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from article Branched polymer
Steps in the synthesis of a starburst polymer. s = surface. o = interior. fr = reactive group. fp = protected group.
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from article Heterocyclic polymer
Structural units in linear polymers. (a) Simple linear polymer. (b) Stepladder polymer. (c) Ladder polymer.
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from article Heterocyclic polymer
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from article Intermolecular forces
Schematic diagram of intermolecular interaction. (a) There is negligible interaction between atoms that are 1 nm apart. (b) For atoms separated by about 0.8 nm or less, attractive dispersion forces result from correlated fluctuations of the electron…
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from article Cheese
Cheese being placed in brining tank (salt bath). (Credit: Westend61/Getty Images)
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from article Cheese
Cheese ripening. (Credit: Tom Paiva Photography/Blend Images)
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from article Cheese
Swiss cheese. (Credit: Tom Paiva Photography/Blend Images)
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from article Nitrogen oxides
Nitrogen-oxide structures. Blue = nitrogen. Red = oxygen.
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from article Food allergy
Children (under the age of 18) who experience food allergies are more likely to experience other allergic conditions, including asthma (black), eczema/skin allergy (blue), and respiratory allergy (green). (Credit: National Center for Health…
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from article Food allergy
Allergic responses (immunological responses mediated by the IgE class of immunoglobulins) can be caused by certain foods. In a person with allergies, mast cells will be coated with IgE against one or a few antigens (allergens) that, upon entering…
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from article Food allergy
Peanuts are a common trigger of food allergies in both adults and children. (Credit: Christian Jung/Shutterstock)
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from article Prairie dog
Black-tailed prairie dogs (Cynomys ludovicianus). (Photo by Ron Singer, U.S. Fish and Wildlife Service)
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from article Alicyclic hydrocarbon
Internal bond angles (α) for (a–c) planar rings and (d) a tetrahedral carbon atom.
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from article Alicyclic hydrocarbon
Nonplanar (a) chair and (b) boat structures of cyclohexane.
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from article Alcohol
Ethanol production plant. (Credit: Julie Kendall/Getty Images)
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from article Alcohol
E85 is a gasoline-ethanol blend containing 51 to 83% ethanol. It is used in flexible-fuel vehicles, which can operate on gasoline or blends of gasoline and ethanol. About 20 million flexible-fuel vehicles are operating in the United States. (Credit:…
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from article Fluids
Probability of finding molecular centers at various separations in gases, liquids, and solids.
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from article Fluids
Conditions of pure-component phase behavior.
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from article Fluids
Behavior of pure-component pressures with density at various temperatures.
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from article Fluids
Behavior of pure-component compressibility factors with pressure at various temperatures.
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from article Desertification
Overgrazing on North American rangelands contributes to soil compaction and alters the composition of vegetation. (Credit: Thomas Wikle)
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from article Desertification
Desertification can be accelerated by cultivation in areas better suited for herding, such as this field in Ethiopia. (Credit: Thomas Wikle)
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from article Desertification
Grazing animals have contributed to desertification in Africa’s Sahel region. (Credit: Thomas Wikle)
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from article Laminariales
Laminaria: (a) sporophyte; (b) cross section of blade, showing a sorus of unilocular sporangia interspersed with sterile hairs (paraphyses); (c) zoospore; (d) male gametophyte with antheridia; (e) antherozoid (sperm); (f) female gametophyte with…
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from article Laminariales
Giant kelp (Macrocystis pyrifera) can grow up to 0.6 m (2 ft) per day. Note the series of frond blades, with each subtended by a bladder. (Photo courtesy of Charlotte Stevenson, University of Southern California Sea Grant, Los Angeles)
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from article Biosynthesis
Biosynthetic relationships of some natural products. Specific examples which belong to the various classes are given in brackets.
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from article Thulium
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from article Chemistry
Periodic table. (Jaap Hart/Getty Images)
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from article Mercury (element)
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from article Mercury (element)
Mercury droplets exhibiting non-wetting of the surface. (Credit: A. Cerar/Getty Images)
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from article Mercury (element)
Tooth with a silver-amalgam filling. (Credit: Szasz-Fabian Jozsef/Shutterstock.com)
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from article Organic conductor
Structures of organic conductors. (a) Electron donors. (b) Acceptor molecule (TCNQ) and two monovalent anions. Abbreviations are explained in the text.
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from article Organic conductor
Stacking of charge-transfer compounds. (a) Segregated stacking of TTF-TCNQ-like materials. (b) Typical zigzag stacking of the (TMTSF)2X series.
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from article Organic conductor
Comparison of the range of electrical conductivities of some AsF5-doped conducting polymers with some metals, semiconductors, and nonconducting polymers.
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from article Organic conductor
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from article Alpine vegetation
Forest-alpine tundra near Hyndman Cirque, Idaho. The trees change in density and form within the ecotone beyond the boundary of the timberline upslope toward the alpine tundra. The distribution of timberline, treeline, and the ecotone is irregular…
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from article Alpine vegetation
Whitebark pine (Pinus albicaulis) showing the classic dwarfed and contorted image of trees within the windswept forest-alpine tundra ecotone of the Beartooth Plateau, Wyoming. (Courtesy of T. Crawford)
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from article Alpine vegetation
Flagged tree, mainly supporting branching on the leeside of the upper trunk; needles have been lost from the lower trunk to the parasitic snow fungus. (Courtesy of T. Crawford)
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from article Killer whale
Killer whales (Orcinus orca) in the waters off Alaska. (Credit: David Ellifrit/Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration)
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from article Killer whale
The tail of a killer whale. (Credit: Janice Waite/Alaska Fisheries Science Center, National Oceanic and Atmospheric Administration)
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from article Hydrido complexes
Structure of ReH92−.
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from article Hydrido complexes
Structure of [HMn(CO)5].
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from article Hydrido complexes
Structure of [HRe(C5H5)2]. The aromatic C5H5 groups are represented by pentagons.
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from article Hydrido complexes
Hydridophosphine structures, with the C6H5 groups not shown. (a) [HRuCl(P{C6H5 }3)3]. (b) [H3Ir(P{C6H5 }3)3].
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from article Hydrido complexes
Reaction scheme for hydrogenation of an olefin using Wilkinson's catalyst.
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from article Hydrido complexes
Structure of [HCr2(CO)10]−.
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from article Hydrido complexes
Structure of [H2W2(CO)8]2−.
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from article Hydrido complexes
Core of the [H8Re2(P{C2H5 }2C6H5)4] molecule. All organic groups are omitted for clarity.
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from article Hydrido complexes
Structure of [H2Th(C5 {CH3 }5)2]2. The hydrogen atoms of the methyl groups are omitted for clarity.
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from article Liquid
Phase diagram of a pure substance.
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from article Mustard
Black mustard (Brassica nigra). (Photo courtesy of Jennifer Anderson, USDA–NRCS PLANTS Database)
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from article Asian vegetables
A head of Chinese cabbage. (Credit: Jiang Hongyan/Shutterstock)
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from article Asian vegetables
Bok choy, also known as pak choy or Chinese mustard. (Credit: Agricultural Research Service, U.S. Department of Agriculture)
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from article Asian vegetables
Daikon (oriental winter radish) is a notable vegetable in Japan. (Credit: Franco Folini)
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from article Asian vegetables
Mung bean sprouts.
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from article Asian vegetables
Chinese okra. The length of the fruit can reach 30–38 cm (12–15 in.). (Credit: Forest and Kim Starr)
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from article Periodic table
Periodic table of the elements.
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from article Lichens
The ascolichen Teloschistes chrysophthalmus. (Credit: Jason Hollinger)
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from article Lichens
Cuplike lichens of the genus Cladonia. (Credit: Jacinta Lluch Valero)
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from article Cotton effect
Behavior of the ORD and CD curves in the vicinity of an absorption band at wavelength λ0 (idealized). (a) Positive Cotton effect. (b) Negative Cotton effect.
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from article Cotton effect
Curves used to determine relative rotatory intensities. (a) Partial ORD curve. (b) Partial CD curve.
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from article Cotton effect
Structural formula of (+)-trans-9-methyl-1,4,9,10- tetrahydronaphthalene.
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from article Cotton effect
Schematic representation of the twisted diene chromophore showing the two possible handednesses; the numbering is as indicated in Fig. 3 (a) Right-handed. (b) Left-handed.
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from article Dune vegetation
A coastal dune profile.
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from article Dune vegetation
American beachgrass (Ammophila breviligulata), which dominates coastal dunes along much of the Eastern seaboard of the United States and the Great Lakes. (Photo by Rob Routledge, Sault College, Sault Ste. Marie, Ontario, Canada)
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from article Dune vegetation
Sea oats (Uniola paniculata) are abundant on the foredunes of the Atlantic coast of the southeastern United States. (Photo by Robert L. Anderson, USDA Forest Sevice)
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from article Dune vegetation
Bitter panicum (bitter panicgrass; Panicum amarum), which is often found on Gulf of Mexico coastal dunes. (Photo by Forest and Kim Starr)
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from article Forage crops
Bahia grass (Paspalum notatum), a popular warm-season grass used as a forage crop. (Photo by James H. Miller and Ted Bodner, Southern Weed Society)
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from article Forage crops
Alfalfa (Medicago sativa), the most important legume forage crop, cut and drying prior to its final harvest. (Photo by Howard F. Schwartz, Colorado State University)
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from article Electrochemistry
Electrolysis of aqueous potassium bromide. (Copyright © McGraw-Hill Education/Stephen Frisch)
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from article Osmium
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from article Osmium
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from article Luminescence analysis
Typical photoluminescence excitation and emission spectra for molecules in solution.
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from article Luminescence analysis
Components of instrumentation for luminescence measurements.
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from article Wheat
A sheaf of wheat (Triticum) surrounded by some small piles of seed (grain). (Credit: Scott Bauer/Agricultural Research Service, U.S. Department of Agriculture)
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from article Wheat
A combined harvester-thresher is used to harvest wheat. (Credit: Scott Bauer/Agricultural Research Service, U.S. Department of Agriculture)
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from article Wheat
Adaptation regions for wheat in the United States. (Credit: U.S. Department of Agriculture)
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from article Wheat
Wheat (Triticum) growing in a field. The wheat inflorescence is a spike bearing sessile spikelets arranged alternately on a zigzag rachis (main axis). (Credit: Tim McCabe/Natural Resources Conservation Service, U.S. Department of Agriculture)
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from article Wheat
Black stem rust of wheat, which produces urediniospores in reddish-brown pustules. The fungus Puccinia graminis f. sp. tritici is responsible for this plant disease. The inset shows a close-up view of an infected stem. (Credit: Agricultural Research…
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from article Wheat
Loose smut of wheat, caused by Ustilago tritici. (Credit: Erik Stromberg/Virginia Polytechnic Institute and State University)
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from article Anthropocene extinction
The relationship between species extinctions and the human population on Earth since the year 1800. As the human population has increased, so too have the numbers of species extinctions. The numbers have been so great that the current Anthropocene…
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from article Camphor
Camphor tree. (Credit: Gyro Photography/amanaimagesRF/Getty Images)
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from article Ginger
Ginger (Zingiber officinale). (USDA)
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from article Copper
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from article Copper
Chalcopyrite (CuFeS2), a copper-iron sulfide mineral, is an important copper-containing ore. (Credit: Linnas/Getty Images)
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from article Copper
Electrical wiring cable. (Credit: Shutterstock/Sydeen)
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from article Fullerene
Buckyball structure.
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from article Fullerene
Some of the more stable members of the fullerene family. (a) C28. (b) C32. (c) C50. (d) C60. (e) C70.
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from article Fullerene
Comparison of the structure of fullerene-60 with that of two giant fullerenes. (a) C60. (b) C240. (c) C540.
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from article Fullerene
Structure of the molecule C60Br6.
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from article Fullerene
A section of a carbon nanotube showing the concentric graphene tubes composing it.
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from article Drug delivery systems
A transdermal nicotine patch is a noninvasive method of controlled drug delivery. (Copyright © Plush Studios/Bill Reitzel/Blend Images)
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from article Drug delivery systems
Three levels of polymer drug delivery. (a) A polymer is used as carrier of drugs. (b) The drugs are connected to the polymer via cleavable peptide linkers. (c) A homing device is added to target specific tissue types. (Credit: Jan van Hest;…
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from article Casein
Flow chart of production of commercial casein products from skim milk.
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from article Casein
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from article Half-life
The decay chain of uranium, which has a half-life of approximately 4.5 billion years and is the most common uranium isotope in nature. The alpha symbol (α) indicates alpha decay, while the beta symbol (β) indicates beta decay. Alpha decay emits an…
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from article Ecology
Egrets and herons in a wetland ecosystem in the Everglades in southern Florida. (Copyright © McGraw-Hill Education)
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from article Ecology
Generalized trophic structure of ecosystems. Arrows indicate flow of energy and chemicals. Primary producers are largely green photosynthetic plants. Primary consumers, or herbivores, feed on the producers. Secondary consumers, or carnivores, feed…
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from article Narcotic
Heroin is an extremely addictive narcotic. (Credit: FotoMaximum/Getty Images)
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from article Narcotic
Chemical structure of a morphine alkaloid. Two important natural alkaloids are morphine and codeine. Heroin is synthesized from morphine by acetylation.
