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HandWiki is the world's largest wiki-style encyclopedia dedicated to science, technology and computing. It allows you to create and edit articles as long as you have external citations and login account. In addition, this is a content management environment that can be used for collaborative editing of original scholarly content, such as books, manuals, monographs and tutorials.

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Life Table
In actuarial science and demography, a life table (also called a mortality table or actuarial table) is a table which shows, for each age, what the probability is that a person of that age will die before their next birthday ("probability of death"). In other words, it represents the survivorship of people from a certain population. They can also be explained as a long-term mathematical way to measure a population's longevity. Tables have been created by demographers including Graunt, Reed and Merrell, Keyfitz, and Greville. There are two types of life tables used in actuarial science. The period life table represents mortality rates during a specific time period of a certain population. A cohort life table, often referred to as a generation life table, is used to represent the overall mortality rates of a certain population's entire lifetime. They must have had to be born during the same specific time interval. A cohort life table is more frequently used because it is able to make a prediction of any expected changes in mortality rates of a population in the future. This type of table also analyzes patterns in mortality rates that can be observed over time. Both of these types of life tables are created based on an actual population from the present, as well as an educated prediction of the experience of a population in the near future. In order to find the true life expectancy average, 100 years would need to pass and by then finding that data would be of no use as healthcare is continually advancing. Other life tables in historical demography may be based on historical records, although these often undercount infants and understate infant mortality, on comparison with other regions with better records, and on mathematical adjustments for varying mortality levels and life expectancies at birth. From this starting point, a number of inferences can be derived. Life tables are also used extensively in biology and epidemiology. An area that uses this tool is Social Security. It examines the mortality rates of all the people who have Social Security to decide which actions to take. The concept is also of importance in product life cycle management. All mortality tables are specific to environmental and life circumstances, and are used to probabilistically determine expected maximum age within those environmental conditions.
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  • 02 Nov 2022
Topic Review
Stage Theory
Stage theories are based on the idea that elements in systems move through a pattern of distinct stages over time and that these stages can be described based on their distinguishing characteristics. Specifically, stages in cognitive development have a constant order of succession, later stages integrate the achievements of earlier stages, and each is characterized by a particular type of structure of mental processes which is specific to it. The time of appearance may vary to a certain extent depending upon environmental conditions. "Stage theory" can also be applied beyond psychology to describe phenomena more generally where multiple phases lead to an outcome. The term "stage theory" can thus be applied to various scientific, sociological and business disciplines. In these contexts, stages may not be as rigidly defined, and it is possible for individuals within the multi-stage process to revert to earlier stages or skip some stages entirely.
  • 11.4K
  • 02 Nov 2022
Topic Review
Chlamydomonas Reinhardtii
Chlamydomonas reinhardtii is a single-cell green alga about 10 micrometres in diameter that swims with two flagella. It has a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an eyespot that senses light. Chlamydomonas species are widely distributed worldwide in soil and fresh water. Chlamydomonas reinhardtii is an especially well studied biological model organism, partly due to its ease of culturing and the ability to manipulate its genetics. When illuminated, C. reinhardtii can grow photoautotrophically, but it can also grow in the dark if supplied with organic carbon. Commercially, C. reinhardtii is of interest for producing biopharmaceuticals and biofuel, as well being a valuable research tool in making hydrogen.
  • 4.4K
  • 02 Nov 2022
Topic Review
Night Thoughts of a Classical Physicist
Night Thoughts of a Classical Physicist is an historical novel by historian of science Russell McCormmach, published in 1982 by Harvard University Press. Set in 1918, the book explores the world of physics in the early 20th century—including the advent of modern physics and the role of physicists in World War I—through the recollections of the fictional Viktor Jakob. Jakob is an old German physicist who spent most of his career during the period of classical physics, a paradigm being confronted by the rapid and radical developments of relativistic physics in 1900s and 1910s. This conflict allows for extensive examination of the various tensions placed on Jakob by the academic environment, the German academic system, and the changing academic culture of the early 20th century. The character of Jakob, a professor at a minor German university, is an amalgam of German physicists based on archival research by McCormmach. In the novel, he recalls interactions and events, documented in extensive footnotes to genuine publications and archival sources, involving many of the well-known physicists of the late 19th and early 20th centuries. Night Thoughts, pointedly criticized for its lack of literary merit by some reviewers, was generally praised for its attempt at forging a new approach to history and historical fiction by incorporating extensive research into the text.
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  • 02 Nov 2022
Topic Review
Single Particle Trajectories
Single particle trajectories (SPTs) consist of a collection of successive discrete points causal in time. These trajectories are acquired from images in experimental data. In the context of cell biology, the trajectories are obtained by the transient activation by a laser of small dyes attached to a moving molecule. Molecules can now by visualized based on recent Super-resolution microscopy, which allow routine collections of thousands of short and long trajectories. These trajectories explore part of a cell, either on the membrane or in 3 dimensions and their paths are critically influenced by the local crowded organization and molecular interaction inside the cell, as emphasized in various cell types such as neuronal cells, astrocytes, immune cells and many others.
  • 607
  • 02 Nov 2022
Topic Review
Bicentric Quadrilateral
In Euclidean geometry, a bicentric quadrilateral is a convex quadrilateral that has both an incircle and a circumcircle. The radii and center of these circles are called inradius and circumradius, and incenter and circumcenter respectively. From the definition it follows that bicentric quadrilaterals have all the properties of both tangential quadrilaterals and cyclic quadrilaterals. Other names for these quadrilaterals are chord-tangent quadrilateral and inscribed and circumscribed quadrilateral. It has also rarely been called a double circle quadrilateral and double scribed quadrilateral. If two circles, one within the other, are the incircle and the circumcircle of a bicentric quadrilateral, then every point on the circumcircle is the vertex of a bicentric quadrilateral having the same incircle and circumcircle. This is a corollary of Poncelet's porism, which was proved by the French mathematician Jean-Victor Poncelet (1788–1867).
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  • 02 Nov 2022
Topic Review
Wolfram Alpha
Wolfram Alpha (also styled WolframAlpha, and Wolfram|Alpha) is a computational knowledge engine or answer engine developed by Wolfram Alpha LLC, a subsidiary of Wolfram Research. It is an online service that answers factual queries directly by computing the answer from externally sourced "curated data", rather than providing a list of documents or web pages that might contain the answer as a search engine might. Wolfram Alpha, which was released on May 18, 2009, is based on Wolfram's earlier flagship product Wolfram Mathematica, a computational platform or toolkit that encompasses computer algebra, symbolic and numerical computation, visualization, and statistics capabilities. Additional data is gathered from both academic and commercial websites such as the CIA's The World Factbook, the United States Geological Survey, a Cornell University Library publication called All About Birds, Chambers Biographical Dictionary, Dow Jones, the Catalogue of Life, CrunchBase, Best Buy, the FAA and optionally a user's Facebook account.
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  • 02 Nov 2022
Topic Review
Airco DH.10
The Airco DH.10 Amiens was a United Kingdom twin-engined medium bomber designed and built towards the end of the First World War. It served briefly postwar with the RAF.
  • 917
  • 08 Nov 2022
Topic Review
Discrete Event Simulation
A discrete-event simulation (DES) models the operation of a system as a discrete sequence of events in time. Each event occurs at a particular instant in time and marks a change of state in the system. Between consecutive events, no change in the system is assumed to occur; thus the simulation can directly jump in time from one event to the next. This contrasts with continuous simulation in which the simulation continuously tracks the system dynamics over time. Instead of being event-based, this is called an activity-based simulation; time is broken up into small time slices and the system state is updated according to the set of activities happening in the time slice. Because discrete-event simulations do not have to simulate every time slice, they can typically run much faster than the corresponding continuous simulation. A more recent method is the three-phased approach to discrete event simulation (Pidd, 1998). In this approach, the first phase is to jump to the next chronological event. The second phase is to execute all events that unconditionally occur at that time (these are called B-events). The third phase is to execute all events that conditionally occur at that time (these are called C-events). The three phase approach is a refinement of the event-based approach in which simultaneous events are ordered so as to make the most efficient use of computer resources. The three-phase approach is used by a number of commercial simulation software packages, but from the user's point of view, the specifics of the underlying simulation method are generally hidden.
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  • 02 Nov 2022
Topic Review
Kidney Paired Donation
Kidney Paired Donation (KPD) or Paired Exchange, is an approach to living donor kidney transplantation where patients with incompatible donors swap kidneys to receive a compatible kidney. KPD is used in situations where a potential donor is incompatible. Because better donor HLA and age matching are correlated with lower lifetime mortality and longer lasting kidney transplants, many compatible pairs are also participating in swaps to find better matched kidneys. In the United States, the National Kidney Registry organizes the majority of U.S. KPD transplants, including the largest swaps. Swaps involving more than two recipients are termed a kidney chain. The first large swap was a 60 participant chain in 2012 that appeared on the front page of the New York Times and the second, even larger swap, included 70 participants and was completed in 2014. Other KPD programs in the U.S. include the UNOS program which was launched in 2010 and completed its 100th KPD transplant in 2014 and the Alliance for Paired Donation. According to a 2019 study, kidney exchanges improve overall transplant quality, which leads to fewer transplant failures. The exchanges also reduce waiting times for patients needing kidney transplants. The study found that the health care cost savings of kidney exchanges are substantial.
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