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examples of exothermic reactions are combustion, precipitation and crystallization, in which ordered solids are formed from disordered gaseous or liquid phases. In contrast, in endothermic reactions, heat is consumed from the environment. This can occur by increasing the entropy of the system, often through the formati...	{ "page_id": 6271, "title": "Chemical reaction" }
other things, on the activities of the involved substances. d U = T ⋅ d S − p ⋅ d V + μ ⋅ d n {\displaystyle {d}U=T\cdot {d}S-p\cdot {d}V+\mu \cdot {d}n} U: internal energy, S: entropy, p: pressure, μ: chemical potential, n: number of molecules, d: small change sign == Kinetics == The speed at which reactions take plac...	{ "page_id": 6271, "title": "Chemical reaction" }
to promote the breaking of bonds to start the reaction. This is particularly true for reactions involving radicals. Several theories allow calculating the reaction rates at the molecular level. This field is referred to as reaction dynamics. The rate v of a first-order reaction, which could be the disintegration of a s...	{ "page_id": 6271, "title": "Chemical reaction" }
yielding one product is another way to identify a synthesis reaction. One example of a synthesis reaction is the combination of iron and sulfur to form iron(II) sulfide: 8 Fe + S 8 ⟶ 8 FeS {\displaystyle {\ce {8Fe + S8->8FeS}}} Another example is simple hydrogen gas combined with simple oxygen gas to produce a more com...	{ "page_id": 6271, "title": "Chemical reaction" }
the 2Cl− anion, giving the compounds BaSO4 and MgCl2. Another example of a double displacement reaction is the reaction of lead(II) nitrate with potassium iodide to form lead(II) iodide and potassium nitrate: Pb ( NO 3 ) 2 + 2 KI ⟶ PbI 2 ↓ + 2 KNO 3 {\displaystyle {\ce {Pb(NO3)2 + 2KI->PbI2(v) + 2KNO3}}} === Forward an...	{ "page_id": 6271, "title": "Chemical reaction" }
an element or compound reacts with an oxidant, usually oxygen, often producing energy in the form of heat or light. Combustion reactions frequently involve a hydrocarbon. For instance, the combustion of 1 mole (114 g) of octane in oxygen C 8 H 18 ( l ) + 25 2 O 2 ( g ) ⟶ 8 CO 2 + 9 H 2 O ( l ) {\displaystyle {\ce {C8H1...	{ "page_id": 6271, "title": "Chemical reaction" }
other words, the sodium lost one electron and is said to have been oxidized. On the other hand, the chlorine gas goes from an oxidation of 0 (also a pure element) to −1: the chlorine gains one electron and is said to have been reduced. Because the chlorine is the one reduced, it is considered the electron acceptor, or ...	{ "page_id": 6271, "title": "Chemical reaction" }
as the oxidizing agent. These reactions are particularly important for the production of chemical elements, such as chlorine or aluminium. The reverse process, in which electrons are released in redox reactions and chemical energy is converted to electrical energy, is possible and used in batteries. === Complexation ==...	{ "page_id": 6271, "title": "Chemical reaction" }
and conjugated base/acid are always in equilibrium. The equilibrium is determined by the acid and base dissociation constants (Ka and Kb) of the involved substances. A special case of the acid-base reaction is the neutralization where an acid and a base, taken at the exact same amounts, form a neutral salt. Acid-base r...	{ "page_id": 6271, "title": "Chemical reaction" }
the time scale of the reaction is in the correct range. Reactions at the solid\|gas interface are in some cases related to catalysis. === Photochemical reactions === In photochemical reactions, atoms and molecules absorb energy (photons) of the illumination light and convert it into an excited state. They can then relea...	{ "page_id": 6271, "title": "Chemical reaction" }
and substances that deactivate catalysts are called catalytic poisons. With a catalyst, a reaction that is kinetically inhibited by high activation energy can take place in the circumvention of this activation energy. Heterogeneous catalysts are usually solids, powdered in order to maximize their surface area. Of parti...	{ "page_id": 6271, "title": "Chemical reaction" }
with an excess of electrons and thus a negative charge or partial charge, replaces another atom or part of the "substrate" molecule. The electron pair from the nucleophile attacks the substrate forming a new bond, while the leaving group departs with an electron pair. The nucleophile may be electrically neutral or nega...	{ "page_id": 6271, "title": "Chemical reaction" }
in the so-called σ-complex, a transition state in which the aromatic system is abolished. Then, the leaving group, usually a proton, is split off and the aromaticity is restored. An alternative to aromatic substitution is electrophilic aliphatic substitution. It is similar to the nucleophilic aliphatic substitution and...	{ "page_id": 6271, "title": "Chemical reaction" }
the SN1 substitution. The E2 mechanism also requires a base, but there the attack of the base and the elimination of the leaving group proceed simultaneously and produce no ionic intermediate. In contrast to the E1 eliminations, different stereochemical configurations are possible for the reaction product in the E2 mec...	{ "page_id": 6271, "title": "Chemical reaction" }
nucleophilic addition plays an important role in the carbon-heteroatom multiple bonds, and especially its most important representative, the carbonyl group. This process is often associated with elimination so that after the reaction the carbonyl group is present again. It is, therefore, called an addition-elimination ...	{ "page_id": 6271, "title": "Chemical reaction" }
a substituted cyclohexene system. Whether a certain cycloaddition would proceed depends on the electronic orbitals of the participating species, as only orbitals with the same sign of wave function will overlap and interact constructively to form new bonds. Cycloaddition is usually assisted by light or heat. These pert...	{ "page_id": 6271, "title": "Chemical reaction" }
used to energize other reactions. Decomposition of organic material by fungi, bacteria and other micro-organisms is also within the scope of biochemistry. == Applications == Chemical reactions are central to chemical engineering, where they are used for the synthesis of new compounds from natural raw materials such as ...	{ "page_id": 6271, "title": "Chemical reaction" }
balance Microscopic reversibility Organic reaction Reaction progress kinetic analysis Reversible reaction == References == == Bibliography == Atkins, Peter W.; Julio de Paula (2006). Physical Chemistry (4th ed.). Weinheim: Wiley-VCH. ISBN 978-3-527-31546-8. Brock, William H. (1997). Viewegs Geschichte der Chemie (in Ge...	{ "page_id": 6271, "title": "Chemical reaction" }
Spectral flatness or tonality coefficient, also known as Wiener entropy, is a measure used in digital signal processing to characterize an audio spectrum. Spectral flatness is typically measured in decibels, and provides a way to quantify how much a sound resembles a pure tone, as opposed to being noise-like. == Interp...	{ "page_id": 8067200, "title": "Spectral flatness" }
the magnitude of bin number n. Note that a single (or more) empty bin yields a flatness of 0, so this measure is most useful when bins are generally not empty. The ratio produced by this calculation is often converted to a decibel scale for reporting, with a maximum of 0 dB and a minimum of −∞ dB. The spectral flatness...	{ "page_id": 8067200, "title": "Spectral flatness" }
The origin of life is an ongoing field of research that requires the study of interactions of many physical and biological processes. One of these physical processes has to do with the characteristics of the host star of a planet, and how stellar influences on an origin of life setting can dictate how life evolves, if ...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
identify exoplanets that may have the right conditions for life. Since the first discovery in 1992, more than 5000 exoplanets have been found, and a subset of these exist within the liquid water habitable zone of their host star. By experimentally estimating how much light is needed for UV photochemistry based on react...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
a lack of biogenic UV-shielding O2 and O3 present in the prebiotic atmosphere, and the fact that a younger Sun at the time had a higher fractional output of UV (see: the young sun paradox), UV is expected to have been common in the prebiotic environment. One study suggested that in the absence of O3, UV light with at w...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
are difficult to constrain due to lack of a full understanding of what the prebiotic Earth environment looked like, understanding how prebiotic chemistry might have proceeded in the presence of solar UV is one step towards a better understanding of abiogenesis. ==== Ribonucleotide synthesis ==== A key issue facing the ...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
radiation and high energy particles. Radiation can be, for example, x-ray coronal emissions or flares. The high energy particles emitted come in the forms of winds, and coronal mass ejections (CMEs). As stars evolve, so do their emissions; younger stars tend to be the most active, meaning they have stronger winds, larg...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
reduce the amount of stellar UV reaching the surface, and can act as a barrier to UV-driven prebiotic chemistry. For example, planets orbiting M dwarfs with inefficient atmospheric sinks of O2 and CO, combined with a CO2 rich atmosphere are more likely to built up UV shields such as O3 that can block the already low NU...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
being said, further work is needed in order to constrain whether shorter duration/higher intensity UV flux from a flare is even sufficient to promote prebiotic chemistry. Additionally, intense flaring events run the risk of completely ablating a planetary atmosphere, which would sterilize the surface, and effectively c...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
confined to volcanic or subsurface reservoirs. All the cons aside, planets in the habitable zones of these late-type, low mass pre-main sequence M dwarfs are still an area of focus for researchers interested in UV-driven prebiotic chemistry. ==== K-type ==== Going beyond M dwarf stars, main sequence K dwarf stars are a...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
influence UV attenuation and hence prebiotic chemistry: CO2, SO2, H2S, CH4, H2O, O2, and O3. For each of these gases, different constraints provide different estimates for their effect on UV transmission. Depending on the amount of transmission, different biologically effective doses (BEDs) of UV will be delivered to t...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
of SO2 reduce BEDs by over 60 orders of magnitude, which implies that UV-driven prebiotic chemistry might not have been sustained. === Hydrogen sulfide (H2S) === Like SO2, H2S is a strong and broad absorber of UV, and is primarily generated through volcanic outgassing. As a result of its vulnerability to atmospheric lo...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
the atmosphere. At such high levels, O2 may start to have a noticeable effect on UV transmission, but at abiogenesis it is unlikely that high levels were achieved given a strong reducing sink from volcanogenic gases, and a lack of a strong source. === Ozone (O3) === Ozone is a well known greenhouse gas that acts as a s...	{ "page_id": 75438211, "title": "Stellar influences on an origin of life setting" }
Selenoxide elimination (also called α-selenation) is a method for the chemical synthesis of alkenes from selenoxides. It is most commonly used to synthesize α,β-unsaturated carbonyl compounds from the corresponding saturated analogues. It is mechanistically related to the Cope reaction. == Mechanism and stereochemistry...	{ "page_id": 15865988, "title": "Selenoxide elimination" }
Scope and limitations == === Selanylating and oxidizing reagents === α-Selanylation of carbonyl compounds can be accomplished with electrophilic or nucleophilic selanylating reagents. Usually, simple phenylseleno compounds are used in elimination reactions; although 2-nitrophenylselenides react more quickly, they are m...	{ "page_id": 15865988, "title": "Selenoxide elimination" }
chloride. Hydrochloric acid generated during the selanylation of transient enol catalyzes tautomerization. (8) The seleno-Pummerer reaction is a significant side reaction that may occur under conditions when acid is present. Protonation of the selenoxide intermediate, followed by elimination of hydroxide and hydrolysis...	{ "page_id": 15865988, "title": "Selenoxide elimination" }
The molecular formula C9H19NO2 (molar mass: 173.25 g/mol, exact mass: 173.1416 u) may refer to: Imagabalin 4-Methylpregabalin	{ "page_id": 35592328, "title": "C9H19NO2" }
The molecular formula C18H20N2O3 (molar mass: 312.36 g/mol) may refer to: 25CN-NBOH ZK-93426 (ethyl-5-isopropoxy-4-methyl-beta-carboline-3-carboxylate)	{ "page_id": 24385673, "title": "C18H20N2O3" }
Slipperiness is when a surface has a low coefficient of friction, allowing objects to glide across the surface. People walking on slippery surfaces are likely to slip or fall. A surface can for example be slippery due to it being wet, or due to it being icy. There are several competing theories about why ice is slipper...	{ "page_id": 55187592, "title": "Slipperiness" }
Oxynitrilase may refer to: (S)-hydroxynitrile lyase, an enzyme Hydroxymandelonitrile lyase, an enzyme	{ "page_id": 39458955, "title": "Oxynitrilase" }
The Babler oxidation, also known as the Babler-Dauben oxidation, is an organic reaction for the oxidative transposition of tertiary allylic alcohols to enones using pyridinium chlorochromate (PCC): It is named after James Babler who first reported the reaction in 1976 and William Dauben who extended the scope to cyclic...	{ "page_id": 67246222, "title": "Babler oxidation" }
Commonly reported stoichiometric reagents for this purpose include di-tert-butyl peroxide, 2-iodoxybenzoic acid or periodates. == Secondary alcohols == The Babler-Dauben oxidation of secondary allylic alcohols proves more difficult to control than that of tertiary analogues, as along with the desired product (a) a mixt...	{ "page_id": 67246222, "title": "Babler oxidation" }
== List of useful microorganisms used in preparation of food and beverage == == See also == Fermentation (food) Food microbiology == References ==	{ "page_id": 35133583, "title": "List of microorganisms used in food and beverage preparation" }
Soumia Fahd is a Moroccan herpetologist at Abdelmalek Essaâdi University in Tétouan. == Life and work == In high school, Fahd studied experimental sciences. For her BSc, she studied Industrial Engineering at the University of Mons (Belgium). She then returned to Morocco to study biology at the Mohammed V University and...	{ "page_id": 70260880, "title": "Soumia Fahd" }
"Phylogeography and ecological niche modeling unravel the evolutionary history of the African green toad, Bufotes boulengeri boulengeri (Amphibia: Bufonidae), through the Quaternary". Journal of Zoological Systematics and Evolutionary Research 56 (1): 102–116. Chergui B, Fahd S, Santos X, Pausas JG (2018). "Socioeconom...	{ "page_id": 70260880, "title": "Soumia Fahd" }
6-Phosphogluconic acid (with conjugate base 6-phosphogluconate) is a phosphorylated sugar acid which appears in the pentose phosphate pathway and the Entner–Doudoroff pathway. During the oxidative phase of the pentose phosphate pathway, it is formed from 6-phosphogluconolactone by 6-phosphogluconolactonase, and in turn...	{ "page_id": 10426512, "title": "6-Phosphogluconic acid" }
The molecular formula C18H19N3O3 may refer to: Ainuovirine RH-34	{ "page_id": 75962511, "title": "C18H19N3O3" }
A series of biochemical switches control transitions between and within the various phases of the cell cycle. The cell cycle is a series of complex, ordered, sequential events that control how a single cell divides into two cells, and involves several different phases. The phases include the G1 and G2 phases, DNA repli...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
leads to its own inhibition through upstream elements, this is canonically negative feedback (red blunt arrow). A negative feedback loop is also known as a balancing loop, and it may be common to see oscillations in which a delayed negative feedback signal is used to maintain homeostatic balance in the system. Feedback...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
Km), known as the Hill equation, when n, the Hill coefficient, is more than 1. The steepness of the sigmoidal curve depends on the value of n. A value of n = 1 produces a hyperbolic or Michaelian response. Ultrasensitivity is achieved in a variety of systems; a notable example is the cooperative binding of the enzyme h...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
a robust reversible switch because it is harder for the system to transition between ‘on’ and ‘off’ states (compared to the equivalent monostable ultrasensitive response). The system could also be poised such that one of the transitions is physically unattainable; for example, no amount of reduction in the stimulus wil...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
preventing it from inhibiting SBF and MBF. Active SBF/MBF drive the G1/S transition by turning on the B-type cyclins and initiating DNA replication, bud formation and spindle body duplication. Moreover, SBF/MBF drives expression of Cln1 and Cln2, which can also interact with Cdk1 to promote phosphorylation of its targe...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
serves as an on/off switch for the cell cycle. Once Rb is phosphorylated, the inhibition is released on the E2F transcriptional activity. This allows for the transcription of S phase genes encoding for proteins that amplify the G1 to S phase switch. Many different stimuli apply checkpoint controls including TGFb, DNA d...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
line in 1998 that it is the spatial location of cyclin B within the cell that initiates mitosis. Known from previous experiments in both human cells and starfish oocytes, Jin et al. summarize that cyclin B1 is abundant in the cytoplasm during non-dividing phases of mitosis, but is identified in the nucleus, in complex ...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
circumstances, don't divide when their genetic information is damaged, but will enter mitosis if endogenous cyclin B is expressed in the nucleus, it is likely that the translocation of the cyclin B to the cytoplasm is a mechanism that prevents immature mitotic entry. This hypothesis was further supported by Jin et al.’...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
translocation to the nucleus. To begin to investigate this, they first reconfirmed some of the results of the Jin et al. experiments, utilizing immunofluorescence to show cyclin B in the cytoplasm prior to division, and translocation to the nucleus to initiate mitosis, which they operationalized by comparing relative t...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
times more favorable in the nucleus than in the cytoplasm, due to the smaller overall volume of the nucleus, allowing a faster phosphorylation rate. The increased translocation due to phosphorylation and increased phosphorylation due to translocation exemplify the positive feedback loop that resembles that previously d...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
cytoplasmic extracts of Xenopus oocytes. They first demonstrated a discontinuous sharp response of Cdk1 to changing concentrations of non-destructible Cyclin B (to decouple the Cdk1 response network from APC-mediated negative feedback). However, such a response would be consistent with both a monostable, ultrasensitive...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
arrive at this conclusion, cytostatic factor released extracts were supplemented with CHX, APH (a DNA polymerase inhibitor), or both, and non-degradable cyclin B was added. The third and last prediction that was tested and proven true in this article was that the rate of Cdc2 activation slows down near the activation t...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
cell strains were arrested in G1 with an alpha factor. These cells stayed in arrest during the development. Esp1-1 mutant cells were used and the experiment was repeated, and Scc1 successfully bound to the chromosomes and remained associated even after the synthesis was terminated. This was crucial in showing that with...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
microtubules, and pronounced outgrowth of astral (non-kinetochore) microtubules. For a normal eukaryotic cell, mitotic exit is irreversible. === Proteolytic degradation === Many speculations were made with regard to the control mechanisms employed by a cell to promote the irreversibility of mitotic exit in a eukaryotic...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
budding yeast cells with cdc28-as1, an INM-PP1 (ATP analog)-sensitive Cdk allele, proved that destruction of B-type cyclins (Clb) is not necessary for triggering irreversible mitotic exit. Clb2 degradation did shorten the Cdk1-inhibition period required for triggering irreversible mitotic exit indicating that cyclin pr...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
regulating eukaryotic cell cycle by inhibiting the activity of CDKs. === Dynamical systems approach === Because eukaryotic cell cycle involves a variety of proteins and regulatory interactions, dynamical systems approach can be taken to simplify a complex biological circuit into a general framework for better analysis....	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
transition and Sic1 level can be represented as a diagram of two saddle-node bifurcations in which the system's behavior changes qualitatively with a small change in control parameter, the amount of Sic1. === Systems-level feedback === Because the behavior of cell cycle critically depends on the amount of Sic1 at the M...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
entry into anaphase and B-type cyclin degradations. In addition, when mitotic spindles are misaligned, MEN and subsequently Cdc14 are inhibited in a Bub2 and Bfa1-dependent manner to prevent degradation of mitotic cyclins and anaphase entry. Sic1 is a nice example demonstrating how systems-level feedbacks interact to s...	{ "page_id": 25368725, "title": "Biochemical switches in the cell cycle" }
An excimer (originally short for excited dimer) is a short-lived polyatomic molecule formed from two species that do not form a stable molecule in the ground state. In this case, formation of molecules is possible only if such atom is in an electronic excited state. Heteronuclear molecules and molecules that have more ...	{ "page_id": 268438, "title": "Excimer" }
with an unexcited monomer to form an excimer. == Usage note == The term excimer (excited state dimer) is, strictly speaking, limited to cases in which a true dimer is formed; that is, both components of the dimer are the same molecule or atom. The term exciplex refers to the heterodimeric case; however, common usage ex...	{ "page_id": 268438, "title": "Excimer" }
the lowest excited electronic state, which provides the formation of an excimer molecule. The most convenient way to excite gases is by an electric discharge. That is why such excimer molecules are generated in a plasma (see excimer molecule formation) or through high energy electron beams. == Fluorescence quenching ==...	{ "page_id": 268438, "title": "Excimer" }
Gold iodide is the chemical compound with the formula AuI3. Although Au2I6 is predicted to be stable, gold(III) iodide remains an example of a nonexistent or unstable compound. Attempts to isolate pure samples result in the formation of gold(I) iodide and iodine: AuI3 → AuI + I2 == References ==	{ "page_id": 36182167, "title": "Gold(III) iodide" }
Evolutionary tinkering is an explanation of how evolution happens in nature. It explains that evolution works as a tinkerer who experiments with miscellaneous items, unsure of the outcome, and utilizes whatever is available to craft functional objects whose utility may only become evident later. None of the materials s...	{ "page_id": 76880025, "title": "Evolutionary tinkering" }
Monod also won the Nobel Prize in 1965 for his work on the lac operon. == Engineering versus tinkering == Natural selection is frequently likened to the work of an engineer, yet this analogy falls short. Unlike the engineer who operates based on meticulous planning and a clear vision of the end product, evolution lacks...	{ "page_id": 76880025, "title": "Evolutionary tinkering" }
wing. It involved adding new structures, particularly the neocortex, onto older ones. This rapid evolution led to a division between the neocortex, responsible for intellectual functions, and the older structures, controlling emotional and visceral activities. These older structures lack the discriminative and symbolic...	{ "page_id": 76880025, "title": "Evolutionary tinkering" }
can result in molecular and phenotypic novelty, primarily by taking apart the Lego blocks of proteins and putting them together again in unique patterns. Generally, these processes add to the organizational complexity of the genome, the proteome, or both. === Internal gene duplication === There are several forms of gen...	{ "page_id": 76880025, "title": "Evolutionary tinkering" }
interactions. One example of novelty associated with domain shuffling is multicellularity. Gene fusion (the creation of a fusion gene by joining two genes together) and gene fission or fragmentation, which results in splitting one gene with many domains into multiple smaller genes, are the other two molecular mechanism...	{ "page_id": 76880025, "title": "Evolutionary tinkering" }
due to its often deleterious nature. In the rare case that gene loss becomes fixed in a population, it is difficult to definitively say what was the cause. == References ==	{ "page_id": 76880025, "title": "Evolutionary tinkering" }
Optics began with the development of lenses by the ancient Egyptians and Mesopotamians, followed by theories on light and vision developed by ancient Greek philosophers, and the development of geometrical optics in the Greco-Roman world. The word optics is derived from the Greek term τα ὀπτικά meaning 'appearance, look...	{ "page_id": 2627738, "title": "History of optics" }
apparent shapes of cylinders and cones when viewed from different angles. Pappus believed these results to be important in astronomy and included Euclid's Optics, along with his Phaenomena, in the Little Astronomy, a compendium of smaller works to be studied before the Syntaxis (Almagest) of Ptolemy. In 55 BC, Lucretiu...	{ "page_id": 2627738, "title": "History of optics" }
Those things seen by a higher ray, appear higher. Right and left rays appear right and left. Things seen within several angles appear clearer. Euclid did not define the physical nature of these visual rays but, using the principles of geometry, he discussed the effects of perspective and the rounding of things seen at ...	{ "page_id": 2627738, "title": "History of optics" }
earliest important optical writers in the Islamic world. In a work known in the west as De radiis stellarum, al-Kindi developed a theory "that everything in the world ... emits rays in every direction, which fill the whole world." This theory of the active power of rays had an influence on later scholars such as Ibn al...	{ "page_id": 2627738, "title": "History of optics" }
was called "the father of modern optics". Avicenna (980–1037) agreed with Alhazen that the speed of light is finite, as he "observed that if the perception of light is due to the emission of some sort of particles by a luminous source, the speed of light must be finite." Abū Rayhān al-Bīrūnī (973-1048) also agreed that...	{ "page_id": 2627738, "title": "History of optics" }
to apply mathematics and the Platonic metaphor of light in many of his writings. He has been credited with discussing light from four different perspectives: an epistemology of light, a metaphysics or cosmogony of light, an etiology or physics of light, and a theology of light. Setting aside the issues of epistemology ...	{ "page_id": 2627738, "title": "History of optics" }
upon nearby objects suited to receive those species. Note that Bacon's optical use of the term species differs significantly from the genus/species categories found in Aristotelian philosophy. Several later works, including the influential A Moral Treatise on the Eye (Latin: Tractatus Moralis de Oculo) by Peter of Limo...	{ "page_id": 2627738, "title": "History of optics" }
solar eclipses presented unexplained phenomena, such as unexpected shadow sizes, the red color of a total lunar eclipse, and the reportedly unusual light surrounding a total solar eclipse. Related issues of atmospheric refraction applied to all astronomical observations. Through most of 1603, Kepler paused his other wo...	{ "page_id": 2627738, "title": "History of optics" }
its properties by separating out a coloured beam and shining it on various objects. Newton noted that regardless of whether it was reflected or scattered or transmitted, it stayed the same colour. Thus, he observed that colour is the result of objects interacting with already-coloured light rather than objects generati...	{ "page_id": 2627738, "title": "History of optics" }
the development of early tunable lasers. === Diffractive optics === The effects of diffraction of light were carefully observed and characterized by Francesco Maria Grimaldi, who also coined the term diffraction, from the Latin diffringere, 'to break into pieces', referring to light breaking up into different direction...	{ "page_id": 2627738, "title": "History of optics" }
to have watched the gladiatorial games using an emerald as a corrective lens. Ibn al-Haytham (Alhacen) wrote about the effects of pinhole, concave lenses, and magnifying glasses in his 11th century Book of Optics (1021 CE). The English friar Roger Bacon, during the 1260s or 1270s, wrote works on optics, partly based on...	{ "page_id": 2627738, "title": "History of optics" }
was invented in 1590 by Zacharias Janssen and/or his father, Hans Martens, claims it was invented by rival spectacle maker, Hans Lippershey, and claims it was invented by expatriate Cornelis Drebbel who was noted to have a version in London in 1619. Galileo Galilei (also sometimes cited as a compound microscope invento...	{ "page_id": 2627738, "title": "History of optics" }
This changed with the invention of the maser in 1953 and the laser in 1960. Laser science—research into principles, design and application of these devices—became an important field, and the quantum mechanics underlying the laser's principles was studied now with more emphasis on the properties of light, and the name q...	{ "page_id": 2627738, "title": "History of optics" }
The latter are of much interest in quantum information theory, a subject which partly emerged from quantum optics, partly from theoretical computer science. Today's fields of interest among quantum optics researchers include parametric down-conversion, parametric oscillation, even shorter (attosecond) light pulses, use...	{ "page_id": 2627738, "title": "History of optics" }
Note by Note cuisine is a style of cooking based on molecular gastronomy, created by French chemist Hervé This. Dishes are made using pure compounds instead of using animal or plant tissues. This said the cuisine is like "a painter using primary colours, or a musician composing electroacoustic music, wave by wave, usin...	{ "page_id": 41031835, "title": "Note by Note cuisine" }
Sexually reproducing animals, plants, fungi and protists are thought to have evolved from a common ancestor that was a single-celled eukaryotic species. Sexual reproduction is widespread in eukaryotes, though a few eukaryotic species have secondarily lost the ability to reproduce sexually, such as Bdelloidea, and some ...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
a population. Sexual reproduction therefore must offer significant fitness advantages because, despite the two-fold cost of sex (see below), it dominates among multicellular forms of life, implying that the fitness of offspring produced by sexual processes outweighs the costs. Sexual reproduction derives from recombina...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
of these phenomena, all of the existing forms of reproduction can be classified as asexual, hermaphrodite or dioecious. The sexual process and sexual differentiation are different phenomena, and, in essence, are diametrically opposed. The first creates (increases) diversity of genotypes, and the second decreases it by ...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
among relatives. For the advantage due to DNA repair, there is an immediate large benefit of removing DNA damage by recombinational DNA repair during meiosis (assuming the initial mutation rate is higher than optimal), since this removal allows greater survival of progeny with undamaged DNA. The advantage of complement...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
different loci on a chromosome in different members of the population, a chromosome containing the two advantageous alleles can be produced within a few generations by recombination. However, should the same two alleles arise in different members of an asexual population, the only way that one chromosome can develop th...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
H, conferring two types of parasite resistance, such that parasites with allele p can attach themselves to hosts with the allele h, and P to H. Such a situation will lead to cyclic changes in allele frequency – as p increases in frequency, h will be disfavoured. In reality, there will be several genes involved in the r...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
in asexuals sharing the same habitat. In 2011, researchers used the microscopic roundworm Caenorhabditis elegans as a host and the pathogenic bacteria Serratia marcescens to generate a host-parasite coevolutionary system in a controlled environment, allowing them to conduct more than 70 evolution experiments testing th...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
sexually when weighed against the relative advantages of alternative forms of reproduction, such as asexual reproduction. Thus, because sexual reproduction abounds in complex multicellular life, there must be some significant benefit(s) to sex and sexual reproduction that compensates for these fundamental disadvantages...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
members of the species are capable of bearing offspring. The two-fold reproductive disadvantage assumes that males contribute only genes to their offspring and sexual females spend half their reproductive potential on sons. Thus, in this formulation, the principal cost of sex is that males and females must successfully...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
sexes reproduce during the haploid and diploid stages of their life cycle and have a 100% chance of passing their genes into their offspring. Some species avoid the 50% cost of sexual reproduction, although they have "sex" (in the sense of genetic recombination). In these species (e.g., bacteria, ciliates, dinoflagella...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
It is effective against many different types of genomic damage, and in particular is highly efficient at overcoming double-strand damages. Studies of the mechanism of meiotic recombination indicate that meiosis is an adaptation for repairing DNA. These considerations form the basis for the first part of the repair and ...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }
by-product. This lesser informational noise generates genetic variation, viewed by some as the major effect of sex, as discussed in the earlier parts of this article. == Deleterious mutation clearance == Mutations can have many different effects upon an organism. It is generally believed that the majority of non-neutra...	{ "page_id": 661661, "title": "Evolution of sexual reproduction" }

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