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from article Microtechnique
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from article Microtechnique
Materials and method for applying cover slip to balsam wholemount. (a) Correct way; notice that the cover slip is held vertically centered over the drop of balsam. (b) Wrong way; this method draws the object to one side. (After P. Gray, Handbook of…
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from article Microtechnique
Making a smear preparation. (a) Place the drop about 1 in. (2.5 cm) from end of slide. (b) Apply a second slide just in front of the drop. (c) Push slide smoothly forward to spread the smear. (After P. Gray, Handbook of Basic Microtechnique, 3d ed.,…
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from article Microtechnique
Rotary microtome produced by the American Optical Co. (From P. Gray, Handbook of Basic Microtechnique, 3d ed., McGraw-Hill, 1964)
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from article Microtechnique
Method of mounting the wax block on the block holder. (After P. Gray, Handbook of Basic Microtechnique, 3d ed., McGraw-Hill, 1964)
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from article Microtechnique
Basic steps in cutting and mounting paraffin ribbons prior to staining. (a) Starting the ribbon. (b) Cutting the ribbon in lengths. (c) Mounting the dry ribbon. (d) Flooding the ribbons. (e) Warming the flooded ribbons to flatten them. (After P.…
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from article Microtechnique
Coplin jars for starting a slide through the reagent series. (After P. Gray, Handbook of Basic Microtechnique, 3d ed., McGraw-Hill, 1964)
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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 Capricornus
Modern boundaries of the constellation Capricornus, the Sea Goat. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension representing…
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from article Bioorganic chemistry
Vancomycin and an analog that is active against vancomycin-resistant bacteria.
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from article Bioorganic chemistry
Foldamers that mimic proteins.
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from article Bioorganic chemistry
The rate of this intramolecular lactonization, relative to that of intermolecular esterification, mimics the rate increase caused by an enzyme's binding and orienting substrates for a bimolecular reaction.
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from article Bioorganic chemistry
Intramolecular models of enzymatic general acid and general base catalysis. (a) Intramolecular general acid catalysis causes this acetal to hydrolyze at pH 7 more than 107 times faster than the corresponding acetal without the carboxylic acid group.…
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from article Bioorganic chemistry
An antibody raised against the phosphonate analog of a tetrahedral intermediate catalyzes the hydrolysis of cocaine to ecgonine methyl ester.
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from article Bioorganic chemistry
A functionalized cyclodextrin mimics the enzyme RNase by catalyzing the regioselective hydrolysis of a model phosphodiester.
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from article Bioorganic chemistry
Enzyme-catalyzed reactions that have been commercialized as industrial processes.
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from article Bioorganic chemistry
Mechanism of DNA scission by calicheamicin. Reductive or nucleophilic cleavage of the trisulfide triggers conjugate (Michael) addition to the enone, rehybridization of the bridgehead carbon, and Bergman cyclization of the enediyne, generating a…
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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 Type 1 diabetes
One characteristic feature of type 1 diabetes is glomerulosclerosis (Kimmelstiel-Wilson lesion), which involves the scarring or hardening of the glomeruli (blood vessels) in the kidneys. (Copyright © McGraw-Hill Education)
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from article Type 1 diabetes
Stages in the development of type 1 diabetes. (Credit: Type 1 Diabetes TrialNet)
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from article Parathyroid gland
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from article Parathyroid gland
Common positions of human parathyroid glands on the posterior aspect of the thyroid. (After W. H. Hollinshead, Anatomy of the endocrine glands, Surg. Clin. N. Amer., 32(4):1115–1140, 1952)
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from article Parathyroid gland
Section of human parathyroid gland, demonstrating the two main parenchymal cell types. Zenker-formal fixation, Mallory-azan stain. (After D. Bloom and D. W. Fawcett, A Textbook of Histology, 9th ed., Saunders, 1968)
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from article Parathyroid gland
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from article Geotechnical engineering
Mike O'Callaghan-Pat Tillman Memorial Bridge over the Colorado River at the Hoover Dam, spanning Nevada and Arizona, USA. Geotechnical engineering of the bridge site included 3D laser scanning of the canyon walls, geologic mapping, core drilling,…
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from article Tanaidacea
Leviapseudes bipartitus. [K. Larsen, Deep-Sea Tanaidacea (Peracarida) from the Gulf of Mexico, Brill, Leiden, 2005]
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from article Tanaidacea
Typhlotanais ohtsukae: (top) female; (bottom) male. [K. Larsen and M. Shimomura, Tanaidacea (Crustacea: Peracarida) from Japan: II. Tanaidomorpha from the East China Sea, the West Pacific Ocean and the Nansei Islands, Zootaxa, 1464:1–43, 2007]
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from article Rock mechanics
Typical rock mass containing numerous discontinuities. The person in picture is conducting a scanline survey, where a tape is placed across the rock and detailed information is gathered on the fractures that intersect the scanline.
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from article Rock mechanics
(a) Uniaxial compression test, where an axial stress is applied to a core sample of rock and increased until failure. (b) Triaxial compression test, where a constant confining stress is first applied, then the axial stress is increased until failure.
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from article Rock mechanics
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from article Rock mechanics
(a) Example of the failure zone around an underground excavation (×, shear failure; o, tensile failure), calculated using the Rocscience Phase2 computer program. (b) Example of a shallow underground excavation where the failure mode is either…
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from article Rock mechanics
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from article Aluminum (metallurgy)
Bauxite washing. (Aluminum Company of America)
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from article Aluminum (metallurgy)
Processing of alumina from bauxite. (Aluminum Company of America)
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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 Incandescent lamp
Parts of an incandescent lamp. (General Electric Co.)
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from article Incandescent lamp
Variations of incandescent lamps. Drawings are not to scale. (a) Bulb shapes and designations. (b) Lamp bases. Designations of International Electrotechnical Commission are shown, where available. (c) Filament structures. (After Illuminating…
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from article Incandescent lamp
Spectral energy distribution for important types of incandescent lamps.
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from article Incandescent lamp
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from article Incandescent lamp
Characteristic curves of general-service lamps. (After Illuminating Engineering Society, IES Lighting Handbook, 8th ed., 1993)
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from article Incandescent lamp
Encapsulated tungsten-halogen lamp with a section cut away, showing installation of the tungsten-halogen source.
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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 Flax
Flax plants (Linum usitatissimum) in bloom. (Photo by Howard F. Schwartz, Colorado State University)
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from article Flax
Flaxseeds. (Photo by Jose Hernandez, U.S. Department of Agriculture–Natural Resources Conservation Service PLANTS Database)
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from article Flax
Yellow wilted leaves of flax plants infected by Fusarium oxysporum. (Photo by J. A. Hoes, Oilseed Diseases Image Collection, Western Committee on Plant Disease, Winnipeg, Manitoba, Canada)
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from article Flax
Blighted and moldy flaxseeds. (Photo by J. A. Hoes, Oilseed Diseases Image Collection, Western Committee on Plant Disease, Winnipeg, Manitoba, Canada)
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from article Beer
Grains of (a) barley before malting and (b) hop plant. (Credit: U.S. Department of Agriculture)
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from article Beer
Fermentation tanks. (Credit: ClarkandCompany/Getty Images)
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from article Cassiduloida
Major features of cassiduloids as shown on a test of Cassidulus caribaearum (a Caribbean species) with spines (upper two figures) and without spines (lower two figures). Top (aboral) views are shown on the left; bottom (oral) views are shown on the…
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from article Peppermint
Peppermint (Mentha piperita). (Photo by Michael Thompson, Agricultural Research Service, U.S. Department of Agriculture)
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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 Liquid chromatography
Chromatogram showing the separation of various ethoxylates (nonionic surfactants) from an environmental water sample by liquid chromatography. EO = ethoxylate. Cx = alkyl. OP = octylphenol. NP = nonylphenol. (Credit: U.S. EPA)
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from article Rhynchosauria
Skull (dorsal view) of the rhynchosaur Paradapedon.
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from article Citron
Citron (Citrus medica), including cross sections of the fruit. (Photo courtesy of California Citrus Clonal Protection Program)
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from article Foodborne disease
Trichrome-stained photomicrograph of a Giardia lamblia trophozoite (a growing stage in the life cycle of certain protozoan parasites). This microorganism often causes giardiasis (a diarrheal foodborne illness). (Credit: Melanie Moser/Centers for…
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from article Foodborne disease
A cluster of norovirus particles. (Credit: Charles D. Humphrey/Centers for Disease Control and Prevention)
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from article Foodborne disease
Colored scanning electron micrograph showing Salmonella enterica bacteria (serotype Typhimurium; colorized red) invading an immune cell (colorized yellow). This bacterial species commonly causes food-associated gastroenteritis. (Credit: National…
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from article Foodborne disease
Close-up view of Campylobacter jejuni bacteria. This scanning electron microscope image shows the characteristic spiral (or corkscrew) shape of C. jejuni cells. (Credit: De Wood and Chris Pooley/Agricultural Research Service, U.S. Department of…
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from article Spider silk
Silk fibers and silk glands in Araneus diadematus. (Reprinted from F. Vollrath, Strength and structure, Rev. Mol. Biotechnol., 74(2):67–83, 2000)
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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 Blattodea
American cockroach (Periplaneta americana). (Credit: Antagain/iStockphoto/Getty Images)
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from article Blattodea
The Madagascar hissing roach (Gromphadorhina portentosa) can compress its body and force air through modified spiracles (breathing pores), producing a loud hissing sound. (Credit: Alamy)
