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Comonotonicity | Upper bounds | Upper bound for the covariance Let (X, Y) be a bivariate random vector such that the expected values of X, Y and the product XY exist. Let (X*, Y*) be a comonotonic bivariate random vector with the same one-dimensional marginal distributions as (X, Y). Then it follows from Höffding's formula for the covariance and the upper Fréchet–Hoeffding bound that Cov Cov (X∗,Y∗) and, correspondingly, E[XY]≤E[X∗Y∗] with equality if and only if (X, Y) is comonotonic.Note that this result generalizes the rearrangement inequality and Chebyshev's sum inequality. |
Becoming (philosophy) | Becoming (philosophy) | Process philosophy, also ontology of becoming, or processism, is an approach in philosophy that identifies processes, changes, or shifting relationships as the only real experience of everyday living. In opposition to the classical view of change as illusory (as argued by Parmenides) or accidental (as argued by Aristotle), process philosophy posits transient occasions of change or becoming as the only fundamental things of the ordinary everyday real world. |
Becoming (philosophy) | Becoming (philosophy) | Since the time of Plato and Aristotle, classical ontology has posited ordinary world reality as constituted of enduring substances, to which transient processes are ontologically subordinate, if they are not denied. If Socrates changes, becoming sick, Socrates is still the same (the substance of Socrates being the same), and change (his sickness) only glides over his substance: change is accidental, and devoid of primary reality, whereas the substance is essential. |
Becoming (philosophy) | Becoming (philosophy) | In physics, Ilya Prigogine distinguishes between the "physics of being" and the "physics of becoming". Process philosophy covers not just scientific intuitions and experiences, but can be used as a conceptual bridge to facilitate discussions among religion, philosophy, and science.Process philosophy is sometimes classified as closer to continental philosophy than analytic philosophy, because it is usually only taught in continental philosophy departments. However, other sources state that process philosophy should be placed somewhere in the middle between the poles of analytic versus continental methods in contemporary philosophy. |
Becoming (philosophy) | History | In ancient Greek thought Heraclitus proclaimed that the basic nature of all things is change. |
Becoming (philosophy) | History | The quotation from Heraclitus appears in Plato's Cratylus twice; in 401d as: τὰ ὄντα ἰέναι τε πάντα καὶ μένειν οὐδένTa onta ienai te panta kai menein ouden"All entities move and nothing remains still"and in 402a"πάντα χωρεῖ καὶ οὐδὲν μένει" καὶ "δὶς ἐς τὸν αὐτὸν ποταμὸν οὐκ ἂν ἐμβαίης"Panta chōrei kai ouden menei kai dis es ton auton potamon ouk an embaies "Everything changes and nothing remains still ... and ... you cannot step twice into the same stream" Heraclitus considered fire as the most fundamental element. |
Becoming (philosophy) | History | "All things are an interchange for fire, and fire for all things, just like goods for gold and gold for goods." The following is an interpretation of Heraclitus's concepts into modern terms by Nicholas Rescher. |
Becoming (philosophy) | History | "...reality is not a constellation of things at all, but one of processes. The fundamental "stuff" of the world is not material substance, but volatile flux, namely "fire", and all things are versions thereof (puros tropai). Process is fundamental: the river is not an object, but a continuing flow; the sun is not a thing, but an enduring fire. Everything is a matter of process, of activity, of change (panta rhei)." An early expression of this viewpoint is in Heraclitus's fragments. He posits strife, ἡ ἔρις (strife, conflict), as the underlying basis of all reality defined by change. The balance and opposition in strife were the foundations of change and stability in the flux of existence. |
Becoming (philosophy) | History | Nietzsche and Kierkegaard In his written works, Friedrich Nietzsche proposed what has been regarded as a philosophy of becoming that encompasses a "naturalistic doctrine intended to counter the metaphysical preoccupation with being", and a theory of "the incessant shift of perspectives and interpretations in a world that lacks a grounding essence".Søren Kierkegaard posed questions of individual becoming in Christianity which were opposed to the ancient Greek philosophers' focus on the indifferent becoming of the cosmos. However, he established as much of a focus on aporia as Heraclitus and others previously had, such as in his concept of the leap of faith which marks an individual becoming. As well as this, Kierkegaard opposed his philosophy to Hegel's system of philosophy approaching becoming and difference for what he saw as a "dialectical conflation of becoming and rationality", making the system take upon the same trait of motionlessness as Parmenides' system. |
Becoming (philosophy) | History | Twentieth century In the early twentieth century, the philosophy of mathematics was undertaken to develop mathematics as an airtight, axiomatic system in which every truth could be derived logically from a set of axioms. In the foundations of mathematics, this project is variously understood as logicism or as part of the formalist program of David Hilbert. Alfred North Whitehead and Bertrand Russell attempted to complete, or at least facilitate, this program with their seminal book Principia Mathematica, which purported to build a logically consistent set theory on which to found mathematics. After this, Whitehead extended his interest to natural science, which he held needed a deeper philosophical basis. He intuited that natural science was struggling to overcome a traditional ontology of timeless material substances that does not suit natural phenomena. According to Whitehead, material is more properly understood as 'process'. In 1929, he produced the most famous work of process philosophy, Process and Reality, continuing the work begun by Hegel but describing a more complex and fluid dynamic ontology. |
Becoming (philosophy) | History | Process thought describes truth as "movement" in and through substance (Hegelian truth), rather than substances as fixed concepts or "things" (Aristotelian truth). Since Whitehead, process thought is distinguished from Hegel in that it describes entities that arise or coalesce in becoming, rather than being simply dialectically determined from prior posited determinates. These entities are referred to as complexes of occasions of experience. It is also distinguished in being not necessarily conflictual or oppositional in operation. Process may be integrative, destructive or both together, allowing for aspects of interdependence, influence, and confluence, and addressing coherence in universal as well as particular developments, i.e., those aspects not befitting Hegel's system. Additionally, instances of determinate occasions of experience, while always ephemeral, are nonetheless seen as important to define the type and continuity of those occasions of experience that flow from or relate to them. |
Becoming (philosophy) | Whitehead's Process and Reality | Alfred North Whitehead began teaching and writing on process and metaphysics when he joined Harvard University in 1924.In his book Science and the Modern World (1925), Whitehead noted that the human intuitions and experiences of science, aesthetics, ethics, and religion influence the worldview of a community, but that in the last several centuries science dominates Western culture. Whitehead sought a holistic, comprehensive cosmology that provides a systematic descriptive theory of the world which can be used for the diverse human intuitions gained through ethical, aesthetic, religious, and scientific experiences, and not just the scientific.Whitehead's influences were not restricted to philosophers or physicists or mathematicians. He was influenced by the French philosopher Henri Bergson (1859–1941), whom he credits along with William James and John Dewey in the preface to Process and Reality. |
Becoming (philosophy) | Whitehead's Process and Reality | Process metaphysics For Whitehead, metaphysics is about logical frameworks for the conduct of discussions of the character of the world. It is not directly and immediately about facts of nature, but only indirectly so, in that its task is to explicitly formulate the language and conceptual presuppositions that are used to describe the facts of nature. Whitehead thinks that discovery of previously unknown facts of nature can in principle call for reconstruction of metaphysics.: 13, 19 The process metaphysics elaborated in Process and Reality posits an ontology which is based on the two kinds of existence of an entity, that of actual entity and that of abstract entity or abstraction, also called 'object'.Actual entity is a term coined by Whitehead to refer to the entities that really exist in the natural world. For Whitehead, actual entities are spatiotemporally extended events or processes. An actual entity is how something is happening, and how its happening is related to other actual entities. The actually existing world is a multiplicity of actual entities overlapping one another.The ultimate abstract principle of actual existence for Whitehead is creativity. Creativity is a term coined by Whitehead to show a power in the world that allows the presence of an actual entity, a new actual entity, and multiple actual entities. Creativity is the principle of novelty. It is manifest in what can be called 'singular causality'. This term may be contrasted with the term 'nomic causality'. An example of singular causation is that I woke this morning because my alarm clock rang. An example of nomic causation is that alarm clocks generally wake people in the morning. Aristotle recognizes singular causality as efficient causality. For Whitehead, there are many contributory singular causes for an event. A further contributory singular cause of my being awoken by my alarm clock this morning was that I was lying asleep near it till it rang. |
Becoming (philosophy) | Whitehead's Process and Reality | An actual entity is a general philosophical term for an utterly determinate and completely concrete individual particular of the actually existing world or universe of changeable entities considered in terms of singular causality, about which categorical statements can be made. Whitehead's most far-reaching and radical contribution to metaphysics is his invention of a better way of choosing the actual entities. Whitehead chooses a way of defining the actual entities that makes them all alike, qua actual entities, with a single exception. |
Becoming (philosophy) | Whitehead's Process and Reality | For example, for Aristotle, the actual entities were the substances, such as Socrates. Besides Aristotle's ontology of substances, another example of an ontology that posits actual entities is in the monads of Leibniz, which are said to be 'windowless'.
Whitehead's actual entities For Whitehead's ontology of processes as defining the world, the actual entities exist as the only fundamental elements of reality.
The actual entities are of two kinds, temporal and atemporal. |
Becoming (philosophy) | Whitehead's Process and Reality | With one exception, all actual entities for Whitehead are temporal and are occasions of experience (which are not to be confused with consciousness). An entity that people commonly think of as a simple concrete object, or that Aristotle would think of as a substance, is, in this ontology, considered to be a temporally serial composite of indefinitely many overlapping occasions of experience. A human being is thus composed of indefinitely many occasions of experience. |
Becoming (philosophy) | Whitehead's Process and Reality | The one exceptional actual entity is at once both temporal and atemporal: God. He is objectively immortal, as well as being immanent in the world. He is objectified in each temporal actual entity; but He is not an eternal object. |
Becoming (philosophy) | Whitehead's Process and Reality | The occasions of experience are of four grades. The first grade comprises processes in a physical vacuum such as the propagation of an electromagnetic wave or gravitational influence across empty space. The occasions of experience of the second grade involve just inanimate matter; "matter" being the composite overlapping of occasions of experience from the previous grade. The occasions of experience of the third grade involve living organisms. Occasions of experience of the fourth grade involve experience in the mode of presentational immediacy, which means more or less what are often called the qualia of subjective experience. So far as we know, experience in the mode of presentational immediacy occurs in only more evolved animals. That some occasions of experience involve experience in the mode of presentational immediacy is the one and only reason why Whitehead makes the occasions of experience his actual entities; for the actual entities must be of the ultimately general kind. Consequently, it is inessential that an occasion of experience have an aspect in the mode of presentational immediacy; occasions of the grades one, two, and three, lack that aspect. |
Becoming (philosophy) | Whitehead's Process and Reality | There is no mind-matter duality in this ontology, because "mind" is simply seen as an abstraction from an occasion of experience which has also a material aspect, which is of course simply another abstraction from it; thus the mental aspect and the material aspect are abstractions from one and the same concrete occasion of experience. The brain is part of the body, both being abstractions of a kind known as persistent physical objects, neither being actual entities. Though not recognized by Aristotle, there is biological evidence, written about by Galen, that the human brain is an essential seat of human experience in the mode of presentational immediacy. We may say that the brain has a material and a mental aspect, all three being abstractions from their indefinitely many constitutive occasions of experience, which are actual entities. |
Becoming (philosophy) | Whitehead's Process and Reality | Time, causality, and process Inherent in each actual entity is its respective dimension of time. Potentially, each Whiteheadean occasion of experience is causally consequential on every other occasion of experience that precedes it in time, and has as its causal consequences every other occasion of experience that follows it in time; thus it has been said that Whitehead's occasions of experience are 'all window', in contrast to Leibniz's 'windowless' monads. In time defined relative to it, each occasion of experience is causally influenced by prior occasions of experiences, and causally influences future occasions of experience. An occasion of experience consists of a process of prehending other occasions of experience, reacting to them. This is the process in process philosophy. |
Becoming (philosophy) | Whitehead's Process and Reality | Such process is never deterministic. Consequently, free will is essential and inherent to the universe. |
Becoming (philosophy) | Whitehead's Process and Reality | The causal outcomes obey the usual well-respected rule that the causes precede the effects in time. Some pairs of processes cannot be connected by cause-and-effect relations, and they are said to be spatially separated. This is in perfect agreement with the viewpoint of the Einstein theory of special relativity and with the Minkowski geometry of spacetime. It is clear that Whitehead respected these ideas, as may be seen for example in his 1919 book An Enquiry concerning the Principles of Natural Knowledge as well as in Process and Reality. In this view, time is relative to an inertial reference frame, different reference frames defining different versions of time. |
Becoming (philosophy) | Whitehead's Process and Reality | Atomicity The actual entities, the occasions of experience, are logically atomic in the sense that an occasion of experience cannot be cut and separated into two other occasions of experience. This kind of logical atomicity is perfectly compatible with indefinitely many spatio-temporal overlaps of occasions of experience. One can explain this kind of atomicity by saying that an occasion of experience has an internal causal structure that could not be reproduced in each of the two complementary sections into which it might be cut. Nevertheless, an actual entity can completely contain each of indefinitely many other actual entities. |
Becoming (philosophy) | Whitehead's Process and Reality | Another aspect of the atomicity of occasions of experience is that they do not change. An actual entity is what it is. An occasion of experience can be described as a process of change, but it is itself unchangeable.
The reader should bear in mind that the atomicity of the actual entities is of a simply logical or philosophical kind, thoroughly different in concept from the natural kind of atomicity that describes the atoms of physics and chemistry. |
Becoming (philosophy) | Whitehead's Process and Reality | Topology Whitehead's theory of extension was concerned with the spatio-temporal features of his occasions of experience. Fundamental to both Newtonian and to quantum theoretical mechanics is the concept of momentum. The measurement of a momentum requires a finite spatiotemporal extent. Because it has no finite spatiotemporal extent, a single point of Minkowski space cannot be an occasion of experience, but is an abstraction from an infinite set of overlapping or contained occasions of experience, as explained in Process and Reality. Though the occasions of experience are atomic, they are not necessarily separate in extension, spatiotemporally, from one another. Indefinitely many occasions of experience can overlap in Minkowski space. |
Becoming (philosophy) | Whitehead's Process and Reality | Nexus is a term coined by Whitehead to show the network actual entity from the universe. In the universe of actual entities spread actual entity. Actual entities are clashing with each other and form other actual entities. The birth of an actual entity based on an actual entity, actual entities around him referred to as nexus.An example of a nexus of temporally overlapping occasions of experience is what Whitehead calls an enduring physical object, which corresponds closely with an Aristotelian substance. An enduring physical object has a temporally earliest and a temporally last member. Every member (apart from the earliest) of such a nexus is a causal consequence of the earliest member of the nexus, and every member (apart from the last) of such a nexus is a causal antecedent of the last member of the nexus. There are indefinitely many other causal antecedents and consequences of the enduring physical object, which overlap, but are not members, of the nexus. No member of the nexus is spatially separate from any other member. Within the nexus are indefinitely many continuous streams of overlapping nexūs, each stream including the earliest and the last member of the enduring physical object. Thus an enduring physical object, like an Aristotelian substance, undergoes changes and adventures during the course of its existence. |
Becoming (philosophy) | Whitehead's Process and Reality | In some contexts, especially in the theory of relativity in physics, the word 'event' refers to a single point in Minkowski or in Riemannian space-time. A point event is not a process in the sense of Whitehead's metaphysics. Neither is a countable sequence or array of points. A Whiteheadian process is most importantly characterized by extension in space-time, marked by a continuum of uncountably many points in a Minkowski or a Riemannian space-time. The word 'event', indicating a Whiteheadian actual entity, is not being used in the sense of a point event. |
Becoming (philosophy) | Whitehead's Process and Reality | Whitehead's abstractions Whitehead's abstractions are conceptual entities that are abstracted from or derived from and founded upon his actual entities. Abstractions are themselves not actual entities. They are the only entities that can be real but are not actual entities. This statement is one form of Whitehead's 'ontological principle'. |
Becoming (philosophy) | Whitehead's Process and Reality | An abstraction is a conceptual entity that refers to more than one single actual entity. Whitehead's ontology refers to importantly structured collections of actual entities as nexuses of actual entities. Collection of actual entities into a nexus emphasizes some aspect of those entities, and that emphasis is an abstraction, because it means that some aspects of the actual entities are emphasized or dragged away from their actuality, while other aspects are de-emphasized or left out or left behind. |
Becoming (philosophy) | Whitehead's Process and Reality | 'Eternal object' is a term coined by Whitehead. It is an abstraction, a possibility, or pure potential. It can be ingredient into some actual entity. It is a principle that can give a particular form to an actual entity.Whitehead admitted indefinitely many eternal objects. An example of an eternal object is a number, such as the number 'two'. Whitehead held that eternal objects are abstractions of a very high degree of abstraction. Many abstractions, including eternal objects, are potential ingredients of processes. |
Becoming (philosophy) | Whitehead's Process and Reality | Relation between actual entities and abstractions stated in the ontological principle For Whitehead, besides its temporal generation by the actual entities which are its contributory causes, a process may be considered as a concrescence of abstract ingredient eternal objects. God enters into every temporal actual entity.
Whitehead's ontological principle is that whatever reality pertains to an abstraction is derived from the actual entities upon which it is founded or of which it is comprised. |
Becoming (philosophy) | Whitehead's Process and Reality | Causation and concrescence of a process Concrescence is a term coined by Whitehead to show the process of jointly forming an actual entity that was without form, but about to manifest itself into an entity Actual full (satisfaction) based on datums or for information on the universe. The process of forming an actual entity is the case based on the existing datums. Concretion process can be regarded as subjectification process.Datum is a term coined by Whitehead to show the different variants of information possessed by actual entity. In process philosophy, datum is obtained through the events of concrescence. Every actual entity has a variety of datum. |
Becoming (philosophy) | Commentary on Whitehead and on process philosophy | Whitehead is not an idealist in the strict sense. Whitehead's thought may be regarded as related to the idea of panpsychism (also known as panexperientialism, because of Whitehead's emphasis on experience).
On God Whitehead's philosophy is complex, subtle, and nuanced regarding the concept of God". In Process and Reality Corrected Edition (1978), wherein regarding "God" the editors elaborate Whitehead's conception. |
Becoming (philosophy) | Commentary on Whitehead and on process philosophy | He is the unconditioned actuality of conceptual feeling at the base of things; so that by reason of this primordial actuality, there is an order in the relevance of eternal objects to the process of creation.: 344 [...] The particularities of the actual world presuppose it; while it merely presupposes the general metaphysical character of creative advance, of which it is the primordial exemplification. [emphasis in original]: 344 Process philosophy, might be considered according to some theistic forms of religion to give God a special place in the universe of occasions of experience. Regarding Whitehead's use of the term "occasions" in reference to "God", Process and Reality Corrected Edition explains: 'Actual entities' - also termed 'actual occasions' - are the final real things of which the world is made up. There is no going behind actual entities to find anything more real. They differ among themselves: God is an actual entity, and so is the most trivial puff of existence in far-off empty space. But, though there are gradations of importance, and diversities of function, yet in the principles which actuality exemplifies all are on the same level. The final facts are, all alike, actual entities; and these actual entities are drops of experience, complex and interdependent.: 18 It also can be assumed within some forms of theology that a God encompasses all the other occasions of experience but also transcends them and this might lead to it being argued that Whitehead endorses some form of panentheism. Since, it is argued theologically, that "free will" is inherent to the nature of the universe, Whitehead's God is not omnipotent in Whitehead's metaphysics. God's role is to offer enhanced occasions of experience. God participates in the evolution of the universe by offering possibilities, which may be accepted or rejected. Whitehead's thinking here has given rise to process theology, whose prominent advocates include Charles Hartshorne, John B. Cobb, Jr., and Hans Jonas, who was also influenced by the non-theological philosopher Martin Heidegger. However, other process philosophers have questioned Whitehead's theology, seeing it as a regressive Platonism.Whitehead enumerated three essential natures of God. The primordial nature of God consists of all potentialities of existence for actual occasions, which Whitehead dubbed eternal objects. God can offer possibilities by ordering the relevance of eternal objects. The consequent nature of God prehends everything that happens in reality. As such, God experiences all of reality in a sentient manner. The last nature is the superjective. This is the way in which God's synthesis becomes a sense-datum for other actual entities. In some sense, God is prehended by existing actual entities. |
Becoming (philosophy) | Legacy and applications | Biology In plant morphology, Rolf Sattler developed a process morphology (dynamic morphology) that overcomes the structure/process (or structure/function) dualism that is commonly taken for granted in biology. According to process morphology, structures such as leaves of plants do not have processes, they are processes.In evolution and in development, the nature of the changes of biological objects are considered by many authors to be more radical than in physical systems. In biology, changes are not just changes of state in a pre-given space, instead the space and more generally the mathematical structures required to understand object change over time. |
Becoming (philosophy) | Legacy and applications | Ecology With its perspective that everything is interconnected, that all life has value, and that non-human entities are also experiencing subjects, process philosophy has played an important role in discourse on ecology and sustainability. The first book to connect process philosophy with environmental ethics was John B. Cobb, Jr.'s 1971 work, Is It Too Late: A Theology of Ecology. In a more recent book (2018) edited by John B. Cobb, Jr. and Wm. Andrew Schwartz, Putting Philosophy to Work: Toward an Ecological Civilization contributors explicitly explore the ways in which process philosophy can be put to work to address the most urgent issues facing our world today, by contributing to a transition toward an ecological civilization. That book emerged from the largest international conference held on the theme of ecological civilization (Seizing an Alternative: Toward an Ecological Civilization) which was organized by the Center for Process Studies in June 2015. The conference brought together roughly 2,000 participants from around the world and featured such leaders in the environmental movement as Bill McKibben, Vandana Shiva, John B. Cobb, Jr., Wes Jackson, and Sheri Liao. The notion of ecological civilization is often affiliated with the process philosophy of Alfred North Whitehead—especially in China. |
Becoming (philosophy) | Legacy and applications | Mathematics In the philosophy of mathematics, some of Whitehead's ideas re-emerged in combination with cognitivism as the cognitive science of mathematics and embodied mind theses. |
Becoming (philosophy) | Legacy and applications | Somewhat earlier, exploration of mathematical practice and quasi-empiricism in mathematics from the 1950s to 1980s had sought alternatives to metamathematics in social behaviours around mathematics itself: for instance, Paul Erdős's simultaneous belief in Platonism and a single "big book" in which all proofs existed, combined with his personal obsessive need or decision to collaborate with the widest possible number of other mathematicians. The process, rather than the outcomes, seemed to drive his explicit behaviour and odd use of language, as if the synthesis of Erdős and collaborators in seeking proofs, creating sense-datum for other mathematicians, was itself the expression of a divine will. Certainly, Erdős behaved as if nothing else in the world mattered, including money or love, as emphasized in his biography The Man Who Loved Only Numbers. |
Becoming (philosophy) | Legacy and applications | Medicine Several fields of science and especially medicine seem to make liberal use of ideas in process philosophy, notably the theory of pain and healing of the late 20th century. The philosophy of medicine began to deviate somewhat from scientific method and an emphasis on repeatable results in the very late 20th century by embracing population thinking, and a more pragmatic approach to issues in public health, environmental health and especially mental health. In this latter field, R. D. Laing, Thomas Szasz and Michel Foucault were instrumental in moving medicine away from emphasis on "cures" and towards concepts of individuals in balance with their society, both of which are changing, and against which no benchmarks or finished "cures" were very likely to be measurable. |
Becoming (philosophy) | Legacy and applications | Psychology In psychology, the subject of imagination was again explored more extensively since Whitehead, and the question of feasibility or "eternal objects" of thought became central to the impaired theory of mind explorations that framed postmodern cognitive science. A biological understanding of the most eternal object, that being the emerging of similar but independent cognitive apparatus, led to an obsession with the process "embodiment", that being, the emergence of these cognitions. Like Whitehead's God, especially as elaborated in J. J. Gibson's perceptual psychology emphasizing affordances, by ordering the relevance of eternal objects (especially the cognitions of other such actors), the world becomes. Or, it becomes simple enough for human beings to begin to make choices, and to prehend what happens as a result. These experiences may be summed in some sense but can only approximately be shared, even among very similar cognitions with identical DNA. An early explorer of this view was Alan Turing who sought to prove the limits of expressive complexity of human genes in the late 1940s, to put bounds on the complexity of human intelligence and so assess the feasibility of artificial intelligence emerging. Since 2000, Process Psychology has progressed as an independent academic and therapeutic discipline: In 2000, Michel Weber created the Whitehead Psychology Nexus: an open forum dedicated to the cross-examination of Alfred North Whitehead's process philosophy and the various facets of the contemporary psychological field. |
Becoming (philosophy) | Legacy and applications | Philosophy of movement The philosophy of movement is a sub-area within process philosophy that treats processes as movements. It studies processes as flows, folds, and fields in historical patterns of centripetal, centrifugal, tensional, and elastic motion. See Thomas Nail's philosophy of movement and process materialism. |
Process trailer | Process trailer | A process trailer, also known as insert trailer and low loader, is a trailer towed by a tracking vehicle for the purpose of being used as a moving camera platform. They are generally very low to the ground to give a realistic perspective of height and can be expanded in width to allow the camera to achieve a wider shot. Process trailers are most often used to shoot dialogue scenes inside cars or other vehicles while reducing risk for actors who would otherwise drive while delivering lines. The trailer is composed of a wheeled platform, low to the ground, with the vehicle secured on top. The vehicle on the platform is known as a "picture car". The platform itself is then towed by another vehicle with crew members and camera equipment to film the actors in the vehicle. Although process trailers are safer for actors, there is still a significant risk to the driver and passengers of the towing vehicle - for this reason, process trailers are often led by a police vehicles to prevent traffic accidents. In Australia, process trailers must be accompanied by police and may only be used with a permit. |
Guluronic acid | Guluronic acid | Guluronic acid is a uronic acid monosaccharide that may be derived from gulose. l-Guluronic acid is a C-3 epimer of l-galacturonic acid and a C-5 epimer of d-mannuronic acid. Along with d-mannuronic acid, l-guluronic acid is a component of alginic acid, a polysaccharide found in brown algae. α-L-Guluronic acid has been found to bind divalent metal ions (such as calcium and strontium) through the carboxylate moiety and through the axial-equatorial-axial arrangement of hydroxyl groups found around the ring. |
Collier's sign | Collier's sign | Collier's sign (also known as Collier's tucked lid sign or posterior fossa stare) is bilateral or unilateral eyelid retraction. |
Collier's sign | Collier's sign | It is an accepted medical sign of a midbrain lesion, first described in 1927 by J Collier. With the eyes in the primary position, the sclera can be seen above the cornea, and further upgaze increases the distance between the eyelids and irises. Causes include upper dorsal midbrain supranuclear lesions such as Parinaud's syndrome, 'top of the basilar syndrome', midbrain infarction, neurodegeneration or tumour, multiple sclerosis, encephalitis, and Miller-Fisher syndrome. The cause is thought to be damage to the posterior commissure levator inhibitory fibres which originate in the M-group of neurons. |
Bell boots | Bell boots | Bell boots, or overreach boots, are a type of protective boot worn by a horse. They encircle the horse's ankle, and protect the back of the pastern and the heels of the animal. |
Bell boots | Uses of bell boots | Bell boots are usually worn to prevent overreaching (when the horse "grabs" his front heels with the toes of his back feet, resulting in injury), or if the horse is wearing shoe studs, to protect him from accidentally injuring himself with the stud of the opposing hoof. In some cases a horse with corrective or poor shoeing wears shoes that protrude behind the foot, making it easier for a horse to overreach and spring or completely pull off the shoe. This is most commonly seen when the horse is jumping, working in mud or on a slippery surface, running cross-country, or longeing, and bell boots can help prevent this from occurring. Bell boots are occasionally worn when shipping a horse, if the bandages or boots used do not provide protection to the heel region, or if a horse tends to pull his front shoes by stepping on them with his back feet. Bell boots are also sometimes used when the horse is turned out, for extra protection or to help prevent him from accidentally pulling a shoe if he is especially exuberant while playing. |
Bell boots | Applying bell boots | Bell boots are usually made of rubber. They may be open, with Velcro or other fastenings to close them, or closed and slipped on over the hoof. Although open bell boots are the easiest to apply, close bell boots are more secure as they have no chance of slipping off.
To apply closed bell boots, it is easiest to turn them inside out, before slipping them over the toe of the foot. It may also help to place them in warm water so they will expand before trying to put them on.
A correctly sized bell boot should just touch the ground behind the bulbs of the heel while the horse is standing. The mouth of the bell boot should be just loose enough to fit a finger or two between it and the horse's pastern. |
Bell boots | Causes of discomfort | Most horses do not mind wearing bell boots and suffer no adverse effects when they are used properly. However, even a correctly fitted bell boot may chafe and cause discomfort to a horse if the material the boot is made of is exceedingly stiff or if the horse has especially sensitive skin. |
Skills-based routing | Skills-based routing | Skills-based routing (SBR), or skills-based call routing, is a call-assignment strategy used in call centres to assign incoming calls to the most suitable agent, instead of simply choosing the next available agent. It is an enhancement to the automatic call distributor (ACD) systems found in most call centres. The need for skills-based routing has arisen as call centres have become larger and dealt with a wider variety of call types. In the past, agents answering calls were generally able to be assigned to only one queue taking one type of call. This meant that agents who could deal with a range of call types had to be manually reassigned to different queue at different times of the day to make the best use of their skills, or face being exposed to a wide variety of calls for which they were not trained. With skills-based routing, the skills needed for a particular call are often assessed by the dialled telephone number and the calling number or caller's identity, as well as choices made in any associated IVR system. Given this assessment, a skills-based routing system then attempts to match the call to a suitably trained agent—the thinking being that an agent with matching skills will be able to provide a better service than one who does not. As a consequence, the separate large queues that were characteristic of the ACD-driven call centre have disappeared. Instead, each caller seems to have their own waiting area that they may share with only one or two others. Instead of being served in the order of their arrival, calls are served as agents with appropriate skills become available. Manufacturers claim that this technology improves customer service, shortens call-handling time, makes training shorter and easier, and thus increases agent utilisation, productivity, and, hence, revenue. Skills-based routing has thus become a major selling point, over the simpler ACD that it replaces. |
Skills-based routing | Skills-based routing | However, independent analysts and consultants argue that the extra complexity of a skills-based routing system might not return the claimed benefits. They outline the difficulty of predetermining the needed skills and suggest that a poorly implemented skills-based routing system might result in poor service, because the wrong measures of service quality are being used.Theoretical work on skills-based routing system tends to be more limited, with researchers trying to identify suitable queueing theory and operations research models to represent the problems that are raised by skills-based routing systems. |
Skills-based routing | Skills-based routing | Some consider it a fruitful area of research. Others claim that the traditional queueing theory formula, such as Erlang-C, are no longer relevant for determining staff schedules, because they are inaccurate. They also imply that theoretical approaches will not be accurate, because of the complexity involved—arguing that simulation needs to be used instead.
Although these claims need to be considered carefully, as it is argued also that the inaccuracies result from failing to understand the assumptions of the Erlang-C approach, instead of actual inaccuracy with the theory. |
KAlgebra | KAlgebra | KAlgebra is a mathematical graph calculator included in the KDE education package. While it is based on the MathML content markup language, knowledge of MathML is not required for use. The calculator includes numerical, logical, symbolic, and analytical functions, and can plot the results onto a 2D or 3D graph. KAlgebra is free and open source software, licensed under the GPL-2.0-or-later license. |
KAlgebra | KAlgebra | KAlgebra has been mentioned by various media sources as free / open source educational programs. |
KAlgebra | User interface and syntax | KAlgebra uses an intuitive algebraic syntax, similar to those used on modern graphing calculators. User-entered expressions are converted to MathML in the background, or they can be entered directly. The program is divided into four views, Console, 2D Graph, 3D Graph, and Dictionary. A series of calculations can be performed with user-defined scripts, which are macros that can be reused and shared. |
KAlgebra | User interface and syntax | The dictionary includes a comprehensive list of all built-in functions in KAlgebra. Functions can be looked up with parameters, examples, formulas and sample plots. Over 100 functions and operations are currently supported. |
KAlgebra | Graphing and dictionary | In the 2D and 3D graph views, functions can evaluated and plotted. Currently KAlgebra only supports 3D graphs explicitly dependent only on the x and y. Both views support defining the viewpoint. The user can hover their cursor over a line and find the exact X and Y values for 2D graphs, as well as create a live tangent line. |
KAlgebra | Graphing and dictionary | In the 3D view, the user can control the viewpoint position with the keyboard's arrow keys, and zooming in and out is done with the W and S keys respectively. The user can also draw lines and make dots on the 3D graph and export the graph in various formats. |
Vaginal microbicide | Vaginal microbicide | A vaginal microbicide is a microbicide for vaginal use. Most commonly such a product would be a topical gel or cream inserted into the vagina so that it may treat some infection in the vagina, such as types of vaginitis.
Along with rectal microbicides, vaginal microbicides are currently the subject of medical research on microbicides for sexually transmitted diseases to determine the circumstances under which and the extent to which they provide protection against infection. Researchers are trying to develop a product which would act as protection against the contraction of a sexually transmitted infection during vaginal sexual intercourse. |
Vaginal microbicide | Vaginal microbicides for sexually transmitted diseases | Scientists are trying to develop effective microbicides to reduce the risk of contracting a sexually transmitted infection, and in particular, to reduce the risk of contracting HIV. |
Vaginal microbicide | Vaginal microbicides for sexually transmitted diseases | Target market Researchers have investigated who has interest in using a vaginal microbicide. Condoms are highly effective in preventing the transmission of infection, but worldwide, the decision to use condoms is more often a decision made by males than females. A vaginal microbicide which could prevent sexual transmission of infection would further empower women to influence the result of their sexual encounters. The demographic interested in using the produce included women with the following characteristics: The number of women interested in using such a product has been characterized as being significant enough to merit product development and marketing. |
Vaginal microbicide | Vaginal microbicides for sexually transmitted diseases | Characteristics The ideal vaginal microbicide would have the following characteristics: provide protection against infection not require application at the time of intercourse not harm the natural tissueThe criteria of not harming natural tissue has been the most troublesome aspect of product design. |
Vaginal microbicide | For HIV | Several unrelated chemical mechanisms have been proposed for vaginal microbicides. In all cases, the medicine would be contained in a gel or cream substrate and then inserted into the vagina, where the medicine would activate.
Surfactants The first vaginal microbicide which researchers studied was nonoxynol-9, which acted as a surfactant.
Blocking HIV binding PRO 2000, carrageenan, and cellulose sulphate have all been studied as microbicides to block HIV binding.
Topical antiretrovirals Tenofovir has been studied as a topical antiretroviral. One example of a tenofovir study is CAPRISA 004. |
False peak | False peak | In mountaineering, a false peak or false summit is a peak that appears to be the pinnacle of the mountain but upon reaching, it turns out the summit is higher. False peaks can have significant and discouraging effects on climbers' psychological states by inducing feelings of lost hope or even failure. The term false peak can also be applied idiomatically to non-mountaineering activities where obstacles posing as the end goal produce the same psychological effects. |
Neoeriocitrin | Neoeriocitrin | Neoeriocitrin is a 7-O-glycoside of the flavanone eriodictyol and the disaccharide neohesperidose (α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranose).
Note that the 'neo' in the name in this case does not refer to the position of the B-ring (which is not in a neo position), but refer to the glycosyl moiety. |
Food Factor | Food Factor | Food Factor is the FIRST Lego League (FLL) competition for 2011-12; released on September 2. It focuses on food safety and methods to prevent contamination.This is the first year that the name of the challenge theme of FLL is different from Jr.FLL. Jr.FLL's theme for 2011-12 is Snack Attack. |
Food Factor | Project | Teams are tasked with identifying a food item and tracking its journey from creation to consumption. From this, teams identify potential sources of contamination and create solutions to those problems. Teams then share their project with the community and with judges at competition. |
Food Factor | Gameplay | The table performance portion of Food Factor is played on a 4 ft by 8 ft field rimmed by wood boards. At competition, two of these fields are placed together to form an 8 ft square. In each 2+1⁄2-minute match, a team competes on each field with their robot to earn up to 452 points manipulating the mission models.
The touch penalty objects are "good" bacteria models. All 12 are worth 6 points each when located in base, but are removed every time the robot is touched outside of base. |
Food Factor | Gameplay | Missions All of the Food Factor missions relate to various food topics and food safety problems: Pollution Reversal - 4 points per ball (up to 8 points) Corn Harvest - up to 9 points Fishing - up to 18 points Pizza and Ice Cream - 7 points each (up to 14 points) Farm Fresh Produce - 9 points Distant Travel - 9 points Cooking Time - 14 points Storage Temperature - 20 points Pest Removal - 15 points each (up to 30 points) Refrigerated Ground Transport - up to 20 points Groceries - 2 points each (up to 24 points) Disinfect - up to 12 points each (up to 48 points) Hand Wash/Bacterial - 3 points each (up to 144 points) Hand Wash/Viral - up to 13 points Good Bacteria - 6 points each (up to 72 points in total) |
C1QL1 | C1QL1 | The complement component 1, q subcomponent-like 1 (or C1QL1) is encoded by a gene located at chromosome 17q21.31. It is a secreted protein and is 258 amino acids in length.
The protein is widely expressed but its expression is highest in the brain and may also be involved in regulation of motor control.
The pre-mRNA of this protein is subject to RNA editing. |
C1QL1 | Protein function | Its physiological function is unknown. It is a member of the C1Q domain proteins which have important signalling roles in inflammation and in adaptive immunity. |
C1QL1 | RNA editing | Editing type The pre-mRNA of this protein is subject to A to I RNA editing, which is catalyzed by a family of adenosine deaminases acting on RNA (ADARs) that specifically recognize adenosines within double-stranded regions of pre-mRNAs and deaminate them to inosine. Inosines are recognised as guanosine by the cell's translational machinery. There are three members of the ADAR family: ADARs 1-3, with ADAR 1 and ADAR 2 being the only enzymatically active members. ADAR 3 is thought to have a regulatory role in the brain. ADAR 1 and ADAR 2 are widely expressed in tissues while ADAR 3 is restricted to the brain. The double-stranded regions of RNA are formed by base-pairing between residues in a region complementary to the region of the editing site. This complementary region is usually found in a neighbouring intron but can also be located in an exonic sequence. The region that pairs with the editing region is known as an Editing Complementary Sequence (ECS). |
C1QL1 | RNA editing | Editing sites The candidate editing sites were determined experimentally by comparison of cDNA sequences and genomically encoded DNA from the same individual to avoid single nucleotide polymorphisms (SNPs). Two of the three editing sites found in mouse gene were found in the human transcript.
However, only the Q/R site was detected in all RNA, with the T/A site detected just once. Both sites are found within exon 1.Q/R site This site is found in exon 1 at position 66. Editing results in a codon change from a Glutamine codon to an Arginine codon. |
C1QL1 | RNA editing | T/A site This site is also found in exon 1, at position 63. It was only detected in one genomic sample indicating that the edited residue may be an SNP. However, the secondary structure of the RNA is predicted, around the editing site, to be highly conserved in mice and humans. This indicates that the T/A site may still be shown to be a site of A to I RNA editing. Editing at this site would result in an amino acid change from a Threonine to an Alanine. |
C1QL1 | RNA editing | The ECS is also predicted to be found within exon 1 at a location 5' to the editing region.
Editing regulation Editing is differentially expressed in the cerebellum and cortex. This regulation is also present in mice suggesting conservation of editing regulation. No editing has been detected in human lung, heart, kidney or spleen tissue. |
C1QL1 | RNA editing | Evolutionary conservation The sequence of exon 1 is highly conserved in mammalian species and editing of the pre-mRNA of this protein is likely to occur in mice, rat, dog and cow as well as humans. Even though the ECS is not conserved in non-mammals, an alternative ECS has been predicted in Zebrafish with a similar structure but in a different location. The Ecs is found downstream of the editing sites. |
C1QL1 | RNA editing | Effects on Protein structure These predicted editing sites result in the translation of an Arginine instead of a Glutamine at the Q/R site and an Alanine instead of a Threonine at the T/A site. These codon changes are nonsynomonous. Since the editing sites are located just before a collagen like trimerization domain, editing may effect protein oligomerization. This region is also likely to be a protease domain. It is not known if the amino acid changes caused by editing could have an effect on these domains. |
Occupy movement hand signals | Occupy movement hand signals | The Occupy movement hand signals are a group of hand signals used by Occupy movement protesters to negotiate a consensus. Hand signals are used instead of conventional audible signals, like applause, shouts, or booing, because they do not interrupt the speaker using the human microphone, a system where the front of the crowd repeats the speaker so that the content can be heard at the back of the crowd. The signals have been compared to other hand languages used by soldiers, cliques and Wall Street traders.Between sharing of information on Facebook, Twitter, and other news reports, the hand signals have become common at other Occupy movement protest locations. Some protesters go to neighboring groups to assist in teaching the hand signals along with other general cooperation. There are YouTube videos showing the hand signals, though the signals are not universal at all locations. |
Occupy movement hand signals | Example signals | Twinkles and down twinkles are referred to as a "temperature check". They indicate if a group is getting close to consensus. Twinkles are also known as "sparkle" or "jazz hands" or spirit fingers. |
Occupy movement hand signals | Origins | In addition to commonalities with various sign languages, and cultural gestures, these or similar hand signals have been used by other groups and events prior to the Occupy Wall Street protests. These include: Camp for Climate Action The Woodcraft Folk Direct Action Network The 15-M Movement beginning in Spain 2011 UK Uncut Civil rights movement Quaker meetings Global Justice Movement |
Occupy movement hand signals | Influence | Some followers of agile software development processes have drawn on the Occupy movement's hand signs in an attempt to improve communication during meetings, notably the UK's Government Digital Service.After the Occupy movements, these hand signals were used by other social movements such as the School strike for the climate, Ende Gelände and Extinction Rebellion. |
Supercritical angle fluorescence microscopy | Supercritical angle fluorescence microscopy | Supercritical angle fluorescence microscopy (SAF) is a technique to detect and characterize fluorescent species (proteins, biomolecules, pharmaceuticals, etc.) and their behaviour close or even adsorbed or linked at surfaces. The method is able to observe molecules in a distance of less than 100 to 0 nanometer from the surface even in presence of high concentrations of fluorescent species around. Using an aspheric lens for excitation of a sample with laser light, fluorescence emitted by the specimen is collected above the critical angle of total internal reflection selectively and directed by a parabolic optics onto a detector. The method was invented in 1998 in the laboratories of Stefan Seeger at University of Regensburg/Germany and later at University of Zurich/Switzerland. |
Supercritical angle fluorescence microscopy | SAF microscopy principle | The principle how SAF Microscopy works is as follows: A fluorescent specimen does not emit fluorescence isotropically when it comes close to a surface, but approximately 70% of the fluorescence emitted is directed into the solid phase. Here, the main part enters the solid body above the critical angle. When the emitter is located just 200 nm above the surface, fluorescent light entering the solid body above the critical angle is decreased dramatically. Hence, SAF Microscopy is ideally suited to discriminate between molecules and particles at or close to surfaces and all other specimen present in the bulk. |
Supercritical angle fluorescence microscopy | Typical SAF-setup | The typical SAF setup consists of a laser line (typically 450-633 nm), which is reflected into the aspheric lens by a dichroic mirror. The lens focuses the laser beam in the sample, causing the particles to fluoresce. The fluorescent light then passes through a parabolic lens before reaching a detector, typically a photomultiplier tube or avalanche photodiode detector. It is also possible to arrange SAF elements as arrays, and image the output onto a CCD, allowing the detection of multiple analytes. |
HTree | HTree | An HTree is a specialized tree data structure for directory indexing, similar to a B-tree. They are constant depth of either one or two levels, have a high fanout factor, use a hash of the filename, and do not require balancing. The HTree algorithm is distinguished from standard B-tree methods by its treatment of hash collisions, which may overflow across multiple leaf and index blocks. HTree indexes are used in the ext3 and ext4 Linux filesystems, and were incorporated into the Linux kernel around 2.5.40. HTree indexing improved the scalability of Linux ext2 based filesystems from a practical limit of a few thousand files, into the range of tens of millions of files per directory. |
HTree | History | The HTree index data structure and algorithm were developed by Daniel Phillips in 2000 and implemented for the ext2 filesystem in February 2001. A port to the ext3 filesystem by Christopher Li and Andrew Morton in 2002 during the 2.5 kernel series added journal based crash consistency. With minor improvements, HTree continues to be used in ext4 in the Linux 3.x.x kernel series. |
HTree | Use | ext2 HTree indexes were originally developed for ext2 but the patch never made it to the official branch. The dir_index feature can be enabled when creating an ext2 filesystem, but the ext2 code won't act on it.
ext3 HTree indexes are available in ext3 when the dir_index feature is enabled.
ext4 HTree indexes are turned on by default in ext4. This feature is implemented in Linux kernel 2.6.23. HTree indexes is also used for file extents when a file needs more than the 4 extents stored in the inode. The large_dir feature of ext4 is implemented in Linux kernel 4.13. |
HTree | PHTree | PHTree (Physically stable HTree) is a derivation intended as a successor. It fixes all the known issues with HTree except for write multiplication. It is used in the Tux3 filesystem. |
Opal | Opal | Opal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered minerals. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt. |
Opal | Opal | The name opal is believed to be derived from the Sanskrit word upala (उपल), which means 'jewel', and later the Greek derivative opállios (ὀπάλλιος), which means 'to see a change in color'. |
Opal | Opal | There are two broad classes of opal: precious and common. Precious opal displays play-of-color (iridescence); common opal does not. Play-of-color is defined as "a pseudo chromatic optical effect resulting in flashes of colored light from certain minerals, as they are turned in white light." The internal structure of precious opal causes it to diffract light, resulting in play-of-color. Depending on the conditions in which it formed, opal may be transparent, translucent, or opaque, and the background color may be white, black, or nearly any color of the visual spectrum. Black opal is considered the rarest, while white, gray, and green opals are the most common. |
Opal | Precious opal | Precious opal shows a variable interplay of internal colors, and though it is a mineraloid, it has an internal structure. At microscopic scales, precious opal is composed of silica spheres some 150–300 nm (5.9×10−6–1.18×10−5 in) in diameter in a hexagonal or cubic close-packed lattice. It was shown by J. V. Sanders in the mid-1960s that these ordered silica spheres produce the internal colors by causing the interference and diffraction of light passing through the microstructure of the opal. The regularity of the sizes and the packing of these spheres is a prime determinant of the quality of precious opal. Where the distance between the regularly packed planes of spheres is around half the wavelength of a component of visible light, the light of that wavelength may be subject to diffraction from the grating created by the stacked planes. The colors that are observed are determined by the spacing between the planes and the orientation of planes with respect to the incident light. The process can be described by Bragg's law of diffraction. |
Opal | Precious opal | Visible light cannot pass through large thicknesses of the opal. This is the basis of the optical band gap in a photonic crystal. The notion that opals are photonic crystals for visible light was expressed in 1995 by Vasily Astratov's group. In addition, microfractures may be filled with secondary silica and form thin lamellae inside the opal during its formation. The term opalescence is commonly used to describe this unique and beautiful phenomenon, which in gemology is termed play of color. In gemology, opalescence is applied to the hazy-milky-turbid sheen of common or potch opal which does not show a play of color. Opalescence is a form of adularescence. |
Opal | Precious opal | For gemstone use, most opal is cut and polished to form a cabochon. "Natural" opal refers to polished stones consisting wholly of precious opal. Opals too thin to produce a "natural" opal may be combined with other materials to form "composite" gems. An opal doublet consists of a relatively thin layer of precious opal, backed by a layer of dark-colored material, most commonly ironstone, dark or black common opal (potch), onyx, or obsidian. The darker backing emphasizes the play of color and results in a more attractive display than a lighter potch. An opal triplet is similar to a doublet but has a third layer, a domed cap of clear quartz or plastic on the top. The cap takes a high polish and acts as a protective layer for the opal. The top layer also acts as a magnifier, to emphasize the play of color of the opal beneath, which is often an inferior specimen or an extremely thin section of precious opal. Triplet opals tend to have a more artificial appearance and are not classed as precious gemstones, but rather "composite" gemstones. Jewelry applications of precious opal can be somewhat limited by opal's sensitivity to heat due primarily to its relatively high water content and predisposition to scratching. Combined with modern techniques of polishing, a doublet opal can produce a similar effect to Natural black or boulder opal at a fraction of the price. Doublet opal also has the added benefit of having genuine opal as the top visible and touchable layer, unlike triplet opals. |
Opal | Common opal | Besides the gemstone varieties that show a play of color, the other kinds of common opal include the milk opal, milky bluish to greenish (which can sometimes be of gemstone quality); resin opal, which is honey-yellow with a resinous luster; wood opal, which is caused by the replacement of the organic material in wood with opal; menilite, which is brown or grey; hyalite, a colorless glass-clear opal sometimes called Muller's glass; geyserite, also called siliceous sinter, deposited around hot springs or geysers; and diatomaceous earth, the accumulations of diatom shells or tests. Common opal often displays a hazy-milky-turbid sheen from within the stone. In gemology, this optical effect is strictly defined as opalescence which is a form of adularescence. |
Opal | Other varieties of opal | "Girasol opal" is a term sometimes mistakenly and improperly used to refer to fire opals, as well as a type of transparent to semitransparent type milky quartz from Madagascar which displays an asterism, or star effect when cut properly. However, the true girasol opal is a type of hyalite opal that exhibits a bluish glow or sheen that follows the light source around. It is not a play of color as seen in precious opal, but rather an effect from microscopic inclusions. It is also sometimes referred to as water opal, too, when it is from Mexico. The two most notable locations of this type of opal are Oregon and Mexico.A Peruvian opal (also called blue opal) is a semi-opaque to opaque blue-green stone found in Peru, which is often cut to include the matrix in the more opaque stones. It does not display a play of color. Blue opal also comes from Oregon and Idaho in the Owyhee region, as well as from Nevada around the Virgin Valley.Opal is also formed by diatoms. Diatoms are a form of algae that, when they die, often form layers at the bottoms of lakes, bays, or oceans. Their cell walls are made up of hydrated silicon dioxide which gives them [structural coloration] and therefore the appearance of tiny opals when viewed under a microscope. These cell walls or "tests" form the “grains” for the diatomaceous earth. This sedimentary rock is white, opaque, and chalky in texture. Diatomite has multiple industrial uses such as filtering or adsorbing since it has a fine particle size and very porous nature, and gardening to increase water absorption. |
Opal | History | Opal was rare and very valuable in antiquity. In Europe, it was a gem prized by royalty. Until the opening of vast deposits in Australia in the 19th century the only known source was Červenica beyond the Roman frontier in Slovakia. Opal is the national gemstone of Australia. |
Opal | Sources | The primary sources of opal are Australia and Ethiopia, but because of inconsistent and widely varying accountings of their respective levels of extraction, it is difficult to accurately state what proportion of the global supply of opal comes from either country. |
Opal | Sources | Australian opal has been cited as accounting for 95–97% of the world's supply of precious opal, with the state of South Australia accounting for 80% of the world's supply. In 2012, Ethiopian opal production was estimated to be 14,000 kg (31,000 lb) by the United States Geological Survey. USGS data from the same period (2012), reveals Australian opal production to be $41 million. Because of the units of measurement, it is not possible to directly compare Australian and Ethiopian opal production, but these data and others suggest that the traditional percentages given for Australian opal production may be overstated. Yet, the validity of data in the USGS report appears to conflict with that of Laurs et al. and Mesfin, who estimated the 2012 Ethiopian opal output (from Wegal Tena) to be only 750 kg (1,650 lb). |
Opal | Sources | Australia The town of Coober Pedy in South Australia is a major source of opal. The world's largest and most valuable gem opal "Olympic Australis" was found in August 1956 at the "Eight Mile" opal field in Coober Pedy. It weighs 17,000 carats (3.4 kg; 7.5 lb) and is 11 inches (280 mm) long, with a height of 4+3⁄4 in (120 mm) and a width of 4+1⁄2 in (110 mm).The Mintabie Opal Field in South Australia located about 250 km (160 mi) northwest of Coober Pedy has also produced large quantities of crystal opal and the rarer black opal. Over the years, it has been sold overseas incorrectly as Coober Pedy opal. The black opal is said to be some of the best examples found in Australia. |