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Reliability theory of aging and longevity is a scientific approach aimed to gain theoretical insights into mechanisms of biological aging and species survival patterns by applying a general theory of systems failure, known as reliability theory.

Reliability theory allows researchers to predict the age-related failure kinetics for a system of given architecture (reliability structure) and given reliability of its components. Applications of reliability-theory approach to the problem of biological aging and species longevity lead to the following conclusions:

1. Redundancy is a key of the notion for understanding aging and the systemic nature of aging in particular. Systems, which are redundant in numbers of irreplaceable elements, do deteriorate (i.e., are aging) over time, even if they are built of non-aging elements.

2. Paradoxically, the apparent aging rate or expression of aging (measured as relative differences in failure rates between compared age groups) is higher for systems with higher redundancy levels.

3. Redundancy exhaustion over the life course explains the observed 'compensation law of mortality' (mortality convergence at later life, when death rates are becoming relatively similar at advanced ages for different populations of the same biological species), as well as the observed late-life mortality deceleration, leveling-off, and mortality plateaus.

4. Living organisms seem to be formed with a high initial load of damage (HIDL hypothesis), and therefore their lifespan and aging patterns may be sensitive to early-life conditions that determine this initial damage load during early development. The idea of early-life programming of aging and longevity may have important practical implications for developing early-life interventions promoting health and longevity.

5. Reliability theory explains why mortality rates increase exponentially with age (the Gompertz law) in many species, by taking into account the initial flaws (defects) in newly formed systems. It also explains why organisms "prefer" to die according to the Gompertz law, while technical devices usually fail according to the Weibull (power) law. Theoretical conditions are specified when organisms die according to the Weibull law: organisms should be relatively free of initial flaws and defects. The theory makes it possible to find a general failure law applicable to all adult and extreme old ages, where the Gompertz and the Weibull laws are just special cases of this more general failure law.

6. Reliability theory helps evolutionary theories to explain how the age of onset of deleterious mutations could be postponed during evolution, which could be easily achieved by a simple increase in initial redundancy levels. From the reliability perspective, the increase in initial redundancy levels is the simplest way to improve survival at particularly early reproductive ages (with gains fading at older ages). This matches exactly with the higher fitness priority of early reproductive ages emphasized by evolutionary theories. Evolutionary and reliability ideas also help in understanding why organisms seem to "choose" a simple but short-term solution of the survival problem through enhancing the systems' redundancy, instead of a more permanent but complicated solution based on rigorous repair (with the potential of achieving negligible senescence). Thus there are promising opportunities for merging the reliability and evolutionary theories of aging.

Overall, the reliability theory provides a parsimonious explanation for many important aging-related phenomena and suggests a number of interesting testable predictions. Therefore, reliability theory seems to be a promising approach for developing a comprehensive theory of aging and longevity integrating mathematical methods with specific biological knowledge and evolutionary ideas.

Reliability theory of aging provides an optimistic perspective on the opportunities for healthy life-extension. According to reliability theory, human lifespan is not fixed, and it could be further increased through better body maintenance, repair, and replacement of the failed body parts in the future.

Source : www.wikipedia.org

A fantasy world is a kind of invented world, part of a imagined life used in fantasy novels and games. Typical worlds involve magic or magical abilities and a medieval theme. A few worlds may be a parallel world tenuously connected to Earth via mysterious portals or items; imaginary Earth set in the remote past or future; or an totally independant world set in a different universe.

Many fantasy worlds describe heavily on real world history, geography and sociology, and also on folklore.

The setting of a fantasy work is often of great importance to the plot and characters of the story. The setting itself can be imperiled by the evil of the story, suffer thinning, and be restored by the transformation the story brings about.Stories that use the setting as merely a backdrop for the story can be criticized for their failure to use it fully.

Even when the land itself is not in danger, it is often used symbolically, for thematic purposes, and to underscore moodes.

Early fantasy worlds appeared as fantasy lands, part of the same planet but separated by geographical barriers. Oz, though a fantasy world in every way, is described as part of this world.Although peasants who seldom if ever traveled far from their villages could not conclusively say that it was impossible that, for example, an ogre could live a day's travel away, distant continents were soon necessary for such fantastic speculation to be plausible, and finally, further exploration rendered such fantasy lands implausible. Even within the span of decades, Oz, which had been set in a desert in the United States,was relocated into the Pacific Ocean.

Dream frames were also once common for encasing the fantasy world with an explanation of its marvels. Such a dream frame was added to the story of The Wonderful Wizard of Oz for the movie version; in the book, Oz is clearly defined as an actual place.These dream-settings have been criticized, and are far less frequent today.

This change is part of a general trend toward more self-consistent and substantive fantasy worlds.This has also altered the nature of the plots; earlier works often feature a solitary individual whose adventures in the fantasy world are of personal significiance, and where the world clearly exists to give scope to these adventures, and later works more often feature characters in a social web, where their actions are to save the world and those in it from peril.

Fantasy worlds created through a process world building are known as a constructed world. Constructed worlds elaborate and make self-consistent the setting of a fantasy work. World building relies on materials and concepts taken from the real world.

Despite the use of magic or other fantastic elements such as dragons, the world is normally presented as one that would function normally, one in which people could actually live, making economic, historical, and ecological sense. It is considered a flaw to have, for example, pirates living in lands far from trade routes, or to assign prices for a night's stay in an inn that would equate to several years' income for a farmer. Furthermore, the fantastic elements should perfectly operate according to self-consistent rules of their own; for example, if wizards' spells sap their strength, a wizard who does not appear to suffer this must either be putting up a facade, or have an alternative explanation. This distinguishes fantasy worlds from surrealism and even from such dream worlds such as are found in Alice's Adventures in Wonderland and Through the Looking-Glass.

Source : www.wikipedia.org