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Topic Review
β-Adrenergic Stimulation
β-adrenergic receptor stimulation (β-ARS) is a physiological mechanism that regulates cardiovascular function under stress conditions or physical exercise, producing a positive inotropic (enhanced contraction), lusitropic (faster relaxation), and chronotropic (increased heart rate) effect. 
  • 6.4K
  • 04 Aug 2021
Topic Review
Short-Faced Bear
The short-faced bear (Arctodus sp.) is an extinct bear genus that inhabited North America during the Pleistocene epoch from about 1.8 Mya until 11,000 years ago. It was the most common tremarctine bear in North America and many of its fossils have been found in the La Brea tar pits in southern California . There are two recognized species: the lesser short-faced bear (Arctodus pristinus) and the giant short-faced bear (Arctodus simus), with the latter considered to be one of the largest known terrestrial mammalian carnivores that has ever existed. It has been hypothesized that their extinction coincides with the Younger Dryas period of global cooling commencing around 10,900 BC.
  • 6.4K
  • 05 Nov 2022
Topic Review
Herfindahl–Hirschman Index
The Herfindahl index (also known as Herfindahl–Hirschman Index, HHI, or sometimes HHI-score) is a measure of the size of firms in relation to the industry they are in and an indicator of the amount of competition among them. Named after economists Orris C. Herfindahl and Albert O. Hirschman, it is an economic concept widely applied in competition law, antitrust and also technology management. HHI is calculated by squaring the market share of each competing firm in the industry and then summing the resulting numbers,(sometimes limited to the 50 largest firms), where the market shares are expressed as fractions or points. The result is proportional to the average market share, weighted by market share. As such, it can range from 0 to 1.0, moving from a huge number of very small firms to a single monopolistic producer. Increases in the Herfindahl index generally indicate a decrease in competition and an increase of market power, whereas decreases indicate the opposite. Alternatively, if whole percentages are used, the index ranges from 0 to 10,000 "points". For example, an index of .25 is the same as 2,500 points. The major benefit of the Herfindahl index in relationship to such measures as the concentration ratio is that it gives more weight to larger firms. Other benefits of the Herfindahl index includes its simple calculation method and the small amount of easily obtainable data required for the calculation. The measure is essentially equivalent to the Simpson diversity index, which is a diversity index used in ecology; the inverse participation ratio (IPR) in physics; and the effective number of parties index in politics.
  • 6.4K
  • 24 Oct 2022
Topic Review
Artificial Flower
Artificial flowers are imitations of natural flowering plants used for commercial or residential decoration. They are sometimes made for scientific purposes (the collection of glass flowers at Harvard University, for example, illustrates the flora of the United States). Artificial plants vary widely from mass-produced varieties that are distinguishable from real plants by casual observation to highly detailed botanical or artistic specimens. Materials used in their manufacture have included painted linen and shavings of stained horn in ancient Egypt, gold and silver in ancient Rome, rice-paper in China , silkworm cocoons in Italy, colored feathers in South America, and wax and tinted shells. Modern techniques involve carved or formed soap, nylon netting stretched over wire frames, ground clay, and mass-produced injection plastic mouldings. Polyester has been the main material for manufacturing artificial flowers since the 1970s. Most artificial flowers in the market nowadays are made of polyester fabric.
  • 6.4K
  • 05 Sep 2025
Topic Review
Mac OS Memory Management
Historically, the classic Mac OS used a form of memory management that has fallen out of favor in modern systems. Criticism of this approach was one of the key areas addressed by the change to Mac OS X. The original problem for the engineers of the Macintosh was how to make optimum use of the 128 KB of RAM with which the machine was equipped, on Motorola 68000-based computer hardware that did not support virtual memory. Since at that time the machine could only run one application program at a time, and there was no fixed secondary storage, the engineers implemented a simple scheme which worked well with those particular constraints. That design choice did not scale well with the development of the machine, creating various difficulties for both programmers and users.
  • 6.4K
  • 15 Nov 2022
Topic Review
Varna Necropolis
The so-called Varna Necropolis (Bulgarian: Варненски некропол) (also Varna Cemetery) is a burial site from 4569–4340 BC in the western industrial zone of Varna (approximately half a kilometre from Lake Varna and 4 km from the city centre), internationally considered one of the key archaeological sites in world prehistory. There were other necropoles dating from later Greek and Roman periods around the ancient city. The oldest gold treasure in the world, dating from this period, was discovered at the site.
  • 6.4K
  • 28 Oct 2022
Topic Review
Royal Ordnance L7
The Royal Ordnance L7 is the basic model of the United Kingdom 's most successful tank gun. The L7 is a 105 mm L/52 rifled design by the Royal Ordnance Factories intended for use in armoured fighting vehicles, replacing the earlier 20-pounder (84 mm) tank gun mounted on the Centurion tank. The successful L7 gun has been fitted on many armored vehicles including the British Centurion (starting from the Mk. 5/2 variant), the German Leopard 1 and early variants of the US M1 Abrams (M1 and M1IP). The L7 is a popular weapon and continued in use even after it was superseded by the L11 series 120 mm rifled tank gun, for some Centurion tanks operating as Artillery Forward Observation and Armoured Vehicle, Royal Engineers (AVRE) vehicles. The L7, and adaptations of it, can be found as standard or retrofitted equipment on a wide variety of tanks developed during the Cold War.
  • 6.4K
  • 08 Nov 2022
Topic Review
Wavelet Scattering Transform
A knowledge-based feature extraction technique has been developed by Bruna and Malat named wavelet scattering transform (WST), which utilizes complex wavelets to balance the discrimination ability and stability of the time-frequency domain signal.
  • 6.4K
  • 09 Dec 2022
Topic Review
Sesquiterpene Lactones
Sesquiterpene lactones, a vast group of terpenoids isolated from Asteraceae family species, exhibit a wide variety of biological activities and several of them are already available on the medicines market, such as artemisinin. Here are presented and discussed the most recent and impactful results in vivo, preclinical and clinical studies, involving a selection of ten sesquiterpene lactones (alantolactone, arglabin, costunolide, cynaropicrin, helenalin, inuviscolide, lactucin, parthenolide, thapsigargin and tomentosin) and some of their derivatives.
  • 6.4K
  • 28 Oct 2020
Topic Review
Wearable Devices for Non-Invasive Sensing
The development of wearable sensors is aimed at enabling continuous real-time health monitoring, which leads to timely and precise diagnosis anytime and anywhere. Unlike conventional wearable sensors that are somewhat bulky, rigid, and planar, research for next-generation wearable sensors has been focused on establishing fully-wearable systems. To attain such excellent wearability while providing accurate and reliable measurements, fabrication strategies should include (1) proper choices of materials and structural designs, (2) constructing efficient wireless power and data transmission systems, and (3) developing highly-integrated sensing systems.
  • 6.4K
  • 09 Feb 2021
Topic Review
Science, Technology, Society and Environment Education
Science, technology, society and environment (STSE) education, originates from the science technology and society (STS) movement in science education. This is an outlook on science education that emphasizes the teaching of scientific and technological developments in their cultural, economic, social and political contexts. In this view of science education, students are encouraged to engage in issues pertaining to the impact of science on everyday life and make responsible decisions about how to address such issues (Solomon, 1993 and Aikenhead, 1994)
  • 6.4K
  • 20 Oct 2022
Topic Review
The Pathogenesis of Epilepsy
Epilepsy is a chronic neurological disorder characterized by recurring spontaneous seizures. Drug resistance appears in 30% of patients and it can lead to premature death, brain damage or a reduced quality of life. The purpose of the study was to analyze the drug resistance mechanisms, especially neuroinflammation, in the epileptogenesis. The information bases of biomedical literature Scopus, PubMed, Google Scholar and SciVerse were used. To obtain full-text documents, electronic resources of PubMed Central and Research Gate were used. The article examines the recent research of the mechanisms of drug resistance in epilepsy and discusses the hypotheses of drug resistance development (genetic, epigenetic, target hypothesis, etc.). Drug-resistant epilepsy is associated with neuroinflammatory, autoimmune and neurodegenerative processes. Neuroinflammation causes immune, pathophysiological, biochemical and psychological consequences. Focal or systemic unregulated inflammatory processes lead to the formation of aberrant neural connections and hyperexcitable neural networks. Inflammatory mediators affect the endothelium of cerebral vessels, destroy contacts between endothelial cells and induce abnormal angiogenesis (the formation of “leaky” vessels), thereby affecting the blood–brain barrier permeability. Thus, the analysis of pro-inflammatory and other components of epileptogenesis can contribute to the further development of the therapeutic treatment of drug-resistant epilepsy.
  • 6.4K
  • 26 May 2021
Topic Review
Metallic Nanowires
The fundamental properties of a material can dramatically change when its dimensions are reduced nanometer scale. Metallic nanowires are one-dimensional nanostructures with diameters that are typically in a range of 10-200 nm, and lengths in a range of 5-100 µm. Metallic nanowires have many unique properties that are not seen in their bulk counterparts, such as good thermal and electrical conductivity, high aspect ratio, low sheet resistance, excellent optical transparency, etc. In the past two decades, research into metallic nanowires has encouraged breakthrough technologies in a variety of fields, including flexible transparent conductive films and electrodes, optoelectronic devices, molecular electronics, solar cells,  touch screens, biomedical science, chemical sensors, heat transfer enhancement, etc.
  • 6.4K
  • 29 Oct 2020
Topic Review
Cigarette Filter
A cigarette filter is a component of a cigarette, along with cigarette paper, capsules and adhesives. It does not make cigarettes less unhealthy. The filter may be made from cellulose acetate fibre, paper or activated charcoal (either as a cavity filter or embedded into the cellulose acetate). Macroporous phenol-formaldehyde resins and asbestos have also been used in cigarette filters. The acetate and paper modify the particulate smoke phase by particle retention (filtration), and finely divided carbon modifies the gaseous phase (adsorption). Filters can reduce "tar" and nicotine smoke yields up to 50%, with a greater removal rate for other classes of compounds (e.g., phenols), but are ineffective in filtering toxins such as carbon monoxide. Most of these measured reductions occur only when the cigarette is smoked on a smoking machine; when a human smokes them, deliveries remain similar with or without a filter. Most factory-made cigarettes are equipped with a filter; those who roll their own can buy them from a tobacconist. The near-universal adoption of filters on cigarettes has not reduced harms to smokers; for instance, lung cancer rates have not declined. Filling a given length of cigarette with filter is cheaper than filling it with tobacco.
  • 6.4K
  • 10 Nov 2022
Topic Review
Fundamentals of Chlorine Disinfection
Chlorine first reacts with organic and inorganic matters before pathogens inactivation. The amount of chlorine consumed in this process is termed chlorine demand. The combined chlorine that forms together with any free available chlorine in the water is called the chlorine residual. This is the component of the added chlorine that disinfects the water. Free available chlorine is formed by differences in the concentrations of hypochlorous and hypochlorite ions, a process that depends on the pH of the water. Even though the chlorination procedure is well-researched, establishing an appropriate chlorine dose remains a difficult task for many field applications. Nevertheless, the effective chlorine dose should be sufficient to destroy pathogens and oxidize the organic contaminants as well as maintain sufficient free available chlorine in the water distribution system, post-chlorination.
  • 6.4K
  • 06 Jun 2022
Topic Review
Non-Ionic Surfactants
Surfactants are essential in the manufacture of polymeric nanoparticles by emulsion formation methods and to preserve the stability of carriers in liquid media. The deposition of non-ionic surfactants at the interface allows a considerable reduction of the globule of the emulsion with high biocompatibility and the possibility of oscillating the final sizes in a wide nanometric range.
  • 6.4K
  • 29 Jun 2021
Topic Review
PC5-Based Cellular-V2X Evolution and Deployment
C-V2X (Cellular Vehicle-to-Everything) is a state-of-the-art wireless technology used in autonomous driving and intelligent transportation systems (ITS). 
  • 6.4K
  • 19 Feb 2021
Topic Review
Constituent State
A constituent state is a state entity that constitutes a part of a sovereign state. A constituent state holds regional jurisdiction over a defined administrative territory, within a sovereign state. Government of a constituent state is a form of regional government. Throughout history, and also in modern political practice, most constituent states are part of complex states, like federations or confederations. Constituent states can have republican or monarchical forms of government. Those of republican form are usually called states or autonomous states, republics or autonomous republics, or cantons. Those that have a monarchical form of government are often defined by traditional hierarchical rank of their ruler (usually a principality, or an emirate).
  • 6.4K
  • 31 Oct 2022
Topic Review
Czochralski Process
The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors (e.g. silicon, germanium and gallium arsenide), metals (e.g. palladium, platinum, silver, gold), salts and synthetic gemstones. The process is named after Polish scientist Jan Czochralski, who invented the method in 1915 while investigating the crystallization rates of metals. He made this discovery by accident: instead of dipping his pen into his inkwell, he dipped it in molten tin, and drew a tin filament, which later proved to be a single crystal. The most important application may be the growth of large cylindrical ingots, or boules, of single crystal silicon used in the electronics industry to make semiconductor devices like integrated circuits. Other semiconductors, such as gallium arsenide, can also be grown by this method, although lower defect densities in this case can be obtained using variants of the Bridgman-Stockbarger technique.
  • 6.4K
  • 24 Nov 2022
Topic Review
Composite Structures
Common types of engineering materials include metals, polymers, ceramics, and composites. Among these, composite materials are often a better alternative for traditional materials, such as metals, ceramics, and polymers due to their light weight, corrosion resistance, high strength and stiffness, ability to withstand high temperatures, and simple manufacturing process. Composite structures are used in a range of different industries from aerospace, marine, aviation, transport, and sports/leisure to civil engineering. For example, advanced composite materials have been used in different structures regarding the above industries, such as rotor blades, aircraft main body, and wing skins.
  • 6.4K
  • 28 Mar 2022
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