The standard uses capital letters S and Z to indicate the direction of twist, as suggested by the direction of slant of the central portions of these two letters. The handedness of the twist is the direction of the twists as they progress away from an observer. Thus Z-twist is said to be right-handed, and S-twist to be left-handed. The convention of using these two letters to unambiguously designate twist direction was already used in the cordage industry by 1957.
Charles Robert Scrivener ISO (2 November 1855 – 26 September 1923) was an Australian surveyor, and the person who surveyed numerous sites in New South Wales for the selection of a site for the Australian Capital Territory and Australia's capital city, Canberra.
Scrivener was born in Windsor, New South Wales. In 1876, he was employed by the New South Wales Department of Lands. He was apprenticed as a surveyor between 1877 and 1879. On 9 July 1880, the government gazette announced that he had been licensed as a surveyor by the Surveyor-General. In 1888, Scrivener was appointed Surveyor in Maitland, New South Wales, by 1896 he was appointed as an Acting District Surveyor in Wagga Wagga and District Surveyor for Hay in 1906. He surveyed numerous sites for the construction of Australia's capital, including Buckley's Crossing, the Hay district, and lastly the Yass-Canberra district. Scrivener's contour map of the selected site was used as the basis for entries in the Canberra design competition. He was appointed first director of Commonwealth lands and surveys in 1910 and retired in 1915. He died aged 67 in Killara, New South Wales.
The Scrivener Dam on Lake Burley Griffin is named in his honour.Cleanroom
A cleanroom or clean room is a facility ordinarily utilized as a part of specialized industrial production or scientific research, including the manufacture of pharmaceutical items and microprocessors. Cleanrooms are designed to maintain extremely low levels of particulates, such as dust, airborne organisms, or vaporized particles. Cleanrooms typically have an cleanliness level quantified by the number of particles per cubic meter at a predetermined molecule measure. The ambient outdoor air in a typical urban area contains 35,000,000 particles for each cubic meter in the size range 0.5 μm and bigger in measurement, equivalent to an ISO 9 cleanroom, while by comparison an ISO 1 cleanroom permits no particles in that size range and just 12 particles for each cubic meter of 0.3 μm and smaller.Group contraction
In theoretical physics, Eugene Wigner and Erdal İnönü have discussed the possibility to obtain from a given Lie group a different (non-isomorphic) Lie group by a group contraction with respect to a continuous subgroup of it. That amounts to a limiting operation on a parameter of the Lie algebra, altering the structure constants of this Lie algebra in a nontrivial singular manner, under suitable circumstances.For example, the Lie algebra of the 3D rotation group SO(3), [X1, X2] = X3, etc., may be rewritten by a change of variables Y1 = εX1, Y2 = εX2, Y3 = X3, as
[Y1, Y2] = ε2 Y3, [Y2, Y3] = Y1, [Y3, Y1] = Y2.The contraction limit ε → 0 trivializes the first commutator and thus yields the non-isomorphic algebra of the plane Euclidean group, E2 ~ ISO(2). (This is isomorphic to the cylindrical group, describing motions of a point on the surface of a cylinder. It is the little group, or stabilizer subgroup, of null four-vectors in Minkowski space.) Specifically, the translation generators Y1, Y2, now generate the Abelian normal subgroup of E2 (cf. Group extension), the parabolic Lorentz transformations.
Similar limits, of considerable application in physics (cf. Correspondence principles), contract
the de Sitter group SO(4, 1) ~ Sp(2, 2) to the Poincaré group ISO(3, 1), as the de Sitter radius diverges: R → ∞; or
the Poincaré group to the Galilei group, as the speed of light diverges: c → ∞; or
the Moyal bracket Lie algebra (equivalent to quantum commutators) to the Poisson bracket Lie algebra, in the classical limit as the Planck constant vanishes: ħ → 0.ISO/IEC 646
ISO/IEC 646 is the name of a set of ISO standards, described as Information technology — ISO 7-bit coded character set for information interchange and developed in cooperation with ASCII at least since 1964. Since its first edition in 1967 it has specified a 7-bit character code from which several national standards are derived.
ISO/IEC 646 was also ratified by ECMA as ECMA-6. The first version of ECMA-6 had been published in 1965, based on work the ECMA's Technical Committee TC1 had carried out since December 1960.Characters in the ISO/IEC 646 Basic Character Set are invariant characters. Since that portion of ISO/IEC 646, that is the invariant character set shared by all countries, specified only those letters used in the ISO basic Latin alphabet, countries using additional letters needed to create national variants of ISO 646 to be able to use their native scripts. Since transmission and storage of 8-bit codes was not standard at the time, the national characters had to be made to fit within the constraints of 7 bits, meaning that some characters that appear in ASCII do not appear in other national variants of ISO 646.ISO 3166-2
ISO 3166-2 is part of the ISO 3166 standard published by the International Organization for Standardization (ISO), and defines codes for identifying the principal subdivisions (e.g., provinces or states) of all countries coded in ISO 3166-1. The official name of the standard is Codes for the representation of names of countries and their subdivisions – Part 2: Country subdivision code. It was first published in 1998.
The purpose of ISO 3166-2 is to establish an international standard of short and unique alphanumeric codes to represent the relevant administrative divisions and dependent territories of all countries in a more convenient and less ambiguous form than their full names. Each complete ISO 3166-2 code consists of two parts, separated by a hyphen:
The first part is the ISO 3166-1 alpha-2 code of the country;
The second part is a string of up to three alphanumeric characters, which is usually obtained from national sources and stems from coding systems already in use in the country concerned, but may also be developed by the ISO itself.Each complete ISO 3166-2 code can then be used to uniquely identify a country subdivision in a global context.
As of 26 November 2018 there are 4,965 codes defined in ISO 3166-2. For some countries, codes are defined for more than one level of subdivisions.Object identifier
In computing, object identifiers or OIDs are an identifier mechanism standardized by the International Telecommunications Union (ITU) and ISO/IEC for naming any object, concept, or "thing" with a globally unambiguous persistent name.Optical resolution
Optical resolution describes the ability of an imaging system to resolve detail in the object that is being imaged.
An imaging system may have many individual components including a lens and recording and display components. Each of these contributes to the optical resolution of the system, as will the environment in which the imaging is done.Race condition
A race condition or race hazard is the behavior of an electronics, software, or other system where the system's substantive behavior is dependent on the sequence or timing of other uncontrollable events. It becomes a bug when one or more of the possible behaviors is undesirable.
The term race condition was already in use by 1954, for example in David A. Huffman's doctoral thesis "The synthesis of sequential switching circuits". Race conditions can occur especially in logic circuits, multithreaded or distributed software programs.Right-hand rule
In mathematics and physics, the right-hand rule is a common mnemonic for understanding orientation of axes in 3-dimensional space.
Most of the various left- and right-hand rules arise from the fact that the three axes of three-dimensional space have two possible orientations. One can see this by holding one's hands outward and together, palms up, with the fingers curled, and the thumb out-stretched. If the curl of the fingers represents a movement from the first or x-axis to the second or y-axis, then the third or z-axis can point along either thumb. Left- and right-hand rules arise when dealing with coordinate axes, rotation, spirals, electromagnetic fields, mirror images, and enantiomers in mathematics and chemistry.Rope
A rope is a group of yarns, plies, fibers or strands that are twisted or braided together into a larger and stronger form. Ropes have tensile strength and so can be used for dragging and lifting. Rope is thicker and stronger than similarly constructed cord, string, and twine.Sigma-2 receptor
The sigma-2 receptor (σ2R) is a sigma receptor subtype that has attracted attention due to its involvement in diseases such as cancer and neurological diseases. It is currently under investigation for its potential diagnostic and therapeutic uses.Although the sigma-2 receptor was identified as a separate pharmacological entity from the sigma-1 receptor in 1990, the gene that codes for the receptor was identified as TMEM97 only in 2016. TMEM97 was shown to regulate the cholesterol transporter NPC1 and to be involved in cholesterol homeostasis. The sigma-2 receptor is a four-pass transmembrane protein located in the endoplasmic reticulum. It has been found to play a role in both hormone signaling and calcium signaling, in neuronal signaling, in cell proliferation and death, and in binding of antipsychotics.Sliver (textiles)
A sliver (rhymes with diver) is a long bundle of fiber that is generally used to spin yarn. A sliver is created by carding or combing the fibre, which is then drawn into long strips where the fibre is parallel. When sliver is drawn further and given a slight twist, it becomes roving.Yarn
Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, or ropemaking. Thread is a type of yarn intended for sewing by hand or machine. Modern manufactured sewing threads may be finished with wax or other lubricants to withstand the stresses involved in sewing. Embroidery threads are yarns specifically designed for needlework.
ISO standards by standard number