Science & Philosophy: Verbena Family (Verbenaceae) - Tropical Hardwoods In The Verbena Family to Welfarism
Vertebrates
Vertebrates are animals classified in the subphylum Vertebrata, phylum Chordata. Vertebrates share a number of features. They all have an internal skeleton of bone and/or cartilage, which includes a bony cranium surrounding the brain and a bony vertebral column enclosing the spinal cord. Vertebrates are all covered by a skin composed of dermal and superficial epidermal layers of scales, feathers o…
Victorianism - Early Victorianism, Values And Beliefs, Anti-victorianism, Victorianism And Progress, Victorianism Beyond Britain
Even seemingly unshakeable axioms are prone to reassessment by historians, and Victorianism is no exception. Even the very period of Victorianism itself stands challenged: historians no longer refer unquestioningly to the North-West Passage (1874) by John Everett Millais. Oil on canvas. A strong patriarchal influence and the importance of family were prominent values in the Victorian Age, possi…
Video Recording - Basic Principles Of Video Recording, Recording Techniques, Frequency Modulation, Video Systems, Digital Recording - Video formats, VHS format, Betamax format, Video-format (8 ), VHS-C format
The term "video recording" refers to storing a video signal (information designed to specify a moving image) in a recording medium such as magnetic tape, optical disc, or computer memory. Video signals have much larger bandwidths ?65 MHz) than do audio signals (?20 kHz), and thus involve a more complex recording and playback technology. The transverse recording technique is based upo…
Violet Family (Violaceae) - Species Native To North America, Ornamental Violets, Other Uses Of Violets
The violet family (Violaceae) includes about 900 species of plants. Species in this family occur in all parts of the world, but are mostly in the temperate zones, and at high altitude in the tropics. The largest group in the family is the genus containing violets and pansies (Viola spp.), with about 500 species. Most species in this family are annual or perennial herbs. The leaves are simple, comm…
Vipers - Old World Vipers, Pitvipers
Vipers are snakes in the family Viperidae, a group of short-tailed, (usually) stout-bodied snakes with long fangs at the front of the mouth, sited on a short jawbone that can be rotated to bring the fangs from their resting position parallel with the palate to an erect position for striking. This efficient venom delivery system allows vipers to eat large (and sometimes dangerous) animals without a…
Viral Genetics
Viral genetics, the study of the genetic mechanisms that operate during the life cycle of viruses, utilizes biophysical, biological, and genetic analyses to study the viral genome and its variation. The virus genome consists of only one type of nucleic acid, which could be a single or double stranded DNA or RNA. Single stranded RNA viruses could contain positive-sense (+RNA), which serves directly…
Vireos - North American Species Of Vireos, Vireos Elsewhere, Vireos And People
Vireos are 44 species of small arboreal birds that comprise the family Vireonidae, in the order Passeriformes. As it is considered here, the Vireonidae is an assembly of three sub-families: the true vireos or Vireoninae, the shrike vireos or Vireolaniinae, and the pepper shrikes or Cyclarhinae. It should be pointed out, however, that some taxonomic treatments consider these to be separate families…
Virtual Particles
Virtual particles are subatomic particles that form out of "nothing" (vacuum fields conceptually analogous to lines of force between magnetic poles) for extremely short periods of time and then disappear again. Such particles permeate space, mediate particle decay, and mediate the exchange of the fundamental forces (electromagnetic, weak, strong, and—in accord with quantum the…
Virtual Reality - Historical Overview, Cultural Implications, Bibliography
Virtual reality, a term that became popularized in the late 1980s with the advent of critical research and new technologies developed by Scott Fisher at NASA-Ames Research Center, has its roots in a broad and colorful evolution of art, technology, and communications. The creation of virtual reality is essentially concerned with the quality and experience of immersion, whether real or simulated. Th…
Virtual Reality - The Origin Of Virtual Reality, Components Of Virtual Reality, Applications Of Virtual Reality, On The Horizon Of Virtual Reality
Virtual reality is a product of the evolution of the computer from an instrument that merely received input from a user to a machine that can adapt to the user's cues to create an almost lifelike experience. The term virtual reality was coined in 1989 by Jaron Lanier. Others have described the concept as "artificial reality," "cyberspace," and "virtual wor…
Virtue Ethics - The Rise Of Modern Virtue Ethics, Virtue Ethics's Criticisms Of Prevailing Orthodoxy, Current Debates About Virtue Ethics
Virtue ethics is one of the three major ethical approaches in modern moral philosophy, the other two being utilitarianism and deontology. Unlike the latter two, it focuses on the virtues. In the Western tradition of philosophy, virtue ethics begins with the ethical writings of Plato and Aristotle, but in the Eastern tradition its origins are even earlier. Confucius discussed in detail what might b…
Virus - Structure Of Viruses, Viral Infection, Poxviruses, Herpesviruses, Adenoviruses, Papoviruses, Hepadnaviruses, Parvoviruses - Types of viruses, Paramyxoviruses, Flaviviruses, Filoviruses, Rhabdoviruses
A virus is a small, infectious agent that consists of a core of genetic material (either deoxyribonucleic acid [DNA] or ribonucleic acid [RNA]) surrounded by a shell of protein. Viruses cause disease by infecting a host cell and commandeering the host cell's synthetic capabilities to produce more viruses. The newly made viruses then leave the host cell, sometimes killing it in the process, …
Viscosity
The viscosity of a fluid is a measure of its resistance to continuous deformation caused by sliding or shearing forces. Imagine a fluid between two flat plates; one plate is stationary and the other is being moved by a force at a constant velocity parallel to the first plate. The applied force per unit area of the plate is called the shear stress. The applied shear stress keeps the plate in motion…
Vision - Our 3-d View Of The World, Ocular Dominance, Memory, Electrochemical Messengers, Color Vision - Optic pathway, Visual field, Accommodation, Common visual problems, Amblyopia, Other common visual problems
Vision is sight, the act of seeing with the eyes. In humans, sight conveys more information to the brain than either hearing, touch, taste, or smell, and contributes enormously to memory and other requirements for our normal, everyday functioning. Because we see objects with two eyes at the same time, human vision is binocular, and therefore stereoscopic. Vision begins when light enters the eye, s…
Vision Disorders - Refractive Errors, Hyperopia/presbyopia, Other Refractive Errors, Strabismus, Nonparalytic Strabismus, Paralytic Strabismus - Myopia, Astigmatism, Glaucoma, Secondary glaucomas, Degeneration of the macula, Retinal dystrophies
Vision disorders are irregularities or abnormalities either of the eye, visual pathway, or brain, which affect one's ability to see. In healthy vision, visual acuity—often referred to as "20/20 vision"—develops rapidly by three to six months of age and generally decreases rapidly as people approach 45. Poor visual acuity is often correctable with glasses or conta…
Visual Culture - The Visual Turn, Visuality, Historical Emergence Of The Field Of Vision As A Site Of Power And Social Control
While visual culture has certainly been around as long as culture itself, the phrase visual culture used to denote a specific component of culture in general, a set of visual practices, or an academic discipline is quite recent. James Elkins, one of this emerging field's leading scholars, dates the term from 1972, saying that it "was used—perhaps for the first time …&#x…
Visual Order to Organizing Collections - Hunting For Precious Objects, Horticulture And Culture, Cabinets Of Curiosity, "portraits" Of Authors
A generation trained to select icons on a desktop computer is able to take a fresh approach to the visual cues within early rooms of collection. Visual cues often preceded catalogs and inventories, helping users to situate themselves in the room and to locate items of the collection. In searching out the modes of conceptualizing, mapping, and classifying of collections, we shall see that the disti…
Vitamin
Vitamins are organic molecules that are needed in small amounts in the diet. They are frequently molecules that bind in the active site of an enzyme and thereby alter its structure in a way that permits it to react more readily. Vitamins serve nearly the same role in all forms of life and many are essential in the metabolism of all living organisms. They are synthesized by plants and micro-organis…
Viviparity
Viviparity is a form of reproduction found in most mammals and in several other species. Viviparous animals give birth to living young that have been nourished in close contact with their mothers' bodies. Humans, dogs, and cats are viviparous animals. Viviparous animals differ from egg-laying animals, such as birds and most reptiles. Egg-laying, or oviparous, animals obtain all nourishment …
Volatility
Volatility is the ease with which a substance is converted to the gaseous, or vapor, state. The term is usually used to describe the speed with which a liquid evaporates, but it can also apply to the process of a solid changing to a gas, known as sublimation. Liquids that boil at low temperatures, such as gasoline, are volatile liquids, while liquids that boil at higher temperatures, such as water…
Volcano - Where Volcanoes Develop, The Origin Of Magma, Types Of Volcanic Eruptions, Different Kinds Of Volcanic Structures
A volcano is an opening in Earth's surface through which molten rock, hot gases, and rocks are ejected. Volcanoes create new land and islands. They can also produce economically important mineral deposits, fertile soils, and beautiful landscapes. However, volcanoes can also destroy lives and property. Therefore, they constitute significant geologic hazards in many parts of the world. With r…
Voles - North American voles
Voles are small mouse-like mammals in the family Muridae, order Rodentia. Other members of this family include the gerbils, hamsters, lemmings, rats, and mice. Voles occur in a wide range of open, often grassy habitats, such as alpine and arctic tundra, prairies, savannas, and pastures and other types of agricultural fields. Voles have a body length of about 3-5 in (8-12 cm), and typically weigh 1…
Volksgeist - Bibliography
Volksgeist (folk or national spirit) is perhaps the best known of a family of terms referring to sets of mental, intellectual, moral, and cultural traits that define particular human groups represented as being "nations" or "peoples." Additional related words include Volksseele ("folk soul"), "national character," esprit de la nation (…
U.S. Volunteerism - Volunteerism In Colonial America, Volunteerism In The Early Republic, Volunteerism During And After The Civil War
The meaning of volunteerism is contingent on the nature of government, particularly the extent and ways in which it enables individuals to make uncompensated donations of money and labor to some form of collective activity or shared purpose. Over the course of the five centuries since European colonists first occupied North America, the meaning and practice of volunteerism has changed as part of t…
Voyager Spacecraft
Twin robotic space probes, Voyager 1 and Voyager 2, were launched by the United States in 1977. Their original mission was to fly by Jupiter and Saturn, but the journey of Voyager 2 was successfully extended to Uranus and Neptune. The Voyagers were the most scientifically fruitful space mission ever launched, collecting, among other data, high-quality photographs of four planets and dozens of moon…
Vulcanization - Rubber as a natural product, Vulcanization and properties of vulcanized rubber
Vulcanization is the process by which rubber molecules (polymers or macromolecules made of repeating units or monomers called isoprene) are cross-linked with each other by heating the liquid rubber with sulfur. Cross-linking increases the elasticity and the strength of rubber by about ten-fold, but the amount of cross-linking must be controlled to avoid creating a brittle and inelastic substance. …
Vultures - Biology Of Vultures, New World Vultures, Old World Vultures
Vultures are large birds of prey specialized to scavenge the bodies of dead animals. Species of vultures are assigned to two families in the order Falconiformes. The vultures of the Americas include seven species in the family Cathartidae. The vultures of Eurasia and Africa, numbering 14 species, are specialized members of the Accipitridae, a family that also includes hawks and eagles. The Cathart…
Wagtails and Pipits
Wagtails and pipits are 48 species of terrestrial birds that make up the family Motacillidae. Species in this group occur on all of the continents but Antarctica. The usual habitat of these birds is deserts and semi-deserts, prairies, tundras, shores, and cultivated fields. Many species are migratory, with northern species travelling to the tropics to spend their nonbreeding season, and alpine spe…
Walkingsticks
Walkingsticks are insects with a long, thin body, lengthy delicate legs and a brown-green color which gives them a striking resemblance to a twig. Walkingsticks are in the family Phasmidae in the order Orthoptera, which also includes the grasshoppers and crickets. There are almost 2,500 species of walkingsticks (phasmids), ranging in size from 1 in (2.5 cm) to 1 ft (30 cm), the largest species occ…
Walruses
The walrus (Odobenus rosmarus) is one of the largest seals, order Pinnipedia. Although similar in many respects to other seals, particularly the eared seals, the walrus is sufficiently different to merit being placed in its own family, Odobenidae. It is the sole member of that family, with only a few subspecies. The genus name is derived from the Greek words for "tooth" and "I…
War - Defining States As Warring Units, Jus Ad Bellum: United Nations Charter Of 1945, Jus In Bello
How does one define a war? How can one distinguish between the war on drugs, the war on terrorism, jihad, anarchy, and wars between states? Definitions are relevant as they provide the rationale for considering a war legitimate and just and contribute to decisions about international interventions, aid, and protocol. This has become particularly important in contemporary international affairs, whe…
Warblers - American Warblers, Old World Warblers, Conservation Of Warblers
Warblers are small, perching song birds with a large number of species distributed throughout the world. There are two families of warblers, one in the New World and one in the Old World. The New World warblers (family Parulidae) comprise 113 species that occur throughout the Americas. The Old World warblers (family Silviidae) occur in Eurasia, Africa, and Australia, and include some 325 species. …
Waste Management - History Of Waste Management, Municipal Solid Waste, Agricultural, Mining, And Industrial Waste, Hazardous Waste
Waste management is the handling of discarded materials. Recycling and composting, which transform waste into useful products, are forms of waste management. The management of waste also includes disposal, such as landfilling. Waste can be almost anything, including food, leaves, newspapers, bottles, construction debris, chemicals from a factory, candy wrappers, disposable diapers, old cars, or ra…
Toxic Waste
Toxins are poisonous materials that interfere with vital metabolic processes to sicken or kill living organisms. Toxins can be either general poisons that kill many types of cells and organisms, or they can be extremely specific in their target and mode of action. Some are extremely reactive and can be lethal even in very dilute concentrations. Ricin, for instance, is a protein found in castor bea…
Water - What Is Water?, An Unusual Liquid
Water is the most abundant liquid on Earth. It covers more than 70% of the earth's surface. Including the clouds (which are, of course, also water), it makes our entire planet look blue and white from space. It is impossible to overstate the importance of water to almost every process on Earth, from the life processes of the lowest bacteria to the shaping of continents. Water is the most fa…
Water Bears
Water bears or tartigrades are about 500 species of tiny aquatic invertebrate animals in the phylum Tartigrada, including about 90 species in North America. Water bears have a very widespread distribution, occurring in moist habitats from the Arctic to the Antarctic and on mountains as high as 19,680 ft (6,000 m). Water bears have roughly cylindrical dark-colored bodies with four body segments and…
Water Conservation - Freshwater Resources, Water Consumption, Efficient Water Utilization Efforts, Economic Incentives For Water Conservation
The hydrosphere refers to that portion of the earth that is made of water, including all oceans, lakes, rivers, streams, glaciers, and underground water. Less than 3% of the water of Earth is freshwater, an amount that includes polar ice caps, glaciers, groundwater, surface water of rivers and freshwater lakes, and even atmospheric water. However, the amount of freshwater useable by people and oth…
Water Lilies - Species Of Water Lilies, Ecological And Economic Importance
The water lily, yellow water lily, lotus, and several other aquatic plants are about 60 species of aquatic herbs that make up the family Nymphaeaceae. These plants occur in shallow, fresh waterbodies from the boreal to the tropical zones. The usual habitats of these plants are ponds and shallow water around lake edges, as well as slowly-flowing pools and stagnant backwaters in streams and rivers. …
Water Microbiology
Water microbiology is concerned with the microorganisms that live in water, or can be transported from one habitat to another by water. Water can support the growth of many types of microorganisms. This can be advantageous. For example, the chemical activities of certain strains of yeasts provide us with beer and bread. As well, the growth of some bacteria in contaminated water can help digest the…
Water Pollution
Any physical, biological, or chemical change in water quality that adversely affects living organisms or makes water unsuitable for desired uses can be considered pollution. Often, however, a change that adversely affects one organism may be advantageous to another. Conversely, antibiotic designed for use at one site, might pose a pollution threat to non-target or beneficial downstream microorgani…
Water Treatment
Water is treated to make it safe to drink and to use for other purposes, such as to spray on agricultural plants. Water that contains domestic and industrial waste is often required to be treated to lessen or remove the contaminants prior to the discharge of the water into a river, lake, or ocean. Some industrial processes require water that is free of impurities and microorganisms. One example is…
Watershed
A watershed refers to land that is drained by an interconnected system of rivulets, streams, rivers, lakes, and groundwater. Water from a watershed eventually drains into a common destination. Both rain and snow contribute to the watershed. Coastal watersheds that begin as rivulets often end as large rivers that empty into a lake or an ocean. Watersheds can range in size from just a few square mil…
Waterwheel
The waterwheel is considered the first rotor mechanism in which an outside force creates power to spin a shaft. The Greeks are said to have first developed the waterwheel, using it to raise water from rivers. Polls or pots were attached around the circumference of a large wheel; then oxen would walk in a circle round a vertical shaft connected through a simple gear to the horizontal shaft of the w…
Wave Motion
A wave is nothing more than a disturbance that moves from place to place in some medium, carrying energy with it. Since the behavior of waves is so closely related to the concept of oscillations, that is a good place to start. There are many examples of simple oscillations, but a very good one is that of an object attached to the end of a spring. Assume that the other end is held fixed, perhaps by…
Waxbills
Waxbills are 107 species of finch-like birds that make up the family Estrilidae. Species of waxbills occur in the tropics of Africa, South and Southeast Asia, New Guinea, Australia, and many islands of the South Pacific. Their usual habitats are grasslands, marshes, savannas, forest edges, and disturbed forests. Waxbills are sedentary, nonmigratory birds. Waxbills are small birds, ranging in body …
Waxwings - The Phainopepla
Waxwings are medium-sized, fruit-eating, perching birds found in northern Eurasia and North America that Cedar waxwing (Bombycilla cedrorum). Photograph by Robert J. Huffman. Field Mark Publications. Reproduced by permission. are included in the family Bombycillidae. Waxwings have a crest on the top of their head, and have soft, sleek, often shiny plumage. The secondary feathers often ha…
Wealth - Wealth And Virtue, Wealth And Power, Status, The Dangers Of Wealth, Conclusion, Bibliography
Wealth has been viewed as a blessing and as a curse; as a prerequisite of virtue and an embodiment of vice; as an expression of merit and of fault. This nonexhaustive list illustrates that not only is the history of wealth a history of contention, it is also intimately bound up with moral evaluations. These differing evaluations themselves indicate a range of divergent cultural judgments. "…
Weasels - Species of weasels
Weasels, ermines, and stoats are various species of small carnivores in the family Mustelidae, which also includes the otters, badgers, martens, minks, skunks, and wolverine. Species of weasels occur in North America, northern South America, northern Africa, Europe, Asia, and Southeast Asia. Weasels have a long, lithe, almost serpentine body, and short legs. This body shape is highly adaptive for …
Weather - Solar Energy, Humidity, Clouds, And Precipitation, Atmospheric Pressure And Winds, Terrestrial Characteristics
Weather can be defined as the condition of the atmosphere at any given time and place. Weather conditions are determined by six major factors: air temperature, air pressure, humidity of the air, amount and kind of cloud cover, amount and kind of precipitation, and speed and direction of the wind. Weather condition patterns for any one region or for the whole planet can be charted on a weather map …
Weather Forecasting - The National Weather Service, Types Of Weather Forecasts, Long-range Forecasting, Numerical Weather Prediction
Weather forecasting is the attempt by meteorologists to predict the state of the atmosphere at some future time and the weather conditions that may be expected. Weather forecasting is the single most important practical reason for the existence of meteorology as a science. It is obvious that knowing the future of the weather can be important for individuals and organizations. Accurate weather fore…
Weather Modification - Cloud Seeding, Methods Of Cloud Seeding, Effectiveness Of Cloud Seeding, Fog And Cloud Dispersal - Wartime applications
The term weather modification refers to any deliberate effort on the part of humans to influence weather patterns for some desirable purpose. Probably the most familiar example of weather modification is the seeding of clouds, most often done in order to increase the amount of precipitation during periods of drought. The earliest scientific programs on weather modification date to the 1940s when V…
Weathering - Physical (mechanical) Weathering, Temperature And Moisture, Chemical Weathering, Rates Of Weathering - Biological weathering
Weathering is the process by which rocks and minerals are broken down into simpler materials by means of physical (mechanical), chemical, and biological processes. Weathering is an extremely important phenomenon for the human species since it is the mechanism by which one of the planet's most important natural resources—soil—is formed. The exact way in which weathering occurs …
Weaver Finches - Species Of Weaver Finches, Conflicts With Humans
Weaver finches are a relatively large family of 156 species of perching birds, comprising the family Ploceidae. Weaver finches are native to Africa, Madagascar, Eurasia, and Malaysia. This group is richest in species in Africa. However, some species have been widely introduced outside of their natural range. Species of weaver finches occur in a wide range of terrestrial habitats, including semi-de…
Weevils
Weevils (Curculionidae) comprise a very large group of insects that are closely related to beetles (order Coleoptera); more than 40,000 species are recognized worldwide, ranging in size from 0.2-2 in (0.5-5 cm). A weevil is easily distinguished from a beetle by its extended head, which forms a rostrum, and long, segmented antennae that are clubbed at the end and are usually bent in an elbow fashio…
Welding - Evolution Of Welding, Welding Methods, Arc Welding, Gas Welding, Resistance Welding
Welding is a group of processes used to join non-metallic and metallic materials, by applying heat, pressure, or a combination of both. Most welding procedures require heat, although some procedures require only extreme pressure (cold welding). The welding process chosen to join materials together depends upon the mechanical, physical, and chemical properties of the materials to be joined, and the…