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from article Regolith
Diagram showing the components of residual regolith.
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from article Manganese
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from article Animal virus
Electron micrograph of negatively stained, purified bovine papilloma virions with icosahedral symmetry. (Credit: David Hill and John P. Sundberg)
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from article Animal virus
Electron micrograph of a thin section of chicken cells containing crystalline inclusion bodies formed by an avian reovirus during infection. (Credit: David Hill and John P. Sundberg)
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from article Oscillatory reaction
Oscillatory behavior in a sulfuric acid medium containing potassium bromate, malonic acid, and cerous nitrate. The upper curve is the potential (in unspecified units) of a tungsten electrode and is related to the concentration ratio of…
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from article Oscillatory reaction
Rotating spiral bands of oxidation in a thin layer of solution containing the same reagents as in Fig. 1 except that the redox indicator ferrous phenanthroline has been substituted for cerous ion. (Courtesy of Prof. A. T. Winfree, University of…
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from article Oscillatory reaction
Layers of crystallization from an initially uniform magma in the Skaergaard Intrusion in Greenland. (From A. R. McBirney and R. M. Noyes, Crystallization and layering of the Skaergaard Intrusion, J. Petrol., 20:487–554, 1979)
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from article Heterodonta
Common heterodont bivalves. (Credit: Ronald V. Dimock, Jr.)
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from article Heterodonta
Common heterodont bivalves. (Credit: Ronald V. Dimock, Jr.)
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from article Restoration ecology
Restored sand dune habitat at Cape Canaveral, Florida. To help prevent erosion, 180,000 shrubs, including grasses, sunflowers, vines, sea grapes, and saw palmettos, were planted. (Credit: Dan Casper/National Aeronautics and Space Administration)
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from article Sol-gel process
Flow chart showing the sol-gel methods used to prepare bulk glasses, thin films of glass or ceramics, and powders; the powders are then sintered to produce ceramics.
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from article Tick virus diseases
A deer or black-legged tick (Ixodes scapularis). (Credit: U.S. Centers for Disease Control and Prevention)
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from article Tick virus diseases
Diagram depicting the life cycle of Ixodes scapularis. This deer tick can transmit viruses and other pathogens that cause a number of important diseases, including Lyme disease, anaplasmosis, and babesiosis. The risk of human infection is greatest…
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from article Tick virus diseases
World map depicting the locations of human tick-borne disease cases. Heartland, Bourbon, and Colorado tick fever virus cases are unique to North America. Powassan encephalitis cases are reported in North America and Russia. Tick-borne encephalitis…
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from article Tick virus diseases
Cases of Powassan encephalitis reported in the United States from 2006 to 2015. Most of the reported cases are in Minnesota, New York, and Wisconsin. (Credit: ArboNET, Arboviral Diseases Branch, U.S. Centers for Disease Control and Prevention)
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from article Anaerobic infection
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from article Degenerative neural diseases
Factors leading to degenerative neural diseases. Abbreviations: AD, Alzheimer's disease; AD/PD, Alzheimer's disease with parkinsonism; ALS, amyotrophic lateral sclerosis; DLB, dementia with Lewy bodies; FTD, frontotemporal dementia; MID,…
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from article Biological productivity
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from article Ergot and ergotism
Ergot life cycle. Parts a–d explained in text.
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from article Exotic viral diseases
A colorized negative stained transmission electron micrograph depicting a number of Marburg virus virions. Marburg virus disease is a rare, exotic viral disease that affects both humans and nonhuman primates. (Credit: Frederick A. Murphy/Centers for…
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from article Turnip
Purple Top turnip (Brassica rapa). (Credit: Stami Kieren Donovan; courtesy of Greenpatch Organic Seeds, Glenthorne, New South Wales, Australia)
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from article Dill
Flowering of dill (Anethum graveolens). (Photo courtesy of Forest and Kim Starr)
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from article Surface and interfacial chemistry
Scheme for reducing bacterial adhesion at an implanted biomaterial.
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from article Surface and interfacial chemistry
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from article Surface and interfacial chemistry
Microscopic surface structures. (a) Surface atoms occupying positions other than the bulk-terminated locations. The first interlayer spacing d12 is greater than the bulk interlayer spacing d34. The second interlayer spacing d23 is smaller than the…
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from article Surface and interfacial chemistry
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from article Surface and interfacial chemistry
Processes of electron spectroscopies. (a) Auger electron spectroscopy. A core-level electron is ejected by excitation from the incident high-energy electron. A second electron fills the vacancy left by the ejected electron. The third electron, the…
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from article Surface and interfacial chemistry
Typical configuration for application of optical spectroscopies to surface analysis. (a) Transmission. (b) External or specular reflection. (c) Internal reflection. I = reflected light intensity. I0 = initial light intensity. θi = angle of incidence…
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from article Surface and interfacial chemistry
Scanning tunneling microscopy and images for (a) constant-current mode and (b) constant-height mode; shown only in x dimension for simplicity.
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from article Fiber crops
Cotton, the most important textile fiber crop grown in the world. (Photo by Gary Kramer, Natural Resources Conservation Service, U.S. Department of Agriculture)
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from article Agricultural soil and crop practices
A crop of wheat is harvested by a combine harvester, which is a key machine that helps to implement various agricultural soil and crop practices. (Credit: Orientaly/Shutterstock)
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from article Agricultural soil and crop practices
A farmer in a tractor plowing the land for sowing. (Credit: Oticki/Shutterstock)
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from article Agricultural soil and crop practices
A tractor pulls a tilling machine. Stubble remains on the cornfield after the previous harvest. The soil must be properly tilled and cultivated for spring planting. (Credit: Lynn Betts, Natural Resources Conservation Service, U.S. Department of…
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from article Agricultural soil and crop practices
A cotton stripper, which harvests a cotton crop by stripping both the cotton and bolls from the stalks. (Credit: David Hughes/Getty Images)
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from article Lignin
Chemical formula representation of lignin, in which bold lines represent linkages between individual phenylpropane lignin monomer units, and shaded area represents the structure of a typical lignin model compound.
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from article Cicada
Brood IX periodical cicada in Athens, West Virginia. (Photo by Louie H. Yang)
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from article Cicada
Periodical cicada life cycle. Counterclockwise from lower left: Nymphal cicada feeding on plant roots belowground; ants and other detrivores feeding on dead cicada litterfall; teneral adult cicada recently emerged from the nymphal exuviae; bird…
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from article Cicada
Brood X periodical cicadas in Boyce, Virginia. (Photo by Louie H. Yang)
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from article Chromium
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from article Reproductive behavior
The mating of dragonflies encompasses a number of reproductive behaviors. Typically, the male is in front and the female is behind. If the female is willing to mate, she bends her abdomen forward to collect sperm from the male's accessory genitalia,…
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from article Reproductive behavior
Sage-grouse lek. Males stake out and defend territories on a traditional breeding ground. Females breed with males in selected territories. (Credit: U.S. Fish and Wildlife Service)
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from article Reproductive behavior
Two bull northern elephant seals fighting for dominance on the beach. (Credit: eoind/Getty Images)
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from article Reproductive behavior
Natterjack toad giving a mating call with its vocal sac expanded. (Credit: Bobby Bok)
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from article Reproductive behavior
Mating behavior of sticklebacks: (a) zigzag dance of a male, which leads a female to the nest; (b) the male stimulates the female in the nest to lay eggs; (c) schematic portrayal of the events in a courtship sequence. (Credit: Based on original…
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from article Reproductive behavior
Lordosis in a female rodent. When mounted, the females of many mammalian species adopt the lordotic posture, rendering copulation possible. Note the concave arching of the spine. (Credit: Based on an original drawing by L. C. Drickamer and S. H.…
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from article Reproductive behavior
A black-browed albatross feeding a chick. This is one example in which parental care may be extensive and prolonged. (Credit: Vetta/Getty Images)
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from article Toxin
Bacteria, such as Clostridium perfringens, often produce exotoxins that have deleterious effects on other organisms. Clostridium perfringens can cause foodborne disease by contamination of raw food materials. (Credit: Don Stalons/Centers for Disease…
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from article Toxin
Taiwan banded krait (Bungarus multicinctus). Certain elapid snakes known as kraits produce a venom that contains bungarotoxins, which are potent neurotoxins. (Credit: LiCheng Shih)
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from article Tree diseases
White pine blister rust (Cronartium ribicola) on eastern white pine (Pinus strobus). The blisters are masses of aeciospores (rust spores). (Photo courtesy of the Minnesota Department of Natural Resources Archive)
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from article Tree diseases
Chestnut blight on an American chestnut tree (Castanea dentata). This devastating disease is caused by Cryphonectria parasitica. (Photo by Joseph O'Brien, U.S. Department of Agriculture Forest Service)
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from article Tree diseases
Sulfur shelf fungus (Laetiporus sulphureus) on a tree. This wood-rotting fungus enters through tree roots and wounds, decaying the heartwood and sapwood of both hardwoods and softwoods. (Photo by William Jacobi, Colorado State University)
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from article Tree diseases
Symptoms of Dutch elm disease, caused by Ophiostoma ulmi, on an elm (Ulmus species). Typically, the foliage of an infected tree will begin to wither and yellow in the summer months. (Photo by Joseph O'Brien, U.S. Department of Agriculture Forest…
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from article Tree diseases
An American elm (Ulmus americana) infected with bacterial wetwood. The causal agent for this disease is Enterobacter nimipressuralis. The bacterial ooze (slime flux) is coming from a wound. (Photo by Mike Schomaker, Colorado State Forest Service)
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from article Celiac disease
Small bowel biopsy showing villous atrophy, which is found in individuals affected by celiac disease. (Credit: Ed Uthman/National Institutes of Health)
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from article Celiac disease
Antigen presentation of gliadin peptide to a CD4 T cell. Gliadin peptides bind to pockets P1, P4, P6, P7, and P9 of the (a) HLA-DQ8 and (b) HLA-DQ2 molecules. (Copyright © McGraw-Hill Education)
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from article Concussion
A three-dimensional magnetic resonance imaging (MRI) view of a human brain. The red-colored areas indicate temporary injury to the brain's covering following a concussion. (Credit: Lawrence Latour, Center for Neuroscience and Regenerative Medicine,…
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from article Barium
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from article Infertility
Illustration of (left) a normal ovary compared to (right) a polycystic ovary. A polycystic ovary can result from an imbalance of reproductive hormones. (Credit: Alila Medical Images)
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from article Infertility
Colored scanning electron micrograph of a deformed sperm cell. The cell has residual cytoplasm (denoted by the pinkish lump) below its head (top right). (Credit: Steve Gschmeissner/Science Photo Library/Alamy Stock Photo)
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from article Slime molds
Close-up view of slime mold on the ground. (Credit: Melinda Fawver/iStock/Getty Images)
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from article Slime molds
Plasmodial slime mold (Physarum polycephalum). (Credit: Jonatha M. Gott/Case Western Reserve University)
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from article Soap
Soap bars. (Credit: Getty Images)
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from article Industrial health and safety
Woodworker wearing safety goggles and hearing protection. (Credit: Shutterstock/Robert Kneschke)
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from article Coral bleaching
Coral reef at Kahului Point, Maui, Hawaii. (Left) Healthy corals are mostly brown or green in color as a result of the partner algae that live in the coral tissue. (Right) Because of heat stress to the corals, the algae can release toxic chemicals…
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from article Coral bleaching
Increases in temperature (in °F) in the surface waters of the Great Barrier Reef in Australia during the month of March since 1960. Water temperatures of just a few degrees above normal conditions have resulted in massive bleaching of corals.…
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from article Coral bleaching
Coral at Lizard Island, Australia. (Left) Bleached coral. (Right) Two months later, the coral had died and been overgrown by fleshy algae. (Credit: Richard Vevers and Christophe Bailhache/The Ocean Agency/XL Catlin Seaview Survey)
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from article Forensic dentistry
A dental identification from a homicide case. (a) Radiograph of the decedent exposed 18 years prior to her murder. (b) Radiograph of the decedent exposed 1 month prior to death. (c) Radiograph of the skeletal remains that were thought to be her.…
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from article Forensic dentistry
Four human bite marks on human skin. The American Board of Forensic Odontology (ABFO) #2 scale is present in each photograph to assist in documenting the size of the injury as well as the positioning of the camera. Bite (a) exhibits a higher degree…
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from article Molecular structure and spectra
Diatomic molecule with nuclei at distance Re apart, built from atoms of radii r and r′.
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from article Molecular structure and spectra
Electric dipole moment p of typical diatomic molecule as function of internuclear distance R; pe is the dipole moment at the equilibrium distance Re.
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from article Molecular structure and spectra
U(R) curve of ground electronic state of H2 with vibrational levels and dissociation continuum. D indicates the dissociation energy. Maximum v here is 14. ( After G. Herzberg, Molecular Spectra and Molecular Structure, vol. 1, 2d ed., Van Nostrand,…
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from article Molecular structure and spectra
Lowest vibrational levels of H2, O2, and I2, numbered by vibrational quantum number v. Vibration level spacings decrease with increasing v. Where spacing reaches zero, the molecule dissociates; dissociation level D is indicated for I2. Energies are…
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from article Molecular structure and spectra
Lowest rotational levels of H2, O2, and I2. For H2 and I2, J is the rotational quantum number, according to Eq. (5) in the text. O2 is in a Hund's case b triplet state, and the rotational levels are designated by N, where the total angular momentum…
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from article Molecular structure and spectra
Normal vibration modes of H2O and CO2. Synchronized displacements of atoms occur in proportion to lengths of the arrows. Diagram corresponds to snapshot taken at one phase of vibration.
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from article Molecular structure and spectra
Relation of band lines (lower part) [see Eqs. (8) and (9)] to rotational levels [see Eq. (6)] for a vibration-rotation band or an electronic band. In the former case, the upper and lower sets of rotational levels belong to two vibrational levels of…
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from article Molecular structure and spectra
Intensity distribution at several temperatures for a diatomic absorption band. Line positions are based on Eq. (9) assuming B′ = B′ for simplicity; frequency increases toward the left (opposite to Fig. 7). (a) and (b) correspond respectively to B…
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from article Molecular structure and spectra
Fundamental (1,0) vibration-rotation band of DCl in absorption showing the intensity distribution of the lines. The wavenumber scale increases to the right (in contrast to Fig. 8), so the R branch is to the right of the band origin, P branch to the…
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from article Molecular structure and spectra
Diatomic U(R) curves for three cases to explain the vibrational intensity distribution according to the Franck-Condon principle. The asymptote of each curve for large R corresponds to dissociation into atoms, with one or both atoms excited in the…
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from article Molecular structure and spectra
Assignment of individual transitions in the spectrum of the S-F stretching fundamental ν3 of sulfur hexafluoride (SF6) as resolving power increases. (a) Fourier transform spectrum; resolution of 0.06 cm−1 [2 GHz]. (b) Spectrum recorded with tunable…
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from article Rutabaga
The fleshy root and leaves of a rutabaga (Brassica napobrassica). (Courtesy of Real Seed Catalogue/Wild Garden Seed)
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from article Rheumatic fever
Photomicrograph of Streptococcus pyogenes illustrates its chain structure. Streptococcus pyogenes stains purple/violet after undergoing a Gram stain test. (Credit: Lisa Burgess; copyright © McGraw Hill)
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from article Cleft lip and cleft palate
Unilateral, incomplete cleft lip in which the notch does not extend to the nose.
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from article Cleft lip and cleft palate
Cleft palate, resulting in a fissure in the palate connecting the nasal and oral cavities.
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from article Protein
Molecular model illustration of myoglobin, which is a protein found in the muscle tissue of mammals. Myoglobin is an important protein that binds to and stores oxygen for use during strenuous exercise. The structure of the globin protein protects…
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from article Protein
The levels of protein structure, including primary, secondary (α-helices and β-sheets), tertiary, and quaternary. (Copyright © McGraw-Hill Education)
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from article Protein
The α-helix of protein structure. The repeating NHCOC units form the backbone, which spirals up in a left-handed or right-handed fashion. (The right-handed configuration is adopted in natural proteins with l-amino acids.) Hydrogen bonds are…
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from article Protein
Illustration of the molecular structure of hemoglobin. A single molecule of hemoglobin is composed of four protein subunits, called globins, with each containing a heme group that holds a single iron ion in its center. (Copyright © McGraw-Hill…
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from article Ixodides
An argasid tick, Otobius megnini, known as the spinose ear tick, shown enlarged. (Photo by Mat Pound, Agricultural Research Service, U.S. Department of Agriculture)
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from article Ixodides
A female ixodid tick, Ixodes scapularis, known as the blacklegged tick or deer tick, shown enlarged. This tick spreads Lyme disease in the eastern half of the United States. (Photo by Scott Bauer, Agricultural Research Service, U.S. Department of…
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from article Myxozoa
Different types of myxospores, the typical myxozoan stage in the fish host. Top row: Species of the most species-rich myxozoan genus Myxobolus—M. aeglefini from the eye cornea of the gadoid fish Melanogrammus aeglefinus (left); Myxobolus species…
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from article Myxozoa
Life cycle of Myxozoa. The myxosporean life cycle involves an annelid definitive host and a vertebrate intermediate host. Actinospores are released from an annelid and typically infect a fish host. Myxospores are produced after the vast…
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from article Supercritical fluid
Typical pressure-temperature diagram of a pure material. cp = critical point.
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from article Supercritical fluid
Typical supercritical-fluid extraction process.
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from article Supercritical fluid
Simplified flow diagram of a commercial hydrothermal oxidation process (supercritical-water oxidation).
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from article Immunotherapy
Numerous points along the cancer immunity cycle are targeted by researchers in attempts at immunotherapy. In general, researchers seek to improve the ability of a tumor-bearing individual (the host) to reject the tumor immunologically. (Copyright ©…
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from article Immunotherapy
Histology slide of glioblastoma brain cancer cells. Glioblastoma is an aggressive form of malignant brain tumor. Various methods of immunotherapy attempt to stimulate the host's intrinsic immune response to the tumor. (Credit: Anna…
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from article Polyolefin
The repeating unit of polyethylene.
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from article Polyolefin
Polyethylene structures. (a) Conventional low-density polyethylene. (b) Linear low-density polyethylene and high-density polyethylene with alpha-olefin comonomer. (c) Linear high-density polyethylene with no comonomer [a polymethylene chain]. (d)…
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from article Polyolefin
Idealized structure of polypropylene materials. (a) Isotactic; methyl group always on same side of chain. (b) Syndiotactic; methyl group position alternating. (c) Atactic; methyl groups randomly distributed.
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from article Bismuth
