title
stringlengths 1
149
⌀ | section
stringlengths 1
1.9k
⌀ | text
stringlengths 13
73.5k
|
|---|---|---|
Quantum cognition
|
Main subjects of research
|
Quantum-like models of information processing ("quantum-like brain") The brain is definitely a macroscopic physical system operating on scales of time, space and temperature that -- from the mainstream view -- differs crucially from the corresponding quantum scales. Macroscopic quantum-physical phenomena, such as the Bose-Einstein condensate, are also characterized by special conditions that are definitely not fulfilled in the brain. In particular, the brain's temperature is simply too high to be able to perform real quantum information processing, i.e., to use quantum carriers of information such as photons, ions or electrons. As is commonly accepted in brain science, the basic unit of information processing is a neuron. It is clear that a neuron cannot be in the superposition of two states: firing and non-firing. Hence, it cannot produce superposition playing the basic role in the quantum information processing. Superpositions of mental states are created by complex networks of neurons (classical neural networks). The quantum cognition community states that the activity of such neural networks can produce effects formally described as interference (of probabilities) and entanglement. In principle, however, the community does not try to create concrete models of "quantum-like" representation of information in the brain.The quantum cognition project is based on the observation that various cognitive phenomena are more adequately described by quantum information theory and quantum probability than by the corresponding classical theories (see examples below). Thus, the quantum formalism is considered an operational formalism that describes non-classical processing of probabilistic data. Recent derivations of the complete quantum formalism from simple operational principles for representation of information support the foundations of quantum cognition.
|
Quantum cognition
|
Main subjects of research
|
Although, at the moment, we cannot present the concrete neurophysiological mechanisms of creation of the quantum-like representation of information in the brain, we can present general informational considerations supporting the idea that information processing in the brain matches with quantum information and probability. Here, contextuality is the key word (see the monograph of Khrennikov for detailed representation of this viewpoint). Quantum mechanics is fundamentally contextual. Quantum systems do not have objective properties which can be defined independently of measurement context. As has been pointed out by Niels Bohr, the whole experimental arrangement must be taken into account. Contextuality implies existence of incompatible mental variables, violation of the classical law of total probability, and constructive or destructive interference effects. Thus, the quantum cognition approach can be considered an attempt to formalize contextuality of mental processes, by using the mathematical apparatus of quantum mechanics.
|
Quantum cognition
|
Main subjects of research
|
Decision making Suppose a person is given an opportunity to play two rounds of the following gamble: a coin toss will determine whether the subject wins $200 or loses $100. Suppose the subject has decided to play the first round, and does so. Some subjects are then given the result (win or lose) of the first round, while other subjects are not yet given any information about the results. The experimenter then asks whether the subject wishes to play the second round. Performing this experiment with real subjects gives the following results: When subjects believe they won the first round, the majority of subjects choose to play again on the second round.
|
Quantum cognition
|
Main subjects of research
|
When subjects believe they lost the first round, the majority of subjects choose to play again on the second round.Given these two separate choices, according to the sure thing principle of rational decision theory, they should also play the second round even if they don't know or think about the outcome of the first round. But, experimentally, when subjects are not told the results of the first round, the majority of them decline to play a second round.
|
Quantum cognition
|
Main subjects of research
|
This finding violates the law of total probability, yet it can be explained as a quantum interference effect in a manner similar to the explanation for the results from double-slit experiment in quantum physics. Similar violations of the sure-thing principle are seen in empirical studies of the Prisoner's Dilemma and have likewise been modeled in terms of quantum interference.The above deviations from classical rational expectations in agents’ decisions under uncertainty produce well known paradoxes in behavioral economics, that is, the Allais, Ellsberg and Machina paradoxes. These deviations can be explained if one assumes that the overall conceptual landscape influences the subject's choice in a neither predictable nor controllable way. A decision process is thus an intrinsically contextual process, hence it cannot be modeled in a single Kolmogorovian probability space, which justifies the employment of quantum probability models in decision theory. More explicitly, the paradoxical situations above can be represented in a unified Hilbert space formalism where human behavior under uncertainty is explained in terms of genuine quantum aspects, namely, superposition, interference, contextuality and incompatibility.Considering automated decision making, quantum decision trees have different structure compared to classical decision trees. Data can be analyzed to see if a quantum decision tree model fits the data better.
|
Quantum cognition
|
Main subjects of research
|
Human probability judgments Quantum probability provides a new way to explain human probability judgment errors including the conjunction and disjunction errors. A conjunction error occurs when a person judges the probability of a likely event L and an unlikely event U to be greater than the unlikely event U; a disjunction error occurs when a person judges the probability of a likely event L to be greater than the probability of the likely event L or an unlikely event U. Quantum probability theory is a generalization of Bayesian probability theory because it is based on a set of von Neumann axioms that relax some of the classic Kolmogorov axioms. The quantum model introduces a new fundamental concept to cognition—the compatibility versus incompatibility of questions and the effect this can have on the sequential order of judgments. Quantum probability provides a simple account of conjunction and disjunction errors as well as many other findings such as order effects on probability judgments.The liar paradox - The contextual influence of a human subject on the truth behavior of a cognitive entity is explicitly exhibited by the so-called liar paradox, that is, the truth value of a sentence like "this sentence is false". One can show that the true-false state of this paradox is represented in a complex Hilbert space, while the typical oscillations between true and false are dynamically described by the Schrödinger equation.
|
Quantum cognition
|
Main subjects of research
|
Knowledge representation Concepts are basic cognitive phenomena, which provide the content for inference, explanation, and language understanding. Cognitive psychology has researched different approaches for understanding concepts including exemplars, prototypes, and neural networks, and different fundamental problems have been identified, such as the experimentally tested non classical behavior for the conjunction and disjunction of concepts, more specifically the Pet-Fish problem or guppy effect, and the overextension and underextension of typicality and membership weight for conjunction and disjunction. By and large, quantum cognition has drawn on quantum theory in three ways to model concepts.
|
Quantum cognition
|
Main subjects of research
|
Exploit the contextuality of quantum theory to account for the contextuality of concepts in cognition and language and the phenomenon of emergent properties when concepts combine Use quantum entanglement to model the semantics of concept combinations in a non-decompositional way, and to account for the emergent properties/associates/inferences in relation to concept combinations Use quantum superposition to account for the emergence of a new concept when concepts are combined, and as a consequence put forward an explanatory model for the Pet-Fish problem situation, and the overextension and underextension of membership weights for the conjunction and disjunction of concepts.The large amount of data collected by Hampton on the combination of two concepts can be modeled in a specific quantum-theoretic framework in Fock space where the observed deviations from classical set (fuzzy set) theory, the above-mentioned over- and under- extension of membership weights, are explained in terms of contextual interactions, superposition, interference, entanglement and emergence. And, more, a cognitive test on a specific concept combination has been performed which directly reveals, through the violation of Bell's inequalities, quantum entanglement between the component concepts.
|
Quantum cognition
|
Main subjects of research
|
Semantic analysis and information retrieval The research in (iv) had a deep impact on the understanding and initial development of a formalism to obtain semantic information when dealing with concepts, their combinations and variable contexts in a corpus of unstructured documents. This conundrum of natural language processing (NLP) and information retrieval (IR) on the web – and data bases in general – can be addressed using the mathematical formalism of quantum theory. As basic steps, (a) K. Van Rijsbergen introduced a quantum structure approach to IR, (b) Widdows and Peters utilised a quantum logical negation for a concrete search system, and Aerts and Czachor identified quantum structure in semantic space theories, such as latent semantic analysis. Since then, the employment of techniques and procedures induced from the mathematical formalisms of quantum theory – Hilbert space, quantum logic and probability, non-commutative algebras, etc. – in fields such as IR and NLP, has produced significant results.
|
Quantum cognition
|
Main subjects of research
|
Gestalt perception There are apparent similarities between Gestalt perception and quantum theory. In an article discussing the application of Gestalt to chemistry, Anton Amann writes: "Quantum mechanics does not explain Gestalt perception, of course, but in quantum mechanics and Gestalt psychology there exist almost isomorphic conceptions and problems: Similarly as with the Gestalt concept, the shape of a quantum object does not a priori exist but it depends on the interaction of this quantum object with the environment (for example: an observer or a measurement apparatus).
|
Quantum cognition
|
Main subjects of research
|
Quantum mechanics and Gestalt perception are organized in a holistic way. Subentities do not necessarily exist in a distinct, individual sense.
|
Quantum cognition
|
Main subjects of research
|
In quantum mechanics and Gestalt perception objects have to be created by elimination of holistic correlations with the 'rest of the world'."Each of the points mentioned in the above text in a simplified manner (Below explanations correlate respectively with the above-mentioned points): As an object in quantum physics doesn't have any shape until and unless it interacts with its environment; Objects according to Gestalt perspective do not hold much of a meaning individually as they do when there is a "group" of them or when they are present in an environment.
|
Quantum cognition
|
Main subjects of research
|
Both in quantum mechanics and Gestalt perception, the objects must be studied as a whole rather than finding properties of individual components and interpolating the whole object.
|
Quantum cognition
|
Main subjects of research
|
In Gestalt concept creation of a new object from another previously existing object means that the previously existing object now becomes a sub entity of the new object, and hence "elimination of holistic correlations" occurs. Similarly a new quantum object made from a previously existing object means that the previously existing object loses its holistic view.Amann comments: "The structural similarities between Gestalt perception and quantum mechanics are on a level of a parable, but even parables can teach us something, for example, that quantum mechanics is more than just production of numerical results or that the Gestalt concept is more than just a silly idea, incompatible with atomistic conceptions."
|
Quantum cognition
|
History
|
Ideas for applying the formalisms of quantum theory to cognition first appeared in the 1990s by Diederik Aerts and his collaborators Jan Broekaert, Sonja Smets and Liane Gabora, by Harald Atmanspacher, Robert Bordley, and Andrei Khrennikov. A special issue on Quantum Cognition and Decision appeared in the Journal of Mathematical Psychology (2009, vol 53.), which planted a flag for the field. A few books related to quantum cognition have been published including those by Khrennikov (2004, 2010), Ivancivic and Ivancivic (2010), Busemeyer and Bruza (2012), E. Conte (2012). The first Quantum Interaction workshop was held at Stanford in 2007 organized by Peter Bruza, William Lawless, C. J. van Rijsbergen, and Don Sofge as part of the 2007 AAAI Spring Symposium Series. This was followed by workshops at Oxford in 2008, Saarbrücken in 2009, at the 2010 AAAI Fall Symposium Series held in Washington, D.C., 2011 in Aberdeen, 2012 in Paris, and 2013 in Leicester. Tutorials also were presented annually beginning in 2007 until 2013 at the annual meeting of the Cognitive Science Society. A Special Issue on Quantum models of Cognition appeared in 2013 in the journal Topics in Cognitive Science.
|
Quillen–Lichtenbaum conjecture
|
Quillen–Lichtenbaum conjecture
|
In mathematics, the Quillen–Lichtenbaum conjecture is a conjecture relating étale cohomology to algebraic K-theory introduced by Quillen (1975, p. 175), who was inspired by earlier conjectures of Lichtenbaum (1973). Kahn (1997) and Rognes & Weibel (2000) proved the Quillen–Lichtenbaum conjecture at the prime 2 for some number fields. Voevodsky, using some important results of Markus Rost, has proved the Bloch–Kato conjecture, which implies the Quillen–Lichtenbaum conjecture for all primes.
|
Quillen–Lichtenbaum conjecture
|
Statement
|
The conjecture in Quillen's original form states that if A is a finitely-generated algebra over the integers and l is prime, then there is a spectral sequence analogous to the Atiyah–Hirzebruch spectral sequence, starting at etale Spec A[ℓ−1],Zℓ(−q/2)), (which is understood to be 0 if q is odd)and abutting to K−p−qA⊗Zℓ for −p − q > 1 + dim A.
|
Quillen–Lichtenbaum conjecture
|
K-theory of the integers
|
Assuming the Quillen–Lichtenbaum conjecture and the Vandiver conjecture, the K-groups of the integers, Kn(Z), are given by: 0 if n = 0 mod 8 and n > 0, Z if n = 0 Z ⊕ Z/2 if n = 1 mod 8 and n > 1, Z/2 if n = 1.
|
Quillen–Lichtenbaum conjecture
|
K-theory of the integers
|
Z/ck ⊕ Z/2 if n = 2 mod 8 Z/8dk if n = 3 mod 8 0 if n = 4 mod 8 Z if n = 5 mod 8 Z/ck if n = 6 mod 8 Z/4dk if n = 7 mod 8where ck/dk is the Bernoulli number B2k/k in lowest terms and n is 4k − 1 or 4k − 2 (Weibel 2005).
|
1,3-beta-D-glucan phosphorylase
|
1,3-beta-D-glucan phosphorylase
|
In enzymology, a 1,3-beta-D-glucan phosphorylase (EC 2.4.1.97) is an enzyme that catalyzes the chemical reaction (1,3-beta-D-glucosyl)n + phosphate ⇌ (1,3-beta-D-glucosyl)n-1 + alpha-D-glucose 1-phosphateThus, the two substrates of this enzyme are (1,3-beta-D-glucosyl)n and phosphate, whereas its two products are (1,3-beta-D-glucosyl)n-1 and alpha-D-glucose 1-phosphate.
This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. The systematic name of this enzyme class is 1,3-beta-D-glucan:phosphate alpha-D-glucosyltransferase. Other names in common use include laminarin phosphoryltransferase, 1,3-beta-D-glucan:orthophosphate glucosyltransferase, and laminarin phosphoryltransferase.
|
Circuit breaker analyzer
|
Circuit breaker analyzer
|
A circuit breaker analyzer is an instrument that measures the parameters of a circuit breaker.In 1984, Megger patented a digital circuit breaker analyzer, controlled by a microprocessor. in 2020 few companies develop software to control circuit breaker analyzers from different devices such as computers, tablet computer, smartphones and others.The following tests can be carried out on the circuit breaker: mechanical, thermal, dielectric, short-circuit.
|
Circuit breaker analyzer
|
Circuit breaker analyzer
|
The analyzer operates the circuit breaker under fault current conditions. After finishing the test of the breaker, the system measures currents, voltages and other main parameters of the breaker and through a set algorithm diagnoses the condition of the device under different conditions. The final result of the analysis give information about trip times, essential synchronism of the poles in the different operations of the circuit breaker.
|
Circuit breaker analyzer
|
Measured values
|
Timing measurements Motion measurements Coil currents Dynamic resistance measurement (DRM) Vibration analysis Dynamic capacitance measurement Static and dynamic resistance measurement
|
Estradiol (medication)
|
Estradiol (medication)
|
Estradiol (E2) is a medication and naturally occurring steroid hormone. It is an estrogen and is used mainly in menopausal hormone therapy and to treat low sex hormone levels in women. It is also used in hormonal birth control for women, in hormone therapy for transgender women, and in the treatment of hormone-sensitive cancers like prostate cancer in men and breast cancer in women, among other uses. Estradiol can be taken by mouth, held and dissolved under the tongue, as a gel or patch that is applied to the skin, in through the vagina, by injection into muscle or fat, or through the use of an implant that is placed into fat, among other routes.Side effects of estradiol in women include breast tenderness, breast enlargement, headache, fluid retention, and nausea among others. Men and children who are exposed to estradiol may develop symptoms of feminization, such as breast development and a feminine pattern of fat distribution, and men may also experience low testosterone levels and infertility. Estradiol may increase the risk of endometrial hyperplasia and endometrial cancer in women with intact uteruses if it is not taken together with a progestogen such as progesterone. The combination of estradiol with a progestin, though not with oral progesterone, may increase the risk of breast cancer. Estradiol should not be used in women who are pregnant or breastfeeding or who have breast cancer, among other contraindications.Estradiol is a naturally occurring and bioidentical estrogen, or an agonist of the estrogen receptor, the biological target of estrogens like endogenous estradiol. Due to its estrogenic activity, estradiol has antigonadotropic effects and can inhibit fertility and suppress sex hormone production in both women and men. Estradiol differs from non-bioidentical estrogens like conjugated estrogens and ethinylestradiol in various ways, with implications for tolerability and safety.Estradiol was discovered in 1933. It became available as a medication that same year, in an injectable form known as estradiol benzoate. Forms that were more useful by mouth, estradiol valerate and micronized estradiol, were introduced in the 1960s and 1970s and increased its popularity by this route. Estradiol is also used as other prodrugs, like estradiol cypionate. Related estrogens such as ethinylestradiol, which is the most common estrogen in birth control pills, and conjugated estrogens (brand name Premarin), which is used in menopausal hormone therapy, are used as medications as well. In 2020, it was the 59th most commonly prescribed medication in the United States, with more than 11 million prescriptions. It is available as a generic medication.
|
Estradiol (medication)
|
Medical uses
|
Hormone therapy Menopause Estradiol is used in menopausal hormone therapy to prevent and treat moderate to severe menopausal symptoms such as hot flashes, vaginal dryness and atrophy, and osteoporosis (bone loss). As unopposed estrogen therapy (using estrogen alone without progesterone) increases the risk of endometrial hyperplasia and endometrial cancer in women with intact uteruses, estradiol is usually combined with a progestogen like progesterone or medroxyprogesterone acetate to prevent the effects of estradiol on the endometrium. This is not necessary if the woman has undergone a hysterectomy (surgical removal of the uterus). A 2017 meta-analysis found that estradiol had no effect on depressive symptoms in peri- and postmenopausal women.
|
Estradiol (medication)
|
Medical uses
|
Hypogonadism Estrogen is responsible for the mediation of puberty in females, and in girls with delayed puberty due to hypogonadism (low-functioning gonads, which can result in low sex hormone levels) such as in Turner syndrome, estradiol is used to induce the development of and maintain female secondary sexual characteristics such as breasts, wide hips, and a female fat distribution. It is also used to restore estradiol levels in adult premenopausal women with hypogonadism, for instance those with premature ovarian failure or who have undergone oophorectomy. It is used to treat women with hypogonadism due to hypopituitarism as well.
|
Estradiol (medication)
|
Medical uses
|
Transgender women Estradiol is used as part of feminizing hormone therapy for transgender women. The drug is used in higher dosages prior to sex reassignment surgery or orchiectomy to help suppress testosterone levels; after this procedure, estradiol continues to be used at lower dosages to maintain estradiol levels in the normal premenopausal female range.
|
Estradiol (medication)
|
Medical uses
|
Birth control Although almost all combined oral contraceptives contain the synthetic estrogen ethinylestradiol, natural estradiol itself is also used in some hormonal contraceptives, including in estradiol-containing oral contraceptives and combined injectable contraceptives. It is formulated in combination with a progestin such as dienogest, nomegestrol acetate, or medroxyprogesterone acetate, and is often used in the form of an ester prodrug like estradiol valerate or estradiol cypionate. Hormonal contraceptives contain a progestin and/or estrogen and prevent ovulation and thus the possibility of pregnancy by suppressing the secretion of the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the peak of which around the middle of the menstrual cycle causes ovulation to occur.
|
Estradiol (medication)
|
Medical uses
|
Hormonal cancer Prostate cancer Estradiol is used as a form of high-dose estrogen therapy to treat prostate cancer and is similarly effective to other therapies such as androgen deprivation therapy with castration and antiandrogens. It is used in the form of long-lasting injected estradiol prodrugs like polyestradiol phosphate, estradiol valerate, and estradiol undecylate, and has also more recently been assessed in the form of transdermal estradiol patches. Estrogens are effective in the treatment of prostate cancer by suppressing testosterone levels into the castrate range, increasing levels of sex hormone-binding globulin (SHBG) and thereby decreasing the fraction of free testosterone, and possibly also via direct cytotoxic effects on prostate cancer cells. Parenteral estradiol is largely free of the cardiovascular side effects of the high oral dosages of synthetic estrogens like diethylstilbestrol ad ethinylestradiol that were used previously. In addition, estrogens may have advantages relative to castration in terms of hot flashes, sexual interest and function, osteoporosis, cognitive function, and quality of life. However, side effects such as gynecomastia and feminization in general may be difficult to tolerate and unacceptable for many men.
|
Estradiol (medication)
|
Medical uses
|
Breast cancer High-dose estrogen therapy is effective in the treatment of about 35% of cases of breast cancer in women who are at least 5 years menopausal and has comparable effectiveness to antiestrogen therapy with medications like the selective estrogen receptor modulator (SERM) tamoxifen. Although estrogens are rarely used in the treatment of breast cancer today and synthetic estrogens like diethylstilbestrol and ethinylestradiol have most commonly been used, estradiol itself has been used in the treatment of breast cancer as well. It has been used orally at very high doses (30 mg/day) in the treatment of therapy-naive breast cancer and orally at low doses (2 to 6 mg/day) in the treatment of breast cancer in women who were previously treated with and benefited from but acquired resistance to aromatase inhibitors. Polyestradiol phosphate is also used to treat breast cancer.
|
Estradiol (medication)
|
Medical uses
|
Other uses Infertility Estrogens may be used in treatment of infertility in women when there is a need to develop sperm-friendly cervical mucous or an appropriate uterine lining.It is also commonly used during in vitro fertilization (IVF). Estrogen helps maintain the endometrial lining of the uterus and help prepare for pregnancy. Research shows higher pregnancy rate if the mother takes estrogen in addition to progesterone. Estradiol is the predominant form of estrogen during reproductive years and is most commonly prescribed.
|
Estradiol (medication)
|
Medical uses
|
Lactation suppression Estrogens can be used to suppress and cease lactation and breast engorgement in postpartum women who do not wish to breastfeed. They do this by directly decreasing the sensitivity of the alveoli of the mammary glands to the lactogenic hormone prolactin.
|
Estradiol (medication)
|
Medical uses
|
Tall stature Estrogens have been used to limit final height in adolescent girls with tall stature. They do this by inducing epiphyseal closure and suppressing growth hormone-induced hepatic production and by extension circulating levels of insulin-like growth factor-1 (IGF-1), a hormone that causes the body to grow and increase in size. Although ethinylestradiol and conjugated estrogens have mainly been used for this purpose, estradiol can also be employed.
|
Estradiol (medication)
|
Medical uses
|
Breast enhancement Estrogens are involved in breast development and estradiol may be used as a form of hormonal breast enhancement to increase the size of the breasts. Both polyestradiol phosphate monotherapy and pseudopregnancy with a combination of high-dosage intramuscular estradiol valerate and hydroxyprogesterone caproate have been assessed for this purpose in clinical studies. However, acute or temporary breast enlargement is a well-known side effect of estrogens, and increases in breast size tend to regress following discontinuation of treatment. Aside from those without prior established breast development, evidence is lacking for a sustained increases in breast size with estrogens.
|
Estradiol (medication)
|
Medical uses
|
Schizophrenia Estradiol has been found to be effective in the adjunctive treatment of schizophrenia in women. It has been found to significantly reduce positive, negative, and cognitive symptoms, with particular benefits on positive symptoms. Other estrogens, as well as selective estrogen receptor modulators (SERMs) like raloxifene, have been found to be effective in the adjunctive treatment of schizophrenia in women similarly. Estrogens may be useful in the treatment of schizophrenia in men as well, but their use in this population is limited by feminizing side effects. SERMs, which have few or no feminizing side effects, have been found to be effective in the adjunctive treatment of schizophrenia in men similarly to in women and may be more useful than estrogens in this sex.
|
Estradiol (medication)
|
Medical uses
|
Sexual deviance Estradiol has been used at high doses to suppress sex drive in men with sexual deviance such as paraphilias and in sex offenders. It has specifically been used for this indication in the forms of intramuscular injections of estradiol valerate and estradiol undecylate and of subcutaneous pellet implants of estradiol.
|
Estradiol (medication)
|
Medical uses
|
Available forms Estradiol is available in a variety of different formulations, including oral, intranasal, transdermal/topical, vaginal, injectable, and implantable preparations. An ester may be attached to one or both of the hydroxyl groups of estradiol to improve its oral bioavailability and/or duration of action with injection. Such modifications give rise to forms such as estradiol acetate (oral and vaginal), estradiol valerate (oral and injectable), estradiol cypionate (injectable), estradiol benzoate (injectable), estradiol undecylate (injectable), and polyestradiol phosphate (injectable; a polymerized ester of estradiol), which are all prodrugs of estradiol.
|
Estradiol (medication)
|
Contraindications
|
Estrogens like estradiol have a number of contraindications. Estradiol should be avoided when there is undiagnosed abnormal vaginal bleeding, known, suspected or a history of breast cancer, current treatment for metastatic disease, known or suspected estrogen-dependent neoplasia, deep vein thrombosis, pulmonary embolism or history of these conditions, active or recent arterial thromboembolic disease such as stroke, myocardial infarction, liver dysfunction or disease. Estradiol should not be taken by people with a hypersensitivity/allergy or those who are pregnant or are suspected pregnant.
|
Estradiol (medication)
|
Side effects
|
Common side effects of estradiol in women include headache, breast pain or tenderness, breast enlargement, irregular vaginal bleeding or spotting, abdominal cramps, bloating, fluid retention, and nausea. Other possible side effects of estrogens may include high blood pressure, high blood sugar, enlargement of uterine fibroids, melasma, vaginal yeast infections, and liver problems. In men, estrogens can cause breast pain or tenderness, gynecomastia (male breast development), feminization, demasculinization, sexual dysfunction (decreased libido and erectile dysfunction), hypogonadism, testicular atrophy, and infertility.
|
Estradiol (medication)
|
Side effects
|
Blood clots Oral estradiol and estradiol valerate, for instance in menopausal hormone therapy or birth control pills, are associated with a significantly higher risk of venous thromboembolism (VTE) than non-use. Higher doses of oral estrogens are associated with higher risks of VTE. In contrast to oral estradiol, transdermal and vaginal estradiol at menopausal replacement dosages are not associated with a higher incidence of VTE. Low doses (e.g., 50 μg/day) and high doses (e.g., 100 μg/day) of transdermal estradiol for menopausal replacement do not differ in terms of VTE risk. The higher risk of VTE with oral estradiol can be attributed to the first pass and a disproportionate effect on liver synthesis of coagulation factors. Even high doses of parenteral estradiol, such as high-dose polyestradiol phosphate, have minimal influence on coagulation factors, in contrast to oral estrogen therapy. However, sufficient doses of parenteral estradiol, for instance very high doses of estradiol valerate by intramuscular injection, can nonetheless activate coagulation, presumably increasing VTE risk.In addition to the route of administration, the type of estrogen influences VTE risk. Oral conjugated estrogens are associated with a higher risk of VTE than oral estradiol. Estradiol- and estradiol valerate-containing birth control pills are associated with a lower risk of VTE than birth control pills containing ethinylestradiol. The relative risk of VTE is thought to be highest with oral ethinylestradiol, intermediate with oral conjugated estrogens, low with oral estradiol and parenteral estradiol valerate, and very low with transdermal estradiol. Conjugated estrogens and ethinylestradiol are thought to have a higher risk of VTE than estradiol because they are resistant to hepatic metabolism and have a disproportionate influence on liver production of coagulation factors.The combination of oral or transdermal estradiol and a progestin is associated with a higher risk of VTE than estradiol alone. Dydrogesterone is associated with a lower risk than other progestins such as medroxyprogesterone acetate and norethisterone, while oral progesterone is associated with no increase in risk of VTE. Older age, higher body weight, lower physical activity, and smoking are all associated with a higher risk of VTE with oral estrogen therapy. Risk of VTE with estrogen therapy is highest at the start of treatment, particularly during the first year, and decreases over time.The absolute risk of VTE with estrogen and/or progestin therapy is small. Women who are not on a birth control pill or hormone therapy have a risk of VTE of about 1 to 5 out of 10,000 women per year. In women taking a birth control pill containing ethinylestradiol and a progestin, the risk of VTE is in the range of 3 to 10 out of 10,000 women per year. Birth control pills containing estradiol valerate and a progestin are associated with about half the risk of VTE of ethinylestradiol/progestin-containing birth control pills. Hormone therapy for transgender women likewise is associated with a lower risk of VTE than birth control pills containing ethinylestradiol and a progestin. The risk of VTE during pregnancy, when estrogens and progesterone increase to very high levels, is 5 to 20 in 10,000 women per year, while the risk is 40 to 65 per 10,000 women per year during the postpartum period.
|
Estradiol (medication)
|
Side effects
|
Long-term effects Uncommon but serious possible side effects of estrogens associated with long-term therapy may include breast cancer, uterine cancer, stroke, heart attack, blood clots, dementia, gallbladder disease, and ovarian cancer. Warning signs of these serious side effects include breast lumps, unusual vaginal bleeding, dizziness, faintness, changes in speech, severe headaches, chest pain, shortness of breath, pain in the legs, changes in vision, and vomiting.Due to health risks observed with the combination of conjugated estrogens and medroxyprogesterone acetate in the Women's Health Initiative (WHI) studies (see below), the United States Food and Drug Administration (FDA) label for Estrace (estradiol) advises that estrogens should be used in menopausal hormone therapy only for the shortest time possible and at the lowest effective dose. While the FDA states that is unknown if these risks generalize to estradiol (alone or in combination with progesterone or a progestin), it advises that in the absence of comparable data, the risks should be assumed to be similar. When used to treat menopausal symptoms, the FDA recommends that discontinuation of estradiol should be attempted every three to six months via a gradual dose taper.The combination of bioidentical transdermal or vaginal estradiol and oral or vaginal progesterone appears to be a safer form of hormone therapy than the combination of oral conjugated estrogens and medroxyprogesterone acetate and may not share the same health risks. Advantages may include reduced or no risk of venous thromboembolism, cardiovascular disease, and breast cancer, among others.
|
Estradiol (medication)
|
Overdose
|
Estrogens are relatively safe in overdose. During pregnancy, levels of estradiol increase to very high concentrations that are as much as 100-fold normal levels. In late pregnancy, the body produces and secretes approximately 100 mg of estrogens, including estradiol, estrone, and estriol, per day. Doses of estradiol of as high as 200 mg per day by intramuscular injection for several weeks have been administered to humans in studies. Serious adverse effects have not been described following acute overdose of large doses of estrogen- and progestogen-containing birth control pills by small children. Symptoms of estrogen overdosage may include nausea, vomiting, bloating, increased weight, water retention, breast tenderness, vaginal discharge, vaginal bleeding, heavy legs, and leg cramps. These side effects can be diminished by reducing the estrogen dosage.
|
Estradiol (medication)
|
Interactions
|
Inducers of cytochrome P450 enzymes like CYP3A4 such as St. John's wort, phenobarbital, carbamazepine and rifampicin decrease the circulating levels of estradiol by accelerating its metabolism, whereas inhibitors of cytochrome P450 enzymes like CYP3A4 such as erythromycin, cimetidine, clarithromycin, ketoconazole, itraconazole, ritonavir and grapefruit juice may slow its metabolism resulting in increased levels of estradiol in the circulation. There is an interaction between estradiol and alcohol such that alcohol considerably increases circulating levels of estradiol during oral estradiol therapy and also increases estradiol levels in normal premenopausal women and with parenteral estradiol therapy. This appears to be due to a decrease in hepatic 17β-hydroxysteroid dehydrogenase type 2 (17β-HSD2) activity and hence estradiol inactivation into estrone due to an alcohol-mediated increase in the ratio of NADH to NAD in the liver. Spironolactone may reduce the bioavailability of high doses of oral estradiol.
|
Estradiol (medication)
|
Pharmacology
|
Pharmacodynamics Estradiol is an estrogen, or an agonist of the estrogen receptors (ERs), the ERα and ERβ. It is also an agonist of membrane estrogen receptors (mERs), including the GPER, Gq-mER, ER-X, and ERx. Estradiol is highly selective for these ERs and mERs, and does not interact importantly with other steroid hormone receptors. It is far more potent as an estrogen than are other bioidentical estrogens like estrone and estriol. Given by subcutaneous injection in mice, estradiol is about 10-fold more potent than estrone and about 100-fold more potent than estriol.The ERs are expressed widely throughout the body, including in the breasts, uterus, vagina, fat, skin, bone, liver, pituitary gland, hypothalamus, and other parts of the brain. In accordance, estradiol has numerous effects throughout the body. Among other effects, estradiol produces breast development, feminization, changes in the female reproductive system, changes in liver protein synthesis, and changes in brain function. The effects of estradiol can influence health in both positive and negative ways. In addition to the aforementioned effects, estradiol has antigonadotropic effects due to its estrogenic activity, and can inhibit ovulation and suppress gonadal sex hormone production. At sufficiently high dosages, estradiol is a powerful antigonadotropin, capable of suppressing testosterone levels into the castrate/female range in men.There are differences between estradiol and other estrogens, such as non-bioidentical estrogens like natural conjugated estrogens and synthetic estrogens like ethinylestradiol and diethylstilbestrol, with implications for pharmacodynamics and pharmacokinetics as well as efficacy, tolerability, and safety.
|
Estradiol (medication)
|
Pharmacology
|
Pharmacokinetics Estradiol can be taken by a variety of different routes of administration. These include oral, buccal, sublingual, intranasal, transdermal (gels, creams, patches), vaginal (tablets, creams, rings, suppositories), rectal, by intramuscular or subcutaneous injection (in oil or aqueous), and as a subcutaneous implant. The pharmacokinetics of estradiol, including its bioavailability, metabolism, biological half-life, and other parameters, differ by route of administration. Likewise, the potency of estradiol, and its local effects in certain tissues, most importantly the liver, differ by route of administration as well. In particular, the oral route is subject to a high first-pass effect, which results in high levels of estradiol and consequent estrogenic effects in the liver and low potency due to first-pass hepatic and intestinal metabolism into metabolites like estrone and estrogen conjugates. Conversely, this is not the case for parenteral (non-oral) routes, which bypass the intestines and liver.Different estradiol routes and dosages can achieve widely varying circulating estradiol levels. For purposes of comparison with normal physiological circumstances, menstrual cycle circulating levels of estradiol in premenopausal women are 40 pg/mL in the early follicular phase, 250 pg/mL at the middle of the cycle, and 100 pg/mL during the mid-luteal phase. Mean integrated levels of circulating estradiol in premenopausal women across the whole menstrual cycle have been reported to be in the range of 80 and 150 pg/mL, according to some sources.
|
Estradiol (medication)
|
Chemistry
|
Estradiol is a naturally occurring estrane steroid. It is also known as 17β-estradiol (to distinguish it from 17α-estradiol) or as estra-1,3,5(10)-triene-3,17β-diol. It has two hydroxyl groups, one at the C3 position and the other at the C17β position, as well as three double bonds in the A ring (the estra-1,3,5(10)-triene core). Due to its two hydroxyl groups, estradiol is often abbreviated as E2. The structurally related estrogens, estrone (E1), estriol (E3), and estetrol (E4) have one, three, and four hydroxyl groups, respectively.
|
Estradiol (medication)
|
Chemistry
|
Hemihydrate A hemihydrate form of estradiol, estradiol hemihydrate, is widely used medically under a large number of brand names similarly to estradiol. In terms of activity and bioequivalence, estradiol and its hemihydrate are identical, with the only disparities being an approximate 3% difference in potency by weight (due to the presence of water molecules in the hemihydrate form of the substance) and a slower rate of release with certain formulations of the hemihydrate. This is because estradiol hemihydrate is more hydrated than anhydrous estradiol, and for this reason, is more insoluble in water in comparison, which results in slower absorption rates with specific formulations of the drug such as vaginal tablets. Estradiol hemihydrate has also been shown to result in less systemic absorption as a vaginal tablet formulation relative to other topical estradiol formulations such as vaginal creams. Estradiol hemihydrate is used in place of estradiol in some estradiol products.
|
Estradiol (medication)
|
Chemistry
|
Derivatives A variety of C17β and/or C3 ester prodrugs of estradiol, such as estradiol acetate, estradiol benzoate, estradiol cypionate, estradiol dipropionate, estradiol enantate, estradiol undecylate, estradiol valerate, and polyestradiol phosphate (an estradiol ester in polymeric form), among many others, have been developed and introduced for medical use as estrogens. Estramustine phosphate is also an estradiol ester, but with a nitrogen mustard moiety attached, and is used as a cytostatic antineoplastic agent in the treatment of prostate cancer. Cloxestradiol acetate and promestriene are ether prodrugs of estradiol that have been introduced for medical use as estrogens as well, although they are little known and rarely used.Synthetic derivatives of estradiol used as estrogens include ethinylestradiol, ethinylestradiol sulfonate, mestranol, methylestradiol, moxestrol, and quinestrol, all of which are 17α-substituted estradiol derivatives. Synthetic derivatives of estradiol used in scientific research include 8β-VE2 and 16α-LE2.
|
Estradiol (medication)
|
History
|
Estradiol was first discovered and synthesized in 1933 via reduction of estrone. Subsequently, estradiol was isolated for the first time in 1935. It was also originally known as dihydroxyestrin, dihydrofolliculin, or alpha-estradiol.Estradiol was first introduced for medical use, in the form of estradiol benzoate, a short-acting ester prodrug of estradiol administered by intramuscular injection in oil solution, under the brand name Progynon B in 1933. Estradiol itself was also marketed in the 1930s and 1940s in the form of oral tablets and solutions, vaginal suppositories, and topical ointments under a variety of brand names including Dimenformon, Gynoestryl, Ovocyclin, Progynon, and Progynon DH. Marketed vaginal estradiol suppositories were also used rectally. Estradiol dipropionate, another short-acting ester of estradiol in oil solution for use by intramuscular injection, was marketed under the brand name Di-Ovocylin by 1939. In contrast to estrone, estradiol was never marketed in oil solution for intramuscular injection. This is attributable to its short duration of action and the availability of longer-acting estradiol esters like estradiol benzoate and estradiol dipropionate.Delivery of estrogens by nasal spray was studied in 1929, and an estradiol nasal spray for local use was marketed by Schering under the brand name Progynon DH Nasal Spray by 1941. Sublingual administration of estradiol was first described in the early 1940s. Buccal estradiol tablets were marketed by Schering under the brand name Progynon Buccal Tablets by 1949. Estradiol tablets for use by the sublingual route were marketed under the brand name Estradiol Membrettes in 1950, as well as under the brand name Diogynets by 1952. Longer-acting esters of estradiol in oil solution like estradiol valerate (Delestrogen, Progynon Depot), estradiol cypionate (Depo-Estradiol), and estradiol undecylate (Delestrec, Progynon Depot 100), as well as the polymeric estradiol ester polyestradiol phosphate in aqueous solution (Estradurin), were developed and introduced for use by intramuscular injection in the 1950s.Due to poor absorption and low potency relative to other estrogens, oral estradiol was not widely used as late as the early 1970s. Instead, synthetic and animal-derived estrogens like conjugated estrogens, ethinylestradiol, and diethylstilbestrol were typically used by the oral route. In 1966, oral estradiol valerate was introduced by Schering for medical use under the brand name Progynova. Esterification of estradiol, as in estradiol valerate, was believed to improve its metabolic stability with oral administration. Studies in the 1960s showed that micronization of steroids such as spironolactone and norethisterone acetate improved their absorption and oral potency by several-fold. In 1972, micronization of estradiol was studied in women and was likewise found to improve the absorption and potency of estradiol by the oral route. Subsequently, oral micronized estradiol was introduced for medical use in the United States under the brand name Estrace in 1975. However, oral micronized estradiol valerate had been introduced by Schering in 1968. Oral micronized estradiol and oral estradiol valerate have similar bioavailability and are both now widely used throughout the world.After the introduction of oral micronized estradiol, vaginal and intranasal micronized estradiol were evaluated in 1977 and both subsequently introduced.The first transdermal estradiol gel, a hydroalcoholic gel known as EstroGel, was initially described in 1980 and was introduced in Europe around 1981. Transdermal estradiol gel did not become available in the United States until 2004, when EstroGel was introduced in this country as well. A transdermal estradiol emulsion, Estrasorb, was marketed in the United States in 2003 as well. One of the earliest reports of transdermal estradiol patches was published in 1983. Estraderm, a reservoir patch and the first transdermal estradiol patch to be marketed, was introduced in Europe in 1985 and in the United States in 1986. The first transdermal matrix estradiol patches to be introduced were Climara and Vivelle between 1994 and 1996, and were followed by many others.Ethinylestradiol, a synthetic derivative of estradiol, was synthesized from estradiol by Inhoffen and Hohlweg in 1938 and was introduced for oral use by Schering in the United States under the brand name Estinyl in 1943. Starting in the 1950s, ethinylestradiol became widely used in birth control pills. Estradiol-containing birth control pills were initially studied in the 1970s, with the first report published in 1977. Development of birth control pills containing estradiol was motivated by the thrombotic risks of ethinylestradiol that were uncovered in the 1960s and 1970s. More than 15 attempts were made at development of an estradiol-containing birth control pill starting in the 1970s, but were unsuccessful due to unacceptable menstrual bleeding patterns. Estradiol valerate/cyproterone acetate (Femilar) was introduced for use as a birth control pill in Finland in 1993, but was never marketed elsewhere. Subsequently, estradiol valerate/dienogest (Natazia, Qlaira) was marketed as a birth control pill in 2008 and estradiol/nomegestrol acetate (Naemis, Zoely) was introduced in 2012.
|
Estradiol (medication)
|
Society and culture
|
Generic names Estradiol is the generic name of estradiol in American English and its INN, USAN, USP, BAN, DCF, and JAN. Estradiolo is the name of estradiol in Italian and the DCIT and estradiolum is its name in Latin, whereas its name remains unchanged as estradiol in Spanish, Portuguese, French, and German. Oestradiol was the former BAN of estradiol and its name in British English, but the spelling was eventually changed to estradiol. When estradiol is provided in its hemihydrate form, its INN is estradiol hemihydrate.
|
Estradiol (medication)
|
Society and culture
|
Brand names Estradiol is marketed under a large number of brand names throughout the world. Examples of major brand names in which estradiol has been marketed in include Climara, Climen, Dermestril, Divigel, Estrace, Natifa, Estraderm, Estraderm TTS, Estradot, Estreva, Estrimax, Estring, Estrofem, EstroGel, Evorel, Fem7 (or FemSeven), Imvexxy, Menorest, Oesclim, OestroGel, Sandrena, Systen, and Vagifem. Estradiol valerate is marketed mainly as Progynova and Progynon-Depot, while it is marketed as Delestrogen in the U.S. Estradiol cypionate is used mainly in the U.S. and is marketed under the brand name Depo-Estradiol. Estradiol acetate is available as Femtrace, Femring, and Menoring.Estradiol is also widely available in combination with progestogens. It is available in combination with norethisterone acetate under the major brand names Activelle, Cliane, Estalis, Eviana, Evorel Conti, Evorel Sequi, Kliogest, Novofem, Sequidot, and Trisequens; with drospirenone as Angeliq; with dydrogesterone as Femoston, Femoston Conti; and with nomegestrol acetate as Zoely. Estradiol valerate is available with cyproterone acetate as Climen; with dienogest as Climodien and Qlaira; with norgestrel as Cyclo-Progynova and Progyluton; with levonorgestrel as Klimonorm; with medroxyprogesterone acetate as Divina and Indivina; and with norethisterone enantate as Mesigyna and Mesygest. Estradiol cypionate is available with medroxyprogesterone acetate as Cyclo-Provera, Cyclofem, Feminena, Lunelle, and Novafem; estradiol enantate with algestone acetophenide as Deladroxate and Topasel; and estradiol benzoate is marketed with progesterone as Mestrolar and Nomestrol.Estradiol valerate is also widely available in combination with prasterone enantate (DHEA enantate) under the brand name Gynodian Depot.
|
Estradiol (medication)
|
Society and culture
|
Slang Names Estradiol has a number of humorous nicknames among the transgender community. Among them are titty skittles, breast mints, femme&m’s, antiboyotics, trans-mission fluid, and the Notorious H.R.T.
Availability Estradiol and/or its esters are widely available in countries throughout the world in a variety of formulations.
|
Estradiol (medication)
|
Society and culture
|
United States As of November 2016, estradiol is available in the United States in the following forms: Oral tablets (Femtrace (as estradiol acetate), Gynodiol, Innofem, generics) Transdermal patches (Alora, Climara, Esclim, Estraderm, FemPatch, Menostar, Minivelle, Vivelle, Vivelle-Dot, generics) Topical gels (Divigel, Elestrin, EstroGel, Sandrena), emulsions (Estrasorb), and sprays (Evamist) Vaginal tablets (Vagifem, generics), creams (Estrace), inserts (Imvexxy), and rings (Estring, Femring (as estradiol acetate)) Oil solution for intramuscular injection (Delestrogen (as estradiol valerate), Depo-Estradiol (as estradiol cypionate))Oral estradiol valerate (Progynova) and other esters of estradiol that are used by injection like estradiol benzoate, estradiol enantate, and estradiol undecylate all are not marketed in the U.S. Polyestradiol phosphate (Estradurin) was marketed in the U.S. previously but is no longer available.Estradiol is also available in the U.S. in combination with progestogens for the treatment of menopausal symptoms and as a combined hormonal contraceptive: Oral oil-filled capsules with progesterone (Bijuva) Oral tablets with drospirenone (Angeliq) and norethisterone acetate (Activella, Amabelz) and as estradiol valerate with dienogest (Natazia) Transdermal patches with levonorgestrel (Climara Pro) and norethisterone acetate (Combipatch)Estradiol and estradiol esters are also available in custom preparations from compounding pharmacies in the U.S. This includes subcutaneous pellet implants, which are not available in the United States as FDA-approved pharmaceutical drugs. In addition, topical creams that contain estradiol are generally regulated as cosmetics rather than as drugs in the U.S. and hence are also sold over-the-counter and may be purchased without a prescription on the Internet.
|
Estradiol (medication)
|
Society and culture
|
Other countries Pharmaceutical estradiol subcutaneous pellet implants were formerly available in the United Kingdom and Australia under the brand name Estradiol Implants or Oestradiol Implants (Organon; 25, 50, or 100 mg), but have been discontinued. However, an estradiol subcutaneous implant with the brand name Meno-Implant (Organon; 20 mg) continues to be available in the Netherlands. Previously, for instance in the 1970s and 1980s, other subcutaneous estradiol implant products such as Progynon Pellets (Schering; 25 mg) and Estropel Pellets (25 mg; Bartor Pharmacol) were marketed. It has been said that pharmaceutical estradiol implants have been almost exclusively used in the United Kingdom. Subcutaneous estradiol implants are also available as custom compounded products in some countries.
|
Estradiol (medication)
|
Society and culture
|
Cost Generic oral estradiol tablets are much less expensive than other forms of estradiol such as transdermal gel and patches and vaginal rings.
|
Estradiol (medication)
|
Research
|
A variety of estradiol-containing combined birth control pills were studied but never marketed. In addition, a variety of estradiol-containing combined injectable contraceptives were studied but never marketed.Estradiol has been studied in the treatment of postpartum depression and postpartum psychosis.Estrogens such as estradiol appear to improve sexual desire and function in women. However, the available evidence overall does not support the use of estradiol and other estrogens for improving sexual desire and function in women as of 2016. An exception is the use of estrogens to treat vaginal atrophy.Estrogen therapy has been proposed as a potential treatment for autism but clinical studies are needed.
|
SKIM
|
SKIM
|
Sea surface kinematics multiscale monitoring (SKIM) was one of the two candidate missions for the 9th Earth Explorer mission of in the Living Planet Programme of the European Space Agency (ESA). SKIM and the other candidate (FORUM) were pre-selected for a detailed study in November 2017. Only one of the two candidates was to be selected in 2019 for immediate implementation and a possible launch by the year 2025, and FORUM was chosen.
|
SKIM
|
Context
|
SKIM builds on the technological heritage of the SWIM instrument now flying on the China-France Ocean Satellite, with the important addition of Doppler measurement and changing from Ku to Ka-band. SKIM also inherits experience with Ka-band altimetry from the Indian-France SARAL-AltiKa mission.
|
SKIM
|
Scientific Objectives
|
The mission's science goals are to determine how the dynamics of the ocean total surface current velocity influence the integrated Earth systemmore specifically, Determine the transport by waves and currents of material at the ocean surface including plankton, nutrients, heat, carbon, oil, and marine plastic debris Map and apply currents and its components to generate better estimates of atmosphere–ocean exchanges of heat, gas, momentum and energy accounting for the full interplay between the surface ocean and the lower atmosphere (including upper ocean mixing) The satellite will overfly Earth from 83°S to 83°N, covering at least 97 percent of the globe.
|
Rydberg matter
|
Rydberg matter
|
Rydberg matter is an exotic phase of matter formed by Rydberg atoms; it was predicted around 1980 by É. A. Manykin, M. I. Ozhovan and P. P. Poluéktov. It has been formed from various elements like caesium, potassium, hydrogen and nitrogen; studies have been conducted on theoretical possibilities like sodium, beryllium, magnesium and calcium. It has been suggested to be a material that diffuse interstellar bands may arise from. Circular Rydberg states, where the outermost electron is found in a planar circular orbit, are the most long-lived, with lifetimes of up to several hours, and are the most common.
|
Rydberg matter
|
Physical
|
Rydberg matter consists of usually hexagonal planar clusters; these cannot be very big because of the retardation effect caused by the finite velocity of the speed of light. Hence, they are not gases or plasmas; nor are they solids or liquids; they are most similar to dusty plasmas with small clusters in a gas. Though Rydberg matter can be studied in the laboratory by laser probing, the largest cluster reported consists of only 91 atoms, but it has been shown to be behind extended clouds in space and the upper atmosphere of planets. Bonding in Rydberg matter is caused by delocalisation of the high-energy electrons to form an overall lower energy state. The way in which the electrons delocalise is to form standing waves on loops surrounding nuclei, creating quantised angular momentum and the defining characteristics of Rydberg matter. It is a generalised metal by way of the quantum numbers influencing loop size but restricted by the bonding requirement for strong electron correlation; it shows exchange-correlation properties similar to covalent bonding. Electronic excitation and vibrational motion of these bonds can be studied by Raman spectroscopy.
|
Rydberg matter
|
Lifetime
|
Due to reasons still debated by the physics community because of the lack of methods to observe clusters, Rydberg matter is highly stable against disintegration by emission of radiation; the characteristic lifetime of a cluster at n = 12 is 25 seconds. Reasons given include the lack of overlap between excited and ground states, the forbidding of transitions between them and exchange-correlation effects hindering emission through necessitating tunnelling that causes a long delay in excitation decay. Excitation plays a role in determining lifetimes, with a higher excitation giving a longer lifetime; n = 80 gives a lifetime comparable to the age of the Universe.
|
Rydberg matter
|
Excitations
|
In ordinary metals, interatomic distances are nearly constant through a wide range of temperatures and pressures; this is not the case with Rydberg matter, whose distances and thus properties vary greatly with excitations. A key variable in determining these properties is the principal quantum number n that can be any integer greater than 1; the highest values reported for it are around 100. Bond distance d in Rydberg matter is given by 2.9 n2a0, where a0 is the Bohr radius. The approximate factor 2.9 was first experimentally determined, then measured with rotational spectroscopy in different clusters. Examples of d calculated this way, along with selected values of the density D, are given in the adjacent table.
|
Rydberg matter
|
Condensation
|
Like bosons that can be condensed to form Bose–Einstein condensates, Rydberg matter can be condensed, but not in the same way as bosons. The reason for this is that Rydberg matter behaves similarly to a gas, meaning that it cannot be condensed without removing the condensation energy; ionisation occurs if this is not done. All solutions to this problem so far involve using an adjacent surface in some way, the best being evaporating the atoms of which the Rydberg matter is to be formed from and leaving the condensation energy on the surface. Using caesium atoms, graphite-covered surfaces and thermionic converters as containment, the work function of the surface has been measured to be 0.5 eV, indicating that the cluster is between the ninth and fourteenth excitation levels.
|
Rydberg matter
|
Disputed
|
The research claiming to create ultradense hydrogen Rydberg matter (with interatomic spacing of ~2.3pm: many orders of magnitude less than in most solid matter) is disputed:″The paper of Holmlid and Zeiner-Gundersen makes claims that would be truly revolutionary if they were true. We have shown that they violate some fundamental and very well established laws in a rather direct manner. We believe we share this scepticism with most of the scientific community. The response to the theories of Holmlid is perhaps most clearly reflected in the reference list of their article. Out of 114 references, 36 are not coauthored by Holmlid. And of these 36, none address the claims made by him and his co-authors. This is so much more remarkable because the claims, if correct, would revolutionize quantum science, add at least two new forms of hydrogen, of which one is supposedly the ground state of the element, discover an extremely dense form of matter, discover processes that violate baryon number conservation, in addition to solving humanity’s need for energy practically in perpetuity.″
|
Isotropic quadratic form
|
Isotropic quadratic form
|
In mathematics, a quadratic form over a field F is said to be isotropic if there is a non-zero vector on which the form evaluates to zero. Otherwise the quadratic form is anisotropic. More explicitly, if q is a quadratic form on a vector space V over F, then a non-zero vector v in V is said to be isotropic if q(v) = 0. A quadratic form is isotropic if and only if there exists a non-zero isotropic vector (or null vector) for that quadratic form. Suppose that (V, q) is quadratic space and W is a subspace of V. Then W is called an isotropic subspace of V if some vector in it is isotropic, a totally isotropic subspace if all vectors in it are isotropic, and an anisotropic subspace if it does not contain any (non-zero) isotropic vectors. The isotropy index of a quadratic space is the maximum of the dimensions of the totally isotropic subspaces.A quadratic form q on a finite-dimensional real vector space V is anisotropic if and only if q is a definite form: either q is positive definite, i.e. q(v) > 0 for all non-zero v in V ; or q is negative definite, i.e. q(v) < 0 for all non-zero v in V.More generally, if the quadratic form is non-degenerate and has the signature (a, b), then its isotropy index is the minimum of a and b. An important example of an isotropic form over the reals occurs in pseudo-Euclidean space.
|
Isotropic quadratic form
|
Hyperbolic plane
|
Let F be a field of characteristic not 2 and V = F2. If we consider the general element (x, y) of V, then the quadratic forms q = xy and r = x2 − y2 are equivalent since there is a linear transformation on V that makes q look like r, and vice versa. Evidently, (V, q) and (V, r) are isotropic. This example is called the hyperbolic plane in the theory of quadratic forms. A common instance has F = real numbers in which case {x ∈ V : q(x) = nonzero constant} and {x ∈ V : r(x) = nonzero constant} are hyperbolas. In particular, {x ∈ V : r(x) = 1} is the unit hyperbola. The notation ⟨1⟩ ⊕ ⟨−1⟩ has been used by Milnor and Husemoller: 9 for the hyperbolic plane as the signs of the terms of the bivariate polynomial r are exhibited.
|
Isotropic quadratic form
|
Hyperbolic plane
|
The affine hyperbolic plane was described by Emil Artin as a quadratic space with basis {M, N} satisfying M2 = N2 = 0, NM = 1, where the products represent the quadratic form.Through the polarization identity the quadratic form is related to a symmetric bilinear form B(u, v) = 1/4(q(u + v) − q(u − v)).
Two vectors u and v are orthogonal when B(u, v) = 0. In the case of the hyperbolic plane, such u and v are hyperbolic-orthogonal.
|
Isotropic quadratic form
|
Split quadratic space
|
A space with quadratic form is split (or metabolic) if there is a subspace which is equal to its own orthogonal complement; equivalently, the index of isotropy is equal to half the dimension.: 57 The hyperbolic plane is an example, and over a field of characteristic not equal to 2, every split space is a direct sum of hyperbolic planes.: 12, 3
|
Isotropic quadratic form
|
Relation with classification of quadratic forms
|
From the point of view of classification of quadratic forms, anisotropic spaces are the basic building blocks for quadratic spaces of arbitrary dimensions. For a general field F, classification of anisotropic quadratic forms is a nontrivial problem. By contrast, the isotropic forms are usually much easier to handle. By Witt's decomposition theorem, every inner product space over a field is an orthogonal direct sum of a split space and an anisotropic space.: 56
|
Isotropic quadratic form
|
Field theory
|
If F is an algebraically closed field, for example, the field of complex numbers, and (V, q) is a quadratic space of dimension at least two, then it is isotropic.
If F is a finite field and (V, q) is a quadratic space of dimension at least three, then it is isotropic (this is a consequence of the Chevalley–Warning theorem).
If F is the field Qp of p-adic numbers and (V, q) is a quadratic space of dimension at least five, then it is isotropic.
|
Integrated Encryption Scheme
|
Integrated Encryption Scheme
|
Integrated Encryption Scheme (IES) is a hybrid encryption scheme which provides semantic security against an adversary who is able to use chosen-plaintext or chosen-ciphertext attacks. The security of the scheme is based on the computational Diffie–Hellman problem.
Two variants of IES are specified: Discrete Logarithm Integrated Encryption Scheme (DLIES) and Elliptic Curve Integrated Encryption Scheme (ECIES), which is also known as the Elliptic Curve Augmented Encryption Scheme or simply the Elliptic Curve Encryption Scheme. These two variants are identical up to the change of an underlying group.
|
Integrated Encryption Scheme
|
Informal description of DLIES
|
As a brief and informal description and overview of how IES works, a Discrete Logarithm Integrated Encryption Scheme (DLIES) is used, focusing on illuminating the reader's understanding, rather than precise technical details.
|
Integrated Encryption Scheme
|
Informal description of DLIES
|
Alice learns Bob's public key gx through a public key infrastructure or some other distribution method.Bob knows his own private key x Alice generates a fresh, ephemeral value y , and its associated public value gy Alice then computes a symmetric key k using this information and a key derivation function (KDF) as follows: KDF (gxy) Alice computes her ciphertext c from her actual message m (by symmetric encryption of m ) encrypted with the key k (using an authenticated encryption scheme) as follows: c=E(k;m) Alice transmits (in a single message) both the public ephemeral gy and the ciphertext c Bob, knowing x and gy , can now compute KDF (gxy) and decrypt m from c .Note that the scheme does not provide Bob with any assurance as to who really sent the message: This scheme does nothing to stop anyone from pretending to be Alice.
|
Integrated Encryption Scheme
|
Formal description of ECIES
|
Required information To send an encrypted message to Bob using ECIES, Alice needs the following information: The cryptography suite to be used, including a key derivation function (e.g., ANSI-X9.63-KDF with SHA-1 option), a message authentication code (e.g., HMAC-SHA-1-160 with 160-bit keys or HMAC-SHA-1-80 with 80-bit keys) and a symmetric encryption scheme (e.g., TDEA in CBC mode or XOR encryption scheme) — noted E The elliptic curve domain parameters: (p,a,b,G,n,h) for a curve over a prime field or (m,f(x),a,b,G,n,h) for a curve over a binary field.
|
Integrated Encryption Scheme
|
Formal description of ECIES
|
Bob's public key KB , which Bob generates it as follows: KB=kBG , where kB∈[1,n−1] is the private key he chooses at random.
Some optional shared information: S1 and S2 O which denotes the point at infinity.
|
Integrated Encryption Scheme
|
Formal description of ECIES
|
Encryption To encrypt a message m Alice does the following: generates a random number r∈[1,n−1] and calculates R=rG derives a shared secret: S=Px , where P=(Px,Py)=rKB (and P≠O uses a KDF to derive symmetric encryption keys and MAC keys: KDF (S‖S1) encrypts the message: c=E(kE;m) computes the tag of encrypted message and S2 : MAC (kM;c‖S2) outputs R‖c‖d Decryption To decrypt the ciphertext R‖c‖d Bob does the following: derives the shared secret: S=Px , where P=(Px,Py)=kBR (it is the same as the one Alice derived because P=kBR=kBrG=rkBG=rKB ), or outputs failed if P=O derives keys the same way as Alice did: KDF (S‖S1) uses MAC to check the tag and outputs failed if MAC (kM;c‖S2) uses symmetric encryption scheme to decrypt the message m=E−1(kE;c)
|
Internal combustion engine cooling
|
Internal combustion engine cooling
|
Internal combustion engine cooling uses either air or liquid to remove the waste heat from an internal combustion engine. For small or special purpose engines, cooling using air from the atmosphere makes for a lightweight and relatively simple system. Watercraft can use water directly from the surrounding environment to cool their engines. For water-cooled engines on aircraft and surface vehicles, waste heat is transferred from a closed loop of water pumped through the engine to the surrounding atmosphere by a radiator.
|
Internal combustion engine cooling
|
Internal combustion engine cooling
|
Water has a higher heat capacity than air, and can thus move heat more quickly away from the engine, but a radiator and pumping system add weight, complexity, and cost. Higher-power engines generate more waste heat, but can move more weight, meaning they are generally water-cooled. Radial engines allow air to flow around each cylinder directly, giving them an advantage for air cooling over straight engines, flat engines, and V engines. Rotary engines have a similar configuration, but the cylinders also continually rotate, creating an air flow even when the vehicle is stationary.
|
Internal combustion engine cooling
|
Internal combustion engine cooling
|
Aircraft design more strongly favors lower weight and air-cooled designs. Rotary engines were popular on aircraft until the end of World War I, but had serious stability and efficiency problems. Radial engines were popular until the end of World War II, until gas turbine engines largely replaced them. Modern propeller-driven aircraft with internal-combustion engines are still largely air-cooled. Modern cars generally favor power over weight, and typically have water-cooled engines. Modern motorcycles are lighter than cars, and both cooling methods are common. Some sport motorcycles were cooled with both air and oil (sprayed underneath the piston heads).
|
Internal combustion engine cooling
|
Overview
|
Heat engines generate mechanical power by extracting energy from heat flows, much as a water wheel extracts mechanical power from a flow of mass falling through a distance. Engines are inefficient, so more heat energy enters the engine than comes out as mechanical power; the difference is waste heat which must be removed. Internal combustion engines remove waste heat through cool intake air, hot exhaust gasses, and explicit engine cooling.
|
Internal combustion engine cooling
|
Overview
|
Engines with higher efficiency have more energy leave as mechanical motion and less as waste heat. Some waste heat is essential: it guides heat through the engine, much as a water wheel works only if there is some exit velocity (energy) in the waste water to carry it away and make room for more water. Thus, all heat engines need cooling to operate.
|
Internal combustion engine cooling
|
Overview
|
Cooling is also needed because high temperatures damage engine materials and lubricants and becomes even more important in hot climates. Internal-combustion engines burn fuel hotter than the melting temperature of engine materials, and hot enough to set fire to lubricants. Engine cooling removes energy fast enough to keep temperatures low so the engine can survive.Some high-efficiency engines run without explicit cooling and with only incidental heat loss, a design called adiabatic. Such engines can achieve high efficiency but compromise power output, duty cycle, engine weight, durability, and emissions.
|
Internal combustion engine cooling
|
Basic principles
|
Most internal combustion engines are fluid cooled using either air (a gaseous fluid) or a liquid coolant run through a heat exchanger (radiator) cooled by air. Marine engines and some stationary engines have ready access to a large volume of water at a suitable temperature. The water may be used directly to cool the engine, but often has sediment, which can clog coolant passages, or chemicals, such as salt, that can chemically damage the engine. Thus, engine coolant may be run through a heat exchanger that is cooled by the body of water.
|
Internal combustion engine cooling
|
Basic principles
|
Most liquid-cooled engines use a mixture of water and chemicals such as antifreeze and rust inhibitors. The industry term for the antifreeze mixture is 'engine coolant'. Some antifreezes use no water at all, instead using a liquid with different properties, such as propylene glycol or a combination of propylene glycol and ethylene glycol. Most air-cooled engines use some liquid oil cooling, to maintain acceptable temperatures for both critical engine parts and the oil itself. Most liquid-cooled engines use some air cooling, with the intake stroke of air cooling the combustion chamber. An exception is Wankel engines, where some parts of the combustion chamber are never cooled by intake, requiring extra effort for successful operation.
|
Internal combustion engine cooling
|
Basic principles
|
There are many demands on a cooling system. One key requirement is to adequately serve the entire engine, as the whole engine fails if just one part overheats. Therefore, it is vital that the cooling system keep all parts at suitably low temperatures. Liquid-cooled engines are able to vary the size of their passageways through the engine block so that coolant flow may be tailored to the needs of each area. Locations with either high peak temperatures (narrow islands around the combustion chamber) or high heat flow (around exhaust ports) may require generous cooling. This reduces the occurrence of hot spots, which are more difficult to avoid with air cooling. Air-cooled engines may also vary their cooling capacity by using more closely spaced cooling fins in that area, but this can make their manufacture difficult and expensive.
|
Internal combustion engine cooling
|
Basic principles
|
Only the fixed parts of the engine, such as the block and head, are cooled directly by the main coolant system. Moving parts such as the pistons, and to a lesser extent the crankshaft and connecting rods, must rely on the lubrication oil as a coolant, or to a very limited amount of conduction into the block and thence the main coolant. High performance engines frequently have additional oil, beyond the amount needed for lubrication, sprayed upwards onto the bottom of the piston just for extra cooling. Air-cooled motorcycles often rely heavily on oil-cooling in addition to air-cooling of the cylinder barrels.
|
Internal combustion engine cooling
|
Basic principles
|
Liquid-cooled engines usually have a circulation pump. The first engines relied on thermosiphon cooling alone, where hot coolant left the top of the engine block and passed to the radiator, where it was cooled before returning to the bottom of the engine. Circulation was powered by convection alone.
Other demands include cost, weight, reliability, and durability of the cooling system itself.
|
Internal combustion engine cooling
|
Basic principles
|
Conductive heat transfer is proportional to the temperature difference between materials. If engine metal is at 250 °C and the air is at 20 °C, then there is a 230 °C temperature difference for cooling. An air-cooled engine uses all of this difference. In contrast, a liquid-cooled engine might dump heat from the engine to a liquid, heating the liquid to 135 °C (Water's standard boiling point of 100 °C can be exceeded as the cooling system is both pressurised, and uses a mixture with antifreeze) which is then cooled with 20 °C air. In each step, the liquid-cooled engine has half the temperature difference and so at first appears to need twice the cooling area.
|
Internal combustion engine cooling
|
Basic principles
|
However, properties of the coolant (water, oil, or air) also affect cooling. As example, comparing water and oil as coolants, one gram of oil can absorb about 55% of the heat for the same rise in temperature (called the specific heat capacity). Oil has about 90% the density of water, so a given volume of oil can absorb only about 50% of the energy of the same volume of water. The thermal conductivity of water is about four times that of oil, which can aid heat transfer. The viscosity of oil can be ten times greater than water, increasing the energy required to pump oil for cooling, and reducing the net power output of the engine.
|
Internal combustion engine cooling
|
Basic principles
|
Comparing air and water, air has vastly lower heat capacity per gram and per volume (4000) and less than a tenth the conductivity, but also much lower viscosity (about 200 times lower: 17.4 × 10−6 Pa·s for air vs 8.94 × 10−4 Pa·s for water).
Continuing the calculation from two paragraphs above, air cooling needs ten times of the surface area, therefore the fins, and air needs 2000 times the flow velocity and thus a recirculating air fan needs ten times the power of a recirculating water pump.
|
Internal combustion engine cooling
|
Basic principles
|
Moving heat from the cylinder to a large surface area for air cooling can present problems such as difficulties manufacturing the shapes needed for good heat transfer and the space needed for free flow of a large volume of air. Water boils at about the same temperature desired for engine cooling. This has the advantage that it absorbs a great deal of energy with very little rise in temperature (called heat of vaporization), which is good for keeping things cool, especially for passing one stream of coolant over several hot objects and achieving uniform temperature. In contrast, passing air over several hot objects in series warms the air at each step, so the first may be over-cooled and the last under-cooled. However, once water boils, it is an insulator, leading to a sudden loss of cooling where steam bubbles form. Steam may return to water as it mixes with other coolant, so an engine temperature gauge can indicate an acceptable temperature even though local temperatures are high enough that damage is being done.
|
Internal combustion engine cooling
|
Basic principles
|
An engine needs different temperatures. The inlet including the compressor of a turbo and in the inlet trumpets and the inlet valves need to be as cold as possible. A countercurrent heat exchanger with forced cooling air does the job. The cylinder-walls should not heat up the air before compression, but also not cool down the gas at the combustion. A compromise is a wall temperature of 90 °C. The viscosity of the oil is optimized for just this temperature. Any cooling of the exhaust and the turbine of the turbocharger reduces the amount of power available to the turbine, so the exhaust system is often insulated between engine and turbocharger to keep the exhaust gasses as hot as possible.
|
Internal combustion engine cooling
|
Basic principles
|
The temperature of the cooling air may range from well below freezing to 50 °C. Further, while engines in long-haul boat or rail service may operate at a steady load, road vehicles often see widely varying and quickly varying load. Thus, the cooling system is designed to vary cooling so the engine is neither too hot nor too cold. Cooling system regulation includes adjustable baffles in the air flow (sometimes called 'shutters' and commonly run by a pneumatic 'shutterstat'); a fan which operates either independently of the engine, such as an electric fan, or which has an adjustable clutch; a thermostatic valve or a thermostat that can block the coolant flow when too cool. In addition, the motor, coolant, and heat exchanger have some heat capacity which smooths out temperature increase in short sprints. Some engine controls shut down an engine or limit it to half throttle if it overheats. Modern electronic engine controls adjust cooling based on throttle to anticipate a temperature rise, and limit engine power output to compensate for finite cooling.
|
Internal combustion engine cooling
|
Basic principles
|
Finally, other concerns may dominate cooling system design. As example, air is a relatively poor coolant, but air cooling systems are simple, and failure rates typically rise as the square of the number of failure points. Also, cooling capacity is reduced only slightly by small air coolant leaks. Where reliability is of utmost importance, as in aircraft, it may be a good trade-off to give up efficiency, longevity (interval between engine rebuilds), and quietness in order to achieve slightly higher reliability; the consequences of a broken airplane engine are so severe, even a slight increase in reliability is worth giving up other good properties to achieve it.
|
Internal combustion engine cooling
|
Basic principles
|
Air-cooled and liquid-cooled engines are both used commonly. Each principle has advantages and disadvantages, and particular applications may favor one over the other. For example, most cars and trucks use liquid-cooled engines, while many small airplane and low-cost engines are air-cooled.
|
Internal combustion engine cooling
|
Generalization difficulties
|
It is difficult to make generalizations about air-cooled and liquid-cooled engines. Air-cooled diesel engines are chosen for reliability even in extreme heat, because air-cooling would be simpler and more effective at coping with the extremes of temperatures during the depths of winter and height of summer, than water cooling systems, and are often used in situations where the engine runs unattended for months at a time.Similarly, it is usually desirable to minimize the number of heat transfer stages in order to maximize the temperature difference at each stage. However, Detroit Diesel two-stroke cycle engines commonly use oil cooled by water, with the water in turn cooled by air.The coolant used in many liquid-cooled engines must be renewed periodically, and can freeze at ordinary temperatures thus causing permanent engine damage when it expands. Air-cooled engines do not require coolant service, and do not suffer damage from freezing, two commonly cited advantages for air-cooled engines. However, coolant based on propylene glycol is liquid to −55 °C, colder than is encountered by many engines; shrinks slightly when it crystallizes, thus avoiding damage; and has a service life over 10,000 hours, essentially the lifetime of many engines.
|
Internal combustion engine cooling
|
Generalization difficulties
|
It is usually more difficult to achieve either low emissions or low noise from an air-cooled engine, two more reasons most road vehicles use liquid-cooled engines. It is also often difficult to build large air-cooled engines, so nearly all air-cooled engines are under 500 kW (670 hp), whereas large liquid-cooled engines exceed 80 MW (107000 hp) (Wärtsilä-Sulzer RTA96-C 14-cylinder diesel).
|
Internal combustion engine cooling
|
Air-cooling
|
Cars and trucks using direct air cooling (without an intermediate liquid) were built over a long period from the very beginning and ending with a small and generally unrecognized technical change. Before World War II, water-cooled cars and trucks routinely overheated while climbing mountain roads, creating geysers of boiling cooling water. This was considered normal, and at the time, most noted mountain roads had auto repair shops to minister to overheating engines.
|
Internal combustion engine cooling
|
Air-cooling
|
ACS (Auto Club Suisse) maintains historical monuments to that era on the Susten Pass where two radiator refill stations remain. These have instructions on a cast metal plaque and a spherical bottom watering can hanging next to a water spigot. The spherical bottom was intended to keep it from being set down and, therefore, be useless around the house, in spite of which it was stolen, as the picture shows.
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.