Death metalDeath metal is an extreme subgenre of heavy metal music. It typically employs heavily distorted and low-tuned guitars, played with techniques such as palm muting and tremolo picking; deep growling vocals; aggressive, powerful drumming, featuring double kick and blast beat techniques; minor keys or atonality; abrupt tempo, key, and time signature changes; and chromatic chord progressions. The lyrical themes of death metal may include slasher film-style violence, political conflict, religion, nature, philosophy, true crime and science fiction.
Metal-phosphine complexA metal-phosphine complex is a coordination complex containing one or more phosphine ligands. Almost always, the phosphine is an organophosphine of the type R3P (R = alkyl, aryl). Metal phosphine complexes are useful in homogeneous catalysis. Prominent examples of metal phosphine complexes include Wilkinson's catalyst (Rh(PPh3)3Cl), Grubbs' catalyst, and tetrakis(triphenylphosphine)palladium(0). Many metal phosphine complexes are prepared by reactions of metal halides with preformed phosphines.
Doom metalDoom metal is an extreme subgenre of heavy metal music that typically uses slower tempos, low-tuned guitars and a much "thicker" or "heavier" sound than other heavy metal genres. Both the music and the lyrics are intended to evoke a sense of despair, dread, and impending doom. The genre is strongly influenced by the early work of Black Sabbath, who formed a prototype for doom metal.
Cell surface receptorCell surface receptors (membrane receptors, transmembrane receptors) are receptors that are embedded in the plasma membrane of cells. They act in cell signaling by receiving (binding to) extracellular molecules. They are specialized integral membrane proteins that allow communication between the cell and the extracellular space. The extracellular molecules may be hormones, neurotransmitters, cytokines, growth factors, cell adhesion molecules, or nutrients; they react with the receptor to induce changes in the metabolism and activity of a cell.
Acid dissociation constantIn chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted K_a) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction HA A^- + H^+ known as dissociation in the context of acid–base reactions. The chemical species HA is an acid that dissociates into , the conjugate base of the acid and a hydrogen ion, .
Metal carbonylMetal 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.
Heavy metalsHeavy metals are generally defined as metals with relatively high densities, atomic weights, or atomic numbers. The criteria used, and whether metalloids are included, vary depending on the author and context. In metallurgy, for example, a heavy metal may be defined on the basis of density, whereas in physics the distinguishing criterion might be atomic number, while a chemist would likely be more concerned with chemical behaviour. More specific definitions have been published, none of which have been widely accepted.
HumusIn classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Latin word for "earth" or "ground". In agriculture, "humus" sometimes also is used to describe mature or natural compost extracted from a woodland or other spontaneous source for use as a soil conditioner. It is also used to describe a topsoil horizon that contains organic matter (humus type, humus form, or humus profile).
Power metalPower metal is a subgenre of heavy metal combining characteristics of traditional heavy metal with speed metal, often within a symphonic context. Generally, power metal is characterized by a faster, lighter, and more uplifting sound, in contrast with the heaviness and dissonance prevalent in, for example, extreme metal. Power metal bands usually have anthem-like songs with fantasy-based subject matter and strong choruses, thus creating a theatrical, dramatic and emotionally "powerful" sound.
Folk metalFolk metal is a fusion genre of heavy metal music and traditional folk music that developed in Europe during the 1990s. It is characterised by the widespread use of folk instruments and, to a lesser extent, traditional singing styles (for example, Dutch Heidevolk, Danish Sylvatica and Spanish Stone of Erech). It also sometimes features soft instrumentation influenced by folk rock. The earliest folk metal bands were Skyclad from England and Cruachan from Ireland.
