Split (1)

train · 2.1M rows

title stringlengths 1 149 ⌀	section stringlengths 1 1.9k ⌀	text stringlengths 13 73.5k
Dungeons & Dragons Companion Set	Contents	The Player's Companion covers information on character levels 15-25. The book begins with commentary on the changes since a character began as an adventurer at level one. It introduces new weapons, armor types, and unarmed combat rules as well as providing details on running a stronghold and its recurrent costs, such as wages of the castle staff. The Player's Companion details the new abilities and increases in skills, spells, and other abilities that accrue to members of each character class as they rise in level. This section concentrates wholly on human characters, treating dwarves, elves, and halflings separately. The concept of "attack rank" is introduced for the three demi-human classes; although, per the Expert Set rules, they are capped at a specified maximum level, further accumulation of experience points increases their combat abilities. It also introduces the optional character class of druid, presented as a special progression for clerics of neutral alignment.
Dungeons & Dragons Companion Set	Contents	The Dungeon Master's Companion begins with general guidelines on running a campaign and planning adventures for characters of level 15 and higher. The introduction also constructs a feudal system to provide a basis for the dominions, which will be granted to or conquered by the player characters. This section ends with notes on the organization and running of tournaments. The next section "The War Machine" was designed by Douglas Niles and Gary Spiegel as a method for coping with large-scale battles, especially those in the campaign's background. This book covers running high-level campaigns, including mass combat, other worlds and planes, and new monsters and treasure. It also contains three mini-scenarios.
Dungeons & Dragons Companion Set	Reception	The Companion Set was reviewed by Megan C. Robertson in issue 61 of White Dwarf magazine (January 1985), rating it a 7 out of 10 overall. Robertson noted that most characters that reach 15th level in the Basic D&D game should be thinking of settling down and retiring and felt that the D&D Companion Set provides: "some ideas for this to be a little more interesting than simple retirement".
Flammé (yarn)	Flammé (yarn)	See flammé (vexillology) for the flag design.Flammé yarns are a kind of novelty yarn. It is generally a loose or untwisted core wrapped by at least one other strand. The extra element can be a metallic thread, or a much-thicker or much-narrower strand of yarn, or yarn that varies between thick and thin. Some companies have come to put twin yarns on the market to show off combinations of one regular yarn and novelty yarns in assorted colors or even two different types of novelty yarns.
Northern Hemisphere	Northern Hemisphere	The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the Solar System as Earth's North Pole.Due to Earth's axial tilt of 23.439281°, winter in the Northern Hemisphere lasts from the December solstice (typically December 21 UTC) to the March equinox (typically March 20 UTC), while summer lasts from the June solstice through to the September equinox (typically on 23 September UTC). The dates vary each year due to the difference between the calendar year and the astronomical year. Within the Northern Hemisphere, oceanic currents can change the weather patterns that affect many factors within the north coast. Such events include El Niño–Southern Oscillation.
Northern Hemisphere	Northern Hemisphere	Trade winds blow from east to west just above the equator. The winds pull surface water with them, creating currents, which flow westward due to the Coriolis effect. The currents then bend to the right, heading north. At about 30 degrees north latitude, a different set of winds, the westerlies, push the currents back to the east, producing a closed clockwise loop.Its surface is 60.7% water, compared with 80.9% water in the case of the Southern Hemisphere, and it contains 67.3% of Earth's land. The continents of Europe and North America are located entirely on Earth's Northern Hemisphere, which also contains almost the entire continent of Asia, about two thirds of Africa, and a small part of South America.
Northern Hemisphere	Geography and climate	During the 2.5 million years of the Pleistocene, numerous cold phases called glacials (Quaternary ice age), or significant advances of continental ice sheets, in Europe and North America, occurred at intervals of approximately 40,000 to 100,000 years. The long glacial periods were separated by more temperate and shorter interglacials which lasted about 10,000–15,000 years. The last cold episode of the last glacial period ended about 10,000 years ago. Earth is currently in an interglacial period of the Quaternary, called the Holocene. The glaciations that occurred during the glacial period covered many areas of the Northern Hemisphere.
Northern Hemisphere	Geography and climate	The Arctic is a region around the North Pole (90° latitude). Its climate is characterized by cold winters and cool summers. Precipitation mostly comes in the form of snow. Areas inside the Arctic Circle (66°34′ latitude) experience some days in summer when the Sun never sets, and some days during the winter when it never rises. The duration of these phases varies from one day for locations right on the Arctic Circle to several months near the Pole, which is the middle of the Northern Hemisphere.
Northern Hemisphere	Geography and climate	Between the Arctic Circle and the Tropic of Cancer (23°26′ latitude) lies the Northern temperate zone. The changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather. Tropical regions (between the Tropic of Cancer and the Equator, 0° latitude) are generally hot all year round and tend to experience a rainy season during the summer months, and a dry season during the winter months.
Northern Hemisphere	Geography and climate	In the Northern Hemisphere, objects moving across or above the surface of the Earth tend to turn to the right because of the Coriolis effect. As a result, large-scale horizontal flows of air or water tend to form clockwise-turning gyres. These are best seen in ocean circulation patterns in the North Atlantic and North Pacific oceans. Within the Northern Hemisphere, oceanic currents can change the weather patterns that affect many factors within the north coast; such as El Niño.For the same reason, flows of air down toward the northern surface of the Earth tend to spread across the surface in a clockwise pattern. Thus, clockwise air circulation is characteristic of high pressure weather cells in the Northern Hemisphere. Conversely, air rising from the northern surface of the Earth (creating a region of low pressure) tends to draw air toward it in a counterclockwise pattern. Hurricanes and tropical storms (massive low-pressure systems) spin counterclockwise in the Northern Hemisphere.The shadow of a sundial moves clockwise on latitudes north of the subsolar point and anticlockwise to the south. During the day at these latitudes, the Sun tends to rise to its maximum at a southerly position. Between the Tropic of Cancer and the Equator, the sun can be seen to the north, directly overhead, or to the south at noon, dependent on the time of year. In the Southern Hemisphere, the midday Sun is predominantly in the north.
Northern Hemisphere	Geography and climate	When viewed from the Northern Hemisphere, the Moon appears inverted compared to a view from the Southern Hemisphere. The North Pole faces away from the Galactic Center of the Milky Way. This results in the Milky Way being sparser and dimmer in the Northern Hemisphere compared to the Southern Hemisphere, making the Northern Hemisphere more suitable for deep-space observation, as it is not "blinded" by the Milky Way.
Northern Hemisphere	Demographics	As of 2015, the Northern Hemisphere is home to approximately 6.4 billion people which is around 87.0% of the earth's total human population of 7.3 billion people.
E-4031	E-4031	E-4031 is an experimental class III antiarrhythmic drug that blocks potassium channels of the hERG-type.
E-4031	Chemistry	E-4031 is a synthesized toxin that is a methanesulfonanilide class III antiarrhythmic drug.
E-4031	Target	E-4031 acts on a specific class of voltage-gated potassium channels mainly found in the heart, the hERG channels. hERG channels (Kv11.1) mediate the IKr current, which repolarizes the myocardial cells. The hERG channel is encoded by ether-a-go-go related gene (hERG).
E-4031	Mode of action	E-4031 blocks hERG-type potassium channels by binding to the open channels. Its structural target within the hERG-channel is unclear, but some other methanesulfonanilide class III antiarrhythmic drugs are known to bind to the S6 domain or C-terminal of the hERG-channel.Reducing IKr in myocardial cells prolongs the cardiac action potential and thus prolongs the QT-interval. In non-cardiac cells, blocking Ikr has a different effect: it increases the frequency of action potentials.
E-4031	Toxicity	As E-4031 can prolong the QT-interval, it can cause lethal arrhythmias.
E-4031	Therapeutic use	E-4031 is solely used for research purposes. So far, one clinical trial has been conducted to test the effect of E-4031 on prolongation of the QT-interval.
Tampermonkey	Tampermonkey	Tampermonkey is a donationware userscript manager that is available as a browser extension. This software enables the user to add and use userscripts, which are JavaScript programs that can be used to modify web pages.
Tampermonkey	History	Tampermonkey was first created in May 2010 by Jan Biniok. It first emerged as a Greasemonkey userscript that was wrapped to support Google Chrome. Eventually the code was re-used and published as a standalone extension for Chrome which had more features than Chrome's native script support. In 2011, Tampermonkey was ported to Android, enabling users to use userscripts on Android's internal browser. By 2019, Tampermonkey had over 10 million users. Tampermonkey is one of 33 extensions on the Chrome Web Store to have at least 10 million users.
Tampermonkey	History	Chrome manifest V3 In January 2019, Biniok wrote in a Google Groups post that the new Chrome manifest V3 would break the extension. The new manifest would ban remotely accessed code which Tampermonkey is dependent on. The userscripts use code that is created by developers not at Google, and instead is created by third-party developers at places like Userscripts.org and Greasyfork. This code is inserted after the extension is installed, however the manifest requires the code to be present at installation.
Tampermonkey	Controversy	On January 6, 2019, Opera banned the Tampermonkey extension from being installed through the Chrome Web Store, claiming it had been identified as malicious. Later, Bleeping Computer was able to determine that a piece of adware called Gom Player would install the Chrome Web Store version of Tampermonkey and likely utilize the extension to facilitate the injection of ads or other malicious behavior. The site stated, "This does not mean that Tampermonkey is malicious, but rather that a malicious program is utilizing a legitimate program for bad behavior," going on to call Opera's blacklisting the extension for this reason a "strange decision".
Mesonet	Mesonet	In meteorology and climatology, a mesonet, portmanteau of mesoscale network, is a network of automated weather and, often also including environmental monitoring stations, designed to observe mesoscale meteorological phenomena and/or microclimates.Dry lines, squall lines, and sea breezes are examples of phenomena observed by mesonets. Due to the space and time scales associated with mesoscale phenomena and microclimates, weather stations comprising a mesonet are spaced closer together and report more frequently than synoptic scale observing networks, such as the WMO Global Observing System (GOS) and US ASOS. The term mesonet refers to the collective group of these weather stations, which are usually owned and operated by a common entity. Mesonets generally record in situ surface weather observations but some involve other observation platforms, particularly vertical profiles of the planetary boundary layer (PBL). Other environmental parameters may include insolation and various variables of interest to particular users, such as soil temperature or road conditions (the latter notable in Road Weather Information System (RWIS) networks).
Mesonet	Mesonet	The distinguishing features that classify a network of weather stations as a mesonet are station density and temporal resolution with sufficiently robust station quality. Depending upon the phenomena meant to be observed, mesonet stations use a spatial spacing of 1 to 40 kilometres (0.6 to 20 mi) and report conditions every 1 to 15 minutes. Micronets (see microscale and storm scale), such as in metropolitan areas such as Oklahoma City, St. Louis, and Birmingham UK, are yet denser in spatial and sometimes temporal resolution.
Mesonet	Purpose	Thunderstorms and other atmospheric convection, squall lines, drylines, sea and land breezes, mountain breeze and valley breezes, mountain waves, mesolows and mesohighs, wake lows, mesoscale convective vortices (MCVs), tropical cyclone and extratropical cyclone rainbands, macrobursts, gust fronts and outflow boundaries, heat bursts, urban heat islands (UHIs), and other mesoscale phenomena, as well as topographical features, can cause weather and climate conditions in a localized area to be significantly different from that dictated by the ambient large-scale conditions. As such, meteorologists must understand these phenomena in order to improve forecast skill. Observations are critical to understanding the processes by which these phenomena form, evolve, and dissipate. The long-term observing networks (ASOS, AWOS, COOP), however, are too sparse and report too infrequently for mesoscale research and forecasting. ASOS and AWOS stations are typically spaced 50 to 100 kilometres (30 to 60 mi) apart and report only hourly at many sites (though over time the frequency of reporting has increased, down to 5-15 minutes in the 2020s at major sites). The Cooperative Observer Program (COOP) database consists of only daily reports recorded manually. That network, like the more recent CoCoRaHS, is large but both are limited in reporting frequency and robustness of equipment. "Mesoscale" weather phenomena occur on spatial scales of a few to hundreds of kilometers and temporal (time) scales of minutes to hours. Thus, an observing network with finer temporal and spatial scales is needed for mesoscale research. This need led to the development of the mesonet. Mesonet data is directly used by humans for decision making, but also boosts the skill of numerical weather prediction (NWP) and is especially beneficial for short-range mesoscale models. Mesonets, along with remote sensing solutions (data assimilation of weather radar, weather satellites, wind profilers), allow for much greater temporal and spatial resolution in a forecast model. As the atmosphere is a chaotic nonlinear dynamical system (i.e. subject to the Butterfly effect), this increase in data increases understanding of initial conditions and boosts model performance. In addition to meteorology and climatology users, hydrologists, foresters, wildland firefighters, transportation departments, energy producers and distributors, other utility interests, and agricultural entities are prominent in their need for fine scale weather information. These organizations operate dozens of mesonets within the US and globally. Environmental, outdoor recreational, emergency management and public safety, military, and insurance interests also are heavy users of mesonet information. In many cases, mesonet stations may, by necessity or sometimes by lack of awareness, be located in positions where accurate measurements may be compromised. For instance, this is especially true of citizen science and crowdsourced data systems, such as the stations built for WeatherBug's network, many of which are located on school buildings. The Citizen Weather Observer Program (CWOP) facilitated by the US National Weather Service (NWS) and other networks such as those collected by Weather Underground help fill gaps with resolutions sometimes meeting or exceeding that of mesonets, but many stations also exhibit biases due to improper siting, calibration, and maintenance. These consumer grade "personal weather stations" (PWS) are also less sensitive and rigorous than scientific grade stations. The potential bias that these stations may cause must be accounted for when ingesting the data into a model, lest the phenomenon of "garbage in, garbage out" occur.
Mesonet	Operations	Mesonets were born out of the need to conduct mesoscale research. The nature of this research is such that mesonets, like the phenomena they were meant to observe, were (and sometimes still are) short-lived and may change rapidly. Long-term research projects and non-research groups, however, have been able to maintain a mesonet for many years. For example, the U.S. Army Dugway Proving Ground in Utah has maintained a mesonet for many decades. The research-based origin of mesonets led to the characteristic that mesonet stations may be modular and portable, able to be moved from one field program to another. Nonetheless, most large contemporary mesonets or nodes within consist of permanent stations comprising stationary networks. Some research projects, however, utilize mobile mesonets. Prominent examples include the VORTEX projects. The problems of implementing and maintaining robust fixed stations are exacerbated by lighter, compact mobile stations and are further worsened by various issues related when moving, such as vehicle slipstream effects, and particularly during rapid changes in the ambient environment associated with traversing severe weather.Whether the mesonet is temporary or semi-permanent, each weather station is typically independent, drawing power from a battery and solar panels. An on-board computer records readings from several instruments measuring temperature, humidity, wind speed and direction, and atmospheric pressure, as well as soil temperature and moisture, and other environmental variables deemed important to the mission of the mesonet, solar irradiance being a common non-meteorological parameter. The computer periodically saves these data to memory, typically using data loggers, and transmits the observations to a base station via radio, telephone (wireless, such as cellular or landline), or satellite transmission. Advancements in computer technology and wireless communications in recent decades made possible the collection of mesonet data in real-time. Some stations or networks report using Wi-Fi and grid powered with backups for redundancy. The availability of mesonet data in real-time can be extremely valuable to operational forecasters, and particularly for nowcasting, as they can monitor weather conditions from many points in their forecast area. In addition to operational work, and weather, climate, and environmental research, mesonet and micronet data are often important in forensic meteorology.
Mesonet	History	Early mesonets operated differently from modern mesonets. Each constituent instrument of the weather station was purely mechanical and fairly independent of the other sensors. Data were recorded continuously by an inked stylus that pivoted about a point onto a rotating drum covered by a sheath of graphed paper called a trace chart, much like a traditional seismograph station. Data analysis could occur only after the trace charts from the various instruments were collected.
Mesonet	History	One of the earliest mesonets operated in the summer of 1946 and 1947 and was part of a field campaign called The Thunderstorm Project. As the name implies, the objective of this program was to better understand thunderstorm convection. The earliest mesonets were typically funded and operated by government agencies for specific campaigns. In time, universities and other quasi-public entities began implementing permanent mesonets for a wide variety of uses, such as agricultural or maritime interests. Consumer grade stations added to the professional grade synoptic and mesoscale networks by the 1990s and by the 2010s professional grade station networks operated by private companies and public-private consortia increased in prominence. Some of these privately implemented systems are permanent and at fixed locations, but many also service specific users and campaigns/events so may be installed for limited periods, and may also be mobile.
Mesonet	History	The first known mesonet was operated by Germany from 1939 to 1941. Early mesonets with project based purposes operated for limited periods of time from seasons to a few years. The first permanently operating mesonet began in the United States in the 1970s with more entering operation in the 1980s-1990s as numbers gradually increased preceding a steeper expansion by the 2000s. By the 2010s there was also an increase in mesonets on other continents. Some wealthy densely populated countries also deploy observation networks with the density of a mesonet, such as the AMeDAS in Japan. The US was an early adopter of mesonets, yet funding has long been scattered and meager. By the 2020s declining funding atop the earlier scarcity and uncertainty of funding was leading to understaffing and problems maintaining stations, the closure of some stations, and the viability of entire networks threatened.Mesonets capable of being moved for fixed station deployments in field campaigns came into use in the US by the 1970s and fully mobile vehicle-mounted mesonets became fixtures of large field research projects following the field campaigns of Project VORTEX in 1994 and 1995, in which significant mobile mesonets were deployed.
Mesonet	Significant mesonets	The following table is an incomplete list of mesonets operating in the past and present: * Not all stations owned or operated by network. ** As these are private stations, although QA/QC measures may be taken, these may not be scientific grade, and may lack proper siting, calibration, sensitivity, durability, and maintenance. Although not labeled a mesonet, the Japan Meteorological Agency (JMA) also maintains a nationwide surface observation network with the density of a mesonet. JMA operates AMeDAS, consisting of approximately 1,300 stations at a spacing of 17 kilometres (11 mi). The network began operating in 1974.
NSPACE	NSPACE	In computational complexity theory, non-deterministic space or NSPACE is the computational resource describing the memory space for a non-deterministic Turing machine. It is the non-deterministic counterpart of DSPACE.
NSPACE	Complexity classes	The measure NSPACE is used to define the complexity class whose solutions can be determined by a non-deterministic Turing machine. The complexity class NSPACE(f(n)) is the set of decision problems that can be solved by a non-deterministic Turing machine, M, using space O(f(n)), where n is the length of the input.Several important complexity classes can be defined in terms of NSPACE. These include: REG = DSPACE(O(1)) = NSPACE(O(1)), where REG is the class of regular languages (nondeterminism does not add power in constant space).
NSPACE	Complexity classes	NL = NSPACE(O(log n)) CSL = NSPACE(O(n)), where CSL is the class of context-sensitive languages. PSPACE = NPSPACE = ⋃k∈NNSPACE(nk) EXPSPACE = NEXPSPACE = ⋃k∈NNSPACE(2nk) The Immerman–Szelepcsényi theorem states that NSPACE(s(n)) is closed under complement for every function s(n) ≥ log n. A further generalization is ASPACE, defined with alternating Turing machines.
NSPACE	Relation with other complexity classes	DSPACE NSPACE is the non-deterministic counterpart of DSPACE, the class of memory space on a deterministic Turing machine. First by definition, then by Savitch's theorem, we have that: DSPACE[s(n)]⊆NSPACE[s(n)]⊆DSPACE[(s(n))2]. Time NSPACE can also be used to determine the time complexity of a deterministic Turing machine by the following theorem: If a language L is decided in space S(n) (where S(n) ≥ log n) by a non-deterministic TM, then there exists a constant C such that L is decided in time O(CS(n)) by a deterministic one.
NSPACE	Limitations	The measure of space complexity in terms of DSPACE is useful because it represents the total amount of memory that an actual computer would need to solve a given computational problem with a given algorithm. The reason is that DSPACE describes the space complexity used by deterministic Turing machines, which can represent actual computers. On the other hand, NSPACE describes the space complexity of non-deterministic Turing machines, which are not useful when trying to represent actual computers. For this reason, NSPACE is limited in its usefulness to real-world applications.
Chemoprotective agent	Chemoprotective agent	A chemo-protective agent is any drug that helps to reduce the side- effects of chemotherapy. These agents protect specific body parts from harmful anti-cancer treatments that could potentially cause permanent damage to important bodily tissues. Chemo-protective agents have only recently been introduced as a factor involved with chemotherapy with the intent to assist those cancer patients that require treatment, which as an end result, improves the patients' quality of life. Examples include: Amifostine, approved by the FDA in 1995, which helps prevent kidney damage in patients undergoing cisplatin and carboplatin chemotherapy Mesna, approved by the FDA in 1988, which helps prevent hemorrhagic cystitis (bladder bleeding) in patients undergoing cyclophosphamide or ifosfamide chemotherapy Dexrazoxane, approved by the FDA in 1995, which helps prevent heart problems in patients undergoing doxorubicin chemotherapy
Chemoprotective agent	Risks	Chemo-protective agents are common drugs and like many other drugs, may have side effects of their own. Each agent has different side effects though the most common consist of dizziness, sleepiness, nausea, fever, etc. It is important to discuss the side effects of these drugs with a doctor before using them to combat any type of chemotherapy to insure the drug will benefit each and every patient.
Metal carbonyl	Metal carbonyl	Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe chemistry. In the Mond process, nickel tetracarbonyl is used to produce pure nickel. In organometallic chemistry, metal carbonyls serve as precursors for the preparation of other organometallic complexes.
Metal carbonyl	Metal carbonyl	Metal carbonyls are toxic by skin contact, inhalation or ingestion, in part because of their ability to carbonylate hemoglobin to give carboxyhemoglobin, which prevents the binding of oxygen.
Metal carbonyl	Nomenclature and terminology	The nomenclature of the metal carbonyls depends on the charge of the complex, the number and type of central atoms, and the number and type of ligands and their binding modes. They occur as neutral complexes, as positively-charged metal carbonyl cations or as negatively charged metal carbonylates. The carbon monoxide ligand may be bound terminally to a single metal atom or bridging to two or more metal atoms. These complexes may be homoleptic, containing only CO ligands, such as nickel tetracarbonyl (Ni(CO)4), but more commonly metal carbonyls are heteroleptic and contain a mixture of ligands.Mononuclear metal carbonyls contain only one metal atom as the central atom. Except vanadium hexacarbonyl, only metals with even atomic number, such as chromium, iron, nickel, and their homologs, build neutral mononuclear complexes. Polynuclear metal carbonyls are formed from metals with odd atomic numbers and contain a metal–metal bond. Complexes with different metals but only one type of ligand are called isoleptic.Carbon monoxide has distinct binding modes in metal carbonyls. They differ in terms of their hapticity, denoted η, and their bridging mode. In η2-CO complexes, both the carbon and oxygen are bonded to the metal. More commonly only carbon is bonded, in which case the hapticity is not mentioned.The carbonyl ligand engages in a wide range of bonding modes in metal carbonyl dimers and clusters. In the most common bridging mode, denoted μ2 or simply μ, the CO ligand bridges a pair of metals. This bonding mode is observed in the commonly available metal carbonyls: Co2(CO)8, Fe2(CO)9, Fe3(CO)12, and Co4(CO)12. In certain higher nuclearity clusters, CO bridges between three or even four metals. These ligands are denoted μ3-CO and μ4-CO. Less common are bonding modes in which both C and O bond to the metal, such as μ3η2.
Metal carbonyl	Structure and bonding	Carbon monoxide bonds to transition metals using "synergistic pi* back-bonding". The M-C bonding has three components, giving rise to a partial triple bond. A sigma (σ) bond arises from overlap of the nonbonding (or weakly anti-bonding) sp-hybridized electron pair on carbon with a blend of d-, s-, and p-orbitals on the metal. A pair of pi (π) bonds arises from overlap of filled d-orbitals on the metal with a pair of π*-antibonding orbitals projecting from the carbon atom of the CO. The latter kind of binding requires that the metal have d-electrons, and that the metal is in a relatively low oxidation state (0 or +1) which makes the back-donation of electron density favorable. As electrons from the metal fill the π-antibonding orbital of CO, they weaken the carbon–oxygen bond compared with free carbon monoxide, while the metal–carbon bond is strengthened. Because of the multiple bond character of the M–CO linkage, the distance between the metal and carbon atom is relatively short, often less than 1.8 Å, about 0.2 Å shorter than a metal–alkyl bond. The M-CO and MC-O distance are sensitive to other ligands on the metal. Illustrative of these effects are the following data for Mo-C and C-O distances in Mo(CO)6 and Mo(CO)3(4-methylpyridine)3: 2.06 vs 1.90 and 1.11 vs 1.18 Å.
Metal carbonyl	Structure and bonding	Infrared spectroscopy is a sensitive probe for the presence of bridging carbonyl ligands. For compounds with doubly bridging CO ligands, denoted μ2-CO or often just μ-CO, the bond stretching frequency νCO is usually shifted by 100–200 cm−1 to lower energy compared to the signatures of terminal CO, which are in the region 1800 cm−1. Bands for face capping (μ3) CO ligands appear at even lower energies. In addition to symmetrical bridging modes, CO can be found to bridge asymmetrically or through donation from a metal d orbital to the π* orbital of CO. The increased π-bonding due to back-donation from multiple metal centers results in further weakening of the C–O bond.
Metal carbonyl	Structure and bonding	Physical characteristics Most mononuclear carbonyl complexes are colorless or pale yellow volatile liquids or solids that are flammable and toxic. Vanadium hexacarbonyl, a uniquely stable 17-electron metal carbonyl, is a blue-black solid. Dimetallic and polymetallic carbonyls tend to be more deeply colored. Triiron dodecacarbonyl (Fe3(CO)12) forms deep green crystals. The crystalline metal carbonyls often are sublimable in vacuum, although this process is often accompanied by degradation. Metal carbonyls are soluble in nonpolar and polar organic solvents such as benzene, diethyl ether, acetone, glacial acetic acid, and carbon tetrachloride. Some salts of cationic and anionic metal carbonyls are soluble in water or lower alcohols.
Metal carbonyl	Analytical characterization	Apart from X-ray crystallography, important analytical techniques for the characterization of metal carbonyls are infrared spectroscopy and 13C NMR spectroscopy. These two techniques provide structural information on two very different time scales. Infrared-active vibrational modes, such as CO-stretching vibrations, are often fast compared to intramolecular processes, whereas NMR transitions occur at lower frequencies and thus sample structures on a time scale that, it turns out, is comparable to the rate of intramolecular ligand exchange processes. NMR data provide information on "time-averaged structures", whereas IR is an instant "snapshot". Illustrative of the differing time scales, investigation of dicobalt octacarbonyl (Co2(CO)8) by means of infrared spectroscopy provides 13 νCO bands, far more than expected for a single compound. This complexity reflects the presence of isomers with and without bridging CO ligands. The 13C NMR spectrum of the same substance exhibits only a single signal at a chemical shift of 204 ppm. This simplicity indicates that the isomers quickly (on the NMR timescale) interconvert.
Metal carbonyl	Analytical characterization	Iron pentacarbonyl exhibits only a single 13C NMR signal owing to rapid exchange of the axial and equatorial CO ligands by Berry pseudorotation.
Metal carbonyl	Analytical characterization	Infrared spectra An important technique for characterizing metal carbonyls is infrared spectroscopy. The C–O vibration, typically denoted νCO, occurs at 2143 cm−1 for carbon monoxide gas. The energies of the νCO band for the metal carbonyls correlates with the strength of the carbon–oxygen bond, and inversely correlated with the strength of the π-backbonding between the metal and the carbon. The π-basicity of the metal center depends on a lot of factors; in the isoelectronic series (titanium to iron) at the bottom of this section, the hexacarbonyls show decreasing π-backbonding as one increases (makes more positive) the charge on the metal. π-Basic ligands increase π-electron density at the metal, and improved backbonding reduces νCO. The Tolman electronic parameter uses the Ni(CO)3 fragment to order ligands by their π-donating abilities.The number of vibrational modes of a metal carbonyl complex can be determined by group theory. Only vibrational modes that transform as the electric dipole operator will have nonzero direct products and are observed. The number of observable IR transitions (but not their energies) can thus be predicted. For example, the CO ligands of octahedral complexes, such as Cr(CO)6, transform as a1g, eg, and t1u, but only the t1u mode (antisymmetric stretch of the apical carbonyl ligands) is IR-allowed. Thus, only a single νCO band is observed in the IR spectra of the octahedral metal hexacarbonyls. Spectra for complexes of lower symmetry are more complex. For example, the IR spectrum of Fe2(CO)9 displays CO bands at 2082, 2019 and 1829 cm−1. The number of IR-observable vibrational modes for some metal carbonyls are shown in the table. Exhaustive tabulations are available. These rules apply to metal carbonyls in solution or the gas phase. Low-polarity solvents are ideal for high resolution. For measurements on solid samples of metal carbonyls, the number of bands can increase owing in part to site symmetry.
Metal carbonyl	Analytical characterization	Nuclear magnetic resonance spectroscopy Metal carbonyls are often characterized by 13C NMR spectroscopy. To improve the sensitivity of this technique, complexes are often enriched with 13CO. Typical chemical shift range for terminally bound ligands is 150 to 220 ppm. Bridging ligands resonate between 230 and 280 ppm. The 13C signals shift toward higher fields with an increasing atomic number of the central metal.
Metal carbonyl	Analytical characterization	NMR spectroscopy can be used for experimental determination of the fluxionality.The activation energy of ligand exchange processes can be determined by the temperature dependence of the line broadening. Mass spectrometry Mass spectrometry provides information about the structure and composition of the complexes. Spectra for metal polycarbonyls are often easily interpretable, because the dominant fragmentation process is the loss of carbonyl ligands (m/z = 28).
Metal carbonyl	Analytical characterization	M(CO)+n → M(CO)+n−1 + COElectron ionization is the most common technique for characterizing the neutral metal carbonyls. Neutral metal carbonyls can be converted to charged species by derivatization, which enables the use of electrospray ionization (ESI), instrumentation for which is often widely available. For example, treatment of a metal carbonyl with alkoxide generates an anionic metallaformate that is amenable to analysis by ESI-MS: LnM(CO) + RO− → [LnM−C(=O)OR]−Some metal carbonyls react with azide to give isocyanato complexes with release of nitrogen. By adjusting the cone voltage or temperature, the degree of fragmentation can be controlled. The molar mass of the parent complex can be determined, as well as information about structural rearrangements involving loss of carbonyl ligands under ESI-MS conditions.Mass spectrometry combined with infrared photodissociation spectroscopy can provide vibrational informations for ionic carbonyl complexes in gas phase.
Metal carbonyl	Occurrence in nature	In the investigation of the infrared spectrum of the Galactic Center of the Milky Way, monoxide vibrations of iron carbonyls in interstellar dust clouds were detected. Iron carbonyl clusters were also observed in Jiange H5 chondrites identified by infrared spectroscopy. Four infrared stretching frequencies were found for the terminal and bridging carbon monoxide ligands.In the oxygen-rich atmosphere of the Earth, metal carbonyls are subject to oxidation to the metal oxides. It is discussed whether in the reducing hydrothermal environments of the prebiotic prehistory such complexes were formed and could have been available as catalysts for the synthesis of critical biochemical compounds such as pyruvic acid. Traces of the carbonyls of iron, nickel, and tungsten were found in the gaseous emanations from the sewage sludge of municipal treatment plants.The hydrogenase enzymes contain CO bound to iron. It is thought that the CO stabilizes low oxidation states, which facilitates the binding of hydrogen. The enzymes carbon monoxide dehydrogenase and acetyl-CoA synthase also are involved in bioprocessing of CO. Carbon monoxide containing complexes are invoked for the toxicity of CO and signaling.
Metal carbonyl	Synthesis	The synthesis of metal carbonyls is a widely studied subject of organometallic research. Since the work of Mond and then Hieber, many procedures have been developed for the preparation of mononuclear metal carbonyls as well as homo- and heterometallic carbonyl clusters.
Metal carbonyl	Synthesis	Direct reaction of metal with carbon monoxide Nickel tetracarbonyl and iron pentacarbonyl can be prepared according to the following equations by reaction of finely divided metal with carbon monoxide: Ni + 4 CO → Ni(CO)4 (1 bar, 55 °C) Fe + 5 CO → Fe(CO)5 (100 bar, 175 °C)Nickel tetracarbonyl is formed with carbon monoxide already at 80 °C and atmospheric pressure, finely divided iron reacts at temperatures between 150 and 200 °C and a carbon monoxide pressure of 50–200 bar. Other metal carbonyls are prepared by less direct methods.
Metal carbonyl	Synthesis	Reduction of metal salts and oxides Some metal carbonyls are prepared by the reduction of metal halides in the presence of high pressure of carbon monoxide. A variety of reducing agents are employed, including copper, aluminum, hydrogen, as well as metal alkyls such as triethylaluminium. Illustrative is the formation of chromium hexacarbonyl from anhydrous chromium(III) chloride in benzene with aluminum as a reducing agent, and aluminum chloride as the catalyst: CrCl3 + Al + 6 CO → Cr(CO)6 + AlCl3The use of metal alkyls, such as triethylaluminium and diethylzinc, as the reducing agent leads to the oxidative coupling of the alkyl radical to form the dimer alkane: WCl6 + 6 CO + 2 Al(C2H5)3 → W(CO)6 + 2 AlCl3 + 3 C4H10Tungsten, molybdenum, manganese, and rhodium salts may be reduced with lithium aluminium hydride. Vanadium hexacarbonyl is prepared with sodium as a reducing agent in chelating solvents such as diglyme.
Metal carbonyl	Synthesis	VCl3 + 4 Na + 6 CO + 2 diglyme → Na(diglyme)2[V(CO)6] + 3 NaCl [V(CO)6]− + H+ → H[V(CO)6] → 1/2 H2 + V(CO)6In the aqueous phase, nickel or cobalt salts can be reduced, for example by sodium dithionite. In the presence of carbon monoxide, cobalt salts are quantitatively converted to the tetracarbonylcobalt(−1) anion: Co2+ + 3/2 S2O2−4 + 6 OH− + 4 CO → Co(CO)−4 + 3 SO2−3 + 3 H2OSome metal carbonyls are prepared using CO directly as the reducing agent. In this way, Hieber and Fuchs first prepared dirhenium decacarbonyl from the oxide: Re2O7 + 17 CO → Re2(CO)10 + 7 CO2If metal oxides are used carbon dioxide is formed as a reaction product. In the reduction of metal chlorides with carbon monoxide phosgene is formed, as in the preparation of osmium carbonyl chloride from the chloride salts. Carbon monoxide is also suitable for the reduction of sulfides, where carbonyl sulfide is the byproduct.
Metal carbonyl	Synthesis	Photolysis and thermolysis Photolysis or thermolysis of mononuclear carbonyls generates di- and polymetallic carbonyls such as diiron nonacarbonyl (Fe2(CO)9). On further heating, the products decompose eventually into the metal and carbon monoxide.
Metal carbonyl	Synthesis	2 Fe(CO)5 → Fe2(CO)9 + COThe thermal decomposition of triosmium dodecacarbonyl (Os3(CO)12) provides higher-nuclear osmium carbonyl clusters such as Os4(CO)13, Os6(CO)18 up to Os8(CO)23.Mixed ligand carbonyls of ruthenium, osmium, rhodium, and iridium are often generated by abstraction of CO from solvents such as dimethylformamide (DMF) and 2-methoxyethanol. Typical is the synthesis of IrCl(CO)(PPh3)2 from the reaction of iridium(III) chloride and triphenylphosphine in boiling DMF solution.
Metal carbonyl	Synthesis	Salt metathesis Salt metathesis reaction of salts such as KCo(CO)4 with [Ru(CO)3Cl2]2 leads selectively to mixed-metal carbonyls such as RuCo2(CO)11.
Metal carbonyl	Synthesis	4 KCo(CO)4 + [Ru(CO)3Cl2]2 → 2 RuCo2(CO)11 + 4 KCl + 11 CO Metal carbonyl cations and carbonylates The synthesis of ionic carbonyl complexes is possible by oxidation or reduction of the neutral complexes. Anionic metal carbonylates can be obtained for example by reduction of dinuclear complexes with sodium. A familiar example is the sodium salt of iron tetracarbonylate (Na2Fe(CO)4, Collman's reagent), which is used in organic synthesis.The cationic hexacarbonyl salts of manganese, technetium and rhenium can be prepared from the carbonyl halides under carbon monoxide pressure by reaction with a Lewis acid.
Metal carbonyl	Synthesis	Mn(CO)5Cl + AlCl3 + CO → [Mn(CO)+6][AlCl−4]The use of strong acids succeeded in preparing gold carbonyl cations such as [Au(CO)2]+, which is used as a catalyst for the carbonylation of alkenes. The cationic platinum carbonyl complex [Pt(CO)4]2+ can be prepared by working in so-called superacids such as antimony pentafluoride. Although CO is considered generally as a ligand for low-valent metal ions, the tetravalent iron complex [Cp2Fe]2+ (16-valence electron complex) quantitatively binds CO to give the diamagnetic Fe(IV)-carbonyl [Cp2FeCO]2+ (18-valence electron complex).
Metal carbonyl	Reactions	Metal carbonyls are important precursors for the synthesis of other organometallic complexes. Common reactions are the substitution of carbon monoxide by other ligands, the oxidation or reduction reactions of the metal center, and reactions at the carbon monoxide ligand.
Metal carbonyl	Reactions	CO substitution The substitution of CO ligands can be induced thermally or photochemically by donor ligands. The range of ligands is large, and includes phosphines, cyanide (CN−), nitrogen donors, and even ethers, especially chelating ones. Alkenes, especially dienes, are effective ligands that afford synthetically useful derivatives. Substitution of 18-electron complexes generally follows a dissociative mechanism, involving 16-electron intermediates.Substitution proceeds via a dissociative mechanism: M(CO)n → M(CO)n−1 + CO M(CO)n−1 + L → M(CO)n−1LThe dissociation energy is 105 kJ/mol (25 kcal/mol) for nickel tetracarbonyl and 155 kJ/mol (37 kcal/mol) for chromium hexacarbonyl.Substitution in 17-electron complexes, which are rare, proceeds via associative mechanisms with a 19-electron intermediates.
Metal carbonyl	Reactions	M(CO)n + L → M(CO)nL M(CO)nL → M(CO)n−1L + COThe rate of substitution in 18-electron complexes is sometimes catalysed by catalytic amounts of oxidants, via electron transfer.
Metal carbonyl	Reactions	Reduction Metal carbonyls react with reducing agents such as metallic sodium or sodium amalgam to give carbonylmetalate (or carbonylate) anions: Mn2(CO)10 + 2 Na → 2 Na[Mn(CO)5]For iron pentacarbonyl, one obtains the tetracarbonylferrate with loss of CO: Fe(CO)5 + 2 Na → Na2[Fe(CO)4] + COMercury can insert into the metal–metal bonds of some polynuclear metal carbonyls: Co2(CO)8 + Hg → (CO)4Co−Hg−Co(CO)4 Nucleophilic attack at CO The CO ligand is often susceptible to attack by nucleophiles. For example, trimethylamine oxide and potassium bis(trimethylsilyl)amide convert CO ligands to CO2 and CN−, respectively. In the "Hieber base reaction", hydroxide ion attacks the CO ligand to give a metallacarboxylic acid, followed by the release of carbon dioxide and the formation of metal hydrides or carbonylmetalates. A well-studied example of this nucleophilic addition is the conversion of iron pentacarbonyl to hydridoiron tetracarbonyl anion: Fe(CO)5 + NaOH → Na[Fe(CO)4CO2H] Na[Fe(CO)4COOH] + NaOH → Na[HFe(CO)4] + NaHCO3Hydride reagents also attack CO ligands, especially in cationic metal complexes, to give the formyl derivative: [Re(CO)6]+ + H− → Re(CO)5CHOOrganolithium reagents add with metal carbonyls to acylmetal carbonyl anions. O-Alkylation of these anions, such as with Meerwein salts, affords Fischer carbenes.
Metal carbonyl	Reactions	With electrophiles Despite being in low formal oxidation states, metal carbonyls are relatively unreactive toward many electrophiles. For example, they resist attack by alkylating agents, mild acids, and mild oxidizing agents. Most metal carbonyls do undergo halogenation. Iron pentacarbonyl, for example, forms ferrous carbonyl halides: Fe(CO)5 + X2 → Fe(CO)4X2 + COMetal–metal bonds are cleaved by halogens. Depending on the electron-counting scheme used, this can be regarded as an oxidation of the metal atoms: Mn2(CO)10 + Cl2 → 2 Mn(CO)5Cl
Metal carbonyl	Compounds	Most metal carbonyl complexes contain a mixture of ligands. Examples include the historically important IrCl(CO)(P(C6H5)3)2 and the antiknock agent (CH3C5H4)Mn(CO)3. The parent compounds for many of these mixed ligand complexes are the binary carbonyls, those species of the formula [Mx(CO)n]z, many of which are commercially available. The formulae of many metal carbonyls can be inferred from the 18-electron rule. Charge-neutral binary metal carbonyls Group 2 elements calcium, strontium, and barium can all form octacarbonyl complexes M(CO)8 (M = Ca, Sr, Ba). The compounds were characterized in cryogenic matrices by vibrational spectroscopy and in gas phase by mass spectrometry. Group 4 elements with 4 valence electrons are expected to form heptacarbonyls; while these are extremely rare, substituted derivatives of Ti(CO)7 are known. Group 5 elements with 5 valence electrons, again are subject to steric effects that prevent the formation of M–M bonded species such as V2(CO)12, which is unknown. The 17-VE V(CO)6 is however well known. Group 6 elements with 6 valence electrons form hexacarbonyls Cr(CO)6, Mo(CO)6, W(CO)6, and Sg(CO)6. Group 6 elements (as well as group 7) are also well known for exhibiting the cis effect (the labilization of CO in the cis position) in organometallic synthesis. Group 7 elements with 7 valence electrons form pentacarbonyl dimers Mn2(CO)10, Tc2(CO)10, and Re2(CO)10. Group 8 elements with 8 valence electrons form pentacarbonyls Fe(CO)5, Ru(CO)5 and Os(CO)5. The heavier two members are unstable, tending to decarbonylate to give Ru3(CO)12, and Os3(CO)12. The two other principal iron carbonyls are Fe3(CO)12 and Fe2(CO)9. Group 9 elements with 9 valence electrons and are expected to form tetracarbonyl dimers M2(CO)8. In fact the cobalt derivative of this octacarbonyl is the only stable member, but all three tetramers are well known: Co4(CO)12, Rh4(CO)12, Rh6(CO)16, and Ir4(CO)12. Co2(CO)8 unlike the majority of the other 18 VE transition metal carbonyls is sensitive to oxygen. Group 10 elements with 10 valence electrons form tetracarbonyls such as Ni(CO)4. Curiously Pd(CO)4 and Pt(CO)4 are not stable. Anionic binary metal carbonyls Group 3 elements scandium and yttrium form monoanions, [M(CO)8]− (M = Sc, Y) which are 20-electron carbonyls, as does the lanthanide lanthanum. Group 4 elements as dianions resemble neutral group 6 derivatives: [Ti(CO)6]2−. Group 5 elements as monoanions resemble again neutral group 6 derivatives: [V(CO)6]−. Group 7 elements as monoanions resemble neutral group 8 derivatives: [M(CO)5]− (M = Mn, Tc, Re). Group 8 elements as dianaions resemble neutral group 10 derivatives: [M(CO)4]2− (M = Fe, Ru, Os). Condensed derivatives are also known. Group 9 elements as monoanions resemble neutral group 10 metal carbonyl. [Co(CO)4]− is the best studied member.Large anionic clusters of nickel, palladium, and platinum are also well known. Many metal carbonyl anions can be protonated to give metal carbonyl hydrides. Cationic binary metal carbonyls Group 2 elements form [M(CO)8]+ (M = Ca, Sr, Ba), characterized in gas phase by mass spectrometry and vibrational spectroscopy. Group 3 elements form [Sc(CO)7]+ and [Y(CO)8]+ in gas phase. Group 7 elements as monocations resemble neutral group 6 derivative [M(CO)6]+ (M = Mn, Tc, Re). Group 8 elements as dications also resemble neutral group 6 derivatives [M(CO)6]2+ (M = Fe, Ru, Os). Nonclassical carbonyl complexes Nonclassical describes those carbonyl complexes where νCO is higher than that for free carbon monoxide. In nonclassical CO complexes, the C-O distance is shorter than free CO (113.7 pm). The structure of [Fe(CO)6]2+, with dC-O = 112.9 pm, illustrates this effect. These complexes are usually cationic, sometimes dicationic.
Metal carbonyl	Applications	Metallurgical uses Metal carbonyls are used in several industrial processes. Perhaps the earliest application was the extraction and purification of nickel via nickel tetracarbonyl by the Mond process (see also carbonyl metallurgy).By a similar process carbonyl iron, a highly pure metal powder, is prepared by thermal decomposition of iron pentacarbonyl. Carbonyl iron is used inter alia for the preparation of inductors, pigments, as dietary supplements, in the production of radar-absorbing materials in the stealth technology, and in thermal spraying.
Metal carbonyl	Applications	Catalysis Metal carbonyls are used in a number of industrially important carbonylation reactions. In the oxo process, an alkene, hydrogen gas, and carbon monoxide react together with a catalyst (such as dicobalt octacarbonyl) to give aldehydes. Illustrative is the production of butyraldehyde from propylene: CH3CH=CH2 + H2 + CO → CH3CH2CH2CHOButyraldehyde is converted on an industrial scale to 2-ethylhexanol, a precursor to PVC plasticizers, by aldol condensation, followed by hydrogenation of the resulting hydroxyaldehyde. The "oxo aldehydes" resulting from hydroformylation are used for large-scale synthesis of fatty alcohols, which are precursors to detergents. The hydroformylation is a reaction with high atom economy, especially if the reaction proceeds with high regioselectivity.
Metal carbonyl	Applications	Another important reaction catalyzed by metal carbonyls is the hydrocarboxylation. The example below is for the synthesis of acrylic acid and acrylic acid esters: Also the cyclization of acetylene to cyclooctatetraene uses metal carbonyl catalysts:In the Monsanto and Cativa processes, acetic acid is produced from methanol, carbon monoxide, and water using hydrogen iodide as well as rhodium and iridium carbonyl catalysts, respectively. Related carbonylation reactions afford acetic anhydride.
Metal carbonyl	Applications	CO-releasing molecules (CO-RMs) Carbon monoxide-releasing molecules are metal carbonyl complexes that are being developed as potential drugs to release CO. At low concentrations, CO functions as a vasodilatory and an anti-inflammatory agent. CO-RMs have been conceived as a pharmacological strategic approach to carry and deliver controlled amounts of CO to tissues and organs.
Metal carbonyl	Related compounds	Many ligands are known to form homoleptic and mixed ligand complexes that are analogous to the metal carbonyls. Nitrosyl complexes Metal nitrosyls, compounds featuring NO ligands, are numerous. In contrast to metal carbonyls, however, homoleptic metal nitrosyls are rare. NO is a stronger π-acceptor than CO. Well known nitrosyl carbonyls include CoNO(CO)3 and Fe(NO)2(CO)2, which are analogues of Ni(CO)4.
Metal carbonyl	Related compounds	Thiocarbonyl complexes Complexes containing CS are known but uncommon. The rarity of such complexes is partly attributable to the fact that the obvious source material, carbon monosulfide, is unstable. Thus, the synthesis of thiocarbonyl complexes requires indirect routes, such as the reaction of disodium tetracarbonylferrate with thiophosgene: Na2Fe(CO)4 + CSCl2 → Fe(CO)4CS + 2 NaClComplexes of CSe and CTe have been characterized.
Metal carbonyl	Related compounds	Isocyanide complexes Isocyanides also form extensive families of complexes that are related to the metal carbonyls. Typical isocyanide ligands are methyl isocyanide and t-butyl isocyanide (Me3CNC). A special case is CF3NC, an unstable molecule that forms stable complexes whose behavior closely parallels that of the metal carbonyls.
Metal carbonyl	Toxicology	The toxicity of metal carbonyls is due to toxicity of carbon monoxide, the metal, and because of the volatility and instability of the complexes, any inherent toxicity of the metal is generally made much more severe due to ease of exposure. Exposure occurs by inhalation, or for liquid metal carbonyls by ingestion or due to the good fat solubility by skin resorption. Most clinical experience were gained from toxicological poisoning with nickel tetracarbonyl and iron pentacarbonyl due to their use in industry. Nickel tetracarbonyl is considered as one of the strongest inhalation poisons.Inhalation of nickel tetracarbonyl causes acute non-specific symptoms similar to a carbon monoxide poisoning, such as nausea, cough, headache, fever, and dizziness. After some time, severe pulmonary symptoms such as cough, tachycardia, and cyanosis, or problems in the gastrointestinal tract occur. In addition to pathological alterations of the lung, such as by metalation of the alveoli, damages are observed in the brain, liver, kidneys, adrenal glands, and spleen. A metal carbonyl poisoning often necessitates a lengthy recovery.Chronic exposure by inhalation of low concentrations of nickel tetracarbonyl can cause neurological symptoms such as insomnia, headaches, dizziness and memory loss. Nickel tetracarbonyl is considered carcinogenic, but it can take 20 to 30 years from the start of exposure to the clinical manifestation of cancer.
Metal carbonyl	History	Initial experiments on the reaction of carbon monoxide with metals were carried out by Justus von Liebig in 1834. By passing carbon monoxide over molten potassium he prepared a substance having the empirical formula KCO, which he called Kohlenoxidkalium. As demonstrated later, the compound was not a carbonyl, but the potassium salt of benzenehexol (K6C6O6) and the potassium salt of acetylenediol (K2C2O2).
Metal carbonyl	History	The synthesis of the first true heteroleptic metal carbonyl complex was performed by Paul Schützenberger in 1868 by passing chlorine and carbon monoxide over platinum black, where dicarbonyldichloroplatinum (Pt(CO)2Cl2) was formed.Ludwig Mond, one of the founders of Imperial Chemical Industries, investigated in the 1890s with Carl Langer and Friedrich Quincke various processes for the recovery of chlorine which was lost in the Solvay process by nickel metals, oxides, and salts. As part of their experiments the group treated nickel with carbon monoxide. They found that the resulting gas colored the gas flame of a burner in a greenish-yellowish color; when heated in a glass tube it formed a nickel mirror. The gas could be condensed to a colorless, water-clear liquid with a boiling point of 43 °C. Thus, Mond and his coworker had discovered the first pure, homoleptic metal carbonyl, nickel tetracarbonyl (Ni(CO)4). The unusual high volatility of the metal compound nickel tetracarbonyl led Kelvin to the statement that Mond had "given wings to the heavy metals".The following year, Mond and Marcellin Berthelot independently discovered iron pentacarbonyl, which is produced by a similar procedure as nickel tetracarbonyl. Mond recognized the economic potential of this class of compounds, which he commercially used in the Mond process and financed more research on related compounds. Heinrich Hirtz and his colleague M. Dalton Cowap synthesized metal carbonyls of cobalt, molybdenum, ruthenium, and diiron nonacarbonyl. In 1906 James Dewar and H. O. Jones were able to determine the structure of diiron nonacarbonyl, which is produced from iron pentacarbonyl by the action of sunlight. After Mond, who died in 1909, the chemistry of metal carbonyls fell for several years in oblivion. BASF started in 1924 the industrial production of iron pentacarbonyl by a process which was developed by Alwin Mittasch. The iron pentacarbonyl was used for the production of high-purity iron, so-called carbonyl iron, and iron oxide pigment. Not until 1927 did A. Job and A. Cassal succeed in the preparation of chromium hexacarbonyl and tungsten hexacarbonyl, the first synthesis of other homoleptic metal carbonyls.Walter Hieber played in the years following 1928 a decisive role in the development of metal carbonyl chemistry. He systematically investigated and discovered, among other things, the Hieber base reaction, the first known route to metal carbonyl hydrides and synthetic pathways leading to metal carbonyls such as dirhenium decacarbonyl. Hieber, who was since 1934 the Director of the Institute of Inorganic Chemistry at the Technical University Munich published in four decades 249 papers on metal carbonyl chemistry.
Metal carbonyl	History	Also in the 1930s Walter Reppe, an industrial chemist and later board member of BASF, discovered a number of homogeneous catalytic processes, such as the hydrocarboxylation, in which olefins or alkynes react with carbon monoxide and water to form products such as unsaturated acids and their derivatives. In these reactions, for example, nickel tetracarbonyl or cobalt carbonyls act as catalysts. Reppe also discovered the cyclotrimerization and tetramerization of acetylene and its derivatives to benzene and benzene derivatives with metal carbonyls as catalysts. BASF built in the 1960s a production facility for acrylic acid by the Reppe process, which was only superseded in 1996 by more modern methods based on the catalytic propylene oxidation.
Metal carbonyl	History	For the rational design of new complexes the concept of the isolobal analogy has been found useful. Roald Hoffmann was awarded the Nobel Prize in chemistry for the development of the concept. This describes metal carbonyl fragments of M(CO)n as parts of octahedral building blocks in analogy to the tetrahedral CH3–, CH2– or CH– fragments in organic chemistry. In example dimanganese decacarbonyl is formed in terms of the isolobal analogy of two d7 Mn(CO)5 fragments, that are isolobal to the methyl radical CH•3. In analogy to how methyl radicals combine to form ethane, these can combine to dimanganese decacarbonyl. The presence of isolobal analog fragments does not mean that the desired structures can be synthesized. In his Nobel Prize lecture Hoffmann emphasized that the isolobal analogy is a useful but simple model, and in some cases does not lead to success.The economic benefits of metal-catalysed carbonylations, such as Reppe chemistry and hydroformylation, led to growth of the area. Metal carbonyl compounds were discovered in the active sites of three naturally occurring enzymes.
Rhodesian Brushstroke	Rhodesian Brushstroke	The Rhodesian Brushstroke is a brushstroke-type camouflage pattern used by the Rhodesian Security Forces from 1965 until its replacement by a vertical lizard stripe in 1980. It was the default camouflage appearing on battledress of the Rhodesian Army and British South Africa Police, although used in smaller quantities by INTAF personnel. The design was also used on uniforms issued to South African Special Forces for clandestine operations. A similar pattern is fielded by the Zimbabwe National Army.
Rhodesian Brushstroke	Development and history	Rhodesian Brushstroke consists of large, contrasting, shapes tailored to break up the outline of an object. Like most disruptive camouflage, the pattern is dependent on countershading, using hues with high-intensity contrast or noticeable differences in chromaticity.Prior to Rhodesia's Unilateral Declaration of Independence, enlisted personnel in the Rhodesian Army were issued with uniforms in khaki drill. The Battle of Sinoia and the outbreak of the Rhodesian Bush War prompted the security forces to devise a more appropriate uniform especially designed for the region. This incorporated a three colour, high contrast, disruptive fabric with green and brown strokes on a sandy background. Early shortages of textile and equipment were overcome with South African and Portuguese technical assistance, and a home industry for the new battledress developed.The pattern was supposedly designed by Di Cameron of David Whitehead Textiles.
Rhodesian Brushstroke	Users	Rhodesia The basic Rhodesian military battledress adopted universally between 1964 and 1966 consisted of a camouflage jacket, field cap, and trousers with wide belt loops for a stable belt and large cargo pockets. Ranks, name tapes, or unit patches were sewn on. In 1969, the jackets were largely superseded by shirts of a lighter material for combat operations in the hot African climate. Late in the bush war, Rhodesian battledress commonly took the form of one-piece coveralls, but uniform regulations remained quite lax in the field. Individual servicemen often modified their uniforms to shorten the sleeves while others wore privately purchased T-shirts with the same camouflage print. The long camouflage trousers were also discarded in large numbers in favour of running shorts.While the brushstroke pattern itself was considered very effective, the fabric in locally-made uniforms was of poor quality and the Rhodesian troops frequently envied foreign volunteers who brought their more durable foreign-produced clothing with them.
Rhodesian Brushstroke	Users	Zimbabwe The Zimbabwe Defence Forces initially discarded its preexisting stocks of Rhodesian battledress in favour of a Portuguese-designed vertical lizardstripe during the 1980s; however, the original brushstroke pattern was re-adopted during the 1990s just prior to the Second Congo War. Zimbabwe currently produces military uniforms in two variations of Rhodesian Brushstroke designed for the dry season and rainy season, respectively. The dry season variant uses a light khaki base while the rainy season variant is designed on a green base. The difference between the original Rhodesian camouflage and the ZNA version is that in the Zimbabwe pattern, brown is printed over the green, and not beneath it.
Rhodesian Brushstroke	Users	South Africa During the late 1970s, South African pilots, technical personnel, and special forces frequently operated alongside the Rhodesian security forces. Due to the covert nature of their presence, they were forbidden from wearing their regulation uniforms and instead issued with Rhodesian battledress. South African units known to have received stocks of Rhodesian uniforms included 3 South African Infantry Battalion and 1 Parachute Battalion. South African special forces also wore Rhodesian battledress during raids in Mozambique during the Mozambican Civil War. This practice was largely discontinued following Zimbabwean independence in 1980. The Rhodesian battledress did continue to be issued to ex-Rhodesian service members serving with South African special forces units operating in Zimbabwe between 1981 and 1984.
Rhodesian Brushstroke	Users	Non-State actors Pilfered Rhodesian fatigues occasionally turned up in the hands of the Zimbabwe People's Revolutionary Army (ZIPRA), which used it to impersonate members of the Rhodesian security forces. Prior to standardising its uniforms during the mid 1970s, the People's Armed Forces for the Liberation of Angola (FAPLA) also adopted Rhodesian battledress uniforms in limited quantities.
Rhodesian Brushstroke	Users	Trials While developing a new disruptive camouflage pattern in the 2000, the United States Marine Corps (USMC) evaluated Rhodesian Brushstroke as one of the three best military camouflage patterns previously developed, along with Canadian Pattern (CADPAT) and tigerstripe. None of the three patterns were adopted because the USMC desired a more distinctive design. In 2002, it adopted the MARPAT digital camouflage pattern, a re-coloured version of CADPAT.
Vitrified clay pipe	Vitrified clay pipe	Vitrified clay pipe (VCP) is pipe made from a blend of clay and shale that has been subjected to high temperature to achieve vitrification, which results in a hard, inert ceramic.
Vitrified clay pipe	Vitrified clay pipe	VCP is commonly used in gravity sewer collection mains because of its long life and resistance to almost all domestic and industrial sewage, particularly the sulfuric acid that is generated by hydrogen sulfide, a common component of sewage. Only hydrofluoric acid and highly concentrated caustic wastes are known to attack VCP. Such wastes would not be permitted to be discharged into a municipal sewage collection system without adequate pretreatment.There are three main types of VCP produced in the U.S.: Bell & Spigot Pipe (with factory-applied compression joints), Band-Seal pipe (with rubber compression couplings) and NO-DIG(R) Pipe (for trenchless installation with an elastomeric gasket and stainless steel collar for a low-profile compression joint). All VCP manufactured in the U.S. must comply with ASTM C425 to provide a flexible leak-free joint.
Vitrified clay pipe	Vitrified clay pipe	Clay pipe has been in-use in sanitary sewer systems for at least 5,000 years
Vitrified clay pipe	Production	VCP pipe is made by forming clay then heating it to 2000 degrees Fahrenheit (1100 degrees Celsius). The pipe is then vitrified. In some areas the pipe is then glazed to ensure that it will be water-tight.
Vitrified clay pipe	Benefits	VCP products use clay as a major component in its production, making its raw materials environmentally friendly. The manufacturing process has been fine-tuned for centuries and was designed to be fiscally responsible which had the added benefit of being environmentally responsible. But the primary benefit (both environmental and fiscal) of using VCP in sanitary sewers is its long service life.As Sanitary Sewer Overflows (SSOs) have become an area of concern for the US EPA and thus a very large potential liability for municipalities, cleaning sewers for condition assessment and maintenance has become a critical factor in system design. Flexible thermoplastic pipe limits the tools available for this cleaning as they are more easily damaged. VCP allows for aggressive cleaning methods which prolongs the service life of a sewer line and frequently eliminates the need for expensive dig-ups.Further, VCP's resistance to a wide variety of acids besides hydrofluoric acid make it a long lasting choice for use in underground sewers.
Dorico	Dorico	Dorico () is a scorewriter software; along with Finale and Sibelius, it is one of the three leading professional-level music notation programs.Dorico's development team consists of most of the former core developers of a rival software, Sibelius. After the developers of Sibelius were laid off in a 2012 restructuring by their corporate owner, Avid, most of the team were re-hired by a competing company, Steinberg, to create a new software. They aimed to build a "next-generation" music notation program, and released Dorico four years later, in 2016.
Dorico	History	The project was unveiled on 20 February 2013 by the Product Marketing Manager, Daniel Spreadbury, on the blog Making Notes, and the software was first released on 19 October 2016.The program's title Dorico was revealed on the same blog on 17 May 2016. The name honours the 16th-century Italian music engraver Valerio Dorico (1500 – c. 1565), who printed first editions of sacred music by Giovanni Pierluigi da Palestrina and Giovanni Animuccia and pioneered the use of a single impression printing process first developed in England and France.The iPad version was released on 28 July 2021; it was the first major desktop scorewriter application to be made available on a mobile platform. It offers most of the functionality of the desktop app.
Dorico	Features	Dorico is known for its stability and reliability in creating aesthetically pleasing scores and its intuitive interface. User feedback influences Dorico's feature design, and the development team actively use the forum and Facebook group. Automation Reviews have claimed that Dorico has become more efficient than other notation software. For example, a signature time-saving feature is its automatic creation of instrumental part layouts. Another signature feature is its automated condensing, where it combines multiple players' parts onto a single staff, such as for a conductor's score. Keyboard input Dorico natively supports note input entirely from the computer keyboard without the need to use the mouse. It also supports MIDI input from a piano keyboard.
Dorico	Features	SMuFL music fonts The Standard Music Font Layout (SMuFL) standard was created by the Dorico development team at Steinberg. It provides a consistent standard way of mapping the thousands of musical symbols required by conventional music notation into a single font that can be used by a variety of software and font designers. It was first implemented in MuseScore, then in Dorico's first release and in Finale.
Limit load (aeronautics)	Limit load (aeronautics)	For aircraft specification calculation in aeronautics, limit load (LL) is the maximum load factor authorized during flight, Mathematically, limit load is LL = LLF x W, where LL = limit load, LLF = limit load factor, and W = weight of the aircraft.
Limit load (aeronautics)	Limit load (aeronautics)	Limit load is constant for all weights above design gross weight. The limit load factor is reduced if gross weight is increased. But the LLF cannot be increased if the gross weight is decreased below the design gross weight. Engine mounts and other structural members are designed for the nominal LLF. The nominal or limit load Bn is the load which should only occur once (or only a very few times) during the lifetime of an aircraft. Bn may therefore only occur once during (e.g.) 60,000 hours of flying. No plastic deformation is allowed at this level of a load.
Limit load (aeronautics)	Limit load (aeronautics)	The limit load can be found relatively easily by statistically analysing the data collected during the many hours of logged flights (which is continuously being gathered).
Fashion museum	Fashion museum	A fashion museum is dedicated to or features a significant collection of accessories or clothing. There is some overlap with textile museums.
Fashion museum	Fashion museum	Notable examples include the Costume Museum of Canada, the Fashion Museum, Bath, the Musée Galliera in Paris, and the Fashion Museum of the Province of Antwerp MoMu. National museums with significant fashion collections include the Victoria and Albert Museum in London. The Metropolitan Museum of Art in New York contains a collection of more than 75,000 costumes and accessories.Another in London is the Fashion and Textile Museum, founded by designer Zandra Rhodes in 2003, and the only museum in Britain dedicated to showcasing developments in contemporary fashion, as well as providing inspiration, support and training for those working in the industry.
OR3A2	OR3A2	Olfactory receptor 3A2 is a protein that in humans is encoded by the OR3A2 gene.Olfactory receptors interact with odorant molecules in the nose, to initiate a neuronal response that triggers the perception of a smell. The olfactory receptor proteins are members of a large family of G-protein-coupled receptors (GPCR) arising from single coding-exon genes. Olfactory receptors share a 7-transmembrane domain structure with many neurotransmitter and hormone receptors and are responsible for the recognition and G protein-mediated transduction of odorant signals. The olfactory receptor gene family is the largest in the genome. The nomenclature assigned to the olfactory receptor genes and proteins for this organism is independent of other organisms.
Press conference	Press conference	A press conference or news conference is a media event in which notable individuals or organizations invite journalists to hear them speak and ask questions. Press conferences are often held by politicians, corporations, non-governmental organizations, as well as organizers for newsworthy events.

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.