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from article Messier Catalog
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from article Active sound control
Results of a computer simulation of the sound field produced by two sources of spherical sound waves in air that have identical source strengths and are separated by a distance of 10 m. The sources are out of phase and radiate sound at a frequency…
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from article Active sound control
Feed-forward active noise control system. Elements of the system below the broken line are entirely digital, the filter H operating on the input sequence x to produce the output sequence y. The characteristics of the filter are designed by using the…
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from article Active sound control
Active control system for the suppression of propeller-induced aircraft cabin noise. The digital filters H1 and H2 are designed to minimize the sum of the squared error signals e1–e4.
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from article Active sound control
Distribution of sound pressure level (in decibels on an arbitrary scale) at head height in a 48-seat propeller aircraft (a) before and (b) after the use of a multichannel active noise control system consisting of 16 loudspeakers and 32 microphones.…
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from article Active sound control
Multichannel feed forward active control system for suppressing noise from multiple primary sources.
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from article Active sound control
Performance of a multichannel feed forward system for the active suppression of road-induced noise in a small passenger car at a speed of 60 km/h (37 mi/h). Reference signals were taken from six vibration sensors on the vehicle suspension. The…
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from article Immunity
The immune response to an invading microbe can generate immunity via antibody production. Steps: (1) Antigen binds to a B cell receptor (antibody) on a B cell. (2) The B cell may also receive more information from a helper T cell about the presence…
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from article Immunity
Colored scanning electron micrograph of an activated human macrophage. Activation of macrophages is often an important aspect of the immune response. (Credit: Steve Gschmeissner/Science Photo Library/Alamy Stock Photo)
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from article Immunity
Colored scanning electron micrograph of B lymphocytes. These white blood cells are involved in the immune response. (Credit: Steve Gschmeissner/Science Photo Library/Alamy Stock Photo)
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from article Deforestation
View of an area of deforestation in Central Kalimantan, Indonesia. In this case, the land is being cleared to develop areas for intensive rice production. (Credit: Australian National University)
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from article Deforestation
The relationship between forest and nonforest (other) land. Preservation of forest lands includes reforestation and natural regeneration. However, deforestation and natural events can lead to nonforest land. Afforestation (the act or process of…
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from article Deforestation
Natural forest areas (in hectares; 1 hectare = 2.47 acres) in various climatic domains (boreal/polar, temperate, subtropical, and tropical) from 1990 to 2015. The data are derived from the Global Forest Resources Assessment 2015 by the Food and…
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from article Deforestation
Former rainforest in northern Queensland, Australia, that was deforested in the early 1900s and is now used for pasture. (Credit: Rodney Keenan)
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from article Deforestation
Aerial view of deforestation in the Amazon region of Brazil. Clearing of trees in the Amazon rainforest has resulted in the elimination of natural resources and numerous species. (Credit: Luoman/Getty Images)
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from article Evolutionary computation
Typical flowchart for an evolutionary algorithm.
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from article Evolutionary computation
Traveling salesperson problem comprising 1000 cities. (a) Best-evolved solution after examination of 4 × 107 possible solutions. (b) Rate of evolutionary optimization.
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from article Evolutionary computation
Arrangement for distributing an evolutionary algorithm across multiple processors. Each processor holds its own population that undergoes random variation and selection. Occasionally, solutions will migrate from one population to another and begin…
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from article Symphyla
Scutigerella immaculata. This symphylan is a garden and greenhouse pest. (Photo by Ivo Antušek; BioLib.cz)
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from article Symphyla
Cercus (enlarged view). (Courtesy of Robert T. Allen, Academy of Natural Sciences, Philadelphia; Amanda Lawrence, Electron Microscope Center, Mississippi State University)
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from article Vacuum fusion
Vacuum-fusion methods of analysis.
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from article Cestida
Structure of Cestum veneris.
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from article Precession of equinoxes
Illustration of the celestial sphere, an imaginary sphere of infinite radius centered on the Earth and projected using Earth's celestial poles and celestial equator. (Credit: NASA)
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from article Precession of equinoxes
Motion of the Earth's axis of rotation.
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from article Soil chemistry
Proper soil chemistry helps a green seedling to sprout out from the soil. Soil chemistry controls the availability of plant nutrients within the soil and thus influences plant growth. (Credit: amenic181/Shutterstock)
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from article Soil chemistry
Extensive chemical weathering can remove essential minerals and elements from soil. Typically, only the most insoluble compounds remain in the soil. For example, iron oxides may persist, imparting a reddish-brown color to the soil. (Credit: Stephen…
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from article Soil chemistry
Factors influencing the chemistry of a soil solution. (Credit: Based on an original illustration created by J. F. Hodson)
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from article Walnut
Pith of two species of Juglans: (left) butternut or white walnut (J. cinerea); (right) black walnut (J. nigra). (Photo by Bill Cook, Michigan State University; Bugwood.org)
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from article Walnut
Black walnut (Juglans nigra). (Photo by D. E. Herman, North Dakota State Soil Conservation Committee, U.S. Department of Agriculture–Natural Resources Conservation Service PLANTS Database)
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from article Walnut
Fruits of black walnut (Juglans nigra). (Photo by Rob Routledge, Sault College, Sault Ste. Marie, Ontario, Canada; Bugwood.org)
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from article Walnut
English or Persian walnut (Juglans regia). (Photo by Milan Kořínek)
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from article Walnut
Kernel of English walnut (Juglans regia). (Photo by Piero Amorati, IC Croce, Casalecchio di Reno, Italy; Bugwood.org)
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from article Walnut
Walnut leaf showing symptoms of anthracnose (caused by the fungus Gnomonia leptostyla). (Photo by Pavel Šinkyřík, Czech Republic)
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from article Walnut
Canker disease (caused by the fungus Sirococcus clavigignenti-juglandacearum) on a butternut (Juglans cinerea). (Photo by Mike Ostry, U.S. Department of Agriculture Forest Service)
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from article Lipidomics
Components of phosphoinositides. (a) General structure of phospholipids, showing positions sn-1 and sn-2, where various fatty acids may attach. X represents a phosphate-linked group; FA represents a fatty acid. (b) Space-filling models of four…
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from article Lipidomics
Selected MS ion chromatograms of synthetic 1,2-diacyl-sn-3-glycerol (DAG) molecular species from polymorphonuclear neutrophilic leukocytes (PMNs) of patients with local aggressive periodontal disease. DAG species were resolved and identified by…
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from article Lipidomics
Families of bioactive lipids. (a) Arachidonic acid is the precursor for many of the known bioactive mediators, such as EETs, prostaglandins, leukotrienes, and lipoxins. (b) Eicosapentanoic acids (C20:5 and C22:6) are precursors to potent new…
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from article Lipidomics
Functional-mediator lipidomics approach to evaluate and profile compounds during experimental inflammation and its resolution.
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from article Thrombosis
Thrombin molecular model. (Credit: Molekuul/Science Photo Library/Getty Images)
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from article Thrombosis
Organized thrombus in an artery with recanalization.
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from article Thrombosis
Organized thrombus in an artery with scar formation; the artery is completely occluded by the fibrotic mass.
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from article Comparator
High-gain nonregenerative operational amplifier as voltage comparator.
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from article Comparator
Regenerative operational amplifier as comparator (Schmitt trigger). The input and output voltages are superimposed, showing hysteresis.
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from article Cephalochordata
European lancelet (Branchiostoma lanceolatum). (After J. E. Webb, On the populations of Branchiostoma lanceolatum and their relations with the West African lancelets, Proc. Zool. Soc. Lond., 127:131, 1956)
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from article Clover
Red clover (Trifolium pratense). (Photo by Tom Heutte, U.S. Department of Agriculture Forest Service)
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from article Clover
White clover (Trifolium repens). (Photo by Pavel Šinkyřík)
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from article Clover
Crimson clover (Trifolium incarnatum). (Photo by Pavel Šinkyřík)
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from article Clover
White sweet clover (Melilotus albus). (Photo by Forest and Kim Starr)
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from article Clover
Leaves of clover affected by leaf spot, which is caused by the fungus Pseudopeziza trifolii. (Photo courtesy of the U.S. Department of Agriculture Cooperative Extension Slide Series, Clemson University)
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from article Decision theory
Decision tree for the problem given in the text. Numbers at nodes represent time past alarm (7:00 A.M.), and numbers at branches refer to the decision mode or state of nature.
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from article Decision theory
From of a decision matrix. Oij = outcome corresponding to the interaction of a strategy (Si) and a state of nature (Nj).
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from article Decision theory
Decision tree structure to determine the subjective utility of lottery outcomes.
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from article Decision theory
Hypothetical subjective utility curves.
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from article Power shovel
Comparison of the boom, dipper handle, and dipper for (a) conventional power shovel, (b) hydraulic backhoe, and (c) hydraulic front shovel. A typical lower frame, crawlers, and machinery frame are shown for the hydraulic shovel.
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from article Mitochondria
A mitochondrion is a specialized compartment (organelle) of a eukaryotic cell (upper left). The electron micrograph (upper right) and the accompanying illustration (bottom) indicate the outer and inner membranes, cristae, and matrix. [Credit…
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from article Mitochondria
Three-dimensional reconstruction of a rat liver mitochondrion produced by electron microscopic tomography. During imaging, the sample is tilted around one or more axes to generate different projections that are later digitally combined to produce a…
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from article Mitochondria
Guard cells of a transgenic tobacco plant expressing green fluorescent protein (GFP) targeted to mitochondria. Chloroplasts (cell plastids) show red chlorophyll autofluorescence and mitochondria show green protein fluorescence. (Credit: Rainer…
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from article Mitochondria
Mitochondria are the powerhouses of the cell, being responsible for energy generation in the form of adenosine triphosphate (ATP). ATP is produced by the coupled processes of electron transport and oxidative phosphorylation in mitochondria.…
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from article Magnetic materials
Identification of properties related to the magnetic hysteresis loop. Colored area is the magnetization energy lost in every cycle (hysteresis loss).
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from article Magnetic materials
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from article Magnetic materials
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from article Sewage collection systems
Various pipe shapes. (a) Round. (b) Vertically elongated (ellipse). (c) Pipe-arch. (d) Underpass. (e) Arch. (After American Iron and Steel Institute, Handbook of Steel Drainage and Highway Construction Products, 2d ed., 1971)
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from article Sewage collection systems
Band-coupled pipe joints. (a) Typical band coupling; (b) standard corrugated steel pipe band connectors; (c) band angle connector (after American Iron and Steel Institute, Modern Sewer Design, 1980). (d) Details of an O-ring compression joint for…
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from article Sewage collection systems
Diagram of a mechanical compression water stop and seal. (Link Seal, Thunderline Corp., Wayne, Michigan)
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from article Sewage collection systems
Some typical sewer manholes with standard 24-in. (61-cm) cover and frame. (a) Inside drop. (b) Outside drop. (c) Unit for a large sewer. (After R. L. Linsley and J. B. Franzini, Water Resources Engineering, 3d ed., McGraw-Hill, 1979)
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from article Sewage collection systems
Drop manhole detail. (a) Vertical section. (b) Horizontal section (A-A in part a). (After National Clay Pipe Institute, Clay Pipe Engineering Manual, 1962)
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from article Sewage collection systems
Typical house sewer connection. (After Metcalf & Eddy, Inc., and G. Tchobanoglous, Wastewater Engineering: Collection and Pumping of Wastewater, McGraw-Hill, 1981)
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from article Sewage collection systems
Typical stormwater street inlets. (a) Gutter. (b) Curb. (c) Combination; grate placed directly in front of curb opening and depressed. (d) Multiple; undepressed. (After Joint Committee of American Society of Civil Engineers and Water Pollution…
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from article Sewage collection systems
Typical catch basin with removable hood trap for cleanout. (Neenah Foundry Co., Neenah, Wisconsin)
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from article Sewage collection systems
Typical contract plan and profile sheet for sewer lateral. (a) Plan. (b) Profile; numbers on horizontal axis refer to sites with same numbers in part a. MH = manhole. Sta = Station. Inv. El. = Invert elevation. RCP = reinforced concrete pipe. S =…
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from article Sewage collection systems
Hydraulic profile for uniform flow condition, showing values at points U and D.
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from article Sewage collection systems
Hydraulic element graphs for conditions of partial flow in terms of full section. (a) Pipe-arch section. (b) Circular section. (After American Iron and Steel Institute, Modern Sewer Design, 1980)
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from article Eye (invertebrate)
Pigment spot ocellus, the simplest invertebrate eye. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Simple open eye of the marine limpet Patella. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Large, complex eye of the marine snail Murex. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Simple pigment cup ocellus of flatworm. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Large, complex eye of the clam worm Nereis. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Simple eye of Ranzania, a marine annelid. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Highly developed eyes at anterior end of pelagic marine annelid Alciopidae. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Scallop Argopecten with one valve removed showing ocelli along the margin of the mantle. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Longitudinal section through the tubelike anterior median eye of jumping spider Salticus. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Octopus eye. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Two ommatidia from compound eye of crayfish Astacus. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Compound eye adapted for opposition image formation. Light rays from points a, b, and c. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed., Brooks/Cole Thomson, Belmont, CA, 2004)
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from article Eye (invertebrate)
Compound eye adapted for superposition image formation. The light from points a, b, and c is concentrated on an ommatidium. (After E. E. Ruppert, R. S. Fox, and R. D. Barnes, Invertebrate Zoology: A Functional Evolutionary Approach, 7th ed.,…
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from article Buxbaumiidae
Morphological features of Buxbaumiidae. (a) Sporophyte of Buxbaumia aphylla (after W. H. Welch, Mosses of Indiana, Indiana Department of Conservation, 1957). Diphyscium foliosum (b) habit sketch, (c) leaves and (d) perichaetial leaf (after H. S.…
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from article Rhinoceros
Black rhinoceros (Diceros bicornis). (Credit: Lloyd Glenn Ingles; copyright © California Academy of Sciences)
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from article Ferret
An endangered black-footed ferret (Mustela nigripes). (Photo copyright © Joseph Dougherty)
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from article Siphonostomatoida
Siphonostomatoida. (a) Representative siphonostomatoid mandible; (b) brachiform maxilla (after Z. Kabata, Parasitic Copepoda of British Fishes, vol. 152, Ray Society, London, 1979). (c) Representative female caligid; (d) female Pennella (after P. A.…
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from article Holothuroidea
Cucumaria, a representative holothurian.
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from article Holothuroidea
Holothurian anatomy.
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from article Engineering
Test firing of NASA’s 3D-printed rocket engine nozzle. 3D printing allows engineers to test new prototypes, including objects designed with multiple materials, speeding the development process and time. (Credit: NASA/MSFC/David Olive)
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from article Turboprop
Typical turboprop configurations. (a) Fixed-turbine turboprop. (b) Free-turbine turboprop. (c) Offset-gearbox turboprop. (d) Counterrotating turboprop. (e) Unducted fan, an ungeared, counterrotating, pusher turboprop. (After R. C. Hawkins, Unducted…
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from article Turboprop
Typical turboprop installations. (a) Conventional tractor-type single-rotation turboprop (Saab Corp.). (b) Unducted fan, a pusher-type counterrotating turboprop (GE Aircraft Engines).
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from article Thermostat
Typical heat-cool thermostat. (Honeywell Inc.)
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from article Thermostat
Comparison of temperature variations using a timed on-off thermostat with and without heat anticipation.
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from article Cosmic background radiation
Timeline of the origin and evolution of the universe from a hot, dense state (left) to the current star-and galaxy-filled cosmos that arose over eons of the universe’s history and through today (right). The cosmic microwave background, labeled the…
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from article Cosmic background radiation
The most detailed map ever made of the cosmic microwave background, a snapshot of the universe at 380,000 years of age, obtained by the Planck spacecraft during its observing run from 2009 to 2013. Anisotropies—tiny temperature fluctuations—are…
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from article Cosmic background radiation
The 15-meter horn antenna at Bell Telephone Laboratories in Holmdel, New Jersey where the first detection of the cosmic microwave background was made. (Credit: NASA)
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from article Plant physiology
The process of photosynthesis is a key feature of plant physiology. Chloroplasts (cell plastids that contain chlorophyll) use solar energy to manufacture carbohydrates and other large molecules. Mitochondria break down these molecules, thereby…
