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from article Forensic botany
Surface of a green bean pod, showing its spines using (a) light microscope (courtesy of David O. Norris) and (b) scanning electron microscope (courtesy of Meredith Lane).
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from article Exposure meter
Basic exposure meter circuits. (a) Photovoltaic type circuit. (b) Photoconductive type circuit.
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from article Donor atom
Pentavalent donor atom, phosphorus (P), in the elemental semiconductor silicon (Si). (a) Phosphorus atom in a substitutional position, that is, replacing silicon, a tetravalent host atom, by completing the four tetrahedral covalent bonds with its…
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from article Pain
Neurophysiology of incoming pain. Sensation from peripheral receptors travels along specific pain nerves, and is modulated throughout the spinal cord and brain. (Copyright © McGraw-Hill Education)
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from article Radiation damage to materials
The five principal mechanisms of radiation damage are ionization, vacancies, interstitials, impurity atoms, and thermal spikes. Diagram shows how a neutron might give rise to each in copper. Grid-line intersections are equilibrium positions for…
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from article Radiation damage to materials
Sensitivity of engineering materials to radiation. Levels are approximate and subject to variation. Changes are in most cases at least 10%. (After O. Sisman and J. C. Wilson, Nucleonics, 14:58–65, 1956)
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from article Nuclear reaction
Formation of the compound nucleus 14N after capture of the deuteron by 12C. Four exit channels are indicated.
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from article Nuclear reaction
A (d, p) transfer reaction.
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from article Virus, defective
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from article Virus, defective
Electron micrographs of virion and defective interfering particles of vesicular stomatitis virus. (a) Defective interfering particle with a 50% deleted RNA. (b) Defective interfering particle with an 85% deleted RNA. (c, d, f) Defective interfering…
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from article Oscilloscope
Four-channel 150-MHz analog oscilloscope. (Credit: Tektronix)
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from article Oscilloscope
Sweep generator waveforms. (a) Single waveform, showing instant of trigger (T). (b) Dual time base in set-up mode: sweep by A, intensified by B. (c) Dual time base in delayed display mode: scan delayed by A, sweep by B.
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from article Oscilloscope
High-speed general-purpose digitizing oscilloscope. (Credit: Tektronix)
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from article Lichens
The ascolichen Teloschistes chrysophthalmus. (Credit: Jason Hollinger)
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from article Lichens
Cuplike lichens of the genus Cladonia. (Credit: Jacinta Lluch Valero)
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from article Adiabatic demagnetization
Entropy–temperature diagram of a paramagnetic substance, showing process of adiabatic demagnetization.
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from article Adiabatic demagnetization
Low-temperature part of two-stage nuclear refrigerator with superconducting magnets. Demagnetization of the second stage from an initial magnetic field of 9 teslas gave measured electronic temperatures of 10–12 μK. (After F. Pobell, Matter and…
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from article Reciprocity principle
Antenna system.
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from article Reciprocity principle
Two-mesh network.
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from article Reciprocity principle
Charged conducting bodies.
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from article Reciprocity principle
Four-terminal, black-box network.
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from article Cotton effect
Behavior of the ORD and CD curves in the vicinity of an absorption band at wavelength λ0 (idealized). (a) Positive Cotton effect. (b) Negative Cotton effect.
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from article Cotton effect
Curves used to determine relative rotatory intensities. (a) Partial ORD curve. (b) Partial CD curve.
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from article Cotton effect
Structural formula of (+)-trans-9-methyl-1,4,9,10- tetrahydronaphthalene.
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from article Cotton effect
Schematic representation of the twisted diene chromophore showing the two possible handednesses; the numbering is as indicated in Fig. 3 (a) Right-handed. (b) Left-handed.
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from article Parity (quantum mechanics)
Beta decay from polarized cobalt-60 nuclei. When the spin axes of the cobalt nuclei are not polarized, the preferential emission of the electrons and antineutrinos in the directions shown does not occur.
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from article Ebony
Persimmon (Diospyros virginiana). (Photograph by Dot Paul, National Resources Conservation Service, USDA)
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from article Crystal optics
Index ellipsoid, showing construction of directions of vibrations of D vectors belonging to a wave normal s . The vectors D ′ and D ″ define the orthogonal decomposition of the displacement vector D and will depend on the orientation in the…
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from article Crystal optics
Huygens construction for a plane wave incident normally on transparent calcite. If one proceeds to find the common tangents to the secondary wavelets shown, the two plane waves labeled OO′ and EE′ are obtained. (After F. A. Jenkins and H. E. White,…
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from article Crystal optics
Huygens construction when the optic axis lies in the plane of incidence. (After F. A. Jenkins and H. E. White, Fundamentals of Optics, 4th ed., McGraw-Hill, New York, 1976)
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from article Crystal optics
X-cut and Z-cut plates in NH4H2PO4 crystal.
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from article Crystal optics
Interference pattern from crystals that have been placed between crossed Nicol prisms. (a) Fluorspar that has been cut perpendicular to the optic axis. (b) Brazil topaz. (After M. Born and E. Wolf, Principles of Optics, 7th ed., reprinted with…
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from article Pirani gage
Diagram of a Pirani gage.
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from article Lipoprotein
Structural model of a lipoprotein.
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from article Thévenin's theorem (electric networks)
Network and its Thévenin equivalent. (a) Original network. (b) Thévenin equivalent circuit.
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from article Thévenin's theorem (electric networks)
Network and its Norton equivalent. (a) Original network. (b) Norton equivalent circuit.
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from article Thévenin's theorem (electric networks)
Power distribution circuit and its Thévenin and Norton equivalents. (a) Original circuit. (b) Thévenin equivalent circuit with its load ZL connected. (c) Norton equivalent circuit.
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from article Thévenin's theorem (electric networks)
Amplifier and its Thévenin and Norton equivalents. Numerical values are given in the text. (a) Original circuit. (b) Circuit constructed to find Thévenin impedance. (c) Thévenin equivalent circuit. (d) Norton equivalent circuit.
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from article Thévenin's theorem (electric networks)
Circuit constructed to demonstrate Thévenin's theorem.
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from article Psychosis
A colorized magnetic resonance imaging (MRI) scan of a human brain. Psychosis is a defective mental state in which there is a critical derangement of the mind (brain) involving abnormal contact with reality. (Credit: Govind Bhagavatheeshwaran and…
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from article Wheat
A sheaf of wheat (Triticum) surrounded by some small piles of seed (grain). (Credit: Scott Bauer/Agricultural Research Service, U.S. Department of Agriculture)
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from article Wheat
A combined harvester-thresher is used to harvest wheat. (Credit: Scott Bauer/Agricultural Research Service, U.S. Department of Agriculture)
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from article Wheat
Adaptation regions for wheat in the United States. (Credit: U.S. Department of Agriculture)
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from article Wheat
Wheat (Triticum) growing in a field. The wheat inflorescence is a spike bearing sessile spikelets arranged alternately on a zigzag rachis (main axis). (Credit: Tim McCabe/Natural Resources Conservation Service, U.S. Department of Agriculture)
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from article Wheat
Black stem rust of wheat, which produces urediniospores in reddish-brown pustules. The fungus Puccinia graminis f. sp. tritici is responsible for this plant disease. The inset shows a close-up view of an infected stem. (Credit: Agricultural Research…
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from article Wheat
Loose smut of wheat, caused by Ustilago tritici. (Credit: Erik Stromberg/Virginia Polytechnic Institute and State University)
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from article Determinism
A wave packet—of wavelength approximately λ, and produced perhaps by opening and closing a shutter—traveling through space.
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from article Determinism
Example of the uncertainty principle.
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from article Apical dominance
Model of strigolactone production. Auxin promotes genes (listed below the arrow) required for strigolactone biosynthesis. This can occur in roots and shoots. Strigolactones move into the bud region and are perceived by the F-box response protein,…
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from article Apical dominance
Simplified view of the interaction of three branching hormones. Auxin promotes production of strigolactones (SL), whereas limiting that of cytokinins (CK) at bud nodes. This blocks bud outgrowth in intact plants (left). After decapitation, supply of…
