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Calcite concretion formed in Paleocene marine siltstone, Moeraki beach, New Zealand. Uncemented siltstone has been eroded away by wave action. Concretion is about 2 m (7 ft) in diameter, which is unusually large.

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from article Authigenic minerals

Scanning electron micrograph of authigenic kaolinite. The clay mineral formed from dissolution of calcic feldspar in a Miocene sandstone, San Joaquin basin, California.

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from article Authigenic minerals

Scanning electron micrograph of clinoptilolite zeolite (white crystals) on smectite-coated (dark background) sand grains. Sample is from Paleocene volcanic sandstone, Baja California, Mexico.

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from article Barracuda

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from article Cardiovascular system

Computerized artwork of the human cardiovascular system, including the heart, lungs, and major arteries and veins. (Credit: Science Photo Library RF/Getty Images)

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from article Cardiovascular system

Diagram of the heart and major vessels of a fetus just before birth. Small arrows within the liver indicate alternative blood routes by way of hepatic sinusoids. (Credit: Based on an original drawing by B. M. Patten; copyright © McGraw-Hill…

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from article Cardiovascular system

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from article Cardiovascular system

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from article Cardiovascular system

Illustration of the human cardiovascular system, which involves pulmonary circulation and systemic circulation. Red vessels transport oxygenated blood; blue vessels transport deoxygenated blood; and purple vessels are involved in gas exchange.…

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from article Sonobuoy

Launch of a sonobuoy from an antisubmarine warfare (ASW) aircraft. (a) In flight. (b) Buoy strikes the water in a nearly vertical attitude. (c) Antenna and hydrophone are positioned automatically.

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from article Hematologic disorders

Myelophthisic anemia results from a space-occupying lesion in the bone marrow, which hinders hematopoiesis (the process by which the cellular elements of the blood are formed). In this photomicrograph, the bone marrow space is expanded, and the…

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from article Hematologic disorders

Scanning electron micrograph of (top) an elongated, flattened sickle cell and (bottom) a normal red blood cell. (Credit: Callista Images/Image Source/Getty Images)

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from article Hematologic disorders

Colored scanning electron micrograph of round leukocytes from a patient with leukemia. (Credit: Steve Gschmeissner/Science Photo Library)

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from article Allometry

Allometric lines for the mass of some organs across mammal species. (These are best-fit lines: individual species may lie above or below them.) Note that the skeleton is disproportionately heavy in large species (positive allometry), whereas the…

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from article Allometry

Three different types of allometry. Each curve shows the growth allometry of organ size in a different species. The adults of each species show static intraspecific allometry. The circles indicate a particular stage of the life history (for example,…

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from article Engineering geology

Diagram of a typical landslide monitoring instrumentation. (Credit: USGS)

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from article Engineering geology

Rock-physics laboratory instrumentation for testing triaxial shear strength. Shearing stresses tend to separate portions of the rock (or soil) mass. Faults and folds are examples of shear failures in nature. In engineering structures, every…

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from article Engineering geology

Geologic map that can be used to identify geologic hazards and for land-use planning. (Credit: USGS)

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from article Sequence stratigraphy

Seismic reflection characterization. (a) Seismic transect across the western margin of Bimini Bank, Bahamas Platform, showing variations in seismic facies. Note the poorly reflective rocks at lower right, representing a sedimentary basement bounded…

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from article Sequence stratigraphy

Clastic-dominated sequence. (a) Model for clastic-dominated sequences on an extensional continental margin, showing the key stratigraphic surfaces and the four major systems tracts that develop within each sequence. Double-headed arrows show three…

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from article Cartography

Paper and smartphone maps for navigation. (Credit: Mmaxer/Shutterstock)

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from article Cartography

Distribution of chronic wasting disease of the deer family in North America, April 2018. (Credit: Bryan Richards, USGS National Wildlife Health Center)

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from article Cartography

Computer rendering of the topography of the 48 contiguous United States based on 12 million elevations. (USGS)

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from article Xenophyophorida

Xenophyophorids. (a) Stannoma dendroides. (b) Stannophyllum zonarium. (c) Psammetta erythrocytomorpha, section showing interlacing tubules and dark inclusions of uncertain nature.

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from article Fungi

Porcini mushrooms (Boletus edulis) are members of the Basidiomycota division of Fungi. (Credit: Digoarpi/Shutterstock)

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from article Fungi

Spore types (upper illustrations) and structures of parent mycelia (lower illustrations) in fungi.

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from article Fungi

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from article Fungi

Sexual mechanisms in fungi: (a) gametic copulation; (b) gametangial copulation; (c) gamete-gametangial copulation; and (d) somatic copulation.

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from article Fungi

Colorized scanning electron micrograph of brewer's yeast cells (Saccharomyces cerevisiae). This fungus consists of single vegetative cells, and small daughter cells can be seen budding off from the larger cells. Brewer's yeast is used in the…

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from article Oolite

Plain light micrographs of thin sections of ooids and pisoids. (a) Oolite of Mississippian age, southwestern Indiana. (b) Pisoids from the hot springs of Karlovy Vary (Carlsbad), Czech Republic. The lower right pisoid shows a rock fragment nucleus…

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from article Medical bacteriology

Microscopic view of bacterial pneumonia, which is a type of pneumonia caused by bacterial infection. (Credit: Stocktrek Images/Corbis)

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from article Medical bacteriology

Bacteria culture growth on agar medium in a petri dish. (Credit: Sompraaong0042/Shutterstock)

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from article Genetically modified organism (GMO)

Transgenic zebrafish cells. Green fluorescent protein (GFP) is a fluorescent protein first discovered in the jellyfish Aequorea victoria. GFP is commonly used as a reporter of gene expression in other species. Here, GFP is expressed by zebrafish…

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from article Genetically modified organism (GMO)

Genome editing technologies. In particular, targeted nucleases are a powerful tool for precise genome editing in GMOs. Among these tools are (a) transcription activator-like effector nucleases (TALENs), (b) zinc-finger proteins (ZFPs), (c) homing…

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from article Channelrhodopsin

Three-dimensional (3D) protein crystal structure of channelrhodopsin variant C1C2. (Image courtesy of Protein Data Bank 3UG9, Molecular Modeling Database 96737)

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from article Melatonin

Chemical structure of melatonin (C13H16N2O2).

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from article Plague

Plague ecology in the United States. The left panel shows how plague occurs in nature among rodents. The right panel shows how plague is spread from rodents to humans and domestic animals. (Credit: Centers for Disease Control and Prevention)

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from article Atmospheric tides

Variation of tidal amplitudes with height. The shaded area shows the general range of solar diurnal and semidiurnal amplitudes (on a logarithmic scale) as a function of height. The line corresponds to amplitude varying inversely with the square root…

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from article Sloan Digital Sky Survey

Sloan Digital Sky Survey (SDSS) 2.5-m (98-in.) telescope at Apache Point Observatory, New Mexico. The secondary mirror is visible in the center of the aperture. The square structure surrounding the primary and secondary mirrors shelters them from…

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from article Sloan Digital Sky Survey

Spectrum of a galaxy (image inset) receding at around 6000 km s−1 (3700 mi s−1), or about 2% of the speed of light. The vertical line shows the wavelength at which one expects to observe the emission line Hα for an object at rest (656.3 nm). The…

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from article Sloan Digital Sky Survey

Distribution of galaxies within 4° of the celestial equator from the SDSS. In this polar plot, the radius indicates the distance from the Milky Way, and the angle is the right ascension. The diameter shown is 8 × 109 light-years. Blank areas have…

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from article Sloan Digital Sky Survey

Map of stars in the SDSS. Grayscale signifies density of stars on the sky. Several streams of stars are noticeable. Areas in background are those unobserved by the survey. (Courtesy of Vasily Belokurov; Sloan Digital Sky Survey)

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from article Sloan Digital Sky Survey

Image of Canes Venatici I, a recently discovered satellite of the Milky Way Galaxy. (Photo courtesy of Vasily Belokurov; Sloan Digital Sky Survey)

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from article Sloan Digital Sky Survey

Hubble sequence of galaxies, as observed by the SDSS. Elliptical galaxies (types marked E0 and E6) are old, spheroidal, and very massive. Spiral galaxies are on average less massive. While some spiral galaxies (S0 and Sa) tend to have very little…

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from article Nursing

Nursing provides physical and emotional care to ailing individuals. (Credit: Fuse/Getty Images)

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from article Musk-ox

Musk-ox (Ovibos moschatus). (Credit: Brent Huffman/Ultimate Ungulate Images)

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from article Binary and multiple asteroids

Asteroid 121 Hermione and its moonlet companion observed with the adaptive optics system mounted on the European Southern Observatory's Very Large Telescope [consisting of four 8.2-m (25-ft) telescopes] at six different times. The satellite revolves…

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from article Phospholipases

Sites at which different phospholipases cleave the typical phospholipid phosphatidylcholine. F1 and F2 are long-chain fatty acids esterified at positions 1 and 2 of the glycerol backbone, respectively.

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from article Phospholipases

Mechanisms by which activated receptors coupled to phospholipase C (PLC) through heterotrimeric G proteins produce their physiological responses. Terms: PIP2, phosphatidylinositol bisphosphate; DAG, diacylglycerol; PKC, protein kinase C; IP3,…

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from article Human-factors engineering

Human-factors engineers design modern computer equipment, including ergonomic keyboards and mouse devices, to accommodate the varied physical contours and dimensions of the human hand. (Credit: JG Photography/Alamy)

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from article Human-factors engineering

Human-factors engineering addresses problems related to the design of seats, workplaces, and consoles in terms of a user's physical size, comfort, strength, and visibility. (Copyright © McGraw-Hill Education)

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from article Human-factors engineering

Cognitive engineering and the development of new technology applications.

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from article Marten

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from article Human ecology

Shacks and garbage along a dirty river in a slum in Manila, Philippines. Human ecology encompasses how individual people and their communities interact with their particular environment. In many cases, though, humans have created polluted…

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from article Human ecology

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from article Igneous rock

Some plutonic rock names and their volcanic equivalents.

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from article Igneous rock

IUGS classifications of gabbroic rocks (triangle AQP) and ultramafic rocks (triangle AFP). (From A. Streckeisen, To each plutonic rock its proper name, Earth Sci. Rev., 12:1–33, 1976)

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from article Igneous rock

Photomicrographs of common igneous rock textures. (a) Hypidiomorphic-granular texture. (b) Porphyritic texture. (c) Pyroclastic texture. Width of field of view is 3.2 mm (0.125 in.).

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from article Igneous rock

Photomicrographs of some mineral textures in igneous rocks. (a) Poikilitic texture in alkali feldspar. (b) Perthitic texture in alkali feldspar. (c) Zoned texture in plagioclase. Width of field of view is 3.2 mm (0.125 in.).

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from article Igneous rock

Some volcanic structures. (a) Lava plateau with flat-lying basalt lava flows, near Sprague, Washington. (b) Composite volcanoes, Atitlan (left) and Toliman in Guatemala. (c) Columnar jointing in andesite near Lost Creek Dam, Oregon. (d) Pillow…

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from article Igneous rock

Some plutonic structures.

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from article Saturn

Saturn viewed on April 25, 2016 by the Cassini orbiter as the planet neared its northern hemisphere's summer solstice. (Credit: NASA/JPL-Caltech/Space Science Institute)

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from article Saturn

Saturn viewed from the Cassini orbiter. The soft velvety appearance of the low-contrast banded structure is due to scattering by the haze layer above the planet's cloud deck. The image has been rotated so that north is up. The Sun illuminates Saturn…

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from article Saturn

Presentations of Saturn's ring system over the course of a Saturnian year.

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from article Saturn

Images from the Cassini spacecraft show the life cycle of Saturn's great northern storm beginning on December 5, 2010, when a small white cloud appeared at latitude 33°N. In these views, the Cassini spacecraft was in the ring plane, and the ring…

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from article Saturn

A natural color view of Saturn's rings from the Cassini Orbiter taken on August 22, 2009, at a distance of 2.05 million km (1.27 million mi) from Saturn. (Credit: NASA/JPL/Space Science Institute)

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from article Saturn

Structure of Saturn's rings observed by two different approaches. The upper half of the image is a natural-color mosaic of images by the Cassini narrow-angle camera. Such images have information about how ring structure differs both with distance…

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from article Saturn

Saturn's F ring viewed from the Cassini orbiter. Features resembling drapes and kinks are visible, and several distinct ringlets are present, in addition to the bright knotted core of the ring. The structure in the ring and its strands has been…

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from article Saturn

Titan superimposed in front of Saturn, captured by the Cassini spacecraft. (Credit: NASA/JPL-Caltech/Space Science Institute)

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from article Saturn

The satellite Phoebe taken during Cassini's flyby on June 11, 2004. The image shows evidence for the theory that Phoebe is an ice-rich body coated with a thin layer of dark material. (Credit: NASA/JPL/Space Science Institute)

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from article DNA methylation

In humans and other mammals, DNA methylation involves the addition of a methyl group to a cytosine ring, forming methylcytosine. The methylation is carried out by a DNA methyltransferase (DNMT). (Copyright © McGraw-Hill Education)

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from article DNA methylation

Transcriptional silencing via DNA methylation. The methylated configuration blocks proteins that activate gene transcription, preventing them from acting as gene activators. (Copyright © McGraw-Hill Education)

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from article Microtechnique

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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 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 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)

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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 Phyllite

Shiny folded phyllite with mica crystals too small to be seen with the naked eye. (Credit: Stephen Reynolds)

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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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