Islands

May 3, 2010 by · Leave a Comment 

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An island or isle is any piece of land that is surrounded by water. Very small islands such as emergent land features on atollsare called islets. A key or cay is another name for a small island or islet. An island in a river or lake may be called an eyot. A grouping of geographically or geologically related islands is called an archipelago.

An island may still be described as such despite the presence of a land bridge, for example Singapore and its causeway, or the various Dutch delta islands, such as IJsselmonde. Some places may even retain “island” in their names for historical reasons after being connected to a larger landmass by a wide land bridge, such as Coney Island.

There are two main types of islands: continental islands and oceanic islands. There are also artificial islands. There is no standard of size which distinguishes islands from islets and continents.

The word island comes from Old English igland (from ‘ig’, similarly meaning ‘island’ when used independently, and -land carrying its contemporary meaning). However, the spelling of the word was modified in the 15th century by association with the etymologically unrelated Old French loanword isle, which itself comes from the latin word insula. Old English ‘ig’ is actually a cognate of Latin aqua(water).

Continental islands are bodies of land that lie on the continental shelf of a continent. Examples include Greenland and Sable Island off North America;Barbados and Trinidad off South America; Great Britain, Ireland and Sicily offEurope; Sumatra, Borneo and Java off Asia; and New Guinea, Tasmania and Kangaroo Island off Australia.

A special type of continental island is the microcontinental island, which results when a continent is rifted. Examples are Madagascar and Socotra offAfrica; New Zealand; the Kerguelen Islands; and some of the Seychelles.

Another subtype is an island or bar formed by deposition of tiny rocks where a water current loses some of its carrying capacity. An example is barrier islands, which are accumulations of sand deposited by sea currents on the continental shelf. Another example is islands in river deltas or in large rivers. While some are transitory and may disappear if the volume or speed of the current changes, others are stable and long-lived. Islets are very small islands.

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House Mouse

April 22, 2010 by · Leave a Comment 

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The house mouse (Mus musculus) is a small rodent, a mouse, one of the most numerous species of the genus Mus.

As a wild animal the house mouse mainly lives associated with humans, causing damage to crops and stored food.

The house mouse has been domesticated as the pet or fancy mouse, and as the laboratory mouse which is one of the most important model organisms in biology and medicine. It is by far the most commonly used genetically altered laboratory mammal.

House mice usually run, walk or stand on all fours; but when eating, fighting or orienting themselves, they stand only on the hind legs, supported by the tail. When running, the horizontal tail serves for balance; the end stands up vertically, unless the mouse is frightened. Mice are good jumpers, climbers, and swimmers.

Mice are mostly active during dusk or night; they do not like bright lights. They have an instinctual fear of so-called “black lighting” and strobe lighting, which leads to a common method of controlling mice in the home. They live in a wide variety of hidden places that are near food sources and construct nests from various soft materials. Mice are territorial and one dominant male usually lives together with several females and young. Dominant males respect each other’s territory and normally enter another’s territory only if it is vacant. If two or more males are held together in a cage, they will often turn aggressive unless they have been raised together from birth.

House mice primarily feed on plant matter, but they will also accept meat and dairy products. Although they are generally known to like fruits, they are repelled by the scent of many varieties of artificial fruit scent, for example strawberry or vanilla-scented candles. The reason for this is unknown, although it dates back to antiquity when Roman Senators used candles scented with strawberry oils to keep mice out of their sleeping chambers. They will drink water but require little of it, relying mainly on the moisture present in their food. They will eat their droppings to acquire nutrients produced by bacteria in their intestines. House mice, like other rodents, do not vomit.

Mice are afraid of rats, which often kill and (partially) eat them. This rat behavior is known as muricide. Despite this behavior free-living populations of rats and mice do exist together in forest areas in North America and elsewhere.

House mice are generally poor competitors and in most areas cannot survive away from human settlements in areas where other small mammals, such as wood mice, are present. However in some areas (such as Australia) mice are able to co-exist with other small rodent species.

House mice usually live in proximity to humans, in or around houses or fields. Originally native to Asia (probably northern India),[17] they spread to the Mediterranean Basin about 8000 BC, only spreading into the rest of Europe around 1000 BC. This time lag is thought to be because the mice require agrarian human settlements above a certain size. They have since been spread to all parts of the globe by humans.

Many studies have been done on mouse phylogenies to reconstruct early human movements. For example one study showed a previously unsuspected early link between Denmark and Madeira on the basis of the origin of the Madeiran mice.

House mice can transmit diseases, and can damage food and food packaging. Some of the diseases the house mouse carries can be deadly; for example, Murine typhus, Rickettsialpox, Tularemia, and the Bubonic plague. These mice can be very dangerous to people if they contaminate anything in their houses, especially food. It is also possible for wild house mice to transmit rabies, therefore a wild house mouse should never be handled. They can also cause substantial damage when feeding on grain. It is thought that house mice were the primary reason for the taming of the domestic cat. Various mousetraps have been developed to catch mice. Generally, rats are more harmful to humans than mice.

The first written reference to mice kept as pets occurs in the Erya, the oldest extant Chinese dictionary, from a mention in an 1100 B.C. version. Human domestication led to numerous strains of “fancy” or hobby mice with a variety of colors and a docile temperament. Domestic varieties of the house mouse called “feeder” mice are also used as food for some carnivorous pet reptiles, arthropods and fish. Mice bred for this purpose are genetically identical to other domestic mice, and can be kept as pets themselves

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Hieroglyphs

March 11, 2010 by · Leave a Comment 

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Hieroglyphs emerged from the preliterate artistic traditions of Egypt. For example, symbols on Gerzean pottery from circa4000 BC resemble hieroglyphic writing. For many years the earliest known hieroglyphic inscription was the Narmer Palette, found during excavations at Hierakonpolis (modern Kawm al-Ahmar) in the 1890s, which has been dated to circa 3200 BC. However, in 1998 a German archaeological team under Günter Dreyer excavating at Abydos (modern Umm el-Qa’ab) uncovered tomb U-j of a Predynastic ruler, and recovered three hundred clay labels inscribed with proto-hieroglyphs, dating to the Naqada IIIA period of the 33rd century BC. The first full sentence written in hieroglyphs so far discovered was found on a seal impression found in the tomb of Seth-Peribsen at Umm el-Qa’ab, which dates from the Second Dynasty. In the era of the Old Kingdom, the Middle Kingdom and the New Kingdom, about 800 hieroglyphs existed. By the Greco-Roman period, they numbered more than 5,000.

Scholars generally believe that Egyptian hieroglyphs “came into existence a little after Sumerian script, and, probably [were], invented under the influence of the latter …” For example, it has been stated that it is “probable that the general idea of expressing words of a language in writing was brought to Egypt from Sumerian Mesopotamia.” On the other hand, it has been stated that “the evidence for such direct influence remains flimsy” and that “a very credible argument can also be made for the independent development of writing in Egypt…”  Given the lack of direct evidence, “no definitive determination has been made as to the origin of hieroglyphics in ancient Egypt.”

Hieroglyphs consist of three kinds of glyphs: phonetic glyphs, including single-consonant characters that functioned like analphabet; logographs, representing morphemes; and determinatives, which narrowed down the meaning of a logographic or phonetic words.

As writing developed and became more widespread among the Egyptian people, simplified glyph forms developed, resulting in the hieratic (priestly) and demotic(popular) scripts. These variants were also more suited than hieroglyphs for use onpapyrus. Hieroglyphic writing was not, however, eclipsed, but existed alongside the other forms, especially in monumental and other formal writing. The Rosetta Stone contains three parallel scripts – hieroglyphic, demotic and Greek.

Hieroglyphs continued to be used under Persian rule (intermittent in the 6th and 5th centuries BC), and after Alexander the Great’s conquest of Egypt, during the ensuingMacedonian and Roman periods. It appears that the misleading quality of comments from Greek and Roman writers about hieroglyphs came about, at least in part, as a response to the changed political situation. Some believe that hieroglyphs may have functioned as a way to distinguish ‘true Egyptians’ from the foreign conquerors. Another reason may be the refusal to tackle a foreign culture on its own terms which characterized Greco-Roman approaches to Egyptian culture generally. Having learned that hieroglyphs were sacred writing, Greco-Roman authors imagined the complex but rational system as an allegorical, even magical, system transmitting secret, mystical knowledge.

By the 4th century, few Egyptians were capable of reading hieroglyphs, and the myth of allegorical hieroglyphs was ascendant. Monumental use of hieroglyphs ceased after the closing of all non-Christian temples in AD 391 by the Roman EmperorTheodosius I; the last known inscription is from Philae, known as the The Graffito of Esmet-Akhom, from AD 396

As active knowledge of the hieroglyphs and the related scripts disappeared, numerous attempts were made to decipher the hidden meaning of the ubiquitous inscriptions. The best known example from Antiquity are the “Hieroglyphica” by Horapollo, which offer an explanation of almost 200 glyphs. Horapollo seems to have had access to some genuine knowledge about the hieroglyphs as some words are identified correctly, although the explanations given are invariably wrong (the goose character used to write the word for ‘son’, z3, for example, is identified correctly, but explained wrongly to have been chosen because the goose loves his offspring the most while the real reason seems to have been purely phonetic). The Hieroglyphica do thus represent the start of more than a millenium of (mis)interpreting the hieroglyphs as symbolic rather than phonetic writing.

In the 9th and 10th century, Arab historians Dhul-Nun al-Misri and Ibn Wahshiyya offered their interpretation of the hieroglyphs. In his English translation of Ibn Wahshiyya’s work[10], Joseph Hammer points out that Athanasius Kirchnerused this among several other Arabic works in his own attempts at decipherment.

Kirchner’s interpretation of the hieroglyphs is probably the best known early modern European attempt at ‘decipherment’ (others include the works of Johannes Goropius Becanus), not least for the fantasticness of his claims. Like other interpretations before, Kirchner’s ‘translations’ were hampered by the fundamental notion that hieroglyphs recorded ideas and not the sounds of the language. As no bilingual texts were available, any such symbolic ‘translation’ could be proposed without the possibility of falsification.

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Tunnel

February 18, 2010 by · Leave a Comment 

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A tunnel is an underground passageway. The definition of what constitutes a tunnel is not universally agreed upon. However, in general tunnels are at least twice as long as they are wide. In addition, they should be completely enclosed on all sides, save for the openings at each end. Some civic planners define a tunnel as 0.1 miles (0.16 km) in length or longer, while anything shorter than this should be called an underpass or a chute. For example, the underpass beneath Yahata Station in Kitakyushu, Japan is only 0.08 miles (0.13 km) long and therefore should not be considered a tunnel.

A tunnel may be for pedestrians or cyclists, for general road traffic, for motor vehicles only, for rail traffic, or for a canal. Some are aqueducts, constructed purely for carrying water — for consumption, for hydroelectric purposes or as sewers — while others carry other services such as telecommunications cables. There are even tunnels designed as wildlife crossings for European badgers and other endangered species. Some secret tunnels have also been made as a method of entrance or escape from an area, such as the Cu Chi Tunnels or the tunnels connecting the Gaza Strip to Egypt. Some tunnels are not for transport at all but are fortifications, for example Mittelwerk and Cheyenne Mountain.

In the United Kingdom a pedestrian tunnel or other underpass beneath a road is called a subway. This term was used in the past in the United States, but now refers to underground rapid transit systems.

The central part of a rapid transit network is usually built in tunnels. To allow non-level crossings, some lines run in deeper tunnels than others. Rail stations with much traffic usually provide pedestrian tunnels from one platform to another, though others use bridges.

It is essential that any tunnel project starts with a comprehensive investigation of ground conditions. The results of the investigation will allow proper choice of machinery and methods for excavation and ground support, and will reduce the risk of encountering unforeseen ground conditions. In the early stages, the horizontal and vertical alignment will be optimized to make use of the best ground and water conditions.

In some cases, conventional desk and site studies will not produce sufficient information to assess, for example, the blocky nature of rocks, the exact location of fault zones, or stand-up times of softer ground. This may be a particular concern in large diameter tunnels. To overcome these problems, a pilot tunnel, or drift, may be driven ahead of the main drive. This smaller diameter tunnel will be easier to support when unexpected conditions occur, and will be incorporated in the final tunnel. Alternatively, horizontal boreholes may sometimes be used ahead of the advancing tunnel face.

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Static Electricity

February 11, 2010 by · Leave a Comment 

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Static electricity refers to the build up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Although charge exchange can happen whenever any two surfaces come into contact and separate, a static charge will only remain when at least one of the surfaces has a high resistance to electrical flow (an electrical insulator). The effects of static electricity are familiar to most people because we can see, feel and even hear the spark as the excess charge is neutralized when brought close to a large electrical conductor (for example a path to ground), or a region with an excess charge of the opposite polarity (positive or negative). The familiar phenomenon of a static ‘shock’ is caused by the neutralization of charge.

The materials we observe and interact with from day to day are formed from atoms and molecules that are electrically neutral, having an equal number of positive charges (protons, in the nucleus) and negative charges (electrons, in shells surrounding the nucleus). The phenomenon of static electricity requires a separation of positive and negative charges.

Removing or preventing a buildup of static charge can be as simple as opening a window or using a humidifier to increase the moisture content of the air, making the atmosphere more conductive. Air ionizers can perform the same task.

Items that are particularly sensitive to static discharge may be treated with the application of an antistatic agent, which adds a conducting surface layer that ensures any excess charge is evenly distributed. Fabric softeners and dryer sheets used in washing machines and clothes dryers are an example of an antistatic agent used to prevent and remove static cling.

Many semiconductor devices used in electronics are particularly sensitive to static discharge. Conductive antistatic bags are commonly used to protect such components, while people working on circuits containing them will often ground themselves using a conductive antistatic strap.

In the industrial settings such as paint or flour plants as well as in hospitals, antistatic safety boots are sometimes used to prevent a buildup of static charge due to contact with the floor. These shoes have soles with good conductivity. Anti-static shoes should not be confused with insulating shoes, which provide exactly the opposite benefit — some protection against serious electric shocks from the mains voltage.

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