawr College)
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from article Biological productivity
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from article Regular polytopes
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from article Regular polytopes
Two regular polyhedrons. (a) Dodecahedron {5,3}. (b) Icosahedron {3,5}.
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from article Regular polytopes
Two of the six regular four-dimensional polytopes. (a) The 5-cell {3,3,3}. (b) The 8-cell {4,3,3}.
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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 Analytic hierarchy
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from article Analytic hierarchy
Analytic hierarchy used to assist a family in buying a new car.
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from article Analytic hierarchy
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from article Analytic hierarchy
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from article Analytic hierarchy
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from article Analytic hierarchy
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from article Analytic hierarchy
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from article Ankerite
Ankerite. (a) Specimen of the mineral (specimen from Department of Geology, Bryn Mawr College). (b) Crystal habits (after C. Klein, Manual of Mineralogy, 21st ed., John Wiley & Sons, Inc., 1993).
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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 Cicada
Brood IX periodical cicada in Athens, West Virginia. (Photo by Louie H. Yang)
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from article Cicada
Periodical cicada life cycle. Counterclockwise from lower left: Nymphal cicada feeding on plant roots belowground; ants and other detrivores feeding on dead cicada litterfall; teneral adult cicada recently emerged from the nymphal exuviae; bird…
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from article Cicada
Brood X periodical cicadas in Boyce, Virginia. (Photo by Louie H. Yang)
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from article Lava
Examples of lava. (a) Pahoehoe lava (in Kilauea, Hawaii) has a smooth and wavy surface formed by a thin layer of cooler lava at the surface. The surface layer is pushed into folds from the faster-moving, hot fluid lava beneath (photograph by J. D.…
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from article Tektite
Dumbbell-shaped tektite (irgizite) from the Zhamanshin meteoritic impact crater, Northern Aral Region, Russia. The glass is so dark brown that it appears black in reflected light.
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from article Chromium
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from article Reproductive behavior
The mating of dragonflies encompasses a number of reproductive behaviors. Typically, the male is in front and the female is behind. If the female is willing to mate, she bends her abdomen forward to collect sperm from the male's accessory genitalia,…
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from article Reproductive behavior
Sage-grouse lek. Males stake out and defend territories on a traditional breeding ground. Females breed with males in selected territories. (Credit: U.S. Fish and Wildlife Service)
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from article Reproductive behavior
Two bull northern elephant seals fighting for dominance on the beach. (Credit: eoind/Getty Images)
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from article Reproductive behavior
Natterjack toad giving a mating call with its vocal sac expanded. (Credit: Bobby Bok)
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from article Reproductive behavior
Mating behavior of sticklebacks: (a) zigzag dance of a male, which leads a female to the nest; (b) the male stimulates the female in the nest to lay eggs; (c) schematic portrayal of the events in a courtship sequence. (Credit: Based on original…
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from article Reproductive behavior
Lordosis in a female rodent. When mounted, the females of many mammalian species adopt the lordotic posture, rendering copulation possible. Note the concave arching of the spine. (Credit: Based on an original drawing by L. C. Drickamer and S. H.…
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from article Reproductive behavior
A black-browed albatross feeding a chick. This is one example in which parental care may be extensive and prolonged. (Credit: Vetta/Getty Images)
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from article Barium
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from article Deep-marine sediments
Bathymetric display of the northern Gulf of Mexico based on high-resolution bathymetric swath data. The data are displayed to give a 3-D perspective of present-day shelf, slope, and basin settings. Note the highly irregular sea-floor topography and…
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from article Deep-marine sediments
Map showing long-distance transport of modern slides of about 300 km (186 mi) downslope from the shelf edge (100-fathom, 183-m, or 600-ft contour line) off northwestern Africa. Thickness of slide = 25 m (82 ft). (From R. D. Jacobi, Sediment slides…
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from article Deep-marine sediments
Conceptual model showing interaction between channelized (axial) turbidity currents, overbank turbidity currents, and bottom currents (contour currents) in deep-sea environments. (From G. Shanmugam, T. D. Spalding, and D. H. Rofheart, Process…
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from article Deep-marine sediments
Amazon Fan. (a) Channel bifurcation through avulsion on the deep-sea Amazon Fan results in unchannelized sandy flows by breaching their confining levee through a crevasse and spreading out initially as unchannelized flows into a lower interchannel…
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from article Deep-marine sediments
Sizes of modern abyssal plains. (From P. P. E. Weaver, J. Thomson, and P. M. Hunter, Introduction, in P. P. E. Weaver and J. Thomson (eds.), Geology and Geochemistry of Abyssal Plains, Geol. Soc. London Spec. Publ., no. 31, pp. vii–xii, 1987)
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from article Deep-marine sediments
GLORIA long-range side-scan sonar imagery showing fingerlike patterns of debris flows in the Bear Island Fan on the continental margin of the modern Norwegian-Barents Sea. These fans are composed of cohesive debris flows. Properties of the Bear…
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from article Slime molds
Close-up view of slime mold on the ground. (Credit: Melinda Fawver/iStock/Getty Images)
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from article Slime molds
Plasmodial slime mold (Physarum polycephalum). (Credit: Jonatha M. Gott/Case Western Reserve University)
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from article Soap
Soap bars. (Credit: Getty Images)
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from article Coral bleaching
Coral reef at Kahului Point, Maui, Hawaii. (Left) Healthy corals are mostly brown or green in color as a result of the partner algae that live in the coral tissue. (Right) Because of heat stress to the corals, the algae can release toxic chemicals…
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from article Coral bleaching
Increases in temperature (in °F) in the surface waters of the Great Barrier Reef in Australia during the month of March since 1960. Water temperatures of just a few degrees above normal conditions have resulted in massive bleaching of corals.…
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from article Coral bleaching
Coral at Lizard Island, Australia. (Left) Bleached coral. (Right) Two months later, the coral had died and been overgrown by fleshy algae. (Credit: Richard Vevers and Christophe Bailhache/The Ocean Agency/XL Catlin Seaview Survey)
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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 Fog
Fogs formed by various processes. (a) Radiation fog; appears first as shallow layers above moist ground. (b) Stratocumulus cloud, formed from lifted fog. (c) Fog bow resulting from large cloud droplets in the fog top.
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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 Rhumb line
Example of a rhumb line.
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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 Altitudinal vegetation zones
Vegetation zones and gradients of mean annual soil temperature, annual precipitation, and community diversity on the south slopes of the Santa Catalina Mountains, Arizona, a temperate mountain range. (After R. H. Whittaker and W. A. Niering,…
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from article Landslide
Madison Canyon rockslide showing slide scar on left wall and slide debris damming the Madison River, forming new lake, in foreground. (J. R. Stacy, USGS)
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from article Weather map
Sea-level map illustrating isobars (solid lines every 8 hectopascals or 8 millibars) for 1200 UTC 13 March 1993. Plotted numbers adjacent to each station denote temperature (top) and dewpoint temperature (bottom) in °C. Present weather is shown by…
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from article Sand
Sand deposit along a stream in the Netherlands. (Shutterstock/Hans Engbers)
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from article Sand
Dunes produced by the transport of sand by wind, White Sands National Monument, New Mexico, United States. The sand in these dunes is made up almost entirely of gypsum (CaSO4). Despite their appearance, the dunes are only a thin veneer of sand that…
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from article Zircon
Zircon. (a) Crystal from Eganville, Ontario, Canada (American Museum of Natural History specimen). (b) Crystal habits (after C. Klein and C. S. Hurlbut, Jr., Manual of Mineralogy, 21st ed., John Wiley and Sons, 1993).
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from article Tertiary
Tertiary, the first period of the of the Cenozoic Era.
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from article Tertiary
Baluchitherium, the largest land mammal known, from the Tertiary (Oligocene Epoch) of Asia. It was 18 ft (5.4 m) high at the shoulders. (After R.A.Stirton, Time, Life and Man, Wiley, 1959)
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from article Tertiary
Mollusk fossils used by Lyell to zone the Tertiary. (a) Miocene. (b) Eocene. (After C.Lyell, Principles of Geology, 1833)
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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 Proterozoic
Proterozoic, the third eon of the Precambrian.
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from article Quartz
Quartz (a) crystal (photo courtesy of John Passaneau) and (b) projection of the atomic structure of α-quartz along the c axis. Each Si4+ cation is surrounded by an O2− coordination tetrahedron (outlined). Unit cell edge measures 0.491 nanometer.
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from article Quartz
Phase diagram for the silica system representing fields of thermodynamic stability for the various silica minerals as a function of pressure and temperature. HP indicates hexagonal-symmetry, primitive unit cell. (After C. Klein and C. S. Hurlbut,…
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from article Migratory behavior
Northern pintail ducks (Anas acuta) in migratory flight. (Credit: Josh Kelly/U.S. Fish and Wildlife Service)
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from article Migratory behavior
Monarch butterflies (Danaus plexippus) migrate from Canada and the northern United States in early autumn on a 2500-km (1550-mi) flight to Mexican wintering sites that are used year after year by individuals that have never been there before and…
