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from article Absorption
Incident sunlight is absorbed, reflected, and scattered by tree leaves. (Credit: Shutterstock / photolinc)
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from article Negative temperature
Populations (n) of states of a thermodynamic system consisting of N magnetically interacting nuclei of spin 2 at absolute temperatures T = +D/k and T = −D/k, where k is Boltzmann's constant and D is the energy spacing between successive states.
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from article Polypodiales
Licorice fern (Polypodium glycyrrhiza), a member of the order Polypodiales, in Olympic National Forest, Washington. (Photo courtesy of the U.S. Department of Agriculture, Forest Service)
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from article Polypodiales
Christmas fern (Polystichum acrostichoides). (Photo by James H. Miller, U.S. Department of Agriculture, Forest Service)
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from article Polypodiales
The sensitive fern (Onoclea sensibilis), a representative of the Polypodiales. (After W. W. Robbins, T. E. Weier, and C. R. Stocking, Botany: An Introduction to Plant Science, 3d ed., Wiley, New York, 1964)
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from article Polypodiales
Types of steles in the Polypodiales: (a) Protostele. (b) Amphiphloic siphonostele. (c) Ectophloic siphonostele. (d) Dictyostele with central pith surrounded by xylem and phloem in the form of discrete vascular bundles; bands of parenchyma cells…
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from article Polypodiales
Life history of a fern: (1) the fern plant, or sporophyte, bearing sori, or clusters of sporangia, on its leaves; (2) a sporangium; (3) a tetrad of young spores; (4) the four mature spores that have come from the tetrad shown in part 3; (5) a spore…
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from article Polypodiales
Diagram of section through a fern leaf, showing details of a sorus. (After W. W. Robbins, T. E. Weier, and C. R. Stocking, Botany: An Introduction to Plant Science, 3d ed., Wiley, New York, 1964)
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from article Polypodiales
Eastern marsh fern (Thelypteris palustris): sori on the pinnules of a fertile frond. (Photo by Rob Routledge, Sault College, Sault Ste. Marie, Ontario, Canada)
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from article Polypodiales
Diagram of a fern prothallium. (After W. W. Robbins, T. E. Weier, and C. R. Stocking, Botany: An Introduction to Plant Science, 3d ed., Wiley, New York, 1964)
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from article Luminescence
Schematic representation of energy levels and electronic transitions in an atomic gas. E1, ground state; E2 and E3, excited states; 1, excitation; 2, emission of resonance luminescence; 3, radiationless transition to lower excited state; 4,…
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from article Luminescence
Configuration coordinate curves for a simple luminescence center. Transition A → B shows absorption, and transition C → D shows emission. Energy EQ is that necessary for the excited state to reach point E, from which a transition to the ground state…
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from article Luminescence
Variation of the brightness of a thallium-activated potassium chloride phosphor with temperature. °F = (K × 1.8) − 459.67.
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from article Luminescence
Variation of the width of the F-center absorption band in potassium chloride at its half-maximum points, FE, as a function of the square root of the temperature. °F = (K × 1.8) − 459.67.
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from article Luminescence
Emission of thallium-activated potassium chloride at 4 K (−452°F). In a plot of this particular form, a gaussian curve would consist of two straight lines which make equal angles with the abscissa.
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from article Luminescence
Graph showing the absorptance (100 minus percent of transmission) and edge emission of cadmium sulfide at 4 K (−452°F).
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from article Luminescence
Excitation spectra for emission of calcium carbonate phosphors, using manganese as an activator, with different impurity sensitizers: 1, no sensitizer; 2, thallium; 3, lead; and 4, cerium.
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from article Luminescence
Energy-band model for luminescence processes in zinc sulfide. Electron energy increases vertically.
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from article Luminescence
Energy-band model for luminescence processes in zinc sulfide which uses copper as the activator and aluminum as the coactivator.
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from article Yeast
Colorized scanning electron micrograph (SEM) of Schizosaccharomyces pombe yeast. This single-celled fungus is studied widely as a model organism for eukaryotic cell division. It is a rod-shaped yeast that grows by elongation at its ends, and it…
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from article Yeast
Cell shapes of yeasts are extremely varied: (a) rectangular; (b) pear-shaped; (c) apiculate; (d) ogival; (e) spherical; (f) globose; (g) ellipsoidal (oval); (h) elongate; (i) tetrahedral.
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from article Yeast
Colorized scanning electron micrograph (SEM) of cells of brewer's yeast (Saccharomyces cerevisiae). This yeast consists of single vegetative cells. Small daughter cells can be seen budding off from the larger cells. Saccharomyces cerevisiae ferments…
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from article Yeast
Yeast mycelia. (a) A true septate mycelium showing a break to form an arthrospore. (b) A pseudomycelium.
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from article Yeast
Heterothallic (bifactorial) life cycle of a basidiomycetous yeast, Leucosporidium scottii.
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from article Yeast
A fluorescent antibody stain reveals the oval budding yeast cells of Candida albicans. This yeast is the most common human fungal pathogen. (Credit: Maxine Jalbert and Leo Kaufman/Centers for Disease Control and Prevention)
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from article Quantized electronic structure (QUEST)
Geometric configurations of (a) quantum well, (b) quantum wires, and (c) quantum dots.
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from article Quantized electronic structure (QUEST)
Electron energy levels and electron standing waves for n = 1, 2, 3, and 4 quantum states in a quantum well.
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from article Quantized electronic structure (QUEST)
Principles of operation of quantum-well devices. (a) Quantum-well laser. (b) Quantum-well infrared detector. (c) High-electron-mobility transistor (HEMT or MODFET). Electrons in the quantum well that came from donor atoms in the barrier are free to…
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from article Flow of granular solids
Bounds on mass flow and funnel flow. (a) Geometry of a transition hopper, showing slope angles θc and θp. (b) Range of kinematic angle of friction (φ′) and θc leading to mass flow and funnel flow. (c) Range of φ′and θp leading to mass flow and…
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from article Flow of granular solids
Flow patterns in a funnel-flow bin, showing segregation of solids. (a) Charge coming in is greater than draw coming out, resulting in draw with a preponderance of fine particles. (b) Draw is greater than charge, resulting in draw with a…
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from article Flow of granular solids
Section of bin with mass-flow conical hopper, together with graph showing relative values of pressure p, compressive strength f, and stress s, and illustrating criterion (f = s) for minimum outlet dimension B. (After A. W. Jenike, Quantitative…
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from article Cabbage
Cabbage (Brassica oleracea var. capitata). (Joseph Harris Co., Inc., Rochester, New York)
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from article Spray flow
Cross section of a vaporizing droplet, showing the relative gas-droplet motion and internal circulation.
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from article Atmospheric acoustics
Frequency dependence of attenuation coefficient in units of decibels per 100 m (dB/328 ft), temperature of 20°C (68°F), and a relative humidity of 70%. Total attenuation from air absorption and contributions from classical absorption (that due to…
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from article Atmospheric acoustics
Diagram of reflection of sound from a flat ground surface with impedance Z, showing direct (R1) and reflected (R2) paths from source to receiver, source height hs, microphone height h, distance of propagation d, and angle of incidence or grazing…
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from article Atmospheric acoustics
Relative sound pressure levels (SPL) for propagation from a source over mown grass for source height of 1.8 m (6 ft), microphone height of 1.5 m (5 ft), and distances of propagation indicated.
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from article Atmospheric acoustics
Curved ray paths. (a) Refraction downward, during temperature inversion or downwind propagation. (b) Refraction upward, during temperature lapse or upwind propagation.
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from article Atmospheric acoustics
Representative long-range ray paths of sound radiating from a source in the atmosphere and traveling from west to east in Northern Hemisphere in winter. 1 km = 0.6 mi. (After T. F. Malone, ed., Compendium of Meteorology, American Meteorological…
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from article Atmospheric acoustics
Contour plot of sound levels in the presence of upward refraction in a turbulent atmosphere. The source is very close to the ground at zero range. The white areas are regions of higher sound levels.
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from article Atmospheric acoustics
Facsimile record of acoustic echo sounding of atmosphere at the South Pole, February 9, 1975. 300 m = 984 ft, 600 m = 1969 ft. Dark regions above 300 m altitude correspond to temperature inhomogeneities associated with the passage of convective…
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from article Surface waves
Definition sketch for an oscillatory wave.
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from article Surface waves
Fluid particle orbital motions in deep-and shallow-water oscillatory waves. SWL = still-water level.
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from article Surface waves
Definition sketch for a solitary wave. SWL = still-water level.
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from article Surface waves
Definition sketch for a surge wave.
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from article Lycopsida
Lycopodium clavatum, a representative homosporous lycopsid. (a) Sporophyte showing typical rhizomatous growth and paired cones. (b) Microphyllous leaf. (c) Sporophyll bearing a sporangium on the upper surface. (From K. R. Sporne, The Morphology of…
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from article Ising model
Specific heat of Onsager's lattice for E2/E1 = 1.
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from article Ising model
Spontaneous magnetization M(0) of Onsager's lattice for E2/E1 = 1.
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from article Ising model
Comparison of the impure Ising model specific heat with the observed specific heat of EuS for T >Tc.
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from article Diamagnetism
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from article Magnetooptics
Index of refraction of light polarized parallel (np) and perpendicular (ns) to the magnetic field in the vicinity of a Zeeman triplet. The Voigt effect is proportional to ns − np (shown as a curve).
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from article Pendulum
Schematic diagram of a pendulum. O represents the axis, C is the center of mass, and P the center of oscillation.
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from article Virtual work principle
Illustration of principle of virtual work. (After R. A. Becker, Introduction to Theoretical Mechanics, McGraw-Hill, 1954)
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from article Bioacoustics, animal
Acoustic absorption loss in air and seawater as a function of frequency.
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from article Bioacoustics, animal
Audiogram of different animals.
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from article Bioacoustics, animal
Single snap of a snapping shrimp, Synalpheus parneomeris (shown in inset). (a) Waveform. Source level is sound pressure level 1 m (3.3 ft) from the source. (b) Spectrum.
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from article Ice point
Arrangement for determining triple point.
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from article Interference of waves
Young's two-slit interference.
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from article Interference of waves
Fresnel's double-mirror interference.
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from article Interference of waves
Fresnel biprism interference.
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from article Interference of waves
Equipment for demonstrating Fresnel biprism interference.
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from article Interference of waves
Interference fringes formed with Fresnel biprism and mercury-arc light source.
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from article Interference of waves
Billet split-lens interference.
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from article Interference of waves
Lloyd's mirror interference.
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from article Interference of waves
Dielectric-plate-reflection interference.
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from article Interference of waves
Multiple reflection of wave between two surfaces.
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from article Interference of waves
The shape of multiple-beam fringes for different values of surface reflectivity.
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from article Ethylene
Structure of ethylene. (Black = carbon. White = hydrogen)
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from article Papaverales
Close-up view of an ornamental poppy flower (Papaver orientale; Oriental poppy) belonging to the family Papaveraceae in the order Papaverales. (Photo by Howard F. Schwartz, Colorado State University)
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from article Plant evolution
Evolutionary history of plants, including some of their most significant evolutionary innovations over the course of geologic time. (Copyright © McGraw-Hill Education)
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from article Plant evolution
Horsetails (genus Equisetum) are primitive vascular plants. Often referred to as living fossils, horsetails typically grow in wet areas, with whorls of needlelike branches radiating at regular intervals from a single vertical stem. (Credit: Richard…
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from article Plant evolution
Two ancient tree leaf fossils embedded in stone. (Credit: Wong Hock Weng/123RF)
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from article Plant growth
Illustrative representation of a plant, showing the key external anatomical structures involved with plant growth. (Copyright © McGraw-Hill Education)
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from article Plant growth
Light micrograph of a plant root tip (meristem) showing the growth of new cells. (Credit: Zoonar GmbH/Alamy Stock Photo)
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from article Plant growth
Graphs showing sigmoid growth curves. (a) Growth in height (cm) of a sunflower stem. (b) Growth of an entire corn plant as measured by an increase in dry weight (grams). (Copyright © McGraw-Hill Education)
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from article Plant growth
Schematic drawing of a plant showing the regions of cell division and cell elongation. (Copyright © McGraw-Hill Education)
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from article Plant growth
Schematic drawing of a plant with the interrelationships of some factors involved in growth and development. (Copyright © McGraw-Hill Education)
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from article Plant growth
The apex of a tomato plant showing the localization of PIN proteins as detected by fluorescence microscopy (arrows). Via the presence of the PIN proteins, auxin accumulates at the locations where leaf branching is occurring or about to occur in the…
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from article Plant growth
The regulation of flower initiation by photoperiod in the long-day plant, Arabidopsis. Under long days, CO (Constans) protein formation in the leaves induces the biosynthesis of FT (Flowering locus T) protein, which constitutes the floral signal,…
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from article Sisal
Sisal (Agave sisalana). (Photo courtesy of Peter Lapshin)
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from article Sundew
Spoonleaf sundew (Drosera intermedia). (Photo by Robert H. Mohlenbrock, U.S. Department of Agriculture–Natural Resources Conservation Service PLANTS Database)
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from article Optical guided waves
Total internal reflection. (a) Geometry of reflection at the plane interface between two media. (b) Light trapped by total internal reflection in a planar optical waveguide of thickness h and refractive index n1. Refractive indices of boundary…
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from article Optical guided waves
Electric field distributions for the three lowest-order modes of a planar optical waveguide of thickness h = 1.5 μm. Electric field magnitudes are plotted as functions of the x coordinate in Fig. 1b for an arbitrary, fixed value of z. (a) Mode m =…
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from article Nuclear molecule
Similarity between (a) a chemical (atomic) molecule and (b) a nuclear molecule. EROT = rotational energy; EVIB = vibrational energy; Ee = electronic energy; En = nuclear energy. (From R. R. Betts and A. H. Wuosmaa, 1997)
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from article Nuclear molecule
Differential cross sections for elastic scattering of 12C on 12C and 16O on 16O for the center-of-mass scattering angle θcm = 90° as functions of the incident center-of-mass energy, Ecm. 1 barn (b) = 10−28 m2; sr = steradian. (From R. R. Betts and…
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from article Nuclear molecule
Differential cross section for elastic scattering of 16O on 16O for the center-of-mass scattering angle θcm = 90° as a function of the incident center-of-mass energy, Ecm. The dots are experimental points, the thin solid curve is the result of a…
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from article Nuclear molecule
The real potential for the elastic scattering of 16O on 16O for different values of the quantum number of angular momentum of relative motion, l. Examples of quasibound and virtual states are shown. The variable r is the distance between the centers…
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from article Nuclear molecule
Molecular window for magnesium-24 (24Mg), depicted as a function of the square of the quantum number of total angular momentum, I, and the excitation energy of 24Mg [Eexc(24Mg)]. In the molecular window, the absorption from the elastic channels into…
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from article Nuclear molecule
Double-resonance effect. In the scattering of 16O on 16O an elastic entrance partial wave can resonate at the center-of-mass energy Ecm = Ei ≈ 20.8 MeV with an l = 12 virtual (v.) state inside its width (∼2 MeV). Then it inelastically excites the 3−…
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from article Nuclear molecule
Potential energy of the dinuclear system in the reaction 54Cr + 208Pb → 262Sg as a function of the mass-fragmentation coordinate, η (initial value of |η|, |ηi| = 0.59) for total angular momentum J = 0. The dotted curve is calculated for spherical…
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from article Nuclear molecule
Calculated capture, fusion, and xn-evaporation residue cross sections (x = 1, 2, 3, 4), the fusion probability PCN, and the ratio between the neutron and fission widths Γn/Γf for the reaction 48Ca + 248Cm leading to the element livermorium (Lv, Z =…
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from article Cowpea
Cowpea (Vigna unguiculata): pods and leaves. (Photo by Howard F. Schwartz, Colorado State University)
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from article Cowpea
Cowpea seeds, which are often called black-eyed peas. (Photo by Joseph Berger; Bugwood.org)
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from article Time constant
Universal time-constant curve indicated (a) for the decreasing function and (b) for the increasing function.
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from article Magnetohydrodynamics
Periodic transverse displacement of a uniform magnetic field B0 and a uniform, frozen-in plasma.
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from article Magnetohydrodynamics
Evolution of a large-amplitude wave. (a) Steepening of wave. (b) Formation of shock wave.
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from article Magnetohydrodynamics
Perfectly conducting fluid in toroidal axisymmetric equilibrium.
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from article Magnetohydrodynamics
Instabilities of a Z-pinch configuration. (a) Initial configuration of magnetically confined plasma. (b) Sausage instability. (c) Kink instability.
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from article Magnetohydrodynamics
Rayleigh-Taylor instability, involving a perturbation in the interface between a light fluid and a heavy fluid above it.
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from article Magnetohydrodynamics
Two flux tubes in a magnetic field configuration.
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from article Magnetohydrodynamics
Effect of nonvanishing resistivity on plasma stability. (a) Location of resonant surface k · B = 0. (b) Breaking and reconnection of magnetic field lines about the resonant surface in a resistive plasma.
