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McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
The earliest demonstrable vascular land plants, appearing in Silurian (mid-Ludlovian) time. Their small, leafless axes were usually branched dichotomously in three planes; adventitious and perhaps pseudomonopodial branching also occurred. Sporangia were usually terminal on the main axes. Some terminated in lateral branches, and some were subtended by adventitious branches. The sporangia were globose, almost reniform, elongate-ellipsoidal, or cylindrical; some were columellate and branched. Dehiscence was unspecialized; some opened by an apical slit, and some by a modified distal region. The spores were simple and produced in tetrads. A possible gametophyte plant, associated with <i>Rhynia</i>, was erect, leafless, and terminated by a gametangiophore bearing antheridia and possible archegonia. The basal parts, where known, were rhizomatous, with rhizoids but no true roots. Stomata have been found on some axes and sporangia. The xylem, where known, was centrarch, and consisted of annular elements. Evidence of phloem sieve cells is unconvincing.
Industry:Science
The generation of a random intensity distribution, called a speckle pattern, when light from a highly coherent source, such as a laser, is scattered by a rough surface or inhomogeneous medium. Although the speckle phenomenon has been known since the time of Isaac Newton, the development of the laser is responsible for the present-day interest in speckle. Speckle has proved to be a universal nuisance as far as most laser applications are concerned, and only in the mid-1970s did investigators turn from the unwanted aspects of speckle toward the uses of speckle patterns, in a wide variety of applications.
Industry:Science
The “winged reptiles” of the Mesozoic Era, constituting the closest major group to Dinosauria and sharing many features with them. Their common ancestor was a small, bipedal, agile archosaur reptile probably similar to the small <i>Scleromochlus</i> of the Late Triassic. This ancestor probably possessed a large, lightly built skull, a short body, long hindlimbs, and digitigrade feet with four long metatarsals. Pterosaurs inherited all these features, and they further evolved the power of flight. Bats have a wing of skin stretched among four fingers and extending from the arms to the legs (and often the tail), and birds have a wing of feathers supported by the arm and the fused wrist–hand bones. Pterosaurs had a wing of skin that was internally supported by long, fine, possibly keratinous stiffening fibers and braced by the forelimb, including a greatly elongated fourth finger (the first three fingers remained small). Their brains were relatively large and somewhat birdlike; the canals of the ear region show that they were well suited for life in the air.
Industry:Science
The largest and most highly evolved superorder of the crustacean class Malacostraca. It contains the orders Euphausiacea, Amphionidacea, and Decapoda. Despite the great morphological and ecological diversity of eucaridans, all share (1) a well-developed carapace that is fused to all the thoracic somites; (2) stalked and movable eyes, although in a few these have been secondarily reduced; (3) mandibles that lack a mobile element between the incisor and molar processes; (4) a telson without a caudal furca; (5) heart and gills that are thoracic in position; and (6) typically metamorphic larval development.
Industry:Science
The Hadean Eon, around 4.5–4.0 billion years ago (Ga), is the dark age of Earth history. There is no known rock record from this period. As a result, our knowledge of the growth history of continental crust is equally consistent with the planet then hosting a massive early crust or essentially none at all. Without support from a rock record, our understanding of pre-Archean continental crust comes largely from investigating Hadean detrital zircons (mineral grains from broken-down rock). We know that these ancient zircons yield relatively low crystallization temperatures and that some are enriched in heavy oxygen, contain inclusions similar to modern crustal processes, and show hafnium (Hf) isotope evidence of silicate differentiation by 4.51 Ga. These observations are interpreted to reflect an early terrestrial hydrosphere, early felsic crust in which granitoids were produced and later weathered under high water activity conditions, and even the possible existence of plate boundary interactions, in profound contrast to the traditional view of this period.
Industry:Science
Symbiotic associations of fungi (mycobionts) and photosynthetic partners (photobionts). These associations always result in a distinct morphological body termed a thallus that may adhere tightly to the substrate or be leafy, stalked, or hanging. A thallus consists of layers, that is, a cortex and medulla made up of the fungus, and a photosynthetic layer of algal or cyanobacterial cells that are closely associated with fungal hyphae. Rhizoids anchor thalli to their substrates. Some lichens (<i>Stereocaulon</i>) with green photobionts have gall-like structures called cephalodia that contain cyanobacteria.
Industry:Science
The genealogical history of organisms, both living and extinct. Phylogeny represents the historical pattern of relationships among organisms which has resulted from the actions of many different evolutionary processes. Phylogenetic relationships are depicted by branching diagrams called cladograms, or phylogenetic trees. Cladograms show relative affinities of groups of organisms called taxa. Such groups of organisms have some genealogical unity, and are given a taxonomic rank such as species, genera, families, or orders. For example, two species of cats—say, the lion (<i>Panthera leo</i>) and the tiger (<i>Panthera tigris</i>)—are more closely related to each other than either is to the gray wolf (<i>Canis latrans</i>). The family including all cats, Felidae, is more closely related to the family including all dogs, Canidae, than either is to the family that includes giraffes, Giraffidae. The lion and tiger, and the Felidae and Canidae, are called sister taxa because of their close relationship relative to the gray wolf, or to the Giraffidae, respectively.
Industry:Science
The division of a cell into daughter cells that receive identical copies of its genetic material. The cell cycle comprises the period between the formation of a cell as a progeny of division and its own subsequent division into two daughter cells. The cell cycle falls into two parts. A relatively long interphase represents the time during which the cell engages in synthetic activities and reproduces its components, even though there is no visible change. The relatively short period of mitosis provides an interlude during which the actual process of visible division into two daughter cells is accomplished.
Industry:Science
The facility of leeches for extracting blood from living organisms has long been known to human society. That influential ancient physicians such as Nicander of Colophon (ca. 200 B.C.), Wang Chung (ca. A.D. 30), and Kunja Lal Sharma (ca. A.D. 50) described therapeutic uses for leeches indicates that medical use of leeches was widespread in the ancient world. However, application of leeches in Europe for relief of a myriad of ailments such as headaches, insomnia, ulcers, and obesity did not reach its acme until the 1800s, when exploitation in France exceeded 50 million leeches per year. Today, legitimate use of medicinal leeches includes hematoma treatment after microsurgical reattachment procedures. There has also been an increase in understanding of the anticoagulation components of leech salivary secretions. Thorough understanding of the evolutionary relationships of leeches provides a means for targeting other therapeutically useful species and permits the elucidation of patterns in the evolution of blood feeding from their common ancestor to the present.
Industry:Science
The generic term for any of several techniques for applying thin coatings of zinc to iron or steel stock or finished products to protect the ferrous base metal from corrosion; more specifically, the hot dipping that is widely practiced with mild steel sheet for garbage cans and corrugated sheets for roofing, sheathing, culverts, and iron pipe; and with fencing wire. During dipping, molten zinc reacts with the steel to form a brittle zinc-iron alloy. Control of temperature and the addition of aluminum reduce formation of the alloy, resulting in a more ductile coating. For marine use, magnesium is added.
Industry:Science
