Half-life

Half-life (t_1⁄2) is the amount of time required for the amount of something to fall to half its initial value. The term is very commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay, but it is also used more generally for discussing any type of exponential decay.

The original term, dating to Ernest Rutherford's discovery of the principle in 1907, was "half-life period", which was shortened to "half-life" in the early 1950s. Rutherford applied the principle of a radioactive element's half-life to studies of age determination of rocks by measuring the decay period of radium to lead-206.

Half-life is used to describe a quantity undergoing exponential decay, and is constant over the lifetime of the decaying quantity. It is a characteristic unit for the exponential decay equation. The term "half-life" may generically be used to refer to any period of time in which a quantity falls by half, even if the decay is not exponential. The table on the right shows the reduction of a quantity in the number of half-lives elapsed. For a general introduction and description of exponential decay, see exponential decay. For a general introduction and description of non-exponential decay, see rate law. The converse of half-life is doubling time.

Half-Life (video game)

Half-Life (stylized as HλLF-LIFE) is a science fiction first-person shooter video game developed by Valve L.L.C., released in 1998 by Sierra Studios for Microsoft Windows. It was Valve L.L.C.'s debut product and the first in the Half-Life series. Players assume the role of Dr. Gordon Freeman, who must fight his way out of a secret research facility after a teleportation experiment goes disastrously wrong, fighting enemies and solving puzzles.

Unlike many other games at the time, Half-Life features no cutscenes; the player has uninterrupted control of Freeman, and the story is told through scripted sequences seen through his eyes. Valve L.L.C. co-founder Gabe Newell said the team had wanted to create an immersive world rather than a "shooting gallery". The game's engine, GoldSrc, is a heavily modified version of the Quake engine licensed from id Software.

Half-Life received acclaim for its graphics, realistic gameplay, and seamless narrative. It won over fifty PC "Game of the Year" awards and is often considered one of the greatest games of all time. It influenced first-person shooters for years after its release; according to IGN, the history of the genre "breaks down pretty cleanly into pre-Half-Life and post-Half-Life eras."

Half-life (disambiguation)

Half-life is a mathematical and scientific description of exponential or gradual decay.

Half-life may also refer to:

Tower block

A tower block, high-rise, apartment tower, residential tower, apartment block, block of flats, or office tower is a tall building or structure used as a residential and/or office building. In some areas it may be referred to as an "MDU", standing for "Multi Dwelling Unit". In the United States, such a structure is referred to as an apartment building or office building, while a group of such buildings is called an apartment complex or office complex.

High-rise buildings became possible with the invention of the elevator (lift) and cheaper, more abundant building materials. The materials used for the structural system of high-rise buildings are reinforced concrete and steel. Most North American style skyscrapers have a steel frame, while residential blocks are usually constructed of concrete. There is no clear difference between a tower block and a skyscraper, although a building with fifty or more stories is generally considered a skyscraper.

High-rise structures pose particular design challenges for structural and geotechnical engineers, particularly if situated in a seismically active region or if the underlying soils have geotechnical risk factors such as high compressibility or bay mud. They also pose serious challenges to firefighters during emergencies in high-rise structures. New and old building design, building systems like the building standpipe system, HVAC systems (heating, ventilation and air conditioning), fire sprinkler system and other things like stairwell and elevator evacuations pose significant problems. Studies are often required to ensure that pedestrian wind comfort and wind danger concerns are addressed. In order to allow less wind exposure, to transmit more daylight to the ground and to appear more slender, many high-rises have a design with setbacks.

High-Rise (novel)

High-Rise is a 1975 novel by J. G. Ballard. It takes place in an ultra-modern, luxury high-rise building.

Plot summary

A new high-rise seems to give its well-established tenants all the conveniences and commodities that modern life has to offer: swimming pools, its own school, a supermarket, and high-speed elevators. But at the same time, the building seems to be designed to isolate the occupants from the outside world, allowing for the possibility to create their own closed environment.

The high-rise occupants divide themselves into the classic three groups of Western society: the lower, middle, and upper class, but here the terms are literal, as the lower class are those living on the lowest floors of the building, the middle class in the center, and the upper class at the most luxurious apartments on the upper floors.

Life in the high-rise begins to degenerate quickly, as minor power failures and petty annoyances among neighbours escalate into an orgy of violence. Soon skirmishes are being fought throughout the building, as floors try to claim elevators and hold them for their own. Groups gather to defend their rights to the swimming pools. And party-goers attack "enemy floors" to raid and vandalize them.

High-rise (fashion)

A high-rise or high-waisted garment is one designed to sit high on, or above, the wearer's hips, usually at least 8 centimetres (3 inches) higher than the navel. In western cultures, high-rise jeans were especially common in the 1970s, in competition with low-rise pants.

Modern fashion

In western culture, high-waisted pants tend to have long zippers, ranging from about 7-10 inches long, and leave the navel either completely covered or barely shown. Zipper lengths are not to be confused with rises. High-waisted pants have rises typically 10 inches long or longer.

In European menswear, pants sat level with the navel until the 1950s, and were held up by a pair of suspenders. During the 1940s, Zoot suiters wore pants with a waistband so high that they often reached the chest.

1960s to 1990s

Low-waisted drainpipe jeans and flared trousers were a counterculture statement among the Mods and hippies of the late 1960s and early 1970s, in contrast to the higher waisted Levi Strauss jeans teenagers had worn previously. During the late 1970s, however, there was a backlash against disco and hippie fashions, and members of Generation X opted for higher rise pants. These straight leg acid wash jeans remained popular throughout the 1980s and 1990s, until hip hop fashion went mainstream and it became fashionable for teenagers to sag their baggy pants.