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Topic Review

Potential Energy of Protein

In the context of chemistry and molecular modelling, a force field is a computational method that is used to estimate the forces between atoms within molecules and also between molecules. More precisely, the force field refers to the functional form and parameter sets used to calculate the potential energy of a system of atoms or coarse-grained particles in molecular mechanics, molecular dynamics, or Monte Carlo simulations. The parameters for a chosen energy function may be derived from experiments in physics and chemistry, calculations in quantum mechanics, or both. Force fields are interatomic potentials and utilize the same concept as force fields in classical physics, with the difference that the force field parameters in chemistry describe the energy landscape, from which the acting forces on every particle are derived as a gradient of the potential energy with respect to the particle coordinates. All-atom force fields provide parameters for every type of atom in a system, including hydrogen, while united-atom interatomic potentials treat the hydrogen and carbon atoms in methyl groups and methylene bridges as one interaction center. Coarse-grained potentials, which are often used in long-time simulations of macromolecules such as proteins, nucleic acids, and multi-component complexes, sacrifice chemical details for higher computing efficiency.

3.2K
23 Nov 2022

Topic Review

Oil Spill Modeling

Several oil spill simulation models exist in the literature, which are used worldwide to simulate the evolution of an oil slick created from marine traffic, petroleum production, or other sources. These models may range from simple parametric calculations to advanced, new-generation, operational, three-dimensional numerical models, coupled to meteorological, hydrodynamic, and wave models, forecasting in high-resolution and with high precision the transport and fate of oil. This study presents a review of the transport and oil weathering processes and their parameterization and critically examines eighteen state-of-the-art oil spill models in terms of their capacity (a) to simulate these processes, (b) to consider oil released from surface or submerged sources, (c) to assimilate real-time field data for model initiation and forcing, and (d) to assess uncertainty in the produced predictions. Based on our review, the most common oil weathering processes involved are spreading, advection, diffusion, evaporation, emulsification, and dispersion. The majority of existing oil spill models do not consider significant physical processes, such as oil dissolution, photo-oxidation, biodegradation, and vertical mixing. Moreover, timely response to oil spills is lacking in the new generation of oil spill models. Further improvements in oil spill modeling should emphasize more comprehensive parametrization of oil dissolution, biodegradation, entrainment, and prediction of oil particles size distribution following wave action and well blow outs.

3.2K
02 Mar 2021

Topic Review

The SPAD is the basic unit cell of all SiPM/PDC technologies. It consists of a photodiode biased above breakdown in a metastable state awaiting to be triggered by a photoelectron or a thermally excited carrier to switch to high current.

3.2K
18 Mar 2021

Topic Review

Nucleation in Polymer Crystallization

Nucleation plays a vital role in polymer crystallization, in which chain connectivity and thus the multiple length and time scales make crystal nucleation of polymer chains an interesting but complex subject. Though the topic has been intensively studied in the past decades, there are still many open questions to answer. The final properties of semicrystalline polymer materials are affected by all of the following: the starting melt, paths of nucleation, organization of lamellar crystals and evolution of the final crystalline structures. In this viewpoint, we attempt to discuss some of the remaining open questions and corresponding concepts: non-equilibrated polymers, self-induced nucleation, microscopic kinetics of different processes, metastability of polymer lamellar crystals, hierarchical order and cooperativity involved in nucleation, etc. Addressing these open questions through a combination of novel concepts, new theories and advanced approaches provides a deeper understanding of the multifaceted process of crystal nucleation of polymers.

3.2K
25 Jun 2021

Topic Review

Fuel Cell Heavy-Duty Vehicle

Long-haul heavy-duty vehicles, including trucks and coaches, contribute to a substantial portion of the modern-day European carbon footprint and pose a major challenge in emissions reduction due to their energy-intensive usage. Depending on the hydrogen fuel source, the use of fuel cell electric vehicles (FCEV) for long-haul applications has shown significant potential in reducing road freight CO2 emissions until the possible maturity of future long-distance battery-electric mobility. Fuel cell heavy-duty (HD) propulsion presents some specific characteristics, advantages and operating constraints, along with the notable possibility of gains in powertrain efficiency and usability through improved system design and intelligent onboard energy and thermal management.

3.2K
14 Feb 2023

Topic Review

A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton (H+) to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a hydrogen ion. On the other hand, a conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid, as in the reverse reaction it is able to gain a hydrogen ion. Because some acids are capable of releasing multiple protons, the conjugate base of an acid may itself be acidic. In summary, this can be represented as the following chemical reaction: Johannes Nicolaus Brønsted and Martin Lowry introduced the Brønsted–Lowry theory, which proposed that any compound that can transfer a proton to any other compound is an acid, and the compound that accepts the proton is a base. A proton is a nuclear particle with a unit positive electrical charge; it is represented by the symbol H+ because it constitutes the nucleus of a hydrogen atom, that is, a hydrogen cation. A cation can be a conjugate acid, and an anion can be a conjugate base, depending on which substance is involved and which acid–base theory is the viewpoint. The simplest anion which can be a conjugate base is the solvated electron whose conjugate acid is the atomic hydrogen.

3.2K
28 Nov 2022

Topic Review

Cyanomethylation Reaction

Cyanomethylation is very useful in organic synthesis because the cyano groups can be hydrolyzed to carboxylic acids and reduced to amines, from which other functional groups can be derived. In addition, the cyano group is the structural unit of many drugs, such as piritramide, diphenozlate, and gallopamil, while acetonitrile is an ideal source of the cyanomethyl functional group due to the difficulty in breaking the C-CN bond.

3.2K
08 May 2023

Topic Review

Turn (Geometry)

A turn is a unit of plane angle measurement equal to 2π radians, 360 degrees or 400 gradians. A turn is also referred to as a cycle (abbreviated cyc), revolution (abbreviated rev), complete rotation (abbreviated rot) or full circle. Subdivisions of a turn include half turns, quarter turns, centiturns, milliturns, points, etc.

3.2K
22 Nov 2022

Topic Review

Triboelectric Nanogenerator

First proposed by Wang in 2012, the triboelectric nanogenerator (TENG, also called Wang generator) derived from Maxwell’s displacement current shows great prospect as a new technology to convert mechanical energy into electricity, based on the triboelectrification effect and electrostatic induction. TENGs present superiorities including light weight, cost-effectiveness, easy fabrication, and versatile material choices. The concept of harvesting blue energy using the TENG and its network was first brought out in 2014. As a new form of blue energy harvester, the TENG surpasses the EMG in that it intrinsically displays higher effectiveness under low frequency, owing to the unique feature of its output characteristics. Moreover, adopting the distributed architecture of light-weighted TENG networks can make it more suitable for collecting wave energy of high entropy compared with EMGs, which are oversized in volume and mass.

3.2K
13 Sep 2021

Topic Review

A Novichok agent (Russian: Новичо́к, "newcomer", "novice", "newbie") is a group of nerve agents, some of which are binary chemical weapons. The agents were developed at the GosNIIOKhT state chemical research institute by the Soviet Union and Russia between 1971 and 1993.[lower-alpha 1] Some Novichok agents at STP are solids while others are liquids. It is thought that dispersal for the solids is possible by ultrafine powder. Russian scientists who developed the nerve agents claim they are the deadliest ever made, with some variants possibly five to eight times more potent than VX, and others up to ten times more potent than soman. As well as Russia, Novichok agents have been known to be produced in Iran. In the 21st century, Novichok agents came to public attention after they were used to poison opponents of the Russian government, including the Skripals and two others in Amesbury, UK (2018) and Alexei Navalny (2020), but civil poisonings with this substance have been known since at least 1995. In November 2019, the Organisation for the Prohibition of Chemical Weapons (OPCW), which is the executive body for the Chemical Weapons Convention (CWC), added the Novichok agents to "list of controlled substances" of the CWC "in one of the first major changes to the treaty since it was agreed in the 1990s" in response to the 2018 poisonings in the UK.

3.2K
11 Nov 2022

Topic Review

Emergency Position-Indicating Radiobeacon Station

An emergency position-indicating radiobeacon (EPIRB) is a type of emergency locator beacon, a portable battery powered radio transmitter used in emergencies to locate airplanes, vessels, and persons in distress and in need of immediate rescue. In the event of an emergency, such as the ship sinking or an airplane crash, the transmitter is activated and begins transmitting a continuous radio signal which is used by search and rescue teams to quickly locate the emergency and render aid. The signal is detected by satellites operated by an international consortium of rescue services, COSPAS-SARSAT. The basic purpose of this system is to help rescuers find survivors within the so-called "golden day" (the first 24 hours following a traumatic event) during which the majority of survivors can usually be saved. The feature distinguishing modern EPIRBs, often called GPIRBs, from other types of emergency beacon is that it contains a GPS receiver and broadcasts its position, usually accurate within 100 metres (330 ft), to facilitate location. The standard frequency of a modern EPIRB is 406 MHz. It is an internationally regulated mobile radiocommunication service that aids search and rescue operations to detect and locate distressed boats, aircraft, and people. It is distinct from a Satellite emergency position-indicating radiobeacon station. The first form of these beacons was the 121.500 MHz ELT, which was designed as an automatic locator beacon for crashed military aircraft. These beacons were first used in the 1950s by the U.S. military and were mandated for use on many types of commercial and general aviation aircraft beginning in the early 1970s. The frequency and signal format used by the ELT beacons was not designed for satellite detection, which resulted in a system with poor location detection abilities and with long delays in detection of activated beacons. The satellite detection network was built after the ELT beacons were already in general use, with the first satellite not being launched until 1982, and even then, the satellites only provided detection, with location accuracy being roughly 20 kilometres (12 mi). The technology was later expanded to cover use on vessels at sea (EPIRB), individual persons (PLB and, starting in 2016, MSLD). All have migrated from using 121.500 MHz as their primary frequency to using 406 MHz, which was designed for satellite detection and location. Since the inception of Cospas-Sarsat in 1982, distress radiobeacons have assisted in the rescue of over 28,000 people in more than 7,000 distress situations. In 2010 alone, the system provided information used to rescue 2,388 persons in 641 distress situations.

3.2K
27 Oct 2022

Topic Review

Chitosan in Fish Biotechnology

Chitosan is increasingly used for safe drug and nucleic acid delivery due to well-known properties such as bioadhesion, low toxicity, biodegradability and biocompatibility. Furthermore, chitosan derivatization can be easily performed to improve solubility and stability of chitosan-nucleic acid polyplexes, and enhance efficient target cell drug delivery, cell uptake, intracellular endosomal escape, unpacking and nuclear import of expression plasmids. This review focus attention on recent advances in chitosan-mediated gene delivery for fish biotechnology applications such as fish vaccination against bacterial and viral infection, control of gonadal development, and gene overexpression and silencing for overcoming metabolic limitations such as dependence on protein-rich diets and low glucose tolerance of farmed fish.

3.2K
27 Oct 2020

Topic Review

Autobiographical Memory

Autobiographical memory is a memory system consisting of episodes recollected from an individual's life, based on a combination of episodic (personal experiences and specific objects, people and events experienced at particular time and place) and semantic (general knowledge and facts about the world) memory. It is thus a type of explicit memory.

3.2K
28 Nov 2022

Topic Review

The first aircraft at the beginning of the 20th century had too weak engines to carry passengers. Air travel that time mainly took place in large airships. The first commercial flight took place on January 1st, 1914, across Tampa Bay, Florida, with one paying passenger. The first regular passenger air transport took place in Germany, between Berlin and Weimar, from 1919. The 1920s brought fast growth of passenger aviation. In 1932, the first serial production of aircraft for passenger air travel started. However, at that time, transatlantic passenger flights were still only performed by airships. Jet aircraft replaced propeller aircraft in the 1950s. Now there are eight million commercial flights every year (status: June 2011). The crew of an airplane consists of the captain, the first, second and third officer, the flight attendants, the flight engineer, the loadmaster, the pilot and the purser. About eight million people fly every day, yielding 3.1 billion passengers in air travel in 2013. Besides people and their luggage, cargo is transported, about 140,000 tons every day, which is equivalent to 50 million tons per year. There are nearly 60 million jobs in air travel; the global turnover of the airline industry is more than 700 billion USD, with about 2.6% net profit. International aviation reached a new record in 2010 with more than 30.5 million commercial flights. 35% of the total departures in 2010 took place in North America, 25% in Asia, 24% in Europe, 10% in Latin America and the Caribbean, 3% in Oceania and 3% in Africa. Fastest growth is in Asia Pacific, Latin America, the Caribbean, Africa and the Middle East. Until 2030, an increase of the number of commercial flights to 52 million is estimated.

3.2K
22 May 2024

Topic Review

Techniques for Dealcoholization of Wines

To adapt to the trends in wine styles, and the effect of climate change on wine alcohol content, different techniques have been used at the various stages of winemaking, among which the physical dealcoholization techniques, particularly membrane separation (nanofiltration, reverse osmosis, evaporative perstraction, and pervaporation) and thermal distillation (vacuum distillation and spinning cone column), have shown promising results and hence are being used for commercial production.

3.2K
29 Oct 2021

Topic Review

Cladistics (/kləˈdɪstɪks/; from grc κλάδος (kládos) 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived characteristics (synapomorphies) that are not present in more distant groups and ancestors. However, from an empirical perspective, common ancestors are inferences based on a cladistic hypothesis of relationships of taxa whose character states can be observed. Theoretically, a last common ancestor and all its descendants constitute a (minimal) clade. Importantly, all descendants stay in their overarching ancestral clade. For example, if the terms worms or fishes were used within a strict cladistic framework, these terms would include humans. Many of these terms are normally used paraphyletically, outside of cladistics, e.g. as a 'grade', which are fruitless to precisely delineate, especially when including extinct species. Radiation results in the generation of new subclades by bifurcation, but in practice sexual hybridization may blur very closely related groupings. As a hypothesis, a clade can only be rejected if some groupings were explicitly excluded. It may then be found that the excluded group did actually descend from the last common ancestor of the group, and thus emerged within the group. ("Evolved from" is misleading, because in cladistics all descendants stay in the ancestral group). Upon finding that the group is paraphyletic this way, either such excluded groups should be granted to the clade, or the group should be abolished. Testifying to human focus, bias and perhaps exceptionalism, humans have never been placed in a paraphyletic group, whereas most other organisms have been. Branches down to the divergence to the next significant (e.g. extant) sister are considered stem-groupings of the clade, but in principle each level stands on its own, to be assigned a unique name. For a fully bifurcated tree, adding a group to a tree also adds an additional (named) clade, and potentially a new level. Specifically, also extinct groups are always put on a side-branch, not distinguishing whether an actual ancestor of other groupings was found. The techniques and nomenclature of cladistics have been applied to disciplines other than biology. (See phylogenetic nomenclature.) Cladistics findings are posing a difficulty for taxonomy, where the rank and (genus-)naming of established groupings may turn out to be inconsistent. Cladistics is now the most commonly used method to classify organisms.

3.2K
19 Oct 2022

Topic Review

Musical Contagion

Music can contaminate us. Sometimes, listeners perceive music as expressing some emotion (say, sadness), and this elicits the same emotion in them (they feel sad). What is musical contagion? Resesarchers presents the main theories of musical contagion that crystallize around the challenge to the leading theory of emotions as experiences of values. How and why does music contaminate us? Does musical contagion elicit garden variety emotions, such as sadness, joy, and anxiety? Does music contaminate us by simply moving us? Which role does imagination play in our affective responses to music? Is musical arousal elicited by automatic mimicry? What does musical contagion teach us about emotions? Musical contagion addresses fundamental theoretical and practical issues.

3.2K
10 Mar 2023

Topic Review

Fabrication Processes of Conductive Textiles

Wearable electronics are gaining popularity as a platform for the next generation of human-friendly electronic devices. Therefore, a new class of devices with various functionality and amenability for the human body is essential. Traditional textile materials, such as fiber, yarn, and fabric, are non-conductive. Innovative methods and novel processing technologies have been introduced to impart conductivity in textile materials to solve this issue. Coating, printing, deposition, and in situ polymerization are common techniques for this purpose. Here, the newly developed methods with significant potential are summarized, which includes their conductivity level in different applications, such as batteries, displays, and sensors.

3.2K
04 Jan 2023

Topic Review

Sunscreens and UV Protection

Excessive UV (ultraviolet) radiation exposure is harmful to skin cells since sunburn is accompanied by oxidative burst, leading to a rapid increase in skin cancer. However, the insufficient UV photoprotection of approved sunscreens and the negative impact of their compositions on ecosystems and human health makes the utility of sunscreen a questionable recommendation. Therefore, discovering UV filters with significant antioxidant activity and improved topical performance and photostability is an urgent need.

3.2K
17 Mar 2023

Topic Review

Millon Clinical Multiaxial Inventory

The Millon Clinical Multiaxial Inventory - Fourth Edition (MCMI-IV) is the most recent edition of the Millon Clinical Multiaxial Inventory. The MCMI is a psychological assessment tool intended to provide information on personality traits and psychopathology, including specific psychiatric disorders outlined in the DSM-5. It is intended for adults (18 and over) with at least a 5th grade reading level who are currently seeking mental health services. The MCMI was developed and standardized specifically on clinical populations (i.e. patients in clinical settings or people with existing mental health problems), and the authors are very specific that it should not be used with the general population or adolescents. However, there is evidence base that shows that it may still retain validity on non-clinical populations, and so psychologists will sometimes administer the test to members of the general population, with caution. The concepts involved in the questions and their presentation make it unsuitable for those with below average intelligence or reading ability. The MCMI-IV authors present their test as unique compared to other personality tests in that it is based on Theodore Millon' evolutionary theory and is organized according to a multiaxial format. Updates to each version of the MCMI coincide with revisions to the DSM. The fourth edition is composed of 195 true-false questions that take approximately 25–30 minutes to complete. It was created by Theodore Millon, Seth Grossman, and Carrie Millon. The test is modeled on four categories of scales:

3.2K
07 Nov 2022

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