text:
Depth-first search

Depth-first search (DFS) is an algorithm for traversing or searching tree or graph data structures. The algorithm starts at the root node (selecting some arbitrary node as the root node in the case of a graph) and explores as far as possible along each branch before backtracking. Extra memory, usually a stack, is needed to keep track of the nodes discovered so far along a specified branch which helps in backtracking of the graph.

A version of depth-first search was investigated in the 19th century by French mathematician Charles Pierre Trémaux as a strategy for solving mazes.

Properties
The time and space analysis of DFS differs according to its application area. In theoretical computer science, DFS is typically used to traverse an entire graph, and takes time V where $$|V|$$ is the number of vertices and $$|E|$$ the number of  edges. This is linear in the size of the graph. In these applications it also uses space $$O(|V|)$$ in the worst case to store the stack of vertices on the current search path as well as the set of already-visited vertices. Thus, in this setting, the time and space bounds are the same as for breadth-first search and the choice of which of these two algorithms to use depends less on their complexity and more on the different properties of the vertex orderings the two algorithms produce.

For applications of DFS in relation to specific domains, such as searching for solutions in artificial intelligence or web-crawling, the graph to be traversed is often either too large to visit in its entirety or infinite (DFS may suffer from non-termination). In such cases, search is only performed to a limited depth; due to limited resources, such as memory or disk space, one typically does not use data structures to keep track of the set of all previously visited vertices. When search is performed to a limited depth, the time is still linear in terms of the number of expanded vertices and edges (although this number is not the same as the size of the entire graph because some vertices may be searched more than once and others not at all) but the space complexity of this variant of DFS is only proportional to the depth limit, and as a result, is much smaller than the space needed for searching to the same depth using breadth-first search. For such applications, DFS also lends itself much better to heuristic methods for choosing a likely-looking branch. When an appropriate depth limit is not known a priori, iterative deepening depth-first search applies DFS repeatedly with a sequence of increasing limits. In the artificial intelligence mode of analysis, with a branching factor greater than one, iterative deepening increases the running time by only a constant factor over the case in which the correct depth limit is known due to the geometric growth of the number of nodes per level.

DFS may also be used to collect a sample of graph nodes. However, incomplete DFS, similarly to incomplete BFS, is biased towards nodes of high degree.

Example
For the following graph:

a depth-first search starting at the node A, assuming that the left edges in the shown graph are chosen before right edges, and assuming the search remembers previously visited nodes and will not repeat them (since this is a small graph), will visit the nodes in the following order: A, B, D, F, E, C, G. The edges traversed in this search form a Trémaux tree, a structure with important applications in graph theory. Performing the same search without remembering previously visited nodes results in visiting the nodes in the order A, B, D, F, E, A, B, D, F, E, etc. forever, caught in the A, B, D, F, E cycle and never reaching C or G.

Iterative deepening is one technique to avoid this infinite loop and would reach all nodes.

Output of a depth-first search
The result of a depth-first search of a graph can be conveniently described in terms of a spanning tree of the vertices reached during the search. Based on this spanning tree, the edges of the original graph can be divided into three classes: forward edges, which point from a node of the tree to one of its descendants, back edges, which point from a node to one of its ancestors, and cross edges, which do neither. Sometimes tree edges, edges which belong to the spanning tree itself, are classified separately from forward edges. If the original graph is undirected then all of its edges are tree edges or back edges.

Vertex orderings
It is also possible to use depth-first search to linearly order the vertices of a graph or tree. There are four possible ways of doing this:

 * A preordering is a list of the vertices in the order that they were first visited by the depth-first search algorithm. This is a compact and natural way of describing the progress of the search, as was done earlier in this article. A preordering of an expression tree is the expression in Polish notation.
 * A postordering is a list of the vertices in the order that they were last visited by the algorithm. A postordering of an expression tree is the expression in reverse Polish notation.
 * A reverse preordering is the reverse of a preordering, i.e. a list of the vertices in the opposite order of their first visit. Reverse preordering is not the same as postordering.
 * A reverse postordering is the reverse of a postordering, i.e. a list of the vertices in the opposite order of their last visit. Reverse postordering is not the same as preordering.

For binary trees there is additionally in-ordering and reverse in-ordering.

For example, when searching the directed graph below beginning at node A, the sequence of traversals is either A B D B A C A or A C D C A B A (choosing to first visit B or C from A is up to the algorithm). Note that repeat visits in the form of backtracking to a node, to check if it has still unvisited neighbors, are included here (even if it is found to have none). Thus the possible preorderings are A B D C and A C D B, while the possible postorderings are D B C A and D C B A, and the possible reverse postorderings are A C B D and A B C D.

 * If-then-else-control-flow-graph.svg

Reverse postordering produces a topological sorting of any directed acyclic graph. This ordering is also useful in control-flow analysis as it often represents a natural linearization of the control flows. The graph above might represent the flow of control in the code fragment below, and it is natural to consider this code in the order A B C D or A C B D but not natural to use the order A B D C or A C D B.

if (A) then { B } else { C } D

Pseudocode
A recursive implementation of DFS: procedure DFS(G, v) is label v as discovered for all directed edges from v to w that are in G.adjacentEdges(v) do if vertex w is not labeled as discovered then recursively call DFS(G, w)

A non-recursive implementation of DFS with worst-case space complexity $$O(|E|)$$, with the possibility of duplicate vertices on the stack: procedure DFS_iterative(G, v) is let S be a stack S.push(v) while S is not empty do v = S.pop if v is not labeled as discovered then label v as discovered for all edges from v to w in G.adjacentEdges(v) do S.push(w) These two variations of DFS visit the neighbors of each vertex in the opposite order from each other: the first neighbor of v visited by the recursive variation is the first one in the list of adjacent edges, while in the iterative variation the first visited neighbor is the last one in the list of adjacent edges. The recursive implementation will visit the nodes from the example graph in the following order: A, B, D, F, E, C, G. The non-recursive implementation will visit the nodes as: A, E, F, B, D, C, G.

The non-recursive implementation is similar to breadth-first search but differs from it in two ways: If $G$ is a tree, replacing the queue of the breadth-first search algorithm with a stack will yield a depth-first search algorithm. For general graphs, replacing the stack of the iterative depth-first search implementation with a queue would also produce a breadth-first search algorithm, although a somewhat nonstandard one.
 * 1) it uses a stack instead of a queue, and
 * 2) it delays checking whether a vertex has been discovered until the vertex is popped from the stack rather than making this check before adding the vertex.

Another possible implementation of iterative depth-first search uses a stack of iterators of the list of neighbors of a node, instead of a stack of nodes. This yields the same traversal as recursive DFS. procedure DFS_iterative(G, v) is let S be a stack label v as discovered S.push(iterator of G.adjacentEdges(v)) while S is not empty do if S.peek.hasNext then w = S.peek.next if w is not labeled as discovered then label w as discovered S.push(iterator of G.adjacentEdges(w)) else S.pop

Applications
Algorithms that use depth-first search as a building block include:
 * Finding connected components.
 * Topological sorting.
 * Finding 2-(edge or vertex)-connected components.
 * Finding 3-(edge or vertex)-connected components.
 * Finding the bridges of a graph.
 * Generating words in order to plot the limit set of a group.
 * Finding strongly connected components.
 * Determining whether a species is closer to one species or another in a phylogenetic tree.
 * Planarity testing.
 * Solving puzzles with only one solution, such as mazes. (DFS can be adapted to find all solutions to a maze by only including nodes on the current path in the visited set.)
 * Maze generation may use a randomized DFS.
 * Finding biconnectivity in graphs.
 * Succession to the throne shared by the Commonwealth realms.

Complexity
The computational complexity of DFS was investigated by John Reif. More precisely, given a graph $$G$$, let $$O=(v_1,\dots,v_n)$$ be the ordering computed by the standard recursive DFS algorithm. This ordering is called the lexicographic depth-first search ordering. John Reif considered the complexity of computing the lexicographic depth-first search ordering, given a graph and a source. A decision version of the problem (testing whether some vertex $u$ occurs before some vertex $v$ in this order) is P-complete, meaning that it is "a nightmare for parallel processing".

A depth-first search ordering (not necessarily the lexicographic one), can be computed by a randomized parallel algorithm in the complexity class RNC. As of 1997, it remained unknown whether a depth-first traversal could be constructed by a deterministic parallel algorithm, in the complexity class NC.

title: Depth-first search


text:
Sutech

Sutech can mean
 * Shiraz University of Technology - a university in Shiraz, Iran
 * SUTECH - Somaliland University of Technology, Hargeisa, Somaliland
 * Set (mythology), an ancient Egyptian god of strength, violence, and disorder

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Sutech


text:
Sutekh (musician)

Sutekh, the alias of Seth Joshua Horvitz, is a music composer and performer of experimental electronic and techno music. He has released on several international record labels such as Mille Plateaux, Plug Research, Soul Jazz, Leaf, Kit Clayton's Orthlorng Musork and his own Context Free Media.

He performed under the name Moron together with Safety Scissors, with whom he shared a flat in Oakland in 1997. Along with Kit Clayton, the three released two albums as Pigeon Funk (the second one without Safety Scissors). He has also performed and recorded under the names Rrose and Suite K.

Horvitz was born in 1973 and grew up in Venice Beach. He holds a BA in Cognitive Science from the University of California at Berkeley (1995) and an MFA in Electronic Music and Recording Media from Mills College (2010).

Albums

 * Periods.Make.Sense (2000), Force Inc. Music Works
 * Deadpan Escapement: Reconstructed with Twerk (2000), Context Free Media
 * Fell (2002), Orthlorng Musork
 * Incest Live (2002), Force Inc. Music Works
 * On Bach (2010), Creaked Records

title: Sutekh (musician)


text:
Succinic acid

Succinic acid  is a dicarboxylic acid with the chemical formula (CH2)2(CO2H)2. In living organisms, succinic acid takes the form of an anion, succinate, which has multiple biological roles as a metabolic intermediate being converted into fumarate by the enzyme succinate dehydrogenase in complex 2 of the electron transport chain which is involved in making ATP, and as a signaling molecule reflecting the cellular metabolic state.

Succinate is generated in mitochondria via the tricarboxylic acid (TCA) cycle. Succinate can exit the mitochondrial matrix and function in the cytoplasm as well as the extracellular space, changing gene expression patterns, modulating epigenetic landscape or demonstrating hormone-like signaling. As such, succinate links cellular metabolism, especially ATP formation, to the regulation of cellular function.

Dysregulation of succinate synthesis, and therefore ATP synthesis, happens in some genetic mitochondrial diseases, such as Leigh syndrome, and Melas syndrome, and degradation can lead to pathological conditions, such as malignant transformation, inflammation and tissue injury.

Succinic acid is marketed as food additive E363. The name derives from Latin succinum, meaning amber.

Physical properties
Succinic acid is a white, odorless solid with a highly acidic taste. In an aqueous solution, succinic acid readily ionizes to form its conjugate base, succinate. As a diprotic acid, succinic acid undergoes two successive deprotonation reactions:
 * (CH2)2(CO2H)2 →   (CH2)2(CO2H)(CO2)−  +  H+
 * (CH2)2(CO2H)(CO2)− →  (CH2)2(CO2)22−  +  H+

The pKa of these processes are 4.3 and 5.6, respectively. Both anions are colorless and can be isolated as the salts, e.g., Na(CH2)2(CO2H)(CO2) and Na2(CH2)2(CO2)2. In living organisms, primarily succinate, not succinic acid, is found.

As a radical group it is called a succinyl group.

Like most simple mono- and dicarboxylic acids, it is not harmful but can be an irritant to skin and eyes.

Commercial production
Historically, succinic acid was obtained from amber by distillation and has thus been known as spirit of amber. Common industrial routes include hydrogenation of maleic acid, oxidation of 1,4-butanediol, and carbonylation of ethylene glycol. Succinate is also produced from butane via maleic anhydride. Global production is estimated at 16,000 to 30,000 tons a year, with an annual growth rate of 10%.

Genetically engineered Escherichia coli and Saccharomyces cerevisiae are proposed for the commercial production via fermentation of glucose.

Chemical reactions
Succinic acid can be dehydrogenated to fumaric acid or be converted to diesters, such as diethylsuccinate (CH2CO2CH2CH3)2. This diethyl ester is a substrate in the Stobbe condensation. Dehydration of succinic acid gives succinic anhydride. Succinate can be used to derive 1,4-butanediol, maleic anhydride, succinimide, 2-pyrrolidinone and tetrahydrofuran.

Applications
In 2004, succinate was placed on the US Department of Energy's list of top 12 platform chemicals from biomass.

Precursor to polymers, resins, and solvents
Succinic acid is a precursor to some polyesters and a component of some alkyd resins. 1,4-Butanediol (BDO) can be synthesized using succinic acid as a precursor. The automotive and electronics industries heavily rely on BDO to produce connectors, insulators, wheel covers, gearshift knobs and reinforcing beams. Succinic acid also serves as the bases of certain biodegradable polymers, which are of interest in tissue engineering applications.

Acylation with succinic acid is called succination. Oversuccination occurs when more than one succinate adds to a substrate.

Food and dietary supplement
As a food additive and dietary supplement, succinic acid is generally recognized as safe by the U.S. Food and Drug Administration. Succinic acid is used primarily as an acidity regulator in the food and beverage industry. It is also available as a flavoring agent, contributing a somewhat sour and astringent component to umami taste. As an excipient in pharmaceutical products, it is also used to control acidity or as a counter ion. Drugs involving succinate include metoprolol succinate, sumatriptan succinate, Doxylamine succinate or solifenacin succinate.

Tricarboxylic acid (TCA) cycle
Succinate is a key intermediate in the tricarboxylic acid cycle, a primary metabolic pathway used to produce chemical energy in the presence of O2. Succinate is generated from succinyl-CoA by the enzyme succinyl-CoA synthetase in a GTP/ATP-producing step:

Succinyl-CoA + NDP + Pi → Succinate + CoA + NTP

Catalyzed by the enzyme succinate dehydrogenase (SDH), succinate is subsequently oxidized to fumarate:

Succinate + FAD → Fumarate + FADH2

SDH also participates in the mitochondrial electron transport chain, where it is known as respiratory complex II. This enzyme complex is a 4 subunit membrane-bound lipoprotein which couples the oxidation of succinate to the reduction of ubiquinone via the intermediate electron carriers FAD and three 2Fe-2S clusters. Succinate thus serves as a direct electron donor to the electron transport chain, and itself is converted into fumarate.

Reductive branch of the TCA cycle
Succinate can alternatively be formed by reverse activity of SDH. Under anaerobic conditions certain bacteria such as A. succinogenes, A. succiniciproducens and M. succiniciproducens, run the TCA cycle in reverse and convert glucose to succinate through the intermediates of oxaloacetate, malate and fumarate. This pathway is exploited in metabolic engineering to net generate succinate for human use. Additionally, succinic acid produced during the fermentation of sugar provides a combination of saltiness, bitterness and acidity to fermented alcohols.

Accumulation of fumarate can drive the reverse activity of SDH, thus enhancing succinate generation. Under pathological and physiological conditions, the malate-aspartate shuttle or the purine nucleotide shuttle can increase mitochondrial fumarate, which is then readily converted to succinate.

Glyoxylate cycle
Succinate is also a product of the glyoxylate cycle, which converts two two-carbon acetyl units into the four-carbon succinate. The glyoxylate cycle is utilized by many bacteria, plants and fungi and allows these organisms to subsist on acetate or acetyl CoA yielding compounds. The pathway avoids the decarboxylation steps of the TCA cycle via the enzyme isocitrate lyase which cleaves isocitrate into succinate and glyoxylate. Generated succinate is then available for either energy production or biosynthesis.

GABA shunt
Succinate is the re-entry point for the gamma-aminobutyric acid (GABA) shunt into the TCA cycle, a closed cycle which synthesizes and recycles GABA. The GABA shunt serves as an alternate route to convert alpha-ketoglutarate into succinate, bypassing the TCA cycle intermediate succinyl-CoA and instead producing the intermediate GABA. Transamination and subsequent decarboxylation of alpha-ketoglutarate leads to the formation of GABA. GABA is then metabolized by GABA transaminase to succinic semialdehyde. Finally, succinic semialdehyde is oxidized by succinic semialdehyde dehydrogenase (SSADH) to form succinate, re-entering the TCA cycle and closing the loop. Enzymes required for the GABA shunt are expressed in neurons, glial cells, macrophages and pancreatic cells.

Metabolic intermediate
Succinate is produced and concentrated in the mitochondria and its primary biological function is that of a metabolic intermediate. All metabolic pathways that are interlinked with the TCA cycle, including the metabolism of carbohydrates, amino acids, fatty acids, cholesterol, and heme, rely on the temporary formation of succinate. The intermediate is made available for biosynthetic processes through multiple pathways, including the reductive branch of the TCA cycle or the glyoxylate cycle, which are able to drive net production of succinate. In rodents, mitochondrial concentrations are approximately ~0.5 mM while plasma concentration are only 2–20 μM.

ROS production
The activity of succinate dehydrogenase (SDH), which interconverts succinate into fumarate participates in mitochondrial reactive oxygen species (ROS) production by directing electron flow in the electron transport chain. Under conditions of succinate accumulation, rapid oxidation of succinate by SDH can drive reverse electron transport (RET). If mitochondrial respiratory complex III is unable to accommodate excess electrons supplied by succinate oxidation, it forces electrons to flow backwards along the electron transport chain. RET at mitochondrial respiratory complex 1, the complex normally preceding SDH in the electron transport chain, leads to ROS production and creates a pro-oxidant microenvironment.

Additional biologic functions
In addition to its metabolic roles, succinate serves as an intracellular and extracellular signaling molecule. Extra-mitochondrial succinate alters the epigenetic landscape by inhibiting the family of 2-oxogluterate-dependent dioxygenases. Alternative, succinate can be released into the extracellular milieu and the blood stream where it is recognized by target receptors. In general, leakage from the mitochondria requires succinate overproduction or underconsumption and occurs due to reduced, reverse or completely absent activity of SDH or alternative changes in metabolic state. Mutations in SDH, hypoxia or energetic misbalance are all linked to an alteration of flux through the TCA cycle and succinate accumulation. Upon exiting the mitochondria, succinate serves as a signal of metabolic state, communicating to neighboring cells how metabolically active the originating cell population is. As such, succinate links TCA cycle dysfunction or metabolic changes to cell-cell communication and to oxidative stress-related responses.

Transporters
Succinate requires specific transporters to move through both the mitochondrial and plasma membrane. Succinate exits the mitochondrial matrix and passes through the inner mitochondrial membrane via dicarboxylate transporters, primarily SLC25A10, a succinate-fumarate/malate transporter. In the second step of mitochondrial export, succinate readily crosses the outer mitochondrial membrane through porins, nonspecific protein channels that facilitate the diffusion of molecules less than 1.5 kDa. Transport across the plasma membrane is likely tissue specific. A key candidate transporter is INDY (I'm not dead yet), a sodium-independent anion exchanger, which moves both dicarboxylate and citrate into the bloodstream.

Extracellular signaling
Extracellular succinate can act as a signaling molecule with hormone-like functions in stimulating a variety of cells such as those in the blood, adipose tissues, immune tissues, liver, heart, retina and kidney. Extracellular succinate works by binding to and thereby activating the GPR91 (also termed SUCNR1 ) receptor on the cells that express this receptor. Most studies have reported that the GPR91 protein consists of 330 amino acids although a few studies have detected a 334 amino acid product of GPR91 gene. Arg99, His103, Arg252, and Arg281 near the center of the GPR91 protein generate a positively charged binding site for succinate. GPR91 resides on its target cells' surface membranes with its binding site facing the extracellular space. It is a G protein-coupled receptor sub-type of receptor that, depending on the cell type bearing it, interacts with multiple G proteins subtypes including Gs, Gi and Gq. This enables GPR91 to regulate a multitude of signaling outcomes.

Succinate has a high affinity for GPR91, with an EC50 (i.e., concentration that induces a half maximal response) for stimulating GPR91 in the 20–50 μM range. Succinate's activation of the GPR91 receptor simulates a wide range of cell types and physiological responses (see Functions regulated by SUCNR1).

Effect on adipocytes
In adipocytes, the succinate-activated GPR91 signaling cascade inhibits lipolysis.

Effect on the liver and retina
Succinate signaling often occurs in response to hypoxic conditions. In the liver, succinate serves as a paracrine signal, released by anoxic hepatocytes, and targets stellate cells via GPR91. This leads to stellate cell activation and fibrogenesis. Thus, succinate is thought to play a role in liver homeostasis. In the retina, succinate accumulates in retinal ganglion cells in response to ischemic conditions. Autocrine succinate signaling promotes retinal neovascularization, triggering the activation of angiogenic factors such as endothelial growth factor (VEGF).

Effect on the heart
Extracellular succinate regulates cardiomyocyte viability through GPR91 activation; long-term succinate exposure leads to pathological cardiomyocyte hypertrophy. Stimulation of GPR91 triggers at least two signaling pathways in the heart: a MEK1/2 and ERK1/2 pathway that activates hypertrophic gene expression and a phospholipase C pathway which changes the pattern of Ca2+ uptake and distribution and triggers CaM-dependent hypertrophic gene activation.

Effect on immune cells
SUCNR1 is highly expressed on immature dendritic cells, where succinate binding stimulates chemotaxis. Furthermore, SUCNR1 synergizes with toll-like receptors to increase the production of proinflammatory cytokines such as TNF alpha and interleukin-1beta. Succinate may enhance adaptive immunity by triggering the activity of antigen-presenting cells that, in turn, activate T-cells.

Effect on platelets
SUCNR1 is one of the highest expressed G protein-coupled receptors on human platelets, present at levels similar to P2Y12, though the role of succinate signaling in platelet aggregation is debated. Multiple studies have demonstrated succinate-induced aggregation, but the effect has high inter-individual variability.

Effect on the kidneys
Succinate serves as a modulator of blood pressure by stimulating renin release in macula densa and juxtaglomerular apparatus cells via GPR91. Therapies targeting succinate to reduce cardiovascular risk and hypertension are currently under investigation.

Intracellular signaling
Accumulation of either fumarate or succinate reduces the activity of 2-oxoglutarate-dependent dioxygenases, including histone and DNA demethylases, prolyl hydroxylases and collagen prolyl-4-hydroxylases, through competitive inhibition. 2-oxoglutarate-dependent dioxygenases require an iron cofactor to catalyze hydroxylations, desaturations and ring closures. Simultaneous to substrate oxidation, they convert 2-oxoglutarate, also known as alpha-ketoglutarate, into succinate and CO2. 2-oxoglutarate-dependent dioxygenases bind substrates in a sequential, ordered manner. First, 2-oxoglutarate coordinates with an Fe(II) ion bound to a conserved 2-histidinyl–1-aspartyl/glutamyl triad of residues present in the enzymatic center. Subsequently, the primary substrate enters the binding pocket and lastly dioxygen binds to the enzyme-substrate complex. Oxidative decarboxylation then generates a ferryl intermediate coordinated to succinate, which serves to oxidize the bound primary substrate. Succinate may interfere with the enzymatic process by attaching to the Fe(II) center first, prohibiting the binding of 2-oxoglutarate. Thus, via enzymatic inhibition, increased succinate load can lead to changes in transcription factor activity and genome-wide alterations in histone and DNA methylation.

Epigenetic effects
Succinate and fumarate inhibit the TET (ten-eleven translocation) family of 5-methylcytosine DNA modifying enzymes and the JmjC domain-containing histone lysine demethylase (KDM). Pathologically elevated levels of succinate lead to hypermethylation, epigenetic silencing and changes in neuroendocrine differentiation, potentially driving cancer formation.

Gene regulation
Succinate inhibition of prolyl hydroxylases (PHDs) stabilizes the transcription factor hypoxia inducible factor (HIF)1α. PHDs hydroxylate proline in parallel to oxidatively decarboxylating 2-oxyglutarate to succinate and CO2. In humans, three HIF prolyl 4-hydroxylases regulate the stability of HIFs. Hydroxylation of two prolyl residues in HIF1α facilitates ubiquitin ligation, thus marking it for proteolytic destruction by the ubiquitin/proteasome pathway. Since PHDs have an absolute requirement for molecular oxygen, this process is suppressed in hypoxia allowing HIF1α to escape destruction. High concentrations of succinate will mimic the hypoxia state by suppressing PHDs, therefore stabilizing HIF1α and inducing the transcription of HIF1-dependent genes even under normal oxygen conditions. HIF1 is known to induce transcription of more than 60 genes, including genes involved in vascularization and angiogenesis, energy metabolism, cell survival, and tumor invasion.

Inflammation
Metabolic signaling involving succinate can be involved in inflammation via stabilization of HIF1-alpha or GPR91 signaling in innate immune cells. Through these mechanisms, succinate accumulation has been shown to regulate production of inflammatory cytokines. For dendritic cells, succinate functions as a chemoattractant and increases their antigen-presenting function via receptor stimulated cytokine production. In inflammatory macrophages, succinate-induced stability of HIF1 results in increased transcription of HIF1-dependent genes, including the pro-inflammatory cytokine interleukin-1β. Other inflammatory cytokines produced by activated macrophages such as tumor necrosis factor or interleukin 6 are not directly affected by succinate and HIF1. The mechanism by which succinate accumulates in immune cells is not fully understood. Activation of inflammatory macrophages through toll-like receptors induces a metabolic shift towards glycolysis. In spite of a general downregulation of the TCA cycle under these conditions, succinate concentration is increased. However, lipopolysaccharides involved in the activation of macrophages increase glutamine and GABA transporters. Succinate may thus be produced from enhanced glutamine metabolism via alpha-ketoglutarate or the GABA shunt.

Tumorigenesis
Succinate is one of three oncometabolites, metabolic intermediates whose accumulation causes metabolic and non-metabolic dysregulation implicated in tumorigenesis. Loss-of-function mutations in the genes encoding succinate dehydrogenase, frequently found in hereditary paraganglioma and pheochromocytoma, cause pathological increase in succinate. SDH mutations have also been identified in gastrointestinal stromal tumors, renal tumors, thyroid tumors, testicular seminomas and neuroblastomas. The oncogenic mechanism caused by mutated SHD is thought to relate to succinate's ability to inhibit 2-oxogluterate-dependent dioxygenases. Inhibition of KDMs and TET hydroxylases results in epigenetic dysregulation and hypermethylation affecting genes involved in cell differentiation. Additionally, succinate-promoted activation of HIF-1α generates a pseudo-hypoxic state that can promote tumorneogensis by transcriptional activation of genes involved in proliferation, metabolism and angiogenesis. The other two oncometabolites, fumarate and 2-hydroxyglutarate have similar structures to succinate and function through parallel HIF-inducing oncogenic mechanisms.

Ischemia reperfusion injury
Succinate accumulation under hypoxic conditions has been implicated in the reperfusion injury through increased ROS production. During ischemia, succinate accumulates. Upon reperfusion, succinate is rapidly oxidized leading to abrupt and extensive production of ROS. ROS then trigger the cellular apoptotic machinery or induce oxidative damage to proteins, membranes, organelles etc. In animal models, pharmacological inhibition of ischemic succinate accumulation ameliorated ischemia-reperfusion injury. As of 2016 the inhibition of succinate-mediated ROS production was under investigation as a therapeutic drug target.

title: Succinic acid


text:
Seti

Seti or SETI may refer to:

Astrobiology

 * SETI, the search for extraterrestrial intelligence.
 * SETI Institute, an astronomical research organization
 * SETIcon, a former convention organized by the SETI Institute
 * Berkeley SETI Research Center, an astronomical research organization
 * SETI@home, a distributed computing project
 * Active SETI, the attempt to send messages to intelligent aliens

Egyptology

 * Seti (commander), grandfather of Seti I
 * Seti (Viceroy of Kush)
 * Seti I (died 1279 BC), pharaoh
 * Seti II (died 1197 BC), pharaoh
 * Seti-Merenptah, a son of Seti II
 * Seti, son of Amun-her-khepeshef
 * Sethi, one of the sons of Ramesses II

Music

 * SETI (band), an ambient music band from New York City
 * SETI (The Kovenant album), an album by metal band The Kovenant

Places

 * Seti River, a tributary of the Karnali River in Nepal
 * Seti Gandaki River or Seti River, a tributary of the Trishuli River in Nepal
 * Seti Zone, one of the fourteen Zones of Nepal

title: Seti


text:
Re

Re or RE may refer to:

Arts, media and entertainment

 * ...Re (film), a 2016 Indian Kannada-language film
 * Realencyclopädie der classischen Altertumswissenschaft, a German encyclopedia of classical scholarship
 * Resident Evil, a horror game franchise

Music

 * Re, the second syllable of the scale in solfège
 * D (musical note) or Re, the second note of the musical scale in fixed do solfège
 * Re: (band), a musical duo based in Canada and the US

Albums

 * Re (Café Tacuba album)
 * Re (Les Rita Mitsouko album)
 * Re., by Aya Ueto
 * Re: (EP), by Kard

Language

 * re (interjection), in Greek
 * Re (kana) (れ and レ), Japanese syllables
 * In re, Latin for 'in the matter of...'
 * RE: and Re:, a standard email subject line prefix

Organisations

 * Renew Europe, a political group in the European Parliament
 * Renovación Española, a former Spanish monarchist political party
 * Royal Engineers, a part of the British Army
 * Royal Society of Painter-Printmakers, whose fellows may use the Post-nominal letters RE
 * Stobart Air (former IATA code: RE), a former Irish regional airline

Places

 * Re, Norway, a former municipality in Vestfold county
 * Re, Vestland, a village in Gloppen municipality, Vestland county, Norway
 * Re, Piedmont, an Italian municipality
 * Île de Ré, an island off the west coast of France
 * Le Bois-Plage-en-Ré, a commune on that island
 * Re di Anfo, a torrent (seasonal stream) in Italy
 * Re di Gianico, Re di Niardo, Re di Sellero, and Re di Tredenus, torrents in the Val Camonica, Lombardy, Italy
 * Réunion (ISO 3166-1 code), a French overseas department and island in the Indian Ocean

Science and technology

 * Effective reproduction number, in epidemiology
 * Relative effectiveness or RE factor, of an explosive's demolition power

 * Reynolds number ($Re$), a dimensionless quantity in fluid mechanics used to help predict flow patterns
 * Rhenium (symbol Re), a chemical element
 * Reference pressure (Re), as sound pressure level
 * Reference pressure (Re), in underwater acoustics

Computing and mathematics

 * RE (complexity) (recursively enumerable), a complexity class of decision problems
 * Recursively enumerable (r.e.), in computability theory
 * Regular expression, a sequence of characters to match text against a specified pattern
 * Re function, in mathematics, where Re(z) denotes the real part of a complex number z

People

 * Giovanni Battista Re (born 1934), Italian cardinal
 * Cayetano Ré (1938–2013), former Paraguayan footballer

Other uses

 * Religious education (RE), the study of religion
 * Re (Egyptian religion), an ancient Egyptian god
 * Regional-Express, a type of regional train in Germany, Luxembourg and Austria

title: Re


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Khepri

Khepri (Egyptian: ḫprj, also transliterated Khepera, Kheper, Khepra, Chepri) is a scarab-faced god in ancient Egyptian religion who represents the rising or morning sun. By extension, he can also represent creation and the renewal of life.

Etymology
The name "Khepri" appeared in the Pyramid texts and usually included the scarab hieroglyph as a determinative or ideogram as a potential means to make any allusions to the god clear. Khepri is also mentioned in the Amduat, as the god is intrinsically linked to cycle of the sun and Ra's nightly journey through the Duat, the Egyptian underworld.

Khepri (ḫprj) is derived from the Egyptian language verb ḫpr, meaning to "develop" or "create". Khepri (ḫprj) can also be spelled "Kheper", which is the Egyptian term used to denote the sun god, the scarab beetle, and the verbs "to come into existence" or "to be born".

Symbolism
The god was connected to and often depicted as a scarab beetle (ḫprr in Egyptian). Scarab beetles lay their eggs within dung balls, and as a result, young beetles emerge from the balls fully formed, having eaten their way out of the mounds. This caused ancient Egyptians to believe that these insects were created from nothingness. They also believed that each day the sun was reborn or created from nothing, thus explaining the connection made between the Sun and the scarab.

In hour twelve of the Amduat, a newly reborn Khepri helms the solar barque that pushes the sun, moving the morning sun across the early day sky. This mirrors the manner in which a scarab beetle pushes large balls of dung along the ground, highlighting the relationship made between Khepri and the insects.

Scarab shaped accessories were common in ancient Egypt, as rings or amulets meant to be attached to necklaces were often fashioned in the shape of these insects. Such objects that depicted scarabs were often handed out to the Egyptian people during public festivials, with them wearing the amulets to bring good fortune, to express their devotion to the king or the gods, or to have the scarabs act as protective charms. These scarab idols, whether they were made of faience, an amalgamated material composed of common minerals like quartz and alkaline salts that was cheap to produce, or turquoise, a rare and highly sought after stone, were often colored blue, which signifies that the color might have been significant in its relation to the gods.

The color had a variety of meanings to the ancient Egyptians. Blue could have represented the sky or the heavens, the primordial flood, which also suggests that the color symbolized a cycle of life, death, and rebirth. Fertility was another characteristic potentially represented by the color blue, as the Nile river was often highlighted by the color. While it is impossible to assume that the blue scarabs depicted in Egyptian art were meant to represent both Khepri and the traits of the color, the correlation between the divine symbolism of the beetle and meaning of the color blue is unlikely to be a mere coincidence.

Religion
Khepri was a solar deity and thus connected to the rising sun and the mythical creation of the world. The god and the scarab beetle represented creation and rebirth. There was no cult devoted to Khepri, as he was seen as a manifestation of the more promient solar deity Ra. The scarab god was however included in the creationist theory of Heliopolis and later Thebes. Often, Khepri and another solar deity, Atum, were seen as aspects of Ra: Khepri represented the morning sun, Ra was the midday sun, and Atum represented the evening sun. As a deity, Khepri's four main functions were creator, protector, sun-god, and the god of resurrection. The central belief surrounding Khepri was the god's ability to renew life, in the same way he restored the sun's existence every morning. Mummified scarab beetles and scarab amulets have been found in pre-dynastic graves, suggesting that Khepri was respected early on in the history of Ancient Egypt.

Appearances in Funerary Texts
Khepri's most important role in ancient Egyptian religion is the integral part he plays in the life and death cycle of the sun. There are three major funerary texts in which Khepri makes an appearance; the Amduat, the Book of Caverns, and the Book of Gates.

Each text is similar in that the lifeless corpse of Khepri is conjoined with the soul of Ra at some point during the god's journey through the underworld. In fact, the Book of Gates and the Amduat have been noted to be very similar, with the only significant difference between the two funerary texts being that the Amduat focuses more on the journey Ra takes through the Underworld, whereas the Book of Gates focuses more on the journey a human soul takes to follow the solar god. Khepri's corpse is reached in both texts in the sixth hour of the night, and he leads the solar barque out of the Underworld in both stories as well.

The Book of Caverns is unique among these funerary texts in that it is not divided into hours as the other two are, rather it is broken up into tableaus. Regardless of this difference, Khepri's corpse is still depicted within the Underworld, appearing in the third tableau instead of the sixth hour.

Khepri's Role in the Amduat
The Amduat is the nightly journey Ra, and by proxy the sun, takes through the underworld, as he is exhausted and aged from his day's work of moving the solar barque across the sky. Through this voyage across the underworld, both the Ra and the sun are reborn, as the god takes the form of Khepri, who leads the sun across the sky during the morning.

There are two hours of the Amduat that Khepri is involved. Hour six sees the solar barque of Ra reach the primordial waters of Nun, in which rests the corpse of Khepri surrounded by an enormous multi-headed snake. It is unclear how Khepri died and how a serpent with five heads came to guard his corpse. Nevertheless, the ba, or soul, of Ra combines itself with Khepri's body, thus resurrecting the solar god.

Khepri is not explictly mentioned again within the Amduat until the twelve hour, the last hour as the sun begins its ascent back into the sky. In this hour, Khepri is at the helm of the solar barque, leading the vessal out of the underworld and, with the help of Shu, the god of air and winds, back into the sky, so that sun may once again bathe the world in its light. Khepri plays a vital role in this journey, as he is the one that guides the sun through the last leg of its voyage through the underworld and ushers in the dawn of a new day as the god of the morning sun.

Gallery
Khepri was depicted as either a scarab holding aloft the sun disk or as a human male with a scarab for a head. The scarab amulets that the Egyptians used as jewelry and as seals allude to Khepri and the newborn sun. The beetle carvings became so common that excavators have found them throughout the Mediterranean.

title: Khepri


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Atum

Atum (, Egyptian: jtm(w) or tm(w), reconstructed ; Coptic Atoum),  sometimes rendered as Atem or Tem, is the primordial God in Egyptian mythology from whom all else arose. He created himself and is the father of Shu and Tefnut, the divine couple, who are the ancestors of the other Egyptian deities. Atum is also closely associated with the evening sun. As a primordial god and as the evening sun, Atum has chthonic and underworld connections. Atum was relevant to the ancient Egyptians throughout most of Egypt's history. He is believed to have been present in ideology as early as predynastic times, becoming even more prevalent during the Old Kingdom and continuing to be worshiped through the Middle and New Kingdom, though he becomes overshadowed by Re around this time.

Name
Atum's name is thought to be derived from the verb tm which means 'to complete' or 'to finish'. Thus, he has been interpreted as being the "complete one" and also the finisher of the world, which he returns to watery chaos at the end of the creative cycle. As creator, he was seen as the progenitor of the world, the deities and universe having received his vital force or ka.

Origins
Atum is one of the most important and frequently mentioned deities from earliest times, as evidenced by his prominence in the Pyramid Texts, where he is portrayed as both a creator and father to the king throughout the collection of spells. Several writings contradict how Atum was brought into existence. According to the Heliopolitan view, Atum originally existed in his egg within the primeval waters, being born during the primordial flood, becoming the source of everything that was created after him. The Memphites (priests of Memphis), on the other hand, believed that Ptah created Atum in a more intellectual way, using his speech and thought, as told on the Shabaka Stone.

Role
In the Heliopolitan creation myth, Atum was considered to be the first god, having created himself, sitting on a mound (benben) (or identified with the mound itself), and rose from the primordial waters (Nu). Early myths state that Atum created the god Shu and goddess Tefnut by spitting them out of his mouth. One text debates that Atum did not create Shu and Tefnut by spitting them out of his mouth by means of saliva and semen, but rather by Atum's lips. Another writing describes Shu and Tefnut being birthed by Atum's hand. That same writing states that Atum's hand is the title of the god's wife based on her Heliopolitan beginning. Other myths state Atum created by masturbation, with the hand he used in this act that may be interpreted as the female principle inherent within him and identified with goddesses such as Hathor or Iusaaset. Yet other interpretations state that he has made union with his shadow.

In the Old Kingdom, the Egyptians believed that Atum lifted the dead king's soul from his pyramid to the starry heavens. He was also a solar deity, associated with the primary sun god Ra. Atum was linked specifically with the evening sun, while Ra or the closely linked god Khepri were connected with the sun at morning and midday.

In the Coffin Texts, Atum has a vital conversation with Osiris in which he describes the end of the universe as a time in which everything will cease to exist with the exception of the elements of the primordial waters, stating that after millions of years he and Osiris would be the only ones to survive the end of time as serpents. He claims that he will destroy everything he created in the beginning of existence and bring it back to Nu, the primeval waters, thus describing the belief that the gods and goddesses would one day cease to exist outside of the primeval waters.

In the Book of the Dead, which was still current in the Graeco-Roman period, the sun god Atum is said to have ascended from chaos-waters with the appearance of a snake, the animal renewing itself every morning.

Atum is the god of pre-existence and post-existence. In the binary solar cycle, the serpentine Atum is contrasted with the scarab-headed god Khepri—the young sun god, whose name is derived from the Egyptian ḫpr "to come into existence". Khepri-Atum encompassed sunrise and sunset, thus reflecting the entire cycle of morning and evening.

Relationship to other gods
Atum was a self-created deity, the first being to emerge from the darkness and endless watery abyss that existed before creation. A product of the energy and matter contained in this chaos, he created his children—the first deities, out of loneliness. He produced from his own sneeze, or in some accounts, semen, Shu, the god of air, and Tefnut, the goddess of moisture. The brother and sister, curious about the primeval waters that surrounded them, went to explore the waters and disappeared into the darkness. Unable to bear his loss, Atum sent a fiery messenger, the Eye of Ra, to find his children. The tears of joy he shed upon their return were the first human beings.

Iconography
Atum is usually depicted in anthropomorphic form, wearing either the royal head-cloth or the dual white and red crown of Upper and Lower Egypt, reinforcing his connection with kingship. He is typically depicted sitting on a throne and will usually be represented with the head of a ram when he is mentioned within the context of his connection to the underworld and his solar attributes. Sometimes he is also shown as a serpent, the form he returns to at the end of the creative cycle, and also occasionally as a mongoose, lion, bull, lizard, or ape. When he is represented as a solar deity, he can also be depicted as a scarab and when in reference to his primeval origins he is also seen depicted as the primeval mound.

Worship
Atum was worshipped throughout Egypt's history; the center of his worship centered on the city of Heliopolis (Egyptian: Annu or Iunu). The only surviving remnant of Heliopolis is the Temple of Ra-Atum obelisk located in Al-Masalla of Al-Matariyyah, Cairo. It was erected by Senusret I of the Twelfth Dynasty, and still stands in its original position. In the Old Kingdom Atum was at the center of the Egyptian belief system, being partly responsible for the origins of existence, having created himself and everything else out of the primordial waters. He is believed to have been present in ideology as early as predynastic times, becoming even more prevalent during the Old Kingdom as indicated by the pyramid texts in which he appears frequently. He continues to be found in the Middle Kingdom, during which he is depicted in the Book of the Dead in which he appears in spells to help with the journey to the Afterlife. Later, in the New Kingdom, there cults attributed to Atum, such as the Theban royal high priestesses known as the Divine Adoratrices of Amun who acted as the Hand of Atum in temple rituals at the time. Re would take centerstage later on but as Atum was overshadowed, the people of ancient Egypt would continue to worship him through cultic rituals in which he is depicted as having close relationships with the king, as well as being represented through lizards on small reliquaries and amulets closer to the Late Period.

title: Atum


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Picardy

Picardy (, Picard and Picardie,, Picard: ) is a historical territory and a former administrative region of France. Since 1 January 2016, it has been part of the new region of Hauts-de-France. It is located in the northern part of France.

History
The historical province of Picardy stretched from Senlis to Calais via the main parts of the Oise and Aisne departments, the whole of the Somme department and the west of the Pas-de-Calais department. The province of Artois (Arras area) separated Picardy from French Flanders.

Middle Ages
From the 5th century, the area formed part of the Frankish Empire and, in the feudal period, it encompassed the six countships of Boulogne, Montreuil, Ponthieu, Amiénois, Vermandois and Laonnois. In accordance with the provisions of the 843 Treaty of Verdun, the region became part of West Francia, the later Kingdom of France.

The name "Picardy" derives from the Old French pic, meaning "pike", the characteristic weapon used by people from this region in ancient times. The term "Picardy" was first used in the early 13th century, during which time the name applied to all lands where the Picard language was spoken including territories from Paris to the Netherlands. In the Latin Quarter of Paris, people identified a "Picard Nation" (Nation Picarde) of students at Sorbonne University, most of whom actually came from Flanders. During the Hundred Years' War, Picardy was the centre of the Jacquerie peasant revolt in 1358.

Beginning in 1419, the Picardy counties (Boulogne, Ponthieu, Amiens, Vermandois) were gradually acquired by the Burgundian duke Philip the Good, acquisitions confirmed by King Charles VII of France at the 1435 Congress of Arras. In 1477, King Louis XI of France led an army and occupied key towns in Picardy. By the end of 1477, Louis would control all of Picardy and most of Artois.

Modern era
In the 15th century, the government (military region) of Picardy was created. This became a new administrative region of France, separate from what was historically defined as Picardy. The new Picardy included the Somme département, the northern half of the Aisne département and a small fringe in the north of the Oise département.

In 1557, Picardy was invaded by Habsburg forces under the command of Emmanuel Philibert, Duke of Savoy. After a seventeen-day siege, St. Quentin would be ransacked, while Noyon would be burned by the Habsburg army.

In the early 18th century, an infectious disease similar to English sweat originated from the region and spread across France. It was called Suette des picards or Picardy sweat.

Sugar beet was introduced by Napoleon I during the Napoleonic Wars in the 19th century in order to counter the United Kingdom which had seized the sugar islands possessed by France in the Caribbean. The sugar industry has continued to play a prominent role in the economy of the region.

One of the most significant historical events to occur in Picardy was the series of battles fought along the Somme during World War I. From September 1914 to August 1918, four major battles, including the Battle of the Somme, were fought by British, Commonwealth, French and German forces in the fields of Northern Picardy.

Picardy today
In 2009, the Regional Committee for local government reform proposed to reduce the number of French regions and cancel additions of new regions in the near future. Picardy would have disappeared and each department would have joined a nearby region. The Oise would have been incorporated in the Île-de-France, the Somme would have been incorporated in the Nord-Pas-de-Calais and Aisne would have been incorporated in the Champagne-Ardenne. The vast majority of Picards were opposed to this proposal and it was scrapped in 2010 (see newspaper: "Courrier Picard").

Today, the modern region of Picardy no longer includes the coastline from Berck to Calais, via Boulogne (Boulonais), that is now in the Nord-Pas-de-Calais region but does incorporate the pays of Beauvaisis, Valois, Noyonnais, Laonnois, Soissonnais, Omois among other departments of France. The older definition of Picardy survives in the name of the Picard language which applies not only to the dialects of Picardy proper but also to the Romance dialects spoken in the Nord-Pas de Calais region, north of Picardy proper, and parts of the Belgian province of Hainaut.

Geography
Between the 1990 and 1999 censuses, the population of Oise increased 0.61% per year, almost twice as fast as France as a whole. Meanwhile the Aisne department lost inhabitants, and the Somme barely grew with a 0.16% growth per year. Today, 41.3% of the population of Picardy live inside the Oise department.

Picardy stretches from the long sand beaches of the Somme estuary in the west to the vast forests and pastures of the Thiérache in the east to Chantilly and Pierrefonds near the Paris Area and vineyards of the border with Champagne to the south.

Administration
The president of the regional council prior to its abolition in 2015 was Claude Gewerc, a Socialist who had been in office since 2004. That year he defeated longtime UDF incumbent Gilles de Robien.

Since 2008, the mayor of the city of Amiens, the regional capital, has been Socialist Gilles Demailly. He defeated longtime mayor Gilles de Robien of the New Centre party.

Language and culture

Historically, the region of Picardy has a strong and proud cultural identity. The Picard (local inhabitants and traditionally speakers of the Picard language) cultural heritage includes some of the most extraordinary Gothic churches (Amiens and Beauvais cathedrals or Saint-Quentin basilica), distinctive local cuisine (including ficelle picarde, flamiche aux poireaux, tarte au maroilles), beer (including from Péronne's de Clercq brewery) and traditional games and sports, such as the longue paume (ancestor of tennis), as well as danses picardes and its own bagpipes, called the pipasso.

The villages of Picardy have a distinct character, with their houses made of red bricks, often accented with a "lace" of white bricks. A minority of people still speak the Picard language, one of the languages of France, which is also spoken in Artois (Nord-Pas de Calais région). "P'tit quinquin", a Picard song, is a symbol of the local culture (and of that of Artois).

Picardy is arguably the birthplace of Gothic architecture, housing six of the world's greatest examples of Gothic cathedrals, which span the history of Gothic architecture in its entirety. Amiens Cathedral, standing as the largest cathedral in Europe, which according to John Ruskin is the "Pantheon of Gothic architecture", could house Notre-Dame de Paris twice over. It was built in as little as 50 years. Picardy also holds the tallest transept in the history of the Gothic period; this transept is located in Saint-Pierre cathedral in Beauvais, Oise.

The Museum of Picardy in Amiens, built between 1855 and 1867, houses a vast array of great works, spanning the centuries and ranging from archaeology from ancient Greece and Egypt to modern works of Pablo Picasso. The museum was closed until the end of 2019 for building work.

Although Picardy is one of the least-known regions in France, its influence from art and most certainly architecture is vivid throughout the world.

Major cities

 * Abbeville
 * Amiens
 * Beauvais
 * Compiègne
 * Péronne
 * Creil
 * Laon
 * Saint-Quentin
 * Soissons
 * Senlis

In popular culture

 * The song "Roses of Picardy" is a ballad written in 1916 during World War I. In 1927, the song title was used as the title of the silent British film of the same name.
 * Picardy is one of the minor characters in the Japanese manga series Hetalia: Axis Powers.
 * The french army song "Reveillez-vous picards" ( "picards awaken") was originally a rally song used by Charles the Bold's picard mercenaries.

title: Picardy


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Shu (Egyptian god)

Shu (Egyptian šw, "emptiness" or "he who rises up") was one of the primordial Egyptian gods, spouse and brother to the goddess Tefnut, and one of the nine deities of the Ennead of the Heliopolis cosmogony. He was the god of peace, lions, air, and wind.

Family
In Heliopolitan theology, Atum created the first couple of the Ennead, Shu and Tefnut by masturbating or by spitting. Shu was the father of Nut and Geb and grandfather of Osiris, Isis, Set, and Nephthys. His great-grandsons are Horus and Anubis.

Myths
As the air, Shu was considered to be a cooling, and thus calming, influence, and pacifier. Due to the association with dry air, calm, and thus Ma'at (truth, justice, order, and balance), Shu was depicted as the dry air/atmosphere between the Earth and sky, separating the two realms after the event of the First Occasion. Shu was also portrayed in art as wearing an ostrich feather. Shu was seen with between one and four feathers. The ostrich feather was symbolic of lightness and emptiness. Fog and clouds were also Shu's elements and they were often called his bones. Because of his position between the sky and Earth, he was also known as the wind.

In a much later myth, representing a terrible weather disaster at the end of the Old Kingdom, it's said that Tefnut and Shu once argued, and Tefnut left Egypt for Nubia (which was always more temperate). It was said that Shu quickly decided that he missed her, but she changed into a cat that destroyed any man or god that approached. Thoth, disguised, eventually succeeded in convincing her to return.

The Greeks associated Shu with Atlas, the primordial Titan who held up the celestial spheres, as they are both depicted holding up the sky.

According to the Heliopolitan cosmology, Shu and Tefnut, the first pair of cosmic elements, created the sky goddess, Nut, and the Earth god, Geb. Shu separated Nut from Geb as they were in the act of love, creating duality in the manifest world: above and below, light and dark, good and evil. Prior to their separation, however, Nut had given birth to the gods Isis, Osiris, Nephthys (Horus) and Set. The Egyptians believed that if Shu did not hold Nut (sky) and Geb (Earth) apart there would be no way for physically-manifest life to exist.

Shu is mostly represented as a man. Only in his function as a fighter and defender as the sun god and he sometimes receives a lion's head. He carries an ankh, the symbol of life.

title: Shu (Egyptian god)


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Tefnut

Tefnut ( tfn.t; ⲧϥⲏⲛⲉ tfēne) is a deity of moisture, moist air, dew and rain in Ancient Egyptian religion. She is the sister and consort of the air god Shu and the mother of Geb and Nut.

Etymology
The name Tefnut has no certain etymology but it may be an onomatopoeia of the sound of spitting, as Atum spits her out in some versions of the creation myth. Additionally, her name was written as a mouth spitting in late texts.

Like most Egyptian deities, including her brother, Tefnut has no single ideograph or symbol. Her name in hieroglyphs consists of four single phonogram signs t-f-n-t. Although the n phonogram is a representation of waves on the surface of water, it was never used as an ideogram or determinative for the word water (mw), or for anything associated with water.

Mythological origins
Tefnut is a daughter of the solar deity Ra-Atum. Married to her twin brother Shu, she is mother of Nut, the sky and Geb, the earth. Tefnut's grandchildren were Osiris, Isis, Set, Nephthys, and, in some versions, Horus the Elder. She was also the great-grandmother of Horus the Younger. Alongside her father, brother, children, grandchildren, and great-grandchild, she is a member of the Ennead of Heliopolis.

There are a number of variants to the myth of the creation of the twins Tefnut and Shu. In every version, Tefnut is the product of parthenogenesis, and all involve some variety of body fluid.

In the Heliopolitan creation myth, Atum sneezed to produce Tefnut and Shu. Pyramid Text 527 says, "Atum was creative in that he proceeded to sneeze while in Heliopolis. And brother and sister were born - that is Shu and Tefnut."

In some versions of this myth, Atum also spits out his saliva, which forms the act of procreation. This version contains a play on words, the tef sound which forms the first syllable of the name Tefnut also constitutes a word meaning "to spit" or "to expectorate".

The Coffin Texts contain references to Shu being sneezed out by Atum from his nose, and Tefnut being spat out like saliva. The Bremner-Rind Papyrus and the Memphite Theology describe Atum as sneezing out saliva to form the twins.

Iconography
Tefnut is a leonine deity, and appears as human with a lioness head when depicted as part of the Great Ennead of Heliopolis. The other frequent depiction is as a lioness, but Tefnut can also be depicted as fully human. In her fully or semi anthropomorphic form, she is depicted wearing a wig, topped either with a uraeus serpent, or a uraeus and solar disk, and she is sometimes depicted as a lion headed serpent. Her face is sometimes used in a double headed form with that of her brother Shu on collar counterpoises.

During the 18th and 19th Dynasties, particularly during the Amarna Period, Tefnut was depicted in human form wearing a low flat headdress, topped with sprouting plants. Akhenaten's mother, Tiye was depicted wearing a similar headdress, and identifying with Hathor-Tefnut. The iconic blue crown of Nefertiti is thought by archaeologist Joyce Tyldesley to be derived from Tiye's headdress, and may indicate that she was also identifying with Tefnut.

Cult centres
Heliopolis and Leontopolis (now ell el-Muqdam) were the primary cult centres. At Heliopolis, Tefnut was one of the members of that city's great Ennead, and is referred to in relation to the purification of the wabet (priest) as part of the temple rite. Here she had a sanctuary called the Lower Menset.

"I have ascended to you

with the Great One behind me

and [my] purity before me:

I have passed by Tefnut,

even while Tefnut was purifying me,

and indeed I am a priest, the son of a priest in this temple.""

- Papyrus Berlin 3055

At Karnak, Tefnut formed part of the Ennead and was invoked in prayers for the health and wellbeing of the pharaoh.

She was worshiped with Shu as a pair of lions in Leontopolis in the Nile Delta.

Mythology
Tefnut was connected with other leonine goddesses as the Eye of Ra. As a lioness she could display a wrathful aspect and is said to have escaped to Nubia in a rage, jealous of her grandchildren's higher worship. Only after receiving the title "honorable" from Thoth, did she return. In the earlier Pyramid Texts she is said to produce pure waters from her vagina.

As Shu had forcibly separated his son Geb from his sister-wife Nut, Geb challenged his father Shu, causing the latter to withdraw from the world. Geb, who was in love with his mother Tefnut, takes her as his chief queen-consort.

title: Tefnut


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Iron–sulfur cluster

Iron–sulfur clusters are molecular ensembles of iron and sulfide. They are most often discussed in the context of the biological role for iron–sulfur proteins, which are pervasive. Many Fe–S clusters are known in the area of organometallic chemistry and as precursors to synthetic analogues of the biological clusters (see Figure). It is believed that the last universal common ancestor had many iron-sulfur clusters.

Organometallic clusters
Organometallic Fe–S clusters include the sulfido carbonyls with the formula Fe2S2(CO)6, H2Fe3S(CO)9, and Fe3S2(CO)9. Compounds are also known that incorporate cyclopentadienyl ligands, such as (C5H5)4Fe4S4.

Biological Fe–S clusters
Iron–sulfur clusters occur in many biological systems, often as components of electron transfer proteins. The ferredoxin proteins are the most common Fe–S clusters in nature. They feature either 2Fe–2S or 4Fe–4S centers. They occur in all branches of life.

Fe–S clusters can be classified according to their Fe:S stoichiometry [2Fe–2S], [4Fe–3S], [3Fe–4S], and [4Fe–4S]. The [4Fe–4S] clusters occur in two forms: normal ferredoxins and high potential iron proteins (HiPIP). Both adopt cuboidal structures, but they utilize different oxidation states. They are found in all forms of life.

The relevant redox couple in all Fe–S proteins is Fe(II)/Fe(III).

Many clusters have been synthesized in the laboratory with the formula [Fe4S4(SR)4]2−, which are known for many R substituents, and with many cations. Variations have been prepared including the incomplete cubanes [Fe3S4(SR)3]3−.

title: Iron–sulfur cluster


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Heliopolis (ancient Egypt)

Heliopolis (Jwnw, Iunu; 𓉺𓏌𓊖, lit. 'the Pillars'; ⲱⲛ; ) was a major city of ancient Egypt. It was the capital of the 13th or Heliopolite Nome of Lower Egypt and a major religious centre. It is now located in Ayn Shams, a northeastern district of Cairo.

Heliopolis was one of the oldest cities of ancient Egypt, occupied since prehistoric Egypt. It greatly expanded under the Old and Middle Kingdoms but is today mostly destroyed, its temples and other buildings having been scavenged for the construction of medieval Cairo. Most information about the ancient city comes from surviving records.

The major surviving remnant of Heliopolis is the obelisk of the Temple of Ra-Atum erected by Senusret I of Dynasty XII. It still stands in its original position, now within Al-Masalla in El Matareya, Cairo. The 21 m high red granite obelisk weighs 120 tons (240,000 lbs) and is believed to be the oldest surviving obelisk in the world. Under Augustus, the Romans took the Obelisk of Montecitorio from Heliopolis to Rome, where it remains. The two smaller obelisks called Cleopatra's Needles, in London and New York, also came from the city.

Names
Heliopolis is the Latinised form of the Greek name Hēlioúpolis (Ἡλιούπολις), meaning "City of the Sun". Helios, the personified and deified form of the sun, was identified by the Greeks with the native Egyptian gods Ra and Atum, whose principal cult was located in the city.

Its native name was iwnw ("The Pillars"), whose exact pronunciation is uncertain because ancient Egyptian recorded only consonantal values. Arabic : Iwan إيوان.

Its traditional Egyptological transcription is Iunu but it appears in biblical Hebrew as ʾŌn, and ʾĀwen. Some scholars to reconstruct its pronunciation in earlier Egyptian as *ʔa:wnu, perhaps from older /ja:wunaw/. Variant transcriptions include Awnu and Annu. The name survived as Coptic ŌN.

The city also appears in the Old Kingdom Pyramid Texts as the "House of Ra".

Ancient
In ancient Egypt, Heliopolis was a regional center from predynastic times.

It was principally notable as the cult center of the sun god Atum, who came to be identified with Ra and then Horus. The primary temple of the city was known as the Great House (Pr Ꜥꜣt or Per Aat, *Par ʻĀʼat) or House of Atum (Pr I͗tmw or Per Atum, *Par-ʼAtāma; פתם, Pithom). Its priests maintained that Atum or Ra was the first being, rising self-created from the primeval waters. A decline in the importance of Ra's cult during Dynasty V led to the development of the Ennead, a grouping of nine major Egyptian deities that placed the others in subordinate status to Ra–Atum. The high priests of Ra are not as well documented as those of other deities, although the high priests of Dynasty VI (c. 2345BC) have been discovered and excavated.

During the Amarna Period of Dynasty XVIII, Pharaoh Akhenaten introduced a kind of henotheistic worship of Aten, the deified solar disc. As part of his construction projects, he built a Heliopolitan temple named "Elevating Aten" (Wṯs I͗tn or Wetjes Aten), whose stones can still be seen in some of the gates of Cairo's medieval city wall. The cult of the Mnevis bull, another embodiment of the Sun, had its altar here as well. The bulls' formal burial ground was situated north of the city.

The city is mentioned as being one of the places that was rebuilt by Hebrew slaves in the Greek Septuagint translation of the Bible (Exodus 1:11). The store-city Pithom in the same passage is, according to one theory, Heliopolis. Today, it is generally believed that Pithom is the archaeological site of either Tell el-Retabeh or Tell el-Maschuta.

Hellenistic
Alexander the Great halted at this city on his march from Pelusium to Memphis.

The temple of Ra was said to have been, to a special degree, a depository for royal records, and Herodotus states that the priests of Heliopolis were the best informed in matters of history of all the Egyptians. Heliopolis flourished as a seat of learning during the Greek period; the schools of philosophy and astronomy are claimed to have been frequented by Orpheus, Homer, Pythagoras, Plato, Solon, and other Greek philosophers. Ichonuphys was lecturing there in 308 BC, and the Greek mathematician Eudoxus, who was one of his pupils, learned from him the true length of the year and month, upon which he formed his octaeterid, or period of 8 years or 99 months. Ptolemy II had Manetho, the chief priest of Heliopolis, collect his history of the ancient kings of Egypt from its archives. The later Greek rulers, the Ptolemies, probably took little interest in their "father" Ra as Greeks were never much of sun worshipers and the Ptolemies favored the cult of Serapis, and Alexandria had eclipsed the learning of Heliopolis; thus with the withdrawal of royal favour Heliopolis quickly dwindled, and the students of native lore deserted it for other temples supported by a wealthy population of pious citizens. By the first century BC, in fact, Strabo found the temples deserted, and the town itself almost uninhabited, although priests were still present.

Heliopolis was well known to the ancient Greeks and Romans, being noted by most major geographers of the period, including Ptolemy, Herodotus, and others, down to the Byzantine geographer Stephanus of Byzantium.

Roman
In Roman Egypt, Heliopolis belonged to the province Augustamnica, causing it to appear as Heliopolis in Augustamnica when it needed to be distinguished from Roman Heliopolis. Its population probably contained a considerable Arabian element. Many of the city's obelisks were removed to adorn more northern cities of the Delta and Rome. Two of these eventually became London's Cleopatra's Needle and its twin in New York's Central Park.

Islamic
During the Middle Ages, the growth of Fustat and Cairo only a few kilometres away caused its ruins to be massively scavenged for building materials, including for their city walls. The site became known as the "Eye of the Sun" (Ayn Shams) and ʻArab al-Ḥiṣn.

Legacy
The importance of the solar cult at Heliopolis is reflected in both ancient pagan and current monotheistic beliefs. Classical mythology held that the Egyptian bennu, renamed phoenix, brought the remains of its predecessor to the altar of the sun god at Heliopolis each time it was reborn. In the Hebrew Bible, Heliopolis is referenced directly and obliquely, usually in reference to its prominent pagan cult. In his prophesies against Egypt, Isaiah claimed the "City of the Sun" (עיר החרס) would be one of the five Egyptian cities to follow the Lord of Heaven's army and speak Hebrew. Jeremiah and Ezekiel mention the House or Temple of the Sun (בֵּית שֶׁמֶשׁ) and Ôn, claiming Nebuchadnezzar II of the Neo-Babylonian Empire would shatter its obelisks and burn its temple and that its "young men of Folly" (Aven) would "fall by the sword".

The "Syrian Heliopolis" Baalbek has been claimed to have gained its solar cult from a priest colony emigrating from Egypt.

The Titular Episcopal See of Heliopolis in Augustamnica remains a titular see of both the Catholic Church and the Eastern Orthodox Church.

Present site
The ancient city is currently located about 15 - 20 m below the streets of the middle- and lower-class suburbs of Al-Matariyyah, Ain Shams, and Tel Al-Hisn in northern Cairo. The area is about 1.5 km west of the modern suburb which bears its name.

Some ancient city walls of crude brick can be seen in the fields, a few granite blocks bearing the name of Ramesses II remain, and the position of the great Temple of Ra-Atum is marked by the Al-Masalla obelisk. Archaeologists excavated some of its tombs in 2004. In 2017, parts of a colossal statue of Psamtik I were found and excavated.

Gallery
A selection of old maps showing Heliopolis are below:

title: Heliopolis (ancient Egypt)


text:
Calesius

In Greek mythology, Calesius (Ancient Greek: Καλήσιος) was the attendant and charioteer of Axylus. He is mentioned in Book VI of Homer's Iliad where he is killed with his master by Diomedes.

title: Calesius


text:
Tum

Tum or TUM can refer to:

Education

 * Technical University of Munich (Technische Universität München)
 * TUM Institute for Advanced Study
 * TUM Asia
 * Technological University (Mandalay)
 * The University of Manila

Places

 * Tum, Poland; a village
 * Tum Collegiate Church
 * Tum, Ethiopia; a village in the Maji District near Tum Airport
 * Tumut Airport, IATA airport code "TUM"
 * Tumbes Region, Peru, ISO 3166-2 code, shortened to TUM
 * Tuen Mun station, Hong Kong; MTR station code

People

 * Tecla Tum, Kenyan politician
 * Stephanie Tum (born 1987), Cameroonian actress
 * Tum Saray (born 1992), Cambodian soccer player
 * Rigoberta Menchú Tum, (born 1959), an indigenous Guatemalan and 1992 Nobel Peace Prize laureate
 * Mehmet Tüm (born 1957), Turkish politician
 * Hervé Tum (born 1979), Cameroonian soccer player
 * Gerard Tum (1040–1120), founder of the Order of St John of Jerusalem (the Knights Hospitaller)

Other uses

 * The human stomach or abdomen
 * Totally Unimodular Matrix, in mathematics
 * Tumbuka language (ISO 639-2 and 639-3 language code )
 * Tum, aka Toum, a variety of the Phong language cluster
 * Tum: A Dangerous Obsession, 2004 Hindi film
 * Tum: My Pledge of Love, 2011 Philippine film
 * Truck Utility Medium, British Army designation for the long wheelbase variant of the Land Rover Wolf

title: Tum


text:
Leghemoglobin

Leghemoglobin (also leghaemoglobin or legoglobin) is an oxygen-carrying phytoglobin found in the nitrogen-fixing root nodules of leguminous plants. It is produced by these plants in response to the roots being colonized by nitrogen-fixing bacteria, termed rhizobia, as part of the symbiotic interaction between plant and bacterium: roots not colonized by Rhizobium do not synthesise leghemoglobin. Leghemoglobin has close chemical and structural similarities to hemoglobin, and, like hemoglobin, is red in colour. It was originally thought that the heme prosthetic group for plant leghemoglobin was provided by the bacterial symbiont within symbiotic root nodules. However, subsequent work shows that the plant host strongly expresses heme biosynthesis genes within nodules, and that activation of those genes correlates with leghemoglobin gene expression in developing nodules.

In plants colonised by Rhizobium, such as alfalfa or soybeans, the presence of oxygen in the root nodules would reduce the activity of the oxygen-sensitive nitrogenase, which is an enzyme responsible for the fixation of atmospheric nitrogen. Leghemoglobin is shown to buffer the concentration of free oxygen in the cytoplasm of infected plant cells to ensure the proper function of root nodules. That being said, nitrogen fixation is an extremely energetically costly process, so aerobic respiration, which necessitates high oxygen concentration, is necessary in the cells of the root nodule. Leghemoglobin maintains a free oxygen concentration that is low enough to allow nitrogenase to function, but a high enough total oxygen concentration (free and bound to leghemoglobin) for aerobic respiration.

Leghemoglobin falls into the class of symbiotic globins, which also include the root nodules globins of actinorhizal plants such as Casuarina. The Casuarina symbiotic globin is intermediate between leghemoglobin and nonsymbiotic phytoglobin-2.

Structure
Leghemoglobins are monomeric proteins with a mass around 16 kDa, and are structurally similar to myoglobin. One leghemoglobin protein consists of a heme bound to an iron, and one polypeptide chain (the globin). Similar to myoglobin and hemoglobin, the iron of heme is found in its ferrous state in vivo, and is the moiety that binds oxygen. Despite similarities in the mechanism of oxygen binding between leghemoglobin and animal hemoglobin, and the fact that leghemoglobin and animal hemoglobin evolved from a common ancestor, there is dissimilarity in amino acid sequence between these proteins at about 80% of positions. Oxygen binding affinities of leghemoglobins are between 11 and 24 times higher than oxygen binding affinities of sperm whale myoglobin. Differences in the affinities are due to differential rates of association between the two types of proteins. One explanation of this phenomenon is that in myoglobin, a bound water molecule is stabilized in a pocket surrounding the heme group. This water group must be displaced in order for oxygen to bind. No such water is bound in the analogous pocket of leghemoglobin, so it is easier for an oxygen molecule to approach the leghemoglobin heme. Leghemoglobin has a slow oxygen dissociation rate, similar to myoglobin. Like myoglobin and hemoglobin, leghemoglobin has a high affinity for carbon monoxide.

In the primary structure of Leghemoglobin A in soybeans, a valine(F7) is found in place where a serine(F7) is in Myoglobin. Without a hydrogen bond fixing the orientation of the proximal histidine side chain the imidazole ring can occupy a staggered conformation between pyrrole nitrogen atoms and can readily move upward to the heme plane. This greatly increases the reactivity of the iron atom and oxygen affinity. In Leghemoglobin A the distal histidine side chain is also rotated away from the bound ligand by formation of a hydrogen bond with Tyrosine.

Heme groups are the same in all known leghemoglobins, but the amino acid sequence of the globin differs slightly depending on bacterial strain and legume species. Even within one leguminous plant, multiple isoforms of leghemoglobins can exist. These often differ in oxygen affinity, and help meet the needs of a cell in a particular environment within the nodule.

Debate on principal function
Results of a 1995 study suggested that the low free oxygen concentration in root nodule cells is actually due to the low oxygen permeability of root nodule cells. It follows that the main purpose of leghemoglobin is to scavenge the limited free oxygen in the cell and deliver it to mitochondria for respiration. But, scientists of a later 2005 article suggest that leghemoglobin is responsible both for buffering oxygen concentration, and for delivery of oxygen to mitochondria. Their leghemoglobin knockout studies showed that leghemoglobin actually does significantly decrease the free oxygen concentration in root nodule cells, and that nitrogenase expression was eliminated in leghemoglobin knockout mutants, assumably due to the degradation of nitrogenase with high free oxygen concentration. Their study also showed a higher ATP/ADP ratio in wild-type root nodule cells with active leghemoglobin, suggesting that leghemoglobin also assists with delivery of oxygen for respiration.

Plants contain both symbiotic and nonsymbiotic hemoglobins. Symbiotic hemoglobins are thought to be important for symbiotic nitrogen fixation (SNF). In legume, SNF takes place in specialized organs called nodules which contain bacteroids, or nitrogen fixing rhizobia. The induction of nodule-specific plant genes, which include those that encode for symbiotic leghemoglobins (Lb), accompany nodule development. Leghemoglobins accumulate to millimolar concentrations in the cytoplasm of infected plant cells prior to nitrogen fixation to buffer free oxygen in the nanomolar range, which can avoid inactivation of oxygen-labile nitrogenase while keeping a high enough oxygen flux for respiration in the cell. The leghemoglobins are required for SNF but are not required for plant growth and development in the presence of an external source of fixed nitrogen. Leghemoglobins make the essential contribution of establishing low free-oxygen concentrations while keep a high energy status in cells. These are the conditions necessary for effective SNF.

Other plant hemoglobins
Globins have since been identified as a protein common to many plant taxa, not restricted to symbiotic ones. In light of this discovery, it has been proposed that the term phytoglobins be used for referring to plant globins in general.

Phytoglobins can be divided into two clades. The 3/3-fold type contains Classes I and II of angiosperm phytoglobins, and is the one common to all eukaryotes (HGT of a bacterial flavohemoglobin). The leghemoglobin sensu stricto is a class II phytoglobin. The 2/2-fold "TrHb2" type contains class III in angiosperm nomenclature, and appears to be acquired from Chloroflexota (formerly Chloroflexi) by the ancestor of land plants.

Commercial use
Impossible Foods asked the American FDA for their approval to use recombinant soy leghemoglobin in foods as an analog of meat-derived hemoglobin. Approval from the FDA came in July 2019, was challenged, and later upheld, on May 3, 2021, by a San Francisco federal appeals court. It is currently being used in their products to mimic the color, taste, and texture of meat.

title: Leghemoglobin


text:
Temu (disambiguation)

Temu is a Chinese e-commerce platform.

Temu may also refer to:
 * Temu (plant), a monotypic genus of plants in family Myrtaceae
 * Temù, a comune in Lombardy, Italy
 * Luma apiculata or temu, a species of flowering plant in the myrtle family
 * Pusô or temu, a rice cake cooked in woven coconut leaves

People with the surname

 * Hoyce Temu, Tanzanian beauty pageant winner
 * Naftali Temu, Kenyan athlete

title: Temu (disambiguation)


text:
Permeability

Permeability, permeable, and semipermeable may refer to:

Chemistry

 * Drug permeability
 * Semipermeable membrane, a membrane which will allow certain molecules or ions to pass through it by diffusion
 * Vascular permeability, the movement of fluids and molecules between the vascular and extravascular compartments
 * Permeation of a gas or vapor through a solid substance

Earth and soil science

 * Permeability (earth sciences), a measure of the ability of a material (such as rocks) to transmit fluids
 * Relative permeability, in multiphase flow in porous media
 * Permeability (foundry sand), a test of the venting characteristics of a rammed foundry sand
 * Hydraulic conductivity, the permeability of soil for water

Electromagnetism

 * Permeability (electromagnetism), the degree of magnetization of a material in response to a magnetic field
 * Vacuum permeability, permeability of free space or magnetic constant, a physical constant, the value of magnetic permeability in a classical vacuum

Vehicles and transport

 * Permeability (nautical), in ship design, the percentage of empty space in a compartment or tank
 * Permeability (spatial and transport planning), the extent to which the layout of urban forms enables people or vehicles to move in different directions

Other uses

 * Air permeability, characteristic of textile fabrics, measuring the ease of passage of air through them
 * "Impermeable" (song), a song by Ha*Ash
 * Permeable Press, an American publishing company

title: Permeability


text:
Ugo Foscolo

Ugo Foscolo (6 February 1778 – 10 September 1827), born Niccolò Foscolo, was a Greek-Italian writer, revolutionary and poet.

He is especially remembered for his 1807 long poem Dei Sepolcri.

Early life
Foscolo was born in Zakynthos in the Ionian Islands. His father Andrea Foscolo was an impoverished Venetian nobleman and doctor, and his mother Diamantina Spathis was Greek.

In 1788, upon the death of his father, who worked as a physician in Spalato (present-day Split, Croatia), the family moved to Venice, and Foscolo completed the studies he began at the Dalmatian grammar school at the University of Padua.

Amongst his Paduan teachers was the Abbé Melchiore Cesarotti, whose version of Ossian was very popular in Italy, and who influenced Foscolo's literary tastes; he knew both modern and Ancient Greek. His literary ambition revealed itself in the appearance in 1797 of his tragedy Tieste—a production that enjoyed a certain degree of success.

Politics and poetry
Foscolo, who, for unknown reasons, had changed his Christian name Niccolò to that of Ugo, began to take an active part in the stormy political discussions which the fall of the Republic of Venice had triggered. He was a prominent member of the national committees, and addressed an ode to Napoleon, expecting Napoleon to overthrow the Venetian oligarchy and create a free republic.

The Treaty of Campo Formio (17 October 1797), under which, the French having indeed forced the dissolution of the ancient Republic of Venice, then handed over the city and the Veneto to the Austrians (in exchange for the Austrian Netherlands) gave a rude shock to Foscolo, but did not quite destroy his hopes. The state of mind produced by that shock is reflected in his novel The Last Letters of Jacopo Ortis (1798), which was described by the 1911 Encyclopædia Britannica as a more politicized version of Johann Wolfgang von Goethe's The Sorrows of Young Werther: "for Foscolo's hero embodies the mental sufferings and suicide of an undeceived Italian patriot just as Goethe's hero places before us the too-delicate sensitiveness, embittering and at last cutting short the life of a private German scholar."

The story of Foscolo's novel, The Last Letters of Jacopo Ortis had a groundwork of melancholy fact. Jacopo Ortis had been a real person; he was a young student from Padua, and committed suicide there under circumstances akin to those described by Foscolo.

Foscolo, like many of his contemporaries, had thought much about suicide. Cato the Younger and the many classical examples of self-destruction described in Plutarch's Lives appealed to the imaginations of young Italian patriots as they had to the heroes and heroines of the Gironde in France. In the case of Foscolo, as in that of Goethe, the effect produced on the writer's mind by the composition of the work seems to have been beneficial. He had seen the ideal of a great national future rudely shattered; but he did not despair of his country, and sought relief in now turning to gaze on the ideal of a great national poet.

After the fall of Venice, Foscolo moved to Milan, where he formed a friendship with the older poet Giuseppe Parini, whom he later remembered with admiration and gratitude. In Milan, he published a selection of 12 Sonnets, blending the passionate sentiments shown in "Ortis" with classical control of language and rhythm.

Still hoping that his country would be freed by Napoleon, in 1799 Foscolo enlisted as a volunteer in the National Guard of Napoleon's Cisalpine Republic, was wounded at Cento, near Bologna, and taken as prisoner to Modena. Liberated after the French armies took Modena, he took part in the battle of the Trebbia (1799) and was wounded again in defence of the siege of Genoa (1800). Following the battle of Marengo (1800), he returned to Milan, and there gave the last touches to his "Ortis", published a translation of and commentary upon Callimachus, commenced a version of the Iliad and began his translation of Laurence Sterne's A Sentimental Journey Through France and Italy. He also took part in a failed memorandum intended to present a new model of unified Italian government to Napoleon.

In 1804, Foscolo returned to military service in Napoleon's cause, attached to the Italian Division of Napoleon's army, based in Boulogne-sur-Mer, as part of Napoleon's invasion force against Britain. Foscolo himself was stationed in Valenciennes, where he fathered a daughter, Floriana, by Sophia St John Hamilton, daughter of Lady Mary Hamilton.

Following the defeat at Trafalgar (1805) and Napoleon's abandonment of his plans for invasion, Foscolo returned to Italy in 1806. Before leaving France, however, Foscolo once again met Alessandro Manzoni in Paris. Some seven years younger, Manzoni was still living in the house of his mother Giulia Beccaria. Studies have noted very close analogies (textual, metrical and biographical) between the poetry of Foscolo and Manzoni in the period 1801 to 1803, such as those between Foscolo's All'amica risanata ("To the healed friend"), an ode to Antonietta Fagnani Arese, and Manzoni's Qual su le cinzie cime ("Who, on the peaks of Cynthus")

In 1807, occasioned by Napoleon's 1804 decree forbidding burials within city limits, Foscolo wrote his Dei Sepolcri ("On Sepulchres"), which may be described as his sublime effort to seek refuge in the past from the misery of the present and the darkness of the future. The mighty dead are summoned from their tombs, as ages before they had been in the masterpieces of Greek oratory, to fight again the battles of their country.

In January 1809, Foscolo was appointed to the chair of Italian rhetoric at the University of Pavia. In Pavia, Foscolo resided at the Palazzo Cornazzani, later home to Contardo Ferrini, to Ada Negri and to Albert Einstein, respectively. His inaugural lecture "On the origin and duty of literature", was conceived in the same spirit as his Dei Sepolcri. In his lecture, Foscolo urged his young countrymen to study literature, not in obedience to academic traditions, but in their relation to individual and national life and growth.

The sensation produced by this lecture played no small part in provoking the decree of Napoleon by which the chair of rhetoric was abolished in all the Italian universities under Napoleonic control. Soon afterwards, in 1811 Foscolo's tragedy of Ajax was presented at Milan, with little success; and because of its supposed allusions to Napoleon, he was forced in 1812 to move from Milan to Tuscany. The chief fruits of his stay in Florence were the tragedy of Ricciarda, the Ode to the Graces, left unfinished, and the completion of his translation of Laurence Sterne's Sentimental Journey, including his own fictional memoir Notizia intorno a Didimo Chierico ("News concerning Didymus the cleric") (1813), covering much of the same ground as that of Sterne's main character, the Reverend Yorick; which he (Foscolo) had begun during his service at Boulogne-sur-Mer. In his account of Didimo Chierico, Foscolo throws much light on his own character. His version of Sterne is an important feature in his personal history.

Foscolo returned to Milan in 1813, until the return of the Austrians in 1815; from there he passed into Switzerland, where he wrote a fierce satire in Latin on his political and literary opponents; and finally he sought the shores of England at the close of 1816.

London
During the eleven years spent by Foscolo in London, until his death there, he enjoyed all the social distinction which the most brilliant circles of the English capital could confer on foreigners of political and literary renown, and experienced all the misery which follows on from a disregard of the first conditions of domestic economy.

His contributions to the Edinburgh Review and Quarterly Review, his dissertations in Italian on the text of Dante Alighieri and Giovanni Boccaccio, and still more his English essays on Petrarch (1821), of which the value was enhanced by Barbarina Brand's admirable translations of some of Petrarch's finest sonnets, heightened his previous fame as a Man of Letters. However, he was frequently accused of financial ineptitude, and ended up spending time in debtors' prison, which affected his social standing after his release.

According to the History of the County of Middlesex, the scientist and businessman William Allen hired Foscolo to teach Italian at the Quaker school he co-founded, the Newington Academy for Girls. His general bearing in society – as reported by Walter Scott – had not been such as to gain and retain lasting friendships. He died at Turnham Green on 10 September 1827, and was buried at St Nicholas Church, Chiswick, where his restored tomb remains to this day; it refers to him as the "wearied citizen poet", and incorrectly states his age as 50. Forty-four years after his death, on 7 June 1871, his remains were exhumed at the request of the King of Italy and taken to Florence, where with all the pride, pomp and circumstance of a great national mourning, found their final resting-place beside the monuments of Niccolò Machiavelli and Vittorio Alfieri, of Michelangelo and Galileo, in the church of Santa Croce, the pantheon of Italian glory he had celebrated in Dei Sepolcri.

As noted by historian Lucy Riall, the glorification of Ugo Foscolo in the 1870s was part of the effort of the Italian government of this time (successful in completing the Italian unification but at the cost of a head-on confrontation with the Catholic Church) to create a gallery of "secular saints" to compete with those of the Church and sway popular feeling in favor of the newly created Italian state.

References in modern culture

 * Ugo Foscolo is the subject of a composition, La fuga di Foscolo, written in 1986 by Italian composer Lorenzo Ferrero.
 * His sonnet "Alla sera" appears in the movie La meglio gioventù.
 * His house in Edwardes Square in Kensington, west London, has an English Heritage blue plaque.

Poetry

 * Ai novelli repubblicani, ode (1797)
 * A Bonaparte liberatore [To Bonaparte the liberator], ode (1797)
 * A Luigia Pallavicini caduta da cavallo [To Luigia Pallavicini fallen from a horse], ode (1800)
 * All'amica risanata [To the healed (female) friend], ode (1802)
 * Non son chi fui, perì di noi gran parte, sonnet (1802)
 * Che stai?, sonnet (1802)
 * Te nudrice alle Muse, sonnet (1802)
 * E tu ne' carmi avrai perenne vita, sonnet (1802)
 * Perché taccia il rumor di mia catena, sonnet (1802)
 * Così gl'interi giorni in lungo incerto, sonnet (1802)
 * Meritamente, però ch'io potei, sonnet (1802)
 * Solcata ho fronte, sonnet (1802)
 * Alla sera [To the night (evening)], sonnet (1803)
 * A Zacinto [To Zakinthos], sonnet (1803)
 * Alla Musa [To the Muse], sonnet (1803)
 * In morte del fratello Giovanni [In death of brother John], sonnet (1803)
 * Dei Sepolcri [Of the sepulchres], carmen (1807)
 * Delle Grazie [Of the Graces], short poem (1803–1827, unfinished)

Novels

 * Sesto tomo dell'io (1799–1801)
 * Ultime lettere di Jacopo Ortis [The last letters of Jacopo Ortis] (1802)

Plays

 * Tieste [Thyestes] (1797)
 * Ajace [Ajax] (1811)
 * Ricciarda (1813)

title: Ugo Foscolo