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Topic Review
Cretaceous–Paleogene Extinction Event
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction,[lower-alpha 2] was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the exception of some ectothermic species such as the sea turtles and crocodilians, no tetrapods weighing more than 25 kilograms (55 pounds) survived. It marked the end of the Cretaceous period, and with it the end of the entire Mesozoic Era, opening the Cenozoic Era that continues today. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows high levels of the metal iridium, which is rare in the Earth's crust, but abundant in asteroids. As originally proposed in 1980 by a team of scientists led by Luis Alvarez and his son Walter, it is now generally thought that the K–Pg extinction was caused by the impact of a massive comet or asteroid 10 to 15 km (6 to 9 mi) wide, 66 million years ago, which devastated the global environment, mainly through a lingering impact winter which halted photosynthesis in plants and plankton. The impact hypothesis, also known as the Alvarez hypothesis, was bolstered by the discovery of the 180 km (112 mi) Chicxulub crater in the Gulf of Mexico's Yucatán Peninsula in the early 1990s, which provided conclusive evidence that the K–Pg boundary clay represented debris from an asteroid impact. The fact that the extinctions occurred simultaneously provides strong evidence that they were caused by the asteroid. A 2016 drilling project into the Chicxulub peak ring confirmed that the peak ring comprised granite ejected within minutes from deep in the earth, but contained hardly any gypsum, the usual sulfate-containing sea floor rock in the region: The gypsum would have vaporized and dispersed as an aerosol into the atmosphere, causing longer-term effects on the climate and food chain. In October 2019, researchers reported that the event rapidly acidified the oceans producing ecological collapse and, in this way as well, produced long-lasting effects on the climate, and accordingly was a key reason for the end-Cretaceous mass extinction. In January 2020, scientists reported new evidence that the extinction event was mostly a result of the meteorite impact and not volcanism. Other causal or contributing factors to the extinction may have been the Deccan Traps and other volcanic eruptions, climate change, and sea level change. A wide range of species perished in the K–Pg extinction, the best-known being the non-avian dinosaurs. It also destroyed a myriad of other terrestrial organisms, including some mammals, pterosaurs, birds, lizards, insects, and plants. In the oceans, the K–Pg extinction killed off plesiosaurs and mosasaurs and devastated teleost fish, sharks, mollusks (especially ammonites, which became extinct), and many species of plankton. It is estimated that 75% or more of all species on Earth vanished. Yet the extinction also provided evolutionary opportunities: In its wake, many groups underwent remarkable adaptive radiation — sudden and prolific divergence into new forms and species within the disrupted and emptied ecological niches. Mammals in particular diversified in the Paleogene, evolving new forms such as horses, whales, bats, and primates. The surviving group of dinosaurs were avians, ground and water fowl who radiated into all modern species of bird. Teleost fish, and perhaps lizards also radiated.
  • 8.6K
  • 03 Nov 2022
Topic Review
Puruṣārtha
Puruṣārtha (Sanskrit: पुरुषार्थ) literally means an "object of human pursuit". It is a key concept in Hinduism, and refers to the four proper goals or aims of a human life. The four puruṣārthas are Dharma (righteousness, moral values), Artha (prosperity, economic values), Kama (pleasure, love, psychological values) and Moksha (liberation, spiritual values). All four Purusarthas are important, but in cases of conflict, Dharma is considered more important than Artha or Kama in Hindu philosophy. Moksha is considered the ultimate ideal of human life. At the same time, this is not a consensus among all Hindus, and many have different interpretations of the hierarchy, and even as to whether one should exist. Historical Indian scholars recognized and debated the inherent tension between active pursuit of wealth (Artha purusartha) and pleasure (Kama), and renunciation of all wealth and pleasure for the sake of spiritual liberation (Moksha). They proposed "action with renunciation" or "craving-free, dharma-driven action", also called Nishkam Karma as a possible solution to the tension.
  • 8.6K
  • 14 Oct 2022
Topic Review
Burden of Proof
The burden of proof (Latin: onus probandi, shortened from Onus probandi incumbit ei qui dicit, non ei qui negat) is the obligation on a party in a dispute to provide sufficient warrant for its position.
  • 8.6K
  • 25 Nov 2022
Topic Review
Benazir Income Support Programme
The Benazir Income Support Programme (BISP) also Known as Ehsaas Programme Pakistan is a federal unconditional cash transfer poverty reduction program in Pakistan . Launched in July 2008, it is the largest single social safety net program in the country with nearly Rs. 90 billion ($900 million) distributed to 5.4 million beneficiaries in 2016. The Department for International Development of the United Kingdom is the largest foreign backer of the program, providing $244 million (or 27%) of the total funds in 2016 with the Pakistani Government providing the rest. As of 2016, the program distributes Rs.19,338 (or approx. $195) per annum distributed per month. The stipend is linked to the Consumer Price Index and is paid through a smart card. For now, Dr Sania Nishtar is Chairman of BISP in regime of PTI governance.
  • 8.6K
  • 21 Oct 2022
Topic Review
Surface Cleaning Methods
It is difficult to avoid surface contaminants in the processes of integrated circuit manufacturing, optical elements processing and additive forging. The presence of surface contaminants will bring great problems to above process. For example, in large- scale integrated circuits manufacturing, the submicron contaminants on silicon wafer surface will cause defects in the chip directly [1]. And in the manufacture of optical elements, the quality of the cleaned surface will directly affect the damage resistance of optical elements [2], and the presence of surface contaminants will affect its service life [3]. Similarly, during the additive forging process, the surface contaminants will affect the interface healing state of the substrate and ultimately affect its bonding performance. However, surface contaminants can be removed effectively by a suitable surface cleaning method, so surface cleaning is of great significance to solve the above problems.
  • 8.6K
  • 29 Oct 2020
Topic Review
Atonement in Christianity
In Christian theology, atonement describes how human beings can be reconciled to God through Christ's sacrificial suffering and death. Atonement refers to the forgiving or pardoning of sin in general and original sin in particular through the suffering, death and resurrection of Jesus, enabling the reconciliation between God and his creation. Within Christianity there are, historically, three or four main theories for how such atonement might work: Other theories include recapitulation theory, the "shared atonement" theory and scapegoat theory. The English word 'atonement' originally meant "at-one-ment", i.e. being "at one", in harmony, with someone. It is used to describe the saving work that God did through Christ to reconcile the world to himself, and also of the state of a person having been reconciled to God. Throughout the centuries, Christians have used different metaphors and given differing explanations of the atonement to express how the atonement might work. Churches and denominations may vary in which metaphor or explanation they consider most accurately fits into their theological perspective; however all Christians emphasize that Jesus is the Saviour of the world and through his death the sins of humanity have been forgiven.
  • 8.6K
  • 01 Nov 2022
Topic Review
Social Media in Speaking Skills
The ubiquitous nature of social media (SM) makes it a very essential tool to use in the world of education, especially with the advent of the COVID-19 pandemic which has led to a paradigm shift in the approaches used in the teaching and learning of English language skills. Findings reveal that there are improvements in speaking skills, as well as confidence to speak and a decline in speaking anxiety. Teachers and educators can now make use of the various social media platforms such as Telegram, Facebook, WhatsApp, and others to provide learners with more practice that is not only restricted to the classroom but has moved beyond it.
  • 8.6K
  • 18 Nov 2021
Topic Review
Standard Conditions for Temperature and Pressure
Standard temperature and pressure (STP) are standard sets of conditions for experimental measurements to be established to allow comparisons to be made between different sets of data. The most used standards are those of the International Union of Pure and Applied Chemistry (IUPAC) and the National Institute of Standards and Technology (NIST), although these are not universally accepted standards. Other organizations have established a variety of alternative definitions for their standard reference conditions. In chemistry, IUPAC changed the definition of standard temperature and pressure in 1982: STP should not be confused with the standard state commonly used in thermodynamic evaluations of the Gibbs energy of a reaction. NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). This standard is also called normal temperature and pressure (abbreviated as NTP). These stated values of STP used by NIST have not been verified and require a source. However, values cited in Modern Thermodynamics with Statistical Mechanics by Carl S. Helrich and A Guide to the NIST Chemistry WebBook by Peter J. Linstrom suggest a common STP in use by NIST for thermodynamic experiments is 298.15 K (25°C, 77°F) and 1 bar (14.5038 psi, 100 kPa). The International Standard Metric Conditions for natural gas and similar fluids are 288.15 K (15.00 °C; 59.00 °F) and 101.325 kPa. In industry and commerce, standard conditions for temperature and pressure are often necessary to define the standard reference conditions to express the volumes of gases and liquids and related quantities such as the rate of volumetric flow (the volumes of gases vary significantly with temperature and pressure): standard cubic meters per second (Sm3/s), and normal cubic meters per second (Nm3/s). However, many technical publications (books, journals, advertisements for equipment and machinery) simply state "standard conditions" without specifying them; often substituting the term with older "normal conditions", or "NC". In special cases this can lead to confusion and errors. Good practice always incorporates the reference conditions of temperature and pressure. If not stated, some room environment conditions are supposed, close to 1 atm pressure, 293 K (20 °C), and 0% humidity.
  • 8.5K
  • 09 Nov 2022
Topic Review
Underwater Wireless Sensor Networks
The underwater wireless sensor network (UWSN) is a network used to perform monitoring of tasks over a specific region; it is equipped with smart sensors and vehicles that are adapted to communicate cooperatively through wireless connections [1]. The surface sink retrieves the data from sensor nodes. The sink node has a transceiver that can control acoustic signals received from underwater nodes. The transceiver also can transmit and receive long-range radio frequency signals for communication with the onshore station. The collected data are used locally or connected to another network for a particular purpose [2].
  • 8.5K
  • 26 Oct 2020
Topic Review
Plasma technology water purification
Plasma technology water purification is a new water treatment technology developed according to the trend of industrial water use in the 21st century. It is effective, efficient, scalable, versatile and customizable. These technologies must be able to adapt to new contaminants, reduce energy consumption, maintain or improve the proportionality between power and flow, demonstrate various flow capacities, minimize the transformation of existing infrastructure, prepare for imminent regulations, and tailor chemistry to site-specific requirements. New methods of water treatment by plasma must have all the above-mentioned properties and pose the least risk to public health. NTAPPs and their chemical reactions release energy and reactive chemical species that can kill bacteria and microorganisms, resulting in the disinfection of water. The advantage of this technique is that it can be performed in ambient air under atmospheric pressure without a vacuum system. Furthermore, NTAPP does not involve chemical products such as Cl. NTAPP can be used for water treatment in three ways: via direct, indirect, and bubbling methods.
  • 8.5K
  • 10 Jun 2021
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