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from article Eclipse
The August 21, 2017 total solar eclipse, as seen from Hopkinsville, Kentucky, USA at 2:25 p.m. EDT. (Credit: NASA)
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from article Eclipse
Circumstances of solar and lunar eclipses (not to scale).
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from article Eclipse
Diamond-ring effect at the beginning of totality during the solar eclipse of July 11, 2010, observed from Easter Island in the middle of the Pacific Ocean. (Credit: Jay M. Pasachoff/Science Faction, Muzhou Lu, and Craig Malamut, Williams College…
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from article Eclipse
Total solar eclipse of July 11, 2010, observed from Easter Island in the Pacific Ocean. (a) Image composited from several exposures using radial filters in order to show a wide dynamic range of intensity of the corona and to bring out the structures…
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from article Eclipse
Solar eclipse of April 8, 2005, observed during totality from a ship in the mid-Pacific Ocean, west of the Galápagos Islands. (Credit: Jay M. Pasachoff and Dava Sobel/Science Faction)
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from article Eclipse
Paths of all total solar eclipses from 2001 through 2025. The point of greatest eclipse is indicated by an asterisk on each eclipse path. (Credit: Eclipse map by Michael Zeiler, www.eclipse-maps.com. Eclipse paths by Xavier Jubier, xjubier.free.fr.)
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from article Eclipse
Cross section through the Earth's shadow cone (umbra) at the Moon's distance, showing the motion of the Moon at three types of lunar eclipses: penumbral eclipse, partial umbral eclipse, and total umbral eclipse.
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from article Eclipse
Stages of the total lunar eclipse of December 21, 2010. (Credit: Glenn Schneider)
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from article Eclipse
Total lunar eclipse of December 9, 1992, which was so dark that it rendered the Moon nearly invisible during totality. (Credit: F. Espenak)
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from article Pituitary gland disorders
Anatomy of the human pituitary gland, which is attached to the base of the brain. (Copyright © McGraw Hill)
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from article Pituitary gland disorders
Infarction (obstruction of the blood supply) of the pituitary gland. This pituitary gland is almost entirely infarcted. Only a thin rim of viable cells remains (arrow). Pituitary infarcts can occur during pregnancy (Sheehan's disease) or as a result…
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from article Strychnos
Strychnos nux-vomica: close-up view of leaves and flowering branch. (Photo courtesy of Dinesh Valke)
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from article Clathrate compounds
Schematic drawing of the lattices of (a, c) urea and (b, d) thiourea; c and d show accommodation of unbranched and branched paraffin chains, respectively.
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from article Clathrate compounds
Molecular model of α-dextrin–iodine compound seen in the direction of the c axis, that is, in the direction of the iodine chains, which lie in channels.
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from article Planet
An artist’s impression of a mere sampling of the planetary diversity expected to exist in nature. [Credit: C. Pulliam & D. Aguilar (CfA)]
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from article Planet
Plan of the solar system's major and dwarf planets. (a) Solar system out to Neptune. (b) Dwarf planets in the outer solar system (Credit: Emily L. Schaller)
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from article Planet
Orbital elements, which determine the position of a planet in its orbit and the orientation of the orbit in space. Symbols explained in text.
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from article Planet
The interiors of the 8 planets and the dwarf planet Pluto. Mercury, Venus, Earth, and Mars are characterized by dense, metallic cores and lower-density mantles and crusts. Jupiter and Saturn have compositions that mimic the Sun's, though…
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from article Planet
Complex lunar crater Bullialdus, 60 km (37 mi) in diameter, shows terraced sides, a central peak, and a flat bottom. It may be compared to the small (less than 8 km or 5 mi) crater in the foreground, which is simple and bowl-shaped. (Credit: NASA)
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from article Planet
Ultraviolet images from the Hubble Space Telescope, which reveal auroral emission surrounding the north magnetic pole of Jupiter. [Credit: NASA, ESA, and J. Nichols (University of Leicester)]
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from article Neandertals
Neandertal cranium excavated from Forbes' Quarry, Gibraltar. Note the pronounced brow ridges, large braincase, and receding forehead. (Credit: Clive Finlayson/Gibraltar Museum)
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from article Neandertals
Gorham's Cave, Gibraltar, is the last known site of Neandertal occupation, being dated possibly to 30,000 years ago. (Credit: Clive Finlayson/Gibraltar Museum)
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from article Neandertals
Reconstructed skull of a Neandertal from the cave at La Chapelle-aux-Saints, France. (Credit: Illustration adapted from an original drawing by M. F. Ashley Montagu)
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from article Wilkinson Microwave Anisotropy Probe
Wilkinson Microwave Anisotropy Probe (WMAP) spacecraft. (Courtesy of NASA/WMAP Science Team)
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from article Wilkinson Microwave Anisotropy Probe
WMAP sky-scan strategy. (a) Location of the satellite relative to the Earth and Sun (not to scale), and the orientation of the satellite and of the lines of sight to the spots on the sky focused by the primary reflectors, which continually changed…
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from article Wilkinson Microwave Anisotropy Probe
WMAP full-sky CMB anisotropy map. The microwaves captured in this picture from WMAP are from when the universe was 378,000 years old, over 13 × 109 years ago. It is a “baby picture” of the universe, equivalent to taking a picture of an 80-year-old…
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from article Folic acid
Chemical structure of folic acid (C19H19N7O6). (Copyright © McGraw Hill)
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from article Digenea
Diagrams of various adult types of digenean trematodes. (After R. M. Cable, An Illustrated Laboratory Manual of Parasitology, Burgess, Minneapolis, 1940)
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from article Digenea
Digenean trematode life cycle. (After R. M. Cable, An Illustrated Laboratory Manual of Parasitology, Burgess, Minneapolis, 1940)
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from article Electrolysis
Electrolysis cell in which the electrolyte is a solution of sodium chloride.
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from article Ultracentrifuge
Diagram of an electrically driven analytical ultracentrifuge. (Beckman Instruments)
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from article Ultracentrifuge
Analytical rotor. (Beckman Instruments)
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from article Ultracentrifuge
Fixed-angle preparative rotor and tubes. (Beckman Instruments)
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from article Animal testing
Mice are the most commonly used vertebrate species in animal testing and research. (Credit: Dolores Bonaparte)
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from article Animal testing
The use of animals in biomedical research remains essential, but the handling of these sentient beings must be done humanely to minimize and prevent animal harm. (Credit: U.S. Department of Agriculture)
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from article Common cold
Adenovirus structure. An adenovirus binds to the host cell via its fiber through the knob at the end of the fiber "spikes" on the capsid (protein coat) surface. (Credit: M. K. Cowan and H. Smith; copyright © McGraw Hill)
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from article Common cold
Human respiratory system. Common cold viruses enter through the nose, mouth, or eyes, infecting epithelial cells of the oropharynx. (Credit: M. K. Cowan and H. Smith; copyright © McGraw Hill)
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from article Common cold
Life cycle of a double-stranded DNA virus, such as an adenovirus. The virus attaches to specific receptors, after which it is taken up by the cell. Following entry into the cell, the viral capsid (protein coat) is digested, releasing DNA, which…
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from article Common cold
Electron micrograph (tinted green) of human coronavirus 229E particles. Coronaviruses are named for the corona, or halo, surrounding the capsid (protein coat). The crown-like corona results from the presence of viral spikes protruding from the viral…
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from article Anthrax
A color-enhanced scanning electron micrograph showing splenic tissue from a monkey with inhalation anthrax. Rod-shaped bacilli of Bacillus anthracis (yellow) and an erythrocyte (red) are shown. (Credit: Arthur Friedlander/National Institute of…
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from article Anthrax
Micrograph (stained with hematoxylin and eosin) showing submucosal hemorrhage in the small intestine of a person fatally affected by gastrointestinal anthrax. (Credit: Marshal Fox/Centers for Disease Control and Prevention)
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from article Triple point
Phase diagram for water, showing gas, liquid, and several solid (ice) phases; triple points at A, B, and C. The pressure scale changes at 101 kilopascals from logarithmic scale at low pressure to linear at high pressure.
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from article Tumor virus
Under certain conditions, human papillomaviruses are capable of causing cancer in humans. (Credit: Laboratory of Tumor Virus Biology, National Cancer Institute)
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from article Macrocyclic compound
Macrocyclic structures. (a) Two crown ethers. (b) A basic structure for three cryptands. (c) A lariat ether. (d) All-aliphatic spherand. (e) All-aromatic spherand.
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from article Macrocyclic compound
Macrocycles with various structural features. (a) Bicyclic cryptand (ditopic receptor). (b) Calix[6]arene; R represents a functional group. (c) Cavitand. (d) Carcerand. (e) Cyclophanes.
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from article Macrocyclic compound
Tetramers. (a) Resorcinarene having the rctt conformation. (b) Pyrogallolarene having the rccc conformation.
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from article Macrocyclic compound
The metal cation is the guest and the organic structure is the host in (a) 18-crown-6 complex of potassium cation (K+) and (b) sodium (Na+) complexed by a calix[4]arene.
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from article Macrocyclic compound
Complexing species. (a) Dibinaphtho-22-crown-6. (b) R,R-dibinaphtho-22-crown-6 complex of phenethylammonium chloride.
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from article Macrocyclic compound
Affinities for anions and cations shown for (a) pyrrole and (b) furan-derived cyclic tetramers.
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from article Macrocyclic compound
Amphiphiles. (a) Crown ether-steroid amphiphile. (b) Crown ether bolaamphiphile.
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from article Salicylate
Chemical structures of (a) salicylate, the conjugate base of (b) salicylic acid, and the nonsteroidal anti-inflammatory drug (NSAID) (c) acetylsalicylic acid (aspirin).
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from article Meningococcus
A photomicrograph reveals the presence of the bacterium Neisseria meningitidis, which can be pathogenic, leading to meningococcal meningitis. (Credit: James Volk/Centers for Disease Control and Prevention)
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from article Marcus equation
Free-energy plot for an electron-transfer reaction with zero standard free-energy change (an electron self-exchange reaction).
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from article Marcus equation
Free-energy plot for an electron-transfer reaction when the free-energy change (|Δ G °|) is less than the reorganization parameter (λ).
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from article Lead
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from article Lead
Galena (lead sulfide, PbS) is an ore mined for lead. (Credit: USGS)
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from article Oxygen toxicity
The dual effect of oxygen on biologic activity. Organisms that avail themselves of the enormous metabolic advantages provided by dioxygen (O2) must defend themselves against its toxicity. (Copyright © McGraw Hill)
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from article Hyperbolic geometry
Examples of simple hyperbolic knots and links. (a) Figure-8 knot. (b) Whitehead link.
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from article Spinal cord disorders
Human spinal cord. (Copyright © McGraw-Hill Education)
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from article Chicxulub impact crater
Bouguer gravity anomaly map over the Chicxulub impact crater. The coastline is designated by a thin white line, cenotes (natural pits) and sinkholes are designated by black dots, and the city of Mérida and the town of Chicxulub Puerto are designated…
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from article Chicxulub impact crater
Seismic line imaging of what lies beneath the seafloor, showing the Chicxulub impact crater. The crater includes many faults that can be grouped into an exterior ring fault, a series of outer ring faults, and a series of inner ring faults. Within…
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from article Bioassay
In conducting bioassays, researchers often employ laboratory culture tests, which use, for example, bacteria cultured in a petri dish (usually to model an effect on the organism of interest or on some basic cellular function). (Credit:…
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from article Surfactant
Foam blankets typically contain less than 1% surfactant to produce a stable foam that blocks oxygen for fire suppression. (Credit: U.S. Navy)
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from article Matrix isolation
Vacuum-vessel base cross section for matrix photoionization experiments. 10 K = −263°C or −442°F.
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from article Matrix isolation
Schematic plan view of the matrix assembly for pulsed-laser ablation.
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from article Matrix isolation
Infrared and Raman spectra of lithium superoxide, Li+O2−, using lithium-7 and 30% 18O2, 50% 16O18O, and 20% 16O2 at concentrations of Ar/O2 = 100. The Raman spectrum was recorded by using 200 mW of 488-nm excitation at the sample.
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from article Matrix isolation
Visible and ultraviolet absorption spectra of naphthalene samples in solid argon at 20 K. Upper curves show Ar/CCl4/N = 3000/4/1, and lower curves show the same sample after 15 s of irradiation at 220–1000 nm from a high-pressure mercury arc.
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from article Matrix isolation
Infrared spectra in the 2000–1200 cm−1 region for the products of the reactions of laser-ablated Al atoms with pure hydrogen co-deposited at 3.5 K. (a) Spectrum obtained from initial deposited sample. (b) Spectrum after >290 nm irradiation. (c)…
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from article Dental caries
The disease of dental caries or tooth decay is largely preventable. Bacteria colonize the tooth surface and often produce sufficient acids to demineralize the tooth's enamel. Then, dental plaque can build up on the tooth's surface, creating…
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from article Dental caries
Early caries (cavity) lesion of a primary first molar (indicated by the arrow). (Copyright © McGraw Hill)
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from article Ursa Minor
Modern boundaries of the constellation Ursa Minor, the Little Bear. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension…
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from article Venus
Venus compared to Earth in size. Note that the image of Venus at left does not include the planet's thick, opaque atmosphere. The image was obtained by the Magellan spacecraft that orbited Venus from 1990 to 1994. Magellan used cloud-penetrating…
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from article Venus
Venus viewed in visible light by the Galileo spacecraft during a 1990 gravity assist flyby on the probe's ultimate journey to Jupiter. (Credit: NASA)
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from article Venus
Global Venus clouds, as viewed in the ultraviolet from Venus Express. These features can be used to track winds and atmospheric motion at the cloud tops. Convection clouds can be seen near the equator (top of image), whereas streaky brighter clouds…
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from article Venus
Inhomogeneities in the total thickness of the clouds between 48 and 70 km (30 and 43 mi) show up in the near-infrared. These clouds, seen only at night, are backlit from the hot atmosphere below it (similar to a Chinese lantern), where bright…
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from article Venus
Perspective view of the southern boundary of Laksmi Planum, a plateau 2.5–4.0 km (1.5–2.5 mi) high. (Credit: NASA/JPL)
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from article Venus
Magellan image of the central and northern parts of the highland region Ovda Regio (north at top). Ridges running approximately east-west (horizontally) have been interpreted as resulting from crustal shortening (compression). Ridges are cut by…
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from article Venus
Perspective view of a portion of the Western Eistla Regio, with a rift valley in the foreground and the volcanoes Gula Mons (right) and Sif Mons (left) on the horizon. (Credit: NASA/JPL)
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from article Venus
Sapas Mons, one of several large volcanic edifices that compose the broad equatorial rise known as Alta Regio. (Credit: NASA/JPL)
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from article Venus
Computer-simulated perspective view, based on data from Magellan spacecraft, showing three impact craters in the northwestern portion of Lavinia Planitia with diameters ranging from 37 to 63 km (23 to 39 mi). (Credit: NASA/JPL)
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from article Platinum
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from article Medical control systems
Diagram of selected portions of the human motor control system. (After G. L. Gottlieb, D. M. Corcos, and G. C. Agarwal, Strategies for the control of voluntary movements with one mechanical degree of freedom, Behav. Brain Sci., 12:189–250, 1989)
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from article Medical control systems
Electric hand, a myoelectric prosthesis. (a) Two views of the hand, 2.5 in. (6 cm) across the knuckles, with the cover removed in one view to show the electric motor drive circuit. (b) Child using the electric hand. (Hugh Steeper Ltd.)
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from article Medical control systems
Hybrid control system using both functional electrical stimulation and orthoses. (a) Hierarchical control scheme. (b) Braces in use. (c) Detail of leg brace. (After Y. Kim and F. A. Spelman, eds., Images of the Twenty-First Century: Proceedings of…
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from article Medical control systems
Autoclavable pacemaker with a lithium silver vanadium pentoxide battery. (After W. Greatbatch, Pacemaker power sources, IEEE Eng. Med. Biol. Mag., 3(2):15–19, June 1984)
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from article Medical control systems
Automatic implantable cardioverter defibrillator (AICD) system with pulse generator, leads, and external programmer. (S. Nisam, Cardiac Pacemakers, Inc.)
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from article Overvoltage
Current density–potential curve.
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from article Overvoltage
Current density curves. (a) Experimental current–potential curve showing theoretical cathodic and anodic components. (b) Tafel plot.
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from article Microbiome
Profile of the human microbiome by anatomical niche. DNA sequence analysis reveals the relative abundances of the six most abundant bacterial phyla in the human body. The phyla shown represent 99.6% of the sequences sampled. Cyanobacteria were…
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from article Microbiome
Cup-and-ball diagrams to conceptualize the ecosystem equilibrium of the microbiota. (a) A diverse microbial ecosystem requires a large amount of applied force (blue arrow; for example, an antibiotic disturbance) to push it out of its stable…
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from article Acquired immune deficiency syndrome (AIDS)
HIV targets helper T lymphocytes. This illustration shows HIV cells attaching to CD4 coreceptors on a helper T lymphocyte. The depletion of these helper T lymphocytes leads to acquired immune deficiency syndrome (AIDS). (Copyright © McGraw Hill)
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from article Acquired immune deficiency syndrome (AIDS)
Scanning electron micrograph of HIV-1 virions budding from a cultured lymphocyte. Multiple round bumps on the cell surface represent sites of assembly and budding of virions (green spheres). (Credit: C. Goldsmith/Centers for Disease Control and…
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from article Radium
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from article Trauma
Traumatic injury to the head can lead to concussions. Head injuries are frequently seen in individuals who participate in contact sports, such as football. (Credit: JoeSAPhotos/Shutterstock)
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from article Auger electron spectroscopy
Schematic diagram of an Auger electron being ejected from a carbon atom for a KL2L2 transition. Round forms are electrons.
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from article Auger electron spectroscopy
Integral (upper) and differential (lower) mode spectra of sputter-cleaned copper with the most intense peaks identified: A, M2,3M4,5M4,5; B, L3M4,5M4,5; C, L3M2,3M4,5; D, L3M2,3M2,3.
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from article Reproductive system disorders
Overview of the human female reproductive system. (Copyright © McGraw-Hill Education)
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from article Reproductive system disorders
Overview of the human male reproductive system. (Copyright © McGraw-Hill Education)
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from article Reproductive system disorders
The ovaries, fallopian tubes, uterus, cervix, and vagina are sites affected by disorders of the human female reproductive system. (Copyright © McGraw-Hill Education)
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from article Reproductive system disorders
The testicles (testes), epididymis, vas deferens and seminal vesicles, prostate gland, urethra, and penis are sites affected by disorders of the human male reproductive system. (Copyright © McGraw-Hill Education)
