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Artist impression of TDRS-L, the 11th member of NASA's Tracking and Data Relay Satellite System, orbiting Earth at 36,000 km (22,300 mi). TDRS-L sends signals, information, and commands from ground controllers to the International Space Station and…

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from article Communications satellite

Communications to and from a satellite.

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from article Communications satellite

Typical communications satellite. TWTA = traveling-wave–tube amplifier. (Credit: Space Systems/Loral)

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from article Communications satellite

Orbit periods of circular orbits.

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from article Forest ecosystem

Forest in Moran State Park on Orcas Island, Washington. (Credit: Chris Willig)

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from article Forest ecosystem

Forest fire in No Name Creek area of Colorado. (Credit: Andrea Booher/FEMA)

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from article Forest ecosystem

Puma and cub in forest. (Credit: Grant Faint/Stockbyte/Getty Images)

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from article Forest ecosystem

Conceptual model of elemental cycling in a terrestial ecosystem, emphasizing the presence and activities of arthropod consumers. The indirect regulation of elemental movement by arthropods is indicated by the hourglass-shaped valves on these flows.…

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from article Forest ecosystem

The southern pine beetle (Dendroctonus frontalis) is a destructive insect pest of coniferous forests in the southern United States. (Credit: U.S. Forest Service)

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from article Forest ecosystem

Belowground food web. (Credit: Elaine Ingham)

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from article Polymer composite

Relation between stiffness and filler type and orientation in polymeric materials. L/D = length/diameter of fiber.

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from article Polymer composite

Load transfer from matrix to fiber in a composite. LC = critical length. σma = matrix stress.

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from article Polymer composite

Tensile modulus for various fibers.

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from article Polymer composite

Unidirectional continuous fiber–reinforced laminated structure. L = longitudinal direction. T = transverse direction.

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from article Polymer composite

Measured and predicted elastic modulus in a unidirectional fiber–reinforced laminate as a function of angle between the loading and fiber direction.

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from article Branched polymer

Examples of branched polymers. (a) Branched polymer (if arms are of composition similar to backbone) or graft polymer (if compositions are different). (b) Star polymer. (c) Comb polymer. (d) Dendritic polymer.

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from article Branched polymer

Reaction for preparation of a star polymer with styrene-butadiene block copolymer arms.

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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 Tangent

Line L tangent to curve C at P.

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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 Patellogastropoda

Whitecap limpet (Acmaea mitra). (Photo by Douglas Eernisse)

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from article Patellogastropoda

Ribbed Mediterranean limpet (Patella ferruginea). (Photo by Georgina Rivera Ingraham)

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from article Patellogastropoda

Radula of the patellogastropod Notoacmea scapha.

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from article Intermolecular force

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 Beef cattle production

Angus bull with overall carcass merit. (Credit: Jim Koch/Agricultural Research Service, U.S. Department of Agriculture)

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from article Beef cattle production

Brahman (zebu) bull (Bos indicus). (Credit: Scott Bauer/Agricultural Research Service, U.S. Department of Agriculture)

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from article Beef cattle production

An exemplary purebred Hereford bull. (Credit: Michael MacNeil/Agricultural Research Service, U.S. Department of Agriculture)

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from article Beef cattle production

A group of Simmental cows. (Credit: Iowa Beef Industry Council)

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from article Beef cattle production

Three Charolais heifers. (Credit: Darcy Vial/Farm Service Agency, U.S. Department of Agriculture)

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from article Beef cattle production

In order to attain market weight, cattle are fed often in feedlots. (Credit: Dave Hughes/Getty Images)

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from article Beef cattle production

In the United States, beef animals used for food must be inspected extensively pre- and postmortem by federal officials. (Credit: Bob Nichols/U.S. Department of Agriculture)

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from article Fruit, tree

Apple trees growing in an orchard. (Photo by Charles Rondeau)

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from article Fruit, tree

Apple scab on fruit. This disease, caused by the fungus Venturia inaequalis, leads to unsightly blemishes on ripe apples. (Photo courtesy of the University of Georgia Plant Pathology Archive)

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from article Fruit, tree

Brown rot, caused by the fungus Monilinia fructicola, on a peach. (Photo by Jonas Janner Hamann, Universidade Federal de Santa Maria, Brazil)

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from article Fruit, tree

Fire blight, caused by the bacterium Erwinia amylovora, on apple fruits and leaves. (Photo courtesy of the University of Georgia Plant Pathology Archive)

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from article Fruit, tree

Blue mold (Penicillium italicum) on a rotting orange. (Photo by G. L. Barron)

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from article Algorithm

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from article Algorithm

An array of n elements.

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from article Algorithm

Inserting and deleting an element from a stack.

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from article Algorithm

Inserting and removing an element from a queue.

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from article Algorithm

An example of a tree.

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from article Algorithm

A graph with four vertices and five edges.

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from article Belladonna

Close-up view of the belladonna plant (Atropa belladonna), showing the leaves and berries, which are toxic. (Credit: Leo Michels)

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from article Masking of sound

Three psychophysical tuning curves, showing the tonal masking effects for tonal signals of 300, 1000, or 3000 Hz. (After F. L. Wightman et al. Factors influencing frequency selectivity in normal and hearing-impaired listeners, in E. F. Evans and J.…

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from article Masking of sound

Width of the critical band in hertz as a function of signal frequency.

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from article Masking of sound

Relative amount of masking obtained in forward, simultaneous, and backward masking. (After W. A. Yost, Fundamentals of Hearing: An Introduction, 4th ed., Academic Press, New York, 2000)

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from article Masking of sound

Masking of a 1000-Hz pure-tone signal in forward masking when the masker is a two-tone complex consisting of a 1000-Hz masker and a second tone. (a) Threshold of signal for the two-tone masker relative to that obtained when only the 1000-Hz tone…

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from article Capability maturity modeling

Capability Maturity Models: the continuous representation.

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from article Capability maturity modeling

Organizational maturity levels.

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from article Capability maturity modeling

Capability Maturity Models: the staged representation.

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from article Capability maturity modeling

CMMI model evolution.

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from article Intelligent machine

Driverless cars use sensor-based data to make decisions. (Credit: monicaodo/Shutterstock)

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from article Intelligent machine

Flow of information and data in a typical intelligent machine.

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from article Television

Interlace scanning pattern (raster) of the television image.

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from article Television

NTSC color television waveform. (a) Principal components. (b) Detail of picture elements. (Electronic Industries Association)

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from article Television

ITU-R Digital terrestrial television broadcasting model of the International Telecommunications Union, Radiocommunication Sector (ITU-R). (From Advanced Television Systems Committee, ATSC Digital Television Standard, Doc. A/53B, 2001)

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from article Television

High-level view of the DTV encoding system, illustrating the relationship and derivation of various clock frequencies within the encoder and the use of forward error correction (FEC). A/D = analog-to-digital. VSB = vestigial sideband. (From Advanced…

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from article Television

Sample organization of functionality in a transmitter-receiver pair for a single DTV program. PSIP = Progam and System Information Protocol, PES = packetized elementary stream, PSI = program-specific information. (From Advanced Television Systems…

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from article Television

Common image aspect ratio formats. (After K. B. Benson and D. G. Fink: HDTV: Advanced Television for the 1990s, McGraw-Hill, New York, 1990)

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from article Nitrogen oxides

Nitrogen-oxide structures. Blue = nitrogen. Red = oxygen.

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from article Lychee

Fruit and leaves of lychee (Litchi chinensis). (Photo courtesy of Forest and Kim Starr)

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from article Data science

Data science is multidisciplinary. (Credit: Brendan Tierney, Technological University Dublin, Oralytics Blog)

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from article Data science

Data science life cycle. [Credit: Kenneth Jensen (CC BY-SA 3.0)]

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from article Nerve agent

Chemical structure of the nerve agent tabun (GA), C5H11N2O2P.

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from article Nerve agent

An example of hazardous materials workers wearing personal protective equipment (PPE), as might be worn to protect against nerve agent exposure. (Credit: CDC Public Health Image Library)

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from article Nerve agent

A practice exercise at the Centers for Disease Control and Prevention showing responders using a decontamination station, as might be used after a nerve agent incident. (Credit: CDC Public Health Image Library/Kathy Nellis Chastney)

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from article Nerve agent

Example of auto-injector syringes for atropine and pralidoxime, two antidotes for nerve agent exposure, from a Mark 1 Nerve Agent Antidote Kit (NAAK). (Credit: ATSDR/CDC)

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from article Sauropterygia

Ceresiosaurus calcagnii, ventral view.

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from article Hyperbola

Hyperbola as a conic section.

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from article Hyperbola

Hyperbola as a locus of points.

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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 Corallinales

Articulated coralline red algae (genus Calliarthron, order Corallinales) found off the California coast in the Pacific Ocean. (Photo by Steve Lonhart, Monterey Bay National Marine Sanctuary, National Oceanic and Atmospheric Administration)

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from article Telephone

A typical corded phone set. This particular phone was used at the White House on July 20, 1969 by President Nixon to speak with the Apollo astronauts that had just landed on the Moon. The voice signals between the parties were converted into radio…

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from article Telephone

A conventional payphone.

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from article Telephone

Cross-section of an electret transmitter.

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from article Telephone

A cordless telephone.

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from article Telephone

Generations of cell phones, from oldest to newest, left to right. The touchscreen phones at right are generally referred to as "smartphones." (Credit: Shutterstock / cheyennezj)

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from article Physical science

An astronaut conducts a physical science experiment aboard the International Space Station involving buoyancy-driven convection and sedimentation, which as force-dependent phenomena occur differently in a microgravity environment. (Credit: NASA)

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from article Model theory

A cutaway model of the Earth's crust under the Bay Area of California, showing various fault lines (such as the San Andreas Fault), and depicting the hypocenter of the devastating 1906 earthquake.

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from article Model theory

Conceptual model of a system.

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from article Model theory

Model of a regional population system.

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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 Human-computer interaction

Graphical user interface on tablet computer. (Credit: Shutterstock/Kaspars Grinvalds)

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from article Computer architecture

Compared to the architecture of buildings, which is largely an issue of esthetics, the architecture of a computer system is principally about efficiency and economy of operation. There may be an esthetic dimension to computer architecture, but when…

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from article Thulium