Calcite seaA calcite sea is a sea in which low-magnesium calcite is the primary inorganic marine calcium carbonate precipitate. An aragonite sea is the alternate seawater chemistry in which aragonite and high-magnesium calcite are the primary inorganic carbonate precipitates. The Early Paleozoic and the Middle to Late Mesozoic oceans were predominantly calcite seas, whereas the Middle Paleozoic through the Early Mesozoic and the Cenozoic (including today) are characterized by aragonite seas.
Magnesium carbonateMagnesium carbonate, (archaic name magnesia alba), is an inorganic salt that is a colourless or white solid. Several hydrated and basic forms of magnesium carbonate also exist as minerals. The most common magnesium carbonate forms are the anhydrous salt called magnesite (), and the di, tri, and pentahydrates known as barringtonite (), nesquehonite (), and lansfordite (), respectively. Some basic forms such as artinite (), hydromagnesite (), and dypingite () also occur as minerals. All of those minerals are colourless or white.
Structural steelStructural steel is a category of steel used for making construction materials in a variety of shapes. Many structural steel shapes take the form of an elongated beam having a of a specific cross section. Structural steel shapes, sizes, chemical composition, mechanical properties such as strengths, storage practices, etc., are regulated by standards in most industrialized countries. Most structural steel shapes, such as -beams, have high second moments of area, which means they are very stiff in respect to their cross-sectional area and thus can support a high load without excessive sagging.
Dolomite (rock)Dolomite (also known as dolomite rock, dolostone or dolomitic rock) is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite, CaMg(CO3)2. It occurs widely, often in association with limestone and evaporites, though it is less abundant than limestone and rare in Cenozoic rock beds (beds less than about 66 million years in age). The first geologist to distinguish dolomite rock from limestone was Belsazar Hacquet in 1778. Most dolomite was formed as a magnesium replacement of limestone or of lime mud before lithification.
Strongly correlated materialStrongly correlated materials are a wide class of compounds that include insulators and electronic materials, and show unusual (often technologically useful) electronic and magnetic properties, such as metal-insulator transitions, heavy fermion behavior, half-metallicity, and spin-charge separation. The essential feature that defines these materials is that the behavior of their electrons or spinons cannot be described effectively in terms of non-interacting entities.
Biological warfareBiological warfare, also known as germ warfare, is the use of biological toxins or infectious agents such as bacteria, viruses, insects, and fungi with the intent to kill, harm or incapacitate humans, animals or plants as an act of war. Biological weapons (often termed "bio-weapons", "biological threat agents", or "bio-agents") are living organisms or replicating entities (i.e. viruses, which are not universally considered "alive"). Entomological (insect) warfare is a subtype of biological warfare.
Germ layerA germ layer is a primary layer of cells that forms during embryonic development. The three germ layers in vertebrates are particularly pronounced; however, all eumetazoans (animals that are sister taxa to the sponges) produce two or three primary germ layers. Some animals, like cnidarians, produce two germ layers (the ectoderm and endoderm) making them diploblastic. Other animals such as bilaterians produce a third layer (the mesoderm) between these two layers, making them triploblastic.
Fine structureIn atomic physics, the fine structure describes the splitting of the spectral lines of atoms due to electron spin and relativistic corrections to the non-relativistic Schrödinger equation. It was first measured precisely for the hydrogen atom by Albert A. Michelson and Edward W. Morley in 1887, laying the basis for the theoretical treatment by Arnold Sommerfeld, introducing the fine-structure constant. The gross structure of line spectra is the line spectra predicted by the quantum mechanics of non-relativistic electrons with no spin.
StructureA structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as biological organisms, minerals and chemicals. Abstract structures include data structures in computer science and musical form. Types of structure include a hierarchy (a cascade of one-to-many relationships), a network featuring many-to-many links, or a lattice featuring connections between components that are neighbors in space.
Fine-structure constantIn physics, the fine-structure constant, also known as the Sommerfeld constant, commonly denoted by α (the Greek letter alpha), is a fundamental physical constant which quantifies the strength of the electromagnetic interaction between elementary charged particles. It is a dimensionless quantity, independent of the system of units used, which is related to the strength of the coupling of an elementary charge e with the electromagnetic field, by the formula 4πε_0ħcα = e^2. Its numerical value is approximately 0.
