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Topic Review
Semaphore Telegraph
A semaphore telegraph is an early system of conveying information by means of visual signals, using towers with pivoting shutters, also known as blades or paddles. Information is encoded by the position of the mechanical elements; it is read when the shutter is in a fixed position. The most widely used system was invented in 1792 in France by Claude Chappe, and was popular in the late eighteenth to early nineteenth centuries. Lines of relay towers with a semaphore rig at the top were built within line-of-sight of each other, at separations of 5–20 miles (8.0–32.2 km). Operators at each tower would watch the neighboring tower through a spyglass, and when the semaphore arms began to move spelling out a message, they would pass the message on to the next tower. This system was much faster than post riders for conveying a message over long distances, and also had cheaper long-term operating costs, once constructed. Semaphore lines were a precursor of the electrical telegraph, which would replace them half a century later, and would also be cheaper, faster, and more private. The line-of-sight distance between relay stations was limited by geography and weather, and prevented the optical telegraph from crossing wide expanses of water, unless a convenient island could be used for a relay station. Modern derivatives of the semaphore system include flag semaphore (a flag relay system) and the heliograph (optical telegraphy using mirror-directed sunlight reflections).
  • 8.3K
  • 28 Nov 2022
Topic Review
Head-Up Display (Video Gaming)
In video gaming, the HUD (heads-up display) or status bar is the method by which information is visually relayed to the player as part of a game's user interface. It takes its name from the head-up displays used in modern aircraft. The HUD is frequently used to simultaneously display several pieces of information including the main character's health, items, and an indication of game progression (such as score or level).
  • 8.3K
  • 31 Oct 2022
Topic Review
PSA XUD
The PSA XUD is a Diesel engine designed and built by PSA - Peugeot and Citroën. It is an Indirect injection (IDI) engine, that uses a version of the Ricardo Consulting Engineers Ricardo Comet V prechamber cylinder head design. The engine comes in 1.8 L (1,769 cc) N/A, 1.8 Turbo, 1.9 L (1,905 cc) N/A, Turbo, 2.1 12 valve N/A and Turbo and was the predecessor to the HDI range of engines. Early HDi Engines were a PSA design, later 16 valve engines were jointly developed with Ford.
  • 8.3K
  • 28 Oct 2022
Topic Review Peer Reviewed
OAM of Light: Origins and Applications
Orbital Angular Momentum (OAM) of light is generating growing interest within the scientific community. This entry reviews the origins and applications of OAM. It is the counterpart of linear momentum for systems in rotation. The general expression of OAM is discussed, followed by its implications in terms of phase distribution and donut-shaped intensity profiles. Applications described include the generation of optical torque, telecommunications enhancement, and the rotational Doppler effect, emphasizing the role and consequences of angular momentum. In particular, its use to manipulate systems or to detect rotations is described. Finally, further developments and technological barriers are considered.
  • 8.3K
  • 17 Sep 2025
Topic Review
Slow Sand Filtration for Raw Water Treatment
Filtration methods are traditional techniques of water purification used by mankind since ancient times. By filtering, water can be cleaned of sand, silt, turbidity, scale, and other suspended particles. Modern slow sand filters (SSFs) for water purification were first used in the 19th century in England. Therefore, they are often called English filters. The first slow filter was built by the English engineer James Simpson in 1829 in London to purify water from the river Thames.
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  • 02 Jun 2023
Topic Review
Biochemistry of Hydrogen Peroxide
Hydrogen Peroxide (H2O2) is the nonionized 2-electron reduction product of unstable molecular oxygen (O2), which plays a central role in maintaining the redox cycle of living cells.
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  • 10 Jan 2022
Topic Review
List of Temples in Tamil Nadu
This is a list of temples in the Indian state of Tamil Nadu which is famed for Hindu temples, culture and tradition and commonly known as the Land of Temples. Tamil Nadu has more temples than any other states of India. Tamil Nadu is home to more than 40,000 Hindu, Buddhist, Jain, local deities, Ayyavazhi temples and is aptly called "the land of temples" by media. Many are at least 800 to 5000 years old and are found scattered all over the state. The rulers of various dynasties constructed these temples over centuries. Vimanas (storeys) and Gopuram (towering gateways to the temple complex) best characterize the temples of Tamil Nadu. As per Tamil Nadu Hindu Endowments Board, there are 38,615 temples. Most of the largest Hindu temples reside here. Studded with complex architecture, variety of sculptures, and rich inscriptions, the temples remain the very essence of the culture and heritage of Tamil land, with historical records dating back to at least 3,000 years. In Madurai, Meenakshi Amman Temple has high ‘Gopuram’ towers ornamented with colourful figures. On Pamban Island, Ramanathaswamy Temple is a famous pilgrimage site. The town of Kanyakumari, at India's southernmost tip, is the site of ritual sunrises. The state also abounds with temple tanks. The state has 2,359 temple tanks located in 1,586 temples. The government has identified 1,068 tanks for renovation. People from all over the world visits Temples of Tamil Nadu and it is the major Tourist attraction in India.
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  • 07 Nov 2022
Topic Review
The Satanic Bible
The Satanic Bible is a collection of essays, observations, and rituals published by Anton LaVey in 1969. It is the central religious text of LaVeyan Satanism, and is considered the foundation of its philosophy and dogma. It has been described as the most important document to influence contemporary Satanism. Though The Satanic Bible is not considered to be sacred scripture in the way that the Christian Bible is to Christianity, LaVeyan Satanists regard it as an authoritative text as it is a contemporary text that has attained for them scriptural status. It extols the virtues of exploring one's own nature and instincts. Believers have been described as "atheistic Satanists" because they believe that God is not an external entity, but rather something that each person creates as a projection of their own personality—a benevolent and stabilizing force in their life. There have been thirty printings of The Satanic Bible, selling over a million copies. The Satanic Bible is composed of four books: The Book of Satan, The Book of Lucifer, The Book of Belial, and The Book of Leviathan. The Book of Satan challenges the Ten Commandments and the Golden Rule, and promotes Epicureanism. The Book of Lucifer holds most of the philosophy in The Satanic Bible, with twelve chapters discussing topics such as indulgence, love, hate, and sex. LaVey also uses the book to dispel rumors surrounding the religion. In The Book of Belial, LaVey details rituals and magic. He discusses the required mindset and focus for performing a ritual, and provides instructions for three rituals: those for sex, compassion, or destruction. The Book of Leviathan provides four invocations for Satan, lust, compassion, and destruction. It also lists the nineteen Enochian Keys (adapted from John Dee's Enochian keys), provided both in Enochian and in English translation. There have been both positive and negative reactions to The Satanic Bible. It has been described as "razor-sharp" and "influential". Criticism of The Satanic Bible stems both from qualms over LaVey's writing and disapproval of the content itself. LaVey has been criticized for plagiarizing sections, and accusations have been made that his philosophies are largely borrowed. Attempts have been made to ban the book in schools, public libraries, and prisons, though these attempts are somewhat rare.
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  • 29 Nov 2022
Topic Review
Laser Absorption Spectroscopy
Laser absorption spectroscopy (LAS) is an absorption spectroscopic method that employs a laser as the light source and measures the chemical concentration based on detection of a variation of laser beam intensity after transmission along the optical path. 
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  • 10 Sep 2020
Topic Review
Various Attachments for Implant Overdentures
This study presents an overview of the biomechanical and biomolecular aspects of various attachments for implant overdenture. We focused on the following topics: attachment systems, retention of various attachments, stress distribution with different attachments, the design and fabrication of attachments, digital techniques in overdenture attachments, and the effects of attachments in peri-implant health. We found that plastic resin is commonly used for ball and bar attachments, whereas nylon resin is commonly used in locator attachments. The locator system offers a valuable attachment option for implant-retained overdenture. Attachment retention reduces while lateral force increases with implant inclination in overdenture. The higher the retention of an overdenture attachment, the higher the transferred stresses. Additionally, clip loading produces more stress in implants and precision elements than bar-retained dentures. As such, we conclude that the ball and locator systems the best overdenture systems due to their superior tissue response, survival rate, and patient satisfaction.
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  • 03 Nov 2021
Topic Review
Self-confidence
The concept of self-confidence is commonly used as self-assurance in one's personal judgment, ability, power, etc. One's self confidence increases from experiences of having satisfactorily completed particular activities. It is a positive belief that in the future one can generally accomplish what one wishes to do. Self-confidence is not the same as self-esteem, which is an evaluation of one's own worth, whereas self-confidence is more specifically trust in one's ability to achieve some goal, which one meta-analysis suggested is similar to generalization of self-efficacy. Abraham Maslow and many others after him have emphasized the need to distinguish between self-confidence as a generalized personality characteristic, and self-confidence with respect to a specific task, ability or challenge (i.e. self-efficacy). Self-confidence typically refers to general self-confidence. This is different from self-efficacy, which psychologist Albert Bandura has defined as a “belief in one’s ability to succeed in specific situations or accomplish a task” and therefore is the term that more accurately refers to specific self-confidence. Psychologists have long noted that a person can possess self-confidence that he or she can complete a specific task (self-efficacy) (e.g. cook a good meal or write a good novel) even though they may lack general self-confidence, or conversely be self-confident though they lack the self-efficacy to achieve a particular task (e.g. write a novel). These two types of self-confidence are, however, correlated with each other, and for this reason can be easily conflated.
  • 8.3K
  • 18 Oct 2022
Topic Review
Two-Dimensional Space
Two-dimensional space (also known as 2D space, 2-space, or bi-dimensional space) is a geometric setting in which two values (called parameters) are required to determine the position of an element (i.e., point). The set [math]\displaystyle{ \mathbb{R}^2 }[/math] of pairs of real numbers with appropriate structure often serves as the canonical example of a two-dimensional Euclidean space. For a generalization of the concept, see dimension. Two-dimensional space can be seen as a projection of the physical universe onto a plane. Usually, it is thought of as a Euclidean space and the two dimensions are called length and width.
  • 8.3K
  • 28 Nov 2022
Topic Review
Urban Open Space
In land-use planning, urban open space is open-space areas reserved for parks, "green spaces", and other open areas. The landscape of urban open spaces can range from playing fields to highly maintained environments to relatively natural landscapes. Generally considered open to the public, urban open spaces are sometimes privately owned, such as higher education campuses, neighborhood/community parks/gardens, and institutional or corporate grounds. Areas outside city boundaries, such as state and national parks as well as open space in the countryside, are not considered urban open space. Streets, piazzas, plazas and urban squares are not always defined as urban open space in land use planning.
  • 8.3K
  • 14 Oct 2022
Topic Review
Frogs in Culture
Frogs play a variety of roles in culture, appearing in folklore and fairy tales such as the Brothers Grimm story of The Frog Prince. In ancient Egypt and Mesopotamia, frogs symbolized fertility, while in classical antiquity, the Greeks and Romans associated frogs with fertility, harmony, and licentiousness. Frogs are the subjects of fables attributed to Aesop, of proverbs in various cultures, and of art. Frog characters such as Kermit the frog and Pepe the Frog feature in popular culture. They are eaten in some parts of the world including France. In Australia, a fondant dessert is known as frog cake.
  • 8.3K
  • 27 Nov 2022
Topic Review
Polyelectrolyte
Polyelectrolytes are polymers of oppositely charged ions and their properties differ profoundly than their repeating units. Over recent years, much advancement has been made in the synthesis, characterization, and application of polyelectrolytes and polyelectrolyte complexes (PECs). It has many applications as flocculation agents, dispersant agents, and as super-plasticizers. In this article, the synthesis, types, characteristics, and application of PECs mainly for drug delivery and dynamics study are reviewed.
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  • 27 Oct 2020
Topic Review
Bonded Marine Hoses for Floating Offshore Structures (FOS)
By characterisation, a marine hose is a unique type of flexible riser used in fluid transfer. By definition, a marine hose is simply a fluid transfer conduit utilised in transferring, discharging, loading, and transporting fluids from an oil well to the platform of a floating platform or a floating structure. The fluid transfer system for bonded marine hoses is dependent on floating offshore structures (FOS). Single Point Mooring (SPM) systems are component aspects of the techno-economic design and FOS operation.
  • 8.3K
  • 28 Mar 2022
Topic Review
Factors Affecting Hair Health
Hair health is associated with personal distress and psychological well-being. Even though hair loss (alopecia) does not affect humans’ biological health, it affects an individual’s social well-being. So, treatment for hair problems and improving hair health are obligatory. 
  • 8.2K
  • 07 Feb 2023
Topic Review
List of Extinct Animals of the Nordics
This is a list of extinct animals of the Nordics (including Sweden, Norway , Denmark , Finland , and Iceland). The list consists of common name, Latin name, known geographical range, and approximate extinction date, with the "†" symbol indicating the species is considered extinct worldwide.
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  • 03 Nov 2022
Topic Review
MPQ (File Format)
MPQ (Mo'PaQ, short for Mike O'Brien Pack, named after its creator), is an archiving file format used in several of Blizzard Entertainment's games. MPQs used in Blizzard's games generally contain a game's data files, including graphics, sounds, and level data. The format's capabilities include compression, encryption, file segmentation, extensible file metadata, cryptographic signature and the ability to store multiple versions of the same file for internationalization, platform-specific differences and patching. MPQ archives can use a variety of compression algorithms which may also be combined.
  • 8.2K
  • 02 Dec 2022
Topic Review
Social Cohesion
Social cohesion refers to the degree of unity, solidarity, and social bonds within a society or community. It encompasses the sense of belonging, trust, and cooperation among individuals and groups, contributing to social stability, resilience, and well-being. Social cohesion is essential for fostering a harmonious and inclusive society where individuals can collaborate, support one another, and collectively address societal challenges.
  • 8.2K
  • 26 Jan 2024
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