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from article Pituitary gland disorders
Anatomy of the human pituitary gland, which is attached to the base of the brain. (Copyright © McGraw Hill)
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from article Pituitary gland disorders
Infarction (obstruction of the blood supply) of the pituitary gland. This pituitary gland is almost entirely infarcted. Only a thin rim of viable cells remains (arrow). Pituitary infarcts can occur during pregnancy (Sheehan's disease) or as a result…
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from article Strychnos
Strychnos nux-vomica: close-up view of leaves and flowering branch. (Photo courtesy of Dinesh Valke)
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from article Colemanite
Fundamental building block in the crystal structure of colemanite.
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from article Colemanite
Crystal structure of colemanite viewed down the a axis. The 〈Δ2□&x3009 x232A; rings link to form chains of borate polyhedra parallel to the c axis.
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from article Breadfruit
Breadfruit (Artocarpus altilis), showing the rounded (or elliptic) fruit and the cylindrical staminate flower cluster. (Photo courtesy of Forest and Kim Starr)
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from article Island biogeography
Equilibrium number of species (Sequilibrium) is determined by the intersection of the immigration ( I ) and extinction ( E ) rate curves. P is the maximum number of species in the source pool.
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from article Folic acid
Chemical structure of folic acid (C19H19N7O6). (Copyright © McGraw Hill)
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from article Digenea
Diagrams of various adult types of digenean trematodes. (After R. M. Cable, An Illustrated Laboratory Manual of Parasitology, Burgess, Minneapolis, 1940)
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from article Digenea
Digenean trematode life cycle. (After R. M. Cable, An Illustrated Laboratory Manual of Parasitology, Burgess, Minneapolis, 1940)
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from article Hydroponics
Green- and red-leaf lettuce growing in a hydroponic vegetable garden on a bamboo fence. The pipes, which supply nutrients and water, are part of the hydroponic system. (Credit: Piyachok Thawornmat, Shutterstock)
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from article Hydroponics
Hydroponic techniques: (a) aerated standing culture; (b) flowing-solution culture with standing solution; (c) nutrient film technique; (d) aeroponics.
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from article Emerald
Emerald crystals. (Credit: Reimphoto/Getty Images)
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from article Mango
Tommy Atkins cultivar of mango (Mangifera indica) growing in Florida. (Credit: Wilhelmina Wasik/Agricultural Research Service, U.S. Department of Agriculture)
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from article Tomato
Tomatoes (Solanum lycopersicum). (Credit: Peggy Greb, Agricultural Research Service, U.S. Department of Agriculture)
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from article Tomato
Tomato affected by anthracnose (caused by the fungus Colletotrichum phomoides). (Credit: U.S. Department of Agriculture Cooperative Extension Slide Series, Clemson University)
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from article Tomato
Tomatoes showing blossom-end rot. (Credit: Mary Ann Hansen, Virginia Polytechnic Institute and State University)
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from article Pine nut
Pine nuts in their hard shell (Mexican piñon pine, Pinus cembroides). (Photo by Steve Hurst, U.S. Department of Agriculture–Natural Resources Conservation Service PLANTS Database)
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from article Pine nut
Cone containing pine nuts (stone pine, Pinus pinea). (Photo by Vito Buono, Bari, Italy)
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from article Biofilm
Biofilms are highly structured communities of microorganisms that are surface-associated or attached to one another, and are enclosed within a self-produced protective extracellular matrix. Biofilm formation and actions involve a number of stages:…
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from article Pyroclastic rock
Pyroclastic rock. Bombs from Mauna Kea, Hawai'i, USA. (Credit: J. P. Lockwood/USGS Photo Library, Denver, CO)
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from article Pyroclastic rock
Distribution downwind of the pyroclastic fall deposit from the climactic eruption of Mount St. Helens, Washington, on May 18, 1980. The contours (isopachs) are drawn through points of measured equal thickness (in centimeters) of this ash layer.…
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from article Pyroclastic rock
Aerial view in March 1998 of the fan-shaped pyroclastic delta formed by repeated entries of pyroclastic flows and surges into the Caribbean Sea during the Soufrière Hills Volcano eruption in 1996–1997. (Credit: R.P. Hoblitt, USGS)
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from article Pyroclastic rock
Observed or postulated mechanisms for the generation of pyroclastic flow and surge deposits. (a, b) Mechanisms that commonly produce block-and-ash flow deposits. (b, c) Mechanisms that trigger laterally directed blasts. (d–f) Mechanisms that…
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from article Pyroclastic rock
Some variations in pyroclastic rock formations. (a) Layers of pyroclastic fall deposits from the eruption plume of the June 15, 1991, explosive eruption of Mount Pinatubo (Luzon, Philippines). This exposure, located about 9 km (5.5 mi) southeast of…
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from article Animal testing
Mice are the most commonly used vertebrate species in animal testing and research. (Credit: Dolores Bonaparte)
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from article Animal testing
The use of animals in biomedical research remains essential, but the handling of these sentient beings must be done humanely to minimize and prevent animal harm. (Credit: U.S. Department of Agriculture)
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from article Common cold
Adenovirus structure. An adenovirus binds to the host cell via its fiber through the knob at the end of the fiber "spikes" on the capsid (protein coat) surface. (Credit: M. K. Cowan and H. Smith; copyright © McGraw Hill)
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from article Common cold
Human respiratory system. Common cold viruses enter through the nose, mouth, or eyes, infecting epithelial cells of the oropharynx. (Credit: M. K. Cowan and H. Smith; copyright © McGraw Hill)
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from article Common cold
Life cycle of a double-stranded DNA virus, such as an adenovirus. The virus attaches to specific receptors, after which it is taken up by the cell. Following entry into the cell, the viral capsid (protein coat) is digested, releasing DNA, which…
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from article Common cold
Electron micrograph (tinted green) of human coronavirus 229E particles. Coronaviruses are named for the corona, or halo, surrounding the capsid (protein coat). The crown-like corona results from the presence of viral spikes protruding from the viral…
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from article Earth's interior
Speculative models of the interiors of the terrestrial planets. All are rocky, divided into a crust (not shown here), mantle, and metallic core. (After R. T. Merrill and M. W. McElhinny, The Earth's Magnetic Field, Academic Press, 1983)
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from article Earth's interior
Preliminary Reference Earth Model (PREM) for P- and S-wave velocities, vp and vs, and density ρ. In the part of the upper mantle where the model is anisotropic, velocities are given in both the vertical and horizontal direction. The broken lines…
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from article Earth's interior
Variations of gravity and pressure inside the Earth. 1 m = 3.3 ft. 1 megabar = 100 GPa. (After P. Melchior, The Physics of the Earth's Core, Pergamon Press, 1986)
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from article Earth's interior
Density versus depth for several mantle constituents along the 1400°C (2552°F) adiabat. Data points show the density variation of PREM. All three constituents shown here contain magnesium-rich silicates. (After D. L. Anderson, Where on Earth is the…
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from article Earth's interior
P-wave velocity anomalies above the core–mantle boundary in terms of spherical harmonics up to degree and order 6, obtained by inverting P-wave travel time data. Positive perturbations indicate faster-than-average material. Contour interval = 25…
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from article Earth's interior
Speculative, schematic model of the core–mantle boundary layer. A heterogeneous chemical boundary layer is embedded in a thermal boundary layer. Large-scale mantle circulation transports chemical heterogeneity to the base of the mantle as well as…
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from article Earth's interior
Schematic temperature profile of the mantle. Subsequent estimates of core temperature are higher than suggested in the figure; the temperature jump across the thermal boundary layer at the base of the mantle will then be correspondingly higher. °F =…
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from article Earth's interior
Schematic temperature profile of the core. The melting-point curve for the core is substantially below the melting point of pure iron. All temperatures may have to be raised to correspond with further estimates of the melting point of iron. °F = (K…
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from article Earth's interior
Contour plots of the radial component of the magnetic field at the core–mantle boundary (a) for the year 1715 and (b) for 1980. The contour interval is 100 microteslas; solid-line contours represent flux into the core, and broken-line contours…
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from article Anthrax
A color-enhanced scanning electron micrograph showing splenic tissue from a monkey with inhalation anthrax. Rod-shaped bacilli of Bacillus anthracis (yellow) and an erythrocyte (red) are shown. (Credit: Arthur Friedlander/National Institute of…
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from article Anthrax
Micrograph (stained with hematoxylin and eosin) showing submucosal hemorrhage in the small intestine of a person fatally affected by gastrointestinal anthrax. (Credit: Marshal Fox/Centers for Disease Control and Prevention)
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from article Tumor virus
Under certain conditions, human papillomaviruses are capable of causing cancer in humans. (Credit: Laboratory of Tumor Virus Biology, National Cancer Institute)
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from article Ecosystem
Levels of organization in ecosystems, which involve both biotic (living) components and abiotic (nonliving, physical) components. (Copyright © McGraw-Hill Education)
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from article Ecosystem
General model of energy flow through ecosystems. (Copyright © McGraw-Hill Education)
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from article Ecosystem
Food chains are limited by energy transfer. In this illustration, energy is transferred from the Sun to a plant (producer) to a primary consumer and to a secondary consumer. Energy is used by the producer and consumer organisms and is lost to the…
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from article Ecosystem
General model of the nitrogen cycle in ecosystems. (Copyright © McGraw-Hill Education)
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from article Ecosystem
General model of the carbon cycle in ecosystems: (A) carbon dioxide (CO2) from the air; (B) carbon from decomposition; (C) carbon from fossil fuels; (D) natural events (for example, forest fires and volcanoes) release CO2 into the air. (Copyright ©…
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from article Salicylate
Chemical structures of (a) salicylate, the conjugate base of (b) salicylic acid, and the nonsteroidal anti-inflammatory drug (NSAID) (c) acetylsalicylic acid (aspirin).
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from article Meningococcus
A photomicrograph reveals the presence of the bacterium Neisseria meningitidis, which can be pathogenic, leading to meningococcal meningitis. (Credit: James Volk/Centers for Disease Control and Prevention)
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from article Poplar
Quaking aspen (Populus tremuloides). (Photo courtesy of North Dakota State Soil Conservation Committee, USDA–NRCS PLANTS Database)
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from article Poplar
Common poplar species. (a) Quaking aspen (P. tremuloides); leaf scar with an axial bud, leaf, and twig. (b) Bigtooth aspen (P. grandidentata); leaf, terminal bud, and twig. (c) Cottonwood poplar (P. deltoides); leaf, leaf scar, terminal bud, and…
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from article Hydrological consequences of global warming
The hydrologic cycle is characterized by evaporation and transpiration from the surfaces; transport of water vapor in the atmosphere by the wind, clouds, and precipitation; and water storage in snow, glaciers, groundwater, and oceans. Units: 1000…
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from article Hydrological consequences of global warming
Spatial patterns of climate model projections of (a) precipitation, (b) soil moisture, (c) runoff, and (d) evaporation for 2090–2099 under the mid-range A1B emission scenario from the Intergovernmental Panel for Climate Change 2007. (Climate Change…
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from article Biodiversity
Global biodiversity hotspots. There are more than 30 biodiversity hotspots located around the world. These areas have experienced severe habitat losses (at least 70%) as the result of human activities, hampering the work of conservationists in their…
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from article Biodiversity
A regional analysis of 25 oceanic regions shows that 92% of all known biodiversity falls into a dozen groups, of which crustaceans (for example, crabs, shrimps, and lobsters), mollusks (for example, snails, bivalves, squids, and octopus), and fish…
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from article Biodiversity
Ecosystem function (a) as a positive, linear function of biodiversity and (b) as a nonlinear, satiating function of biodiversity. (Copyright © McGraw Hill)
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from article Micrometeorology
Soundings of temperature versus height for (a) day time and (b) nighttime obtained by radiosonde measurements during the Wangara experiment near Hay, New South Wales, Australia, in 1967. Soundings are shown for 9 A.M. through 9 P.M. on day 33 of the…
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from article Micrometeorology
The 3 P.M. sounding from Fig. 1a showing the layers of the daytime convective boundary layer.
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from article Urodela
A typical member of the order Urodela: the longtail salamander (Eurycea longicauda). (Credit: Ryan Hagerty/U.S. Fish and Wildlife Service)
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from article Urodela
Southern dwarf siren (Pseudobranchus axanthus), which has undergone limb degeneration and retains only tiny forelimbs. (Credit: U.S. Geological Survey)
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from article Urodela
World distribution of salamanders (order Urodela), indicated by areas of shaded blue color. (Copyright © McGraw Hill)
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from article Urodela
California tiger salamander (Ambystoma californiense). (Credit: John Cleckler/U.S. Fish and Wildlife Service)
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from article Urodela
The two-toed amphiuma salamander (Amphiuma means). (Credit: Southeast Ecological Center, U.S. Geological Survey)
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from article Urodela
The northern red salamander (Pseudotriton ruber ruber) is a member of the family Plethodontidae. (Credit: Alicia Lafever/U.S. National Park Service)
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from article Spinal cord disorders
Human spinal cord. (Copyright © McGraw-Hill Education)
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from article Earth's heat flow
Geographic distribution of heat flow measurement sites. (After H. N. Pollack, S. J. Hurter, and J. R. Johnson, Heat flow from the Earth's interior: Analysis of the global data set, Rev. Geophys., 31(3):267–280, 1993)
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from article Earth's heat flow
Heat flow–versus–age relationships for continents and oceans. (After D. Sprague and H. N. Pollack, Heat flow in the Mesozoic and Cenozoic, Nature, 285:393–395, 1980)
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from article Earth's heat flow
Geographic distribution of 17 heat flow provinces where the linear relationship between measured heat flow and radiogenic heat production from near-surface rocks has been empirically determined. (After I. Vitorello and H. N. Pollack, On the…
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from article Earth's heat flow
Present-day global heat flow (degree 12 spherical harmonic representation). Contours are in milliwatts per square meter. (After H. N. Pollack, S. J. Hurter, and J. R. Johnson, Heat flow from the Earth's interior: Analysis of the global data set,…
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from article Environmental management
Environmental management seeks to provide solutions to the practical problems that humans encounter or create, including the production of garbage and waste. (Credit: Walter Zerla/Getty Images)
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from article Environmental management
Without proper environmental management, economic and industrial development often lead to environmental pollution, especially in urban environments. (Credit: Simon Alvinge/123RF)
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from article Chicxulub impact crater
Bouguer gravity anomaly map over the Chicxulub impact crater. The coastline is designated by a thin white line, cenotes (natural pits) and sinkholes are designated by black dots, and the city of Mérida and the town of Chicxulub Puerto are designated…
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from article Chicxulub impact crater
Seismic line imaging of what lies beneath the seafloor, showing the Chicxulub impact crater. The crater includes many faults that can be grouped into an exterior ring fault, a series of outer ring faults, and a series of inner ring faults. Within…
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from article Bioassay
In conducting bioassays, researchers often employ laboratory culture tests, which use, for example, bacteria cultured in a petri dish (usually to model an effect on the organism of interest or on some basic cellular function). (Credit:…
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from article Osage orange
Fruit and foliage of osage orange (Maclura pomifera). (Photo copyright © Karren Wcisel)
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from article Marine ecology
Marine ecology investigates the basic structural and functional relationships within and among living populations and their physical–chemical environments in marine ecosystems. In this photograph, a cold water reef in California is host to a…
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from article Marine ecology
The snaking waterways of a mangrove estuary in northwestern Madagascar. (Credit: Michael Fay/Getty Images/National Geographic RF)
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from article Marine ecology
Estuary salt marshes in the Grand Bay National Estuarine Research Reserve, Mississippi. (Credit: P. R. Hoar/National Oceanic and Atmospheric Administration)
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from article Marine ecology
Coral bleaching in the lagoon of Huahine Island, French Polynesia. Coral bleaching is the response of corals to environmental stress in which they eject the single-cell algae that live within the transparent coral tissue, making the white coral…
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from article Magnolia
Flowers and leaves of the southern magnolia (Magnolia grandiflora). (Photo courtesy of Forest and Kim Starr)
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from article Dental caries
The disease of dental caries or tooth decay is largely preventable. Bacteria colonize the tooth surface and often produce sufficient acids to demineralize the tooth's enamel. Then, dental plaque can build up on the tooth's surface, creating…
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from article Dental caries
Early caries (cavity) lesion of a primary first molar (indicated by the arrow). (Copyright © McGraw Hill)
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from article Hackberry
Hackberry (Celtis occidentalis). (Credit: North Dakota State Soil Conservation Committee, USDA–NRCS PLANTS Database)
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from article Swamp, marsh, and bog
Young cypress trees growing out of a swamp located in the Florida Everglades. (Credit: Getty Images)
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from article Medical control systems
Diagram of selected portions of the human motor control system. (After G. L. Gottlieb, D. M. Corcos, and G. C. Agarwal, Strategies for the control of voluntary movements with one mechanical degree of freedom, Behav. Brain Sci., 12:189–250, 1989)
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from article Medical control systems
Electric hand, a myoelectric prosthesis. (a) Two views of the hand, 2.5 in. (6 cm) across the knuckles, with the cover removed in one view to show the electric motor drive circuit. (b) Child using the electric hand. (Hugh Steeper Ltd.)
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from article Medical control systems
Hybrid control system using both functional electrical stimulation and orthoses. (a) Hierarchical control scheme. (b) Braces in use. (c) Detail of leg brace. (After Y. Kim and F. A. Spelman, eds., Images of the Twenty-First Century: Proceedings of…
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from article Medical control systems
Autoclavable pacemaker with a lithium silver vanadium pentoxide battery. (After W. Greatbatch, Pacemaker power sources, IEEE Eng. Med. Biol. Mag., 3(2):15–19, June 1984)
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from article Medical control systems
Automatic implantable cardioverter defibrillator (AICD) system with pulse generator, leads, and external programmer. (S. Nisam, Cardiac Pacemakers, Inc.)
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from article Plant vulnerability to climate change
Subarctic tundra and vegetation of the Denali National Park and Preserve in Alaska. As a result of climate change and the resultant poleward and upward shift of plant ranges, plants and their ecosystems may become particularly vulnerable. (Credit:…
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from article Plant vulnerability to climate change
Blue grama (Bouteloua gracilis) growing in Montana. As a result of warming temperatures, this type of grass could face decreased productivity, allowing forbs to increase and making the ecosystem less tolerant of drought and grazing. (Credit: Matt…
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from article Plant vulnerability to climate change
Modeled distribution of suitable climate space in Europe for stiff sedge (Carex bigelowii), which is an Arctic-Alpine plant: (a) during the period 1961–1990 (green color = suitable climate space during the 1961–1990 period); (b) climate model…
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from article Plant vulnerability to climate change
The endangered western prairie fringed orchid (Platanthera praeclara) is declining across much of its range in North America. (Credit: U.S. Fish and Wildlife Service)
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from article Geologic time scale
Geologic time scale. CLICK on image to enlarge. (Credit: International Commission on Stratigraphy, 2022)
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from article Geophysical exploration
Bouguer gravity of a portion of the Perth Basin, Western Australia. Contour interval is 1 milliGal; datum is arbitrary. Departures from regularity are called anomalies. The bulge A results from an uplift area, the contour offset along BB′ is an…
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from article Geophysical exploration
Variation of shape measurements across an anomaly. Among the shape factors sometimes measured are A, the distance over which the slope is maximum; B, the distance between points where the slope is half of the maximum slope; C, half the width of the…
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from article Geophysical exploration
Bending of seismic waves at interface; V2 > V1.
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from article Geophysical exploration
Wavefronts become more widely spaced and ray paths become curved as velocity increases with depth.
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from article Geophysical exploration
Measuring reflected seismic wave energy. (a) Dipping reflector. (b) Flat reflector.
