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from article Branched polymer
Steps in the synthesis of a starburst polymer. s = surface. o = interior. fr = reactive group. fp = protected group.
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from article Heterocyclic polymer
Structural units in linear polymers. (a) Simple linear polymer. (b) Stepladder polymer. (c) Ladder polymer.
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from article Heterocyclic polymer
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from article Convection in the Earth
Pattern of magnetic stripes over the Reykjanes Ridge southwest of Iceland. (After J. R. Heirtzler, X. LePichon, and J. G. Baron, Magnetic anomalies over the Reykjanes Ridge, Deep Sea Res., 13:427, 1966)
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from article Convection in the Earth
Geographic setting of the Kurile Trench off the Kamchatka Peninsula, showing the deep ocean trench and the characteristic line of volcanoes in the vicinity of the subduction zone. The sections A′ and B′ illustrate the bathymetry normal to the trench…
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from article Convection in the Earth
Characteristic variation of heat flow and bathymetry. (a) Variation of surface heat flow as a function of age of the ocean floor in millions of years before present for the Pacific, South Atlantic, and Indian oceans. (b) Variation of sea-floor…
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from article Convection in the Earth
Global seismicity showing surface projections of all earthquakes which occurred during 1965–1975 with magnitudes in the range 4.5–5.5. Plate boundaries are located along the seams marked by high frequency of earthquake occurrence.
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from article Convection in the Earth
Map of global tectonic and volcanic activity over the past million years. (After The Physical World, National Geographic Society, Van der Grinten projection, 1975)
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from article Seawater
Vertical distribution of phosphate (PO43−) at three stations to show a range of characteristics found in major oceanic regions. North Atlantic is from a region in the central North Atlantic northeast of Bermuda and North Pacific is from the central…
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from article Seawater
Vertical distribution of total carbon dioxide concentrations at locations in the North Atlantic and North Pacific. Below depths of a few hundred meters, the distributions are generally characteristic of fairly large regions in the two oceans.
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from article Seawater
Layers in seawater in a section through the Atlantic Ocean from the Greenland Sea (right) to the Weddell Sea (left). The thick line represents depth. (a) Potential temperature; contour values are in °C (°F). (b) Salinity; contours are in parts per…
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from article Seawater
Layers in seawater in a section through the western Indian Ocean from India (right) to Antarctica (left). The thick line represents depth. (a) Potential temperature; contour values are in °C (°F). (b) Salinity; contours are in parts per thousand.
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from article Seawater
Layers in seawater in a section through the Pacific Ocean from the Aleutian Islands (right) to the Ross Sea (left). The thick line represents depth. (a) Potential temperature; contour values are in °C (°F). (b) Salinity; contours are in parts per…
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from article Intermolecular forces
Schematic diagram of intermolecular interaction. (a) There is negligible interaction between atoms that are 1 nm apart. (b) For atoms separated by about 0.8 nm or less, attractive dispersion forces result from correlated fluctuations of the electron…
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from article Ultrahigh-pressure metamorphism
Schematic cross-section contrasting the tectonic setting of generation and exhumation of (a) Alpine-type and (b) Pacific-type HP-UHP belts. (Modified after Maruyama et al., 1996)
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from article Ultrahigh-pressure metamorphism
P-T diagram showing (a) HP-UHP regimes and stability of coesite and diamond, (b) P-T-time paths for Dabie-Sulu eclogite and garnet peridotite, and (c) zoned zircon domains with sensitive high-resolution ion microprobe (SHRIMP) U/Pb ages for Sulu…
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from article Ultrahigh-pressure metamorphism
Photomicrographs of UHP index minerals. Inclusions of coesite in omphacite from (a) Dabie, and coesite pseudomorph in epidote from (b) Sulu, central-eastern China. Inclusions of (c) microdiamond in zircon, and (d) diamond + phengite in garnet, from…
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from article Barrier islands
Generalized profile across a barrier island complex showing various environments.
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from article Barrier islands
Sediment budget for barrier island complex. Solid lines are major interactions; broken lines are relatively minor intersections.
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from article Barrier islands
Maps showing major coastal environments and directions, and directions of coastal processes of (a) wave-dominated barrier islands and (b) mixed-energy barrier islands. Large arrows indicate wave direction, and small arrows indicate direction of…
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from article Stishovite
Comparison of the mean index of refraction and specific gravity of stishovite and other polymorphic modifications of silica.
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from article Nitrogen oxides
Nitrogen-oxide structures. Blue = nitrogen. Red = oxygen.
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from article Melanterite
Fibrous crust of melanterite (a common mineral) in a sample from Kremnitz, Hungary. (Specimen from Department of Geology, Bryn Mawr College)
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from article Tidal bore
Tidal curve of a river with a tidal bore.
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from article Tidal bore
Tidal bore of the Petitcodiac River, Bay of Fundy, New Brunswick, Canada. Rise of water is about 4 ft (1. 2 m). (New Brunswick Travel Bureau)
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from article Earth
The famous "Blue Marble" picture of Earth taken by astronauts during the Apollo 17 mission on December 7, 1972, while en route to the Moon. (Credit: NASA)
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from article Earth
Principal layers of Earth. (USGS)
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from article Earth
Global histogram (distribution of elevations) and hypsographic curve (cumulative elevations) of Earth's surface. (NOAA)
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from article Earth
Seafloor spreading. (USGS)
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from article Earth
Plate collisions: (a) continent-ocean plate collision; (b) continent-continent plate collision; (c) ocean-ocean plate collision. (USGS)
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from article Earth
Structure of the atmosphere. The log scale applies only to the ionization curve. 1 km = 0.6 mi; °F = (°C × 1.8) + 32.
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from article Baltic Sea
Postglacial development of the Baltic: (a) Baltic Ice Sea, 12,000–8000 B.C.; (b) Yoldia Sea, 8000–7250 B.C.; (c) Ancylus Sea, 7250–2000 B.C.; (d) Littorina Sea, 2000–A.D. 500. (After K. Grasshoff, in S. P. Riley and G. Skirrow, eds., Chemical…
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from article Prairie dog
Black-tailed prairie dogs (Cynomys ludovicianus). (Photo by Ron Singer, U.S. Fish and Wildlife Service)
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from article Ocean
Pacific Ocean, Santa Cruz, California, USA. (Credit: Shutterstock/Lerner Vadim)
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from article Ocean
Range of (a) salinity and (b) temperature in the world’s oceans.
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from article Ocean
Major currents of the world’s oceans.
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from article Ocean
Role of the winds in establishing major current gyres that span ocean basins. Gyres are closed circulatory systems that are larger than whirlpools or eddies.
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from article Alicyclic hydrocarbon
Internal bond angles (α) for (a–c) planar rings and (d) a tetrahedral carbon atom.
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from article Alicyclic hydrocarbon
Nonplanar (a) chair and (b) boat structures of cyclohexane.
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from article Alcohol
Ethanol production plant. (Credit: Julie Kendall/Getty Images)
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from article Alcohol
E85 is a gasoline-ethanol blend containing 51 to 83% ethanol. It is used in flexible-fuel vehicles, which can operate on gasoline or blends of gasoline and ethanol. About 20 million flexible-fuel vehicles are operating in the United States. (Credit:…
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from article Fluids
Probability of finding molecular centers at various separations in gases, liquids, and solids.
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from article Fluids
Conditions of pure-component phase behavior.
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from article Fluids
Behavior of pure-component pressures with density at various temperatures.
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from article Fluids
Behavior of pure-component compressibility factors with pressure at various temperatures.
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from article Amblygonite
Amblygonite. (Credit: RF Company/Alamy)
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from article Phlogopite
Polyhedral models showing the one-layer monoclinic phlogopite atomic structure illustrating (a) a projection down the b axis and (b) near a-axis projection. The structural unit consists of only one layer; note that both layers shown are identical.…
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from article Desertification
Overgrazing on North American rangelands contributes to soil compaction and alters the composition of vegetation. (Credit: Thomas Wikle)
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from article Desertification
Desertification can be accelerated by cultivation in areas better suited for herding, such as this field in Ethiopia. (Credit: Thomas Wikle)
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from article Desertification
Grazing animals have contributed to desertification in Africa’s Sahel region. (Credit: Thomas Wikle)
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from article Rock
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from article Rock
Classification of psammitic and pelitic rocks based on proportions of the three most common clastic minerals: quartz, feldspars, and clays—excluding calcilutites and calcarenites. (After E. W. Heinrich, Microscopic Petrography, McGraw-Hill, 1956)
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from article Rock
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from article Rock
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from article Rock
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from article Varve
Varved sediment in two lake-bottom cores from modern glacier-fed lake (Hector lake, Alberta, Canada) Varves collected closer to the river inlet (left) are thicker and represent higher annual sedimentation rates. The length of each sequence shown is…
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from article Laminariales
Laminaria: (a) sporophyte; (b) cross section of blade, showing a sorus of unilocular sporangia interspersed with sterile hairs (paraphyses); (c) zoospore; (d) male gametophyte with antheridia; (e) antherozoid (sperm); (f) female gametophyte with…
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from article Laminariales
Giant kelp (Macrocystis pyrifera) can grow up to 0.6 m (2 ft) per day. Note the series of frond blades, with each subtended by a bladder. (Photo courtesy of Charlotte Stevenson, University of Southern California Sea Grant, Los Angeles)
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from article Biosynthesis
Biosynthetic relationships of some natural products. Specific examples which belong to the various classes are given in brackets.
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from article Geochemical prospecting
Recognition of regional and local anomaly thresholds is the basis for geochemical exploration. (From A. W. Rose et al., Geochemistry in Mineral Exploration, 2d ed., Academic Press, London, 1979)
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from article Geochemical prospecting
Gold, lead, copper, and molybdenum with respect to a GIS for the northern Nevada rhomboid. GIS provides topography, geology, and geophysical background for the metal occurrences. The rhomboid is shown in all frames. Boundaries in the top panel are…
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from article Geyser
Old Faithful, Yellowstone Park, Wyoming. (National Park Service, U.S. Department of the Interior)
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from article Thulium
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from article Turbidite
Ideal sequence of structures in a turbidite. (After H. Blatt, G. Middleton and R. Murray, Origin of Sedimentary Rocks, 2d ed., Prentice-Hall, 1980)
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from article Lidar
Block diagram of a typical monostatic system used for ranging or altimetry applications.
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from article Lidar
Block diagram of a typical atmospheric lidar system. Range to scattering volume = z; thickness of scattering volume = Δz.
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from article Lidar
Photon count profile measured with a sodium resonance fluorescence lidar.
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from article Nearshore processes
Longshore currents, generated when waves approach the beach at an angle. At Oceanside, California, the longshore current is flowing toward the observer. (Photo courtesy of Department of Engineering, University of California, Berkeley)
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from article Nearshore processes
Definition sketches for nearshore circulation cells. (a) Asymmetrical cell for breakers oblique to the shore. (b) Symmetrical cell for breakers parallel to the shore.
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from article Nearshore processes
Beach profile, showing characteristic features.
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from article Nearshore processes
Effect of headlands on the accretion of beach sand at Point Mugu, California. The point forms a natural obstruction that interrupts the longshore transport of sand, causing accretion and a wide beach to form (foreground). The regularly spaced…
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from article Nearshore processes
Sand delta at Rio de la Concepción on the arid coast of the Gulf of California. Such deltas are important sources of sand for beaches. (Courtesy of D. L. Inman)
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from article Chemistry
Periodic table. (Jaap Hart/Getty Images)
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from article Mercury (element)
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from article Mercury (element)
Mercury droplets exhibiting non-wetting of the surface. (Credit: A. Cerar/Getty Images)
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from article Mercury (element)
Tooth with a silver-amalgam filling. (Credit: Szasz-Fabian Jozsef/Shutterstock.com)
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from article Organic conductor
Structures of organic conductors. (a) Electron donors. (b) Acceptor molecule (TCNQ) and two monovalent anions. Abbreviations are explained in the text.
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from article Organic conductor
Stacking of charge-transfer compounds. (a) Segregated stacking of TTF-TCNQ-like materials. (b) Typical zigzag stacking of the (TMTSF)2X series.
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from article Organic conductor
Comparison of the range of electrical conductivities of some AsF5-doped conducting polymers with some metals, semiconductors, and nonconducting polymers.
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from article Organic conductor
Image
from article Alpine vegetation
Forest-alpine tundra near Hyndman Cirque, Idaho. The trees change in density and form within the ecotone beyond the boundary of the timberline upslope toward the alpine tundra. The distribution of timberline, treeline, and the ecotone is irregular…
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from article Alpine vegetation
Whitebark pine (Pinus albicaulis) showing the classic dwarfed and contorted image of trees within the windswept forest-alpine tundra ecotone of the Beartooth Plateau, Wyoming. (Courtesy of T. Crawford)
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from article Alpine vegetation
Flagged tree, mainly supporting branching on the leeside of the upper trunk; needles have been lost from the lower trunk to the parasitic snow fungus. (Courtesy of T. Crawford)
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from article Orpiment
Orpiment crystal habit. (After C. S. Hurlbut, Jr., Dana's Manual of Mineralogy, 17th ed., John Wiley and Sons, 1959)
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from article Killer whale
Killer whales (Orcinus orca) in the waters off Alaska. (Credit: David Ellifrit/Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration)
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from article Killer whale
The tail of a killer whale. (Credit: Janice Waite/Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration)
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from article Globe (Earth)
Globe gores from collections of the Library of Congress. (Istituto Geografico di Agostini, Novara, Italy)
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from article Globe (Earth)
The ocean relief globe reveals both land relief and worldwide submarine relief. (National Oceanic & Atmospheric Administration)
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from article Globe (Earth)
Globe with hinged horizon ring. At the North Pole is a small disk which rotates independently to show simultaneous times over the Earth. (Rand McNally and Co.)
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from article Globe (Earth)
Wilson globe, from collections of the Library of Congress. This globe is dated 1822. Note that the upper part of the analemma extends north of the horizon ring.
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from article Hydrido complexes
Structure of ReH92−.
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from article Hydrido complexes
Structure of [HMn(CO)5].
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from article Hydrido complexes
Structure of [HRe(C5H5)2]. The aromatic C5H5 groups are represented by pentagons.
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from article Hydrido complexes
Hydridophosphine structures, with the C6H5 groups not shown. (a) [HRuCl(P{C6H5 }3)3]. (b) [H3Ir(P{C6H5 }3)3].
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from article Hydrido complexes
Reaction scheme for hydrogenation of an olefin using Wilkinson's catalyst.
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from article Hydrido complexes
Structure of [HCr2(CO)10]−.
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from article Hydrido complexes
Structure of [H2W2(CO)8]2−.
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from article Hydrido complexes
Core of the [H8Re2(P{C2H5 }2C6H5)4] molecule. All organic groups are omitted for clarity.
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from article Hydrido complexes
Structure of [H2Th(C5 {CH3 }5)2]2. The hydrogen atoms of the methyl groups are omitted for clarity.
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from article Earthquake
Destruction and debris following the magnitude 9 Japan, 2011 (Fukushima) earthquake and tsunami. (Credit: MC1 Matthew M. Bradley/US Navy)
