Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Most Viewed Latest Alphabetical (A-Z) Alphabetical (Z-A)
Filter:
All Topic Review Biography Peer Reviewed Entry Video Entry
Topic Review
Lahar
A lahar ( /ˈlɑːhɑːr/, from Template:Lang-jv) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extremely destructive: they can flow tens of metres per second, they have been known to be up to 140 metres (460 ft) deep, and large flows tend to destroy any structures in their path. Notable lahars include those at Mount Pinatubo and Nevado del Ruiz, the latter of which killed thousands of people in the town of Armero.
  • 2.1K
  • 17 Oct 2022
Topic Review
Solar Storm of August 1972
The solar storms of August 1972 were a historically powerful series of solar storms with intense to extreme solar flare, solar particle event, and geomagnetic storm components in early August 1972, during solar cycle 20. The storm caused widespread electric‐ and communication‐grid disturbances through large portions of North America as well as satellite disruptions. On August 4, 1972, the storm caused the accidental detonation of numerous U.S. naval mines near Haiphong, North Vietnam. The coronal cloud's transit time from the Sun to the Earth is the fastest ever recorded.
  • 2.1K
  • 05 Dec 2022
Topic Review
Rodrigues
Rodrigues (French: Île Rodrigues [il ʁɔdʁiɡ]; Creole: Rodrig) is a 108 km2 (42 sq mi) autonomous outer island of the Republic of Mauritius in the Indian Ocean, about 560 km (350 mi) east of Mauritius. It is part of the Mascarene Islands, which include Mauritius and Réunion. Rodrigues is of volcanic origin and is surrounded by coral reef, and some tiny uninhabited islands lie just off its coast. The island used to be the tenth District of Mauritius; it gained autonomous status on 10 December 2002, and it is governed by the Rodrigues Regional Assembly. The capital of the island is Port Mathurin. Its inhabitants are Mauritian citizens. (As of 2014), the island's population was about 41,669, according to Statistics Mauritius. Most of the inhabitants are of African descent. Its economy is based mainly on fishing, farming, handicraft and a developing tourism sector. The island (together with Agaléga and Saint Brandon) forms part of the larger territory of the Republic of Mauritius with the President as head of state and the Chief Commissioner as head of government.
  • 2.1K
  • 11 Nov 2022
Topic Review
Multiple Attribute-based Decision-making Models
Sustainability of agricultural practices depends on economic, environmental, and social conditions. The Rajasthan state of India has arid climatic conditions where kharif crops are commonly grown. In this work, the four major criteria are considered such as the farm area, crop yield per unit area, the cost prices, and the market sales price. Merged analytic hierarchy process (AHP) and entropy techniques have been employed to give reasonable weight coefficients for the objective and subjective weights to each criterion. Multiple attribute-based decision-making models (MADM) have been developed using three proven techniques, namely the Exprom2, the technique for order of preference by similarity to ideal solution (TOPSIS), and the VlseKriterijumska Optimizacija I KompromisnoResenje (VIKOR). The crop Pennisetum glaucum emerged as the most productive kharif crop in the arid climatic conditions of Rajasthan, India under the given criteria. The sensitivity analysis of the three methods identifies the most significant criteria and validates that Pennisetum glaucum is the first ranked crop despite the interchange of the weights. The methodology used in this study may be applied across the globe to select appropriate crops for maximizing the profit, optimizing the natural resources, and promoting sustainable agricultural practices. This study may be used to enhance the agricultural gross domestic product (GDP) to make the agriculturalists self-sufficient and to help the state policymakers in making elective regional policies.
  • 2.0K
  • 05 Nov 2020
Topic Review
Mercator 1569 World Map
The Mercator world map of 1569 is titled Nova et Aucta Orbis Terrae Descriptio ad Usum Navigantium Emendate Accommodata (Renaissance Latin for "New and more complete representation of the terrestrial globe properly adapted for use in navigation"). The title shows that Gerardus Mercator aimed to present contemporary knowledge of the geography of the world and at the same time 'correct' the chart to be more useful to sailors. This 'correction', whereby constant bearing sailing courses on the sphere (rhumb lines) are mapped to straight lines on the plane map, characterizes the Mercator projection. While the map's geography has been superseded by modern knowledge, its projection proved to be one of the most significant advances in the history of cartography, inspiring map historian Nordenskiöld to write "The master of Rupelmonde stands unsurpassed in the history of cartography since the time of Ptolemy." The projection heralded a new era in the evolution of navigation maps and charts and it is still their basis. The map is inscribed with a great deal of text. The framed map legends (or cartouches) cover a wide variety of topics: a dedication to his patron and a copyright statement; discussions of rhumb lines, great circles and distances; comments on some of the major rivers; accounts of fictitious geography of the north pole and the southern continent. The full Latin texts and English translations of all the legends are given below. Other minor texts are sprinkled about the map. They cover such topics as the magnetic poles, the prime meridian, navigational features, minor geographical details, the voyages of discovery and myths of giants and cannibals. These minor texts are also given below. A comparison with world maps before 1569 shows how closely Mercator drew on the work of other cartographers and his own previous works, but he declares (Legend 3) that he was also greatly indebted to many new charts prepared by Portuguese and Spanish sailors in the portolan tradition. Earlier cartographers of world maps had largely ignored the more accurate practical charts of sailors, and vice versa, but the age of discovery, from the closing decade of the fifteenth century, stimulated the integration of these two mapping traditions: Mercator's world map is one of the earliest fruits of this merger.
  • 2.0K
  • 22 Nov 2022
Topic Review
Sinkhole
A sinkhole, also known as a cenote, sink, sink-hole, swallet, swallow hole, or doline (the different terms for sinkholes are often used interchangeably), is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes – the chemical dissolution of carbonate rocks or suffosion processes. Sinkholes vary in size from 1 to 600 m (3.3 to 2,000 ft) both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.
  • 2.0K
  • 11 Oct 2022
Topic Review
Evolutionary History of Life
The evolutionary history of life on Earth traces the processes by which living and fossil organisms evolved, from the earliest emergence of life to the present. Earth formed about 4.5 billion years (Ga) ago and evidence suggests life emerged prior to 3.7 Ga. (Although there is some evidence of life as early as 4.1 to 4.28 Ga, it remains controversial due to the possible non-biological formation of the purported fossils.) The similarities among all known present-day species indicate that they have diverged through the process of evolution from a common ancestor. Approximately 1 trillion species currently live on Earth of which only 1.75–1.8 million have been named and 1.6 million documented in a central database. These currently living species represent less than one percent of all species that have ever lived on earth. The earliest evidence of life comes from biogenic carbon signatures and stromatolite fossils discovered in 3.7 billion-year-old metasedimentary rocks from western Greenland. In 2015, possible "remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia. In March 2017, putative evidence of possibly the oldest forms of life on Earth was reported in the form of fossilized microorganisms discovered in hydrothermal vent precipitates in the Nuvvuagittuq Belt of Quebec, Canada, that may have lived as early as 4.28 billion years ago, not long after the oceans formed 4.4 billion years ago, and not long after the formation of the Earth 4.54 billion years ago. Microbial mats of coexisting bacteria and archaea were the dominant form of life in the early Archean Epoch and many of the major steps in early evolution are thought to have taken place in this environment. The evolution of photosynthesis, around 3.5 Ga, eventually led to a buildup of its waste product, oxygen, in the atmosphere, leading to the great oxygenation event, beginning around 2.4 Ga. The earliest evidence of eukaryotes (complex cells with organelles) dates from 1.85 Ga, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism. Later, around 1.7 Ga, multicellular organisms began to appear, with differentiated cells performing specialised functions. Sexual reproduction, which involves the fusion of male and female reproductive cells (gametes) to create a zygote in a process called fertilization is, in contrast to asexual reproduction, the primary method of reproduction for the vast majority of macroscopic organisms, including almost all eukaryotes (which includes animals and plants). However the origin and evolution of sexual reproduction remain a puzzle for biologists though it did evolve from a common ancestor that was a single celled eukaryotic species. Bilateria, animals having a left and a right side that are mirror images of each other, appeared by 555 Ma (million years ago). The earliest complex land plants date back to around 850 Ma, from carbon isotopes in Precambrian rocks, while algae-like multicellular land plants are dated back even to about 1 billion years ago, although evidence suggests that microorganisms formed the earliest terrestrial ecosystems, at least 2.7 Ga. Microorganisms are thought to have paved the way for the inception of land plants in the Ordovician. Land plants were so successful that they are thought to have contributed to the Late Devonian extinction event. (The long causal chain implied seems to involve the success of early tree archaeopteris (1) drew down CO2 levels, leading to global cooling and lowered sea levels, (2) roots of archeopteris fostered soil development which increased rock weathering, and the subsequent nutrient run-off may have triggered algal blooms resulting in anoxic events which caused marine-life die-offs. Marine species were the primary victims of the Late Devonian extinction.) Ediacara biota appear during the Ediacaran period, while vertebrates, along with most other modern phyla originated about 525 Ma during the Cambrian explosion. During the Permian period, synapsids, including the ancestors of mammals, dominated the land, but most of this group became extinct in the Permian–Triassic extinction event 252 Ma. During the recovery from this catastrophe, archosaurs became the most abundant land vertebrates; one archosaur group, the dinosaurs, dominated the Jurassic and Cretaceous periods. After the Cretaceous–Paleogene extinction event 66 Ma killed off the non-avian dinosaurs, mammals increased rapidly in size and diversity. Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify.
  • 2.0K
  • 24 Nov 2022
Topic Review
Canopy
In biology, the canopy is the aboveground portion of a plant cropping or crop, formed by the collection of individual plant crowns. In forest ecology, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms (epiphytes, lianas, arboreal animals, etc.). The communities that inhabit the canopy layer are thought to be involved in maintaining forest diversity, resilience, and functioning. Sometimes the term canopy is used to refer to the extent of the outer layer of leaves of an individual tree or group of trees. Shade trees normally have a dense canopy that blocks light from lower growing plants.
  • 1.9K
  • 25 Nov 2022
Topic Review
Hydrogen Production in Arctic Region
The development of markets for low-carbon energy sources requires reconsideration of issues related to extraction and use of oil and gas. Significant reserves of hydrocarbons are concentrated in Arctic territories, e.g., 30% of the world’s undiscovered natural gas reserves and 13% of oil. Associated petroleum gas, natural gas and gas condensate could be able to expand the scope of their applications. Natural gas is the main raw material for the production of hydrogen and ammonia, which are considered promising primary energy resources of the future, the oxidation of which does not release CO2. Complex components contained in associated petroleum gas and gas condensate are valuable chemical raw materials to be used in a wide range of applications.
  • 1.9K
  • 17 Apr 2024
Topic Review
One Tree Hill (New Zealand)
Maungakiekie / One Tree Hill is a 182-metre (597 ft) volcanic peak in Auckland, New Zealand. It is an important memorial place for both Māori and other New Zealanders. The suburb around the base of the hill is also called One Tree Hill. It is surrounded by the suburbs of Royal Oak to the west, and clockwise, Epsom, Greenlane, Oranga, and Onehunga. The summit provides views across the Auckland area, and allows visitors to see both of Auckland's harbours. The hill's scoria cones were erupted from three craters – one is intact and two have been breached by lava flows that rafted away part of the side of the scoria cone. Lava flows went in all directions, many towards Onehunga, covering an area of 20 square kilometres (7.7 sq mi), making it the second largest (in area covered) of the Auckland volcanic field, behind Rangitoto Island. The volcano erupted approximately 60,000 years ago.
  • 1.9K
  • 10 Nov 2022
Topic Review
Verneuil Process
The Verneuil process, also called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in the late 1800s by the French chemist Auguste Verneuil. It is primarily used to produce the ruby, sapphire and padparadscha varieties of corundum, as well as the diamond simulants rutile and strontium titanate. The principle of the process involves melting a finely powdered substance using an oxyhydrogen flame, and crystallising the melted droplets into a boule. The process is considered to be the founding step of modern industrial crystal growth technology, and remains in wide use to this day.
  • 1.9K
  • 18 Oct 2022
Topic Review
ELVs Recycling in Developing Countries
End-of-life vehicle is a vehicle that has reached the end of its useful life and requires proper treatment.
  • 1.8K
  • 28 Sep 2021
Topic Review
List of Volcanic Eruptions on Iceland
This is a list of recorded volcanic eruptions on Iceland.
  • 1.8K
  • 01 Nov 2022
Topic Review
Wolf Distribution
Wolf distribution is the species distribution of the wolf (Canis lupus). Originally, wolves occurred in Eurasia above the 12th parallel north and in North America above the 15th parallel north. However, deliberate human persecution has reduced the species' range to about one-third, because of livestock predation and fear of wolf attacks on humans. The species is now extirpated (made locally extinct) in much of Western Europe, Mexico, and the contiguous United States , and completely from the British Isles and the Japanese archipelago. In modern history, the gray wolf occurs mostly in wilderness and remote areas, particularly in Canada , Alaska, the Northern United States, Europe and Asia from about the 75th parallel north to the 12th parallel north. Wolf population declines have been arrested since the 1970s, and have fostered recolonization and reintroduction in parts of its former range, due to legal protection, changes in land-use and rural human population shifts to cities. Competition with humans for livestock and game species, concerns over the danger posed by wolves to people, and habitat fragmentation pose a continued threat to the species. Despite these threats, because of the gray wolf's relatively widespread range and stable population, it is classified as Least Concern on the IUCN Red List. In Africa the population of wolves is limited to the northern regions with the African golden wolf (Canis lupaster) north of the Sahara and the Ethiopian wolf (Canis simensis) in Ethiopia.
  • 1.7K
  • 25 Oct 2022
Topic Review
Varangian Guard
The Varangian Guard (Greek: Τάγμα τῶν Βαράγγων, Tágma tōn Varángōn) was an elite unit of the Byzantine Army, from the 10th to the 14th centuries, whose members served as personal bodyguards to the Byzantine Emperors. They are known for being primarily composed of Germanic peoples, specifically Norsemen from modern day Sweden (the Guard was formed approximately 200 years into the Viking Age) and Anglo-Saxons (after the Norman Conquest of England created an Anglo-Saxon diaspora, part of which found employment in Constantinople). The Rus' provided the earliest members of the Varangian Guard. They were in Byzantine service from as early as 874. The Guard was first formally constituted under Emperor Basil II in 988, following the Christianization of Kievan Rus' by Vladimir I of Kiev. Vladimir, who had recently usurped power in Kiev with an army of Varangian warriors, sent 6,000 men to Basil as part of a military assistance agreement. Basil's distrust of the native Byzantine guardsmen, whose loyalties often shifted, with fatal consequences, as well as the proven loyalty of the Varangians, many of whom had previously served in Byzantium, led the Emperor to employ them as his personal guardsmen. Immigrants from Sweden, Denmark , Norway and Iceland kept a predominantly Norse cast to the organization until the late 11th century. According to the late Swedish historian Alf Henrikson in his book Svensk Historia (History of Sweden), the Scandinavian Varangian guardsmen were recognized by long hair, a red ruby set in the left ear and ornamented dragons sewn on their chainmail shirts. In these years, Scandinavian men left to enlist in the Byzantine Varangian Guard in such numbers that a medieval Swedish law, Västergötlagen, from Västergötland declared no one could inherit while staying in "Greece"—the then Scandinavian term for the Byzantine Empire—to stop the emigration, especially as two other European courts simultaneously also recruited Scandinavians: Kievan Rus' c. 980–1060 and London 1018–1066 (the Þingalið). Composed primarily of Norsemen and Rus for the first 100 years, the Guard began to see increased numbers of Anglo-Saxons after the Norman conquest of England. By the time of the Emperor Alexios Komnenos in the late 11th century, the Varangian Guard was largely recruited from Anglo-Saxons and "others who had suffered at the hands of the Vikings and their cousins the Normans". The Anglo-Saxons and other Germanic peoples shared with the Vikings a tradition of faithful (to death if necessary) oath-bound service, and the Norman invasion of England resulted in many fighting men who had lost their lands and former masters and were looking for positions elsewhere. The Varangian Guard not only provided security for the Byzantine emperors, but also participated in many wars, often playing a decisive role, since they were usually deployed at critical moments of a battle. By the late 13th century, Varangians were mostly ethnically assimilated by the Byzantine Greeks, though the Guard remained in existence until at least mid-14th century. In 1400, there were still some people identifying themselves as "Varangians" in Constantinople.
  • 1.7K
  • 04 Nov 2022
Topic Review
Locative Media
Locative media or location-based media (LBM) are media of communication functionally bound to a location. The physical implementation of locative media, however, is not bound to the same location to which the content refers. Location-based media delivers multimedia and other content directly to the user of a mobile device dependent upon their location. Location information determined by means such as mobile phone tracking and other emerging real-time locating system technologies like Wi-Fi or RFID can be used to customize media content presented on the device. Locative media are digital media applied to real places and thus triggering real social interactions. While mobile technologies such as the Global Positioning System (GPS), laptop computers and mobile phones enable locative media, they are not the goal for the development of projects in this field.
  • 1.7K
  • 24 Oct 2022
Topic Review
Measuring Overtourism
The tourism debate prior to the COVID-19 pandemic was dominated by the problems inherent in overtourism, reflecting an inadequate land management. Although publications on overtourism have grown exponentially in recent years, its scientific study still has major shortcomings, particularly with regard to measurement. With the aim of overcoming this insufficiency, we have carried out a review of the literature (using the mapping review method) and, based on its conclusions, we have drawn up a proposal to systematise the measurement of overtourism by combining several tools: indicators, surveys, interviews, and other tools linked to the Internet and social networks. The results of the research make a contribution to the expansion of the literature on the topic and may have important practical implications in formulating effective land-use policies by guiding policy makers in the management of overtourism. They could be of use in both the early detection of overtourism and the design of policies that prevent and/or detect situations of risk and that correct existing problems. This is especially relevant in the current international context to implement the effective transition to a responsible tourism model post-COVID-19.
  • 1.7K
  • 06 Sep 2021
Topic Review
Hunga Tonga
Template:Infobox Island Hunga Tonga-Hunga Haʻapai is a volcanic island located about 30 kilometres (19 miles) south-southeast of Fonuafoʻou island in Tonga. The volcano is part of the highly active Tonga-Kermadec Islands volcanic arc, a subduction zone extending from New Zealand north-northeast to Fiji. It lies about 100 kilometres (62 mi) above a very active seismic zone. The island arc is formed at the convergent boundary where the Pacific Plate subducts under the Indo-Australian Plate.
  • 1.7K
  • 24 Oct 2022
Topic Review
Selenography
Selenography is the study of the surface and physical features of the Moon. Historically, the principal concern of selenographists was the mapping and naming of the lunar maria, craters, mountain ranges, and other various features. This task was largely finished when high resolution images of the near and far sides of the Moon were obtained by orbiting spacecraft during the early space era. Nevertheless, some regions of the Moon remain poorly imaged (especially near the poles) and the exact locations of many features (like crater depths) are uncertain by several kilometers. Today, selenography is considered to be a subdiscipline of selenology, which itself is most often referred to as simply "lunar science." The word selenography is derived from the Greek lunar deity Σελήνη Selene and γράφω graphō, "I write".
  • 1.7K
  • 11 Nov 2022
Topic Review
Behavioural Archaeology
Behavioural archaeology is an archaeological theory that expands upon the nature and aims of archaeology in regards to human behaviour and material culture. The theory was first published in 1975 by American archaeologist Michael B. Schiffer and his colleagues J. Jefferson Reid, and William L. Rathje. The theory proposes four strategies that answer questions about past, and present cultural behaviour. It is also a means for archaeologists to observe human behaviour and the archaeological consequences that follow. The theory was developed as a reaction to changes in archaeological thought, and expanding archaeological practise during the mid-late 20th century. It reacted to the increasing number of sub-disciplines emerging within archaeology as each came with their own unique methodologies. The theory was also a reaction to the processual thought process that emerged within the discipline some years prior. In recent years the use of behavioural archaeology has been regarded as a significant contribution to the archaeological community. The strategies outlined by Schiffer and his colleagues have developed into sub-disciplines or methodologies that are used and well-regarded in contemporary archaeological practise. Behavioural archaeology has positive effects on the method in which archaeologists use to reconstruct human behaviour.
  • 1.7K
  • 30 Nov 2022
  • Page
  • of
  • 16
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
ScholarVision Creations
Feedback