Instruct: Given a question, retrieve relevant documents that answer the question.
Query: What is an aerosol?
An aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog, dust, forest exudates and geyser steam. Examples of anthropogenic aerosols are haze, particulate air pollutants and The liquid or solid particles have diameters typically <1 μm; larger particles with a significant settling speed make the mixture a suspension, but the distinction is not clear-cut. In general conversation, "aerosol" usually refers to an aerosol spray that delivers a consumer product from a can or similar container. Other technological applications of aerosols include dispersal of pesticides, medical treatment of respiratory illnesses, and convincing technology. Diseases can also spread by means of small droplets in the breath, also called aerosols (or sometimes bioaerosols).
A very wide variety of fuels may occur as gases, droplet fogs, or dust suspensions. Oxidants include halogens, ozone, hydrogen peroxide and oxides of nitrogen. Gaseous detonations are often associated with a mixture of fuel and oxidant in a composition somewhat below conventional flammability ratios. They happen most often in confined systems, but they sometimes occur in large vapor clouds. Other materials, such as acetylene, ozone, and hydrogen peroxide are detonable in the absence of dioxygen.
Recent research at CERN's CLOUD facility examined links between cosmic rays and cloud condensation nuclei, demonstrating the effect of high-energy particulate radiation in nucleating aerosol particles that are precursors to cloud condensation nuclei. Kirby (CLOUD team leader) said, "At the moment, it [the experiment] actually says nothing about a possible cosmic-ray effect on clouds and climate." After further investigation, the team concluded that "variations in cosmic ray intensity do not appreciably affect climate through nucleation."
Filtered oxygen masks have the ability to prevent exhaled, potentially infectious particles from being released into the surrounding environment. These masks are normally of a closed design such that leaks are minimized and breathing of room air is controlled through a series of one-way valves. Filtration of exhaled breaths is accomplished either by placing a filter on the exhalation port, or through an integral filter that is part of the mask itself. These masks first became popular in the Toronto (Canada) healthcare community during the 2003 SARS Crisis. SARS was identified as being respiratory based and it was determined that conventional oxygen therapy devices were not designed for the containment of exhaled particles. Common practices of having suspected patients wear a surgical mask was confounded by the use of standard oxygen therapy equipment. In 2003, the HiOx oxygen mask was released for sale. The HiOx mask is a closed design mask that allows a filter to be placed on the exhalation port. Several new designs have emerged in the global healthcare community for the containment and filtration of potentially infectious particles. Other designs include the ISO- oxygen mask, the FloMax oxygen mask, and the O-Mask. The use of oxygen masks that are capable of filtering exhaled particles is gradually becoming a recommended practice for pandemic preparation in many jurisdictions.
Airsoft guns are replica weapons used in airsoft sports. They are a special type of very low-power smoothbore air guns designed to shoot non-metallic spherical projectiles often colloquially (and incorrectly) referred to as "BBs", which are typically made of (but not limited to) plastic or biodegradable resin materials. Airsoft gun powerplants are designed to have low muzzle energy ratings (generally less than 1.5 J, or 1.1 ft⋅lb) and the pellets have significantly less penetrative and stopping powers than conventional air guns, and are generally safe for competitive sporting and recreational purposes if proper protective gear is worn.
Volcanic bombs are extrusive igneous rocks ranging from the size of books to small cars, that are explosively ejected from stratovolcanoes during their climactic eruptive phases. These "bombs" can travel over away from the volcano, and present a risk to buildings and living beings while shooting at very high speeds (hundreds of kilometers/miles per hour) through the air. Most bombs do not themselves explode on impact, but rather carry enough force so as to have destructive effects as if they exploded.
Airsoft originated from Japan in the early 1970s, trademarked as "soft air guns", tailoring to the needs of shooting enthusiasts while conforming to Japan's strict gun control. The name "soft air" referred to the compressed Freon-silicone oil mixture (known as "green gas") that was used as a propellant, which was significantly weaker than the carbon dioxide used in proper airguns. Originally designed for target shooting, their plastic pellets can be shot at humans without causing injury and this became popular for casual war-games. Airsoft guns spread to the UK in the late 1980s and early 1990s with a company called LS. The guns were sold in pieces and had to be assembled before they were capable of firing pellets. Airsoft equipment was designed to closely emulate real guns. Since the mid-1980s, airsoft guns have been adapted with a purely recreational application in mind, and the sport is enjoyed by all ages. Airsoft replicas are produced globally, with the majority being manufactured in Asia. Many law enforcement agencies and military units within the United States now use Airsoft for force-on-force training drills.
The term "asbestos ware" refers to vessels containing 90% asbestos and 10% clay. Asbestos ware can resist heat up to 900–1000 °C. The clay made shaping of the vessel possible, but the high amount of asbestos does not classify it as pottery in a formal sense. It is believed that the asbestos ware was used in iron production such as spearheads, arrowheads and artefacts. The vessel is also drilled with many holes. The fact that the reduction of iron ore (FeO) with abundant carbon generates large amounts of carbon monoxide (CO) may suggest that the drilled holes were used to increase the influx of air (oxygen) required for proper glowing process. Iron ore is abundant in lakes e.g. in Finland.
Airsoft is a competitive sport similar in concept to paintball, in which participants from opposing teams eliminate opponents by hitting each other with solid round plastic pellets launched from low-powered smoothbore air guns called airsoft guns. It is different to paintball in that airsoft pellets do not visibly mark the targets like paintballs, and thus the sport relies heavily on an honor system where a hit player has the ethical duty to call himself out of play, regardless of whether anyone else sees it happen. Most airsoft guns are also magazine-fed (unlike the commonly top-mounting pellet loader of paintball markers) with mounting platforms compatible with real firearm accessories, and tend to more closely resemble real guns in appearance, making them more popular for military simulation and historical reenactments. The greater toughness of airsoft pellets also allows the use of better powerplants and apparatus such as hop-up device for improved external ballistics, making the gameplay more accurately resemble real gunfights. They are also much cheaper for casual players to participate than paintball.
Traditionally, small bodies orbiting the Sun were classified as comets, asteroids, or meteoroids, with anything smaller than one meter across being called a meteoroid. Beech and Steel's 1995 paper proposed a meteoroid definition including size limits. The term "asteroid", from the Greek word for "star-like", never had a formal definition, with the broader term minor planet being preferred by the International Astronomical Union.
Internal combustion engines such as reciprocating internal combustion engines produce air pollution emissions, due to incomplete combustion of carbonaceous fuel. The main derivatives of the process are carbon dioxide , water and some soot—also called particulate matter (PM). The effects of inhaling particulate matter have been studied in humans and animals and include asthma, lung cancer, cardiovascular issues, and premature death. There are, however, some additional products of the combustion process that include nitrogen oxides and sulfur and some uncombusted hydrocarbons, depending on the operating conditions and the fuel-air ratio.
Lahars (from a Javanese term for volcanic mudflows) are mixtures of volcanic debris and water. Lahars usually come from two sources: rainfall or the melting of snow and ice by hot volcanic elements, such as lava. Depending on the proportion and temperature of water to volcanic material, lahars can range from thick, gooey flows that have the consistency of wet concrete to fast-flowing, soupy floods. As lahars flow down the steep sides of stratovolcanoes, they have the strength and speed to flatten or drown everything in their paths. Hot ashes, lava flows and pyroclastic surges ejected during 1985 eruption of Nevado del Ruiz in Colombia melted snow and ice atop the high Andean volcano. The ensuing lahar flooded the city of Armero and nearby settlements, killing 25,000 people.
Aerojet Rocketdyne is an American rocket and missile propulsion manufacturer. Headquartered in Sacramento, California, the company is owned by Aerojet Rocketdyne Holdings. Aerojet Rocketdyne was formed in 2013 when Aerojet (then owned by GenCorp) and Pratt & Whitney Rocketdyne were merged, following the latter's acquisition by GenCorp from Pratt & Whitney. On April 27, 2015, the name of the holding company, GenCorp, was changed from "GenCorp, Inc." to "Aerojet Rocketdyne Holdings, Inc".
The AR1 is a thrust RP-1/LOX advanced oxidizer-rich staged combustion cycle engine project. Aerojet Rocketdyne proposed in 2014 to "lobby the government to fund an all-new, U.S.-sourced rocket propulsion system." In June 2014, Aerojet's initially projected it would cost under per pair of engines, not including the up to estimated development cost to be funded by the government. Later in 2014, the US Congress passed a law requiring the US Air Force to "develop a new propulsion system by 2019 to replace the RD-180 engine" that powers Atlas V used by United Launch Alliance (ULA). Dynetics is a key partner in development of the AR1 engine. Under a joint venture agreement, Dynetics is to supply elements of the engine's main propulsion system, the ignition system, and ground support equipment, along with analysis support to critical engine designs.
An NBC (nuclear, biological, chemical) suit, also called a chemsuit or chem suit or chemical suit is a type of military personal protective equipment. NBC suits are designed to provide protection against direct contact with and contamination by radioactive, biological or chemical substances, and provides protection from contamination with radioactive materials and some types of radiation, depending on the design. It is generally designed to be worn for extended periods to allow the wearer to fight (or generally function) while under threat of or under actual nuclear, biological, or chemical attack. The civilian equivalent is the Hazmat suit. The term NBC has been replaced by CBRN (chemical, biological, radiological, nuclear), with the addition of a new threat, radiological, meaning radiological weapon.
When discovered, asteroids were seen as a class of objects distinct from comets, and there was no unified term for the two until "small Solar System body" was coined by the IAU in 2006. The main difference between an asteroid and a comet is that a comet shows a coma due to sublimation of near-surface ices by solar radiation. A few objects have ended up being dual-listed because they were first classified as minor planets but later showed evidence of cometary activity. Conversely, some (perhaps all) comets are eventually depleted of their surface volatile ices and develop the appearance of asteroids. A further distinction is that comets typically have more eccentric orbits than most asteroids; most "asteroids" with notably eccentric orbits are probably dormant or extinct comets. Also, they are theorized to be common objects amongst the celestial bodies orbiting close to the Sun.
Common plants used to remediate indoor air pollutants include: English ivy ("Hedera helix"), Peace lily ("Spathiphyllum ‘Mauna Loa’"), Chinese evergreen ("Aglaonema modestum"), Bamboo palm ("Chamaedorea seifrizii"), and Chrysanthemum ("Chrysanthemum morifolium"). There are several studies that cite the plant microcosm as a mechanism to reduce indoor VOCs. Controls of just pots alone and just a tray of water suggest that it is the soil microcosm that provides the pollutant sink. The role of the plants is to establish and maintain the species specific root-zone microbial communities. This mechanism was first suggested by Wolverton et al. in 1985. Houseplants also aid in humidity, temperature, and noise control.
Transport helicopters are operated in assault, medium and heavy classes. Air assault helicopters are usually the smallest of the transport types, and designed to move an infantry squad or section and their equipment. Helicopters in the assault role are generally armed for self-protection both in transit and for suppression of the landing zone. This armament may be in the form of door gunners, or the modification of the helicopter with stub wings and pylons to carry missiles and rocket pods. For example, the Sikorsky S-70, fitted with the ESSM (External Stores Support System), and the "Hip E" variant of the Mil Mi-8 can carry as much disposable armament as some dedicated attack helicopters. The assault helicopter can be thought of as the modern successor to the military glider. Finally, there is the generic term utility helicopter, which generally refers to medium-lift designs.
Mobile source air pollution includes any air pollution emitted by motor vehicles, airplanes, locomotives, and other engines and equipment that can be moved from one location to another. Many of these pollutants contribute to environmental degradation and have negative effects on human health. To prevent unnecessary damage to human health and the environment, environmental regulatory agencies such as the U.S. Environmental Protection Agency have established policies to minimize air pollution from mobile sources. Similar agencies exist at the state level. Due to the large number of mobile sources of air pollution, and their ability to move from one location to another, mobile sources are regulated differently from stationary sources, such as power plants. Instead of monitoring individual emitters, such as an individual vehicle, mobile sources are often regulated more broadly through design and fuel standards. Examples of this include corporate average fuel economy standards and laws that ban leaded gasoline in the United States. The increase in the number of motor vehicles driven in the U.S. has made efforts to limit mobile source pollution challenging. As a result, there have been a number of different regulatory instruments implemented to reach the desired emissions goals.
Pollution in California relates to the degree of pollution in the air, water, and land of the state of California. Pollution is defined as the addition of any substance (solid, liquid, or gas) or any form of energy (such as heat, sound, or radioactivity) to the environment at a faster rate than it can be dispersed, diluted, decomposed, recycled, or stored in some harmless form. The combination of three main factors are the cause of notable unhealthy levels of air pollution in California: the activities of over 39 million people, a mountainous terrain that traps pollution, and a warm climate that helps form ozone and other pollutants. Eight of the ten cities in the US with the highest year-round concentration of particulate matter between 2013 and 2015 were in California, and seven out of the ten cities in the US with the worst ozone pollution were also in California. Studies show that pollutants prevalent in California are linked to several health issues, including asthma, lung cancer, birth complications, and premature death. In 2016, Bakersfield, California recorded the highest level of airborne pollutants of any city in the United States.
By 1964, the department had developed an AQI called the SCS Air Pollution Index (SCS API), combining measurements of sulfur dioxide (SO), carbon monoxide (CO), and coefficient of haze (also called smoke shade) into a single number. The city laboratory recorded the presence of those three pollutants measured in amount (by concentration in the air) and duration. SO and CO were measured by parts-per-million, or ppm, and smoke shade was measured in mppcf (millions of particles per cubic foot); the department continuously monitored these pollutant levels and recorded their hourly averages. The data for those three pollutants were combined into a single number using a weighted formula developed by department co-founder Moe Mordecai Braverman. The SCS API formula was:
Vacuum technology is a method used to evacuate air from a closed volume by creating a pressure differential from the closed volume to some vent, the ultimate vent being the open atmosphere. When using an industrial vacuum system, a vacuum pump or generator creates this pressure differential. A variety of technical inventions were created based on the idea of vacuum discovered during the 17th century. These range from vacuum generation pumps to X-ray tubes, which were later introduced to the medical field for use as sources of X-ray radiation. The vacuum environment has come to play an important role in scientific research as new discoveries are being made by looking back to the basic fundamentals of pressure. The idea of “perfect vacuum” cannot be realized, but very nearly approximated by the technological discoveries of the early 20th century. Vacuum engineering today uses a range of different material, from aluminum to zirconium and just about everything in between. There may be the popular belief that vacuum technology deals only with valves, flanges, and other vacuum components, but novel scientific discoveries are often made with the assistance of these traditional vacuum technologies, especially in the realm of high-tech. Vacuum engineering is used for compound semiconductors, power devices, memory logic, and photovoltaics.
E-cigarettes produce particles, in the form of an aerosol. In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas. The aerosol is made-up of liquid sub-micron particles of condensed vapor, which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals. This aerosol that is produces resembles cigarette smoke. After a puff, inhalation of the aerosol travels from the device into the mouth and lungs.
Stability of nanoparticle agglomerates is critical for estimating size distribution of aerosolized particles from nano-powders or other sources. At nanotechnology workplaces, workers can be exposed via inhalation to potentially toxic substances during handling and processing of nanomaterials. Nanoparticles in the air often form agglomerates due to attractive inter-particle forces, such as van der Waals force or electrostatic force if the particles are charged. As a result, aerosol particles are usually observed as agglomerates rather than individual particles. For exposure and risk assessments of airborne nanoparticles, it is important to know about the size distribution of aerosols. When inhaled by humans, particles with different diameters are deposited in varied locations of the central and periphery respiratory system. Particles in nanoscale have been shown to penetrate the air-blood barrier in lungs and be translocated into secondary organs in the human body, such as the brain, heart and liver. Therefore, the knowledge on stability of nanoparticle agglomerates is important for predicting the size of aerosol particles, which helps assess the potential risk of them to human bodies.
The aerosol of e-cigarettes is generated when the e-liquid reaches a temperature of roughly 100-250 °C within a chamber. The user inhales the aerosol, commonly called vapor, rather than cigarette smoke. In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas. The aerosol is made-up of liquid sub-micron particles of condensed vapor, which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals. After a puff, inhalation of the aerosol travels from the device into the mouth and lungs. The particle size distribution and sum of particles emitted by e-cigarettes are like traditional cigarettes, with the majority of particles in the ultrafine range.
Although all hydrometeors, solid and liquid, can be described as aerosols, a distinction is commonly made between such dispersions (i.e. clouds) containing activated drops and crystals, and aerosol particles. The atmosphere of Earth contains aerosols of various types and concentrations, including quantities of: