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from article Precipitation (chemistry)
Precipitation of calcium fluoride. (Copyright © McGraw-Hill Education/Stephen Frisch)
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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 Polystyrene
Polystyrene foam. (Credit: Raywoo/123RF)
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from article Polaron
An electron self-trapped by the displacements of equilibrium positions of atoms that surround it.
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from article Polaron
Energy levels of quasifree and self-trapped states when the polaron is energetically stable.
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from article Polaron
Polaron mobilities versus inverse temperature.
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from article Ionic crystals
Sodium chloride lattice. The darker circles represent positive ions and the lighter circles negative ions. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)
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from article Ionic crystals
Cesium chloride lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)
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from article Ionic crystals
Wurtzite lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)
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from article Ionic crystals
Zinc blende lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)
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from article Ionic crystals
Calcium fluoride lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)
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from article Ionic crystals
Rutile lattice. (After F. Seitz, The Modern Theory of Solids, Dover, 1987)
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from article Ionic crystals
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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 Vacuum fusion
Vacuum-fusion methods of analysis.
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from article Cohesion (physics)
Calculated pressure-volume curves for molybdenum and xenon at absolute zero. Negative-pressure portions of curves are represented by broken lines because they cannot be directly measured. 1 kilobar = 0.1 GPa; 1 Å3 = 0.001 nm3.
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from article Ordovician
Ordovician, the second period of the Paleozoic Era.
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from article Ordovician
Early Ordovician (Arenig) paleogeography, major rock suites and potential ocean surface currents; based on remanent magnetism data supplemented by plots of the positions of shelf sea carbonates and reefs.
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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 Supercritical-fluid chromatography
Block diagram of supercritical-fluid chromatograph. With some detectors (for example, flame ionization), the pressure/flow restrictor is mounted in the detector.
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from article Supercritical-fluid chromatography
High-resolution separation of the oligomers of a methyl silicone by pressure-programmed supercritical-fluid chromatography; each peak in the chromatogram is due to an oligomer with one more Si(CH3)2O group than the previous peak. Pressure is held at…
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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)
