Computer security, cybersecurity (cyber security), or information technology security (IT security) is the protection of computer systems and networks from attack by malicious actors that may result in unauthorized information disclosure, theft of, or damage to hardware, software, or data, as well as from the disruption or misdirection of the services they provide.The field has become of significance due to the expanded reliance on computer systems, the Internet, and wireless network standards such as Bluetooth and Wi-Fi, and due to the growth of smart devices, including smartphones, televisions, and the various devices that constitute the Internet of things (IoT). Cybersecurity is one of the most significant challenges of the contemporary world, due to both the complexity of information systems and the societies they support. Security is of especially high importance for systems that govern large-scale systems with far-reaching physical effects...

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Met-enkephalin, also known as metenkefalin (INN), sometimes referred to as opioid growth factor (OGF), is a naturally occurring, endogenous opioid peptide that has opioid effects of a relatively short duration. It is one of the two forms of enkephalin, the other being leu-enkephalin. The enkephalins are considered to be the primary endogenous ligands of the δ-opioid receptor, due to their high potency and selectivity for the site over the other endogenous opioids. History Met-enkephalin was discovered and characterized by John Hughes, Hans Kosterlitz, et al. in 1975 after a search for endogenous ligands of the opioid receptors. Chemistry Met-enkephalin is a pentapeptide with the amino acid sequence tyr-gly-gly-phe-met. The tyrosine residue at position 1 is thought to be analogous to the 3-hydroxyl group on morphine. Biochemistry Distribution Met- enkephalin is found mainly in the adrenal medulla and throughout the central nervous system (CNS), including in the striatum, cerebral...

The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. It does not require the user to transmit any data, and operates independently of any telephonic or Internet reception, though these technologies can enhance the usefulness of the GPS positioning information. It provides critical positioning capabilities to military, civil, and commercial users around the world. Although the United States government created, controls and maintains the GPS system, it is freely accessible to anyone with a GPS receiver.The GPS project was started by the U.S. Department of Defense in 1973. The first prototype spacecraft was launched in 1978 and the full constellation of 24 satellites became operational...

Polymer physics is the field of physics that studies polymers, their fluctuations, mechanical properties, as well as the kinetics of reactions involving degradation and polymerisation of polymers and monomers respectively.While it focuses on the perspective of condensed matter physics, polymer physics is originally a branch of statistical physics. Polymer physics and polymer chemistry are also related with the field of polymer science, where this is considered the applicative part of polymers. Polymers are large molecules and thus are very complicated for solving using a deterministic method. Yet, statistical approaches can yield results and are often pertinent, since large polymers (i.e., polymers with many monomers) are describable efficiently in the thermodynamic limit of infinitely many monomers (although the actual size is clearly finite). Thermal fluctuations continuously affect the shape of polymers in liquid solutions, and modeling their effect requires using principles from statistical mechanics and dynamics. As a corollary, temperature strongly affects the physical behavior of polymers in solution, causing phase transitions, melts, and so on...

Aerodynamics, from Ancient Greek: ἀήρ aero (air) + Ancient Greek: δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dynamics and its subfield of gas dynamics. The term aerodynamics is often used synonymously with gas dynamics, the difference being that "gas dynamics" applies to the study of the motion of all gases, and is not limited to air. The formal study of aerodynamics began in the modern sense in the eighteenth century, although observations of fundamental concepts such as aerodynamic drag were recorded much earlier. Most of the early efforts in aerodynamics were directed toward achieving heavier-than-air flight, which was first demonstrated by Otto Lilienthal in 1891. Since then, the use of aerodynamics through mathematical analysis, empirical approximations, wind tunnel experimentation, and computer simulations has formed a rational basis for the development of heavier-than-air flight and a number of other technologies. Recent work in aerodynamics has focused on issues related...

Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.9.2 billion tonnes of plastic are estimated to have been made between 1950 and 2017. More than half this plastic has been produced since 2004. In 2020, 400 million tonnes of plastic were produced. If global trends on plastic demand continue, it is estimated that by 2050 annual global plastic production will reach over 1,100 million tonnes. The success and dominance of plastics starting in the early 20th century has caused widespread environmental problems, due to their slow decomposition...

The flintlock mechanism is a type of lock used on muskets, rifles, and pistols from the early 17th to the mid-19th century. It is commonly referred to as a "flintlock" (without the word mechanism), though that term is also commonly used for the weapons themselves as a whole, and not just the lock mechanism. The flintlock mechanism, also known as the true flintlock, was developed in France in the early 17th century. It quickly replaced earlier technologies, such as the matchlock and wheellock and the earlier flintlocks. It continued to be in common use for over two centuries, until it was finally replaced by the percussion lock. History Flintlock firing mechanisms made their appearance in the 16th century in the form of the snaplock, the snaphance, the miquelet, and the doglock. The so-called true flintlock was developed in France in the early 17th century. Though its exact origins are not known, credit for the development of the true flintlock is usually given to Marin le Bourgeoys, an artist, gunsmith, luthier, and inventor from Normandy, France. Marin le Bourgeoys's basic design became the standard for flintlocks...

A ballpoint pen, also known as a biro (British English), ball pen (Hong Kong, Indian and Philippine English), or dot pen (Nepali) is a pen that dispenses ink (usually in paste form) over a metal ball at its point, i.e. over a "ball point". The metal commonly used is steel, brass, or tungsten carbide. The design was conceived and developed as a cleaner and more reliable alternative to dip pens and fountain pens, and it is now the world's most-used writing instrument; millions are manufactured and sold daily. It has influenced art and graphic design and spawned an artwork genre. Some pen manufacturers produce designer ballpoint pens for the high-end and collectors' markets. History Origins The concept of using a "ball point" within a writing instrument to apply ink to paper has existed since the late 19th century. In these inventions, the ink was placed in a thin tube whose end was blocked by a tiny ball, held so that it could not slip into the tube or...

An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power generation), heat energy (e.g. geothermal), chemical energy, electric potential and nuclear energy (from nuclear fission or nuclear fusion). Many of these processes generate heat as an intermediate energy form, so heat engines have special importance. Some natural processes, such as atmospheric convection cells convert environmental heat into motion (e.g. in the form of rising air currents). Mechanical energy is of particular importance in transportation, but also plays a role in many industrial processes such as cutting, grinding, crushing, and mixing. Mechanical heat engines convert heat into work via various thermodynamic processes. The internal combustion engine is perhaps the most common example of a mechanical heat engine, in which heat from the combustion of a fuel causes rapid pressurisation of the gaseous combustion products in the combustion chamber, causing them to expand and drive a piston, which turns a crankshaft...