|
Late-life Mortality Deceleration
In gerontology, late-life mortality deceleration is the disputed theory that hazard rate increases at a decreasing rate in late life rather than increasing exponentially as in the Gompertz law. Late-life mortality deceleration is a well-established phenomenon in insects, which often spend much of their lives in a constant hazard rate region, but it is much more controversial in mammals. animal testing on rodents, Rodent studies have found varying conclusions, with some finding short-term periods of mortality deceleration in mice, others not finding such. Baboon studies show no mortality deceleration. An analogous deceleration occurs in the failure rate of manufactured products; this analogy is elaborated in the reliability theory of aging and longevity. Late-life mortality deceleration was first proposed as occurring in human aging in (which also introduced the Gompertz law), and observed as occurring in humans in , and has since become one of the pillars of the biodemography ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radioactive Decay
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha decay ( ), beta decay ( ), and gamma decay ( ), all of which involve emitting one or more particles. The weak force is the mechanism that is responsible for beta decay, while the other two are governed by the electromagnetism and nuclear force. A fourth type of common decay is electron capture, in which an unstable nucleus captures an inner electron from one of the electron shells. The loss of that electron from the shell results in a cascade of electrons dropping down to that lower shell resulting in emission of discrete X-rays from the transitions. A common example is iodine-125 commonly used in medical settings. Radioactive decay is a stochastic (i.e. random) proce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Age (journal)
Gerontology ( ) is the study of the social, cultural Culture () is an umbrella term which encompasses the social behavior, institutions, and Social norm, norms found in human Society, societies, as well as the knowledge, beliefs, arts, laws, Social norm, customs, capabilities, and habits of the ..., Psychology, psychological, cognitive, and Biology, biological aspects of aging. The word was coined by Ilya Ilyich Mechnikov in 1903, from the Ancient Greek, Greek , ''geron'', "old man" and , ''-logia'', "study of". The field is distinguished from geriatrics, which is the branch of medicine that specializes in the treatment of existing disease in older adults. Gerontologists include researchers and practitioners in the fields of biology, nursing, medicine, criminology, dentistry, social work, physical and occupational therapy, psychology, psychiatry, sociology, economics, political science, architecture, geography, pharmacy, public health, housing, and anthropology. The mult ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baby Boom
A baby boom is a period marked by a significant increase of birth rate. This demographic phenomenon is usually ascribed within certain geographical bounds of defined national and cultural populations. People born during these periods are often called baby boomers. The cause of baby booms involves various fertility factors. The best-known baby boom occurred in the mid-twentieth century, sometimes considered to have started after the end of the Second World War, sometimes from the late 1930s, and ending in the 1960s. Africa "According to the new UNICEF report, almost 2 billion babies will be born in Africa between 2015 and 2050 and the 2 main driving forces behind this surge in births and children are continued high fertility rates and rising numbers of women able to have children of their own." By 2050, Africa is predicted to account for about 55% of all births in the world, 40% of all children under the age of five, and 37% of all children worldwide (under 18). Africa will be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Logistic Function
A logistic function or logistic curve is a common S-shaped curve (sigmoid curve) with equation f(x) = \frac, where For values of x in the domain of real numbers from -\infty to +\infty, the S-curve shown on the right is obtained, with the graph of f approaching L as x approaches +\infty and approaching zero as x approaches -\infty. The logistic function finds applications in a range of fields, including biology (especially ecology), biomathematics, chemistry, demography, economics, geoscience, mathematical psychology, probability, sociology, political science, linguistics, statistics, and artificial neural networks. A generalization of the logistic function is the hyperbolastic function of type I. The standard logistic function, where L=1,k=1,x_0=0, is sometimes simply called ''the sigmoid''. It is also sometimes called the ''expit'', being the inverse of the logit. History The logistic function was introduced in a series of three papers by Pierre François Verhulst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reliability Theory Of Aging
The reliability theory of aging is an attempt to apply the principles of reliability theory to create a mathematical model of senescence. The theory was published in Russian by Leonid A. Gavrilov and Natalia S. Gavrilova as ''Biologiia prodolzhitelʹnosti zhizni'' in 1986, and in English translation as ''The Biology of Life Span: A Quantitative Approach'' in 1991. One of the models suggested in the book is based on an analogy with the reliability theory. The underlying hypothesis is based on the (previously suggested) premise that humans are born in a highly defective state. This is then made worse by environmental and mutational damage; exceptionally high redundancy due to the extremely high number of low-reliable components (e.g.., cells) allows the organism to survive for a while. The theory suggests an explanation of two aging phenomena for higher organisms: the Gompertz law Gomperz, Gompertz, Gumpertz, Gumperz, Gomperts or Gompers is a surname. Notable people with the su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Difference Quotient
In single-variable calculus, the difference quotient is usually the name for the expression : \frac which when taken to the limit as ''h'' approaches 0 gives the derivative of the function ''f''. The name of the expression stems from the fact that it is the quotient of the difference of values of the function by the difference of the corresponding values of its argument (the latter is (''x'' + ''h'') - ''x'' = ''h'' in this case). The difference quotient is a measure of the average rate of change of the function over an interval (in this case, an interval of length ''h''). The limit of the difference quotient (i.e., the derivative) is thus the instantaneous rate of change. By a slight change in notation (and viewpoint), for an interval 'a'', ''b'' the difference quotient : \frac is called the mean (or average) value of the derivative of ''f'' over the interval 'a'', ''b'' This name is justified by the mean value theorem, which states that for a differentiable function ''f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Estimator
In statistics, an estimator is a rule for calculating an estimate of a given quantity based on observed data: thus the rule (the estimator), the quantity of interest (the estimand) and its result (the estimate) are distinguished. For example, the sample mean is a commonly used estimator of the population mean. There are point and interval estimators. The point estimators yield single-valued results. This is in contrast to an interval estimator, where the result would be a range of plausible values. "Single value" does not necessarily mean "single number", but includes vector valued or function valued estimators. ''Estimation theory'' is concerned with the properties of estimators; that is, with defining properties that can be used to compare different estimators (different rules for creating estimates) for the same quantity, based on the same data. Such properties can be used to determine the best rules to use under given circumstances. However, in robust statistics, statistica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sacher Formula
Sacher is a surname. Origins can be traced back to Germany. Notable people with the surname include: *Franz Sacher, Austrian baker ** Hotel Sacher, a five-star hotel in Vienna *Harry Sacher, British Zionist and lawyer *Lara Sacher, Australian actress * Paul Sacher, Swiss conductor, patron and impresario *Sarolta Zalatnay (born Charlotte Sacher, 1947), Hungarian singer *Helmut Sacher Helmut is a German name. Variants include Hellmut, Helmuth, and Hellmuth. From old German, the first element deriving from either ''heil'' ("healthy") or ''hiltja'' ("battle"), and the second from ''muot'' ("spirit, mind, mood"). Helmut may refer ..., German painter See also * Leopold von Sacher-Masoch, Austrian writer and journalist {{surname, Sacher German-language surnames ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Death Master File
The Death Master File (DMF) is a computer database file made available by the United States Social Security Administration since 1980. It is known commercially as the Social Security Death Index (SSDI). The file contains information about persons who had Social Security numbers and whose deaths were reported to the Social Security Administration from 1962 to the present; or persons who died before 1962, but whose Social Security accounts were still active in 1962. , the file contained information on 111 million deaths. In 2011, some records were removed from the file. Overview The data include: * Name (Given name, surname), since 1990s the middle initial * Date of birth (Year, Month, Day) * Date of death (Year, Month), since 2000 the day of month * Social Security number * Whether death has been verified or a death certificate has been observed. In 2011, the following information was removed: * Last ZIP code of the person while alive * ZIP code to which the lump sum death benefi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exponential Decay
A quantity is subject to exponential decay if it decreases at a rate proportional to its current value. Symbolically, this process can be expressed by the following differential equation, where is the quantity and (lambda) is a positive rate called the exponential decay constant, disintegration constant, rate constant, or transformation constant: :\frac = -\lambda N. The solution to this equation (see derivation below) is: :N(t) = N_0 e^, where is the quantity at time , is the initial quantity, that is, the quantity at time . Measuring rates of decay Mean lifetime If the decaying quantity, ''N''(''t''), is the number of discrete elements in a certain set, it is possible to compute the average length of time that an element remains in the set. This is called the mean lifetime (or simply the lifetime), where the exponential time constant, \tau, relates to the decay rate constant, λ, in the following way: :\tau = \frac. The mean lifetime can be looked at as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gerontology
Gerontology ( ) is the study of the social, cultural, psychological, cognitive, and biological aspects of aging. The word was coined by Ilya Ilyich Mechnikov in 1903, from the Greek , ''geron'', "old man" and , ''-logia'', "study of". The field is distinguished from geriatrics, which is the branch of medicine that specializes in the treatment of existing disease in older adults. Gerontologists include researchers and practitioners in the fields of biology, nursing, medicine, criminology, dentistry, social work, physical and occupational therapy, psychology, psychiatry, sociology, economics, political science, architecture, geography, pharmacy, public health, housing, and anthropology. The multidisciplinary nature of gerontology means that there are a number of sub-fields which overlap with gerontology. There are policy issues, for example, involved in government planning and the operation of nursing homes, investigating the effects of an aging population on society, and the de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
