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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 Electric filter

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from article Electric filter

Passive, lumped-element filters. (a) RC low-pass filter. (b) LC band-pass filter.

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from article Electric filter

Ladder structure. (a) Overall structure with alternating series and shunt arms. (b) LC circuit whose impedance contains both a finite-frequency pole and a zero. Such circuits are used in the series and shunt arms of the ladder structure.

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from article Electric filter

Mechanical filter.

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from article Electric filter

Single-amplifier filters. (a) Low-pass Sallen-Key filter. (b) Low-pass, infinite-gain, single-amplifier filter. (c) Cascade of second-order filter realizations.

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from article Electric filter

Multiple-amplifier filters. (a) State-variable (KHN) filter. (b) Tow-Thomas filter.

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from article Electric filter

Simulated-inductor realization of fifth-order high-pass filter. (a) RLC prototype, normalized for cutoff frequency of 1 rad/s (0.159 Hz). (b) Direct active-RC realization.

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from article Satellite television broadcasting

Direct broadcasting television satellite system.

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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 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