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from article Galliformes
White-tailed ptarmigan (Lagopus leucurus), Glacier National Park, Montana. (Photo by Gerald and Buff Corsi, copyright © California Academy of Sciences)
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from article Crystal growth
Schematic representation of cross section of crystal at three stages of regular growth.
Image
from article Crystal growth
A model of a crystal surface showing the inequivalent binding sites at which the atoms labeled A and B are located. (General Electric Co.)
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from article Crystal growth
A dendrite. Growth direction is upward for primary protuberances; side branches grow perpendicularly; side branches on the side branches are also seen growing perpendicularly. (After W. Kurz and D. J. Fisher, Fundamentals of Solidification, Trans…
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from article Crystal growth
Hypothetical binary system AB having simple compound formation. (a) Phase diagram. (b) Corresponding partial pressure curves. The extent of the stoichiometry range is greatly exaggerated for illustration.
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from article Crystal growth
Czochralski crystal growth and temperature distribution.
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from article Crystal growth
Vertical Bridgman crystal and temperature distribution.
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from article Crystal growth
An isotherm in the aluminum-gallium-arsenic (Al-Ga-As) ternary phase diagram. Each corner represents a pure element and each point within the diagram a unique composition, all at a given temperature. Each composition on the liquidus is in…
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from article Crystal growth
Molecular-beam epitaxy apparatus.
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from article Crystal growth
Cross section of a gallium arsenide–aluminum arsenide (GaAs–AlAs) single crystal with individual gallium arsenide and aluminum arsenide layers each about 5 × 10−10 m thick.
Image
from article Echinoida
Tripneustes ventricosus (Lamarck), tropical eastern and western Atlantic, found at depths of 0–55 m (0–180 ft). (From G. Hendler et al., Sea Stars, Sea Urchins and Allies: Echinoderms of Florida and the Caribbean, Smithsonian Press, Washington, DC,…
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from article Echinoida
A pyramid from Aristotle's lantern, showing epiphyses joined and tooth with keel. (After H. L. Hawkins, The lantern and girdle of some Recent and fossil Echinoidea, Philos. Trans. R. Soc. Lond. Ser. B, 223:617–649, 1934)
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from article Echinoida
An ambulacral plate from the test, with the lowest element being the largest. (After T. Mortensen, A monograph of the Echinoidea: Camarodonta, C. A. Reitzel, Copenhagen, 1943)
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from article Thermodynamic principles
An internal combustion engine, a kind of heat engine that performs work to propel a hot rod car. (Andre Kudyusov/Getty Images)
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from article Thermodynamic principles
The observation that the same work is done whatever the adiabatic path between two specified states of a system implies that each state has a characteristic property such that the difference in its values is equal to the adiabatic work required to…
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from article Thermodynamic principles
Representation of the statements of the second law of thermodynamics by (a) Lord Kelvin and (b) Rudolf Clausius. In each case, the law states that the device shown cannot operate as shown.
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from article Thermodynamic principles
Criterion for ability of a device to produce work. (a) This device cannot produce work because there is a decrease in entropy of the hot reservoir as energy leaves it as heat, but no compensating increase in entropy of the cold sink; overall,…
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from article Thermodynamic principles
Representation of the experimental determination of entropy. Measurements are made of the heat capacity, C, down to as low a temperature, T′, as possible, and C/T′ is plotted against T′. The area under the curve up to the temperature of interest, T,…
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from article Thermodynamic principles
Gibbs energy of a system. A spontaneous change (under conditions of constant temperature and pressure) corresponds to a decrease in Gibbs energy. This is a disguised form of the identification of the spontaneous direction of change with an increase…
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from article Thermodynamic principles
Simple phase diagram for a one-component system (C = 1) and its interpretation in terms of the phase rule. The lines (F = 1) show the conditions under which two phases (P = 2) are in mutual equilibrium; the triple point (F = 0) is the unique set of…
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from article Paramecium
Photomicrograph of Paramecium caudatum. (Credit: Nancy Nehring/Getty Images)
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from article Heterodonta
Common heterodont bivalves. (Credit: Ronald V. Dimock, Jr.)
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from article Heterodonta
Common heterodont bivalves. (Credit: Ronald V. Dimock, Jr.)
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from article Superposition principle
Superposition principle for a linear system (such as a driven harmonic oscillator). (a) Total force equals the sum of two forces, Fa and Fb. (b) Resulting total displacement is equal to the sum of displacements, xa and xb, due to each of the forces…
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from article Superposition principle
Superposition of two waves on the surface of water, or of two quantum wave functions. (a) Double-slit experiment. (b) Intensities, I1 and I2 (given by the square of the local amplitude of the wave, ψ1 or ψ2), when slits 1 and 2 are open, one at a…
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from article Shadowgraph
Schematic of the shadowgraph method applied to reveal convection patterns in a fluid layer. A cross section of the apparatus perpendicular to the convection rolls is shown.
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from article Shadowgraph
Background-divided shadowgraph image of convection in high-pressure carbon dioxide gas. The convection rolls are in the form of a two-armed spiral lying within a set of concentric circular rolls. (From E. Bodenschatz et al., Transitions between…
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from article Aye-aye
Aye-aye (Daubentonia madagascariensis). (Photograph by Urs Thalmann, Anthropological Institute, University of Zürich)
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from article Tick virus diseases
A deer or black-legged tick (Ixodes scapularis). (Credit: U.S. Centers for Disease Control and Prevention)
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from article Tick virus diseases
Diagram depicting the life cycle of Ixodes scapularis. This deer tick can transmit viruses and other pathogens that cause a number of important diseases, including Lyme disease, anaplasmosis, and babesiosis. The risk of human infection is greatest…
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from article Tick virus diseases
World map depicting the locations of human tick-borne disease cases. Heartland, Bourbon, and Colorado tick fever virus cases are unique to North America. Powassan encephalitis cases are reported in North America and Russia. Tick-borne encephalitis…
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from article Tick virus diseases
Cases of Powassan encephalitis reported in the United States from 2006 to 2015. Most of the reported cases are in Minnesota, New York, and Wisconsin. (Credit: ArboNET, Arboviral Diseases Branch, U.S. Centers for Disease Control and Prevention)
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from article Atom laser
Principle of the radio-frequency output coupler of an atom laser. (a) Bose-Einstein condensate confined in an atom trap. (b) Tilting of the spins of the atoms by a short radio-frequency pulse. (c) Splitting of the cloud into a trapped cloud and an…
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from article Atom laser
Pulsed atom laser in operation, with pulses of coherent sodium atoms coupled out from a Bose-Einstein condensate that is confined in a magnetic trap.
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from article Euryalida
Aboral body of a basket star, Euryale aspera (family Euryalidae, order Euryalida), clinging to a red soft coral colony and spreading its branching arms.
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from article Euryalida
A snake star, Astrochele pacifica (family Gorgonocephalidae, order Euryalida): (a) aboral body; (b) aboral arms; and (c) a scanning electron microscope (SEM) image of a separated microscopic hook. (Credit for photo a: Shimoda Marine Research Center,…
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from article Crystal
Structure of a simple crystal. Spheres, representing atoms, are packed together into a cubic lattice. This crystal has 4-fold symmetry axes passing through the front face; after a 90° rotation the structure appears unchanged.
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from article Pinnipeds
Walrus (Odobenus rosmarus). (Credit: Donna Dewhurst Collection/U.S. Fish and Wildlife Service)
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from article Pinnipeds
Steller sea lion and pup (Eumetopias jubatus). (Credit: Alaska Image Library/U.S. Fish and Wildlife Service)
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from article Pinnipeds
Evolutionary relationships and stratigraphic ranges of major groups of pinnipeds. Shaded bars correspond to known ranges, and white bars correspond to inferred ranges. Ma = million years ago. (Copyright © McGraw-Hill Education)
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from article Panda
Giant panda (Ailuropoda melanoleuca). (Credit: John White)
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from article Panda
Red panda (Ailurus fulgens). (Credit: John White)
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from article Eocrinoidea
Reconstructions of Cambrian and Ordovician eocrinoids. (a) Gogia spiralis, from the Middle Cambrian of Utah, showing the primitive holdfast; sutural pores between the numerous thecal plates; and long, spiraled brachioles attached to the summit…
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from article Arrow of time
Depiction of the possible course of evolution of a closed universe (one that starts with a big bang and ends in a big crunch). (a) Time-symmetric universe in which the final singularity is no more complex than the initial singularity. (b)…
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from article Arrow of time
The three basic irreversibilities of nature which ensure that events are irreversible: (a) dispersion of matter, (b) dispersion of energy, and (c) disorganization of orderly motion.
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from article Kinetoplastida
Representative genera of families of order Kinetoplastida. (a) Oikomonas (family Oikomonadidae), one anterior flagellum. (b) Amphimonas (family Amphimonadidae), two equally long anterior flagella. (c) Monas (family Monadidae), two unequally long…
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from article Electric transient
Resistance and inductance in series.
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from article Electric transient
Resistance and capacitance in series.
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from article Electric transient
Resistance, inductance, and capacitance in series for three cases.
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from article Electric transient
RLC circuit with alternating current source.
